Hippocampus-Cerebellum Axis Specific Transcriptomic Stratification to Discriminate Mild from Moderate TBI

The variations of psycho- and physiological deficits caused by TBI correlate with the degree of brain injury. However, the objective stratification of TBI is yet elusive. A modified closed-head injury Marmarou model was used based on the release of a 500 gram steel slug on top of the rat skull from a height of 100 cm or 120 cm to induce differential injury models for mild TBI and moderate TBI, respectively. The skull was covered by a helmet to mimic the warfighter’s condition in theater. The hippocampus was at the focal point of injury, and the cerebellum, was susceptible to diffused shock (secondary injury). The HC-CB axis coordinates visuomotor performance, which is known to be vulnerable to TBI. The rats that received moderate TBI showed deficient visuomotor performance by the Barnes maze test for longer time periods than those inflicted with mild TBI. The time resolved and HC-CB specific transcriptomic analysis focused on genes that enabled discrimination of mild from moderate TBI at 14d post injury which is equivalent to nearly 1.5 years of human lifetime. The functional analysis elucidated an active healing mechanism in the HC exposed to mild TBI. In contrast, moderate TBI caused delayed healing and active cell death in the HC. In conclusion, the graded brain injuries differentially implicated the HC-CB axis, despite the use of a helmet to reduce the impact. Time resolved functional dynamics informed the distinct consequences of mild vs. moderate TBI.创伤性脑损伤（Traumatic Brain Injury, TBI）引发的心理与生理功能缺损程度，与脑损伤的严重程度密切相关。然而，目前仍难以实现TBI的客观分层。本研究采用改良的闭合性颅脑损伤Marmarou模型：通过将一枚500克的钢质弹丸分别从100厘米、120厘米高度释放至大鼠颅骨上方，以此分别构建轻度TBI与中度TBI的差异化损伤模型。为模拟战场环境下作战人员的损伤场景，大鼠颅骨佩戴了防护头盔。损伤的核心靶点为海马体（Hippocampus, HC），而小脑（Cerebellum, CB）则易受弥漫性冲击引发的继发性损伤影响。HC-CB轴负责协调视运动功能，而已知该功能易受TBI损害。相较于轻度TBI模型组，中度TBI模型组的大鼠在Barnes迷宫测试中表现出视运动功能缺陷的持续时间更长。本研究针对损伤后14天（约相当于人类1.5年生命周期）的样本，开展了时间分辨率HC-CB特异性转录组学分析，重点筛选可区分轻度与中度TBI的差异基因。功能分析结果显示，暴露于轻度TBI的海马体存在活跃的修复机制；与之相反，中度TBI则会导致海马体修复延迟，并引发活跃的细胞死亡。综上，尽管佩戴头盔可降低冲击强度，但分级脑损伤仍对HC-CB轴产生了差异化影响。基于时间分辨率的功能动态特征分析，清晰揭示了轻度与中度TBI各自独特的病理结局。