Proteoglycan Synthesis After Refractive Surgery

Abstract

Abstract: : Purpose: The objetive of the present study is to evaluate the effects of corneal refractive surgery upon PG biosynthesis, using two different techniques: LASER in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). PRK, which consists in epithelial removal and laser application, is an effective procedure for the correction of low and moderate myopia, and LASIK, an intrastromal procedure that maintains the integrity of the Bowman’s membrane and overlying epithelium, is effective to treat a wide range of refractive errors. Methods: Human corneas that were rejected for transplants were obtained at Banco de Olhos do Hospital São Paulo. For each eye pair, one cornea was submitted to refractive surgery and the other was used as matched control. After surgery, the corneas are excised from the eyes and immediately placed in Ham F-12 nutrient mixture supplemented with ³⁵S-sulfate (100 µCi) for the metabolic labeling of PGs. After 24 h incubation at 37°C in 2.5% CO₂ atmosphere, PGs are extracted by 4 M GuHCl and identified by a combination of agarose gel electrophoresis, autoradiography, immunoblotting, and enzymatic degradation with protease and specific mucopolysaccharidases. Results: Our results indicate a marked decrease in ³⁵S-sulfate incorporation in PGs after refractive surgery after LASIK. Conclusion: There is a marked decrease in proteoglycan sinthesis after LASIK. The reasons leading to this effect are now under investigation.

Keywords: cornea: basic science • refractive surgery: LASIK • proteoglycans/glycosaminoglycans