Distribution of type VII collagen in the epithelial basement membranes of mouse palate, tongue and lip mucosa

Dithiothreitol effectively separated the laminae densae and the laminae fibroreticulares of the basement membranes of oral mucosal epithelia as it does the epidermis and dermis. Dithiothreitol-separated epithelial basement membranes of palate, tongue, and lip were immunoreacted with colloidal gold-conjugated anti-type VII collagen antibody. By transmission electron microscopy, gold particles were observed only on the anchoring fibrils. For three-dimensional observation of the distribution of type VII collagen by scanning electron microscopy, secondary and backscattered electron images were compared. The secondary image showed the fine structure of the laminae densae and anchoring fibrils, and the backscattered images showed the gold particles conjugated with the antibody. By using an osmium conductive metal coating under optimal conditions, secondary and backscattered electron images of sufficient quality could be obtained. With the osmium coating, the backscattered electron image could show not only the gold particles but also the general morphological outline, making possible a comparison of the two images, which revealed the three-dimensional distribution of type VII collagen. Type VII collagen was also seen only on the anchoring fibrils, as in the epidermal basement membrane.