小鼠心脏发育的形态学研究

Morphological Observation and Study on the Development of the Heart in Mice

目的建立小鼠心脏正常发育的时间表以及对应的形态学特征模式。方法小鼠胚胎ED8.5、ED9.5、ED10.5、ED11.5、ED12.5、ED14.5、ED16.5、ED18.5和P1(postnatal day)(出生后1 d的仔鼠)标本,进行整体或心脏部位不同轴向切片,HE染色,采用PCTV图像分析系统,对各时相小鼠心脏形态发育特征进行研究。结果⑴细胞结构发育的时空模式:①ED8.5时,生心板形成;ED9.5时,心肌细胞呈不规则的纺锤形,细胞的大小多样化,细胞核小;ED10.5时,小血管和着色较浅的肌原纤维出现,细胞之间连接较松;ED11.5时,心肌纤维排列较紧,纵断面上呈细长形,横断面上呈不规则多角形;ED12.5时,细胞核着色更清晰,心肌细胞形状逐渐规则,细胞之间紧密连接,同时闰盘结构出现在心室心肌细胞。②ED12.5时心肌小梁结构第一次在心室出现,ED14.5时增厚,而在心房少见心肌小梁。⑵心室结构的形成和心脏发育的成熟:①心肌间充质网络结构在ED10.5的心室中明显呈现,随着它的发育,心室的心内膜在ED11.5出现,心室心外膜可以辨认。②房室隔在ED12.5完全形成,心内膜垫在ED12.5开始发生并快速发育,促进室间隔在ED14.5完全形成。③心包膜在ED16.5可明显辨认,心包膜腔形成,此时近段流出道心内膜垫完全心肌细胞替换。结论肌原纤维细胞和心肌间充质细胞同时在ED10.5出现,提示肌原纤维对心肌细胞的成型和心肌化起作用。细胞的结构变化和心肌层的成熟过程,显示小鼠心脏部位成熟时间的不同,心室成熟相对较晚。

Objective To figure out a pattern of the morphologic characterization and the time-table on development of mice hearts. Methods The transverse and vertical sections of the developing heart at ED8.5, ED9.5, ED10.5, ED11.5, ED12.5, ED14.5, ED16.5, ED18.5, P1 （ postnatal day 1 ） were stained with hematoxylin and eosin （H＆E） and morphologic observation was performed by graphic analysis system of PETV. Results （1）Spatiotemporal development pattern of the cell structure ： ①The cardiogenic plate developed at ED8.5 ; The cardiac muscle cell at ED9.5 was irregularly spindly and the cell size was more variable with many cell nuclei smaller than the ones at ED11.5. At ED10.5 tiny blood vessels in the myocardium first appeared and the myofibril, which was weakly stained compared to the cardiac muscle cell, first appeared in the ventricle. At ED11.5, the cardiac muscle cells arranged regularly and formed a longitudinally and obliquely sectioned cardiac muscle fiber. At ED12.5 the cell nuclei were clear stained and cardiac muscle cell became progressively more regular and well connected to each other. The intercalated disk was also found in ventricle myocardium at the same time. ② At ED12.5 the cardiac trabecular structures in ventricle were first observed, which were becoming thicker at ED14.5, whereas there were fewer in atrium during this period. （2） The structural formation of the ventricle and maturation of the mouse heart ： ① The myocardial matrix network was evident in ventricle at ED10.5, the endocardium of ventricle appeared and epicardium of ventricle became identifiable at ED11.5.②The atrioventricular septum formed completely at ED12.5. The endocardial cushion occurred at ED12.5 which grew rapidly as result of the interventricular spetum completed at ED14.5 ③At ED16.5, the pericardium was identifiable and the cavity of pericardium formed while the whole proximal outflow tract septum was mostly occupied by myocardium. Conclusion The simultaneous appearance of myofibril and myocardial matrix network suggests that myofibril contribute to the formation of cell structure and the myocardialization. The structural alteration of the cell and the process of maturation of myocardium revealed regional differences in various parts of the embryonic heart. The ventricle shows a relatively slower pace of maturation compared with atrium.