Self‐maintenance capacity of CFU‐S

Abstract

The numbers of CFU-S which developed in spleen colonies were measured 11 days after injection of irradiated mice with marrow from normal mice or mice which had been treated in one of a variety of ways. The broad spread of CFU-S numbers, seen by other authors, in colonies derived from normal marrow was confirmed. However, the range and distribution of CFU-S per colony was generally different in colonies derived from the marrow of mice which were recovering or had recovered from some form of depopulation. From the data obtained, the mean CFU-S/colony, M1, and the probability of self-renewal, p, of the CFU-S were calculated. These values are used to calculate the number of cell cycles undergone during development of the colony and, by making certain assumptions, the cell cycle time of the CFU-S. The plot of p against log M for the various samples measured should be linear if all CFU-S proliferate at the same rate in a growing colony. It is not linear, however, so that CFU-S obtained under different experimental conditions do not all undergo the same number of cycles. In general, treatments given to the mice result in a lowering of the capacity for self-renewal of their CFU-S and also to a shortening of their cell cycle time. Some of the possible implications of these findings are discussed.

Cells with marrow and spleen repopulating ability and forming spleen colonies on day 16, 12, and 8 are sequentially ordered on the basis of increasing rhodamine 123 retention

“…MRA cells therefore meet the criteria for genuine pre-CFU-S. Accepting the existance of a pre-CFU-S, it is plausible that the amply reported differences in selfrenewal capacity of CFU-S (Worton et al, 1969;Schofield and Lajtha, 1973;Micklem et al, 1975;Rosendaal et al, 1976Rosendaal et al, , 1979Hellman et al, 1978;Hodgson and Bradley, 1979;Schofield et a]., 1980;Johnson and Nicola, 1984;Mulder and Visser, 1987) should be explained at least partly by assuming various admixtures of pre-CFU-S in the cell populations studied. In addition, the previously proposed mechanisms of CFU-S self-renewal and differentiation need reappraisal.…”

True

“…53 We have previously shown significant in vivo protection of day 12 CFU-S against the toxic effects of the methylating agent temozolomide, in combination with O 6 -beG, following reconstitution of mice with bone marrow which had been induced to express hATPA/GA as a result of retroviral gene transfer. 49 In the present study, we have investigated the ability of hATPA/GA expression to provide protection against BCNU, which has been used in a number of preclinical studies by other workers and is a potential agent for use in a clinical trial of ATase-mediated myeloprotection.…”

“…The day 12 CFU-S, under certain conditions of transplantation, can exhibit long-term repopulating ability despite their relatively low self-maintenance capacity. 53,54 Thus, while most day 12 CFU-S have only a transient reconstitution potential, 53,54 they are nonetheless somewhat characteristic of the multipotent cells that represent the ideal target for genetic chemoprotection. These studies showed a reduction in toxicity even in the presence of O 6 -beG.…”

“…These observations have stimulated interest in a clinical trial to protect bone marrow against BCNUinduced myelosuppression, even though evidence of enhanced resistance to BCNU in multipotent haemopoietic progenitors has not yet been reported. Recently, we have investigated whether expressing a mutant of hAT (hATPA/GA) 51,52 that is essentially resistant to O 6 -beG in bone marrow of mice can protect day 12 spleen colony-forming cells (CFU-S) 53 from the toxic effects of temozolomide. The day 12 CFU-S, under certain conditions of transplantation, can exhibit long-term repopulating ability despite their relatively low self-maintenance capacity.…”

A possible change in doubling time of haemopoietic progenitor cells with stem cell development

“…Previous studies using 3 H-thymidine labelling and CFU-S assay explored the kinetics of growth of haemopoietic progenitors (Testa & Lord, 1973;Schofield et al, 1980). In prior studies we found that the doubling time of haemopoietic progenitors can be modulated by growth factors, determined by monitoring the proliferative kinetics of haemopoietic progenitors during the early phase of an in vitro clonal assay (Tanaka et al, 1995;Ohishi et al, 1996).…”