Responsiveness of bone marrow erythropoietic stem cells (CFU‐E and BFU‐E) to recombinant human erythropoietin (rh‐Ep) in vitro in aplastic anemia and myelodysplastic syndrome

Responsiveness of bone marrow erythropoietic stem cells (CFU‐E and BFU‐E) to recombinant human erythropoietin (rh‐Ep) was examined in vitro in 23 patients with aplastic anemia and 14 with myelodysplastic syndrome (MDS) to investigate the clinical use of rh‐Ep for these diseases. Bone marrow mononuclear cells were cultured by methylcellulose methods for CFU‐E and BFU‐E assays. In normals, the CFU‐E numbers reached a plateau of increase at Ep doses of almost 2–5 units, and no further increase was observed with the addition of larger Ep doses. In aplastic anemia, the responses of CFU‐E to Ep were relatively good in nonsevere type and generally poor in severe type. However, the CFU‐E numbers increased with increasing doses of Ep in some of the patients with aplastic anemia. Among the patients with MDS, the responses of CFU‐E to Ep were relatively good in primary acquired refractory anemia (PARA) and primary acquired sideroblastic anemia. On the other hand, the responses of CFU‐E to Ep were poor in refractory anemia with an excess of blasts (RAEB) and RAEB in transformation among the MDS patients. BFU‐E responses to Ep were poor in severe aplastic anemia, RAEB, and RAEB‐T. However, there are Ep responsive patients in some of aplastic anemia and PARA. High titers of rh‐Ep were suggested to be effective clinically in some patients with aplastic anemia and those with PARA.