Cell-cell interactions in the process of differentiation of thyroid epithelial cells into follicles: A study by microinjection and fluorescence microscopy on in vitro reconstituted thyroid follicles (original) (raw)
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Proceedings of the National …, 1980
We have been investigating the extent to which separated thyroid follicles in suspension culture, free of endothelium and fibroblasts, have the properties of follicles in vivo. To test whether thyrotropin (TSH) can cause thyroid epithelial cells to undergo mitosis, preparations of follicles suspended in Coon's modified F-12 medium with 0.5% calf serum were incubated with 10 milliunits of impure or pure TSH per ml. Three results were obtained: (i) TSH preparations stimulated the incorporation of [hymidine into cell nuclei; (ii) mitotic figures were induced and they had the same characteristic ultrastructural features as those observed in vivo; and (iii) the cell number doubled in the course of 3 days of exposure to TSH. The results suggest that TSH is a mitogen for the principal thyroid epithelial ce I and that other substances found in the usual impure TSH preparations are not necessary for the mitogenic activity. It can act in the absence of nonfollicular cells. The initial multiplication rates are similar to those in vivo. The cells do not have to spread to divide in contrast to the requirement for spreading in the case of fibroblasts.
The Journal of Cell Biology, 1980
Separated thyroid follicles can be maintained in suspension culture in Coon's modified F-12 medium in 0.5% calf serum. If the serum concentration is raised to 5%, the follicles undergo inversion in 3-5 d. During the process of inversion, epithelial cells can be observed in intermediate stages of polarity reversal. The earliest ultrastructural changes recognized are surface changes in which tight junctions and microvilli appear at the lateral margins of the cell near the medium. Later, changes in the distribution of intracellular organelles occur. The Golgi apparatus shifts towards the end of the cell facing the medium, and lysosomes shift toward the luminal end of the cell. The right junctions and microvilli at the luminal end of the cell disappear sometime after the cytoplasmic organelles rearrange. The luminal colloid disappears only after the surface changes (loss of tight junctions and microvilli) occur at the luminal end of the cell. There appears to be some regulation of t...
Experimental Cell Research, 1982
induces morphological changes in cultures of normal rat thyroid cell lines and in primary bovine thyroid cells. It also induces a specific reorganization of the microfilaments of the thyroid cells. Both effects are fully reversible and are mimicked by S-bromo-CAMP. These results indicate that the trophic response of TSH involves changes in the organization of the actin-containing filaments, probably mediated through CAMP, followed by changes in cell shape. Permanent address:
Scanning microscopy, 1987
Separated thyroid follicles maintained in suspension culture can be used to study the properties of thyroid epithelium in the virtual absence of other cell types and to study the effect of extracellular materials on the follicles. They can be prepared by enzymatic separation of thyroid into single cells followed by reaggregation of the epithelial cells and also by collagenase treatment of thyroids to release follicles and sheets of epithelia that can be separated from other materials by differential filtration. The follicles can exist with normal orientation or inverted (inside out). The follicles are inverted in the presence of high serum concentrations (5%) but can have normal orientation when embedded in a type I collagen gel, even at high serum concentrations. When normally oriented follicles invert, the polarity of the epithelial cells reverses while they are connected to neighbors. During inversion, bipolar cells are observed having microvilli-bearing surfaces at both lumen an...
Journal of …, 1999
Interactions between follicular epithelial cells and extracellular matrix (ECM) are supposed to play an important role in the development and maintenance of thyroid tissue architecture. In the present study we have therefore investigated the synthesis of ECM components by a feline thyroid cell line which is able to form follicle-like structures in vitro, and also in v-ras-transfected and controltransfected sublines. Transfections were performed by lipofection with pZSR (viral Harvey ras gene; neo) and pSV2-neo (control, neo only) plasmids. We have adapted a semisolid culture system composed exclusively of polymerized alginate and therefore devoid of ECM components. Feline cells embedded in alginate gels as single cells and cultured for up to 90 days formed cell clusters within 10 days. Follicle-like structures were formed in the original cell lines and also in the v-ras-and controltransfected cells. Differences in proliferation rates were observed, the v-ras-transfected cells growing up to two to three times faster than the non-transfected cells. Immunostaining was done using rabbit first antibodies directed against mouse collagen IV, human fibronectin, laminin (tumor Engelbreth-Holm-Swarm laminin), perlecan and other ECM components. For comparison, immunostaining was also performed on cryosections of nodular goiters of six hyperthyroid cats. The cell lines and their transfected clones stained strongly positive for collagen IV and fibronectin, and positively but less strongly for laminin and perlecan. The cat goiter tissue stained positively for collagen IV, laminin, perlecan, and fibronectin, and positive staining for S-laminin (containing the 2-chain) was seen in blood vessel walls in this tissue. In conclusion, cat cell lines grow three-dimensionally in alginate beads over several weeks, they form follicle-like structures and express the same ECM components as the native cat goiter tissue. Transfection with v-ras does increase proliferation rate, but does not fundamentally alter formation of follicle-like structures and ECM expression. Alginate gel culture is a promising new tool for the study of follicular morphogenesis, polarity, the expression pattern of ECM components and of the interaction between thyrocytes and ECM. It avoids interference caused by gels composed of ECM components.
Cancer research, 1987
The proliferation pattern of some scattered clones of naturally occurring follicular cells with an exceedingly high intrinsic growth potential was investigated in the mouse thyroid gland. In particular, evidence was sought to demonstrate that the high propensity to replicate is a stable trait transmitted from the progenitor cells to their offspring. We hypothesize that these cell clones are at the origin of the multiple adenomas that invariably arise in chronically stimulated thyroid. Growth stimulation was induced either by hemithyroidectomy or by methimazole feeding. In a first series of experiments, involving hemithyroidectomized animals, [3H]thymidine was administered continuously for 3 weeks by means of osmotic minipumps, so that all cells entering the mitotic cycle during that time were labeled. Hemithyroidectomy led to a 3-fold increase of the fraction of labeled cells in the remaining lobe. The increase was prevented by thyroxine treatment in thyroid-stimulating hormone-supp...