【作者】 杨艳萍；

【导师】 景雅；

【作者基本信息】 山西医科大学 ， 组织胚胎学， 2002， 硕士

【摘要】 研究背景：早期胚胎心脏流出道原始心肌、主肺动脉隔及心内膜α-SMA阳性间充质细胞参与了流出道的分隔，但不同的细胞成分在流出道分隔中的作用机理仍然不明。本研究对小鼠流出道原始心肌在发育过程中的分化特点及心内膜α-SMA阳性间充质细胞在流出道分隔过程中分布的时空规律进行了研究，以阐明流出道心肌分化及α-SMA阳性细胞和流出道分隔、缩短的关系。 研究方法：本研究应用免疫组化PAP法，用抗α-SCA、抗α-SMA、抗结蛋白单克隆抗体对胎龄9-16天小鼠心脏连续切片进行了染色，并用TUNEL凋亡染色法对胎龄11、13、14、15天小鼠心脏流出道进行了凋亡染色。 结果：胚胎发育第9天，流出道心肌远侧界即达动脉囊近弓动脉分支处，发育第10天，由于间充质细胞不断分化成心肌细胞，流出道长度增加。胚胎发育的11-12天，流出道远端心肌细胞开始失去横纹肌特异性的α-SCA表达，尤以右侧壁明显。失去α-SCA表达的细胞，仍显较强的α-SMA表达。TUNEL染色未见流出道心肌细胞凋亡现象。在心肌细胞失去α-SCA表达部位，心内膜细胞密度明显增加，并显α-SMA强阳性，失去细胞排列较稀疏的心内膜特征。提示丧失α-SCA表达的心肌山岌盯医科J吮学硕士学t比们仑文细胞及其内侧的心内膜转分化为升主动脉和肺动脉游离壁的细胞成分。由于流出道远端心肌细胞的转分化，心肌性的流出道缩短。 流出道分隔始于胚胎发育第10天，可见动脉囊后壁Q一SMA阳性的主肺动脉隔形成，主肺动脉隔形成的同时，Q一SMA阳性细胞沿弓动脉壁迁入流出道心胶质，随发育，Q一SMA阳性细胞数量增多。胎龄11天，流出道下端心肌内侧，Q一SMA阳性和Q一SMA阴性间充质细胞聚集，形成两条纵行的动脉球靖。胚胎发育第12一13天，主肺动脉隔将半月瓣远端流出道分隔为升主动脉和肺动脉干，主肺动脉隔分化为升主动脉和肺动脉干相对的内侧壁，在升主动脉和肺动脉千分隔过程中偶见凋亡细胞。第13天后，半月瓣近侧，左右动脉球峭愈合，形成心室流出道隔，将流出道分为左右心室流出道。流出道隔中可见部分Q一SMA阳性细胞聚集呈漩涡状。胎龄13天后，间充质性流出道隔逐渐心肌化。随间充质性流出道隔的心肌化，部分间充质细胞凋亡。 结论:流出道远端心肌Q一SCA表达的消失是由于心肌细胞转分化为升主动脉和肺动脉干近端游离壁的平滑肌或成纤维细胞，并非细胞的凋亡。流出道远端心肌细胞的转分化，是心肌性流出道缩短的主要原因。流出道隔心肌化伴随间充质细胞的凋亡。心内膜和主肺动脉隔的Q一SMA强阳性细胞来自神经晴，迁入心脏流出道的神经晴细胞是异质性细胞群体，流出道不同部位的Q一SMA阳性神经峭细胞功能不同，神经峭细胞和流出道其它细胞成分相互作用，完成流出道发育过程中的分隔和重建。更多还原

【Abstract】 Background: Primary myocardium, aortico-pulmonary septum (AP-septum) and a -SMA positive cells in the endocardial ridges are involved in the septation of the outflow tract, considerable controversy continues to exist on the cellular mechanism by which the outflow tract is septated. We investigated the differentiation characteristics of the outflow tract primary myocardium and the spatio-temporal distribution pattern of the a -SMA positive cells during the septation of the outflow tract of the embryonic mouse heart to elucidate the relationship of outflow tract shortening and septation with the differentiation of the outflow tract primary myocardium and the spatio-temporal distribution pattern of a -SMA positive cells.Methods: Serial sections of mouse embryos from embryonic day 9 (ED9) to embryonic day 16 (ED 16) were stained with monoclonal antibodies against a -SCA, a -SMA and Desmin, while apoptosis was determined by the TUNEL assays.Results: In ED 9 embryos, distal boundary of the outflow tractmyocardium has reached to the bifurcation of the branchial arteries. At ED 10, the length of the outflow tract is greatly increased because of continuous differentiation of mesenchymal cells into the cardiomyocytes. During period of ED 11 to ED 12, the cardiomyocytes in the distal part of the outflow tract shed their a -SCA expression, especially on the right side, without going onto apoptosis, indicating the transdifferentiation of the myocytes into the mesenchymal cells. However, the transdifferentiated myocytes still show strong a -SMA expression. The disappearance of the myocardial phenotype in the distal part of the outflow tract is accompanied by the increase in the cell density of the endocardium that shows increased a -SMA expression when compared with the endocardium surrounded by the myocardial cuff, suggesting that the myocytes and the endocardium in the distal part of the outflow tract transdifferentiate into the free wall of the ascending aorta and pulmonary trunk near the semilunar valves. As a result of the transdifferentiation of the myocytes in the distal part of the outflow tract, the distal boundary of the outflow tract myocytes regresses proximally towards the ventricle and the outflow tract becomes shortened.The septation of the outflow tract starts at ED 10 with the formation of the a -SMA positive AP septum on the dorsal wall of the aortic sac and the migration of the a -SMA positive cells into the cardiac jelly of the outflow tract along the branchial arteries. With the development, the number of a -SMA positive cells is increased. At ED 11, in the proximal part of the outflow tract, endocardium lining the inside of the myocardial tube begin to accumulate locally to form two endocardial ridges being composed of a -SMA positive and a -SMA negative cells. From ED 12 to ED 13, theoutflow tract distal to the semilunar valves is septated into ascending aorta and pulmonary trunk by the AP septum. The AP septum is developed into the facing walls of both arteries. Few apoptotic cells are discovered in the AP septum. Proximal to the semilunar valves, after ED 13, the two endocardial ridges fuse to form the outlet septum between the subpulmonary and subaortic outlet of the ventricles. Fusion of the ridges is followed by accumulation of the a -SMA positive cells into a highly characteristic central whorl. From ED 13 onwards, the outlet septum is gradually myocardialized. The myocardialization of the outlet septum is accompanied by some of the mesenchymal cell apoptosis.Conclusion: The disappearance of the a -SCA expression in the distal part of the outflow tract is due to the transdifferentiation of the primary myocytes into the smooth muscle or fibroblast in the free walls of the aorta and pulmonary trunk close to the semilunar valves rather than apoptosis of myocytes. The transdifferentiation of the myocytes may be an important cellular mechanism for outflow tract shortening. During the myocardialization of the outlet septum, apoptotic mesenchymal cells are observed, a -SMA positiv更多还原