Proliferative response toward angiogenic factors of EPCs. cbEPCs at different passage numbers (P4, P6, P9, P12, and P15) were seeded on FN-coated plates in EMB-2 supplemented with 5% FBS (control medium). After the initial 24-hour period, cells were treated with control medium in the presence or absence of either 10 ng/mL VEGF or 1 ng/mL bFGF and assayed for cell number after 48 hours. Each bar represents the mean of 3 separate cultures ± SD, with values normalized to the values of cell density obtained at 24 hours when treatment began. *P < .05 compared with control. †P < .05 compared with equivalent treatment on HDMECs.