Duchenne Muscular Dystrophy Research Articles

BMN 351-Induced Exon Skipping and Dystrophin Expression in Skeletal and Cardiac Muscle Lead to Preservation of Motor Function in a Mouse Model of Exon 51 Skip-Amenable Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is caused by mutations of the DMD gene that prevent the expression of functional dystrophin protein. BMN 351 is an antisense oligonucleotide (ASO) designed to induce skipping of exon 51 of dystrophin pre-mRNA and production of internally deleted but functional dystrophin. We determined whether extended-term BMN 351 dosing leads to exon skipping, dystrophin production, and improved motor function in hDMDdel52/mdx mice containing a human exon 52-deleted DMD transgene. Weekly intravenous doses of vehicle, 6 mg/kg BMN 351, or 18 mg/kg BMN 351 were administered for 25 weeks, and samples were analyzed 4 and 12 weeks post-dosing. BMN 351 produced dose-dependent exon skipping levels in the heart and quadriceps muscles, accompanied by dose-dependent increases in mean dystrophin levels of 17% to 55% 12 weeks post-dosing. Compared with vehicle-treated hDMDdel52/mdx mice, BMN 351 ameliorated DMD-related histopathologic changes in the gastrocnemius muscle and heart. Both BMN 351 doses preserved fine motor kinematics, which was worse in vehicle-treated hDMDdel52/mdx mice compared with wild-type 4 and 12 weeks post-dosing. Liver samples demonstrated findings consistent with ASO accumulation, to which mice are considered especially sensitive compared to humans and other non-clinical species. These results support further non-clinical and clinical development of BMN 351.

Targeting a Novel Site in Exon 51 with Antisense Oligonucleotides Induces Enhanced Exon Skipping in a Mouse Model of Duchenne Muscular Dystrophy.

Exon skipping with antisense oligonucleotides (ASOs) can correct disease-causing mutations of Duchenne muscular dystrophy (DMD) through RNA-targeted splice correction. This correction restores the reading frame and supports expression of near full-length dystrophin. First-generation exon 51-skipping ASOs targeted the same binding site, with limited clinical efficacy. We characterized a novel binding site within exon 51 that induced highly efficient exon skipping. A precursor ASO (AON-C12) and clinical ASO (BMN 351) were designed using 2'-O-methyl-modified phosphorothioate (2'OMePS) RNA and locked nucleic acids. hDMDdel52/mdx mice were given AON-C12 or BMN 351 for 13 weeks and evaluated for molecular and phenotypic correction of dystrophin deficiency. BMN 351 treatment induced durable, dose-dependent levels of exon skipping and dystrophin production in all muscles evaluated. In the heart, 8 weeks after the last BMN 351 dose at 18 mg/kg, exon-skipped transcripts remained at 44.3% of total, and dystrophin levels were 21.8% of wild type. BMN 351 reached higher tissue concentrations and percent exon skipping in the heart than a clinically relevant peptide-conjugated phosphorodiamidate morpholino oligomer comparator. BMN 351 also improved gait scores and clinical and anatomical muscle pathology parameters compared with vehicle-treated hDMDdel52/mdx mice. The pharmacologic activity and safety of BMN 351 warrant further nonclinical and clinical development.

