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A sweet perspective on the COVID-19 pandemic – glycobiologist view on the effort to curb the pandemic
Author: Dr. Ofer Markman
AN EXPERT OPINION
A sweet perspective on the COVID-19 pandemic – glycobiologist view on the effort to curb the pandemic.
The sugars involved in a viral disease are unique in many ways when compared with the DNA/RNA or the proteins involved: they are almost totally dependent on the infected cells and tus are not affected by the viral mutation rate or by the virus at all. Nevertheless they are affected by the cells, their type and their sugar production mechanisms and in some respect to the production rate by which the virus in manufactured by the infected cells. Mutations may have neverthless major effect not on the structures of the glycans but rather on the axsistance of the glycosylation site, and thus the glycan at all, but not on its structures.
This may make the gycomolecule a good target for diagnostics as stability in the molecule may mean longer life time of the diagnostic kits.
Unique sugars are already predicted/found in the virus from certain chinese origin, in this case an o-linked glycan/s not previously detected.
Nevertheless, if the virus can infect multiple cells once current cells are not going to be available for any reason those viruses may present other glycans.
Once one starts to treat the infected person via modulation of protein production or by other means the change in the dynamic of protein production vs. protein glycosylation may cause changes in protein glycosyation, including their structures, this is well known to biotechnologists producing glycoproteins in labs and production.
This may either be a problem in understanding the state of disease or an advantage as it may help following response to the treatment and help as a co-treament diagnostics.
For that purpose we are starting to see pioneering players in that regard:
Glycans may play a role in treatment as well, TAMIFLU is uch an example. Tamiflu is directed to the flu enzyme Neuraminidaze that is part of the viral structures. This approch was also explored to develop treatments.
but glycans do not only effect their own involvement in treatment/diagnostics they also are effecting protein based diagnostics for this see statement by Dr. Michael Mercier of UAH
Glycobiology vs Proteomics: Glycobiologists Prespective in the effort to explain the origin, etiology and potential therapeutics for the Coronavirus Pandemic (COVID-19)
Curator: Ofer Markman, PhD
The sugars involved in a viral disease are unique in many ways when compared with the DNA/RNA or the proteins involved: they are almost totally dependent on the infected cells and thus are not affected by the viral mutation rate or by the virus at all. Nevertheless they are affected by the cells, their type and their sugar production mechanisms and in some respect to the production rate by which the virus is replicated in the infected cells. Mutations may have nevertheless major effect not on the structures of the glycans but rather on the existence of the glycosylation site, and thus the glycan at all, but not on its structures.
This may make the gycomolecule a good target for diagnostics as stability in the molecule may mean longer life shelve of diagnostics kits.
Unique sugars are already predicted/found in the virus from certain Chinese origin, in this case an o-linked glycan/s not previously detected.
Nevertheless, if the virus can infect multiple cells once current cells are not going to be available for any reason those viruses may present other glycans.
Once one starts to treat the infected person via modulation of protein production or by other means the change in the dynamic of protein production vs. protein glycosylation may cause changes in protein glycosyation, including their structures, this is well known to biotechnologists producing glycoproteins in labs and production.
This may either be a problem in understanding the state of disease or an advantage as it may help following response to the treatment and help as a co-treatment diagnostics.
Early Studies include the following:
Carbohydrate-based Diagnostics: A New Approach to COVID-19 Testing?
Glycans may play a role in treatment as well. TAMIFLU a case in point. Tamiflu is directed to the flu enzyme Neuraminidaze that is part of the viral structures. This approach was also explored to develop treatments.
Pneumagen Ltd Leverages its Novel Glycan Approach to Target Coronavirus (COVID-19) Infections
Glycans do not only effect their own involvement in treatment/diagnostics they also are effecting protein based diagnostics for this see statement by Dr. Michael Mercier of UAH
We’re dealing with COVID-19, but what’s a virus in the first place?
Obesity is a global concern that is associated with many chronic complications such as type 2 diabetes, insulin resistance (IR), cardiovascular diseases, and cancer. Growing evidence has implicated the digestive system, including its microbiota, gut-derived incretin hormones, and gut-associated lymphoid tissue in obesity and IR. During high fat diet (HFD) feeding and obesity, a significant shift occurs in the microbial populations within the gut, known as dysbiosis, which interacts with the intestinal immune system. Similar to other metabolic organs, including visceral adipose tissue (VAT) and liver, altered immune homeostasis has also been observed in the small and large intestines during obesity.
A link between the gut microbiota and the intestinal immune system is the immune-derived molecule immunoglobulin A (IgA). IgA is a B cell antibody primarily produced in dimeric form by plasma cells residing in the gut lamina propria (LP). Given the importance of IgA on intestinal–gut microbe immunoregulation, which is directly influenced by dietary changes, scientists hypothesized that IgA may be a key player in the pathogenesis of obesity and IR. Here, in this study it was demonstrate that IgA levels are reduced during obesity and the loss of IgA in mice worsens IR and increases intestinal permeability, microbiota encroachment, and downstream inflammation in metabolic tissues, including inside the VAT.
IgA deficiency alters the obese gut microbiota and its metabolic phenotype can be recapitulated into microbiota-depleted mice upon fecal matter transplantation. In addition, the researchers also demonstrated that commonly used therapies for diabetes such as metformin and bariatric surgery can alter cellular and stool IgA levels, respectively. These findings suggested a critical function for IgA in regulating metabolic disease and support the emerging role for intestinal immunity as an important modulator of systemic glucose metabolism.
Overall, the researchers demonstrated a critical role for IgA in regulating intestinal homeostasis, metabolic inflammation, and obesity-related IR. These findings identify intestinal IgA+ immune cells as mucosal mediators of whole-body glucose regulation in diet-induced metabolic disease. This research further emphasized the importance of the intestinal adaptive immune system and its interactions with the gut microbiota and innate immune system within the larger network of organs involved in the manifestation of metabolic disease.
Future investigation is required to determine the impact of IgA deficiency during obesity in humans and the role of metabolic disease in human populations with selective IgA deficiency, especially since human IgA deficiency is associated with an altered gut microbiota that cannot be fully compensated with IgM. However, the research identified IgA as a critical immunological molecule in the intestine that impacts systemic glucose homeostasis, and treatments targeting IgA-producing immune populations and SIgA may have therapeutic potential for metabolic disease.
After significant studies have been completed, particularly on a relationship between anthocyanins consumption and decreasd risk of Parkinson’s Disease in men, it is unclear why a comparable effect is not seen in women. This would lead one to ask questions about predominant time course of development in relationship to androgen activity. Pre- and postmenopausal status would seem to make no difference. It is reported that the anthocyanins cross the blood brain barrier. There are other questions that need to be raised. There is a decline in the production of transthyretin by the choroid plexus in the elderly – not sex related – with an elevation of homocysteine that is reciprocal to decline in transthyretin-RBP complex, that is related to AD. This is mediated by cystathionine-beta synthase, and involves matrix metalloproteinases. A mechanism for Parkinson’s Disease has been postulated to be related to Parkin gene expression, but how does this work, and why do we see the sex assymetry?
Eating flavonoids protects men against Parkinson’s disease
Men who eat flavonoid-rich foods such as berries, tea, apples and red wine significantly reduce their risk of developing Parkinson’s disease, according to new research by Harvard University and the University of East Anglia (UEA).
Published today in the journal Neurology ®, the findings add to the growing body of evidence that regular consumption of some flavonoids can have a marked effect on human health. Recent studies have shown that these compounds can offer protection against a wide range of diseases including heart disease, hypertension, some cancers and dementia.
This latest study is the first study in humans to show that flavonoids can protect neurons against diseases of the brain such as Parkinson’s.
Around 130,000 men and women took part in the research. More than 800 had developed Parkinson’s disease within 20 years of follow-up. After a detailed analysis of their diets and adjusting for age and lifestyle, male participants who ate the most flavonoids were shown to be 40 per cent less likely to develop the disease than those who ate the least. No similar link was found for total flavonoid intake in women.
The research was led by Dr Xiang Gao of Harvard School of Public Health in collaboration with Prof Aedin Cassidy of the Department of Nutrition, Norwich Medical School at UEA.
“These exciting findings provide further confirmation that regular consumption of flavonoids can have potential health benefits,” said Prof Cassidy.
“This is the first study in humans to look at the associations between the range of flavonoids in the diet and the risk of developing Parkinson’s disease and our findings suggest that a sub-class of flavonoids called anthocyanins may have neuroprotective effects.”
Prof Gao said: “Interestingly, anthocyanins and berry fruits, which are rich in anthocyanins, seem to be associated with a lower risk of Parkinson’s disease in pooled analyses. Participants who consumed one or more portions of berry fruits each week were around 25 per cent less likely to develop Parkinson’s disease, relative to those who did not eat berry fruits. Given the other potential health effects of berry fruits, such as lowering risk of hypertension as reported in our previous studies, it is good to regularly add these fruits to your diet.”
Flavonoids are a group of naturally occurring, bioactive compunds found in many plant-based foods and drinks. In this study the main protective effect was from higher intake of anthocyanins, which are present in berries and other fruits and vegetables including aubergines, blackcurrants and blackberries. Those who consumed the most anthocyanins had a 24 per cent reduction in risk of developing Parkinson’s disease and strawberries and blueberries were the top two sources in the US diet.
The findings must now be confirmed by other large epidemiological studies and clinical trials.
Parkinson’s disease is a progresssive neurological condition affecting one in 500 people, which equates to 127,000 people in the UK. There are few effective drug therapies available. Dr Kieran Breen, director of research at Parkinson’s UK said: “This study raises lots of interesting questions about how diet may influence our risk of Parkinson’s… there are still a lot of questions to answer and much more research to do before we really know how important diet might be for people with Parkinson’s.”
ST. PAUL, Minn. –New research shows men and women who regularly eat berries may have a lower risk of developing Parkinson’s disease, while men may also further lower their risk by regularly eating apples, oranges and other sources rich in dietary components called flavonoids. The study was released today and will be presented at the American Academy of Neurology’s 63rd Annual Meeting in Honolulu April 9 to April 16, 2011.
Flavonoids are found in plants and fruits and are also known collectively as vitamin P and citrin. They can also be found in berry fruits, chocolate, and citrus fruits such as grapefruit.
The study involved 49,281 men and 80,336 women. Researchers gave participants questionnaires and used a database to calculate intake amount of flavonoids. They then analyzed the association between flavonoid intakes and risk of developing Parkinson’s disease. They also analyzed consumption of five major sources of foods rich in flavonoids: tea, berries, apples, red wine and oranges or orange juice. The participants were followed for 20 to 22 years.
During that time, 805 people developed Parkinson’s disease. In men, the top 20 percent who consumed the most flavonoids were about 40 percent less likely to develop Parkinson’s disease than the bottom 20 percent of male participants who consumed the least amount of flavonoids. In women, there was no relationship between overall flavonoid consumption and developing Parkinson’s disease. However, when sub-classes of flavonoids were examined, regular consumption of anthocyanins, which are mainly obtained from berries, were found to be associated with a lower risk of Parkinson’s disease in both men and women.
“This is the first study in humans to examine the association between flavonoids and risk of developing Parkinson’s disease,” said study author Xiang Gao, MD, PhD, with the Harvard School of Public Health in Boston. “Our findings suggest that flavonoids, specifically a group called anthocyanins, may have neuroprotective effects. If confirmed, flavonoids may be a natural and healthy way to reduce your risk of developing Parkinson’s disease.” May 10, 2013
New research reveals that Solanaceae—a flowering plant family with some species producing foods that are edible sources of nicotine—may provide a protective effect against Parkinson’s disease. The study appearing today inAnnals of Neurology, a journal of the American Neurological Association and Child Neurology Society, suggests that eating foods that contain even a small amount of nicotine, such as peppers and tomatoes, may reduce risk of developing Parkinson’s.
Parkinson’s disease is a movement disorder caused by a loss of brain cells that produce dopamine. Symptoms include facial, hand, arm, and leg tremors, stiffness in the limbs, loss of balance, and slower overall movement. Nearly one million Americans have Parkinson’s, with 60,000 new cases diagnosed in the U.S. each year, and up to ten million individuals worldwide live with this disease according to the Parkinson’s Disease Foundation. Currently, there is no cure for Parkinson’s, but symptoms are treated with medications and procedures such as deep brain stimulation.
Previous studies have found that cigarette smoking and other forms of tobacco, also a Solanaceae plant, reduced relative risk of Parkinson’s disease. However, experts have not confirmed if nicotine or other components in tobacco provide a protective effect, or if people who develop Parkinson’s disease are simply less apt to use tobacco because of differences in the brain that occur early in the disease process, long before diagnosis.
For the present population-based study Dr. Susan Searles Nielsen and colleagues from the University of Washington in Seattle recruited 490 patients newly diagnosed with Parkinson’s disease at the university’s Neurology Clinic or a regional health maintenance organization, Group Health Cooperative. Another 644 unrelated individuals without neurological conditions were used as controls. Questionnaires were used to assess participants’ lifetime diets and tobacco use, which researchers defined as ever smoking more than 100 cigarettes or regularly using cigars, pipes or smokeless tobacco.
Vegetable consumption in general did not affect Parkinson’s disease risk, but as consumption of edible Solanaceae increased, Parkinson’s disease risk decreased, with peppers displaying the strongest association. Researchers noted that the apparent protection from Parkinson’s occurred mainly in men and women with little or no prior use of tobacco, which contains much more nicotine than the foods studied.
“Our study is the first to investigate dietary nicotine and risk of developing Parkinson’s disease,” said Dr. Searles Nielsen. “Similar to the many studies that indicate tobacco use might reduce risk of Parkinson’s, our findings also suggest a protective effect from nicotine, or perhaps a similar but less toxic chemical in peppers and tobacco.” The authors recommend further studies to confirm and extend their findings, which could lead to possible interventions that prevent Parkinson’s disease.
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This study is published in Annals of Neurology. Media wishing to receive a PDF of this article may contact sciencenewsroom@wiley.com.
Full citation: “Nicotine from Edible Solanaceae and Risk of Parkinson Disease.” Susan Searles Nielsen, Gary M. Franklin, W.T. Longstreth Jr, Phillip D. Swanson and Harvey Checkoway. Annals of Neurology; Published May 9, 2013 (DOI:10.1002/ana.23884).
Author Contact: To arrange an interview with Dr. Susan Searles Nielsen, please contact Leila Gray with the University of Washington Health Sciences News Office at +1 206-685-0381 or at leilag@uw.edu.
About the Journal
Annals of Neurology, the official journal of the American Neurological Association and the Child Neurology Society, publishes articles of broad interest with potential for high impact in understanding the mechanisms and treatment of diseases of the human nervous system. All areas of clinical and basic neuroscience, including new technologies, cellular and molecular neurobiology, population sciences, and studies of behavior, addiction, and psychiatric diseases are of interest to the journal. The journal is published by Wiley on behalf of the
American Neurological Association and Child Neurology Society. For more information, please visit http://onlinelibrary.wiley.com/journal/10.1002/ana.
