Circulating Muscle-specific miRNAs in Duchenne Muscular Dystrophy Patients

The Role of MicroRNA in the Pathogenesis of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked progressive disorder associated with muscle wasting and degeneration. The disease is caused by mutations in the gene that encodes dystrophin, a protein that links the cytoskeleton with cell membrane proteins. The current treatment methods aim to relieve the symptoms of the disease or partially rescue muscle functionality. However, they are insufficient to suppress disease progression. In recent years, studies have uncovered an important role for non-coding RNAs (ncRNAs) in regulating the progression of numerous diseases. ncRNAs, such as micro-RNAs (miRNAs), bind to their target messenger RNAs (mRNAs) to suppress translation. Understanding the mechanisms involving dysregulated miRNAs can improve diagnosis and suggest novel treatment methods for patients with DMD. This review presents the available evidence on the role of altered expression of miRNAs in the pathogenesis of DMD. We discuss the involvement of these molecules in the processes associated with muscle physiology and DMD-associated cardiomyopathy.

Creatine Kinase-MM/Proto-oncogene Tyrosine-Protein Kinase Receptor as a Sensitive Indicator for Duchenne Muscular Dystrophy Carriers

Duchenne muscular dystrophy (DMD), a lethal X-linked recessive genetic disease, is characterized by progressive muscle wasting which will lead to premature death by cardiorespiratory complications in their late twenties. And 2.5-19% DMD carriers that also suffer from skeletal muscle damage or dilated cardiomyopathy when diagnosed as soon as possible is meaningful for prenatal diagnosis and advance warning for self-health. The current DMD carrier screening mainly relies on detecting serum creatine kinase activity, covering only 50-70% DMD carriers which will cause many false negatives and require the discovery of highly effective biomarker and simple detection procedure for DMD carriers. In this article, we have compiled a comprehensive summary of all documented biomarkers associated with DMD and categorized them based on their expression patterns. We specifically pinpointed novel DMD biomarkers, previously unreported in DMD carriers, and conducted further investigations to explore their potential. Compared to creatine kinase activity alone in DMD carriers, creatine kinase-MM can improve the specificity from 73 to 81%. And our investigation revealed another promising protein: proto-oncogene tyrosine-protein kinase receptor (RET). When combined with creatine kinase-MM (creatine kinase-MM/RET ratio), it significantly enhances the specificity (from 81 to 83%) and sensitivity (from 71.4 to 93%) of detecting DMD carriers in serum. Moreover, we successfully devised an efficient method for extracting RET from dried blood spots. This breakthrough allowed us to detect both creatine kinase-MM and RET using dried blood spots without compromising the detection rate.

An evolutionary learning-based method for identifying a circulating miRNA signature for breast cancer diagnosis prediction

Breast cancer (BC) is one of the most commonly diagnosed cancers worldwide. As key regulatory molecules in several biological processes, microRNAs (miRNAs) are potential biomarkers for cancer. Understanding the miRNA markers that can detect BC may improve survival rates and develop new targeted therapeutic strategies. To identify a circulating miRNA signature for diagnostic prediction in patients with BC, we developed an evolutionary learning-based method called BSig. BSig established a compact set of miRNAs as potential markers from 1280 patients with BC and 2686 healthy controls retrieved from the serum miRNA expression profiles for the diagnostic prediction. BSig demonstrated outstanding prediction performance, with an independent test accuracy and area under the receiver operating characteristic curve were 99.90% and 0.99, respectively. We identified 12 miRNAs, including hsa-miR-3185, hsa-miR-3648, hsa-miR-4530, hsa-miR-4763-5p, hsa-miR-5100, hsa-miR-5698, hsa-miR-6124, hsa-miR-6768-5p, hsa-miR-6800-5p, hsa-miR-6807-5p, hsa-miR-642a-3p, and hsa-miR-6836-3p, which significantly contributed towards diagnostic prediction in BC. Moreover, through bioinformatics analysis, this study identified 65 miRNA-target genes specific to BC cell lines. A comprehensive gene-set enrichment analysis was also performed to understand the underlying mechanisms of these target genes. BSig, a tool capable of BC detection and facilitating therapeutic selection, is publicly available at https://github.com/mingjutsai/BSig.

MicroRNAs as a Tool for Differential Diagnosis of Neuromuscular Disorders

Neuromuscular disorders (NMD) are a class of progressive disorders that are characterized by wasting of the muscles. Some of the disorders like Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), congenital muscular dystrophies (CMDs), limb-girdle muscular dystrophies (LGMD), and mild spinal muscular atrophy (SMA) type III share several presenting clinical features, and hence, diagnosis is usually a challenging task. In this study, the diagnostic potential of some species of microRNAs (miRNAs) that are known to play roles in normal and pathological contexts of myocytes (myomiRs) were evaluated to assess their potential in differential diagnosis of NMDs. In this study, seventy-four patients with different neuromuscular disorders along with thirty age-matched healthy control subjects were enrolled. Peripheral blood samples were collected from enrolled subjects followed by miRNA extraction and reverse transcription followed by quantification of the circulating levels of the studied miRNAs (miR-499, miR-206, miR-208a, miR-223, miR-191, miR-103a-3p, miR-103a-5p), by real-time PCR and statistical analysis. The data indicated that miR-499 level showed high circulating levels in DMD patients as well as in patients with other related disorders such as BMD. However, the levels of miR-499 were much higher in DMD patients and it can be used to diagnose DMD. In addition, miR-206 can selectively differentiate between DMD and all other disorders. The results also revealed that miR-208a and miR-223 were significantly dysregulated in SMA patients, and miR-103a-3p could distinguish DMD from BMD. The expression levels of some miRNA species can be utilized in the process of differential diagnosis of NMDs and can serve as a diagnostic biomarker, and such findings will pave the way towards generating targeted therapies.

Glimepiride Compared to Liraglutide Increases Plasma Levels of miR-206, miR-182-5p, and miR-766-3p in Type 2 Diabetes Mellitus: A Randomized Controlled Trial

BACKGRUOUND

Diabetes is a chronic disease with several long-term complications. Several glucose-lowering drugs are used to treat type 2 diabetes mellitus (T2DM), e.g., glimepiride and liraglutide, in which both having different modes of action. Circulating microRNAs (miRNAs) are suggested as potential biomarkers that are associated with the disease development and the effects of the treatment. In the current study we evaluated the effect of glimepiride, liraglutide on the expression of the circulating miRNAs.

