庆大霉素中毒后豚鼠耳蜗毛细胞的再生

背景:以往一直认为损伤的毛细胞不具有修复能力。近年研究表明,哺乳动物前庭毛细胞破坏后也保持一定的修复能力。那么,哺乳类动物耳蜗毛细胞破坏后是否具有再生能力?目的:应用扫描电镜技术并结合听性脑干反应测试,观察庆大霉素中毒后不同时间豚鼠耳蜗毛细胞情况和听性脑干反应阈值变化,以观察哺乳动物耳蜗毛细胞受损后能否再生。设计:随机对照动物实验。单位:沈阳医学院生理教研室。材料:实验于2001-11/2002-05在中国医科大学听力研究室完成。选用清洁级耳郭反射灵敏的健康成年白色红目豚鼠60只,随机分为庆大霉素组、正常对照组,每组30只。方法:庆大霉素组每日腹腔注射庆大霉素100mg/kg。正常对照组每日腹腔注射与庆大霉素等量的生理盐水2.5mL/kg,各组皆连续用药10d。每日测量体质量调整药量。在用药前和停药后1,3,30d分别检测听性脑干反应阈值;停药处死后应用扫描电镜技术观察各组豚鼠耳蜗毛细胞情况。主要观察指标:①听性脑干反应阈值。②庆大霉素中毒后不同时间豚鼠耳蜗毛细胞变化。结果:实验动物60只中途无脱落,全部进入结果分析。①庆大霉素组停药后1,3,30d其听性脑干反阈值显著高于正常对照组,差异有显著性(38.00±3.75),(2.22±3.63)dBnHL,t=30.651,P<0.001];(39.09±4.22),(2.50±3.54)dBnHL,t=29.708,P<0.001];(14.50±3.69),(1.50±2.42)dBnHL,t=13.175,P<0.001]。30d时听性脑干反应阈值有明显恢复,但未达到正常水平。②庆大霉素组停药后1d豚鼠耳蜗第二转外毛细胞静纤毛显示融合、扭曲、倒伏、缺失或残缺不全等病理改变,尤其是第三排外毛细胞更为严重,且内毛细胞静纤毛外侧有囊状突出物;停药后3d豚鼠耳蜗第二转外毛细胞静纤毛融合、缺失、倒伏等病理改变仍然存在,内毛细胞静纤毛仍有倒伏现象,而其外侧囊状突出物减少;停药后30d豚鼠耳蜗第二转外毛细胞静纤毛融合、缺失、倒伏等病理改变,明显弱于庆大霉素停药1d和3d,同时耳蜗第三转有新生的静纤毛出现。结论:庆大霉素耳中毒后豚鼠耳蜗毛细胞损伤后存活30d者其耳蜗毛细胞形态上有所恢复,且听性脑干反应阈值也有一定程度的恢复,说明庆大霉素耳中毒后豚鼠耳蜗毛细胞具有再生修复能力。庆大霉素损伤后的毛细胞可以再生。

Regeneration of cochlear hair cells of guinea pigs following gentamicin ototoxicity

BACKGROUND: Formerly, it was thought that the damaged hair cells could not have the repair ability. Recent studies demonstrate that mammal vestibule hair cells also possess certain repair ability after being destroyed.Then, whether mammalia animal cochlea hair cells possess regenerative ability after being destroyed is disputed.OBJECTIVE: To observe cochlear hair cells condition and threshold value change of auditory brainstem response (ABR) at different time following gentamicin ototoxicity by using scanning electron microscope (SEM) technique combined with ABR test, so as to investigate whether cochlear hair cells of mammals can be regenerated after being injured.DESIGN: A randomized and controlled animal experiment.SETTING: Department of Physiology, Shenyang Medical College.MATERIALS: This experiment was carried out at the Hearing Research Room of China Medical University from November 2001 to May 2002. Totally 60 healthy adult white Guinea pigs, with red eyes and sensitive auricle reflex, of clean degree, were used and randomly divided into gentamicin group and normal control group with 30 guinea pigs in each one.METHODS: 100 mg/kg gentamicin was intraperitoneally daily injected into the guinea pigs, serving as gentamicin group. Same volume of normal saline (2.5 mL/kg) was intraperitoneally daily injected into the guinea pigs,serving as normal control group. All the guinea pigs were given medication for 10 successive days. Threshold value of ABR was detected respectively pre-operatively and at the 1st, 3rd, 30th days postoperatively; after withdrawal and execution, scanning electron microscope was used to observe cochlear hair cells of guinea pigs in each group.MAIN OUTCOME MEASURES: ① Threshold value of ABR. ②Cochlear hair cell change of guinea pigs at different time following gentamicin ototoxicity.RESULTS: All the 60 experimental animals entered the stage of result analysis with no loss in the midway. ①At 1,3 and 30 days after withdrawal of gentamicin, threshold value of ABR was significantly higher as compared with normal control group, with significant difference (38.00±3.75), (2.22 ±3.63) dB nHL,t=30.651, P ＜ 0.001];(39.09±4.22), (2.50±3.54) dB nHL, t=29.708, P ＜ 0.001];(14.50±3.69), (1.50±2.42) dB nHL,t =13.175, P ＜ 0.001]. Threshold value of ABR recovered obviously on day 30, but did not reach the normal level. ②On the first day after withdrawal of gentamicin , stereocilium of hair cells in second turn of cochlea of guinea pigs presented fusion, distortion, lodging, loss or incompetence and other pathological changes , especially severe in the third turn , also cystic form protrutions appeared outside the stereocilium of inner hair cell; On day 3 after withdrawal of gentamicin, stereocilium of outer hair cells in the second turn of cochlea of guinea pigs still presented fusion, loss, lodging and other pathological changes. Stereocilium of inner hair cell still showed lodging,but the outside cystic form protrutions decreased; On day 30 after withdrawal of gentamicin, stereocilium of outer hair cells in the second turn of cochlea presented fusion, loss , lodging and other pathological change ,which were obviously weaker than those on the 1st day and 3rd day after withdrawal of gentamicin , and at the same time , new born stereocilium appeared in the third turn of cochlea.CONCLUSION: Cochlear hair cell morphology recovery appears in those which survive for 30 days after cochlear hair cells of guinea pigs are damaged following gentamicin ototoxicity, and threshold value of ABR also recovers to some extent, suggesting that cochlear hair cells possess regenerative and repair ability following gentamicin ototoxicity. Hair cells after gentamicin-induced cochlear damage possess regenerative ability.