Skeletal adaptations in young male mice after 4 weeks aboard the International Space Station

Abstract

Gravity has an important role in both the development and maintenance of bone mass. This is most evident in the rapid and intense bone loss observed in both humans and animals exposed to extended periods of microgravity in spaceflight. Here, cohabitating 9-week-old male C57BL/6 mice resided in spaceflight for ~4 weeks. A skeletal survey of these mice was compared to both habitat matched ground controls to determine the effects of microgravity and baseline samples in order to determine the effects of skeletal maturation on the resulting phenotype. We hypothesized that weight-bearing bones would experience an accelerated loss of bone mass compared to non-weight-bearing bones, and that spaceflight would also inhibit skeletal maturation in male mice. As expected, spaceflight had major negative effects on trabecular bone mass of the following weight-bearing bones: femur, tibia, and vertebrae. Interestingly, as opposed to the bone loss traditionally characterized for most weight-bearing skeletal compartments, the effects of spaceflight on the ribs and sternum resembled a failure to accumulate bone mass. Our study further adds to the insight that gravity has site-specific influences on the skeleton.

Targeting myostatin/activin A protects against skeletal muscle and bone loss during spaceflight

“…2A). Although additional studies will be required to understand the basis of this phenomenon, we speculate that this increase may reflect an adaptation in locomotion behavior in response to microgravity, with mice preferentially loading their forelimbs relative to their hindlimbs, as was also proposed by Maupin et al (28), along with an overall increase in physical activity (such as circling and "racetracking") observed for mice at the ISS (29). Consistent with this hypothesis, the relative magnitude of muscle loss was also greater in the lower body (quadriceps, gastrocnemius, soleus) compared to the upper body (triceps, pectoralis) ( Fig.…”

Gene-Metabolite Network Linked to Inhibited Bioenergetics in Association With Spaceflight-Induced Loss of Male Mouse Quadriceps Muscle

“…Five of 10 mice/group were reserved for imaging studies. (11) For the remaining five mice, the carcasses were snap-frozen at -80 C. FLT samples were returned to Earth; and all samples were processed at the same time in the same laboratory. Therefore, a maximum of five mice/group were available for these studies.…”

Validation of a New Rodent Experimental System to Investigate Consequences of Long Duration Space Habitation

“…The Rodent Habitat differs from other long duration spaceflight housing systems 12,17 in that it provides for both group-housing and internal wire grating that enable grabbing and purposeful locomotion throughout the cage, much like human crew do throughout the cabin. To accommodate unique aspects of the Dragon transport vehicle and the ISS, flight hardware was modified from the Animal Enclosure Module (AEM), that was used successfully in 27 missions with rats or mice aboard the Space Shuttle 3 followed by multiple RR missions 14,[18][19][20][21][22][23][24][25] .…”