老化耳蜗主动放大机制的研究

Age-related hearing loss, or presbycusis, is the cumulative effect of aging on hearing. Also known as presbyacusis, it is defined as a progressive bilateral symmetrical age-related sensorineural hearing loss. The hearing loss is most marked at higher frequencies. Hearing loss that accumulates with age but is caused by factors other than normal aging is not presbycusis, although differentiating the individual effects of multiple causes of hearing loss can be difficult. The detection of high-pitched sounds becomes more difficult, and speech perception is affected, particularly of sibilantsand fricatives. Both ears tend to be affected. Despite this, age-related hearing loss may only become noticeable later in life. The effects of age can be exacerbated by exposure to environmental noise, whether at work or in leisure time (shooting, music, etc). Examples of microscopic changes seen in this condition are hair cell degeneration of the cochlea and giant stereociliary degeneration..Siting above the basllar membrane, outer hair cells（OHCs）appear able to perceive its vibration through their mechanosensitive hair bundles and to feed back mechanical forces that enhance both auditory system's sensitivity and its frsquency selectivity．They are mechanical components of the cochlea and have been the subject of many experiments designed to discover just exactly how they generate mechanical forces and how these forces contribute to the micromechanics of the cochlea.Prestin is required for OHC motility and plays a central role in OHC electromotility. Today, we still have no knowledge of Prestin's most nature to the active cochlear. Without definitive information, it is difficult to understand how is alters electromechanical coupleing the OHC in the aged cochlea, how is involved in the mammalian cochlear amplifier. .In this study, we verified whether the function of Deiters cells (DCs) can induce aged cochlear OHCs movement and mediate OHCs electromotility or not. These findings could provide new possible understandings of age-related hearing control and gap junction function in the inner ear.

耳聋是重要的感觉系统疾病，严重影响人们的工作生活。1978年Kemp发现耳声发射，即人耳在听到声音的同时也向外发出特定的声音。随后的研究发现，耳声发射由耳蜗外毛细胞的电运动产生，Presin是电运动的分子基础，但目前老化耳蜗Prestin在相互作用、动力传递及功能调控等方面仍缺乏直接实验依据。本研究拟以Prestin功能调控为切入点，通过综合运用免疫电镜、原子力显微镜、基因转染、膜片钳及高速影像系统等病理生理学的技术手段，动态观察老化耳蜗外毛细胞及与正常外毛细胞在动力蛋白表达、细胞结构、电运动的强度和频率特性上的异同，揭示老化耳蜗与正常耳蜗主动放大机制功能与结构的异同，阐明老化对听器功能调控方式。以老化耳蜗主动放大机制的研究入手，可以为老年性耳聋的发生机制及治疗提供新理论依据和思路，对提高国民健康水平、改善老年耳聋人群的生活质量具有重要意义。

本课题以支持细胞网络对老年耳蜗外毛细胞动力蛋白调控的研究入手，在 膜蛋白与分子水平对老年耳蜗主动运动的机理与调控机制进行了初步的探索。通过课题组全体成员的努力工作，本研究通过普查的方法共收集到622名不同听力水平的中老年人研究对象60岁至80岁根据听力下降水平共分为四组首先选取基因、基因及基因作为老年性耳聋的遗传易感候选基因，通过直接测序和多重的方法，研究了和基因与老年性耳聋遗传易感性的关系，初步探讨了不同听力水平中老年人的老年性耳聋遗传易感性差异的遗传学基础。还在离体耳蜗细胞上进行电生理研究，当给予电压或电流刺激时，Deiters细胞能够直接影响源自Prestin蛋白的外毛细胞电运动的状态。Deiters细胞去极化时能够降低与外毛细胞电运动直接相关的NLC及频率响应。当Deiters细胞与外毛细胞间的机械耦合或Deiters细胞的细胞骨架被破坏后，Deiters细胞对非线性电容的影响消失。同时我们观察到Deiters细胞间的缝隙连接（Gap junction，GJ）被破坏后可使膜电位及NLC的电压依赖特性发生改变。另外与外毛细胞连接在一起的Deiters细胞可以提高ATP对外毛细胞电运动调控的效能。这一发现很好的解释了支持细胞间的缝隙连接对外毛细胞状态有着直接的调控作用的现象，为耳聋的临床治疗提供了直接的依据。