Microgravity-induced alterations of mouse bones are compartment- and site-specific and vary with age

The age at which astronauts experience microgravity is a critical consideration for skeletal health and similarly has clinical relevance musculoskeletal disuse on Earth. While are extensively studied bone other physiological changes, rodent studies enable direct evaluation of changes with microgravity. Yet, mouse spaceflight have predominately evaluated tissues from young, growing mice. We microarchitecture in tibiae femurs Young (9-week-old) Mature (32-weeks-old) female, C57BL/6N mice flown ~2 ~3 weeks, respectively. Microgravity-induced were both compartment- site-specific. Changes greater trabecular versus cortical exposed to (−40.0% Tb. BV/TV vs −4.4% Ct. BV/TV), loss was the proximal tibia as compared distal femur. Trabecular thickness increased by +25.0% Earth no significant difference following In microgravity, rapidly decreased (−24.5%) while change detected age-matched that maintained experienced than net growth. Moreover, machine learning classification models confirmed exposure-driven decrements structure occurred disproportionately Our results suggest onset may implications osteoporotic or at-risk populations contribute understanding patterns astronauts.