[Animal models for muscular dystrophy--muscular dystrophy in mice].
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Animals↗
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Fibronectin, laminin, type I, III and IV collagens in Duchenne's muscular dystrophy, congenital muscular dystrophies and congenital myopathies: an immunocytochemical study.
The distribution pattern of fibronectin, laminin, type I, III and IV collagens in human skeletal muscle was studied by immunofluorescence. In normal muscle, as well as in congenital myopathies (CM), type I and III collagens were localized in the endomysium and the perimysium. Laminin and type IV collagen delineated precisely each muscle fiber but did not stain the perimysium. In Duchenne's muscular dystrophy (DMD) as well as in congenital muscular dystrophies (CMD) the extensive proliferation of connective tissue consisted mainly of fibronectin and type I and III collagens. Laminin and type IV collagen delineated principally the basal lamina but suprisingly were found to be distributed to some extent all over the extracellular matrix. No disease--specific accumulation of components of the extracellular matrix was found which would enable us to differentiate these last two diseases, though the immunofluorescence reactions for all components were stronger in DMD than in CMD.
Adolescent↗
Human growth hormone in myopathy: myotonic dystrophy, duchenne muscular dystrophy, and limb-girdle muscular dystrophy.
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Adolescent↗
Erythrocyte flexibility, ATPase activities and Ca efflux in patients with Duchenne muscular dystrophy, myotonic muscular dystrophy and congenital myotonia.
Erythrocyte flexibility measured by a polycarbonate membrane filtration method showed increased fragility (265 +/- 163 Hb mg/l vs. controls 86 +/- 72 Hb mg/l; mean +/- SD; P less than 0.0025) and increased rigidity (123 +/- 96 mm Hg vs. 79 +/- 19 mm Hg; P less than 0.05) in patients with congenital myotonia, while both parameters were normal in patients with Duchenne muscular dystrophy or with myotonic dystrophy. Erythrocyte ghosts obtained from patients with MyD displayed highly significant increases in both (Na+ + K+)-ATPase and (Ca2+ + Mg2+)-ATPase activities (P less than 0.005) and to a lesser extent in Mg2+-ATPase activity (P less than 0.05), while no difference was seen between patients with DMD and age-matched controls. The efflux of Ca2+ was increased from erythrocytes of patients with DMD as compared to age-matched controls (82 +/- 2% vs. 70 +/- 4%; P less than 0.005), while no difference was detected between patients with MyD and age-matched controls.
Adenosine Triphosphatases↗
Muscular dystrophy.
Muscular dystrophy is a group of genetically determined muscular disorders marked by progressive wasting and weakness of the skeletal muscle, but which often affect cardiac and smooth muscles or other tissues. The patterns of inheritance are either dominant or recessive although the gene may be defective because of a new mutation. Growing evidence revealed the marked heterogeneity of the muscle disorders, and considerable numbers of Japanese scientists and physicians have contributed to the research progress in muscular dystrophy. Among these the discovery of an increased serum creatine kinase activity in muscular dystrophy opened the way for the most reliable laboratory test for muscular dystrophy in 1959, and subsequently accelerated progress in a broad range of research areas in medicine. Progress in modern genetics and molecular pathology provided another breakthrough in muscular dystrophy research and, in 1987, dystrophin was identified, a deficiency of which causes DMD. The present review article highlights contributions of Japanese scientists to muscular dystrophy research.
Calpain↗
[Molecular therapy of muscular dystrophy].
Muscular dystrophy is a nosology for a group of hereditary muscle disorders characterized by progressive wasting and weakness of skeletal muscle, where degeneration of muscle fibers is detected by pathological examination. Since the causative gene of Duchenne muscular dystrophy (DMD), the most severe and abundant form of muscular dystrophy, the DMD gene, and its product dystrophin was isolated by positional cloning by Dr. Kunkel and his colleagues, the studies on molecular pathologies of muscular dystrophy has been extensively developed. The current therapeutic approaches of muscular dystrophy, such as DMD involves pharmacological suppression of the inflammatory and immure responses, which usually provides only modest and temporary beneficial effects. Future approaches depend on cell and gene therapy technology and will require different strategies, none of which are currently ready to enter clinical practice. These approaches involve the efficient, non-antigenic gene transfer for in vivo gene therapy, pharmacological upregulation of the synthesis of utrophin, a related protein that compensates for the loss of dystrophin, and myogenic stem cell transplantation. These approaches could be integrated each other and called as molecular therapy.
Animals↗
Nuclear envelope defects in muscular dystrophy.
Muscular dystrophies are a heterogeneous group of disorders linked to defects in 20-30 different genes. Mutations in the genes encoding a pair of nuclear envelope proteins, emerin and lamin A/C, have been shown to cause the X-linked and autosomal forms respectively of Emery-Dreifuss muscular dystrophy. A third form of muscular dystrophy, limb girdle muscular dystrophy 1b, has also been linked to mutations in the lamin A/C gene. Given that these two genes are ubiquitously expressed, a major goal is to determine how they can be associated with tissue specific diseases. Recent results suggest that lamin A/C and emerin contribute to the maintenance of nuclear envelope structure and at the same time may modulate the expression patterns of certain mechanosensitive and stress induced genes. Both emerin and lamin A/C may play an important role in the response of cells to mechanical stress and in this way may help to maintain muscle cell integrity.
