Prominent mitochondrial pathology in a case of refractory dermatomyositis: coincidence or concause?

INTRODUCTION: Mitochondrial alterations are a common finding in muscle biopsy of sporadic inclusion body myositis (s-IBM) and polymyositis with mitochondrial pathology (PM-Mito). Both disorders generally have poor treatment response. Nevertheless, mitochondrial myopathology has been rarely reported in dermatomyositis (DM) outside areas of perifascicular atrophy and a relationship with therapeutic outcome is not established. METHODS: We report on clinical, immunological, radiological, and myopathological findings of a case of severe, treatment-refractory anti-Mi-2-positive DM. RESULTS: A 77-year-old woman developed anti-Mi-2 DM with severe diffuse muscle weakness associated with abundant mitochondrial abnormalities at muscle biopsy, beside the typical features of inflammatory myopathy. The patient was poorly responsive to multiple-line therapies and finally anti-JAK (anti-Janus activated kinase) was administered, leading to partial clinical improvement. DISCUSSION: Given the usual satisfactory treatment response and favorable outcome of anti-Mi-2 DM, we suppose that mitochondrial dysfunction on muscle biopsy could represent a marker of disease severity in DM, predicting a worse response to treatment and a poor clinical outcome. JAK-inhibitors could represent a good treatment option in refractory anti-Mi-2 DM with mitochondrial abnormalities.

The genetics of mitochondrial disease: dissecting mitochondrial pathology using multi-omic pipelines.

Mitochondria play essential roles in numerous metabolic pathways including the synthesis of adenosine triphosphate through oxidative phosphorylation. Clinically, mitochondrial diseases occur when there is mitochondrial dysfunction - manifesting at any age and affecting any organ system; tissues with high energy requirements, such as muscle and the brain, are often affected. The clinical heterogeneity is parallel to the degree of genetic heterogeneity associated with mitochondrial dysfunction. Around 10% of human genes are predicted to have a mitochondrial function, and defects in over 300 genes are reported to cause mitochondrial disease. Some involve the mitochondrial genome (mtDNA), but the vast majority occur within the nuclear genome. Except for a few specific genetic defects, there remains no cure for mitochondrial diseases, which means that a genetic diagnosis is imperative for genetic counselling and the provision of reproductive options for at-risk families. Next-generation sequencing strategies, particularly exome and whole-genome sequencing, have revolutionised mitochondrial diagnostics such that the traditional muscle biopsy has largely been replaced with a minimally-invasive blood sample for an unbiased approach to genetic diagnosis. Where these genomic approaches have not identified a causative defect, or where there is insufficient support for pathogenicity, additional functional investigations are required. The application of supplementary 'omics' technologies, including transcriptomics, proteomics, and metabolomics, has the potential to greatly improve diagnostic strategies. This review aims to demonstrate that whilst a molecular diagnosis can be achieved for many cases through next-generation sequencing of blood DNA, the use of patient tissues and an integrated, multidisciplinary multi-omics approach is pivotal for the diagnosis of more challenging cases. Moreover, the analysis of clinically relevant tissues from affected individuals remains crucial for understanding the molecular mechanisms underlying mitochondrial pathology. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Recent Advances in Pathology: the 2021 Annual Review Issue of The Journal of Pathology.

The 2021 Annual Review Issue of The Journal of Pathology contains 14 invited reviews on current research areas of particular importance in pathology. The subjects included here reflect the broad range of interests covered by the journal, including both basic and applied research fields but always with the aim of improving our understanding of human disease. This year, our reviews encompass the huge impact of the COVID-19 pandemic, the development and application of biomarkers for immune checkpoint inhibitors, recent advances in multiplexing antigen/nucleic acid detection in situ, the use of genomics to aid drug discovery, organoid methodologies in research, the microbiome in cancer, the role of macrophage-stroma interactions in fibrosis, and TGF-ß as a driver of fibrosis in multiple pathologies. Other reviews revisit the p53 field and its lack of clinical impact to date, dissect the genetics of mitochondrial diseases, summarise the cells of origin and genetics of sarcomagenesis, provide new data on the role of TRIM28 in tumour predisposition, review our current understanding of cancer stem cell niches, and the function and regulation of p63. The reviews are authored by experts in their field from academia and industry, and provide comprehensive updates of the chosen areas, in which there has been considerable recent progress. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Subclinical Leber's hereditary optic neuropathy with pediatric acute spinal cord onset: more than meets the eye.