Flavonoids from berries shown to protect men against Parkinson’s disease
by: John Phillip, John is a Certified Nutritional Consultant and Health Researcher
(NaturalNews) Past research bodies have confirmed the health-protective effect of a natural diet rich in flavonoids to protect against a wide range of diseases including heart disease, hypertension, some cancers, and dementia. Researchers from Harvard University and the University of East Anglia have published the result of a study in the journalNeurology that demonstrates how these plant-based phytonutrients can significantly lower the risk of developing Parkinson’s disease, especially in men.
Flavonoids from healthy foods such as berries, tea, apples, and red wine cross the delicate blood-brain barrier to protect neurons against neurologic diseases such as Parkinson’s. This large scale study included more than 130,000 men and women participants that were followed for a period of twenty years. During this time, more than 800 individuals developed Parkinson’s disease.
A diet high in flavonoids from berries lowers Parkinson’s disease risk by forty percent
After a detailed analysis of their diets and adjusting for age and lifestyle, male participants who ate the most flavonoids were shown to be forty percent less likely to develop the disease than those who ate the least. No similar link was found for total flavonoid intake in women.
”This was the first study to examine the connection between flavonoid consumption and the development of Parkinson’s disease. The findings suggest that a sub-class of flavonoids called anthocyanins may exhibit neuroprotective effects. Participants consuming one or more portions of berry fruits each week were around twenty-five percent less likely to develop Parkinson’s disease, relative to those who did not eat berry fruits.
Flavonoids are the bioactive, naturally occurring chemical compounds found in many plant-based foods and drinks.
This study demonstrated the main protective effect was from the consumption of anthocyanins, which are present in berries and other fruits and vegetables including aubergines, blackcurrants, and blackberries. Strawberries and blueberries are the two most common sources of flavonoids in the US diet, contributing to a twenty-four percent lowered risk in this research.
Parkinson’s disease is among a group of chronic diseases presently affecting one in 500 people, with new cases on the rise. Drug therapies are ineffective and bear significant side effects.
Nutrition experts recommend adding a minimum of three to five servings of flavonoids to your diet each week. Include all varieties of berries, apples, and green tea to guard against Parkinson’s disease and other neurodegenerative illnesses.
Cell-free Protein Synthesis from a Release Factor 1 Deficient Escherichia coli Activates Efficient and Multiple Site-specific Nonstandard Amino Acid Incorporation
†Department of Chemical and Biological Engineering,‡Chemistry of Life Processes Institute, §Department of Chemistry, and Department of Molecular Biosciences,Northwestern University, Evanston, Illinois 60208,United States of America
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520, United States of America
# Systems Biology Institute, Yale University, West Haven, Connecticut 06516, United States of America
Member, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, United States of America
Institute of Bionanotechnology in Medicine, Northwestern University, Chicago, Illinois 60611, United States of America
Site-specific incorporation of nonstandard amino acids (NSAAs) into proteins
Site-specific incorporation of nonstandard amino acids (NSAAs) into proteins enables the creation of biopolymers, proteins, and enzymes with new chemical properties, new structures, and new functions. To achieve this, amber (TAG codon) suppression has been widely applied. However, the suppression efficiency is limited due to the competition with translation termination by release factor 1 (RF1), which leads to truncated products. Recently, we constructed a genomically recoded Escherichia coli strain lacking RF1 where 13 occurrences of the amber stop codon have been reassigned to the synonymous TAA codon (rEc.E13.ΔprfA). Here, we assessed and characterized cell-free protein synthesis (CFPS) in crude S30 cell lysates derived from this strain. We observed the synthesis of 190 ± 20 μg/mL of modified soluble superfolder green fluorescent protein (sfGFP) containing a single p-propargyloxy-l-phenylalanine (pPaF) or p-acetyl-l-phenylalanine. As compared to the parentrEc.E13 strain with RF1, this results in a modified sfGFP synthesis improvement of more than 250%. Beyond introducing a single NSAA, we further demonstrated benefits of CFPS from the RF1-deficient strains for incorporating pPaF at two- and five-sites per sfGFP protein. Finally, we compared our crude S30 extract system to the PURE translation system lacking RF1. We observed that our S30 extract based approach is more cost-effective and high yielding than the PURE translation system lacking RF1, 1000 times on a milligram protein produced/$ basis. Looking forward, using RF1-deficient strains for extract-based CFPS will aid in the synthesis of proteins and biopolymers with site-specifically incorporated NSAAs.
Sharks have survived some 400 million years on Earth. Could their longevity be due in part to an extraordinary resistance to cancer and other diseases? If so, humans might someday benefit from the shark’s secrets—but leading researchers caution that today’s popular shark cartilage “cancer cures” aren’t part of the solution.
The belief that sharks do not get cancer is not supported in fact, but it is the basis for decimating a significant part of the shark population for shark fins, and for medicinal use. The unfortunate result is that there is no benefit.
A basis for this thinking is that going back to the late 1800s, sharks have been fished commercially and there have been few reports of anything out of the ordinary when removing internal organs or preparing meat for the marketplace. In addition, pre-medical students may have dissected dogfish sharks in comparative anatomy, but you don’t see reports of cancerous tumors.
Carl Luer of the MOTE Marine Laboratory’s Center for Shark Research in Sarasota, Florida, has been studying sharks’ cancer resistance for some 25 years. Systematic surveys of sharks are difficult to conduct, as capturing the animals in large numbers is time-consuming, and cancer tests would likely require the deaths of large numbers of sharks. Of the thousands of fish tumors in the collections of the Smithsonian Institution, only about 15 are from elasmobranchs, and only two of these are thought to have been malignant.
Scientists have been studying cancerous tumors in sharks for 150 years.
The first chondrichthyes’ (cartilaginous fishes, including sharks) tumor was found on a skate and recorded by Dislonghamcps in 1853. The first shark tumor was recorded in 1908. Scientists have since discovered benign and cancerous tumors in 18 of the 1,168 species of sharks. Scarcity of studies on shark physiology has perhaps allowed this myth to be accepted as fact for so many years.
In April 2000, John Harshbarger and Gary Ostrander countered this shark myth with a presentation on 40 benign and cancerous tumors known to be found in sharks, and soon after a blue shark was found with cancerous tumors in both its liver and testes. Several years later a cancerous gingival tumor was removed from the mouth of a captive sand tiger shark, Carcharias Taurus. Advances in shark research continue to produce studies on types of cancer found in various species of shark. Sharks, like fish, encounter and take in large quantities of environmental pollutants, which may actually make them more susceptible to tumorous growth. Despite recorded cases of shark cancer and evidence that shark cartilage has no curative powers against cancer sharks continue to be harvested for their cartilage.
Sharks and their relatives, the skates and rays, have enjoyed tremendous success during their nearly 400 million years of existence on earth, according to Dr. Luer. He points out that one reason for this certainly is their uncanny ability to resist disease. Sharks do get sick, but their incidence of disease is much lower than among the other fishes. While statistics are not available on most diseases in fishes, reptiles, amphibians, and invertebrates, tumor incidence in these animals is carefully monitored by the Smithsonian Institution in Washington, D.C.
The Smithsonian’s enormous database, called the Registry of Tumors in Lower Animals, catalogs tissues suspected of being tumorous, including cancers, from all possible sources throughout the world. Of the thousands of tissues in the Registry, most of them are from fish but only a few are from elasmobranchs. Only 8 to 10 legitimate tumors are among all the shark and ray tissues examined, and only two of these are thought to have been malignant.
An observation by Gary Ostrander, a Professor at Johns Hopkins University, is that there may be fundamental differences in shark immune systems so that they aren’t as prone to cancer. The major thrust of the Motes research focuses on the immunity of sharks and their relatives the skates and rays. While skates aren’t as interesting to the public as their shark relatives, their similar biochemical immunology and their ability to breed in captivity make them perhaps more vital to Luer’s lab work. The result is to study the differences and similarities to the higher animals, and what might possibly be the role of the immune system in their low incidence of disease.
This low incidence of tumors among the sharks and their relatives has prompted biochemists and immunologists at Mote Marine Laboratory (MML) to explore the mechanisms that may explain the unusual disease resistance of these animals. To do this, they established the nurse shark and clearnose skate as laboratory animals. They designed experiments to see whether tumors could be induced in the sharks and skates by exposing them to potent carcinogenic (cancer-causing) chemicals, and then monitored pathways of metabolism or detoxification of the carcinogens in the test animals. While there were similarities and differences in the responses when compared with mammals, no changes in the target tissues or their genetic material ever resulted in cancerous tumor formation in the sharks or skates.
The chemical exposure studies led to investigations of the shark immune system. As with mammals, including humans, the immune system of sharks probably plays a vital role in the overall health of these animals. But there are some important differences between the immune arsenals of mammals and sharks. The immune system of mammals typically consists of two parts which utilize a variety of immune cells as well as several classes of proteins called immunoglobulins (antibodies).
Compared to the mammalian system, which is quite specialized, the shark immune system appears primitive but remarkably effective. Sharks apparently possess immune cells with the same functions as those of mammals, but the shark cells appear to be produced and stimulated differently. Furthermore, in contrast to the variety of immunoglobulins produced in the mammalian immune system, sharks have only one class of immunoglobulin (termed IgM). This Immunoglobulin normally circulates in shark blood at very high levels and appears to be ready to attack invading substances at all times.
Another difference lies in the fact that sharks, skates, and rays lack a bony skeleton, and so do not have bone marrow. In mammals, immune cells are produced and mature in the bone marrow and other sites, and, after a brief lag time, these cells are mobilized to the bloodstream to fight invading substances. In sharks, the immune cells are produced in the spleen, thymus and unique tissues associated with the gonads (epigonal organ) and esophagus (Leydig organ). Some maturation of these immune cells occurs at the sites of cell production, as with mammals. But a significant number of immune cells in these animals actually mature as they circulate in the bloodstream. Like the ever-present IgM molecule, immune cells already in the shark’s blood may be available to respond without a lag period, resulting in a more efficient immune response.
Research was being carried out during the 1980’s at the Massachusetts Institute of Technology (MIT) and at Mote Marine Laboratory designed to understand how cartilage is naturally able to resist penetration by blood capillaries. If the basis for this inhibition could be identified, it was reasoned, it might lead to the development of a new drug therapy. Such a drug could control the spread of blood vessels feeding a cancerous tumor, or the inflammation associated with arthritis.
The results of the research showed only that a very small amount of an active material, with limited ability to control blood vessel growth, can be obtained from large amounts of raw cartilage. The cartilage must be subjected to several weeks of harsh chemical procedures to extract and concentrate the active ingredients. Once this is done, the resulting material is able to inhibit blood vessel growth in laboratory tests on animal models, when the concentrated extract is directly applied near the growing blood vessels. One cannot assume that comparable material in sufficient amount and strength is released passively from cartilage when still in the animal to inhibit blood vessel growth anywhere in the body.
Tumors release chemicals stimulating the capillary growth so a nutrient-rich blood supply is created to feed the tumorous cells. This process is called angiogenesis. If scientists can control angiogenesis, they could limit tumor growth. Cartilage lacks capillaries running through it. Why should this be a surprise? Cartilage cells are called chondrocytes, and they fuction to produce a acellular interstitial matrix consisting of hyaluronan (complex carbohydrate formed from hyaluronic acid and chondroitin sulfate) which is protective of interlaced collagen. Early research into the anti-angiogenesis properties of cartilage revealed that tiny amounts of proteins could be extracted from cartilage, and, when applied in concentration to animal tumors, the formation of capillaries and the spread of tumors was inhibited.
Henry Brem and Judah Folkman from the Johns Hopkins School of Medicine first noted that cartilage prevented the growth of new blood vessels into tissues in the 1970s. The creation of a blood supply, called angiogenesis, is a characteristic of malignant tumors, as the rapidly dividing cells need lots of nutrients to continue growing. It is valuable to consider that these neovascular generating cells are not of epithelial derivation, but are endothelial and mesenchymal. To support their very high metabolism, tumors secrete a hormone called ‘angiogenin’ which causes nearby blood vessels to grow new branches that surround the tumor, bringing in nutrients and carrying away waste products
Brem and Folkman began studying cartilage to search for anti-angiogenic compounds. They reasoned that since all cartilage lacks blood vessels, it must contain some signaling molecules or enzymes that prevent capillaries from forming. They found that inserting cartilage from baby rabbits alongside tumors in experimental animals completely prevented the tumors from growing. Further research showed calf cartilage, too, had anti-angiogenic properties.
A young researcher by the name of Robert Langer repeated the initial rabbit cartilage experiments, except this time using shark cartilage. Indeed, shark cartilage, like calf and rabbit cartilage, inhibited blood vessels from growing toward tumors. Research by Dr. Robert Langer of M.I.T. and other workers revealed a promising anti-tumor agent obtainable in quantity from shark cartilage. The compound antagonistic to the effects of angiogenin, called ‘angiogenin inhibitor’, inhibits the formation of new blood vessels, neovascularization, that is essential for supporting cancer growth.
The consequence of the”shark myth” is not surprising. An inhabitant of the open ocean, the Silky Shark is ‘hit’ hard by the shark fin and shark cartilage industries – away from the prying eyes of a mostly land bound public. As a consequence of this ‘invisibility’, mortality of Silkies is difficult to estimate or regulate. North American populations of sharks have decreased by up to 80% in the past decade, as cartilage companies harvest up to 200,000 sharks every month in US waters to create their products. One American-owned shark cartilage plant in Costa Rica is estimated to destroy 2.8 million sharks per year. Sharks are slow growing species compared to other fish, and simply cannot reproduce fast enough to survive such sustained, intense fishing pressure. Unless fishing is dramatically decreased worldwide, a number of species of sharks will go extinct before we even notice.
Sources:
1. National Geographic News: NATIONALGEOGRAPHIC.COM/NEWS
2. Do Sharks Hold Secret to Human Cancer Fight?
by Brian Handwerk for National Geographic News. August 20, 2003
3. Busting Marine Myths: Sharks DO Get Cancer!
by Christie Wilcox November 9th 2009
This discussion is a novel piece of investigations now and earlier published in the Proceedings of the National Academy of Sciences, and another in Nature pertaining to aging, longevity, and cancer. The blind mole rat has an unexpected lifespan compared to other rodents. There are also findings of a related naked mole rat that comes into the picture. They are related, but not exactly the same. In both cases, the moles are cold-blooded, live underground with a queen and workers and they don’t develop cancer. The naked mold rates don’t develop cancer because of the presence of an imbalance in the intercellular matrix caused by abundant naturally produced, sticky complex carbohydrate also found in human joints that repels the cells at their interstices.