Clinical and Molecular Profile of Dystrophin Gene Deletions in Eastern Morocco

Dystrophinopathies are genetic muscular disorders with recessive inheritance linked to the X chromosome due to mutations in the dystrophin gene, the <em>DMD</em> gene located in Xp21. The best-known forms are Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). Our study aims to determine the molecular profile and genotype/phenotype correlations of dystrophinopathies in the eastern region of Morocco. We report patients referred for 4 years (2020-2023) to the Medical Genetics Laboratory of the Mohammed VI University Hospital in Oujda for suspected dystrophinopathy and confirmed by a genetic study of the <em>DMD</em> gene using the PCR- Multiplex technique. A total of 15 patients were recruited. They had a mean age of 7.3 years at diagnosis, with a mean age of symptom onset of 3.37 years. Consanguinity was estimated at 46.66%, with 13.33% of familial forms. All patients have a DMD phenotype; calf hypertrophy was present in 86.66% of cases, a positive GOWERS sign, and elevated CK levels were present in all patients. Analysis of the <em>DMD</em> gene using the PCR-Multiplex technique showed that 80% of deletions are located in the central region of the gene, exon 50 being the most frequently deleted. 80% of patients had a deletion disrupting the reading frame, and the genotype/phenotype correlation in these cases was explained by the Monaco rule. The molecular analysis of the <em>DMD</em> gene is essential for accurate diagnosis, appropriate genetic counseling, and improved patient care. The PCR-Multiplex technique remains a good first-line strategy in the public health system, with a good cost/benefit ratio, enabling the detection of large deletions by analyzing the most frequently deleted exons.<strong> </strong>Dystrophinopathies represent a frequent reason for requesting genetic analysis in our practice. Multiplex PCR being a simple, rapid, non-invasive and cost-effective tool allowed us to provide a molecular description of this pathology in Eastern Morocco.

A structural genomics approach to investigate Dystrophin mutations and their impact on the molecular pathways of Duchenne muscular dystrophy

BackgroundDystrophin is a key protein encoded by the DMD gene, serves as a scaffold linking the cytoskeleton to the extracellular matrix that plays a critical role in muscle contraction, relaxation, and structural integrity. Mutations, particularly single-point amino acid substitutions, can lead to dysfunctional Dystrophin, causing muscular dystrophies, with Duchenne muscular dystrophy (DMD) being the most severe form.ObjectiveThis study aimed to evaluate the effects of 184 single-point amino acid substitutions on the structure and function of Dystrophin using computational approaches.MethodsMany computational tools were used to predict the impact of amino acid substitutions on protein stability, solubility, and function. Pathogenic potential was assessed using disease phenotype predictors and CADD scores, while allele frequency data from gnomAD contextualized mutation prevalence. Additionally, aggregation propensity, frustration analysis, and post-translational modification sites were analyzed for functional disruptions.ResultsOf the 184 substitutions analyzed, 50 were identified as deleterious, with 41 predicted to be pathogenic. Seventeen mutations were localized in the Calponin-homology (CH) 1 domain, a critical functional region of Dystrophin. Six substitutions (N26H, N26K, G47W, D98G, G109A, and G109R) were predicted to decrease protein solubility and were located in minimally frustrated regions, potentially compromising Dystrophin functionality and contributing to DMD pathogenesis.ConclusionThis study provides novel insights into the molecular mechanisms of DMD, highlighting specific mutations that disrupt Dystrophin’s solubility and function. These findings could inform future therapeutic strategies targeting Dystrophin mutations to address DMD pathogenesis.

Exon-Skipping Therapy for Duchenne Muscular Dystrophy: 30 Years Since Its Proposal and the Future of Pseudoexon Skipping

Thirty years ago, in 1995, I proposed a fundamental treatment for Duchenne Muscular Dystrophy (DMD) using antisense oligonucleotides (ASOs) to induce exon skipping and restore dystrophin expression. DMD is a progressive and fatal muscular dystrophy, and the establishment of an effective therapy has been a pressing demand among patients worldwide. Exon-skipping therapy utilizing ASOs has garnered significant attention as one of the most promising treatments for DMD, stimulating global research and development efforts in ASO technology. Two decades later, in 2016, one ASO was conditionally approved by the U.S. FDA as the first DMD treatment. This review summarizes the current status and challenges of ASO-based exon-skipping therapies for DMD and explores the prospects of pseudoexon skipping using ASOs, which holds the potential for achieving a complete cure for DMD.

The reliability and validity of the Greek version of the Pediatric Quality of Life Inventory™ 3.0 Duchenne muscular dystrophy module in children with Duchenne muscular dystrophy

The reliability and validity of the Greek version of the Pediatric Quality of Life Inventory™ 3.0 Duchenne muscular dystrophy module in children with Duchenne muscular dystrophy

Type-2 innate signals are dispensable for skeletal muscle regeneration and pathology linked to Duchenne muscular dystrophy.

