DIFFERENTIATION OF MURINE MARROW MEGAKARYOCYTE PROGENITORS (CFUM): HUMORAL CONTROL IN VITRO

Publisher Website
Google Scholar
Abstract
Differentiation of mouse marrow megakaryocyte progenitors (CFUm) was studied in vitro by a colony assay using a plasma clot system. Erythropoietin (EPO) from sheep plasma (6 units/mg protein) in doses from 1-5 units/ml induced a linear increase in CFUm to a maximum of 20 colonies/105 cells plated. Human urinary EPO also induced a dose-responsive increase in CFUm, but the maximum was 9 colonies/105 with 2.0 units/ml of EPO and there was a decrease in colonies above that concentration. Thrombocytopoiesis-stimulating factor (TSF) derived from human embryonic kidney culture supernatant fluids induced a dose-responsive increase in CFUm in concentrations from 0.01 to 0.32 mg protein/ml in the absence of added EPO. TSF did not support the growth in vitro of erythroid colonies from mouse marrow (CFUe [erythroid colony-forming units] and BFUe [erythropoietic burst-forming cells]), indicating an absence of EPO activity. Sheep EPO appeared more effective in supporting CFUe growth than human EPO. TSF also had a stimularory function in megakaryocyte differentiation at a precursor level. Multiple humoral factors play a role in megakaryocytopoiesis in vitro.