Effect of epithelial debridement on glycosaminoglycan synthesis by human corneal explants

The purpose of the present work was to investigate the effects of mechanical epithelial debridement upon glycosaminoglycan synthesis by human corneal explants. Corneal explants were maintained under tissue culture conditions for 2-72 days and the glycosaminoglycans synthesized in 24 h were metabolically labeled by addition of 35S-sulfate to the culture medium. These compounds were isolated from the tissue explants and analyzed by a combination of agarose gel electrophoresis and enzymatic degradation with specific mucopolysaccharidases. The glycosaminoglycans synthesized by isolated epithelial cells and by corneas previously submitted to epithelial cell debridement were compared to controls. Keratan sulfate (26 kDa) and dermatan sulfate (43 kDa) were the main corneal glycosaminoglycans, each one corresponding to about 50% of the total. Nevertheless, the main 35S-labeled glycosaminoglycan was 35S-dermatan sulfate (73%), with smaller amounts of 35S-keratan sulfate (15%) and 35S-heparan sulfate (12%), suggesting a lower synthesis rate for keratan sulfate. The main glycosaminoglycan synthesized by isolated epithelial cells was heparan sulfate. The removal of epithelial layer caused a decrease in heparan sulfate labeling and induced the synthesis of dermatan sulfate by stromal cells. This increased synthesis of dermatan sulfate suggests a relationship between epithelium and stroma and could be related to the corneal opacity that may appear after epithelial cell debridement.