Anoxia-Induced VEGF-Release from Rat Cardiomyocites Promotes VascularDifferentiation of Human Mesenchymal Stem Cells.

BackgroundAlbeit several studies show that cellular therapy with bone marrow mesenchymal stem cells (BM-hMSCs) improves cardiac function after myocardial infarction (MI), the underlying mechanism is subject of controversy. Here we hypothesized that soluble factors, including VEGF, secreted by cardiomyocytes and BM-hMSCs under a low oxygen environment promote vascular differentiation of BM-hMSCs.\n\nMethodsHuman BM-MSCs were isolated and expanded in vitro by the same procedure we employed to prepare cells suitable for cardiac cell therapy. BM-hMSCs were characterized by flow cytometry and functional analysis. Vascular differentiation was induced by VEGF or by conditioned media from neonate rat ventricular cardiomyocytes (NRVCs) cultured in anoxia and confirmed by immunostaining, tube formation over matrigel and cell migration across transwells. Presence of VEGF in conditioned media was determined by ELISA and activation of VEGF signaling by Western blot.\n\nResultsBM-hMSCs used in this study met the criteria recommended by International Society for Cellular Therapy for defining mesenchymal stromal cells. Von Willebrand factor (vWF) expression and tube formation in matrigel indicate that these cells had the capacity to differentiate into the endothelial lineage, which was further enhanced by VEGF and conditioned media from NRVCs cultured in anoxia. Furthermore, condition media and VEGF stimulated cell migration across transwells, which demonstrates the migratory capacity of BM-hMSCs. Finally, when VEGF signaling was blocked by neutralizing anti-VEGF, vascular differentiation of BM-hMSCs was reduced to basal levels.\n\nConclusionsSoluble VEGF released in the culture media after exposure to low oxygen conditions is responsible for endothelial differentiation of BM-hMSCs.