Erythropoiesis in murine long-term bone-marrow cell cultures: dependence on erythropoietin and endogenous production of an erythropoietic stimulating activity.

Erythropoiesis was obtained in murine long-term bone-marrow cell cultures (LTBMCs) in the presence of erythropoietin (Epo) when the medium was frequently renewed. The level of the erythropoietic differentiation was shown to be a function of the erythropoietin concentration. In response to Epo addition, an activity which stimulates CFU-E proliferation in semisolid cultures of fresh bone marrow cells was detected in the LTBMC supernatants. These results suggest that another factor, whose synthesis may be under Epo control, participates in the stimulation of erythropoiesis in vitro.

Normal human serum stimulates murine erythroid precursor growth in in vitro culture.

When introduced into cultures of murine CFU-E human sera inhibited the formation of erythroid colonies. However, after absorbtion on murine cells and heating all tested sera became stimulatory. Crude sera were separated into two fractions by DEAE chromatography: the first fraction was stimulatory. The second was toxic but the toxicity could be eliminated by heating; the fraction then became slightly stimulatory. Attempts at characterizing the molecular weight of the stimulatory activity led to variable results, suggesting either that the stimulatory activity(ies) could polymerize or be fixed on different serum proteins. All sera from 11 different anemic patients were also shown to be stimulatory.