BACKGROUND: Leber's hereditary optic neuropathy (LHON) is a mitochondrial disease characterized by visual loss consequent to optic nerve atrophy. In some cases, LHON is associated with heterogeneous neurological extraocular manifestations and is referred to as "Leber plus disease"; rarely it is associated with a multiple sclerosis (MS)-like syndrome known as Harding disease, but no pediatric extraocular acute spinal onset is reported. CASE PRESENTATION: We describe the case of a 5-year-old girl carrying the G3460A mtDNA mutation who was referred to clinical examination for bilateral upper and lower limb weakness with no sign of optic neuropathy. Spinal cord MRI showed hyperintense signal alterations in T2-weighted and restricted diffusion in DWI sequences in the anterior portion of the cervical and dorsal spinal cord resembling a spinal cord vascular injury. No association between this mutation and pediatric spinal cord lesions has previously been reported. Alternative diagnostic hypotheses, including infective, ischemic and inflammatory disorders, were not substantiated by clinical and instrumental investigations. CONCLUSIONS: Our case reports a novel pediatric clinical manifestation associated with the m.3460G > A mtDNA mutation, broadening the clinical spectrum of this disease. Early identification of new cases and monitoring of carriers beginning in childhood is important to prevent neurological deterioration and preserve long-term function.

Proteomic Characterization of Synaptosomes from Human Substantia Nigra Indicates Altered Mitochondrial Translation in Parkinson's Disease.

The pathological hallmark of Parkinson's disease (PD) is the loss of neuromelanin-containing dopaminergic neurons within the substantia nigra pars compacta (SNpc). Additionally, numerous studies indicate an altered synaptic function during disease progression. To gain new insights into the molecular processes underlying the alteration of synaptic function in PD, a proteomic study was performed. Therefore, synaptosomes were isolated by density gradient centrifugation from SNpc tissue of individuals at advanced PD stages (N = 5) as well as control subjects free of pathology (N = 5) followed by mass spectrometry-based analysis. In total, 362 proteins were identified and assigned to the synaptosomal core proteome. This core proteome comprised all proteins expressed within the synapses without regard to data analysis software, gender, age, or disease. The differential analysis between control subjects and PD cases revealed that CD9 antigen was overrepresented and fourteen proteins, among them Thymidine kinase 2 (TK2), mitochondrial, 39S ribosomal protein L37, neurolysin, and Methionine-tRNA ligase (MARS2) were underrepresented in PD suggesting an alteration in mitochondrial translation within synaptosomes.

Mitochondrial dysfunction and its role in tissue-specific cellular stress.

Mitochondrial bioenergetics require the coordination of two different and independent genomes. Mutations in either genome will affect mitochondrial functionality and produce different sources of cellular stress. Depending on the kind of defect and stress, different tissues and organs will be affected, leading to diverse pathological conditions. There is no curative therapy for mitochondrial diseases, nevertheless, there are strategies described that fight the various stress forms caused by the malfunctioning organelles. Here, we will revise the main kinds of stress generated by mutations in mitochondrial genes and outline several ways of fighting this stress.

Heterogeneity of Brain Ribosomal Genes Expression Following Positive Fighting Experience in Male Mice as Revealed by RNA-Seq.

Repeated positive fighting experience in daily agonistic interactions is accompanied by changes of brain neurotransmitter activity and genes' expression in male mice. This paper is focused on the analysis of ribosomal genes expression data as revealed by whole-transcriptome analysis (RNA-Seq) in five brain regions of male mice with long repeated experience of aggression accompanied by wins (winners). Downregulation of most Rps, Rpl, Mrps, and Mrpl genes was found in the midbrain raphe nuclei and striatum and upregulation-in the hippocampus and hypothalamus of the winners. There were no changes in ribosomal gene expression in the ventral tegmental area. The data allow considering the alteration in ribosomal gene expression as an animal model of ribosomal dysfunction developed under positive fighting experience in male mice.

