A possible mechanism of phenotypic expression of normal and dystrophic genomes on succinic dehydrogenase activity and fiber size within a single myofiber of muscle transplants

Caveolin-3: A Causative Process of Chicken Muscular Dystrophy

The etiology of chicken muscular dystrophy is the synthesis of aberrant WW domain containing E3 ubiquitin-protein ligase 1 (WWP1) protein made by a missense mutation of WWP1 gene. The β-dystroglycan that confers stability to sarcolemma was identified as a substrate of WWP protein, which induces the next molecular collapse. The aberrant WWP1 increases the ubiquitin ligase-mediated ubiquitination following severe degradation of sarcolemmal and cytoplasmic β-dystroglycan, and an erased β-dystroglycan in dystrophic αW fibers will lead to molecular imperfection of the dystrophin-glycoprotein complex (DGC). The DGC is a core protein of costamere that is an essential part of force transduction and protects the muscle fibers from contraction-induced damage. Caveolin-3 (Cav-3) and dystrophin bind competitively to the same site of β-dystroglycan, and excessive Cav-3 on sarcolemma will block the interaction of dystrophin with β-dystroglycan, which is another reason for the disruption of the DGC. It is known that fast-twitch glycolytic fibers are more sensitive and vulnerable to contraction-induced small tears than slow-twitch oxidative fibers under a variety of diseased conditions. Accordingly, the fast glycolytic αW fibers must be easy with rapid damage of sarcolemma corruption seen in chicken muscular dystrophy, but the slow oxidative fibers are able to escape from these damages.

Metabolic status of patients with muscular dystrophy in early phase of the disease: In vitro, high resolution NMR spectroscopy based metabolomics analysis of serum

AIMS

Proton Nuclear Magnetic Resonance (NMR) based metabolomics analysis is extensively used to explore the metabolic profiling of biofluids. This approach was used for the analysis of metabolites in serum of patients with major types of muscular dystrophy in early phase of the disease.

MATERIAL AND METHODS

Proton NMR spectroscopy based qualitative (assignment of metabolites) and quantitative (quantification of metabolites) analysis of metabolites in native serum of patients with Duchenne muscular dystrophy (DMD) [n=88; n represent the number], Becker muscular dystrophy (BMD) [n=40], facioscapulohumeral dystrophy (FSHD) [n=22], limb girdle muscular dystrophy (LGMD)-2B [n=35] and myotonic dystrophy (DM) [n=21] as compared to normal subjects [n=50] were performed.

KEY FINDINGS

Quantity of branched chain amino acids was elevated in serum of patients with DMD, BMD, FSHD and DM-1 as compared to normal subjects. Acetate level was elevated in serum of patients with DMD, BMD, FSHD, LGMD-2B and DM-1 as compared to normal subjects. Level of glutamine was reduced in serum of patients with DMD, BMD, LGMD-2B, FSHD and elevated in DM-1 patients as compared to normal subjects. Quantity of tyrosine was increased in serum of BMD patients as compared to normal subjects. There was a reduction in the level of lysine in serum of FSHD, LGMD-2B and DM-1 patients as compared to normal subjects. Citrate level was reduced in serum of FSHD patients, but elevated in LGMD-2B patients. Lactate level was reduced in serum of LGMD-2B patients and histidine was reduced in serum of patients with FSHD as compared to normal subjects.

SIGNIFICANCE

Outcome of this study may be useful as supportive information for the existing diagnostic methods of the muscular dystrophy.

Electroporation as a method to induce myofiber regeneration and increase the engraftment of myogenic cells in skeletal muscles of primates

Engraftment of intramuscularly transplanted myogenic cells in mice can be optimized after induction of massive myofiber damage that triggers myofiber regeneration and recruitment of grafted cells; this generally involves either myotoxin injection or cryodamage. There are no effective methods to produce a similar process in the muscles of large mammals such as primates. In this study, we tested the use of intramuscular electroporation for this purpose in 11 macaques. The test sites were 1 cm of skeletal muscle. Each site was treated with 3 penetrations of a 2-needle electrode with 1 cm spacing, applying 3 pulses of 400 V/cm, for a duration of 5 milliseconds and a delay of 200 milliseconds during each penetration. Transplantation of β-galactosidase-labeled myoblasts was done in electroporated and nonelectroporated sites. Electroporation induced massive myofiber necrosis that was followed by efficient muscle regeneration. Myoblast engraftment was substantially increased in electroporated compared with nonelectroporated sites. This suggests that electroporation may be a useful tool to study muscle regeneration in primates and other large mammals and as a method for increasing the engraftment of myoblasts and other myogenic cells in intramuscular transplantation.

Intramuscular cell transplantation as a potential treatment of myopathies: clinical and preclinical relevant data

INTRODUCTION

Myopathies produce deficits in skeletal muscle function and, in some cases, literally progressive loss of skeletal muscles. The transplantation of cells able to differentiate into myofibers is an experimental strategy for the potential treatment of some of these diseases.

