DMD
Dystrophin
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Aldehyde dehydrogenases (ALDHs) are key players in cell survival, protection, and differentiation via the metabolism and detoxification of aldehydes. ALDH activity is also a marker of stem cells. The skeletal muscle contains populations of ALDH-positive cells amenable to use in cell therapy, whose distribution, persistence in aging, and modifications in myopathic context have not been investigated yet. The Aldefluor® (ALDEF) reagent was used to assess the ALDH activity of muscle cell populations, whose phenotypic characterizations were deepened by flow cytometry. The nature of ALDH isoenzymes expressed by the muscle cell populations was identified in complementary ways by flow cytometry, immunohistology, and real-time PCR ex vivo and in vitro. These populations were compared in healthy, aging, or Duchenne muscular dystrophy (DMD) patients, healthy non-human primates, and Golden Retriever dogs (healthy vs. muscular dystrophic model, Golden retriever muscular dystrophy [GRMD]). ALDEF cells persisted through muscle aging in humans and were equally represented in several anatomical localizations in healthy non-human primates. ALDEF cells were increased in dystrophic individuals in humans (nine patients with DMD vs. five controls: 14.9 ± 1.63% vs. 3.6 ± 0.39%, P = 0.0002) and dogs (three GRMD dogs vs. three controls: 10.9 ± 2.54% vs. 3.7 ± 0.45%, P = 0.049). In DMD patients, such increase was due to the adipogenic ALDEF /CD34 populations (11.74 ± 1.5 vs. 2.8 ± 0.4, P = 0.0003), while in GRMD dogs, it was due to the myogenic ALDEF /CD34 cells (3.6 ± 0.6% vs. 1.03 ± 0.23%, P = 0.0165). Phenotypic characterization associated the ALDEF /CD34 cells with CD9, CD36, CD49a, CD49c, CD49f, CD106, CD146, and CD184, some being associated with myogenic capacities. Cytological and histological analyses distinguished several ALDH isoenzymes (ALDH1A1, 1A2, 1A3, 1B1, 1L1, 2, 3A1, 3A2, 3B1, 3B2, 4A1, 7A1, 8A1, and 9A1) expressed by different cell populations in the skeletal muscle tissue belonging to multinucleated fibres, or myogenic, endothelial, interstitial, and neural lineages, designing them as potential new markers of cell type or of metabolic activity. Important modifications were noted in isoenzyme expression between healthy and DMD muscle tissues. The level of gene expression of some isoenzymes (ALDH1A1, 1A3, 1B1, 2, 3A2, 7A1, 8A1, and 9A1) suggested their specific involvement in muscle stability or regeneration in situ or in vitro. This study unveils the importance of the ALDH family of isoenzymes in the skeletal muscle physiology and homeostasis, suggesting their roles in tissue remodelling in the context of muscular dystrophies.
Keywords
- Aging
- Aldehyde dehydrogenase
- Dog model
- Duchenne muscular dystrophy
- Human
- Myogenic
- Non-human primate
- Skeletal muscle
Several studies indicate that prognosis for survival in Duchenne muscular dystrophy (DMD) has improved in recent decades. However, published evidence is inconclusive and some estimates may be obsolete due to improvements in standards of care, in particular the routine use of mechanical ventilatory support in advanced stages of the disease. In this systematic review and meta-analysis (PROSPERO identifier: CRD42019121800), we searched MEDLINE (through PubMed), CINAHL, Embase, PsycINFO, and Web of Science for studies published from inception up until December 31, 2018, reporting results of life expectancy in DMD. We pooled median survival estimates from individual studies using the median of medians, and weighted median of medians, methods. Risk of bias was established with the Newcastle-Ottawa Scale. Results were stratified by ventilatory support and risk of bias. We identified 15 publications involving 2662 patients from 12 countries from all inhabited continents except Africa. Median life expectancy without ventilatory support ranged between 14.4 and 27.0 years (pooled median: 19.0 years, 95% CI 18.0-20.9; weighted pooled median: 19.4 years, 18.2-20.1). Median life expectancy with ventilatory support, introduced in most settings in the 1990s, ranged between 21.0 and 39.6 years (pooled median: 29.9 years, 26.5-30.8; weighted pooled median: 31.8 years, 29.3-36.2). Risk of bias had little impact on pooled results. In conclusion, median life expectancy at birth in DMD seems to have improved considerably during the last decades. With current standards of care, many patients with DMD can now expect to live into their fourth decade of life.
MeSH Terms
- Female
- Humans
- Life Expectancy
- Male
- Muscular Dystrophy, Duchenne
- Parturition
- Pregnancy
- Prognosis
- Quality of Life
- Respiration, Artificial
- Survival
Keywords
- Mechanical ventilation
- Mortality
- Prognosis
- Survival
Fibro-adipogenic progenitors (FAPs), a muscle-resident stem cell population, have recently emerged as important actors of muscle regeneration by interacting with myogenic progenitors (MPs) to promote the formation of new muscle fibers. However, FAPs are also considered as main contributors of intramuscular fibrotic and fat depositions, resulting in a poor quality of muscles and a defective regeneration in aging and Duchenne Muscular Dystrophy disease (DMD). Therefore, the understanding of the control of FAP fate is an important aspect of muscle repair and homeostasis, but little is known in humans. We wondered the extent to which human FAP proliferation, adipogenesis and fibrogenesis can be regulated by human myogenic progenitors (MPs) in physiological and pathological contexts. FAPs and MPs were isolated from skeletal muscles of healthy young or old donors and DMD patients. FAP/MP contact co-cultures and conditioned-media from undifferentiated MPs or differentiated myotubes were assessed on both proliferation and fibro-adipogenic differentiation of FAPs. We showed that soluble molecules released by MPs activate the phosphoinositide 3-kinase (PI3Kinase)/Akt pathway in FAPs, resulting in the stimulation of FAP proliferation. FAP differentiation was regulated by MP-derived myotubes through the secretion of pro-fibrogenic factors and anti-adipogenic factors. Importantly, the regulation of FAP adipogenic and fibrogenic fates by myotubes was found to be mediated by Smad2 phosphorylation and the gene expression of glioma-associated oncogene homolog 1 (GLI1). Surprisingly, the regulations of proliferation and differentiation were disrupted for FAPs and MPs derived from aged individuals and patients with DMD. Our results highlight a novel crosstalk between FAPs and the myogenic lineage in humans that could be crucial in the formation of adipocyte and myofibroblast accumulation in dystrophic and aged skeletal muscle.
MeSH Terms
- Adipogenesis
- Adolescent
- Adult
- Adult Stem Cells
- Aged
- Aging
- Cells, Cultured
- Child
- Child, Preschool
- Female
- Humans
- Infant
- Male
- Middle Aged
- Muscle Development
- Muscular Dystrophy, Duchenne
- Myoblasts
- Young Adult
Keywords Adipocytes; Myofibroblasts; Muscle progenitors; Myopathies
With improved treatments, patients with Duchenne muscular dystrophy (DMD) can survive far beyond adolescence. However, advanced-stage DMD patients are at risk of developing renal dysfunction. In this study, long-term renal function outcomes and associated risk factors in advanced stage DMD were analyzed. Fifty-one patients were classified into three different age groups (<20, 20-29, and ≥30 years of age), and cystatin C (CysC) levels were compared among groups. Median serum CysC levels were 0.74 mg/L, 0.63 mg/L, and 0.76 mg/L in the age groups of <20, 20-29, and ≥30 years, respectively (P = .003). Five of the nine patients in the ≥30 years age group showed elevated serum CysC and decreased cardiac function compared with the other four in the group (P = .014). Our results indicate an association between cardiac and renal dysfunction in patients with advanced-stage DMD.
