Role Of Integrins In Endothelial Cell Differentiation Of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) can differentiate into endothelial cells in vitro or in vivo. Our previous study confirmed that 50 ng/mL VEGF could induce endothelial cell differentiation of MSCs. Integrins are highly expressed in vascular endothelial cells and play an important role in angiogenesis. In the present study, we aimed to further investigate the role of integrins in endothelial cell differentiation of MSCs and angiogenesis.Firstly, MSCs were induced to differentiate into endothelial cells by 50 ng/mL VEGF. Uptake of DiI-Ac-LDL assay confirmed that the differentiated MSCs could uptake Ac-LDL. The angiogenesis of the differentiated MSCs was detected by Matrigel assay.Then the expression of integrins (α1, α5, αV, β1,β4,β5) were markedly enhanced in VEGF-treated MSCs by RT-PCR and Western-blot.Rho signal pathway is involved in VEGF-induced cell differentiation of MSCs. To determine whether the expression of integrins was regulated by Rho signal pathway, the differentiated cells were treated with Rho pathway inhibitor either Y-27632 or C3 transferase. The results demonstrated that the inhibitors blocked the VEGF-induced capillary-tube formation and downregulation of integrins in differentiated cells.It is reported that the activation of Rho signal pathway can promote the nucleus translocation of MRTF-A to activate target genes. To test whether the transcription of integrins was regulated by MRTF-A, MSCs were transfected with sh-MRTF-A or siMRTF-A in the presence of VEGF. The results demonstrated that knockdown of MRTF-A inhibited formation of capillary-tube and expression of integrins. Then wound heal assay and transwell assay showed that MRTF-A suppressed VEGF-induced MSCs migration. Moreover, luciferase report assay showed MRTF-A could enhance transcriptional activity of Integrin al and Integrin a5 promoters in MSCs.Finally, the effect of MRTF-A on integrins was investigated in HUVECs. Cells were transfected with siMRTF-A in the presence of VEGF. MTT assay confirmed that knockdown of MRTF-A did not affect cellular proliferation. Transfection with siMRTF-A could reduce adhesion, migration and capillary-tube formation of HUVECs by phalloidin staining, wound healing and matrigel assay. Konckdown of MRTF-A suppressed the expression of MYL9, CYR61 and integrins. Moreover, luciferase report assay showed MRTF-A could enhance transcriptional activity of Integrin al and Integrin a5 promoters in HUVECs.