Are stem cells exposed to ionizing radiation in vivo as effective as nonirradiated transfused stem cells in restoring hematopoiesis?
Are the stem cells that survive graded doses of ionizing radiation as effective in restoring hematopoiesis in irradiated mice as transfused nonirradiated stem cells? This question was addressed by determining animal dose mortality and 10-day colony-forming units (CFU-S) survival curves and then replotting the percent animal survival against the number of CFU-S surviving the different doses of radiation, and by determining the number of nonirradiated CFU-S injected into fatally irradiated mice that result in a CFU-S dose mortality response curve. The number of CFU-S surviving per mouse after doses of radiation resulting in 95, 50 and 5% animal survival were calculated to be 520, 300 and 153, respectively. From the transfused CFU-S dose mortality curve of otherwise fatally irradiated mice (8.5 Gy), the number of transfused normal CFU-S required for 95, 50 and 5% animal survival was estimated to be 153, 24 and 3, respectively. The ratios of surviving CFU-S to nonirradiated, injected CFU-S are: at 95% survival (6.3 Gy), 3.4; at 50% survival (6.88 Gy), 12.5; and at 5% survival (7.4 Gy), 51.0. These data show that, in addition to a reduced number of CFU-S, as radiation dose increases, the quality of surviving CFU-S responsible for 30-day survival decreases. By implication, the long-term repopulating cell (LTRC) that is now known not to be the 10-day CFU-S must also decrease.
Cronkite
E P
EP
Medical Department, Brookhaven National Laboratory, Upton, NY 11973.
Inoue
T
T
Hirabayashi
Y
Y
Bullis
J
J
D000818:Animals; D016913:Blood Component Transfusion; D001854:Bone Marrow Cells; D002470:Cell Survival / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D004307:Dose-Response Relationship, Radiation; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000502:physiology* / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D033581:Stem Cell Transplantation; D013997:Time Factors