Yougui pills exert osteoprotective effects on rabbit steroid-related osteonecrosis of the femoral head by activating β-catenin.

Objective: To investigate the effect and underlying mechanism of Yougui pills (YGPs) on steroid-related osteonecrosis of the femoral head (SONFH). Methods: Male New Zealand white rabbits were divided into three groups: control group, SONFH group and YGPs group. Rabbit SONFH was induced by methylprednisolone (MPS) combined with lipopolysaccharide (LPS). At 6 weeks post induction, the femoral heads were harvested for tissue analyses, including histopathology, mechanical test of femoral heads, micro-CT, tartrate-resistant acid phosphatase (TRAP) staining, and immunohistochemistry for osteocalcin (OCN), vascular endothelial growth factor (VEGF) and beta-catenin. Protein levels of cathepsin K (CTSK), phospho-glycogen synthase kinase-3 beta (p-Ser9 GSK-3 beta) and total glycogen synthase kinase-3 beta (GSK-3 beta) in femoral heads were also detected. Additionally, the serum TRAP activity was measured using enzyme-linked immunosorbent assay (ELISA). Finally, the effects of YGPs treatment on osteoclast differentiation and osteoblast formation were evaluated in vitro. Results: The ratio of empty lacuna was markedly lower in YGPs group than SONFH group. Micro-CT evaluation indicated that YGPs has a preventive effect on bone loss in rabbit SONFH. YGPs treatment could suppress bone resorption by reducing TRAP(+) osteoclast and serum TRACP5b levels in necrotic femoral heads. Moreover, YGPs treatment could promote bone formation by up-regulating the expression of OCN, VEGF and beta-catenin, while increasing load-bearing capacity of femoral heads. Interestingly, p-Ser9 GSK-3 beta downregulation, and CTSK upregulation in necrotic femoral head could be reversed by YGPs treatment, which also effectively inhibited RANKL-induced osteoclast differentiation and promoted osteoblast formation in vitro. Conclusion: YGPs could suppress osteoclastogenesis and promote bone formation during SONFH in rabbits by activating beta-catenin.