Matrix Metalloproteinases and Regenerative Plasticity Following Brain Injury

描述（由申请人提供）：数百万美国人是创伤性脑损伤 (TBI) 的受害者，这使其成为严重的健康挑战。 TBI 常常涉及严重的轴突损伤，并伴有神经元传入神经阻滞和突触丧失。虽然大脑具有固有的突触重组能力，但这种可塑性在 TBI 后往往会失效，导致严重的功能缺陷。我们研究了细胞外基质 (ECM) 蛋白在 TBI 诱导的反应性突触发生过程中的作用。某些 ECM 蛋白及其调节基质金属蛋白酶 (MMP) 似乎会影响 TBI 后恢复的程度。我们的初步研究对比了恢复性适应性损伤（单侧内嗅皮质病变或 UEC）和非恢复性适应不良性损伤（液体打击 TBI 双侧内嗅皮质病变或 TBI BEC）中的 ECM/MMP 反应。两种明胶酶 (MMP 2,9)、基质溶解素-1 (MMP 3) 和膜结合 MT-5 MMP 均表现出表达和功能的变化，这与反应性突触发生的不同阶段相关。在损伤后恢复期间，集聚蛋白、腱蛋白、RPTP-2 和 N-钙粘蛋白的 ECM 变化也发生。我们还发现异常的 MMP 激活与 TBI BEC 后可塑性失败有关。当应用 MMP 抑制剂时，可塑性会发生积极或消极的改变，具体取决于剂量和损伤的复杂性。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 和适应不良 TBI BEC 后这些基质蛋白的概况，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所实现的恢复程度。我们将测试 MMP3/agrin 在突触恢复的轴突萌芽阶段的促进作用、tenascin/RPTP-2/2-catenin 在突触发生期的促进作用以及 MT-5MMP/N-cadherin 在突触成熟期间的促进作用。对于每个分子，我们将记录蛋白质/mRNA 表达、突触分布以及（如果适用）结合相互作用。最后，我们将通过药理学抑制或 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检查恢复情况。这些研究将更好地确定基质在 TBI 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大脑连接恢复不良。拟议的研究将确定细胞外基质蛋白在恢复过程中的作用，并确定可改善恢复的基质操作。

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.