From Lab to Clinic: Ex Vivo Models for Biotherapeutic Testing in Osteoarthritis

OBJECTIVE: The primary aim of this study was to establish reliable ex vivo models to evaluate the efficacy of biotherapeutics in pathological settings. Specifically, we investigated the potential of adipose-derived stem/stromal cell (ASC)-derived secretome (or conditioned medium, CM) to mitigate inflammation and degenerative processes associated with osteoarthritis (OA). MATERIALS AND METHODS: Ex vivo experiments were conducted using human cartilage, osteochondral interface, and synovial membrane explants. An inflammatory phenotype was induced with OA-relevant cytokines, namely TNFα and/or IL-1β. Control and stimulated groups were compared with those treated with CM or primed CM (pCM), a “potentiated” CM derived from cytokine-primed ASCs. Markers relevant to tissue viability, catabolic processes, and inflammation were assessed. For cartilage, MMP activity, GAG release, and specific gene and protein expression were analyzed. In the synovial membrane, nitric oxide production, COX2, and PGE2 expression served as key inflammatory markers. RESULTS: The results demonstrated that all ex vivo explants remained viable for several days and responded to inflammatory cytokines. Cartilage explants provided rapid and informative insights to identify the most effective cytokine stimulation and gave evidence of CM effect on catabolic MMP activity. The osteochondral interface model proved particularly effective, enabling the separation of cartilage and bone compartments for localized treatment and analysis. CM, both standard and primed, proved effective in modulating catabolic activity also in the osteochondral model. The synovial membrane model revealed CM action in reducing several inflammatory markers. CONCLUSIONS: In conclusion, this study highlights the utility of ex vivo models as robust platforms for replicating OA features and testing biotherapeutics. CM demonstrated the ability to reduce catabolic activity and inflammation, supporting its therapeutic potential in OA treatment. These findings suggest that ex vivo models can be effectively integrated into drug testing pipelines, and further studies are warranted to validate these results and facilitate the clinical translation of CM.