Comparison between type-I vascular endothelial cells (VECs) and type-II VECs

Human VECs are categorized into two groups regarding their effects on the proliferation of vascular smooth muscle cells (VSMCs):type-I, pro-proliferative VECs and type-II anti-proliferative VECs. The effects of VECs on VSMC proliferation were quantitatively assessed according to the following method: human aortic smooth muscle cells, which were stained by PKH-26 in advance, were cultured on the layer of CFSE-stained VECs, and VSMC proliferation were evaluated after four days by flow cytometry analyses using ModFit LT™ software (Verity Software House Inc., Topsham, ME). Commercially available primary human VECs including HUVEC, HAEC and HMVEC as well as the majority of endothelial progenitor cell (EPC)-derived VECs (EPCdECs), whether EPCs were obtained from adult or fetal tissues, enhanced VSMC proliferation, showing type-I phenotype. EPCdECs of minor donors including EPC1dEC suppressed VSMC proliferation, showing type-II phenotype. However, type-II VECs turned into type-I VECs after a few rounds of subcultures. Comparative analyses on gene expression profiles between type-I VECs and type-II VECs revealed that regulator of G-protein signaling 5 (RGS5) was the only gene that showed the discriminative expression pattern: high expressions in type-I VECs and low expressions in type-II VECs. Totally six samples of type-I VECs (HUVEC, HAEC, HMVEC, EPC1dEC[P12], UCEPC1dEC, EPC2dEC[P7]) and two samples of type-II VECs (EPC1dEC[P7] and EPC1dEC[P7] purchased at a different time point) were subjected to the analyses.