MeSH Terms
- Adolescent
- Adult
- Aging
- Child
- Child, Preschool
- Cystatin C
- Disease Progression
- Female
- Heart Diseases
- Heart Function Tests
- Humans
- Kidney Diseases
- Kidney Function Tests
- Male
- Muscular Dystrophy, Duchenne
- Risk Factors
- Young Adult
Keywords
- Duchenne muscular dystrophy
- advanced stage
- cystatin C
- ejection fraction
- fractional shortening
- renal dysfunction
Mutations in dystrophin are the major cause of muscular dystrophies. Continuous muscular degeneration and late stage complications, including cardiomyopathy and respiratory insufficiency, dominate the clinical phenotype. Gene expression and regulation of the dystrophin gene outside of muscular tissue is far more complex. Multiple tissue-specific dystrophin gene products are widely expressed throughout the body, including the central nervous system and eye, predisposing affected patients to secondary complications in non-muscular tissues. In this study, we evaluated the impact of the full-length dystrophin gene product, Dp427, on retinal homeostasis and angiogenesis. Based on the clinical case of a Duchenne muscular dystrophy (DMD) patient who developed severe fibrovascular changes in the retina in response to hypoxic stress, we hypothesized that defects in Dp427 make the retina more susceptible to stresses such as ageing and ischemia. To further study this, a mouse strain lacking Dp427 expression (Mdx) was studied during retinal development, ageing and in the oxygen-induced retinopathy (OIR) model. While retinal vascular morphology was normal during development and ageing, retinal function measured by electroretinography (ERG) was slightly reduced in young adult Mdx mice and deteriorated with age. Mdx mice also had increased retinal neovascularization in response to OIR and more pronounced long-term deterioration in retinal function following OIR. Based on these results, we suggest that DMD patients with a mutation in Dp427 may experience disturbed retinal homeostasis with increasing age and therefore be prone to develop excessive retinal neovascular changes in response to hypoxic stress. DMD patients in late disease stages should, thus, be regularly examined to detect asymptomatic retinal abnormalities and prevent visual impairment.
MeSH Terms
- Aging
- Animals
- Cell Hypoxia
- Dystrophin
- Exons
- Fibrosis
- Gene Duplication
- Humans
- Ischemia
- Male
- Mice
- Muscular Dystrophy, Animal
- Muscular Dystrophy, Duchenne
- Oxygen
- Protein Isoforms
- Retina
- Retinal Diseases
- Retinal Neovascularization
- Retinal Vessels
- Sepsis
- Young Adult
Keywords
- Angiogenesis
- Dp427
- Duchenne muscular dystrophy
- Electroretinography
- Hypoxia
- Oxygen-induced retinopathy
- Proliferative retinopathy
Muscle wasting occurs in response to various physiological and pathological conditions, including ageing and Duchenne muscular dystrophy (DMD). Transforming growth factor-β1 (TGF-β1) contributes to muscle pathogenesis in elderly people and DMD patients; inhibition of TGF-β1 signalling is a promising therapeutic strategy for muscle-wasting disorders. Hemojuvelin (HJV or Hjv as the murine homologue) is a membrane-bound protein that is highly expressed in skeletal muscle, heart, and liver. In hepatic cells, Hjv acts as a coreceptor for bone morphogenetic protein, a TGF-β subfamily member. The aim of this study was to investigate whether Hjv plays an essential role in muscle physiological and pathophysiological processes by acting as a coreceptor for TGF-β1 signalling. Conventional and conditional Hjv knockout mice as well as mdx and aged mice transfected with Hjv overexpression vector were used to study the role of Hjv in muscle physiology and pathophysiology. qRT-PCR, western blotting, and immunohistochemistry examinations were conducted to evaluate gene, protein, and structural changes in vivo and in vitro. Exercise endurance was determined using treadmill running test, and muscle force was detected by an isometric transducer. RNA interference, immunoprecipitation, and dual-luciferase reporter assays were utilized to explore the mechanism by which Hjv regulates TGF-β1 signalling in skeletal muscle. Conventional and conditional Hjv knockout mice displayed muscle atrophy, fibrosis, reduced running endurance, and muscle force. HJV was significantly down-regulated in the muscles of DMD patients (n = 3, mean age: 11.7 ± 5.7 years) and mdx mice as well as in those of aged humans (n = 10, 20% women, mean age: 75.1 ± 9.5 years) and mice. Overexpression of Hjv rescued dystrophic and age-related muscle wasting. Unlike its function in hepatic cells, the bone morphogenetic protein downstream phosphorylated p-Smad1/5/8 signalling pathway was unchanged, but TGF-β1, TGF-β receptor II (TβRII), and p-Smad2/3 expression were increased in Hjv-deficient muscles. Mechanistically, loss of Hjv promoted activation of Smad3 signalling induced by TGF-β1, whereas Hjv overexpression inhibited TGF-β1/Smad3 signalling by directly interacting with TβRII on the muscle membrane. Our findings identify an unrecognized role of HJV in skeletal muscle by regulating TGF-β1/Smad3 signalling as a coreceptor for TβRII. Unlike the TGF-β1/Smad3 pathway, HJV could be a reliable drug target as its expression is not widespread. Novel therapeutic strategies could potentially be devised to interfere only with the muscle function of HJV to treat DMD and age-related muscle wasting.
MeSH Terms
- Adolescent
- Aged
- Aged, 80 and over
- Aging
- Animals
- Child
- Disease Models, Animal
- Female
- GPI-Linked Proteins
- Hemochromatosis Protein
- Humans
- Male
- Mice
- Mice, Inbred mdx
- Mice, Knockout
- Muscle, Skeletal
- Muscular Dystrophy, Duchenne
- Receptor, Transforming Growth Factor-beta Type II
- Signal Transduction
- Smad3 Protein
- Transforming Growth Factor beta1
- Wasting Syndrome
- Young Adult
Keywords
- Age-related muscle wasting
- Coreceptor
- Duchenne muscular dystrophy
- Hemojuvelin
- TGF-β1 signalling
Duchenne Muscular Dystrophy (DMD) is a fatal X-linked genetic disorder. In DMD, the absence of the dystrophin protein causes decreased sarcolemmal integrity resulting in progressive replacement of muscle with fibrofatty tissue. The effects of lacking dystrophin on muscle and systemic metabolism are still unclear. Therefore, to determine the impact of the absence of dystrophin on metabolism, we investigated the metabolic and lipid profile at two different, well-defined stages of muscle damage and stabilization in mdx mice. We measured NMR-detectable metabolite and lipid profiles in the serum and muscles of mdx mice at 6 and 24 weeks of age. Metabolites were determined in muscle in vivo using H MRI/MRS, in isolated muscles using H-HR-MAS NMR, and in serum using high resolution H/ C NMR. Dystrophic mice were found to have a unique lipid saturation profile compared with control mice, revealing an age-related metabolic change. In the 6-week-old mdx mice, serum lipids were increased and the degree of lipid saturation changed between 6 and 24 weeks. The serum taurine-creatine ratio increased over the life span of mdx, but not in control mice. Furthermore, the saturation index of lipids increased in the serum but decreased in the tissue over time. Finally, we demonstrated associations between MRI-T , a strong indicator of inflammation/edema, with tissue and serum lipid profiles. These results indicate the complex temporal changes of metabolites in the tissue and serum during repetitive bouts of muscle damage and regeneration that occur in dystrophic muscle.
MeSH Terms
- Aging
- Animals
- Blood Glucose
- Carbon-13 Magnetic Resonance Spectroscopy
- Lipids
- Magnetic Resonance Imaging
- Metabolome
- Metabolomics
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Multivariate Analysis
- Muscle, Skeletal
- Muscular Dystrophy, Animal
- Principal Component Analysis
Keywords
- Duchenne muscular dystrophy (DMD)
- lipids
- metabolism
- metabolomics
- muscle
- neuromuscular disease
Patients with Duchenne muscular dystrophy (DMD) demonstrate decreased bone mineral density (BD). It is not clear which factors exert the greatest impact on BD loss in these patients. In 63 patients with DMD, serum cytokines (interleukin [IL]-1, IL-6, and tumor necrosis factor-beta [TNF-β]), C-reactive protein (CRP), creatine kinase (CK), muscle function (by Vignos scale), body composition, and total BD (the latter 2 measured by dual-energy X-ray absorptiometry, or DEXA) were determined. The main factors associated with BD loss were muscle function (34.0%; β = -0.139; P < 0.023) and age (36.7%; β = -0.151; P = 0.004). Cytokines, CRP, body fat mass, and CK did not contribute to BD loss. Muscle function and age contribute to BD loss in DMD. We propose that a cut-off of at least 6 points for the Vignos scale and at least 10.5 years of age predict a Z-score of less than or equal to -2.0. Muscle Nerve 59:417-421, 2019.
