Medical Student Rush University Medical Center Chicagio, Illinois, United States
Abstract Body : Endochondral ossification is an important biological process in determining the size, shape, and mechanical strength of adult long bones that is affected by mechanical loading. However, how unloading could alter this process as well as the overall development of long bones is unclear. The purpose of this study was to determine the potential effects of long bone development of growing rodents experiencing unloading from spaceflight. The primary hypothesis of this study was that spaceflight animals would have longer bones as compared to their age and sex matched ground controls. Male Sprague Dawley rats were exposed either to ground or spaceflight conditions during STS-40 and STS-58 missions for 9 and 14 days respectfully. At the time of launch, the rats were aged 8 weeks and 5 weeks old respectfully. Rodent bones were harvested postflight and length of humeri, femora, and tibae was determined by caliper. Groups were compared using a student’s t-test. An average, standard deviation, and percent difference was also calculated. No significant differences were found between the length of humeri, femora, and tibae of spaceflight animals as compared to ground control animals. On average the bones of the spaceflight group were longer than the ground controls. The percent difference of the spaceflight group ranged from +1.2-+2.1% as compared to the ground control group. The primary hypothesis of this study was not supported as the spaceflight animals did not have statistically significant longer bones as compared to their age and sex match ground controls. Despite of this, the finding that the spaceflight animals consistently had longer bones from a relatively short exposure to unloading may mean that longer durations would demonstrate an appreciable difference. Future work should examine not only length but other osteologic parameters.
