Chondroitin sulfate in inflammatory joint diseases: How structural variability shapes its therapeutic effects

Inflammatory joint diseases, including rheumatoid arthritis and osteoarthritis (OA), are characterized by pain, inflammation, and progressive cartilage degeneration. Chondroitin sulfate (CS) is widely used as a symptomatic treatment, but the influence of structural variability on its biological activity remains unclear. We compared two pharmaceutical CS preparations with distinct structural features: CS-A, predominantly 4-sulfated, and CS-C, predominantly 6-sulfated. Disaccharide composition was determined by chondroitinase AC digestion followed by SAX-HPLC and compared with previously reported HSQC NMR data. Biological effects were evaluated in complete Freund's adjuvant (CFA)-induced arthritis in rats and monosodium iodoacetate (MIA)-induced OA in mice. Hypernociception, edema, locomotor behavior, inflammatory mediators, myeloperoxidase (MPO) activity, leukocyte migration, and histopathological alterations were assessed. Both preparations attenuated inflammatory and joint alterations without signs of systemic toxicity. In the CFA model, CS-A and CS-C increased the hypernociceptive threshold by 52.71% and 53.28% and reduced MPO activity by 84.7% and 70.2%, respectively. In the MIA model, they increased the hypernociceptive threshold by 69.7% and 37.3% and reduced synovial inflammatory infiltration by 98% and 70%, respectively. Both preparations reduced IL-6, TNF-α, and PGE₂, whereas CS-A markedly increased IL-10. Histological analyses showed reduced inflammatory damage, increased tibial chondrocyte area, and lower OARSI scores. Overall, both CS preparations exhibited anti-inflammatory, antihypernociceptive, and chondroprotective effects, with response magnitude varying across outcomes. These findings suggest that structural characteristics, including sulfation pattern and molecular weight, may contribute to differences in CS biological activity.