International Journal of Cell Cloning, Vol 6, 116-124, Copyright © 1988 by AlphaMed Press
Observations on the contributions of environmental restraints and innate stem cell ability to hematopoietic regeneration
JS Duke-Cohan
Lautenberg Center for General and Tumor Immunology, Hebrew University- Hadassah Hospital Medical School, Jerusalem, Israel.
A competitive repopulation assay utilizing chromosome markers was used to
assay the reconstituting potential of hematopoietic populations. The test
populations consisted of tibial murine marrow locally irradiated with doses
ranging from 1.5 Gy to 8.5 Gy and of marrow generated from either murine
splenic or marrow stem cells. The purpose of this assay was to assess the
innate proliferative potential and microenvironmental influences on the
ability to repopulate. Regardless of origin, spleen repopulating ability
consistently agreed with spleen colony-forming unit (CFU-s) content. Doses
of radiation from 5 Gy to 8.5 Gy diminished, by a factor of 2, the ability
to repopulate marrow despite maintenance of CFU-s levels. Marrow generated
from splenic stem cells had one-fifth the repopulating ability of marrow
derived from marrow stem cells, even though CFU-s levels were equivalent.
The results imply that the splenic environment can only maintain stem cells
at the level of the CFU-s, even if the stem cells were originally of higher
quality, and that their original potential cannot be regained in a marrow
environment. Nevertheless, the marrow can maintain more primitive stem
cells, but this reserve is drained to support CFU-s levels.
