Intraarticular injection of platelet‐rich plasma reduces inflammation in a pig model of rheumatoid arthritis of the knee joint

Abstract Objective Treatment options for rheumatoid arthritis range from symptomatic approaches to modern molecular interventions such as inhibition of inflammatory mediators. Inhibition of inflammation by platelet‐rich plasma (PRP) has been proposed as a treatment for tendinitis and osteoarthritis. The present study was undertaken to investigate the effect of PRP on antigen‐induced arthritis (AIA) of the knee joint in a large animal model. Methods Six‐month‐old pigs (n = 10) were systemically immunized by bovine serum albumin (BSA) injection, and arthritis was induced by intraarticular BSA injection. PRP was injected into the knee joints of 5 of the animals after 2 weeks. An additional 5 animals received no systemic immunization (controls). Signs of arthritis were documented by plain histologic analysis, Safranin O staining, and immunohistochemistry analysis for type II collagen (CII), interleukin‐6 (IL‐6), and vascular endothelial growth factor (VEGF). Interleukin‐1β (IL‐1β), IL‐6, tumor necrosis factor α (TNFα), VEGF, and insulin‐like growth factor 1 (IGF‐1) protein content was measured by Luminex assay. Results In the pigs with AIA, plain histologic analysis revealed severe arthritic changes in the synovium. Safranin O and CII staining showed decreased proteoglycan and CII content in cartilage. Immunohistochemistry analysis revealed increased levels of IL‐6 and VEGF in synovium and cartilage, and protein concentrations of IL‐6, VEGF, IL‐1β, and IGF‐1 in synovium and cartilage were elevated as well; in addition, TNFα protein was increased in cartilage. Treatment with PRP led to attenuation of these arthritic changes in the synovium and cartilage. Conclusion We have described a porcine model of AIA. Experiments using this model demonstrated that PRP can attenuate arthritic changes as assessed histologically and based on protein synthesis of typical inflammatory mediators in the synovial membrane and cartilage.