Rodent tracheal epithelial cells in vitro: A comparative study of normal cells, enhanced growth variants, SV-40 transformed cells and their interactions

Tracheal epithelial cells of the golden Syrian hamster can be successfully cultivated in vitro and applied as a model system of respiratory tract epithelium. By morphology and growth characteristics of tracheal epithelial cells, ''normal cells'', ''enhanced growth variants'' and ''transformed cells'' were distinguished in vitro. Hamster tracheal epithelial cells, transformed by Simian virus (SV)-40 expressed in cell nuclei the specific tumor (T-) antigen and showed an accumulation of tumor suppressor protein p53 by immunofluorescence. Cocultivation of ''enhanced growth variants'' and of ''transformed cells'' on a 'feeder layer'' of normal hamster tracheal epithelial cells revealed remarkable differences in loss of ''contact inhibition of growth''. A ''cytokine'' released by NIH-3T3 cells stimulated cell proliferation and seems to be important for cell growth of hamster tracheal epithelial cells. Preliminary characterization of the ''cytokine'' disclosed a molecular weight of more than 30 kDa, a relative thermostability and a loss of activity by treatment with mercaptoethanol indicating disulfide bridges in a molecule.