Erythroid progenitor cells and cells capable of producing erythropoietic activity from fetal mouse liver

Trypsin dissociation of fetal mouse liver proved successful in obtaining a single cell suspension of fetal liver which upon culture was capable of producing an erythropoietic stimulating activity (ESA). A cell dose response for the erythropoietic activity was obtained with increased plating of fetal liver cells. In addition, conditioned media from trypsin dissociated fetal liver cultures were capable of stimulating erythroid colony formation (CFU(E)) from both mouse bone marrow cells and mouse fetal liver cells. A dose response for (CFU(E)) was seen with mouse fetal liver as target cells and a correlation between the in vivo bioassay and in vitro (CFU(E)) assay was also demonstrated. Serial trypsin digestion of fetal mouse liver tissue resulted in a cell population which contained less erythroid cells. Greater amounts of erythropoietic activity were found in conditioned media obtained from these cell populations. Kinetic studies, using cells obtained from 60 to 140 min of trypsin digestion, demonstrated that the number of cells per flask and the amount of ESA/flask present in the conditioned media increased with time in culture. Thus, ESA was being produced and released by the cultured fetal hepatic cells. Erythroid colony forming cells (BFU(E) and CFU(E)) were also present in trypsin dissociated fetal liver tissue with both erythroid progenitors exhibiting an erythropoietin dose response. CFU(E) demonstrated a cell dose response both in the presence and absence of added erythropoietin while BFU(E) were not expressed in the absence of erythropoietin. These studies suggest that trypsin digestion does not alter the ability of fetal liver cells to produce erythropoietic stimulating activity nor does it alter the capability of fetal liver cells to form erythroid colonies in vitro. In addition, the erythropoietic stimulating activity obtained from fetal liver cultures was capable of stimulating both in vivo and in vitro erythropoiesis.