Effect of hyaluronic acid on cytokines and immune cells change in patients of knee osteoarthritis.

Purpose: To evaluate the changes of cytokines and immune cells after Intra-articular hyaluronic acid(IAHA)injections in patients with knee osteoarthritis (KOA).

Patients And Methods: Sixteen patients were included in the study, with a total of 65 IAHA injections. The Numeric Rating Scale (NRS) and Lysholm scores were evaluated at each visit. The immune cells and 14 cytokines of synovial fluid were analyzed at each visit. The association between immune cells and cytokines were examined.

Results: IL-6 and IL-8 were the most common cytokines in the synovial fluid of KOA patients. The synovial fluid was orchestrated by macrophages (69%) and Lymphocytes (18%). Neutrophils were less to count of the total cell population (< 2%). The cytokines decreased significantly after the first injection and then tended to be stable. Lymphocytes increased a lot, while Macrophages decreased in the early stage, then increased after multiple injections. The proposition of M1 decreased in the early stage, then increased after multiple injections, while M2 increased consistently. M1 and M2 were positively associated with IL-6 and IL-8.

Conclusion: The synovial fluid of KOA patients was orchestrated by macrophages (69%) and Lymphocytes (18%) and cytokines like IL-6 and IL-8. IAHA may play an anti-inflammatory functional role through the decreased production of IL-6 and IL-8 by macrophages through polarization. The results from this study partially revealed the effect of IAHA on cytokines and immune cells change in KOA patients, and therapies targeting pathogenic cytokines and immune cells might be used to attenuate the knee joint inflammation and release pain.

Trial Registration: ChiCTR2100050133; date registered 17 August 2021.