TRANSFORMING GROWTH-FACTOR-BETA REGULATES THE EXPRESSION OF FIBRONECTIN AND TENASCIN IN BEAS 2B HUMAN BRONCHIAL EPITHELIAL-CELLS

We used monoclonal antibodies to study expression and extracellular matrix (ECM) incorporation of tenascin (Tn) and isoforms of fibronectin (Fn) in BEAS 2B immortalized human bronchial epithelial cells and the regulation of their synthesis by transforming growth factor (TGF)-beta 1 and -beta 2. In immunofluorescence microscopy, the control cells appeared negative for Tn. Extradomain A (EDA)-Fn was mainly seen in association with ECM fibers and, in a few cells, in an intracellular location. Immunoreactivity for oncofetal (onc)-Fn and extradomain B (EDB)-Fn was only seen in a few cells. In TGF-beta 1 and -beta 2-treated cells, a greatly enhanced immunostaining for Tn and three isoforms of Fn was seen both as to the number of positive cells and to the amount of immunoreactive material around them. In Western blotting of the untreated cells, EDA-Fn and onc-Fn were detected in the cell-free ECM and in the culture medium, whereas EDB-Fn was not detectable. An enhanced secretion and deposition of both EDA-Fn and onc-Fn and also secretion of EDB-Fn was seen upon treatment with TGF-beta s. In TGF-beta-treated cells, Tn was found exclusively in the ECM and not in the culture medium as shown by Western blotting of cell-free ECM and culture medium, respectively. Accentuation of tenascin staining in TGF-beta-treated cells was due to a greatly enhanced production of M(r) 280,000 and M(r) 190,000 isoforms of Tn. Also, Northern blotting demonstrated a much higher level of message for both Tn and Fn after exposure to TGF-beta, suggesting either a transcriptional activation or an extended half-life of the message.