Morphological analysis of cardiac malformations in developing WKY/NCrj rat embryos raised in whole embryo

1.全胚胎培养的WKY/NCrj和对照大鼠胚胎心脏的形态学分析。1）在从妊娠11.5天开始培养12小时的WKY/NCrj和对照大鼠胚胎中均检测到第六主动脉弓。在培养48小时期间，这两个品系的胚胎之间没有观察到第六主动脉弓的形态学差异。2）由于培养超过48小时的胚胎与年龄匹配的对照相比表现出发育延迟，该全胚胎培养系统仅在进行48小时时才显示出有用。2. WKY/HKG小鼠心脏中细胞外分子包括迁移神经嵴细胞标记物的免疫定位。在妊娠11.5、12.5和13.5天的WKY/NCrj和对照鼠胚胎的第6主动脉弓中HNK-1、N-CAM、Fibronectin和Cytokerin均呈免疫阳性。这些标记在WKY/NCrj和对照胚胎中的分布模式基本相同。N-CAM显示从前肠周围的神经纤维经第六主动脉弓到动脉干的免疫阳性组织链，表明第六主动脉弓是神经嵴细胞从内脏间充质组织迁移到动脉干的途径之一。但本研究也提示，第六主动脉弓发育不良或神经嵴细胞异常迁移可能不是导致WKY/NCrj大鼠心脏畸形的主要原因，因此，妊娠14.5d的WKY/NCrj大鼠胚胎第六主动脉弓发育不良可能是由于胚胎干细胞异常分裂所致。因此，我们计划阐明心脏神经嵴细胞的分布模式或迁移途径，这可能在干细胞分裂中发挥重要作用。

1.Morphological analysis of the heart in WKY/NCrj and control rat embryos raised in whole embryo culture.1) Sixth aortic arches were detected in both WKY/NCrj and control rat embryos cultured for 12 hours from 11.5 days of gestation. No morphological differences of the sixth aortic arches were observed between these two strains of embryos during 48 hours of culture.2) As the embryos cultured over 48 hours showed developmental delay compared with age-matched controls, this whole embryo culture system appeared useful only when performed for 48 hours.2.Immunolocalizations of extracellular molecules including migrating neural crest cell markers in the heart of WKY/NCrj and control rat embryos.HNK-1, N-CAM,fibronectine and cytotactin were immunopositive in the sixth aortic arches of both WKY/NCrj and control rat embryos at 11.5,12.5 and 13.5 day of gestation. The distributional patterns of those markers were almost same between WKY/NCrj and control rat embryos. N-CAM showed a chain of immunopositive tissues from nerve fibers around the foregut to the truncus arteriosus via the sixth aortic arch, which indicated that the sixth aortic arch was one of the pathways neural crest cells migrate through from splanchnic mesenchymal tissues to the truncus arteriosus. However, this study also suggested that cardiac malformations in WKY/NCrj rat might not be induced by hypoplastic sixth aortic arches or abnormal migrations of neural crest cells through this pathway.Conclusively, the hypoplastic sixth aortic arches in WKY/NCrj rat embryos at 14.5 day of gestation were supposed to be secondarily brought by an abnormal truncal division. Therefore, we are planning to clarify the distributional patterns or migratory pathways of cardiac neural crest cells which may play an important role in truncal division.