Studies have shown that placing an animal (mouse, rat, turkey, or sheep) on a slightly vibrating platform (.3 g at 30 Hz) for 10 to 20 minutes daily will stimulate muscle and bone interaction to increase density and bone strength. Dr. Clinton Rubin is studying the method’s effectiveness on inhibiting bone loss as well as its effect on the expression of genes that are critical to bone formation. This research will provide a means of understanding the molecular basis for a biomechanical countermeasure for bone loss induced by weightlessness. Currently, human trials using post-menopausal women, children with disabling conditions such as cerebral palsy, children with low bone density, and patients with spinal cord injury are under way.
Overview
A Biomechanical Countermeasure for Disuse Osteopenia
Principal Investigator:
Clinton Rubin, Ph.D.
Organization:
State University of New York - Stony Brook
Technical Summary
Osteoporosis, the progressive loss of bone density that cripples tens of millions on our planet, distinguishes itself as perhaps the greatest physiologic obstacle to an extended human presence in space. Harnessing bone's strong sensitivity to mechanical signals, there is increasing evidence that extremely low magnitude (<100 microstrain) mechanical signals can be strongly osteogenic if applied at a high frequency (15 to 60 Hz). Such high-frequency, low-magnitude strains comprise a dominant component of a bone's strain history, indicating that these mechanical events represent a significant determinant of bone morphology.
With this in mind, we have been examining if small perturbations in high frequency loading, induced noninvasively into the lower appendicular skeleton, will stimulate an increase in bone mass without sacrificing bone quality. The principal objectives of our research have been to establish the efficacy of this unique, biomechanical countermeasure to inhibit bone loss in an animal model of disuse osteoporosis, and correlate this regulatory influence to the expression patterns of several genes critical to bone formation and resorption.
Ten minutes per day of these low-level signals (0.25g), induced noninvasively using an oscillating platform, are able to retain bone mass despite 23 hours and 50 minutes of disuse, while ten minutes of normal weight bearing fails to do to. Longer term animal studies (one year), have shown that low-level mechanical loading, inducing cortical strains on the order of five microstrain, can increase cancellous bone volume fraction, thicken trabeculae, increase trabecular number and enhance bone stiffness and strength. Considering these strain levels are far below (<1/1000th) those which may cause damage to the tissue, we believe these signals hold great potential as a mechanical prophylaxis for osteoporosis.
Earth Applications
Early clinical trials with the LMMS device, including cerebral palsy children, adolescent girls with osteopenia, or post-menopausal women have been encouraging in their ability to inhibit and/or reverse osteoporosis.
As we move towards further clinical evaluation of this device for the aging and infirm population, as well as consider it for use to curb bone loss in astronauts during long-term space flight, it is clear that this unique intervention affords the ability to examine the molecular basis of an anabolic signal, as well as establish the extent to which noninvasive mechanical signals can provide an effective countermeasure for disuse osteopenia. Importantly, correlating early gene expression to a longer-term bone response will also permit extrapolation of results from short-term space flights to long-term missions.
This project's funding ended in 2004