Duchenne muscular dystrophy

[Advances and Challenges in Microdystrophin gene therapy for Duchenne Muscular Dystrophy: progress and future directions]

Duchenne muscular dystrophy (DMD) is a severe degenerative genetic muscle disease affecting mainly young boys, characterized by a significant alteration or absence of dystrophin expression. Significant strides have been made in comprehending and treating DMD, particularly with the recent approval of the first gene therapy using a recombinant adeno-associated vector (rAAV) to deliver a shortened form of dystrophin (microdystrophin). Nevertheless, major challenges remain in improving therapeutic outcomes. The use of rAAV vectors is hindered by major limitations, notably the risks of immunotoxicity and hepatotoxicity, linked to high-dose administration. Additionally, microdystrophin exhibits inherent functional limitations and immunological risks. This article examines these challenges and explores the avenues for enhancing gene therapy for DMD.

Wilkie's syndrome in a patient with Duchenne's muscular dystrophy: A Case Report

Superior mesenteric artery syndrome, or Wilkie's syndrome, is one of the rarest gastrointestinal disorders known to medical science. It is characterized by the vascular clamp of the third portion of the duodenum, between the superior mesenteric artery and the aorta. It presents as an uncommon cause of upper intestinal obstruction. Imaging is required, preferably with a contrast-enhanced CT or an MRI; conservative management is preferred, leaving surgery for the most complex cases. We present the case of a 34-year-old man with Duchenne's muscular dystrophy and a history of substantial weight loss after hospital admission for aspiration pneumonia. He underwent an abdominal CT scan that showed enlargement of the stomach, the second and third parts of the duodenum; without observing masses, the patient received conservative management with a nasojejunal feeding tube. At the outpatient reevaluation, 1 month postdischarge, he became asymptomatic and had progressive weight gain.

[Muscle stem cells and metabolism in Duchenne muscular dystrophy, focus on AMPK]

Through their myogenic activity, adult muscle stem cells (MuSCs) are crucial for the regeneration of striated skeletal muscle. Once activated, they proliferate, differentiate and then fuse to repair or form new muscle fibers (myofibers). Their progression through myogenesis requires a complex regulation involving multiple players such as metabolism, in particular via AMPK. This protein kinase regulates the self-renewal and myonuclear accretion of MuSCs after acute skeletal muscle injury or skeletal muscle contraction. However, in a context of dystrophy such as Duchenne muscular dystrophy (DMD), the regenerative capacity of MuSCs is reduced, presumably due to an increase of the proliferation that is detrimental to differentiation. We are interested here in the potential of metabolism to regulate the myogenic activity of MuSCs in DMD via AMPK.

Similar disease progression in nonsense Duchenne muscular dystrophy boys as general natural history: Single Brazilian center 15 years registry view

Duchenne muscular dystrophy is a progressive and fatal X-linked neuromuscular disease. Emergent disease-modifying therapy (DMT) in nonsense Duchenne muscular dystrophy (nmDMD) has brought new perspectives to slow down functional decline in this fatal disease. To investigate if there are differences in natural history between nmDMD and other genotypes, we described a retrospective cohort analysis of 25 nonsense mutation DMD (nmDMD) boys without disease-modifying therapy, aged between 1 and 22 years, over the last 15 years (2007-2022) in a single neuromuscular center in Rio de Janeiro and use published data on DMD natural history for comparison. Regarding prognostic factors, there were remarkable and statistically significant early loss of ambulation (at 9.1y ±2.1) and shortening of life expectancy (17.6y ±2.1) in our nmDMD group. Late acquisition of neurodevelopmental milestones and annual rates of decline in respiratory, cardiac, and timed motor function tests are the same between nmDMD patients with standard care and other DMD genotypes as described in the literature. Our data indicates the similarity of natural history and disease progression among DMD boys with nmDMD mutations compared to different mutations.

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.

Muscular dystrophy patients show low exercise-induced blood flow in muscles with normal strength

OBJECTIVE

Neuromuscular evaluation increasingly employs muscle ultrasonography to determine muscle thickness, mean grayscale echointensity, and visual semiquantitative echotexture attenuation. However, these measures provide low sensitivity for detection of mild muscle abnormality. Exercise-induced intramuscular blood flow is a physiologic phenomenon, which may be impaired in mildly affected muscles, particularly in dystrophinopathies, and may indicate functional muscle ischemia. We aimed to determine if muscle blood flow is reduced in patients with neuromuscular disorders and preserved muscle strength, and if it correlates with echointensity and digital echotexture measurements.

METHODS

Peak exercise-induced blood flow, echointensity, and echotexture were quantified in the elbow flexor muscles of 15 adult patients with Becker muscular dystrophy (BMD) and 13 patients with other muscular dystrophies (OMD). These were compared to 17 patients with Charcot-Marie-Tooth type 1 (CMT1) neuropathy and 21 healthy adults from a previous study.

RESULTS

Muscle blood flow was reduced in all patient groups compared to controls, most prominently in BMD patients (p < 0.0001). Echointensity was similarly increased in all patient groups (p < 0.05), while echotexture was reduced only in muscular dystrophy patients (p ≤ 0.002). In BMD, blood flow correlated with echotexture (Pearson r = 0.6098, p = 0.0158) and strength (Spearman r = 0.5471; p = 0.0370). In patients with normal muscle strength, reduced muscle blood flow was evident in all patient groups (p < 0.001), echotexture was reduced in BMD and OMD (p < 0.01), and echointensity was increased in CMT (p < 0.05).

INTERPRETATION

Muscle blood flow is a sensitive measure to detect abnormality, even in muscles with normal strength. Increased echointensity may indicate a neurogenic disorder when strength is preserved, while low echotexture suggests a dystrophic disease.

Hypoxia-induced PD-L1 expression and modulation of muscle stem cell allograft rejection

Stem cell therapy has shown immense promise in treating genetic disorders, particularly muscular diseases like Duchenne muscular dystrophy (DMD). This study investigates a novel method to enhance the viability of stem cell transplants in DMD by upregulating Programmed Death Ligand 1 (PD-L1) in muscle stem cells (MuSCs) through preconditioning with hypoxia and/or interferon-γ (IFN-γ) to mitigate T cell immune rejection. MuSCs were treated with 5% hypoxia for 72 h and further treated with IFN-γ to enhance PD-L1 expression. Additionally, gain and loss experiments using a PD-L1 inhibitor (BMS-1) were conducted to investigate cellular expression profiles in vitro and cell transplantation outcomes in vivo. Our results showed significant upregulation of PD-L1 in MuSCs under hypoxia and IFN-γ conditions without affecting cellular proliferation and differentiation in vitro. In vivo, these preconditioned MuSCs led to decreased infiltration of CD4+ and CD8+ T cells in implanted limb muscles of mouse models. Blocking PD-L1 reduced graft survival in muscles treated with MuSCs. Conversely, increased PD-L1 expression and reduced T cell infiltration correlated with improved graft survival, as identified by pre-labeled LacZ + MuSCs following transplantation. This study provides evidence that hypoxia and IFN-γ preconditioning of MuSCs can significantly enhance the efficacy of cell therapy for DMD by mitigating immune rejection. Our strategic approach aimed to improve donor cell survival and function post-transplantation by modifying immune responses towards the donor cells.

