Correlation between Circulating Stem Cell Count and Stem Cell Regeneration in Locally Irradiated Bone Marrow

Stem cell regeneration in 650 R locally irradiated mouse bone marrow was studied as a function of the blood CFU level. The number of circulating stem cells was kept at a low level by total body irradiation (the locally irradiated tibia excepted) or at a high level by repeated endotoxin injections. A certain correlation between the number of circulating CFU and regeneration of CFU in locally irradiated bone marrow has been found. In the locally irradiated tibias of otherwise nontreated mice, with slightly elevated blood CFU level, CFU content was 38% of the normal value on day 12 after irradiation. In the experimental groups with a blood CFU level lower than the normal, 5-17% CFU regeneration was found. In mice with a circulating CFU number two to three times higher than the normal, CFU regeneration reached 53% of the normal level. A possible role of circulating CFU in the regeneration of locally irradiated, partially damaged bone marrow is suggested.