This is fascinating because it is also an important aspect of joint mobility. In the situation of chondomalacia before erosion of the articular cartilage, the movement and shearing stresses initially induced production of more chondrocytes and with that, a thickened cartilage that becomes taxed until it loses matrix fluid, followed by loss of matrix and loss of collagen by shearing stress. This type of motion and shear stress plays no part in the life of the nakedmole rat, which has a rough skin. The property of the cellular matrix seems to be characterized by both the production of the intercellular goo…called hyalurenan (like hyaluronic acid) and sparse hyaluronidase to remove and remodel the cell architecture. How this is related to extreme aging and no loss of cellular growth control, having sparce ubiqitination that is involve in cell death and repair is unclear.
The hyaluronidases (EC 3.2.1.35) are a family of enzymes that degrade hyaluronic acid. In humans, there are six associated genes, including HYAL1, HYAL2, HYAL3, and PH-20/SPAM1. By catalyzing the hydrolysis of hyaluronan, a constituent of the extracellular matrix (ECM), hyaluronidase lowers the viscosity of hyaluronan. http://upload.wikimedia.org/wikipedia/commons/2/2f/Hyaluronidase-1OJN.png
The blind mole ratis closely related, but it differs in that it has a mechanism by which the cells have limited proliferation and don’t proliferate to the point of getting out of control. This is because after several generations of cellular proliferation they produce a protein, IFN-β. This protein induces massive apoptosis, limiting the size of the sell population. There are findings in these investigations that might be relevant to understanding cancer resistance, and perhaps it could provide clues to treatment approaches. If that is too much to ask for, it gives us great insight into how cells organize.
Cancer resistance in the blind mole rat is mediated by concerted necrotic cell death mechanism
Gorbunovaa V, Hinea C, Tiana X, Ablaevaa J, Gudkovb AV, Nevoc E, and Seluanova A.
Contributed by Eviatar Nevo, October 3, 2012 (sent for review August 28, 2012)
Abstract
Blind mole rats Spalax (BMR) are small subterranean rodents common in the Middle East. BMR is distinguished by its adaptations to life underground, remarkable longevity (with a maximum documented lifespan of 21 y), and resistance tocancer. Spontaneous tumors have never been observed in spalacids. To understand the mechanisms responsible for this resistance, we examined the growth of BMR fibroblasts in vitro of the species Spalax judaei and Spalax golani. BMR cells proliferated actively for 7–20 population doublings, after which the cells began secreting IFN-β, and the cultures underwent massive necrotic cell death within 3 d. The necrotic cell death phenomenon was independent of culture conditions or telomere shortening. Interestingly, this cell behavior was distinct from that observed in another long-lived and cancer-resistant African mole rat, Heterocephalus glaber, the naked mole rat in which cells display hypersensitivity to contact inhibition. Sequestration of p53 and Rb proteins using SV40 large T antigen completely rescued necrotic cell death. Our results suggest that cancer resistance of BMR is conferred by massive necrotic response to overproliferation mediated by p53 and Rb pathways, and triggered by the release of IFN-β. Thus, we have identified a unique mechanism that contributes to cancer resistance of this subterranean mammal extremely adapted to life underground.
Source:
1To whom correspondence may be addressed. E-mail: vera.gorbunova@rochester.edu, nevo@research.haifa.ac.il, or andrei.seluanov@rochester.edu.
2Present address: Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115.
The extraordinarily durable proteins in the world’s longest-lived rodent may contain a vital piece of the puzzle of aging.
Like short-lived mice, the cells of naked mole rats are suffused with free-floating, cell-damaging oxygen free radicals.
Unlike the mice — and every other species that appears compromised by oxidative deterioration, including humans — they’ve found a way to live with it.
“When we compare the lab mouse with the naked mole rat, we find a striking difference in their systems,” said study co-author Asish Chaudhuri, a University of Texas Health Science Center biochemist. “Their proteins are still working. Even when damaged, the functions are maintained.”
The findings, published Monday in the Proceedings of the National Academy of Sciences, represent a new wrinkle in the oxidative-stress theory of aging. According to the theory, mitochondria — cellular machines that produce our bodies’ energy — pump out highly reactive oxygen molecules during respiration. Called free radicals, these molecules bind easily with other molecules, including DNA. Over time, DNA breaks down, compromising cellular function. Eventually whole tissues and organs no longer function. Multiple studies have found evidence of mitochondrial malfunction in a range of diseases that become more common with age, from heart disease to neurodegeneration to cancer. Drugs designed to rejuvenate mitochondria have shown promise in treating diabetes, and are celebrated as possible therapies for other conditions.
DNA repair rate is an important determinant of cell pathology (Photo credit: Wikipedia)
Chaudhuri’s team’s findings don’t contradict the role of mitochondria, but expand the theory to include cellular proteins other than DNA. They also explain a condundrum: some long-lived species display plenty of oxidative damage. “We’ve studied a dozen species, half short-lived and the others long-lived. One long-lived species would have lots of oxidative damage, and another would have little. The one thing that seemed to be consistent was protein stability,” said University of Texas Health Sciences Center gerontologist Steven Austad, who was not involved in the current study. “Until recently I’ve focused on DNA damage and repair, but this strikes me as even more fundamental. For DNA repair to work, you need all the repair proteins to work properly.” Mole rats caught the researchers’ attention because they can live for 30 years, or ten times longer than lab mice, even though the two are similarly sized.
They found that mole rats do have efficient mitochondria that release fewer free radicals than expected. But their mitochondria aren’t perfect. Free radicals still gather and cause damage. Two-year-old mole rats show just as much oxidative stress two-year-old mice — and then live for another quarter-century. The key appears to be their proteins, which continue to function despite damage. Study co-author Rochelle Buffenstein, a University of Texas Health Sciences Center physiologist, likened the phenomena to rusting cars: in other species, the axles rust, but in naked mole rats, it’s just the doors. With heat and urea — both of which typically cause complex protein spools to unfold — the researchers tried to break down the proteins, but to no avail. “You can basically hit them with a sledgehammer, and the proteins don’t unfold,” said Buffenstein. “Something makes them inherently more stable. There might be small molecules that tack on to proteins and help them retain structure in the face of cellular stress.”
Mole rats also appear to delay protein repair until the last possible moment, thus saving energy and resources. When proteins finally do break down, mole rats do an especially efficient job of cleaning them up. Only a tiny bit of ubiquitin — the chemical tag used to label damaged proteins for disposal — is required. Finally, specialized protein-disposal structures, called proteosomes (tied to ubiqitination), don’t appear to break down with age in mole rats.
The researchers will next try to determine what maintains the mole rat’s proteins and proteosome. If, as Buffenstein suspects, it turns out to be an as-yet-unidentified protein protectant, scientists could apply the findings to people. “If we can identify those proteins, we can use them to study aging and age-related diseases. These animals don’t have any symptoms of neurodegeneration, even in old age,” said Chaudhuri. “Then we can design peptides that act like the protein, and take it as a drug.”
Citation:
Protein stability and resistance to oxidative stress are determinants of longevity in the longest-living rodent, the naked mole-rat.
By Viviana I. Perez, Rochelle Buffenstein, Venkata Masamsetti, Shanique Leonard, Adam B. Salmon, James Meleb, Blazej Andziak, Ting Yang, Yael Edrey, Bertrand Friguet, Walter Ward, Arlan Richardson and Asish Chaudhuri. Proceedings of the National Academy of Sciences, Vol. 106 No. 7, Feb. 16, 2009.
Why Blind Mole Rats Don’t Get Cancer
By Ian Steadman, Wired UK
Blind mole rats don’t get cancer. in 2011 it was found they have a gene that stops cancerous cells from forming. The same team thought that two other cancer-proof mole rat species might have similar genes, but instead it turns out that they do develop cancerous cells. It’s just that those cells are programmed to destroy themselves if they become dangerous.
The blind mole rat (Spalax typhlus) has tiny eyes completely covered by a layer of skin. (Photo credit: Wikipedia)
Mole rats, which live in underground burrows throughout Southern and Eastern Africa, and the Middle East, are fascinating creatures. The naked mole rat, in particular, is the only cold-blooded mammal known to man, doesn’t experience pain, and is also arguably the only mammal (along with the Damaraland mole rat) to demonstrate eusociality — that is, they live in large hierarchical communities with a queen and workers, like ants or bees.
The two species examined by the University of Rochester’s Vera Gorbunova and her team were the Judean Mountains blind mole rat (Spalax judaei) and the Golan Heights blind mole rat (Spalax golani), which live within small regions of Israel. The team took cells from the rodents and put them in a culture that would force them to multiply beyond what would happen within the animals’ bodies. For the first seven to 20 multiplications, things looked fine, but beyond 20 multiplications the cells started rapidly dying off. Examining the cells as they died revealed that they had started to produce a protein, IFN-β, that caused them to undergo “massive necrotic cell death within three days”. In effect, once the cells had detected that they had multiplied beyond a certain point, they killed themselves. The cells of naked mole ratshave a self-preservation mechanism tied to a hypersensitivity to overcrowding, which stops them from multiplying too much. On the one hand (blind mole rat) you have self-destruction at a point at which there is crowding due to IFN-β. On the other hand, you find an aversion to overcrowding (naked mole rat).
In the Proceedings of the National Academy of Sciences, Gorbunova hypothesizes that the blind mole rats’ unique habitat — almost entirely underground — might mean that they “could perhaps afford to evolve a long lifespan, which includes developing efficient anti-cancer defences”. Blind mole rats have extremely long lifespans by rodent standards, often living beyond 20 years at a time.
The reasons why this is, though, are still all hypothetical, as the precise mechanism that triggers the production of the IFN-β is still unknown. The hope is that this research could eventually lead to new therapies for cancer in humans.
Super Sugar Keeps Naked Mole Rats Cancer-Free
BY ELIZABETH PENNISI, SCIENCENOW 06.20.13
Although they are quite ugly and confined to a life underground, naked mole ratshave at least one attribute that other animals, even humans, might aspire to: They don’t get cancer. Now, researchers have discovered that the secret to this rodent’s good health is a complex sugar that helps keeps cells from clumping together and forming tumors. It exists in the spaces between cells called the extracellular matrix, “the work underlines the very important regulatory role of [the] extracellular matrix in cancer,” says Bryan Toole, a cancer biologist at the Medical University of South Carolina in Charleston who was not involved with the study. Molecular and cell biologist Vera Gorbunova of the University of Rochester in New York wanted to take a different tack and focus on animals that seem protected from tumors. So she tracked down the lifespans of 20 different rodents, looking for the ones that live a long time. Beavers and gray squirrels last a couple of decades, but naked mole rats outlive those larger animals by 10 years. Furthermore, naked mole rats have a unique social structure, with one queen that produces all the young for an underground colony full of helpers. Thanks to these studies, scientists know for sure that this species doesn’t get cancer. Given that naked mole rats live long and are resistant to cancer, “we fell in love with them right away,” Gorbunova says.
At first, she and her colleagues did not know where to look for the source of animals’ cancer resistance. But when they grew naked mole rat cells in a lab dish, they noticed that cells wouldn’t get too close together. Furthermore, the dish contents got very gooey, and when they eliminated the goo, the cells would clump together. The researchers tracked the stickiness to a complex sugar called hyaluronan, which cells make and release into the extracellular matrix. Hyaluronan exists in all animals, helping lubricate joints and serving as an essential component in skin and cartilage. However, naked mole rat hyaluronan is unusual in that each molecule is about 5 times the size of hyaluronan molecules from mice, rats, and humans. In addition, the researchers discovered that the enzyme that breaks down this sugar (hyaluronidase) is not very active in naked mole rats, allowing the compound to accumulate to higher concentrations than it does in other animals. The researchers think that this sugar evolved to make naked mole rat skin more elastic and able to cope with the tight squeeze of the narrow underground tunnels.
But does it prevent cancer? Gorbunova and her colleagues tried to stimulate naked mole rat cells to form tumors by exposing them to viral proteins that in mice lead to tumor growth. These proteins inactivate genes that suppress cancer, yet still naked mole rat cells did not show uncontrolled growth. However, when the researchers interfered with the production of hyaluronan or revved up the activity of the enzyme that breaks the sugar down, thereby reducing its concentrations, tumors did form in live animals, they report online today in Nature.
The work is “very thought-provoking [and] adds an interesting wrinkle to the role of the extracellular matrix in cancer,” says Roy Zent, a cell biologist at Vanderbilt University Medical Center in Nashville. Toole agrees. “It pushes our thoughts forward [about hyaluronan] in a very dramatic way,” he notes. “It establishes hyaluronan as an important player in cancer.” “If we could alter our [hyaluronan] or stabilize it somehow, we may be able to suppress cancers,” suggests Carlo Maley, an evolutionary cancer biologist at the University of California, San Francisco, who was not involved with the work. The next step, he adds, is to “put the naked mole rat [hyaluronan] gene into mice and test if they are cancer resistant.”
Cardio-Metabolic Drug Targets, Inaugural, September 25 – 26, 2013, Westin Waterfront | Boston, Massachusetts
Reporter: Aviva Lev-Ari, PhD, RN
ABOUT THIS CONFERENCE
Cardiovascular disease, diabetes, obesity and dyslipidemia, though traditionally treated as separate entities, are often conditions that appear together in individuals because of defects in underlying metabolic processes. Researchers are therefore now seeking compounds that target biological points of intersection of these related diseases in the hopes of ‘killing more birds with one stone.’ Or they are approaching drug development of a compound for a specific disease with a greater awareness of the backdrop of related conditions.
Join fellow biomedical researchers from academia and industry at our day and a half conference, Cardio-Metabolic Drug Targets to discuss the impact of this paradigm change in the way drugs are discovered and developed in the cardio-metabolic arena and to stay abreast of the latest targets and drug development candidates in the pipeline.
SUGGESTED EVENT PACKAGE:
September 23: Allosteric Modulators of GPCRsShort Course September 24 – 25: Novel Strategies for Kinase Inhibitors Conference September 25: Setting Up Effective Functional Screens Using 3D Cell Cultures Dinner Short Course September 25 – 26: Cardio-Metabolic Drug Targets Conference
This is the second article of a three part series recognizing the immense contribution of Elazer Edelman, MD, PhD, and his laboratory group at MIT to vascular biology, cardiovascular disease studies, and the bioengineering, development, and use of stenting technology for drug delivery, vascular repair, and limitation of vessel damage caused by stent placement.
The first article, published on this Open Access Online Scientific Journal
was concerned with vascular biology, and largely on both the impact of drug delivery design and placement on the endothelium of the vessel wall, and on the kinetics of drug delivery based on the location of stent placement versus intravascular injection as well as the metabolic events taking place in the arterial endothelium, intima, and muscularis.
This second article, is concerned with stents and drug delivery as it has evolved since the last decade of the 20th century based on biomaterials development and vascular biology principles to minimize inherent injury risk over this period.
The third. will be concerned with the lessons from biomaterials and stent mechanics going forward.
Heart care is in the midst of a transformation. Patients who once required heart surgery are treated with a stent, catheters for repair of valves, rhythm abnormalities, and a growing number of heart or vascular distrbances.