Gene editing in common cardiovascular diseases

Cardiovascular diseases are the leading cause of morbidity and mortality worldwide, highlighting the high socioeconomic impact. Current treatment strategies like compound-based drugs or surgeries are often limited. On the one hand, systemic administration of substances is frequently associated with adverse side effects; on the other hand, they typically provide only short-time effects requiring daily intake. Thus, new therapeutic approaches and concepts are urgently needed. The advent of CRISPR-Cas9 genome editing offers great promise for the correction of disease-causing hereditary mutations. As such mutations are often very rare, gene editing strategies to correct them are not broadly applicable to many patients. Notably, there is recent evidence that gene editing technology can also be deployed to disrupt common pathogenic signaling cascades in a targeted, specific, and efficient manner, which offers a more generalizable approach. However, several challenges remain to be addressed ranging from the optimization of the editing strategy itself to a suitable delivery strategy up to potential immune responses to the editing components. This review article discusses important CRISPR-Cas9-based gene editing approaches with their advantages and drawbacks and outlines opportunities in their application for treatment of cardiovascular diseases.

Characterization of patients with Duchenne muscular dystrophy across previously developed health states

Project HERCULES has developed a natural history model (NHM) of disease progression in Duchenne muscular dystrophy (DMD) that comprises eight ordered health states (two ambulatory states, one transfer state indicating increased caregiver burden in which patients cannot walk/run 10m or rise from floor but can still support their own weight, and five non-ambulatory states). The current study used data from nine sources (clinical trial placebo arms, one real-world dataset, and three natural history datasets) to further characterize patients with DMD according to these health states. The study included 1,173 patients across 5,306‬ visits. Patients were on average older and exhibited worse ambulatory, pulmonary, upper limb, and cardiac functions with each successive health state. Mean±SE ages increased monotonically across health states, starting with 8.47±0.07 for early ambulatory, 10.86±0.13 for late ambulatory, 11.65±0.35 for transfer state, and ranging from 13.17±0.32 to 16.84±0.37 for the non-ambulatory states. North Star Ambulatory Assessment (NSAA) total score, which measures motor function and ranges from 34 (best) to 0 (worst), was 23.7 (interquartile range [IQR]: 20-30) for early ambulatory patients, 12.7 (IQR: 9-16) for late ambulatory patients, and 3.9 (IQR: 2-5) for transfer patients. Pulmonary function as measured by mean±SE of forced vital capacity percent predicted (FVC%p) was 94.5±0.8 for early ambulatory, 89.1±1.4 for late ambulatory, and 80.2±2.8 for transfer states, and decreased from 77.2±1.7 to 20.6±1.6 across the five non-ambulatory health states. In summary, these findings further characterize health states and their interpretation in economic modeling and decision-making in DMD management.

Hereditary Neuromuscular Disorders in Reproductive Medicine

Neuromuscular disorders (NMDs) encompass a broad range of hereditary and acquired conditions that affect motor units, significantly impacting patients' quality of life and reproductive health. This narrative review aims to explore in detail the reproductive challenges associated with major hereditary NMDs, including Charcot-Marie-Tooth disease (CMT), dystrophinopathies, Myotonic Dystrophy (DM), Facioscapulohumeral Muscular Dystrophy (FSHD), Spinal Muscular Atrophy (SMA), Limb-Girdle Muscular Dystrophy (LGMD), and Amyotrophic Lateral Sclerosis (ALS). Specifically, it discusses the stages of diagnosis and genetic testing, recurrence risk estimation, options for preimplantation genetic testing (PGT) and prenatal diagnosis (PND), the reciprocal influence between pregnancy and disease, potential obstetric complications, and risks to the newborn.

Investigating Inherited Heart Diseases Using Human Induced Pluripotent Stem Cell-Based Models

Inherited heart diseases (IHDs) are caused by genetic mutations that disrupt the physiological structure and function of the heart. Understanding the mechanisms behind these diseases is crucial for developing personalised interventions in cardiovascular medicine. Development of induced pluripotent stem cells, which can then be differentiated to any nucleated adult cell type, has enabled the creation of personalised single-cell and multicellular models, providing unprecedented insights into the pathophysiology of IHDs. This review provides a comprehensive overview of recent advancements in human iPSC models used to dissect the molecular and genetic underpinnings of common IHDs. We examine multicellular models and tissue engineering approaches, such as cardiac organoids, engineered heart tissue, and multicellular co-culture systems, which simulate complex intercellular interactions within heart tissue. Recent advancements in stem cell models offer a more physiologically relevant platform to study disease mechanisms, enabling researchers to observe cellular interactions, study disease progression, and identify therapeutic strategies. By leveraging these innovative models, we can gain deeper insights into the molecular and cellular mechanisms underlying IHDs, ultimately paving the way for more effective diagnostic and therapeutic strategies.

Cancer Risk in Patients With Muscular Dystrophy and Myotonic Dystrophy: A Register-Based Cohort Study

BACKGROUND AND OBJECTIVES

Muscular dystrophies and myotonic disorders are genetic disorders characterized by progressive skeletal muscle degeneration and weakness. Epidemiologic studies have found an increased cancer risk in myotonic dystrophy, although the cancer risk spectrum is poorly characterized. In patients with muscular dystrophy, the cancer risk is uncertain. We aimed to determine the overall cancer risk and cancer risk spectrum in patients with muscular dystrophy and myotonic dystrophy using data from the Swedish National registers.

METHODS

We performed a matched cohort study in all patients with muscular dystrophy or myotonic dystrophy born in Sweden 1950-2017 and 50 matched comparisons by sex, year of birth, and birth county per individual. The association with cancer overall and specific malignancies was estimated using stratified Cox proportional hazard models.

RESULTS

We identified 2,355 and 1,968 individuals with muscular dystrophy and myotonic dystrophy, respectively. No increased overall cancer risk was found in muscular dystrophy. However, we observed an increased risk of astrocytomas and other gliomas during childhood (hazard ratio [HR] 8.70, 95% CI 3.57-21.20) and nonthyroid endocrine cancer (HR 2.35, 95% CI 1.03-5.34) and pancreatic cancer (HR 4.33, 95% CI 1.55-12.11) in adulthood. In myotonic dystrophy, we found an increased risk of pediatric brain tumors (HR 3.23, 95% CI 1.16-9.01) and an increased overall cancer risk in adults (HR 2.26, CI 1.92.2.66), specifically brain tumors (HR 10.44, 95% CI 7.30-14.95), thyroid (HR 3.92, 95% CI 1.70-9.03), and nonthyroid endocrine cancer (HR 7.49, 95% CI 4.47-12.56), endometrial (HR 8.32, 95% CI 4.22-16.40), ovarian (HR 4.00, 95% CI 1.60-10.01), and nonmelanoma skin cancer (HR 3.27, 95% CI 1.32-8.13).

