Human erythropoietin stimulates murine megakaryopoiesis in serum-free culture.

: Recombinant erythropoietin (Epo) was capable of stimulating murine megakaryopoiesis both in serum-containing and serum-free cultures, although a relatively high amount of Epo was necessary to provide sufficient stimulus for colony growth. This observation was further confirmed by experiments using nonadherent, nonphagocytic, and T-cell-depleted marrow cells in which Epo stimulated the growth of single megakaryocytes, as well as clusters or colonies. Total plate analysis revealed that twice as many single megakaryocytes and two-cell aggregates were generated by Epo than generated by pokeweed mitogen-stimulated spleen cell-conditioned medium (PWM-SCM). The number of colonies with four or more cells formed by PWM-SCM, however, was significantly higher than that generated by Epo. These results suggest that in comparison to the factor(s) in PWM-SCM, Epo stimulates the growth of more mature progenitors.