White matter injury in germinal matrix hemorrhage

描述(申请人提供)：生发基质出血(GMH)-脑室出血(IVH)发生在数以千计的早产儿，并使他们的脑白质损伤和伴随而来的神经功能障碍-脑瘫和认知障碍。这些婴儿最常见的脑白质损伤是“髓鞘过少和胶质细胞增多症”。IVH和由此引起的脑白质损伤的治疗和预防都是不存在的。因此，有必要阐明与IVH相关的脑白质损伤的机制，然后制定预防或减少其发生的治疗策略。我们已经建立了一种IVH模型，在该模型中，患有IVH的早产幼鼠表现出前少突胶质细胞(Pre-OL)的凋亡和增殖，随后成熟-停滞在Pre-OL阶段，导致髓鞘减少和胶质增生。少突胶质细胞的发育受转录因子的调控，包括Olig-1、Olig-2、Mash 1、Id2、Id4、Nkx2.2和Sox 10，这些因子受Sonic Hedgehog(Shh)、Notch和骨形态发生蛋白(BMP)信号通路的调控。Notch和BMP过表达促进星形细胞增多并抑制OL的发育。值得注意的是，在动物模型中抑制BMP水平增加了OL密度；而Notch调节促进了神经恢复。甲状腺激素是少突胶质细胞发生和髓鞘形成的关键促进剂。因此，我们的实验显示，与非IVH对照组相比，IVH早产儿生发基质中BMP-4和Notch水平更高。更重要的是，甲状腺激素治疗或BMP抑制恢复了IVH幼鼠的髓鞘(O1+)OL密度和髓鞘密度(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信号影响参与OL规范和分化的转录因子的表达；2)通过调节BMP和Notch信号或甲状腺激素治疗，IVH中被干扰的OL发育、髓鞘减少、胶质增生和运动障碍可以恢复。我们的方法是使用我们的兔仔模型和早产儿的尸检材料。具体目标如下：目的1：比较有IVH和无IVH的早产兔幼鼠(E29)和人类婴儿(23-35周)OL系细胞的增殖、成熟和凋亡。目的#2：检测IVH早产兔幼鼠(E29)和胎龄23~35周的婴儿(胎龄23~35周)与非IVH对照组大鼠前脑中转录因子(Orig1、Odon2、Mash1、Id2、Id4、Nkx2.2和Sox10)的时间表达及参与OL特化和分化的关键信号通路(BMP、Shh和Notch)。目的#3：通过a)甲状腺激素治疗和b)调节BMP和Notch信号通路，促进OL的发育和髓鞘形成，以促进IVH早产幼鼠的神经恢复。因此，这项拟议的研究将阐明IVH中脑白质损伤的机制，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.