The catheters are threaded in through the femoral artery, and sometimes through the radial artery. The American College of Cardiology annual meeting highlights research on these devices. The procedure allows patients to leave the hospital after a day or two post-implant, but the initial cost of the novel devices is high. Not everyone qualifies for the treatment, and it will take a few years to compare the long term results with the benefits from surgery. But these procedures have allowed many patients treatment alternatives to surgery, and they offer an option for people who cannot be successfully managed by conservative medical therapy.
The effects of stent placement on vascular injury and the initiation of an inflammatory response
Leukocytes are recruited early and abundantly to experimentally injured vessels,
in direct proportion to cell proliferation and intimal growth.
Activated circulating leukocytes and Mac-1 (CD11 by CD18, aMb2) (monocytic) expression are
markers of restenosis risk in patients undergoing angioplasty.
Angioplastied vessels lack endothelium but have extensive fibrin(ogen) and platelet deposition. Consequently, Mac-1-dependent adhesion to fibrin(ogen) would be expected to
signal leukocyte recruitment and function, thereby
promote intimal growth
In this study
M1/70, an anti-CD11b blocking mAb, was administered to rabbits before, and every 48 hr for 3, 6, or 14 days after iliac artery balloon denudation.
M1/70 was bound to isolated rabbit monocytes.
The result was
Mac-1-mediated dose-dependent
inhibition of fibrinogen binding in vitro, thereby,
reducing by half leukocyte recruitment at 3, 6, and 14 days after injury.
Neointimal growth 14 days after injury was markedly attenuated by treatment with M1/70 –
intimal area after balloon injury, 0.12+0.09 mm2, compared with
0.32+0.08 mm2 in vehicle treated controls, P<0.01, and
intimal area after stent injury, 0.56+0.16 mm2, compared with
0.84+ 0.13 mm2 in vehicle-treated controls, P <0.05, and
0.90+0.15 mm2 in IgG-treated controls, P <0.02).
Mac-1 blockade reduces experimental neointimal thickening. These findings suggest that
leukocyte recruitment to and
infiltration of injured arteries
may be a valid target for preventing intimal hyperplasia. (1) Emerging data indicate that the inflammatory response after mechanical arterial injury
correlates with the severity of neointimal hyperplasia in animal models
and post angioplasty restenosis in humans.
The present study was designed to examine whether a nonspecific
stimulation of the innate immune system,
induced in close temporal proximity to the vascular injury,
would modulate the results of the procedure.
A LPS dose was chosen to be sufficient to induce systemic inflammation but not septic shock. Key markers of inflammation increased after LPS administration were:
serum interleukin-1 levels, and
monocytic stimulation (CD14 levels on monocytes)
Arterial macrophage infiltration at 7 days after injury was
1.7+1.2% of total cells in controls and
4.2+1.8% in LPS-treated rabbits (n=4, P<0.05).
The injured arteries 4 weeks after injury had significantly increased
luminal stenosis: 38+4.2% versus 23+2.6%, mean+SEM; n=8, P<0.05; and
neointima-to-media ratio: 1.26+0.21 versus 0.66+0.09, P<0.05 in LPS-treated animals compared with controls.
This effect was abolished by anti-CD14 Ab administration. Serum Il-1 levels and monocyte CD14 expression were significantly increased
in correlation with the severity of intimal hyperplasia.
LPS treatment increased neointimal area after stenting
from 0.57+0.07 to 0.77+0.1 mm2, and
stenosis from 9+1% to 13+1.7% (n=5, P<0.05).
Nonspecific systemic stimulation of the innate immune system
concurrently with arterial vascular injury
facilitates neointimal formation, and conditions associated with
increased inflammation may increase restenosis.(2)
The efficacy and toxicity of these local therapeutics depend upon
arterial drug deposition,
distribution, and
retention.
To examine how administered dose and drug release kinetics control arterial drug uptake, a model was created using principles of
computational fluid dynamics and
transient drug diffusion–convection.
The modeling predictions for drug elution were validated using
empiric data from stented porcine coronary arteries.
Inefficient, minimal arterial drug deposition was predicted when a bolus of drug was released and depleted within seconds.
Month-long stent-based drug release
efficiently delivered nearly continuous drug levels, but
the slow rate of drug presentation limited arterial drug uptake.
Uptake was only maximized when
the rates of drug release and absorption matched,
which occurred for hour-long drug release.
Of the two possible means for increasing the amount of drug on the stent,
modulation of drug concentration potently impacts
the magnitude of arterial drug deposition,
while changes in coating drug mass affect duration of release.
We demonstrate the importance of drug release kinetics and administered drug dose
in governing arterial drug uptake and suggest
novel drug delivery strategies for controlling spatio-temporal arterial drug distribution.(3)
Arterial drug concentrations determine local toxicity. Therefore, the emergent safety concerns surrounding drug-eluting stents mandate an investigation of the factors contributing to fluctuations in arterial drug uptake.
Drug-eluting stents were implanted into porcine coronary arteries, arterial drug uptake was followed and modeled using 2-dimensional computational drug transport.
Arterial drug uptake in vivo occurred faster than predicted by free drug diffusion, thus
an alternate, mechanism for rapid transport has been proposed involving carrier-mediated transport.
Though there was minimal variation in vivo in release kinetics from stent to stent,
arterial drug deposition varied by up to 114% two weeks after stent implantation.
extent of adherent mural thrombus fluctuated by 113% within 3 days.
The computational drug transport model predicted that focal and diffuse thrombi
elevate arterial drug deposition in proportion to the thrombus size
by reducing drug washout subsequently increasing local drug availability.
Variable peristrut thrombus can explain fluctuations in arterial drug uptake even in the face of a narrow range of drug release from the stent. The mural thrombus effects on arterial drug deposition may be circumvented by forcing slow rate limiting arterial transport, that cannot be further hindered by mural thrombus. (4)
1. A mAb to the b2-leukocyte integrin Mac-1 (CD11byCD18) Reduces Intimal Thickening after Angioplasty or Stent Implantation in Rabbits. C Rogers, ER Edelman, and DI Simon. PNAS Aug 1998; 95: 10134–10139.
2. Formation After Balloon and Stent Injury in Rabbits Systemic Inflammation Induced by Lipopolysaccharide increases Neointimal Formation After Balloon and Stent Injury in Rabbits. HD Danenberg, FGP Welt, M Walker, III, P Seifert, et al. Circulation 2002;105;2917-2922; http://dx.doi.org/10.1161/01.CIR.0000018168.15904.BB
3. Intravascular drug release kinetics dictate arterial drug deposition, retention, and distribution.
4. Thrombus causes fluctuations in arterial drug delivery from intravascular stents. B Balakrishnan, J Dooley, G Kopia, ER Edelman. J Control Release 2008. http://dx.doi.org/10.1016/j.jconrel.2008.07.027
Perivascular Graft Repair
Heparin remains the gold-standard inhibitor of the processes involved in the vascular response to injury. Though this compound has profound and wide-reaching effects on vascular cells, its clinical utility is unclear. It is clear that the mode of heparin delivery is critical to its potential and it may well be that
routine forms of administration are insufficient
to observe benefit given the heparin’s short half-life and complex pharmacokinetics.
When ingested orally, heparin is degraded to inactive oligomer fragments while systemic administration
is complicated by the need for continuous infusion
and the potential for uncontrolled hemorrhage.
Thus alternative heparin delivery systems have been proposed to maximize regional effects while limiting systemic toxicity. Yet, as heparin is such a potent antithrombotic compound and since existing local delivery systems lack the ability to
precisely regulate release kinetics,
even site-specific therapy is prone to bleeding.
Authors now describe the design and development of a novel biodegradable system for the perivascular delivery of heparin to the blood vessel wall with well-defined release kinetics.
This system consists of heparin-encapsulated
poly(DL lactide-co-glycolide) (pLGA) microspheres sequestered in an alginate gel.
Controlled release of heparin from this heterogeneous system is obtained for a period of 25 days.
The experimental variables affecting heparin release from these matrices were investigated by
gel permeation chromatography (GPC) and scanning electron microscopy (SEM)
to monitor the degradation process and correlated well with the release kinetics.
Heparin-releasing gels inhibited growth in tissue culture of
bovine vascular smooth muscle cells in a dose-dependent manner.
and also controlled vascular injury in denuding and
interposition vascular graft animal models of disease even when uncontrolled bleeding was evident with standard matrix-type release.
This system provided an effective means of examining
the effects of various compounds in
the control of smooth muscle cell proliferation in accelerated arteriopathies and also
shed light on the biologic nature of these processes.(1)
Soft tissue adhesives are employed to repair and seal many different organs that range in both
tissue surface chemistry and
mechanical effects during organ function.
This complexity motivates the development of tunable adhesive materials with
high resistance to uniaxial or multiaxial loads
dictated by a specific organ environment.
Co-polymeric hydrogels comprising
aminated star polyethylene glycol and
dextran aldehyde (PEG:dextran)
are materials exhibiting physico-chemical properties that can be modified
Here we report that resistance to failure
under specific loading conditions, as well as
tissue response at the adhesive material–tissue interface, can be modulated through regulation of
the number and density of adhesive aldehyde groups.
Author found that atomic force microscopy (AFM) can
characterize the material aldehyde density available for tissue interaction,
facilitating rapid, informed material choice.
Further, the correlation between AFM quantification of nanoscale unbinding forces
with macroscale measurements of adhesion strength
by uniaxial tension or multiaxial burst pressure allows the design of materials with specific cohesion and adhesion strengths.
However, failure strength alone does not predict optimal in vivo reactivity. The development of adhesive materials is significantly enabled when
experiments are integrated along length scales to consider
organ chemistry and mechanical loading states concurrently
with adhesive material properties and tissue response. (2)
Cell culture and animal data support the role of endothelial cells and endothelial-based compounds in regulating vascular repair after injury.
Authors describe a long-term study in pigs in which the biological and immunological
responses to endothelial cell implants were investigated 3 months after angioplasty,
approximately 2 months after the implants have degraded.
Confluent porcine or bovine endothelial cells grown in polymer matrices were implanted adjacent to 28 injured porcine carotid arteries.
Porcine and bovine endothelial cell implants significantly
reduced experimental restenosis compared to control by 56 and 31%, respectively.
Host humoral responses were investigated by detection of an increase in serum antibodies that bind to the bovine or porcine cell strains used for implantation.
A significant increase in titer of circulating antibodies to the bovine cells was observed
after 4 days in all animals implanted with xenogeneic cells.
Detected antibodies returned to presurgery levels after Day 40.
No significant increase in titer of antibodies to the porcine cells was observed during the experiment in animals implanted with porcine endothelial cells.
No implanted cells, Gelfoam, or focal inflammatory reaction could be detected
histologically at any of the implant sites at 90 days.
Suggesting that tissue engineered endothelial cell implants
may provide long term control of vascular repair after injury,
rather than simply delaying lesion formation and that
allogeneic implants are able to provide a greater benefit than xenogeneic implants. (3)
Vascular access complications are a major problem in hemodialysis patients. Native arteriovenous fistulae, historically the preferred mode of access, have a patency rate of only 60% at 1 year.
The most common mode of failure is due to progressive stenosis at the anastomotic site.
Authors have previously demonstrated that perivascular endothelial cell implants
inhibit intimal thickening following acute balloon injury in pigs, and now seek to determine if these
implants provide a similar benefit in the chronic and more complex injury model of arteriovenous anastomoses.
Side-to-side femoral artery-femoral vein anastomoses were created in 24 domestic swine.
toxicological,
biological and
immunological responses
were investigated 3 days and 1 and 2 months postoperatively to allogeneic endothelial cellimplants . The anastomoses were wrapped with polymer matrices containing
confluent porcine aortic endothelial cells (PAE; n = 14) or
control matrices without cells (n = 10).
PAE implants significantly reduced intimal hyperplasia at the anastomotic sites
compared to controls by 68% (p ! 0.05) at 2 months.
The beneficial effects of the PAE implants were not due to
differences in the rates of reendothelialization between the groups.
No significant immunological response to the allogeneic endothelial cells that impacted on efficacy was detected in any of the pigs.
No apparent toxicity was observed in any of the animals treated with endothelial implants.
These data suggest that perivascular endothelial cell implants
are safe and reduce early intimal hyperplasia in a porcine model of arteriovenous anastomoses. (4)
1. Perivascular graft heparin delivery using biodegradable polymer wraps. ER Edelman, A Nathan,
3. Endothelial Implants Provide Long-Term Control of Vascular Repair in a Porcine Model of Arterial Injury. HM Nugent, ER Edelman. J Surg Res 2001; 99:228–234. http://dx.doi.org/10.1006/jsre.2001.6198
4. Perivascular Endothelial Implants Inhibit Intimal Hyperplasia in a Model of Arteriovenous Fistulae: A Safety and Efficacy Study in the Pig. HM Nugent, A Groothuis, P Seifert, et al. J Vasc Res 2002;39:524–533.
Endovascular stents reside in a dynamic flow environment and yet the impact of flow
on arterial drug deposition after stent-based delivery is only now emerging.
Authors employed computational fluid dynamic modeling tools to investigate
the influence of luminal flow patterns on arterial drug deposition and distribution.
Flow imposes recirculation zones distal and proximal to the stent strut that extend
the coverage of tissue absorption of eluted drug and
induce asymmetry in tissue drug distribution.
Our analysis now explains how the disparity in
sizes of the two recirculation zones and
the asymmetry in drug distribution are determined by a complex interplay of local flow and strut geometry.
When temporal periodicity was introduced as a model of
pulsatile flow,
the net luminal flow served as an index of flow-mediated spatiotemporal tissue drug uptake.
Dynamically changing luminal flow patterns are intrinsic to the coronary arterial tree. Coronary drug-eluting stents should be appropriately considered where
luminal flow,
strut design and
pulsatility
have direct effects on tissue drug uptake after local delivery.(1)
The efficacy of drug-eluting stents (DES) requires delivery of potent compounds directly to the underlying arterial tissue.
The commercially available DES drugs rapamycin and paclitaxel bind specifically to
their respective therapeutic targets, FKBP12 and polymerized microtubules,
while also associating in a more general manner with other tissue elements.
As it is binding that provides biological effect, the question arises as to whether other
locally released or systemically circulating drugs can
displace DES drugs from their tissue binding domains.
Specific and general binding sites for both drugs are distributed across the media and adventitia with higher specific binding associated with the binding site densities in the media.
The ability of rapamycin and paclitaxel to compete for specific protein binding and general tissue deposition
was assessed for both compounds simultaneously and
in the presence of other commonly administered cardiac drugs.
Drugs classically used to treat standard cardiovascular diseases, such as hypertension and hypercoaguability,
displace rapamycin and paclitaxel from general binding sites, possibly
decreasing tissue reserve capacity for locally delivered drugs.
Paclitaxel and rapamycin do not affect the other’s binding
to their biologically relevant specific protein targets, but
can displace each other from tissue at three log order molar excess,
decreasing arterial loads by greater than 50%.
