White matter injury in germinal matrix hemorrhage

描述（由申请人提供）：生发基质出血(GMH)-脑室内出血（IVH）发生在成千上万的早产儿中，易导致白质损伤和随之而来的神经功能障碍——脑瘫和认知缺陷。这些婴儿中最常见的白质损伤是“髓鞘退化和神经胶质瘤”。治疗和预防IVH和由此产生的白质损伤是不存在的。因此，有必要阐明与IVH相关的白质损伤机制，然后制定预防或减少其治疗策略。我们已经建立了一个IVH模型，其中IVH早产儿表现出前少突胶质细胞（pre- oligodendrocytes, pre-OL）的凋亡和增殖，随后在前ol阶段成熟停滞，导致髓鞘退化和胶质瘤形成。少突胶质细胞（oligodendrocytes， OL）的发育受转录因子调控，包括olig1、olig2、Mash 1、Id2、Id4、Nkx2.2和Sox 10；这些因素是由音猬（Shh）、Notch和骨形态发生蛋白（BMP）信号通路控制的。Notch和BMP的过表达促进星形细胞增生，抑制OL的发展。值得注意的是，在动物模型中，抑制BMP水平会增加OL密度；Notch调节促进神经恢复。甲状腺激素是少突胶质形成和髓鞘形成的关键促进因子。因此，我们的实验显示，与非IVH对照组相比，早产IVH受试者的生发基质中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幼崽的髓鞘（O1+） OL密度和髓鞘形成（初步数据）。在此基础上，我们的总体假设是：1)IVH通过BMP、Shh和Notch信号干扰OL的发育，影响OL规范和分化的转录因子的表达；2)通过调节BMP和Notch信号或甲状腺素治疗，可以恢复IVH中被干扰的OL发育、低髓鞘化、胶质瘤和运动障碍。我们的方法是使用我们的兔崽模型和早产儿的尸检材料。目的1：比较IVH与非IVH对兔幼崽（E29）和人类婴儿（妊娠23-35周）OL谱系细胞增殖、成熟和凋亡的影响。目的# 2：与非IVH对照组相比，确定IVH早产儿（E29）和人类婴儿（妊娠23-35周）前脑中参与OL规范和分化的转录因子（Olig1, Olig2, Mash 1, Id2, Id4, Nkx2.2和Sox 10）和关键信号通路（BMP， Shh和Notch）的时间表达。目的3：通过a)甲状腺素治疗和b)调节BMP和Notch信号通路，促进IVH早产儿OL发育和髓鞘形成，促进神经系统恢复。因此，本研究将阐明IVH中白质损伤的机制，并可能为早产儿脑瘫的预防提供新的策略。

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.