White matter injury in germinal matrix hemorrhage

描述（由申请人提供）：老年性基质出血（GMH）-脑室内出血（IVH）发生在数千名早产儿中，使其易于发生白色物质损伤和伴随的神经功能障碍-脑瘫加认知缺陷。这些婴儿最常见的白色物质损伤是“髓鞘形成不足和神经胶质增生”。对IVH和由此产生的白色损害的治疗和预防是不存在的。因此，有必要阐明与IVH相关的白色物质损伤的机制，然后制定一种治疗策略，以防止或尽量减少它。我们已经开发了一种模型IVH中，早产儿IVH表现出凋亡和增殖的前少突胶质细胞（前OL）与随后的成熟，逮捕在前OL阶段，导致髓鞘形成不足和胶质细胞增生。 寡突胶质细胞（Oligodendrocyte，OL）的发育受转录因子Olig-1、Olig-2、Mash 1、Id 2、Id 4、Nkx2.2和Sox 10的调控，这些转录因子又受Shh、Notch和BMP信号通路的调控。Notch和BMP过表达促进星形胶质细胞增生并抑制OL发展。值得注意的是，动物模型中BMP水平的抑制增加了OL密度;并且Notch调节改善了神经恢复。甲状腺激素是少突胶质细胞发生和髓鞘形成的关键启动子。因此，我们的实验揭示了与非IVH对照相比，患有IVH的早产受试者的生殖基质中的BMP-4和Notch水平更高。更重要的是，甲状腺素治疗或BMP抑制恢复了IVH幼崽中髓鞘形成（O 1+）OL和髓鞘形成的密度（初步数据）。在此基础上，我们的总体假设是：1）IVH干扰OL发育，并通过BMP、Shh和Notch信号传导影响参与OL特化和分化的转录因子的表达，以及2）IVH中被干扰的OL发育、髓鞘形成不足、胶质增生和运动障碍可以通过调节BMP和Notch信号传导或甲状腺素治疗来恢复。我们的方法是使用我们的兔幼仔模型和早产儿尸检材料。 将解决以下具体目标：目标#1：比较有IVH与无IVH的早产兔幼仔（E29）和人类婴儿（妊娠23-35周）中OL谱系细胞的增殖、成熟和凋亡。目标二：与非IVH对照相比，测定早产兔幼仔（E29）和人类婴儿（妊娠23-35周）前脑中参与OL特化和分化的转录因子（Olig 1、Olig 2、Mash 1、Id 2、Id 4、Nkx2.2和Sox 10）和关键信号通路（BMP、Shh和Notch）的时间表达。目标三：通过a）甲状腺素治疗和B）调节BMP和Notch信号通路，促进OL发育和髓鞘形成，以促进患有IVH的早产幼仔的神经恢复。因此，这项研究将阐明IVH中白色物质损伤的机制，并可能导致预防早产儿脑性瘫痪的新策略。

DESCRIPTION (provided by applicant): Germinal matrix hemorrhage (GMH)-intraventricular hemorrhage (IVH) occurs in thousands of premature infants and predisposes them to white matter injury and to the attendant neurologic dysfunctions-- cerebral palsy plus cognitive deficits. The most common white matter injury in these infants is "hypomyelination and gliosis". Treatment and prevention of both the IVH and the resultant white matter damage is non-existent. Therefore, it is necessary to elucidate the mechanism of white matter injury associated with IVH and then to develop a therapeutic strategy either to prevent or minimize it. We have developed a model of IVH in which premature pups with IVH exhibit apoptosis and proliferation of pre-oligodendrocyte (pre-OL) with subsequent maturation-arrest in pre-OL stage, resulting in hypomyelination and gliosis. Oligodendrocyte (OL) development is regulated by transcription factors, including Olig-1, Olig-2, Mash 1, Id2, Id4, Nkx2.2 and Sox 10; and these factors are controlled by sonic hedgehog (Shh), Notch and Bone Morphogenetic Protein (BMP) signaling pathways. Notch and BMP overexpression promotes astrocytosis and inhibits OL development. Of note, suppression of BMP levels in animal models increases OL density; and Notch modulation improves the neurological recovery. Thyroid hormone is a key promoter of oligodendrogenesis and myelination. Accordingly, our experiments have revealed higher BMP-4 and Notch levels in the germinal matrix of premature subjects with IVH compared to non-IVH controls. More importantly, thyroxine treatment or BMP inhibition restored the density of myelinating (O1+) OL and myelination in IVH pups (Preliminary data). On this basis our overall hypotheses are that 1) IVH disturbs the OL development and affects the expression of transcription factors involved in OL specification and differentiation via BMP, Shh and Notch signaling, and that 2) the disturbed OL development, hypomyelination, gliosis and motor impairment in IVH can be restored by modulating BMP and Notch signaling or thyroxine treatment. Our approach is to use our rabbit pup model and autopsy materials from premature infants. The following specific aims will be addressed: Aim # 1: Compare proliferation, maturation and apoptosis of cells of OL lineage in premature rabbit pups (E29) and human infants (23-35 weeks gestation) with IVH vs. without IVH. Aim # 2: Determine temporal expression of transcription factors (Olig1, Olig2, Mash 1, Id2, Id4, Nkx2.2 and Sox 10) and the key signaling pathways (BMP, Shh and Notch) involved in OL specification and differentiation in the forebrain of the premature rabbit pups (E29) and human infants (23-35 weeks gestation) with IVH compared to non-IVH controls. Aim # 3: Promote OL development and myelination to facilitate neurological recovery in premature pups with IVH by a) thyroxine treatment and by b) modulating BMP and Notch signaling pathways. Hence, the proposed study will elucidate the mechanism of white matter injury in IVH and may lead to novel strategies in prevention of cerebral palsy in premature infants.