DISCUSSION

Here, we analyze the cancer risk spectrum of patients with muscular dystrophy and myotonic dystrophy. To the best of our knowledge, this is the first report of an increased risk for CNS tumors in childhood and adult nonthyroid endocrine and pancreatic cancer in muscular dystrophy. Furthermore, for myotonic dystrophy, we confirmed previously reported associations with cancer and expanded the cancer spectrum, finding an unreported increased risk for nonthyroid endocrine cancer. Additional studies confirming the cancer risk and delineating the cancer spectrum in different genetic subtypes of muscular dystrophies are warranted before considering altered cancer screening recommendations than for the general population.

Cultural adaptation, validity and reliability of the Turkish version of north star ambulatory assessment

PURPOSE

The North Star Ambulatory Assessment (NSAA) is a functional motor outcome measure originally developed for patients with Duchenne muscular dystrophy (DMD). The aim of this study was to perform the cultural adaptation and investigate the validity and reliability of the Turkish version of the NSAA (T-NSAA) in DMD.

METHODS

After translation process, internal consistency, interrater and test-retest reliability of the NSAA were determined by using the Cronbach Alpha Coefficient and Intraclass Correlation Coefficient (ICC), respectively. Absolute reliability was determined by using the Standard Error of Measurement (SEM) with minimal detectable change at 95% limits of confidence (MDC95). Lower limb functionality of children was evaluated by Vignos Lower Extremity Scale (VLERS). To establish convergent validity, the correlations between T-NSAA and Motor Function Measure (MFM-32), 6-minute walk test (6-MWT), and VLERS were analyzed by using the Spearman's correlation coefficient.

RESULTS

The study was completed with 86 patients with DMD whose age were mean 104.56 ± 24.66 months. The internal consistency (Cronbach's α = 0.94), intra-reliability (ICC = 0.977) and inter-reliability (ICC = 0.972) of T-NSAA were excellent. SEM and MDC values were low indicating satisfactory absolute agreement (< %10). The T-NSAA had strong correlations with the MFM-total score, 6-MWT, and VLERS (p < 0.01).

CONCLUSION

T-NSAA is a valid and reliable tool to assess ambulatory status of Turkish-speaking DMD population.

CLINICAL TRIAL NUMBER

NCT05549999, Date of registration: September 19, 2022.

The Gut Microbiota Involvement in the Panorama of Muscular Dystrophy Pathogenesis

Muscular dystrophies (MDs) are genetically heterogeneous diseases characterized by primary skeletal muscle atrophy. The collapse of muscle structure and irreversible degeneration of tissues promote the occurrence of comorbidities, including cardiomyopathy and respiratory failure. Mitochondrial dysfunction leads to inflammation, fibrosis, and adipogenic cellular infiltrates that exacerbate the symptomatology of MD patients. Gastrointestinal disorders and metabolic anomalies are common in MD patients and may be determined by the interaction between the intestine and its microbiota. Therefore, the gut-muscle axis is one of the actors involved in the spread of inflammatory signals to all muscles. In this review, we aim to examine in depth how intestinal dysbiosis can modulate the metabolic state, the immune response, and mitochondrial biogenesis in the course and progression of the most investigated MDs such as Duchenne Muscular Dystrophy (DMD) and Myotonic Dystrophy (MD1), to better identify gut microbiota metabolites working as therapeutic adjuvants to improve symptoms of MD.

Size-reduced DREADD derivatives for AAV-assisted multimodal chemogenetic control of neuronal activity and behavior

Designer receptors exclusively activated by designer drugs (DREADDs) are engineered G-protein-coupled receptors that afford reversible manipulation of neuronal activity in vivo. Here, we introduce size-reduced DREADD derivatives miniDq and miniDi, which inherit the basic receptor properties from the Gq-coupled excitatory receptor hM3Dq and the Gi-coupled inhibitory receptor hM4Di, respectively, while being approximately 30% smaller in size. Taking advantage of the compact size of the receptors, we generated an adeno-associated virus (AAV) vector carrying both miniDq and the other DREADD family receptor (κ-opioid receptor-based inhibitory DREADD [KORD]) within the maximum AAV capacity (4.7 kb), allowing us to modulate neuronal activity and animal behavior in both excitatory and inhibitory directions using a single viral vector. We confirmed that expressing miniDq, but not miniDi, allowed activation of striatum activity in the cynomolgus monkey (Macaca fascicularis). The compact DREADDs may thus widen the opportunity for multiplexed interrogation and/or intervention in neuronal regulation in mice and non-human primates.

Suppressing PDGFRβ Signaling Enhances Myocyte Fusion to Promote Skeletal Muscle Regeneration

Muscle cell fusion is critical for forming and maintaining multinucleated myotubes during skeletal muscle development and regeneration. However, the molecular mechanisms directing cell-cell fusion are not fully understood. Here, we identify platelet-derived growth factor receptor beta (PDGFRβ) signaling as a key modulator of myocyte fusion in adult muscle cells. Our findings demonstrate that genetic deletion of Pdgfrβ enhances muscle regeneration and increases myofiber size, whereas PDGFRβ activation impairs muscle repair. Inhibition of PDGFRβ activity promotes myonuclear accretion in both mouse and human myotubes, whereas PDGFRβ activation stalls myotube development by preventing cell spreading to limit fusion potential. Transcriptomics analysis show that PDGFRβ signaling cooperates with TGFβ signaling to direct myocyte size and fusion. Mechanistically, PDGFRβ signaling requires STAT1 activation, and blocking STAT1 phosphorylation enhances myofiber repair and size during regeneration. Collectively, PDGFRβ signaling acts as a regenerative checkpoint and represents a potential clinical target to rapidly boost skeletal muscle repair.

Aligning with the 3Rs: alternative models for research into muscle development and inherited myopathies

Inherited and acquired muscle diseases are an important cause of morbidity and mortality in human medical and veterinary patients. Researchers use models to study skeletal muscle development and pathology, improve our understanding of disease pathogenesis and explore new treatment options. Experiments on laboratory animals, including murine and canine models, have led to huge advances in congenital myopathy and muscular dystrophy research that have translated into clinical treatment trials in human patients with these debilitating and often fatal conditions. Whilst animal experimentation has enabled many significant and impactful discoveries that otherwise may not have been possible, we have an ethical and moral, and in many countries also a legal, obligation to consider alternatives. This review discusses the models available as alternatives to mammals for muscle development, biology and disease research with a focus on inherited myopathies. Cell culture models can be used to replace animals for some applications: traditional monolayer cultures (for example, using the immortalised C2C12 cell line) are accessible, tractable and inexpensive but developmentally limited to immature myotube stages; more recently, developments in tissue engineering have led to three-dimensional cultures with improved differentiation capabilities. Advances in computer modelling and an improved understanding of pathogenetic mechanisms are likely to herald new models and opportunities for replacement. Where this is not possible, a 3Rs approach advocates partial replacement with the use of less sentient animals (including invertebrates (such as worms Caenorhabditis elegans and fruit flies Drosophila melanogaster) and embryonic stages of small vertebrates such as the zebrafish Danio rerio) alongside refinement of experimental design and improved research practices to reduce the numbers of animals used and the severity of their experience. An understanding of the advantages and disadvantages of potential models is essential for researchers to determine which can best facilitate answering a specific scientific question. Applying 3Rs principles to research not only improves animal welfare but generates high-quality, reproducible and reliable data with translational relevance to human and animal patients.

