关键词: 核纤层蛋白A, TBX3, 缝隙连接蛋白43, 工作心肌, 传导系心肌, 免疫组织化学, 免疫荧光, 小鼠

Abstract:

Objective To explore the morphogenesis and differentiation of working myocardium and conduction myocardium in mouse embryonic heart and expression patterns of lamin A, TBX3 and connexin 43 (Cx43). Methods Both the immunohistochemical and immunofluorescent methods were used to observe the relationship of α-smooth muscle actin(α-SMA), myosin heavy chain(MHC), islet-1(ISL-1), Cx43, lamin A and TBX3 distribution patterns in 46 mice embryos from embryonic day(ED)8 to 15 with the myocardial differentiation. Results At ED9, strong TBX3 expression was mainly displayed in the myocardium of the atrioventricular canal. From ED10 onwards, TBX3 expression extended towards the sinus node along the venous valves and the dorsal wall of the right atrium, including interatrial septum. At ED12-13, the prototype of central conduction system of embryonic heart composed by the sinus node, the left and right venous valves, interatrial septum, atrioventricular canal, atrioventricular node and the atrioventricular bundle was recognized, which showed TBX3 positive expression. Cx43 weak expression first appeared in the ventral wall of the left ventricle and part of the trabecular myocardium at ED9. With the development, the expression of Cx43 was displayed in the atrial and ventricular working myocardium with the TBX3 negative expression. Lamin A expression first appeared in ectomesenchymal cells of atrioventricular canal endocardial cushion and part of the left ventricular trabecular myocardium at ED10. Then the expression of lamin A displayed in the right ventricular trabecular myocardium. At ED15, the positive expression of lamin A distributed in the atrioventricular valves, ventricular and atrial trabecular myocardium. However, lamin A expression in compact myocardium and central conduction system remained negative. Conclusion The prototype of central conduction system is formed at ED13, showing TBX3 positive expression and Cx43 negative expression, which is a kind of complementary expression. The expression of lamin A in the compact myocardium and central conduction system myocardium remain negative at ED15, indicating that these parts of myocardium are matured later.

Key words: Lamin A, TBX3, Connexin 43, Working myocardium, Conduction myocardium, Immunohistochemisty, Immunofluorescence, Mouse