Promotion of survival and proliferation by interleukin 3, kit-ligand and erythropoietin on early and late appearing spleen colony forming units in culture

Abstract

We examined the effects of interleukin 3 (IL-3), kit-ligand and erythropoietin (EPO) on the survival and growth of early appearing spleen colony forming units (CFU-S8) and late appearing CFU-S (CFU-S12) in short-term liquid culture (SLC). In the control cultures, without any additive, CFU-S8 and CFU-S12 declined; nearly 10% of the initial number of CFU-S still survived by the second day of culture. The addition of IL-3 or kit-ligand increased the survival both of CFU-S8 and CFU-S12, with an increased dose of concentration, at final concentrations of 10-200 U/ml and 500-50x dilution, respectively. However, only the survival of CFU-S8 increased when EPO was added up to 10 U/ml, while the frequency of CFU-S12 was not higher than in the control culture. The percentage of CFU-S8 and CFU-S12 in DNA synthesis, evaluated in 3H-TdR cytocide experiments, increased after one day in culture with each of the three factors. The results suggest that all three factors stimulated the proliferation of both populations of CFU-S, but the two populations showed different patterns of response to each factor; EPO stimulates the proliferation of CFU-S12 that differentiate into CFU-S8 that have less capacity for self-renewal, while the addition of IL-3 or kit-ligand causes an increase in the number of both populations due to the stimulation of an earlier stage of stem cell differentiation or self-renewal of CFU-S12. Our experimental system (SLC-CFU-S assay) is useful for evaluating the response of hematopoietic stem cells to cytokines which promote the in vitro survival and proliferation of these cells.