Age Dependence of Hematopoietic Progenitor Survival and Chemokine Family Gene Induction after Gamma Irradiation in Bone Marrow Tissue in C3H/He Mice

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 ...