MeSH Terms
- Absorptiometry, Photon
- Adipose Tissue
- Adiposity
- Adolescent
- Aging
- Body Composition
- Bone Density
- C-Reactive Protein
- Child
- Child, Preschool
- Cohort Studies
- Cytokines
- Female
- Humans
- Inflammation
- Male
- Muscle Weakness
- Muscle, Skeletal
- Muscular Dystrophy, Duchenne
- Osteoporosis
- Prospective Studies
Keywords
- Duchenne muscular dystrophy
- adipose tissue
- bone mineral density
- cytokines
- inflammation
- muscle
Patients with Duchenne muscular dystrophy (DMD) exhibit low bone mineral density and increased fracture risk. Because glucocorticoid therapy results in delayed puberty and short stature, it is important to account for delayed skeletal development when interpreting patients' bone mineral density. Twelve glucocorticoid-treated patients with DMD were evaluated by dual x-ray absorptiometry scans and wrist x-rays to estimate bone density and bone age, respectively. Z-scores were determined on the basis of chronological age. Each patient was assigned a "corrected" birth date that was calculated according to bone age, and a bone-age-corrected z-score was determined. Z-scores adjusted for chronological age were lower than those adjusted for bone age. We suggest the use of bone age as an alternative to chronological age for analysis of bone mineral density in glucocorticoid-treated patients with DMD. Additional research is required to determine the optimal method to predict fracture risk in this patient group. Muscle Nerve 59:422-425, 2019.
MeSH Terms
- Absorptiometry, Photon
- Adolescent
- Age Determination by Skeleton
- Aging
- Bone Density
- Bone Development
- Child
- Female
- Glucocorticoids
- Humans
- Male
- Muscular Dystrophy, Duchenne
- Retrospective Studies
- Young Adult
Keywords
- DXA
- Duchenne muscular dystrophy
- bone mineral density
- glucocorticoid
- osteoporosis
Age-related deterioration of force control is evident on behavioral and neural levels. Extensive and deliberate practice can decrease these changes. This study focused on detecting electrophysiological correlates of age- and expertise-related differences in force control. We examined young (20-27 years) and late middle-aged (57-67 years) novices as well as late middle-aged experts in the field of fine motor control. Therefore, EEG data were recorded while participants performed a force maintenance task. Variability and complexity of force data were analyzed. To detect electrophysiological correlates, dynamic mode decomposition (DMD) was applied to EEG data. DMD allows assessing brain network dynamics by extracting electrode interrelations and their dynamics. Defining clusters of electrodes, we focused on sensorimotor and attentional networks. We confirmed that force control in late middle-aged novices was more variable and less complex than in other groups. Analysis of task-related overall network characteristics, showed a decrease within the α band and increase within low β, high β, and θ band. Compared to the other groups young novices presented a decreased α magnitude. High β magnitude was lower in late middle-aged novices than for other groups. Comparing left and right hands' performance, young novices showed higher low β magnitude for the left hand. Late middle-aged novices showed high values for both hands while late middle-aged experts showed higher values for the right than for their left hand. Activation of attentional networks was lower in late middle-aged experts compared to novices. These results may relate to different control strategies of the three groups.
MeSH Terms
- Adult
- Aged
- Aging
- Electroencephalography
- Female
- Hand
- Humans
- Male
- Middle Aged
- Motor Skills
- Neural Pathways
- Professional Competence
- Sensorimotor Cortex
- Signal Processing, Computer-Assisted
- Young Adult
Keywords
- aging
- attentional networks
- dynamic mode decomposition
- fine motor expertise
- sensorimotor maps
- variability
Mineralocorticoid receptor antagonists added to angiotensin converting enzyme inhibitors have shown preclinical efficacy for both skeletal and cardiac muscle outcomes in young sedentary dystrophin-deficient mdx mice also haploinsufficient for utrophin, a Duchenne muscular dystrophy (DMD) model. The mdx genotypic DMD model has mild pathology, making non-curative therapeutic effects difficult to distinguish at baseline. Since the cardiac benefit of mineralocorticoid receptor antagonists has been translated to DMD patients, it is important to optimize potential advantages for skeletal muscle by further defining efficacy parameters. We aimed to test whether therapeutic effects of mineralocorticoid receptor antagonists added to angiotensin converting enzyme inhibitors are detectable using three different reported methods of exacerbating the mdx phenotype. We tested treatment with lisinopril and the mineralocorticoid receptor antagonist spironolactone in: 10 week-old exercised, 1 year-old sedentary, and 5 month-old isoproterenol treated mdx mice and performed comprehensive functional and histological measurements. None of the protocols to exacerbate mdx phenotypes resulted in dramatically enhanced pathology and no significant benefit was observed with treatment. Since endogenous mineralocorticoid aldosterone production from immune cells in dystrophic muscle may explain antagonist efficacy, it is likely that these drugs work optimally during the narrow window of peak inflammation in mdx mice. Exercised and aged mdx mice do not display prolific damage and inflammation, likely explaining the absence of continued efficacy of these drugs. Since inflammation is more prevalent in DMD patients, the therapeutic window for mineralocorticoid receptor antagonists in patients may be longer.
MeSH Terms
- Adrenergic beta-Agonists
- Aging
- Angiotensin-Converting Enzyme Inhibitors
- Animals
- Disease Models, Animal
- Heart
- Inflammation
- Isoproterenol
- Mice
- Mice, Inbred mdx
- Mineralocorticoid Receptor Antagonists
- Muscle Strength
- Muscle, Skeletal
- Muscular Dystrophy, Duchenne
- Physical Conditioning, Animal
- Sedentary Behavior
- Spironolactone
Keywords
- Duchenne muscular dystrophy
- Mineralocorticoid receptors
- lisinopril
- mdx mice
- spironolactone
Duchenne muscular dystrophy (DMD), caused by mutations in the gene encoding for the cytoskeletal protein dystrophin, is linked with severe cardiac complications including cardiomyopathy development and cardiac arrhythmias. We and others recently reported that currents through L-type calcium (Ca) channels were significantly increased, and channel inactivation was reduced in dystrophin-deficient ventricular cardiomyocytes derived from the mdx mouse, the most commonly used animal model for human DMD. These gain-of-function Ca channel abnormalities may enhance the risk of Ca-dependent arrhythmias and cellular Ca overload in the dystrophic heart. All studies, which have so far investigated L-type Ca channel properties in dystrophic cardiomyocytes, have used hearts from either neonatal or young adult mdx mice as cell source. In consequence, the dimension of the Ca channel abnormalities present in the severely-diseased aged dystrophic heart has remained unknown. Here, we have studied potential abnormalities in Ca currents and intracellular Ca transients in ventricular cardiomyocytes derived from aged dystrophic mdx mice. We found that both the L-type and T-type Ca current properties of mdx cardiomyocytes were similar to those of myocytes derived from aged wild-type mice. Accordingly, Ca release from the sarcoplasmic reticulum was normal in cardiomyocytes from aged mdx mice. This suggests that, irrespective of the presence of a pronounced cardiomyopathy in aged mdx mice, Ca currents and Ca release in dystrophic cardiomyocytes are normal. Finally, our data imply that dystrophin- regulation of L-type Ca channel function in the heart is lost during aging.
