Peroral endoscopic myotomy in a pregnant woman diagnosed with mitochondrial disease:A case report

BACKGROUND Achalasia is a primary esophageal motility disease characterized by impairment of normal esophageal peristalsis and absence of relaxation of the lower esophageal sphincter.Sometimes is can be a part of some genetic disorders.One of the causes of gastrointestinal motility disorders,including achalasia,is mitochondrial defects.CASE SUMMARY We report about a pregnant woman with a history of symptoms associated with inherited mitochondrial disease,which was confirmed by genetic tests,and who was treated via peroral endoscopic myotomy.CONCLUSION Peroral endoscopic myotomy is possible treatment option for a pregnant woman with achalasia caused by mitochondrial disease.

Mitochondrial transplantation as a promising therapy for mitochondrial diseases

Mitochondrial diseases are a group of inherited or acquired metabolic disorders caused by mitochondrial dysfunction which may affect almost all the organs in the body and present at any age.However,no satisfactory therapeutic strategies have been available for mitochondrial diseases so far.Mitochondrial transplantation is a burgeoning approach for treatment of mitochondrial diseases by recovery of dysfunctional mitochondria in defective cells using isolated functional mitochondria.Many models of mitochondrial transplantation in cells,animals,and patients have proved effective via various routes of mitochondrial delivery.This review presents different techniques used in mitochondrial isolation and delivery,mechanisms of mitochondrial internalization and consequences of mitochondrial transplantation,along with challenges for clinical application.Despite some unknowns and challenges,mitochondrial transplantation would provide an innovative approach for mitochondrial medicine.

Mitochondrial replacement techniques or therapies (MRTs) to improve embryo development and to prevent mitochondrial disease transmission

The mitochondrion which contains its own double-stranded circular DNA is a semi-independent organelle that plays critical roles in cell activity. Mitochondrial DNA （mtDNA） is maternally inherited through several mechanisms that have been proposed （Luo et al., 2013） and, if mitochondrial mutations are inherited to the offspring, it is possible to cause mitochondrial diseases such as neuropathy, cardiomyopathy, myopathy, and liver failure.

Emerging roles of cardiolipin remodeling in mitochondrial dysfunction associated with diabetes,obesity,and cardiovascular diseases

Cardiolipin （CL） is a phospholipid exclusively localized in inner mitochondrial membrane where it is required for oxidative phosphorylation, ATP synthesis, and mitochondrial bioenergetics. The biological functions of CL are thought to depend on its acyl chain composition which is dominated by linoleic acids in metabolically active tissues. This unique feature is not derived from the de novo biosynthesis of CL, rather from a remodeling process that involves in phospholipases and transacylase/acyltransferase. The remodeling process is also believed to be responsible for generation of CL species that causes oxidative stress and mitochondrial dysfunction. CL is highly sensitive to oxidative damages by reactive oxygen species （ROS） due to its high content in polyunsaturated fatty acids and location near the site of ROS production. Consequently, pathological remodeling of CL has been implicated in the etiology of mitochondrial dysfunction commonly associated with diabetes, obesity, heart failure, neurodegeneration, and aging that are characterized by oxidative stress, CL deficiency, and abnormal CL species. This review summarizes recent progresses in molecular, enzymatic, lipidomic, and metabolic studies that support a critical regulatory role of pathological CL remodeling as a missing link between oxidative stress and mitochondrial dysfunction in metabolic diseases and aging.

Mitochondrial malfunction in vanishing white matter disease： a disease of the cytosolic translation machinery

Vanishing white matter （VWM） disease - a disease of the cytosolic translation machinery： VWM is a recessive genet- ic neurodegenerative disease caused by mutations in any of the five genes encoding the subunits of translation initiation factor 2B （eIF2B） （Leegwater et al., 2001; OMIM 306896）.

The inherent high vulnerability of dopaminergic neurons toward mitochondrial toxins may contribute to the etiology of Parkinson＇s disease

Although the exact mechanism（s）of the degeneration of dopaminergic neurons in Parkinson’s disease（PD）is not well understood,mitochondrial dysfunction is proposed to play a central role.This proposal is strongly strengthened by the findings that compromised mitochondrial functions and/or exposure to mitochondrial toxins such as rotenone,paraquat,or MPTP causes degeneration of the midbrain dopaminergic.

