Discovery and characterization of novel microRNAs during endothelial differentiation of human embryonic stem cells.

MicroRNAs (miRNAs) are small RNAs that participate in the regulation of genes associated with the differentiation and proliferation. In this study, 5 novel miRNAs were identified from human mesenchymal stem cells and characterized using various analyses. To investigate the potential functions associated with the regulation of cell differentiation, the differences in miRNA expression were examined in undifferentiated and differentiated human embryonic stem (ES) cells using reverse transcription (RT)-PCR analysis. Specifically, 3 miRNAs exhibited decreased expression levels in human umbilical vein endothelial cells (HUVECs) and endothelial cells derived from human ES cells. Putative target genes related to differentiation or maturation of endothelial cells were predicted by seed sequences of 2 novel miRNAs and analyzed for their expression via miRNA-mediated regulation using a luciferase assay. In HUVECs, CDH5 gene expression was directly repressed by hsa-miR-6086. Similarly, hsa-miR-6087 significantly downregulated endoglin expression. Therefore, the roles of these 2 miRNAs may be to directly suppress their target genes, popularly known as endothelial cell markers. Taken together, our results demonstrate that several novel miRNAs perform critical roles in human endothelial cell development.