A novel partial gravity ground-based analog for rats via quadrupedal unloading.

Musculoskeletal deconditioning is a well-known consequence of microgravity. However, the effects of partial gravity, such as that experienced on the moon (0.16 g) or Mars (0.38 g), on musculoskeletal health remain relatively unexplored. Because Mars is being increasingly viewed as the likely next extraterrestrial site for human exploration, there is an increasing need for Earth-based models that can replicate the long-term physiological effects of microgravity. These models would also offer the opportunity to explore the potential impact of partial artificial gravity (as would be achieved by centrifugation). In this study, we describe a novel partial gravity model that can be employed in rats over extended periods of time. We demonstrate that 2 wk of partial weight bearing at 20, 40, or 70% of normal loading affects the musculoskeletal health of the animals, as evidenced by decreased trabecular bone density (ranging from -7.5 ± 2.7% at 70% of normal loading to -27.9 ± 2.9% at 20%), hindlimb muscle mass, and impaired muscle function as characterized by grip force. This new model will facilitate studies of the physiological changes occurring in partial gravity and allow for the design of potential countermeasures to mitigate these changes. NEW & NOTEWORTHY This research article describes the first quadrupedal unloading model in rats that is sustainable for investigating the physiological alterations occurring in partial gravity environments, providing a new and adaptable model for ground-based research for future space exploration.