[Effects of hindlimb unloading on bone histomorphometry and bone mass in rats].

OBJECTIVE: To study the effects of hindlimb unloading on bone histomorphometry, bone local growth factor, bone biomechanical properties and bone contents in rats. METHOD: Male SD rats were arranged into free active control group (CON) and tail-suspended group (TS) with 9 rats in each group. The experiment lasted for 3 weeks. Bone histomorphometry, bone local growth factor, biomechanical properties and bone contents were measured before and after tail suspension. RESULT: Structure of the trabecular bone was disorganized. Compared with CON, trabecular bone volume (% Tb. Ar), mean trabecular plate thickness (Tb. Th), osteoblast surface (Ob. S) were significantly reduced in TS. The eroded surface (Oc. N/BS) tended to be higher, though not significant at this stage of tail suspension; alkaline phosphatase (ALP) activity in the tibia were significantly reduced, but NO content in the femoral trunk was significantly decreased; bone biomechanical properties, bone mineral content (BMC), bone density (BD) and bone collagen density (BCD) in the femur were significantly reduced. CONCLUSION: Hindlimb unloading may lead to regression of bone microstructure, change of bone local growth factor content, reduction of bone biomechanical properties and bone content.