Physcion-8-O-β-D-glucopyranoside enhances the commitment of mouse mesenchymal progenitors into osteoblasts and their differentiation: Possible involvement of signaling pathways to activate BMP gene expression

Here, we show the involvement of signaling pathways to induce the gene expression of bone morphogenetic protein (BMP) in the osteogenic activity of physcion-8-O-β-D-glucopyranoside (physcion-Glu); it stimulated osteoblast differentiation in mouse osteoblast MC3T3-E1 subclone 4 cells and induced BMP-2 gene expression and activation of Akt and ERK/MAP kinases. Physcion-Glu-induced BMP-2 expression and mineralization were attenuated by LY294002, an inhibitor of PI3K that lies upstream of Akt and MAP kinases, suggesting that physcion-Glu induces osteoblast differentiation via PI3K-Akt/MAP kinase signaling pathways, which play important roles in inducing BMP-2 gene expression. Physcion-Glu also enhanced BMP-2-induced commitment of mouse bi-potential mesenchymal precursor C2C12 cells into osteoblasts while inducing the transcription of several osteogenic BMP isoforms, such as BMP-2, -4, -7, and -9. Osteogenic synergy between BMP-2 and physcion-Glu was supported by the fact that noggin inhibited BMP-2 and physcion-Glu-induced alkaline phosphatase expression and activity. Considering that physcion-Glu induced Runx2 activity and the nuclear translocation of p-Smad, physcion-Glu could act by enhancing the BMP signaling pathway that induces Smad activation and translocation to activate Runx2. In conclusion, physcion-Glu could enhance the commitment of mesenchymal progenitors into osteoblasts and their differentiation by activating signaling pathways to induce BMP gene expression.