Injectable hydrogel microspheres delivering cartilage-targeted LGR5-engineered exosomes for osteoarthritis therapy.

Osteoarthritis (OA) is a progressive degenerative joint disease characterized by cartilage destruction and impaired intrinsic repair capacity. Here, we developed a cartilage-targeted delivery system by engineering human umbilical cord mesenchymal stem cells (hUC-MSCs) to co-express LGR5 and a cartilage affinity peptide (CAP), generating LGR5-engineered CAP-exosomes (CAP/LGR5-EXO), which were subsequently encapsulated within hyaluronic acid methacrylate (HAMA) hydrogel microspheres to enhance intra-articular retention. In vitro, CAP/LGR5-EXO promoted chondrocyte proliferation, enhanced extracellular matrix synthesis, and suppressed catabolic mediators, while also restoring mitochondrial homeostasis and relieving p21-driven cell cycle arrest. Bulk RNA-seq revealed that CAP/LGR5-EXO activated pathways related to cell cycle progression, mitochondrial protection, and oxidative stress resistance, as further supported by integrative analyses of three independent single-cell RNA-seq datasets. In vivo, CAP/LGR5-EXO@HMs exhibited prolonged joint retention, facilitated cartilage regeneration, reduced osteophyte formation, and significantly improved OARSI scores in a destabilization of the medial meniscus (DMM) mouse model. Collectively, our findings demonstrate that cartilage-targeted HAMA microspheres delivering LGR5-engineered exosomes effectively restore chondrocyte function and ameliorate OA progression, providing a promising therapeutic strategy for cartilage regeneration and OA treatment.