Background: Outflow tract (OFT) septation defects are a common cause of congenital heart disease. Numerous studies have focused on the septation mechanism of the OFT, but have reported inconsistent conclusions. This study, therefore, aimed to investigate the septation of the aortic sac and the OFT in the early embryonic human heart.
Methods: Serial sections of 27 human embryonic hearts from Carnegie stage (CS) 10 to CS19 were immunohistochemically stained with antibodies against α-smooth muscle actin (α-SMA) and myosin heavy chain.
Results: At CS10-CS11, the OFT wall was an exclusively myocardial structure that was continuous with the aortic sac at the margin of the pericardial cavity. From CS13 onward, the OFT was divided into nonmyocardial and myocardial portions. The cushion formed gradually, and its distal border with the OFT myocardium was consistently maintained. The aortic sac between the fourth and sixth aortic arch arteries was degenerated. At CS16, the α-SMA-positive aortopulmonary septum formed and fused with the two OFT cushions, thus septating the nonmyocardial portion of the OFT into two arteries. At this stage, the cushions were not fused. At CS19, the bilateral cushions were fused to septate the myocardial portion of the OFT.
Conclusions: Data suggest that the OFT cushion is formed before the aortopulmonary septum is formed. Thus, the OFT cushion is not derived from the aortopulmonary septum. In addition, the nonmyocardial part of the OFT is septated into the aorta and pulmonary trunk by the aortopulmonary septum, while the main part of the cushion fuses and septates the myocardial portion of the OFT.
早期人胚心脏心包内动脉干的分隔摘要背景：流出道分隔缺陷是先天性心脏病的一个常见原因。因此，大量研究聚焦于探讨流出道分隔机制，但结论尚不一致。所以本研究旨在探讨早期人胚心脏动脉囊与流出道的分隔过程。 方法：选用抗α-平滑肌肌动蛋白(α-smooth muscle actin，α-SMA) 、抗肌球蛋白重链 (myosin heavy chain，MHC)抗体对27例Carnegie stage (CS) 10-CS19人胚心脏连续切片进行免疫组织化学染色。 结果：CS10-CS11，流出道壁为心肌性结构，与动脉囊在心包腔边缘相连。CS13后，流出道分为非心肌部和心肌部。流出道心内膜垫逐渐形成，其远端界限与流出道壁心肌界限保持一致。第4、6弓动脉之间的动脉囊退化消失。在CS16，α-SMA阳性主肺动脉隔形成且与流出道心内膜垫融合，将流出道非心肌部分隔为主、肺动脉。此期，流出道心内膜垫未融合。至CS19，两侧流出道心内膜垫融合分隔流出道心肌部。 结论：流出道心内膜垫的形成早于主肺动脉隔。因此，前者并非来源于主肺动脉隔。流出道非心肌部由主肺动脉隔分隔为主动脉与肺动脉干；而流出道心内膜垫的大部融合将流出道心肌部进行分隔。.
Keywords: Aortopulmonary Septum; Human Embryonic Heart; Immunohistochemistry; Outflow Tract; Outflow Tract Cushion.