A germline PAF1 paralog complex ensures cell type-specific gene expression

Animal germline development and fertility rely on paralogs of general transcription factors that recruit RNA polymerase II to ensure cell type-specific gene expression. It remains unclear whether gene expression processes downstream from such paralog-based transcription is distinct from that of canonical RNA polymerase II genes. In Drosophila, the testis-specific TBP-associated factors (tTAFs) activate over a thousand spermatocyte-specific gene promoters to enable meiosis and germ cell differentiation. Here, we show that efficient termination of tTAF-activated transcription relies on testis-specific paralogs of canonical polymerase-associated factor 1 complex (PAF1C) proteins, which form a testis-specific PAF1C (tPAF). Consequently, tPAF mutants show aberrant expression of hundreds of downstream genes due to read-in transcription. Furthermore, tPAF facilitates expression of Y-linked male fertility factor genes and thus serves to maintain spermatocyte-specific gene expression. Consistently, tPAF is required for the segregation of meiotic chromosomes and male fertility. Supported by comparative in vivo protein interaction assays, we provide a mechanistic model for the functional divergence of tPAF and the PAF1C and identify transcription termination as a developmentally regulated process required for germline-specific gene expression.

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

BACKGROUND

Cytosolic 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.

METHODS

Given 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.

RESULTS

In 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.

CONCLUSIONS

Our study adds new knowledge to the understanding of muscle calcium regulation in normal and dystrophic canines.

Iron homeostasis and ferroptosis in human diseases: mechanisms and therapeutic prospects

Iron, an essential mineral in the body, is involved in numerous physiological processes, making the maintenance of iron homeostasis crucial for overall health. Both iron overload and deficiency can cause various disorders and human diseases. Ferroptosis, a form of cell death dependent on iron, is characterized by the extensive peroxidation of lipids. Unlike other kinds of classical unprogrammed cell death, ferroptosis is primarily linked to disruptions in iron metabolism, lipid peroxidation, and antioxidant system imbalance. Ferroptosis is regulated through transcription, translation, and post-translational modifications, which affect cellular sensitivity to ferroptosis. Over the past decade or so, numerous diseases have been linked to ferroptosis as part of their etiology, including cancers, metabolic disorders, autoimmune diseases, central nervous system diseases, cardiovascular diseases, and musculoskeletal diseases. Ferroptosis-related proteins have become attractive targets for many major human diseases that are currently incurable, and some ferroptosis regulators have shown therapeutic effects in clinical trials although further validation of their clinical potential is needed. Therefore, in-depth analysis of ferroptosis and its potential molecular mechanisms in human diseases may offer additional strategies for clinical prevention and treatment. In this review, we discuss the physiological significance of iron homeostasis in the body, the potential contribution of ferroptosis to the etiology and development of human diseases, along with the evidence supporting targeting ferroptosis as a therapeutic approach. Importantly, we evaluate recent potential therapeutic targets and promising interventions, providing guidance for future targeted treatment therapies against human diseases.

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.

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.

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.

In Vivo Raman Spectroscopy of Muscle Is Highly Sensitive for Detection of Healthy Muscle and Highly Specific for Detection of Disease

Raman spectroscopy of muscle provides a molecular fingerprint to identify the disease. Previous work has demonstrated effectiveness in differentiating between two groups of equal sizes (e.g., healthy vs disease) but imbalanced multiclass scenarios are more common in medicine. We performed in vivo Raman spectroscopy in a total of 151 mice across four different histopathologies (healthy, acute myopathy, chronic myopathy, neurogenic), with variable numbers in each (class "imbalance"). Using hierarchical modeling and synthetic data generation, we demonstrate high sensitivity (94%) for detection of healthy muscle and high specificity (≥97%) for disease. Further, we demonstrate the potential for unique biomarker development by demonstrating variations in the protein structure across different pathologies. The findings demonstrate the potential of Raman spectroscopy to provide accurate disease identification and unique molecular insights.

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.

Pig models for translational Duchenne muscular dystrophy research

Duchenne muscular dystrophy (DMD) is caused by mutations in the X-linked DMD gene, resulting in the absence of dystrophin, progressive muscle degeneration, and heart failure. Genetically tailored pig models resembling human DMD mutations recapitulate the biochemical, clinical, and pathological hallmarks of DMD with an accelerated disease progression compared to human patients. DMD pigs have been used to evaluate therapeutic concepts such as gene editing to reframe a disrupted DMD reading frame or the delivery of artificial chromosome vectors carrying the complete DMD gene. Moreover, DMD pigs have been instrumental in validating new diagnostic modalities such as multispectral optoacoustic tomography (MSOT) for non-invasive monitoring of disease progression. DMD pigs may thus help to bridge the gap between proof-of-concept studies in cellular or rodent models and clinical studies in patients.

Utilization of Multi-Parametric Quantitative Magnetic Resonance Imaging in the Early Diagnosis of Duchenne Muscular Dystrophy

BACKGROUND

It is challenging to diagnose suspected Duchenne muscular dystrophy (DMD) patients in the very early stage of the disease. More evidence is needed to demonstrate the potential of quantitative MRI (qMRI) in precisely identifying patients before substantial physical decline occurs.

PURPOSE

To assess the early diagnostic performance of multi-parametric qMRI for DMD patients, and the ability to identify DMD patients with mild functional decline.

STUDY TYPE

Prospective.

SUBJECTS

One hundred and forty DMD subjects (9.0 ± 2.2 years old), 24 male healthy controls (HCs) (9.2 ± 2.5 years old).

FIELD STRENGTH/SEQUENCE

3.0 T/3-point Dixon, T1-mapping, and T2-mapping.

ASSESSMENT

qMRI measurements (fat fraction [FF], T1, and T2) of 11 thigh muscles (rectus femoris [RF], vastus lateralis [VL], vastus intermedius, vastus medialis, gracilis, sartorius, adductor longus, adductor magnus [AM], semitendinosus, semimembranosus, biceps femoris long head [BFLH]) on the right side were conducted. NorthStar ambulatory assessment (NSAA) score used to evaluate the function of DMD patients and divided them into three subgroups: mild (76-100 score), moderate (51-75 score), and severe (0-50 score) functional decline.

STATISTICAL TESTS

Independent t-test, ANOVA analysis, and receiver operating characteristic (ROC) curves. A P-value <0.05 was considered statistically significant.

RESULTS

Compared with HCs, FF and T2 were significantly higher in the group of all DMD patients, while T1 was significantly lower. The combination of T1 and T2 in RF, VL, AM, and BFLH achieved excellent area under curve (AUCs) (0.967-0.992) in differentiating five DMD patients without abnormal fat infiltration from HCs. Overall, T2 reached higher AUCs than FF and T1 in distinguishing DMD with mild functional decline from HCs, whereas FF achieved higher AUCs than T1 and T2 in distinguishing three DMD subgroups with functional decline.

