Canine models of Duchenne muscular dystrophy and their use in therapeutic strategies

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder in which the loss of dystrophin causes progressive degeneration of skeletal and cardiac muscle. Potential therapies that carry substantial risk, such as gene and cell-based approaches, must first be tested in animal models, notably the mdx mouse and several dystrophin-deficient breeds of dogs, including golden retriever muscular dystrophy (GRMD). Affected dogs have a more severe phenotype, in keeping with that of DMD, so may better predict disease pathogenesis and treatment efficacy. We and others have developed various phenotypic tests to characterize disease progression in the GRMD model. These biomarkers range from measures of strength and joint contractures to magnetic resonance imaging. Some of these tests are routinely used in clinical veterinary practice, while others require specialized equipment and expertise. By comparing serial measurements from treated and untreated groups, one can document improvement or delayed progression of disease. Potential treatments for DMD may be broadly categorized as molecular, cellular, or pharmacologic. The GRMD model has increasingly been used to assess efficacy of a range of these therapies. While some of these studies have largely provided general proof-of-concept for the treatment under study, others have demonstrated efficacy using the biomarkers discussed. Importantly, just as symptoms in DMD vary among patients, GRMD dogs display remarkable phenotypic variation. While confounding statistical analysis in preclinical trials, this variation offers insight regarding the role that modifier genes play in disease pathogenesis. By correlating functional and mRNA profiling results, gene targets for therapy development can be identified

Collagen VI-Related Myopathies: Navigating through the Molecular Maze, Myomatrix and Clinical Manifestations on a Journey toward Clinical Trials

The congenital muscular dystrophies are a clinically and genetically heterogeneous group of disorders characterised by a congenital onset of weakness and hypotonia, typically associated with dystrophic-appearing muscle biopsy findings. The spectrum of clinical phenotypes associated with the congenital muscular dystrophy subgroup resulting from a deficiency of collagen VI in the extracellular matrix of muscle are collectively termed ‘collagen VI-related myopathies’ and include the early onset Ullrich congenital muscular dystrophy and the milder and later onset Bethlem myopathy as well as a phenotype of intermediate severity called ‘intermediate collagen VI-related myopathy.’ A major goal of this research has been to study the natural history of respiratory insufficiency in the collagen VI-related myopathies by analyzing longitudinal forced vital capacity data in a large, international cohort. A total of 486 forced vital capacity measurements obtained in 145 genetically and/or biochemically confirmed collagen VI-related myopathy patients from 10 neuromuscular centres [United States (2), United Kingdom (2), Australia (2), Italy (2), France (1) and Belgium (1)] were analysed and the resulting clarification of the phenotypic stratification of collagen VI-related myopathies reported. Another focus of this research has been the evaluation and the refining of the challenging diagnostic pathway for collagen VI-related myopathy patients, including evaluations of the diagnostic role of muscle histopathology, skin fibroblast immunocytochemistry and flow cytometry studies as well as muscle ultrasound and muscle magnetic resonance imaging studies. Finally, this research has studied the role of next generation genetic sequencing technologies including whole-genome and exome sequencing in the assessment of patients evaluated for collagen VI-related myopathies and related conditions

Understanding Neuromuscular Health and Disease: Advances in Genetics, Omics, and Molecular Function

This compilation focuses on recent advances in the molecular and cellular understandingof neuromuscular biology, and the treatment of neuromuscular disease.These advances are at the forefront of modern molecular methodologies, oftenintegrating across wet-lab cell and tissue models, dry-lab computational approaches,and clinical studies. The continuing development and application ofmultiomics methods offer particular challenges and opportunities in the field,not least in the potential for personalized medicine

Neuromuscular Disorders in Children and Adolescents

Significant scientific and therapeutic advances have been made in recent decades, particularly in hereditary but also in acquired neuromuscular diseases. As a result of our increasing etiological understanding, the classification of these diseases has changed from a clinical–descriptive and formal–genetic to a molecular–genetic and pathophysiological one. This has led to an intensification of research into the diagnosis and treatment of these diseases, resulting in the first effective gene-modifying treatments for DMD and SMA in recent years and, more recently, gene replacement therapy for the most severe form of SMA. In addition, great strides have been made in symptomatic and rehabilitative treatment, making it possible to improve the functioning and quality of life of those affected and their families. This Special Issue of Children contains a collection of 12 studies and reviews dealing with genetic and acquired peripheral nerve and muscle disorders

