Fernández B, Fernández M C, Durán A C, López D, Martire A, Sans-Coma V
Department of Animal Biology, Faculty of Science, University of Málaga, Spain.
Anat Rec. 1998 Jan;250(1):70-9. doi: 10.1002/(SICI)1097-0185(199801)250:1<70::AID-AR7>3.0.CO;2-I.
Congenital bicuspid and quadricuspid pulmonary valves have received little attention because of their limited clinical relevance. However, knowledge of the mechanisms by which these anomalous valves develop is essential to obtain a more accurate survey of the etiological factors implicated in the malformations of the cardiac outflow tract in mammals. The present study was designed to assess the anatomical features of bicuspid and quadricuspid pulmonary valves in Syrian hamsters as well as to elucidate the mechanisms involved in the formation of these defective valves.
The sample examined consisted of 206 adults and 28 embryos belonging to a laboratory-inbred family of Syrian hamsters with a high incidence of congenital anomalies of the pulmonary and aortic valves. The study was carried out using histological techniques for light microscopy, semithin sections, and scanning electron microscopy.
The pulmonary valve was tricuspid in 140 of the 206 adult hamsters, and in 124 of these tricuspid valves the dorsal commissure was more or less extensively fused. Another 45 hamsters possessed a bicuspid pulmonary valve with the sinuses oriented ventrodorsally. In 43 of these bicuspid valves, a raphe was located in the dorsal pulmonary sinus. The pulmonary valve was quadricuspid in a further nine specimens. The remaining 12 hamsters had a tricuspid pulmonary valve with a raphe-like ridge located in the right pulmonary sinus. In seven of these valves, the dorsal commissure showed a more or less extensive fusion. The embryos examined, aged between 11 days, 3 hours and 12 days, 6 hours postcoitum, were at the beginning of the valvulogenesis. In five of the 28 embryos, the pulmonary valve consisted of three mesenchymal valve cushions, right, left, and dorsal. In a further 17 embryos, the right and left valve cushions were more or less fused toward the lumen of the pulmonary artery. In the remaining six embryos, the left and dorsal valve cushions were normal, whereas the right cushion was divided into two lobes.
The present findings suggest that in the Syrian hamster: (1) bicuspid pulmonary valves result from the extensive fusion of the right and left pulmonary valve cushions at the beginning of the valvulogenesis, (2) the partial fusion of the right and left pulmonary valve cushions leads to the formation of tricuspid pulmonary valves with a more or less extensive fusion of the dorsal commissure, (3) quadricuspid pulmonary valves result from the partition of one of the three valve cushions at a very early stage of the valvulogenesis, and (4) the partial division of the right pulmonary valve cushion may lead to the development of tricupsid pulmonary valves with a raphe-like ridge located in the right pulmonary sinus. In addition, the present findings, together with previous observations in Syrian hamsters, indicate that in this species the mechanisms by which bicuspid and quadricuspid pulmonary valves develop are similar to those by which bicuspid and quadricuspid aortic valves form, respectively. However, the primary factor or factors that induce the malformations of the pulmonary valve operate independently from those inducing the malformations of the aortic valve.
先天性二叶式和四叶式肺动脉瓣因其临床相关性有限而很少受到关注。然而，了解这些异常瓣膜的发育机制对于更准确地探究哺乳动物心脏流出道畸形的病因至关重要。本研究旨在评估叙利亚仓鼠中二叶式和四叶式肺动脉瓣的解剖特征，并阐明这些有缺陷瓣膜形成所涉及的机制。
所检查的样本包括206只成年叙利亚仓鼠和28只胚胎，它们来自一个实验室近交系的叙利亚仓鼠家族，该家族中肺动脉瓣和主动脉瓣先天性异常的发生率很高。本研究采用组织学技术进行光学显微镜检查、半薄切片检查和扫描电子显微镜检查。
在206只成年仓鼠中，140只的肺动脉瓣为三叶式，在这140个三叶式瓣膜中，124个背侧连合或多或少广泛融合。另外45只仓鼠拥有二叶式肺动脉瓣，其窦呈腹背向排列。在这45个二叶式瓣膜中，43个在背侧肺动脉窦中有一条嵴。另有9个标本的肺动脉瓣为四叶式。其余12只仓鼠的肺动脉瓣为三叶式，但在右肺动脉窦中有一条类似嵴的隆起。在其中7个瓣膜中，背侧连合或多或少广泛融合。所检查的胚胎处于交配后11天3小时至12天6小时，处于瓣膜发生的起始阶段。在28个胚胎中的5个中，肺动脉瓣由右、左和背侧三个间充质瓣膜垫组成。在另外17个胚胎中，右、左瓣膜垫或多或少向肺动脉腔融合。在其余6个胚胎中，左和背侧瓣膜垫正常，而右瓣膜垫分为两叶。
目前的研究结果表明，在叙利亚仓鼠中：（1）二叶式肺动脉瓣是由于瓣膜发生起始时右、左肺动脉瓣垫广泛融合所致；（2）右、左肺动脉瓣垫部分融合导致三叶式肺动脉瓣形成，且背侧连合或多或少广泛融合；（3）四叶式肺动脉瓣是由于在瓣膜发生的极早期三个瓣膜垫之一发生分隔所致；（4）右肺动脉瓣垫部分分隔可能导致在右肺动脉窦中有一条类似嵴的隆起的三叶式肺动脉瓣的发育。此外，目前的研究结果与先前在叙利亚仓鼠中的观察结果一起表明，在该物种中，二叶式和四叶式肺动脉瓣的发育机制分别与二叶式和四叶式主动脉瓣的形成机制相似。然而，诱导肺动脉瓣畸形的一个或多个主要因素与诱导主动脉瓣畸形的因素独立起作用。
