Diagnostic delay in patients with FKRP-related muscular dystrophy

Diagnostic journey for people with FKRP mutations participating in a dystroglycanopathy natural history study (n = 68; NCT00313677) was analyzed. Earliest symptoms and age at muscular dystrophy diagnosis were abstracted from subject-reported medical history and record review. Initial signs/symptoms were classified as chronic motor dysfunction (e.g., delayed motor milestones, weakness, falling; n = 40, 59%), elevated transaminases (n = 7, 10%), or acute/intermittent symptoms (myoglobinuria, myalgia, febrile illness-associated acute weakness; n = 21, 31%). Median time from sign/symptom onset to diagnosis was 6.5 years and differed by symptom group: 7.5 years for motor group, 9 years for acute/intermittent group, and 4 years for elevated transaminases group. The sign/symptom category that most commonly resulted in a diagnosis was chronic motor dysfunction (n = 45). Of those without clear weakness as first symptom (n = 55), 36.4% were not diagnosed with MD until weakness became apparent. Median time to diagnosis was shortest for those with febrile illness-associated acute weakness (0.25 years). Median time from first sign/symptom to MD diagnosis has decreased incrementally from 18.8 years for those with onset in the 1970s to < 10 years for symptom onset occurring after 2000. Awareness of disease presentation variability will aid in earlier diagnosis, which is increasingly important with treatments in development.

Effect of Chinese herbal medicines on the overall survival of patients with muscular dystrophies in Taiwan

ETHNOPHARMACOLOGICAL RELEVANCE

Muscular dystrophies are a rare, severe, and genetically inherited group of disorders characterized by progressive loss of muscle fibers, leading to muscle weakness. The current treatment plan for muscular dystrophies includes the use of steroids to slow muscle deterioration by dampening the inflammatory response.

AIM OF THE STUDY

Chinese herbal medicine (CHM) has been offered as an adjunctive therapy in Taiwan's medical healthcare plan, making it possible to track CHM usage in patients with muscular dystrophic disease. Therefore, we explored the long-term effects of CHM use on the overall mortality of patients with muscular dystrophies.

MATERIALS AND METHODS

A total of 581 patients with muscular dystrophies were identified from the database of Registry for Catastrophic Illness Patients in Taiwan. Among them, 80 and 201 patients were CHM users and non-CHM users, respectively. Student's t-test, chi-squared test, Cox proportional hazard model, and Kaplan-Meier curve (log-rank test) were used for evaluation. Association rules and network analyses were performed to explore the combination of CHMs used in muscular dystrophies.

RESULTS

Compared to non-CHM users, there were more female patients, more comorbidities, including chronic pulmonary disease and peptic ulcer disease in the CHM user group. Patients with prednisolone usage exhibited a lower risk of overall mortality than those who did not, after adjusting for age, sex, use of CHM, and comorbidities. CHM users showed a lower risk of overall mortality after adjusting for age, sex, prednisolone use, and comorbidities. The cumulative incidence of the overall survival was significantly higher in CHM users. Association rule and network analysis showed that one main CHM cluster was commonly used to treat patients with muscular dystrophies in Taiwan. The cluster includes Yin-Qiao-San, Ban-Xia-Bai-Zhu-Tian-Ma-Tang, Zhi-Ke (Citrus aurantium L.), Yu-Xing-Cao (Houttuynia cordata Thunb.), Che-Qian-Zi (Plantago asiatica L.), and Da-Huang (Rheum palmatum L.).

CONCLUSIONS

Our data suggest that adjunctive therapy with CHM may help to reduce the overall mortality among patients with muscular dystrophies. The identification of the CHM cluster allows us to narrow down the key active compounds and may enable future therapeutic developments and clinical trial designs to improve overall survival in these patients.

Increased tissue stiffness triggers contractile dysfunction and telomere shortening in dystrophic cardiomyocytes

Duchenne muscular dystrophy (DMD) is a rare X-linked recessive disease that is associated with severe progressive muscle degeneration culminating in death due to cardiorespiratory failure. We previously observed an unexpected proliferation-independent telomere shortening in cardiomyocytes of a DMD mouse model. Here, we provide mechanistic insights using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Using traction force microscopy, we show that DMD hiPSC-CMs exhibit deficits in force generation on fibrotic-like bioengineered hydrogels, aberrant calcium handling, and increased reactive oxygen species levels. Furthermore, we observed a progressive post-mitotic telomere shortening in DMD hiPSC-CMs coincident with downregulation of shelterin complex, telomere capping proteins, and activation of the p53 DNA damage response. This telomere shortening is blocked by blebbistatin, which inhibits contraction in DMD cardiomyocytes. Our studies underscore the role of fibrotic stiffening in the etiology of DMD cardiomyopathy. In addition, our data indicate that telomere shortening is progressive, contraction dependent, and mechanosensitive, and suggest points of therapeutic intervention.

Novel dominant distal titinopathy phenotype associated with copy number variation

The aim of this study was to analyze patients from two distinct families with a novel distal titinopathy phenotype associated with exactly the same CNV in the TTN gene. We used an integrated strategy combining deep phenotyping and complete molecular analyses in patients. The CNV is the most proximal out-of-frame TTN variant reported and leads to aberrant splicing transcripts leading to a frameshift. In this case, the dominant effect would be due to dominant-negative and/or haploinsufficiency. Few CNV in TTN have been reported to date. Our data represent a novel phenotype-genotype association and provides hypotheses for its dominant effects.

Valproic acid stimulates myogenesis in pluripotent stem cell-derived mesodermal progenitors in a NOTCH-dependent manner

Muscular dystrophies are debilitating neuromuscular disorders for which no cure exists. As this disorder affects both cardiac and skeletal muscle, patients would benefit from a cellular therapy that can simultaneously regenerate both tissues. The current protocol to derive bipotent mesodermal progenitors which can differentiate into cardiac and skeletal muscle relies on the spontaneous formation of embryoid bodies, thereby hampering further clinical translation. Additionally, as skeletal muscle is the largest organ in the human body, a high myogenic potential is necessary for successful regeneration. Here, we have optimized a protocol to generate chemically defined human induced pluripotent stem cell-derived mesodermal progenitors (cdMiPs). We demonstrate that these cells contribute to myotube formation and differentiate into cardiomyocytes, both in vitro and in vivo. Furthermore, the addition of valproic acid, a clinically approved small molecule, increases the potential of the cdMiPs to contribute to myotube formation that can be prevented by NOTCH signaling inhibitors. Moreover, valproic acid pre-treated cdMiPs injected in dystrophic muscles increase physical strength and ameliorate the functional performances of transplanted mice. Taken together, these results constitute a novel approach to generate mesodermal progenitors with enhanced myogenic potential using clinically approved reagents.

Responsiveness and Minimal Clinically Important Difference of the Motor Function Measure in Collagen VI-Related Dystrophies and Laminin Alpha2-Related Muscular Dystrophy

OBJECTIVES

To investigate the responsiveness of the motor function measure (MFM) and determine the minimal clinically important difference (MCID) in individuals with 2 common types of congenital muscular dystrophy (CMD).

DESIGN

Observational, prospective, single center, cohort study.

SETTING

National Institute of Neurological Disorders and Stroke (NINDS) of the National Institutes of Health (NIH).

PARTICIPANTS

Individuals (N=44) with collagen VI-related dystrophies (COL6-RD, n=23) and 21 individuals laminin alpha2-related muscular dystrophy (LAMA2-RD, n=21) enrolled in a 4-year longitudinal natural history study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Responsiveness of the MFM-32 and the Rasch-scaled MFM-25 and the MCID of the MFM-32 determined from a patient-reported anchor with 2 different methods, within-patient and between-patient.

