Mitochondrial extracellular vesicles between pathology and regeneration

Mitochondria are central regulators of cellular energy production, metabolic homeostasis, and stress responses, and their dysfunction represents a critical hallmark of neurodegenerative and neuroinflammatory diseases. To preserve mitochondrial integrity, cells rely on an intricate mitochondrial quality control system encompassing mitochondrial dynamics, mitophagy, biogenesis, and vesicle-mediated pathways. Emerging evidence highlights the pivotal role of mitochondria-derived vesicles as vehicles for trafficking mitochondrial components within cells, thereby contributing significantly to intracellular communication and mitochondrial quality control. In parallel, mitochondrial extracellular vesicles have been identified as dynamic mediators of intercellular communication, enabling the transfer of mitochondrial proteins, lipids, and even mitochondrial DNA between cells. Mitochondria-derived vesicles selectively remove damaged mitochondrial components and coordinate intracellular stress responses, whereas mitochondrial extracellular vesicles can transfer mitochondrial material, including proteins, mitochondrial DNA, and even intact mitochondria, between cells, thereby modulating inflammation, immune activation, and cellular bioenergetics. Interestingly, mitochondrial extracellular vesicles play a dual, context-dependent role: they can exacerbate pathology when carrying damaged or dysfunctional mitochondrial cargo, or promote cellular resilience when delivering healthy, functional mitochondrial components. Likewise, extracellular vesicles derived from mesenchymal stem cells, including larger extracellular vesicle populations capable of transferring functional mitochondria, are emerging as promising cell-free therapeutic candidates with the potential to restore mitochondrial function and promote tissue repair across multiple diseases, including neurodegenerative disorders. Collectively, these insights establish mitochondrial vesicular trafficking as a transformative frontier for diagnostic innovation, biomarker development, and novel therapeutic strategies in neurodegenerative and mitochondria-related central nervous system disorders. Implications for the field include: the recognition of mitochondrial vesicular pathways as fundamental regulators of central nervous system homeostasis highlights their crucial roles in sustaining neuronal function, cellular resilience, and overall brain health. When enriched with dysfunctional mitochondrial cargo, mitochondrial extracellular vesicles are emerging as key contributors to the etiopathogenesis of neurodegenerative and neuroinflammatory diseases, thereby driving disease initiation and progression. In parallel, their ability to reflect mitochondrial status positions mitochondrial extracellular vesicles - particularly those containing mitochondrial DNA and mitochondrial proteins - as promising biomarkers for monitoring mitochondrial stress, disease activity, and therapeutic response. At the translational level, advancing mitochondrial extracellular vesicles and mitochondrial vesicular pathways as therapeutic tools opens new opportunities to restore mitochondrial integrity, modulate neuroinflammation, and potentially modify disease trajectories. The objectives of this review are to: (1) delineate the mechanisms of mitochondrial dysfunction and mitochondrial quality control failure in neurodegenerative and neuroinflammatory diseases; (2) comprehensively characterize the biogenesis, trafficking pathways, and functional roles of mitochondria-derived vesicles; (3) evaluate experimental and clinical evidence supporting the role of mitochondrial extracellular vesicles as mediators of neuroimmune communication and mitochondrial transfer; (4) critically assess the therapeutic potential of mesenchymal stem cell-derived mitochondrial extracellular vesicles.