MeSH Terms
- Action Potentials
- Aging
- Animals
- Calcium
- Calcium Channels, L-Type
- Calcium Channels, T-Type
- Calcium Signaling
- Cells, Cultured
- Heart Ventricles
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Muscular Dystrophy, Duchenne
- Myocytes, Cardiac
Keywords
- Aging
- Ca channel function
- Ca transients
- Duchenne muscular dystrophy
- mdx mouse
Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder, caused by mutations in the dystrophin gene, affecting 1:3500-5000 boys worldwide. The lack of dystrophin induces degeneration of muscle cells and elicits an immune response characterized by an intensive secretion of pro-inflammatory cytokines. Immunoglobulins modulate the inflammatory response through several mechanisms and have been widely used as an adjuvant therapy for autoimmune diseases. Here we evaluated the effect of immunoglobulin G (IG) injected intraperitoneally in a severely affected double knockout (dko) mouse model for Duchenne muscular dystrophy. The IG dko treated mice were compared regarding activity rates, survival and histopathology with a control untreated group. Additionally, dendritic cells and naïve lymphocytes from these two groups and WT mice were obtained to study in vitro the role of the immune system associated to DMD pathophysiology. We show that IG therapy significantly enhances activity rate and lifespan of dko mice. It diminishes muscle tissue inflammation by decreasing the expression of costimulatory molecules MHC, CD86 and CD40 and reducing Th1-related cytokines IFN-γ, IL-1β and TNF-α release. IG therapy dampens the effector immune responses supporting the hypothesis according to which the immune response accelerates DMD progression. As IG therapy is already approved by FDA for treating autoimmune disorders, with less side-effects than currently used glucocorticoids, our results may open a new therapeutic option aiming to improve life quality and lifespan of DMD patients.
MeSH Terms
- Animals
- Cells, Cultured
- Cytokines
- Dendritic Cells
- Dystrophin
- Humans
- Immunoglobulin G
- Immunotherapy
- Injections, Intraperitoneal
- Longevity
- Lymphocytes
- Mice
- Mice, Inbred mdx
- Muscular Dystrophy, Duchenne
- Phenotype
- Utrophin
Mechanical ventilation has allowed a greater number of patients with Duchenne muscular dystrophy (DMD) to transition into adulthood. However, the role of a child's parent as a caregiver lasts throughout the child's lifetime. We explored parents' experiences of prolonged caregiving using serial interviews, analyzed using constructivist grounded theory. Fourteen parents (average age 53.9 years) with sons with DMD (average age 23.2 years) were interviewed two to four times, over a 3-year period. Data were analyzed using a grounded theory approach. Two categories of responses were defined as strengths, and four as weaknesses. The strengths were related to family member support and confidence in parenting ability. The weaknesses were related to the anticipation of aging with the ongoing burden of caring for adult sons, regrets, sharing of responsibility versus having a fixed role as the primary caregiver, and economic burden. The weaknesses became more pronounced as the duration of caregiving increased. Parents' acceptance of and immobilization in their role of primary caregiver led to prolonged derivative dependency. Practical support for parental caregivers, who experience a marked increase in the duration of their caregiving role while facing their own aging-related challenges, are required. Implications for Rehabilitation Children with DMD are living longer and are transitioning into adulthood; a successful transition involves becoming as independent as possible and maintaining a positive sense of personal identity. Despite entering adulthood, the parental caregiver's caregiving role continues. Rehabilitation professionals, who are able to provide long-term, continued support from childhood into adulthood, should be aware that parental caregivers' weakness are exacerbated as the duration of caregiving increases. Families affected by DMD require multifaceted support that should include support for the parental caregiver.
MeSH Terms
- Adult
- Adult Children
- Caregivers
- Cost of Illness
- Empathy
- Female
- Humans
- Long-Term Care
- Male
- Middle Aged
- Muscular Dystrophy, Duchenne
- Parenting
- Parents
- Qualitative Research
- Self Concept
- Social Support
Keywords
- Parenting
- aging
- burden of care
- care-dependent
- disability
- transition to adulthood
Duchenne muscular dystrophy (DMD) is a progressive degenerative disease that results in fibrosis and atrophy of muscles. The main cause of death associated with DMD is failure of the diaphragm. The diaphragm is a dome-shaped muscle with a fiber microstructure that differs across regions of the muscle. However, no studies to our knowledge have examined spatial variations of muscle fibers in dystrophic diaphragm or how aging affects those variations in DMD. In this study, diaphragms were obtained from mdx and healthy mice at ages three, seven, and ten months in the dorsal, midcostal, and ventral regions. Through immunostaining and confocal imaging, we quantified sarcomere length, interstitial space between fibers, fiber branching, fiber cross sectional area (CSA), and fiber regeneration measured by centrally located nuclei. Because DMD is associated with chronic inflammation, we also investigated the number of macrophages in diaphragm muscle cross-sections. We saw regional differences in the number of regenerating fibers and macrophages during the progression of DMD in the mdx diaphragm. Additionally, the number of regenerating fibers increased with age, while CSA and the number of branching fibers decreased. Dystrophic diaphragms had shorter sarcomere lengths than age-matched controls. Our results suggest that the dystrophic diaphragm in the mdx mouse is structurally heterogeneous and remodels non-uniformly over time. Understanding regional changes in dystrophic diaphragms over time will facilitate the development of targeted therapies to prevent or minimize respiratory failure in DMD patients.
MeSH Terms
- Age Factors
- Aging
- Animals
- Diaphragm
- Disease Models, Animal
- Male
- Mice
- Mice, Inbred C57BL
- Microscopy, Confocal
- Muscular Dystrophy, Duchenne
The aim of this study was to describe the longitudinal changes in facial morphology, dental arch alterations and oral functional capacities that occur in growing patients with Duchenne muscular dystrophy (DMD) in order to identify the effects of the progression of the disease. Twelve DMD patients (6.5-17.5 years of age) and 12 matched controls were screened on two different occasions (T1 and T2), 2 years apart. Dental casts, lateral cephalometric radiographs, maximal posterior bite force and labial force were measured to determine changes in their functional capacities and dentofacial morphology. Furthermore, the thickness and echogenicity of the masseter muscle were measured during clenching. Unpaired t-tests were performed to evaluate the differences between the DMD patients and their healthy matched controls; paired t-tests were used to assess the changes that occurred within each group between T1 and T2. Between T1 and T2 the following changes were observed: widening of the lower dental arch for the DMD patients of 2.6mm (±0.9mm) compared to a slight reduction of -0.1mm (±0.8mm) for the control group (P = 0.001). We found a statistically significant reduction of the sagittal skeletal intermaxillary relationship (ANB-angle) of 2.0° (±2.0°) in the DMD group (P = 0.012). In T1 and T2, the maximal posterior bite force and the labial force were lower for the DMD patients compared to the control group (P = 0.001), who showed an increase during this period. The results indicate that DMD influences the facial morphology, dental arch dimensions and oral functional capacities. The longitudinal perspective of this study revealed that the worsening of most of the measured parameters is associated with the progression of the disease. Besides the expected deterioration of the functional measurements, we found in all patients, a marked transverse increase of the posterior part of the dental arches, more in the lower than in the upper, resulting in posterior crossbites, as well as a tendency towards a skeletal Class III relationship.
MeSH Terms
- Adolescent
- Aging
- Bite Force
- Case-Control Studies
- Cephalometry
- Child
- Dental Arch
- Disease Progression
- Face
- Humans
- Lip
- Longitudinal Studies
- Male
- Malocclusion
- Masseter Muscle
- Muscular Dystrophy, Duchenne
Duchenne muscular dystrophy, one of the most common lethal genetic disorders, is caused by mutations in the DMD gene and a lack of dystrophin protein. In most DMD patients and animal models, sporadic dystrophin-positive muscle fibres, called revertant fibres (RFs), are observed in otherwise dystrophin-negative backgrounds. RFs are thought to arise from skeletal muscle precursor cells and clonally expand with age due to the frequent regeneration of necrotic fibres. Here we examined the effects of genetic background on muscle regeneration and RF expansion by comparing dystrophin-deficient mdx mice on the C57BL/6 background (mdx-B6) with those on the DBA/2 background (mdx-DBA), which have a more severe phenotype. Interestingly, mdx-DBA muscles had significantly lower RF expansion than mdx-B6 in all age groups, including 2, 6, 12, and 18 months. The percentage of centrally nucleated fibres was also significantly lower in mdx-DBA mice compared to mdx-B6, indicating that less muscle regeneration occurs in mdx-DBA. Our study aligns with the model that RF expansion reflects the activity of precursor cells in skeletal muscles, and it serves as an index of muscle regeneration capacity.
