Cytokine-Activated Mesenchymal-Stem-Cell-Derived Extracellular Matrix Facilitates Cartilage Repair by Enhancing Chondrocyte Homeostasis and Chondrogenesis of Recruited Stem Cells

Current strategies for cartilage repair, including decellularized cartilage matrices and synthetic bioactive materials, often encounter challenges such as immune responses and donor morbidity. In this study, we optimized an extracellular matrix (ECM) derived from mesenchymal stem cells through preconditioning with disease-associated inflammatory factors, specifically interleukin 6, tumor necrosis factor alpha, and interferon gamma (IFN-γ). Our in vitro experiments demonstrated that the cytokine-preconditioned stem-cell-derived ECM, especially IFN-γ-ECM, supports chondrocyte homeostasis by restoring mitochondrial energy metabolism. Furthermore, bioactive molecules secreted from this preconditioned ECM boost the recruitment of endogenous stem cells and facilitate their differentiation into chondrocytes. Notably, we found that IFN-γ-ECM facilitates the chondrogenic differentiation of mesenchymal stem cells through the activation of the integrin/phosphatidylinositol 3-kinase/Akt pathway and the Smad2/3 signaling cascade. These results highlight the potential of the cytokine-stimulated ECM, especially IFN-γ-ECM, to restore chondrocyte homeostasis, optimize the mobilization of endogenous stem cells, and substantially improve the regeneration of cartilage defects, offering a promising strategy for acellular cartilage graft reconstruction.