Putative malignant hyperthermia mutation CaV1.1-R174W is insufficient to trigger a fulminant response to halothane or confer heat stress intolerance

Malignant hyperthermia susceptibility (MHS) is an autosomal dominant pharmacogenetic disorder that manifests as a hypermetabolic state when carriers are exposed to halogenated volatile anesthetics or depolarizing muscle relaxants. In animals, heat stress intolerance is also observed. MHS is linked to over 40 variants in RYR1 that are classified as pathogenic for diagnostic purposes. More recently, a few rare variants linked to the MHS phenotype have been reported in CACNA1S, which encodes the voltage-activated Ca2+ channel CaV1.1 that conformationally couples to RyR1 in skeletal muscle. Here, we describe a knock-in mouse line that expresses one of these putative variants, CaV1.1-R174W. Heterozygous (HET) and homozygous (HOM) CaV1.1-R174W mice survive to adulthood without overt phenotype but fail to trigger with fulminant malignant hyperthermia when exposed to halothane or moderate heat stress. All three genotypes (WT, HET, and HOM) express similar levels of CaV1.1 by quantitative PCR, Western blot, [3H]PN200-110 receptor binding and immobilization-resistant charge movement densities in flexor digitorum brevis fibers. Although HOM fibers have negligible CaV1.1 current amplitudes, HET fibers have similar amplitudes to WT, suggesting a preferential accumulation of the CaV1.1-WT protein at triad junctions in HET animals. Never-the-less both HET and HOM have slightly elevated resting free Ca2+ and Na+ measured with double barreled microelectrode in vastus lateralis that is disproportional to upregulation of transient receptor potential canonical (TRPC) 3 and TRPC6 in skeletal muscle. CaV1.1-R174W and upregulation of TRPC3/6 alone are insufficient to trigger fulminant malignant hyperthermia response to halothane and/or heat stress in HET and HOM mice.

Identification of vacuolar autophagic aggregates in the skeletal muscles of inbred C57BL/6NCrl mice

A comprehensive pathological analysis of inbred strains is essential to define strain-specific spontaneous lesions and to understand whether a specific phenotype results from experimental intervention or reflects a naturally occurring disease. This study aimed to report and describe a novel condition affecting the skeletal muscles of an inbred C57BL/6NCrl mouse colony characterised by large sarcoplasmic vacuoles in the muscle fibres of male mice in the subsarcolemmal spaces and the intermyofibrillary network. There was no muscle weakness, loss of ambulation or cardiac/respiratory involvement. Post-mortem evaluation and histological analysis excluded the presence of pathological accumulations or lesions in other tissues and organs. Changes were seen in fibre size, with many hypotrophic and some slightly hypertrophic fibres. Histological, immunohistochemical and molecular analyses of the vacuolar content revealed dysregulation of the autophagy machinery while ruling out a morphologically similar condition marked by the accumulation of tubular aggregates.

The Importance of mTORC1-Autophagy Axis for Skeletal Muscle Diseases

The mechanistic target of rapamycin (mTOR) complex 1, mTORC1, integrates nutrient and growth factor signals with cellular responses and plays critical roles in regulating cell growth, proliferation, and lifespan. mTORC1 signaling has been reported as a central regulator of autophagy by modulating almost all aspects of the autophagic process, including initiation, expansion, and termination. An increasing number of studies suggest that mTORC1 and autophagy are critical for the physiological function of skeletal muscle and are involved in diverse muscle diseases. Here, we review recent insights into the essential roles of mTORC1 and autophagy in skeletal muscles and their implications in human muscle diseases. Multiple inhibitors targeting mTORC1 or autophagy have already been clinically approved, while others are under development. These chemical modulators that target the mTORC1/autophagy pathways represent promising potentials to cure muscle diseases.

