Reinnervation of inner hair cells following excitotoxic trauma

兴奋性毒性创伤后内毛细胞的神经再支配

基本信息

批准号：
8108029
负责人：
STEVEN H GREEN
金额：
$ 30.99万
依托单位：
UNIVERSITY OF IOWA
依托单位国家：
美国
项目类别：
财政年份：
2011
资助国家：
美国
起止时间：
2011-06-07 至 2016-05-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8108029
关键词：
Affect Aging Animals Axon Biological Assay Brain-Derived Neurotrophic Factor Cell Communication Cells Cessation of life Characteristics Cochlea Code Coupled Culture Media Data Dendrites Dominant-Negative Mutation Exposure to Gene Transfer Generations Genes Glutamate Agonist Glutamates Hair Cells Hearing Human Image Individual Inner Hair Cells Knockout Mice Ligands Mediating Modeling Molecular Genetics Morphology Mus NGFR Protein Natural regeneration Nerve Growth Factor Receptors Neurons Noise Organ of Corti Outer Hair Cells Pattern Peripheral Recovery Rodent Model Role Signal Transduction Synapses System Tamoxifen Testing Time Transgenic Mice Trauma Trauma recovery Virus Youth base cell type excitotoxicity experience hearing impairment improved in vitro Model in vivo interest kainate nerve supply neuronal cell body neurotrophic factor novel partial recovery postsynaptic prevent public health relevance receptor reinnervation research study spatiotemporal spiral ganglion synaptogenesis

项目摘要

DESCRIPTION (provided by applicant): To experimentally investigate reinnervation and synaptogenesis in excitotoxically-damaged cochleae, we developed an organotypic cochlear explant in which a portion of the organ of Corti and corresponding portion of the spiral ganglion are removed intact, maintaining normal morphology and synaptic interactions. Briefly treating the explant with high levels of glutamate agonists results in excitotoxic degeneration of inner hair cell (IHC) - type I spiral ganglion neuron (SGN) synapses but does not affect hair cell or SGN viability. The synapses regenerate but the restored innervation is aberrant: the number of synapses is reduced, and individual SGN axons contact multiple IHCs. In all these respects, the in vitro model mimics what has been observed following noise or glutamatergic excitotoxic damage in vivo. Exogenous neurotrophins - BDNF or NT-3 - significantly improve recovery: the number of synapses on IHCs is increased, synapse number is increased, and innervation of multiple IHCs by single axons is reduced. In Aim 1, we quantitatively compare the ability of BDNF and NT-3 to promote regeneration with an extended recovery period and seek to improve our model by extending it to older animals. Our core set of experiments in Aims 2-4 use molecular genetic approaches, including the use of transgenic mice, to test specific hypotheses, suggested by our preliminary data, regarding the function of neurotrophins in recovery and reinnervation of IHCs after excitotoxic trauma. In Aim 2 we test whether NT-3, the endogenous neurotrophin, acts in a highly spatially restricted manner to maintain synapses on individual IHCs. We will delete NT-3 from a small number of IHCs or inhibit TrkC function in a small number of SGNs and quantitatively compare these with their unmodified neighbors. In Aim 3, we replace NT-3 with BDNF to test the hypothesis that NT-3 has a distinctive function in maintaining IHCSGN synapses and BDNF can't substitute. Finally, in Aim 4, we use p75NTR knockout mice to test the hypothesis that the neurotrophin receptor p75NTR promotes reinnervation after excitotoxic trauma. We will also assay post-trauma expression of p75NTR and putative ligands and test a specific mechanism: whether p75NTR promotes reinnervation by upregulating NT-3.

描述（由申请人提供）：为了实验研究兴奋性损伤的Cochleae中的重新感染和突触发生，我们开发了一种器官的耳蜗外植体，其中Corti器官的一部分以及螺旋神经节的相应部分被删除完整，以保持正常的形态和突触相互作用。短暂地用高水平的谷氨酸激动剂处理外植体会导致内部毛细胞（IHC）的兴奋性变性 - I型螺旋神经节神经元（SGN）突触，但不会影响毛细胞或SGN生存能力。突触再生，但恢复的神经是异常的：突触的数量减少，单个SGN轴突接触多个IHC。在所有这些方面，体外模型模拟了体内噪声或谷氨酸能兴奋性损伤后观察到的内容。外源性神经营养蛋白-BDNF或NT -3-显着改善了恢复：IHCS上的突触数量增加，突触数量增加，并减少了多个IHC的神经支配。在AIM 1中，我们定量比较了BDNF和NT-3随着延长的恢复期促进再生的能力，并试图通过将其扩展到老动物来改善我们的模型。我们在目标2-4中使用分子遗传方法的核心实验集，包括使用转基因小鼠，测试我们的初步数据建议的特定假设，神经营养蛋白在兴奋性创伤后恢复和加剧IHC。在AIM 2中，我们测试是否内源性神经营养蛋白NT-3以高度限制的方式起作用，以维持单个IHC的突触。我们将从少数IHC中删除NT-3或在小的trkc函数中删除NT-3 SGN的数量和定量将它们与未修改的邻居进行比较。在AIM 3中，我们用BDNF替换NT-3，以测试NT-3在维持IHCSGN突触中具有独特功能的假设，而BDNF无法替代。最后，在AIM 4中，我们使用P75NTR基因敲除小鼠来检验以下假设：神经营养蛋白受体p75NTR促进兴奋性创伤后促进了增强作用。我们还将测定P75NTR和推定配体的创伤后表达后，并测试一种特定机制：P75NTR是否通过上调NT-3来促进重新支配。