SLP-2: a potential new target for improving mitochondrial function in Parkinson's disease

Parkinson＇s disease （PD） is a progressive neurodegenerative disease, which is generally considered a multifactorial disorder that arises owing to a combination of genes and environmental factors. While most cases are idiopathic, in about 10% of the patients a genetic cause can be detected, ascribable to mutations in more than a dozen genes. PD is characterized clinically by tremor, rigidity, reduced mo- tor activity （bradykinesia）, and postural instability and pathological- ly by loss of dopaminergic （DA） neurons in the substantia nigra pars compacta, loss of DA innervation in the striatum, and the presence of a-synuclein positive aggregates in the form of Lewy bodies. The symptomatic treatment of PD with levodopa, which aims at replac- ing dopamine, remains the gold standard, and no neuroprotective or disease-modifying therapy is available. During treatment, the disease continues to progress, and long-term use of levodopa has import- ant limitations including motor complications termed dyskinesias. Therefore, a pharmacological therapy able to prevent or halt the neu- rodegenerative process is urgently required.

The Mitochondrial DNA Mutation at Position 11778 in Chinese Families with Leber's Hereditary Optic Neuropathy

We amplified the 340 bp of mitochondrial DMA (mtDNA) by PCR including the recognized sequence of restriction enzyme of SfaN I . After amplification and digestion of SfaN I , two bands of 190 bp and 150 bp appeared in the mtDNA of four normal individuals but only one band of 340 bp appeared in the mtDNA with the mutation of G to A at the site of the nucleotide 11778 because such mutation destroyed the recognized sequence of SfaN I . We studied the mtDNAs of the patients with Leber's hereditary optic neur...

Stem Cell Ophthalmology Treatment Study (SCOTS)： bone marrow-derived stem cells in the treatment of Leber＇s hereditary optic neuropathy

The Stem Cell Ophthalmology Treatment Study （SCOTS） is currently the largest-scale stem cell ophthal- mology trial registered at ClinicalTrials.gov （identifier： NCT01920867）. SCOTS utilizes autologous bone marrow-derived stem cells （BMSCs） to treat optic nerve and retinal diseases. Treatment approaches include a combination of retrobulbar, subtenon, intravitreal, intra-optic nerve, subretinal, and intravenous injection of autologous BMSCs according to the nature of the disease, the degree of visual loss, and any risk factors related to the treatments. Patients with Leber＇s hereditary optic neuropathy had visual acuity gains on the Early Treatment Diabetic Retinopathy Study （ETDRS） of up to 35 letters and Snellen acuity improvements from hand motion to 20/200 and from counting fingers to 20/100. Visual field improvements were noted. Macular and optic nerve head nerve fiber layer typically thickened. No serious complications were seen. The increases in visual acuity obtained in our study were encouraging and suggest that the use of autolo- gous BMSCs as provided in SCOTS for ophthalmologic mitochondrial diseases including Leber＇s hereditary optic neuropathy may be a viable treatment option.

HPDL deficiency causes a neuromuscular disease by impairing the mitochondrial respiration

Mitochondrial diseases are caused by variants in both mitochondrial and nuclear genomes.A nuclear gene HPDL(4-hydroxyphenylpyruvate dioxygenase-like),which encodes an intermembrane mitochondrial protein,has been recently implicated in causing a neurodegenerative disease characterized by pediatric-onset spastic movement phenotypes.Here,we report six Chinese patients with bi-allelic HPDL pathogenic variants from four unrelated families showing neuropathic symptoms of variable severity,including developmental delay/intellectual disability,spasm,and hypertonia.Seven different pathogenic variants are identified,of which five are novel.Both fibroblasts and immortalized lymphocytes derived from patients show impaired mitochondrial respiratory function,which is also observed in HPDL-knockdown(KD)He La cells.In these He La cells,overexpression of a wild-type HPDL gene can rescue the respiratory phenotype of oxygen consumption rate.In addition,a decreased activity of the oxidative phosphorylation(OXPHOS)complex II is observed in patient-derived lymphocytes and HPDL-KD He La cells,further supporting an essential role of HPDL in the mitochondrial respiratory chain.Collectively,our data expand the clinical and mutational spectra of this mitochondrial neuropathy and further delineate the possible disease mechanism involving the impairment of the OXPHOS complex II activity due to the bi-allelic inactivations of HPDL.

Research progress on pathogenesis of ulcerative colitis

The incidence of ulcerative colitis is increasing year by year,yet the pathogenesis is still not clear.Many scholars have studied the genetic factors,environmental factors,intestinal microecological imbalance,intestinal mucosal barrier disorder,abnormal immune response and mitochondrial diseases,and abundant achievements have been made.In order to further understand the possible pathogenesis of ulcerative colitis,this paper reviews its research progress,in order to better guide clinical medication,and provide new ideas for further study of its pathogenesis.