RESULTS

The original MFM-32 and Rasch-scaled MFM-25 performed similarly overall in both the COL6-RD and LAMA2-RD populations, with all subscores (D1, standing and transfers; D2, axial and proximal; D3, distal) showing a significant decrease over time, except MFM D1 and D3 for LAMA2-RD. The MFM D1 subscore was the most sensitive to change for ambulant individuals, whereas the MFM D2 subscore was the most sensitive to change for nonambulant individuals. The MCID for the MFM-32 total score was calculated as 2.5 and 3.9 percentage points according to 2 different methods.

CONCLUSIONS

The MFM showed strong responsiveness in individuals with LAMA2-RD and COL6-RD. Because a floor effect was identified more prominently with the Rasch-Scaled MFM-25, the use of the original MFM-32 as a quantitative variable with the assumption of scale linearity appears to be a good compromise. When designing clinical trials in congenital muscular dystrophies, the use of MCID for MFM should be considered to determine if a given intervention effects show not only a statistically significant change but also a clinically meaningful change.

A Wearable Device for Breathing Frequency Monitoring: A Pilot Study on Patients with Muscular Dystrophy

Patients at risk of developing respiratory dysfunctions, such as patients with severe forms of muscular dystrophy, need a careful respiratory assessment, and periodic follow-up visits to monitor the progression of the disease. In these patients, at-home continuous monitoring of respiratory activity patterns could provide additional understanding about disease progression, allowing prompt clinical intervention. The core aim of the present study is thus to investigate the feasibility of using an innovative wearable device for respiratory monitoring, particularly breathing frequency variation assessment, in patients with muscular dystrophy. A comparison of measurements of breathing frequency with gold standard methods showed that the device based on the inertial measurement units (IMU-based device) provided optimal results in terms of accuracy errors, correlation, and agreement. Participants positively evaluated the device for ease of use, comfort, usability, and wearability. Moreover, preliminary results confirmed that breathing frequency is a valuable breathing parameter to monitor, at the clinic and at home, because it strongly correlates with the main indexes of respiratory function.

Mechanisms Regulating Muscle Regeneration: Insights into the Interrelated and Time-Dependent Phases of Tissue Healing

Despite a massive body of knowledge which has been produced related to the mechanisms guiding muscle regeneration, great interest still moves the scientific community toward the study of different aspects of skeletal muscle homeostasis, plasticity, and regeneration. Indeed, the lack of effective therapies for several physiopathologic conditions suggests that a comprehensive knowledge of the different aspects of cellular behavior and molecular pathways, regulating each regenerative stage, has to be still devised. Hence, it is important to perform even more focused studies, taking the advantage of robust markers, reliable techniques, and reproducible protocols. Here, we provide an overview about the general aspects of muscle regeneration and discuss the different approaches to study the interrelated and time-dependent phases of muscle healing.

Pathogenic variants in COL6A3 cause Ullrich-like congenital muscular dystrophy in young Labrador Retriever dogs

The collagen VI-related muscular dystrophies in people include a broad spectrum of diseases ranging from the severe Ullrich congenital muscular dystrophy to the mild Bethlem myopathy. Clinical features are attributable to both muscle and connective tissue and include progressive muscle weakness and respiratory failure, hyperlaxity of distal joints, and progressive contracture of large joints. Here we describe two different COL6A3 pathogenic variants in Labrador Retriever dogs that result in autosomal recessive or autosomal dominant congenital myopathies with hyperlaxity of distal joints and joint contracture, similar to the condition in people.

Congenital Muscular Dystrophy and Congenital Myopathy

PURPOSE OF REVIEW

Congenital muscular dystrophies and congenital myopathies are a heterogeneous group of disorders resulting in hypotonia, muscle weakness, and dystrophic or myopathic features on muscle biopsy. This article summarizes the clinical and genetic aspects of these disorders.

RECENT FINDINGS

Historically, diagnoses of congenital muscular dystrophy and congenital myopathy have been made by clinical features and histopathology; however, recent advances in genetics have changed diagnostic practice by relying more heavily on genetic findings. This article reviews the clinical and genetic features of the most common congenital muscular dystrophies including laminin subunit alpha 2 (LAMA2)-related (merosin deficient), collagen VI-related, and α-dystroglycan-related congenital muscular dystrophies and reviews the most common congenital myopathies including nemaline rod, core, and centronuclear myopathies. With the increasing accessibility of genetic testing, the number of genes found to be associated with these disorders has increased dramatically. A wide spectrum of severity and onset (from birth to adulthood) exist across all subtypes. Progression and other features are variable depending on the subtype and severity of the specific genetic mutation.

SUMMARY

Congenital muscular dystrophy and congenital myopathy are increasingly recognized disorders. A growing appreciation for the breadth of phenotypic variability and overlap between established subtypes has challenged long-standing phenotypic and histopathologic classifications of these disorders but has driven a greater understanding of pathogenesis and opened the door to the development of novel treatments.

Adolescent Hyperuricemia with Lipid Storage Myopathy: A Clinical Study

BACKGROUND In this study, we investigated the clinical and pathological features of patients with lipid storage myopathy (LSM) complicated with hyperuricemia, to improve clinicians' understanding of metabolic multi-muscular disorder with metabolic disorders, and to reduce the risk of missed diagnosis of LSM. MATERIAL AND METHODS From January 2005 to December 2017, 8 patients underwent muscle biopsy and diagnosed by muscle pathology and genetic testing in our hospital. All 8 patients were in compliance with LSM diagnosis. We collected data on the patient's clinical performance, adjuvant examination, treatment, and outcomes to provide a comprehensive report and description of LSM patients with hyperuricemia. RESULTS All patients were diagnosed as having ETFDH gene mutations. The main clinical manifestations of patients were chronic limb and trunk weakness, limb numbness, and muscle pain. The serum creatine kinase (CK) values in all patients were higher than normal values. Electromyography showed 3 cases of simple myogenic damage and 3 cases of neurogenic injury. Hematuria metabolic screening showed that 2 patients had elevated glutaric aciduria, and 1 patient had elevated fatty acyl carnitine in the blood. All patients were given riboflavin treatment, and the clinical symptoms were significantly improved, and 3 patients returned to normal uric acid levels after treatment. Pathological staining showed an abnormal deposition of lipid droplets in muscle fibers. CONCLUSIONS If an adolescent hyperuricemia patient has abnormal limb weakness, exercise intolerance, and elevated serum CK values, clinicians need to be highly alert to the possibility of LSM. Early diagnosis and treatment of LSM should improve the clinical symptoms and quality of life and reduce complications.

A Promising Future for Stem-Cell-Based Therapies in Muscular Dystrophies-In Vitro and In Vivo Treatments to Boost Cellular Engraftment

Muscular dystrophies (MD) are a group of genetic diseases that lead to skeletal muscle wasting and may affect many organs (multisystem). Unfortunately, no curative therapies are available at present for MD patients, and current treatments mainly address the symptoms. Thus, stem-cell-based therapies may present hope for improvement of life quality and expectancy. Different stem cell types lead to skeletal muscle regeneration and they have potential to be used for cellular therapies, although with several limitations. In this review, we propose a combination of genetic, biochemical, and cell culture treatments to correct pathogenic genetic alterations and to increase proliferation, dispersion, fusion, and differentiation into new or hybrid myotubes. These boosted stem cells can also be injected into pretreate recipient muscles to improve engraftment. We believe that this combination of treatments targeting the limitations of stem-cell-based therapies may result in safer and more efficient therapies for MD patients. Matricryptins have also discussed.

