In vitro culture of proerythroblasts: characterization of proliferative response to erythropoietin and steroids.

This study characterized variables affecting the in vitro liquid culture of proerythroblasts. When bone marrow from mice depleted of haemoglobin containing cells, was cultured in vitro in the presence of human urinary erythropoietin (Ep) a significant degree of erythroid cell proliferation and maturation occurred as measured directly by 3H-thymidine (3H-TdR) incorporation into DNA (autoradiographical measurement). Proliferation increased in direct proportion to the dose of Ep added to the culture. We also demonstrated a highly significant positive correlation between proliferation measured directly by 3H-TdR incorporation into DNA or indirectly by 59Fe incorporation into haem. Ep was a potent stimulator of proerythroblast proliferation. We also examined the role of the androgenic and non-androgenic steroids on in vitro proliferation. All the hormones tested were stimulatory but only in the presence of Ep. The androgenic steroids primarily affected the more mature erythroid precursors whereas the glucocorticoids were more general growth promoters. Their addition in physiologic concentration to liquid culture reduced Ep requirements. Thus when both testosterone and hydrocortisone were added to culture the Ep concentration that produced the same degree of proliferation as a culture containing Ep alone was decreased by 90%. This finding is important as it indicates that in vitro culture conditions can be created that more closely mimic in vivo erythropoiesis where Ep requirements are far less.