The Effects of GDNF on Peripheral Nerve Regeneration

GDNF对周围神经再生的影响

• 批准号: 7147870
• 负责人: SUSAN E MACKINNON
• 金额: $ 20.75万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-15 至 2011-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7147870
• 关键词: axon; injury; nerve injury; regeneration

DESCRIPTION (provided by applicant): Despite timely and meticulous surgical reconstruction, recovery following proximal traumatic peripheral nerve injuries is often poor. Muscles that are denervated for over a year are characterized by fibrosis and loss of motor end plates and cannot be effectively reinnervated even when regenerating axons reach their motor targets. Agents capable of increasing the rate of axonal regeneration and appropriately directing regenerating motor axons down motor paths and sensory axons down sensory paths after injury have been sought to optimize recovery from peripheral nerve injuries. The exogenous administration of neurotrophic factors and neuroimmunophilin ligands have demonstrated variable neuroregenerative efficacy. Glial-derived neurotrophic factor (GDNF) is an especially potent motor neuron survival factor that has shown some benefit in recovery following peripheral nerve injury. However, the effects of GDNF on the rate and specificity (motor vs. sensory) of axonal regeneration, the importance of its route of administration, and its mechanism of action have not been rigorously tested in clinically relevant peripheral nerve injury paradigms. To address these issues, we have developed two distinct lines of transgenic mice with well-characterized patterns of GDNF overexpression in the central nervous system or peripheral muscle. In addition, these mice express enhanced yellow fluorescent protein in most of their motor and sensory axons or green fluorescent protein in only a few peripheral motor nerves to enable serial tracking of nerve regeneration. In our specific aims we use these murine models to study the neuroenhancing effects of central or peripheral GDNF overexpression following nerve injury. In aims 1a and 1b, the neuroregenerative effects of central or peripheral GDNF overexpression are compared between proximal and distal peripheral nerve crush and repaired transection injuries both morphologically and functionally. We will also study GDNF-mediated downstream signaling pathways and GDNF-mediated transcriptional regulation involved in nerve regeneration. In aim 2a the neuroenhancing effects of GDNF overexpression from central and peripheral sources are evaluated in transection injuries repaired in an acute or delayed fashion with nerve grafts or end- to-side repair. In aim 2b we study the additive effects of GDNF and FK506 on nerve regeneration both histologically and mechanistically following end-to-end repair of sciatic nerve transection injury. In addition to establishing the route of GDNF delivery, peripheral- or central-, that will most effectively stimulate regeneration after peripheral nerve injury, in aim 3 we utilize our transgenic model to study preferential motor reinnervation - a concept with extreme clinical relevance to peripheral nerve surgeons. We will determine which source of trophic support, target- or pathway-derived has the most influence in directing regenerating axons to their appropriate targets.

描述（由申请人提供）：尽管进行了及时、细致的手术重建，但近端外伤性周围神经损伤后的恢复往往很差。失去神经支配一年以上的肌肉的特点是纤维化和运动终板丧失，即使再生轴突达到其运动目标，也无法有效地重新神经支配。人们一直在寻求能够在损伤后增加轴突再生速率并适当引导再生运动轴突沿着运动路径和感觉轴突沿着感觉路径向下的药剂，以优化周围神经损伤的恢复。神经营养因子和神经亲免素配体的外源给药已证明具有不同的神经再生功效。胶质源性神经营养因子（GDNF）是一种特别有效的运动神经元存活因子，已显示出对周围神经损伤后恢复的一些益处。然而，GDNF 对轴突再生的速率和特异性（运动与感觉）的影响、其给药途径的重要性及其作用机制尚未在临床相关的周围神经损伤范例中得到严格的测试。为了解决这些问题，我们开发了两种不同的转基因小鼠品系，它们在中枢神经系统或外周肌肉中具有明确的 GDNF 过度表达模式。此外，这些小鼠在大部分运动和感觉轴突中表达增强的黄色荧光蛋白，或仅在少数外周运动神经中表达绿色荧光蛋白，从而能够连续跟踪神经再生。在我们的具体目标中，我们使用这些小鼠模型来研究神经损伤后中枢或外周 GDNF 过度表达的神经增强作用。在目标 1a 和 1b 中，从形态和功能上比较了近端和远端周围神经挤压和修复的横断损伤之间中枢或外周 GDNF 过度表达的神经再生效应。我们还将研究 GDNF 介导的下游信号通路和 GDNF 介导的神经再生转录调控。在目标 2a 中，在通过神经移植或端侧修复以急性或延迟方式修复的横断损伤中评估中枢和外周来源的 GDNF 过度表达的神经增强作用。在目标 2b 中，我们研究了坐骨神经横断损伤端到端修复后 GDNF 和 FK506 对神经再生的组织学和机制上的累加效应。除了建立外周或中枢的 GDNF 递送途径（最有效地刺激外周神经损伤后再生）外，在目标 3 中，我们利用转基因模型来研究优先运动神经支配——这一概念与外周神经外科医生具有极大的临床相关性。我们将确定哪种营养支持来源（目标来源或途径来源）在引导再生轴突到达适当目标方面影响最大。