Role of myofascia in the recovery of bone loss after reloading in tail-suspended rats

Abstract

Astronauts experience severe musculoskeletal degradation in space. After returning to earth, bone loss recovery did not parallel muscle recovery. Fascia may play an important role as a considerable part of muscle force is transmitted to bone through fascia. However, little is known about how fascia changes in microgravity and its effect on the development of musculoskeletal degeneration. In this study, a rat hindlimb unloading model was used to simulate microgravity (21 days of tail suspension) and then reloading for 7 days, 14 days and 21 days. After different periods, bone mineral density (BMD) and microstructure of the tibia were analyzed by μCT, the mechanical properties of the tibia were determined by the three-point bending test and the mechanical properties of fascia were explored by tensile test. The results show that, after tail suspension, collagen Ⅰ in myofascia was significantly increased (p < 0.05), the myofascial elastic modulus was significantly decreased (p < 0.05), BMD of the tibia was significantly decreased (p < 0.05) and the microstructure of the tibia had deteriorated. After 21 days of reloading, there was no significant improvement in the myofascial elastic modulus as well as in the tibial maximum load. Correlation analysis results showed that the myofascial elastic modulus was significantly correlated with the tibial maximum load. In summary, the deterioration of mechanical property of myofascia induced by tail suspension did not recover when the time of reloading was the same as the time of unloading. This indicates that the delayed bone recovery after being exposed to microgravity was associated with deterioration of myofascia.