Effects of Various Types of Extracellular Matrices on Adhesion, Proliferation, Differentiation, and c-fos Protein Expression of Porcine Thyroid Follicle Cells

Thyroid follicles in vivo are embedded in extracellular matrix (ECM). The composing epithelial cells are in close contact with ECM at the basal side. To examine cell-to-ECM interactions, we studied adhesion, proliferation and differentiation of porcine follicle cells monolayer-cultured on type I and IV collagen, fibronectin or laminin. At 3 h in culture, laminin had the lowest rate of cell adhesion. In proliferation, type IV collagen induced the highest level of nuclear bromodeoxyuridine intake. In a functional differentiation, laminin had about 3 times as much triiodothyronine production as the other ECM molecules. In confluent, culture cells, we also examined an expression of c-fos protein, a transcription factor that plays crucial roles in signal transduction. Immunocytochemistry detected the protein mainly in the nuclei. Western blot showed that laminin induced the highest level of its expression. Thyrotropin (TSH, 10 mU/ml) did not affect adhesion of the cells on any of the substrata or proliferation of the cells on fibronectin ; nor did TSH affect c-fos protein expression of the cells on the substrata except for fibronectin. Our results suggest that type IV collagen and laminin, major components of basement membrane, play positive roles in proliferation and differentiation of follicle cells, respectively, while laminin has no positive effect on adhesion of the cells at early culture ; that the cells express c-fos protein even in contact inhibition of growth and its expression is regulated in part by ECM ; and that ECM controls some behaviors of the cells in a TSH-dependent or TSH-independent manner.