Oridonin promotes osteogenesis through Wnt/β-catenin pathway and inhibits RANKL-induced osteoclastogenesis in vitro

Aims: To study the molecular mechanism of oridonin (ORI) on osteoblast differentiation and osteoclast formation in vitro. Main methods: Rat bone marrow mesenchymal stem cells (BMSCs) were treated with different concentrations of ORI in osteogenic medium (OM). CCK-8 assay and were used to detect the effect on BMSCs viability. Alizarin red staining and ALP activity were used to illuminate the effect of ORI on osteogenic differentiation. Expressions of osteogenic differentiation related genes were detected by real-time quantitative PCR (qRT-PCR), and expressions of osteogenic related proteins were detected by Western blot (WB) and immunofluorescence. Similarly, bone marrow mononuclear cells (BMMs) were treated with different concentrations of ORI. CCK-8 assay and Live/Dead staining were used to detect the effect of ORI on BMMs activity. TRAP staining was used to detect its effect on osteoclast differentiation. Expressions of osteoclast-related genes were detected by qRT-PCR, and expressions of osteoclast-related proteins were detected by WB and immunofluorescence. Key findings: (1) ORI (2 mu M) promoted the ALP activity of BMSCs differentiation into osteoblasts and increased the number of calcium nodules. (2) ORI stimulated the expressions of wnt1, beta-catenin and Runx2, but with no significantly effect on p-GSK-3 beta and GSK-3 beta. (3) ORI promoted the expression of OPG and inhibited the expression of RANKL. (4) ORI directly/indirectly inhibited the osteoclast formation and expressions of osteoclast-related genes TRAP, NFATc1 and c-Fos. Significance: ORI may promote BMSCs differentiate into osteoblasts through the Wnt/beta-catenin signaling pathway. At the same time, it may also inhibit the formation of osteoclasts mediated by RANKL.