Animals↗
Orthopedic management of the muscular dystrophies.
Muscular dystrophy is a collective group of inherited, noninflammatory, progressive muscle wasting diseases. The initial pathologic feature is an abnormality in the genetic code for dystrophin or one of its associated glycoproteins, which leads to the various clinical syndromes. Despite minor variations between the different types, all muscular dystrophies have in common progressive muscle weakness, which is best typified by Duchenne muscular dystrophy. The weakness occurs in a proximal to distal direction and can compromise ambulatory status as well as cardiopulmonary function. Additionally, structural soft tissue contractures and spinal deformities may develop from poor posturing secondary to the progressive muscle weakness and imbalance. The rapidly developing scoliosis and its associated pelvic obliquity can even compromise sitting. Recent advances in molecular biology and gene therapy research raise the hope for a cure for muscular dystrophy in the near future. Until that time, however, the role of orthopedic surgeons in treating patients with muscular dystrophy is to preserve or prolong their functional status for as long as possible. This can be achieved by physical therapy, bracing, soft tissue releases for joint contractures, and early stabilization of the spine.
Child↗
New therapies in muscular dystrophies.
Muscular dystrophies are a group of hereditary muscle disorders that often result in severe disability. Curative therapy is not yet available for muscular dystrophies (MD). In the near future, it is not expected that gene-replacement therapy will be available. Other strategies to decrease the rate of muscle necrosis and to increase strength in patients are necessary. Therefore the interest in symptomatic drug treatment has recently increased. A few trials have been performed on different types of muscular dystrophies, and some have generated positive results on muscle strength or muscle mass. We review the state of the art in therapy of MD and summarize the drugs that have been used and the evidence and results of such clinical trials.
Clinical Trials as Topic↗
Myoglobin in primary muscular disease. I. Duchenne muscular dystrophy. II. Muscular dystrophy of distal type.
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Adult↗
Stem cell therapy for muscular dystrophy.
Muscular dystrophy is a heterogeneous group of neuromuscular disorders that manifests as progressive muscle weakness, muscle wasting and, in many cases, death. Although there has been enormous progress in the molecular understanding of muscular dystrophy, there is still no cure. There are, however, several different therapeutic options under investigation, including adult-derived stem cell transplantation. Encouraging and pioneering experiments in mouse models for Duchenne's muscular dystrophy (DMD) demonstrated that myoblasts could be transplanted into dystrophic muscle; these myoblasts repaired a small proportion of damaged myofibres. Subsequent work has been devoted to optimisation of this technique. In doing so, a number of adult-derived stem cells have been isolated, characterised and used in promising animal transplantation experiments. Further research is ongoing, and is clearly necessary to make this therapy a viable treatment option for patients with muscular dystrophy.
Animals↗
Molecular basis of muscular dystrophies.
Muscular dystrophies represent a heterogeneous group of disorders, which have been largely classified by clinical phenotype. In the last 10 years, identification of novel skeletal muscle genes including extracellular matrix, sarcolemmal, cytoskeletal, cytosolic, and nuclear membrane proteins has changed the phenotype-based classification and shed new light on the molecular pathogenesis of these disorders. A large number of genes involved in muscular dystrophy encode components of the dystrophin-glycoprotein complex (DGC) which normally links the intracellular cytoskeleton to the extracellular matrix. Mutations in components of this complex are thought to lead to loss of sarcolemmal integrity and render muscle fibers more susceptible to damage. Recent evidence suggests the involvement of vascular smooth muscle DGC in skeletal and cardiac muscle pathology in some forms of sarcoglycan-deficient limb-girdle muscular dystrophy. Intriguingly, two other forms of limb-girdle muscular dystrophy are possibly caused by perturbation of sarcolemma repair mechanisms. The complete clarification of these various pathways will lead to further insights into the pathogenesis of this heterogeneous group of muscle disorders.
Humans↗
[Genes and their functional mechanisms in the pathogenesis of muscular dystrophy].
Muscular dystrophy (MD), a group of inherited disorders characterized by progressive skeletal muscle wasting and weakness, can be classified into several groups according to Mendelian inheritance patterns and clinical features. Many genes related to MD have been identified and cloned by genetic linkage analysis and positional cloning strategy. Our understanding of the molecular mechanisms giving rise to muscular dystrophy have made a progress by the functional analysis of proteins encoded by candidate genes for MD. This article reviews genes and their functional mechanisms in the pathogenesis of muscular dystrophy.
Calpain↗
Dysferlin and the plasma membrane repair in muscular dystrophy.
