The role of macrophages in chronic suppurative otitis media associated sensory hearing loss

项目摘要/摘要 我们请求美国国立卫生研究院提供支持，以调查慢性化脓性中耳炎是如何导致感觉性听力损失(SHL)的 中耳炎(CSOM)或严重的慢性中耳感染。CSOM，一种被忽视的热带疾病，困扰330人 全世界有数百万人，是世界上儿童永久性听力损失的最常见原因 发展中世界。它的特点是慢性排出感染的中耳，目前没有 有效的药物治疗或治愈。铜绿假单胞菌(PA)是罪魁祸首。帕 通过鼓膜上的一个洞定居中耳，并建立自己的生物膜群落， 使治疗和完全根除感染的努力复杂化。在疾病的整个过程中，感染逐渐加重 随着生物膜内的细菌数量部分地对免疫攻击或局部攻击做出反应，细菌数量就会减少 抗生素。细菌感染的这种起伏导致永久性感觉性听力损失 未知的机制。我们的实验室最近创建并验证了一种新的PA CSOM动物模型，该模型模拟 人类的处境。具体地说，我们通过在正确的状态(表型)接种PA来创造感染 导致感染持续六个月以上的剂量，在局部使用时会起伏不定 氟喹诺酮类药物治疗，随着时间的推移，会导致毛细胞死亡，就像在人类疾病中一样。上一首 其他人的研究依赖于基于非PA细菌的急性感染模型。相比之下，我们独一无二的 PA CSOM模型现在允许我们观察内耳感染的发展并识别病原体 和/或可能导致由此导致的感觉性听力损失的过程。我们的研究将有助于确定 永久性听力损失在CSOM中是否可以预防，如果是，指导治疗干预策略。 我们的目标包括：(1)确定耳蜗内发生结构性变化的时间和性质 以及在这些变化发生时评估巨噬细胞的分布，(2)调查潜在的直接毛细胞 (HC)通过CSOM外淋巴采样获得毒素和巨噬细胞诱导剂，以及(3)评估贡献 结合我们的CSOM小鼠模型研究CSOM中驻留和迁移的巨噬细胞对毛细胞丢失的影响 分别用CD68-GFP转基因报告鼠和三重敲除小鼠品系 巨噬细胞不能产生活性氧(ROS)，同时也评估NLRP3 炎症小体功能是耳蜗内HC丢失所必需的。 总之，这些目标是治疗CSOM引起的感觉性听力损失的一种全新的方法。如果成功， 这些研究将支持未来对CSOM和铅的病理生理学机制的研究 介绍PA的新治疗方法和预防CSOM感觉性听力损失的可能策略。

Project Summary / Abstract We request NIH support to investigate how sensory hearing loss (SHL) is caused by chronic suppurative otitis media (CSOM) or severe chronic middle ear infections. CSOM, a neglected tropical disease that afflicts 330 million people worldwide, is the most common cause of permanent hearing loss among children in the developing world. It is characterized by a chronically discharging infected middle ear, and there is currently no effective medical therapy or cure. The bacterium, Pseudomonas aeruginosa (PA), is the leading culprit. PA colonizes the middle ear via a hole in the tympanic membrane and establishes itself into a biofilm community, complicating attempts to treat and fully eradicate infection. Over the course of the disease, the infection waxes and wanes as the population of bacteria within the biofilm responds, in part, to immune attack or topical antibiotics. This waxing and waning of bacterial infection leads to permanent sensory hearing loss via an unknown mechanism. Our lab has recently created and validated a novel PA CSOM animal model that mimics the human condition. Specifically, we create the infection by inoculating PA in the right state (phenotype) and dose, which results in an infection that persists beyond six months, waxes and wanes upon topical fluoroquinolone therapy, and leads to hair cell death, over time, like in the human disease. Previous investigations by others relied on acute infection models based on non-PA bacteria. In contrast, our unique model of PA CSOM now allows us to observe development of the infection in the inner ear and identify agents and/or processes that may be causing the resulting sensory hearing loss. Our studies would help determine whether permanent hearing loss is preventable in CSOM and, if so, guide strategies for therapeutic intervention. Our Aims encompass: (1) determining the timing and nature of structural changes occurring within the cochlea and assessing the macrophage distribution as these changes occur, (2) investigating potential direct hair cell (HC) toxins and macrophage inducers through CSOM perilymph sampling, and (3) evaluating the contributions of resident and migrating macrophages towards hair cell loss in CSOM by combining our CSOM mouse model with the CD68-GFP transgenic reporter mouse and, separately, with a triple knockout mouse strain with macrophages unable to produce reactive oxygen species (ROS) while also evaluating whether NLRP3 inflammasome function is necessary for HC loss in the cochlea. Altogether these aims are a completely new approach to sensory hearing loss caused by CSOM. If successful, these studies will support future investigations into the mechanisms in the pathophysiology of CSOM and lead to novel treatments for PA and potential strategies to prevent sensory hearing loss in CSOM.