Double administration of self-complementary AAV9NDUFS4 prevents Leigh disease in Ndufs4-/- mice.

Leigh disease, or subacute necrotizing encephalomyelopathy, a genetically heterogeneous condition consistently characterized by defective mitochondrial bioenergetics, is the most common oxidative-phosphorylation related disease in infancy. Both neurological signs and pathological lesions of Leigh disease are mimicked by the ablation of the mouse mitochondrial respiratory chain subunit Ndufs4-/-, which is part of, and crucial for, normal Complex I activity and assembly, particularly in the brains of both children and mice. We previously conveyed the human NDUFS4 gene to the mouse brain using either single-stranded adeno-associated viral 9 recombinant vectors or the PHP.B adeno-associated viral vector. Both these approaches significantly prolonged the lifespan of the Ndufs4-/- mouse model but the extension of the survival was limited to a few weeks by the former approach, whereas the latter was applicable to a limited number of mouse strains, but not to primates. Here, we exploited the recent development of new, self-complementary adeno-associated viral 9 vectors, in which the transcription rate of the recombinant gene is markedly increased compared with the single-stranded adeno-associated viral 9 and can be applied to all mammals, including humans. Either single intra-vascular or double intra-vascular and intra-cerebro-ventricular injections were performed at post-natal Day 1. The first strategy ubiquitously conveyed the human NDUFS4 gene product in Ndufs4-/- mice, doubling the lifespan from 45 to ≈100 days after birth, when the mice developed rapidly progressive neurological failure. However, the double, contemporary intra-vascular and intra-cerebroventricular administration of self-complementary-adeno-associated viral NDUFS4 prolonged healthy lifespan up to 9 months of age. These mice were well and active at euthanization, at 6, 7, 8 and 9 months of age, to investigate the brain and other organs post-mortem. Robust expression of hNDUFS4 was detected in different cerebral areas preserving normal morphology and restoring Complex I activity and assembly. Our results warrant further investigation on the translatability of self-complementary-adeno-associated viral 9 NDUFS4-based therapy in the prodromal phase of the disease in mice and eventually humans.

NAD(+)-dependent activation of Sirt1 corrects the phenotype in a mouse model of mitochondrial disease.

Mitochondrial disorders are highly heterogeneous conditions characterized by defects of the mitochondrial respiratory chain. Pharmacological activation of mitochondrial biogenesis has been proposed as an effective means to correct the biochemical defects and ameliorate the clinical phenotype in these severely disabling, often fatal, disorders. Pathways related to mitochondrial biogenesis are targets of Sirtuin1, a NAD(+)-dependent protein deacetylase. As NAD(+) boosts the activity of Sirtuin1 and other sirtuins, intracellular levels of NAD(+) play a key role in the homeostatic control of mitochondrial function by the metabolic status of the cell. We show here that supplementation with nicotinamide riboside, a natural NAD(+) precursor, or reduction of NAD(+) consumption by inhibiting the poly(ADP-ribose) polymerases, leads to marked improvement of the respiratory chain defect and exercise intolerance of the Sco2 knockout/knockin mouse, a mitochondrial disease model characterized by impaired cytochrome c oxidase biogenesis. This strategy is potentially translatable into therapy of mitochondrial disorders in humans.