A new system for the study of erythroid cell differentiation

Highly purified erythroid progenitor cells (CFU-E), were cultured in vitro for 48 h. Cell division was monitored regularly and cells were isolated at times when maximal colony formation occurred. The cell mixture after one and two cell divisions consisted mainly of proerythroblasts and basophilic erythroblasts (early erythroid cells). After four cell divisions, predominantly polychromatic and orthochromatic cells (late erythroid) were present. After two days of culture, the majority of inoculated cells had differentiated into reticulocytes. This time course in vitro was comparable to the differentiation of CFU-E in vivo. As judged by cytochrome-c oxidase activity, there was an increase in total mitochondrial activity per culture; however, the activity per cell decreased during the differentiation process. The formation of hemoglobin started after the first cell division. This system is presented as a new tool for the study of biochemical processes accompanying erythroid cell differentiation