THE EFFECTS OF GDNF ON PERIPHERAL NERVE REGENERATION

描述（由申请人提供）：严重的周围神经损伤很常见，并导致显著的长期功能性疾病。尽管最近在神经再生和手术技术的改进相关的神经生物学的理解的进步，修复后的完全功能恢复是罕见的。再生时间延长和手术重建延迟是功能恢复不良的两个主要因素。外源性递送生长因子（GF）具有解决这两个障碍的潜力。特别是，胶质源性神经营养因子（GDNF）是一种有效的运动神经元存活因子，可增强慢性神经损伤后的运动轴突再生。已知GDNF在外周（即骨骼肌）和神经损伤部位的递送对外周神经损伤具有积极影响。 再生然而，参数（位置，时间，和持续时间）适当管理GDNF作为周围神经损伤的治疗干预和其对雪旺细胞（SC）的影响是未知的。该建议的统一假设是，在远端神经和肌肉中适当的外源性GDNF的空间和时间调节将促进长间隙慢性周围神经损伤后的功能恢复。目前的提议结合了药物递送系统和病毒载体技术，以在损伤的远端神经和失神经肌肉中，沿着再生轴突的路径沿着顺序地增加GDNF的水平。从药物递送系统中暂时递送GDNF将用于在损伤时提高水平，以支持轴突再生的初始阶段。来自SC的GDNF的早期过表达（其可以被四环素诱导的基因切除抑制）将在再生的中期（没有轴突捕获）在远端神经中提供增加的GDNF水平，并且晚期四环素诱导的GDNF在肌肉中的表达将在延长的去神经支配后刺激肌肉的再神经支配。此外，该提案还将系统地评估外周神经系统的主要支持细胞SC如何在神经损伤后对GDNF水平的增加做出反应，以及它们在GDNF增强的神经再生中的作用。本研究的主要目的是：（1）研究GDNF在慢性长神经间隙损伤后，通过在损伤部位进行短期蛋白递送和在远端神经和肌肉中进行延迟的、顺序诱导的蛋白递送，来研究GDNF在时间和空间上的控制作用，以促进慢性长神经间隙损伤后的恢复。(2)确定GDNF水平增加对SC的影响，并确定其在GDNF促进周围神经损伤后再生中的作用。

DESCRIPTION (provided by applicant): Severe peripheral nerve injuries are common and result in significant long-term functional morbidity. Despite recent advances in the understanding of the neurobiology related to nerve regeneration and refinement in surgical techniques, complete functional recovery after repair is rare. Extended regeneration times and delayed surgical reconstruction are two major factors in poor functional recovery. Exogenous delivery of growth factors (GFs) has the potential to address both of these barriers. In particular, glial derived neurotrophic factor (GDNF) is a potent motor neuron survival factor that enhances motor axon regeneration after chronic nerve injury. It is known that delivery of GDNF in the periphery (i.e. skeletal muscle) and site of nerve injury has a positive impact on peripheral nerve regeneration. However, the parameters (location, timing, and duration) for appropriate administration of GDNF as a therapeutic intervention for peripheral nerve injury and its effects on Schwann cells (SCs) are unknown. The unifying hypothesis of this proposal is that appropriate spatial and temporal regulation of exogenous GDNF in distal nerve and muscle will enhance functional recovery following long gap chronic peripheral nerve injury. The current proposal combines a drug delivery system, and viral vector technology to sequentially increase the levels of GDNF along the path of regenerating axons; at the sight of injury, in the distal nerve, and denervated muscle. Temporary delivery of GDNF from a drug delivery system will be used to enhance levels at the sight of injury to support the initial phase of axonal regeneration. Early phase overexpression of GDNF from SCs (that can be repressed by tetracycline induced gene excision) will provide increased GDNF levels in the distal nerve in the middle phase of regeneration (without axonal trapping), and late phase tetracycline-induced GDNF expression in the muscle will stimulate reinnervation of the muscle after prolonged denervation. Additionally, the proposal will systematically evaluate how SCs, the major support cell of the peripheral nervous system, respond to increased levels of GDNF after nerve injury and their role in GDNF-enhanced nerve regeneration. The aims of this proposal are: (1) To investigate the effect of spatially and temporally controlled GDNF using short term protein delivery at the site of injury and delayed, sequentially-induced delivery in the distal nerve and muscle to enhance recovery after chronic long nerve gap injury. (2) To determine the effect of increased GDNF levels on SCs and define their role in GDNF enhanced regeneration after peripheral nerve injury.