Isolation of endothelial progenitor cell colonies derived from adult peripheral and umbilical cord blood. (A) Number of EPC-derived ECCs isolated per 20 mL adult peripheral blood (AB) and umbilical cord blood (CB). Results represent the mean ± SEM ECCs of 18 independent experiments for adult donors and 13 independent experiments for cord blood samples. ^*P < .0001 by Student paired t test. (B) Time of initial EPC-derived ECC appearance after culture initiation from equivalent volumes of AB and CB blood. Results represent the mean ± SEM number of days before initial ECC appearance of 18 independent experiments for AB donors and 13 independent experiments for CB donors. ^*P < .0001 by Student paired t test. (C) Representative photomicrographs (50 × magnification) of EPC-derived ECCs from mononuclear cells isolated from AB (day 17) and CB (day 9). Arrows outline a representative ECC from cord and adult blood. Similar colonies were observed from 18 other adult samples and 13 other cord blood donors. (D) Representative photomicrographs (50 × magnification) of cell monolayers derived from either adult or cord blood EPC-derived ECCs. Similar cell monolayers were observed after initial passage of EPC-derived ECCs harvested from 18 other adult donors and 13 other cord blood samples. Scale bar represents 100 μm.