Abstract: Objective: To investigate the effect of recombinant human BMP-9 (rhBMP-9) on the differentiation of human periodontal ligament fibroblasts into osteoblasts. Methods: Human periodontal ligament fibroblasts were cultured in vitro and osteogenic differentiation was induced by osteogenic differentiation medium (ODM). Then the cells were treated with different concentrations of rhBMP-9 in the presence or absence of p38 and extracellular signal-regulated kinase 1/2 (ERK1/2). Alkaline phosphatase (ALP) activity was measured using LabAssayTM ALP assay kit. The total RNA was extracted and real time fluorescence quantitative (qPCR) was used to detect the expressions of Runt-related transcription factor 2 (RUNX2),inhibitor of differentiation factor 1 (ID1),bone sialoprotein (BSP) and osteopontin (OPN). Results: RhBMP-9 stimulation significantly increased the ALP activity of human periodontal ligament fibroblasts in a concentration and time-dependent manner. Osteogenic differentiation-related transcription factors RUNX2 and ID1, as well as the expression of late osteogenic markers BSP and OPN, were also significantly increased by stimulation with rhBMP-9. Compared with rhBMP-9 alone, the effect of rhBMP-9 on osteogenic differentiation of human periodontal ligament fibroblasts was completely abolished by adding SB203580 and U0126 costimulation. Conclusion: RhBMP-9 could induce the osteogenic differentiation of human periodontal ligament fibroblasts, which might relate to the adjustment of p38 and ERK1/2 pathways.

Key words: Recombinant human bone morphogenetic protein-9, Fibroblasts, Osteoblasts, Extracellular signal-regulated kinase 1/2