Dystrophin Protein Research Articles

A mathematical model to study the role of dystrophin protein in tumor micro-environment.

In this research work, the authors have developed a mathematical model to examine the interaction between dystrophin protein and tumor. The authors formulated a system of ordinary differential equations to describe the dynamics of the dystrophin-tumor interaction system. Jacobian matrix and Routh-Hurwitz stability techniques were used to determine equilibrium points, perform stability and bifurcation analysis, and establish the conditions required for the stability of the proposed model. Numerical simulations are performed using Euler's method to investigate the temporal evolution of the proposed model under different parameter values, such as tumor growth rate and feedback strength of dystrophin protein. The numerical results are presented in tables, and corresponding to each table, a graphical analysis is done. The graphical analysis includes creating phase portraits to visually represent stability regions around the equilibrium points, bifurcation diagrams to identify critical points, and time series analysis to highlight the behavior of the proposed model. The authors explore how variations in dystrophin expression impact tumor progression, identifying potential therapeutic implications of maintaining higher dystrophin levels. This comprehensive analysis enhances our understanding of the dystrophin-tumor interaction, providing a basis for further experimental validation and potential therapeutic strategies.

Macrophages producing chondroitin sulfate proteoglycan-4 induce neuro-cardiac junction impairment in Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is caused by the absence of the full form of the dystrophin protein, which is essential for maintaining the structural integrity of muscle cells, including those in the heart and respiratory system. Despite progress in understanding the molecular mechanisms associated with DMD, myocardial insufficiency persists as the primary cause of mortality, and existing therapeutic strategies remain limited. This study investigates the hypothesis that a dysregulation of the biological communication between infiltrating macrophages (MPs) and neurocardiac junctions exists in dystrophic cardiac tissue. In a mouse model of DMD (mdx), this phenomenon is influenced by the over-release of chondroitin sulfate proteoglycan-4 (CSPG4), a key inhibitor of nerve sprouting and a modulator of the neural function, by MPs infiltrating the cardiac tissue and associated with dilated cardiomyopathy, a hallmark of DMD. Givinostat, the histone deacetylase inhibitor under current development as a clinical treatment for DMD, is effective at both restoring a physiological microenvironment at the neuro-cardiac junction and cardiac function in mdx mice in addition to a reduction in cardiac fibrosis, MP-mediated inflammation, and tissue CSPG4 content. This study provides novel insight into the pathophysiology of DMD in the heart, identifying potential new biological targets. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

In Vitro Gene Therapy Using Human iPS-Derived Mesoangioblast-Like Cells (HIDEMs) Combined with Microdystrophin (μDys) Expression as the New Strategy for Duchenne Muscular Dystrophy (DMD) Experimental Treatment

Duchenne Muscular Dystrophy (DMD) is a genetic disorder characterized by disruptions in the dystrophin gene. This study aims to investigate potential a therapeutic approach using genetically modified human iPS-derived mesoangioblast-like cells (HIDEMs) in mdx mouse model. This study utilizes patient-specific myoblasts reprogrammed to human induced pluripotent stem cells (iPSCs) and then differentiated into HIDEMs. Lentiviral vectors carrying microdystrophin sequences have been employed to deliver the genetic construct to express a shortened, functional dystrophin protein in HIDEMs. The study indicated significant changes within redox potential between healthy and pathological HIDEM cells derived from DMD patients studied by catalase and superoxide dismutase activities. Microdystrophin expressing HIDEMs also improved expression of genes involved in STARS (striated muscle activator of Rho signaling) pathway albeit in selective DMD patients (with mild phenotype). Although in vivo observations did not bring progress in the mobility of mdx mice with HIDEMs, microdystrophin interventions this may argue against “treadmill test” as suitable for assessment of mdx mice recovery. Low-level signaling of the Rho pathway and inflammation-related factors in DMD myogenic cells can also contribute to the lack of success in a functional study. Overall, this research contributes to the understanding of DMD pathogenesis and provides insights into potential novel therapeutic strategy, highlighting the importance of personalized gene therapy.