Impact of the COVID-19 pandemic on neuromuscular rehabilitation setting. Part 2: patients and families' views on the received health care during the pandemic

This study explored views of users with muscular dystrophies and their caregivers on staff-user relationships and the treatments provided by a Rehabilitation Centre during the pandemic. Patients and relatives were asked to anonymously complete an open-ended questionnaire exploring their views on these aspects. Fifty-four patients and 40 caregivers gave their informed consent and participated in the survey. Fifty-three patients were adults, 28% suffering from Duchenne/Becker muscular dystrophy. Patients reported 269 comments on health care services provided during the pandemic, 132 (49%) concerning positive aspects and 137 (51%) negative aspects. The prompt restart of the rehabilitation therapies and the staff closeness over the pandemic were the practical aspects most frequently appreciated (46.9%), while closer family contacts and the perception of being able to rely on the Centre's constant support were the most cited psychological aspects (53.1%). Architectural barriers, difficulties in accessing public health services, economic difficulties, and lack of support from welfare and other agencies were the practical critical points most frequently reported (89%). In addition, social isolation, and loneliness due to fear of contagion were the most negative psychological aspects (10.1%). As regard the caregivers' views, participants reported 151 comments. Of these, 86 (56.9%) were positive and 65 (43.1%) were negative. Among the positive aspects, the psychological ones - such as closer family contacts, not feeling abandoned and counting on the constant Centre's professional support prevailed (53.5%). As for the negative aspects, most caregivers (92.6%) believe that the pandemic exacerbated their financial and bureaucratic difficulties, particularly in poorer families.

Alpha B-Crystallin in Muscle Disease Prevention: The Role of Physical Activity

HSPB5 or alpha B-crystallin (CRYAB), originally identified as lens protein, is one of the most widespread and represented of the human small heat shock proteins (sHSPs). It is greatly expressed in tissue with high rates of oxidative metabolism, such as skeletal and cardiac muscles, where HSPB5 dysfunction is associated with a plethora of human diseases. Since HSPB5 has a major role in protecting muscle tissues from the alterations of protein stability (i.e., microfilaments, microtubules, and intermediate filament components), it is not surprising that this sHSP is specifically modulated by exercise. Considering the robust content and the protective function of HSPB5 in striated muscle tissues, as well as its specific response to muscle contraction, it is then realistic to predict a specific role for exercise-induced modulation of HSPB5 in the prevention of muscle diseases caused by protein misfolding. After offering an overview of the current knowledge on HSPB5 structure and function in muscle, this review aims to introduce the reader to the capacity that different exercise modalities have to induce and/or activate HSPB5 to levels sufficient to confer protection, with the potential to prevent or delay skeletal and cardiac muscle disorders.

Part 1: professionals' views on the changes in routine care provided by a rehabilitation centre for patients with muscle diseases

The outbreak of COVID-19 has forced the health care system to undergo profound rearrangements in services and facilities, especially during the periods of lockdown. In this context, inpatient and outpatient services had to rethink and reorganize their activities to meet the needs of severely disabled patients, as those affected by Muscular Dystrophies (MDs).

We present the preliminary results of a survey aiming to explore the staff views on the changes in the care provided by the Gaetano Torre Rehabilitation Centre, and, the impact of these changes on professionals, patients and their families.

The survey was carried out using an open-ended questionnaire including six-items, on the practical and psychological aspects emerged during the pandemic in relation to the healthcare services provided by the Centre and to the patients/caregivers conditions. The participants, most of them physiotherapists, highlighted 169 aspects emerging in the pandemic, 48.5% referring to the resources used to cope with critical issues and 51.5% concerning the difficulties encountered. Emotional aspects prevailed on practical aspects both in resources (52.4 vs 47.6%) and in difficulties (57.5 vs 42.5%) categories. In particular, with regard to patients’ resources, psychological benefits, despite the burden, were greater than practical ones (87 vs 13%), in the form of improved intra-family relationships, feeling more cared for, and satisfaction for the received care. As for the patients’ relatives, the staff indicated more resources than difficulties (72.8 vs 17.2%). Among the former, 75% concerned the emotional sphere, such as the perception of having a point of reference even in such a difficult time.

Italian version of the cornell musculoskeletal discomfort questionnaire (CMDQ-I): Translation, cultural adaptation and validation

BACKGROUND

Almost 25%of workers in the European Union suffer from back pain, and 23%complain of muscle pain. Sixty-two percent of workers carry out repetitive operations with their hands or arms, 46%work in painful or tired positions and 35%carry or handle loads.

OBJECTIVE

This study aimed to translate, culturally adapt and validate the Italian version of the Cornell Musculoskeletal Discomfort Questionnaire (CMDQ-I).

METHODS

Translation and cultural adaptation procedures followed international guidelines. Participants were recruited from among the personnel components of the Italian Air Force, who were between 18 and 65 years old. Cronbach's alpha and the intraclass correlation coefficient (ICC) were calculated to assess internal consistency and stability, respectively. The CDMQ-I was administered together with the Visual Analogic Scale (VAS), and the validity was evaluated using Pearson's correlation coefficient.

