Effects of rhTGF-β1 on proliferation and osteogenic differentiation of MSCs in SD rats

AIM：To investigate the effects of recombinant human transforming growth factor β1 (rhTGF-β1) on the ability of proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells (MSCs), as well as its effects on the expression of bone morphogenetic protein 2 (BMP-2), Smad4 and core binding factor α1 (Cbfa1). METHODS：SD rat MSCs were isolated and purified by the differential time adherent method. MTT assay was used to confirm the optimal concentration of rhTGF-β1 for the proliferation of MSCs. The optimal concentration for differentiation of MSCs into osteoblast was also determined by observing the activity and positive staining of alkaline phosphatase. According to the different induction conditions, MSCs were divided into 4 groups:control group, classic group, rhTGF-β1 group, and rhTGF-β1+classic group. Alkaline phosphatase, type I collagen, bone Gla protein and calcium nodes were detected to evaluate the osteogenic differentiation. BMP-2 was detected by ELISA and the mRNA expression of Smad4 and Cbfa1 was analyzed by real-time quantitative PCR. RESULTS：The optimal concentrations of rhTGF-β1 for the proliferation of MSCs and for the osteogenic differentiation of MSCs were 10 and 5 μg/L, respectively. The MSCs in classical group and rhTGF-β1 group were promoted to osteogenic differentiation, and the mRNA expression of BMP-2, Smad4 and Cbfa1 was increased. rhTGF-β1 induced osteogenic differentiation of MSCs in the early and middle terms. However, in rhTGF-β1+classic group, the osteogenic differentiation of MSCs was more obvious in the late term. CONCLUSION:The induction conditions of classical group, rhTGF-β1 group and rhTGF-β1+ classical group promote the differentiation of MSCs by increasing BMP-2 secretion and starting the TGF-β superfamily/Smads signaling pathway to regulate the differentiation of MSCs.