title: Radiation-induced, cell cycle-related gene expression in aging hematopoietic stem cells: enigma of their recovery.
abstract: This paper reviews quantitative and qualitative studies conducted to identify changes in the characteristics of hematopoietic stem/progenitor cells (HSCs/HPCs) with or without radiation exposure. The numerical recovery of HSCs/HPCs after radiation exposure is lower than for other types of cells, an effect that may depend on hierarchical ordering of generation age during blood cell differentiation, from primitive HSCs to various differentiated HPCs. Studies are in progress to evaluate gene expression in bone marrow cells and cells in the lineage-negative, c-Kit(+), stem cell antigen(+) (LKS) fraction from 21-month-old mice, with or without radiation exposure. Preliminary data suggest that cell cycle-related genes, that is, cyclin D1 (Ccnd1), phosphatidylinositol 3 kinase regulatory subunit polypeptide 1 (PiK3r1), and Fyn, are upregulated solely in the LKS fraction from 21-month-old mice irradiated at 6 weeks of age, compared with the LKS fraction from age-matched nonirradiated control mice. Additional studies may provide evidence that the aging phenotype is exaggerated following exposure to ionizing radiation, specifically in the LKS fraction.
authors.affiliation: Division of Cellular and Molecular Toxicology, Center for Biological Safety and Research, National Institute of Health Sciences, Tokyo, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hirabayashi
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000235:genetics / Q000528:radiation effects; D049109:Cell Proliferation / Q000528:radiation effects; D016922:Cellular Senescence / Q000235:genetics / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000528:radiation effects*; D018816:Genes, cdc / Q000528:radiation effects*; D006412:Hematopoietic Stem Cells / Q000502:physiology* / Q000528:radiation effects*; D006801:Humans; D051379:Mice
keywords: aging; apoptosis; gene expression; hematopoietic stem/progenitor cells; radiation effects; stochasticity