Immune responses play an integral role in skeletal muscle regeneration. In the genetically inherited muscle disease Duchenne muscular dystrophy (DMD), muscle regeneration is disrupted, leading to chronic inflammation, fibrosis, and early mortality. Previously, it has been suggested that type-2 innate immune cells, particularly eosinophils and their production of IL-4, play an essential role in effective muscle regeneration after acute injury. We here re-investigate the role of eosinophils in skeletal muscle repair using mice deficient in eosinophils (ΔdblGATA), or deficient in IL-4R/IL-13R signaling through STAT6 (Stat6-/-). We show that neither deficiency has an impact on skeletal muscle regeneration in response to acute injury as quantified by fiber size, immune cell infiltration, or muscle-resident stem cell proliferation. We also investigate the role of STAT6 signaling in mdx:Stat6-/- mice, a model of DMD and, again, find that ablation of STAT6 signaling has no effect on the rate or severity of fibrotic scar formation or disease progression. In contrast to previous models, our data suggest a negligible role for eosinophils and STAT6 signaling in skeletal muscle regeneration after acute or chronic injury.

Beta-hydroxy-beta-methylbutyrate (HMB) improves daily activity and whole-body protein metabolism in Duchenne muscular dystrophy dogs: a pilot study

Duchenne muscular dystrophy (DMD) is a severe neuromuscular disease due to loss of dystrophin, leading to progressive muscle wasting and physical inactivity. In this pilot study, we studied the effect of daily supplementation of the anabolic substrate beta-hydroxy-beta-methylbutyrate (HMB) on whole body protein and amino acid kinetics using novel isotope methods and daily activity in a canine model of DMD. Six DMD dogs were administered 3 g daily of HMB or placebo for 28 days according to a randomized, placebo-controlled, double-blinded crossover design. We measured pre- and post-intervention daily activity, biochemistry markers, and whole-body amino acid kinetics. We tracked daily activity with an activity monitoring device and measured plasma creatine kinase and standard clinical biochemistry panels to monitor muscle and organ function. To calculate whole body and intracellular amino acid production, we administered in the postabsorptive state an IV stable isotope solution containing 20 amino acid tracers. We collected blood before and six times after until two hours post tracer pulse administration and measured amino acid enrichments and concentrations by LC–MS/MS, subsequently followed by (non) compartmental modeling of the decay enrichment curves. Results were expressed as mean with 95% CI. Whole body production, plasma concentrations, and intra-/extracellular compartmental analyses of various amino acids were attenuated in HMB-dosed DMD dogs. Specifically, the plasma concentration of hydroxyproline (marker of collagen breakdown) was significantly higher in the placebo group compared to the HMB group. The intra- and extracellular pool sizes and flux between the two compartments of hydroxyproline was reduced in HMB treated dogs. DMD dogs treated with HMB as compared to placebo had a respective 40% increase in exertional (play) (951 [827, 1075] versus 569 [491, 647]; p < 0.0001) and 10.5% increase in non-exertional (active) activity (15,366 [14742, 15990] versus 13,806 [13148,14466]; p = 0.0016). In addition, a 6% reduction was found in rest time after HMB supplementation compared to placebo (23,857 [23,130, 24,584], versus 25,363 [24500, 26225]; p = 0.0122). Creatine kinase was not statistically different between groups. We did not observe any adverse clinical or biochemical-related effects of HMB dosing. Daily HMB supplementation in DMD dogs can safely and positively influence protein and amino acid metabolism and improve overall daily activity.

Safety and efficacy of tamoxifen in non-ambulant patients with Duchenne muscular dystrophy: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial (TAMDMD Group B).

