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Posts Tagged ‘Angioplasty’

Introduction to e-Series A: Cardiovascular Diseases, Volume Four Part 2: Regenerative Medicine


Introduction to e-Series A: Cardiovascular Diseases, Volume Four Part 2: Regenerative Medicine

Author and Curator: Larry H Bernstein, MD, FCAP

and

Curator: Aviva Lev-Ari, PhD, RN

This document is entirely devoted to medical and surgical therapies that have made huge strides in

  • simplification of interventional procedures,
  • reduced complexity, resulting in procedures previously requiring surgery are now done, circumstances permitting, by medical intervention.

This revolution in cardiovascular interventional therapy is regenerative medicine.  It is regenerative because it is largely driven by

  • the introduction into the impaired vasculature of an induced pleuripotent cell, called a stem cell, although
  • the level of differentiation may not be a most primitive cell line.

There is also a very closely aligned development in cell biology that extends beyond and including vascular regeneration that is called synthetic biology.  These developments have occurred at an accelerated rate in the last 15 years. The methods of interventional cardiology were already well developed in the mid 1980s.  This was at the peak of cardiothoracic bypass surgery.

Research on the endothelial cell,

  • endothelial cell proliferation,
  • shear flow in small arteries, especially at branch points, and
  • endothelial-platelet interactions

led to insights about plaque formation and vessel thrombosis.

Much was learned in biomechanics about the shear flow stresses on the luminal surface of the vasculature, and there was also

  • the concomitant discovery of nitric oxide,
  • oxidative stress, and
  • the isoenzymes of nitric oxide synthase (eNOS, iNOS, and nNOS).

It became a fundamental tenet of vascular biology that

  • atherogenesis is a maladjustment to oxidative stress not only through genetic, but also
  • non-genetic nutritional factors that could be related to the balance of omega (ω)-3 and omega (ω)-6 fatty acids,
  • a pro-inflammatory state that elicits inflammatory cytokines, such as, interleukin-6 (IL6) and c-reactive protein(CRP),
  • insulin resistance with excess carbohydrate associated with type 2 diabetes and beta (β) cell stress,
  • excess trans- and saturated fats, and perhaps
  • the now plausible colonic microbial population of the gastrointestinal tract (GIT).

There is also an association of abdominal adiposity,

  • including the visceral peritoneum, with both T2DM and with arteriosclerotic vessel disease,
  • which is presenting at a young age, and has ties to
  • the effects of an adipokine, adiponectin.

Much important work has already been discussed in the domain of cardiac catheterization and research done to

  • prevent atheroembolization.and beyond that,
  • research done to implant an endothelial growth matrix.

Even then, dramatic work had already been done on

  • the platelet structure and metabolism, and
  • this has transformed our knowledge of platelet biology.

The coagulation process has been discussed in detailed in a previous document.  The result was the development of a

  • new class of platelet aggregation inhibitors designed to block the activation of protein on the platelet surface that
  • is critical in the coagulation cascade.

In addition, the term long used to describe atherosclerosis, atheroma notwithstanding, is “hardening of the arteries”.  This is particularly notable with respect to mid-size arteries and arterioles that feed the heart and kidneys. Whether it is preceded by or develops concurrently with chronic renal insufficiency and lowered glomerular filtration rate is perhaps arguable.  However, there is now a body of evidence that points to

  • a change in the vascular muscularis and vessel stiffness, in addition to the endothelial features already mentioned.

This has provided a basis for

  • targeted pharmaceutical intervention, and
  • reduction in salt intake.

So we have a  group of metabolic disorders, which may alone or in combination,

  • lead to and be associated with the long term effects of cardiovascular disease, including
  • congestive heart failure.

This has been classically broken down into forward and backward failure,

  • depending on decrease outflow through the aorta (ejection fraction), or
  • decreased venous return through the vena cava,

which involves increased pulmonary vascular resistance and decreased return into the left atrium.

