| Objective To investigate the effect of activation of BMP signaling in MLO-Y4 cells on osteogenic and adipogenic differentiation by ST2 cells and its mechanism. Methods After MLO-Y4 cells were treated with 0.5‰ DMSO and 0.5μmol/L BMP agonist (FK506) for 24h, the cell activity was tested using CCK-8. The expression of target genes BMP, ID1, and ID2 was detected with quantitative real-time PCR. ST2 cells were cultured with 20% supernatant collected from MLO-Y4 culture and 80% fresh medium. The cells were divided into DMSO group and FK506 group. Alkaline phosphatase (ALP) staining represented the ability of osteogenic differentiation. The mRNA expression of osteogenic markers ALP, osteocalcin (OCN), bonesialoprotein (BSP), and Runx2, and the adipogenesis-related markers peroxisome proliferators-activated receptors γ4 (PPARγ4) and C/EBP were detected using qPCR. Western blotting was used to detect the protein expression levels of β-catenin and p-smad5, the downstream signal of Wnt and BMP in ST2 cells. Results Compared to those in DMSO group, BMP signal target genes ID1 and ID2 were upregulated in FK506-activited MLO-Y4 cells, with no effect on cell liability. The osteoblastic differentiation factors ALP, OCN, BSP, and Runx2 increased and expression of PPARγ4 and C/EBP decreased (P<0.001) in ST2 cells of FK506 group, compared to those in DMSO group. The protein expression of β-catenin in ST2 cells was up-regulated (P<0.05). Conclusion After BMP signal in MLO-Y4 cells is stimulated, the supernatant promotes osteogenic differentiation and inhibits lipogenesis in ST2 cells. The enhancement of osteogenesis ability is related to the enhancement of intracellular Wnt signal. |