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.

摘要： 在听觉发育过程中，听觉神经元在定性和定量上都是正确的， 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。 听神经通路的成熟明显地沿功能性音调频率轴延伸沿着， 与神经营养因子（NT）的时间和空间/位置依赖性梯度相关。此外，SGN 发展对声音的耳蜗定位反应，并实现对耳蜗核（CN）的耳蜗定位投射。的 SGN的活性维持CN中细胞的数量、大小和功能。以前的研究表明， 这一过程部分受神经营养因子（例如脑源性神经营养因子（BDNF））调节。表达 数据显示，BDNF表达在其细胞中经历发育和年龄依赖性变化， 听觉通路中的纵向表达模式。这种模式被提出来指示不同的apico- 听觉神经元电特性的基础功能，反过来又要求耳蜗和中枢听觉 神经元微调尽管NT梯度和年龄依赖性假设对听觉神经元的吸引力， 属性，这个想法依赖于相关的证据，有争议的一些。我们寻求明确的测试和澄清 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） 我们推测BDNF信号的逐渐下降是ARHL的常见原因之一。 我们将使用特征良好的cre系（例如， Rosa 26-creER; Fgf 8-cre，Atoh 1-cre）选择性地减少或消除floxed系中的BDNF，以研究长- 脑源性神经营养因子水平对衰老小鼠听觉信号处理的长期影响在目标1中，我们将定量BDNF 信号在听觉系统中的表达，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 技术将用于定量mRNA和蛋白质表达以及BDNF的年龄相关变化。 此外，将定量BDNF受体表达的年龄相关变化。在目标2中，我们将确定 BDNF介导的听觉可塑性伴部分或延迟性BDNF缺失这些目标将通过使用 诱导型cre系（例如Rosa 26-creER），以在从约3周至2岁的不同老化阶段消除所有BDNF 老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，在Aim 3、我们将鉴定BDNF介导的神经和突触可塑性与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萼突触功能的变化，由于 BDNF损失/下降。这种中枢听觉突触起源于耳蜗腹侧核（VCN）， 对侧的内侧核的斜方体（MNTB），并发现进行形态和 老化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BDNF的表达如何影响衰老过程中SGN/VCN/MNTB功能， 为BDNF信号传导作为听觉下降的常见原因提供了证据。这些知识将告知 在治疗策略中使用BDNF来保护ARHL后的听神经元活力和功能的努力。