Ab0096 Oxidative Stress and Low-Level Inflammation in the Severity of Knee Osteoarthritis

Background: Calcium pyrophosphate crystals (CPP) are associated with cartilage lesions and increased severity of osteoarthritis (OA) and can induce an inflammatory process. Oxidative stress (OS) is associated with joint inflammation and destruction, reactive oxygen species (ROS) are mediators of joint damage in OA. Objectives: To identify the oxidative and inflammatory characteristics of intra-articular CPP deposits and their association with the degree of knee OA. Methods: Synovial fluid (SF) with and without CPP were collected and analyzed from patients with degrees of OA according to the Kellgren-Lawrence (KL) radiographic scale: grade 3 (moderate) and 4 (severe). CPP were detected by polarized light microscopy, inflammatory status was assessed by total leukocyte count, and quantification of ROS and H₂O₂ by fluorimetric assays. The risk of association was estimated using the Chi-squared test. ROS were classified according to the percentage of stressed cells in SF as: low (0-5%), medium (6-11%) and high (12-21%); for H₂O₂ they were also classified as 0-10% low, 11-20% medium and 21-44% high. Results: Fifty-six SF were analyzed, of which 39.28% were from patients with KL-3 and 60.71% as KL-4. CPP were detected in 35 samples (60.5%), of which 46.57% had moderate OA and 51.42% severe OA. In moderate OA, 77.3% of SF had low inflammation, 18.2% moderate and 4.5% high. In severe OA, 82.4% had low inflammation, 11.8% moderate inflammation and 5.9% high inflammation. No differences were found between inflammation and OA severity. Of the total SF examined, 64.3% contained low levels of ROS, 19.6% contained moderate levels and a small proportion contained high levels (16.1%). In moderate OA, 77.3% had low, 13.6% medium and 9.1% high levels. In severe OA, 55.9% had low, 23.5% medium and 20.6% high values. A trend towards higher risk was observed for high ROS and severe knee OA, but this was not significant. CPP were more frequent in severe OA (32.14%). In moderate OA, there was an association with low ROS and high H₂O₂ levels, but they are not associated with CPP. Conclusion: The identified ROS cannot be considered potential biomarkers of pathogenesis or predictors of severe OA, since no differences were found between moderate and severe stages, more studies are needed considering early stages. REFERENCES: [1] Liu YZ, Jackson AP, Cosgrove SD. Contribution of calcium containing crystals to cartilage degradation and synovial inflammation in osteoarthritis. Osteoarthritis Cartilage. 2009; 17:1333-40. [2] Jiang Y, Li T, Yang J, Wang X, Song X, Chen G, Dai G, Li R, Yao C, Chen J, Chen C, Gong X and Yang L (2023) Sustained intra-articular reactive oxygen species scavenging and alleviation of osteoarthritis by biocompatible amino-modified tantalum nanoparticles. Front. Bioeng. Biotechnol. 11:1118850. doi: 10.3389/fbioe.2023.1118850. [3] Liu L, Luo P, Yang M, Wang J, Hou W and Xu P (2022) The role of oxidative stress in the development of knee osteoarthritis: A comprehensive research review. Front. Mol. Biosci. 9:1001212. doi: 10.3389/fmolb.2022.1001212. [4] Tudorachi NB, Totu EE, Fifere A, Ardeleanu V, Mocanu V, Mircea C, Isildak I, Smilkov K, Cărăuşu EM. The Implication of Reactive Oxygen Species and Antioxidants in Knee Osteoarthritis. Antioxidants (Basel). 2021, 21;10(6):985. doi: 10.3390/antiox10060985. Acknowledgements: To Iván Alejandro Juárez and Xiadani Ruíz Dávila for updating the physical and electronic database of the synovial fluid analyses. Disclosure of Interests: None declared.