Hypoxia maintains and interleukin-3 reduces the pre-colony-forming cell potential of dividing CD34(+) murine bone marrow cells.
OBJECTIVE
The aim of this study was to determine whether the combination of a sizable generation of colony-forming cells (CFC) with the maintenance of their progenitors (pre-CFC) ensured by incubation in hypoxia is associated with a certain degree of cell cycling, ultimately responsible for "self-renewal" of pre-CFC. The effects of interleukin-3 (IL-3) on the cycling and CFC-generation potential of pre-CFC also was investigated.


METHODS
In severely hypoxic (0.9% O(2)) murine bone marrow cell cultures containing stem cell factor, interleukin-6, and granulocyte colony-stimulating factor, pre-CFC maintenance was characterized by the culture-repopulating ability assay, an in vitro analogue of the marrow-repopulating ability assay. The proliferative history of CD34(+) cells in primary cultures was determined by PKH2 staining and related to their CFC-generation potential. In some experiments, subsets of CD34(+) cells sorted on the basis of the number of cell divisions (0, 1, >1) were independently characterized.


RESULTS
In hypoxia, the numbers of CFC and CD34(+) cells were markedly reduced, whereas pre-CFC were maintained better than in air. Addition of 5-fluorouracil to hypoxic cultures for 2 days suppressed their CFC-generation potential. The CFC-generation potential of divided CD34(+) cells was maintained or increased with respect to that of undivided cells in hypoxia but not in air. IL-3 decreased CFC-generation potential at both oxygen concentrations. IL-3 also increased the number of CD34(+) cells that divided more than once in hypoxia, decreasing their CFC-generation potential.


CONCLUSIONS
Maintenance of CFC-generation potential in hypoxia occurs mainly in a subset of cycling progenitors, despite their proliferation (self-renewal). IL-3 decreased CFC-generation potential by increasing the rate of pre-CFC proliferation beyond the first cycle, which probably results in their differentiation and loss of CFC-generation potential.
Ivanovic
Zoran
Z
Laboratoire Universitaire d'Hématologie, Université Victor Segalen Bordeaux 2, Bordeaux, France.
Belloc
Francis
F
Faucher
Jean-Luc
JL
Cipolleschi
Maria-Grazia
MG
Praloran
Vincent
V
Dello Sbarba
Persio
P
D000818:Animals; D018952:Antigens, CD34; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D015687:Cell Hypoxia; D002478:Cells, Cultured; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D007377:Interleukin-3 / Q000494:pharmacology*; D051379:Mice; D008808:Mice, Inbred CBA
D018952:Antigens, CD34; D007377:Interleukin-3