METHODS

The present study is a post hoc trial from a previously randomized control trial comparing liraglutide versus glimepiride both in combination with metformin in subjects with T2DM, and subclinical heart failure. miRNAs were determined in the subjects' serum samples with next generation sequencing. Expression patterns of the circulating miRNAs were analyzed using bioinformatic univariate and multivariate analyses (clinical trial registration: NCT01425580).

RESULTS

Univariate analyses show that treatment with glimepiride altered expression of three miRNAs in patient serum, miR-206, miR-182-5p, and miR-766-3p. Both miR-182-5p and miR-766-3p were also picked up among the top contributing miRNAs with penalized regularised logistic regressions (Lasso). The highest-ranked miRNAs with respect to Lasso coefficients were miR-3960, miR-31-5p, miR-3613-3p, and miR-378a-3p. Liraglutide treatment did not significantly influence levels of circulating miRNAs.

CONCLUSION

Present study indicates that glucose-lowering drugs differently affect the expression of circulating miRNAs in serum in individuals with T2DM. More studies are required to investigate possible mechanisms by which glimepiride is affecting the expression of circulating miRNAs.

The discovery of the DNA methylation episignature for Duchenne muscular dystrophy

Duchenne Muscular Dystrophy (DMD) is an X-linked recessive neuromuscular disorder characterized by progressive muscle weakness due to loss of function mutations in the dystrophin gene. Variation in clinical presentation, the rate of disease progression, and treatment responsiveness have been observed amongst DMD patients, suggesting that factors beyond the loss of dystrophin may contribute to DMD pathophysiology. Epigenetic mechanisms are becoming recognized as important factors implicated in the etiology and progression of various diseases. A growing number of genetic syndromes have been associated with unique genomic DNA methylation patterns (called "episignatures") that can be used for diagnostic testing and as disease biomarkers. To further investigate DMD pathophysiology, we assessed the genome-wide DNA methylation profiles of peripheral blood from 36 patients with DMD using the combination of Illumina Infinium Methylation EPIC bead chip array and EpiSign technology. We identified a unique episignature for DMD that whose specificity was confirmed in relation other neurodevelopmental disorders with known episignatures. By modeling the DMD episignature, we developed a new DMD episignature biomarker and provided novel insights into the molecular pathogenesis of this disorder, which have the potential to advance more effective, personalized approaches to DMD care.

Natural history of circulating miRNAs in Duchenne disease: Association with muscle injury and metabolic parameters

OBJECTIVES

This study aimed to evaluate whether the expression of circulating dystromiRs and a group of oxidative stress-related (OS-R) miRNAs is associated with muscle injury and circulating metabolic parameters in Duchenne muscular dystrophy (DMD) patients.

METHODS

Twenty-four DMD patients were included in this cross-sectional study. Clinical scales to evaluate muscle injury (Vignos, GMFCS, Brooke, and Medical Research Council), enzymatic muscle injury parameters (CPK, ALT, and AST), anthropometry, metabolic indicators, physical activity, serum dystromiRs (miR-1-3p, miR-133a-3p, and miR-206), and OS-R miRNAs (miR-21-5p, miR-31-5p, miR-128-3p, and miR-144-3p) levels were measured in ambulatory and non-ambulatory DMD patients.

RESULTS

DystromiRs (except miR-1-3p) and miRNAs OS-R levels were lower (p-value <.05) in the non-ambulatory group than the ambulatory group. The expression of those miRNAs correlated with Vignos scale score (For instance, rho = -0.567, p-value <0.05 for miR-21-5p) and with other scales scores of muscle function and strength. CPK, AST, and ALT concentration correlated with expression of all miRNAs (For instance, rho = 0.741, p-value <.05 between miR-206 level and AST concentration). MiR-21-5p level correlated with glucose concentration (rho = -0.369, p-value = .038), and the miR-1-3p level correlated with insulin concentration (rho = 0.343, p-value = .05).

CONCLUSIONS

Non-ambulatory DMD patients have lower circulating dystromiRs and OS-R miRNAs levels than ambulatory DMD patients. The progressive muscle injury is associated with a decrease in the expression of those miRNAs, evidencing DMD progress. These findings add new information about the natural history of DMD.

Novel miRNA Biomarkers for Patients With Duchenne Muscular Dystrophy

Creatine kinase (CK) as a biomarker has long been expected to be replaced by other fluid biomarkers for Duchenne muscular dystrophy (DMD) because it is independent of disease severity. Growing evidence has demonstrated that muscle-specific microRNAs, known as myomiRs, can act as biomarkers for monitoring muscle pathology and disease severity of DMD patients. To gain insights into the relationship between serum myomiRs and clinical assessment, we measured serum levels of miR-1, miR-133a, miR-133b, miR-206, miR-208a, miR-208b, and miR-499 in 48 DMD patients by using real-time quantitative reverse transcription polymerase chain reaction. These were then compared with age, muscle strength, muscle functions, CK levels, cardiac manifestations, and mutation types (deletions, duplications, and small mutations). When compared to 53 controls, the expression levels of myomiRs were all significantly elevated (p < 0.05). The receiver operating characteristic curves of all seven myomiRs reflected marked differences between DMD patients and healthy controls (p < 0.05). We also showed that serum levels of myomiRs were positively correlated with lower limb distal muscle strength in patients of all age groups. The levels of miR-499, miR-208b, miR-133a, and miR-133b had significant negative correlations with the time to be upright from the supine position (Gowers' time) and the time taken to climb four stairs in DMD patients older than 7 years. Serum levels of miR-1, miR-133a, miR-133b, and miR-499 in patients with cardiac involvement were remarkably higher than those in non-cardiac-involved patients. There was no significant difference in levels of myomiRs between the different mutation groups. Our results indicated that serum myomiRs could be considered as novel biomarkers for monitoring pathology/pathophysiology of DMD patients. In particular, miR-499, miR-208b, miR-133a, and miR-133b might have the ability to reflect the extent of muscle impairment.

