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Stem Cell Research & Therapy Jun 2022Mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage in the retinal pigment epithelium (RPE) have been implicated in the pathogenesis of age-related macular...
BACKGROUND
Mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage in the retinal pigment epithelium (RPE) have been implicated in the pathogenesis of age-related macular degeneration (AMD). However, a deeper understanding is required to determine the contribution of mitochondrial dysfunction and impaired mitochondrial autophagy (mitophagy) to RPE damage and AMD pathobiology. In this study, we model the impact of a prototypical systemic mitochondrial defect, mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), in RPE health and homeostasis as an in vitro model for impaired mitochondrial bioenergetics.
METHODS
We used induced pluripotent stem cells (iPSCs) derived from skin biopsies of MELAS patients (m.3243A > G tRNA leu mutation) with different levels of mtDNA heteroplasmy and differentiated them into RPE cells. Mitochondrial depletion of ARPE-19 cells (p cells) was also performed using 50 ng/mL ethidium bromide (EtBr) and 50 mg/ml uridine. Cell fusion of the human platelets with the p cells performed using polyethylene glycol (PEG)/suspension essential medium (SMEM) mixture to generate platelet/RPE "cybrids." Confocal microscopy, FLowSight Imaging cytometry, and Seahorse XF Mito Stress test were used to analyze mitochondrial function. Western Blotting was used to analyze expression of autophagy and mitophagy proteins.
RESULTS
We found that MELAS iPSC-derived RPE cells exhibited key characteristics of native RPE. We observed heteroplasmy-dependent impairment of mitochondrial bioenergetics and reliance on glycolysis for generating energy in the MELAS iPSC-derived RPE. The degree of heteroplasmy was directly associated with increased activation of signal transducer and activator of transcription 3 (STAT3), reduced adenosine monophosphate-activated protein kinase α (AMPKα) activation, and decreased autophagic activity. In addition, impaired autophagy was associated with aberrant lysosomal function, and failure of mitochondrial recycling. The mitochondria-depleted p cells replicated the effects on autophagy impairment and aberrant STAT3/AMPKα signaling and showed reduced mitochondrial respiration, demonstrating phenotypic similarities between p and MELAS iPSC-derived RPE cells.
CONCLUSIONS
Our studies demonstrate that the MELAS iPSC-derived disease models are powerful tools for dissecting the molecular mechanisms by which mitochondrial DNA alterations influence RPE function in aging and macular degeneration, and for testing novel therapeutics in patients harboring the MELAS genotype.
Topics: Autophagy; DNA, Mitochondrial; Energy Metabolism; Epithelial Cells; Humans; Induced Pluripotent Stem Cells; MELAS Syndrome; Macular Degeneration; Mitochondria; Retinal Pigment Epithelium; Retinal Pigments
PubMed: 35715869
DOI: 10.1186/s13287-022-02937-6 -
Brain and Nerve = Shinkei Kenkyu No... May 2023In MELAS, taurine modification defect in the anticodon of mitochondrial leucine tRNA causes codon translation failure. An investigator-started clinical trials of...
In MELAS, taurine modification defect in the anticodon of mitochondrial leucine tRNA causes codon translation failure. An investigator-started clinical trials of high-dose taurine therapy, that showed its efficacy in preventing stroke-like episodes, and improving the taurine modification rate. The drug was found to be safe. Taurine has been approved as a drug covered by public insurance for prevention of stroke-like episodes since 2019. Recently, L-arginine hydrochloride has also been approved for off-label use as a treatment for both acute and intermittent stages of stroke-like episodes.
Topics: Humans; MELAS Syndrome; Stroke; Arginine; Taurine; Mitochondria
PubMed: 37194524
DOI: 10.11477/mf.1416202371 -
Seizure Oct 2023
Topics: Humans; MELAS Syndrome; Seizures; Mutation
PubMed: 37827598
DOI: 10.1016/j.seizure.2023.03.001 -
The Neurologist Jul 2021Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, is a multisystemic entity of mitochondrial inheritance. To date, there is no...
Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS) Syndrome: Frequency, Clinical Features, Imaging, Histopathologic, and Molecular Genetic Findings in a Third-level Health Care Center in Mexico.
INTRODUCTION
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, is a multisystemic entity of mitochondrial inheritance. To date, there is no epidemiological information on MELAS syndrome in Mexico.
