White Matter Protection in the Fetus with Congenital Heart Disease

项目总结/摘要 严重的神经发育迟缓正在成为患者当前最重要的挑战之一 先天性心脏病（CHD）生命早期异常的白色物质（WM）发育是导致 CHD儿童中观察到的神经功能缺损类型/程度。在这些儿童中，WM在出生时不成熟 因为子宫内氧气供应减少心脏手术后进一步的WM损伤通常发生在这些 由于胎儿缺氧而导致WM不成熟的相同个体。因此，为了减少 神经发育缺陷的CHD人群，这将是必要的，以减轻缺氧诱导的 先天性心脏病胎儿的WM不成熟。然而，目前没有治疗选择。 少突胶质细胞是WM中最主要的细胞群。一氧化氮合酶（NOS）的激活 随后产生有毒的过氧亚硝酸盐是少突胶质细胞毒性的关键分子事件， 缺氧缺血四氢生物蝶呤（BH 4）的可用性显着降低后，激活NOS和 导致NOS解偶联和有毒的过氧亚硝酸盐的产生，引起氧化应激。重要的是BH 4 水平：i）在正常胎儿发育过程中增加; ii）在缺氧胎儿脑中减少;和iii）确定 胎儿脑对缺氧缺血的脆弱性。我们的数据表明，在小鼠慢性缺氧 会导致大脑BH 4水平下降此外，在缺氧救援期间补充BH 4 减少少突胶质细胞发育不良和髓鞘形成不足，并改善缺氧诱导的运动协调缺陷。 这些结果导致了我们的主要假设，即BH 4水平的降低在 引发一系列氧化应激反应，这些反应是胎儿不成熟WM发育的基础， 冠心病苯丙酮尿症治疗的广泛安全性记录证明了BH 4治疗的可行性， 孕妇在苯丙酮尿症治疗的儿童中发现了WM损伤的显著改善 早期的BH 4。因此，在大脑发育的最早可行阶段重新利用BH 4是一种潜力。 治疗方法总的来说，本提案的目的是建立一个最佳的保护方案 使用我们独特的仔猪模型（Aim 1）和药代动力学， 方法（目标2）。在小鼠模型中利用复杂的遗传工具和生化技术， 将阐明尚不清楚的BH 4生物利用度和BH 4在少突胶质细胞中的治疗作用 发育不良（目标3）。 拟议的研究将建立一个高度转化的BH 4治疗，旨在减少冠心病中的WM损伤。 通过定义BH 4诱导WM恢复的机制，我们的建议具有很大的潜力， 为WM发育不良开发更有针对性和有效的治疗方案。我们的研究成果将 可能有益于WM损伤是发病来源的其他人群，如早产儿。

PROJECT SUMMARY/ABSTRACT Significant neurodevelopmental delay is emerging as one the most important current challenges for patients with congenital heart disease (CHD). Abnormal white matter (WM) development early in life accounts for the type/degree of neurological deficits observed in children with CHD. In these children, WM is immature at birth due to reduced oxygen supply in utero. Further WM injury after cardiac surgery commonly occurs in these same individuals who have WM immaturity due to fetal hypoxia. Therefore, in order to reduce neurodevelopmental deficits in the CHD population, it will be necessary to mitigate hypoxia-induced WM immaturity in the fetus with CHD. However no treatment options are currently available. Oligodendrocytes are the most prominent cell population in WM. Activation of nitric oxide synthase (NOS) followed by production of the toxic peroxynitrite are crucial molecular events in oligodendrocyte toxicity due to hypoxia-ischemia. Tetrahydrobiopterin (BH4) availability is significantly reduced upon activation of NOS and leads to NOS uncoupling and production of the toxic peroxynitrite, causing oxidative stress. Importantly BH4 levels: i) increase during normal fetal development; ii) decrease in the hypoxic fetal brain; and iii) determine the vulnerability of fetal brain to hypoxia-ischemia. Our data have demonstrated that in mice chronic hypoxia causes a depletion of brain BH4 level. In addition BH4 supplementation during hypoxia rescues oligodendrocyte dysmaturation and hypomyelination and improves hypoxia-induced motor coordination deficits. These results have led to our principal hypothesis that decreased BH4 levels play a critical role in triggering a series of oxidative stress reactions underlying immature WM development in the fetus with CHD. Extensive safety records in the treatment of phenylketonuria demonstrate feasibility of BH4 treatment for pregnant women. Marked improvements in WM injury have been found in children with phenylketonuria treated early with BH4. Thus repurposing BH4 for use at the earliest feasible stage of brain development is a potential therapeutic approach. Overall the aims of this proposal are designed to establish an optimal protective regimen of maternal BH4 treatment for the fetus with CHD using our unique piglet model (Aim 1) and pharmacokinetic approach (Aim 2). Leveraging sophisticated genetic tools and biochemical techniques in the mouse model, we will elucidate poorly understood BH4 bioavailability and therapeutic actions of BH4 in oligodendrocyte dysmaturation (Aim 3). The proposed studies will establish a highly translational BH4 treatment aimed at reducing WM injury in CHD. By defining mechanistic insight underlying BH4-induced WM recovery, our proposal has significant potential to develop more targeted and effective treatment options for WM dysmaturation. The outcome of our studies will likely benefit other populations in whom WM injury is a source of morbidity, such as premature infants.