Functional rescue in a mouse model of congenital muscular dystrophy with megaconial myopathy

Congenital muscular dystrophy with megaconial myopathy (MDCMC) is an autosomal recessive disorder characterized by progressive muscle weakness and wasting. The observation of megamitochondria in skeletal muscle biopsies is exclusive to this type of MD. The disease is caused by loss of function mutations in the choline kinase beta (CHKB) gene which results in dysfunction of the Kennedy pathway for the synthesis of phosphatidylcholine. We have previously reported a rostrocaudal MD (rmd) mouse with a deletion in the Chkb gene resulting in an MDCMC-like phenotype, and we used this mouse to test gene therapy strategies for the rescue and alleviation of the dystrophic phenotype. Introduction of a muscle-specific Chkb transgene completely rescues motor and behavioral function in the rmd mouse model, confirming the cell-autonomous nature of the disease. Intramuscular gene therapy post-disease onset using an adeno-associated viral 6 (AAV6) vector carrying a functional copy of Chkb is also capable of rescuing the dystrophy phenotype. In addition, we examined the ability of choline kinase alpha (Chka), a gene paralog of Chkb, to improve dystrophic phenotypes when upregulated in skeletal muscles of rmd mutant mice using a similar AAV6 vector. The sum of our results in a preclinical model of disease suggest that replacement of the Chkb gene or upregulation of endogenous Chka could serve as potential lines of therapy for MDCMC patients.

Muscle satellite cells and impaired late stage regeneration in different murine models for muscular dystrophies

Satellite cells (SCs) are the main muscle stem cells responsible for its regenerative capacity. In muscular dystrophies, however, a failure of the regenerative process results in muscle degeneration and weakness. To analyze the effect of different degrees of muscle degeneration in SCs behavior, we studied adult muscle of the dystrophic strains: DMDmdx, Largemyd, DMDmdx/Largemyd, with variable histopathological alterations. Similar results were observed in the dystrophic models, which maintained normal levels of PAX7 expression, retained the Pax7-positive SCs pool, and their proliferation capacity. Moreover, elevated expression of MYOG, an important myogenic factor, was also observed. The ability to form new fibers was verified by the presence of dMyHC positive regenerating fibers. However, those fibers had incomplete maturation characteristics, such as small and homogenous fiber caliber, which could contribute to their dysfunction. We concluded that dystrophic muscles, independently of their degeneration degree, retain their SCs pool with proliferating and regenerative capacities. Nonetheless, the maturation of these new fibers is incomplete and do not prevent muscle degeneration. Taken together, these results suggest that the improvement of late muscle regeneration should better contribute to therapeutic approaches.

Tempol treatment shows phenotype improvement in mdx mice

Considering potential Tempol effects on mdx muscle fibers, in this study we evaluated its effects on relevant dystrophic phenotypic characteristics, such as muscle degeneration, inflammatory process and angiogenesis, which as yet have not been investigated. Mdx mice were randomly assigned into three groups: mdxS, the control group receiving intraperitoneal (i.p.) injections of saline solution (100μL); mdxP, positive control group receiving prednisolone (1mg/kg) by oral gavage; and mdxT, treated group receiving i.p. injections of tempol (100 mg/kg). C57BL/10 mice were also used as controls. Tempol treatment promoted gain in muscle strength and reduced myonecrosis and inflammatory response in the dystrophic diaphragm (DIA) and biceps brachii (BB) muscles. No evidence of Tempol's beneficial performance on angiogenesis in DIA and BB mdx muscles was found. The findings presented here show that Tempol treatment improves dystrophic phenotype, supporting its use as a potential therapeutic strategy in DMD.

Frequency of reported pain in adult males with muscular dystrophy

INTRODUCTION

The purpose of this study was to present and compare pain between adult males with Duchenne (DMD), Becker's (BMD), Limb-Girdle (LGMD) Facioscapulohumeral (FSHD) forms of Muscular Dystrophy (MD), and healthy controls (CTRL), using three different methods of assessment.

METHODS

Pain was assessed using 1) a whole body visual analogue scale (VAS) of pain, 2) a generalised body map and 3) a localised body map.

RESULTS

All types of MD reported more VAS pain than CTRL, with 97% of all MD participants reporting pain; however, no differences were reported between types of MD. The generalised body map approach identified more frequent pain in the shoulders of FSHD (93%) than other groups (13-43%), hips of DMD (87%) and LGMD (75%) than other groups (0-29%), and legs of all MD (64-78%) than CTRL (25%). The localised body map approach identified common areas of frequent pain across types of MD, posterior distal leg and distal back, as well as condition specific regions of frequent pain, for example posterior trapezius in FSHD, and anterior hip pain in DMD and LGMD.

CONCLUSIONS

Using a single pain value (VAS), increased pain was reported by adults with MD compared to CTRL, with no clear differences between different MD groups, suggesting pain is symptomatic of MD. The use of the generalised body map approach, and to an even greater extent the localised body map approach, identified specific areas of frequent pain relevant to each individual condition. These results indicate that whist the commonly used generalised approach can be used to identify broad anatomical regions, the localised approach provides a more comprehensive understanding of pain, reflective of clinical assessment, and should be utilised in future research.

Dysphagia diagnosis with questionnaire, tongue strength measurement, and FEES in patients with childhood-onset muscular dystrophy

INTRODUCTION

Dysphagia in progressive muscle diseases is primarily due to muscle weakness. Objective of our study is to investigate the prevalence and phenotypes of dysphagia in patients with childhood onset muscular dystrophy (MD) with the use of a validated questionnaire, the measurement of tongue strength and Flexible Endoscopic Evaluation of Swallowing (FEES).

METHODS

Prospective observational longitudinal study of dysphagia in a cohort of 58 patients attending the Pediatric Department Center for Neuromuscular Diseases. Control participants were 56 age and sex matched healthy volunteers. Dysphagia was evaluated with the Eating Assessment Tool-10 (EAT-10), and the measurement of Maximal Isometric Tongue Pressure (MITP) and tongue endurance (Iowa Oral Performance Instrument-IOPI). Dysphagic patients were submitted to FEES. Recorded data included demographic and anthropometric characteristics, type of MD, feeding status, and spirometry.

RESULTS

Our patients' cohort consisted of 41 children, 11 adolescents, and 6 adults. Based on EAT-10, 20.7% of the patients were dysphagic: 14.63% of children, 27.3% of adolescents and 50% of adults. The main complain was solid food dysphagia. Spirometry parameters mean values for children and adolescent patients corresponded to lower than the fifth percentile. Means of FVC and FEV1 expressed as % predicted for adult patients were 27.8 (SD:25.05) and 28.8 (SD:28.44) respectively. Reduced tongue strength was measured to children aged 9-10, adolescent and adult MD patients. The main FEES findings were pharyngeal residue, spillage of food before the swallow, and supraglottal penetration.

DISCUSSION

This is the first study to use a validated questionnaire to evaluate dysphagia in childhood onset MD and report dyphagia prevalence at different patients' age. This is the first study reporting MITP in children and adults with generalised MD. Tongue pressures are reduced well before clinical signs of dysphagia are present.

CONCLUSION

Screening of potentially dysphagic MD patients can be based on a validated questionnaire. Patients with an EAT-10 score suggestive of dysphagia at regular follow-up can have the MITP measured and in the case of reduced values a thorough dysphagia evaluation with FEES is indicated.

The cardiorespiratory response and physiological determinants of the assisted 6-minute handbike cycle test in adult males with muscular dystrophy

INTRODUCTION

The assisted 6-minute cycle test (A6MCT) distance was assessed in adults with muscular dystrophy (MD).

METHODS

Forty-eight males, including those with Duchenne MD (DMD), limb-girdle MD (LGMD), fascioscapulohumeral MD (FSHD), and Becker MD (BMD), as well as a group without MD (CTRL), completed handgrip strength (HGS), lung function [forced expiratory volume in 1 second (FEV1 ) and forced vital capacity (FVC)], body fat, and biceps thickness assessments. During the A6MCT, ventilation (VE), oxygen uptake (VO2 ), carbon dioxide (VCO2 ), and heart rate (HR) were recorded.

