Mechanisms of Growth Factor Responsiveness in the Aging Auditory System

衰老听觉系统中生长因子反应的机制

• 批准号: 9896749
• 负责人: BERND FRITZSCH
• 金额: $ 54.37万
• 依托单位: UNIVERSITY OF NEVADA RENO
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2023-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9896749
• 关键词: 2 year old; Affect; Age; Aging; Animal Model; Antibody Specificity; Auditory; Auditory system; Brain; Brain Stem; Brain-Derived Neurotrophic Factor; Cell Nucleus; Cell physiology; Cochlea; Cochlear nucleus; Complex; Contralateral; Data; Development; Disputes; Ear; Embryonic Development; Environment; Etiology; Expression Profiling; Fluorescent in Situ Hybridization; Frequencies; Goals; Growth Factor; Hair Cells; Hearing; In Vitro; Knowledge; Location; Longitudinal Studies; LoxP-flanked allele; Medial; Mediating; Messenger RNA; Modeling; Modernization; Molecular; Morphology; Mus; Nerve; Nerve Degeneration; Nerve Fibers; Neural Pathways; Neuronal Plasticity; Neurons; Neurotrophic Tyrosine Kinase Receptor Type 2; Newborn Infant; Noise; Pattern; Peptide Hydrolases; Play; Presbycusis; Process; Production; Property; Proteins; Psyche structure; Regulation; Reporting; Rest; Role; Signal Transduction; Source; Supporting Cell; Synapses; Synaptic plasticity; Tamoxifen; Techniques; Testing; Therapeutic; Time; Work; age related; aging auditory system; auditory nuclei; auditory pathway; electrical property; extracellular; functional decline; functional plasticity; hearing restoration; in vivo; in vivo evaluation; insight; mRNA Expression; nerve supply; neurosensory; neurotrophic factor; preservation; protein expression; receptor; receptor expression; receptor sensitivity; relating to nervous system; response; signal processing; single molecule; sortilin; sound; spiral ganglion; synaptic function; transcriptional coactivator p75; trapezoid body

Abstract: During hearing development, auditory neurons are wired correctly, both qualitatively and quantitatively, with specific types of spiral ganglion neurons (SGN; auditory afferents) and cochlear nucleus (CN) nerve fibers. Maturation of the auditory neural pathway ensues along the functional tonotopic frequency axis, apparently correlating with time and space/location-dependent gradients in neurotrophins (NTs). In addition, the SGNs develop cochleotopic responses to sound and achieve cochleotopic projections to the cochlear nuclei (CN). The activity of SGNs maintains the number, size and functions of cells in the CN. Previous studies suggest that this process is regulated in part by neurotrophic factors (e.g. brain-derived neurotrophic factor (BDNF)). Expression data show that BDNF expression undergo developmental and age-dependent shifts in their cellular and longitudinal patterns of expression in the auditory pathway. This pattern was proposed to dictate distinct apico- basal function of auditory neuron electrical properties, in turn requirements for cochleotopic and central auditory neuron fine tuning. Despite the appeal of the NT-gradient and age-dependent hypothesis for auditory neural properties, this idea rests on correlative evidence, disputed by some. We seek to unequivocally test and clarify the NT-gradient predictions, and to understand BDNF-mediated auditory functional plasticity and how it sculpts age-related hearing loss (ARHL). We hypothesize that gradual decline in BDNF signaling is one of the common cause for ARHL. We will unravel the function of BDNF in auditory neuronal plasticity using well-characterized cre lines (e.g. Rosa26-creER; Fgf8-cre, Atoh1-cre) to selectively reduce or eliminate BDNF in floxed lines, to study the long- term influence of BDNF levels on auditory signal processing in aging mice. In Aim 1, we will quantify BDNF signaling expression in the auditory system, determine the source/s and the ensuing age-related changes in the auditory neural pathway. Single molecule fluorescent in situ hybridization (SmFISH) and immunocytochemical techniques will be used to quantify mRNA and protein expression and the age-related changes of BDNF. Additionally, age-related changes in BDNF-receptors expression will be quantified. In Aim 2, we will determine BDNF-mediated auditory plasticity with partial or delayed loss of BDNF. These goals will be accomplished using inducible cre lines (e.g. Rosa26-creER) to eliminate all BDNF at various stages of aging from ~3-week to 2-year old mice. We will determine the age-related cellular properties of auditory neurons (e.g. SGNs). Finally, in Aim 3, we will identify BDNF-mediated neural and synaptic plasticity with partial and delayed loss of BDNF. We will use the animal models outlined in Aim 2 to identify changes in synaptic function at the calyx of Held, due to BDNF loss/decline. This central auditory synapse, originates in the ventral cochlear nucleus (VCN), and project contralaterally to the medial nucleus of the trapezoid body (MNTB), and is found to undergo morphological and molecular alterations during aging. We will also examine CN functional changes. Thus, we will resolve how the expression of BDNF impacts SGN/VCN/MNTB functions during aging, providing evidence for BDNF signaling as a common cause for auditory decline. This knowledge will inform efforts to use BDNF in therapeutic strategies to preserve auditory neuron viability and function after ARHL.