This also has ties to several causes, which may be cardiac or vascular. This document, as the previous, has four pats.  They are broadly:

  1. Stem Cells in Cardiovascular Diseases
  2. Regenerative Cell and Molecular Biology
  3. Therapeutics Levels In Molecular Cardiology
  4. Research Proposals for Endogenous Augmentation of circulating Endothelial Progenitor Cells (cEPCs)

As in the previous section, we start with the biology of the stem cell and the degeneration in cardiovascular diseases, then proceed to regeneration, then therapeutics, and finally – proposals for augmenting therapy with circulating endogenous endothelial progenitor cells (cEPCs).

 

context

stem cells

 

theme

regeneration

 

 

 

 

theme

Therapeutics

 

theme

augmentation

 

 

 

 

 

 

 

 

 

 

Key pathways involving NO

Key pathways involving NO

 

 

 

 

stem cell lin28

stem cellLlin28

1479-5876-10-175-1-l  translational research with feedback loops

Tranlational Research -Lab to Bedside

 

 

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Larry H Bernstein, MD, FCAP, Reporter and curator

αllbβ3 Antagonists As An Example of Translational Medicine Therapeutics

http://phrmaceuticalintelligence.com/2013-10-12/larryhbern_BS-Coller/αllbβ3 Antagonists As An Example of Translational Medicine Therapeutics

by Barry S. Coller, MD
Rockefeller University

Introduction

This article is a segment in several articles about platelets, platelet function, and advances in applying the surge of knowledge to therapy.  In acute coronary syndromes, plaque rupture leads to thrombotic occlusion.  We have also seen that the development of a plaque occurs in 3 stages, only the last of which involves plaque rupture.  Platelets interact with the vascular endothelium, and platelet-endothelial as well as platelet-platelet interactions are known to be important in atherogenesis.  We learned that platelets are derived from megakaryocytes that break up and these elements are released into the blood stream.  It has recently been discovered that platelets can replicate in the circulation.  The turnover of platelets is rapid, and platelets sre stored at room temperature with shaking, and are viable for perhaps only 3-4 days once they are received in the blood bank for use.  In cardiology, the identification, isolation, and characterization of GPIIb/IIIa from the platelet was a huge advance in the potential for coronary intervention, and that potential became of paramount importance with the introduction of GPIIb/IIIa inhibitors as a standard in coronary vascular therapeutic procedures.   The following manuscript by Barry Coller, at Rockefeller University,  is a presentation of the GPIIb/IIIa story as an excellent example of Translational Medicine.

Search for GPIIb/IIIa inhibitor of the (anti-αIIb133 (GPIIb/IIIa) receptor)

The deliberate search for drugs to inhibit the αIIb133 (GPIIb/IIIa) receptor ushered in the era of rationally designed antiplatelet therapy and thus represents an important milestone in the evolution of antiplatelet drug development. The selection of the αIIb133 receptor as a therapeutic target rested on a broad base of basic and clinical research conducted by many investigators in the 1960s and 1970s working in the fields of platelet physiology, the rare bleeding disorder Glanzmann thrombasthenia, platelet membrane glycoproteins, integrin receptors, coronary artery pathology, and experimental thrombosis. Thus, αIIb133 was found to mediate platelet aggregation by virtually all of the physiology agonists (e.g., ADP, epinephrine, and thrombin) through a mechanism in which platelet activation by these agents results in a change in the conformation of the receptor. This is followed by increased affinity of the receptor for the multivalent ligands fibrinogen and von Willebrand factor, both of which are capable of binding to receptors on two platelets simultaneously, producing platelet crosslinking and aggregation. At about the same time, experimental studies demonstrated platelet thrombus formation at sites of vascular injury, and biochemical studies in humans demonstrated evidence of platelet activation during acute ischemic cardiovascular events.

