Duchenne Muscular Dystrophy Research Articles

Cerebellar dysfunction in the mdx mouse model of Duchenne muscular dystrophy: An electrophysiological and behavioural study.

Patients with Duchenne muscular dystrophy (DMD) commonly show specific cognitive deficits in addition to a severe muscle impairment caused by the absence of dystrophin expression in skeletal muscle. These cognitive deficits have been related to the absence of dystrophin in specific regions of the central nervous system, notably cerebellar Purkinje cells (PCs). Dystrophin has recently been involved in GABAA receptors clustering at postsynaptic densities, and its absence, by disrupting this clustering, leads to decreased inhibitory input to PC. We performed an in vivo electrophysiological study of the dystrophin-deficient muscular dystrophy X-linked (mdx) mouse model of DMD to compare PC firing and local field potential (LFP) in alert mdx and control C57Bl/10 mice. We found that the absence of dystrophin is associated with altered PC firing and the emergence of fast (~160-200 Hz) LFP oscillations in the cerebellar cortex of alert mdx mice. These abnormalities were not related to the disrupted expression of calcium-binding proteins in cerebellar PC. We also demonstrate that cerebellar long-term depression is altered in alert mdx mice. Finally, mdx mice displayed a force weakness, mild impairment of motor coordination and balance during behavioural tests. These findings demonstrate the existence of cerebellar dysfunction in mdx mice. A similar cerebellar dysfunction may contribute to the cognitive deficits observed in patients with DMD.

Transcriptional changes of genes encoding sarcoplasmic reticulum calcium binding and up-taking proteins in normal and Duchenne muscular dystrophy dogs

BackgroundCytosolic calcium overload contributes to muscle degradation in Duchenne muscular dystrophy (DMD). The sarcoplasmic reticulum (SR) is the primary calcium storage organelle in muscle. The sarco-endoplasmic reticulum ATPase (SERCA) pumps cytosolic calcium to the SR during muscle relaxation. Calcium is kept in the SR by calcium-binding proteins.MethodsGiven the importance of the canine DMD model in translational studies, we examined transcriptional changes of SERCA (SERCA1 and SERCA2a), SERCA regulators (phospholamban, sarcolipin, myoregulin, and dwarf open reading frame), and SR calcium-binding proteins (calreticulin, calsequestrin 1, calsequestrin 2, and sarcalumenin) in skeletal muscle (diaphragm and extensor carpi ulnaris) and heart (left ventricle) in normal and affected male dogs by droplet digital PCR before the onset (≤ 2-m-old), at the active stage (8 to 16-m-old), and at the terminal stage (30 to 50-m-old) of the disease. Since many of these proteins are expressed in a fiber type-specific manner, we also evaluated fiber type composition in skeletal muscle.ResultsIn affected dog skeletal muscle, SERCA and its regulators were down-regulated at the active stage, but calcium-binding proteins (except for calsequestrin 1) were upregulated at the terminal stage. Surprisingly, nominal differences were detected in the heart. We also examined whether there exists sex-biased expression in 8 to 16-m-old dogs. Multiple transcripts were significantly downregulated in the heart and extensor carpi ulnaris muscle of female dogs. In fiber type analysis, we found significantly more type I fiber in the diaphragm of 8 to 16-m-old affected dogs, and significantly more type II fibers in the extensor carpi ulnaris of 30 to 50-m-old affected dogs. However, no difference was detected between male and female dogs.ConclusionsOur study adds new knowledge to the understanding of muscle calcium regulation in normal and dystrophic canines.

CRISPR/Cas system in human genetic diseases

The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) system is an adaptive immune system derived from bacteria which is designed to recognize and cleave invading DNA, such as viruses and plasmids. The advent of this innovative gene-editing technology has emerged as influential force in the category of medicine, delivering unprecedented precision in targeting and modifying genetic material. This review explores the potential and challenges of CRISPR in the context of human diseases. Specific applications in diseases affecting hemoglobin, muscle, the eye, and the liver are examined, demonstrating the versatility of CRISPR in addressing both monogenic and complex diseases. The use of CRISPR for gene therapy in conditions like sickle cell disease, Duchenne muscular dystrophy, retinal degeneration, and liver disorders is discussed, showcasing early clinical trials and preclinical studies that underscore the promise of CRISPR in medicine. Finally, it is expected that CRISPR will be able to play a greater role in human health and bring more precise and personalized treatment plans to patients.

Obesity Management in Youth with Duchenne Muscular Dystrophy: A Review of Metformin and Alternative Pharmacotherapies.

