PURPOSE: To develop a reliable live-animal imaging method for monitoring muscle pathology in mouse models of myopathy. PROCEDURES: A caged near-infrared Cathepsin B (CTSB) substrate, ProSense 680, is evaluated in the dystrophin deficient mdx mice, a genetic homologue of Duchenne muscular dystrophy via optical imaging. RESULTS: We show high levels of infrared signal in dystrophic muscle relative to healthy muscle at 24 h post-injection. Imaging for CTSB presence revealed localization to inflammatory infiltrates and regenerating muscle fibers. A time series myotoxin-induced muscle injury experiment showed that CTSB activity and its mRNA levels peaked at the interface between inflammation and myoblast fusion stage of recovery. Prednisone treatment in mdx mice resulted in decreased CTSB activity and increased grip strength in forelimbs and hindlimbs. CONCLUSIONS: Optical imaging of CTSB activity is an ideal method to sensitively monitor inflammation, regeneration, and response to therapy in myopathic skeletal muscle.

Several subtypes of facioscapulohumeral muscular dystrophy (FSHD) with atypical clinical presentation have been described. We report a new, distinct phenotype with progressive bent spine syndrome solely affecting the paraspinal muscles. Magnetic resonance imaging study of the lumbar spine revealed marked atrophy of the paraspinal muscles. The diagnosis was confirmed by DNA testing, which revealed shortened restriction fragments of the D4Z4 repeat on haplotype A in connection with a positive family history. Muscle Nerve 42:273-275, 2010.

BACKGROUND: Laminin alpha2 chain mutations cause congenital muscular dystrophy with dysmyelination neuropathy (MDC1A). Previously, we demonstrated that laminin alpha1 chain ameliorates the disease in mice. Dystroglycan and integrins are major laminin receptors. Unlike laminin alpha2 chain, alpha1 chain binds the receptors by separate domains; laminin globular (LG) domains 4 and LG1-3, respectively. Thus, the laminin alpha1 chain is an excellent tool to distinguish between the roles of dystroglycan and integrins in the neuromuscular system. METHODOLOGY/PRINCIPAL FINDINGS: Here, we provide insights into the functions of laminin alpha1LG domains and the division of their roles in MDC1A pathogenesis and rescue. Overexpression of laminin alpha1 chain that lacks the dystroglycan binding LG4-5 domains in alpha2 chain deficient mice resulted in prolonged lifespan and improved health. Importantly, diaphragm and heart muscles were corrected, whereas limb muscles were dystrophic, indicating that different muscles have different requirements for LG4-5 domains. Furthermore, the regenerative capacity of the skeletal muscle did not depend on laminin alpha1LG4-5. However, this domain was crucial for preventing apoptosis in limb muscles, essential for myelination in peripheral nerve and important for basement membrane assembly. CONCLUSIONS/SIGNIFICANCE: These results show that laminin alpha1LG domains and consequently their receptors have disparate functions in the neuromuscular system. Understanding these interactions could contribute to design and optimization of future medical treatment for MDC1A patients.

To investigate the role of tissue inhibitors of metalloproteinases (TIMPs) in muscular dystrophy, we examined the expression of TIMP-1 using plasma and biopsied muscle from patients with various muscular dystrophies by ELISA, immunohistochemistry, and Western blot analysis. TIMP-1 immunolocalization was also studied in mouse models of muscular dystrophy. Plasma TIMP-1 was elevated and correlated with TGF-beta1 in Duchenne muscular dystrophy (DMD) and congenital muscular dystrophy (CMD), but not in Becker muscular dystrophy. In dystrophic human muscles, TIMP-1 was immunopositive in the regenerating and non-regenerating muscle fibers, and interstitial cells that consist of activated fibroblasts and macrophages. TIMP-1 immunoreactivity was also closely associated with TGF-beta1. Western blot analysis showed elevated TIMP-1 protein in muscles in DMD. The semiquantitative analysis of TIMP-1 staining intensity and tissue fibrosis showed that TIMP-1 immunoreactivity is closely associated with the extent of tissue fibrosis in human and mouse dystrophic muscles. In conclusion, the present study implied that the TGF-beta1-TIMP-1 pathway is activated in dystrophic muscles and the overexpression of TIMP-1 may result in increased deposition of extracellular matrix leading to tissue fibrosis. Copyright © 2010 Elsevier B.V. All rights reserved.

