Iwakami K, Isokawa K, Sejima H, Shimizu O, Morikawa T, Ootsu H, Numata K, Fukai M, Kubota S, Komiyama T, Toda Y
Department of Oral, Nihon University Dental Research Center, Tokyo, Japan.
J Oral Sci. 2000 Sep;42(3):169-75. doi: 10.2334/josnusd.42.169.
In the developing chick heart, endothelial cells in the atrioventricular canal (AV) undergo a series of morphological changes and transform into cushion mesenchymal cells. In the present scanning electron microscopic study, we examined the abluminal surface features of the AV endothelium through an artificial window in the myocardial wall. The AV endothelial cell at stages 12 or earlier had a smooth, flattened basal surface with only a few blebs. In the successive stages, the abluminal surface exhibited remarkable changes; 1) the number of blebs increased, 2) elongated microvillous projections emerged, and 3) a thick filopodium, or a migratory appendage developed. It appeared, however, that these changes do not occur synchronously within the entire AV endothelium but were initially observed mostly in the proximity of the endothelial "crease" which was a limited invagination of the endothelial sheet towards the underlying acellular matrix. In addition, even in the proximity of the crease, endothelial cells with flattened basal surfaces were also observed next to endothelial cells that showed apparent morphological indications of transition into mesenchymal cells. These findings suggest that AV endothelial cells are possibly heterogeneous in the competency of transformation into mesenchymal cells and such heterogeneity would be important for maintaining the continuity of the AV endothelium.
在发育中的鸡心脏中，房室管（AV）中的内皮细胞会经历一系列形态变化，并转化为垫状间充质细胞。在本扫描电子显微镜研究中，我们通过心肌壁上的人工窗口检查了AV内皮的腔外表面特征。12期或更早阶段的AV内皮细胞具有光滑、扁平的基底表面，只有少数小泡。在随后的阶段，腔外表面出现了显著变化：1）小泡数量增加；2）出现了细长的微绒毛突起；3）形成了粗大的丝状伪足或迁移性附属物。然而，这些变化似乎并非在整个AV内皮中同步发生，而是最初主要在靠近内皮“褶皱”的部位观察到，内皮“褶皱”是内皮细胞片朝向下方无细胞基质的有限内陷。此外，即使在褶皱附近，在显示出向间充质细胞转变明显形态迹象的内皮细胞旁边，也观察到了基底表面扁平的内皮细胞。这些发现表明，AV内皮细胞在转化为间充质细胞的能力上可能存在异质性，这种异质性对于维持AV内皮的连续性可能很重要。
