Schisandrin A induces osteoblast differentiation to treat glucocorticoid-induced osteoporosis through activating Wnt pathway

Schisandrin A (SchA) efficacy in addressing glucocorticoid-induced osteoporosis (GIOP) remains unexplored, and its underlying mechanisms are yet to be clarified. We developed a GIOP mouse model. The efficacy of SchA was assessed comprehensively through micro-CT analysis, biomechanical testing. Using transcriptomic profiling, we investigated the impact of SchA on gene expression in the bone tissue of GIOP mice. Additionally, biochemical assays and Western blot were performed to evaluate SchA's effects on osteogenic growth-related factors in GIOP mice. To complement these findings, we first established an osteoblast injury model to validate the effects of SchA on osteoblast differentiation. We then assessed the activity of the Wnt/β-catenin signaling pathway using a dual luciferase assay and further identified its molecular targets. Our findings demonstrate that SchA intervention significantly improved bone mass parameters, bone mineral density, and bone volume fraction, as well as bone strength indicators in GIOP mice. SchA treatment also elevated serum calcium and phosphorus levels and mitigated pathological damage in the femur. Transcriptomic analysis revealed that SchA upregulated key transcription factors associated with osteoblast differentiatio. Western blot analysis confirmed that SchA intervention increased the expression of key proteins involved in the Wnt signaling pathway. In vitro experiments further validated that SchA upregulated differentiation factors and key Wnt pathway proteins in osteoblasts. The TOP/FOP flash ratio in osteoblasts increased noticeably after SchA treatment, indicating activation of the Wnt/β-catenin signaling pathway. However, when Wnt5a was inhibited using Box5, the regulatory effect of SchA on osteoblast differentiation was abolished. This study comprehensively evaluates the therapeutic effects of SchA on GIOP and suggests that its efficacy likely involves activation of the Wnt signaling pathway in bone cells, thereby promoting osteoblast differentiation and activation, and facilitating bone formation.