量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Background: Age–at–exposure is a critical factor that influences the risk of radiation leukemogenesis. Whereas adult C3H/He mice are prone to develop myeloid leukemia after ionizing-radiation (IR) exposure, fetal and neonatal mice are resistant. Nakano et al. reported that dose response of chromosomal translation in hematopoietic cells was not observed in mice irradiated in utero or soon after birth. They hypothesized that the fetal or neonatal hematopoietic stem cells are genetically highly sensitive to ionizing radiation, so that the aberrant cells disappear soon after IR exposure. The purpose of this study was to determine the sensitivity to IR of developing hematopoietic cells both in vitro and in vivo.
\nExperimental procedures: After in vivo gamma-ray irradiation to the 1 week-old to 14 week-old C3H/He mice, the survival of hematopoietic progenitor cells was determined by both colony forming assay in vitro using MthoCult kit and spleen colony formation assay in vivo. The gene expression profiles of bone marrow cells from 1 week-old and 8 week-old mice were also examined.
\nResults: A marked reduction in the number of colony forming cells was observed after in vivo irradiation in the 1 week-old mice; the colony forming unit-granulocyte macrophage (CFU-GM), burst-forming unit-erythroid (BFU-E) and colony forming unit-spleen (CFU-S) of irradiated 1 week-old mice were more radiosensitive than those of older ages. Interestingly, in vitro irradiation did not show age difference between 1 week-old mice to 14 week-old mice. This suggests that in vivo microenvironment and/or its response to IR critically affects the radiation sensitivity of hematopoietic progenitor cells.
Further, the gene expression profiles of bone marrow cells revealed that expression of cytokines and chemokines which can stimulate hematopoietic progenitor cell growth or survival, were reduced in 1 week-old mice compared to those of 8 week-old mice.
\nConclusion: These results demonstrate that hematopoietic progenitor cells of neonatal stage are radiation sensitive, which may associate the lack of expression of survival cytokine and chemokine after ionizing radiation.
Radiation-induced marked reduction in hematopoietic progenitor cells in infant leukemia prone C3H/He mouse
