Pathogenesis of Nerve Injury: Role of Matrix Metalloproteinases

描述（由申请人提供）： 周围神经损伤（PNI）主要是由外伤引起的，占战伤的60%以上。尽管周围神经有再生的倾向，但PNI患者通常无法获得有用程度的感觉运动恢复，并遭受严重的神经性疼痛（NP）。促进PNI后恢复的新治疗方法旨在提供（1）修复和/或人工桥接切断神经所需的足够的雪旺细胞（SC）数量和SC释放因子，以及（2）抑制纤维SAR形成并促进轴突生长的细胞外基质环境。在VA Merit Review项目的过程中，我们开创了一项研究，该研究涉及基质金属蛋白酶-9（MMP-9）作为一种蛋白酶，仅在PNI参与通过激活NRG 1/ErbB-ERK介导的细胞周期阻滞抑制SC分裂后才在成人神经中表达。我们令人兴奋的新数据表明，在PNI的第一天内，MMP-9的催化活性是SC介导的髓鞘再生和NP发展的决定因素。PNI后立即进行的MMP药理学抑制（MMPi）通过提高SC有丝分裂速率和防止纤维性瘢痕的发展来促进感觉神经再生。使用明胶-琼脂糖珠从PNI位点纯化MMP-9鉴定了多种MMP-9同种型，其可以被选择性和独特的抗MMP-9抑制剂靶向。我们提供了新的数据，暗示内源性MMP-9抑制剂TIMP-1作为PNI后DRG中cAMP诱导的促再生程序的介质，能够促进DRG神经元的生长。我们的突破性数据表明，TIMP-1/CD 63信号在SC中的存在，独立于MMP。我们还提供了第一个研究涉及MMP-14在PNI，使用一种新的，高选择性MMP-14抑制剂。我们的数据表明，MMP-14调节周围神经再生的蛋白水解层粘连蛋白，神经胶质抗原2（NG 2）蛋白多糖和MMP-2。使用最先进的和专门的分子和细胞生物学工具，以及神经病理学和行为学技术，我们将表征MMP-9（Aim 1）和MMP-14（Aim 2）调节SC和DRG神经元功能的机制和治疗价值，以及MMP依赖性和MMP非依赖性TIMP在PNI中的作用。凭借尖端的选择性MMPi试剂和支持其使用的强大初步研究，我们预计该计划将提供新的机制见解和有针对性的治疗策略，以改善VA患者中与战斗和其他流行疾病相关的PNI。

DESCRIPTION (provided by applicant): Extremity trauma, accounting for the majority (>60%) of combat wounds, results in peripheral nerve injury (PNI). Despite the propensity of peripheral nerve for regeneration, PNI patients commonly achieve no useful degree of sensorimotor recovery and suffer severe neuropathic pain (NP). New therapeutic approaches to facilitate recovery after PNI aim to provide (1) adequate Schwann cell (SC) numbers and SC-released factors required for repair and/or artificial bridging of a severed nerve, and (2) extracellular matrix milieu that inhibits fibrous sar formation and promotes axonal growth. In the course of this VA Merit Review program, we pioneered studies implicating matrix metalloproteinase-9 (MMP-9) as a protease uniquely expressed in adult nerve only after PNI involved in suppression of SC division via activation of NRG1/ErbB-ERK mediated cell cycle arrest. Our exciting new data implicates catalytic MMP-9 activity within the first days of PNI as determinant to SC-mediated remyelination, and the development of NP. Pharmacological MMP inhibition (MMPi) immediately after PNI facilitates sensory nerve regrowth by enhancing the rate of SC mitosis and preventing the development of a fibrous scar. Purification of MMP-9 from the PNI site using gelatin-sepharose beads identified multiple MMP-9 isoforms, which may be targeted by selective and unique anti-MMP-9 inhibitors. We provide novel data implicating an endogenous MMP-9 inhibitor, TIMP-1, as mediator of cAMP- induced pro-regenerative program in DRG after PNI, able to promote outgrowth of DRG neurons. Our groundbreaking data implies the existence of TIMP-1/CD63 signaling in SCs, independent of MMPs. We also offer the first studies implicating MMP-14 in PNI, using a new, highly selective MMP-14 inhibitor. Our data suggests that MMP-14 regulates peripheral nerve regeneration by proteolysis of laminin, neuron-glial antigen 2 (NG2) proteoglycan and MMP-2. Using state-of-the-art and specialized molecular and cell biological tools, as well as neuropathological and behavioral techniques, we will characterize the mechanisms and therapeutic value of MMP-9 (Aim 1) and MMP-14 (Aim 2) regulation of SC and DRG neuronal function, and MMP- dependent and MMP-independent TIMP actions in PNI. With cutting-edge, selective MMPi reagents and strong Preliminary Studies supporting their use, we anticipate this program will provide novel mechanistic insights and targeted therapeutic strategies to improve PNI related to combat and other prevalent conditions amongst VA patients.