Effect of Epo treatment on peripheral progenitor cells. Epo treatment for 3 days significantly increased the number of GM-CFUs in spleen (A) and peripheral blood (B). FACS analysis showed that Epo dose-dependently enhanced the number of CD34⁺/flk-1⁺ cells in spleen (C) and peripheral blood (D). Consistently, a similar increase in the number of peripheral EPCs was observed in the EPC culture assay for spleen (E) and peripheral blood mononuclear cells (F). Data are shown as means ± SD.