MicroRNAs as serum biomarkers in Becker muscular dystrophy

Becker muscular dystrophy (BMD) is an X‐linked neuromuscular disorder due to mutation in the DMD gene, encoding dystrophin. Despite a wide clinical variability, BMD is characterized by progressive muscle degeneration and proximal muscle weakness. Interestingly, a dysregulated expression of muscle‐specific microRNAs (miRNAs), called myomirs, has been found in patients affected with muscular dystrophies, although few studies have been conducted in BMD. We analysed the serum expression levels of a subset of myomirs in a cohort of 29 ambulant individuals affected by BMD and further classified according to the degree of alterations at muscle biopsy and in 11 age‐matched healthy controls. We found a significant upregulation of serum miR‐1, miR‐133a, miR‐133b and miR‐206 in our cohort of BMD patients, supporting the role of these miRNAs in the pathophysiology of the disease, and we identified serum cut‐off levels discriminating patients from healthy controls, confiming the potential of circulating miRNAs as promising noninvasive biomarkers. Moreover, serum levels of miR‐133b were found to be associated with fibrosis at muscle biopsy and with patients' motor performances, suggesting that miR‐133b might be a useful prognostic marker for BMD patients. Taken together, our data showed that these serum myomirs may represent an effective tool that may support stratification of BMD patients, providing the opportunity of both monitoring disease progression and assessing the treatment efficacy in the context of clinical trials.

MicroRNAs in Dystrophinopathy

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), which represent the range of dystrophinopathies, account for nearly 80% of muscle dystrophy. DMD and BMD result from the loss of a functional dystrophin protein, and the leading cause of death in these patients is cardiac remodeling and heart failure. The pathogenesis and progression of the more severe form of DMD have been extensively studied and are controlled by many determinants, including microRNAs (miRNAs). The regulatory role of miRNAs in muscle function and the differential miRNA expression in muscular dystrophy indicate the clinical significance of miRNAs. This review discusses the relevant microRNAs as potential biomarkers and therapeutic targets for DMD and DMD cardiomyopathy as examples of dystrophinopathies.

Circulating small RNA signatures differentiate accurately the subtypes of muscular dystrophies: small-RNA next-generation sequencing analytics and functional insights

Muscular dystrophies are a group of rare and severe inherited disorders mainly affecting the muscle tissue. Duchene Muscular Dystrophy, Myotonic Dystrophy types 1 and 2, Limb Girdle Muscular Dystrophy and Facioscapulohumeral Muscular Dystrophy are some of the members of this family of disorders. In addition to the current diagnostic tools, there is an increasing interest for the development of novel non-invasive biomarkers for the diagnosis and monitoring of these diseases. miRNAs are small RNA molecules characterized by high stability in blood thus making them ideal biomarker candidates for various diseases. In this study, we present the first genome-wide next-generation small RNA sequencing in serum samples of five different types of muscular dystrophy patients and healthy individuals. We identified many small RNAs including miRNAs, lncRNAs, tRNAs, snoRNAs and snRNAs, that differentially discriminate the muscular dystrophy patients from the healthy individuals. Further analysis of the identified miRNAs showed that some miRNAs can distinguish the muscular dystrophy patients from controls and other miRNAs are specific to the type of muscular dystrophy. Bioinformatics analysis of the target genes for the most significant miRNAs and the biological role of these genes revealed different pathways that the dysregulated miRNAs are involved in each type of muscular dystrophy investigated. In conclusion, this study shows unique signatures of small RNAs circulating in five types of muscular dystrophy patients and provides a useful resource for future studies for the development of miRNA biomarkers in muscular dystrophies and for their involvement in the pathogenesis of the disorders.

Therapeutic Application of Extracellular Vesicles-Capsulated Adeno-Associated Virus Vector via nSMase2/Smpd3, Satellite, and Immune Cells in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is caused by loss-of-function mutations in the dystrophin gene on chromosome Xp21. Disruption of the dystrophin-glycoprotein complex (DGC) on the cell membrane causes cytosolic Ca2+ influx, resulting in protease activation, mitochondrial dysfunction, and progressive myofiber degeneration, leading to muscle wasting and fragility. In addition to the function of dystrophin in the structural integrity of myofibers, a novel function of asymmetric cell division in muscular stem cells (satellite cells) has been reported. Therefore, it has been suggested that myofiber instability may not be the only cause of dystrophic degeneration, but rather that the phenotype might be caused by multiple factors, including stem cell and myofiber functions. Furthermore, it has been focused functional regulation of satellite cells by intracellular communication of extracellular vesicles (EVs) in DMD pathology. Recently, a novel molecular mechanism of DMD pathogenesis-circulating RNA molecules-has been revealed through the study of target pathways modulated by the Neutral sphingomyelinase2/Neutral sphingomyelinase3 (nSMase2/Smpd3) protein. In addition, adeno-associated virus (AAV) has been clinically applied for DMD therapy owing to the safety and long-term expression of transduction genes. Furthermore, the EV-capsulated AAV vector (EV-AAV) has been shown to be a useful tool for the intervention of DMD, because of the high efficacy of the transgene and avoidance of neutralizing antibodies. Thus, we review application of AAV and EV-AAV vectors for DMD as novel therapeutic strategy.

Circulating microRNA responses to acute whole-body vibration and resistance exercise in postmenopausal women

Evaluating alterations in circulating microRNA (c-miRNA) expression may provide deeper insight into the role of exercise in the attenuation of the negative effects of aging on musculoskeletal health. Currently, there are sparse data on c-miRNA responses to acute exercise in postmenopausal women. The purpose of this study was to characterize the effects of acute bouts of resistance exercise and whole-body vibration on expression of selected c-miRNAs in postmenopausal women aged 65-76 years (n=10). We also examined relationships between c-miRNAs and muscle strength and bone characteristics. This randomized crossover design study compared c-miRNA responses to a bout of resistance exercise (RE) (3 sets 10 reps 70% 1 repetition maximum (1RM), 5 exercises) and a bout of whole-body vibration (WBV) (5 sets 1 min bouts 20Hz 3.38mm peak to peak displacement, Vibraflex vibration platform). DXA was used to measure body composition and areal bone mineral density (aBMD) of the total body, AP lumbar spine, and dual proximal femur. pQCT was used to measure tibia bone characteristics (4%, 38%, 66% sites). Blood samples were collected before exercise (Pre), immediately-post (IP), 60 minutes post (60P), 24 hours (24H), and 48 hours (48H) after exercise to measure serum miR-21-5p, -23a-3p, -133a-3p, -148a-3p (qPCR) and TRAP5b (ELISA). There was a significant modality × time interaction for c-miR-21-5p expression (p=0.019), which decreased from 60P to 24H after WBV only. TRAP5b serum concentrations significantly increased IP then decreased below Pre at 24H for both WBV and RE (p<0.01). Absolute changes in TRAP5b were negatively correlated with c-miR-21-5p fold changes (r= -0.642 to -0.724, p<0.05) for both exercise modalities. There were significant negative correlations between baseline c-miRNAs and bone status variables (r= -0.639 to -0.877, p<0.05). Our findings suggest that whole-body vibration is a sufficient mechanical stimulus for altering c-miR-21-5p expression, whereas a high intensity resistance exercise protocol did not elicit any c-miRNA responses in postmenopausal women. Increases in the bone resorption marker, TRAP5b, were associated with greater downregulation of c-miR-21-5p expression.

