Proliferation and cell death of embryonic primitive erythrocytes

Objective, Erythropoietin (EPO) is the principal regulator for the producti on of adult-type definitive erythrocytes (EryD). EPO not only stimulates bo th the proliferation and differentiation of EryD progenitors, but also main tains the viability of EryD progenitor. Compared to the abundant knowledge about the function of EPO in EryD production, the roles of EPO in the produ ction of embryonic-type primitive erythrocytes (EryP) are less clear. Material and Methods. The effects of EPO on EryP proliferation and differen tiation were investigated using EryP purified from developing mouse embryos and the cells obtained from mouse embryonic stem cells using an in vitro d ifferentiation induction. Results. Immature EryP of both in vivo and in vitro origin responded to EPO stimulation and underwent apoptosis with EPO deprivation. In contrast, the re were no significant differences between the cultures with and without EP O, when fully mature EryP were examined, that is, EryP lost its dependency on EPO stimulation with maturation. Conclusion. These results show that EPO functions as a survival factor for immature embryonic EryP as well as immature EryD progenitors. (C) 2000 Inte rnational Society for Experimental Hematology. Published by Elsevier Scienc e Inc.