Flow Shear Stress And Vascular Smooth Muscle Cells Promote Endothelial Differentiation Of Endothelial Progenitor Cell Via Activation Of Akt

Background: Endothelial progenitor cells (EPCs) is a population of pluripotent cells, which have a crucial role in maintaining the integrity of the endothelium, but the mechanisms regulating the differentiation of EPCs have not been understood completely. In this study the influence of shear stress and vascular smooth muscle cells (VSMCs) on the differentiation of EPCs, as well as a role of Akt was detected in a coculture model. Moreover, the adhesion and the proliferation of EPCs were examined under coculture condition.Method: Human EPCs were separated from cord blood and identified by double staining for the fluorescent labeled ac-LDL and UEA-lectin. VSMCs/EPCs coculture system were made up by a parallel-plate coculture flow chamber. Flow cytometry assessed the expression of CD133, CD34, CD31 and von Willebrand factor (vWF). Activation of Akt was detected by western blot. The adhesive ability of EPCs was examined by adhesion experiment and the proliferation of EPCs was detected by the number of clone forming units (CFUs).Results: Shear stress and VSMCs increase expression of CD31, vWF, but simultaneously decrease expression of CD133, CD34 in EPCs respectively. The influence of shear stress is more significant when EPCs were cocultured with VSMCs. Akt was activated in EPCs by shear stress or VSMCs or both. Furthermore, when blockage of Akt with its inhibitor Akti in the cocultured EPCs exposed to shear stress both CD133 and CD34 were upregulated, and CD31 and vWF were downregulated significantly. The adhesion of EPCs was upregulated by 63% and the number of CFUs increased by 60%.Conclusions: The results demonstrate that shear stress and VSMCs promote endothelial differentiation of EPCs via activation of Akt. Moreover, the adhesion of EPCs was upregulated but the proliferation of EPCs was downregulted.