Pathogenesis of Nerve Injury: Role of Matrix Metalloproteinases

描述(由申请人提供)： 四肢创伤是导致周围神经损伤(PNI)的主要原因，占战斗创伤的60%。尽管周围神经有再生的倾向，但PNI患者通常没有有效程度的感觉运动恢复，并遭受严重的神经病理性疼痛(NP)。促进PNI后恢复的新的治疗方法旨在提供(1)足够的雪旺细胞(SC)数量和SC释放的因子，以修复和/或人工桥接切断的神经，以及(2)抑制纤维sar形成和促进轴突生长的细胞外基质环境。在这个VA Merit Review项目的过程中，我们率先进行了一些研究，发现只有在PNI参与通过激活NRG1/ErbB-ERK介导的细胞周期停滞来抑制SC分裂之后，基质金属蛋白酶-9(MMP9)才是一种在成年神经中唯一表达的蛋白。我们令人兴奋的新数据表明，在PNI的最初几天内，催化的MMP-9活性是SC介导的再髓鞘形成和NP发展的决定因素。PNI后立即给予药物性基质金属蛋白酶抑制(MMPI)，通过提高SC有丝分裂的比率和防止纤维瘢痕的发展，促进感觉神经的再生。用明胶-琼脂糖珠从PNI部位纯化的基质金属蛋白酶-9鉴定出多种基质金属蛋白酶-9亚型，它们可能是选择性和独特的抗基质金属蛋白酶-9抑制剂的靶点。我们提供了新的数据暗示内源性的基质金属蛋白酶-9抑制剂，TIMP-1，作为cAMP诱导的PNI后DRG促再生程序的中介物，能够促进DRG神经元的生长。我们的突破性数据表明，在干细胞中存在TIMP-1/CD63信号，而不依赖于MMPs。我们还利用一种新的、高选择性的基质金属蛋白酶-14抑制剂，首次研究了基质金属蛋白酶-14与PNI的关系。我们的研究结果提示，基质金属蛋白酶-14通过分解层粘连蛋白、神经胶质抗原2蛋白多糖和基质金属蛋白酶-2来调节周围神经再生。我们将利用最先进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，研究基质金属蛋白酶-9(Aim 1)和基质金属蛋白酶-14(Aim 2)对脊髓和背根节神经元功能的调节机制和治疗价值，以及基质金属蛋白酶依赖和非基质金属蛋白酶依赖性和非依赖性TIMP在PNI中的作用。随着尖端的、选择性的MMPI试剂和强有力的初步研究支持它们的使用，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，以改善与战斗和VA患者其他流行情况相关的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.