Quantitation of the clonogenic and proliferative potential of single cord blood and adult endothelial cells derived from EPC colonies. (A) Schematic of single-cell assays using endothelial cells derived from adult or cord EPC colonies. (B) The percentage of single adult peripheral blood (AB) or umbilical cord blood (CB) EPC-derived endothelial cells undergoing at least 1 cell division after 14 days of culture. Results represent the average ± SEM of 5 independent experiments using single endothelial cells derived from different donors. ^*P < .01 by Student paired t test. (C) Average number of cell progeny derived from a single adult (AB) or cord (CB) EPC-derived endothelial cell after 14 days in culture. Results represent the average ± SEM of 5 independent experiments using single endothelial cells derived from different donors. ^*P < .01 by Student paired t test. (D) Number of cell progeny derived from a single adult (AB) or cord (CB) EPC-derived endothelial cell in an individual well after 14 days of culture. Results represent the average ± SEM of 5 independent experiments. ^*P < .01 by Student paired t test. (E) Representative photomicrographs (50 × magnification) of the different endothelial cell clusters (fewer than 50 cells) or colonies (more than 50 cells) derived from a single cord blood or adult EPC-derived endothelial cell. Results are representative of 4 other independent experiments using cells from different donors. Scale bar represents 100 μm.