Lapseeas alanud pärilike neuromuskulaarsete haiguste molekulaargeneetiliste ja morfoloogiliste uuringutulemuste võrdlus

Väitekirja elektrooniline versioon ei sisalda publikatsioonePärilike neuromuskulaarsete haiguste (NMH-de) alla kuuluvad seljaaju motoneuronite, närvide, närv-lihas ülekande ja lihaste talitluse häired, mis on põhjustatud ühe geeni veast. Nende haiguste diagnoosimisel on lisaks patsiendi haigusloole ja läbivaatusele abiks erinevad instrumentaalsed uuringud, sealhulgas lihasbiopsia. Lihaskoe analüüsimiseks kasutatakse mitmeid erinevaid värvinguid ja tehnikaid, mis võimaldavad näha lihaskiudude struktuuri, keemilisi ja ensümaatilisi omadusi ning erinevate valkude olemasolu või puudumist. Lihaskoe histoloogilised muutused on ajalooliselt olnud aluseks mitmete pärilike NMH-de tuvastamisele ja diagnoosimisele ning andnud suuna, milliseid geene uurida. Kuid tänapäeval on võimalik ühe analüüsiga (kogu eksoomi sekveneerimine) uurida kõiki geene korraga, mis on näidanud ka head diagnostilist efektiivsust. Seega on lihasbiopsia roll NMH-de diagnostikas muutumas. Käesolevasse uuringusse kaasati 70 päriliku NMH või mitokondriaalse haiguse kahtlusega patsienti, kellest 44-l kinnitus geneetiline diagnoos. Uuringust selgus, et lihasbiopsia mängis diagnostilises protsessis olulist rolli paljudel juhtudel, kusjuures 15 patsiendi lihaskoes esinesid spetsiifilised histoloogilised muutused. Mitmel juhul oli lihasbiopsia vajalik mitokondriaalses DNA-s esinevate muutuste tuvastamiseks. Lisaks andsid lihaskoest tehtud uuringud väärtuslikku lisainformatsiooni paljudel juhtudel, kus geneetilisel analüüsil leiti varem kirjeldamata geenivariant, tuvastati muutused kandidaatgeenis või kus leide polnudki. Näiteks ühel lihasdüstroofiaga patsiendil avastasime muutused uudses JAG2 geenis, mille haigusseoselisus kinnitus rahvusvahelise koostöö tulemusena. Uurides geenide ja teatud valkude avaldumist selle patsiendi lihaskoes, saime viite, et haiguse teke võib olla seotud lihase tüvirakkude talitluse häirumisega. Samas enamikel peamiselt kesknärvisüsteemi mõjutava haigusega patsientidel ei andnud lihasbiopsia informatsiooni juurde. Lisaks kirjeldati SPATA5 geeni defekti seost mitokondrite talitluse ja närvijätkete kasvu häiretega ning ühte patsienti, kellel oli kahtlus kongenitaalsele müopaatiale, kuid diagnoositi hoopis PRPS1 geeniga seotud puriinide ainevahetushaigus.Hereditary neuromuscular disorders (NMDs) include spinal motor neuron, nerve, neuromuscular junction, and muscle diseases caused by a single gene defect. In addition to the patient's disease history and examination, the diagnosis of NMDs can be reached using various instrumental investigations, including muscle biopsy. Several different stains and techniques are used to analyze muscle tissue, showing the structure and chemical and enzymatic properties of muscle fibers and the presence or absence of various proteins. Histological changes in muscle tissue have historically been the basis for identifying and diagnosing several hereditary NMDs and have provided guidance on which genes to study. However, nowadays, it is possible to study all genes at once with one analysis (whole exome sequencing), which has also shown good diagnostic efficiency. Thus, the role of muscle biopsy in NMD diagnostics is changing. The present study included 70 patients with a suspected hereditary NMD or mitochondrial disease, of whom 44 received a genetic diagnosis. The study found that muscle biopsy played a vital role in the diagnostic process in many cases, with 15 patients having specific histological changes in the muscle tissue. In several cases, a muscle biopsy was necessary to detect changes in mitochondrial DNA. In addition, studies of muscle tissue provided valuable additional information in many cases with previously undescribed gene variants, changes in a candidate gene, or without genetic findings. For example, in one patient with muscular dystrophy, we discovered changes in the new JAG2 gene and confirmed its disease association owing to international cooperation. Of note, by studying the expression of genes and specific proteins in the muscle tissue of this patient, we got an indication that the development of the disease may be related to the dysfunction of muscle stem cells. However, muscle biopsy did not provide additional information in most patients with a disease affecting the central nervous system. Lastly, the dissertation described the association of SPATA5 gene defect with mitochondrial dysfunction and nerve growth impairment and one patient with a suspected congenital myopathy, eventually diagnosed with PRPS1 gene-related inborn error of purine metabolism.https://www.ester.ee/record=b552434

