Chondroitin Sulfate Proteoglycan and Myelination in Intraventricular Hemorrhage

描述（由申请人提供）：早产儿脑室内出血（IVH）易导致白质损伤和随后的脑瘫。早产儿最常见的白质损伤是“轴突完整的神经胶质瘤和低髓鞘形成”。在我们的早产兔IVH模型中，在髓鞘形成前阶段，少突胶质细胞（OL）成熟被阻止。然而，导致ol前期和随后的髓鞘退化的机制尚不清楚。髓鞘形成是一个动态过程，需要一个包含生长因子、细胞外基质分子和髓鞘生成OL的适宜微环境。硫酸慢黄素蛋白聚糖（CSPG）——神经蛋白聚糖、磷蛋白聚糖、brevican、decorin、NG2和versican——是细胞外基质（ECM）的重要组成部分，在成人和新生儿脑损伤中增加。它们主要由反应性星形胶质细胞产生，并受转化生长因子-2 （TGF-2）和表皮生长因子（EGF）的调节。CSPGs在pre-OL的迁移、增殖和分化过程中具有关键的调控功能。具体来说，软骨素酶或蛋白酶对CSPGs的降解促进了OL的迁移，放松了ECM中的物理屏障，增强了OL过程产物的形成，从而使轴突脱鞘，并改善了生长因子与OL的相互作用。尽管有这些证据，CSPGs对髓鞘形成的直接影响尚未研究。我们假设CSPG在IVH早产儿中升高，抑制CSPG的形成将恢复轴突的髓鞘形成和前OL成熟为髓鞘OL。我们的初步数据显示，CSPGs和生长因子（TGF2和EGF）在IVH早产儿和兔仔中的表达升高；用一种CSPG和TGF-2的天然拮抗剂decorin治疗可以降低它们的水平。我们的方法是使用兔模型，腹腔内注射甘油诱导IVH。该模型的结果是，与没有IVH的对照组相比，出血的幼崽表现出炎症、细胞死亡，随后髓鞘形成减少，胶质瘤形成增强（第14天）。具体目标如下：目标1。确定CSPGs（神经蛋白、磷蛋白、brevican、decorin、NG2和versican）及其调节生长因子（TGF-2和EGF）在IVH早产儿和IVH婴儿中的表达是否高于未IVH对照组。目标2。确定软骨素酶或decorin（通过抑制TGF-2）抑制CSPGs是否促进了IVH兔幼崽的前ol成熟、髓鞘形成和神经系统恢复。我们的研究将CSPG与髓鞘化失败联系起来，并结合我们调节CSPG表达的新方法，可能为预防IVH婴儿脑瘫提供有效的策略。公共卫生相关性：在美国，每年约有12240名早产儿在脑室（腔）内及周围出血，这增加了白质损伤和随之而来的脑瘫（四肢无力）以及认知缺陷（写作和阅读困难）的风险。在这项建议中，我们试图确定这些出血婴儿脑损伤的机制，导致行走，阅读和写作障碍。此外，我们将测试可以减少或预防脑瘫的治疗策略。为了解决这些问题，我们将使用早产的兔崽作为实验动物，也将使用有或没有脑出血的早产儿的尸检材料。

DESCRIPTION (provided by applicant): Intraventricular hemorrhage (IVH) in premature infants predisposes to white matter injury and subsequent cerebral palsy. The most common white matter injury in premature infants is 'gliosis and hypomyelination with intact axons'. In our model of IVH in premature rabbits, there is an arrest of oligodendrocyte (OL) maturation at a pre-myelinating stage. However, the mechanism underlying the maturational arrest of pre-OL and subsequent hypomyelination is unclear. Myelination is a dynamic process that needs an appropriate microenvironment containing growth factors, extracellular matrix molecules and myelinating OL. Chrondroitin sulfate proteoglycans (CSPG)-- neuracan, phosphacan, brevican, decorin, NG2 & versican--are important components of the extracellular matrix (ECM) and are increased in adult and neonatal brain injuries. They are primarily produced by reactive astrocytes and are regulated by transforming growth factor-2 (TGF-2) and epidermal growth factor (EGF). CSPGs have key regulatory functions during migration, proliferation and differentiation of pre-OL. Specifically, degradation of CSPGs by either chondroitinase or protease facilitates migration of OL, loosens the physical barriers in ECM, enhances formation of OL process outgrowths to unsheathe axons and improves interaction of growth factors with OL. Despite this evidence, direct effect(s) of CSPGs on myelination have not been studied. We hypothesize that CSPGs are elevated in premature newborns with IVH and that suppression of CSPG formation will restore myelination of axons and maturation of pre- OL into myelinating OL. Our preliminary data show that expression of CSPGs and growth factors (TGF2 and EGF) are elevated in premature infants and rabbit pups with IVH; and treatment with decorin, a CSPG and natural antagonist of TGF-2, reduces their levels. Our approach is to use a rabbit model that induces IVH with intraperitoneal glycerol. This model results in pups with hemorrhage to exhibit inflammation, cell death and subsequently, lesser myelination and more enhanced gliosis (day 14) compared to controls without IVH. The following specific aims will be addressed: Aim #1. Determine whether the expression of CSPGs (neuracan, phosphacan, brevican, decorin, NG2 & versican) and their regulating growth factors (TGF-2 and EGF) are higher in both premature rabbit pups and infants with IVH compared to controls without IVH. Aim # 2. Determine whether suppression of CSPGs either by chondroitinase or decorin (via TGF-2 inhibition) facilitates maturation of pre-OL, myelination and neurological recovery in premature rabbit pups with IVH. Our study that links CSPGs with failure to myelinate coupled with our novel approaches to regulate CSPG expression may provide effective strategies for prevention of cerebral palsy in infants with IVH. PUBLIC HEALTH RELEVANCE: In the United States, about 12,240 premature infants develop bleeding in and around the ventricle (cavity) of the brain each year, which enhances the risk of white matter injuries and consequent cerebral palsy (weakness in extremities), and cognitive deficits--writing and reading difficulties. In this proposal, we seek to determine the mechanism of brain injuries in these infants with hemorrhage that leads to impairment in walking, reading and writing. In addition, we will test therapeutic strategies that can minimize or prevent cerebral palsy in them. To address these issues, we will use prematurely delivered rabbit pups as an experimental animal and will also use autopsy materials from premature infants with and without brain hemorrhage.