Plural cells organize thyroid follicles through aggregation and linkage in collagen gel culture of porcine follicle cells

Some follicle cells organize thyroid follicles through proliferation of single cells in collagen gel culture. The aim of this study was to clarify whether two or more (plural) cells can form follicles through aggregation and linkage in this culture system. To address this question, we performed collagen gel culture of porcine follicle cells, using cell labeling with PKH 2 dye. A mixture of dye-labeled and nonlabeled cells was cultured in collagen gel. Organized follicles consisted of both dyed and nondyed cells. This suggested that plural cells reconstructed follicles through aggregation and linkage. To further confirm this finding, cells embedded in collagen gel were cultured in inhibition of cell proliferation with 2 micrograms/ml aphidicolin. Forty to 60 percent of the cells formed follicles, which did not grow larger. Electron microscopy showed that intracytoplasmic cavities appeared in the cells. In contrast, 20-30% of the embedded cells developed into cavity-embracing single cells, which remained signet rings. These results indicate that follicle cells organize follicles in collagen gel culture by two means: through cell division of cavity-embracing single cells and through aggregation and linkage of plural cells.