International Journal of Cell Cloning, Vol 1, 206-215, Copyright © 1983 by AlphaMed Press
Decrease in hematopoietic stem cell domains as a delayed effect of x- irradiation
MA Maloney, RA Lamela and HM Patt
Although the hematopoietic integrity of locally X-irradiated sites can be
restored for a time even after fairly large doses, a secondary aplasia
often occurs some months later. To gain further insight into this delayed
effect within the framework of the stem cell regulatory domain hypothesis,
we characterized the growth kinetics of spleen colony forming units (CFU-S)
in WBB6FI-+/+ bone marrow transplanted into WBB6FI-W/WV mice in which one
leg had been exposed to 10-30 Gy of X rays 4-5 months previously. Compared
to unirradiated contralateral marrow, fewer CFU-S either reached the
previously irradiated marrow or were seeded into sites that could support
growth. The initial exponential growth of effectively seeded CFU-S was
unchanged, but growth deceleration (inflection point) occurred at a lower
level of CFU- S in marrow previously irradiated with 20-30 Gy. This change
in the inflection point indicates a radiation dose-dependent decrease
consistent with the decrease in bone marrow cellularity. The decrease in
effective stem cell domains after 20 Gy was calculated to be about 35%. We
interpret these results to reflect the highly localized nature of delayed
radiation damage to the marrow microenvironment.
