Effects of amifostine on the proliferation and differentiation of megakaryocytic progenitor cells.

This study investigated the effects of amifostine, a clinically usable radioprotector or chemoprotector, on the proliferation and differentiation of normal and X-irradiated cluster of differentiation 34 positive (CD34+) megakaryocytic progenitor cells (colony-forming unit in megakaryocytes, CFU-Meg) from human placental and umbilical cord blood (CB) in vitro. Amifostine significantly accelerated megakaryocyte colony formation in a plasma clot culture supplemented with recombinant human thrombopoietin because of an increase in immature CFU-Meg-derived large megakaryocyte colony formation. An analysis of the cells that were harvested from the culture showed that amifostine induced a 70- and an 83-fold increase in the total cell and CFU-Meg numbers, respectively, and produced hyperploid megakaryocytes of more than 8 N ploidy. The radioprotective effect of amifostine on the clonal growth of X-irradiated CD34+ CFU-Meg was observed by treatment before or after irradiation. These findings suggest that the action of amifostine extends from immature CFU-Meg to the terminal differentiation of megakaryopoiesis, and its radioprotective effect is shown in megakaryopoiesis and thrombopoiesis.