Aberrations in oligodendrocyte development resulting from congenital heart disease and its surgical treatment

 描述(申请人提供)：出生时患有先天性心脏病(CHD)的新生儿，大脑发育迟缓和脑白质(WM)损伤是常见的。两者都已被临床核磁共振研究记录在案。在这些新生儿心脏手术后的冠心病患者中，新的WM损伤也很常见，很可能是继发于体外循环(CPB)的有害影响。新的WM损伤更有可能出现在CHD诱导的宫内缺氧所致的未成熟脑中。然而，CHD延迟成熟和WM损伤的细胞机制以及CPB对未成熟脑的影响仍然知之甚少。对这些机制的深入了解将有助于预防和/或开发对冠心病患者新生儿WM损伤的有效治疗。以往的研究证明，在新生啮齿类动物中，脑缺氧和缺血改变了少突胶质前体细胞(OPC)的生成和迁移。在导致WM髓鞘减少的小鼠模型中，长时间的缺氧也会延迟OPC的分化。WM髓鞘过少是临床应用的脑不成熟量表的一个组成部分。因此，我们将检验以下假设：i)术前低氧导致的WM中OPC的生成和分化受阻，导致WM髓鞘减少和脑不成熟；ii)CPB的炎症效应以及循环停止的再灌注和复氧都加剧了OPC的生成受损和延迟的OPC迁移和成熟。将使用的第一个模型是仔猪缺氧模型。在这个实验范式中，猪脑的不成熟发育与在患有CHD的新生儿中观察到的非常相似。CPB对未成熟大脑的影响将通过使用暴露在低氧和CPB中的仔猪的组合范式来研究。为了分析猪脑中OPC的成熟，我们从猪的干细胞/祖细胞中产生了OPC。用免疫组织化学方法检测OPC的增殖情况。OPC的迁移将通过使用超顺磁性氧化铁标记的新的细胞跟踪MRI技术在体内持续监测。从OPC到成熟少突胶质细胞的发育将通过荧光标记组织学来定义。WM的微结构成熟度将通过连续体积分析和扩散张量成像来分析。最后，将确定显微结构成熟和大脑不成熟之间的相关性。这项拟议的研究将确定CHD新生儿大脑不成熟和WM损伤的关键细胞机制。这些发现将有助于关于最佳手术时机和技术的决策。拟议的研究有可能确定和评估治疗脑不成熟和WM损伤的新策略，并定义CHD患者围产期护理的新标准。由此产生的神经发育结果的改善将对那些患有CHD的人带来巨大的好处。

 DESCRIPTION (provided by applicant): Delayed brain development and white matter (WM) injury are common in neonates with congenital heart disease (CHD) at the time of birth. Both have been documented by clinical MRI studies. New WM injury is also common in these same individuals with CHD following neonatal cardiac surgery, most likely secondary to the deleterious effects of cardiopulmonary bypass (CPB). New WM injury is more likely to be seen in the immature brain resulting from CHD-induced in utero hypoxia. However, cellular mechanisms underlying delayed maturation and WM injury in CHD and effects of CPB on immature brain remain poorly understood. Insights into these mechanisms would allow prevention and/or development of effective treatment for neonatal WM injury in patients with CHD. Previous studies have documented that in the neonatal rodent brain hypoxia and ischemia alter generation and migration of oligodendrocyte progenitor cells (OPCs). Prolonged hypoxia also delays OPC differentiation in a mouse model leading to WM hypomyelination. WM hypomyelination is one component of a clinically-applied scale for brain immaturity. Therefore, we will test the following hypotheses: i) Impairment of OPC generation and differentiation in the WM due to preoperative hypoxia results in WM hypomyelination and brain immaturity; ii) Both the inflammatory effects of CPB as well as the reperfusion and reoxygenation of circulatory arrest exacerbate the impaired generation and delayed OPC migration and maturation. The first model that will be used will be a piglet hypoxia model. Immature development of the porcine brain in this experimental paradigm is very similar to that observed in newborns with CHD. The impact of CPB on the immature brain will be investigated with a combined paradigm using piglets exposed to both hypoxia and CPB. To analyze OPC maturation in the porcine brain, we have generated OPCs derived from porcine stem/progenitor cells. Proliferation of OPCs will be measured using immunohistochemical methods. OPC migration will be continuously monitored by novel cell tracking MRI techniques using superparamagnetic iron oxide labeling in vivo. Development from OPCs to mature oligodendrocytes will be defined by fluorescent marker histology. Microstructural maturation of WM will be analyzed by serial volumetric analysis and diffusion tensor imaging. Finally correlation between microstructural maturation and brain immaturity will be defined. The proposed studies will define crucial cellular mechanisms underlying the causes of brain immaturity and WM injury in the neonate with CHD. The findings will assist decision-making regarding optimal timing and techniques of surgery. The proposed studies have the potential to identify and assess novel strategies to treat brain immaturity and WM injury, and define new standards of perinatal care in the patient with CHD. The resulting improved neurodevelopmental outcomes would be of enormous benefit to those individuals with CHD.