The Effects of Cardiotrophin-1 on Early Synaptic Mitochondrial Dysfunction and Synaptic Pathology in APPswe/PS1dE9 Mice.

The coexistence of neuronal mitochondrial pathology and synaptic dysfunction is an early pathological feature of Alzheimer's disease (AD). Cardiotrophin-1 (CT-1) has been shown to exhibit impressive neuroprotective effects. Previous studies have shown positive effects of CT-1 on brain glucose metabolism and cognition in APPswe/PS1dE9 transgenic mice; however, little is known about the effects of CT-1 on early synaptic mitochondrial dysfunction and resultant synaptic pathology in the brain. In this study, 4-month-old transgenic mice with brain tissue-specific CT-1 expression were used alone or in combination with APPswe/PS1dE9 transgenic mice to evaluate the effect of CT-1 on synaptic mitochondrial dysfunction and resultant synaptic pathology, and cryptic memory deficits in the APPswe/PS1dE9 transgenic mice. The potential mechanism of action of CT-1 was also examined. Young CT-1×APPswe/PS1dE9 transgenic mice exhibited improvements in long-term learning and memory ability and ameliorations of synaptic mitochondrial/synaptic impairments compared to young APPswe/PS1dE9 transgenic mice. Moreover, CT-1 upregulated the expression of AMPAR and increased AMP-activated protein kinase (AMPK) activity in the hippocampus of APPswe/PS1dE9 transgenic mice. However, AMPK inhibition through shRNA knockdown of AMPKα blocked the neuroprotective effects of CT-1 on the expression of AMPAR and mitochondrial/synaptic dysfunction in Aß-treated mouse neurons. These results suggest that CT-1 may be a potent candidate for the early prevention and treatment of AD.

Attention deficit-hyperactivity disorder suffers from mitochondrial dysfunction.

BACKGROUND: Pathophysiology of attention-deficit hyperactivity disorder (ADHD) is not known, and therefore the present study investigated mitochondrial defects, if any in cybrids created from patients and control population. METHODS: To investigate mitochondrial pathology in ADHD, cybrids cell lines were created from ADHD probands and controls by fusing their platelets with ρ0-cells prepared from SH-SY5Y neuroblastoma cell line. Cellular respiration, oxidative stress, mitochondrial membrane potential and morphology were evaluated employing oxygraph, mitochondria-specific fluorescence staining and evaluation by FACS, and immunocytochemistry. HPLC-electrochemical detection, quantitative RT-PCR and Blue Native PAGE were employed respectively for assays of serotonin, mitochondrial ATPase 6/8 subunits levels and complex V activity. RESULTS: Significantly low cellular and mitochondrial respiration, ATPase6/8 transcripts levels, mitochondrial complex V activity and loss of mitochondrial membrane potential and elevated oxidative stress were observed in ADHD cybrids. Expression of monoamine oxidizing mitochondrial enzymes, MAO-A and MAO-B levels remained unaffected. Two-fold increase in serotonin level was noted in differentiated cybrid-neurons. CONCLUSIONS: Since cybrids are shown to replicate mitochondrial defects seen in post-mortem brains, these observed defects in ADHD cybrids strongly suggest mitochondrial pathology in this disorder. GENERAL SIGNIFICANCE: Mitochondrial defects are detected in ADHD cybrids created from patients' platelets, implying bioenergetics crisis in the mitochondria could be a contributory factor for ADHD pathology and/or phenotypes.

Mitochondrial DNA Damage and Diseases.

