核纤层蛋白A、转录因子TBX3、缝隙连接蛋白43表达与小鼠胚胎心发育

目的 探讨小鼠胚胎心脏工作心肌和传导系心肌在形态发生和分化过程中核纤层蛋白A（lamin A）、转录因子TBX3、缝隙连接蛋白43（Cx43）的表达特点。
方法 用抗α-平滑肌肌动蛋白（α-SMA）、抗心肌肌球蛋白重链（MHC）、抗α-横纹肌肌动蛋白（α-SCA）、抗胰岛因子1（ISL-1）、抗Cx43、抗lamin A和抗转录因子TBX3，对46只胚龄8～15d小鼠胚胎心脏连续石蜡切片进行免疫组织化学及免疫荧光染色。 结果 胚龄9d，TBX3在原始心管的表达集中在房室管壁。10d始，TBX3阳性的表达逐渐从房室管壁沿着静脉瓣延续至窦房结、右心房背侧壁和房间隔。胚龄12～13d，TBX3阳性表达结构构成了中枢传导系雏形，包括窦房结、左右静脉瓣、房间隔、房室管、房室结和房室束。Cx43首先在胚龄9d的左心室腹侧壁和部分小梁心肌出现弱阳性表达，随着发育，Cx43逐渐在TBX3阴性的心房、心室工作心肌表达。Lamin A首先出现在10d房室管心内膜垫间充质细胞和左心室部分小梁心肌，随后在右心室小梁心肌出现，至胚龄15d，心室和心房小梁心肌及房室瓣均可见lamin A阳性表达，但致密心肌和中枢传导系心肌持续呈阴性表达。 结论 中枢传导系统雏形在小鼠胚龄13d形成，呈TBX3阳性，Cx43阴性的互补性表达。致密心肌和中枢传导系心肌在15d仍为lamin A表达阴性，说明此部分心肌分化成熟较晚。

Expression patterns of lamin A,TBX3 and connexin 43 in developing mouse embryonic hearts

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.