摘要目的 探讨心脏近端流出道隔心肌化的分子机制及其对胎鼠心脏圆锥动脉干畸形(CTD)的影响.方法 以胎龄11.5～16.5 d的连接蛋白43(Cx43)基因敲除(Cx43KO)纯合型(Cx43-/-)、杂合型(Cx43+/-)和野生型(Cx43+/+)胎鼠胚胎作为研究对象,采用PCR方法鉴定其基因型,免疫组织化学法测定骨形成蛋白Ⅱ型受体(Bmpr2)和α横纹肌肌动蛋白(α-SCA)的表达.结果 Cx43KO鼠胚心脏近端流出道隔心肌化细胞明显减少,尤其以胎龄13.5和14.5 d的Cx43-/-为著.胎龄11.5～13.5 d,Cx43+/+胎鼠心脏的心房、心外膜均有Bmpr2表达,心室肌也有微弱的表达;Cx43+/-和Cx43-/-胎鼠心脏仅心房和心外膜区有Bmpr2的微弱表达.胎龄14.5～16.5 d,Cx43+/+胎鼠心脏的心房、心外膜、心内膜、小梁、心室肌及流出道隔已心肌化区域均有Bmpr2表达,流出道隔未心肌化区域Bmpr2未见表达,与α-SCA表达一致;胎龄14.5 d的Cx43+/-和Cx43-/-胎鼠心脏的心房、心外膜、心内膜、小梁均有Bmpr2表达,而心室肌、流出道膈未见Bmpr2表达;胎龄15.5与16.5 d的Cx43+/-和Cx43-/-胎鼠心脏的心房、心外膜、心内膜、小梁、心室肌及流出道隔已心肌化区域均有Bmpr2表达,而且Bmpr2在流出道膈未心肌化区域部分表达.结论 Cx43KO胎鼠心脏近端流出道隔存在明显心肌化延迟.Bmpr2很可能涉及心外膜和心肌细胞相互作用的分子机制,参与心肌细胞的成熟过程.

abstractsObjective To investigate the mechanism of myocardialization of proximal outflow tract septum and its effect on the conotruncal anomaly in mice. Methods The C57/BL6 mice of embryonic day (E) 1 1. 5 - 16. 5 were selected. The phenotypes of connexin 43 ( Cx43 ) homozygotes ( Cx43 -/- ),heterozygotes (Cx43+/-) and wild-types (Cx43+/+) were genetically typed by polymerase chain reaction (PCR). Bone morphogenetic protein receptor 2 (Bmpr2) and α-sarcomeric acti (α-SCA) were detected by immunohistochemistry. Results The expression of α-SCA in the proximal outflow tract (OFT) septum was delayed obviously in Cx43 -/- predominantly at E13.5 and E14. 5. From E11. 5 to E13. 5, the expression of Bmpr2 was detected in cardiac atrium and epicardium of Cx43+/+ fetal heart. And Bmpr2 was slightly expressed in ventricular muscle of Cx43 +/+ fetal heart. And it was expressed slightly only in cardiac atrium and epicardium of Cx43 +/- and Cx43 -/- fetal heart. From E14. 5 to E16. 5, its expression was detected obviously in cardiac atrium, epicardium, endocardium, trabeculum, ventricular muscle and OFT septum of Cx43 +/+ fetal heart. At E14. 5, its expression was detected obviously in cardiac atrium, epicardium,endocardium and trabeculum of Cx43 +/- and Cx43 -/- fetal heart while none in ventricular muscle and OFT septum. At E15.5 and E16.5, its expression was detected obviously in cardiac atrium, epicardium,endocardium, trabeculum, ventricular muscle and OFT septum of Cx43 +/- and Cx43-/- fetal heart. Its expression was also detected obviously in OFT septum of Cx43 +/- and Cx43 -/- fetal heart with incompleted myocardialization. Conclusion Cx43KO embryonic mice exhibit delayed myocardialization. As compared with the Cx43 +/+, the expression of Bmpr2 in proximal OFT septum was delayed obviously in Cx43 +/- and Cx43 -/- mice. And the expression of Bmpr2 is abnormal in OFT septum of Cx43 +/- and Cx43 -/- fetal heart. Bmpr2 may be involved in the interaction between epicardium and myocardium. It may be a critical mechanism in the maturation process of cardiac muscles.