Engineered exosomal miR140 modulates mitophagy of chondrocytes through targeting CAPN1 to alleviate osteoarthritis.

Osteoarthritis (OA) is a prevalent degenerative disease involving mitophagy dysfunction of chondrocytes. As OA progresses, miR140 expression in chondrocytes decreases, and its therapeutic potential has shown protective effects. However, the variation in mitophagy across different stages of OA in human chondrocytes, as well as the role of miR140 in modulating mitophagy, have remained insufficiently elucidated. In this study, we observed that mitochondrial morphology deteriorates with OA progression, from mild swelling in the early stage of OA (E-OA) to disrupted cristae in the mid-to-late stage of OA (ML-OA). Mitophagy levels were mildly elevated in E-OA chondrocytes compared with normal controls, whilst ML-OA chondrocytes exhibited significantly reduced and impaired mitophagy. Notably, miR140 was found to down-regulate CAPN1, an intracellular cysteine protease affecting mitochondrial and lysosomal membranes. Targeting the miR140/CAPN1 axis was revealed to improve mitochondrial morphology, decrease reactive oxygen species (ROS) accumulation, and promote mitophagy in chondrocytes. To further overcome the inherent instability and limited bioavailability of miR140 when administered directly, engineered exosomes overexpressing miR140 derived from human urine-derived stem cells (hUSCs-140-Exos) were constructed. In vitro, hUSCs-140-Exos were demonstrated to promote mitophagy and preserve mitochondrial function. Moreover, intra-articular injection of hUSCs-140-Exos in vivo effectively delivered miR140 to OA chondrocytes, resulting in improved gait, restoration of subchondral bone structure, and mitigation of OA progression. Overall, this study provides a novel and promising strategy for OA treatment, demonstrating significant therapeutic potential.