RESUMEN
BACKGROUND: This exploratory study investigates if intra-articular injected gold microparticles in knee osteoarthritis (KOA) reduce immunomodulatory-based pain via proteomic changes in the synovial fluid (SF) and serum. METHODS: Thirty patients with moderate KOA were included. Intraarticular injections with 20 mg gold microparticles (72.000 particles, 20-40 µm in diameter) using the patient's synovial fluid (SF) as carrier were performed. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscores for pain, stiffness, and function were assessed at inclusion, 8 weeks and 2 years The PainDetect questionnaire, pain pressure threshold (PPT), temporal summation (TS), and conditioned pain modulation (CPM), and pain diary were assessed at inclusion and 8 weeks. Proteome analysis was performed on SF and blood samples before and after 8 weeks of treatment. RESULTS: A decrease in WOMAC scores (pain (p = 0.0001), stiffness (p = 0.0088), activity (p = 0.0001)), PainDetect (p = 0.0002) and increase in PPT (p = 0.001) and CPM (p = 0.021) and a decrease in TS (p = 0.03) were found after 8 weeks compared to inclusion assessments. At 2 years follow-up compared to baseline there was a decrease in WOMAC scores (pain (p = 0.0001), stiffness (p = 0.007), activity (p = 0.0001)) and PainDetect (p = 0.0001). In SF, 28 different proteins were downregulated and 11 upregulated (p < 0.05) mainly associated immune response. Similarly, 31 proteins were downregulated and 1 upregulated in serum (p < 0.05) reflecting key immune response and anatomical structure development processes. No adverse effects related to the treatment were recorded. CONCLUSIONS: Gold microparticles injected intra-articular in KOA joints may provide pain relief and an inflammatory modulatory effect based on proteome changes found in SF and serum. A randomized, controlled, double-blind study is needed to infer a conclusion. SIGNIFICANCE: This study indicates that intra-articular gold may provide advantages in clinical practice for managing knee osteoarthritic pain. The use of intraarticular gold can add new knowledge to the treatment of inflammation and pain.
