SIGNIFICANCE OF EARLY INTRAALVEOLAR FIBROTIC LESIONS AND INTEGRIN EXPRESSION IN LUNG-BIOPSY SPECIMENS FROM PATIENTS WITH IDIOPATHIC PULMONARY FIBROSIS

To study the pulmonary structural remodeling in idiopathic pulmonary fibrosis (IPF), ultrastructural, immunohistochemical, and light microscopic molphometric observations were made on 11 pulmonary biopsy specimens from patients with IPF. The morphometric study was done using sequentially cut tissue sections stained for keratin-alcian blue periodic acid-Schiff (PAS), fibronectin, and type IV collagen-alcian blue PAS. Most of the early fibrotic lesions, which were alcian blue- and fibronectin-positive, were intra-alveolar in location. Intra-alveolar fibrosis is considered to be essential for the fusion of alveolar walls in IPF. A strong reaction for integrin alpha 5 beta 1 and vinculin was found in epithelial cells and mesenchymal cells in areas of intra-alveolar fibrosis. These finding show that these cells are active in adhesion to fibronectin in areas of early intra-alveolar fibrosis. Some of the epithelial cells, including cytoplasmic hyaline-laden cells, showed evidence of inadequate adhesion to the extracellular matrix, and this may constitute one of the mechanisms of progression of fibrosis in IPF. HUM PATHOL 26:53-61. Copyright (C) 1995 by W.B. Saunders Company