GROWTH AND DIFFERENTIATION OF HUMAN STEM-CELL FACTOR ERYTHROPOIETIN-DEPENDENT ERYTHROID PROGENITOR CELLS IN-VITRO

Stem cell factor (SCF) and erythropoietin(Epo) effectively support ery throid cell development in vivo and in vitro. We have studied here an SCF/Epo-dependent erythroid progenitor cell from cord blood that can b e efficiently amplified in liquid culture to large cell numbers in the presence of SCF, Epo, insulin-like growth factor-1 (IGF-1), dexametha sone, and estrogen. Additionally, by changing the culture conditions a nd by administration of Epo plus insulin, such progenitor cells effect ively undergo terminal differentiation in culture and thereby faithful ly recapitulate erythroid cell differentiation in vitro. This SCF/Epo- dependent erythroid progenitor is also present in CD34(+) peripheral b lood stem cells and human bone marrow and can be isolated, amplified, and differentiated in vitro under the same conditions. Thus, highly ho mogenous populations of SCF/Epo-dependent erythroid progenitors can be obtained in large cell numbers that are most suitable for further bio chemical and molecular studies. We demonstrate that such cells express the recently identified adapter protein p62(dok) that is involved in signaling downstream of the c-kit/SCF receptor. Additionally, cells ex press the cyclin-dependent kinase (CDK) inhibitors p21(cip1) and p27(k ip1) that are highly induced when cells differentiate. Thus, the in vi tro system described allows the study of molecules and signaling pathw ays involved in proliferation or differentiation of human erythroid ce lls. (C) 1998 by The American Society of Hematology.