Our own studies initially focused on platelet-fibrinogen interactions using an assay in which normal platelets agglutinated fibrinogen-coated beads. The agglutination was enhanced with platelet activators. Platelets from patients with Glanzmann thrombasthenia, who lack the αIIb133 receptor, did not agglutinate the beads. We adapted this assay to a microtiter plate system to identify monoclonal antibodies that inhibited platelet-fibrinogen interactions and then demonstrated that these antibodies bound to αIIb133. They were also more potent inhibitors of platelet aggregation than any known antiplatelet agent and produced a pattern of aggregation that was virtually identical to that found using platelets from patients with Glanzmann thrombasthenia.

I recognized the theoretical potential of using an antibody to inhibit platelets in vivo but also recognized the challenges and limitations. Since experimental models of thrombosis had been developed in the dog, and since the antibody we initially worked with did not react with dog platelets, we had to go back to our original samples to identify an antibody (7E3) that reacted with dog platelets in addition to human platelets. Since coating platelets with immunoglobulins results in their rapid elimination of the platelets from the circulation, and since the clearance is mediated by the immunoglobulin Fc region, we prepared F(ab’)2 fragments of 7E3 for our in vivo studies. Additional challenges included preparing large quantities of antibody on a very limited budget and purifying the antibodies so they contained only minimal amounts of endotoxin. With the small amount of 7E3-F(ab’)2 we initially prepared, we were able to show dose response inhibition of platelet aggregation in three dogs, achieving greater inhibition than with aspirin or ticlopidine, the only antiplatelet agents approved for human use at that time. We also devised an assay using radiolabeled 7E3 to quantify the percentage of platelet αIIbβ3 receptors that were blocked when a specific dose of 7E3-F(ab’)2 was administered in vivo. This allowed us to directly measure the effect of the agent on its target receptor on its target cell.

I considered two criteria most important in selecting the initial animal models in which to test the efficacy and safety of administering 7E3-F(ab’)2:

  • 1) the model had to convincingly simulate a human vascular disease, and
  • 2) aspirin had to have failed to produce complete protection from thrombosis.

The latter criterion was particularly important because I planned to stop this line of research if the 7E3-F(ab’)2 was not more efficacious than aspirin.

Ultimately, we collaborated with Dr. John Folts of the University of Wisconsin, who had developed a dog model of unstable angina by attaching a short cylindrical ring to partially occlude a coronary artery and using a hemostat to induce vascular injury. Pretreatment of the animal with 7E3-F(ab’)2 was more effective than aspirin or any other compound Dr. Folts had previously tested in preventing platelet thrombus formation, as judged by its effects on the characteristic repetitive cycles of platelet deposition and embolization. Electron microscopy of the vessels confirmed the reduction in platelet thrombi by 7E3-F(ab’)2, with only a monolayer of platelets typically deposited.

Dr. Chip Gold and his colleagues at Massachusetts General Hospital had developed a dog model to assess the effects of tissue plasminogen activator (t-PA) on experimental thrombi induced in the dog coronary artery. Although t-PA was effective in lysing the thrombi, the blood vessels rapidly reoccluded with new thrombi that were rich in platelets. Aspirin could not prevent reocclusion, whereas 7E3-F(ab’)2 not only prevented reocclusion, but also increased the speed of reperfusion by t-PA.

The next steps in drug development could not be performed in my laboratory because they required resources far in excess of those in my grant from the National Heart, Lung, and Blood Institute to study basic platelet physiology. As a result, in 1986 the Research Foundation of the State University of New York licensed the 7E3 antibody to Centocor, Inc., a new biotechnology company specializing in the diagnostic and therapeutic application of monoclonal antibodies.