MeSH Terms
- Aging
- Animals
- Cell Proliferation
- Disease Models, Animal
- Dystrophin
- Female
- Gene Expression
- Genetic Background
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Inbred mdx
- Muscle Fibers, Skeletal
- Muscular Dystrophy, Duchenne
- Mutation
- Myoblasts
- Phenotype
- Regeneration
- Severity of Illness Index
- Species Specificity
Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder in which loss of the dystrophin protein causes progressive skeletal/cardiac muscle degeneration and death within the third decade. For clinical trials and supportive animal studies, DMD disease progression and response to treatment must be established using outcome parameters (biomarkers). The 6-minute walk test (6MWT), defined as the distance an individual can walk in 6 minutes, is commonly used in DMD clinical trials and has been employed in dogs to characterize cardiac and respiratory disease severity. Building on methods established in DMD and canine clinical studies, we assessed the 6MWT in dogs with the DMD genetic homolog, golden retriever muscular dystrophy (GRMD). Twenty-one cross-bred golden retrievers were categorized as affected (DMD mutation and GRMD phenotype), carrier (female heterozygous for DMD mutation and no phenotype), and normal (wild type DMD gene and normal phenotype). When compared to grouped normal/carrier dogs, GRMD dogs walked shorter height-adjusted distances at 6 and 12 months of age and their distances walked declined with age. Percent change in creatine kinase after 6MWT was greater in GRMD versus normal/carrier dogs at 6 months, providing another potential biomarker. While these data generally support use of the 6MWT as a biomarker for preclinical GRMD treatment trials, there were certain limitations. Results of the 6MWT did not correlate with other outcome parameters for GRMD dogs when considered alone and an 80% increase in mean distance walked would be necessary to achieve satisfactory power.
MeSH Terms
- Aging
- Animals
- Creatine Kinase
- Disease Progression
- Dog Diseases
- Dogs
- Female
- Heterozygote
- Male
- Muscular Dystrophy, Animal
- Prodromal Symptoms
- Walk Test
Keywords
- Biomarker
- Creatine kinase
- Duchenne muscular dystrophy
- Golden retriever muscular dystrophy
- Six-minute walk test
Duchenne muscular dystrophy (DMD) is characterized by the loss of the protein dystrophin, leading to muscle fragility, progressive weakening, and susceptibility to mechanical stress. Although dystrophin-negative mdx mouse models have classically been used to study DMD, phenotypes appear mild compared to patients. As a result, characterization of muscle pathology, especially in the heart, has proven difficult. We report that injection of mdx embryonic stem cells (ESCs) into Wild Type blastocysts produces adult mouse chimeras with severe DMD phenotypes in the heart and skeletal muscle. Inflammation, regeneration and fibrosis are observed at the whole organ level, both in dystrophin-negative and dystrophin-positive portions of the chimeric tissues. Skeletal and cardiac muscle function are also decreased to mdx levels. In contrast to mdx heterozygous carriers, which show no significant phenotypes, these effects are even observed in chimeras with low levels of mdx ESC incorporation (10%-30%). Chimeric mice lack typical compensatory utrophin upregulation, and show pathological remodeling of Connexin-43. In addition, dystrophin-negative and dystrophin-positive isolated cardiomyocytes show augmented calcium response to mechanical stress, similar to mdx cells. These global effects highlight a novel role of mdx ESCs in triggering muscular dystrophy even when only low amounts are present. Stem Cells 2017;35:597-610.
MeSH Terms
- Aging
- Animals
- Calcium
- Chimera
- Connexin 43
- Dystrophin
- Embryonic Stem Cells
- Female
- Heart Function Tests
- Humans
- Inflammation
- Male
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Muscle, Skeletal
- Muscular Dystrophy, Animal
- Myocardium
- Myocytes, Cardiac
- Regeneration
Keywords
- Cardiomyopathy
- Chimeras
- Connexin-43
- Dystrophin
- Embryonic stem cells
- Muscular dystrophy
- Utrophin
Duchenne muscular dystrophy (DMD) is caused by genetic deficiency of dystrophin and characterized by massive structural and functional changes of skeletal muscle tissue, leading to terminal muscle failure. We recently generated a novel genetically engineered pig model reflecting pathological hallmarks of human DMD better than the widely used mdx mouse. To get insight into the hierarchy of molecular derangements during DMD progression, we performed a proteome analysis of biceps femoris muscle samples from 2-day-old and 3-month-old DMD and wild-type (WT) pigs. The extent of proteome changes in DMD vs. WT muscle increased markedly with age, reflecting progression of the pathological changes. In 3-month-old DMD muscle, proteins related to muscle repair such as vimentin, nestin, desmin and tenascin C were found to be increased, whereas a large number of respiratory chain proteins were decreased in abundance in DMD muscle, indicating serious disturbances in aerobic energy production and a reduction of functional muscle tissue. The combination of proteome data for fiber type specific myosin heavy chain proteins and immunohistochemistry showed preferential degeneration of fast-twitch fiber types in DMD muscle. The stage-specific proteome changes detected in this large animal model of clinically severe muscular dystrophy provide novel molecular readouts for future treatment trials.
MeSH Terms
- Aging
- Animals
- Disease Models, Animal
- Dystrophin
- Immunohistochemistry
- Mitochondrial Proteins
- Muscle Fibers, Fast-Twitch
- Muscle Fibers, Slow-Twitch
- Muscle Proteins
- Muscle, Skeletal
- Muscular Dystrophy, Animal
- Myosin Heavy Chains
- Proteome
- Sus scrofa
Dystrophinopathies are a group of distinct neuromuscular diseases that result from mutations in the structural cytoskeletal Dystrophin gene. Dystrophinopathies include Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), X-linked dilated cardiomyopathy, as well as DMD and BMD female carriers. The primary presenting symptom in most dystrophinopathies is skeletal muscle weakness. However, cardiac muscle is also a subtype of striated muscle and is similarly affected in many of the muscular dystrophies. Cardiomyopathies associated with dystrophinopathies are an increasingly recognized manifestation of these neuromuscular disorders and contribute significantly to their morbidity and mortality. Recent studies suggest that these patient populations would benefit from cardiovascular therapies, annual cardiovascular imaging studies, and close follow-up with cardiovascular specialists. Moreover, patients with DMD and BMD who develop end-stage heart failure may benefit from the use of advanced therapies. This review focuses on the pathophysiology, cardiac involvement, and treatment of cardiomyopathy in the dystrophic patient.