Background: Individuals with Duchenne muscular dystrophy (DMD) have increased risk of obesity from prolonged glucocorticoid use and progressive muscle weakness. Over 50% have obesity by the teenage years. Objectives: The current study examines literature on obesity management in DMD and describes how obesity pharmacotherapy can be used in this high-risk cohort. Methods: This review was conducted in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews checklist. A Pubmed Database search was conducted from January 2000 to May 2024. Included terms were DMD and topiramate, phentermine, metformin, glucagon-like peptide-1 receptor agonist, semaglutide, and liraglutide. Eligible studies were cataloged to examine obesity pharmacotherapy, side effect profiles, and clinical outcomes. Results: Twenty studies met inclusion criteria, 18 on metformin. Reviewed studies varied in duration from 4 to 24 weeks, ages 6.5-44 years old, with 112 participants total (range: 1-30 participants). Included studies were: eight animal studies, six clinical trials, four reviews, one cohort study, and one case report. Primary outcomes varied among studies: muscular degeneration and function (15 articles), cardiac function (2 articles), weight loss (2 articles), and general endocrine care (1 article). Conclusions: Adjunct obesity pharmacotherapy use in youth with DMD is promising but needs to be confirmed. Large gaps include appropriate agent selection, side effect monitoring, and dose escalation. The overall quality of pediatric-specific evidence for the use of obesity pharmacotherapy in youth with DMD is low. Future research is needed to investigate how to safely utilize these agents.

Developing Advanced Chimeric Cell Therapy for Duchenne Muscular Dystrophy.

Duchenne Muscular Dystrophy (DMD) is a lethal, X-linked disorder leading to muscle degeneration and premature death due to cardiopulmonary complications. Currently, there is no cure for DMD. We previously confirmed the efficacy of human Dystrophin-Expressing Chimeric (DEC) cells created via the fusion of myoblasts from normal and DMD-affected donors. The current study aimed to optimize the development of DEC therapy via the polyethylene glycol (PEG)-mediated fusion protocol of human myoblasts derived from normal, unrelated donors. The optimization of cell fusion assessed different factors influencing fusion efficacy, including myoblast passage number, the efficacy of PKH myoblast staining, the ratio of the single-stained myoblasts in the MIX, and PEG administration time. Additionally, the effect of PEG fusion procedure on cell viability was assessed. A correlation was found between the number of cells used for PKH staining and staining efficacy. Furthermore, the ratio of single-stained myoblasts in the MIX and PEG administration time correlated with fusion efficacy. There was no correlation found between the myoblast passage number and fusion efficacy. This study successfully optimized the myoblast fusion protocol for creation of human DEC cells, introducing DEC as a new Advanced Therapy Medicinal Product (ATMP) for DMD patients.

Identification and analysis of differentially expressed lncRNAs and their ceRNA networks in DMD/mdx primary myoblasts

This study explored the significance of long non-coding RNAs (lncRNAs), particularly their role in maintaining dystrophin protein stability and regulating myocyte proliferation and differentiation. The investigation focused on DMD/mdx mouse skeletal muscle primary myoblasts, aiming to identify lncRNAs potential as biomarkers and therapeutic targets for Duchenne muscular dystrophy (DMD). Utilizing CLC Genomics Workbench software, 554 differentially expressed lncRNAs were identified in DMD/mdx mice compared to wild-type (WT) control. Among them, 373 were upregulated, and 181 were downregulated. The study highlighted specific lncRNAs (e.g., 5930430L01Rik, Gm10143, LncRNA1490, LncRNA580) and their potential regulatory roles in DMD key genes like IGF1, FN1, TNNI1, and MYOD1. By predicting miRNA and their connections with lncRNA and mRNA (ceRNA network) using tools such as miRNet, miRSYSTEM and miRCARTA, the study revealed potential indirect regulation of Dystrophin, IGF1R and UTRN genes by identified lncRNAs (e.g. 2310001H17Rik-203, C130073E24Rik-202, LncRNA2767, 5930430L01Rik and LncRNA580). These findings suggest that the identified lncRNAs may play crucial roles in the development and progression of DMD through their regulatory influence on key gene expression, providing valuable insights for potential therapeutic interventions.

AAV gene therapy for Duchenne muscular dystrophy: the EMBARK phase 3 randomized trial.

