HIF-1synergizes with glucocorticoids to promote BFU-E progenitor self-renewal

With the aim of finding small molecules that stimulate erythropoiesis earlier than erythropoietin and that enhance CFU-E production, we studied the mechanism by which glucocorticoids increase CFU-E formation. Using BFU-E and CFU-E progenitors purified by a new technique, we demonstrate that glucocorticoids stimulate the earliest (BFU-E) progenitors to undergo limited self-renewal, which increases formation of CFU-E cells > 20-fold. Interestingly, glucocorticoids induce expression of genes in BFU-E cells that contain promoter regions highly enriched for hypoxia-induced factor 1 alpha (HIF1a) binding sites. This suggests activation of HIF1a may enhance or replace the effect of glucocorticoids on BFU-E self-renewal. Indeed, HIF1a activation by a prolyl hydroxylase inhibitor (PHI) synergizes with glucocorticoids and enhances production of CFU-Es 170-fold. Since PHIs are able to increase erythroblast production at very low concentrations of glucocorticoids, PHI-induced stimulation of BFU-E progenitors thus represents a conceptually new therapeutic window for treating Epo-resistant anemia. RNA-Seq was performed on enriched populations of BFU-E, CFU-E and Ter119+ as well as BFU-E enriched cells treated with Dex and DMOG