In vivo studies on the regeneration kinetics of haemopoietic spleen colony-forming cells from long-term bone marrow cultures.

Abstract

Production of murine haemopoietic progenitor cells, capable of forming colonies on the spleens of irradiated recipients (CFU-s), can be maintained in vitro for up to several months. We have examined the properties of the suspension (SUSP) and adherent (ADH) CFU-s from these long-term marrow cell cultures in the spleen colony assay system. The numbers of colonies formed was linear with the numbers of SUSP or ADH cells injected, although the concentrations were only 20-25% of that found in normal bone marrow (NBM). The seeding efficiencies for SUSP and ADH CFU-s, measured in spleen and femur 24 hr after transplantation, were not significantly different from those for CFU-s from NBM. The results demonstrate that the CFU-s assay can give valid estimates of colony-forming cell numbers in the cultured cell populations. We therefore used the CFU-s assay to study the regeneration of SUSP, ADH and NBM CFU-s in spleen and femur at various times after transplantation. The growth of the cultured cells appeared to be delayed by 36-48 hr compared to the regeneration of CFU-s from NBM. Thereafter, ADH CFU-s grew at the same rate as NBM CFU-s, whereas the rate of SUSP CFU-s regeneration was slightly, but not significantly, slower. This similarity in growth rates indicates that the CFU-s from long-term marrow cultures have similar self-renewal probabilities to normal CFU-s.