Duchenne muscular dystrophy (DMD) is a rare, X-linked neuromuscular disease caused by pathogenic variants in the DMD gene that result in the absence of functional dystrophin, beginning at birth and leading to progressive impaired motor function, loss of ambulation and life-threatening cardiorespiratory complications. Delandistrogene moxeparvovec, an adeno-associated rh74-viral vector-based gene therapy, addresses absent functional dystrophin in DMD. Here the phase 3 EMBARK study aimed to assess the efficacy and safety of delandistrogene moxeparvovec in patients with DMD. Ambulatory males with DMD, ≥4 years to <8 years of age, were randomized and stratified by age group and North Star Ambulatory Assessment (NSAA) score to single-administration intravenous delandistrogene moxeparvovec (1.33 × 1014 vector genomes per kilogram; n = 63) or placebo (n = 62). At week 52, the primary endpoint, change from baseline in NSAA score, was not met (least squares mean 2.57 (delandistrogene moxeparvovec) versus 1.92 (placebo) points; between-group difference, 0.65; 95% confidence interval (CI), -0.45, 1.74; P = 0.2441). Secondary efficacy endpoints included mean micro-dystrophin expression at week 12: 34.29% (treated) versus 0.00% (placebo). Other secondary efficacy endpoints at week 52 (between-group differences (95% CI)) included: Time to Rise (-0.64 (-1.06, -0.23)), 10-meter Walk/Run (-0.42 (-0.71, -0.13)), stride velocity 95th centile (0.10 (0.00, 0.19)), 100-meter Walk/Run (-3.29 (-8.28, 1.70)), time to ascend 4 steps (-0.36 (-0.71, -0.01)), PROMIS Mobility and Upper Extremity (0.05 (-0.08, 0.19); -0.04 (-0.24, 0.17)) and number of NSAA skills gained/improved (0.19 (-0.67, 1.06)). In total, 674 adverse events were recorded with delandistrogene moxeparvovec and 514 with placebo. There were no deaths, discontinuations or clinically significant complement-mediated adverse events; 7 patients (11.1%) experienced 10 treatment-related serious adverse events. Delandistrogene moxeparvovec did not lead to a significant improvement in NSAA score at week 52. Some of the secondary endpoints numerically favored treatment, although no statistical significance can be claimed. Safety was manageable and consistent with previous delandistrogene moxeparvovec trials. ClinicalTrials.gov: NCT05096221.

Can Sniff Nasal Inspiratory Pressure be a guide in detecting of sleep-disordered breathing in children with Duchenne Muscular Dystrophy?

PurposeDuchenne muscular dystrophy (DMD) is a severe, progressive condition characterized by muscle degeneration and weakness, significantly affecting respiratory function. This study aimed to evaluate the presence of sleep-disordered breathing (SDB) in children with DMD and investigate the relationships between sleep and respiratory function using spirometry, sniff nasal inspiratory pressure (SNIP), and polysomnography (PSG) along with capnography. Research questionCan low SNIP be a guide for detecting respiratory muscle involvement early and determining the right time to perform early PSG and capnography in DMD? Study designProspective, observational, cross-sectional study. MethodsThis study included DMD patients aged <18 years. Pulmonary function tests were conducted using spirometry and SNIP, and maximum inspiratory and expiratory pressure were measured. PSG and capnography were performed within two weeks after the pulmonary function tests, and their relationships with each other were investigated. ResultsThe study included 44 children. Obstructive sleep apnea syndrome (OSAS) was present in 70.5 % of patients, while nocturnal hypoventilation was observed in 4.5 %. SNIP values were significantly lower in patients with moderate-to-severe OSAS than in those without OSAS. An SNIP value below 40 cm H2O was associated with a 92.8 % prevalence of OSAS. ConclusionSNIP is a valuable, noninvasive marker for the early detection of respiratory muscle involvement and SDB in patients with DMD. This study highlights the need for early and regular respiratory monitoring in children with DMD to enhance care and quality of life.

Lessons from a negative gene therapy trial for Duchenne muscular dystrophy.

Lessons from a negative gene therapy trial for Duchenne muscular dystrophy.

Safety and efficacy of viltolarsen in ambulatory and nonambulatory males with Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is an X-linked recessive disease characterized by mutations in the dystrophin gene, causing motor and pulmonary function decline. Viltolarsen is indicated for patients with dystrophin gene mutations amenable to exon 53 skipping. Here, we report safety, motor function, and the first pulmonary function results from the open-label, phase II Galactic53 trial of viltolarsen (NCT04956289). Male participants aged ≥ 8years with DMD received 80mg/kg intravenous viltolarsen once weekly for 48weeks. Results from participants receiving viltolarsen were compared with an external control cohort group-matched for multiple variables. All treatment-emergent adverse events were mild or moderate, 4 were considered treatment-related, and no participants discontinued. Participants receiving viltolarsen experienced clinically meaningful benefits in pulmonary function with higher percent predicted forced vital capacity and higher peak cough flow at Week 49 compared with the control cohort for both ambulatory and nonambulatory participants. Viltolarsen also stabilized upper limb motor function over the Treatment Period. These results support viltolarsen as an important part of the treatment armamentarium for both ambulatory as well as nonambulatory patients with DMD.

