LAUSR

Abstract Inflammation of the synovium and joint capsule is a main driver of pain in an osteoarthritic (OA) joint. Triamcinolone acetonide (TAA) is a classical corticosteroid that reduces synovitis and alleviates pain, albeit transiently. Biomaterial-based local TAA release may prolong the suppression of pain without the need for multiple injections. Polylactic-co-glycolic acid (PLGA) formulations of TAA prolong OA pain relief to a limited extent. A novel polyesteramide (PEA) microsphere platform allows for extended release in the OA joint for over 3 months. To evaluate their effect on pain and inflammation, TAA-loaded microspheres were intra-articularly delivered to the knee joint in a rat model of acute arthritis induced by intra-articular injection of streptococcal cell wall peptidoglycan-polysaccharide (PGPS) and subsequent flare-ups by intravenous PGPS injections. PEA-loaded microspheres were benchmarked with TAA-loaded PLGA microspheres and bolus TAA injection. TAA treatments were injected intra-articularly before the first induced flare-up. TAA-loaded PEA and PLGA microspheres reduced joint swelling and signs of pain-like behavior over the entire study period, as assessed by weight bearing and referred mechanical hypersensitivity, whereas bolus suspension was effective for a shorter time period. TAA-loaded PEA microspheres reduced lameness to a greater extent than TAA-loaded PLGA microspheres. In conclusion, a single intra-articular injection of TAA-loaded PEA microspheres reduced joint swelling and induced longer pain relief compared to bolus injection. Hence relief of inflammation and pain by PEA-based delivery of TAA may prove to be effective and durable.