Subsequent Development of 7E3

The subsequent development of 7E3 as a therapeutic agent required extensive collaboration among myself, a large number of outstanding scientists at Centocor, and many leading academic cardiologists. Many decisions and hurdles remained for us, including the decision to develop a mouse/human chimeric 7E3 Fab (c7E3 Fab); the design and execution of the toxicology studies; the assessment of the potential toxicity of 7E3 crossreactivity with αVβ3; the development of sensitive and specific assays to assess immune responses to c7E3 Fab; the design, execution, and analysis of the Phase I, II, and III studies; and the preparation, submission, and presentation of the Product Licensing  Application to the Food and Drug Administration, and comparable documents to European and Scandinavian agencies.

Based on the results of the 2,099 patient EPIC trial, in which conjunctive treatment with a bolus plus infusion of c7E3 Fab significantly reduced the risk of developing an ischemic complication (death, myocardial infarction, or need for urgent intervention) after coronary artery angioplasty or atherectomy in patients at high risk of such complications, the Food and Drug Administration approved the conjunctive use of c7E3 Fab (generic name, abciximab) in high-risk angioplasty and atherectomy on December 22, 1994. Since then it has been administered to more than 2.5 million patients in the U.S., Europe, Scandinavia, and Asia. Its optimal role in treating cardiovascular disease continues to evolve in response to the introduction of new anticoagulants, antiplatelet agents, stents, and procedures.

Extended Investigations

We have also been able to apply the monoclonal antibodies we prepared to αIIb33 to the prenatal detection of Glanzmann thrombasthenia, and have used the antibodies as probes for characterizing both the biogenesis of the receptor and the conformational changes that the receptor undergoes with activation. We have been able to precisely map the 7E3 epitope on 33, providing additional insights into the mechanism by which it prevents ligand binding. We have also exploited the ability of another antibody to αIIb33 to stabilize the receptor complex in order to facilitate production of crystals of the αIIb33 headpiece; the x-ray diffraction properties of these crystals were studied in collaboration with Dr. Timothy Springer’s group at Harvard and provide the first structural information on the receptor.

In landmark studies in the 1980s, Pierschbacher and Ruoslahti demonstrated the importance of the arginine-aspartic acid (RGD) sequence in the interaction of the integrin α531 with fibronectin, and they went on to show that peptides with the RGD sequence could inhibit this interaction. Subsequent studies by many groups demonstrated that these peptides could also inhibit the interaction of platelet αIIb33 with fibrinogen and von Willebrand factor. Dr. David Phillip and Dr. Robert Scarbrough led the team at Cor Therapeutics that made a cyclic pentapeptide with high selectivity for αIIb33 over αV33 by patterning their compound on the KGD sequence in the snake venom barbourin. The resulting antiplatelet agent, eptifibatide, received FDA approval in May 1998. At Merck, Dr. Robert Gould led the team that developed the nonpeptide RGD-mimetic tirofiban, which also is selective for αIIb33 compared to αV33. It also received FDA approval in May 1998. Our recent x-ray crystallographic studies in collaboration with Dr. Springer’s group provided structural information on the mechanisms and sites of binding of these drugs with αIIb33.

Translation of Basic Science into Therapy

Many important elements and an enormous amount of good fortune were needed for the translation of the basic science information about platelet aggregation into the drug abciximab, including, but not limited to:

  • 1) the support of basic studies of platelet physiology by the National Institutes of Health in my laboratory and many other laboratories,
  • 2) the creation and ongoing funding of a core facility available to all faculty members to prepare monoclonal antibodies at the State University of New York at Stony Brook under the direction of Dr. Arnold Levine,
  • 3) the 1988 Bayh-Dole Act and its subsequent amendments, and the expertise of the Technology Transfer Office at Stony Brook in licensing 7E3 to Centocor, which then provided the capital and additional expertise required for its development, and
  • 4) the expert and enthusiastic collaboration by two large and disciplined cooperative groups of interventional cardiologists (TAMI, EPIC) under the dynamic leadership of Drs. Eric Topol and Rob Califf,

tirofiban, that were eager to test the safety and efficacy of the 7E3 derivatives. Although the translation of each new scientific discovery into improved health via novel preventive, diagnostic, or therapeutic strategies requires the blazing of a unique path, optimizing these elements and similar ones may allow the path to be shorter and/or to be traversed more easily, at a lower cost, or in a shorter period of time.

