Study On The Role Of PI3K/AKT-SIRT1 In TGF-β1 Promoting Osteogenic Differentiation Of MSCs Induced By BMP9

TGFβ is a large family group with at least 6 subtypes.Its members are widely expressed in bone and cartilage,in which TGF-β1 can regulate cell proliferation and differentiation.The PI3K/Akt pathway is composed of phosphatidylinositol 3-kinase(PI3K)and its downstream molecule serine / threonine protein kinase B(PKB/Akt).It is mainly involved in the signal transduction of cytokines,extracellular matrix and a variety of growth factors,as well as the regulation of cell functions such as cell proliferation,differentiation and apoptosis.Both TGF-β1 and PI3K/Akt signal can promote the osteogenic differentiation of MSCs induced by BMP9,but the related mechanism is not clear.On the basis of the previous research of our group,this study further explored the role and mechanism of TGF-β1 and PI3K/Akt signals in regulating the osteogenic differentiation of MSCs induced by BMP9.Alkaline phosphatase staining(ALP),alizarin red staining,PCR,Western blot and other experimental methods were used.Firstly,to determine the effect of PI3K/Akt signal on osteogenic differentiation of MSCs induced by BMP9,and then to analyze the relationship between the effect of TGF-β1 on osteogenic differentiation of MSCs induced by BMP9 and PI3K/Akt signal,and the relationship between Sirt1 and TGFβ-1 promoting osteogenic differentiation of MSCs induced by BMP9.Finally,to explore the possible mechanism of TGF-β1 and BMP9 regulating the expression of Sirt1.The results showed that both LY294002 and Rapmycin inhibited the osteogenic differentiation of MSCs induced by BMP9,and TGF-β1 could not cancel or weaken the inhibitory effect of LY294002 and Rapmycin on the osteogenic differentiation of MSCs induced by BMP9.Resveratrol(Resverstrol)can promote the osteogenic differentiation of MSCs induced by BMP9,while Ex527 can inhibit the osteogenic differentiation of BMP9 and decrease the level of p-Akt,but the total AKT level has no change.TGF-β1 could not reverse the inhibitory effect of Ex527 on osteogenic differentiation of MSCs induced by BMP9,and its effect on the levels of p-Akt and Akt.These results suggest that PI3K/Akt-SIRT1 is involved in regulating the effect of TGF-β1 on osteogenic differentiation of MSCs induced by BMP9.