Thrombopoietic factor enhances murine megakaryopoiesis induced by recombinant erythropoietin.

Partially purified thrombopoietic factor (TPF) potentiated in vitro murine megakaryopoiesis induced by recombinant human erythropoietin (rh-Epo). High doses (2.5-10 units) of rh-Epo generated a considerable number of megakaryocytes in a dose-dependent manner in a serum-free liquid culture, whereas low doses of rh-Epo (0.5-1 units) failed to generate megakaryocytes. The addition of high doses of rh-Epo and TPF caused a significant increase of megakaryocytes in comparison with high doses of rh-Epo alone. Furthermore, low doses of rh-Epo with TPF caused generation of a small number of megakaryocytes, although TPF alone did not generate megakaryocytes. In addition, TPF enhanced the acetylcholinesterase (Ach-E) activity of megakaryocytes induced by rh-Epo. The potentiating effects of both factors, rh-Epo and thrombopoietic factor, may play an important role in thrombocytopenic states in vivo as well as in in vitro megakaryopoiesis.