Nitric oxide-primed engineered extracellular vesicles restore bioenergetics in acute kidney injury via mitochondrial transfer.

Background: The disruption of mitochondrial homeostasis in acute kidney injury (AKI) is an important factor that drives persistent renal dysfunction. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have shown great therapeutic potential in AKI, but insufficient specificity of targeting the impaired mitochondrial function. Herein, we developed an engineered nitric oxide (NO)-primed MSC-EVs (pEVs) to restore mitochondrial homeostasis for AKI therapy. Methods: A cisplatin-induced AKI model was established to investigate the therapeutic effects of MSC-EVs. Proteomic and Western blot analyses compared mitochondrial cargos and functional assays included mitochondrial complex I activity and Adenosine triphosphate (ATP) quantification. Mitochondrial transfer was tracked using flow cytometry and confocal imaging. Mitochondrial dynamics, oxidative stress, and apoptosis were evaluated through ATP measurement, western blotting and rotenone-mediated respiratory chain inhibition. Results: Our data indicated that pEVs outperformed cEVs in restoring renal function and histopathology. Additionally, a reduction in mitochondria-associated oxidative stress and cell death was observed. Proteomic profiling revealed that NO priming enriched pEVs with mitochondrial complex I components, which directly enhanced their bioenergetic capacity, as evidenced by higher mitochondrial complex I activity and elevated ATP production compared to cEVs. In vivo tracking confirmed targeted delivery of pEV-derived mitochondrial contents to renal tubular cells, reducing mitochondrial reactive oxygen species (ROS) and restoring mitochondrial mass. Crucially, mitochondria-depleted pEVs abolished these therapeutic effects, establishing mitochondrial cargos as the primary therapeutic driver. Furthermore, pEVs activated a pro-survival cascade in recipient cells, showing superior efficacy in promoting mitochondrial biogenesis, dynamics, and mitophagy, thereby restoring renal mitochondrial homeostasis. Conclusion: Our study elucidated a mitochondria-targeted therapeutic strategy enabled by engineered EVs that deliver functional cargo to restore mitochondrial homeostasis. These advances provide transformative potential for AKI and other mitochondrial disorders.