VARS2 gene mutation leading to overall developmental delay in a child with epilepsy: A case report

BACKGROUND The mitochondrial respiratory chain defects have become the most common cause of neurometabolic disorders in children and adults,which can occur at any time in life,often associated with neurological dysfunction,and lead to chronic disability and premature death.Approximately one-third of patients with mitochondrial disease have biochemical defects involving multiple respiratory chain complexes,suggesting defects in protein synthesis within the mitochondria.We here report a child with VARS2 gene mutations causing mitochondrial disease.CASE SUMMARY A girl,aged 3 years and 4 mo,had been unable to sit and crawl alone since birth,with obvious seizures and microcephaly.Brain magnetic resonance imaging showed symmetrical,flaky,long T1-weighted and low T2-weighted signals in the posterior part of the bilateral putamen with a high signal shadow.T2 fluidattenuated inversion recovery imaging showed a slightly high signal and diffusion-weighted imaging showed an obvious high signal.Whole-exome gene sequencing revealed a compound heterozygous mutation in the VARS2 gene,c.1163(exon11)C>T and c.1940(exon20)C>T,which was derived from the parents.The child was diagnosed with combined oxidative phosphorylation deficiency type 20.CONCLUSION In this patient,mitochondrial disorders including Leigh syndrome and MELAS syndrome(mitochondrial myopathy,encephalopathy,lactic acidosis,and stroke-like episodes)were ruled out,and combined oxidative phosphorylation deficiency type 20 was diagnosed,expanding the phenotypic spectrum of the disease.

MELAS, MIDD and Beyond: m.3243A>G MT-TL1 Mutation in Adult Patients

m.3243A>G MT-TL1 mutation is the most common mitochondrial DNA mutation that results in a wide spectrum of disorders in a maternally inherited pedigree. In adult patients, many present with symptoms and signs indistinguishable from acquired diseases and the correct diagnosis is often delayed after many years. Nevertheless, clues suggesting m.3243A>G usually exist early in the disease course but are only realized late. These hints, from the evolution of symptoms and signs, family background, investigation results, or a combination of these, enable the physician to make the correct diagnosis early, which is important for appropriate treatment and better patient care. As with other inheritable diseases, genetic counselling should be offered regarding the disease management, inheritance mode, recurrence risk, usefulness and limitations of genetic testing and reproductive options.

Human iPSCs derived astrocytes rescue rotenone-induced mitochondrial dysfunction and dopaminergic neurodegeneration in vitro by donating functional mitochondria

Background Parkinson’s disease(PD)is one of the neurodegeneration diseases characterized by the gradual loss of dopaminergic(DA)neurons in the substantia nigra region of the brain.Substantial evidence indicates that at the cellular level mitochondrial dysfunction is a key factor leading to pathological features such as neuronal death and accumulation of misfoldedα-synuclein aggregations.Autologous transplantation of healthy purified mitochondria has shown to attenuate phenotypes in vitro and in vivo models of PD.However,there are significant technical difficulties in obtaining large amounts of purified mitochondria with normal function.In addition,the half-life of mitochondria varies between days to a few weeks.Thus,identifying a continuous source of healthy mitochondria via intercellular mitochondrial transfer is an attractive option for therapeutic purposes.In this study,we asked whether iPSCs derived astrocytes can serve as a donor to provide functional mitochondria and rescue injured DA neurons after rotenone exposure in an in vitro model of PD.Methods We generated DA neurons and astrocytes from human iPSCs and hESCs.We established an astroglial-neuronal co-culture system to investigate the intercellular mitochondrial transfer,as well as the neuroprotective effect of mitochondrial transfer.We employed immunocytochemistry and FACS analysis to track mitochondria.Results We showed evidence that iPSCs-derived astrocytes or astrocytic conditioned media(ACM)can rescue DA neurons degeneration via intercellular mitochondrial transfer in a rotenone induced in vitro PD model.Specifically,we showed that iPSCs-derived astrocytes from health spontaneously release functional mitochondria into the media.Mito-Tracker Green tagged astrocytic mitochondria were detected in the ACM and were shown to be internalized by the injured neurons via a phospho-p38 depended pathway.Transferred mitochondria were able to significantly reverse DA neurodegeneration and axonal pruning following exposure to rotenone.When rotenone injured neurons were cultured in presence of ACM depleted of mitochondria(by ultrafiltration),the neuroprotective effects were abolished.Conclusions Our studies provide the proof of principle that iPSCs-derived astrocytes can act as mitochondria donor to the injured DA neurons and attenuate pathology.Using iPSCs derived astrocytes as a donor can provide a novel strategy that can be further developed for cellular therapy for PD.