AREAS COVERED

Among the two routes used to deliver cells to skeletal muscles, that is intramuscular and intravascular, this paper focuses on the intramuscular route due to our expertise and because it is the most used in animal experiments and the only tested so far in humans. Given the absence of recent reviews about clinical observations and the profusion based on mouse results, this review prioritizes observations made in humans and non-human primates. The review provides a vision of cell transplantation in myology centered on what can be learned from clinical trials and from preclinical studies in non-human primates and leading mouse studies.

EXPERT OPINION

Experiments on myogenic cell transplantation in mice are essential to quickly identify potential treatments, but studies showing the possibility to scale up the methods in large mammals are indispensable to determine their applicability in humans and to design clinical protocols.

Passive stretch of adult chicken muscle produces a myopathy remarkably similar to hereditary muscular dystrophy

The wings of 10 chickens between 1 and 5 years of age were passively extended. An increase in plasma creatine phosphokinase activity was observed in 30 min, continued to rise for 24 h, and then declined, suggesting mechanically induced damage to muscle fibers. Wing muscles were removed and examined histologically at various times after stretch. Patagialis muscles, but not biceps brachii, showed the development of muscle fiber pathology. The patagialis muscle is less active than the biceps brachii and is stretched to a greater degree by wing extension. Susceptibility of muscles to development of pathology appeared to be correlated with the age of the chickens. Pathology was remarkably similar to that observed in young chickens with hereditary muscular dystrophy. Necrotic fibers exhibiting segmental necrosis, abnormal shapes, enlargement, splitting, vacuolation, and phagocytosis were evident. Of particular interest was the appearance of abnormal clusters of acetylcholinesterase activity along the sarcolemma. These sites were shown to appear on fibers of 2-week-old dystrophic chicks prior to necrosis and increase in plasma creatine phosphokinase activity. It is suggested that aging of inactive muscles may promote adhesions between muscle fibers rendering them susceptible to damage when stretched and that necrosis of dystrophic fibers may be initiated by a similar mechanism. Such could occur if the genetic defect resulted in interfiber adhesions. Support for this hypothesis by other reports in the literature is discussed.

Transplantation of extensor carpi radialis longus muscle in normal and dystrophic chicks

The etiology of avian muscular dystrophy was examined by a cross-transplantation technique. Care was taken for the transplants to regenerate and develop under neural influence, by using the small extensor carpi radialis longus (ECRL) muscle. The ECRL muscles were exchanged between normal and dystrophic chicks 2 to 3 days ex ovo, and the muscle weight, number of muscle fibers, muscle fiber size, and contractile properties of the transplanted muscles were observed 60 to 65 days after operation when the tissue reconstitution was virtually complete. The results obtained for the physiologic, anatomic, and histologic parameters strongly suggested that there exists some failure in the host environment of the dystrophic chicken. The analyses of the histologic parameters suggested that a genetic disorder may also reside in the muscle tissue itself. The myotonic nature of the muscle membrane, however, probably does not contribute significantly to the abnormal behavior of dystrophic chickens. The importance of some neurogenic abnormalities in avian muscular dystrophy is discussed in relation to the results reported by other investigators.

Stretch-induced growth in chicken wing muscles: effects on hereditary muscular dystrophy

Skeletal muscle growth induced by passive stretch was characterized in the Patigialis muscle of chicks with hereditary muscular dystrophy. When the muscle of 6-wk-old chicks was stretched for 1 wk, the effects on muscle growth and on muscle pathology were variable, but in general few differences between stretched and unstretched muscles were observed. However, when the muscle of 1-wk-old chicks was stretched for 6 wk, the effects on muscle growth and on prevention of pathology were dramatic. Similar to results obtained previously when normal chick muscles were stretched [Holly et al., Am. J. Physiol. 238 (Cell Physiol. 7): C62-C71, 1980; Barnett et al., Am. J. Physiol. 239 (Cell Physiol. 8): C39-C46, 1980], stretched dystrophic muscle increased in weight (200%), cross-sectional area (107%), and fiber cross-sectional area (82%). DNA concentration, which is severalfold higher in unstretched dystrophic muscle compared with unstretched normal muscle, fell to values not different from normal values after being stretched. Nuclei per square millimeter also were the same for stretched dystrophic and stretched normal muscle. Histograms indicated that stretching induced a fiber distribution in dystrophic muscle qualitatively similar to that found in stretched normal muscle. Cytochemical observations revealed a dramatic protective effect of stretch against the progressive pathology of dystrophy. It is concluded that stretch of muscle applied to newly hatched dystrophic chicks is a powerful deterrent of symptoms characteristic of hereditary muscular dystrophy. Stretch imposed after the symptoms of dystrophy are apparent provides little, if any, protection.