Icariin promotes osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) by activating PI3K-AKT-UTX/EZH2 signaling in steroid-induced femoral head osteonecrosis.

BACKGROUND: Differentiation of bone marrow mesenchymal stem cells (BMSCs) is pivotal in the pathogenesis of steroid-induced femoral head osteonecrosis. Icariin, an active ingredient in Epimedii herba, has the potential to regulate osteogenic differentiation of BMSCs. Nevertheless, the related mechanism is still unclear. The study aimed to explore whether icariin can affect osteogenic differentiation by activating PI3K/AKT signaling to alter UTX and EZH2 expression and thus regulating osteogenesis-related genes in BMSCs. METHODS: BMSCs were collected from Sprague Dawley rats and identified by measuring the positive ratios of cell markers using flow cytometry. Cells were treated with 1 μmol/L dexamethasone (DEX) for 24 h with or without 0.1-10 μM of icariin treatment. Cell counting Kit-8 (CCK-8) assays and flow cytometry analyses were performed to measure cell viability and apoptosis. Western blotting was conducted for measurement of apoptotic markers, factors involved in the PI3K/AKT-UTX/EZH2 pathway, osteogenic markers, and adipogenesis-related factors. Alizarin red S staining and Oil-red O staining were performed to measure the effect of DEX, icariin, UTX overexpression, or EZH2 knockdown on osteogenic and adipogenic differentiation of BMSCs. RESULTS: Icariin ameliorated DEX-induced rat BMSC injury. Icariin activated the PI3K/AKT signaling, thereby upregulating UTX and phosphorylated EZH2 levels while inhibiting EZH2 and H3K27me3 expression. Additionally, icariin promoted osteogenic differentiation and inhibited adipogenic differentiation of BMSCs. Importantly, overexpressing UTX or silencing EZH2 exerted similar effects on BMSC differentiation as icariin did. CONCLUSIONS: Icariin promotes osteogenic differentiation of DEX-treated BMSCs by activating PI3K/AKT signaling to upregulate UTX and inhibit EZH2, finally inducing H3K27me3 depletion.