Watanabe M, Choudhry A, Berlan M, Singal A, Siwik E, Mohr S, Fisher S A
Division of Pediatric Cardiology, Department of Pediatrics, Rainbow Babies and Childrens Hospital, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
Development. 1998 Oct;125(19):3809-20. doi: 10.1242/dev.125.19.3809.
The embryonic outflow tract is a simple tubular structure that connects the single primitive ventricle with the aortic sac and aortic arch arteries. This structure undergoes a complex sequence of morphogenetic processes to become the portion of the heart that aligns the right and left ventricles with the pulmonary artery and aorta. Abnormalities of the outflow tract are involved in many clinically significant congenital cardiac defects; however, the cellular and molecular processes governing the development of this important structure are incompletely understood. Histologic and tissue-tagging studies indicate that the outflow tract tissues compact and are incorporated predominantly into a region of the right ventricle. The hypothesis tested in the current study was that cell death or apoptosis in the muscular portion of the outflow tract is an important cellular mechanism for outflow tract shortening. The tubular outflow tract myocardium was specifically marked by infecting myocytes of the chicken embryo heart with a recombinant replication-defective adenovirus expressing beta-galactosidase (beta-gal) under the control of the cytomegalovirus promoter. Histochemical detection of the beta -gal-labeled outflow tract myocytes revealed that the tubular structure shortened to become a compact ring at the level of the pulmonic infundibulum over several days of development (stages 25-32, embryonic days 4-8). The appearance of apoptotic cardiomyocytes was correlated with OFT shortening by two histologic assays, TUNEL labeling of DNA fragments and AnnexinV binding. The rise and fall in the number of apoptotic myocytes detected by histologic analyses paralleled the change in activity levels of Caspase-3, a protease in the apoptotic cascade, measured in outflow tract homogenates. These results suggest that the elimination of myocytes by programmed cell death is one mechanism by which the outflow tract myocardium remodels to form the proper connection between the ventricular chambers and the appropriate arterial trunks.
胚胎流出道是一个简单的管状结构，它将单一的原始心室与主动脉囊和主动脉弓动脉相连。这个结构经历一系列复杂的形态发生过程，成为使右心室和左心室与肺动脉和主动脉对齐的心脏部分。流出道异常与许多具有临床意义的先天性心脏缺陷有关；然而，控制这个重要结构发育的细胞和分子过程尚未完全了解。组织学和组织标记研究表明，流出道组织致密，并主要并入右心室区域。本研究中检验的假设是，流出道肌肉部分的细胞死亡或凋亡是流出道缩短的重要细胞机制。通过用在巨细胞病毒启动子控制下表达β-半乳糖苷酶（β-gal）的重组复制缺陷腺病毒感染鸡胚心脏的心肌细胞，特异性标记管状流出道心肌。对β-gal标记的流出道心肌细胞进行组织化学检测发现，在几天的发育过程中（第25-32阶段，胚胎第4-8天），管状结构缩短，在肺动脉漏斗水平变成一个致密的环。通过两种组织学检测方法，即DNA片段的TUNEL标记和膜联蛋白V结合，凋亡心肌细胞的出现与流出道缩短相关。组织学分析检测到的凋亡心肌细胞数量的增减与在流出道匀浆中测量的凋亡级联反应中的一种蛋白酶Caspase-3的活性水平变化平行。这些结果表明，通过程序性细胞死亡消除心肌细胞是流出道心肌重塑以在心室腔和适当的动脉干之间形成正确连接的一种机制。
