Glycosaminoglycan Sulfation in Human Osteoarthritis

Abstract

Chondroitin lyase products of aggrecan and small proteoglycans from normal and osteoarthritic cartilages were analyzed for chain internal ⌬disaccharides and terminal mono-or disaccharides. Chondroitin and dermatan sulfate chains from arthritic cartilages were of essentially normal size and internal sulfation but had significantly altered sulfation of the terminal residues. Whereas in normal cartilage, ϳ60% of terminal GalNAc4S was 4,6-disulfated, it was reduced to ϳ30% in osteoarthritic cartilage. This is most likely due to a lower terminal GalNAc4,6S-disulfotransferase activity and reveals that metabolic changes in osteoarthritis can affect this distinct sulfation step during chondroitin and dermatan sulfate synthesis. GlcA␤1,3GalNAc6S-, the mimotope for antibody 3B3(؊), was present on ϳ8 and ϳ10% of chains from normal and osteoarthritic cartilages, respectively. 3B3(؊) assayed by immunodot blot was within the normal range for most osteoarthritic samples, with only 5 of 24 displaying elevated reactivity. This resulted not from a higher content of mimotope, but possibly from other structural changes in the proteoglycan that increase mimotope reactivity. In summary, chemical determination of sulfation isomers at the non-reducing termini of chondroitin and dermatan sulfate provides a reliable assay for monitoring proteoglycan metabolism not only during normal growth of cartilage but also during remodeling of cartilage in osteoarthritis.The function of normal adult joint cartilage resides in its ability to provide resistance to compressive, tensile, and shear forces that occur during normal joint motion. The specialized extracellular matrix consists of a fibrillar collagen network (1), highly organized and stabilized through inter-and intramolecular cross-links that restrain the swelling pressure exerted by the high concentration of negatively charged aggrecan aggregates (2). The metabolic activity of chondrocytes in adult cartilage is adapted to maintain the composition of a functional extracellular matrix. The collagen network is relatively metabolically inert (3), whereas other constituents, such as aggrecan aggregates, undergo a distinct turnover process (4, 5) in which catabolic cleavage (6, 7) and removal of molecules from the extracellular matrix (8, 9) are in balance with synthesis and deposition of new molecules. However, at the onset and throughout progression of degenerative joint disease, such as OA, 1 this metabolic balance is perturbed, and episodes of increased catabolism (10, 11) and increased synthesis (12-16) of matrix components by the chondrocyte take place.It has been proposed that the increased anabolic activity in OA is related to a change in the differentiated state of the chondrocyte (17) with expression of pathways that are characteristic of cells in fetal or postnatal growth cartilages. This hypothesis has been particularly supported by published reports (18 -21) that the GAG composition of aggrecan synthesized during the early stages of cartilage degeneration in animal models of OA or ac...

Mechanical and biochemical properties of human cervical tissue

“…It has also been shown that the finer structure of the GAG relating to the length of the GAG disaccharide chain and the degree of sulfation is important in the biomechanics of hydrated tissue (e.g. in cornea tissue [52] and osteoarthritic cartilage [53]). Our current DMB assay only measures total sulfated GAG content.…”

Direct Measurement of Glycosaminoglycan Intermolecular Interactions via High-Resolution Force Spectroscopy

“…[1][2][3] As part of the aggrecan macromolecule, individual CS-GAGs have the tendency to assume an extended, rodlike conformation rather than a random coil under normal physiological conditions of 0.15 M salt concentration due to intramolecular electrostatic repulsion between neighboring negatively charged carboxylate and sulfate groups (i.e., intercharge distance ) 0.64 nm), 3 as well as the high chain packing density.…”

Enhanced detection of sulfated glycosylation sites in glycoproteins

“…1 Parenthetical numbers refer to the sulfated glycopeptides described in Table 4. 2 Mass accuracy compromised due to isobaric interference. 3 Nonsulfated glycopeptides were identified previously in reference [16].…”

“…It is an integral, ubiquitous component of the polymeric glycosaminoglycans, present in the extra-cellular matrix [1]. Changes in glycosaminoglycan sulfation have been linked to arthritis and other disease states [2][3][4]. Sulfation also is prevalent on cell-surface oligosaccharides in virtually all mammalian tissues, and its presence is fundamental in cellular communication events [5].…”

“…When present in glycoproteins, sulfation can alter biological recognition [10,11] and/or facilitate rapid clearance of the protein from the body [12]. Because sulfation is a pervasive, functionally significant biological modification, analytical methods that can monitor its presence are required to better understand its role in protein function, in cell signaling events, and in diseases where sulfation patterns are altered, like arthritis [2,3] and cystic fibrosis [5,7,8].…”