Mature cardiac tissues modeling Duchenne muscular dystrophy related cardiomyopathy

Abstract Background The major cause of mortality in patients with Duchenne muscular dystrophy (DMD) is cardiomyopathy. This disease is caused by dystrophin gene mutations that result in the loss of dystrophin protein. Gene replacement therapies have been approved for skeletal muscle symptoms of DMD. However, these therapeutic modalities are not indicated for cardiomyopathy due to their low efficiency of delivery to the heart. Despite the significant unmet needs, a limitation in this area of research is the divergence of cardiomyopathy symptoms in model animals from those in patients. Alternatively, cardiomyocytes differentiated from patient-derived iPS cells have recently been analyzed. However, existing results are based on a single time point analysis and do not model disease progression or non-cardiomyocyte involvement. Purpose Our research aims to establish an in vitro model that can reproduce the pathological progression of DMD cardiomyopathy. Methods We have generated cardiac organoids and engineered heart tissues (EHTs) from patient-derived iPS cells, consisting of cardiomyocytes and epicardial-derived non-cardiomyocytes. An iPS cell line in which the dystrophin mutation was repaired by genome editing was used as a control. The cardiac organoids or EHTs were subjected to transient activation of fatty acid metabolism to promote the maturation of iPS-derived cardiomyocytes. Pathological conditions were then induced in these 3D-models by applying loads that mimicked the DMD-disease environment. Results The mature cardiac organoids displayed adult-like gene expression profiles in the components of dystrophin-associated-protein-complex and calcium handling. After continuous mechanical loading, cell death appeared in DMD-EHTs, although there was only a slight decrease in contractility and fibrosis. Elevated mitochondrial ROS production and DNA damage were observed as a part of the cell death mechanism. Furthermore, pathological stimuli in addition to mechanical loading reproduced progressive contractile dysfunction and further increase in fibrosis in DMD-EHTs. Conclusions From these observations, we concluded that our DMD-EHT model recapitulate the pathological development of DMD-cardiomyopathy. These results suggest that the key factors involved in the progression of DMD cardiomyopathy are (i) the fragility of cardiomyocytes to stress in early stages and (ii) the involvement of non-cardiomyocytes such as fibrosis. Our model provides insight into the molecular mechanisms underlying disease progression and novel therapeutic targets.

Reduced Na current in dystrophin-deficient ventricular cardiomyocytes is rescued by tenascin-C inhibition

Abstract Background Duchenne muscular dystrophy (DMD) is an X-linked hereditary disease triggered by the deficiency of the structural protein dystrophin, which leads to muscular degeneration mainly affecting young males. Major contributors to early death in DMD patients are cardiac arrhythmias and dystrophic cardiomyopathy. One cause for arrhythmias is impaired ventricular impulse conduction, which leads to ventricular asynchrony and reentrant mechanisms. We recently showed that the disruption of dystrophin results in a significant reduction of Na current in ventricular cardiomyocytes (vCMs) of the dystrophin-deficient mdx mouse model for human DMD. Na current reduction provides a mechanistic explanation for the impaired ventricular conduction and accompanying arrhythmias in the dystrophic heart. The extracellular matrix protein tenascin-C (TN-C) is a significant remodeling factor in the injured and diseased heart and is strongly upregulated in dystrophic cardiomyopathy. To this date, it is unknown how the upregulation of TN-C in DMD patients affects dystrophic cardiomyopathy. Purpose In this study, we examined the effect of TN-C inhibition on diminished Na currents in dystrophin-deficient vCMs. Methods We compared four different mouse genotypes with each other, namely wild-type, dystrophin-deficient mdx, TN-C-deficient and dystrophin- plus TN-C-deficient mice. Furthermore, a cohort of mdx mice was injected with TN-C siRNA twice a week for 9 weeks to investigate the effect of TN-C knockdown. Hearts from adult male mice were enzymatically digested using a Langendorff system to isolate single vCMs. Na currents were then measured with the whole cell patch clamp technique. Results Na current densities were increased in TN-C deficient vCMs compared to wild-type vCMs. Accordingly, 24-hour incubation of wild-type vCMs with human recombinant TN-C resulted in a significant decrease in Na current. Na currents of vCMs from mdx mice were reduced, but restored to the wild-type level in vCMs from TN-C-deficient mdx mice. Moreover, vCMs of TN-C siRNA-treated mdx mice had significantly increased Na currents compared to control mdx vCMs. Conclusion Upregulation of TN-C in dystrophin-deficient vCMs reduces Na currents, whereas inhibition of TN-C prevents this reduction. Therefore, inhibition of TN-C in DMD patients may be considered as a potential new therapeutic strategy to improve ventricular conduction and reduce arrhythmia vulnerability.