RESULTS

All CDMQ-I items were either identical or similar in meaning to the original version's items. The scale was administered twice with a retest after seven to 10 days to 66 participants. Cronbach's alpha was higher than 0.761, and the ICC ranged between 0.737 and 0.952. Pearson's correlation coefficient showed positive and significant correlations (p > 0.01).

CONCLUSIONS

The study produced an Italian version of the CMDQ with good reliability and validity. This scale is a useful tool to investigate the frequency and intensity of musculoskeletal disorders in various categories of workers.

Coping in Children and Adolescents with a Genetic Muscle Disorder -Findings from a Population-Based Study

BACKGROUND

The impact of genetic muscle disorders on quality of life in affected children are well-documented. However, few studies have investigated children's coping strategies and relationships between coping and quality of life.

OBJECTIVES

To determine coping strategy use, efficacy, and associations with quality of life in children with a genetic muscle disorder.

METHODS

Forty-eight children (6-15 years, 58%male) with a genetic muscle disorder were identified as part of a national prevalence study. Children completed the Kidcope in response to a specific stressor (doctors visits) and the Pediatric Quality of Life Inventory Neuromuscular Module.

RESULTS

'Wishful thinking' (75%, 36/48) and 'cognitive restructuring' (71%, 34/48) were the most frequently used coping strategies. 'Self-criticism' (12%, 6/48), and blaming others' and 'resignation' (both 19%, 9/48) were the least used strategies. Coping strategy use did not differ across age andsex groups (p's from 0.08 to 1.00). Positive coping strategies tended to be more effective (medians from 2.00 to 2.75) than negative strategies (medians ranged from 1.38 to 2.50). Using a greater number of different types of positive (F(4, 46) = 5.79, p = 0.001) and/or negative (F(4, 44) = 5.64, p 0.001) coping strategies was linked to poorer health-related quality of life.

CONCLUSION

We conclude that children with genetic muscle disorders use a wide range of positive and/or negative coping strategies in response to stressors associated with a doctor visit and may benefit from greater support to improve health-related quality of life. Findings support the value of routine screening of children's coping to identify those who would benefit from support.

Exercise therapy in muscle diseases: open issues and future perspectives

In muscle diseases different molecular mechanisms are responsible, by distinct cellular pathways, of muscle fibers contraction insufficiency and exercise intolerance. Depending on that, exercise therapy is a promising avenue to efficaciously counteract the loss of muscle fiber function or also the secondary effects due to the sedentary lifestyle as a consequence of the motor impairment. It has been debated whether or not muscle exercise is beneficial or harmful for patients with myopathic disorders, especially in some conditions as eccentric or maximal exercise. Several reports now suggest that supervised aerobic exercise training is safe and may be considered effective in improving oxidative capacity and muscle function in patients with various muscle disorders, including muscular dystrophies and metabolic myopathies, providing that it can be personalized and sized over the single patient capability. In doing that, advancement in outcomes measure recording and exercise delivery monitoring with comfortable investigation methods to assess muscle function and structure can be useful to detect the beneficial effects of a supervised motor training. Based on these considerations, but also especially considering the emerging new therapies in the field of neuromuscular disorders, exercise training can be included as part of the rehabilitation program for patients with a muscle disease, assumed it should be strictly supervised for its effects and to prevent involuntary muscle damage.

MicroRNA-206 regulates cell proliferation by targeting G6PD in skeletal muscle

Skeletal muscle is a major component of body mass and plays a central role in the control of whole-body metabolism in humans and animals. Therefore, elucidation of the underlying mechanisms of skeletal growth and development are expected to lead to the discovery of novel genes and pathways related to muscle disease. miR-206, a skeletal muscle-specific microRNA, plays a crucial role in myogenesis; however, miR-206 is known to function in myogenic differentiation, whether or not it affects muscle cells' proliferation, and the underlying mechanisms are unknown. In this study, we investigated the effect of miR-206 on muscle cell proliferation and differentiation, as well as its effect on myofiber type conversion using mouse C2C12 myoblasts. The results showed that overexpression of miR-206 inhibited cell proliferation and promoted muscle cell differentiation, but it did not affect myofiber type conversion. Intriguingly, we found that overexpression of miR-206 suppressed muscle cell proliferation and induced cell cycle arrest in G₀/G₁ phase by inhibiting the glucose-6-phosphate dehydrogenase (G6PD) gene. Taken together, we demonstrated that the miR-206-G6PD pathway suppresses muscle cell proliferation, and these findings may facilitate the treatment of muscle diseases.-Jiang, A., Dong, C., Li, B., Zhang, Z., Chen, Y., Ning, C., Wu, W., Liu, H. MicroRNA-206 regulates cell proliferation by targeting G6PD in skeletal muscle.