CASE SERIES
A retrospective, cross-sectional design was employed to collect and analyze the data. The clinical records of patients with mitochondrial cytopathies in the period ranging from January 2018 to March 2020 were reviewed. Patients who met definitive Yatsuga diagnostic criteria for MELAS syndrome were included to describe frequency, clinical, imaging, histopathologic, and molecular studies. Of 56 patients diagnosed with mitochondrial cytopathy, 6 patients met definitive Yatsuga criterion for MELAS (10.7%). The median age at diagnosis was 34 years (30 to 34 y), 2 females and the median time from onset of symptoms at diagnosis 3.5 years (1 to 10 y). The median of the number of stroke-like episodes before the diagnosis was 3 (range, 2 to 3). The main findings in computed tomography were basal ganglia calcifications (33%), whereas in magnetic resonance imaging were a lactate peak in the spectroscopy sequence in 2 patients. Five patients (84%) had red-ragged fibers and phantom fibers in the Cox stain in the muscle biopsy. Four patients (67%) had presence of 3243A>G mutation in the mitochondrial MT-TL1 gene. One patient died because of status epilepticus.
CONCLUSIONS
MELAS syndrome represents a common diagnostic challenge for clinicians, often delaying definitive diagnosis. It should be suspected in young patients with stroke of undetermined etiology associated with other systemic and neurological features.
Topics: Cross-Sectional Studies; Delivery of Health Care; Female; Humans; MELAS Syndrome; Mexico; Molecular Biology; Retrospective Studies; Stroke
PubMed: 34190208
DOI: 10.1097/NRL.0000000000000331 -
Nature Metabolism Dec 2023Nuclease-mediated editing of heteroplasmic mitochondrial DNA (mtDNA) seeks to preferentially cleave and eliminate mutant mtDNA, leaving wild-type genomes to repopulate...
Nuclease-mediated editing of heteroplasmic mitochondrial DNA (mtDNA) seeks to preferentially cleave and eliminate mutant mtDNA, leaving wild-type genomes to repopulate the cell and shift mtDNA heteroplasmy. Various technologies are available, but many suffer from limitations based on size and/or specificity. The use of ARCUS nucleases, derived from naturally occurring I-CreI, avoids these pitfalls due to their small size, single-component protein structure and high specificity resulting from a robust protein-engineering process. Here we describe the development of a mitochondrial-targeted ARCUS (mitoARCUS) nuclease designed to target one of the most common pathogenic mtDNA mutations, m.3243A>G. mitoARCUS robustly eliminated mutant mtDNA without cutting wild-type mtDNA, allowing for shifts in heteroplasmy and concomitant improvements in mitochondrial protein steady-state levels and respiration. In vivo efficacy was demonstrated using a m.3243A>G xenograft mouse model with mitoARCUS delivered systemically by adeno-associated virus. Together, these data support the development of mitoARCUS as an in vivo gene-editing therapeutic for m.3243A>G-associated diseases.
Topics: Humans; Animals; Mice; DNA, Mitochondrial; MELAS Syndrome; Mitochondria; Mutation
PubMed: 38036771
DOI: 10.1038/s42255-023-00932-6 -
Mitochondrion May 2021This study aimed to evaluate the sensitivity and specificity of the vessel signs, including the Vessel Flow Void Sign (VFVS) and the Hyperintense Vessel Sign (HVS) in...
OBJECTIVE
This study aimed to evaluate the sensitivity and specificity of the vessel signs, including the Vessel Flow Void Sign (VFVS) and the Hyperintense Vessel Sign (HVS) in Fluid Attenuated Inversion Recovery (FLAIR) images during the differentiation of Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS) in Acute Ischemic Stroke (AIS).
METHODS
Magnetic Resonance Imaging (MRI) scans of 13 MELAS and 20 AIS patients were obtained during the acute stage of the diseases (median time to scan <1 day from symptom onset). To evaluate VFVS and HVS on the FLAIR images, Logistic Regression was used to analyze their correlation with MELAS. Then, a new scale of scoring, involving two aspects (VFVS and HVS) on FLAIR images was established. Receiver operating characteristic (ROC) curves were used to evaluate the efficacy of the developed criterion.
