Changes in HNK-1 epitope and collagen type IX in the aqueous humour of patients with pseudoexfoliation syndrome.

PURPOSE: To investigate alterations in the proteoglycan (PG) and glycosaminoglycan (GAG) content of the aqueous humour in patients with pseudoexfoliation syndrome (PEX). MATERIALS AND METHODS: Aqueous humor samples were obtained during cataract surgery from nineteen patients bearing PEX features and twenty-three age-matched normal controls. Protein and IgG were quantified densitometrically after their electrophoretic separation. Collagen type IX, 3-sulphoglucuronic acid (HNK-1 epitope), biglycan and heparan sulphate proteoglycans were detected in Western and dot blots by using specific monoclonal antibodies (MAbs). The immunochemical analysis was performed in native aqueous humour or after degradation of the glycosaminoglycans with chondroitinases. RESULTS: Degradation of the samples with chondroitinases ABC, AC and B revealed that, in the aqueous humour from PEX eyes, collagen type IX and biglycan had a more dermatan sulphate than did normal eyes. In addition, more HNK-1 epitope was observed in PEX eyes, which after similar enzymatic treatment was found to be located mainly in dermatan sulphate sequences. 3-sulphoglucuronic acid was a constituent of the GAG chains of the collagen type IX. We found that the electrophoretic mobility of the bands of collagen type IX and HNK-1 epitope was exactly the same in the aqueous humour of normal and PEX samples; both migrated as four bands at 120, 113, 92.6 and 56 kDa. The PGs bearing heparan sulphate were found only in normal samples. Other PGs were not detected. CONCLUSIONS: Because no significant difference was observed in the concentration of albumin and IgG in PEX and normal samples, the blood-aqueous barrier was probably not significantly compromised in PEX patients with cataract but without open-angle glaucoma. The results support the hypothesis that the pathogenesis of PEX can be linked to disturbed metabolism of GAGs and PGs.

Solid phase assays in glycoconjugate research: applications to the analysis of proteoglycans, glycosaminoglycans and metalloproteinases.

Glycoconjugates are a class of macromolecules consisting of different constituents, one of which is sugar moieties. Glycoconjugates comprise the majority of tissue constituents, both intracellular and extracellular. Extracellular glycoconjugates (glycoproteins and proteoglycans) participate in a wide variety of interactions, through which they maintain tissue integrity. Therefore, their analysis or the study of their possible interactions would give evidence for the state of tissues. Since the amounts of some of the extracellular glycoconjugates are usually low or the amounts of tissue to be examined come from biopsies, specific analytical systems are developed for their study, the most familiar being solid phase assays, which have the advantages of analysis of multiple samples on the same time, cheap instrumentation and high specificity.

Matrix metalloproteinases and their inhibitors in exfoliation syndrome.

The purpose of this study was to determine the expression of metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in the aqueous humour of patients with exfoliation syndrome (XFS). XFS and control samples were analysed for their MMP content by zymography and for their tissue inhibitors by ELISA. In XFS eyes, an increase for up to 60% in almost all MMPs was observed, as compared to the controls. MMP-2 and MMP-9 were found to predominate. TIMP-1 levels in XFS samples were slightly decreased, while TIMP-2 levels were similar to those of the controls. Our findings suggest that MMPs may be crucial in the progression of XFS, by degrading the abnormal fibrillar matrix components in the anterior segment tissues of XFS eyes. However, the increased levels of MMPs seem not to be able to overcome the overproduction and accumulation of the exfoliative material.