In vitro supplementation with deoxynucleoside monophosphates rescues mitochondrial DNA depletion

Abstract

Mitochondrial DNA depletion syndromes are a genetically heterogeneous group of often severe diseases, characterized by reduced cellular mitochondrial DNA content. Investigation of potential therapeutic strategies for mitochondrial DNA depletion syndromes will be dependent on good model systems. We have previously suggested that myotubes may be the optimal model system for such studies. Here we firstly validate this technique in a diverse range of cells of patients with mitochondrial DNA depletion syndromes, showing contrasting effects in cell lines from genetically and phenotypically differing patients.Secondly, we developed a putative therapeutic approach using variable combinations of deoxynucleoside monophosphates in different types of mitochondrial DNA depletion syndromes, showing near normalization of mitochondrial DNA content in many cases. Furthermore, we used nucleoside reverse transcriptase inhibitors to precisely titrate mtDNA depletion in vitro. In this manner we can unmask a physiological defect in mitochondrial depletion syndrome cell lines which is also ameliorated by deoxynucleoside monophosphate supplementation. Finally, we have extended this model to study fibroblasts after myogenic transdifferentiation by MyoD transfection, which similar to primary myotubes also showed deoxynucleoside monophosphate responsive mitochondrial DNA depletion in vitro, thus providing a more convenient method for deriving future models of mitochondrial DNA depletion.Our results suggest that using different combinations of deoxynucleoside monophosphates depending on the primary gene defect and molecular mechanism may be a possible therapeutic approach for many patients with mitochondrial DNA depletion syndromes and is worthy of further clinical investigation.

Mitochondrial DNA Depletion Syndromes: Review and Updates of Genetic Basis, Manifestations, and Therapeutic Options

“…Therefore, the use of deoxynucleoside monophosphate combinations may be a possible therapeutic approach for individuals with MDS [128]. Further clinical investigation is needed to investigate this approach.…”

Increased dNTP pools rescue mtDNA depletion in human POLG‐deficient fibroblasts

“…The first approach involved bypassing defective mitochondrial dN kinases with dN monophosphates (dNMPs). This strategy was proven efficient in both in vitro (10)(11)(12) and in vivo (13) disease models. However, dNMPs are challenging with respect to therapeutics because of their fast in vivo degradation and their difficult cellular internalization (14).…”

“…These mutant proteins could benefit from finding a higher dNTP concentration at the replication fork. In fact, previous studies, both in yeast and in human cells, suggested that increasing the dNTP pool could alleviate mtDNA damage due to POLG mutations (11,20,21).…”

Strategies for fighting mitochondrial diseases

“…Out of 9, 1 patient who required mechanical ventilation became able to breathe independently. Diarrhoea was the most common side effect but did not require discontinuation of the therapy [93].…”