Most patients with Duchenne muscular dystrophy (DMD) are non-ambulant. Preserving proximal motor function is crucial, rarely studied. Tamoxifen, a selective oestrogen receptor modulator, reduced signs of muscular pathology in a DMD mouse model. Our objective was to assess the safety and efficacy of tamoxifen over 48 weeks in non-ambulant DMD patients. In this multicentre, randomised, double-blind, placebo-controlled, phase 3 trial at six European centres boys aged 10-16 years with genetically diagnosed DMD, non-ambulant and off corticosteroid treatment for ≥6 months, randomly assigned (1:1) to either 20 mg/day tamoxifen orally or placebo were included. The primary outcome was change in D2 motor function measure from baseline to week 48. Of 15 non-ambulant male patients with DMD screened, 14 were enrolled from January 24th, 2019, to January 6th, 2021. Eight patients were randomised to the treatment and six to the placebo group. The primary efficacy outcome did not differ significantly between tamoxifen and placebo (7.8 percentage points, 95 % CI, -26.82 to 11.22, p=0.359) with a trend not favouring tamoxifen. No deaths or life-threatening serious AEs occurred. Tamoxifen was safe but due to insufficient clinical evidence, it cannot be recommended as a treatment option for DMD. Trial registration: ClinicalTrials.gov (NCT03354039).

Real-world treatment and health care utilization among patients with Duchenne muscular dystrophy by race and ethnicity in a Medicaid population.

Duchenne muscular dystrophy (DMD) is a rare neuromuscular disorder, and data on the impact of patients' race on treatment outcomes and health care resource utilization are lacking. To describe the real-world treatment and health care utilization among patients with DMD, by race, in a Medicaid population. This was a retrospective cohort study of patients with DMD in the Merative Multi-State Medicaid Database between January 2017 and June 2021. Patients with DMD were identified using a validated algorithm and included male patients with at least 2 DMD diagnoses (earliest DMD diagnosis date = index date), aged 40years or younger, with at least 12 months of continuous enrollment prior to index date, and with at least 12 months (or evidence of death) following the index date were selected. Demographics, clinical characteristics, treatment utilization, and health care utilization and costs were reported by race and ethnicity in the 12-month baseline and 12-month follow-up periods. A total of 561 patients were included in the study, of which 360 (64.2%) were White, 50 (8.9%) were Black, 33 (5.9%) were Hispanic, and 118 (21.0%) were of other/unknown race and ethnicity. The median age on the index date was 16, 13, 14, and 15years among the race and ethnicity categories, respectively. In the follow-up, period clinical characteristics were similar across cohorts. Corticosteroids were the most commonly received treatment, with the highest use among Hispanic patients (73%) and lowest use among Black patients (52%). A third of patients treated with corticosteroids received deflazacort, with similar utilization across groups. Exon-skipping therapy use was rare, with 3% utilization overall, and highest use among White patients (4.2%). In both the baseline and follow-up periods, differences in health care costs were not statistically significant. White patients had the highest total costs in the follow-up period (mean [SD] = $108,895 [$346,934]) compared with $59,501 [$85,758] in the Black cohort, $61,199 [$67,021] in the Hispanic cohort, and $65,247 [$119,733] in the unknown/other cohort. Differences in total health care costs were driven by outpatient pharmacy costs, likely because of the larger proportion of White patients having a prescription for an exon-skipping therapy. Differences were seen across race and ethnicities in select clinical characteristics, DMD treatments, and health care utilization and costs in a Medicaid population.

Clinical Characteristics of Patients With Becker Muscular Dystrophy Having Pathogenic Microvariants or Duplications.