MeSH Terms
- Adrenergic beta-Antagonists
- Aging
- Angiotensin Receptor Antagonists
- Angiotensin-Converting Enzyme Inhibitors
- Arrhythmias, Cardiac
- Cardiomyopathies
- Cardiomyopathy, Dilated
- Disease Progression
- Dystrophin
- Echocardiography
- Electrocardiography
- Gene Editing
- Genetic Therapy
- Glucocorticoids
- Heart Transplantation
- Heart-Assist Devices
- Heterozygote
- Humans
- Magnetic Resonance Imaging, Cine
- Mineralocorticoid Receptor Antagonists
- Muscular Dystrophy, Duchenne
- Mutation
Keywords
- Becker muscular dystrophy cardiomyopathy
- Duchenne muscular dystrophy cardiomyopathy
- muscular dystrophy cardiomyopathy
Muscle regeneration is an important process for skeletal muscle growth and recovery. Repair of muscle damage is exquisitely programmed by cellular mechanisms inherent in myogenic stem cells, also known as muscle satellite cells. We demonstrated previously the involvement of homeobox transcription factors, SIX1, SIX4 and SIX5, in the coordinated proliferation and differentiation of isolated satellite cells in vitro. However, their roles in adult muscle regeneration in vivo remain elusive. To investigate SIX4 and SIX5 functions during muscle regeneration, we introduced knockout alleles of Six4 and Six5 into an animal model of Duchenne Muscular Dystrophy (DMD), mdx (Dmd(mdx) /Y) mice, characterized by frequent degeneration-regeneration cycles in muscles. A lower number of small myofibers, higher number of thick ones and lower serum creatine kinase and lactate dehydrogenase activities were noted in 50-week-old Six4( /-) 5( /-) Dmd(mdx) /Y mice than Dmd(mdx) /Y mice, indicating improvement of dystrophic phenotypes of Dmd(mdx) /Y mice. Higher proportions of cells positive for MYOD1 and MYOG (markers of regenerating myonuclei) and SIX1 (a marker of regenerating myoblasts and newly regenerated myofibers) in 12-week-old Six4( /-) 5( /-) Dmd(mdx) /Y mice suggested enhanced regeneration, compared with Dmd(mdx) /Y mice. Although grip strength was comparable in Six4( /-) 5( /-) Dmd(mdx) /Y and Dmd(mdx) /Y mice, treadmill exercise did not induce muscle weakness in Six4( /-) 5( /-) Dmd(mdx) /Y mice, suggesting higher regeneration capacity. In addition, Six4( /-) 5( /-) Dmd(mdx) /Y mice showed 33.8% extension of life span. The results indicated that low Six4 and Six5 gene dosage improved dystrophic phenotypes of Dmd(mdx) /Y mice by enhancing muscle regeneration, and suggested that SIX4 and SIX5 are potentially useful de novo targets in therapeutic applications against muscle disorders, including DMD.
MeSH Terms
- Animals
- Gene Dosage
- Homeodomain Proteins
- Longevity
- Mice
- Mice, Inbred mdx
- Mice, Knockout
- Muscle, Skeletal
- MyoD Protein
- Myogenin
- Regeneration
- Trans-Activators
Keywords
- Six4
- Six5
- mdx
- muscle satellite cell
- skeletal muscle regeneration
Satellite cells are adult myogenic stem cells that repair damaged muscle. The enduring capacity for muscle regeneration requires efficient satellite cell expansion after injury, their differentiation to produce myoblasts that can reconstitute damaged fibres and their self-renewal to replenish the muscle stem cell pool for subsequent rounds of injury and repair. Emerging studies indicate that misregulation of satellite cell fate and function can contribute to age-associated muscle dysfunction and influence the severity of muscle diseases, including Duchenne muscular dystrophy (DMD). It has also become apparent that satellite cell fate during muscle regeneration and ageing, and in the context of DMD, is governed by an intricate network of intrinsic and extrinsic regulators. Targeted manipulation of this network may offer unique opportunities for muscle regenerative medicine.
MeSH Terms
- Aging
- Animals
- Cell Differentiation
- Cell Self Renewal
- Humans
- Muscle Proteins
- Muscle, Skeletal
- Muscular Diseases
- Regeneration
- Satellite Cells, Skeletal Muscle
- Signal Transduction
Patients with Duchenne muscular dystrophy (DMD) are at risk of developing cardiomyopathy and cardiac arrhythmias. Studies in a mouse model of DMD revealed that enhanced sarcoplasmic reticulum (SR) Ca(2 ) leak contributes to the pathogenesis of cardiac dysfunction. In view of recent data suggesting the involvement of altered phosphorylation and oxidation of the cardiac ryanodine receptor (RyR2)/Ca(2 ) release channel, we hypothesized that inhibition of RyR2 phosphorylation in a mouse model of DMD can prevent SR Ca(2 ) leak by reducing RyR2 oxidation. Confocal Ca(2 ) imaging and single RyR2 channel recordings revealed that both inhibition of S2808 or S2814 phosphorylation, and inhibition of oxidation could normalize RyR2 activity in mdx mice. Moreover, Western blotting revealed that genetic inhibition of RyR2 phosphorylation at S2808 or S2814 reduced RyR2 oxidation. Production of reactive oxygen species (ROS) in myocytes from mdx mice was reduced by both inhibition of RyR2 phosphorylation or the ROS scavenger 2-mercaptopropionyl glycine (MPG). Finally, it was shown that ROS production in mdx mice is proportional to the activity of RyR2-mediated SR Ca(2 ) leak, and likely generated by Nox2. Increased ROS production in the hearts of mdx mice drives the progression of cardiac dysfunction. Inhibition of RyR2 phosphorylation can suppress SR Ca(2 ) leak in mdx mouse hearts in part by reducing RyR2 oxidation.
MeSH Terms
- Aging
- Animals
- Calcium Signaling
- Heart
- Mice, Inbred mdx
- Muscular Dystrophy, Duchenne
- Oxidation-Reduction
- Phosphorylation
- Reactive Oxygen Species
- Ryanodine Receptor Calcium Release Channel
Keywords
- Duchenne muscular dystrophy
- Oxidation
- Phosphorylation
- Reactive oxygen species
- Ryanodine receptor type 2
To describe muscle size and architecture of the gastrocnemius medialis (GM) muscle in eleven adult males with Duchenne Muscular Dystrophy (DMD, age 24.5±5.4 years), and a control group of eleven males without DMD (CTRL, age 22.1±0.9 years). GM anatomical cross sectional area (ACSA), volume (VOL), physiological cross sectional area (PCSA), fascicle length (Lf) and pennation angle (θ) were assessed using B-Mode Ultrasonography. GM ACSA was measured at 25, 50 and 75% of muscle length (Lm), from which VOL was calculated. At 50% of Lm, sagittal plane images were analysed to determine GM Lf and θ. GM PCSA was calculated as: VOL/Lf. The ratio of Lf and Lm was also calculated. GM ACSA at 50% Lm, VOL and PCSA were smaller in DMD males compared to CTRL males by 36, 47 and 43%, respectively (P<0.01). There were no differences in Lf and θ. GM Lm was 29% shorter in DMD compared to CTRL. Lf/Lm was 29% longer in DMD (P<0.01). Unlike previous data in children with DMD, our results show significant atrophy in adult males with DMD, and no change in Lf or θ. The shorter Lm may have implications for joint flexibility.
MeSH Terms
- Adult
- Aging
- Anatomy, Cross-Sectional
- Body Height
- Body Weight
- Humans
- Male
- Muscle, Skeletal
- Muscular Dystrophy, Duchenne
- Ultrasonography
- Young Adult
Duchenne muscular dystrophy (DMD) is a chronic and life-threatening disease that is initially supported by muscle regeneration but eventually shows satellite cell exhaustion and muscular dysfunction. The life-long maintenance of skeletal muscle homoeostasis requires the satellite stem cell pool to be preserved. Asymmetric cell division plays a pivotal role in the maintenance of the satellite cell pool. Here we show that granulocyte colony-stimulating factor receptor (G-CSFR) is asymmetrically expressed in activated satellite cells. G-CSF positively affects the satellite cell population during multiple stages of differentiation in ex vivo cultured fibres. G-CSF could be important in developing an effective therapy for DMD based on its potential to modulate the supply of multiple stages of regenerated myocytes. This study shows that the G-CSF-G-CSFR axis is fundamentally important for long-term muscle regeneration, functional maintenance and lifespan extension in mouse models of DMD with varying severities.
