Mechanisms of Regeneration: Facial Nerve Injury and Repair

项目概要/摘要 该提案提出了一个为期五年的研究职业发展计划，重点是研究刺猬 (Hh)面神经损伤反应中的信号通路。候选人目前是助理教授， 斯坦福大学医学院的耳鼻喉科。概述的建议建立在候选人以前的 在世界知名的Hh通路信号专家的指导下， 博士菲尔·比奇拟议的实验和教学工作将定位候选人与一套独特的 技能，使他能够过渡到独立的医生科学家在神经损伤的机制 反应和神经纤维化。 面瘫导致受影响患者的严重残疾，影响面部功能和整体 生活质量对于永久性瘫痪的患者，手术是最有效的治疗方法，以改善面部 在某些情况下，还能恢复部分运动。然而，现有的治疗方法并不完全 恢复正常的面部运动。在临床上，受伤的面神经变得纤维化，这可以阻碍 康复和治疗。尽管这在临床上很重要，但神经纤维化的潜在机制是 不太了解。考虑到hedgehog通路在神经束膜发育中的关键作用，我们探讨了 刺猬反应元件在损伤后小鼠面神经中的功能。我们首先确认了 刺猬反应性成纤维细胞（Gli 1+）在鼠面神经。面部Gli 1+成纤维细胞 神经损伤后显著扩张，并构成再生神经的大部分神经束膜。 这些细胞与激活的雪旺细胞和再生轴突密切相关， 在损伤后的前两周内血管生成。然而，到损伤后10周，Gli 1+成纤维细胞似乎 在神经内形成纤维组织根据这些发现，我们假设Hh信号促进了 损伤后早期神经再生，但在损伤后较晚的时间点转变为促纤维化状态。到 评估这些假设，我们提出了以下目标：1）表征Hh信号转导的作用后，面部 神经损伤使用强大的遗传和药理学模型，2）描述Gli 1+细胞的变化， 神经再生和纤维化通过下一代测序。完成本建议书中的研究 将能够彻底解剖Hh信号传导在面神经损伤中的作用， 介导损伤后再生和纤维化，并揭示了新的治疗靶点，用于临床应用。

Project Summary/Abstract This proposal presents a five-year research career development program focused on the study of Hedgehog (Hh) pathway signaling in facial nerve injury response. The candidate is currently an Assistant Professor of Otolaryngology at the Stanford School of Medicine. The outlined proposal builds on the candidate’s previous research and clinical experience under the supervision of a world-renowned expert in Hh pathway signaling, Dr. Phil Beachy. The proposed experiments and didactic work will position the candidate with a unique set of skills that will enable his transition to independence as a physician scientist in the mechanisms of nerve injury response and nerve fibrosis. Facial paralysis results in significant disability for affected patients, impacting both facial function and overall quality of life. For patients with permanent paralysis, surgery is the most effective treatment to improve facial symmetry and – in some cases – restore partial movement. However, existing treatments do not completely restore normal facial movement. Clinically, the injured facial nerve becomes fibrotic, which can impede recovery and treatment. Despite the clinical importance of this, the mechanism underlying nerve fibrosis is poorly understood. Given the critical role of the hedgehog pathway in perineurial development, we explored the function of hedgehog-responsive elements in the murine facial nerve after injury. We first verified the presence of hedgehog-responsive fibroblasts (Gli1+) within the murine facial nerve. Gli1+ fibroblasts within the facial nerve expand impressively after injury and compose the majority of the perineurium of the regenerating nerve. These cells closely associate with activated Schwann cells and regenerating axons and appear to promote angiogenesis in the first two weeks after injury. By 10 weeks after injury, however, Gli1+ fibroblasts appear to form fibrotic tissue within the nerve. Following on these findings, we hypothesize that Hh signaling promotes early nerve regeneration after injury but transitions to a pro-fibrotic state at later time points after injury. To assess these hypotheses, we propose the following aims: 1) Characterize the role of Hh signaling after facial nerve injury using powerful genetic and pharmacologic models, 2) Describe changes in Gli1+ cells during facial nerve regeneration and fibrosis via Next Generation Sequencing. Completion of the research in this proposal will enable a thorough dissection of the role of Hh signaling in facial nerve injury, vet this pathway as a mediator of both regeneration and fibrosis after injury, and reveal new therapeutic targets for clinical use.