title: Age dependence of hematopoietic progenitor survival and chemokine family gene induction after gamma irradiation in bone marrow tissue in C3H/He mice.
abstract: Age at exposure is a critical factor that influences the risk of radiation-induced leukemia, which arises from hematopoietic stem and progenitor cells. However, little is known about the effect of age on the radiation response of these cells. In this study, we examined the radiation response of hematopoietic stem and progenitor cells in infant (1-week-old), juvenile (3-week-old), and adult (8- and 14-week-old) C3H/He mice, which are susceptible to radiation-induced myeloid leukemia. We first observed an age-dependent increase in the radioresistance of hematopoietic stem and progenitor cells after in vivo irradiation. However, in vitro irradiation of progenitor cells did not show any age differences, suggesting that radiation sensitivity in vivo is dependent on the bone marrow microenvironment rather than to intrinsic properties of progenitors themselves. Expression profiles of bone marrow tissues identified chemokine and cytokine family genes, whose expression differed between infant and adult tissues at time points before and after irradiation. Among the selected thirteen cytokines reported to be radioprotective, we observed increased expression of Csf1, Csf2, Cxcl12, Fgf1, Fgf7, Il1a, Il1b and Kitl after irradiation, mostly in adult tissues. Specifically, Csf2, Fgf1 and Il1b expression, as revealed by qPCR, were significantly enhanced in adult bone marrow tissue after irradiation, but were unresponsive to irradiation in infant tissue. These results suggest that the higher susceptibility of infant hematopoietic stem and progenitor cells to the cell killing effect of ionizing radiation may be attributed to a failure to induce a subset of radioprotective cytokines in the immature bone marrow microenvironment.
authors.affiliation: Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ariyoshi
authors.forename: Takashi
authors.initials: T
authors.lastname: Takabatake
authors.forename: Mayumi
authors.initials: M
authors.lastname: Shinagawa
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kadono
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Daino
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Imaoka
authors.forename: Shizuko
authors.initials: S
authors.lastname: Kakinuma
authors.forename: Mayumi
authors.initials: M
authors.lastname: Nishimura
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Shimada
mesh_terms: D000375:Aging / Q000235:genetics* / Q000528:radiation effects; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology*; D002470:Cell Survival / Q000528:radiation effects; D018925:Chemokines / Q000235:genetics*; D005260:Female; D005720:Gamma Rays / Q000009:adverse effects*; D020869:Gene Expression Profiling; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000528:radiation effects*; D051379:Mice; D011836:Radiation Tolerance / Q000502:physiology; D015533:Transcriptional Activation / Q000528:radiation effects*
chemical_list: D018925:Chemokines