BASAL LAMINA FORMATION BY PORCINE THYROID-CELLS GROWN IN COLLAGEN-DEFICIENT AND LAMININ-DEFICIENT MEDIUM

Porcine thyroid cells isolated by dispase treatment were cultured in e ither (a) Matrigel, (b) agarose with the addition of different combina tions of basic fibroblast growth factor and laminin, or (c) on agarose -coated dishes. The formation of follicles and the presence of a basal lamina was investigated by routine electron microscopy of Araldite-em bedded material and by Light and electron microscopical immunocytochem ical detection of the basal lamina components, laminin and collagen ty pe IV. After 10 days of culture in Matrigel or agarose, a basal lamina -like structure surrounded most follicles. Follicles of cells growing in agarose and overlaid with a medium containing thyrotropin and fibro blast growth factor showed a fluorescent band at the basal side of the follicles after immunocytochemical staining with anti-laminin and ant i-collagen antibodies. Routine electron microscopy showed that a basal lamina-like structure Lined the outside of the follicle. This structu re could be subdivided into a lamina lucida and a lamina densa. Electr on microscopical immunogold labelling revealed that immunologically de tectable laminin was confined to the lamina densa. These findings sugg est that even in the absence of basal lamina components in the culture medium, thyroid cells are able to form follicles with a regular basal lamina when they are cultured in a three-dimensional environment.