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

1.WKY/NCrj及对照大鼠全胚培养心脏形态学分析。1)妊娠11.5 d培养12 h的WKY/NCrj大鼠胚胎和对照大鼠胚胎均可检测到第六主动脉弓。培养48小时后，两种胚胎的第6主动脉弓形态无明显差异。2)由于培养超过48小时的胚胎与年龄匹配的对照组相比发育迟缓，因此整个胚胎培养系统只有在进行48小时时才有用。细胞外分子包括迁移神经嵴细胞标记物在WKY/NCrj和对照大鼠胚胎心脏中的免疫定位妊娠11.5、12.5和13.5 d时，WKY/NCrj和对照大鼠胚胎第6主动脉弓中HNK-1、N-CAM、纤维连接素和细胞趋动素均呈免疫阳性。这些标记物在WKY/NCrj和对照大鼠胚胎中的分布规律基本相同。N-CAM显示前肠周围神经纤维经第6主动脉弓向动脉干呈免疫阳性组织链，提示第6主动脉弓是神经嵴细胞从内脏间充质组织向动脉干迁移的途径之一。然而，本研究也提示WKY/NCrj大鼠心脏畸形可能不是由第六主动脉弓发育不全或神经嵴细胞异常迁移引起的。综上所述，妊娠14.5天WKY/NCrj大鼠胚胎第六主动脉弓发育不全可能是由主动脉截裂异常继发所致。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，这些细胞可能在心脏神经嵴细胞的残端分裂中起重要作用。

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.