Glucocorticoids Induce the Expansion of an Immature Human CFU-E Population

Despite effective clinical use, the mechanistic bases for the regulation of human erythropoiesis by glucocorticoids remain poorly understood. Here, we employed an erythroid culture system to differentiate primary human CD34+ cells isolated from control peripheral blood, cord blood and patients with Diamond Blackfan anemia (DBA), as model of an erythropoietic disorder treated with glucocorticoids. We found that the response to Dexamethasone is dependent on the developmental origin of the source of CD34+ cells, specifically increasing the expansion of CD34+ cells from peripheral blood but not cord blood. We also demonstrated that Dex treatment leads to the expansion of a novel immature colony-forming unit-erythroid (CFU-E) population in peripheral blood which is uniquely responsible for the proliferative effects observed during human adult erythropoiesis. Dex treatment of peripheral blood CFU-E cells also induced p57Kip2 expression while patients with DBA resistant to steroids had altered p57Kip2 expression that did not increase with Dex. Furthermore, shRNA knockdown of p57Kip2 reduced proliferation and abrogated the effects of Dex. Finally, proteomics of Dex-treated CFU-E from peripheral blood and cord blood additionally revealed novel Dex targets in the erythroid system. Altogether, these results provide novel insights into the regulation of human erythropoiesis by glucocorticoids.