In vitro reorganization of porcine thyroid cells from the ATHOS line into follicle-like structures

Abstract

Formation of the thyroid follicle is studied in vitro using the porcine thyroid cell line ATHOS. When preformed monolayers of ATHOS cells, grown after more than 50 passages, are cultured in a sandwich of collagen in the presence of thyrotropin (TSH 10 mU/ml) figures, resembling follicles are observed under light microscopy. The mixture forskolin (5 microM) + isobutyl-methyl-xantine (0.25 mM) is as efficient as TSH. From day 2 on, cells form follicle-like structures. These histiotypical figures, that mimic the thyroid architecture, are maintained 4-5 weeks. By electron microscopy, cells appear correctly located inside the follicle-like structure with microvilli facing follicle lumina. Numerous microfollicles and intracellular cavities are also observed. In TSH-free control cell cultures, very small lumina are formed between day 2 and 7. If TSH (10 mU/ml) is acutely added, new large lumina appear in 24 hrs. Removal of TSH or stimulators or addition of calf serum (0.5-10%) results in a complete disorganization of follicles and in the formation of a regular monolayer. Readdition of TSH or stimulators in serum-free medium reinduces the formation of histiotypical figures. This paper indicates that porcine thyroid cells from the ATHOS line even after more than 50 passages in vitro are a suitable tool to study the mechanisms involved in the supraorganization of the thyroid cells into three dimensional follicles.