We defined the time course of ionizing radiation-induced senescence in lung compared to bone marrow of p16^+/LUC mice in which the senescence-induced biomarker (p16) is linked to a luciferase reporter gene. Periodic in situ imaging revealed increased luciferase activity in the lungs of 20 Gy thoracic irradiated, but not 8 Gy total-body irradiated (TBI) mice beginning at day 75 and increasing to day 170. In serial sections of explanted lungs, senescent cells appeared in the same areas as did fibrosis in the 20 Gy thoracic irradiated, but not the 8 Gy TBI group. Lungs from 8 Gy TBI mice at one year did show increased RNA levels for p16, p21, p19 and TGF-β. Individual senescent cells in 20 Gy irradiated mouse lung included those with epithelial, endothelial, fibroblast and hematopoietic cell biomarkers. Rare senescent cells in the lungs of 8 Gy TBI mice at one year were of endothelial phenotype. Long-term bone marrow cultures (LTBMCs) were established at either day 60 or one year after 8 Gy TBI. In freshly removed marrow at both times after irradiation, there were increased senescent cells. In LTBMCs, there were increased senescent cells in both weekly harvested single cells and in colonies of multilineage hematopoietic progenitor cells producing CFU-GEMM (colony forming unit-granulocyte, erythrocyte, monocyte/macrophage, mega-karyocyte) that were formed in secondary cultures when these single cells were plated in semisolid media. LTBMCs from TBI mice produced fewer CFU-GEMM; however, the relative percentage of senescent cell-containing colonies was increased as measured by both p16-luciferase and β-galactosidase. Therefore, 20 Gy thoracic radiation, as well as 8 Gy TBI, induces senescent cells in the lungs. With bone marrow, 8 Gy TBI induced senescence in both hematopoietic cells and in colony-forming progenitors. The p16^+/LUC mouse strain provides a valuable system in which to compare the kinetics of radiation-induced senescence between organs in vivo, and to evaluate the potential role of senescent cells in irradiation pulmonary fibrosis.

我们定义了与 p16 ^+/LUC小鼠的骨髓相比，电离辐射诱导的肺部衰老的时间过程，其中衰老诱导的生物标志物 (p16) 与荧光素酶报告基因相关。定期原位成像显示，从第 75 天开始并增加到第 170 天，20 Gy 胸部照射的小鼠肺部荧光素酶活性增加，但 8 Gy 全身照射 (TBI) 小鼠的肺部荧光素酶活性没有增加。在外植肺部的连续切片中，衰老细胞出现在与 20 Gy 胸部照射组的纤维化区域相同，但与 8 Gy TBI 组不同。一年后 8 Gy TBI 小鼠的肺确实显示 p16、p21、p19 和 TGF-β 的 RNA 水平增加。 20 Gy 照射的小鼠肺中的单个衰老细胞包括具有上皮细胞、内皮细胞、成纤维细胞和造血细胞生物标志物的细胞。 8 Gy TBI 小鼠一年后肺部的罕见衰老细胞具有内皮表型。在 8 Gy TBI 后第 60 天或一年建立长期骨髓培养物 (LTBMC)。在辐射后两次新鲜取出的骨髓中，衰老细胞均有所增加。在 LTBMC 中，每周收获的单细胞和产生 CFU-GEMM（粒细胞、红细胞、单核细胞/巨噬细胞、巨核细胞的集落形成单位）的多谱系造血祖细胞集落中的衰老细胞均有所增加，这些细胞在二次培养中形成将这些单细胞铺板于半固体培养基中。来自 TBI 小鼠的 LTBMC 产生的 CFU-GEMM 较少；然而，根据 p16-荧光素酶和 β-半乳糖苷酶的测量，含有衰老细胞的集落的相对百分比有所增加。因此，20 Gy 胸部辐射以及 8 Gy TBI 会诱导肺部细胞衰老。 对于骨髓，8 Gy TBI 诱导造血细胞和集落形成祖细胞衰老。 p16 ^+/LUC小鼠品系提供了一个有价值的系统，可以比较体内器官之间辐射诱导衰老的动力学，并评估衰老细胞在辐射肺纤维化中的潜在作用。