Tognella C., Peter H.J., Wagner H., et al.
Interactions between follicular epithelia cells and extracellular matrix (EM)/basal membrane (BM) are supposed to play an important role in development and maintenance of thyroid tissue architecture. In the present study, we have therefore investigated the synthesis of ECM/BM components by a feline thyroid cell line which is able to form follicle-like structures in vitro and in 5 ras-transfected sublines. We have used a new semisolid culture system composed completely exclusively of polymerized alginate and therefore devoid of ECM/BM components. Cells were cultured as described (Peter et al, Thyroid 1: 331, 1991). Transfection was performed by lipofection with pZIP stre-ras (human Harvey ras; neo) and pSV2-neo (control, neo only) plasmids kindly provided by R. Fries (University of Berne). Immunostaining was done using rabbit first antibodies directed against mouse collagen IV, human fibronectin, tumor laminin (EHS), and other ECM/BM components and second antibodies coupled either to a fluorescent system or alkaline phosphatase. For comparison, immunostaining was also performed in cryosections of nodular goiters of 6 hyperthyroid cats. Feline cells imbedded in alginate gels as single cells and cultured for up to 30 days formed cell clusters within 10 days. Follicle-like structures were formed in the original cell lines and also in the ras-transfected cells. Differences in proliferation rates were observed, the transfected cells growing up to 5-10 times faster than the non-transfected cells. The cell lines and their tranfected clones were staining strongly positive for collagen IV and fibronectin, less so also for laminin. The cat goiter tissue stained positively for collagen IV, EHS-laminin, but negative for fibronectin and various other ECM/BM components. – In conclusion, cat cell lines grow three dimensionally in alginate over several weeks, they form follicle like structures and express with one rate, but does not fundamentally alter formation of follicle like structures and ECM/BM expression. Alginate gel culture is a promising new tool for the study of follicular morphogenesis, polarity, the expression pattern of ECM/BM components and of the interaction between thyrocytes and ECM/BM, avoiding interference caused by gels composed of ECM/BM components.