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  • Title: Thyrocytes, but not C cells, actively undergo growth and folliculogenesis at the periphery of thyroid tissue fragments in three-dimensional collagen gel culture.
    Author: Toda S, Aoki S, Suzuki K, Koike E, Ootani A, Watanabe K, Koike N, Sugihara H.
    Journal: Cell Tissue Res; 2003 Jun; 312(3):281-9. PubMed ID: 12733056.
    Abstract:
    In the thyroid, new follicle formation from preexisting follicles (mother follicle-derived folliculogenesis) has been poorly understood. To address this issue, we analyzed mother follicle-derived folliculogenesis, using a thyroid tissue-organotypic culture that retains three-dimensional follicles with both thyrocytes and C cells over a long period. Three types of mother follicle-derived folliculogenesis occurred only at the periphery of the tissue fragments embedded in collagen gel: (1) solid nest, (2) budding and (3) lumen-dividing types. Immunohistochemistry showed that neogenic follicles rarely had calcitonin-positive C cells. Electron microscopy showed that their component thyrocytes expressed normal polarity. In growth, bromodeoxyuridine uptake of thyrocytes at the tissue periphery was about 5 times the uptake that occurred at the center. C cells had no uptake. Thyrotropin (TSH, 10 mU/ml) and free calcium (0.17~1.95 mM), which are associated with the biological behavior of thyrocytes and C cells, respectively, did not affect the events described above. The data indicate that thyrocytes, but not C cells, actively undergo growth and three types of mother follicle-derived folliculogenesis at the tissue periphery in a TSH- or free calcium-independent manner. This suggests that the tissue periphery, which may escape from contact inhibition of cell growth, is the regenerative site.
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