Skin transcriptomics predict outcome after ionizing radiation exposure with potential dosimetric applications in a mouse model

Increased use of nuclear reactors and radioactive materials for energy production and proliferation of nuclear weaponry increases risk of radiation exposure or nuclear accidents. Development of radiation countermeasures for the diagnosis, prognosis, and radiation treatment are trailing behind, and knowledge of the deleterious radiation effects on health and responses to exposure at the molecular, cellular, and systems biology level are still not fully understood. In this work, skin biopsies collected at h2, d4, d7, d21, and d28 from mice exposed to 1, 3, 6, 20Gy of whole-body x-ray ionizing radiation were used in a transcriptomic approach to evaluate the potential of radiation-induced transcriptional alterations in diagnosis and prognosis of a radiation event. Mice exposed to 20Gy were euthanized under the humane endpoint of an IACUC approved study protocol at d7 while mice that received 1, 3, 6Gy survived the full 28 days time course. Sammon plot analysis showed a clear separation of samples based on survival and timepoints within lethal (20Gy) and in the sublethal (1, 3, 6Gy) IR doses. Differences in the numbers, regulation mode, and fold change of significantly differentially transcribed genes (SDTGs, p < 0.05 and FC > 2) were identified between lethal and sublethal doses. Down and upregulation dominated transcriptomes during the first post-exposure week, respectively. Numbers of SDTGs and percentages of upregulated SDTGs revealed stationary transcription and low upregulation percentages after lethal dose in contrary to transcription responses that were dynamic and largely upregulated after exposure to sublethal doses. Longitudinal variations in numbers of up/downregulated SDTGs suggested delayed and extended responses with increasing IR doses in the sublethal range with lethal-like responses in late time points suggesting more than a single-phase response. This was supported further by the distributions of common and unique genes across the TPs within each dose. Several genes with potential use as markers for radiation exposure and dosimetric applications were identified. Pathways enrichment analysis showed strong modulations of immune responses, fibrosis development, detoxification responses, hematological responses, skin reactions, neurological system disruptions, maintenance of gastric mucosa, and cell survival, migration, and proliferation pathways. The majority of the identified pathways were predicted activated after sublethal and inactivated after lethal exposures, particularly during the first post-exposure week. In this work, skin biopsies collected at h2 (d0), d4, d7, d21, and d28 from mice exposed to 1, 3, 6, 20Gy of whole-body x-ray ionizing radiation were used in a transcriptomic approach to evaluate the potential of radiation-induced transcriptional alterations in diagnosis and prognosis of a radiation event.

随着核能发电领域对核反应堆与放射性材料的应用日益增多，加之核武器扩散问题加剧，辐射暴露或核事故发生的风险持续攀升。当前用于辐射暴露诊断、预后评估及放射治疗的辐射应对措施研发进度相对滞后；同时，学界对于辐射对健康的有害影响，以及机体在分子、细胞及系统生物学层面的辐射暴露应答机制，仍未完全阐明。本研究中，研究人员对接受全身X射线电离辐射（剂量分别为1、3、6、20Gy）的小鼠，在辐射后2小时（h2）、4天（d4）、7天（d7）、21天（d21）及28天（d28）采集皮肤活检样本，通过转录组学方法探究辐射诱导的转录组改变在辐射事件诊断与预后评估中的应用潜力。接受20Gy辐射的小鼠在辐射后第7天，按照经实验动物管理与使用委员会（IACUC）批准的研究方案中人道终点标准实施安乐死；而接受1、3、6Gy辐射的小鼠则存活至完整的28天实验周期。萨蒙图（Sammon Plot）分析结果显示，在致死剂量（20Gy）与亚致死剂量（1、3、6Gy）电离辐射组中，样本可依据小鼠存活状态与采样时间点实现清晰区分。研究人员在致死与亚致死剂量组间，发现显著差异转录基因（Significantly Differentially Transcribed Genes, SDTGs，P<0.05且折叠变化（Fold Change, FC）>2）的数量、调控模式及折叠倍数均存在显著差异。辐射暴露后第一周，转录组分别以基因下调与上调调控为主。致死剂量组的SDTGs数量与上调SDTGs占比均趋于平稳，且上调比例较低；与之相反，亚致死剂量组的转录应答呈动态变化，且以基因上调为主。不同剂量组中上调/下调SDTGs数量的纵向变化显示，亚致死剂量范围内，随着电离辐射剂量升高，机体应答呈现延迟且持续的特征；晚期采样点出现类似致死剂量的应答模式，提示应答并非单一时相过程。各剂量组内不同时间点（Time Points, TPs）共有与特有基因的分布特征，进一步验证了上述结论。研究人员筛选出多个具备辐射暴露标记与剂量学应用潜力的基因。通路富集分析结果显示，免疫应答、纤维化进程、解毒反应、血液系统应答、皮肤损伤反应、神经系统功能紊乱、胃黏膜维持以及细胞存活、迁移与增殖等通路均受到显著调控。多数已鉴定通路在亚致死剂量暴露后被预测激活，而在致死剂量暴露后则被抑制，这一现象在辐射后第一周尤为明显。本研究中，研究人员对接受全身X射线电离辐射（剂量分别为1、3、6、20Gy）的小鼠，在辐射后2小时（h2，即d0）、4天（d4）、7天（d7）、21天（d21）及28天（d28）采集皮肤活检样本，通过转录组学方法探究辐射诱导的转录组改变在辐射事件诊断与预后评估中的应用潜力。