轴突细胞骨架对非中断性轴索损伤的反应及在亚低温治疗后的早期改变

Effect of mild hypothermia on axonal cytoskeleton after non-disruptive axonal injury

目的 观察轴索损伤早期轴突细胞骨架超微结构的改变和早期亚低温处理后细胞骨架的改变 ,为亚低温治疗弥漫性轴索损伤 (DAI)寻找实验依据。 方法 实验组豚鼠右侧视神经受牵拉致伤。伤后常温实验组动物体温维持在 36 .0～ 37.5℃ ,低温实验组动物体温降至 32 .0～32 .5℃ ,两组于伤后 2h和 4h各处死一半动物。电镜下观察轴突细胞骨架的变化 ,并用电脑图像分析系统进行定量分析。 结果 常温实验组伤后 2h ,大、中、小轴突组平均微管总数均显著减少 (P <0 .0 0 1) ,平均微管间距显著增大 (P <0 .0 5或P <0 .0 1) ,大、中轴突组平均神经丝总数也显著减少 (P <0 .0 1)。伤后 4h ,中、小轴突组平均神经丝总数显著增多 (P <0 .0 5 ) ,平均神经丝间距显著缩小 (P <0 .0 5 )。亚低温实验组的各直径轴突内的微管总数及间距 ,神经丝总数及间距与对照组相比 ,无明显改变 (P >0 .0 5 )。 结论 轴突损伤早期轴突细胞骨架有显著的结构改变 ,早期亚低温处理 ,能明显改善细胞骨架的异常。

Objective To document the ultrastructural change of axonal cytoskeleton in early stage of axonal injury and the effect of mild hypothermia on the alteration of axonal cytoskeleton. Methods Stretch injury was induced in the right optic nerves of 12 adult guinea pigs. Then the body temperature of the animals was maintained at 36.0～37.5℃ in the normothermic group (n = 6) and it was cooled to 32.0～32.5℃ in the hypothermic group (n = 6). Half animals of each group were killed at 2 h and the other half were killed at 4 h after stretch injury. The ultrastructural change of the axonal cytoskeleton was examined under a transmission electron microscope and analyzed by quantitative analysis with a computer image analysis system. Results At 2 h after stretch injury, the mean number of microtubules decreased significantly ( P < 0.001) in the large, medium and small axons and the mean space between the microtubules increased significantly ( P <0.05 or P <0.01) in axons of all sizes, and the mean number of neurofilaments also decreased statistically ( P <0.01) in the large and medium axons at 2 h in the normothermic animals. By 4 h, the large axons in the normothermic group still demonstrated a significant drop in the mean number of microtubules ( P <0.01) and an increase in the mean space between the microtubules ( P <0.05), while the medium and small axons in the same group displayed a significant increase in the mean number of neurofilaments ( P <0.05) and a reduction in the mean space between the neurofilaments ( P <0.05). However, either the number of and the space between microtubules, or the number of and the space between neurofilaments from the mild hypothermic group had no significant difference compared with the control group at either 2 or 4 h after stretch injury. Conclusions Prominent changes of axonal cytoskeleton occur in the early stage of axonal injury, and immediate mild hypothermic treatment can significantly ameliorate the abnormality of the axonal cytoskeleton.