Extracellular Matrix Mediates Axonal Integrity Following Brain Injury

描述（由申请人提供）：创伤性脑损伤（TBI）是美国一个重要的健康问题，每年有超过170万的新病例。脑回路的丧失是受害者持续认知缺陷的基础，而轴突损伤是主要原因。以损伤的胼胝体（CC）为模型，我们发现损伤后基质金属蛋白酶（MMPs）的变化与不同的髓鞘和无髓鞘纤维病理相关。MMPs是影响脑轴突完整性的脑细胞外基质（ECM）的重要调节剂。我们发现CC明胶酶MMP2和mmp9的活性在不同的损伤后时间间隔达到峰值，以反应性胶质反应为标志。我们还观察到这种MMP活性与无髓鞘轴突病理在时间上相关。用神经保护化合物FK-506和二甲胺四环素治疗导致这种明胶酶活性选择性的、时间依赖性的降低，并减少CC复合动作电位（CAPs）的缺陷。微阵列研究显示，骨桥蛋白（OPN）是一种分泌到ECM并与MMP功能相互关联的细胞因子，在受损的CC中显著上调。根据这些数据，我们假设明胶酶对创伤性轴索损伤的反应是通过反应性胶质细胞中OPN的急性激活来介导的。我们还假设，在这一途径中的时间过程和神经胶质的作用在无髓鞘和有髓鞘纤维之间是不同的。为了验证这些假设，将在TBI的流体冲击模型中探讨以下目标：1)在无髓鞘（ON，嗅觉神经）和有髓鞘纤维（IC，内囊）丰富的纤维环境中记录轴突损伤期间的OPN/MMP2,9，并确定OPNKO和MMP9KO是否改变了这些变化，2)在体外使用原代CC和ON胶质培养物解剖细胞特异性OPN/MMP2,9相互作用，3)测试OPNKO或MMPKO是否改变了轴突神经保护药物FK-506和米诺环素的疗效。然后确定最佳药物联合OPN/MMP9操作是否会改变大鼠FPTBI模型的功能或结构结果。这些研究可能为脑外伤后轴突损伤患者的局部和纤维靶向治疗提供新的选择。

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) is a significant U.S. health concern, with over 1.7 million new cases each year. Loss of brain circuitry underlies persistent cognitive deficits suffered by its victims, with axonal damage as a major contributor. Using the injured corpus callosum (CC) as a model, we have shown that postinjury change in matrix metalloproteinases (MMPs) is correlated with distinct myelinated and unmyelinated fiber pathology. MMPs are critical modulators of brain extracellular matrix (ECM) which affect axonal integrity. We found that CC gelatinases MMP2 and 9 peak in activity at different postinjury intervals which are marked by reactive glial response. We also observed that this MMP activity was temporally correlated with unmyelinated axon pathology. Treatment with neuroprotective compounds FK-506 and minocycline resulted in selective, time- dependent reduction of this gelatinase activity and reduced deficits in CC compound action potentials(CAPs). Pilot microarray studies revealed that osteopontin (OPN), a cytokine secreted into the ECM and reciprocally linked to MMP function, was significantly upregulated in injured CC. From these data we hypothesize that gelatinase response to traumatic axonal injury is mediated through acute activation of OPN within reactive glia. We also posit that the time course and glial role in this pathway will differ between unmyelinated and myelinated fibers. To test these hypotheses, the following aims will be explored in the fluid percussion model of TBI : 1) to document OPN/MMP2,9 during axonal injury within fiber environments enriched in unmyelinated (ON, olfactory nerve) and myelinated fibers (IC, internal capsule), and determine if OPN KO and MMP9KO alters these changes, 2) to dissect cell specific OPN/MMP2,9 interaction in vitro using primary CC and ON glial cultures, and 3) to test whether OPNKO or MMPKO alters efficacy of axonal neuroprotective drugs FK-506 and minocycline, then determine if combining optimal drug and OPN/MMP9 manipulation alters functional or structural outcome in the rat model of FPTBI. These studies are likely to identify novel options for regional and fiber targeted therapy in patients suffering from axonal damage after TBI.