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

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

386P Dark-adaptation visual thresholds in Duchenne muscular dystrophy patients with genetic backgrounds affecting different dystrophin proteins

386P Dark-adaptation visual thresholds in Duchenne muscular dystrophy patients with genetic backgrounds affecting different dystrophin proteins

Exonisation of an intronic L1 element in the dystrophin gene associated with X-linked muscular dystrophy in a Border Collie dog.

X-linked recessive dystrophinopathies are the most common muscular dystrophies (MDs) in humans and dogs. To date, 20 breed-specific MD-associated variants are described in the canine dystrophin gene (DMD), including one associated with dystrophin-deficient MD in the Border Collie mixed breed. Here, we report the diagnosis and follow-up of mild dystrophin-deficient MD in a 5-month-old male Border Collie, associated with a novel DMD variant. Diagnosis was based on neurological examination and laboratory evaluations including creatine kinase activity, electromyography and muscle biopsies with immunofluorescent staining. Inspection of the Sashimi plots of the RNA-seq data from the affected muscle biopsy led to the discovery of a 162-bp L1 pseudoexon in DMD intron 63, introducing a frameshift and a premature stop codon (NM_001003343.1: c.9271_9272insN[162] p.(Ala3091fs*21)). Reduced DMD mRNA levels were detected for both the non-pseudoexon (50× less) and pseudoexon (3× less) containing transcripts in the affected muscle, compared with the level of the non-pseudoexon containing transcript in a control muscle, resulting in very low dystrophin protein levels and the upregulation of utrophin. Because the variant was only found in the affected dog, not in the healthy mother and grandmother, or in 108 unrelated Border Collies from the Belgian population (46 males and 62 females), it was considered a de novo variant. Although the prognosis for dystrophinopathy is generally regarded as poor, the dog stabilised at the age of 6 months and is still clinically stable at the age of 2 years.

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

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

In Silico Structural Prediction for the Generation of Novel Performant Midi-Dystrophins Based on Intein-Mediated Dual AAV Approach.

Duchenne Muscular Dystrophy (DMD) is a pediatric disorder characterized by progressive muscle degeneration and premature death, and has no current cure. The current, most promising therapeutic avenue is based on gene replacement mediated by adeno-associated viruses (AAVs) using a shortened, but still functional, version of dystrophin, known as micro-dystrophin (µDys), to fit AAV capacity. The limited improvements observed in clinical trials suggest a sub-optimal performance of µDys in the human context that could be due to the lack of key domains in the protein. Therefore, expressing larger dystrophin proteins may be necessary for a more complete correction of the disease phenotype. In this study, we developed three novel midi-dystrophin constructs using a dual-AAV approach, leveraging split-intein-based protein trans-splicing. The midi-dystrophins include additional domains compared to µDys, such as the central cytoskeleton-binding domain, nNOS and Par1b interacting domains, and a complete C-terminal region. Given the limited capacity of each AAV vector, we strategically partially reduced hinge regions while ensuring that the structural stability of the protein remains intact. We predicted the interactions between the two halves of the split midi-Dys proteins thanks to the deep learning algorithm AphaFold3. We observed strong associations between the N- and C-termini in midi-Dys 1 and 2, while a weaker interaction in midi-Dys 3 was revealed. Our subsequent experiments confirmed the efficient protein trans-splicing both in vitro and in vivo in DBA2/mdx mice of the midi-Dys 1 and 2 and not in midi-Dys 3 as expected from the structural prediction. Additionally, we demonstrated that midi-Dys 1 and 2 exhibit significant therapeutic efficacy in DBA2/mdx mice, highlighting their potential as therapeutic agents for DMD. Overall, these findings highlight the potential of deep learning-based structural modeling for the generation of intein-based dystrophin versions and pose the basis for further investigation of these new midi-dystrophins versions for clinical studies.