MeSH Terms
- Animals
- Cell Differentiation
- Cell Division
- Disease Models, Animal
- Gene Expression Regulation
- Granulocyte Colony-Stimulating Factor
- Longevity
- Mice
- Mice, Inbred mdx
- Mice, Knockout
- Muscle Cells
- Muscle, Skeletal
- Muscular Dystrophy, Duchenne
- MyoD Protein
- PAX7 Transcription Factor
- Primary Cell Culture
- Receptors, Granulocyte Colony-Stimulating Factor
- Regeneration
- Satellite Cells, Skeletal Muscle
- Signal Transduction
- Stem Cells
Dp71 is the main product of the Duchenne muscular dystrophy (DMD) gene in the central nervous system. While studying the impact of its absence on retinal functions, we discovered that mice lacking Dp71 also developed a progressive opacification of the crystalline lens. The purpose of this study was to perform a detailed characterization of the cataract formation in Dp71 knockout (KO-Dp71) mice. Cataract formations in KO-Dp71 mice and wild-type (wt) littermates were assessed in vivo by slit-lamp examination and ex vivo by histological analysis as a function of aging. The expression and cellular localization of the DMD gene products were monitored by western blot and immunohistochemical analysis. Fiber cell integrity was assessed by analyzing the actin cytoskeleton as well as the expression of aquaporin-0 (AQP0). As expected, a slit-lamp examination revealed that only one of the 20 tested wt animals presented with a mild opacification of the lens and only at the most advanced age. However, a lack of Dp71 was associated with a 40% incidence of cataracts as early as 2 months of age, which progressively increased to full penetrance by 7 months. A subsequent histological analysis revealed an alteration in the structures of the lenses of KO-Dp71 mice that correlated with the severity of the lens opacity. An analysis of the expression of the different dystrophin gene products revealed that Dp71 was the major DMD gene product expressed in the lens, especially in fiber cells. The role of Dp71 in fiber cells was also suggested by the progressive disorganization of the lens fibers, which was observed in the absence of Dp71 and demonstrated by irregular staining of the actin network and the aqueous channel AQP0. While its role in the retina has been well characterized, this study demonstrates for the first time the role played by Dp71 in a different ocular tissue: the crystalline lens. It primarily demonstrates the role that Dp71 plays in the maintenance of the integrity of the secondary lens fibers.
MeSH Terms
- Actin Cytoskeleton
- Aging
- Animals
- Aquaporins
- Cataract
- Dystrophin
- Eye Proteins
- Gene Expression
- Lens, Crystalline
- Mice
- Mice, Knockout
- Retina
- Slit Lamp
Duchenne muscular dystrophy (DMD) is a lethal X-inherited disease caused by dystrophin deficiency. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with a dilated cardiomyopathy that leads to progressive heart failure at the end of the second decade. The aim of the present study was to characterize the diastolic Ca(2 ) concentration ([Ca(2 )]d) and diastolic Na( ) concentration ([Na( )]d) abnormalities in cardiomyocytes isolated from 3-, 6-, 9-, and 12-month old mdx mice using ion-selective microelectrodes. In addition, the contributions of gadolinium (Gd(3 ))-sensitive Ca(2 ) entry and inositol triphosphate (IP3) signaling pathways in abnormal [Ca(2 )]d and [Na( )]d were investigated. Our results showed an age-dependent increase in both [Ca(2 )]d and [Na( )]d in dystrophic cardiomyocytes compared to those isolated from age-matched wt mice. Gd(3 ) treatment significantly reduced both [Ca(2 )]d and [Na( )]d at all ages. In addition, blockade of the IP3-pathway with either U-73122 or xestospongin C significantly reduced ion concentrations in dystrophic cardiomyocytes. Co-treatment with U-73122 and Gd(3 ) normalized both [Ca(2 )]d and [Na( )]d at all ages in dystrophic cardiomyocytes. These data showed that loss of dystrophin in mdx cardiomyocytes produced an age-dependent intracellular Ca(2 ) and Na( ) overload mediated at least in part by enhanced Ca(2 ) entry through Gd(3 ) sensitive transient receptor potential channels (TRPC), and by IP3 receptors.
MeSH Terms
- Aging
- Animals
- Calcium
- Cardiomyopathies
- Cells, Cultured
- Diastole
- Dystrophin
- Inositol 1,4,5-Trisphosphate Receptors
- Mice
- Mice, Inbred mdx
- Muscular Dystrophy, Duchenne
- Myocytes, Cardiac
- Sodium
Keywords
- Aging
- Calcium
- Duchenne cardiomyopathy
- Inositol triphosphate receptors
- Sodium
- Transient receptor potential channels
Youth with progressive conditions are living longer, and there is increased health care focus on assisting them with "transitioning" to adult services and adult life. The purpose of this investigation was to examine key discourses and normative assumptions underpinning transitions best practices and how they are reflected in the experiences of young men with Duchenne muscular dystrophy (DMD). Using a critical perspective, we qualitatively analyzed influential transitions best practice documents to identify their underpinning discursive assumptions. We compared these to the analysis of qualitative interviews and diary data from a study of 11 young men with DMD. Transitions best practices are underpinned by discourses of developmental progression. They reproduce notions that associate successful transitions with becoming as independent as possible, approximating normal life trajectories, and planning for future adulthood. The accounts of youth with DMD both reflected and resisted these future-oriented discourses in creative ways that maintained positive personal identities. Normal developmental progression towards typical adult roles constitutes the generally accepted aims of transitions practices. Such aims may not be appropriate for all youth with disabilities. We suggest that alternative understandings of the life course and approaches to care need to be considered alongside dominant practices. Implications for Rehabilitation Children and youth with progressive conditions, such as DMD, are living longer and there is increased interest in designing programs that will assist them with "transitioning" to adulthood. Transitions best practices reflect dominant social values and assumptions about what constitutes a successful adulthood, embedded in goals such as independent living, self-management and obtaining work. Rehabilitation professionals should be aware of both positive (e.g. feelings of achievement) and negative (e.g. anxiety about the future) consequences of transitions practices that emphasize normal social developmental trajectories and milestones. Discussions with youth should offer multiple possibilities for living a good life in the present and provide support to address negative feelings and the progressive effects of DMD.
MeSH Terms
- Adolescent
- Adult
- Aging
- Disabled Persons
- Disease Progression
- Humans
- Interviews as Topic
- Life Change Events
- Male
- Muscular Dystrophy, Duchenne
- Practice Guidelines as Topic
- Self Care
- Transition to Adult Care
- Young Adult
Keywords
- Development
- Duchenne muscular dystrophy
- life course perspective
- transitions
- young men
It is expected that serum protein biomarkers in Duchenne muscular dystrophy (DMD) will reflect disease pathogenesis, progression and aid future therapy developments. Here, we describe use of quantitative in vivo stable isotope labeling in mammals to accurately compare serum proteomes of wild-type and dystrophin-deficient mdx mice. Biomarkers identified in serum from two independent dystrophin-deficient mouse models (mdx-Δ52 and mdx-23) were concordant with those identified in sera samples of DMD patients. Of the 355 mouse sera proteins, 23 were significantly elevated and 4 significantly lower in mdx relative to wild-type mice (P-value < 0.001). Elevated proteins were mostly of muscle origin: including myofibrillar proteins (titin, myosin light chain 1/3, myomesin 3 and filamin-C), glycolytic enzymes (aldolase, phosphoglycerate mutase 2, beta enolase and glycogen phosphorylase), transport proteins (fatty acid-binding protein, myoglobin and somatic cytochrome-C) and others (creatine kinase M, malate dehydrogenase cytosolic, fibrinogen and parvalbumin). Decreased proteins, mostly of extracellular origin, included adiponectin, lumican, plasminogen and leukemia inhibitory factor receptor. Analysis of sera from 1 week to 7 months old mdx mice revealed age-dependent changes in the level of these biomarkers with most biomarkers acutely elevated at 3 weeks of age. Serum analysis of DMD patients, with ages ranging from 4 to 15 years old, confirmed elevation of 20 of the murine biomarkers in DMD, with similar age-related changes. This study provides a panel of biomarkers that reflect muscle activity and pathogenesis and should prove valuable tool to complement natural history studies and to monitor treatment efficacy in future clinical trials.
