Impaired synovial macrophage-mediated efferocytosis in a rat model of post-traumatic knee osteoarthritis

Purpose: The synovial lining is critical for maintaining joint health. Synovial macrophages that inhabit the synovium have a large role in maintaining tissue homeostasis through the clearance of metabolic products, cell debris and recycling components of the synovial fluid. A large part of maintaining homeostasis is the efficient clearance of apoptotic cells which is accomplished by macrophages, termed efferocytosis. However, our lab has previously found that the apoptotic cell burden in the synovium was significantly higher and that synovial-derived macrophage-mediated efferocytosis was impaired in patients with end-stage knee osteoarthritis (OA). Since uncleared apoptotic cells can promote inflammation through the leakage of pro-inflammatory factors, they therefore could contribute to the unresolving inflammation, pain and/or joint damage caused by OA. Our objectives were to determine the effect of efferocytosis impairment on structural and pain-related behavioural outcomes in a rat model of post-traumatic OA (PTOA).