Local competitive binding therefore should not limit the placement of rapamycin and paclitaxel eluting stents in close proximity.(2)
Stent thrombosis is a lethal complication of endovascular intervention. There is concern about the inherent risk associated with specific stent designs and drug-eluting coatings
Authored examined whether drug-eluting coatings are inherently thrombogenic and whether the response to these materials was determined to any degree
by stent design and
stent deployment with custom-built stents.
Drug/polymer coatings uniformly reduce rather than increase thrombogenicity relative to matched bare metal counterparts (0.65-fold; P 0.011).
Thick-strutted (162 m) stents were 1.5-fold more thrombogenic than otherwise
identical thin-strutted (81 m) devices in ex vivo flow loops (P< 0.001),
commensurate with 1.6-fold greater thrombus coverage
3 days after implantation in porcine coronary arteries (P 0.004).
When bare metal stents were deployed in
malapposed or overlapping configurations, thrombogenicity increased compared with apposed, length-matched controls (1.58-fold, P < 0.001; and 2.32-fold, P <0.001).
The thrombogenicity of polymer-coated stents with thin struts was
lowest in all configurations and remained insensitive to incomplete deployment.
Computational modeling– based
predictions of stent-induced flow derangements
correlated with spatial distribution of formed clots.
Drug/polymer coatings do not inherently increase acute stent clotting;
they reducethrombosis.
However, strut dimensions and positioning relative to the vessel wall
are critical factors in modulating stent thrombogenicity.
Optimal stent geometries and surfaces, as demonstrated with thin stent struts,
help reduce the potential for thrombosis
despite complex stent configurations and variability in deployment. (Circulation. 2011;123:1400-1409.) (3)
1. Luminal flow patterns dictate arterial drug deposition in stent-based delivery.
VB Kolachalama, AR Tzafriri, DY Arifin, ER Edelman. J Control Release 2009; 133:24–30.
Multiple studies have shown that diabetes mellitus (DM) can affect the
efficacy of revascularization therapies and subsequent clinical outcomes.
Selecting the appropriate myocardial revascularization strategy is critically important
in the setting of multivessel coronary disease.
Optimal medical therapy is an appropriate first-line strategy in patients with DM and mild symptoms. When medical therapy does not adequately control symptoms,
revascularization with either PCI or CABG may be used.
In patients with treated DM, moderate to severe symptoms and complex multivessel coronary disease,
coronary artery bypass graft surgery provides better survival,
fewer recurrent infarctions and
greater freedom from re-intervention.
Decisions regarding revascularization in patients with DM must take into account multiple factors and as such require a multidisciplinary team approach (‘heart team’). (1)
An incomplete understanding of the transport forces and local tissue structures
that modulate drug distribution has hampered
local pharmacotherapies in many organ systems.
These issues are especially relevant to arteries, where stent-based delivery allows fine control of locally directed drug release.
Local delivery produces tremendous drug concentration gradients
these are in part derived from transport forces,
differences in deposition from tissue to tissue
This suggests that tissue ultrastructure also plays an important role.
Authors measured the equilibrium drug uptake and the penetration and diffusivity of
dextrans (a model hydrophilic drug similar to heparin) and albumin
in orthogonal planes in arteries explanted from different vascular beds.
Authors found significant variations in drug distribution with
geometric orientation and
arterial connective tissue content.
Drug diffusivities parallel to the connective tissue sheaths were
one to two orders of magnitude greater than across these sheaths.
This diffusivity difference remained relatively constant for drugs up to 70 kDa
before decreasing for larger drugs.
Drugs also distributed better into elastic arteries, especially at lower molecular weights,
with almost 66% greater transfer into the thoracic aorta
than into the carotid artery.
Arterial drug transport is thus highly anisotropic and
dependent on arterial tissue content.
The role of the local composition and geometric organization of arterial tissue
in influencing vascular pharmacokinetics
is likely to become a critical consideration for local vascular drug delivery (2)
Radiolabeled drug-eluting stents have been proposed
to potentially reduce restenosis in coronary arteries.
A P-32 labeled oligonucleotide (ODN) loaded on a polymer coated stent
is slowly released in the arterial wall to deliver a therapeutic dose to the target tissue.
A relatively low proportion of drugs is transferred to the arterial wall (< 2%– 5% typically). This raises questions about the degree to which radiolabeled drugs eluted from the stent
can contribute to the total radiation dose delivered to tissues.
A three-dimensional diffusion-convection transport model is used
to model the transport of a hydrophilic drug released
from the surface of a stent to the arterial media.
Large drug concentration gradients are observed
near the stent struts giving rise to a
non-uniform radiation activity distribution for the drug
in the tissues as a function of time.
A voxel-based kernel convolution method is used to calculate the radiation dose rate
resulting from this activity build-up in the arterial wall
based on the medical internal radiation dose formalism.
Measured residence time for the P-32 ODN in the arterial wall and
at the stent surface obtained from animal studies
are used to normalize the results in terms of absolute dose to tissue.
The results indicate radiation due to drug eluted from the stent
contributes only a small fraction of the total radiation delivered to the arterial wall,
the main contribution comes from the activity embedded in the stent coating.
For hydrophilic compounds with rapid transit times in arterial tissue and minimal binding interactions,
the activity build-up in the arterial wall contributes only a small fraction
to the total dose delivered by the P-32 ODN stent.
For these compounds, it is concluded that radiolabeled drug-eluting stent
would not improve the performance of radioactive stents in treating restenosis.
Also, variability in the efficacy of drug delivery devices
makes accurate dosimetry difficult and
the drug washout in the systemic circulatory system
may yield an unnecessary activity build-up and dose to healthy organs. (3)
The first compounds considered for stent-based delivery,
such as heparin have failed to stop restenosis clinically.
More recent compounds, such as paclitaxel, are of a different sort.
They are hydrophobic, and their effects after local release seem far more profound.
This dichotomy raises the question of whether drugs that have an effect when released from a stent do so because of
differences in biology or differences in physicochemical properties and targeting.
Authored applied continuum pharmacokinetics to examine the effects of
transport forces and device geometry on
the distribution of stent-delivered hydrophilic and hydrophobic drugs.
Stent-based delivery leads to large concentration gradients.
Drug concentrations range from nil to several times the
mean tissue concentration over a few micrometers.
Concentration variations were a function of the Peclet number (Pe),
the ratio of convective to diffusive forces.
Although hydrophobic drugs exhibit greater variability than hydrophilic drugs,
more negatively than hydrophobic drugs, and notably
affect local concentrations without changing mean concentrations.
Local concentrations and gradients are inextricably linked to biological effect. Therefore,
these results provide a potential explanation for the variable success of stent-based delivery.
Authors conclude that mere proximity of delivery devices to tissues
does not ensure adequate targeting,
because physiological transport forces cause
local concentrations to deviate significantly from mean concentrations. (4)
1. Role of CABG in the management of obstructive coronary arterial disease in patients with diabetes mellitus. D Aronson, ER Edelman. Curr Opin Pharmacol 2012, 12:134–141. Issue on Cardiovascular and renal. [Eds: JY Jeremy, K Zacharowski, N Shukla, S Wan]. http://dx.doi.org/10.1016/j.coph.2012.01.011
3. Dose model for stent-based delivery of a radioactive compound for the treatment of restenosis in coronary arteries. C Janickia, Chao-Wei Hwang, ER Edelman. Med Phys 2003; 30(10), 2622-7. http://dx.doi.org/10.1118/1.1607506
4. Physiological Transport Forces Govern Drug Distribution for Stent-Based Delivery. Chao-Wei Hwang, D Wu, ER Edelman. Circulation. 2001;104(5) :600-605; e14 – e9010. http://dx.doi.org/10.1161/hc3101.09221
Stent-Versus-Stent Equivalency Trials. Are Some Stents More Equal Than Others? Elazer R. Edelman, Campbell Rogers Circulation. 1999; 100(9): 896-898; e47 – e47. http://dx.doi.org/10.1161/01.CIR.100.9.896
New endovascular stent designs are displacing tried and-true devices for use in an ever-broader array of lesions. There is disagreement as to which device is most advantageous and whether design determines outcome. Preclinical research says that this should be the case. Clinical trials have failed to validate design dependence. Can the divergent results be reconciled? More than 50 different stent configurations are available. The processes of industrial development and federal regulatory evaluation support the importance of design.
Stents are made from
a spectrum of materials
a range of manufacturing techniques, and have
variable surfaces,
dimensions,
surface coverage, and
strut configurations.
The number of parameters involved may doom the number of subsets to approach the number of designs. Moreover, each device seems to have a unique optimal mode of placement. Differences have been reported in
flexibility,
tracking ability,
expansion,
radiovisibility,
side-branch access, and
resistance to compression and recoil for different devices.
Regulatory approval includes standards for safety:
toxicity,
biocompatibility,
structural and material analysis, and
fatigue testing
It has been suggested that
hoop strength,
surface cracking,
uniformity of expansion, and
other features become standardized as well.
Four different direct comparisons of first-generation Palmaz-Schatz slotted-tube stents and
second-generation stents have been made. In several studies there were no significant differences
in restenosis at follow-up, including
minimal luminal diameter (MLD),
percent diameter stenosis,
late loss, or
binary restenosis rate.
In the fourth study, restenosis was far greater for the Gianturco-Roubin II (GR-II) stent (Cook) than
the Palmaz-Schatz stent (Cordis-Johnson & Johnson).
The data for all stents bunch across trials: with the exception of the GR-II stent,
variability between the test stent groups was no greater than
the variability between the Palmaz-Schatz stent groups in the different trials.
Three distinct possibilities exist to explain the absence of clinical evidence that different designs behave differently:
(1) no differences in clinical outcomes exist between devices;
(2) differences exist but are so slight as to be clinically meaningless; and
(3) differences exist that may be clinically meaningful, but trials performed to date were not designed to detect them.
Schematic representation of device performance plotting outcome against indication indicates that
complication rates rise as lesion complexity increases.
When 2 devices are clinically different, their curves are displaced, and when they are indistinguishable, their curves overlap.
Clinical trials that restrict the test population to lesions low on the complexity scale
ensure safety for all patients but are not the ideal venues in which to detect differences between devices.
Thus, although stents 1 and 2 may have different clinical outcomes, in a restricted-criteria equivalency trial with low complexity, they appear identical. It is only when the test device performs worse than the standard, that differences can be appreciated.
In contrast, an open registry will not only show when a test stent is worse than the standard stent but also when it is better.
Equivalency Trials
Stent-versus-stent trials are equivalency trials, designed to show that a test device performs “as well as” a standard, currently acceptable device. This is a valid regulatory threshold but
not the means to evaluate the full potential of a device.
Equivalency trials must by definition commence with a patient population for whom the standard device is safe. Trials with currently approved devices as the standard necessitate that
patient entry and lesion selection be determined by
limitations of the standard, not the device.
to observe a difference in such a trial
the test device performs worse
For the test device to perform better, both the test and the standard must be challenged.
This was not the case for the trials in which
the average reference vessel size was 3.0+0.05 mm and
American College of Cardiology type B2 and C lesions accounted for only ~65% of lesions.
These lesions are those for which the Palmaz-Schatz stent is approved and technically suited, but
they represent only a minority of those lesions now receiving stents
Complexity, Equivalence, and Better
In truth, it may be most appropriate to think about parameters of device success and safety as a continuum, describing a correlation between events such as
thrombosis or restenosis and
a continuous measure of indication,
vessel dimension, or lesion complexity (Figure).
A given device may be represented by a characteristic response over a range of indications.
When there is a lateral offset to the curves,
differences in potential performance are anticipated.
Curves might even cross, rather than run parallel, indicating that devices might be matched
to lesions and indications. Open trials would consider the entire range of the curves.
equivalency trials are limited to a small region of the curve.
The first-generation stents were a major innovation in interventional cardiology, and their place in medical history and biotechnology is unassailable.
Demonstration that new stents are better than old will require that evaluations be
performed in lesions for which current devices have marginal or limited application.
Complex or acutely unstable lesions, small arteries, and diseased bypass grafts are
the next great challenges of interventional cardiology.
Perhaps in these settings, future stent trials will provide firm evidence that
the manner in which blood vessels are manipulated dictates biological sequelae.
Proof that stent design can alter clinical outcomes may then unleash the potential
to change the way in which we consider design, approval, and use of new devices.
REFERENCES
Menichelli, M. (2006). Sirolimus Stent vs. Bare Stent in Acute Myocardial Infarction Trial. Presented at The European Paris Course on Revascularization (EuroPCR), May 16-19, 2006, Paris, France Paris, France.http://www.medscape.com/viewprogram/5505?rss
Pfisterer, P.E. (2006). Basel Stent Cost-effectiveness Trial-Late Thrombotic events (BASKET LATE) Trial. Presented at American College of Cardiology 55th Annual Scientific Session, March 11 – 14, 2006, Atlanta, Georgia.http://www.medscape.com/viewprogram/5185
Rogers, C. Edelman E.R. (2006). Pushing drug-eluting stents into uncharted territory, Simpler then you think – more complex than you imagine. Circulation,113, 2262-2265.
Shirota, T., Yasui, H., Shimokawa, H. & Matsuda, T. (2003). Fabrication of endothelial progenitor cell (EPC)-seeded intravascular stent devices and in vitro endothelialization on hybrid vascular tissue. Biomaterials 24(13), 2295–2302.
Simonton, C. (2006). The STENT Registry: A real-world look at Sirolimus- and Pacitaxel-Eluting Stents. Cath Lab Digest, 14 (1), 1-10.
Turco, M. (2006). TAXUS ATLAS Trial – 9-Month results: Evaluation of TAXUS Liberte vs. TAXUS Express. Presented at The European Paris Course on Revascularization (EuroPCR), May 16-19, 2006, Paris, France Paris, France.http://www.medscape.com/viewprogram/5505?rss
Hypertriglyceridemia concurrent Hyperlipidemia: Vertical Density Gradient Ultracentrifugation a Better Test to Prevent Undertreatment of High-Risk Cardiac Patients
Fight against Atherosclerotic Cardiovascular Disease: A Biologics not a Small Molecule – Recombinant Human lecithin-cholesterol acyltransferase (rhLCAT) attracted AstraZeneca to acquire AlphaCore
High-Density Lipoprotein (HDL): An Independent Predictor of Endothelial Function & Atherosclerosis, A Modulator, An Agonist, A Biomarker for Cardiovascular Risk
Peroxisome proliferator-activated receptor (PPAR-gamma) Receptors Activation: PPARγ transrepression for Angiogenesis in Cardiovascular Disease and PPARγ transactivation for Treatment of Diabetes
Clinical Trials Results for Endothelin System: Pathophysiological role in Chronic Heart Failure, Acute Coronary Syndromes and MI – Marker of Disease Severity or Genetic Determination?