Community-engaged approaches to explore research priorities in Duchenne and Becker muscular dystrophy

This thesis presents a series of translational research studies to explore topics of importance to a patient stakeholder community--Duchenne and Becker muscular dystrophy. The overarching objective was to inform a patient/family foundation's interventions and policy and advocacy approaches. Results from a longitudinal study on mothers__ wellbeing support the need for systematic exploration of caregivers__ unmet support needs, especially those related to coping with DMD-related uncertainty and fear. Efforts to improve mothers__ adaptation should focus on fostering resilience and enhancing benefit finding. A study on treatment preferences and disease impact that used Best-Worst Scaling found that caregivers were willing to accept a serious or fatal risk when balanced with a non-curative treatment, even absent lifespan improvement. Parents__ most pressing worries were about symptom progression and access to medical care. The final qualitative studies highlight the complexity of clinical trial decision making, especially for rare, progressive pediatric disorders, where participants equated doing __nothing__ with doing harm. Parents developed intentions to participate in trials before the informed consent process. Parents__ decisions were strongly influenced by the anticipation of individual benefit. The adaptive optimism engendered by the availability of trial was highly valued by both parents and clinicians on trial teams.UBL - phd migration 201

Quantitative magnetic resonance imaging in muscular dystrophies

PhD ThesisMuscular dystrophies are rare diseases characterised by progressive muscle wasting and weakness. Putative therapies are being evaluated; the slowly progressive nature makes outcome measures difficult to design. Four pathological hallmarks of muscular dystrophies include: muscle necrosis, inflammation, fibrosis, and adipose transformation. This thesis evaluates novel methods of quantifying pathological hallmarks of muscular dystrophy in both skeletal and cardiac muscle using magnetic resonance imaging (MRI). To quantify fibrosis in a mouse model of Duchenne muscular dystrophy, EP3533, a collagen-specific contrast agent, was assessed in quantification of fibrosis in muscle. EP3533-measures correlated with functional tests and histological quantification of fibrosis. Extracellular volume (ECV) was calculated in a limb muscular dystrophy type R9 cohort (LGMDR9), a Becker muscular dystrophy cohort and healthy controls. ECV was found comparable to traditional measures of cardiac dysfunction and demonstrated regional dysfunction. A multicentre study followed up 24 participants with LGMDR9 over 6 years. The three-point Dixon method of fat fraction calculation was evaluated in this cohort and compared to functional assessments. All muscles showed significantly increased fat fractions over 6 years, which was more responsive than functional assessments. As patients with muscular dystrophies can have difficulties remaining supine during scanning, a method of reducing acquisition time in measurement of left ventricular (LV) indices was evaluated. Accelerated images were compared to conventional imaging with accelerated imaging producing images with a high fidelity. No significant changes were seen in LV functional indices or cardiac tagging measures over five years was assessed in an LGMDR9 cohort, this may be due to confounding variables. The MRI methods described can be successfully used to quantify progression of disease pathology in muscular dystrophies. These findings can be used to support further trials of EP3533 and ECV as an outcome measure in muscular dystrophies and to inform study design of future trials into LGMDR