Curator and Reporter: Ritu Saxena, Ph.D.
Recently, an article published in the journal Bone described that the low magnitude vibrations might be helpful in mitigating osteopenia in spontaneous granulosa cell ovarian cancer.
Osteopenia is defined as the bone mineral density (BMD) that is lower than normal peak BMD but not low enough to be classified as the diseased condition called osteoporosis. Bone mineral density is a measurement of the level of minerals in the bones, that shows how dense and strong they are. Having osteopenia means there is a greater risk that, as time passes, you may develop BMD that is very low compared to normal, known as osteoporosis
Cancer progression is often paralleled by a decline in bone mass, raising risk of fracture. Loss in bone mass can be therapeutically treated by using bone anabolic agents that increase the process of bone formation compared to bone resorption thus leading to an overall increase in bone mass. However, use of anabolic agents for preventing cancer associated bone loss presents a lot of concern as they may exacerbate cancer tissue expansion.
Bone is a mechanosensitive organ. Osteoblastogenesis, or the process of differentiation of precursor cells to bone forming cells (osteoblasts) is encouraged by low intensity vibration (LIV) via a mechanical signal. Rubin et al explored the possibility of slow cancer-associated bone loss, but this goal must be achieved without fostering disease progression. The hypothesis was tested in the murine model.
Seventy female F1-SWRxSWXJ-9 mice, a strain prone to developing granulosa cell tumors, were divided into three groups – baseline control (BC: n=10), age-matched control (AC: n=30), and LIV (n=30), which received mechanical signals (90Hz @ 0.3g) for 15m/day, 5day/w over the course of 1year. Survival curves observed in the three groups indicated that longevity was unperturbed by LIV. Rubin et al stated that “1year, bone volume of proximal tibiae in LIV mice was 25% greater than AC while bone volume of L5 vertebrae was 16% higher in LIV over AC (p<0.02). Primary lesions and peripheral metastases were apparent in both LIV and AC; however, overall tumor incidence was approximately 30% less in LIV (p=0.27) and, when disease was evident, involved fewer organ systems (p=0.09).”
These experiments indicate that LIV helps protect bone mass in mice inherently susceptible to cancer without compromising life expectancy, perhaps through mechanical control of stem cell fate. Further, these data reflect the numerous system-level benefits of exercise in general, and mechanical signals in particular, in the preservation of bone density and the suppression of cancer progression.