Becker muscular dystrophy (BMD) is an allelic disorder of Duchenne muscular dystrophy (DMD) in which pathogenic variants in DMD cause progressive worsening of motor dysfunction, muscle weakness and atrophy, and death due to respiratory and cardiac failure. BMD often has in-frame deletions that preserve the amino acid reading frame, but there are some cases with microvariants or duplications. In recent years, the importance of therapeutic development and care for BMD has been emphasized. Therefore, the purpose of this study was to understand the clinical characteristics of BMD patients with microvariants or duplications and to determine the genotype-phenotype relationship. The study focused on patients with pathogenic microvariants or duplications in DMD who were ambulatory after 16 years of age or had specific muscle biopsy results between June 13, 2017, and March 31, 2023. Informed consent was obtained from the patients or their surrogates. Data concerning DMD variants, muscle biopsy findings, skeletal muscle, respiratory and cardiac function, and CNS involvement were collected and analyzed statistically. Thirty-three patients with BMD had pathogenic microvariants (missense variants, nonsense variants, splice site variants, and other microvariants), and 16 patients had in-frame duplications in DMD. Many patients with microvariants had abnormal ECG findings. The effect of variant type on patient outcomes varied. Regardless of the type of microvariant, skeletal muscle and respiratory dysfunction was more severe in mutants of the cysteine-rich/C-terminal domain than in rod domain mutants. On the other hand, there was no significant difference in the complication rate of CNS disorders among the 3 domains of dystrophin. Microvariant forms, in particular, tend to vary in clinical severity according to the site of the dystrophin protein mutation rather than the type of pathogenic variant. The results of this study may be useful for genetic counseling, care, and treatment of patients with BMD.

Cardio-metabolic and cytoskeletal proteomic signatures differentiate stress hypersensitivity in dystrophin-deficient mdx mice.

Extreme heterogeneity exists in the hypersensitive stress response exhibited by the dystrophin-deficient mdx mouse model of Duchenne muscular dystrophy. Because stress hypersensitivity can impact dystrophic phenotypes, this research aimed to understand the peripheral pathways driving this inter-individual variability. Male and female mdx mice were phenotypically stratified into "stress-resistant" or "stress-sensitive" groups based on their response to two laboratory stressors. Quantitative proteomics of striated muscle revealed that stress-resistant females were most dissimilar from all other groups, with over 250 proteins differentially regulated with stress hypersensitivity. Males showed less proteomic variation with stress hypersensitivity; however, these changes were associated with pathway enrichment. In the heart, stress-sensitive males had significant enrichment of pathways related to mitochondrial ATP synthesis, suggesting that increased cardio-metabolic capacity is associated with stress hypersensitivity in male mdx mice. In both sexes, stress hypersensitivity was associated with greater expression of beta-actin-like protein 2, indicative of altered cytoskeletal organisation. Despite identifying proteomic signatures associated with stress hypersensitivity, these did not correlate with differences in the serum metabolome acutely after a stressor. These data suggest that the heterogeneity in stress hypersensitivity in mdx mice is partially driven by cytoskeletal organisation, but that sex-specific cardio-metabolic reprogramming may also underpin this phenotype. SIGNIFICANCE: Duchenne muscular dystrophy (DMD) is a fatal muscle wasting disease which is associated with a premature loss of ambulation and neurocognitive dysfunction. The hypersensitive stress response in DMD is a heterogeneous phenotype which is poorly understood. This study provided the first investigation of the peripheral mechanisms regulating the hypersensitive stress response by undertaking multi-omics analysis of phenotypically stratified mdx mice. Variations in behaviour and the striated muscle proteomic profiles suggest that cardio-metabolic remodelling and cytoskeletal organisation may contribute to this phenotype. This research offers significant insights into understanding how peripheral dystrophin deficiency relates to the cognitive abnormalities seen in patients with DMD.

A Dual Diagnosis of Okur-Chung Neurodevelopmental Syndrome and Becker Muscular Dystrophy: Inquiry Into the Lower Limits of Neurodevelopmental Functioning Attributable to Muscular Dystrophy.