RESULTS

A6MCT and HGS were lower in MD than CTRL subjects. FEV1 , FVC, and biceps thickness were lower in MD than CTRL; lower in DMD than BMD, LGMD, and FSHD; but were not different between BMD, LGMD, and FSHD. A6MCT correlated with HGS, FEV1 , FVC, body fat, VO2 , VCO2 , HR, and VE (r = 0.455-0.708) in pooled BMD, LGMD, and FSHD participants.

DISCUSSION

A shorter A6MCT distance in adult males with MD was attributable to HGS and lung function. The A6MCT is appropriate for assessment of physical function in adults with MD. Muscle Nerve 58: 427-433, 2018.

Muscular MRI-based algorithm to differentiate inherited myopathies presenting with spinal rigidity

OBJECTIVES

Inherited myopathies are major causes of muscle atrophy and are often characterized by rigid spine syndrome, a clinical feature designating patients with early spinal contractures. We aim to present a decision algorithm based on muscular whole body magnetic resonance imaging (mWB-MRI) as a unique tool to orientate the diagnosis of each inherited myopathy long before the genetically confirmed diagnosis.

METHODS

This multicentre retrospective study enrolled 79 patients from referral centres in France, Brazil and Chile. The patients underwent 1.5-T or 3-T mWB-MRI. The protocol comprised STIR and T1 sequences in axial and coronal planes, from head to toe. All images were analyzed manually by multiple raters. Fatty muscle replacement was evaluated on mWB-MRI using both the Mercuri scale and statistical comparison based on the percentage of affected muscle.

RESULTS

Between February 2005 and December 2015, 76 patients with genetically confirmed inherited myopathy were included. They were affected by Pompe disease or harbored mutations in RYR1, Collagen VI, LMNA, SEPN1, LAMA2 and MYH7 genes. Each myopathy had a specific pattern of affected muscles recognizable on mWB-MRI. This allowed us to create a novel decision algorithm for patients with rigid spine syndrome by segregating these signs. This algorithm was validated by five external evaluators on a cohort of seven patients with a diagnostic accuracy of 94.3% compared with the genetic diagnosis.

CONCLUSION

We provide a novel decision algorithm based on muscle fat replacement graded on mWB-MRI that allows diagnosis and differentiation of inherited myopathies presenting with spinal rigidity.

KEY POINTS

• Inherited myopathies are rare, diagnosis is challenging and genetic tests require specialized centres and often take years. • Inherited myopathies are often characterized by spinal rigidity. • Whole body magnetic resonance imaging is a unique tool to orientate the diagnosis of each inherited myopathy presenting with spinal rigidity. • Each inherited myopathy in this study has a specific pattern of affected muscles that orientate diagnosis. • A novel MRI-based algorithm, usable by every radiologist, can help the early diagnosis of these myopathies.

A Homozygous LAMA2 Mutation of c.818G>A Caused Partial Merosin Deficiency in a Japanese Patient

A complete loss of merosin, which is encoded by LAMA2, causes congenital muscular dystrophy with leukoencephalopathy. Partial merosin deficiency can be caused not only by primarily LAMA2 mutations, but also secondarily by dystroglycanopathy. Although it can be molecularly diagnosed based on a genetic analysis, this method is labor-intensive because of its huge genome size. A 26-year-old male patient presented with mild muscular weakness, joint contractures, and epilepsy. Double immunofluorescence staining of a muscle biopsy specimen showed mislocalization of merosin, and a genetic analysis revealed a homozygous c.818G>A (p.Arg273Lys) mutation in LAMA2. Double immunofluorescence staining and whole exome sequencing were useful for the diagnosis of partial merosin deficiency.

Detection of early nocturnal hypoventilation in neuromuscular disorders

Objective Nocturnal hypoventilation (NH) is a complication of respiratory involvement in neuromuscular disorders (NMD) that can evolve into symptomatic daytime hypercapnia if not treated proactively with non-invasive ventilation. This study aimed to assess whether NH can be detected in the absence of other signs of nocturnal altered gas exchange. Methods We performed nocturnal transcutaneous coupled (tc) pCO2/SpO2 monitoring in 46 consecutive cases of paediatric-onset NMD with a restrictive respiratory defect (forced vital capacity < 60%). Nocturnal hypoventilation was defined as tcPCO2 > 50 mmHg for > 25% of recorded time, and hypoxemia as tcSpO2 < 88% for > 5 minutes. Daytime symptoms and bicarbonate were recorded after overnight monitoring. Results Twenty-nine of 46 consecutive patients showed NH. Twenty-three patients did not have nocturnal hypoxemia and 18 were clinically asymptomatic. In 20 patients, PaCO2 in daytime blood samples was normal. Finally, 13/29 patients with NH had isolated nocturnal hypercapnia without nocturnal hypoxia, clinical NH symptoms, or daytime hypercapnia. Conclusions Paediatric patients with NMD can develop NH in the absence of clinical symptoms or significant nocturnal desaturation. Therefore, monitoring of NH should be included among nocturnal respiratory assessments of these patients as an additional tool to determine when to commence non-invasive ventilation.

A Qualitative Approach to Health Related Quality-of-Life in Congenital Muscular Dystrophy

Congenital muscular dystrophies (CMD) cause progressive muscle weakness resulting in severe motor disabilities. Previous studies focused on the effects of motor disability. Here, we explore other factors affecting health related quality-of-life (HRQOL) in CMD. Qualitative interviews were conducted with participant-parent dyads to identify symptoms having the greatest impact on HRQOL. Symptoms were classified into themes and domains representing physical, mental, social health, and disease specific issues. Social role limitations and specific activity impairment were frequently mentioned. A greater understanding of symptoms impacting HRQOL will provide a framework for improved clinical care and patient centered outcomes as new therapies are developed.

Transcriptome profiling identifies regulators of pathogenesis in collagen VI related muscular dystrophy

Objectives

The collagen VI related muscular dystrophies (COL6-RD), Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM) are among the most common congenital muscular dystrophies and are characterized by distal joint laxity and a combination of distal and proximal joint contractures. Inheritance can be dominant negative (DN) or recessive depending on the type and location of the mutation. DN mutations allow incorporation of abnormal chains into secreted tetramers and are the most commonly identified mutation type in COL6-RD. Null alleles (nonsense, frameshift, and large deletions) do not allow incorporation of abnormal chains and act recessively. To better define the pathways disrupted by mutations in collagen VI, we have used a transcriptional profiling approach with RNA-Seq to identify differentially expressed genes in COL6-RD individuals from controls.

Methods

RNA-Seq allows precise detection of all expressed transcripts in a sample and provides a tool for quantification of expression data on a genomic scale. We have used RNA-Seq to identify differentially expressed genes in cultured dermal fibroblasts from 13 COL6-RD individuals (8 dominant negative and 5 null) and 6 controls. To better assess the transcriptional changes induced by abnormal collagen VI in the extracellular matrix (ECM); we compared transcriptional profiles from subjects with DN mutations and subjects with null mutations to transcriptional profiles from controls.

Results

Differentially expressed transcripts between COL6-RD and control fibroblasts include upregulation of ECM components and downregulation of factors controlling matrix remodeling and repair. DN and null samples are differentiated by downregulation of genes involved with DNA replication and repair in null samples.

Conclusions

Differentially expressed genes identified here may help identify new targets for development of therapies and biomarkers to assess the efficacy of treatments.