Lessons learned from the RE(ACT) conference on medical devices for rare diseases

The field of rare disease therapeutics has witnessed significant growth in recent years, highlighting the need for diverse therapeutic approaches to cater to the unique needs of individuals with rare diseases. Rare disease therapies encompass a broad spectrum of interventions, including orphan medicinal products, orphan medical devices, rehabilitative therapies, and digital therapeutics, with the lines between these categories blurring. This paper covers the session of the RE (ACT)-IRDiRC Conference 2023 and delves into the landscape of orphan medical device research and development, shedding light on the challenges and opportunities in this burgeoning field. It provides a short overview of the different international legislations in the field. In addition, it highlights several exemplary orphan medical devices. The first example is an exoskeleton for boys with Duchenne Muscular Dystrophy, enabling them to maintain arm functionality and independence. Another example presented was an EEG device linked to an app detecting seizures in rare epilepsy conditions, which alerts caregivers to seizures in real-time but also facilitates objective seizure reporting for clinicians, aiding in diagnosis and treatment optimization. It also showcases the role of gamification and enabling technologies in addressing rare diseases, by showing a game designed for children with cystic fibrosis, and a telemedicine system for rehabilitation therapy. Both solutions aim to improve patients' understanding of their conditions and enhance their self-management. In conclusion, this paper underscores the critical need for patient-centric orphan and pediatric medical devices to provide therapeutic options for individuals with rare diseases. It highlights the impact of existing devices on enhancing the quality of life for rare disease patients and emphasizes the necessity for greater incentives and support for research and development in this field.

A model-informed clinical trial simulation tool with a graphical user interface for Duchenne muscular dystrophy.

Quantitative model-based clinical trial simulation tools play a critical role in informing study designs through simulation before actual execution. These tools help drug developers explore various trial scenarios in silico to select a clinical trial design to detect therapeutic effects more efficiently, therefore reducing time, expense, and participants' burden. To increase the usability of the tools, user-friendly and interactive platforms should be developed to navigate various simulation scenarios. However, developing such tools challenges researchers, requiring expertise in modeling and interface development. This tutorial aims to address this gap by guiding developers in creating tailored R Shiny apps, using an example of a model-based clinical trial simulation tool that we developed for Duchenne muscular dystrophy (DMD). In this tutorial, the structural framework, essential controllers, and visualization techniques for analysis are described, along with key code examples such as criteria selection and power calculation. A virtual population was created using a machine learning algorithm to enlarge the available sample size to simulate clinical trial scenarios in the presented tool. In addition, external validation of the simulated outputs was conducted using a placebo arm of a recently published DMD trial. This tutorial will be particularly useful for developing clinical trial simulation tools based on DMD progression models for other end points and biomarkers. The presented strategies can also be applied to other diseases.

Exploring novel natural compound-based therapies for Duchenne muscular dystrophy management: insights from network pharmacology, QSAR modeling, molecular dynamics, and free energy calculations.

Muscular dystrophies encompass a heterogeneous group of rare neuromuscular diseases characterized by progressive muscle degeneration and weakness. Among these, Duchenne muscular dystrophy (DMD) stands out as one of the most severe forms. The present study employs an integrative approach combining network pharmacology, quantitative structure-activity relationship (QSAR) modeling, molecular dynamics (MD) simulations, and free energy calculations to identify potential therapeutic targets and natural compounds for DMD. Upon analyzing the GSE38417 dataset, it was found that individuals with DMD exhibited 290 upregulated differentially expressed genes (DEGs) compared to healthy controls. By utilizing gene ontology (GO) and protein-protein interaction (PPI) network analysis, this study provides insights into the functional roles of the identified DEGs, identifying ten hub genes that play a critical role in the pathology of DMD. These key genes include DMD, TTN, PLEC, DTNA, PKP2, SLC24A, FBXO32, SNTA1, SMAD3, and NOS1. Furthermore, through the use of ligand-based pharmacophore modeling and virtual screening, three natural compounds were identified as potential inhibitors. Among these, compounds 3874518 and 12314417 have demonstrated significant promise as an inhibitor of the SMAD3 protein, a crucial factor in the fibrotic and inflammatory mechanisms associated with DMD. The therapeutic potential of the compounds was further supported by molecular dynamics simulation and Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) analysis. These findings suggest that the compounds are viable candidates for experimental validation against DMD.

