Further characterization of the hemin-induced enhancement of primitive erythroid progenitor cell growth in vitro.

We have previously demonstrated that hemin specifically enhances the in vitro plating efficiency of primitive murine erythroid progenitors (day 7 BFUE), whereas it does not appear to affect more mature progenitors (mature BFUE or CFUE). In this report, we further characterize the effects of hemin on marrow-derived day 7 BFUE growth in vitro. BFUE were enhanced by hemin in a dose-dependent manner and to a greater extent in methyl cellulose than in plasma clot cultures. That hemin might increase the rate of cell division was suggested by the greater size of colonies grown in its presence as well as their earlier appearance in culture. In contrast, the addition of hemin to marrow cell cultures did not appear to affect the survival rate of BFUE or their progeny. While significantly augmenting the frequency of BFUE, hemin had no consistent stimulatory effect on CFUGM. Lastly, hemin was equally capable of augmenting burst growth in adherent cell-depleted as in whole marrow cell preparations. These experiments suggest that hemin augments directly and in a cell-specific manner the proliferation and/or differentiation of primitive marrow erythroid progenitors in vitro.