Cell transplantation-mediated dystrophin supplementation efficacy in Duchenne muscular dystrophy mouse motor function improvement demonstrated by enhanced skeletal muscle fatigue tolerance

BackgroundDuchenne muscular dystrophy (DMD) is an incurable neuromuscular disease leading to progressive skeletal muscle weakness and fatigue. Cell transplantation in murine models has shown promise in supplementing the lack of the dystrophin protein in DMD muscles. However, the establishment of novel, long-term, relevant methods is needed to assess its efficiency on the DMD motor function. By applying newly developed methods, this study aimed to evaluate the functional and molecular effects of cell therapy-mediated dystrophin supplementation on DMD muscles.MethodsDystrophin was supplemented in the gastrocnemius of a 5-week-old immunodeficient DMD mouse model (Dmd-null/NSG) by intramuscular xenotransplantation of healthy human immortalized myoblasts (Hu5/KD3). A long-term time-course comparative study was conducted between wild-type, untreated DMD, and dystrophin supplemented-DMD mouse muscle functions and histology. A novel GO-ATeam2 transgenic DMD mouse model was also generated to assess in vivo real-time ATP levels in gastrocnemius muscles during repeated contractions.ResultsWe found that 10.6% dystrophin supplementation in DMD muscles was sufficient to prevent low values of gastrocnemius maximal isometric contraction torque (MCT) at rest, while muscle fatigue tolerance, assessed by MCT decline after treadmill running, was fully ameliorated in 21-week-old transplanted mice. None of the dystrophin-supplemented fibers were positive for muscle damage markers after treadmill running, with 85.4% demonstrating the utilization of oxidative metabolism. Furthermore, ATP levels in response to repeated muscle contractions tended to improve, and mitochondrial activity was significantly enhanced in dystrophin supplemented-fibers.ConclusionsCell therapy-mediated dystrophin supplementation efficiently improved DMD muscle functions, as evaluated using newly developed evaluation methods. The enhanced muscle fatigue tolerance in 21-week-old mice was associated with the preferential regeneration of damage-resistant and oxidative fibers, highlighting increased mitochondrial activity, after cell transplantation. These findings significantly contribute to a more in-depth understanding of DMD pathogenesis.

Possibility of exon skipping therapy for Duchenne muscular dystrophy in Russian patients: present and future

Background. Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy in children, that occurs between one and three years of age. DMD is caused by pathogenic and likely pathogenic variants in the DMD gene, which lead to a deficit of various isoforms of the dystrophin protein, the main protein of the muscle cytoskeleton. Drugs aimed at slowing the progression of the disease are being actively developed around the world. One of the perspective approaches to pathogenetic therapy is therapy using exon skipping. As a result of this treatment, the reading frame is restored due to the exon skipping enabling the production of truncated dystrophin.Aim. To evaluate the applicability of exon skipping therapy in Russian patients with DMD.Materials and methods. The applicability of therapy aimed at exon skipping was analyzed for a sample of 1519 patients admitted to the laboratory of DNA diagnostics of the Research Centre for Medical Genetics with a referral diagnosis of Duchenne/Becker muscular dystrophy from October 1, 2018 to September 1, 2023.Results. As a result of the study and analysis of the spectrum of mutations in the DMD gene among patients with DMD in the Russian Federation, the theoretical applicability of exon skipping therapy was assessed: for 29.3 % of patients this approach to treatment is applicable. The proportions of patients for whom existing exon skipping therapies are available were also estimated. In total, skipping of frequent exons 51, 53, 45 is applicable for 14.6 % of patients. Conclusion. One of the effective and accessible types of therapy for DMD is exon skipping. This type of therapy is mutation-specific. In this regard, the assessment of applicability will allow us to estimate the proportion of patients for whom a particular exon skipping will be available.

