Department of Otorhinolaryngology, Union Hospital of Tongji Medical College, Huazhong Science and Technology University, Jiefang Avenue 1277, Wuhan 430022, PR China.
Brain Res. 2010 May 17;1331:28-38. doi: 10.1016/j.brainres.2010.02.058. Epub 2010 Mar 2.
We investigated the time sequence of morphological changes of the spiral ganglion cell (SGC) and auditory nerve (AN) following chronic kanamycin-induced deafness. Guinea pigs were treated with kanamycin by subcutaneous injection at 500 mg/kg per day for 7 days. Histological changes in hair cells, SGCs, Schwann cells and the area of the cross-sectional of the AN with vestibular ganglion (VG) in the internal acoustic meatus were quantified at 1, 7, 14, 28, 56 and 70 days after kanamycin treatment. Outer hair cells decreased at 7 and 14 days. Loss of inner hair cells occurred at 14 and 28 days. The cross-sectional area of the AN with VG increased at 1 day and decreased shortly following loss of SGCs and Schwann cells at 7, 14 and 28 days after deafening. There was a similar time course of morphological changes in the overall cochlea and the basal turn. Thus, the effects of kanamycin on hair cells, spiral ganglion and Schwann cells are progressive. Early degeneration of SGC and Schwann cell mainly results from the direct toxic effect of kanamycin. However, multiple factors such as loss of hair cell, degeneration of Schwann cell and the progressive damage of kanamycin, may participate in the late degeneration process of SGCs. The molecular mechanism of the degeneration of SGC and Schwann cell should be investigated in the future. Moreover, there is a different time sequence of cell degeneration between acute and chronic deafness by kanamycin.
我们研究了慢性卡那霉素致聋后螺旋神经节细胞（SGC）和听神经（AN）形态变化的时间序列。豚鼠每天通过皮下注射 500mg/kg 的卡那霉素连续 7 天。在卡那霉素处理后 1、7、14、28、56 和 70 天，对内耳道内前庭神经节（VG）的毛细胞、SGC、施万细胞和 AN 横截面积的组织学变化进行了定量分析。第 7 天和第 14 天外毛细胞减少。第 14 天和第 28 天内毛细胞丢失。AN 与 VG 的横截面积在失聪后 1 天增加，在 SGC 和施万细胞丢失后 7、14 和 28 天短暂减少。整个耳蜗和基底回的形态变化具有相似的时间进程。因此，卡那霉素对毛细胞、螺旋神经节和施万细胞的影响是渐进的。SGC 和施万细胞的早期退化主要是由于卡那霉素的直接毒性作用。然而，毛细胞的丧失、施万细胞的退化以及卡那霉素的进行性损伤等多种因素可能参与了 SGC 晚期退化过程。SGC 和施万细胞退化的分子机制有待进一步研究。此外，卡那霉素引起的急性和慢性耳聋的细胞退化具有不同的时间顺序。
