TGF­ß1 promotes the osteoinduction of human osteoblasts via the PI3K/AKT/mTOR/S6K1 signalling pathway.

ABSTRACT

Transforming growth factor ß1 (TGF­ß1) has been suggested to be a candidate cytokine in the field of bone tissue engineering. Cytokines serve important roles in tissue engineering, particularly in the repair of bone damage; however, the underlying molecular mechanisms remain unclear. In the present study, the effects of TGF­ß1 on the osteogenesis and motility of hFOB1.19 human osteoblasts were demonstrated via the phenotype and gene expression of cells. Additionally, the role of the phosphatidylinositol 3­kinase/protein kinase B/mammalian target of rapamycin/S6 kinase 1 (PI3K/AKT/mTOR/S6K1) signalling pathway in the effects of TGF­ß1 on osteoblasts was investigated. It was demonstrated using Cell Counting Kit­8 and flow cytometry assays that the proliferation of human osteoblasts was promoted by 1 ng/ml TGF­ß1. In addition, alkaline phosphatase activity, Alizarin red staining, scratch­wound and Transwell assays were conducted. It was revealed that osteogenesis and the migration of cells were regulated by TGF­ß1 via the upregulation of osteogenic and migration­associated genes. Alterations in the expression of osteogenesis­ and migration­associated genes were evaluated following pre­treatment with a PI3K/AKT inhibitor (LY294002) and an mTOR/S6K1 inhibitor (rapamycin), with or without TGF­ß1. The results indicated that TGF­ß1 affected the osteogenesis and mineralisation of osteoblasts via the PI3K/AKT signalling pathway. Furthermore, TGF­ß1 exhibited effects on mTOR/S6K1 downstream of PI3K/AKT. The present study demonstrated that TGF­ß1 promoted the proliferation, differentiation and migration of human hFOB1.19 osteoblasts, and revealed that TGF­ß1 affected the biological activity of osteoblasts via the PI3K/AKT/mTOR/S6K1 signalling pathway. Our findings may provide novel insight to aid the development of bone tissue engineering methods for the treatment of bone injury.