大鼠脑弥漫性轴索损伤不同轴索损伤类型的形态学观察

Morphological changes in rat brain with different types of diffuse axonal injuries

目的观察脑弥漫性轴索损伤（DAI）急性期轴索损伤的类型和形态学改变，并探讨其相关机制。方法SD大鼠24只随机数字表法分为实验组（n=16）和对照组（n=8）。实验组又按损伤后不同时间（6、24h）分为2组，每组8只，运用自制联合损伤装置致实验组大鼠DAI模型，于损伤后急性期不同时间点行HE染色，免疫荧光染色检测脑组织轴浆运输障碍标志物β-淀粉样前体蛋白（β-APP）和神经微丝结构破坏标志物（NF-68）的表达，并在电镜下观察损伤轴索的超微结构变化。结果与对照组[（6．5±1．0）min]相比，实验组[（11．9±2．7）min]大鼠伤后出现昏迷时间延长，差异有统计学意义（P〈0．05）。β-APP免疫组化染色显示轴索肿胀扭曲、膨胀断裂及轴索球形成；NF-68免疫荧光染色显示轴索缩窄变细呈分割状。电镜下肿胀类型的轴索骨架溶解絮乱、细胞器聚集，而另一类损伤轴索骨架排列仍较清晰，但轴索内有较多空泡形成及神经微丝汇聚。结论DAI急性期损伤轴索存在着轴浆运输障碍和神经微丝结构破坏等病理生理过程，相应损伤轴索的形态不同。多种检测方法的使用能更全面地评估轴索损伤的严重程度及轴索对损伤的复杂反应。

Objective To investigate the morphological changes of different types of axonal injury in acute stage in rat brain with diffuse axonal injury （DAI） caused by combined head injuries, and explore their relevant injury mechanisms. Methods SD rats were randomized into experimental （n=16） and normal control （n=8） groups. According to the different injury times （6, 24 h）, the experimental group was equally divided into two subgroups （n=8）. A new experimental facility was employed to induce DAI in rats. HE staining was conducted in different time points in the acute stage. Immunofluorescence assay was performed to detect the expressions of antibodies to β-Amyloid precursor protein （β-APP） and antibodies to neurofilament-68 （NF-68） and electron microscope was also introduced to investigate the changes of axonemal ultrastructure. Results All injured rats experienced behavioral suppression： the coma in the experimental group was significantly prolonged as compared to that in the normal control group （P〈0.05）. Immunofluorescence assay for antibodies to β-APP and NF-68 revealed two distinct types of axonal injury： β-APP confined to focal spheroidal axonal swellings and axonal retraction bulbs; while NF-68 was only found within thin and elongate axonal segments. Electron microscope also demonstrated two different types of ultrastructure of axonal injury. Conclusion Impaired axonal transport and neurofilament compaction can occur independently in the process of axonal injury with different morphological changes. Multiple immunocytochemical approaches can help to fully assess the overall axonal response to traumatic brain injury.