Highly sulphated glycosaminoglycans in articular cartilage and other tissues containing <italic>β</italic><sub>2</sub> microglobulin dialysis amyloid deposits

Abstract

Highly sulphated glycosaminoglycans (GAGs) are a common constituent of amyloid deposits and an integral component of articular connective tissues where beta 2-microglobulin (beta 2M) amyloid is most often found. Using alcian blue, magnesium chloride, critical electrolyte concentration, mucin histochemistry, and immunohistochemistry, the GAGs composition of beta 2M amyloid deposits in joint capsule and cartilage, carpal, and heart tissues of 22 uraemic patients was determined. Highly sulphated GAGs were found in beta 2M amyloid deposits not only within cartilage, where such GAGs are normally found in high concentration, but also in other articular and extra-articular connective tissues. Keratan sulphate was often specifically localized to beta 2M amyloid deposits in articular cartilage and to a lesser extent in periarticular tissues, with one case showing colocalization with systemic vascular amyloid deposition. Other sulphated GAGs, chondroitin 4 and 6 sulphate, dermatan sulphate, and heparan sulphate were also identified in tissues containing beta 2M amyloid deposits, but with the exception of heparan sulphate (identified by mucin histochemistry) were not specifically localized to the deposits themselves. These findings suggest that qualitative or quantitative changes in the composition of highly sulphated GAGs may play a role in localization of beta 2M amyloid deposits in articular and extra-articular tissues.