Matrix Metalloproteinases and Regenerative Plasticity Following Brain Injury

描述（由申请人提供）：数以百万计的美国人是创伤性脑损伤（TBI）的受害者，使其成为严重的健康挑战。创伤性脑损伤常伴有显著的轴突损伤，并伴有神经元神经传递和突触丧失。虽然大脑具有突触重组的固有能力，但这种可塑性往往在脑外伤后失效，导致严重的功能缺陷。我们研究了细胞外基质（ECM）蛋白在脑外伤诱导的反应性突触发生中的作用。某些ECM蛋白及其调控基质金属蛋白酶（MMPs）似乎影响脑外伤后恢复的程度。我们最初的研究对比了适应性损伤恢复期（单侧内嗅皮质损伤或UEC）和非恢复期适应性损伤（液体冲击性TBI+双侧内嗅皮质损伤或TBI+BEC）的ECM/MMP反应。两种明胶酶（MMPs 2、9）、基质溶素-1 （MMP 3）和膜结合的MT-5 MMP均表现出表达和功能的变化，这些变化与反应性突触发生的不同阶段有关。损伤后恢复期间，agrin、tenascin、RPTP-2和N-cadherin的ECM也发生了变化。我们还发现异常的MMP激活与TBI+BEC后的可塑性失败有关。当使用MMP抑制剂时，可塑性会根据剂量和损伤的复杂性而发生积极或消极的改变。鉴于这些结果，我们现在假设特定的基质酶/底物对介导突触前和突触后恢复的不同阶段，以及随后的突触稳定。通过对比适应性UEC和非适应性TBI+BEC后这些基质蛋白的特征，我们将确定突触发生特定阶段的个体蛋白功能障碍是否可以解释实现的恢复程度。我们将测试MMP3/agrin在突触恢复的轴突发芽期的促进作用，tenascin/RPTP-2/2-catenin在突触发生期的促进作用，以及MT-5MMP/N-cadherin在突触成熟期的促进作用。对于每个分子，我们将记录蛋白质/mRNA的表达，突触分布，以及适用时的结合相互作用。最后，我们将通过药物抑制或siRNA敲低来操纵MMP3， RPTP-2和MT-5MMP，并使用突触可塑性的结构和生理指标来检查恢复情况。这些研究将更好地明确基质在脑外伤诱导的突触可塑性中的作用，并提供新的治疗策略。公共卫生相关性：头部损伤的共同特征是受损的脑连接恢复不良。拟议的研究将确定细胞外基质蛋白在这种恢复过程中的作用，并确定可以提高恢复的基质操作。

DESCRIPTION (provided by applicant): Millions of Americans are victims of traumatic brain injury (TBI), making it a serious health challenge. TBI often involves significant axonal injury with attendant neuronal deafferentation and synaptic loss. While the brain has an inherent capacity for synaptic reorganization, this plasticity often fails after TBI, resulting in serious functional deficits. We have examined the role of extracellular matrix (ECM) proteins during reactive synaptogenesis induced by TBI. Certain ECM proteins and their regulatory matrix metalloproteinases (MMPs) appear to influence the extent of recovery achieved after TBI. Our initial studies contrasted ECM/MMP response in a recovering adaptive injury (unilateral entorhinal cortical lesion or UEC) and a non-recovering maladaptive insult (fluid percussion TBI + bilateral entorhinal cortical lesion or TBI+BEC). Two gelatinases (MMPs 2,9), stromelysin-1 (MMP 3) and the membrane bound MT-5 MMP all showed change in expression and function which correlated with different phases of reactive synaptogenesis. ECM shifts in agrin, tenascin, RPTP-2 and N-cadherin occurred during postinjury recovery as well. We also found that aberrant MMP activation was linked with failed plasticity after TBI+BEC. When MMP inhibitors were applied, plasticity was altered either positively or negatively depending upon dosing and complexity of injury. Given these results, we now posit that specific matrix enzyme/substrate pairs mediate different phases of pre and postsynaptic recovery, as well as the subsequent synapse stabilization. By contrasting profiles of these matrix proteins after adaptive UEC and maladaptive TBI+BEC, we will determine if individual protein dysfunction at specific phases of synaptogenesis can account for the extent of recovery achieved. We will test the facilitative role of MMP3/agrin during the axonal sprouting phase of synaptic recovery, tenascin/RPTP-2/2-catenin during the synaptogenic period, and MT-5MMP/N-cadherin at synapse maturation. For each molecule we will document protein/mRNA expression, synaptic distribution and, when applicable, binding interactions. Finally, we will manipulate MMP3, RPTP-2 and MT-5MMP by either pharmacological inhibition or siRNA knockdown and examine recovery using structural and physiological indices of synaptic plasticity. These studies will better define matrix role in TBI-induced synaptic plasticity and provide new treatment strategies. PUBLIC HEALTH RELEVANCE: Common feature of head injury is poor recovery of damaged brain connections. The proposed studies will determine the role of extracellular matrix proteins during this recovery and identify matrix manipulations which would improve recovery.