This case discusses the limits of neurodevelopmental functioning attributable to Duchenne's Muscular Dystrophy (DMD) dysfunction. A 3-year-old male presented with global developmental delay, growth failure, and dysmorphic facial features. An SNP microarray revealed an interstitial duplication in exon 55 of DMD suggestive of Becker Muscular Dystrophy (BMD), but his degree of delays led to follow-up exome sequencing revealing a pathogenic CSNK2A1 variant diagnostic for Okur-Chung Neurodevelopmental Syndrome. Large cohorts predict a full-scale IQ (FSIQ) of 88.3±13.9 among all patients with BMD and 86.1±15.0 among all patients with DMD, while variants impacting the brain dystrophin isoform Dp140 are associated with FSIQ of 77.7±10.8 in BMD and 78.8±18.6 in DMD. An FSIQ one standard deviation below these expected ranges should prompt screening for alternative causes of neurodevelopmental delays, and an FSIQ two standard deviations below these ranges should prompt broad-spectrum genetic testing.

Dual pH-responsive CRISPR/Cas9 ribonucleoprotein xenopeptide complexes for genome editing.

Clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR associated (Cas) protein has been proved as a powerful tool for the treatment of genetic diseases. The Cas9 protein, when combined with single-guide RNA (sgRNA), forms a Cas9/sgRNA ribonucleoprotein (RNP) capable of targeting and editing the genome. However, the limited availability of effective carriers has restricted the broader application of CRISPR/Cas9 RNP. In this study, we evaluated dual pH-responsive amphiphilic xenopeptides (XPs) for delivering CRISPR/Cas9 RNP. These artificial lipo-XPs contain apolar cationizable lipoamino fatty acid (LAF) and polar cationizable oligoaminoethylene acid units such as succinoyl-tetraethylenepentamine (Stp) in various ratios and U-shaped topologies. The carriers were screened for functional Cas9/sgRNA RNP delivery in four different reporter cell lines, including a Duchenne muscular dystrophy (DMD) exon skipping reporter cell model. Significantly enhanced cellular uptake into HeLa cells, effective endosomal disruption in HeLa gal8-mRuby3 cells, and potent genome editing by several Cas9/sgRNA RNP complexes was observed in four different cell lines in the 5 nM sgRNA range. Comparing Cas9/sgRNA RNP complexes with Cas9 mRNA/sgRNA polyplexes in the DMD reporter cell model demonstrated similar splice site editing and high exon skipping of the two different molecular Cas9 modalities. Based on these studies, analogues of two potent U1 LAF2-Stp and LAF4-Stp2 structures were deployed, tuning the amphiphilicity of the polar Stp group by replacement with the six oligoamino acids dmGtp, chGtp, dGtp, Htp, Stt, or GEIPA. The most potent LAF2-Stp analogues (containing dGtp, chGtp or GEIPA) demonstrated further enhanced gene editing efficiency with EC50 values of 1 nM in the DMD exon skipping reporter cell line. Notably, the EC50 of LAF2-dGtp reached 0.51 nM even upon serum incubation. Another carrier (LAF4-GEIPA2) complexing Cas9/sgRNA RNP and donor DNA, facilitated up to 43 % of homology-directed repair (HDR) in HeLa eGFPd2 cells visualized by the switch from green fluorescent protein (eGFP) to blue fluorescent protein (BFP). This study presents a delivery system tunable for Cas9 RNP complexes or Cas9 RNP/donor DNA polyplexes, offering an effective and easily applicable strategy for gene editing.

Adeno-Associated Virus 8 and 9 Myofibre Type/Size Tropism Profiling Reveals Therapeutic Effect of Microdystrophin in Canines.