Long-term course of gastrostomy nutritional management in patients with Duchenne muscular dystrophy: A retrospective cohort study

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease that commonly requires gastrostomy due to dysphagia. This study aimed to investigate the proportion of patients with DMD requiring gastrostomy and to assess the timing and outcomes of gastrostomy in patients with DMD to optimize perioperative care and improve long-term management. We conducted a retrospective cohort study by reviewing the medical records of patients with DMD treated between March 1991 and November 2023 at Kobe University Hospital. To identify risk factors for gastrostomy, Fisher’s two-tailed test and logistic analysis were used to compare the gastrostomy (group G) and comparison group without gastrostomy (group C) groups. We identified patients >18 years with DMD. We excluded those without medical records from the last decade and those on nasogastric tube feeding. Among the 135 eligible patients, five (median age, 23 years) underwent percutaneous endoscopic gastrostomy (PEG; uptake rate, 3.7 %), and their data were analyzed for perioperative outcomes. Complications included ventilatory disturbances, aspiration pneumonia, and hemorrhagic shock. Two patients experienced significant postoperative complications, underscoring the high-risk nature of PEG in this population. Participants’ postoperative weight changes varied significantly. The presence or absence of ventilatory management, cardiomyopathy treatment, scoliosis, and steroid treatment were examined as risk factors between groups G and C, but no significant differences were observed. This study highlights low gastrostomy usage among patients with DMD, with varying outcomes. Meticulous planning and early consideration of gastrostomy are crucial to enhance the quality of life and nutritional outcomes in these patients.

Progressive cardiomyopathy with intercalated disc disorganization in a rat model of Becker dystrophy

Becker muscular dystrophy (BMD) is an X-linked disorder due to in-frame mutations in the DMD gene, leading to a less abundant and truncated dystrophin. BMD is less common and severe than Duchenne muscular dystrophy (DMD) as well as less investigated. To accelerate the search for innovative treatments, we developed a rat model of BMD by deleting the exons 45–47 of the Dmd gene. Here, we report a functional and histopathological evaluation of these rats during their first year of life, compared to DMD and control littermates. BMD rats exhibit moderate damage to locomotor and diaphragmatic muscles but suffer from a progressive cardiomyopathy. Single nuclei RNA-seq analysis of cardiac samples revealed shared transcriptomic abnormalities in BMD and DMD rats and highlighted an altered end-addressing of TMEM65 and Connexin-43 at the intercalated disc, along with electrocardiographic abnormalities. Our study documents the natural history of a translational preclinical model of BMD and reports a cellular mechanism for the cardiac dysfunction in BMD and DMD offering opportunities to further investigate the organization role of dystrophin in intercellular communication.

Two novel deep intronic variants cause Duchenne muscular dystrophy by splice-altering mechanism

Duchenne muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration and weakness, due to mutations in the DMD gene, which encodes the dystrophin protein. While mutations within the coding regions of DMD have been extensively studied, recent focus has shifted to deep intronic variants for their potential impact on disease severity. Here, we characterize two deep intronic variants, c.8669-19_8669-24del and c.6439-1016_6439-3376del, in unrelated DMD patients. These variants were identified using targeted long-read sequencing on patients' DNA. RNA sequencing/reverse transcription polymerase chain reaction on RNA extracted from muscle biopsies revealed the presence of a pseudoexon or retention of part of the intron in the transcript, resulting in the introduction of premature termination codons. This study enhances our understanding of pseudoexon activation mechanisms in DMD and underscores the diverse genetic abnormalities contributing to the disease's complexity.

223P Mental health support for children and young people with Duchenne muscular dystrophy – who, when and how across the UK

223P Mental health support for children and young people with Duchenne muscular dystrophy – who, when and how across the UK

305P Investigation of the clinical significance of serum titin in Duchenne muscular dystrophy

305P Investigation of the clinical significance of serum titin in Duchenne muscular dystrophy

370P Gait analysis in children with Duchenne muscular dystrophy: overground vs. treadmill walking

370P Gait analysis in children with Duchenne muscular dystrophy: overground vs. treadmill walking

371P Screening for psychosocial needs in adults with Duchenne muscular dystrophy: preliminary findings on using the GAD7 and PHQ9

371P Screening for psychosocial needs in adults with Duchenne muscular dystrophy: preliminary findings on using the GAD7 and PHQ9