Contribution of Macrophages and Fractalkine Towards Degeneration and Repair of Cochlear Synapses

巨噬细胞和分形蛋白对耳蜗突触退化和修复的贡献

• 批准号: 10579968
• 负责人: Tejbeer Kaur
• 金额: $ 26.05万
• 依托单位: CREIGHTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-03-05 至 2022-06-07
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10579968
• 关键词: Acoustic Nerve; Animals; Attenuated; Auditory; Axon; Binding; Brain; CX3CR1 gene; Cells; Cessation of life; Cochlea; Cochlear Implants; Data; Development; Diagnosis; Environment; FDA approved; Fractalkine; Functional disorder; Future; Genetic; Glutamates; Goals; Hair Cells; Hearing; Hearing Tests; Hearing problem; Immune; Immunotherapy; Impairment; Individual; Injury; Innate Immune System; Inner Hair Cells; Intervention; Macrophage; Measures; Membrane; Microglia; Molecular; Mus; Natural regeneration; Nerve Degeneration; Nerve Fibers; Neurites; Neurons; Neuropathy; Noise; Noise-Induced Hearing Loss; Outcome; Pathology; Peptides; Performance; Peripheral; Pharmaceutical Preparations; Prevention; Protein Isoforms; Research Design; Role; Sensory Hair; Signal Transduction; Synapses; Testing; Therapeutic; Trauma; afferent nerve; axonal degeneration; cochlear synaptopathy; cytokine; density; drug preservation; efficacy testing; excitotoxicity; experience; hair cell regeneration; hearing loss treatment; hearing preservation; hearing restoration; hidden hearing loss; improved; in vivo; insight; interest; migration; neural; neuron loss; neuron regeneration; neuronal survival; neuroprotection; neurotrophic factor; noise trauma; novel; overexpression; preservation; prevent; receptor; recruit; regenerative therapy; repaired; ribbon synapse; speech recognition; spiral ganglion

PROJECT SUMMARY/ABSTRACT Noise trauma can primarily damage the synaptic connections between the inner hair cells and the peripheral axons of the spiral ganglion neurons. Noise-induced synaptopathy is attributed to glutamate excitotoxicity and leads to gradual axonal degeneration and ultimately death of the spiral ganglion neurons. The consequences of loss of synapses and neurons include auditory perceptual dysfunctions leading to difficulty in speech recognition and listening in noisy environments. This type of auditory dysfunction is known as “hidden hearing loss” because it is not readily diagnosed through standard hearing tests. Moreover, absence of spiral ganglion neurons limits the performance of primary therapies for hearing loss such as cochlear implants and future hair cell regeneration strategies. Currently, there are no approved drugs that promote neuron survival or elicit regeneration of lost auditory nerves and replenish their synaptic connections with surviving hair cells. Therefore, it is of great interest to understand the mechanisms for synaptic and neuron degeneration and regeneration for the development of better ototherapeutics. We recently demonstrated that synaptopathic noise trauma is sufficient to recruit macrophages (innate-immune cells) towards the damaged inner hair cell-synaptic region. While the damaged synapses can undergo spontaneous repair however, disruption of fractalkine signaling (by genetic deletion of fractalkine (FKN) receptor CX3CR1 on macrophages) impairs such spontaneous synaptic repair and increases spiral ganglion neuron loss after trauma. These data imply that intact fractalkine signaling is necessary for synaptic repair and neuron survival in the damaged cochlea. Here, we propose to investigate the effect of activation of fractalkine signaling on prevention and repair of loss of synapses and neuron survival following cochlear trauma. Aim 1 will determine whether FKN treatment repairs damaged synapses after noise trauma or excitotoxic insult in mammalian mouse cochlea. Specifically, FKN peptide will be injected either (transtympanically) after synaptopathic noise trauma in vivo or after glutamate- induced excitotoxicity in cochlear explants. The precise contribution of FKN membrane or soluble isoforms towards synaptic repair will be examined. Aim 2 will determine whether FKN treatment reduces degeneration of synapses following noise trauma or glutamate excitotoxicity. We will treat with FKN membrane or soluble isoforms prior to glutamate treatment in ex vivo cochlear explants or prior to noise trauma in vivo (transtympanically). In Aim 3, we will eliminate cochlear macrophages and examine the influence of this intervention on the degree of synaptic degeneration and repair after synaptopathic noise trauma. For each aim, auditory function along with morphometric analyses of hair cell, macrophage, synapse and spiral ganglion neuron counts will be performed. Together, the study design will aid in investigating the effect of macrophages and fractalkine treatment on cochlear synapse degeneration and repair and hearing restoration and may lead to identification of novel fractalkine-based therapeutics for “hidden-hearing loss”.

项目概要/摘要 噪音创伤主要会损害内毛细胞和外周毛细胞之间的突触连接 螺旋神经节神经元的轴突。噪声引起的突触病归因于谷氨酸兴奋毒性和 导致逐渐的轴突变性并最终导致螺旋神经节神经元死亡。后果 突触和神经元的丧失包括听觉感知功能障碍，导致言语困难 在嘈杂的环境中进行识别和聆听。这种听觉障碍被称为“隐性听力” 损失”，因为它不容易通过标准听力测试来诊断。此外，缺乏螺旋 神经节神经元限制了听力损失主要疗法的效果，例如人工耳蜗和 未来的毛细胞再生策略。目前，尚无批准的促进神经元存活的药物 或引起失去的听觉神经的再生，并用幸存的毛细胞补充它们的突触连接。 因此，了解突触和神经元变性的机制和研究具有重要意义。 再生以开发更好的耳科疗法。我们最近证明了突触噪声 创伤足以将巨噬细胞（先天免疫细胞）招募到受损的内毛细胞突触 地区。虽然受损的突触可以进行自发修复，但分形蛋白的破坏 信号传导（通过基因删除巨噬细胞上的 fractalkine (FKN) 受体 CX3CR1）会损害此类信号 自发性突触修复并增加创伤后螺旋神经节神经元的损失。这些数据意味着 完整的 fractalkine 信号对于受损耳蜗中的突触修复和神经元存活是必需的。这里， 我们建议研究 fractalkine 信号传导的激活对预防和修复损失的影响 耳蜗创伤后突触和神经元存活的影响。目标 1 将确定是否进行 FKN 治疗 修复哺乳动物小鼠耳蜗噪声损伤或兴奋性毒性损伤后受损的突触。 具体而言，FKN 肽将在体内突触噪声创伤后（经鼓膜）注射 或在耳蜗外植体中谷氨酸诱导的兴奋性毒性之后。 FKN 膜的精确贡献或 将检查突触修复的可溶性亚型。目标 2 将确定是否进行 FKN 治疗 减少噪音创伤或谷氨酸兴奋性毒性后突触的退化。我们将用 FKN 进行治疗 离体耳蜗外植体中谷氨酸处理之前或噪音创伤之前的膜或可溶性亚型 体内（经鼓膜）。在目标 3 中，我们将消除耳蜗巨噬细胞并检查 这种干预对突触噪音创伤后突触变性和修复的程度。为了 每个目标、听觉功能以及毛细胞、巨噬细胞、突触和螺旋的形态测量分析 将进行神经节神经元计数。总之，研究设计将有助于调查 巨噬细胞和 fractalkine 治疗耳蜗突触变性和修复以及听力恢复 并可能导致发现基于 fractalkine 的新型治疗“隐性听力损失”的疗法。