Partial restoration of mitochondrial dysfunction by AAV-Ant1 protects from dilated cardiomyopathy in Ant1-/- plus mtDNA mutant mice

: Primary mitochondrial disease (PMD) patients manifesting cardiomyopathy are twice as likely to die as other PMD patients. One PMD with cardiomyopathy is caused by null mutations in the heart-muscle isoform of the adenine nucleotide translocator (SLC25A4, ANT1) gene, with the severity of cardiomyopathy mediated by mitochondrial DNA. To optimize strategies for addressing mitochondrial cardiomyopathy, we generated an Ant1 null mouse and combined it with the ND6P25L mitochondrial DNA mutation to mimic the hypertrophic versus dilated cardiomyopathies observed in patients. Here, we transduce the neonatal Ant1-/- and Ant1-/-+ND6P25L mouse hearts with an AAV2/9-pDes-Gfp-mAnt1 cDNA vector. We show that restoration of just 10% of Ant1 gene expression was sufficient to ameliorate the cardiomyopathies in these mice. Proteomics and single-nucleus RNA sequencing reveal the reversal of dysregulated mitochondrial metabolic genes, including PGC1α, as well as cardiac contractile and extracellular matrix proteins. Hence, a modest increase in cardiac mitochondrial energetics can have profound benefits on cardiac function and is effective in treating mitochondrial cardiomyopathy.