Peripheral blood mononuclear cells (PBMC)-derived endothelial colony-forming cells (ECFC) have characteristic endothelial immunophenotype and considerable tube-forming activity in Matrigel. (A) Flow cytometry immunophenotyping (representative graphs) found both ECFC and human umbilical vein endothelial cells (HUVEC) having CD31+vWF+KDR+CD146+CD34-CD133-CD45-CD90- expression signature suggestive of endothelial identity. Black color defines isotype control while red color is for specific staining; (B) Confocal microscopy (representative images) corroborates flow cytometry results demonstrating CD31-positive (red color, cell surface receptor) and vWF-positive (green color, Weibel–Palade bodies inside the cytosol) ECFC and HUVEC. Nuclear counterstaining was performed using 4′,6-diamidino-2-phenylindole (DAPI, blue color); (C) Phase contrast microscopy (representative images). Both ECFC and HUVEC have pronounced capability to assemble capillary-like tubes in Matrigel; (D) Semi-quantitative analysis of the tube-forming activity from the experiment in C. Each dot represents a representative image from one well of the culture plate (n = 5 wells per group). Whiskers indicate range, box bounds indicate 25th and 75th percentiles, center lines indicate median. P values are provided above the graphs in a numerical manner according to Mann–Whitney U test.