Non-Coding RNA Regulates the Myogenesis of Skeletal Muscle Satellite Cells, Injury Repair and Diseases

Skeletal muscle myogenesis and injury-induced muscle regeneration contribute to muscle formation and maintenance. As myogenic stem cells, skeletal muscle satellite cells have the ability to proliferate, differentiate and self-renew, and are involved in muscle formation and muscle injury repair. Accumulating evidence suggests that non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), are widely involved in the regulation of gene expression during skeletal muscle myogenesis, and their abnormal expression is associated with a variety of muscle diseases. From the perspective of the molecular mechanism and mode of action of ncRNAs in myogenesis, this review aims to summarize the role of ncRNAs in skeletal muscle satellite cells’ myogenic differentiation and in muscle disease, and systematically analyze the mechanism of ncRNAs in skeletal muscle development. This work will systematically summarize the role of ncRNAs in myogenesis and provide reference targets for the treatment of various muscle diseases, such as muscle dystrophy, atrophy and aberrant hypertrophy.

Acceptance and Commitment Therapy for Muscle Disease (ACTMus): protocol for a two-arm randomised controlled trial of a brief guided self-help ACT programme for improving quality of life in people with muscle diseases

INTRODUCTION

In adults, muscle disease (MD) is often a chronic long-term condition with no definitive cure. It causes wasting and weakness of the muscles resulting in a progressive decline in mobility, alongside other symptoms, and is typically associated with reduced quality of life (QoL). Previous research suggests that a psychological intervention, and in particular Acceptance and Commitment Therapy (ACT), may help improve QoL in MD. ACT is a newer type of cognitive behavioural treatment that aims to improve QoL by virtue of improvement in a process called psychological flexibility. The primary aim of this randomised controlled trial (RCT) is to evaluate the efficacy of a guided self-help ACT programme for improving QoL in people with MD. Main secondary outcomes are mood, symptom impact, work and social adjustment and function at 9-week follow-up.

METHODS AND ANALYSIS

Acceptance and Commitment Therapy for Muscle Disease is an assessor-blind, multicentre, two-armed, parallel-group RCT to assess the efficacy of ACT plus standard medical care (SMC) compared with SMC alone. Individuals with a diagnosis of one of four specific MDs, with a duration of at least 6 months and with mild to moderate anxiety or depression (Hospital Anxiety and Depression Scale score ≥8) will be recruited from UK-based MD clinics and MD patient support organisations. Participants will be randomised to either ACT plus SMC or SMC alone by an independent randomisation service. Participants will be followed up at 3, 6 and 9 weeks. Analysis will be intention to treat, conducted by the trial statistician who will be blinded to treatment allocation.

ETHICS AND DISSEMINATION

The study has received full ethical approval. Study results will be disseminated via peer-reviewed publications, conference presentations and journal articles. Data obtained from the trial will enable clinicians and health service providers to make informed decisions regarding the efficacy of ACT for improving QoL for patients with MD.

TRIAL REGISTRATION NUMBER

NCT02810028.

PROTOCOL VERSION

V.11 (4 April 2017).

Idiopathic Inflammatory Myopathies: A Review of the Classification and Impact of Pathogenesis

Idiopathic inflammatory myopathies (IIMs) are a group of autoimmune muscle diseases with significant morbidity and mortality. This review details and updates the pathogenesis and emerging importance of myositis-specific antibodies in the development of IIMs. An increase in the understanding of how these myositis-specific antibodies play a role in IIMs has led to the further categorization of IIMs from the traditional polymyositis versus dermatomyositis, to additional subcategories of IIMs such as necrotizing autoimmune myositis (NAM). The diagnosis of IIMs, including manual muscle testing, laboratory studies, and non-invasive imaging have become important in classifying IIM subtypes and for identifying disease severity. Treatment has evolved from an era where glucocorticoid therapy was the only option to a time now that includes traditional steroid-sparing agents along with immunoglobulin therapy and biologics, such as rituximab.