DATA CONCLUSION

Multi-parametric qMRI demonstrate effective diagnostic capabilities for DMD patients in the early stage of the disease, and can identify patients with mild physical decline.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 3.

In dystrophic mdx hindlimb muscles where fibrosis is limited, versican haploinsufficiency transiently improves contractile function without reducing inflammation

Versican is increased with inflammation and fibrosis, and is upregulated in Duchenne muscular dystrophy. In fibrotic diaphragm muscles from dystrophic mdx mice, genetic reduction of versican attenuated macrophage infiltration and improved contractile function. Versican is also implicated in myogenesis. Here, we investigated whether versican modulated mdx hindlimb muscle pathology, where inflammation and regeneration are increased but fibrosis is minimal. Immunohistochemistry and qRT-PCR were used to assess how fiber type and glucocorticoids (α-methylprednisolone) modify versican expression. To genetically reduce versican, female mdx and male versican haploinsufficient (hdf) mice were bred resulting in male mdx-hdf and mdx (control) pups. Versican expression, contractile function, and pathology were evaluated in hindlimb muscles. Versican immunoreactivity was greater in slow versus fast hindlimb muscles. Versican mRNA transcripts were reduced by α-methylprednisolone in soleus, but not in fast extensor digitorum longus, muscles. In juvenile (6-wk-old) mdx-hdf mice, versican expression was most robustly decreased in soleus muscles leading to improved force output and a modest reduction in fatiguability. These functional benefits were not accompanied by decreased inflammation. Muscle architecture, regeneration markers, and fiber type also did not differ between mdx-hdf mice and mdx littermates. Improvements in soleus contractile function were not retained in adult (20-wk-old) mdx-hdf mice. In conclusion, soleus muscles from juvenile mdx mice were most responsive to pharmacological or genetic approaches targeting versican; however, the benefits of versican reduction were limited due to low fibrosis. Preclinical matrix research in dystrophy should account for muscle phenotype (including age) and the interdependence between inflammation and fibrosis. NEW & NOTEWORTHY The proteoglycan versican is upregulated in muscular dystrophy. In fibrotic diaphragm muscles from mdx mice, versican reduction attenuated macrophage infiltration and improved performance. Here, in hindlimb muscles from 6- and 20-wk-old mdx mice, where pathology is mild, versican reduction did not decrease inflammation and contractile function improvements were limited to juvenile mice. In dystrophic mdx muscles, the association between versican and inflammation is mediated by fibrosis, demonstrating interdependence between the immune system and extracellular matrix.

Hotspots and trends in satellite cell research in muscle regeneration: A bibliometric visualization and analysis from 2010 to 2023

Background

The incidence of muscle atrophy or sports injuries is increasing with time and population aging, thereby attracting considerable attention to muscle generation research. Muscle satellite cells, which play an important role in this process, lack comprehensive literature regarding their use for muscle regeneration. Hence, this study aimed to analyze the hotspots and trends in satellite cell research from 2010 to 2023, providing a reference for muscle regeneration research.

Methods

Studies on satellite cells' role in muscle regeneration from 2010 to 2023 were retrieved from the Web of Science Core Collection. Using CiteSpace and VOSviewer, we analyzed annual publications, authors and co-citing authors, countries and institutions, journals and co-citing journals, co-citing references, and keywords.

Results

From 2010 to 2023, 1468 papers were retrieved, indicating an overall increasing trend in the number of annual publications related to satellite cells in muscle regeneration. The United States had the highest number of publications, while the Institut National de la Santé et de la Recherche Médicale was the institution with the most publications. Among journals, " PloS One" had the highest number of published papers, and "Cell" emerged as the most co-cited journal. A total of 7425 authors were involved, with Michael A. Rudnicki being the author with the highest number of publications and the most co-cited author. The most cited reference was "Satellite cells and the muscle stem cell niche." Among keywords, "satellite cells" was the most common, with "heterogeneity" having the highest centrality. Frontier themes included "Duchenne muscular dystrophy," "skeletal muscle," "in-vivo," "muscle regeneration," "mice," "muscle atrophy," "muscle fibers," "inflammation," " mesenchymal stem cells," and "satellite cell."

Conclusion

This study presents the current status and trends in satellite cell research on muscle regeneration from 2010 to 2023 using bibliometric analyses, providing valuable insights into numerous future research directions.

Effect of Oral Zinc Supplementation on Phase Angle and Bioelectrical Impedance Vector Analysis in Duchenne Muscular Dystrophy: A Non-Randomized Clinical Trial

Zinc plays a crucial role in cell structure and functionality. Neurodegenerative Duchenne muscular dystrophy (DMD) alters muscle membrane structure, leading to a loss of muscle mass and strength. The objective of this study was to evaluate the changes in phase angle (PA) and bioelectrical impedance vector analysis (BIVA) results in patients with DMD after oral zinc supplementation. This clinical trial included 33 boys aged 5.6 to 24.5 years diagnosed with DMD. They were divided into three groups according to age (G1, G2, and G3) and supplemented with oral zinc. The mean serum zinc concentration was 74 μg/dL, and 29% of patients had concentrations below the reference value. The baseline values (mean (standard deviation)) of the bioelectrical impedance parameters PA, resistance (R), and reactance (Xc) were 2.59° (0.84°), 924.36 (212.31) Ω, and 39.64 (8.41) Ω, respectively. An increase in R and a decrease in PA and lean mass proportional to age were observed, along with a negative correlation (r = -0.614; p < 0.001) between age and PA. The average cell mass in G1 was greater than that in G3 (p = 0.012). There were no significant differences in serum zinc levels or bioelectrical impedance parameters before and after zinc supplementation. We conclude that this population is at risk of zinc deficiency and the proposed dosage of zinc supplementation was not sufficient to alter serum zinc levels, PA and BIVA results.

Lower Healthcare Access and Its Association With Individual Factors and Health-Related Quality of Life in Adults With Rare Diseases in Switzerland

Objectives

This study aims to determine clusters of access to healthcare among adults with rare diseases in Switzerland, identify associated individual characteristics of access, and impact on health-related quality of life (HRQoL).

Methods

Swiss adults (N = 341) diagnosed with a rare disease completed an online survey including the Perception of Access to Healthcare Questionnaire (PAHQ) and Short Form Health Survey (SF-12). We employed partition around medoids algorithm to identify patient clusters based on the PAHQ. Various sociodemographic/disease-related factors and HRQoL were assessed.

Results

We identified two patient clusters: higher (n = 227) and lower access (n = 114). Significantly associated with lower access were an unstable disease course (p < 0.05), increased number of misdiagnoses (p < 0.05), and diseases affecting the nervous system (p < 0.01). Membership in the lower access cluster was significantly associated with worse HRQoL (p < 0.05).

Conclusion

Findings highlight the need for comprehensive assessment of healthcare access in adults with rare diseases and identifies potential targets for tailored interventions.

