Use of Spaceflight and Spaceflight Simulation to Evaluate Osteoprotegerin for Treatment of Disuse Osteoporosis

摘要

Spaceflight effects on the human skeleton include loss of calcaneal (heal) bone density and hypercalciurea, indicative of the mobilization of calcium from the skeleton caused partialy by increased osteoclast activity leading to greater bone resorption. These effects are due in part to the loss of mechanical loading during spaceflight. The result is bone density being decreased 0.5-2percent per month. The average calcium loss in astronauts is exacerbated in bones that ordinarily support weight. Long-term space missions will not be possible until the risk of bone fracture during and upon return from these missions is minimized. Because of the need for relatively noninvasive assays and modest ample sizes in humans, spaceflight research on the skeleton has been focused on rats. In growing rats spaceflight is accompanied by a reduction in bone formation rather than an increase in resorption. Space Station experiments are expected to use more mature animals (rats and mice) for extended periods. It is hypothesized that this may better model the effects of extended exposure to microgravity on adult humans by increasing osteoclastic bone resorption.