Adeno-Associated virus-based approaches for mitochondrial diseases: advances and challenges

Mitochondrial diseases, caused by mutations in either mitochondrial or nuclear DNA, are highly complex genetic disorders characterized by faulty oxidative phosphorylation. Adeno-associated virus (AAV)-based gene therapy with its broad and customizable tissue tropism achieved through natural and engineered serotypes offers a highly effective platform for delivering therapeutic genes to affected tissues. However, the intricate genetics and biology of mitochondria present unique challenges for the development of AAV-based therapies. While gene replacement therapy remains a viable strategy for correcting nuclear gene defects, mutations in mtDNA require specialized approaches, such as mitochondrially targeted, RNA-free base editors and nucleases capable of precise editing within the mitochondrial genome. As an alternative, allotopic expression, which involves expressing mitochondrial genes from the nuclear genome, is currently being evaluated in clinical trials but remains controversial, due to issues related to mitochondrial import and functional integration in the respiratory complexes. The clinical translation of AAV-mediated therapies for mitochondrial diseases still confronts several interrelated challenges, including efficient targeting of multiple affected organs, scalable and cost-effective vector manufacturing, and minimizing vector-associated toxicity. By integrating advanced genome editing technologies with sophisticated vector engineering and delivery strategies, AAV-based gene therapy stands as a transformative approach for addressing the broad and heterogeneous spectrum of primary mitochondrial disorders. Continued progress in overcoming current biological and technical barriers will be essential to realize the full therapeutic potential of AAVs.