Therapeutic targeting of RNA for neurological and neuromuscular disease

Neurological and neuromuscular diseases resulting from familial, sporadic, or de novo mutations have devasting personal, familial, and societal impacts. As the initial product of DNA transcription, RNA transcripts and their associated ribonucleoprotein complexes provide attractive targets for modulation by increasing wild-type or blocking mutant allele expression, thus relieving downstream pathological consequences. Therefore, it is unsurprising that many existing and under-development therapeutics have focused on targeting disease-associated RNA transcripts as a frontline drug strategy for these genetic disorders. This review focuses on the current range of RNA targeting modalities using examples of both dominant and recessive neurological and neuromuscular diseases.

The bench to bedside journey of tricyclo-DNA antisense oligonucleotides for the treatment of Duchenne muscular dystrophy

The development of antisense oligonucleotide (ASO)-based therapeutics has made tremendous progress over the past few years, in particular for the treatment of neuromuscular disorders such as Duchenne muscular dystrophy and spinal muscular atrophy. Several ASO drugs have now reached market approval for these diseases and many more are currently under clinical evaluation. Among them, ASOs made of the tricyclo-DNA originally developed by Christian Leumann have shown particularly interesting properties and demonstrated promise for the treatment of Duchenne muscular dystrophy. In this review, we examine the bench to bedside journey of tricyclo-DNA-ASOs from their early preclinical evaluation as fully phosphorotiated-ASOs to the latest generation of lipid-conjugated-ASOs. Finally we discuss the remaining challenges of ASO-mediated exon-skipping therapy for DMD and future perspectives for this promising chemistry of ASOs.

Distribution of MRI-derived T2 values as a biomarker for in vivo rapid screening of phenotype severity in mdx mice

BACKGROUND

The pathology in Duchenne muscular dystrophy (DMD) is characterized by degenerating muscle fibers, inflammation, fibro-fatty infiltrate, and edema, and these pathological processes replace normal healthy muscle tissue. The mdx mouse model is one of the most commonly used preclinical models to study DMD. Mounting evidence has emerged illustrating that muscle disease progression varies considerably in mdx mice, with inter-animal differences as well as intra-muscular differences in pathology in individual mdx mice. This variation is important to consider when conducting assessments of drug efficacy and in longitudinal studies. We developed a magnetic resonance imaging (MRI) segmentation and analysis pipeline to rapidly and non-invasively measure the severity of muscle disease in mdx mice.

METHODS

Wildtype and mdx mice were imaged with MRI and T2 maps were obtained axially across the hindlimbs. A neural network was trained to rapidly and semi-automatically segment the muscle tissue, and the distribution of resulting T2 values was analyzed. Interdecile range and Pearson Skew were identified as biomarkers to quickly and accurately estimate muscle disease severity in mice.

RESULTS

The semiautomated segmentation tool reduced image processing time approximately tenfold. Measures of Pearson skew and interdecile range based on that segmentation were repeatable and reflected muscle disease severity in healthy wildtype and diseased mdx mice based on both qualitative observation of images and correlation with Evans blue dye uptake.

CONCLUSION

Use of this rapid, non-invasive, semi-automated MR image segmentation and analysis pipeline has the potential to transform preclinical studies, allowing for pre-screening of dystrophic mice prior to study enrollment to ensure more uniform muscle disease pathology across treatment groups, improving study outcomes.

The cryptic complex rearrangements involving the DMD gene: etiologic clues about phenotypical differences revealed by optical genome mapping

BACKGROUND

Deletion or duplication in the DMD gene is one of the most common causes of Duchenne and Becker muscular dystrophy (DMD/BMD). However, the pathogenicity of complex rearrangements involving DMD, especially segmental duplications with unknown breakpoints, is not well understood. This study aimed to evaluate the structure, pattern, and potential impact of rearrangements involving DMD duplication.

METHODS

Two families with DMD segmental duplications exhibiting phenotypical differences were recruited. Optical genome mapping (OGM) was used to explore the cryptic pattern of the rearrangements. Breakpoints were validated using long-range polymerase chain reaction combined with next-generation sequencing and Sanger sequencing.

RESULTS

A multi-copy duplication involving exons 64-79 of DMD was identified in Family A without obvious clinical symptoms. Family B exhibited typical DMD neuromuscular manifestations and presented a duplication involving exons 10-13 of DMD. The rearrangement in Family A involved complex in-cis tandem repeats shown by OGM but retained a complete copy (reading frame) of DMD inferred from breakpoint validation. A reversed insertion with a segmental repeat was identified in Family B by OGM, which was predicted to disrupt the normal structure and reading frame of DMD after confirming the breakpoints.

CONCLUSIONS

Validating breakpoint and rearrangement pattern is crucial for the functional annotation and pathogenic classification of genomic structural variations. OGM provides valuable insights into etiological analysis of DMD/BMD and enhances our understanding for cryptic effects of complex rearrangements.

High mobility group box 1 (HMGB1) is a potential disease biomarker in cell and mouse models of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disorder affecting 1:3500 male births and is associated with myofiber degeneration, regeneration, and inflammation. Glucocorticoid treatments have been the standard of care due to immunomodulatory/immunosuppressive properties but novel genetic approaches, including exon skipping and gene replacement therapy, are currently being developed. The identification of additional biomarkers to assess DMD-related inflammatory responses and the potential efficacy of these therapeutic approaches are thus of critical importance. The current study uses RNA sequencing of skeletal muscle from two mdx mouse models to identify high mobility group box 1 (HMGB1) as a candidate biomarker potentially contributing to DMD-related inflammation. HMGB1 protein content was increased in a human iPSC-derived skeletal myocyte model of DMD and microdystrophin treatment decreased HMGB1 back to control levels. In vivo, HMGB1 protein levels were increased in vehicle treated B10-mdx skeletal muscle compared to B10-WT and significantly decreased in B10-mdx animals treated with adeno-associated virus (AAV)-microdystrophin. However, HMGB1 protein levels were not increased in D2-mdx skeletal muscle compared to D2-WT, demonstrating a strain-specific difference in DMD-related immunopathology.

Reduction of Mitochondrial Calcium Overload via MKT077-Induced Inhibition of Glucose-Regulated Protein 75 Alleviates Skeletal Muscle Pathology in Dystrophin-Deficient mdx Mice

Duchenne muscular dystrophy is secondarily accompanied by Ca2+ excess in muscle fibers. Part of the Ca2+ accumulates in the mitochondria, contributing to the development of mitochondrial dysfunction and degeneration of muscles. In this work, we assessed the effect of intraperitoneal administration of rhodacyanine MKT077 (5 mg/kg/day), which is able to suppress glucose-regulated protein 75 (GRP75)-mediated Ca2+ transfer from the sarcoplasmic reticulum (SR) to mitochondria, on the Ca2+ overload of skeletal muscle mitochondria in dystrophin-deficient mdx mice and the concomitant mitochondrial dysfunction contributing to muscle pathology. MKT077 prevented Ca2+ overload of quadriceps mitochondria in mdx mice, reduced the intensity of oxidative stress, and improved mitochondrial ultrastructure, but had no effect on impaired oxidative phosphorylation. MKT077 eliminated quadriceps calcification and reduced the intensity of muscle fiber degeneration, fibrosis level, and normalized grip strength in mdx mice. However, we noted a negative effect of MKT077 on wild-type mice, expressed as a decrease in the efficiency of mitochondrial oxidative phosphorylation, SR stress development, ultrastructural disturbances in the quadriceps, and a reduction in animal endurance in the wire-hanging test. This paper discusses the impact of MKT077 modulation of mitochondrial dysfunction on the development of skeletal muscle pathology in mdx mice.

