Microenvironment-educated MSC-EVs loaded injectable smart hydrogel for targeting senescent nucleus pulposus cells and inhibiting ferroptosis against intervertebral disc degeneration.

Intervertebral disc degeneration (IDD) is a predominant contributor to spinal disorders. Previous studies have indicated that ferroptosis-induced senescence of nucleus pulposus cells (NPC) plays a critical role in IDD pathogenesis. This underscores therapeutic strategies aimed at inhibiting ferroptosis and delaying NPC senescence. Mesenchymal stem cell-derived exosomes (MSC-EVs), serving as a form of regenerative nanotherapy, inherit parental biological properties. In this study, we pretreated MSCs by simulating a senescent microenvironment to obtain "domesticated vesicles" (D-EVs) with enhanced targeting and anti-senescence properties. Multi-omics analysis revealed that D-EVs are enriched with GPX4 protein and achieve specific binding to senescent NPCs via the CXCL10-CXCR3 chemokine axis. Functionally, D-EVs delivered GPX4 protein to recipient NPCs, thereby inhibiting ferroptosis and alleviating cellular senescence. To enable sustained and on-demand release within the degenerative microenvironment, we anchored D-EVs to thermosensitive hydrogel via ROS-responsive peptides. This ROS-responsive hydrogel further potentiated D-EVs' efficacy in alleviating NPC ferroptosis and reversing senescence-associated metabolic dysfunction. Both in vitro and in vivo experiments revealed that this senescence-targeting system significantly suppresses ferroptosis and senescence pathways, and prevents conversion of the senescence phenotype in NPCs. This study presents a novel approach to inhibit ferroptosis, thereby delaying NPC senescence and mitigating IDD progression.