Culture system for studying thyroid biology

The thyroid is composed of many ball-like structures called thyroid follicles, which are supported by the interfollicular extracellular matrix and a dense network of fenestrated capillaries. The follicles consist of many thyrocytes and a few parafollicular cells (C cells). In this microenvironment, the component thyrocytes are highly integrated in their specific structural and functional polarization. In conventional monolayer and floating culture systems, thyrocytes are unable to organize themselves into the follicles with normal cellular polarity. By contrast, in three-dimensional collagen gel culture, thyrocytes easily form stable follicle structures with normal polarity. However, these culture systems cannot reconstruct follicle structures that consist of both thyrocytes and C cells. To overcome this issue, we developed a new organotypic culture system of thyroid tissue fragments, which contain the two cell types, using three-dimensional collagen gel culture with air-liquid interface. Our thyroid tissue-organotypic culture system retains three-dimensional follicle structures with both thyrocytes and C cells for a long term. In relation to our method, we propose a new approach to the cell type-specific culture systems on the basis of in vivo microenvironments of various cell types. We review here four culture systems above to study thyroid biology.