Structure-Activity Relationship of Antibody-Oligonucleotide Conjugates: Evaluating Bioconjugation Strategies for Antibody-Phosphorodiamidate Morpholino Oligomer Conjugates for Drug Development

Antibody-oligonucleotide conjugates (AOCs) are promising treatments for Duchenne muscular dystrophy (DMD). They work via induction of exon skipping and restoration of dystrophin protein in skeletal and heart muscles. The structure-activity relationships (SARs) of AOCs comprising antibody-phosphorodiamidate morpholino oligomers (PMOs) depend on several aspects of their component parts. We evaluate the SAR of antimouse transferrin receptor 1 antibody (αmTfR1)-PMO conjugates: cleavable and noncleavable linkers, linker location on the PMO, and the impact of drug-to-antibody ratios (DARs) on plasma pharmacokinetics (PK), oligonucleotide delivery to tissues, and exon skipping. AOCs containing a stable linker with a DAR9.7 were the most effective PMO delivery vehicles in preclinical studies. We demonstrate that αmTfR1-PMO conjugates induce dystrophin protein restoration in the skeletal and heart muscles of mdx mice. Our results show that αmTfR1-PMO conjugates are a potentially effective approach for the treatment of DMD.

An engineered AAV targeting integrin alpha V beta 6 presents improved myotropism across species

Current adeno-associated virus (AAV) gene therapy using nature-derived AAVs is limited by non-optimal tissue targeting. In the treatment of muscular diseases (MD), high doses are often required but can lead to severe adverse effects. Here, we rationally design an AAV capsid that specifically targets skeletal muscle to lower treatment doses. We computationally integrate binding motifs of human integrin alphaV beta6, a skeletal muscle receptor, into a liver-detargeting capsid. Designed AAVs show higher productivity and superior muscle transduction compared to their parent. One variant, LICA1, demonstrates comparable muscle transduction to other myotropic AAVs with reduced liver targeting. LICA1's myotropic properties are observed across species, including non-human primate. Consequently, LICA1, but not AAV9, effectively delivers therapeutic transgenes and improved muscle functionality in two mouse MD models (male mice) at a low dose (5E12 vg/kg). These results underline the potential of our design method for AAV engineering and LICA1 variant for MD gene therapy.

Splice-switching antisense oligonucleotide controlling tumor suppressor REST is a novel therapeutic medicine for neuroendocrine cancer

RNA splicing regulation has revolutionized the treatment of challenging diseases. Neuroendocrine cancers, including small cell lung cancer (SCLC) and neuroendocrine prostate cancer (PCa), are highly aggressive, with metastatic neuroendocrine phenotypes, leading to poor patient outcomes. We investigated amido-bridged nucleic acid (AmNA)-based splice-switching oligonucleotides (SSOs) targeting RE1-silencing transcription factor (REST) splicing as a novel therapy. We designed AmNA-based SSOs to alter REST splicing. Tumor xenografts were generated by subcutaneously implanting SCLC or PCa cells into mice. SSOs or saline were intraperitoneally administered and tumor growth was monitored. Blood samples were collected from mice after SSO administration, and serum alanine aminotransferase and aspartate aminotransferase levels were measured to assess hepatotoxicity using a biochemical analyser. In vitro, REST_SSO reduced cancer cell viability. In a tumor xenograft model, it exhibited significant antitumor effects. It repressed REST-controlled RE1-harboring genes and upregulated miR-4516, an SCLC biomarker. Our findings suggest that REST_SSO suppresses tumorigenesis in neuroendocrine cancers by restoring REST function. This novel therapeutic approach holds promise for intractable neuroendocrine cancers such as SCLC and neuroendocrine PCa.

Case Report: Acute myocarditis in a patient with Duchenne muscular dystrophy

Background

Cardiovascular complications are the leading cause of death among individuals with Duchenne muscular dystrophy (DMD). However, due to the difficulty in evaluating individuals with inactive DMD, acute myocardial injury may be overlooked.

Case presentation

An 11-year-old boy with DMD presented to the emergency department with a 5-day history of persistent nasal congestion, runny nose, and cough. He was regularly taking prednisolone acetate, angiotensin-converting enzyme (ACE) inhibitors, and β-blockers for suspected DMD-associated cardiomyopathy. Upon presentation, a substantially elevated cardiac troponin I (cTnI) level of 19.8 μg/L and abnormal electrocardiogram (ECG) results were detected. Further cardiac magnetic resonance imaging (CMR) showed myocardial inflammation with localized T2 hyperintensity from the basal to middle lateral and inferior walls, as well as late gadolinium enhancement (LGE) from the basal to apical inferior lateral walls, supporting a diagnosis of acute myocarditis. Subsequently, the patient showed clinical improvement in response to combination treatment with intravenous immunoglobulin, oral prednisolone acetate, potassium chloride sustained-release tablets, anti-heart failure medication, and broad-spectrum antibiotics.

Conclusions

We report a rare case of acute myocarditis in a patient with DMD, potentially due to upper respiratory tract infection. This case highlights the importance of early myocarditis recognition and treatment in patients with DMD.

Assessing Pharmacogenomic loci Associated with the Pharmacokinetics of Vamorolone in Boys with Duchenne Muscular Dystrophy

Human genetic variation (polymorphisms) in genes coding proteins involved in the absorption, distribution, metabolism, and elimination (ADME) of drugs can have a strong effect on drug exposure and downstream efficacy and safety outcomes. Vamorolone, a dissociative steroidal anti-inflammatory drug for treating Duchenne muscular dystrophy (DMD), primarily undergoes oxidation by CYP3A4 and CYP3A5 and glucuronidation by UDP-glucuronosyltransferases. This work assesses the pharmacokinetics (PKs) of vamorolone and sources of interindividual variability (IIV) in 81 steroid-naïve boys with DMD aged 4 to <7 years old considering the genetic polymorphisms of CYPS3A4 (CYP3A4*22, CYP3A4*1B), CYP3A5 (CYP3A5*3), and UGT1A1 (UGT1A1*60) utilizing population PK modeling. A one-compartment model with zero-order absorption (Tk0, duration of absorption), linear clearance (CL/F), and volume (V/F) describes the plasma PK data for boys with DMD receiving a wide range of vamorolone doses (0.25-6 mg/kg/day). The typical CL/F and V/F values of vamorolone were 35.8 L/h and 119 L, with modest IIV. The population Tk0 was 3.14 h yielding an average zero-order absorption rate (k0) of 1.16 mg/kg/h with similar absorption kinetics across subjects at the same vamorolone dose (i.e., no IIV on Tk0). The covariate analysis showed that none of the genetic covariates had any significant impact on the PKs of vamorolone in boys with DMD. Thus, the PKs of vamorolone is very consistent in these young boys with DMD.

