外源性脑源性神经因子对遗传性聋动物模型耳蜗形态和功能的影响

Effects of exogenous brain-derived neurotrophic factor on the morphology and function of cochlea in the animal model of hereditary hearing loss

目的:研究外源性脑源性神经因子(BDNF)对条件敲除缝隙链接蛋白26(Cx26)小鼠耳蜗形态和功能的影响。方法:选取条件敲除的Cx26小鼠为动物模型,在出生后2d(P0-P2)通过中阶注射给予外源性BDNF。分别观察BDNF在耳蜗中的表达情况及其对神经纤维生长的促进作用,注射后60d,BDNF对corti器及螺旋神经节细胞的保护作用,并检测注射后动物听力的改变情况。结果:(1)外源性BDNF可在实验动物体内良好表达;(2)外源性BDNF对动物耳蜗神经纤维生长有良好的促进作用;(3)外源性BDNF可有效保护corti器的形态;计数耳蜗各回螺旋神经节细胞数,以未注射耳顶回的密度值作为标准单位,注射耳中回和底回的密度值分别为0.81±0.02、0.65±0.02,与未注射耳相比,均差异有统计学意义(均P<0.05);(4)通过计算注射耳与未注射耳各频率ABR阈值,显示两者差异无统计学意义。结论:早期给予外源性BDNF可有效保护条件敲除Cx26小鼠耳蜗的corti器及螺旋神经节细胞的形态,但对于听功能则无保护作用。

Objective： To study the effect of early administration exogenous BDNF on the morphology and function of conditional knockout Cx26 mice cochlea. Method：Conditional knockout Cx26 mice was chosen as animal model, early after birth （P0-P2） exogenous BDNF （rAAV mediated BDNF plasmid, AAV-BDNF） was injected through scala media. Expression of BDNF in the cochlea was observed by western-blot, the growth promoting effect of nerve fibers was detected by IHC; 2m after injection, the protective effect of BDNF on corti and spiral ganglion cells were detected by resin section; animal hearing were tested by ABR. Result： ① Exogenous BDNF could be well expressed in the inner ear;②Exogenous BDNF has a good effect on the growth of cochlea nerve fi- ber; ③Exogenous BDNF could protect the morphology of organ of corti; to count the number of spiral ganglion cells, using the density value of top-turn in non-injected ear as the standard unit, the values of middle and basal turn in injected ear were 0.81 ± 0.02, 0.65 ±0.02, compared with non-injected ears, both statistically significant difference could be found, indicates that exogenous BDNF can effectively improve the number of spiral ganglion cells. ④By calculating the ABR threshold of different frequencies of the injected and non-injected ear, there was no statistical difference between them. Indicates that exogenous BDNF has no effect on improving the function of cochlea. Conclusion：The protective effect of early administration exogenous BDNF was effective in the cochlea and spiral ganglion cells of conditional knockout Cx26 mice, but no protective effect for auditory function.