ECG artifact cancellation in surface EMG signals by fractional order calculus application

BACKGROUND AND OBJECTIVE

New aspects for automatic electrocardiography artifact removal from surface electromyography signals by application of fractional order calculus in combination with linear and nonlinear moving window filters are explored. Surface electromyography recordings of skeletal trunk muscles are commonly contaminated with spike shaped artifacts. This artifact originates from electrical heart activity, recorded by electrocardiography, commonly present in the surface electromyography signals recorded in heart proximity. For appropriate assessment of neuromuscular changes by means of surface electromyography, application of a proper filtering technique of electrocardiography artifact is crucial.

METHODS

A novel method for automatic artifact cancellation in surface electromyography signals by applying fractional order calculus and nonlinear median filter is introduced. The proposed method is compared with the linear moving average filter, with and without prior application of fractional order calculus. 3D graphs for assessment of window lengths of the filters, crest factors, root mean square differences, and fractional calculus orders (called WFC and WRC graphs) have been introduced. For an appropriate quantitative filtering evaluation, the synthetic electrocardiography signal and analogous semi-synthetic dataset have been generated. The examples of noise removal in 10 able-bodied subjects and in one patient with muscle dystrophy are presented for qualitative analysis.

RESULTS

The crest factors, correlation coefficients, and root mean square differences of the recorded and semi-synthetic electromyography datasets showed that the most successful method was the median filter in combination with fractional order calculus of the order 0.9. Statistically more significant (p < 0.001) ECG peak reduction was obtained by the median filter application compared to the moving average filter in the cases of low level amplitude of muscle contraction compared to ECG spikes.

CONCLUSIONS

The presented results suggest that the novel method combining a median filter and fractional order calculus can be used for automatic filtering of electrocardiography artifacts in the surface electromyography signal envelopes recorded in trunk muscles.

Muscular dystrophy meets protein biochemistry, the mother of invention

Muscular dystrophies result from a defect in the linkage between the muscle fiber cytoskeleton and the basement membrane (BM). Congenital muscular dystrophy type MDC1A is caused by mutations in laminin α2 that either reduce its expression or impair its ability to polymerize within the muscle fiber BM. Defects in this BM lead to muscle fiber damage from the force of contraction. In this issue of the JCI, McKee and colleagues use a laminin polymerization-competent, designer chimeric BM protein in vivo to restore function of a polymerization-defective laminin, leading to normalized muscle structure and strength in a mouse model of MDC1A. Delivery of such a protein to patients could ameliorate many aspects of their disease.

Myogenic Satellite Cells: Biological Milieu and Possible Clinical Applications

Adult skeletal muscle is a post-mitotic terminally differentiated tissue that possesses an immense potential for regeneration after injury. This regeneration can be achieved by adult stem cells named satellite cells that inhabit the muscular tissue. These cells were first identified in 1961 and were described as being wedged between the plasma membrane of the muscle fiber and the surrounding basement membrane. Since their discovery, many researchers investigated their embryological origin and the exact role they play in muscle regeneration and repair. Under normal conditions, satellite cells are retained in a quiescent state and when required, these cells are activated to proliferate and differentiate to repair pre-existing muscle fibers or to a lesser extent fuse with each other to form new myofibers. During skeletal muscle regeneration, satellite cell actions are regulated through a cascade of complex signaling pathways that are influenced by multiple extrinsic factors within the satellite cell micro-environment. Here, the basic concepts were studied about satellite cells, their development, function, distribution and the different cellular and molecular mechanisms that regulate these cells. The recent findings about some of their clinical applications and potential therapeutic use were also discussed.

[Skeletal muscle stem cell.]

Adult skeletal muscle has its own stem cell population known as satellite cells. After muscle injury, quiescent satellite cells are activated and then proliferate and differentiate into mature skeletal muscle to ensure that muscle function is recovered. In our screen for myocyte differentiation-promoting factors, we noted markedly elevated expression of granulocyte-colony stimulating factor receptor(G-CSFR, encoded by csf3r)in the skeletal muscle developing area. Furthermore, G-CSFR was transiently expressed in regenerating myocytes of adult injured skeletal muscle, and extrinsic G-CSF supported short-term and long-term muscle regeneration in mouse model of skeletal muscle injury.

Muscular dystrophy modeling in zebrafish

Skeletal muscle performs an essential function in human physiology with defects in genes encoding a variety of cellular components resulting in various types of inherited muscle disorders. Muscular dystrophies (MDs) are a severe and heterogeneous type of human muscle disease, manifested by progressive muscle wasting and degeneration. The disease pathogenesis and therapeutic options for MDs have been investigated for decades using rodent models, and considerable knowledge has been accumulated on the cause and pathogenetic mechanisms of this group of human disorders. However, due to some differences between disease severity and progression, what is learned in mammalian models does not always transfer to humans, prompting the desire for additional and alternative models. More recently, zebrafish have emerged as a novel and robust animal model for the study of human muscle disease. Zebrafish MD models possess a number of distinct advantages for modeling human muscle disorders, including the availability and ease of generating mutations in homologous disease-causing genes, the ability to image living muscle tissue in an intact animal, and the suitability of zebrafish larvae for large-scale chemical screens. In this chapter, we review the current understanding of molecular and cellular mechanisms involved in MDs, the process of myogenesis in zebrafish, and the structural and functional characteristics of zebrafish larval muscles. We further discuss the insights gained from the key zebrafish MD models that have been so far generated, and we summarize the attempts that have been made to screen for small molecules inhibitors of the dystrophic phenotypes using these models. Overall, these studies demonstrate that zebrafish is a useful in vivo system for modeling aspects of human skeletal muscle disorders. Studies using these models have contributed both to the understanding of the pathogenesis of muscle wasting disorders and demonstrated their utility as highly relevant models to implement therapeutic screening regimens.

Progressive Dystrophic Pathology in Diaphragm and Impairment of Cardiac Function in FKRP P448L Mutant Mice

Mutations in the gene for fukutin-related protein represent a subset of muscular dystrophies known as dystroglycanopathies characterized by loss of functionally-glycosylated-alpha-dystroglycan and a wide range of dystrophic phenotypes. Mice generated by our lab containing the P448L mutation in the fukutin-related protein gene demonstrate the dystrophic phenotype similar to that of LGMD2I. Here we examined the morphology of the heart and diaphragm, focusing on pathology of diaphragm and cardiac function of the mutant mice for up to 12 months. Both diaphragm and heart lack clear expression of functionally-glycosylated-alpha-dystroglycan throughout the observed period. The diaphragm undergoes progressive deterioration in histology with increasing amount of centranucleation and inflammation. Large areas of mononuclear cell infiltration and fibrosis of up to 60% of tissue area were detected as early as 6 months of age. Despite a less severe morphology with only patches of mononuclear cell infiltration and fibrosis of ~5% by 12 months of age in the heart, cardiac function is clearly affected. High frequency ultrasound reveals a smaller heart size up to 10 months of age. There are significant increases in myocardial thickness and decrease in cardiac output through 12 months. Dysfunction in the heart represents a key marker for evaluating experimental therapies aimed at cardiac muscle.

Sickness impact in people with muscular dystrophy: a longitudinal study over 10 years

Objective: To describe changes of function in terms of sickness impact over 10 years in adult patients with different types of muscular dystrophy.

Design: Patients with muscular dystrophy answered the Sickness Impact Profile and Self-report ADL questionnaires in 1991 and 2001.

Setting: The study population was identified in a comprehensive prevalence study in the county of Örebro, Sweden.

Subjects: The study group comprised 44 people grouped according to whether they had myotonic dystrophy or muscular dystrophy with proximal or distal muscles affected.

Main measures: Comparison was made between assessments of sickness impact in terms of function at the two time points.

