Composition and organization of corneal scar tissue

Purpose. We hypothesize that Type VI collagen plays an important role in maintaining proper fibril sparing during corneal morphogenesis by interacting with fibrillar collagens, proteoglycans and other collagens in the interfibrillar space. Methods. To test this hypothesis we biochemically and immunocyto-chemically characterized native type VI collagen from corneal tissues to determine its interaction with other matrix proteins. Results. We have discovered that type VI collagen is associated with corneal the proteoglycans decorin and lumican, and a novel extracellular matrix protein, ßig-h3, previously described in corneal epithelium and a human adenocarcinoma cell line. Type VI collagen and ßig-h3 co-elute in a gel filtration column, they are separated upon reduction with mercaptoethanol, and they co-localize immunocytochemically. In addition to numerous ocular and non-ocular tissues, ßig-h3 is expressed in fetal corneal stroma, in corneal scars, and in the sub-epithelial matrix and posterior collagenous layer of Fuchs' dystrophic cornea. ßig-h3 mRNA is located in corneal epithelium, fetal stromal cells, and healing corneal wounds. Conclusions. The novel protein ßig-h3 is present in the extracellular matrix of corneal tissues where it is associated with filaments of type VI collagen. The ubiquitous distribution of ßig-h3 in fetal tissues and the temporal expression of ßig-h3 message suggest this protein together with type VI collagen play a role in normal and pathological morphogenesis of extracellular matrices.