Inhibition of ET-1, ETA and ETA-ETB, Induction of NO production, stimulation of eNOS and Treatment Regime with PPAR-gamma agonists (TZD): cEPCs Endogenous Augmentation for Cardiovascular Risk Reduction – A Bibliography
Positioning a Therapeutic Concept for Endogenous Augmentation of cEPCs — Therapeutic Indications for Macrovascular Disease: Coronary, Cerebrovascular and Peripheral
Cardiovascular Outcomes: Function of circulating Endothelial Progenitor Cells (cEPCs): Exploring Pharmaco-therapy targeted at Endogenous Augmentation of cEPCs
Vascular Medicine and Biology: CLASSIFICATION OF FAST ACTING THERAPY FOR PATIENTS AT HIGH RISK FOR MACROVASCULAR EVENTS Macrovascular Disease – Therapeutic Potential of cEPCs
Cardiac Surgery Theatre in China vs. in the US: Cardiac Repair Procedures, Medical Devices in Use, Technology in Hospitals, Surgeons’ Training and Cardiac Disease Severity”
Dilated Cardiomyopathy: Decisions on implantable cardioverter-defibrillators (ICDs) using left ventricular ejection fraction (LVEF) and Midwall Fibrosis: Decisions on Replacement using late gadolinium enhancement cardiovascular MR (LGE-CMR)
Competition in the Ecosystem of Medical Devices in Cardiac and Vascular Repair: Heart Valves, Stents, Catheterization Tools and Kits for Open Heart and Minimally Invasive Surgery (MIS)
Global Supplier Strategy for Market Penetration & Partnership Options (Niche Suppliers vs. National Leaders) in the Massachusetts Cardiology & Vascular Surgery Tools and Devices Market for Cardiac Operating Rooms and Angioplasty Suites
Diagram showing the location of vascular smooth muscle cells (Photo credit: Wikipedia)
English: simplified diagram of the human Arterial system in anterior view. Français : Diagramme simplifié du système artériel humain en vue antérieure (en anglais). (Photo credit: Wikipedia)
This is the first of a three part series on the evolution of vascular biology and the studies of the effects of biomaterials in vascular reconstruction and on drug delivery, which has embraced a collaboration of cardiologists at Harvard Medical School , Affiliated Hospitals, and MIT, requiring cardiovascular scientists at the PhD and MD level, physicists, and computational biologists working in concert, and an exploration of the depth of the contributions by a distinguished physician, scientist, and thinker.
The first part – Vascular Biology and Disease – will cover the advances in the research on
vascular biology,
signaling pathways,
drug diffusion across the endothelium and
the interactions with the underlying muscularis (media),
with additional considerations for type 2 diabetes mellitus.
The second part – Stents and Drug Delivery – will cover the
purposes,
properties and
evolution of stent technology with
the acquired knowledge of the pharmacodynamics of drug interactions and drug distribution.
The third part – Problems and Promise of Biomaterials Technology – will cover the shortcomings of the cardiovascular devices, and opportunities for improvement
Early work on endothelial injury and drug release principles
The insertion of a catheter for the administration of heparin is not an innocuous procedure. Heparin is infused to block coagulation, lowering the risk of a dangerous
clot formation and
dissemination.
It was shown experimentally that the continuous infusion of heparin
suppresses smooth muscle proliferation after endothelial injury. It may lead to
hemorrhage as a primary effect.
The anticoagulant property of heparin was removed by chemical modification without loss of the anti-proliferative effect.
In this study, MIT researches placed ethylene-vinyl acetate copolymer matrices containing standard and modified heparin adjacent to rat carotid arteries at the time of balloon deendothelialization.
Matrix delivery of both heparin compounds effectively diminished this proliferation in comparison to controls without producing systemic anticoagulation or side effects.
This mode of therapy appeared more effective than administering the agents by either
intravenous pumps or
heparin/polymer matrices placed in a subcutaneous site distant from the injured carotid artery
This indicated that the site of placement at the site of injury is a factor in the microenvironment, and is a preference for avoiding restenosis after angioplasty and other interventions.
This raised the question of why the proliferation of vascular muscle occurs in the first place. Edelman, Nugent and Karnovsky (1) showed that the proliferation required first the denudation of vascular surface endothelium. This exposed the underlayer to the effect of basic fibroblast growth factor, which stimulates mitogenesis of the exposed cell, explained by the endothelium as a barrier from circulating bFGF.
To answer this question, they compared the effect of
125I-labelled bFGF intravenously given with perivascular controlled bFGF release.
Polymeric controlled release devices delivered bFGF to the extravascular spacewithout transendothelial transport. Deposition within the blood vessel wall was rapidly distributed circumferentially and was substantially greater than that observed following intravenous injection.
The amount of bFGF deposited in arteries adjacent to the release devices was 40 times that deposited in similar arteries in animals who received a single intravenous bolus of bFGF.
The presence of intimal hyperplasia increased deposition of perivascularly released bFGF 2.4-fold but decreased the deposition of intravenously injected bFGF by 67%.
bFGF was 5- to 30-fold more abundant in solid organs after intravenous injection than it was following perivascular release, and
bFGF deposition was greatest in the kidney, liver, and spleen and was substantially lower in the heart and lung.
This result indicated that vascular deposition of bFGF is independent of endothelium, and
bFGF delivery is effectively perivascular. (2)
Drug activity studies have to be done in well controlled and representative conditions. Edelsman’s Lab researchers studied the
dose response of injured arteries to exogenous heparin in vivo by providing steady and predictable arterial levels of drug.
Controlled-release devices were fabricated to direct heparin uniformly and at a steady rate to the adventitial surface of balloon-injured rat carotid arteries.
Researchers predicted the distribution of heparin throughout the arterial wall using computational simulations and correlated these concentrations with the biologic response of the tissues.
Researchers determined from this process that an in vivo arterial concentration of 0.3 mg/ml of heparin is required to maximallyinhibit intimal hyperplasia after injury.
This estimation of the required tissue concentration of a drug is
independent of the route of administration and
applies to all forms of drug release.
In this way the Team was able to
evaluate the potential of widely disparate forms of drug release and, to finally
create some rigorous criteria by which to guide the development of particular delivery strategies for local diseases. (3)
(2) Perivascular and intravenous administration of basic fibroblast growth factor: Vascular and solid organ deposition. ER Edelman, MA Nugent, and MJ Karnovsky. PNAS Feb 1993; 90: 1513-1517.
(3) Tissue concentration of heparin, not administered dose, correlates with the biological response of injured arteries in vivo. MA Lovich and ER Edelman. PNAS Sep 1999; 96: 11111–11116.
Perlecan is a heparin-sulfate proteoglycan that might be critical for regulation of vascular repair by inhibiting the binding and mitogenic activity of basic fibroblast growth factor-2 (bFGF-2) in vascular smooth muscle cells .
The Team generated
Clones of endothelial cells expressing an antisense vector targeting domain III of perlecan. The transfected cells produced significantly less perlecan than parent cells, and they had reduced bFGF in vascular smooth muscle cells.
Endothelial cells were seeded onto three-dimensional polymeric matrices and implanted adjacent to porcine carotid arteries subjected to deep injury.
The parent endothelial cells prevented thrombosis, but perlecan deficient cells were ineffective.
The ability of endothelial cells to inhibit intimal hyperplasia, however, was only in part suppressed by perlecan. The differential regulation by perlecan of these aspects of vascular repair may clarify why control of clinical clot formation does not lead to full control of intimal hyperplasia.
The use of genetically modified tissue engineered cells provides a new approach for dissecting the role of specific factors within the blood vessel wall.(1) Successful implementation of local arterial drug delivery requires transmural distribution of drug. The physicochemical properties of the applied compound govern its transport and tissue binding.
Hydrophilic compounds are cleared rapidly.
Hydrophobic drugs bind to fixed tissue elements, potentially prolonging tissue residence and biological effect.
Local vascular drug delivery provides
elevated concentrations of drug in the target tissue while
minimizing systemic side effects.
To better characterize local pharmacokinetics the Team examined the arterial transport of locally applied dextran and dextran derivatives in vivo.
Using a two-compartment pharmacokinetic model to correct
The measured transmural flux of these compounds for systemic
Redistribution and elimination as delivered from a photo-polymerizable hydrogel.
The diffusivities and the transendothelial permeabilities were strongly dependent on molecular weight and charge
For neutral dextrans, the diffusive resistance increased with molecular weightapproximately 4.1-fold between the molecular weights of 10 and 282 kDa.
Endothelial resistance increased 28-fold over the same molecular weight range.
The effective medial diffusive resistance was unaffected by cationic charge as such molecules moved identically to neutral compounds, but increased approximately 40% when dextrans were negatively charged.
Transendothelial resistance was 20-fold lower for the cationic dextrans, and 11-fold higher for the anionic dextrans, when both were compared to neutral counterparts.
These results suggest that, while
low molecular weight drugs will rapidly traverse the arterial wall with the endothelium posing a minimal barrier,
the reverse is true for high molecular weight agents.
The deposition and distribution of locally released vascular therapeutic compounds might be predicted based upon chemical properties, such as molecular weight and charge. (2)
Paclitaxel is hydrophobic and has therapeutic potential against proliferative vascular disease. The favorable preclinical data with this compound may, in part, result from preferential tissue binding. The complexity of Paclitaxel pharmacokinetics required in-depth investigation if this drug is to reach its full clinical potential in proliferative vascular diseases.
Equilibrium distribution of Paclitaxel reveals partitioning above and beyond perfusate concentration and a spatial gradient of drug across the arterial wall.
The effective diffusivity (Deff) was estimated from the Paclitaxel distribution data to
facilitate comparison of transport of Paclitaxel through arterial parenchyma with that of other vasoactive agents and to
characterize the disparity between endovascular and perivascular application of drug.
This transport parameter described the motion of drug in tissues given an applied concentration gradient and includes, in addition to diffusion,
the impact of steric hindrance within the arterial interstitium;
nonspecific binding to arterial elements; and, in the preparation used here,
convective effects from the applied transmural pressure gradient.
At all times, the effective diffusivity for endovascular delivery exceeded that of perivascular delivery. The arterial transport of Paclitaxel was quantified through application ex vivo and measurement of the subsequent transmural distribution.
Arterial Paclitaxel deposition at equilibrium varied across the arterial wall.
Permeation into the wall increased with time, from 15 minutes to 4 hours, and
varied with the origin of delivery.
In contrast to hydrophilic compounds, the concentration in tissue exceeded the applied concentration and the rate of transport was markedly slower. Furthermore, endovascular and perivascular Paclitaxel application led to differences in deposition across the blood vessel wall.
This leads to a conclusion that Paclitaxel interacts with arterial tissue elements as it moves under the forces of
diffusion and
convection and
can establish substantial partitioning and spatial gradients across the tissue. (3)
Endovascular drug-eluting stents have changed the practice of cardiovascular vascularization, and yet it is unclear how they so dramatically reduce restenosis
We don’t know how to distinguish between the different formulations available. Researchers are now questioning whether individual properties of different drugs beyond lipid avidity effect arterial transport and distribution.
In bovine internal carotid segments, tissue-loading profiles for
Hydrophobic Paclitaxel and Rapamycin are indistinguishable, reaching load steady state after 2 days.
Hydrophilic dextran reaches equilibrium in hours.
Paclitaxel and Rapamycin bind to the artery at 30–40 times bulk concentration, and bind to specific tissue elements.
Transmural drug distribution profiles are markedly different for the two compounds.
Rapamycin binds specifically to FKBP12 binding protein and it distributes evenly through the artery,
Paclitaxel binds specifically to microtubules, and remains primarily in the subintimal space.
The binding of Rapamycin and Paclitaxel to specific intracellular proteins plays an essential role in
determining arterial transport and distribution and in
distinguishing one compound from another.
These results offer further insight into the
mechanism of local drug delivery and the
specific use of existing drug-eluting stent formulations. (4)
The Role of Amyloid beta (A) in Creation of Vascular Toxic Plaque
Amyloid beta (A) is a peptide family produced and deposited in neurons and endothelial cells (EC). It is found at subnanomolar concentrations in the plasma of healthy individuals. Simple conformational changes produce a form of A-beta , A-beta 42, which creates toxic plaque in the brains of Alzheimer’s patients.
Oxidative stress induced blood brain barrier degeneration has been proposed as a key factor for A-beta 42 toxicity.
This cannot account for lack of injury from the same peptide in healthy tissues. Researchers hypothesized that cell state mediates A-beta’s effect. They examined the viability in the presence of A-beta secreted from transfected Chinese hamster ovary cells (CHO) of
aortic Endothelial Cells (EC),
vascular smooth muscle cells (SMC) and
epithelial cells (EPI) in different states
A-beta was more toxic to all cell types when they were subconfluent. Subconfluent EC sprouted and SMC and EPI were inhibited by A-beta. Confluent EC were virtually resistant to A-beta and suppressed A-beta production by A-beta +CHO.
Products of subconfluent EC overcame this resistant state, stimulating the production and toxicity of A-beta 42. Confluent EC overgrew >35% beyond their quiescent state in the presence of A-beta conditioned in media from subconfluent EC.
These findings imply that A-beta 42 may well be even more cytotoxic to cells in injured or growth states and potentially explain the variable and potent effects of this protein.
One may now need to consider tissue and cell state in addition to local concentration of and exposure duration to A-beta.
The specific interactions of A-beta and EC in a state-dependent fashion may help understand further the common and divergent forms of vascular and cerebral toxicity of A-beta and the spectrum of AD. (5)
(1) Perlecan is required to inhibit thrombosis after deep vascular injury and contributes to endothelial cell-mediated inhibition of intimal hyperplasia. MA Nugent, HM Nugent, RV Iozzoi, K Sanchack, and ER Edelman. PNAS Jun 2000; 97(12): 6722-6727
(2) Correlation of transarterial transport of various dextrans with their physicochemical properties. O Elmalak, MA Lovich, E Edelman. Biomaterials 2000; 21: 2263-2272
(3) Arterial Paclitaxel Distribution and Deposition. CJ Creel, MA Lovich, ER Edelman. Circ Res. 2000;86:879-884
Autoimmunity may drive vascular disease through anti-endothelial cell (EC) antibodies. This raises a question about whether an increased morbidity of cardiovascular diseases in concert with systemic illnesses may involve these antibodies.
Matrix-embedded ECs act as powerful regulators of vascular repair accompanied by significant reduction in expected systemic and local inflammation.
The Lab researchers compared the immune response against free and matrix-embedded ECs in naive mice and mice with heightened EC immune reactivity. Mice were presensitized to EC with repeated subcutaneous injections of saline-suspended porcine EC (PAE) (5*10^5 cells).
On day 42, both naive mice (controls) and mice with heightened EC immune reactivity received 5*10^5 matrix-embedded or free PAEs. Circulating PAE-specific antibodies and effector T-cells were analyzed 90 days after implantation for –
PAE-specific antibody-titers,
frequency of CD4+-effector cells, and
xenoreactive splenocytes
These were 2- to 4-fold lower (P<0.0001) when naıve mice were injected with matrix-embedded instead of saline-suspended PAEs.
