胎羊体外循环心功能不良的发生机制及其对策研究

Complex congenital heart disease is one of the main causes of death of the newborns and infants. It is believed that in utero correction of complex congenital heart defects may benefit the growth and development of the heart, preventing secondary changes from abnormal blood flow patterns. The safe and reasonable fetal extracorporeal circulation is the prerequisite and guarantee for fetal cardiac surgery. Previous studies showed that extracorporeal circulation in fetal lambs, with physiological hypoxia and without cardiac arrest, were detrimental to fetal survival due to fetal myocardial dysfunction. The cardiovascular physiology of fetal lamb is similar to that of human fetus, living in the intrauterine physiological hypoxia. Intrauterine hypoxia enhances the hypoxia inducible factor 1 (HIF-1) activity that involves in multiple aspects of fetal heart development. This research is to study the mechanism of HIF-1 activity on fetal myocardial calcium ion channels during fetal lamb extracorporeal circulation and clarify the core effect of HIF-1 in the mechanism of fetal myocardial dysfunction. Through the disturbance of combination of HIF-1 two subunits and the supplement of fetal energy substrates, the relief of HIF-1 excess activity improves fetal myocardial dysfunction and ameliorates anaerobic glycolysis and energy shortage during extracorporeal circulation. After this study, we could explore a new method of fetal myocardial protection under hypoxic conditions and enhance the safety of fetal extracorporeal circulation.

复杂先心病是新生儿和婴幼儿死亡的主要原因之一。宫内矫治胎儿心脏结构畸形是提高复杂先心病救治成功率的重要手段。安全、合理的胎儿体外循环是胎儿心脏手术的必要前提和技术保障。然而临床前期的动物实验显示胎儿心脏不停跳、生理性低氧体外循环导致胎儿心功能不良，对胎儿存活不利。既往研究显示胎儿生理性低氧增强缺氧诱导因子1（HIF-1）的活性，其调控基因涉及胎儿心脏发育的多个环节。本课题拟以与人类胎儿心血管生理非常接近的胎羊为对象，探讨胎羊体外循环下HIF-1对胎羊心肌细胞钙离子转运的调节机制，阐明HIF-1在胎羊心功能不良发生机制中的关键作用。通过干扰HIF-1两个亚基的结合，阻止HIF-1的过度激活，避免心肌细胞钙离子超载；并且针对HIF-1促进无氧糖酵解引发的胎羊能量匮乏对心功能的影响，研究供应能量底物对胎羊心肌的保护。从而探索低氧条件下胎儿心肌保护的新方法，为提高胎儿体外循环的安全性提供实验依据。

宫内矫治胎儿心脏结构畸形是提高复杂先心病救治成功率的重要手段。胎儿体外循环是胎儿心脏手术的重要技术保障之一。动物实验显示胎儿心脏不停跳、生理性低氧体外循环导致胎儿心功能不良，对胎儿存活不利。缺氧诱导因子1（HIF-1）参与调控的基因涉及胎儿心脏发育的多个环节。本课题探讨胎羊体外循环下HIF-1对胎羊心肌细胞钙离子转运的调节机制，阐明HIF-1在胎羊心功能不良发生机制中的作用并探索胎羊体外循环心肌保护方法。.通过研究证实低氧条件下HIF-1的激活影响胎羊心肌细胞钙离子转运。在胎羊体外循环中HIF-1过度激活，抑制心肌细胞SERCA2a，影响胎羊心肌细胞钙离子转运，导致钙离子超载，影响心功能。通过HIF-1抑制剂和磷酸肌酸的补充抑制胎羊体外循环中HIF-1过度激活，减轻心肌细胞SERCA2a的抑制，改善胎羊心肌细胞钙离子转运，维持胎羊体外循环期间的心功能。说明HIF-1是胎羊心功能不良发生机制中的重要靶点。然而脱离体外循环后胎羊心功能因胎盘功能不良而逐渐恶化，最终胎羊难以长期存活。研究中还发现。胎羊体外循环中胎盘组织内miR-34a转录水平显著升高，高表达miR-34a通过下调钙调神经磷酸酶1（RCAN1）进而影响Ca++/ NFAT通路的激活，导致炎症因子过表达，影响胎盘功能。因此胎羊体外循环心肌保护不能仅局限于心肌，胎盘保护也是心肌保护的重要环节。研究结果有利地推动了胎儿体外循环研究的发展，同时利用研究结果和胎儿动物实验经验，成功开展产时人类胎儿非体外循环心脏手术，率先实现我国胎儿心脏病外科治疗。