Stem Cell Secretome-Enriched Hydrogels: A Novel Therapeutic Strategy for Osteoarthritis

Background: 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 a novel strategy that combines a biomimetic HA‑g‑CS hydrogel with ASC‑derived secretome as an integrated, secretome‑enriched viscosupplement for OA. Methods: ASC secretome was characterised by nanoparticle tracking analysis and LC‑MS/MS proteomics, revealing a stable profile enriched in matrix‑remodelling enzymes, angiogenic and pro‑survival factors, and proteins linked to osteochondral repair. The SH‑HA‑g‑CS hydrogel was synthesised via sequential CS grafting and thiolation, and subsequently loaded with secretome at a 1:1 ratio for in vitro testing on human chondrocytes. Results: In a TNF+γ-IFN‑driven inflammatory model, samples treated with liquid HA+CS and CM preserved metabolic activity, supported migration, and modulated inflammatory and matrix‑related genes, with CM inducing the strongest downregulation of IL‑1α/IL‑6. Multiplex proteomics showed that HA+CS and CM reduced pro‑inflammatory and metalloproteinase outputs while maintaining controlled angiogenic signalling, whereas SH‑HA‑g‑CS, particularly when combined with CM, promoted a delayed yet sustained shift towards a lower‑inflammatory, reparative‑aligned secretory profile. Conclusions: Overall, these findings support secretome‑enriched HA‑g‑CS hydrogels as a promising cell‑free, disease‑modifying viscosupplement approach that integrates mechanical support with finely tuned immunomodulatory and regenerative cues in OA.