Erythropoietin and hydroxyurea can act on early erythroid progenitors from adult human peripheral blood to modulate fetal globin mRNA levels.

Fetal hemoglobin production in adult human erythroid progenitors can be influenced by exogenous factors. In this report, we examine the effects of erythropoietin (Epo) and hydroxyurea (HU) in serum-free media on fetal (gamma-) globin mRNA levels when present during the first week of peripheral blood burst-forming unit-erythroid (BFU-E) culture. Fetal calf serum (FCS) is known to elevate gamma-globin mRNA levels in BFU-E culture and has been shown to do so even when added after the first week of culture. Removal of FCS from the first week of our BFU-E cultures did not significantly reduce gamma-globin mRNA levels, in agreement with these earlier findings. Addition of Epo to BFU-E cultures 4 days before addition of FCS led to a significant drop in gamma-globin mRNA levels; Epo addition also led to a significant increase in the number of erythroid bursts. Culture conditions, including Epo in serum-free liquid medium for 1 week followed by plating in semisolid medium containing FCS and Epo, resulted in low gamma-globin mRNA levels, similar to levels found in vivo, and high burst numbers. These conditions were used to demonstrate significant elevation of gamma-globin mRNA levels by HU present during the first week of BFU-E culture. Our findings suggest that gamma-globin mRNA levels can be influenced early in erythropoiesis by Epo and HU.