Calsequestrin depolymerizes when calcium is depleted in the sarcoplasmic reticulum of working muscle

Calsequestrin, the only known protein with cyclical storage and supply of calcium as main role, is proposed to have other functions, which remain unproven. Voluntary movement and the heart beat require this calcium flow to be massive and fast. How does calsequestrin do it? To bind large amounts of calcium in vitro, calsequestrin must polymerize and then depolymerize to release it. Does this rule apply inside the sarcoplasmic reticulum (SR) of a working cell? We answered using fluorescently tagged calsequestrin expressed in muscles of mice. By FRAP and imaging we monitored mobility of calsequestrin as [Ca²⁺] in the SR--measured with a calsequestrin-fused biosensor--was lowered. We found that calsequestrin is polymerized within the SR at rest and that it depolymerized as [Ca²⁺] went down: fully when calcium depletion was maximal (a condition achieved with an SR calcium channel opening drug) and partially when depletion was limited (a condition imposed by fatiguing stimulation, long-lasting depolarization, or low drug concentrations). With fluorescence and electron microscopic imaging we demonstrated massive movements of calsequestrin accompanied by drastic morphological SR changes in fully depleted cells. When cells were partially depleted no remodeling was found. The present results support the proposed role of calsequestrin in termination of calcium release by conformationally inducing closure of SR channels. A channel closing switch operated by calsequestrin depolymerization will limit depletion, thereby preventing full disassembly of the polymeric calsequestrin network and catastrophic structural changes in the SR.

A compact unc45b-promoter drives muscle-specific expression in zebrafish and mouse

Summary: Gene therapeutic approaches to cure genetic diseases require tools to express the rescuing gene exclusively within the affected tissues. Viruses are often chosen as gene transfer vehicles but they have limited capacity for genetic information to be carried and transduced. In addition, to avoid off‐target effects the therapeutic gene should be driven by a tissue‐specific promoter in order to ensure expression in the target organs, tissues, or cell populations. The larger the promoter, the less space will be left for the respective gene. Thus, there is a need for small but tissue‐specific promoters. Here, we describe a compact unc45b promoter fragment of 195 bp that retains the ability to drive gene expression exclusively in skeletal and cardiac muscle in zebrafish and mouse. Remarkably, the described unc45b promoter fragment not only drives muscle‐specific expression but presents heat‐shock inducibility, allowing a temporal and spatial quantity control of (trans)gene expression. Here, we demonstrate that the transgenic expression of the smyd1b gene driven by the unc45b promoter fragment is able to rescue the embryonically lethal heart and skeletal muscle defects in smyd1b‐deficient flatline mutant zebrafish. Our findings demonstrate that the described muscle‐specific unc45b promoter fragment might be a valuable tool for the development of genetic therapies in patients suffering from myopathies. genesis 54:431–438, 2016. © 2016 The Authors. Genesis Published by Wiley Periodicals, Inc.

P(NIPAAM-co-HEMA) thermoresponsive hydrogels: an alternative approach for muscle cell sheet engineering

Loss of skeletal muscle tissue caused by traumatic injury or damage due to myopathies produces a deficit of muscle function for which there is still no clinical treatment. Transplantation of myogenic cells, themselves or combined with materials, has been proposed to increase the regenerative capacity of skeletal muscle but it is hampered by many limitations, such as low cell survival and engraftment or immunological reaction and low biocompatibility of the exogenous materials. Recently, myoblast sheet engineering, obtained with thermoresponsive culture dishes, has attracted attention as a new technique for muscle damage treatment. For this purpose, a series of thermoresponsive hydrogels, constituted by poly(N-isopropylacrylamide-co-2-hydroxyethylmethacrylate) [p(NIPAAM-co-HEMA)] were synthesized by a simple and inexpensive free-radical polymerization of the two co-monomers with a redox initiator. Different ratios of N-isopropylacrylamide (NIPAAm) and 2-hydroxyethylmethacrylate (HEMA) have been examined to evaluate the effects on physicochemical, mechanical and optical hydrogel properties. The murine muscle cell line C₂ C₁₂ has been exploited to test the cytotoxicity of the thermoresponsive hydrogels, depending on different synthesis conditions. In this study, we have identified a thermoresponsive hydrogel that allows cell adhesion and viability, together with the detachment of viable sheet of muscle cells, giving the chance to develop further applications for muscle damage and disease. Copyright © 2014 John Wiley & Sons, Ltd.