OCT4 Remodels the Phenotype and Promotes Angiogenesis of HUVECs by Changing the Gene Expression Profile

It has been shown that forced expression of four mouse stem cell factors (OCT4, Sox2, Klf4, and c-Myc) changed the phenotype of rat endothelial cells to vascular progenitor cells. The present study aimed to explore whether the expression of OCT4 alone might change the phenotype of human umbilical vein endothelial cells (HUVECs) to endothelial progenitor cells and, if so, to examine the possible mechanism involved. A Matrigel-based in vitro angiogenesis assay was used to evaluate the angiogenesis of the cells; the gene expression profile was analyzed by an oligonucleotide probe-based gene array chip and validated by RT-QPCR. The cellular functions of the mRNAs altered by OCT4 were analyzed with Gene Ontology. We found that induced ectopic expression of mouse OCT4 in HUVECs significantly enhanced angiogenesis of the cells, broadly changed the gene expression profile and particularly increased the expression of CD133, CD34, and VEGFR2 (KDR) which are characteristic marker molecules for endothelial progenitor cells (EPCs). Furthermore by analyzing the cellular functions that were targeted by the mRNAs altered by OCT4 we found that stem cell maintenance and cell differentiation were among the top functional response targeted by up-regulated and down-regulated mRNAs upon forced expression of OCT4. These results support the argument that OCT4 remodels the phenotype of HUVECs from endothelial cells to EPCs by up-regulating the genes responsible for stem cell maintenance and down-regulating the genes for cell differentiation.