Expression of Transforming Growth Factor-β1, -β2, and -β3 mRNA and Protein in the Murine Lung

Evidence has accumulated suggesting that the various isoforms of β-type transforming growth factors (TGF-βs) regulate important functions in the lung; however, the cellular source of these proteins is not well defined. Northern blot analysis of murine lung tissue demonstrates that mRNA transcripts for all three TGF-β isoforms are found from birth through adulthood. Although the level of expression for each TGF-β is variable during the first 2 wk post partum, all three isoforms are equal in the adult lung. Using in situ hybridization and immunohistochemical analysis, we have localized both mRNA and protein expression for all three isoforms of TGF-β in the adult murine lung. At low magnification, immunohistochemical localization of TGF-β proteins appears coincident in their pattern of expression with TGF-β mRNAs in the large proximal conducting airways of the lung. However, on closer analysis, protein expression of all three TGF-β isoforms is confined to the bronchiolar epithelium, while TGF-β mRNA transcri...