Adeno-associated virus (AAV) 8 and 9 are in clinical trials for treating neuromuscular diseases such as Duchenne muscular dystrophy (DMD). Muscle consists of myofibres of different types and sizes. However, little is known about the fibre type and fibre size tropism of AAV in large mammals. We evaluated fibre type- and size-specific transduction properties of AAV8 and AAV9 in 17 dogs that received systemic gene transfer (dose 1.94 ± 0.52 × 1014 vg/kg; injected at 2.86 ± 0.30 months; harvested at 20.79 ± 3.30 months). For AAV8, two DMD dogs and three carrier dogs received an alkaline phosphatase (AP) reporter vector, and five DMD dogs received a four-repeat microdystrophin (uDys) vector. For AAV9, one normal and one DMD dog received the AP vector, and five DMD dogs received a five-repeat uDys vector. Association between AAV transduction and the fibre type/size was studied in three muscles that showed mosaic transgene expression, including the biceps femoris, teres major and latissimus dorsi. Transgene expression was detected in 30%-45% of myofibres. In the AP reporter vector-injected dogs, neither AAV8 nor AAV9 showed a statistically significant fibre type preference. Interestingly, AP expression was enriched in smaller fibres. In uDys-treated DMD dogs, slow and fast myofibres were equally transduced. Notably, uDys-expressing myofibres were significantly larger than uDys-negative myofibres irrespective of the AAV serotype (p < 0.0001). In AAV8 uDys vector-injected dogs, the mini-Feret diameter was 15%, 16% and 23% larger in uDys-positive slow, fast and hybrid fibres, respectively; the cross-sectional area was 30%, 34% and 46% larger in uDys-positive slow, fast and hybrid fibres, respectively. In AAV9 uDys vector-injected dogs, the mini-Feret diameter was 12%, 13% and 25% larger in uDys-positive slow, fast and hybrid fibres, respectively; the cross-sectional area was 25%, 28% and 59% larger in uDys-positive slow, fast and hybrid fibres, respectively. Our studies suggest that AAV8 and AAV9 transduce fast and slow myofibres at equivalent efficiency. Importantly, uDys therapy effectively prevented dystrophic myofibre atrophy. Our study provides important insight into systemic muscle AAV delivery in large mammals and supports further development of uDys gene therapy for DMD.

Inhibition of hippocampal interleukin-6 receptor-evoked signalling normalises long-term potentiation in dystrophin-deficient mdx mice.

Duchenne muscular dystrophy (DMD), an X-linked neuromuscular disorder, characterised by progressive immobility, chronic inflammation and premature death, is caused by the loss of the mechano-transducing signalling molecule, dystrophin. In non-contracting cells, such as neurons, dystrophin is likely to have a functional role in synaptic plasticity, anchoring post-synaptic receptors. Dystrophin-expressing hippocampal neurons are key to cognitive functions such as emotions, learning and the consolidation of memories. In the context of disease-induced chronic inflammation, we have explored the role of the pleiotropic cytokine, interleukin (IL)-6 in hippocampal dysfunction using immunofluorescence, electrophysiology and metabolic measurements in dystrophic mdx mice. Hippocampal long-term potentiation (LTP) of the Schaffer collateral-CA1 projections was suppressed in mdx slices. Given the importance of mitochondria-generated ATP in synaptic plasticity, reduced maximal respiration in the CA1 region may impact upon this process. Consistent with a role for IL-6 in this observation, early LTP was suppressed in dystrophin-expressing wildtype slices exposed to IL-6. In dystrophic mdx mice, exposure to IL-6 suppressed mitochondrial-mediated basal metabolism in CA1, CA3 and DG hippocampal regions. Furthermore, blocking IL-6-mediated signalling by administering neutralising monoclonal IL-6 receptor antibodies intrathecally, normalised LTP in mdx mice. The impact of dystrophin loss from the hippocampus was associated with modified cellular bioenergetics, which underpin energy-driven processes such as the induction of LTP. The additional challenge of pathophysiological levels of IL-6 resulted in altered cellular bioenergetics, which may be key to cognitive deficits associated with the loss of dystrophin.

Targeting Drug Delivery System to Skeletal Muscles: A Comprehensive Review of Different Approaches.

