EPCs are less sensitive to oxidative stress–induced apoptosis as compared with HUVECs or CD14⁺ monocytes. EPCs and HUVECs were incubated with (A) LY-83583 or (B) H₂O₂ for 18 hours. (C) EPCs, HUVECs, and HMVECs were incubated with serum-free medium for 18 hours. (A-C) Apoptosis was detected by annexin-V staining using FACS analysis. Data are mean ± SD, n = 3-6. *P < .05 versus control, #P < .05 versus EPCs with same treatment, **P = .07 versus control.