To determine concentrations of chondroitin sulphate (CS) disaccharides in knee synovial fluid (SF) from normal subjects and patients with osteoarthritis (OA) or rheumatoid arthritis (RA), to test whether these variables differ between different diseases and subsets of OA.
OA was subdivided into large joint OA (LJOA), nodal generalised OA (NGOA), and OA with calcium pyrophosphate crystal deposition (CPA), with 25, 9, and 11 people in each subset respectively. The SF of 13 normal subjects was also volunteered for analysis along with 15 RA patients. Clinical assessment of inflammation (0-6) was undertaken on OA and RA knees. Concentrations of unsaturated CS disaccharides Deltadi6S and Deltadi4S were measured by capillary zone electrophoresis.
Concentrations of Deltadi6S were lower in RA (5.90 ng/ml) and OA (13.24 ng/ml) fluids compared with normal (21.0 ng/ml) but no significant differences were seen between disease and normal fluids for Deltadi4S (about 4-6 ng/ml). The ratio of Deltadi6S:Deltadi4S were RA<OA<normal subjects (p<0.001 for all comparisons). The disaccharide concentration values along with the ratios are below. Higher Deltadi6S:Deltadi4S ratios were obtained for LJOA and CPA compared with NGOA. Uninflamed knees had lower concentrations of Deltadi6S than inflamed knees (p<0.01). In patients with bilateral samples, there were strong correlations between right and left knees for all SF variables.
Altered ratios of CS sulphation patterns occur in OA and within OA subsets. These further justify considering NGOA as a subset with a different aetiopathogenesis.