Formation and early morphogenesis of endocardial endothelial precursor cells and the role of endoderm.
Formation and early morphogenesis of endocardial endothelial precursor cells and the role of endoderm.
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心内膜内皮前体细胞的形成和早期形态发生以及内胚层的作用。
DOI：
10.1006/dbio.1996.0096
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Markwald,RR
中科院分区：
文献类型：
--
作者：
Sugi,Y;Markwald,RR
本文用活体和体外培养系统研究了鹌鹑胚胎心内膜内皮细胞的形成。根据内皮标记物QH-1的表达，胚胎中内皮前体细胞最初出现在7+期(两个体节)，位于双侧心脏形成区的后部。表达QH-1抗原的细胞是间充质细胞，位于心脏区域的中胚层上皮和内胚层之间。在共聚焦显微镜下，QH-1阳性细胞在两个心脏区域之间呈不对称分布：尤其是在7+~8−之间，右侧的前体细胞多于左侧。直到第8阶段−(三个体节)，内皮前体细胞才出现在心脏形成区之外。心脏区域固有的游离间充质样内皮祖细胞也表达两种细胞外抗原，JB3，一种纤维素样蛋白，和细胞肌动蛋白，两者都与初级心管的节段有关，在那里内皮细胞在心脏垫状组织形成过程中重新转化回间质表型。在第8期和第9期之间(4到7个体节)，(1)心脏形成区内的QH-1阳性细胞与位于心脏区域外的QH-1阳性细胞建立了血管样联系，如Coffin和Poole(1988)所示，(2)在心脏区域融合后，在前肠腹侧形成了QH-1阳性细胞丛，以及(3)初级心内膜直接由内皮前体细胞腹侧丛形成。由于每个心脏形成区域的QH-1阳性的内皮前体细胞总是与前内胚层密切相关，我们试图确定内胚层是否介导了致力于心脏内皮细胞谱系的前体细胞的形成，这反映在它们的QH-1、JB3抗原和细胞肌动蛋白的表达上。为了验证这一假设，在表达心内膜或心肌标志物之前，从第5期心脏形成区域分离出心脏前中胚层外植体，并在有或没有内胚层的情况下将其培养在胶原凝胶表面。在无内胚层的情况下，5期外植体的心前中胚层仍保持上皮，形成收缩组织，但未见QH-1阳性细胞或间充质细胞。相反，当外植体与内胚层或内胚层条件培养液共培养时，除了形成收缩组织外，外植体还形成间充质细胞。后者侵入凝胶格子，在体内表达QH-1抗原、JB3抗原和细胞肌动蛋白。这些发现表明，内胚层诱导心野中胚层经历上皮向间充质的转化，从而导致心肌和心内膜前体细胞的分离。
The formation of endocardial endothelium in quail embryos was investigated usingin vivoandin vitrosystems. Based on the expression of an quail endothelial marker, QH-1, the initial emergence of endothelial precursor cells in the embryo occurs at stage 7+(two somites) in the posterior parts of the bilateral heart forming regions. Cells that expressed the QH-1 antigen were mesenchymal and positioned between the mesodermal epithelium of the heart region and the endoderm. By confocal microscopy, an asymmetrical distribution of QH-1 positive cells was observed between the two heart regions: specifically between 7+and 8−, more precursor cells were seen in the right region than the left. Endothelial precursor cells did not appear outside of the heart forming regions until stage 8−(three somites). Free, mesenchymal-like endothelial precursor cells intrinsic to the heart regions also expressed two extracellular antigens, JB3, a fibrillin-like protein, and cytotactin, both associated with segments of the primary heart tube where endothelial cells “re-transform” back to a mesenchymal phenotype during cardiac cushion tissue formation. Between stages 8 and 9 (four to seven somites), (1) QH-1 positive cells within the heart forming region established vascular-like connections with QH-1 positive cells located outside of the heart region, as initially shown by Coffin and Poole (1988), (2) after fusion of the heart regions, a plexus of QH-1 positive cells was formed ventral to the foregut, and (3) the definitive endocardial lining of the primary heart tube formed directly from the ventral plexus of endothelial precursor cells. Because the QH-1 positive, endothelial precursor cells of each heart forming region were always in close association with anterior endoderm, we sought to determine if the endoderm mediated the formation of precursor cells committed to a cardiac endothelial lineage as reflected by their expression of QH-1, JB3 antigen, and cytotactin. To test this hypothesis, precardiac mesodermal explants were isolated from stage 5 heart forming regions prior to their expressing of either endocardial or myocardial markers and cultured on the surface of collagen gels in the presence or absence of endoderm. In the absence of endoderm, precardiac mesoderm of each stage 5 explant remained epithelial, formed contractile tissue, but did not exhibit any QH-1 positive cells or mesenchymal cells. Conversely, when cocultured with endoderm or endoderm conditioned medium, in addition to the formation of contractile tissue, the explant formed mesenchymal cells. The latter invaded the gel lattice and, asin vivo,expressed QH-1 antigen, JB3 antigen, and cytotactin. These findings suggest that endoderm induces mesoderm of the heart fields to undergo an epithelial to mesenchyme transformation that results in the segregation of myocardial and endocardial precursor cells.