RESULTS
FLAIR images from 12 of the 13 MELAS patients exhibited VFVS while none exhibited HVS. Moreover, FLAIR images from 3 of the 20 AIS patients exhibited VFVS while 17 exhibited HVS. Logistic Regression showed that VFVS and the absence of HVS (NoHVS) were independent MELAS predictors. If there were VFVS, the patient scored 2 points, while there were NoHVS, the patient scored 1 point. Patients with >1.5 scores were prone to be MELAS, while patients with <1.5 scores were prone to be AIS. Sensitivity was found to be 92.3%, specificity was 85%, with an AUC of 0.94.
CONCLUSION
We have established a new scoring criterion, with a high sensitivity and specificity, for differentiating between MELAS and AIS in patients during the acute stage.
Topics: Adult; Cerebrovascular Circulation; Diagnosis, Differential; Female; Humans; Ischemic Stroke; MELAS Syndrome; Magnetic Resonance Angiography; Male; Middle Aged
PubMed: 33713868
DOI: 10.1016/j.mito.2021.02.015 -
International Journal of Cardiology Jul 2016
Topics: Adult; Heart Diseases; Humans; MELAS Syndrome; Male
PubMed: 27061651
DOI: 10.1016/j.ijcard.2016.03.098 -
Neurobiology of Aging Jan 2021Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) and cerebral autosomal dominant arteriopathy with subcortical infarcts and...
Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) are 2 monogenic cerebral small vessel diseases sharing several common clinical features including young stroke, migraine, and cognitive dysfunction. The aim of this study was to understand the role of MELAS in patients with CADASIL-like manifestations. We screened 429 unrelated patients with genetically unassigned CADASIL-like syndrome for mitochondrial DNA m.3243A>G mutation. None of them were found to have the mutation. Our finding suggests that m.3243A>G rarely causes CADASIL-like phenotype. It may be not necessary to consider MELAS as a differential diagnosis of CADASIL. Screening m.3243A>G in patients with CADASIL-like phenotype is of limited value.
Topics: CADASIL; DNA, Mitochondrial; Diagnosis, Differential; Female; Humans; MELAS Syndrome; Male; Mutation; Phenotype
PubMed: 32950272
DOI: 10.1016/j.neurobiolaging.2020.08.016 -
Journal of Neurology Jun 2021Mitochondrial disorders are clinically complex and have highly variable phenotypes among all inherited disorders. Mutations in mitochon drial DNA (mtDNA) and nuclear...
BACKGROUND
Mitochondrial disorders are clinically complex and have highly variable phenotypes among all inherited disorders. Mutations in mitochon drial DNA (mtDNA) and nuclear genome or both have been reported in mitochondrial diseases suggesting common pathophysiological pathways. Considering the clinical heterogeneity of mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) phenotype including focal neurological deficits, it is important to look beyond mitochondrial gene mutation.
METHODS
The clinical, histopathological, biochemical analysis for OXPHOS enzyme activity, and electron microscopic, and neuroimaging analysis was performed to diagnose 11 patients with MELAS syndrome with a multisystem presentation. In addition, whole exome sequencing (WES) and whole mitochondrial genome sequencing were performed to identify nuclear and mitochondrial mutations.
RESULTS
Analysis of whole mtDNA sequence identified classical pathogenic mutation m.3243A > G in seven out of 11 patients. Exome sequencing identified pathogenic mutation in several nuclear genes associated with mitochondrial encephalopathy, sensorineural hearing loss, diabetes, epilepsy, seizure and cardiomyopathy (POLG, DGUOK, SUCLG2, TRNT1, LOXHD1, KCNQ1, KCNQ2, NEUROD1, MYH7) that may contribute to classical mitochondrial disease phenotype alone or in combination with m.3243A > G mutation.
CONCLUSION
Individuals with MELAS exhibit clinical phenotypes with varying degree of severity affecting multiple systems including auditory, visual, cardiovascular, endocrine, and nervous system. This is the first report to show that nuclear genetic factors influence the clinical outcomes/manifestations of MELAS subjects alone or in combination with m.3243A > G mutation.
Topics: Acidosis, Lactic; DNA, Mitochondrial; Genes, Mitochondrial; Humans; MELAS Syndrome; Mitochondrial Encephalomyopathies; Mutation; Stroke
PubMed: 33484326
DOI: 10.1007/s00415-020-10390-9 -
Parkinsonism & Related Disorders Oct 2023
Topics: Humans; MELAS Syndrome; Brain; Mutation; Head; DNA, Mitochondrial
PubMed: 37607851
DOI: 10.1016/j.parkreldis.2023.105801