Murine haemopoietic stem cells with long-term engraftment and marrow repopulating ability are more resistant to gamma-radiation than are spleen colony forming cells.
The radiation sensitivity of various subsets in the haemopoietic stem cell hierarchy was defined using a limiting dilution type long-term bone marrow culture technique that was previously shown to allow quantification of cells with spleen colony-forming potential (day-12 CFU-S) and in vivo marrow repopulating ability (MRA). Primitive stem cells that generate new in vitro clonable colony-forming cells (CFU-C) in the irradiated marrow (MRA) and have long-term repopulation ability (LTRA) in vitro (cobblestone area forming cell, CAFC day-28) had D0 values of 1.25 and 1.38 Gy, respectively. A lower D0 was found for the less primitive CFU-S day-12, CAFC day-12 and cells with erythroid repopulating ability (0.91, 1.08 and 0.97 Gy, respectively). CFU-S day-7 were the most radiosensitive (D0 equalling 0.79 Gy), while CFU-C and CAFC day-5 were relatively resistant to irradiation (D0 1.33 and 1.77 Gy). Split-dose irradiation with a 6 h interval gave dose sparing for stem cells with MRA and even more with in vitro LTRA, less for CFU-S day-12 and CAFC day-10 and none for CFU-S day-7. The cell survival data of the specified stem cell populations were compared with the ability of a fixed number of B6-Gpi-1a donor bone marrow cells to provide for short- and long-term engraftment in single- and split-dose irradiated congenic B6-Gpi-1b mice. Serial blood glucose phosphate isomerase (Gpi) phenotyping showed less chimerism in the split as compared to the single radiation dose groups beyond 4 weeks after transplant. Radiation dose-response curves corresponding to stable chimerism at 12 weeks for single and fractionated doses revealed appreciable split-dose recovery (D2-D1) in the order of 2 Gy. This was comparable to D2-D1 estimates for MRA and late-developing CAFC (1.27 and 1.43 Gy, respectively), but differed from the poor dose recovery in cells corresponding to the committed CFU-S day-7/12 and CAFC day-10 population (0.14-0.33 Gy). These data are together consistent with differential radiosensitivity and repair in the haemopoietic stem cell hierarchy, and provide a cellular basis for explaining the dose-sparing effect of fractionated total-body irradiation conditioning on long-term host marrow repopulation.
Ploemacher
R E
RE
Department of Cell Biology II, Erasmus University, Rotterdam, The Netherlands.
van Os
R
R
van Beurden
C A
CA
Down
J D
JD
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D002588:Cesium Radioisotopes; D005720:Gamma Rays; D006412:Hematopoietic Stem Cells / Q000000981:diagnostic imaging* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011836:Radiation Tolerance / Q000502:physiology*; D011859:Radiography; D013154:Spleen / Q000166:cytology*; D013234:Stem Cells / Q000502:physiology / Q000528:radiation effects*
D002588:Cesium Radioisotopes