Clinical and Molecular Characteristics in 100 Chinese Pediatric Patients with m.3243A〉G Mutation in Mitochondrial DNA

Background： Mitochondrial diseases are a group of energy metabolic disorders with multisystem involvements. Variable clinical features present a major challenge in pediatric diagnoses. We summarized the clinical spectrum of m.3243A〉G mutation in Chinese pediatric patients, to define the common clinical manifestations and study the correlation between heteroplasmic degree of the mutation and clinical severity of the disease. Methods： Clinical data of one-hundred pediatric patients with symptomatic mitochondrial disease harboring m.3243A〉G mutation from 2007 to 2013 were retrospectively reviewed. Detection of m.3243A〉G mutation ratio was performed by polymerase chain reaction （PCR）-restriction fragment length polymorphism. Correlation between m.3243A〉G mutation ratio and age was evaluated. The differences in clinical symptom frequency of patients with low, middle, and high levels of mutation ratio were analyzed by Chi-square test. Results： Sixty-six patients （66%） had suffered a delayed diagnosis for an average of 2 years. The most frequent symptoms were seizures （76%）, short stature （73%）, elevated plasma lactate （70%）, abnormal magnetic resonance imaging/computed tomography （MRI/CT） changes （68%）, vomiting （55%）, decreased vision （52%）, headache （50%）, and muscle weakness （48%）. The mutation ratio was correlated negatively with onset age （r = -0.470, P 〈 0.001）. Myopathy was more frequent in patients with a high level of mutation ratio. However, patients with a low or middle level of m.3243A〉G mutation ratio were more likely to suffer hearing loss, decreased vision, and gastrointestinal disturbance than patients with a high level of mutation ratio. Conclusions： Our study showed that half of Chinese pediatric patients with m.3243A〉G mutation presented seizures, short stature, abnormal MRI/CT changes, elevated plasma lactate, vomiting, and headache. Pediatric patients with these recurrent symptoms should be considered for screening m.3243A〉G mutation. Clinical manifestations and laboratory abnormalities should be carefully monitored in patients with this point mutation.

Reference Intervals of Mitochondrial DNA Copy Number in Peripheral Blood for Chinese Minors and Adults

Background： Mitocbondrial DNA （mtDNA） content measured by different techniques cannot be compared between studies, and age- and tissue-related control values are hardly available. In the present study, we aimed to establish the nonllal reference range of mtDNA copy number in the Chinese population. Methods： Two healthy cohorts of 200 Chinese minors （0.1 18.0 years） and 200 adults （18.0-88.0 years） were recruited. Then, they were further categorized into eight age groups. The absolute mtDNA copy number per cell was measured by a quantitative real-time polymerase chain reaction. We subsequently used this range to evaluate mtDNA content in tbur patients （0.5-4.0 years） with molecularly proven mitochondrial depletion syndromes （MDSs） and 83 cases of mitochondrial disease patients harboring the m.3243A〉G mutation. Results： The reference range ofmtDNA copy number in peripheral blood was 175-602 copies/cell （mean： 325 copies/cell） in minors and 164 500 copies/cell （mean： 287 copies/cell） in adults. There was a decreasing trend in mtDNA copy number in blood with increasing age, especially in 0-2-year-old and 〉50-year-old donors. The mean mtDNA copy number level among the mitochondrial disease patients with m.3243A〉G mutation was significantly higher than that ofhealtby controls. The intDNA content ofPOLG, DGUOK, TK2, and SUCLA2 genes in blood samples from MDS patients was reduced to 25%, 38%, 32%, and 24%, respectively. Conclusions： We primarily establish the refeerence intervals of mtDNA copy number, which might contribute to the clinical diagnosis and monitoring of mitochondrial disease.

The current landscape for the treatment of mitochondrial disorders

The mitochondrial organelle is crucial to the energy metabolism of the eukaryotic cell. Defects in mitochondrial function lie at the core of a wide range of disorders, including both rare primary mitochondrial disorders and more common conditions such as Parkinson＇s disease and diabetes. Inherited defects in mitochondrial function can be found in both the nuclear genome and the mitochondrial genome, with the latter creating unique challenges in the treatment and understanding of disease passed on through the mitochondrial genome. In this review, we will describe the limited treatment regimens currently used to alleviate primary mitochondrial disorders, as well as the potential for emerging technologies（in particular, those involving direct manipulation of the mitochondrial genome） to more decisively treat this class of disease. We will also emphasize the critical parallels between primary mitochondrial disorders and more common ailments such as cancer and diabetes.