COCHLEAR NERVE DEVELOPMENT

耳蜗神经发育

• 批准号: 2900019
• 负责人: STEPHEN M ECHTELER
• 金额: $ 25.32万
• 依托单位: CHILDREN'S HOSP OF PHILADELPHIA
• 依托单位国家: 美国
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-03-01 至 2002-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2900019
• 关键词: apoptosis; chimeric proteins; cochlear nerve; confocal scanning microscopy; developmental neurobiology; ear hair cell; epithelium; gerbil /jird; growth factor receptors; immunoglobulin G; in situ hybridization; macrophage; neurogenesis; neurons; neurotrophic factors; organ culture; protein tyrosine kinase; synapses; tissue /cell culture

The major aim of this research is to learn about the cellular, and ultimately the molecular, interactions that produce an ordered set of neuronal connections within the mammalian auditory periphery. Mammals possess two classes of auditory receptors, termed inner and outer hair cells, that project to the brain through separate neural components of the auditory nerve. Within the cochlea, auditory neurons innervate hair cells with astonishing accuracy; most form a single punctate synapse with only one receptor. Past work has shown that, during cochlear development, this neural specificity arises through extensive structural remodeling of individual cochlear neuron arbors, most of which form transient, supernumerary connections with outer hair cell receptors. During this process, up to 30% of all cochlear neurons die within the neonatal ear. This application, for renewal of a project in its 6th year, proposes to continue investigations into the formation of cochlear innervation by examining the cellular interactions between developing auditory neurons and hair cells, in-vivo, within the developing gerbil and, in vitro, within developing organotypic cultures of gerbil cochlea. Three sets of experiments are proposed: 1) The timecourse and spatial distribution of programmed auditory neuron death will be determined within the developing ear, by DNA labeling of apoptotic cells and serial reconstruction of the developing spiral ganglion; 2) Factors affecting the survival and programmed death of auditory neurons within the developing ear will be investigated by examining, both in vivo and in vitro, the cellular expression patterns of two cochlear neurotrophic molecules (BDNF and NT-3) and their receptors (trk B and trkC) using in situ hybridization and immunocytochemistry. 3) The influence of these neurotrophic factors on the formation of neural connections to inner and outer hair cells will be assessed by examining the structural development of individual auditory neuron arbors, labeled with neural tracers and reconstructed by light and confocal microscopy, within organotypic cultures that have been enriched for NT-3 and/or BDNF or depleted of these neurotrophins by the addition of trkB-IgG and trkC-IgG fusion proteins. Eighty-percent of all significant hearing impairment in the U.S is caused by the permanent loss of auditory neurons and receptors. It is crucial to understand the cellular interactions that form and maintain these sensorineural elements if effective biological strategies are to be devised for their protection or repair.

这项研究的主要目的是了解细胞，以及 归根结底，分子的相互作用产生了一组有序的 哺乳动物听觉外周的神经元连接。哺乳动物 拥有两类听觉感受器，称为内毛和外毛 细胞，通过独立的神经组件投射到大脑中 听觉神经。在耳蜗内，听觉神经元支配毛细胞。 以惊人的准确性；大多数只与一个点状突触形成 一种受体。过去的研究表明，在耳蜗发育过程中， 神经特异性是通过广泛的结构重塑产生的 单个耳蜗神经元束，其中大部分是暂时性的， 与外毛细胞受体的额外连接。在此期间 在这一过程中，多达30%的耳蜗神经元在新生儿的耳朵内死亡。 这份申请是为了续签第6年的项目，它建议 继续研究耳蜗神经的形成 研究发育中的听神经细胞与 发育中的沙土鼠体内的毛细胞和体外培养的毛细胞 发展沙土鼠耳蜗器型培养。三套 实验内容包括：1)时间序列和空间分布 程序性听神经元死亡将在发育过程中确定 EAR，通过DNA标记凋亡细胞和序列重建 螺旋神经节的发育；2)影响存活和 发育中的耳朵内听觉神经元的程序性死亡将是 通过检查体内和体外的细胞 两种耳蜗神经营养分子BDNF和NT-3的表达模式 和它们的受体(trk B和trkC) 免疫细胞化学。3)这些神经营养因子对神经营养因子的影响。 与内外毛细胞的神经连接的形成将是 通过检查个体听觉的结构发育来评估 神经元乔木，用神经示踪剂标记，并通过光和 共聚焦显微镜，在已被丰富的器官类型培养中 NT-3和/或BDNF或这些神经营养因子通过添加 TrkB-Ig G和TrkC-Ig G融合蛋白。 在美国，80%的重大听力障碍是由 由于听觉神经元和感受器的永久性丧失。这是至关重要的 了解形成和维持这些的细胞相互作用 如果要设计有效的生物策略，就需要感觉神经成分 用来保护或修理它们。