Objective To assess the effect of transforming growth factorβ1(TGF-β1) on cell proliferation，cell migration and Snail，MMP-2 expression of mesenchymal stem cells(MSCs)，and to further investigate its mechanisms. Methods Density gradient centrifugalization combined with adherence method were used to segregate and cultivate rat MSCs.MSCs cultivated to the 3rd passage were characterized using immunofluorescence technique.The effects of different concentrations of TGF-β1 on the migration was detected by the modified Transwell chambers.The effects of TGF-β1 at different time points on the expression of Snail and MMP-2 mRNA were measured by RT-PCR，and Snail expression was detected by immunofluorescence technology.siRNA for Snail was synthesized and transfected into MSCs by liposomel before TGF-β1 were treated.The expression of Snail and MMP-2 before and after the transfection were measured by Western blotting. Results Density gradient centrifugalization combined with adherence method could segregate and purify rat MSCs effectively.The results of immunofluorescence staining showed that CD29 and CD44 expressions were positive while CD34 and CD45 expression was negative for MSCs.The TGF-β1 induced a dose-dependent increase in cell migration,which peaked at 2μg/L.The expression level of Snail mRNA with TGF-β1 treatment for 6 hours and the expression level of MMP-2 mRNA for 12 hours were significantly higher than the expression level of those at other time points.24 hours later,the expression of Snail in TGF-β1treated group was significantly higher than t