Circular RNA circUSP13 sponges miR-29c to promote differentiation and inhibit apoptosis of goat myoblasts by targeting IGF1

Circular RNAs (circRNAs) are an indispensable element of post-transcriptional gene regulation, influencing a variety of biological processes including myogenic differentiation; however, little is known about the function of circRNA in goat myogenic differentiation. Using RNA-sequencing data from our laboratory, we explored the influences of circUSP13, as a candidate circRNA, on myoblast differentiation since its expression is higher in myoblasts of lamb (first day of age) than that of the fetus (75th day of pregnancy). In in vitro experiments, circUSP13 significantly promoted differentiation and inhibited apoptosis in goat primary myoblasts. Mechanistically, circUSP13 localized with miR-29c in the cytoplasm of goat myoblasts to regulate IGF1 expression. We further demonstrated that circUSP13 sponges miR-29c, promoting IGF1 expression that upregulated the expression of MyoG and MyHC. Thus, our results identified circUSP13 as a molecular marker for breeding programs of mutton production, as well as the circUSP13-miR-29c-IGF1 axis as a potential therapeutic target for combating muscle wasting.

Therapeutic Implications of miRNAs for Muscle-Wasting Conditions

MicroRNAs (miRNAs) are small, non-coding RNA molecules that are mainly involved in translational repression by binding to specific messenger RNAs. Recently, miRNAs have emerged as biomarkers, relevant for a multitude of pathophysiological conditions, and cells can selectively sort miRNAs into extracellular vesicles for paracrine and endocrine effects. In the overall context of muscle-wasting conditions, a multitude of miRNAs has been implied as being responsible for the typical dysregulation of anabolic and catabolic pathways. In general, chronic muscle disorders are associated with the main characteristic of a substantial loss in muscle mass. Muscular dystrophies (MDs) are a group of genetic diseases that cause muscle weakness and degeneration. Typically, MDs are caused by mutations in those genes responsible for upholding the integrity of muscle structure and function. Recently, the dysregulation of miRNA levels in such pathological conditions has been reported. This revelation is imperative for both MDs and other muscle-wasting conditions, such as sarcopenia and cancer cachexia. The expression levels of miRNAs have immense potential for use as potential diagnostic, prognostic and therapeutic biomarkers. Understanding the role of miRNAs in muscle-wasting conditions may lead to the development of novel strategies for the improvement of patient management.

miRNome profiling in Duchenne muscular dystrophy; identification of asymptomatic and manifesting female carriers

Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disorder that occurs due to inactivating mutations in DMD gene, leading to muscular dystrophy. Prediction of pathological complications of DMD and the identification of female carriers are important research points that aim to reduce disease burden. Herein, we describe a case of a late DMD patient and his immediate female family members, who all carry same DMD mutation and exhibited varied degrees of symptoms. In our study, we sequenced the whole miRNome in leukocytes and plasma of the family members and results were validated using real-time PCR. Our results highlighted the role of miR-409-3p, miR-424-5p, miR-144-3p as microRNAs that show correlation with the extent of severity of muscular weakness and can be used for detection of asymptomatic carriers. Cellular and circulating levels of miR-494-3p had shown significant increase in symptomatic carriers, which may indicate significant roles played by this miRNA in the onset of muscular weakness. Interestingly, circulating levels of miR-206 and miR-410-3p were significantly increased only in the severely symptomatic carrier. In conclusion, our study highlighted several miRNA species, which could be used in predicting the onset of muscle and/or neurological complications in DMD carriers.

Circulating Biomarkers in Neuromuscular Disorders: What Is Known, What Is New

The urgent need for new therapies for some devastating neuromuscular diseases (NMDs), such as Duchenne muscular dystrophy or amyotrophic lateral sclerosis, has led to an intense search for new potential biomarkers. Biomarkers can be classified based on their clinical value into different categories: diagnostic biomarkers confirm the presence of a specific disease, prognostic biomarkers provide information about disease course, and therapeutic biomarkers are designed to predict or measure treatment response. Circulating biomarkers, as opposed to instrumental/invasive ones (e.g., muscle MRI or nerve ultrasound, muscle or nerve biopsy), are generally easier to access and less “time-consuming”. In addition to well-known creatine kinase, other promising molecules seem to be candidate biomarkers to improve the diagnosis, prognosis and prediction of therapeutic response, such as antibodies, neurofilaments, and microRNAs. However, there are some criticalities that can complicate their application: variability during the day, stability, and reliable performance metrics (e.g., accuracy, precision and reproducibility) across laboratories. In the present review, we discuss the application of biochemical biomarkers (both validated and emerging) in the most common NMDs with a focus on their diagnostic, prognostic/predictive and therapeutic application, and finally, we address the critical issues in the introduction of new biomarkers.

Development of outcome measures according to dystrophic phenotypes in canine X-linked muscular dystrophy in Japan

Duchenne muscular dystrophy (DMD) is an X-linked lethal muscle disorder characterized by primary muscle degeneration. Therapeutic strategies for DMD have been extensively explored, and some are in the stage of human clinical trials. Along with the development of new therapies, sensitive outcome measures are needed to monitor the effects of new treatments. Therefore, we investigated outcome measures such as biomarkers and motor function evaluation in a dystrophic model of beagle dogs, canine X-linked muscular dystrophy in Japan (CXMD_J). Osteopontin (OPN), a myogenic inflammatory cytokine, was explored as a potential biomarker in dystrophic dogs over the disease course. The serum OPN levels of CXMD_J dystrophic dogs were elevated, even in the early disease phase, and this could be related to the presence of regenerating muscle fibers; as such, OPN would be a promising biomarker for muscle regeneration. Next, accelerometry, which is an efficient method to quantify performance in validated tasks, was used to evaluate motor function longitudinally in dystrophic dogs. We measured three-axis acceleration and angular velocity with wireless hybrid sensors during gait evaluations. Multiple parameters of acceleration and angular velocity showed notedly lower values in dystrophic dogs compared with wild-type dogs, even at the onset of muscle weakness. These parameters accordingly decreased with exacerbation of clinical manifestations along with the disease course. Multiple parameters also indicated gait abnormalities in dystrophic dogs, such as a waddling gait. These outcome measures could be applicable in clinical trials of patients with DMD or other muscle disorders.