Muscular dystrophies are clinically, genetically, and molecularly a heterogeneous group of neuromuscular disorders. Considerable advances have been made in recent years in the identification of causative genes, the differentiation of the different forms and in broadening the understanding of pathogenesis. Muscle pathology has an important role in these aspects, but correlation of the pathology with clinical phenotype is essential. Immunohistochemistry has a major role in differential diagnosis, particularly in recessive forms where an absence or reduction in protein expression can be detected. Several muscular dystrophies are caused by defects in genes encoding sarcolemmal proteins, several of which are known to interact. Others are caused by defects in nuclear membrane proteins or enzymes. Assessment of both primary and secondary abnormalities in protein expression is useful, in particular the hypoglycosylation of alpha-dystroglycan. In dominantly inherited muscular dystrophies it is rarely possible to detect a change in the expression of the primary defective protein; an exception to this is caveolin-3.

Choline kinase (CK) was discovered in 1953. Progress in understanding the function of CK was slow until its purification in 1984. The subsequent cloning and expression of the cDNA led to the description of the gene structures. Two genes encode choline kinase, Chka and Chkb, and 3 isoforms of the enzyme have been identified – CKalpha-1, CKalpha-2, and CKbeta – and the active form of CK is a hetero- or homo-dimer. More recently, gene-disrupted mice have been described. Mice that lack CKalpha die early in embryogenesis. In contrast, mice that lack CKbeta survive to adulthood, but develop hindlimb muscular dystrophy and forelimb bone deformity. It has been shown that this hindlimb muscular dystrophy is due to decreased biosynthesis of phosphatidylcholine and increased catabolism of phosphatidylcholine in the hindlimbs, but not the forelimbs, of mice. CK and its product phosphocholine have also been implicated in development of numerous cancers. Thus, a possible treatment for some kinds of cancer may involve drug inhibition of CK or targeting the expression of CK with RNA interference. In the mid 1950s it was clear that CK was important for the biosynthesis of phosphatidylcholine, but no one predicted a role for CK in muscular dystrophy, bone deformities, or cancer.

Duchenne muscular dystrophy (DMD) is the most frequent muscular dystrophy. Currently, there is no cure for the disease. The transplantation of muscle precursor cells (MPCs) is one of the possible treatments, because it can restore the expression of dystrophin in DMD muscles. In this study, we investigated the effects of myoblasts injected with cardiotoxin on the contractile properties and resistance to eccentric contractions of transplanted and nontransplanted muscles. We used the extensor digitorum longus (EDL) as a model for our study. We conclude that the sole presence of dystrophin in a high percentage of muscle fibers is not sufficient by itself to increase the absolute or the specific force in the EDL of transplanted mdx muscle. This lack of strength increase may be due to the extensive damage that was produced by the cardiotoxin, which was coinjected with the myoblasts. However, the dystrophin presence is sufficient to protect muscle from eccentric damage as indicated by the force drop results.

