Effects of Partial Vibration on Morphological Changes in Bone and Surrounding Muscle of Rats Under Microgravity Condition: Comparative Study by Gender

Musculoskeletal disorders during and after spaceflight are considered as a serious health issue. In space, weight-bearing exercise recognized as the main countermeasure to bone loss, since many anti-resorptive medications have not yet been approved for spaceflight or have been unsuccessful in their limited application. We need to investigate a complementary or alternative way to prevent bone loss and muscle atrophy resulting from microgravity condition. Partial vibration was chosen because it is one of the most feasible ways to adopt safely and effectively. Moreover, although the influence of hind-limb suspension has been studied in both male and female rodents, only rarely are both genders evaluated in the same study. Thus, to further extend our knowledge, the present study performed comparative analysis between genders. A total of 36 12-week-old male and female Sprague-Dawley rats were used and were randomly assigned to control (CON), hind-limb suspension without vibration stimulus (HS), and hind-limb suspension with vibration stimulus (HV) groups. Hind-limb suspension has led to increasing the rate of bone loss and muscle atrophy regardless of gender. The rates of bone loss in male group obviously increased than that of female group. All structural parameters were showed significant difference between HS and HV (p < 0.05) in male group whereas there are no significant differences in female group. In female, the muscle volume with treatment of partial vibration stimulus significantly increased which compared with that of hind-limb suspension (p < 0.05) whereas there are no significant differences in male group. Thus partial vibration could prevent bone loss of tibia in males and muscle atrophy in females induced by hind-limb suspension. In other words, partial vibration has positive effects on damaged musculoskeletal tissues that differ based on gender.