Crum Anthony B, Nielson Cara D, Lopez Kaylin J Sevilla, Meeks Julian P
Neuroscience Graduate Program, University of Rochester, Rochester, NY.
Graduate Program in Neuroscience, University of Washington, Seattle, WA.
bioRxiv. 2025 Jul 31:2025.07.25.666403. doi: 10.1101/2025.07.25.666403.
Repetitive mild traumatic brain injury (rmTBI) is a major contributor to long-term neurological dysfunction, yet many preclinical models lack precise control and quantification of biomechanical forces across impacts. We developed a reproducible, closed-skull mouse model of rmTBI using a custom-built weight-drop apparatus featuring a solenoid-based rebound arrest system, integrated high-speed videography, and accelerometry to track head kinematics during impact. Adult male and female mice received either a single impact or nine daily impacts. Linear and angular acceleration data were analyzed alongside behavioral and histological outcomes. Our apparatus delivered consistent impact and velocity forces with minimal inter-subject variability. Additionally, the animals experienced consistent linear and angular acceleration as measured using high-speed video capture. These impacts did not cause skull fracture or acute vascular hemorrhage, but impacted animals had increased return of righting reflex (RoRR) time, consistent with mild, concussion-like symptoms. Behavioral testing revealed reduced performance of rmTBI-affected mice in an olfaction-mediated foraging task (buried food task), particularly at later timepoints, consistent with progressive olfactory impairment. Immunohistochemical analysis of Iba1 and CD68 in the brain demonstrated sex-dependent microglial activation, with males showing higher expression levels in both single- and nine-impact models. Among the brain regions investigated, microglial activation was most pronounced in the corpus callosum, neocortex, and olfactory tubercle. These findings underscore the importance of including sex as a biological variable in rmTBI research and support the utility of this model for probing injury thresholds, regional vulnerability, and potential therapeutic interventions in repetitive head trauma.
重复性轻度创伤性脑损伤（rmTBI）是导致长期神经功能障碍的主要因素，但许多临床前模型缺乏对多次撞击过程中生物力学力的精确控制和量化。我们使用定制的落重装置开发了一种可重复的、闭合颅骨的rmTBI小鼠模型，该装置具有基于螺线管的回弹制动系统、集成高速摄像和加速度测量功能，以跟踪撞击过程中的头部运动学。成年雄性和雌性小鼠接受单次撞击或每日9次撞击。分析了线性和角加速度数据以及行为和组织学结果。我们的装置产生了一致的撞击和速度力，受试者间变异性最小。此外，使用高速视频捕获测量，动物经历了一致的线性和角加速度。这些撞击没有导致颅骨骨折或急性血管出血，但受撞击的动物恢复翻正反射（RoRR）的时间增加，这与轻度脑震荡样症状一致。行为测试显示，受rmTBI影响的小鼠在嗅觉介导的觅食任务（埋藏食物任务）中的表现下降，特别是在后期时间点，这与进行性嗅觉损伤一致。大脑中Iba1和CD68的免疫组织化学分析显示了性别依赖性小胶质细胞激活，在单次和9次撞击模型中，雄性的表达水平都更高。在所研究的脑区中，胼胝体、新皮层和嗅结节中的小胶质细胞激活最为明显。这些发现强调了在rmTBI研究中纳入性别作为生物学变量的重要性，并支持该模型在探究重复性头部创伤的损伤阈值、区域易损性和潜在治疗干预方面的实用性。