Results: Most obvious deterioration over time was in activities of daily living that require finger and arm strength. Ambulation was significantly decreased in myotonic dystrophy and proximal muscular dystrophy. Those walking without assistive devices decreased from 91% to 52%, and the number with a disability pension increased from 36 to 55%. There was a relatively small influence with regard to psychosocial dysfunction assessed by the Sickness Impact Profile.

Conclusions: This longitudinal study shows the deteriorating functions reported by patients with muscular dystrophy. This knowledge could be used to formulate new interventions in order to offer appropriate support and treatment to this patient group.

Clinical and muscle imaging findings in 14 mainland chinese patients with oculopharyngodistal myopathy

Oculopharyngodistal myopathy (OPDM) is an extremely rare, adult-onset hereditary muscular disease characterized by progressive external ocular, pharyngeal, and distal muscle weakness and myopathological rimmed vacuole changes. The causative gene is currently unknown; therefore, diagnosis of OPDM is based on clinical and histopathological features and genetic exclusion of similar conditions. Moreover, variable manifestations of this disorder are reported in terms of muscle involvement and severity. We present the clinical profile and magnetic resonance imaging (MRI) changes of lower limb muscles in 14 mainland Chinese patients with OPDM, emphasizing the role of muscle MRI in disease identification and differential diagnosis. The patients came from 10 unrelated families and presented with progressive external ocular, laryngopharyngeal, facial, distal limb muscle weakness that had been present since early adulthood. Serum creatine kinase was mildly to moderately elevated. Electromyography revealed myogenic changes with inconsistent myotonic discharge. The respiratory function test revealed subclinical respiratory muscle involvement. Myopathological findings showed rimmed vacuoles with varying degrees of muscular dystrophic changes. All known genes responsible for distal and myofibrillar myopathies, vacuolar myopathies, and muscular dystrophies were excluded by PCR or targeted next-generation sequencing. Muscle MRI revealed that the distal lower legs had more severe fatty replacement than the thigh muscles. Serious involvement of the soleus and long head of the biceps femoris was observed in all patients, whereas the popliteus, gracilis and short head of biceps femoris were almost completely spared, even in advanced stages. Not only does our study widen the spectrum of OPDM in China, but it also demonstrates that OPDM has a specific pattern of muscle involvement that may provide valuable information for its differential diagnosis and show further evidence supporting the conclusion that OPDM is a unique disease phenotype.

Development of a tool to describe overall health, social independence and activity limitation of adolescents and young adults with disability

There is a need for research that focuses on the correlation between self-perceived quality of life (QoL) and the health outcomes of adolescents with disability transitioning to adulthood. To better understand the transition experience of adolescents and young adults with disability, we developed a questionnaire to assess the impact of disability on QoL. We recruited 174 participants who were 15-24 years old and diagnosed with Fragile X syndrome (FXS), spina bifida (SB) or muscular dystrophy (MD) and conducted an exploratory factor analysis to identify factors that characterize QoL. Five factors emerged: emotional health, physical health, independence, activity limitation, and community participation. To validate the tool, we linked medical claims and other administrative data records and examined the association of the factor scores with health care utilization and found the questionnaire can be utilized among diverse groups of young people with disability.

The toxic effect of R350P mutant desmin in striated muscle of man and mouse

Mutations of the human desmin gene on chromosome 2q35 cause autosomal dominant, autosomal recessive and sporadic forms of protein aggregation myopathies and cardiomyopathies. We generated R349P desmin knock-in mice, which harbor the ortholog of the most frequently occurring human desmin missense mutation R350P. These mice develop age-dependent desmin-positive protein aggregation pathology, skeletal muscle weakness, dilated cardiomyopathy, as well as cardiac arrhythmias and conduction defects. For the first time, we report the expression level and subcellular distribution of mutant versus wild-type desmin in our mouse model as well as in skeletal muscle specimens derived from human R350P desminopathies. Furthermore, we demonstrate that the missense-mutant desmin inflicts changes of the subcellular localization and turnover of desmin itself and of direct desmin-binding partners. Our findings unveil a novel principle of pathogenesis, in which not the presence of protein aggregates, but disruption of the extrasarcomeric intermediate filament network leads to increased mechanical vulnerability of muscle fibers. These structural defects elicited at the myofiber level finally impact the entire organ and subsequently cause myopathy and cardiomyopathy.

Laminin-α2 Chain-Deficient Congenital Muscular Dystrophy: Pathophysiology and Development of Treatment

Laminin-211 is a major constituent of the skeletal muscle basement membrane. It stabilizes skeletal muscle and influences signal transduction events from the myomatrix to the muscle cell. Mutations in the gene encoding the α2 chain of laminin-211 lead to congenital muscular dystrophy type 1A (MDC1A), a life-threatening disease characterized by severe hypotonia, progressive muscle weakness, and joint contractures. Common complications include severely impaired motor ability, respiratory failure, and feeding difficulties. Several adequate animal models for laminin-α2 chain deficiency exist and analyses of different MDC1A mouse models have led to a significant improvement in our understanding of MDC1A pathogenesis. Importantly, the animal models have been indispensable tools for the preclinical development of new therapeutic approaches for laminin-α2 chain deficiency, highlighting a number of important disease driving mechanisms that can be targeted by pharmacological approaches. In this chapter, I will describe laminin-211 and discuss the cellular and molecular pathophysiology of MDC1A as well as progression toward development of treatment.

Autophagic vacuolar pathology in desminopathies

Autophagic vacuolar myopathies are an emerging group of muscle diseases with common pathologic features. These include autophagic vacuoles containing both lysosomal and autophagosomal proteins sometimes lined with sarcolemmal proteins such as dystrophin. These features have been most clearly described in patients with Danon's disease due to LAMP2 deficiency and X-linked myopathy with excessive autophagy (XMEA) due to mutations in VMA21. Disruptions of these proteins lead to lysosomal dysfunction and subsequent autophagic vacuolar pathology. We performed whole exome sequencing on two families with autosomal dominantly inherited myopathies with autophagic vacuolar pathology and surprisingly identified a p.R454W tail domain mutation and a novel p.S6W head domain mutation in desmin, DES. In addition, re-evaluation of muscle tissue from another family with a novel p.I402N missense DES mutation also identified autophagic vacuoles. We suggest that autophagic vacuoles may be an underappreciated pathology present in desminopathy patient muscle. Moreover, autophagic vacuolar pathology can be due to genetic etiologies unrelated to primary defects in the lysosomes or autophagic machinery. Specifically, cytoskeletal derangement and the accumulation of aggregated proteins such as desmin may activate the autophagic system leading to the pathologic features of an autophagic vacuolar myopathy.

Wnt7a stimulates myogenic stem cell motility and engraftment resulting in improved muscle strength

Wnt7a/Fzd7 signaling stimulates skeletal muscle growth and repair by inducing the symmetric expansion of satellite stem cells through the planar cell polarity pathway and by activating the Akt/mTOR growth pathway in muscle fibers. Here we describe a third level of activity where Wnt7a/Fzd7 increases the polarity and directional migration of mouse satellite cells and human myogenic progenitors through activation of Dvl2 and the small GTPase Rac1. Importantly, these effects can be exploited to potentiate the outcome of myogenic cell transplantation into dystrophic muscles. We observed that a short Wnt7a treatment markedly stimulated tissue dispersal and engraftment, leading to significantly improved muscle function. Moreover, myofibers at distal sites that fused with Wnt7a-treated cells were hypertrophic, suggesting that the transplanted cells deliver activated Wnt7a/Fzd7 signaling complexes to recipient myofibers. Taken together, we describe a viable and effective ex vivo cell modulation process that profoundly enhances the efficacy of stem cell therapy for skeletal muscle.