Though basal levels of circulating antibodies were significantly elevated after serial PAE injections (2210+341 mean fluorescence intensity, day 42) and almost doubled again 90 days after injection of a fourth set of free PAEs, antibody levels declined by half in recipients of matrix-embedded PAEs at day 42 (P<0.0001), as did levels of CD4+-effector cells and xenoreactive splenocytes.
A significant immune response to implantation of free PAE is elicited in naıve mice, that is even more pronounced in mice with pre-developed anti-endothelial immunity.
Matrix-embedding protects xenogeneic ECs against immune reaction in naive mice and in mice with heightened immune reactivity.
Matrix-embedded EC might offer a promising approach for treatment of advanced cardiovascular disease. (1)
Researchers examined the molecular mechanisms through which
mechanical force and hypertension modulate
endothelial cell regulation of vascular homeostasis.
Exposure to mechanical strain increased the paracrine inhibition of vascular smooth muscle cells (VSMCs) by endothelial cells.
Mechanical strain stimulated the production by endothelial cells of perlecan and heparan-sulfate glycosaminoglycans. By inhibiting the expression of perlecan with an antisense vector researchers demonstrated that perlecan was essential to the strain-mediated effects on endothelial cell growth control.
Mechanical regulation of perlecan expression in endothelial cells was
governed by a mechano-transduction pathway
requiring transforming growth factor (TGF-β) signaling and
intracellular signaling through the ERK pathway.
Immunohistochemical staining of the aortae of spontaneously hypertensive rats demonstrated strong correlations between
endothelial TGF-β,
phosphorylated signaling intermediates, and
arterial thickening.
Studies on ex vivo arteries exposed to varying levels of pressure demonstrated that
ERK and TGF-beta signaling were required for pressure-induced upregulation of endothelial HSPG.
The Team’s findings suggest a novel feedback control mechanism in which
net arterial remodeling to hemodynamic forces is controlled by a dynamic interplay between growth stimulatory signals from vSMCs and
growth inhibitory signals from endothelial cells. (2)
Heparan-sulfate proteoglycans (HSPGs) are potent regulators of vascular remodeling and repair. The major enzyme capable of degrading HSPGs is heparanase, which led us to examine the role of heparanase in controlling
arterial structure,
mechanics, and
remodeling.
In vitro studies suggested heparanase expression in endothelial cells serves as a negative regulator of endothelial inhibition of vascular smooth muscle cell (vSMC) proliferation.
ECs inhibit vSMC proliferation through the interplay between
growth stimulatory signals from vSMCs and
growth inhibitory signals from ECs.
This would be expected if ECs had HSPGs that are degraded by heparanase. Arterial structure and remodeling to injury is modified by heparanase expression. Transgenic mice overexpressing heparanase had
increased arterial thickness,
cellular density, and
mechanical compliance.
Endovascular stenting studies in Zucker rats demonstrated increased heparanase expression in the neointima of obese, hyperlipidemic rats in comparison to lean rats.
The extent of heparanase expression within the neointima strongly correlated with the neointimal thickness following injury. To test the effects of heparanase overexpression on arterial repair, researchers developed a novel murine model of stent injury using small diameter self-expanding stents.
Using this model, researchers found that increased
neointimal formation and
macrophage recruitment occurs in transgenic mice overexpressing heparanase.
Taken together, these results support a role for heparanase in the regulation of arterial structure, mechanics, and repair. (3)
The first host–donor reaction in transplantation occurs at the blood–tissue interface. When the primary component of the implant (donor) is the endothelial cells, it incites an immunologic reaction. Injections of free endothelial cell implants elicit a profound major histocompatibility complex (MHC) II dominated immune response.
Endothelial cells embedded within three-dimensional matrices behave like quiescent endothelial cells.
Perivascular implants of such embedded ECs cells are the most potent inhibitor of intimal hyperplasia and thrombosis following controlled vascular injury, but without any immune reactivity.
Allo- and even exenogenic endothelial cells evoke no significant humoral or cellular immune response in immune-competent hosts when embedded within matrices. Moreover, endothelial implants are immune-modulatory, reducing the extent of the memory response to previous free cell implants.
Attenuated immunogenicity results in muted activation of adaptive and innate immune cells. These findings point toward a pivotal role of matrix–cell-interconnectivity for
the cellular immune phenotype and might therefore assist in the design of
extracellular matrix components for successful tissue engineering. (4)
Because changes in subendothelial matrix composition are associated with alterations of the endothelial immune phenotype, researchers sought to understand if
cytokine-induced NF-κB activity and
downstream effects depend on substrate adherence of endothelial cells (EC).
The team compared the upstream
phosphorylation cascade,
activation of NF-ĸβ, and
expression/secretion
of downstream effects of EC grown on tissue culture polystyrene plates (TCPS) with EC embedded within collagen-based matrices (MEEC).
Adhesion of natural killer (NK) cells was quantified in vitro and in vivo.
NF-κβ subunit p65 nuclear levels were significantly lower and
p50 significantly higher in cytokine-stimulated MEEC than in EC-TCPS.
Despite similar surface expression of TNF-α receptors, MEEC had significantly decreased secretion and expression of IL-6, IL-8, MCP-1, VCAM-1, and ICAM-1.
Attenuated fractalkine expression and secretion in MEEC (two to threefold lower than in EC-TCPS; p < 0.0002) correlated with 3.7-fold lower NK cell adhesion to EC (6,335 ± 420 vs. 1,735 ± 135 cpm; p < 0.0002).
Furthermore, NK cell infiltration into sites of EC implantation in vivo was significantly reduced when EC were embedded within matrix.
Matrix embedding enables control of EC substratum interaction.
This in turn regulates chemokine and surface molecule expression and secretion, in particular – of those compounds within NF-κβ pathways,
chemoattraction of NK cells,
local inflammation, and
tissue repair. (5)
Monocyte recruitment and interaction with the endothelium is imperative to vascular recovery.
Tie2 plays a key role in endothelial health and vascular remodeling. Researchers studied monocyte-mediated Tie2/angiopoietin signaling following interaction of primary monocytes with endothelial cells and its role in endothelial cell survival.
The direct interaction of primary monocytes with subconfluent endothelial cells
resulted in transient secretion of angiopoietin-1 from monocytes and
the activation of endothelial Tie2. This effect was abolished by preactivation of monocytes with tumor necrosis factor-α (TNFα).
Although primary monocytes contained high levels of
Seeding of monocytes on serum-starved endothelial cells reduced caspase-3 activity by 46+5.1%, and 52+5.8% after TNFα treatment, and it decreased single-stranded DNA levels by 41+4.2% and 40+ 3.5%, respectively.
This protective effect of monocytes on endothelial cells was reversed by Tie2 silencing with specific short interfering RNA.
The antiapoptotic effect of monocytes was further supported by the
activation of cell survival signaling pathways involving phosphatidylinositol 3-kinase,
STAT3, and
AKT.
Monocytes and endothelial cells form a unique Tie2/angiopoietin-1 signaling system that affects endothelial cell survival and may play critical a role in vascular remodeling and homeostasis. (6)
(5) NF-kB Activity in Endothelial Cells Is Modulated by Cell Substratum Inter-actions and Influences Chemokine-Mediated Adhesion of Natural Killer Cells. S Hess, H Methe, Jong-Oh Kim, ER Edelman. Cell Transplantation 2009; 18: 261–273
Rabbits fed on a hypercholesterolemic diet underwent bilateral iliac artery balloon denudation and stent deployment.
Liposomal alendronate (3 or 6 mg/kg) was given concurrently with stenting.
Monocyte counts were reduced by 90% 24 to 48 hours aftera single injection of liposomal alendronate, returning to basal levels at 6 days.
This treatment significantly reduced
intimal area at 28 days, from 3.88+0.93 to 2.08+0.58 and 2.16 +0.62 mm2.
Lumen area was increased from 2.87+0.44 to 3.57+0.65 and 3.45+0.58 mm2, and
arterial stenosis was reduced from 58 11% to 37 8% and 38 7% in controls, in rabbits treated with 3 mg/kg, and with 6 mg/kg, respectively (mean+SD, n=8 rabbits/group, P< 0.01 for all 3 parameters).
No drug-related adverse effects were observed. Reduction in neointimal formation was associated with
reduced arterial macrophage infiltration and proliferation at 6 days and with an
equal reduction in intimal macrophage and smooth muscle cell content at 28 days after injury.
Conversely, drug regimens ineffective in reducing monocyte levels did not inhibit neointimal formation. Researchers have shown that a
single liposomal bisphosphonates injection concurrent with injury reduces in-stent neointimal formation and
arterial stenosis in hypercholesterolemic rabbits, accompanied by systemic transient depletion of monocytes and macrophages. (1)
Diabetes and insulin resistance are associated with increased disease risk and poor outcomes from cardiovascular interventions.
Even drug-eluting stents exhibit reduced efficacy in patients with diabetes. Researchers reported the first study of vascular response to stent injury in insulin-resistant and diabetic animal models.
Endovascular stents were expanded in the aortae of
obese insulin-resistant and
type 2 diabetic Zucker rats,
in streptozotocin-induced type 1 diabetic Sprague-Dawley rats, and
in matched controls.
Insulin-resistant rats developed thicker neointima (0.46+0.08 versus 0.37+0.06 mm2, P 0.05), with decreased lumen area (2.95+0.26 versus 3.29+0.15 mm2, P 0.03) 14 days after stenting compared with controls, but without increased vascular inflammation (tissue macrophages).
Insulin-resistant and diabetic rat vessels did exhibit markedly altered signaling pathway activation 1 and 2 weeks after stenting, with up to a 98% increase in p-ERK (anti-phospho ERK) and a 54% reduction in p-Akt (anti-phospho Akt) stained cells. Western blotting confirmed a profound effect of insulin resistance and diabetes on Akt and ERK signaling in stented segments. p-ERK/p-Akt ratio in stented segments uniquely correlated with neointimal response (R2 = 0.888, P< 0.04) , but not in lean controls.
Transfemoral aortic stenting in rats provides insight into vascular responses in insulin resistance and diabetes.
Shifts in ERK and Akt signaling related to insulin resistance may reflect altered tissue repair in diabetes accompanied by a
shift in metabolic : proliferative balance.
These findings may help explain the increased vascular morbidity in diabetes and suggest specific therapies for patients with insulin resistance and diabetes. (2)
Researchers investigated the role of Valsartan (V) alone or in combination with Simvastatin (S) on coronary atherosclerosis and vascular remodeling, and tested the hypothesis that V or V/S attenuate the pro-inflammatory effect of low endothelial shear stress (ESS).
Twenty-four diabetic, hyperlipidemic swine were allocated into Early (n = 12) and Late (n=12) groups. Diabetic swine in each group were treated with Placebo (n=4), V (n = 4) and V/S (n = 4) and followed for 8 weeks in the Early group and 30 weeks in the Late group.
Blood pressure, serum cholesterol and glucose were similar across the treatment subgroups. ESS was calculated in plaque-free subsegments of interest (n = 109) in the Late group at week 23. Coronary arteries of this group were harvested at week 30, and the subsegments of interest were identified, and analyzed histopathologically.
Intravascular geometrically correct 3-dimensional reconstruction of the coronary arteries of 12 swine was performed 23 weeks after initiation of diabetes mellitus and a hyperlipidemic diet. Local endothelial shear stress was calculated
in plaque-free subsegments of interest (n=142) with computational fluid dynamics, and
the coronary arteries (n=31) were harvested and the same subsegments were identified at 30 weeks.
V alone or with S
reduced the severity of inflammation in high-risk plaques. Both regimens attenuated the severity of enzymatic degradation of the arterial wall, reducing the severity of expansive remodeling.
attenuated the pro-inflammatory effect of low ESS. V alone or with S
exerts a beneficial effect of reducing and stabilizing high-risk plaque characteristics independent of a blood pressure- and lipid-lowering effect. (3)
This study tested the hypothesis that low endothelial shear stress augments the
expression of matrix-degrading proteases, promoting the
formation of thin-capped atheromata.
Researchers assessed the messenger RNA and protein expression, and elastolytic activity of selected elastases and their endogenous inhibitors.
Subsegments with low endothelial shear stress at week 23 showed
reduced endothelial coverage,
enhanced lipid accumulation, and
intense infiltration of activated inflammatory cells at week 30.
These lesions showed increased expression of messenger RNAs encoding
matrix metalloproteinase-2, -9, and -12, and cathepsins K and S
relative to their endogenous inhibitors and
increased elastolytic activity.
Expression of these enzymes correlated positively with the severity of internal elastic lamina fragmentation.
Thin-capped atheromata in regions with
lower preceding endothelial shear stress had
reduced endothelial coverage,
intense lipid and inflammatory cell accumulation,
enhanced messenger RNA expression and
elastolytic activity of MMPs and cathepsins with
severe internal elastic lamina fragmentation.
Low endothelial shear stress induces endothelial discontinuity and
accumulation of activated inflammatory cells, thereby
augmenting the expression and activity of elastases in the intima and
shifting the balance with their inhibitors toward matrix breakdown.
Team’s results provide new insight into the mechanisms of regional formation of plaques with thin fibrous caps. (4)
Elevated CRP levels predict increased incidence of cardiovascular events and poor outcomes following interventions. There is the suggestion that CRP is also a mediator of vascular injury.
Transgenic mice carrying the human CRP gene (CRPtg) are predisposed to arterial thrombosis post-injury.
Researchers examined whether CRP similarly modulates the proliferative and hyperplastic phases of vascular repair in CRPtg when thrombosis is controlled with daily aspirin and heparin at the time of trans-femoral arterial wire-injury.
Complete thrombotic arterial occlusion at 28 days was comparable for wild-type and CRPtg mice (14 and 19%, respectively). Neointimal area at 28d was 2.5 fold lower in CRPtg (4190±3134 m2, n = 12) compared to wild-types (10,157±8890 m2, n = 11, p < 0.05).
Likewise, neointimal/media area ratio was 1.10±0.87 in wild-types and 0.45±0.24 in CRPtg (p < 0.05).
Seven days post-injury, cellular proliferation and apoptotic cell number in the intima were both less pronounced in CRPtg than wild-type.
No differences were seen in leukocyte infiltration or endothelial coverage. CRPtg mice had significantly reduced p38 MAPK signaling pathway activation following injury.
The pro-thrombotic phenotype of CRPtg mice was suppressed by aspirin/heparin, revealing CRP’s influence on neointimal growth after trans-femoral arterial wire-injury.
