Kishimoto Y, Murate M, Sugiyama T
Department of Life Science, Graduate University for Advanced Studies, Mishima, Japan.
J Cell Sci. 1996 Apr;109 ( Pt 4):763-72. doi: 10.1242/jcs.109.4.763.
Cell-cell interaction and cell rearrangement were examined in the process of epithelial sheet formation during regeneration from hydra cell aggregates. The ectodermal and endodermal epithelial cell layers of Hydra magnipapillata were separated by procaine treatment. Each of the separated layers was then dissociated into single cells and reaggregated to produce ectodermal or endodermal cell aggregates. When the two aggregate types were recombined, a firm adhesion was quickly established between them. This was followed by a vigorous spreading of the ectodermal epithelial cells as a thin layer over the endoderm in a manner similar to the 'epiboly' in some developing embryos. Cell movement in this spreading process was examined using fluorescent dyestaining. It revealed that cells initially located in the inside of the aggregate migrated to intercalate themselves among the cells originally present in the contact surface. This radial cell intercalation took place continuously in the contact surface of both the ectodermal and endodermal aggregates, and produced a rapid growth of the contact surface, eventually leading to complete envelopment of the entire endoderm by the ectoderm. The resulting structure was a small sphere having a two-layered epithelial organization as in normal hydra. This sphere regenerated into a complete hydra a few days later. A tryptic extract of hydra membrane fraction specifically inhibited the ectodermal spreading over the endoderm, but not the initial adhesion or the later regeneration processes. These observations suggest that radial cell intercalation at the contact surface plays a crucial role in producing ectodermal spreading and establishing epithelial sheet organization in the recombined aggregates. The intercalation is presumably activated by a signal exchange through the contact surface. The inhibitory effect of the membrane extract suggests that it contains a factor that is involved in some way in this signaling mechanism.
在水螅细胞聚集体再生过程中上皮层形成的过程中，研究了细胞间相互作用和细胞重排。通过普鲁卡因处理将大型乳头水螅的外胚层和内胚层上皮细胞层分离。然后将每个分离的层解离成单个细胞并重新聚集，以产生外胚层或内胚层细胞聚集体。当将两种聚集体类型重新组合时，它们之间迅速建立了牢固的粘附。随后，外胚层上皮细胞以类似于某些发育胚胎中的“外包”方式，作为薄层在内胚层上剧烈铺展。使用荧光染料染色检查了这种铺展过程中的细胞运动。结果表明，最初位于聚集体内部的细胞迁移并插入到最初存在于接触表面的细胞之间。这种径向细胞插入在外胚层和内胚层聚集体的接触表面持续发生，并使接触表面迅速生长，最终导致外胚层完全包裹整个内胚层。所形成的结构是一个具有两层上皮组织的小球体，如同正常水螅一样。几天后，这个球体再生为一个完整的水螅。水螅膜组分的胰蛋白酶提取物特异性地抑制外胚层在内胚层上的铺展，但不影响初始粘附或后期再生过程。这些观察结果表明，接触表面的径向细胞插入在产生外胚层铺展和在重组聚集体中建立上皮层组织方面起着关键作用。这种插入大概是通过接触表面的信号交换而被激活的。膜提取物的抑制作用表明它含有某种以某种方式参与这种信号传导机制的因子。
