Aim To investigate the effects of vascular endothelial growth factor(VEGF) and shear stress on the differentiation of bone marrow mesenchymal stem cells(MSC). Methods MSC were isolated from adult marrow mononuclear cells by attaching growth.MSC were subjected to VEGF,different levels of shear stress(8 and 15 dyn/cm2) and VEGF+shear stress respectively,for 7 d,24 h or 24 h.Cell shape and orientation were observed at 0 h,24 h during shear stress.Indirect IF staining was employed to identify the endothelial cell-specific marker von Willebrand factor(vWF).A functional marker of mature endothelial cells was examined by the uptake of Dil labled acetylated low density lipoproteins(Dil-ac-LDL). Results After subjection to VEGF,shear stress of 8 dyn/cm2 for 7 d,24 h respectively,MSC tended to be a more rounder,polygon-like cell shape,and MSC of shear stress group aligned parallel to the flow,MSC were positive for vWF staining,indicating the endothelial phenotype,and also positive for the uptaking of Dil-ac-LDL,indicating the possession of mature endothelial function.Cells treated with VEGF and shear stress of 15 dyn/cm2 for 24 h were negative for both the vWF staining and the uptaking of Dil-ac-LDL,indicating the lack of differentiation.After VEGF and shear stress acted 24 h together,MSC can be induced into endothelial cell. Conclusion Shear stress can induce the differentiation of MSC into endothelial cells in a stress level dependent way.Shear stress combined with VEGF not only induce the differentiation of MSC into endothelial cells,but also cause cell proliferation,which seems to have a better effect than only shear stress.