DEVELOPMENT OF AN EX VIVO OSTEOARTHRITIC KNEE MODEL

Osteoarthritis (OA) is a leading cause of disability worldwide. Pathological changes during OA include cartilage breakdown, subchondral bone remodelling, and synovial inflammation, all of which contribute to joint dysfunction. These processes are driven by the production of inflammatory cytokines, particularly interleukin 1 (IL-1), which serves as a major driving force in OA pathogenesis. Investigating these pathways in an ex vivo model that replicates the complex interactions between cartilage, bone, and synovium is crucial for understanding disease mechanisms and evaluating potential therapeutic strategies. This study aimed to develop an ex vivo co-culture model to replicate joint tissue interactions and investigated cytokine driven inflammation in OA. The model will enhance our understanding of OA disease progression and offers a valuable platform to explore the therapeutic potential of targeting IL-1 signalling in OA. An ex vivo model was developed using human osteochondral and synovium explants harvested from patients undergoing joint replacement surgery (Ethical approval granted by Sheffield Research Ethics Committee: 20/SC/)144, 12182). Cultures were maintained in physiologically relevant hypoxic, low-glucose ad serum-free conditions. Both high and low-grade osteochondral explants were used, either alone or co-cultured with patient-matched synovium, preserving cell-ECM compositions, inter-tissue crosstalk and local immune responses. Observations were conducted over a 21-day culture period to monitor changes and interactions within the model. Tissue integrity and viability were assessed using histology and immunohistochemistry, secretome analysis performed using Luminex technology. Synovial and osteochondral explants maintained key extracellular matrix components after 21 days in culture. The synovium explants retained cellular populations, including macrophages and fibroblasts, while osteochondral explants maintained collagen type II expression. These findings highlight the model's ability to sustain tissue-specific features and interactions, making it a robust system for further therapeutic investigations. Secretome analysis revealed elevated inflammatory markers most markedly in synovium cultures. Co-culture of osteochondral explants with synovium intensified inflammatory and catabolic activity, emphasising the synovium's role in driving inflammation. This study successfully developed a co-culture system that captures the complex interactions between osteochondral and synovium explants. Results suggest that within the model the synovium plays a central role in driving inflammatory factors. This model can be used to explore the crosstalk between intra-articular tissues, furthering our understanding of OA pathophysiology and informing the development of targeted OA therapies. This model lays the foundation for future work aimed at testing therapeutics within the system and advancing the development of targeted treatments for OA.