Non-enzymatic glycation in corneas from normal and diabetic donors and its effects on epithelial cell attachment in vitro.

BACKGROUND: Diabetic keratopathy manifests as persistent and recurrent erosions and delayed wound healing. To investigate the role of non-enzymatic glycation of proteins in the pathogenesis of diabetic keratopathy, we studied the presence of advanced glycation end products in corneas normal and diabetic donors, and the ability of human comeal epithelial cells to attach to non-enzymatically glycated extracellular matrix proteins.
METHODS: Corneas from normal donors and donors with diabetes were sectioned and immunostaining was performed using a primary antibody that detects N(epsilon)-(carboxymethyl) lysine. Collagen I and fibronectin-coated tissue culture plates were non-enzymatically glycated by incubating with 500-mM glucose-6-phosphate for three weeks at 37 degrees C. To determine attachment corneal epithelial cells were allowed to adhere to glycated plates (1 to 4 hours, 37 degrees C). Non-adherent cells were removed by gentle washing and the number of attached cells was quantitated using Calcein-AM.
RESULTS: Corneas from donors with diabetes showed more-intense immunostaining for N(epsilon)-(carboxymethyl) lysine than normal donors of similar ages. Non-enzymatic glycation of collagen I and fibronectin significantly reduced the ability of corneal epithelial cells to adhere to these extracellular matrix proteins.
CONCLUSION: Our data suggest that non-enzymatically glycated proteins may interfere with attachment and hence migration of epithelial cells across the corneal surface, and therefore may contribute to some of the clinical manifestations of diabetic keratopathy. Diabetes leads to an accelerated aging process resulting in a cornea that may be much older than the chronological age of the patient. From a clinical perspective, particular care should be taken when considering the use of contact lenses and following corneal injury in these patients.