Keratan sulfate in body fluids in joint disease

Abstract

Keratan sulfate (KS) is a highly-negatively charged glycosaminoglycan which is found principally in aggrecan, the most abundant proteoglycan in the extracellular matrix of hyaline, fibrous and elastic cartilage. In 1985, we discovered that small peptidoglycans bearing antigenic KS (agKS) were present in small amounts in human serum and postulated that the great majority of these were derived from the degradation of cartilage aggrecan (Thonar et al. 1985). During the past decade, studies of antigenic KS in joint fluid and serum have provided strong evidence in support of this hypothesis. By asking questions which could not have been addressed previously, these studies have shed new light upon the metabolism of aggrecan in vivo. In this manuscript, we describe some of these findings and put in perspective their contribution to our understanding of the metabolism of aggrecan in joint diseases.