Phenotypic and proliferative modulation of human mesenchymal stem cells via crosstalk with endothelial cells.

The purpose of this work was to investigate if a coculture system of human mesenchymal stem cells (hMSC) with endothelial cells (human umbilical vein endothelial cells, HUVEC) could modulate the phenotype and proliferation of harvested MSCs. In addition to previous investigations on the crosstalk between these two cell types, in the present work different relative cell ratios were analyzed for long, therapeutically relevant, culture periods. Moreover, MSCs osteogenic commitment was assessed in a non-osteogenic medium and in the presence of HUVECs through magnetic cell separation, cell quantification by flow cytometry, morphology by fluorescent microscopy, metabolic activity and gene expression of osteogenic markers. Collectively, the present findings demonstrate that, by coculturing MSCs with HUVECs, there was not only the promotion of osteogenic differentiation (and its enhancement, depending on the relative cell ratios used), but also a significant increase on MSCs proliferation. This augmentation in cell proliferation occurred independently of relative cell ratios, but was favored by higher relative amounts of HUVECs. Taken together, this data suggests that HUVECs not only modulate MSC phenotype but also their proliferation rate. Therefore, a coculture system of MSCs and HUVECs can a have a broad impact on bone tissue engineering approaches.