抽象的： 在听力开发过程中，听觉神经元在定性和定量上正确连接 特定类型的螺旋神经神经元（SGN；听觉传入）和耳蜗核（CN）神经纤维。 听觉神经通路的成熟沿功能性调整频率轴发生，显然是 与神经营养蛋白（NTS）中的时间和空间/位置依赖性梯度相关。另外，SGNS 对声音产生了对声音的耳蜗反应，并实现对耳蜗核（CN）的耳蜗投影。这 SGN的活性维持CN中细胞的数量，大小和功能。先前的研究表明这一点 过程部分由神经营养因子（例如脑衍生的神经营养因子（BDNF））调节。表达 数据表明，BDNF表达在其细胞中经历了发育和年龄依赖性转移 听觉途径中表达的纵向模式。提出了这种模式来决定不同的apico- 听觉神经元电性能的基础功能又对终精性和中央听觉的要求 神经元微调。尽管NT梯度和年龄依赖性假设对听觉神经具有吸引力 属性，这一想法基于相关证据，有些人提出了争议。我们寻求明确测试并澄清 NT梯度预测，并了解BDNF介导的听觉功能可塑性及其雕刻 与年龄有关的听力损失（ARHL）。 我们假设BDNF信号逐渐下降是ARHL的常见原因之一。 我们将使用特征良好的CRE系（例如 Rosa26-Creer; fgf8-cre，atoh1-cre）有选择地减少或消除floxed系的BDNF，以研究长期 BDNF水平对老化小鼠听觉信号处理的术语影响。在AIM 1中，我们将量化BDNF 听觉系统中的信号传导表达，确定源/s和随后的年龄相关的变化 听觉神经通路。单分子荧光原位杂交（Smfish）和免疫细胞化学 技术将用于量化mRNA和蛋白质表达以及BDNF与年龄相关的变化。 此外，将量化与年龄相关的BDNF受体表达变化。在AIM 2中，我们将确定 BDNF介导的听觉可塑性，部分或延迟的BDNF损失。这些目标将使用 可诱导的CRE线（例如Rosa26-Creer）在〜3周至2年的各个衰老阶段消除所有BDNF 老鼠。我们将确定听觉神经元（例如SGN）的年龄相关细胞特性。最后，目标 3，我们将以BDNF的部分和延迟损失确定BDNF介导的神经和突触可塑性。我们将 使用AIM 2中概述的动物模型来识别Held的花萼的突触功能的变化 BDNF损失/下降。这个中央听觉突触，起源于腹侧耳蜗核（VCN），并发出。 与梯形体（MNTB）的内侧核对侧，发现发生形态学和 衰老过程中的分子改变。我们还将检查CN功能变化。 因此，我们将解决BDNF的表达如何影响SGN/VCN/MNTB在衰老期间的功能， 提供BDNF信号传导的证据是听觉下降的常见原因。这些知识将告知 努力在治疗策略中使用BDNF来保留ARHL后听觉神经元的生存能力和功能。