Cholesterol metabolism is a potential therapeutic target in Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a lethal muscle disease detected in approximately 1:5000 male births. DMD is caused by mutations in the DMD gene, encoding a critical protein that links the cytoskeleton and the extracellular matrix in skeletal and cardiac muscles. The primary consequence of the disrupted link between the extracellular matrix and the myofibre actin cytoskeleton is thought to involve sarcolemma destabilization, perturbation of Ca2+ homeostasis, activation of proteases, mitochondrial damage, and tissue degeneration. A recently emphasized secondary aspect of the dystrophic process is a progressive metabolic change of the dystrophic tissue; however, the mechanism and nature of the metabolic dysregulation are yet poorly understood. In this study, we characterized a molecular mechanism of metabolic perturbation in DMD.

METHODS

We sequenced plasma miRNA in a DMD cohort, comprising 54 DMD patients treated or not by glucocorticoid, compared with 27 healthy controls, in three groups of the ages of 4-8, 8-12, and 12-20 years. We developed an original approach for the biological interpretation of miRNA dysregulation and produced a novel hypothesis concerning metabolic perturbation in DMD. We used the mdx mouse model for DMD for the investigation of this hypothesis.

RESULTS

We identified 96 dysregulated miRNAs (adjusted P-value <0.1), of which 74 were up-regulated and 22 were down-regulated in DMD. We confirmed the dysregulation in DMD of Dystro-miRs, Cardio-miRs, and a large number of the DLK1-DIO3 miRNAs. We also identified numerous dysregulated miRNAs yet unreported in DMD. Bioinformatics analysis of both target and host genes for dysregulated miRNAs predicted that lipid metabolism might be a critical metabolic perturbation in DMD. Investigation of skeletal muscles of the mdx mouse uncovered dysregulation of transcription factors of cholesterol and fatty acid metabolism (SREBP-1 and SREBP-2), perturbation of the mevalonate pathway, and the accumulation of cholesterol in the dystrophic muscles. Elevated cholesterol level was also found in muscle biopsies of DMD patients. Treatment of mdx mice with Simvastatin, a cholesterol-reducing agent, normalized these perturbations and partially restored the dystrophic parameters.

CONCLUSIONS

This investigation supports that cholesterol metabolism and the mevalonate pathway are potential therapeutic targets in DMD.

Inherited Neuromuscular Disorders: Which Role for Serum Biomarkers?

Inherited neuromuscular disorders (INMD) are a heterogeneous group of rare diseases that involve muscles, motor neurons, peripheral nerves or the neuromuscular junction. Several different lab abnormalities have been linked to INMD: sometimes they are typical of the disorder, but they usually appear to be less specific. Sometimes serum biomarkers can point out abnormalities in presymtomatic or otherwise asymptomatic patients (e.g., carriers). More often a biomarker of INMD is evaluated by multiple clinicians other than expert in NMD before the diagnosis, because of the multisystemic involvement in INMD. The authors performed a literature search on biomarkers in inherited neuromuscular disorders to provide a practical approach to the diagnosis and the correct management of INMD. A considerable number of biomarkers have been reported that support the diagnosis of INMD, but the role of an expert clinician is crucial. Hence, the complete knowledge of such abnormalities can accelerate the diagnostic workup supporting the referral to specialists in neuromuscular disorders.

Tiny Regulators of Massive Tissue: MicroRNAs in Skeletal Muscle Development, Myopathies, and Cancer Cachexia

Skeletal muscles are the largest tissues in our body and the physiological function of muscle is essential to every aspect of life. The regulation of development, homeostasis, and metabolism is critical for the proper functioning of skeletal muscle. Consequently, understanding the processes involved in the regulation of myogenesis is of great interest. Non-coding RNAs especially microRNAs (miRNAs) are important regulators of gene expression and function. MiRNAs are small (~22 nucleotides long) noncoding RNAs known to negatively regulate target gene expression post-transcriptionally and are abundantly expressed in skeletal muscle. Gain- and loss-of function studies have revealed important roles of this class of small molecules in muscle biology and disease. In this review, we summarize the latest research that explores the role of miRNAs in skeletal muscle development, gene expression, and function as well as in muscle disorders like sarcopenia and Duchenne muscular dystrophy (DMD). Continuing with the theme of the current review series, we also briefly discuss the role of miRNAs in cancer cachexia.

Novel free-circulating and extracellular vesicle-derived miRNAs dysregulated in Duchenne muscular dystrophy

Aim: To perform cross-sectional and longitudinal miRNA profiling in plasma from Duchenne muscular dystrophy (DMD) subjects and find non-invasive biomarkers in DMD. Subjects/materials & methods: Plasma was collected from 14 age and sex matched controls and 46 DMD subjects. Free-circulating and extracellular vesicle (EV)-derived miRNA expression was measured by RT-qPCR. Results: Free-circulating and EVs derived miR-29c-3p and miR-133a-3p are dysregulated in DMD subjects. Free-circulating and EV-derived miR-29c-3p are reduced in DMD subjects undergoing daily corticosteroid treatment. Free-circulating miR-1-3p and miR-122-5p are longitudinally upregulated in ambulant DMD subjects. Conclusion: We detected novel free-circulating and EV-derived dysregulated miRNAs in plasma from DMD subjects and characterized the longitudinal profile of free-circulating miRNA on plasma from DMD subjects.

