Influence of extraneous transforming growth factor β1 on the expression of receptors I and II in rat bone marrow-derived mesenchymal stem cells

Objective To investigate the expression of transforming growth factor (TGF) β1 receptors Ⅰ and Ⅱ in cultures of rat bone marrow-derived mesenchymal stem cells (MSCs) and the influence of extraneous TGF-β1 on them.Methods The effects of different concentrations of TGF-β1 on the proliferation and ALP activity were detected by MTT and PNP in MSCs.The expression of TGF-β1 receptors Ⅰand Ⅱ in MSCs and the influence of extraneous TGF-β1 on them were examined by immunohistochemical technique and Western blot analyses.Results The extraneous TGF-β1 induced a dose-dependent decrease in cell proliferation and a dose-dependent increase in ALP activity,which plateaued at 5 μg/L.The ALP activity was increased gradually with 5 μg/L TGF-β1 as compared with control groups (P0.05).MSCs could express TβRⅠ and TβRⅡ.The total amount of TβRⅡ protein remained unchanged before and after TGF-β1 treatment (P0.05),but the expression level of TβRⅠ was increased markedly after 12 h treatment (P0.05).A positive correlation was observed between the ratio of TβRⅠ and TβRⅡ and the developmental marker ALP.Conclusion The responsiveness of MSCs to TGF-β1 might be modulated with the adaptive changes of receptors and TβRⅠ/TβRⅡ ratio,which can trigger the osteoblastic differentiation.The expression of TβRⅠ is the limiting factor in determining the responsiveness of MSCs to TGF-β1.