Fig. 5

Immunohistochemical staining, claudin-1. a-c Immunohistochemical staining against claudin-1 of respiratory epithelial cells seeded onto pure fibrin gel after 7, 14, 33 days of ALI-culture, cells show a decreasing signal over time. d-f Immunohistochemical staining against claudin-1 of respiratory epithelial cells seeded onto fibrin gel with embedded fibroblasts after 7, 14, 33 days of ALI- culture. Cells stay positive until day 33 with an almost stable signal. A deposit of claudin-1 is seen to the fibrin gel at day 33. g-i Negative control of immunohistochemical staining against claudin-1 of respiratory epithelial cells seeded onto fibrin gel with embedded fibroblasts and respiratory epithelial cells seeded onto pure fibrin gel. j Native tracheal epithelium stained against claudin-1, a high signal level is seen at all cell boundaries. k Negative control of immunohistochemical staining against claudin-1 of native trachea. Scale: 20 μm