Involvement of the phosphoinositide 3‐kinase/Akt signaling pathway in bone morphogenetic protein 9‐stimulated osteogenic differentiation and stromal cell‐derived factor 1 production in human periodontal ligament fibroblasts

Recent studies have shown that bone morphogenetic protein 9 (BMP-9) can induce osteogenic differentiation in human periodontal stem cells and human periodontal ligament fibroblasts (PDLFs). Bone morphogenetic protein 9 may be used in periodontal tissue regeneration because of its potent osteoinductive ability. Human periodontal ligament cells also have been demonstrated to produce stromal cell-derived factor 1 (SDF-1), which is important for stem-cell homing and recruitment to injured sites. In the present study, we examined the involvement of the phosphoinositide 3-kinase (PI3K)/Akt signaling axis in osteogenic differentiation and SDF-1 production in human PDLFs stimulated with BMP-9 in osteogenic medium supplemented with dexamethasone and ascorbic acid. Pretreatment of the cells with LY294002, a PI3K-specific inhibitor, suppressed not only BMP-9-enhanced alkaline phosphatase activity but also expression of a BMP-response gene (inhibitor of DNA binding 1) and osteogenic marker genes (runt-related transcription factor 2, osterix, bone sialoprotein, and osteopontin). In addition, BMP-9 up-regulated SDF-1 production, and the production of SDF-1 was suppressed by LY294002. The protein SDF-1-alpha was identified as a major isoform of SDF-1 that was regulated by BMP-9. Our data suggest involvement of the PI3K/Akt pathway in BMP-9-stimulated osteogenic differentiation and SDF-1 production in PDLFs cultured in osteogenic medium.