Bach JR, Martinez D, Saulat B: Duchenne muscular dystrophy: The effect of glucocorticoids on ventilator use and ambulation. OBJECTIVE:: To describe the effect of glucocorticoid treatment on age at wheelchair dependence and at dependence on part-time (<23 hrs/day) and continuous noninvasive mechanical ventilation. DESIGN:: In this retrospective study, patients with Duchenne muscular dystrophy who received glucocorticoid therapy were compared with those who did not for ages at wheelchair dependence and when beginning part-time (nocturnal) and continuous noninvasive intermittent positive pressure ventilation (NIV). Respiratory symptoms, end-tidal carbon dioxide, oximetry, and vital capacity were noted every 4-12 mos, and NIV was initiated for symptomatic nocturnal hypoventilation. The daily NIV use increased until some required it continuously to survive. RESULTS:: The 117 untreated patients became wheelchair-dependent at 9.7 +/- 1.3 yrs of age. Four then died from cardiac failure, and five were older than 19 yrs without using NIV. The remaining 108 began nocturnal NIV at 19.2 +/- 3.7 yrs of age. Ninety of the 108 became continuously NIV-dependent at 21.9 +/- 4.5 yrs of age, and the 17 treated with glucocorticoid therapy became wheelchair-dependent significantly later at 10.8 +/- 1.3 yrs of age (P = 0.02). Three died from cardiac failure, and three were older than 19 yrs without using NIV. The remaining 11 began nocturnal NIV at 22.9 +/- 5.3 yrs of age (P = 0.05). Eight of the 11 became continuously NIV-dependent at age 28.9 +/- 7.3 yrs (P = 0.005). CONCLUSIONS:: Intermittent glucocorticoid therapy delays wheelchair dependence and may delay ventilator dependence for patients with Duchenne muscular dystrophy.

Objective Heart failure is one of the most serious complications in Duchenne muscular dystrophy (DMD). Beta-blocker medication is known to improve the prognosis of chronic heart failure of adults, but its efficacy and safety for DMD patients has not been fully assessed. Thus we conducted a multicenter open trial. Methods Fifty-four DMD patients participated; 41 received carvedilol (BB group) and 13 did not (non BB group). All patients with an ejection fraction of less than 50% received angiotensin-converting enzyme inhibitor. Then, patients in BB group were started on carvedilol. The mean maintenance dose of carvedilol in BB group was 7.85+/-2.80 mg/day. Clinical signs and cardiac function were monitored regularly and statistical analysis was done. Results The survival rate free from primary endpoints (death, deterioration of heart failure and severe arrhythmia) was higher in the BB group. The survival rate free from all-cause death was also higher in the BB group, although not significantly higher. Patients with primary endpoints received lower maintenance doses of carvedilol and presented higher mean heart rates (HR) during the observation period. In the BB group, mean HR at enrollment and the reduction of mean HR were correlated with the change of ejection fraction. Although serious adverse events were rare during the introduction of carvedilol, patients with advanced cardiac dysfunction required a longer period for up-titration and frequently presented with minor complaints. Conclusion The present study suggests that carvedilol is relatively safe and can prevent cardiac events even in patients with DMD.

Walker-Warburg syndrome, a progressive muscular dystrophy, is a severe disease with various kinds of symptoms such as muscle weakness and occasional seizures. The genes of protein O-mannosyltransferases 1 and 2 (POMT1 and POMT2), fukutin, and fukutin-related protein are responsible for this syndrome. In our previous study, we cloned Drosophila orthologs of human POMT1 and POMT2 and identified their activity. However, the mechanism of onset of this syndrome is not well understood. Furthermore, little is known about the behavioral properties of the Drosophila POMT1 and POMT2 mutants, which are called rotated abdomen (rt) and twisted (tw), respectively. First, we performed various kinds of behavioral tests and described in detail the muscle structures by using these mutants. The mutant flies exhibited abnormalities in heavy exercises such as climbing or flight but not in light movements such as locomotion. Defective motor function in mutants appeared immediately after eclosion and was exaggerated with aging. Along with motor function, muscle ultrastructure in the tw mutant was altered, as seen in human patients. We demonstrated that expression of RNA interference (RNAi) for the rt gene and the tw mutant was almost completely lethal and semi-lethal, respectively. Flies expressing RNAi had reduced lifespans. These findings clearly demonstrate that Drosophila POMT mutants are models for human muscular dystrophy. We then observed a high density of myoblasts with an enhanced degree of apoptosis in the tw mutant, which completely lost enzymatic activity. In this paper, we propose a novel mechanism for the development of muscular dystrophy: POMT mutation causes high myoblast density and position derangement, which result in apoptosis, muscle disorganization, and muscle cell defects.