Mechanisms of Neuromuscular Repair by Schwann Cells

雪旺细胞修复神经肌肉的机制

• 批准号: 6746040
• 负责人: YOUNG-JIN SON
• 金额: $ 24.94万
• 依托单位: DREXEL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2007-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6746040
• 关键词: Schwann cells; acetylcholine; biological signal transduction; cadherins; fibroblasts; genetically modified animals; insulinlike growth factor; laboratory mouse; muscarinic receptor; nervous system regeneration; neural cell adhesion molecules; neuronal guidance; neurotrophic factors; transfection

DESCRIPTION (provided by applicant): Intact motor nerve terminals sprout in response to paralysis or partial denervation and re-establish functional synaptic connections with inactive muscle fibers, thus insuring the maintenance of muscle innervation and strength. This remarkable feature of neuromuscular plasticity has been studied intensively, both because it is essential to our understanding of synapse formation and maintenance and because it provides a potential avenue for promoting repair of nerve injuries. However, the mechanisms underlying this type of neural plasticity are poorly understood. We and others have recently shown that the terminal Schwann cells (tSCs) that cap the nerve terminal play a central role in this process, by extending processes that trigger terminals to sprout and that guide these sprouts to inactive muscle fibers. We now propose to identify the molecules that activate quiescent tSCs to extend processes and the molecules that activated tSCs use to elicit sprouting. Aim 1 will test the hypothesis that reduced neurotransmitter release, and subsequent inactivation of muscarinic signaling, activates tSCs. Pharmacological inhibition of this muscarinic signaling in vivo and analyses of knockout mouse lines that are defective in muscarinic signaling will be used. Aim 2 will assess the role of tSCs in mediating growth factor induced sprouting. We will test this by exogenous application of IGFs and CNTF, two growth factors known to elicit sprouting, to determine whether these agents activate tSCs to extend processes. We will then examine CNTF -/- mice, whose nerve terminals apparently do not sprout in response to partial denervation or botulinum toxin, to determine whether their tSCs are defective in their response to normal sprouting stimuli. In Aim 3, we will test the hypothesis that NCAM and N-cadherin, the two cell adhesion molecules (CAMs) upregulated in activated tSCs, elicit sprouting. We will exploit the ballistic transfection technique to overexpress these CAMs selectively in quiescent tSCs in vivo, and examine the incidence of terminal sprouting. Secondly, we will transplant fibroblasts genetically modified to express the CAMs to intact endplates, to determine whether these fibroblasts acquire the ability to induce terminal sprouting. Through this work, we attempt to further define the role of Schwann cells in the reactive sprouting and to gain new insights into the inter- and intracellular signaling associated with terminal sprouting.

描述（由申请人提供）：完整的运动神经终端响应于瘫痪或部分神经疗法，并与无效的肌肉纤维重新建立功能突触连接，从而确保维持肌肉神经支配和力量。已经对神经肌肉可塑性的这种显着特征进行了深入的研究，这既是我们对突触形成和维护的理解至关重要的，并且因为它为促进修复神经损伤提供了潜在的途径。但是，这种神经可塑性的基础机制知之甚少。我们和其他人最近表明，通过扩展触发末端发芽的过程，并指导这些芽剂到无活性的肌肉纤维，将神经末端限制的末端Schwann细胞（TSC）在此过程中起着核心作用。现在，我们建议确定激活静态TSC的分子，以扩展激活TSC用于引起发芽的过程的过程和分子。 AIM 1将测试降低神经递质释放并随后失活的假设会激活TSC。将使用这种在体内对这种毒蕈碱信号传导的药理抑制作用以及对毒蕈碱信号有缺陷的基因敲除小鼠系的分析。 AIM 2将评估TSC在介导生长因子引起的发芽中的作用。我们将通过外源应用IGF和CNTF（已知引起发芽的两个生长因子）来测试这一点，以确定这些试剂是否激活TSC来扩展过程。然后，我们将检查CNTF - / - 小鼠，它们的神经末端显然不会响应部分神经膜或肉毒杆菌毒素，以确定它们的TSC在对正常发芽刺激的反应中是否有缺陷。在AIM 3中，我们将检验以下假设：NCAM和N-钙粘着蛋白，即在活化的TSC中上调的两个细胞粘附分子（CAM），引起发芽。我们将利用弹道转染技术在体内选择性地表达这些凸轮，并检查末端发芽的发生率。其次，我们将移植基因修饰的成纤维细胞以表达凸轮的完整终板，以确定这些成纤维细胞是否获得诱导末端发芽的能力。通过这项工作，我们试图进一步定义Schwann细胞在反应性发芽中的作用，并获得与末端发芽相关的细胞间和细胞内信号传导的新见解。