Project 2: Mechanistic studies of age-related hearing loss using animal models and human tissue

项目总结/摘要-项目2 老年性耳聋是一种常见的神经退行性疾病， 与耳蜗外侧壁中几种特化细胞类型的损失和/或功能障碍相关（代谢 老年性聋）和听觉神经（神经性老年性聋）。临床研究中心的项目2旨在 鉴定人类代谢和神经性老年性聋的关键细胞和分子机制 小鼠模型和来自年轻和老年捐赠者的死后人类颞骨。失调 小胶质细胞/巨噬细胞和补体级联，先天免疫的两个基本要素 系统，已被证明在几个年龄相关的神经退行性疾病中发挥重要作用。我们 初步研究表明，耳蜗巨噬细胞可能经历结构和分子 随着年龄的增长而变化，指示功能变化，并且这些变化与 老年小鼠耳蜗外侧壁微血管的病理变化。鞘氨醇-1-磷酸 (S1P)脂质信号分子调节巨噬细胞活性。基因表达的初步研究 小鼠耳蜗组织中与年龄相关的巨噬细胞功能障碍表明， S1 P生物利用度随着年龄的增长和耳蜗外侧壁巨噬细胞功能障碍而增加。此外，本发明还提供了一种方法， 小鼠听神经中的差异基因表达分析已经确定了随着听觉神经的增加而发生的主要变化。 年龄在先天免疫反应和补体级联途径。其他研究的最新进展 神经退行性疾病已经表明补体失调可导致脱髓鞘和神经退行性疾病， 退化基于这些观察，我们的总体假设是，年龄依赖性失调 耳蜗先天性免疫系统的免疫功能的下降导致了老化侧膜中特化细胞的退化。 壁和听神经，导致与代谢和神经功能一致的听觉功能下降， 老年性聋项目2将1）确定S1 P介导的巨噬细胞功能障碍与 老年小鼠外侧壁微血管变性（目的2.1）; 2）阐明 年龄相关的补体系统失调与退化和功能下降之间的关系， 听觉神经纤维，特别是自发频率低的纤维（目标2.2）。外侧壁动物模型 项目2中描述的听神经退化也将用于验证遗传和 从项目1、3和4中研究的人类受试者获得的病理生理学结果。的比较研究 这些关键的免疫应答调节分子的表达模式也将在人类中进行检测。 颞骨，通过人类受试者核心（核心B）进入。比较的能力 动物模型、人类颞骨和人类受试者的结果提供了一个无与伦比的机会， 为了解决有关耳蜗巨噬细胞功能障碍和补体的具体作用的问题， 调节与人类老年性聋相关的血管和髓鞘形成神经胶质病理生理学。

PROJECT SUMMARY/ABSTRACT – PROJECT 2 Age-related hearing loss (presbyacusis) is a common neurodegenerative disorder that can be associated with loss and/or dysfunction of several specialized cell types in the cochlear lateral wall (metabolic presbyacusis) and the auditory nerve (neural presbyacusis). Project 2 of the Clinical Research Center aims to identify critical cellular and molecular mechanisms underlying human metabolic and neural presbyacusis using mouse models and post-mortem human temporal bones from younger and older donors. Dysregulation of microglia/macrophages and the complement cascade, two fundamental elements of the innate immune system, have been shown to play vital roles in several age-related neurodegenerative disorders. Our preliminary studies have revealed that cochlear macrophages may undergo structural and molecular alterations with increasing age, indicative of functional changes, and that these alterations are associated with pathological changes in the cochlear lateral wall microvasculature of aged mice. Sphingosine-1-phosphate (S1P), a lipid signaling molecule, regulates macrophage activity. Preliminary studies of gene expression patterns and age-related macrophage dysfunction in mouse cochlear tissue suggest a link between a reduction in S1P bioavailability with increasing age and macrophage dysfunction in the cochlear lateral wall. In addition, differential gene expression analysis in the mouse auditory nerve has identified major changes with increasing age in the innate immune response and complement cascade pathways. Recent studies of other neurodegenerative disorders have shown that complement dysregulation can lead to demyelination and neural degeneration. Based on these observations, our overarching hypothesis is that age-dependent dysregulation of the cochlear innate immune system contributes to the degeneration of specialized cells in the aging lateral wall and auditory nerve, leading to declines in auditory function consistent with metabolic and neural presbyacusis. Project 2 will 1) determine the relationship between S1P-mediated macrophage dysfunction and strial microvasculature degeneration in the lateral wall of aged mice (Aim 2.1); and 2) elucidate the links between age-related dysregulation of the complement system with degeneration and functional declines in auditory nerve fibers, in particular fibers with low spontaneous rates (Aim 2.2). Animal models of lateral wall and auditory nerve degeneration characterized in Project 2 will also be used to validate genetic and pathophysiology results obtained from human subjects studied in Projects 1, 3, and 4. Comparative studies of the expression patterns of these key immune response regulatory molecules will also be examined in human temporal bones, which are accessed through the Human Subjects Core (Core B). The ability to compare results from animal models, human temporal bones, and human subjects provides an unparalleled opportunity to address questions regarding the specific role of the cochlear macrophage dysfunction and complement regulation in vascular and myelinating glial pathophysiology associated with human presbyacusis.