Two-phase liquid culture system models normal human adult erythropoiesis at the molecular level

We have studied the patterns of expression of various genes during maturation of normal human adult erythroid precursors cultured in a two-phase liquid culture method. In the first phase, peripheral blood mononuclear cells are cultured for one week in the presence of a combination of growth factors, but not erythropoietin (Epo). In Phase II, Epo is included in the medium. Cell samples were taken throughout phase II, and expression of globins, transcription factors, and cytokine receptors was assayed by RT-PCR and quantified by phosphor imaging. We have divided phase II into stages: early (days 0-5), intermediate (days 6-10) and late (days 11-15) and measured maximum expression of each gene. During early phase II, gamma-globin, Sp1, and GATA-2 mRNAs were expressed at their highest levels. As the cells matured during the intermediate period, GATA-2 levels remained high, and then declined, while the transcription factors GATA-1, EKLF, NF-E2, and the Epo receptor (EpoR) reached maximum expression. In late phase II, beta-globin increased and reached its maximum level of expression. This erythroid culture system appears to recapitulate normal adult erythropoiesis at the molecular level, and thus may be a suitable model to examine the molecular basis of severe congenital or acquired disorders of erythropoiesis.