Current Challenges of Using Patient-Level Claims and Electronic Health Record Data for the Longitudinal Evaluation of Duchenne Muscular Dystrophy Outcomes

INTRODUCTION

Insurance claims data and electronic health records (EHRs) have been used to characterize Duchenne muscular dystrophy (DMD) in real-world populations. The ability to assess patient-level DMD disease progression within insurance claims or EHR data infrastructures is unknown. Insurance claims and EHR data were comprehensively examined for availability and reliability of DMD outcomes that describe functional status and disease progression at the individual patient level over time.

METHODS

MarketScan Commercial and Medicaid claims, and EHR-linked Clarivate open claims datasets were examined for data measuring 54 previously identified DMD-relevant outcomes in patients with DMD. Each outcome was assigned to one of five categories: functional and clinical events, clinical measures, biomarkers, functional measures, or patient-reported outcomes (PROs). Patients were identified using published coding algorithms. Annual 5-year attrition and data availability for each outcome was determined. The ability to distinguish disease severity and identify test results was also considered where applicable.

RESULTS

A total of 1964 (MarketScan Commercial), 2007 (MarketScan Medicaid), and 10,639 (Clarivate) patients were identified. At 5 years, 31.7%, 35.1%, and 59.1% of patients remained in MarketScan Commercial, MarketScan Medicaid, and Clarivate, respectively. Claims were available for five of six functional and clinical events, with 45.5% (MarketScan Commercial), 48.0% (Clarivate), and 48.5% (MarketScan Medicaid) of patients with ≥ 1 claim for the most frequently identified clinical event (cardiomyopathy diagnosis). No data were available to describe frequency of wheelchair use or loss of ambulation. Very limited EHR data (≤ 2% of patients) were available to indicate tests were ordered for clinical measures, biomarkers, or functional assessments. No PRO notes or scores were observed. Data existed for inferring disease severity (e.g., hospitalization for cardiomyopathy); however, it was not apparent whether these events were incident.

CONCLUSION

Insurance claims and EHR-linked open claims data are of limited utility for holistically evaluating the progression and burden of DMD in individual patients.

Health-related quality of life in 153 children with neuromuscular disorders in Latin America: is it age, functional dependence or diagnosis?

Neuromuscular diseases impact on children's health related quality of life but there is a lack of studies in Latin America that measured this construct. To respond to this need, this study aimed to explore quality of life and its relationship with age, functional dependence and specific diagnosis in children and adolescents in Latin America. A cross-sectional correlation study was carried out with 133 caregivers on children (2-18 years old) with various neuromuscular disorders. Parents reported on their children's health related quality of life through the PedsQL GCS and the PedsQL NMM. Differences in quality of life were found when comparing children with high functional dependence with those with mild dependence (p = 0.05). No significant differences were found regarding the child diagnosis. Finally, quality of life was highly correlated with the child's age, even when controlling for functional dependence differences between ages. Children and adolescents with neuromuscular show a diminished health related quality of life, not only in physical functioning but in their psychosocial functioning. Health related quality of life may vary according to the child's age and functional dependence.

Precision Genetic Therapies: Balancing Risk and Benefit in Patients with Heart Failure

PURPOSE OF REVIEW

Precision genetic medicine is evolving at a rapid pace and bears significant implications for clinical cardiology. Herein, we discuss the latest advancements and emerging strategies in gene therapy for cardiomyopathy and heart failure.

RECENT FINDINGS

Elucidating the genetic architecture of heart failure has paved the way for precision therapies in cardiovascular medicine. Recent preclinical studies and early-phase clinical trials have demonstrated encouraging results that support the development of gene therapies for heart failure arising from a variety of etiologies. In addition to the discovery of new therapeutic targets, innovative delivery platforms are being leveraged to improve the safety and efficacy of cardiac gene therapies. Precision genetic therapy represents a potentially safe and effective approach for improving outcomes in patients with heart failure. It holds promise for radically transforming the treatment paradigm for heart failure by directly targeting the underlying etiology. As this new generation of cardiovascular medicines progress to the clinic, it is especially important to carefully evaluate the benefits and risks for patients.

Transition and management of patients with Duchenne Muscular Dystrophy: a narrative review based on Italian experts' opinion and real-world experience

Objectives

Duchenne Muscular Dystrophy (DMD) is a severe, progressive, X-linked disorder resulting in muscle wasting, progressive functional loss and cardiomyopathy. Therapeutic strategies feature glucocorticoid corticosteroids plus gene therapy/stop codon read-through, plus standards of care. Prolonged survival, delayed loss of ambulation (LoA), and innovative treatment prescriptions pose new clinical challenges, including identification of new outcome measures/targets and implementation of continuity of care.

Methods

We report on the results of an Italian experts' meeting held in Rome, Italy on 20th April 2022. We aimed to: discuss challenges linked to transitioning from the ambulatory to the non-ambulatory phase, and from pediatric to adult care; collect experience on the importance of ongoing care and treatment in advanced disease stages and on the need to measure clinically relevant outcomes during disease progression after LoA.

Results

Following LoA the main management focus shifts to cardiac, respiratory, orthopaedics, nutrition and upper limbs function. More data on clinical needs, available treatments, standards of care, frequency of follow-up, and transition should be collected in order to facilitate management optimisation. Shared protocols should be developed, especially to improve patients' management in the acute setting.

Conclusions

Transition from paediatric to adult services and from the ambulatory to the non-ambulatory phase require a multidisciplinary approach and the Identification of clinically meaningful outcome measures, which should be described in long-term longitudinal studies.

Secondary mitochondrial dysfunction across the spectrum of hereditary and acquired muscle disorders

Mitochondria form a dynamic network within skeletal muscle. This network is not only responsible for producing adenosine triphosphate (ATP) through oxidative phosphorylation, but also responds through fission, fusion and mitophagy to various factors, such as increased energy demands, oxidative stress, inflammation, and calcium dysregulation. Mitochondrial dysfunction in skeletal muscle not only occurs in primary mitochondrial myopathies, but also other hereditary and acquired myopathies. As such, this review attempts to highlight the clinical and histopathologic aspects of mitochondrial dysfunction seen in hereditary and acquired myopathies, as well as discuss potential mechanisms leading to mitochondrial dysfunction and therapies to restore mitochondrial function.

Targeting histone deacetylases: Emerging applications beyond cancer

Histone deacetylases (HDACs) are a special class of hydrolase enzymes, which through epigenetic control of cellular acetylation, play regulatory roles in various processes including chromatin packing, cytokine signaling, and gene expression. Widespread influence on cell function has implicated dysregulated HDAC activity in human disease. While traditionally an oncology target, in the past decade, there has been a notable rise in inhibition strategies within several therapeutic areas beyond cancer. This review highlights advances in four of these indications, neurodegenerative disease, metabolic disorders, cardiovascular disease, and viral infections, focusing on the role of deacetylases in disease, small molecule drug discovery, and clinical progress.