Recombinant human erythropoietin activates a broad spectrum of progenitor cells.

Twenty uremic patients on regular hemodialysis received recombinant human Erythropoietin (rhEPO) in a dosage of 50 U/kg body wt (N = 9) and 80 U/kg body wt (N = 11), respectively, three times weekly. The number of circulating hemopoietic progenitor cells colony-forming unit-granulocyte-erythrocyte-macrophage (CFU-mix), burst-forming unit-erythroid (BFU-E) and colony-forming-granulocyte-macrophage (CFU-GM) in peripheral blood were assayed weekly by means of a commonly applied in vitro clonal assay. A significant increase of peripheral CFU-mix, BFU-E and CFU-GM could be observed within one week of supplementation therapy in both groups. The increase of BFU-E was followed by a rise of hematocrit within four and three weeks, respectively. These results suggest that the stimulatory in vivo effect of rhEPO administered in therapeutical doses is not restricted to the erythroid lineage but also includes progenitor cells committed to the myeloid lineage (CFU-GM) as well as the multipotent progenitors CFU-mix. The increment of circulating progenitor cells was seen with a dosage of 80 U/kg body wt and 50 U/kg body wt as well.