A - 45 Duchenne and Becker Muscular Dystrophy: Sibling Case Studies

Abstract Objective Duchenne Muscular Dystrophy (DMD) is an X-linked recessive neuromuscular condition primarily affecting males. Progressive proximal muscle wasting and weakness is seen and a shortened life span can occur due to cardiac involvement. Becker Muscular Dystrophy (BMD) is a milder form of DMD. Non-progressive cognitive impairment (e.g., lower IQ) in DMD has been well established, while the cognitive profile in BMD is less known. DMD/BMD are caused by mutations in the dystrophin protein. Research suggests that mutations downstream of exon 63 in the DMD gene are associated with poorer cognitive outcomes compared to upstream 1–30. Our cases explore the association between genetic/medical factors upon cognitive and behavioral outcomes, and neuropsychological similarities/differences between DMD and BMD. Method The current sibling case studies include one BMD set (mutations at exon 45–49) and two DMD sets (exon 61–74, and 13, respectively). They are part of a larger IRB-approved research dataset. Notably in DMD set two, the siblings have different biological fathers. Results The BMD siblings have comparable neuropsychological profiles (e.g., below average IQ, academic challenges, attention/executive problems). In DMD set one, one sibling has average intelligence with no academic challenges, while the other sibling has a low average IQ with challenges in math and spelling. In DMD set two, one sibling has intact cognitive functioning, while the other sibling performs well below average across neurocognitive domains. Conclusions Our results indicate variabilities in DMD/BMD, highlighting the contributing role of established factors (e.g., mutation location) and additional non-DMD influences (e.g., genetic contributions from biological father) to understand neuropsychological profiles.

Correction of exon 2, exon 2–9 and exons 8–9 duplications in DMD patient myogenic cells by a single CRISPR/Cas9 system

Duchenne Muscular dystrophy (DMD), a yet-incurable X-linked recessive disorder that results in muscle wasting and loss of ambulation is due to mutations in the dystrophin gene. Exonic duplications of dystrophin gene are a common type of mutations found in DMD patients. In this study, we utilized a single guide RNA CRISPR strategy targeting intronic regions to delete the extra duplicated regions in patient myogenic cells carrying duplication of exon 2, exons 2–9, and exons 8–9 in the DMD gene. Immunostaining on CRISPR-corrected derived myotubes demonstrated the rescue of dystrophin protein. Subsequent RNA sequencing of the DMD cells indicated rescue of genes of dystrophin related pathways. Examination of predicted close-match off-targets evidenced no aberrant gene editing at these loci. Here, we further demonstrate the efficiency of a single guide CRISPR strategy capable of deleting multi-exon duplications in the DMD gene without significant off target effect. Our study contributes valuable insights into the safety and efficacy of using single guide CRISPR strategy as a potential therapeutic approach for DMD patients with duplications of variable size.

Low-intensity aerobic training reduces macrophages infiltration and improves morphological characteristics of soleus skeletal muscle from mdx mice

Duchenne Muscular Dystrophy (DMD) is characterized by the absence of the dystrophin protein. The absence of this protein determines recurrent injuries in muscle tissue progressing to necrosis and generalized weakness, leading to the patient’s death due to respiratory and/or cardiac failure. There is no cure for DMD. However, some exercise programs could minimize the disease's progression. Low-intensity training has been used as a rehabilitation program for dystrophic muscles, although the effects are still unclear. This study aimed to analyze the effects of low-intensity aerobic training on the general morphological aspects of the skeletal muscle of mdx mice. Eighteen male mice were divided into three groups with six animals each: (mdx sedentary, mdx trained, and wild-type sedentary). The low-intensity training was performed on a treadmill running during the 37 sessions. After the experiments, the animals were euthanized, and the soleus muscle was excised for histological and immunofluorescence analyses. The training (37 sessions) showed an improvement intoning the morphological aspects of soleus mdx mice and a reduction of macrophage infiltration. The low-intensity training can minimize the inflammatory process and reverse morphological alteration in the soleus muscle of the 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.

A Voyage on the Role of Nuclear Factor Kappa B (NF-kB) Signaling Pathway in Duchenne Muscular Dystrophy: An Inherited Muscle Disorder.

A recessive X-linked illness called Duchenne muscular dystrophy (DMD) is characterized by increasing muscle weakening and degradation. It primarily affects boys and is one of the most prevalent and severe forms of muscular dystrophy. Mutations in the DMD gene, which codes for the essential protein dystrophin, which aids in maintaining the stability of muscle cell membranes during contraction, are the cause of the illness. Dystrophin deficiency or malfunction damages muscle cells, resulting in persistent inflammation and progressive loss of muscular mass. The pathophysiology and genetic foundation of DMD are thoroughly examined in this review paper, focusing on the function of the NF-κB signaling system in the disease's progression. An important immune response regulator, NF-κB, is aberrantly activated in DMD, which exacerbates the inflammatory milieu in dystrophic muscles. Muscle injury and fibrosis are exacerbated and muscle regeneration is hampered by the pro-inflammatory cytokines and chemokines that are produced when NF-κB is persistently activated in muscle cells. The paper also examines our existing knowledge of treatment approaches meant to inhibit the progression of disease by modifying NF-κB signaling. These include new molecular techniques, gene treatments, and pharmacological inhibitors that are intended to lessen inflammation and improve muscle healing. Furthermore covered in the analysis is the significance of supportive care for DMD patients, including physical therapy and corticosteroid treatment, in symptom management and quality of life enhancement. The article seeks to provide a thorough understanding of the mechanisms causing DMD, possible therapeutic targets, and developing treatment options by combining recent research findings. This will provide clinicians and researchers involved in DMD care and research with invaluable insights.