The skeletal muscle is one of the largest organs in the body and is responsible for the mechanical activity required for posture, movement and breathing. The effects of current pharmaceutical therapies for skeletal muscle diseases are far from satisfactory; approximately 24% of Duchenne muscular dystrophy (DMD) trials have been terminated because of unsatisfactory outcomes. The lack of a skeletal muscle-targeting strategy is a major reason for these unsuccessful trials, contributing to low efficiency and severe side effects. The development of targeting strategies for skeletal muscle-specific drug delivery has shown the potential for increasing drug concentrations in the skeletal muscle, minimising off-target effects, and thereby improving the therapeutic effects of drugs. Over the past few decades, novel methods for specifically delivering cargo to skeletal muscles have been developed. In this review, we categorise targeting methods into four types: peptides, antibodies, small molecules and aptamers. Most research has focused on peptide and antibody ligands, and there are several well-established drugs in this category; however, drawbacks such as protease degradation and immunogenicity limit their use. Aptamers and small molecules have low immunogenicity and are simple to chemically produce. However, small molecule ligands generally exhibit lower affinity because of their small size and high mobility. Aptamers are promising ligands for skeletal muscle-targeting delivery systems. Additionally, if the active site of the cargo is located inside the cell, an internalisation pathway becomes necessary. The order of internalisation ligands and targeting ligands in the complex is a crucial factor, because an inappropriate order could lead to much lower targeting and internalisation efficiencies. Moreover, ligand density also merits consideration, as increasing the density of the targeting ligands may result in steric hindrance, which could impact the accessibility of the receptor and cause enlargement of the targeted ligands. More efforts are required to optimise drug delivery systems that specifically recognise skeletal muscle, with the aim of enhancing quality of life and promoting patient well-being.

Unlocking the Genetic Blueprint of Duchenne Muscular Dystrophy: A Personalized Approach with MLPA and WES

Unlocking the Genetic Blueprint of Duchenne Muscular Dystrophy: A Personalized Approach with MLPA and WES

Wearable sensors in paediatric neurology.

Wearable sensors have the potential to transform diagnosis, monitoring, and management of children who have neurological conditions. Traditional methods for assessing neurological disorders rely on clinical scales and subjective measures. The snapshot of the disease progression at a particular time point, lack of cooperation by the children during assessments, and susceptibility to bias limit the utility of these measures. Wearable sensors, which capture data continuously in natural settings, offer a non-invasive and objective alternative to traditional methods. This review examines the role of wearable sensors in various paediatric neurological conditions, including cerebral palsy, epilepsy, autism spectrum disorder, attention-deficit/hyperactivity disorder, as well as Rett syndrome, Down syndrome, Angelman syndrome, Prader-Willi syndrome, neuromuscular disorders such as Duchenne muscular dystrophy and spinal muscular atrophy, ataxia, Gaucher disease, headaches, and sleep disorders. The review highlights their application in tracking motor function, seizure activity, and daily movement patterns to gain insights into disease progression and therapeutic response. Although challenges related to population size, compliance, ethics, and regulatory approval remain, wearable technology promises to improve clinical trials and outcomes for patients in paediatric neurology.

Behavioral characterization of the mdx5cv, mdx52 and DMD-null mouse models of Duchenne muscular dystrophy.

Duchenne muscular dystrophy is a severe neuromuscular disorder, caused by mutations in the DMD gene. Normally, the DMD gene gives rise to multiple dystrophin isoforms, of which multiple are expressed in the brain. The location of the mutation determines the number of dystrophin isoforms affected, and the absence thereof leads to behavioral and cognitive impairments. Even though behavioral studies have thoroughly investigated the effects of the loss of Dp427, and to a lesser extend of Dp140, in mice, direct comparisons between models lacking multiple dystrophin isoforms are sparse. Furthermore, a behavioral characterization of the DMD-null mouse, which lacks all dystrophin isoforms, has never been undertaken. Using a wide variety of behavioral tests, we directly compared impairments between mdx5cv, mdx52 and DMD-null mice. We confirmed the role of Dp427 in emotional reactivity. We did not find any added effects of loss of Dp140 on fear, but showed the involvement of Dp140 in spontaneous behavior, specifically in habituation and activity changes due to light/dark switches. Lastly, Dp71/Dp40 seems to play an important role in many behavioral domains, including anxiety and spontaneous behavior.