Expression Patterns of Cysteine Cathepsins in Cultured Corneal Fibroblasts of Granular Corneal Dystrophy Type II Patients

Abstract

Purpose:: ßig-h3 protein is associated with amyloid deposition in the extracellular matrix (ECM) in granular corneal dystrophy type II (GCDII). Cathepsins, secreted lysosomal cysteine proteases, are involved in the degradation of the ECM. The expression of cysteine cathepsins and cystatin C (an endogenous inhibitor of cysteine proteases) were studied in cultured corneal fibroblasts to determine how the degradation of the ECM affects amyloid deposition of ßig-h3.

Methods:: Keratocytes were isolated from the corneal stroma and cultured in DMEM media with or without serum. Cathepsins expression was analyzed with RT-PCR, immunoblotting, and immunocytochemistry.

Results:: Expression patterns of protein and mRNA of ßig-h3 were unchanged between the cultured corneal fibroblasts of normals and patients with a heterozygous or homozygous R124H mutation. The mRNA levels and protein levels for cathepsins B, K and L were significantly decreased in cultured corneal fibroblasts with the heterozygous or homozygous R124H mutation. Additionally, cathepsins B, K and L were predominantly localized to the cytosol, but immunoreactivities of cystatin C were detected on the surface of cultured corneal fibroblasts.

Conclusions:: Decreased expression of cysteine cathepsins may contribute to degradation of ECM as well as amyloid deposition of ßig-h3 in GCDII.

Keywords: cornea: basic science • degenerations/dystrophies • cornea: stroma and keratocytes