Current serological possibilities for the diagnosis of arthritis with special focus on proteins and proteoglycans from the extracellular matrix.

This review discusses our current understanding of how the expression and turnover of components of the cartilage extracellular matrix (ECM) have been investigated, both as molecular markers of arthritis and as indicators of disease progression. The cartilage ECM proteome is well studied; it contains proteoglycans (aggrecan, perlecan and inter-α-trypsin inhibitor), collagens and glycoproteins (cartilage oligomeric matrix protein, fibronectin and lubricin) that provide the structural and functional changes in arthritis. However, the changes that occur in the carbohydrate structures, including glycosaminoglycans, with disease are less well studied. Investigations of the cartilage ECM proteome have revealed many potential biomarkers of arthritis. However, a clinical diagnostic or multiplex assay is yet to be realized due to issues with specificity to the pathology of arthritis. The future search for clinical biomarkers of arthritis is likely to involve both protein and carbohydrate markers of the ECM through the application of glycoproteomics.