MeSH Terms
- Adolescent
- Aging
- Animals
- Biomarkers
- Blood Proteins
- Child
- Child, Preschool
- Cluster Analysis
- Dystrophin
- Female
- Gene Expression
- Humans
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Molecular Sequence Annotation
- Muscular Dystrophy, Animal
- Muscular Dystrophy, Duchenne
- Species Specificity
Duchenne muscular dystrophy (DMD) is a devastating disease characterized by muscle wasting, loss of mobility and death in early adulthood. Satellite cells are muscle-resident stem cells responsible for the repair and regeneration of damaged muscles. One pathological feature of DMD is the progressive depletion of satellite cells, leading to the failure of muscle repair. Here, we attempted to explore the molecular mechanisms underlying satellite cell ablation in the dystrophin mutant mdx mouse, a well-established model for DMD. Initial muscle degeneration activates satellite cells, resulting in increased satellite cell number in young mdx mice. This is followed by rapid loss of satellite cells with age due to the reduced self-renewal ability of mdx satellite cells. In addition, satellite cell composition is altered even in young mdx mice, with significant reductions in the abundance of non-committed (Pax7 and Myf5-) satellite cells. Using a Notch-reporter mouse, we found that the mdx satellite cells have reduced activation of Notch signaling, which has been shown to be necessary to maintain satellite cell quiescence and self-renewal. Concomitantly, the expression of Notch1, Notch3, Jag1, Hey1 and HeyL are reduced in the mdx primary myoblast. Finally, we established a mouse model to constitutively activate Notch signaling in satellite cells, and show that Notch activation is sufficient to rescue the self-renewal deficiencies of mdx satellite cells. These results demonstrate that Notch signaling is essential for maintaining the satellite cell pool and that its deficiency leads to depletion of satellite cells in DMD.
MeSH Terms
- Aging
- Animals
- Cell Count
- Cell Proliferation
- Mice, Inbred mdx
- Muscles
- Muscular Dystrophy, Animal
- Receptors, Notch
- Satellite Cells, Skeletal Muscle
- Signal Transduction
Keywords
- Muscular dystrophy
- Notch signaling
- Stem cell
Retrospective study over the last 30 years of life expectancy in patients suffering from Duchenne muscular dystrophy (DMD). Analysis of the role of ventilatory assistance and causes of death. One hundred and nineteen adult DMD patients were hosted during 1981 to 2011 at AFM Yolaine de Kepper centre, Saint-Georges-sur-Loire, France. Patients' life expectancy was calculated using Kaplan-Meier model. Life expectancy without or with ventilatory assistance was 22.16 and 36.23 years, respectively. Similarly, life expectancy of patients born from 1970 (mostly with ventilatory assistance) was 40.95 years old from 1970 and 25.77 years old before 1970. Causes of death changed. Cardiac origins of death have increased from 8% to 44%. Ventilator assistance, in this study mostly through tracheotomy prolongs by more than 15 years life expectancy of DMD patients. It allows conservation of a satisfactory quality of life, and should be systematically proposed to patients.
MeSH Terms
- Adolescent
- Adult
- Cause of Death
- Humans
- Kaplan-Meier Estimate
- Life Expectancy
- Muscular Dystrophy, Duchenne
- Respiration, Artificial
- Retrospective Studies
- Young Adult
Keywords
- Assistance ventilatoire
- Duchenne muscular dystrophy
- Dystrophie musculaire de Duchenne
- Espérance de vie
- Survival
- Tracheotomy
- Trachéotomie
- Ventilatory assistance
Duchenne muscular dystrophy (DMD) is caused by mutations in the X-linked dystrophin (DMD) gene. The absence of dystrophin protein leads to progressive muscle weakness and wasting, disability and death. To establish a tailored large animal model of DMD, we deleted DMD exon 52 in male pig cells by gene targeting and generated offspring by nuclear transfer. DMD pigs exhibit absence of dystrophin in skeletal muscles, increased serum creatine kinase levels, progressive dystrophic changes of skeletal muscles, impaired mobility, muscle weakness and a maximum life span of 3 months due to respiratory impairment. Unlike human DMD patients, some DMD pigs die shortly after birth. To address the accelerated development of muscular dystrophy in DMD pigs when compared with human patients, we performed a genome-wide transcriptome study of biceps femoris muscle specimens from 2-day-old and 3-month-old DMD and age-matched wild-type pigs. The transcriptome changes in 3-month-old DMD pigs were in good concordance with gene expression profiles in human DMD, reflecting the processes of degeneration, regeneration, inflammation, fibrosis and impaired metabolic activity. In contrast, the transcriptome profile of 2-day-old DMD pigs showed similarities with transcriptome changes induced by acute exercise muscle injury. Our studies provide new insights into early changes associated with dystrophin deficiency in a clinically severe animal model of DMD.
MeSH Terms
- Aging
- Animals
- Birth Weight
- Dystrophin
- Exons
- Female
- Gene Targeting
- Humans
- Male
- Muscle, Skeletal
- Muscular Dystrophy, Animal
- Muscular Dystrophy, Duchenne
- Nuclear Transfer Techniques
- Phenotype
- Sequence Deletion
- Stress, Mechanical
- Swine
- Transcriptome
The ability of young and mature horses to digest DM, OM, and NDF was compared using 6 weanling colts and 6 mature (13.2 ± 3.0 yr) geldings. Each colt was paired with a gelding, and the pair was adapted to a diet containing 67% alfalfa cubes and 33% concentrate for 21 d. During the adaptation period, horses were accustomed to housing and all handling procedures. The adaptation period was also used to adjust the amount of feed offered to minimize orts and to maintain similar rates of intake within a pair. After the adaptation period, a 5-d fecal collection period using fecal collection harnesses ensued. The average age of the weanling colts at the start of the 5-d collection period was 181.8 ± 2.9 d. On the morning of the first collection day, Co-EDTA (9 mg Co/kg BW(0.75)) and ytterbium-labeled hay fiber (9 mg Yb/kg BW(0.75)) were added to the concentrate portion of the diet, and horses were closely observed for complete consumption of the markers before additional feed was offered. The fecal collection bags were emptied every 1 to 2 h, and each collection was weighed and subsampled for later measurement of Co and Yb concentrations, which were used to determine the mean retention time (MRT) of the fluid and particulate phases of digesta, respectively. The remaining feces for each horse were composited each day and then subsampled for measurement of DM digestibility (DMD), NDF digestibility (NDFD), and OM digestibility (OMD). During the fecal collection period, DMI was similar between colts and geldings (91.4 and 91.2 g/kg BW(0.75), respectively). There were no differences between colts and mature geldings for DMD, OMD, or NDFD. Across both ages, the MRT of the particulate phase was 24.9 h compared with 21.8 h for the fluid phase (P = 0.002). However, MRT for the particulate phase was not different between colts and mature geldings (24.7 and 25.2 h, respectively). There was no difference in the MRT for the fluid phase between colts and mature geldings (21.5 and 22.0 h, respectively). The results indicated that the digestibility of DM, OM, and NDF in a diet consisting of good-quality cubed forage and concentrate is similar for weanling colts and mature geldings.
MeSH Terms
- Aging
- Animal Feed
- Animal Nutritional Physiological Phenomena
- Animals
- Diet
- Dietary Fiber
- Dietary Supplements
- Digestion
- Feces
- Horses
- Male
- Spectrophotometry, Atomic
Embryonic and postnatal development of skeletal muscle entails highly regulated processes whose complexity continues to be deconstructed. One key stage of development is the satellite cell, whose niche is composed of multiple cell types that eventually contribute to terminally differentiated myotubes. Understanding these developmental processes will ultimately facilitate treatments of myopathies such as Duchenne muscular dystrophy (DMD), a disease characterized by compromised cell membrane structure, resulting in severe muscle wasting. One theoretical approach is to use pluripotent stem cells in a therapeutic setting to help replace degenerated muscle tissue. This chapter discusses key myogenic developmental stages and their regulatory pathways; artificial myogenic induction in pluripotent stem cells; advantages and disadvantages of DMD animal models; and therapeutic approaches targeting DMD. Furthermore, skeletal muscle serves as an excellent paradigm for understanding general cell fate decisions throughout development.
MeSH Terms
- Aging
- Animals
- Dogs
- Embryoid Bodies
- Gene Expression Regulation, Developmental
- Humans
- Mice
- MicroRNAs
- Muscle Development
- Muscle, Skeletal
- Muscular Dystrophy, Animal
- Myoblasts, Skeletal
- Pluripotent Stem Cells
- Receptors, Notch
- Regeneration
- Regenerative Medicine
- Satellite Cells, Skeletal Muscle
- Signal Transduction
- Stem Cell Niche
- Wnt Signaling Pathway