VEGF secreted by mesenchymal stem cells mediates the differentiation of endothelial progenitor cells into endothelial cells via paracrine mechanisms.

Stem cell therapy is a promising treatment strategy for ischemic diseases. Mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) adhere to each other in the bone marrow cavity and in in vitro cultures. We have previously demonstrated that the adhesion between MSCs and EPCs is critical for MSC self‑renewal and their multi‑differentiation into osteoblasts and chondrocytes. In the present study, the influence of the indirect communication between EPCs and MSCs on the endothelial differentiation potential of EPCs was investigated, and the molecular mechanisms underlying MSC‑mediated EPC differentiation were explored. The effects of vascular endothelial growth factor (VEGF), which is secreted by MSCs, on EPC differentiation via paracrine mechanisms were examined via co‑culturing MSCs and EPCs. Reverse transcription-quantitative polymerase chain reaction and western blot analysis were used to detect the expression of genes and proteins of interest. The present results demonstrated that co‑culturing EPCs with MSCs enhanced the expression of cluster of differentiation 31 and von Willebrand factor, which are specific markers of an endothelial phenotype, thus indicating that MSCs may influence the endothelial differentiation of EPCs in vitro. VEGF appeared to be critical to this process. These findings are important for the understanding of the biological interactions between MSCs and EPCs, and for the development of applications of stem cell‑based therapy in the treatment of ischemic diseases.