Nakajima Y, Mironov V, Yamagishi T, Nakamura H, Markwald R R
Department of Anatomy and Cell Biology, Medical College of Wisconsin, Milwaukee, USA.
Dev Dyn. 1997 Jul;209(3):296-309. doi: 10.1002/(SICI)1097-0177(199707)209:3<296::AID-AJA5>3.0.CO;2-D.
During early cardiac morphogenesis, outflow tract (OT) and atrio-ventricular (AV) endothelial cells differentiate into mesenchymal cells, which have characteristics of smooth muscle-like myofibroblasts, and which form endocardial cushion tissue, the primordia of valves, and septa in the adult heart. During this embryonic event, transforming growth factor beta3 (TGF beta3) is an essential element in the progression of endothelial-transformation into mesenchyme. TGF beta(s) are known to be a potent inducer for mesodermal differentiation and a promoter for differentiation of endothelial cells into smooth muscle-like cells. Using a monoclonal antibody against smooth muscle-specific alpha-actin (SMA), we examined the immunohistochemical staining of this form of actin in avian endocardial cushion tissue formation. To determine whether TGF beta3 initiates the expression of SMA, the pre-migratory AV endothelial monolayer was cultured with or without chicken recombinant TGF beta3 and the expression of SMA was examined immunochemically. Migrating mesenchymal cells expressed SMA beneath the cell surface membrane. These cells showed a reduction of endothelial specific marker antigen, QH1. Stationary endothelial cells did not express SMA. The deposition of SMA in the mesenchymal tissue persisted until the end of the fetal period. Pre-migratory endothelial cells cultured in complete medium (CM199) that contained TGF beta3 expressed SMA, whereas cells cultured in CM199 alone did not. At the onset of the endothelial-mesenchymal transformation, migrating mesenchymal cells express SMA and the expression of this form of actin is upregulated by TGF beta3. The induction of the expression of SMA by TGF beta3 is one of the initial events in the cytoskeletal reorganization in endothelial cells which separate from one another during the initial phenotypic change associated with the endothelial-mesenchymal transformation.
在心脏早期形态发生过程中，流出道（OT）和房室（AV）内皮细胞分化为间充质细胞，这些间充质细胞具有平滑肌样肌成纤维细胞的特征，并形成心内膜垫组织，即成年心脏中瓣膜和隔膜的原基。在这个胚胎事件中，转化生长因子β3（TGFβ3）是内皮细胞向间充质细胞转化过程中的一个关键要素。已知TGFβ是中胚层分化的强效诱导剂，也是内皮细胞向平滑肌样细胞分化的促进剂。我们使用抗平滑肌特异性α-肌动蛋白（SMA）的单克隆抗体，检查了这种肌动蛋白形式在禽类心内膜垫组织形成中的免疫组织化学染色。为了确定TGFβ3是否启动SMA的表达，将迁移前的AV内皮单层细胞在添加或不添加鸡重组TGFβ3的情况下进行培养，并通过免疫化学方法检测SMA的表达。迁移的间充质细胞在细胞膜表面下方表达SMA。这些细胞显示内皮特异性标志物抗原QH1减少。静止的内皮细胞不表达SMA。SMA在间充质组织中的沉积一直持续到胎儿期结束。在含有TGFβ3的完全培养基（CM199）中培养的迁移前内皮细胞表达SMA，而仅在CM199中培养的细胞则不表达。在内皮-间充质转化开始时，迁移的间充质细胞表达SMA，并且这种肌动蛋白形式的表达被TGFβ3上调。TGFβ3诱导SMA表达是内皮细胞细胞骨架重组的初始事件之一，在内皮-间充质转化相关的初始表型变化过程中，内皮细胞彼此分离。
