Protection of Developing White Matter during Cardiac Surgery

描述(由申请人提供)： 关于先天性心脏病手术后儿童发育的前瞻性临床试验和回顾性临床研究都证明，运动技能的结果比认知能力更差。这一发现与最近几项使用磁共振成像(MRI)对新生儿和心脏手术后婴儿进行的研究一致，这些研究记录了脑白质损伤(WMI)的证据。假定新生儿对WMI具有选择性易感性，这导致一些人建议，尽管矫正手术有许多优点，但在新生儿期应该避免进行矫正手术。新生儿WMI的可疑致病因素包括对体外循环(CPB)有害影响的独特易感性，包括夸大的全身炎症反应以及缺血/再灌注风险。包括快速冷却、极端血液稀释和严重碱度在内的搭桥策略以及一些循环停止技术已被记录为严重限制氧气输送。由于超低出生体重的早产儿也容易出现运动发育障碍，而且MRI也证明了WMI的证据，因此人们对脑白质发育的理解给予了相当大的关注。免疫组织化学方法和专门开发的转基因小鼠可以鉴定导致成熟少突胶质细胞的细胞谱系，而少突胶质细胞负责髓鞘的形成。这项拟议的研究将检验以下假设：i)白质对CPB炎症效应的年龄相关性易感性，ii)CPB期间白质对缺血/再灌注的年龄相关性易感性，iii)年龄相关性易感性是特定少突胶质前体细胞选择性易损性的结果，这将被定义，iv)特定的旁路策略和抗炎辅助治疗可以降低与CPB相关的WMI的风险。将使用的模型是存活到3天和24天的体外循环仔猪模型。终点将包括行为研究、白质MRI评估和详细的组织学评估，包括使用我们最近鉴定的仔猪合适的抗体鉴定少突胶质细胞谱系。第二个模型是使用定制灌注室的小鼠脑片模型，该灌注室允许控制细胞因子水平、温度、pH、氧气和葡萄糖水平，从而重现CPB的压力。这个模型将允许对专门为研究白质而开发的转基因小鼠进行研究。该项目的目标是在儿科心脏手术期间改善对发育中的白质的保护，并减少先天性心脏病手术中儿童运动技能缺陷的发生率。

DESCRIPTION (provided by applicant): Both prospective clinical trials and retrospective clinical studies of development of children following surgery for congenital heart disease have documented worse outcomes for motor skills than cognitive abilities. This finding is consistent with several recent studies using magnetic resonance imaging (MRI) in newborns and infants after cardiac surgery which have documented evidence of white matter injury (WMI). A presumed selective vulnerability of the newborn to WMI has led some to suggest that corrective surgery should be avoided in the newborn period despite its many advantages. Suspected causative factors of WMI in the newborn include a unique susceptibility to the deleterious effects of cardiopulmonary bypass (CPB) including an exaggerated systemic inflammatory response as well as a risk of ischemia/reperfusion. Bypass strategies that include rapid cooling, extreme hemodilution and severe alkalinity as well as some techniques of circulatory arrest have been documented to critically limit oxygen delivery. Considerable attention has been directed towards understanding white matter development because ultra-low birthweight premature infants are also susceptible to deficits in motor development and also demonstrate evidence of WMI by MRI. Immunohistochemistry methods and specifically developed transgenic mice allow identification of the cell lineage leading to mature oligodendrocytes which are responsible for the laying down of myelin. The proposed study will test the following hypotheses: i) There is an age-dependent susceptibility of white matter to the inflammatory effects of CPB, ii) There is an age- dependent susceptibility of white matter to ischemia/reperfusion during CPB, iii) Age- dependent susceptibility is a consequence of selective vulnerability of specific oligodendrocyte precursor cells which will be defined, iv) Specific bypass strategies and anti-inflammatory adjunctive treatment can reduce the risk of WMI associated with CPB. The models that will be used will be a piglet model of CPB with survival to 3 and 24 days. End points will include behavioral studies, MRI assessment of white matter and detailed histological assessment including identification of oligodendrocyte cell lineage using piglet appropriate antibodies that we have recently identified. The second model is a mouse brain slice model using a custom built perfusion chamber that allows manipulation of conditions including cytokine levels, temperature, pH, oxygen and glucose levels, thereby recreating the stresses of CPB. This model will allow investigation of transgenic mice specifically developed for the study of white matter. The goal of this project is improve protection of developing white matter during pediatric cardiac surgery and to reduce the incidence of deficits in motor skills in children undergoing surgery for congenital heart disease.