Megakaryocyte ex vivo expansion potential of three hematopoietic sources in serum and serum-free medium

Megakaryocytes (MK) were expanded from purified human CD34(+) cells obtaine d from three sources, bone marrow (BM), mobilized peripheral blood progenit or cells (PB), and umbilical cord (UC) blood. CD34(+)-selected cells were c ultured for 12 days with 10 ng/ml thrombopoietin (TPO), 10 ng/ml IL-3, 10 n g/ml TPO + 10 ng/ml IL-3, or 200 ng/ml promegapoietin (PMP), a chimeric dua l agonist of the c-Mpl and human IL-3 receptors, MK production was compared in serum-free versus human serum-supplemented liquid media. PMP and the co mbination of TPO and IL-3 (TPO + IL-3) increased MK production similarly. C ulturing CD34(+) cells with PMP in serum-free medium resulted in a twofold increase in MK yield compared with serum-supplemented medium. CD34(+) cells from UC proliferated more than those from either BM or PB in liquid cultur e, resulting in much greater MK production under all conditions. Phenotypic analysis of the uncultured CD34(+) cells showed that BM had a higher frequ ency of CD34(+)/CD41(+) cells than PB or UC. TPO + IL-3 or PMP produced lar ger and greater numbers of BFU-MK and CFU-MK per seeded CD34(+)/CD41(+) cel l from UC than from either BM or PB. Thus, although uncultured CD34(+)-sele cted BM cells contained a higher frequency of committed mature MK progenito rs, UC CD34(+) cells had a greater proliferative capacity and, therefore, w ere more productive. PMP induced megakaryocytopoietic activity comparable t o that achieved with TPO + IL-3 and may be useful for ex vivo expansion of MK for clinical trials.