Immunohistochemistry of type XII collagen in the healing rabbit cornea

Purpose. The temporal and spatial distribution of type XII collagen is indicative of its interactions with other macromolecules in the interfibrillar matrix during scar formation. Previous studies (IOVS 1994;35:1991a) showed that mRNA of this collagen is present in cells synthesizing scar tissue. We hypothesized that type XII collagen is deposited in this tissue by cells derived from stroma and endothelium. Methods. Rabbit corneas of 3-days to 2-weeks after a 2-mm diameter keratectomy were processed for immunohisto-chemical analysis with the use of mouse anti-rabbit type XII collagen prepared in our laboratory using synthetic peptides. Results. No type XII collagen-specific fluorescence was detected in wounds 3-days after wounding, but was seen in 1 and 2 week scar tissue. In the 2 week-old wound type XII collagen was detected in the basal cells of regenerating epithelium, the sub-epithelial region adjacent to the wound, the anterior scar tissue, and along the edge of the wound extending to Descemet's membrane. Conclusions. The evidence supports previous data showing the presence of type XII collagen mRNA in stromal-derived and endothelial-derived cells in the healing cornea. Fluorescence associated with epithelial cells is not substantiated by the presence of mRNA, and thus the identification of this material is questionable. The appearance and localization of type XII collagen in healing cornea suggest that it plays an important role in scar morphogenesis.