Stem cell secretome-enriched hydrogels as a potential therapeutic approach for osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by progressive cartilage loss and synovial inflammation, for which current therapies are mainly symptomatic and fail to durably modify disease progression. Hyaluronic acid (HA) and chondroitin sulfate (CS) are widely used in viscosupplementation, but the rapid clearance of HA and limited bioactivity of simple mixtures restrict their long‑term benefit. In parallel, adipose‑derived mesenchymal stromal cell (ASC) secretome has emerged as a promising cell‑free therapeutic due to its pleiotropic anti‑inflammatory and regenerative actions. Here, we evaluated an injectable SH-HA-g-CS hydrogel as a sustained-delivery platform for the ASC-derived secretome and compared its biological performance with the corresponding soluble formulations in an in vitro model of OA. The ASC-derived conditioned medium (secretome) was characterized by nanoparticle tracking analysis (NTA) and LC-MS/MS proteomics. Human chondrocytes were treated with soluble HA, CS, HA + CS, ASC-derived secretome, SH-HA-g-CS hydrogel or SH-HA-g-CS loaded with secretome (2:1 hydrogel: secretome, v/v) under basal and TNF/IFN-γ-induced inflammatory conditions. Cell metabolic activity, wound closure, gene expression and multiplex proteomic profiles were subsequently evaluated. In the inflammatory model, soluble HA + CS and ASC-derived secretome preserved metabolic activity, supported wound closure, and reduced IL1A and IL6 gene expression, with the secretome producing the lowest expression levels of both cytokines. Multiplex proteomic analysis showed that HA + CS and ASC-derived secretome were associated with lower levels of several pro-inflammatory mediators, whereas the secretome-loaded SH-HA-g-CS hydrogel showed lower recovered levels of several pro-inflammatory mediators than the unloaded hydrogel at Day 14. The ASC-derived secretome-loaded SH-HA-g-CS hydrogel showed the potential to provide sustained immunomodulatory effects while maintaining good cytocompatibility, supporting its further development as a cell-free therapeutic strategy for osteoarthritis. Further in vivo studies are required to confirm its therapeutic efficacy and translational potential.