Abnormal deposition of laminin and type IV collagen at corneal epithelial basement membrane during wound healing in diabetic rats.

PURPOSE To understand the pathophysiology of the corneal basement membrane in diabetes, we compared the localization of laminin and type IV collagen in the epithelial basement membrane during corneal epithelial wound healing in diabetic and nondiabetic rats. METHODS Streptozotocin was used to induce diabetes in half the rats. Two weeks later, the whole corneal epithelium was debrided. Diabetic and healthy rats (3-5 per group) were sacrificed before debridement and 1, 3, and 7 days and 1 month afterwards. The localization of laminin and type IV collagen was observed in cryosections by epifluorescence microscopy. RESULTS In unwounded corneas of both diabetic and normal rats, laminin and type IV collagen were localized in the corneal epithelial basement. The intensity of fluorescence, however, was clearly stronger in the diabetic rats. In normal rats, wounding initially removed laminin and type IV collagen, but during healing these two proteins reappeared beneath the resurfacing corneal epithelium. Although similar results were observed in diabetic rats, the expression of laminin and type IV collagen was delayed, and their deposition was fragmented and irregular. CONCLUSIONS These results suggest that delayed corneal epithelial wound healing in diabetes might involve delayed reappearance and abnormal reformation of epithelial basement membrane proteins.