Smith et al., brainsci 2948380.xlsx

Traumatic brain injury (TBI) is one of the leading causes of death and disability. TBI is associated with neuroinflammation, but temporal changes in immune and inflammatory signaling following TBI have not been fully elucidated. Furthermore, there have been no previous studies on changes in immune cell populations following TBI via the Closed Head Injury Model of Engineered Rotational Acceleration (CHIMERA). The current study aimed to determine the time course changes to inflammatory marker mRNA expression in the acute period following TBI in juvenile rats and to determine acute changes to brain and circulating immune cell populations. For this study, post-natal day (PND)-30 male Long Evans rats sustained a TBI or Sham TBI and were euthanized at 0, 3, 6, 12, 24, or 96 h post-injury. Prefrontal cortex and hippocampus samples were used to determine mRNA expression changes of inflammatory factors. The mRNA expression of the pro-inflammatory cytokine TNF-α was significantly elevated at 6 h post-injury in both regions evaluated. To evaluate immune cell populations, male Long Evans rats were euthanized at 48 h post-injury, and brain and blood samples were used for cell sorting by marker-specific antibodies. In the peripheral blood, there was an elevation in CD3⁺ total T cells, CD45R⁺total B cells, and CD3⁺CD4⁺ helper T cells in the TBI subjects. However, there were no changes to natural killer cells or CD3⁺CD8⁺ cytotoxic T cell populations. In the brain, there was a reduction in CD11b/c⁺ monocytes/macrophages, but no changes in other immune cell populations. At 48 h post-injury, the TBI subjects also demonstrated expansion of the thymic medulla. These changes in the cerebral and blood immune cell populations and thymic medulla expansion may implicate the subacute recovery timeframe as a vulnerable window for the immune system in the pediatric population.

创伤性脑损伤（Traumatic Brain Injury, TBI）是导致死亡与残疾的主要诱因之一。TBI与神经炎症密切相关，但目前学界尚未完全阐明TBI发生后免疫与炎症信号通路的动态变化过程。此外，此前尚无研究通过工程化旋转加速度闭合性颅脑损伤模型（Closed Head Injury Model of Engineered Rotational Acceleration, CHIMERA）探讨TBI后的免疫细胞群体变化。本研究旨在明确幼年大鼠TBI后急性期炎症标志物mRNA表达的时序变化，并探究其脑部与循环系统免疫细胞群体的急性改变。本研究选用出生后第30天（post-natal day, PND）的雄性Long Evans大鼠，构建TBI模型或假手术（Sham TBI）模型，并分别于损伤后0、3、6、12、24、96小时实施安乐死。采集前额叶皮层与海马体样本，用于检测炎症因子的mRNA表达变化。经检测，在两个受试脑区中，损伤后6小时促炎细胞因子TNF-α（Tumor Necrosis Factor-α）的mRNA表达水平均显著升高。为评估免疫细胞群体变化，本研究于损伤后48小时对雄性Long Evans大鼠实施安乐死，采集脑部与血液样本，通过标记物特异性抗体进行细胞分选。在外周血中，TBI模型组大鼠的CD3⁺总T细胞、CD45R⁺总B细胞以及CD3⁺CD4⁺辅助T细胞水平均出现升高。但自然杀伤细胞与CD3⁺CD8⁺细胞毒性T细胞群体未出现明显变化。在脑部组织中，CD11b/c⁺单核细胞/巨噬细胞群体数量减少，但其他免疫细胞群体未发生显著改变。损伤后48小时，TBI模型组大鼠还出现了胸腺髓质的扩张现象。上述脑部与血液免疫细胞群体的变化，以及胸腺髓质扩张现象，提示亚急性恢复期可能是儿科人群免疫系统的易感窗口。