Noncoding RNAs in Duchenne and Becker muscular dystrophies: role in pathogenesis and future prognostic and therapeutic perspectives

Noncoding RNAs (ncRNAs), such as miRNAs and long noncoding RNAs, are key regulators of gene expression at the post-transcriptional level and represent promising therapeutic targets and biomarkers for several human diseases, including Duchenne and Becker muscular dystrophies (DMD/BMD). A role for ncRNAs in the pathogenesis of muscular dystrophies has been suggested, even if it is still incompletely understood. Here, we discuss current progress leading towards the clinical utility of ncRNAs for DMD/BMD. Long and short noncoding RNAs are differentially expressed in DMD/BMD and have a mechanism of action via targeting mRNAs. A subset of muscle-enriched miRNAs, the so-called myomiRs (miR-1, miR-133, and miR-206), are increased in the serum of patients with DMD and in dystrophin-defective animal models. Interestingly, myomiRs might be used as biomarkers, given that their levels can be corrected after dystrophin restoration in dystrophic mice. Remarkably, further evidence demonstrates that ncRNAs also play a role in dystrophin expression; thus, their modulations might represent a potential therapeutic strategy with the aim of upregulating the dystrophin protein in combination with other oligonucleotides/gene therapy approaches.

microRNA exchange via extracellular vesicles in cancer

Cells utilize different means of inter-cellular communication to function properly. Here, we review the crosstalk between cancer cells and their surrounding environment through microRNA (miRNA)-containing extracellular vesicles (EVs). The current findings suggest that the export of miRNAs and uptake of miRNA-containing EVs might be an active process. As post-transcriptional regulators of gene expression, cancer-derived miRNAs that are taken up by normal cells can change the translational profile of the recipient cell towards a transformed proteome. Stromal cells can also deliver miRNAs via EVs to cancer cells to support tumour growth and cancer progression. Therefore, gaining a better understanding of EV-mediated inter-cellular communication in the tumour microenvironment might lead to the development of novel diagnostic and therapeutic strategies.

Serum MyomiRs as Biomarkers for Female Carriers of Duchenne/Becker Muscular Dystrophy

Background: Duchenne/Becker muscular dystrophy (DMD/BMD) is an X-linked recessive lethal neuromuscular disease. MicroRNAs expressed in striated muscle, myomiRs, have been proposed as its potential biomarkers. Serum creatine kinase (CK) is commonly used as a biomarker in clinical practice, but it is not reliable. The aim of this study was to assess whether serum levels of myomiRs has diagnostic value for detection of female DMD/BMD carriers with normal or elevated CK.

Methods: Thirty four female carriers and 33 age-matched healthy female controls were enrolled. Peripheral blood samples were collected and serum miRNAs were extracted for measurement of miR-1, miR-133a, miR-133b, miR-206, miR-208a, miR-208b, and miR-499 by quantitative real-time polymerase chain reaction.

Results: MiR-1, miR-133a, miR-133b, miR-206, miR-208a, miR-208b, and miR-499 were upregulated in all female carriers in comparison to healthy controls. MiR-1 (Spearman's rho = +0.406, p = 0.017) was correlated with CK in the female carrier group. Receiver operating characteristic curve analysis of all seven myomiRs showed that the area under the curve (AUC) for miR-499, miR-133b, miR-1, miR-208b, and miR-133a exceeded 70.0%, and for miR-206 and miR-208a exceeded 60.0%. MiR-133b and miR-499 were significantly increased in all female carriers, even those with normal CK. AUC for the combination of all seven miRNAs was 87.2%. CK (OR 0.406, 95% CI 0.000–0.001, p < 0.0001) and miR-499 (OR 0.323, 95% CI 0.023–0.106, p = 0.003) were considered to be independent predictors for female carriers presence in the multivariable regression analysis model.

Conclusions: MiR-133b and miR-499 are potentially useful biomarkers for female carriers with DMD/BMD (including those with normal CK). The combination of all seven serum miRNAs and their respective combinations with CK have better diagnostic value for female carriers than either CK or any separate miRNA.

Age-Associated Salivary MicroRNA Biomarkers for Oculopharyngeal Muscular Dystrophy

Small non-coding microRNAs (miRNAs) are involved in the regulation of mRNA stability. Their features, including high stability and secretion to biofluids, make them attractive as potential biomarkers for diverse pathologies. This is the first study reporting miRNA as potential biomarkers for oculopharyngeal muscular dystrophy (OPMD), an adult-onset myopathy. We hypothesized that miRNA that is differentially expressed in affected muscles from OPMD patients is secreted to biofluids and those miRNAs could be used as biomarkers for OPMD. We first identified candidate miRNAs from OPMD-affected muscles and from muscles from an OPMD mouse model using RNA sequencing. We then compared the OPMD-deregulated miRNAs to the literature and, subsequently, we selected a few candidates for expression studies in serum and saliva biofluids using qRT-PCR. We identified 126 miRNAs OPMD-deregulated in human muscles, but 36 deregulated miRNAs in mice only (pFDR < 0.05). Only 15 OPMD-deregulated miRNAs overlapped between the in humans and mouse studies. The majority of the OPMD-deregulated miRNAs showed opposite deregulation direction compared with known muscular dystrophies miRNAs (myoMirs), which are associated. In contrast, similar dysregulation direction was found for 13 miRNAs that are common between OPMD and aging muscles. A significant age-association (p < 0.05) was found for 17 OPMD-deregulated miRNAs (13.4%), whereas in controls, only six miRNAs (1.4%) showed a significant age-association, suggesting that miRNA expression in OPMD is highly age-associated. miRNA expression in biofluids revealed that OPMD-associated deregulation in saliva was similar to that in muscles, but not in serum. The same as in muscle, miRNA expression levels in saliva were also found to be associated with age (p < 0.05). Moreover, the majority of OPMD-miRNAs were found to be associated with dysphagia as an initial symptom. We suggest that levels of specific miRNAs in saliva can mark muscle degeneration in general and dysphagia in OPMD.

Serum miR-206 as a biomarker for drug-induced skeletal muscle injury in rats

Creatine kinase (CK) and lactate dehydrogenase (LDH) serve as biomarkers for skeletal muscle injury in preclinical toxicity studies, but have a limitation regarding tissue specificity. Circulating miR-206 was recently reported to be a useful biomarker for skeletal muscle disorders in humans. Here, we sought to determine whether serum miR-206 can be used as a biomarker in preclinical toxicity studies to detect drug-induced skeletal muscle injury with higher sensitivity and specificity than the biomarkers CK, LDH, skeletal troponin I (sTnI), and myosin light chain 3 (Myl3). We established rat models of skeletal muscle injury through treatment with the muscle toxicant 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD) as well as four in-house compounds. We found that serum miR-206 levels significantly increased after treatment with TMPD, and tended to be higher in rats treated with in-house compounds than in control rats. ROC analysis revealed that the specificity of serum miR-206 for detection of skeletal muscle injury was higher compared with those of other markers. Further, serum miR-206 levels were unchanged in rats with isoproterenol-induced cardiotoxicity. These findings demonstrate that serum miR-206 may serve as a highly specific biomarker for preclinical analysis of rats with drug-induced skeletal muscle injuries.

