局部应用糖皮质激素对大鼠面神经损伤后修复的影响

The effect of topically applied glucocorticoids on the injured facial nerve in rats

目的观察局部应用地塞米松(dexamethasone,Dex)对面神经损伤后再生修复的影响。方法健康雌性SD大鼠63只,建立大鼠面神经横断伤后端端吻合模型,分为生理盐水(normal saline,NS)对照组、地塞米松(Dex)2mg组和Dex5mg组,分别将浸泡于NS、2mg/ml及5mg/ml地塞米松磷酸钠溶液至饱和后的明胶海绵敷于各组动物的端端吻合口处。术后1、2、3、7天取远端近吻合口处神经行劳克坚牢蓝(Luxol Fast Blue,LFB)染色及ED1免疫组化染色,光镜下观察髓鞘和巨噬细胞;术后2、4、8周光镜下(锇酸染色)观察远端相同部位神经再生情况并进行轴突计数。结果光镜下观察,术后第1天髓鞘形态变化不明显,术后第2天出现明显变性崩解,至第3天崩解加快,第7天已见不到完整的髓鞘,仅余部分髓鞘碎片。术后第1天巨噬细胞数量较少,第2天开始增多,第7天较前3天显著增多。三组间髓鞘残余及巨噬细胞数量均无显著性差异(P>0.05)。术后2周,各组均出现新生髓鞘,三组间轴突计数无统计学差异(P>0.05)。结论本实验条件下,局部应用小剂量地塞米松对髓鞘清除速度、巨噬细胞及轴突再生数量没有明显影响。

Objective To investigate the influence of topical glucocorticoids on facial nerve recovery following transection injury in rats. Methods Sixty-three rats were assigned to an NS control group and two topical steroid groups. The marginal mandibula branch of the facial nerve was subjected to standardized transection injury and subsequent end to end repair on each animal. Dexamethasone saturated Gelfoam（two different concentrations, 2 mg/ml and 5 mg/ml respectively） was placed at the site of injury in the topical steroid groups whereas NS saturated Gelfoam was placed at the site of injury in the control group. Daily myelin clearance was observed at the 1, 2, 3, 7 days post operation （dpo） using Luxol fast blue（LFB） staining and the number of macrophages was counted at the same time points using immunohistochemistry. Osmium tetroxide staining was performed at 2, 4, 8 weeks post operation and axons were counted microscopically. Results Myelin clearance was not obvious until at 2 dpo and was progressing from 3 to 7 dpo. Only some myelin debris remained at 7 dpo in each group. The number of macrophages significantly increased at 7 dpo. No significant difference was observed either in myelin clearance or in macrophage recruitment among 3 groups. Regeneration was confirmed at 2 weeks in all groups. In steroid groups, no significant differences were found either in morphology or in axonal counts compared to NS group. Conclusion Topical application of low-dose dexamethasone has no influences on myelin clearance, macrophage recruitment and axonal counts in transected facial nerve branches anastomosed end-to-end with 8-0 nylon sutures. Clinical use of steroids to promote peripheral nerve regeneration warrants further study.