耳蜗毛细胞严重缺失后螺旋神经节细胞的病理变化

The Fate of the Spiral Ganglion Cells After the Cochlear Hair Cells Serious Injuried

目的观察耳蜗毛细胞严重损伤后螺旋神经节细胞的病变过程。方法豚鼠肌肉注射硫酸卡那霉素(1000mg/kg)2小时后给予速尿(100mg/kg)静脉注射,分别于用药3天、7天、1月及2月行听觉脑干诱发电位(auditory brainstem response ABR)及耳蜗形态学检测。结果联合应用速尿和硫酸卡那霉素后,豚鼠鼠ABR阈值出现很大程度提高,给药3天、7天、1月、2个月组各频率ABR阈值比较无差别;对药物损伤致聋豚鼠进行耳蜗切片、扫描电镜观察,发现用药7天后耳蜗毛细胞严重受损,以外毛细胞(OHCs)缺失为主,严重致聋的豚鼠内毛细胞(IHCs)也广泛缺失,但是切片显示柯替氏器的支持细胞存在;螺旋神经节细胞正常。联合用药1月后螺旋神经节细胞大量缺失,Corti’s器塌陷。结论药物性耳聋首先损伤毛细胞,螺旋神经节细胞的损伤延后发生,螺旋神经节细胞缺失程度取决于致聋后的时间长短,致聋后螺旋神经节细胞变性可以持续数年。这为我们植入电子耳蜗提够了宝贵的时间窗。

Objective To study morphological changes of spiral ganglion cells （SGN） following severe cochlear hair ceils injury. Methods Guinea pigs were given kanamycin sulfate （1000 mg/kg） intramuscularly followed by furosemide （100 mg/kg） intravenously 2 hours later. Auditory brainstem responses （ABRs） and cochlear morphology were examined at 3 days, 7 days, 1 month and 2 months respectively after the treatment. Results ABR thresholds were greatly elevated after the treatment, with no significant difference among the different time groups. Scanning electron microscopy revealed severe damage to cochlear hair ceils, especially out hair cells （OHC） after 7 days. There was also extensive loss of inner hair cells in animals with severe auditory function damage while supporting cells in the organ of Corti were preserved. The SGN showed no change on Day 7, al- though severe SGN loss was seen after 1 month, with total collapse of the organ of Corti. Conclusion Drug-induced hearing loss starts with hair cell loss, followed by SGN loss. In addition, the extent of SGN damage seems to correlate to time lapse after drug administration and can take years to develop, which may provide a time window for cochlear implant.