Endothelial Colony-Forming Cells Promote the Biological Activity of Mature Cells by Paracrine Effects

Several studies have reported that endothelial colony-forming cells (ECFCs) have an auxo-action on ischemic injury. Previous studies have found a possible correlation between this effect and the paracrine effects of ECFCs; however, their specific influencing factors and the mechanism of action are unknown and need further research. In the present study, we isolated and cultivated ECFCs from human umbilical cord blood and identified the cells. The differential cytokine expression of ECFC conditioned medium (ECFC-CM) with various culture times and conditions was detected in human umbilical cord blood, and we observed the effect of ECFC-CM on proliferation, migration, tube formation, and angiopoietic ability of human umbilical vein endothelial cells (HUVECs) by CCK-8 assay, cell scratch test, and Matrigel tube assay. Cytokines in serum-free ECFC-CM were detected using antibody microarrays; ECFC-CM under normoxic conditions was used for comparison. According to experimental results, we found that the primary cultured cells grew like "paving stones", expressing CD34, KDR, and CD144. The primary cultured cells did not express CD45 and CD133, were ac-LDL uptake and UEA-I binding double positive, and could form tube-like structures in Matrigel. Thus, the characteristics of the primary cultured cells were consistent with those of ECFCs. Antibody microarray results showed that the expression of amphiregulin, osteoprotegerin, EGF, McP-2, HGF, and LAP and 33 angiogenic factors in ECFC-CM was significantly upregulated after 48 h of normoxic culture. The results of CCK-8 assay revealed that the proliferative activity of HUVECs in the experimental group was significantly higher than that in the control group (P < 0.01) at 24, 48, and 72 h. The cell scratch test revealed that the mobility of HUVECs in the experimental group at 12 and 24 h was statistically different (P < 0.01). Compared with the control group, the experimental group HUVECs could form more tubular structures on Matrigel matrix gel (P < 0.01). These results indicate that ECFCs can promote the biological activity of mature endothelial cells via paracrine effects.