Comparative Effects of Dexamethasone and ASC Secretome in an Ex Vivo Osteoarthritis Co-Culture Model

Osteoarthritis (OA) is a multifactorial disease characterized by inflammation, extracellular matrix remodeling, and joint degeneration, and it still lacks disease-modifying treatments. Here, we applied an ex vivo OA model based on transwell co-cultures of cartilage and synovial membrane explants harvested from OA patients to compare the effects of adipose-derived stem/stromal cell (ASC) conditioned medium (CM) with dexamethasone (DEX), a clinically used corticosteroid. Explants were treated for 48 h with 100 nM DEX, CM derived from 5 × 10⁵ ASCs, or left untreated. Outcomes included gene and protein expression of key mediators, metalloprotease and aggrecanase activities, and nitric oxide release. DEX significantly reduced inflammatory markers (e.g., <i>PTGS</i>, <i>IL-1β</i>, and IDO) and <i>VEGF</i> expression in both tissues, while CM did not elicit consistent anti-inflammatory effects. Regarding matrix remodeling, both treatments reduced metalloprotease activity, with DEX modulating <i>MMP3</i> and <i>MMP13</i> expression in both tissues and CM reducing only <i>MMP3</i> expression in cartilage while presenting high levels of TIMP-1. These results confirm the robustness of the model, demonstrated by reproducible responses to DEX and its high-throughput potential, and underscore the need for mechanistic studies to optimize novel biotherapeutics.