Effect of rhEPO on EPCs in vitro. (A) Quantitative assessment of cultured endothelial progenitor cells (EPCs) of 2 healthy subjects with supplementation of rhEPO in the cell culture medium. With supplementation of 1.2 IU rhEPO/mL to the medium, we observed a significant, approximately 2-fold increase in the total number of EPCs (*P < .05 versus baseline). (B) Representative Western immunoblots of Akt phosphorylation are shown as time-dependent changes in Akt phosphorylation at Ser473 after exposure of EPCs to rhEPO (1.2 IU/mL).