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是常见的，并导致显著的长期功能障碍。尽管最近对神经再生和外科技术的完善相关的神经生物学的了解取得了进展，但修复后完全恢复功能的情况很少见。再生时间延长和手术重建延迟是功能恢复差的两个主要因素。外源性递送生长因子(GFS)具有解决这两个障碍的潜力。尤其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，可促进慢性神经损伤后运动轴突再生。已知GDNF在周围(即骨骼肌)和神经损伤部位的传递对周围神经有积极的影响 再生。然而，GDNF作为周围神经损伤的治疗干预措施及其对雪旺细胞(SCs)的影响的参数(位置、时间和持续时间)尚不清楚。这一建议的统一假设是，在远端神经和肌肉中适当的时间和空间调节外源性GDNF将促进长间隙慢性周围神经损伤后的功能恢复。目前的方案结合了药物递送系统和病毒载体技术，在再生轴突的路径上顺序增加GDNF的水平；在看到损伤时，在远端神经和失神经肌肉中。从药物输送系统中临时输送GDNF将用于提高损伤时的水平，以支持轴突再生的初始阶段。SCs早期过表达GDNF(可被四环素诱导的基因切除抑制)将使再生中期远端神经中GDNF水平增加(无轴突捕获)，晚期四环素诱导的GDNF在肌肉中的表达将刺激肌肉在长时间失神经后重新支配神经。此外，该提案将系统地评估作为周围神经系统主要支持细胞的干细胞如何应对神经损伤后GDNF水平的增加，以及它们在GDNF增强的神经再生中的作用。本研究的目的是：(1)探讨在慢性长神经间隙损伤后，采用损伤部位短期蛋白递送和远端神经肌肉延迟递增递送的方法，在空间和时间上控制GDNF的效果。(2)探讨周围神经损伤后GDNF水平升高对SCs的影响及其在促进再生中的作用。

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.