To investigate the effect and underlying mechanism of Yougui pills (YGPs) on steroid-related osteonecrosis of the femoral head (SONFH).

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 β-catenin. Protein levels of cathepsin K (CTSK), phospho-glycogen synthase kinase-3 beta (p-Ser9 GSK-3β) and total glycogen synthase kinase-3 beta (GSK-3β) 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.

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 β-catenin, while increasing load-bearing capacity of femoral heads. Interestingly, p-Ser9 GSK-3β 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.

YGPs could suppress osteoclastogenesis and promote bone formation during SONFH in rabbits by activating β-catenin.