Metabolic regulation of MODS in pediatric mitochondrial disorders

PROJECT SUMMARY Devastating human primary mitochondrial disorders are caused by pathogenic mtDNA variants and frequently evolve into organ failures referred to, as mitochondrial-induced multiple organ dysfunction syndrome (MIMODS). The underlying pathophysiologic mechanisms are more complex than a mere decrease in ATP pro- duction and very little is known about these complex processes in a tissue-specific manner. There is thus an urgent unmet need to assess the impact of the widespread mitochondrial dysfunction in multiple tissues leading to MIMODS. We have demonstrated deleterious outcomes of widespread mitochondrial dysfunction (lowered bioenergetics health index, abnormal mitochondrial morphology, elevated putrescine levels) in multiple pediat- ric PMD dermal fibroblasts carrying unique pathogenic mtDNA variants. Based on our findings, we hypothesize that elevated putrescine levels cause oxidative stress response and widespread mitochondrial dysfunction that contributes to MIMODS in cellular models of primary mitochondrial disorders. Our collaborative team will de- sign experiments and build upon established expertise in mitochondrial genetics and physiology, stem cell biol- ogy and differentiation, next-generation sequencing analysis and metabolite profiling to address the following research aims: In Aim 1, we will comprehensively assess mitochondrial dysfunction in twenty pediatric diseased fibroblasts with a confirmed diagnosis of PMDs, along with five age matched controls. We will assess the oxida- tive stress markers, NAD/NADH redox biochemistry, metabolomics, mitochondrial respiration and morphology. In aim 2, we will seek to understand tissue-specific abnormalities associated with mitochondrial dysfunction in neurons, cardiomyocytes and podocytes. In aim 3, we will assess the effect of targeted interventions of reducing oxidative stress and improving mitochondrial respiration in multiple differentiated cell types that exhibit ele- vated putrescine levels; and in multiple tissues from preclinical mouse models of PMD. The completion of these aims will contribute to a newer understanding of putrescine metabolism in multiple energy-intensive cell types derived from patients with pediatric PMD and its role in triggering MIMODS. In the long-term, our studies have the potential to develop strategies for individualized testing of patient cells with candidate therapeutics to drive rational, personalized therapies.