Effects of different hyaluronic acid products on synovial fluid NO levels in knee osteoarthritis

The aim of the present study was to evaluate the effects of different hyaluronic acid forms on synovial fluid nitric oxide (NO) levels and glutathione peroxidase (GSHPx) activities in the treatment of patients with knee osteoarthritis (OA). Forty patients were equally randomized into two groups and treated with native sodium hyaluronate (group I) or with cross-linked hylan G-F 20 (group II). Clinical evaluations and synovial fluid aspirations were performed before the first (baseline), the second (week 1), and third injections (week 2), and a week after the third injection (week 3). NO levels were reduced at the end of the study in both groups (p<0.01 in group I, p=0.001 in group II), while no significant change was found in GSHPx activity. Also, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scores and WOMAC physical function scores were gradually improved at all follow-ups in the two groups. No significant differences between the two groups of NO levels, GSHPx activity, WOMAC pain scores, WOMAC stiffness scores, and WOMAC physical function scores were recorded during the study. Intra-articular hyaluronic acid therapy may reduce synovial fluid NO levels. These effects do not seem to be dependent on the molecular weight and various structural changes of hyaluronan products.