Chlapowski F J, Haynes L
J Cell Biol. 1979 Dec;83(3):605-14. doi: 10.1083/jcb.83.3.605.
The development of rat transitional epithelial cells grown on conventional non-permeable surfaces was compared with development on permeable collagen supports. On glass or plastic surfaces, cells grew as expanding nomolayer sheets. Once confluent, growth continued with a bilayer being formed in most areas and apical cells being continuously sloughed off. Although most cells were interconnected by desmosomes, and junctional complexes were formed, no other indications of differentiation were observed. After 2-3 wk of growth, division stopped and cel death ensued. In contrast, single-cell suspensions plated on collagen-coated nylon disks reassociated into multicellular islands and commenced growth. Mitoses were confined to the basal cells in contact with the permeable substrate. The islands developed into epithelial trilayers, tapering to monolayers along spreading edges. Once the islands were confluent, stratification was completed and appeared similar to that observed in vivo. Germinal cells formed a basal lamina, and the upper layer was composed of large, flattened cells with an unusually thick asymmetrical plasma membrane on the apical surface. Electron microscopic and radioactive tracers demonstrated "leaky" zonulae occludentes with a restricted permeability to small molecules. The movement of urea was retarded in comparison to water. Unlike the slow turnover of adult epithelium in vivo, maturation and sloughing of apical cells were measurable. Transfer of cells could be effected and growth maintained for up to 4 mo. These results may indicate the necessity of a nutrient-permeable growth surface for the polarized differentiation of adult transitional epithelium.
将常规非渗透性表面上生长的大鼠移行上皮细胞的发育与渗透性胶原支架上的发育进行了比较。在玻璃或塑料表面上，细胞以扩张的单层片层形式生长。一旦汇合，生长继续，大多数区域形成双层，顶端细胞不断脱落。尽管大多数细胞通过桥粒相互连接并形成连接复合体，但未观察到其他分化迹象。生长2 - 3周后，细胞停止分裂并随后发生细胞死亡。相比之下，接种在胶原包被的尼龙圆盘上的单细胞悬液重新聚集成多细胞岛并开始生长。有丝分裂局限于与渗透性底物接触的基底细胞。这些岛发育成上皮三层结构，沿扩展边缘逐渐变细为单层。一旦这些岛汇合，分层完成，看起来与体内观察到的相似。生发细胞形成基膜，上层由大的扁平细胞组成，顶端表面有异常厚的不对称质膜。电子显微镜和放射性示踪剂显示“渗漏”的紧密连接，对小分子的通透性有限。与水相比，尿素的转运受到阻碍。与体内成年上皮细胞缓慢的更新不同，顶端细胞的成熟和脱落是可以测量的。细胞转移可以实现，并且生长可以维持长达4个月。这些结果可能表明营养物质可渗透的生长表面对于成年移行上皮细胞极化分化的必要性。