Muscular dystrophy covers a group of genetically determined disorders that cause progressive weakness and wasting of the skeletal muscles. Dysferlin was identified as a gene mutated in limb-girdle muscular dystrophy (type 2B) and Miyoshi myopathy. The discovery of dysferlin revealed a new family of proteins, known as the ferlin family, which includes four different genes. Recent work suggests the function of dysferlin in membrane repair and demonstrates that defective membrane repair is a novel mechanism of muscle degeneration. These findings reveal the importance of a basic cellular function in skeletal muscle and a new class of muscular dystrophy where the defect lies in the maintenance, not the structure, of the plasma membrane. Here, we discuss the current knowledge of dysferlin function in the repair of the plasma membrane of the skeletal muscle cells.
Animals↗
Defective membrane repair in dysferlin-deficient muscular dystrophy.
Muscular dystrophy includes a diverse group of inherited muscle diseases characterized by wasting and weakness of skeletal muscle. Mutations in dysferlin are linked to two clinically distinct muscle diseases, limb-girdle muscular dystrophy type 2B and Miyoshi myopathy, but the mechanism that leads to muscle degeneration is unknown. Dysferlin is a homologue of the Caenorhabditis elegans fer-1 gene, which mediates vesicle fusion to the plasma membrane in spermatids. Here we show that dysferlin-null mice maintain a functional dystrophin-glycoprotein complex but nevertheless develop a progressive muscular dystrophy. In normal muscle, membrane patches enriched in dysferlin can be detected in response to sarcolemma injuries. In contrast, there are sub-sarcolemmal accumulations of vesicles in dysferlin-null muscle. Membrane repair assays with a two-photon laser-scanning microscope demonstrated that wild-type muscle fibres efficiently reseal their sarcolemma in the presence of Ca2+. Interestingly, dysferlin-deficient muscle fibres are defective in Ca2+-dependent sarcolemma resealing. Membrane repair is therefore an active process in skeletal muscle fibres, and dysferlin has an essential role in this process. Our findings show that disruption of the muscle membrane repair machinery is responsible for dysferlin-deficient muscle degeneration, and highlight the importance of this basic cellular mechanism of membrane resealing in human disease.
Animals↗
Muscular dystrophy.
Muscular dystrophy can be a devastating diagnosis for children and their families. Understanding the potential course, prognosis, and genetic implications for the child and his/her family is dependent on the diagnosis of the specific type of dystrophy. This article suggests a sequential evaluation of children with possible muscular dystrophy and reviews the more common types.
Child↗
Sarcoglycans in muscular dystrophy.
Muscular dystrophy is a heterogeneous genetic disease that affects skeletal and cardiac muscle. The genetic defects associated with muscular dystrophy include mutations in dystrophin and its associated glycoproteins, the sarcoglycans. Furthermore, defects in dystrophin have been shown to cause a disruption of the normal expression and localization of the sarcoglycan complex. Thus, abnormalities of sarcoglycan are a common molecular feature in a number of dystrophies. By combining biochemistry, molecular cell biology, and human and mouse genetics, a growing understanding of the sarcoglycan complex is emerging. Sarcoglycan appears to be an important, independent mediator of dystrophic pathology in both skeletal muscle and heart. The absence of sarcoglycan leads to alterations of membrane permeability and apoptosis, two shared features of a number of dystrophies. beta-sarcoglycan and delta-sarcoglycan may form the core of the sarcoglycan subcomplex with alpha- and gamma-sarcoglycan less tightly associated to this core. The relationship of epsilon-sarcoglycan to the dystrophin-glycoprotein complex remains unclear. Animals lacking alpha-, gamma- and delta-sarcoglycan have been described and provide excellent opportunities for further investigation of the function of sarcoglycan. Dystrophin with dystroglycan and laminin may be a mechanical link between the actin cytoskeleton and the extracellular matrix. By positioning itself in close proximity to dystrophin and dystroglycan, sarcoglycan may function to couple mechanical and chemical signals in striated muscle. Sarcoglycan may be an independent signaling or regulatory module whose position in the membrane is determined by dystrophin but whose function is carried out independent of the dystrophin-dystroglycan-laminin axis.
Amino Acid Sequence↗
Stem cell based therapies to treat muscular dystrophy.
Muscular dystrophies comprise a heterogeneous group of neuromuscular disorders, characterized by progressive muscle wasting, for which no satisfactory treatment exists. Multiple stem cell populations, both of adult or embryonic origin, display myogenic potential and have been assayed for their ability to correct the dystrophic phenotype. To date, many of these described methods have failed, underlying the need to identify the mechanisms controlling myogenic potential, homing of donor populations to the musculature, and avoidance of the immune response. Recent results focus on the fresh isolation of satellite cells and the use of multiple growth factors to promote mesangioblast migration, both of which promote muscle regeneration. Throughout this chapter, various stem cell based therapies will be introduced and evaluated based on their potential to treat muscular dystrophy in an effective and efficient manner.
Animals↗