Engineered Stem Cell Clusters for Extracellular Vesicles-Mediated Gene Delivery to Rejuvenate Chondrocytes and Facilitate Chondrogenesis in Osteoarthritis Therapy.

Gene therapy offers an ideal potential treatment strategy for osteoarthritis (OA). However, the safe and efficient delivery of therapeutic genes remains highly challenging because of the inactivation in direct delivery of miRNA, low transfection efficiency, and a short half-life. This study introduced a gene therapy strategy using mesenchymal stem cells (MSCs) as a gene delivery platform and achieved the sustained delivery of therapeutic genes via engineered MSCs-derived extracellular vesicles (EVs). The miRNA-874-3p is combined with an exosome-targeting motif and transfected into bone marrow mesenchymal stem cells (BMSCs). The BMSCs are then seeded onto hydrogel microspheres, creating the BMSC/MS system for OA treatment. In vitro experiments demonstrated that miRNA-874-3p not only alleviated inflammation and oxidative stress-induced damage to chondrocytes by downregulating the NF-κB signaling pathway, thereby rejuvenating chondrocytes, but also promoted chondrogenesis in the inflammatory microenvironment. Furthermore, the engineered BMSCs in the system demonstrated prolonged retention in vivo, thereby enabling the sustained delivery of the therapeutic gene, miRNA-874-3p, over an extended duration. In the rat OA model, BMSC/MS successfully delivered miRNA-874-3p to the articular cartilage and effectively alleviated cartilage degeneration. In conclusion, this EVs-mediated therapeutic gene delivery approach enables miRNA-based gene therapy a viable alternative to surgery for OA treatment and provides a novel option for gene therapy.