Diagnostic approach to the congenital muscular dystrophies

Congenital muscular dystrophies (CMDs) are early onset disorders of muscle with histological features suggesting a dystrophic process. The congenital muscular dystrophies as a group encompass great clinical and genetic heterogeneity so that achieving an accurate genetic diagnosis has become increasingly challenging, even in the age of next generation sequencing. In this document we review the diagnostic features, differential diagnostic considerations and available diagnostic tools for the various CMD subtypes and provide a systematic guide to the use of these resources for achieving an accurate molecular diagnosis. An International Committee on the Standard of Care for Congenital Muscular Dystrophies composed of experts on various aspects relevant to the CMDs performed a review of the available literature as well as of the unpublished expertise represented by the members of the committee and their contacts. This process was refined by two rounds of online surveys and followed by a three-day meeting at which the conclusions were presented and further refined. The combined consensus summarized in this document allows the physician to recognize the presence of a CMD in a child with weakness based on history, clinical examination, muscle biopsy results, and imaging. It will be helpful in suspecting a specific CMD subtype in order to prioritize testing to arrive at a final genetic diagnosis.

Body composition, muscle strength, and physical function of patients with Bethlem myopathy and Ullrich congenital muscular dystrophy

OBJECTIVE

To determine the contributions of body mass, adiposity, and muscularity to physical function and muscle strength in adult patients with Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD).

MATERIALS AND METHODS

Evaluation involved one UCMD and 7 BM patients. Body composition was determined by body mass index (BMI) and dual-energy-X-ray-absorptiometry (DXA), muscle strength by dynamometry, physical function by the distance walked in 6 minutes (6MWD), forced vital capacity (FVC) by a spirometer.

RESULTS

Six participants were of normal weight and 2 overweight based on BMI; all were sarcopenic based on appendicular fat free mass index (AFFMI); and 7 were sarcopenic obese based on AFFMI and % fat mass. Average muscle strength was reduced below 50% of normal. The 6MWD was in BM patients 30% less than normal. FVC was reduced in 4 of the BM patients. Muscle strength had a good correlation with the physical function variables. Correlation between muscle strength and BMI was poor; it was very high with AFFMI. AFFMI was the best single explicator of muscle strength and physical function.

CONCLUSION

Muscle mass determined by DXA explains most of the variability of the measures of muscle strength and physical function in patients with BM and UCMD.

[Clinical and pathological features in children with progressive muscular dystrophy]

OBJECTIVE

To investigate the clinical and pathological features of progressive muscular dystrophy (PMD) in children and to provide help for the early and accurate diagnosis of PMD.

METHODS

Retrospective analysis was performed on the clinical data of 99 hospitalized children with PMD, including clinical manifestations, age of onset, family history, creatase, electromyogram (EMG) and pathological changes of muscles.

RESULTS

Of the 99 children with PMD, the age of onset was 0.5-14.5 (4.7 ± 3.1) years. Eleven cases (11%) had a family history of PMD. Twenty-six (26%) were misdiagnosed as other diseases. All patients presented with muscle weakness when seeing the doctor, and 66 (67%) of them had muscle atrophy and/or hypertrophy. All patients had elevated creatine kinase (CK) levels. The 2-7-year-old group (n=51) had a mean CK level of 9965 ± 8876 U/L, and the 7-15-year-old group (n=48) had a mean CK level of 5110 ± 4498 U/L, with a significant difference between the two groups (P<0.01). The EMG examination performed on 66 patients showed that 54 cases (82%) had myogenic damage and 10 cases (15%) had neurogenic damage. Light microscopy revealed coexistence of atrophy and hypertrophy of muscle fibers, hyaline degeneration and granular degeneration. Electron microscopy showed that muscle fibers were different in thickness, some atrophic or hypertrophic; muscle cell nuclei moved inwardly, myofilaments dissolved and disappeared mildly under the sarcolemma, there were scattered melting lesions within muscle fibers, the numbers of glycogen granules and mitochondria increased, mild hyperplasia and expansion of sarcoplasmic reticulum were seen, and a small number of muscle fibers had necrosis.

CONCLUSIONS

Weakness of both lower extremities remains the main reason for PMD patients seeing the doctor. CK is the main laboratory indicator for diagnosis of PMD. PMD is mainly manifested as myogenic damage in the early stage and may be accompanied by neurogenic damage in the late stage, according to the EMG examination. With a high misdiagnosis rate, PMD may be misdiagnosed as many other diseases. Pathological examination under light microscope and electron microscope is the main means for confirming a PMD diagnosis.

Omigapil treatment decreases fibrosis and improves respiratory rate in dy(2J) mouse model of congenital muscular dystrophy

Introduction

Congenital muscular dystrophy is a distinct group of diseases presenting with weakness in infancy or childhood and no current therapy. One form, MDC1A, is the result of laminin alpha-2 deficiency and results in significant weakness, respiratory insufficiency and early death. Modification of apoptosis is one potential pathway for therapy in these patients.

Methods

dy^2J mice were treated with vehicle, 0.1 mg/kg or 1 mg/kg of omigapil daily via oral gavage over 17.5 weeks. Untreated age matched BL6 mice were used as controls. Functional, behavioral and histological measurements were collected.

Results

dy^2J mice treated with omigapil showed improved respiratory rates compared to vehicle treated dy^2J mice (396 to 402 vs. 371 breaths per minute, p<0.03) and similar to control mice. There were no statistical differences in normalized forelimb grip strength between dy^2J and controls at baseline or after 17.5 weeks and no significant differences seen among the dy^2J treatment groups. At 30–33 weeks of age, dy^2J mice treated with 0.1 mg/kg omigapil showed significantly more movement time and less rest time compared to vehicle treated. dy^2J mice showed normal cardiac systolic function throughout the trial. dy^2J mice had significantly lower hindlimb maximal (p<0.001) and specific force (p<0.002) compared to the control group at the end of the trial. There were no statistically significant differences in maximal or specific force among treatments. dy^2J mice treated with 0.1 mg/kg/day omigapil showed decreased percent fibrosis in both gastrocnemius (p<0.03) and diaphragm (p<0.001) compared to vehicle, and in diaphragm (p<0.013) when compared to 1 mg/kg/day omigapil treated mice. Omigapil treated dy^2J mice demonstrated decreased apoptosis.

Conclusion

Omigapil therapy (0.1 mg/kg) improved respiratory rate and decreased skeletal and respiratory muscle fibrosis in dy^2J mice. These results support a putative role for the use of omigapil in laminin deficient congenital muscular dystrophy patients.

Epigenetic regulation of skeletal muscle development and differentiation

Skeletal muscle cells have served as a paradigm for understanding mechanisms leading to cellular differentiation. Formation of skeletal muscle involves a series of steps in which cells are committed towards the myogenic lineage, undergo expansion to give rise to myoblasts that differentiate into multinucleated myotubes, and mature to form adult muscle fibers. The commitment, proliferation, and differentiation of progenitor cells involve both genetic and epigenetic changes that culminate in alterations in gene expression. Members of the Myogenic regulatory factor (MRF), as well as the Myocyte Enhancer Factor (MEF2) families control distinct steps of skeletal muscle proliferation and differentiation. In addition, -growing evidence indicates that chromatin modifying enzymes and remodeling complexes epigenetically reprogram muscle promoters at various stages that preclude or promote MRF and MEF2 activites. Among these, histone deacetylases (HDACs), histone acetyltransferases (HATs), histone methyltransferases (HMTs) and SWI/SNF complexes alter chromatin structure through post-translational modifications to impact MRF and MEF2 activities. With such new and emerging knowledge, we are beginning to develop a true molecular understanding of the mechanisms by which skeletal muscle development and differentiation is regulated. Elucidation of the mechanisms by which epigenetic regulators control myogenesis will likely provide a new foundation for the development of novel therapeutic drugs for muscle dystrophies, ageing-related regeneration defects that occur due to altered proliferation and differentiation, and other malignancies.