miR-379 links glucocorticoid treatment with mitochondrial response in Duchenne muscular dystrophy

Duchenne Muscular Dystrophy (DMD) is a lethal muscle disorder, caused by mutations in the DMD gene and affects approximately 1:5000-6000 male births. In this report, we identified dysregulation of members of the Dlk1-Dio3 miRNA cluster in muscle biopsies of the GRMD dog model. Of these, we selected miR-379 for a detailed investigation because its expression is high in the muscle, and is known to be responsive to glucocorticoid, a class of anti-inflammatory drugs commonly used in DMD patients. Bioinformatics analysis predicts that miR-379 targets EIF4G2, a translational factor, which is involved in the control of mitochondrial metabolic maturation. We confirmed in myoblasts that EIF4G2 is a direct target of miR-379, and identified the DAPIT mitochondrial protein as a translational target of EIF4G2. Knocking down DAPIT in skeletal myotubes resulted in reduced ATP synthesis and myogenic differentiation. We also demonstrated that this pathway is GC-responsive since treating mice with dexamethasone resulted in reduced muscle expression of miR-379 and increased expression of EIF4G2 and DAPIT. Furthermore, miR-379 seric level, which is also elevated in the plasma of DMD patients in comparison with age-matched controls, is reduced by GC treatment. Thus, this newly identified pathway may link GC treatment to a mitochondrial response in DMD.

Lack of miR-378 attenuates muscular dystrophy in mdx mice

The severity of Duchenne muscular dystrophy (DMD), an incurable disease caused by the lack of dystrophin, might be modulated by different factors, including miRNAs. Among them, miR-378 is considered of high importance for muscle biology, but intriguingly, its role in DMD and its murine model (mdx mice) has not been thoroughly addressed so far. Here, we demonstrate that dystrophic mice additionally globally lacking miR-378 (double-KO [dKO] animals) exhibited better physical performance and improved absolute muscle force compared with mdx mice. Accordingly, markers of muscle damage in serum were significantly decreased in dKO mice, accompanied by diminished inflammation, fibrosis, and reduced abundance of regenerating fibers within muscles. The lack of miR-378 also normalized the aggravated fusion of dystrophin-deficient muscle satellite cells (mSCs). RNA sequencing of gastrocnemius muscle transcriptome revealed fibroblast growth factor 1 (Fgf1) as one of the most significantly downregulated genes in mice devoid of miR-378, indicating FGF1 as one of the mediators of changes driven by the lack of miR-378. In conclusion, we suggest that targeting miR-378 has the potential to ameliorate DMD pathology.

Uniform sarcolemmal dystrophin expression is required to prevent extracellular microRNA release and improve dystrophic pathology

BACKGROUND

Duchenne muscular dystrophy (DMD) is a fatal muscle-wasting disorder caused by genetic loss of dystrophin protein. Extracellular microRNAs (ex-miRNAs) are putative, minimally invasive biomarkers of DMD. Specific ex-miRNAs (e.g. miR-1, miR-133a, miR-206, and miR-483) are highly up-regulated in the serum of DMD patients and dystrophic animal models and are restored to wild-type levels following exon skipping-mediated dystrophin rescue in mdx mice. As such, ex-miRNAs are promising pharmacodynamic biomarkers of exon skipping efficacy. Here, we aimed to determine the degree to which ex-miRNA levels reflect the underlying level of dystrophin protein expression in dystrophic muscle.

METHODS

Candidate ex-miRNA biomarker levels were investigated in mdx mice in which dystrophin was restored with peptide-PMO (PPMO) exon skipping conjugates and in mdx-Xist^Δhs mice that express variable amounts of dystrophin from birth as a consequence of skewed X-chromosome inactivation. miRNA profiling was performed in mdx-Xist^Δhs mice using the FirePlex methodology and key results validated by small RNA TaqMan RT-qPCR. The muscles from each animal model were further characterized by dystrophin western blot and immunofluorescence staining.

RESULTS

The restoration of ex-myomiR abundance observed following PPMO treatment was not recapitulated in the high dystrophin-expressing mdx-Xist^Δhs group, despite these animals expressing similar amounts of total dystrophin protein (~37% of wild-type levels). Instead, ex-miRNAs were present at high levels in mdx-Xist^Δhs mice regardless of dystrophin expression. PPMO-treated muscles exhibited a uniform pattern of dystrophin localization and were devoid of regenerating fibres, whereas mdx-Xist^Δhs muscles showed non-homogeneous dystrophin staining and sporadic regenerating foci.

CONCLUSIONS

Uniform dystrophin expression is required to prevent ex-miRNA release, stabilize myofiber turnover, and attenuate pathology in dystrophic muscle.

Biomarkers for Duchenne muscular dystrophy: myonecrosis, inflammation and oxidative stress

Duchenne muscular dystrophy (DMD) is a lethal, X-linked disease that causes severe loss of muscle mass and function in young children. Promising therapies for DMD are being developed, but the long lead times required when using clinical outcome measures are hindering progress. This progress would be facilitated by robust molecular biomarkers in biofluids, such as blood and urine, which could be used to monitor disease progression and severity, as well as to determine optimal drug dosing before a full clinical trial. Many candidate DMD biomarkers have been identified, but there have been few follow-up studies to validate them. This Review describes the promising biomarkers for dystrophic muscle that have been identified in muscle, mainly using animal models. We strongly focus on myonecrosis and the associated inflammation and oxidative stress in DMD muscle, as the lack of dystrophin causes repeated bouts of myonecrosis, which are the key events that initiate the resultant severe dystropathology. We discuss the early events of intrinsic myonecrosis, along with early regeneration in the context of histological and other measures that are used to quantify its incidence. Molecular biomarkers linked to the closely associated events of inflammation and oxidative damage are discussed, with a focus on research related to protein thiol oxidation and to neutrophils. We summarise data linked to myonecrosis in muscle, blood and urine of dystrophic animal species, and discuss the challenge of translating such biomarkers to the clinic for DMD patients, especially to enhance the success of clinical trials.

