人胚心静脉窦和传导系统的早期发育

目的 探讨早期人胚心静脉窦及传导系的发生发育机制. 方法 用抗α-平滑肌肌动蛋白(α-SMA)、抗α-横纹肌肌动蛋白(α-SCA)和抗结蛋白(DES)抗体对29例C10～C16期人胚心连续切片行免疫组织化学染色. 结果 人胚发育C12～C13期,系统静脉汇集形成的静脉窦出现于心包腔尾端原始横膈间充质中,静脉窦壁间充质细胞逐渐分化为α-SCA阳性的静脉窦心肌细胞.C14期,心包腔的扩张使静脉窦进入心包腔内,参与了右心房的形成.DES阳性传导系心肌的分化始于C10期心房室管右侧壁,随发育逐渐向室间沟心肌扩展,发育为房室传导系的希氏束、左右束支及心室腔面的小梁心肌.在心房,DES表达首先出现于C11期心房背侧壁,在C13期,可见静脉窦左背侧壁α-SCA、α-SMA、DES阳性心肌带与左心房底部、房室管背侧壁相延续,这条心肌带可能参与了人胚心静脉窦至房室管传导系的发育.C14～C16期,DES强阳性染色从窦房结经左、右静脉瓣及心房的背、腹侧壁延伸至房室管右侧壁,可能是原始的心房传导通路. 结论 心包腔尾端原始横膈间充质是人胚静脉窦心肌发生区,原始横膈间充质细胞逐渐分化为心肌细胞,添加到人胚心管静脉端,形成心静脉窦心肌.人胚心传导系心肌的分化始于房室管,随心管发育逐渐向动、静脉端扩展,在C16期,已分化为形态清晰可辨的DES阳性胚胎心传导系.

Early development of the sinus venosus and the cardiac conduction system in human embryonic heart

Objective To investigate the early development of the sinus venosus and the cardiac conduction system (CCS) of human embryonic hearts. Methods Serial transverse sections of 29 human embryonic hearts from Carnegie stage 10 to Carnegie stage 16 (C10-C16) were stained immunohistochemically with antibodies against α-smooth muscle actin(α-SMA),α-sarcomeric actin(α-SCA) and desmin ( DES ). Results During C12 and C13, the sinus venosus formed by confluence of systematic veins at the caudal end of the pericardial cavity could be recognized in the mesenchyme of primitive transverse septum. The mesenchymal cells of the sinus venosus gradually differentiated into α-SCA positive cardiocyocytes. At C14, the sinus venosus was within the pericardial cavity due to expansion of the pericardial cavity and incorporated into the right atrium. Differentiation of DES positive conductive cardiomyocyte was initiated in the right wall of atrio-ventricular canal of C10 embryonic heart and with the development, extended towards the myocardium of the interventricular sulcus to form His bundle, left and right bundle branches as well as the ventricular trabecular myocardium. In the atium, the strong expression of DES was first detected in the dorsal wall of C11 atrium. At C13, unique myocardial band showing α-SCA, α-SMA and DES expression in the left dorsal wall of the sinus venosus were found to be continuous with the basal wall of left atium and the dorsal wall of the atrio-ventricular canal, this band might be related to the development of conduction system from sinoatrial node to atrio-ventricular canal. During C14 to C16, primary conduction pathway of atria with strong DES expression was formed that extended from sinoatrial node along venous valves, DES positive myocardium in the dorsal and ventral walls of the atria to the right atrio-ventricular canal, respectively. Conclusions The mesenchyme of the primitive transverse septum is the heart forming field of human embryos responsible for formation of sinus venosus myocardium, cardiomyocytes are differentiated from mesenchymal cells in the primitive transverse septum and progressively added to the venous pole of the heart tube to form myocardial sinus venosus. The differentiation of CCS of the early human embryo initiates in the atrio-ventricular canal and develops gradually towards the arterial and venous poles of the heart tube. By C16, DES positive embryonic CCS can be clearly recognized morphologically.