Partial opening and subconductance gating of mechanosensitive ion channels in dystrophic skeletal muscle

We recorded the activity of single mechanosensitive (MS) ion channels in skeletal muscle from the mdx mouse, a deletion mutant that lacks the cytoskeletal protein, dystrophin. Experiments were designed to examine the influence of dystrophin, a major component of skeletal muscle costameres, on the behaviour of single MS channels. In the majority of recordings from cell-attached patches, MS channels have a conductance of ∼23 pS. Recordings from some patches, however, showed a smaller conductance channel of ∼7-14 pS. Large and small conductance channels were detected in a single patch and showed serial, non-random gating, suggesting different opening levels of a single channel. Analysis of the distribution of current amplitudes within the open channel showed MS channels fluctuate between subconductance levels. MS channels in dystrophic muscle spend ∼60% of the time at smaller subconductance levels, often failing to reach the fully open level. Applying pressure to the membrane of mdx fibres increases in a graded manner occupancy of the fully open state, while reducing occupancy of subconductance levels. Recordings also show partial openings of MS channels in both wild-type and mdx muscle that fail to reach the fully open state. Partial openings occur at a higher frequency in mdx muscle and reflect occupancy of subconductance levels seen during complete activations. In muscle from mdx/utrn(-/-) double knockout mice, MS channels also spend more time at subconductance levels than the fully open state. Conductance variability of MS channels may represent gating of a heteromeric protein composed of different channel subunits. The results also show that partial opening and prolonged burst duration are distinct mechanisms that contribute to excess Ca(2+) entry in dystrophic muscle.

The increase of pericyte population in human neuromuscular disorders supports their role in muscle regeneration in vivo

Pericytes are periendothelial cells that have been involved in many different functions including a possible role as mesodermal stem/progenitor cells. In the present study we demonstrate that alkaline phosphatase (AP) expression is specific for human muscular pericytes and can be used as a marker to identify them in skeletal muscle biopsies. We studied the pericyte population in skeletal muscle biopsies from controls, myopathic and neuropathic patients. We observed a significant increase in the number of pericytes only in myopathies that correlated with the number of NCAM(+) fibres, suggesting that an active muscular degenerative/regenerative process is related to an increase in the pericyte population. AP(+) pericytes sorted from skeletal muscle samples were able to activate the myogenic programme and fuse with both mononucleate satellite cells and mature multinucleated myotubes in vitro, demonstrating that they could participate in muscle regeneration. In accordance, pericytes expressing the myogenic transcription factor MyoD were found in biopsies of myopathic biopsies. All these data support the hypothesis that, apart from satellite cells, pericytes may play an important role in muscle regeneration in adult human muscles in vivo.

A splice site mutation in laminin-α2 results in a severe muscular dystrophy and growth abnormalities in zebrafish

Congenital muscular dystrophy (CMD) is a clinically and genetically heterogeneous group of inherited muscle disorders. In patients, muscle weakness is usually present at or shortly after birth and is progressive in nature. Merosin deficient congenital muscular dystrophy (MDC1A) is a form of CMD caused by a defect in the laminin-α2 gene (LAMA2). Laminin-α2 is an extracellular matrix protein that interacts with the dystrophin-dystroglycan (DGC) complex in membranes providing stability to muscle fibers. In an N-ethyl-N-nitrosourea mutagenesis screen to develop zebrafish models of neuromuscular diseases, we identified a mutant fish that exhibits severe muscular dystrophy early in development. Genetic mapping identified a splice site mutation in the lama2 gene. This splice site is highly conserved in humans and this mutation results in mis-splicing of RNA and a loss of protein function. Homozygous lama2 mutant zebrafish, designated lama2^cl501/cl501, exhibited reduced motor function and progressive degeneration of skeletal muscles and died at 8–15 days post fertilization. The skeletal muscles exhibited damaged myosepta and detachment of myofibers in the affected fish. Laminin-α2 deficiency also resulted in growth defects in the brain and eye of the mutant fish. This laminin-α2 deficient mutant fish represents a novel disease model to develop therapies for modulating splicing defects in congenital muscular dystrophies and to restore the muscle function in human patients with CMD.

Hmgb3 is regulated by microRNA-206 during muscle regeneration

Background

MicroRNAs (miRNAs) have been recently involved in most of human diseases as targets for potential strategies to rescue the pathological phenotype. Since the skeletal muscle is a spread-wide highly differentiated and organized tissue, rescue of severely compromised muscle still remains distant from nowadays. For this reason, we aimed to identify a subset of miRNAs major involved in muscle remodelling and regeneration by analysing the miRNA-profile of single fibres isolated from dystrophic muscle, which was here considered as a model of chronic damage.

Methodology/Principal Findings

The miRNA-signature associated to regenerating (newly formed) and remodelling (resting) fibres was investigated in animal models of muscular dystrophies and acute damage, in order to distinguish which miRNAs are primary related to muscle regeneration. In this study we identify fourteen miRNAs associated to dystrophic fibres responsible for muscle regeneration and remodelling, and confirm over-expression of the previously identified regeneration-associated myomiR-206. In particular, a functional binding site for myomiR-206 was identified and validated in the 3′untranslated region (3′UTR) of an X-linked member of a family of sequence independent chromatin-binding proteins (Hmgb3) that is preferentially expressed in hematopoietic stem cells. During regeneration of single muscle fibres, Hmgb3 messenger RNA (mRNA) and protein expression was gradually reduced, concurrent with the up-regulation of miR-206.

Conclusion/Significance

Our results elucidate a negative feedback circuit in which myomiR-206 represses Hmgb3 expression to modulate the regeneration of single muscle fibres after acute and chronic muscle damage. These findings suggest that myomiR-206 may be a potential therapeutic target in muscle diseases.

Respiratory and cardiac function in congenital muscular dystrophies with alpha dystroglycan deficiency

The aim of this retrospective study was to assess respiratory and cardiac function in a large cohort of patients with congenital muscular dystrophies (CMD) with reduced glycosylation of alphadystroglycan (α-DG). Thirteen of the 115 patients included in the study died between the age of 1 month and 20 years. The age at last follow up of the surviving 102 ranged between 1 year and 68 years (median: 9.3 years). Cardiac involvement was found in 7 of the 115 (6%), 5 with dilated cardiomyopathy, 1 cardiac conductions defects and 1 mitral regurgitation. Respiratory function was impaired in 14 (12%). Ten of the 14 required non invasive nocturnal respiratory support, while the other four required invasive ventilation. Cardiac or respiratory involvement was found in patients with mutations in FKRP, POMT1, POMT2. All of the patients in whom mutation in POMGnT1 were identified had normal cardiac and respiratory function.

The multifaceted character of lymphotoxin β in inflammatory myopathies and muscular dystrophies

Lymphotoxin beta (LTβ) regulates some inflammatory mechanisms that could be operative in idiopathic inflammatory myopathies (IM). We studied LTβ and LTβR in inflammatory myopathies, normal and disease controls with immunohistochemistry, Western blotting and in situ hybridisation. LTβ occurs in myonuclei of normal controls, implying its role in normal muscle physiology. LTβ is strongly upregulated in regenerating muscle fibres in all myopathies, but not in denervated myofibres. Normal-appearing myofibres in inflammatory myopathies and muscular dystrophies express LTβ possibly reflecting early myofibre damage, representing a hitherto undescribed pathologic hallmark. Furthermore, we visualised LTβ in several inflammatory cell types in inflammatory myopathies, suggesting its involvement in the different inflammatory mechanisms underlying inflammatory myopathy subgroups.