[Serum keratan sulfate studies and their significance in the evaluation of cartilage degradation in degenerative and inflammatory joint diseases].

Fragments of high density cartilage proteoglycan (aggrecan) are released during either the normal or pathological turnover of cartilage proteoglycans, which fragments diffuse into the synovial fluids and then appear in the serum. The keratan sulphate (KS; a glycosaminoglycan side chain of aggrecan) is resistant to enzymatic degradation, it has a relatively low clearance and has a "standard" serum level indicating the actual level of cartilage (proteoglycan) breakdown. Using anti-KS monoclonal antibody in ELISA (enzyme-linked immunosorbent assay), we measured serum KS levels in patients with different joint diseases. The highest KS content (595 ng/ml) was measured in the sera of patients with articular chondrocalcinosis (calcium pyrophosphate crystal deposition disease/pseudogout). Slightly lower KS levels were determined in osteoarthrosis (OA; 578 ng/ml) and much less in rheumatoid arthritis (RA; 421 ng/ml). All these patient groups (either with degenerative or inflammatory joint diseases) expressed slightly higher KS levels compared to control blood donors (295 ng/ml). However, there were remarkable variations between these diseased groups, i. e., KS levels in patients with RA were significantly lower than in patients with OA (p < 0.001) and this difference was more pronounced in rheumatoid patients with I-II Steinbrocker stage (370 ng/ml) or in those treated with non-steroid anti-inflammatory drugs (NSAIDs) (382 ng/ml). Keratan sulphate levels in RA patients chronically treated with corticosteroid (460 ng/ml) or auro-thiomalat (473 ng/ml) indicate that these drugs may influence the cartilage metabolism more effectively than the NSAIDs.(ABSTRACT TRUNCATED AT 250 WORDS)