Distribution and isoform characterization of type XII collagen in bovine cornea

Streptavidin peroxidase immunohistochemistry and immunoelectron microscopy were used to determine the localization of type XII collagen in sections fr om bovine corneas, Type XII collagen extracted from bovine cornea and skin was assayed by Western blotting. Immunohistochemical experiments showed tha t type XII collagen was restricted to the corneal stroma; it was not presen t in corneal epithelium, epithelial basement membrane, Descemet's membrane or endothelium. Type XII collagen was distributed throughout the corneal st roma, and it was prominently localized at the superficial stroma. Immunoele ctron-microscopic examination demonstrated that type XII collagen was regul arly found along the surface of banded collagen fibrils with a periodic dis tribution. By Western blot analysis, we observed that extracts from bovine cornea contained both the long and short isoforms of type Xll collagen, whe reas extracts from bovine skin contained only the short isoform, The homo-g eneous distribution and/or presence of the long isoform of type XII collage n may be related to the characteristically regular arrangement of collagen fibrils and thereby the transparency of corneal tissue, Copyright (C) 2000 S.Karger AG,Basel.