Various endogenous and environmental factors can cause mitochondrial DNA (mtDNA) damage.  One of the reasons for enhanced mtDNA damage could be its proximity to the source of oxidants, and lack of histone-like protective proteins. Moreover, mitochondria contain inadequate DNA repair pathways, and, diminished DNA repair capacity may be one of the factors responsible for high mutation frequency of the mtDNA. mtDNA damage might cause impaired mitochondrial function, and, unrepaired mtDNA damage has been frequently linked with several diseases. Exploration of mitochondrial perspective of diseases might lead to a better understanding of several diseases, and will certainly open new avenues for detection, cure, and prevention of ailments.

Síndrome de Sjögren primario que debuta con polimiositis mitocondrial, neuropatía axonal y parálisis hipopotasémica: reporte de caso / Onset of primary Sjögren syndrome with mitochondrial polymyositis, axonal neuropathy, and hypokalaemic paralysis: Case report

RESUMEN El síndrome de Sjögren es una entidad multisistémica de naturaleza autoinmune, clásicamente considerada una exocrinopatía debido a la alta frecuencia de síntomas secos (queratoconjuntivitis seca, xerostomía) como resultado de infiltración poliglandular por linfocitos autorreactivos. Sin embargo, menos del 10% de estos pacientes puede iniciar con manifestaciones extraglandulares severas, traducidas en peores desenlaces a largo plazo. Se presenta el caso de una gestante que inició con síndrome de debilidad aguda proximal relacionada con miositis con enfermedad mitocondrial e hipopotasemia severa, en el contexto de acidosis tubular renal distal, como manifestación extraglandular de síndrome de Sjögren primario. Se discuten brevemente manifestaciones neurológicas de esta entidad, incluyendo aquellas secundarias a trastornos metabólicos precipitados por compromiso autoinmune.

ABSTRACT Sjögren's syndrome is a multisystemic autoimmune disorder. It is classically considered as an exocrine disease, given the high frequency of dry symptoms (keratoconjunctivitis sicca, xerostomia) as a result of poly-glandular infiltration by autoreactive lymphocytes. However, less than 10% of these patients can onset with severe extra-glandular manifestations, resulting in worse long-term outcomes. The case of a pregnant woman is presented, who debuted with acute proximal weakness syndrome related to myositis with mitochondrial pathology and severe hypokalaemia in the context of distal renal tubular acidosis, as an extra-glandular manifestation of primary Sjögren's syndrome. Neurological manifestations of this condition are briefly discussed, including those secondary to metabolic disorders precipitated by autoimmune compromise.

Two novel compound heterozygous mutations in OPA3 in two siblings with OPA3-related 3-methylglutaconic aciduria.

OPA3-related 3-methylglutaconic aciduria, or Costeff Optic Atrophy syndrome, is a neuro-ophthalmologic syndrome of early-onset bilateral optic atrophy and later-onset spasticity, and extrapyramidal dysfunction. Urinary excretion of 3-methylglutaconic acid and of 3-methylglutaric acid is markedly increased. OPA3-related 3-methylglutaconic aciduria is due to mutations in the OPA3 gene located at 19q13.2-13.3. Here we describe two siblings with novel compound heterozygous variants in OPA3: c.1A>G (p.1M>V) in the translation initiation codon in exon 1 and a second variant, c.142+5G>C in intron 1. On cDNA sequencing the c.1A>G appeared homozygous, indicating that the allele without the c.1A>G variant is degraded. This is likely due to an intronic variant; possibly the IVS1+5 splice site variant. The older female sibling initially presented with motor developmental delay and vertical nystagmus during her first year of life and was diagnosed subsequently with optic atrophy. Her brother presented with mildly increased hip muscle tone followed by vertical nystagmus within the first 6 months of life, and was found to have elevated urinary excretion of 3-methylglutaconic acid and 3-methylglutaric acid, and optic atrophy by 1.5 years of age. Currently, ages 16 and 7, both children exhibit ataxic gaits and dysarthric speech. Immunofluorescence studies on patient's cells showed fragmented mitochondrial morphology. Thus, though the exact function of OPA3 remains unknown, our experimental results and clinical summary provide evidence for the pathogenicity of the identified OPA3 variants and provide further evidence for a mitochondrial pathology in this disease.