Signaling pathway activation,
cellular proliferation, and
neointimal formation
were all reduced in CRPtg following vascular injury. Increasingly the Team was aware of CRP multipotent effects. Once considered only a risk factor, and recently a harmful agent, CRP is a far more complex regulator of vascular biology. (5)
(1) Liposomal Alendronate Inhibits Systemic Innate Immunity and Reduces In-Stent Neointimal Hyperplasia in Rabbits. HD Danenberg, G Golomb, A Groothuis, J Gao…, ER Edelman. Circulation. 2003;108:2798-2804
(2) Vascular Neointimal Formation and Signaling Pathway Activation in Response to Stent Injury in Insulin-Resistant and Diabetic Animals. M Jonas, ER Edelman, A Groothuis, AB Baker, P Seifert, C Rogers. Circ. Res. 2005;97;725-733. http://dx.doi.org/10.1161/01.RES.0000183730.52908.C6 http://circres.ahajournals.org/cgi/content/full/97/7/725
(3) Attenuation of inflammation and expansive remodeling by Valsartan alone or in combination with Simvastatin in high-risk coronary atherosclerotic plaques. YS Chatzizisis, M Jonas, R Beigel, AU Coskun… ER Edelman, CL Feldman, PH Stone. Atherosclerosis 203 (2009) 387–394
(5) Neointimal formation is reduced after arterial injury in human crp transgenic mice HD Danenberg, E Grad, RV Swaminathan, Z Chenc,…ER Edelman Atherosclerosis 201 (2008) 85–91
A Rattle Bag of Science and the Art of Translation
Elazer R. Edelman is the Thomas D. and Virginia W. Cabot Professor of Health Sciences and Technology at MIT, Professor of Medicine at Harvard Medical School, a coronary care unit cardiologist at the Brigham and Women’s Hospital, and Director of the Harvard-MIT Biomedical Engineering Center. E-mail: ere@mit.edu
Garret A. FitzGerald is the McNeil Professor in Translational Medicine and Therapeutics, Chair of the Department of Pharmacology, and Director of the Institute for Translational Medicine & Therapeutics, University of Pennsylvania. E-mail: garret@upenn.edu
In 2011, the American Association for the Advancement of Science (AAAS) founded Science Translational Medicine (STM) to disseminate interdisciplinary science integrating basic and clinical research that defines and fosters new therapeutics, devices, and diagnostics.
Conceived and nourished under the creative vision of Elias Zerhouni and Katrina Kelner, the journal has attracted widespread attention. Now, as we assume the mantle of co-chief scientific advisors, we look back on the journal’s early accomplishments, restate our mission, and make clear the kinds of manuscripts we seek and accept for publication.
STM’s mission, as articulated by Elias and Katrina, was to
“promote human health by providing a forum for communication and cross-fertilization among basic, translational, and clinical research practitioners and trainees from all relevant established and emerging disciplines.”
This statement remains relevant and accurate today. With this mission on our masthead, STM now receives ~25 manuscripts (full-length research articles) per week and publishes ~10% of them. Roughly half of the submissions are deemed inappropriate for the journal and are returned without review within 8 to 10 days of receipt.
Of those papers that undergo full peer review,
decisions to reject are made within 48 days and
the mean time to acceptance (including the revision period) is 125 days.
There is now an average wait of only 24 days between acceptance and publication.
Defining TRANSLATIONAL Medicine
In accord with the journal’s broad readership, the ideal manuscript meets five criteria: It (i) reports a discovery of translational relevance with high-impact potential; (ii) has a conceptual focus with interdisciplinary appeal; (iii) elucidates a biological mechanism; (iv) is innovative and novel; and (v) is presented in clear, broadly accessible language. STM seeks to publish research that describes
how innovative concepts drive the creative biomedical science
that ultimately improves the quality of people’s lives—
This is the broadest of our journal’s criteria but is the one that sets us apart as well. Translational relevance does not require demonstration of benefit in humans but does require the evident potential to advance clinical medicine, thus impacting the direction of our culture and the welfare of our communities. Conceptual focus and mechanistic emphasis discriminate our papers from those that contain observational descriptions of technical findings for which value is restricted to a specific discipline.
However, innovation and novelty may apply to a fundamental scientific discovery or to the nature of its application and relevance to the translational process. Criteria enable the journal to consider versatile technological advances that apply new and creative thinking but may not necessarily offer fresh insights into biological mechanisms. Finally, while the subsequent additional efforts of the STM editorial staff are not to be discounted, the clarity of writing and coherence of argument presented within a submitted manuscript are likely to facilitate its progress through the challenge of peer review.
On Causes – Hippocrates, Aristotle, Robert Koch, and the Dread Pirate Roberts
The idea of risk factors for vascular disease has evolved
from a dichotomous to continuous hazard analysis and
from the consideration of a few factors to
mechanistic investigation of many interrelated risks.
However, confusion still abounds regarding issues of association and causation. Originally, the simple presence of
tobacco abuse, hypertension, and/or hypercholesterolemia were tallied, and
the cumulative score was predictive of subsequent coronary artery disease.
Since then, dose responses have been defined for these and other factors and it has been suggested that almost 300 factors place patients at risk; these factors include elevations in plasma homocysteine. Recent studies shed interesting light on the mechanism of this potentially causal relationship, which was first noted in 1969.
Aside from putative effects on vessel wall dynamics, there is now direct evidence that homocysteine is atherogenic. Twenty-fold increases in plasma homocysteine achieved by dietary manipulation of apoE–/– mice increased aortic root lesion size 2-fold and produced a prolonged chronic inflammatory mural response accompanied by elevations in vascular cell adhesion molecule-1 (VCAM) and tumor necrosis factor-a (TNF-a).
In long term followup, homocysteine levels elevated by
dietary supplementation with methionine or homocysteine
promoted lesion size and plaque fibrosis in these
atherosclerosis-prone mice early in life, but without influencing ultimate plaque burden as the animals aged.
A number of mechanisms were proposed by which homocysteine achieved this effect, including
promotion of inflammation,
regulation of lipoprotein metabolism, and
modification of critical biochemical pathways and
metabolites including nitric oxide (NO).
See p 2569 In the present issue of Circulation,
Stühlinger et al 7 advance these mechanistic insights one critical step further by defining homocysteine’s effects at an enzymatic level.
The group led by Lentz published an association between levels of the
endogenous inhibitor of Nirtic Oxide synthase,
asymmetric dimethyl arginine (ADMA), and
homocysteine in cultured endothelial cells and in the serum of cynomolgus monkeys.
Such an association is interesting because the L-arginine–NO synthase pathway seems to be a critical component in the full range of endothelial cell biology and vascular dysfunction.
Stühlinger et al 7 now show that increased cultured endothelial cell elaboration of ADMA by homocysteine and its precursor L-methionine is associated with a dose-dependent impairment of the activity of endothelial dimethylarginine dimethylaminohydrolase (DDAH), the enzyme that degrades ADMA. Homocysteine directly inhibited DDAH activity in a cell-free system by targeting a critical sulfhydryl group on this enzyme.
Thus, one could envision that the balance of cardiovascular health and disease could well be determined by the ability of an intact Nirtic Oxide synthase system to overcome environmental, dietary, and even genetic factors.
In patients with altered enzymatic defense systems,
elevated homocysteine,
oxidized lipoproteins,
inflammation, and other
vasotoxins
may dominate even the most potent defense mechanisms. These studies raise a number of issues. Do we need to add to our list of established cardiovascular risk factors to accommodate new findings and associations? Is there a final common pathway for all risk factors or perhaps even a unified factor theory into which all potential risks can be grouped? And, as always, should we consider Nirtic Oxide at the core of this universality? Finally, should we change our focus altogether and speak not of risk factors but of
genetic predisposition,
extent of biochemical aberration, and
degree of physical damage?
Some would view these remarkable success stories and the repeated association of hyperhomocyst(e)inemia with coronary, cerebral, and peripheral vascular disease and simply advocate for increased folic acid intake for all.
Indeed, this intervention of negligible cost and
insignificant side effect is already partially in place;
many foods are fortified with folate to prevent congenital neural tube defects.
This reader considers the seminal work by Vernon Young and Yves Ingenbleek on the relationship between
S8 and regions distant from lava flows in Asia and Indian subcontinents,
where they have determined hyperhomocysteinemia and the consequence associated with:
veganism (not voluntary)
impaired methyl donor reactions and transsulfuration pathways (not corrected by B12, folate)
loss of lean body mass due to the constant relationship of S:N (insufficient from plant sources)
What happens, when we fail to continue to pursue causality,
the linkage of biological significance or scientific plausibility with
epidemiologically or statistically significant association?
In medicine, risk becomes the likelihood that people without a disease will acquire the disease through contact with factors thought to increase disease risk.
All of these risk factors are then, by nature, imprecise and nonspecific. They are stochastic measures of what will happen to normal people who fall into particular measures of these parameters.
The daring may be willing to accept these risks, citing friend and foe who live well beyond or for far lesser times than anticipated by risk alone. Such concerns may well become moot if we can simultaneously identify patients at risk
by linking phenotype with genotype,
gene expression with protein elaboration, and
environmental exposures with the biochemical consequences and
direct anatomic aberrations they induce.
This kind of characterization may well replace a family history of arterial disease as a rough estimate of
genotype,
serum cholesterol as an indirect measure of the health of lipoprotein metabolism,
serum glucose as a crude determinant of the ravages of diabetes mellitus,
blood pressure measurement as a marker of long-standing endogenous exposure to altered flow, and
tobacco abuse as a maker of long-standing exposure to exogenous toxins.
Rather than identifying patients on the basis of their serum cholesterol, we will have a direct measure of their
LDL receptor number,
internalization rate,
macrophage content in the blood vessel wall,
metalloproteinase activity, etc.
insulin receptor metabolism,
oxidative state, and
glycated burden.
Serum glucose will similarly give way to these tests
Evaluating a new way to open clogged arteries: Computational model offers insight into mechanisms of drug-coated balloons.
A new study from MIT analyzes the potential usefulness of a new treatment that combines the benefits of angioplasty balloons and drug-releasing stents, but may pose fewer risks. With this new approach, a balloon is inflated in the artery for only a brief period, during which it releases a drug that prevents cells from accumulating and clogging the arteries over time.
While approved for limited use in Europe, these drug-coated balloons are still in development in the United States and have not received FDA approval. The MIT study, which models the behavior of the balloons, should help scientists optimize their performance and aid regulators in evaluating their effectiveness and safety.
“Until now, people who evaluate such technology could not distinguish hype from promise,” says Elazer Edelman, the Thomas D. and Virginia W. Cabot Professor of Health Sciences and Technology and senior author of the paper describing the study, which appeared online recently in the journal Circulation.
Lead author of the paper is Vijaya Kolachalama, a former MIT postdoc who is now a principal member of the technical staff at the Charles Stark Draper Laboratory.
Edelman’s lab is investigating a possible alternative to the current treatments: drug-coated balloons. “We’re trying to understand how and when this therapy could work and identify the conditions in which it may not,” Kolachalama says. “It has its merits; it has some disadvantages.”
Modeling drug release
The drug-coated balloons are delivered by a catheter and inflated at the narrowed artery for about 30 seconds, sometimes longer. During that time, the balloon coating, containing a drug such as Zotarolimus, is released from the balloon. The properties of the coating allow the drug to be absorbed in the body’s tissues. Once the drug is released, the balloon is removed.
In their new study, Kolachalama, Edelman and colleagues set out to rigorously characterize the properties of the drug-coated balloons. After performing experiments in tissue grown in the lab and in pigs, they developed a computer model that explains the dynamics of drug release and distribution. They found that factors such as the size of the balloon, the duration of delivery time, and the composition of the drug coating all influence how long the drug stays at the injury site and how effectively it clears the arteries.
One significant finding is that when the drug is released, some of it sticks to the lining of the blood vessels. Over time, that drug is slowly released back into the tissue, which explains why the drug’s effects last much longer than the initial 30-second release period.
“This is the first time we can explain the reasons why drug-coated balloons can work,” Kolachalama says. “The study also offers areas where people can consider thinking about optimizing drug transfer and delivery.”
MIT’s Edelman’s Lab conducted the pioneering work in Vascular biology, animal models of drug eluting stents and was at the forefront of Empirical Molecular Cardiology in its studies in vascular physiology, biology and biomaterials for medical devices.
Hypertriglyceridemia concurrent Hyperlipidemia: Vertical Density Gradient Ultracentrifugation a Better Test to Prevent Undertreatment of High-Risk Cardiac Patients
Fight against Atherosclerotic Cardiovascular Disease: A Biologics not a Small Molecule – Recombinant Human lecithin-cholesterol acyltransferase (rhLCAT) attracted AstraZeneca to acquire AlphaCore
High-Density Lipoprotein (HDL): An Independent Predictor of Endothelial Function & Atherosclerosis, A Modulator, An Agonist, A Biomarker for Cardiovascular Risk
Peroxisome proliferator-activated receptor (PPAR-gamma) Receptors Activation: PPARγ transrepression for Angiogenesis in Cardiovascular Disease and PPARγ transactivation for Treatment of Diabetes
Clinical Trials Results for Endothelin System: Pathophysiological role in Chronic Heart Failure, Acute Coronary Syndromes and MI – Marker of Disease Severity or Genetic Determination?
Inhibition of ET-1, ETA and ETA-ETB, Induction of NO production, stimulation of eNOS and Treatment Regime with PPAR-gamma agonists (TZD): cEPCs Endogenous Augmentation for Cardiovascular Risk Reduction – A Bibliography
Positioning a Therapeutic Concept for Endogenous Augmentation of cEPCs — Therapeutic Indications for Macrovascular Disease: Coronary, Cerebrovascular and Peripheral
Cardiovascular Outcomes: Function of circulating Endothelial Progenitor Cells (cEPCs): Exploring Pharmaco-therapy targeted at Endogenous Augmentation of cEPCs
Vascular Medicine and Biology: CLASSIFICATION OF FAST ACTING THERAPY FOR PATIENTS AT HIGH RISK FOR MACROVASCULAR EVENTS Macrovascular Disease – Therapeutic Potential of cEPCs
Cardiac Surgery Theatre in China vs. in the US: Cardiac Repair Procedures, Medical Devices in Use, Technology in Hospitals, Surgeons’ Training and Cardiac Disease Severity”
Dilated Cardiomyopathy: Decisions on implantable cardioverter-defibrillators (ICDs) using left ventricular ejection fraction (LVEF) and Midwall Fibrosis: Decisions on Replacement using late gadolinium enhancement cardiovascular MR (LGE-CMR)
Competition in the Ecosystem of Medical Devices in Cardiac and Vascular Repair: Heart Valves, Stents, Catheterization Tools and Kits for Open Heart and Minimally Invasive Surgery (MIS)
Global Supplier Strategy for Market Penetration & Partnership Options (Niche Suppliers vs. National Leaders) in the Massachusetts Cardiology & Vascular Surgery Tools and Devices Market for Cardiac Operating Rooms and Angioplasty Suites
Visceral Myopathy in Statins (Photo credit: Snipergirl)
Medical science has advanced significantly since 1507, when Leonardo da Vinci drew this diagram of the internal organs and vascular systems of a woman. (Photo credit: Wikipedia)
English: Lee Hood, MD, PhD, President and Co-found of the Institute for Systems Biology (Photo credit: Wikipedia)
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