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: 9762822
• 负责人: BERND FRITZSCH
• 金额: $ 54.86万
• 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/9762822
• 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： 在听力发育过程中，听觉神经元在质量和数量上都正确连接， 特定类型的螺旋神经节神经元（SGN；听觉传入）和耳蜗核（CN）神经纤维。 显然，听觉神经通路的成熟沿着功能性音调频率轴进行 与神经营养素（NT）的时间和空间/位置依赖性梯度相关。此外，SGN 发展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 该过程部分受到神经营养因子（例如脑源性神经营养因子（BDNF））的调节。表达 数据显示，BDNF 的表达在其细胞和细胞中经历发育和年龄依赖性的变化。 听觉通路中的纵向表达模式。提出这种模式是为了规定不同的 apico- 听觉神经元电特性的基础功能，进而要求耳蜗位和中枢听觉 神经元微调。尽管 NT 梯度和年龄相关的听觉神经假说很有吸引力 属性，这个想法依赖于相关证据，但受到一些人的争议。我们力求明确地测试和澄清 NT 梯度预测，并了解 BDNF 介导的听觉功能可塑性及其如何塑造 年龄相关性听力损失（ARHL）。 我们假设 BDNF 信号逐渐减弱是 ARHL 的常见原因之一。 我们将使用充分表征的 cre 线（例如 Rosa26-creER； Fgf8-cre、Atoh1-cre）选择性减少或消除 floxed 品系中的 BDNF，以研究长期 BDNF 水平对衰老小鼠听觉信号处理的长期影响。在目标 1 中，我们将量化 BDNF 听觉系统中的信号表达，确定来源以及随之而来的与年龄相关的变化 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，BDNF 受体表达与年龄相关的变化也将被量化。在目标 2 中，我们将确定 BDNF 介导的听觉可塑性，伴有 BDNF 部分或延迟丧失。这些目标将通过使用来实现 诱导型 cre 系（例如 Rosa26-creER）可消除从约 3 周到 2 岁的各个衰老阶段的所有 BDNF 老老鼠。我们将确定听觉神经元（例如 SGN）与年龄相关的细胞特性。最后，在目标 3，我们将识别 BDNF 介导的神经和突触可塑性以及 BDNF 的部分和延迟损失。我们将 使用目标 2 中概述的动物模型来识别 Held 花萼突触功能的变化，这是由于 BDNF 损失/下降。该中枢听觉突触起源于腹侧耳蜗核 (VCN)，并投射 梯形体内侧核（MNTB）的对侧，被发现经历形态学和 衰老过程中的分子变化。我们还将研究 CN 功能的变化。 因此，我们将解决衰老过程中 BDNF 的表达如何影响 SGN/VCN/MNTB 功能， 为 BDNF 信号传导作为听力下降的常见原因提供证据。这些知识将告知 努力在 ARHL 后的治疗策略中使用 BDNF 来保留听觉神经元的活力和功能。