Failure to Resolve Inflammation Contributes to Juvenile-Onset Cardiomyopathy in a Mouse Model of Duchenne Muscular Dystrophy.

The absence of dystrophin protein causes cardiac dysfunction in boys with Duchenne Muscular Dystrophy (DMD). However, the common mouse model of DMD (B10-mdx) does not manifest cardiac deficits until late adulthood limiting our understanding of the mechanism and therapeutic approaches to target the pediatric-onset cardiac pathology in DMD. We show the mdx mouse model on the DBA/2J genetic background (D2-mdx) displays juvenile-onset cardiomyopathy. Molecular and histological analysis revealed heightened leukocyte chemotactic signaling and failure to resolve inflammation, leading to chronic inflammation and extracellular matrix (ECM) fibrosis, causing cardiac pathology in juvenile D2-mdx mice. We show that pharmacologically activating the N-formyl peptide receptor 2 (FPR2) - a receptor that physiologically resolves acute inflammation, mitigated chronic cardiac inflammation and fibrosis, and prevented juvenile onset cardiomyopathy in the D2-mdx mice. These studies offer insights into pediatric onset of cardiac damage in DMD, a new therapeutic target, and identify a drug-based potential therapy.

Generation and characterization of a novel mouse model of Becker Muscular Dystrophy with a deletion of exons 52 to 55.

Becker Muscular Dystrophy (BMD) is a rare X-linked recessive neuromuscular disorder frequently caused by in-frame deletions in the DMD gene that result in the production of a truncated, yet functional, dystrophin protein. The consequences of BMD-causing in-frame deletions on the organism are difficult to predict, especially in regard to long-term prognosis. Here, we employed CRISPR-Cas9 to generate a new Dmd del52-55 mouse model by deleting exons 52-55, resulting in a BMD-like in-frame deletion. To delineate the long-term effects of this deletion, we studied these mice over 52 weeks by performing histology and echocardiography analyses and assessing motor functions. Our results suggest that a truncated dystrophin is sufficient to maintain wildtype-like muscle and heart histology and functions in young mice. However, the truncated protein appears insufficient to maintain normal muscle homeostasis and protect against exercise-induced damage at 52 weeks. To further delineate the effects of this exon52-55 in-frame deletion, we performed RNA-Seq pre- and post-exercise and identified several differentially expressed pathways that reflect the abnormal muscle phenotype observed at 52 weeks in the BMD model.

"If you cannot measure it, you cannot improve it". Outcome measures in Duchenne Muscular Dystrophy: current and future perspectives.

Duchenne Muscular Dystrophy (DMD) is an X-linked recessive neuromuscular disorder primarily affecting males, caused by mutations in the dystrophin gene. The absence of dystrophin protein leads to progressive skeletal muscle degeneration. Recent advances in the therapeutic landscape underscore the need to identify appropriate outcome measures to assess treatment efficacy in ambulant and non-ambulant DMD patients, across clinical and research settings. This is essential for accurately evaluating new treatments and attributing therapeutic benefits.It is crucial to establish a robust correlation between outcome scores and disease progression patterns. This task is challenging since functional test performance may be influenced by different patient's characteristics, including the physiological evolution of the neurodevelopment together with the disease progression. While widely used DMD outcomes such as the North Star Ambulatory Assessment, the 6-Minute Walking Test, the 4 stairs climbed, and the Performance of the Upper Limb exhibit reliability and validity, their clinical significance is influenced by the wide phenotype and progression variability of the disease.We present and discuss the features (relevance, quantifiability, validity, objectivity, reliability, sensitivity, specificity, precision) of available DMD outcome measures, including new potential measures that may be provided by digital tools and artificial intelligence.