Stable chromosomal aberrations in haemopoietic stem cells in the blood of radiation accident victims

Purpose: The detection of long-term persistent chromosome aberrations in ci rculating haemopoietic stem cells after accidental radiation exposure. Material and Methods: Peripheral blood samples from highly exposed persons were collected 7-25 years after the radiation accidents in Moscow (1971), K azan (1975) and Chernobyl (1996). Haemopoietic blood stem cells were analys ed when investigating individual colonies derived from haemopoietic progeni tor cells: burst-forming units-erythroid (BFU-E), granulocyte-macrophage-co lony-forming cells (GM-CFC) and multipotent granulocyte-erythrocyte-macroph age-megakaryocyte-colony-forming cells (GEMM-CFC). Colony formation was obt ained in methylcelluose cultures. Chromosome preparations in single colonie s were performed using a microtechnique. Results: Nine patients were investigated at 1 to 4 follow-up time points af ter radiation exposure. Three hundred and thirty-four single colonies were analyzed resulting in 1375 mitoses. It was found that colonies showed chrom osome aberrations (ChA) up to 25 years after radiation exposure by classica l cytogenetics and by fluorescence in situ hybridization (FISH). Stable abe rrations were detected in 21% of colonies. They were clonal in 19% of colon ies, i.e. the same abnormality was found in all cells derived from a single colony. In 2% of colonies ChA were stable but non-clonal; unstable ChA wer e not observed. Conclusions: The results indicate that blood-derived haemopoietic stem cell s may serve as a biological indicator to detect radiation-induced ChA. Sinc e they are considered to be in dynamic and Functional exchange with stem ce lls in the medullary sites of blood cell formation such as bone marrow, the use of blood stem cells as a marker of radiation effects should be explore d to assess the repair status of the stem cell pool as such.