 

Related articles in Pharmaceutical Intelligence:

Platelets in Translational Research – 1   Larry H. Bernstein, MD, FCAP
https://pharmaceuticalintelligence.com/10-6-2013/larryhbern/Platelets_in_Translational_Research-1
Platelets in Translational Research – 2  Larry H. Bernstein, MD, FCAP
http://phramaceuticalintelligence.com/2013-10-7/larryhbern/Platelets-in-Translational-Research-2/

Do Novel Anticoagulants Affect the PT/INR? The Cases of XARELTO (rivaroxaban) and PRADAXA (dabigatran)
Vivek Lal, MBBS, MD, FCIR, Justin D Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2013/09/23/do-novel-anticoagulants-affect-the-ptinr-the-cases-of-xarelto-rivaroxaban-and-pradaxa-dabigatran/

 

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BARI 2D Trial Outcomes

Reporter: Larry H Bernstein, MD, FCAP
Results from the BARI 2D (Bypass Angioplasty Revascularization Investigation 2 Diabetes) Trial
GR. Dagenais, MD; Jiang Lu, MS; David P. Faxon, MD; Peter Bogaty, MD, et. Al.

Prognostic Impact of the Presence and Absence of Angina on Mortality and Cardiovascular Outcomes in Patients With Type 2 Diabetes and Stable Coronary Artery Disease

 

Results from the BARI 2D Trial…Bypass Angioplasty Revascularization Investigation 2 Diabetes

Objectives

The purpose of this analysis was

  1. to assess in patients with type 2 diabetes and stable coronary artery disease (CAD)
  2. whether the risk of all-cause mortality and cardiovascular events
  3. varied according to the presence or absence of angina and angina equivalent symptoms.

Background  Data on the prognostic value of symptoms in these patients are limited.

Methods

Post-hoc analysis was performed in 2,364 patients with type 2 diabetes and documented CAD enrolled in the BARI 2D (Bypass Angioplasty Revascularization Investigation 2 Diabetes) trial to determine

  1. the occurrence of death and composite of death,
  2. myocardial infarction, and
  3. stroke

during a 5-year follow-up according to cardiac symptoms at baseline.

Results

There were 1,434 patients with angina (A), 506 with angina equivalents (E), and 424 with neither of these (N).
The cumulative death rates (total 316) were

  • 12% in A,
  • 14% in E, and
  • 10% in N (p = 0.3), and

cardiovascular composite rates (total 548) were

  • 24% in A,
  • 24% in E, and
  • 21% in N (p = 0.5).

Compared with N, the hazard ratios adjusted for confounders were not different for death in

  • A (1.11; 99% CI: 0.81 to 1.53) and
  • E (1.17; 99% CI: 0.81 to 1.68) or

for cardiovascular events in

  • A (1.17; 99% CI: 0.92 to 1.50) and
  • E (1.11; 99% CI: 0.84 to 1.48).

Conclusions

Whatever their symptom status,

    • patients with type 2 diabetes and stable CAD were at similar risk of cardiovascular events and death.

These findings suggest that these patients

      • may be similarly managed in terms of risk stratification and preventive therapies.

(Bypass Angioplasty Revascularization Investigation 2 Diabetes [BARI 2D]; NCT00006305)

Key Words
  • angina;
  • coronary artery disease;
  • silent ischemia;
  • type 2 diabetes

Abbreviations and Acronyms

  • BMI, body mass index;
  • CABG, coronary artery bypass graft surgery;
  • CAD, coronary artery disease;
  • CVD,cardiovascular disease;
  • HbA1c, glycosylated hemoglobin;
  • MI, myocardial infarction;
  • PCI, percutaneous coronary intervention
Prognostic Impact of the Presence and Absence of Angina on Mortality and Cardiovascular Outcomes in Patients With Type 2 Diabetes and Stable Coronary Artery Disease
http://www.ncbi.nlm.nih.gov/pubmed/23410541

