| Abstract: | The decision of the differentiation pathways taken by pluripotent stem cells seems to be under the influence, at least in part, of humoral factors acting at the CFU-S level. This differentiation is assessed by histological examinations of the recipient spleen colonies in order to determine the E/G ratios. In vitro cultures are made to determine GM-CFC and BFUE concentrations. After AraC treatment, CFU-S differentiate preferentially towards erythropoiesis. After total body irradiation, preferential differentiation is toward granulopoiesis. In both cases, there is a competitive phenomenon between the two cell lineages. This is observed in vivo and also in the in vivo-in vitro experiments where the responder cell population is in contact only with the eventual diffusible factors and not with the secreting cells or with the drug. These factors do not seem to be EPO, in the case of AraC, nor GM-CSF in the case of irradiation. We therefore suggest that humoral mediators other than those acting at the progenitor cell level can modulate CFU-S differentiation in a specific way after various types of aggression to the bone marrow. |
