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目的探讨小鼠胚胎心发育过程中前肠呼吸内胚层与第一生心区和第二生心区及胚胎心流出道的形态发生关系。方法胚龄7.5～13d小鼠胚胎心各3个,连续石蜡切片,用抗胰岛素增强子结合蛋白1(ISL-1)、抗心肌肌球蛋白重链(MHC)、抗α-平滑肌肌动蛋白(α-SMA)、抗Nkx2.5和抗增殖细胞核抗原(PCNA)抗体进行免疫组织化学或免疫荧光染色。结果胚胎发育7.5d,ISL-1在生心板心肌前体细胞表达并与发育中的第二生心区ISL-1阳性细胞连续。胚胎发育第10～13天,可见ISL-1强阳性的前肠腹侧呼吸内胚层细胞增生,排列不规则,失去极性,细胞间间隙明显,变为间充质样细胞,与周围ISL-1阳性间充质细胞无明确界限。紧邻动脉囊背侧壁,局部增生的内胚层向动脉囊方向生长,形成实心细胞索,ISL-1阳性间充质细胞围绕前肠腹侧呼吸内胚层及细胞索形成特征性锥体样结构。结论第一和第二生心区是连续结构,ISL-1同时是两个生心区心肌前体细胞的标记蛋白。呼吸内胚层和内胚层细胞索可能诱导第二生心区的扩展,并通过上皮-间充质转化,保持第二生心区细胞数量稳定。
OBJECTIVE: To investigate the morphological relationship between the respiratory syncytial endoderm and the first-and-third-heart area and the second-triad-of-heart area and embryo cardiac outflow tract during the development of mouse embryos. METHODS: Three embryos from 7.5 to 13 days embryos were stained with serial sections of paraffin and stained with anti-insulin enhancer binding protein 1 (ISL-1), anti-myocardial myosin heavy chain (MHC), anti-α-smooth muscle actin (α-SMA), anti-Nkx2.5 and anti-proliferating cell nuclear antigen (PCNA) antibodies by immunohistochemistry or immunofluorescence staining. Results After embryonic development for 7.5 days, ISL-1 was expressed in precursor of cardiomyocytes and was continuous with ISL-1 positive cells in developing second-heart area. From embryonic day 10 to day 13, ISL-1 strongly positive foregut ventral respiratory endoderm cells were hyperplasia, irregular arrangement, loss of polarity, interstitial space was obvious, into mesenchymal cells, and the surrounding ISL- 1 positive mesenchymal cells without a clear boundary. Immediately adjacent to the dorsal wall of the arterial sac, locally proliferating endoderm grows in the direction of the arterial sac, forming a solid cell line. ISL-1-positive mesenchymal cells form characteristic pyramidal structures around the ventral respiratory endoderm and cell cord. Conclusions The first and second centrioles are continuous structures. ISL-1 is also a marker protein of two precursory cardiac precursors. Respiratory endoderm and endoderm cords may induce the expansion of the second heart area and maintain the number of cells in the second heart area via epithelial-mesenchymal transition.