Yap A S, Manley S W
Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Brisbane, Australia.
Exp Cell Res. 1994 Sep;214(1):408-17. doi: 10.1006/excr.1994.1274.
The regulation of cell locomotion is a fundamental determinant of tissue architecture. Even in solid tissues of adult organisms cells often retain an intrinsic locomotor capacity which is activated during wound healing or tumor metastasis. In this study we have examined the role of cell locomotion in an in vitro model of thyroid epithelial pattern generation. Primary cultures of adult porcine thyroid cells reorganize to form follicles within three-dimensional cell aggregates when stimulated by thyrotropin (thyroid-stimulating hormone, TSH). Removal of TSH from the culture medium caused established follicles to reorganize into a confluent, two-dimensional epithelioid monolayer. The earliest observed change was the appearance of spreading cells at the peripheries of aggregates. These cells displayed broad lamellipodia whose formation was associated with the redistribution of microfilaments and microtubules and the accumulation of myosin. Spreading cells could migrate into, and fill, artificial wounds several millimeters wide without evidence of cell proliferation, indicating that cells became locomotile as they spread from follicles to form monolayer. Both spreading and migration were inhibited by cytochalasin B. In contrast, cells spread in the presence of colchine, but failed to migrate subsequently. Thyroid cell locomotility from follicles was inhibited by TSH, a cAMP analog, and a cell-free membrane fraction. However, migration from established monolayer cultures was not affected by these regulatory agents. This indicated that cell spreading was an important regulatory locus in thyroid cell patterning. We conclude that the tonic inhibition of thyroid cell locomotility contributes to the maintenance of follicular architecture in vitro. TSH and cell-cell contact may inhibit locomotion by preventing follicular cells from spreading, the earliest step in the morphogenetic conversion of follicles to monolayer.
细胞运动的调控是组织结构的一个基本决定因素。即使在成年生物体的实体组织中，细胞通常也保留着一种内在的运动能力，这种能力在伤口愈合或肿瘤转移过程中被激活。在本研究中，我们在甲状腺上皮模式生成的体外模型中研究了细胞运动的作用。成年猪甲状腺细胞的原代培养物在促甲状腺素（促甲状腺激素，TSH）刺激下，在三维细胞聚集体内重新组织形成滤泡。从培养基中去除TSH会导致已形成的滤泡重新组织成汇合的二维上皮样单层。最早观察到的变化是聚集体周边出现铺展细胞。这些细胞展示出宽阔的片状伪足，其形成与微丝和微管的重新分布以及肌球蛋白的积累有关。铺展细胞可以迁移到几毫米宽的人工伤口中并填充伤口，而没有细胞增殖的迹象，这表明细胞从滤泡扩散形成单层时变得具有运动性。铺展和迁移均受到细胞松弛素B的抑制。相比之下，细胞在秋水仙碱存在的情况下铺展，但随后未能迁移。来自滤泡的甲状腺细胞运动性受到TSH、一种环磷酸腺苷类似物和无细胞膜组分的抑制。然而，来自已建立的单层培养物的迁移不受这些调节因子的影响。这表明细胞铺展是甲状腺细胞模式形成中的一个重要调节位点。我们得出结论，甲状腺细胞运动性的持续性抑制有助于在体外维持滤泡结构。TSH和细胞间接触可能通过阻止滤泡细胞铺展来抑制运动，而铺展是滤泡向单层形态发生转化的最早步骤。