J Am Coll Cardiol. 2013 Feb 19;61(7):702-11.   http://dx. doi.org/ 10.1016/j.jacc.2012.11.036.

http://www.j.JACC.org/Prognostic Impact of the Presence and Absence of Angina on Mortality and Cardiovascular Outcomes in Patients With Type 2 Diabetes and Stable Coronary Artery Disease

Prognostic Impact of the Presence and Absence of Angina on Mortality and Cardiovascular Outcomes in Patients With Type 2 Diabetes and Stable Coronary Artery Disease: Results from the BARI 2D (Bypass Angioplasty Revascularization Investigation 2 Diabetes) Trial.
Dagenais GR, Lu J, Faxon DP, Bogaty P, Adler D, Fuentes F, Escobedo J, Krishnaswami A, Slater J, Frye RL; BARI 2D Study Group.        PMID: 23410541 [PubMed – in process]
Source: Quebec Heart and Lung University Institute, Quebec City, Quebec, Canada. Electronic address: gilles.dagenais@criucpq.ulaval.ca.

Diabetes Mellitus

Diabetes Mellitus (Photo credit: anaxolotl)

Micrograph of an artery that supplies the hear...

Micrograph of an artery that supplies the heart with significant atherosclerosis and marked luminal narrowing. Tissue has been stained using Masson’s trichrome. (Photo credit: Wikipedia)

Bildbeschreibung: Deutsch: Koronarangiografie ...

Bildbeschreibung: Deutsch: Koronarangiografie und PTCA bei akutem Hinterwandinfarkt (li.: RCA verschlossen, re.: RCA erfolgreich dilatiert) Quelle: Deutsch: Scan von 2 Videoprints einer selbst durchgeführten Prozedur Fotograf/Zeichner: selbst gescannt / own work Datum: ca. 1999 (hochgeladen 03. Oktober 2005) andere Versionen: (Photo credit: Wikipedia)

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Percutaneous Transluminal Angioplasty and Stenting (PTAS) – Stenting versus Aggressive Medical Therapy for Intracranial Arterial Stenosis

Reporter: Aviva Lev-Ari, PhD, RN

 

RESULTS

Stenting versus Aggressive Medical Therapy for Intracranial Arterial Stenosis (Original Article, N Engl J Med 2011 ; 365 : 993 – 1003) . In the first paragraph of Results (page 996), the penultimate sentence should have read, “Of the 224 patients in the PTAS group, 16 (7.1%) did not have a stent placed (the procedure was not performed in 4 patients, the procedure was aborted before the lesion was accessed in 7, and angioplasty alone was performed in 5),”

http://www.nejm.org/doi/full/10.1056/NEJMx120039?query=TOC

BACKGROUND

Atherosclerotic intracranial arterial stenosis is an important cause of stroke that is increasingly being treated with percutaneous transluminal angioplasty and stenting (PTAS) to prevent recurrent stroke. However, PTAS has not been compared with medical management in a randomized trial.

METHODS

We randomly assigned patients who had a recent transient ischemic attack or stroke attributed to stenosis of 70 to 99% of the diameter of a major intracranial artery to aggressive medical management alone or aggressive medical management plus PTAS with the use of the Wingspan stent system. The primary end point was stroke or death within 30 days after enrollment or after a revascularization procedure for the qualifying lesion during the follow-up period or stroke in the territory of the qualifying artery beyond 30 days.

CONCLUSIONS

In patients with intracranial arterial stenosis, aggressive medical management was superior to PTAS with the use of the Wingspan stent system, both because the risk of early stroke after PTAS was high and because the risk of stroke with aggressive medical therapy alone was lower than expected.

http://www.nejm.org/doi/full/10.1056/nejmoa1105335

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