Summary: This Review discusses biomarkers in blood and urine linked to myonecrosis, inflammation and oxidative stress, to enhance development of therapies for DMD, and the challenges to be overcome for clinical translation.

circINSR Promotes Proliferation and Reduces Apoptosis of Embryonic Myoblasts by Sponging miR-34a

As a diverse and abundant class of endogenous RNAs, circular RNAs (circRNAs) participate in processes including cell proliferation and apoptosis. Nevertheless, few researchers have investigated the function of circRNAs in bovine muscle development. Based on existing sequencing data, we identified circINSR. The localization of circINSR in bovine myoblasts was investigated by fluorescence in situ hybridization. Molecular and biochemical assays were used to confirm the role of circINSR in myoblast proliferation and the cell cycle. Mitochondrial membrane potential and annexin V-PE/7-AAD staining assays were performed to assess cell apoptosis. Additionally, interactions between circINSR, miR-34a, and target mRNAs were examined using bioinformatics, a luciferase assay, and RNA immunoprecipitation. We found that circINSR was highly expressed in embryonic muscle tissue. Overexpression of circINSR significantly promoted proliferation and reduced apoptosis of embryonic myoblasts. Our data suggested that circINSR may act as a sponge of miR-34a and could function through de-repression of target genes in muscle cells. This study proposes that circINSR may function as a regulator of embryonic muscle development. circINSR regulates cells proliferation and apoptosis through miR-34a-modulated Bcl-2 and CyclinE2 expression.

Evaluation of speed-accuracy trade-off in a computer task to identify motor difficulties in individuals with Duchenne Muscular Dystrophy - A cross-sectional study

INTRODUCTION

Individuals with Duchenne Muscular Dystrophy (DMD) present with progressive loss of motor function which can impair both control of speed and accuracy of movement.

AIM

to evaluate movement time during a task at various levels of difficulty and to verify whether the level of difficulty affects the speed and/ or accuracy during the task.

METHODS

the DMD group comprised of 17 individuals age matched with 17 individuals with typical development (TD group). The task evaluates the relationship between speed and accuracy, consisting of the execution of manual movements (using the mouse of the computer) aimed at a target at three different levels of difficulty (ID).

RESULTS

A MANOVA demonstrated statistically significant differences in dispersion data and intercept values between the groups with greater movement time in the DMD group. An ANOVA indicated differences between groups for ID, except for when there was a higher accuracy demand (higher ID). In the other IDs that required lower accuracy demand, individuals in the DMD group had significantly longer movement time when compared to the TD group.

CONCLUSION

These results show that the TD and DMD did not differ in the higher ID, therefore it can be concluded that for those with DMD, motor performance is more affected by speed than accuracy of movement.

Circulating MicroRNAs in Duchenne Muscular Dystrophy

OBJECTIVE

The diagnosis of Duchenne Muscular Dystrophy (DMD) currently depends on non-specific measures such as Creatine kinase (CK) levels. MicroRNAs (miRNAs) are a class of small, endogenous RNAs of 21-25 nucleotides, that are important regulators for numerous physiological and pathological processes. The aim of the current study is to assess the potential of miRNAs as non-invasive biomarker for the diagnosis of DMD and for identifying carriers.

PATIENTS AND METHODS

Thirty healthy subjects and 29 families with one member diagnosed with DMD were enrolled in the study. Peripheral blood samples were collected from all subjects where microRNAs were extracted from plasma followed by the quantification of miR-499, miR-103a-3p, miR-103a-5p, miR-206, miR-208a, miR-223 and miR-191-5p. MLPA and NGS were carried out as a gold standard technique to identify the mutations in the participants.

RESULTS

Our data revealed that miR-499 was significantly upregulated in all DMD patients, and true carriers (mothers), while 78 % of potential carriers (sisters) exhibited high levels of this miRNA. Similarly, miR-103a-3p showed an increase in the patients' families although to a lesser extent. On the other hand, miR-206 and miR-191-5p were significantly downregulated in the majority of the DMD patients and the tested female family members. MicroRNA miR-103a-5p and miR-208a followed a comparable trend in patients and mothers.

CONCLUSIONS

Ourresults suggest that the plasma levels of miRNAs have the capability to diagnose DMD patients and more importantly, miRNAs can be used to identify female carriers.

[A review on muscle-specific microRNAs as the biomarker for Duchenne muscular dystrophy]

MicroRNA (miRNA) is a non-coding single-stranded RNA with a length of approximately 22 nucleotides and is mainly responsible for the regulation of gene expression at the post-transcriptional level. At present, miRNA have become potential biomarkers for various diseases such as tumor, leukemia, and nervous system disease. Muscle-specific microRNAs are enriched in the skeletal muscle of patients with Duchenne muscular dystrophy (DMD) and also play an important role in the pathogenesis of DMD. Creatine kinase has limited specificity in the diagnosis of DMD since its level is not significantly associated with disease severity, and therefore, it is of great clinical significance to explore whether muscle-specific microRNAs can be used as ideal biomarkers for DMD. This article reviews the research advances in this field.

[A review on muscle-specific microRNAs as the biomarker for Duchenne muscular dystrophy]

MicroRNA (miRNA) is a non-coding single-stranded RNA with a length of approximately 22 nucleotides and is mainly responsible for the regulation of gene expression at the post-transcriptional level. At present, miRNA have become potential biomarkers for various diseases such as tumor, leukemia, and nervous system disease. Muscle-specific microRNAs are enriched in the skeletal muscle of patients with Duchenne muscular dystrophy (DMD) and also play an important role in the pathogenesis of DMD. Creatine kinase has limited specificity in the diagnosis of DMD since its level is not significantly associated with disease severity, and therefore, it is of great clinical significance to explore whether muscle-specific microRNAs can be used as ideal biomarkers for DMD. This article reviews the research advances in this field.

miR-1 is a novel biomarker for polymyositis/dermatomyositis-associated interstitial lung disease

Objectives: Although intensive immunosuppressive treatment is necessary for the severe cases with polymyositis (PM)/dermatomyositis (DM), the prognostic factors or disease activity indices for PM/DM have not been established. Here we investigated the association between serum microRNA-1 (miR-1) level and clinical course of patients with PM/DM.Methods: We retrospectively reviewed baseline clinical and laboratory findings, treatment regimens and outcomes in patients with PM/DM. The serum samples were collected from PM/DM patients and healthy controls (HC). Serum miR-1 levels were determined by quantitative real-time PCR.Results: Twenty-two patients were recruited. The average serum miR-1 level was significantly higher in the PM/DM as compared to HC (p = .0085) and was decreased by treatment (p = .032). We divided the PM/DM-ILD patients into two groups, high and normal miR-1 groups. Although there were no significant differences in the clinical data and the initial prednisolone (PSL) dose between the two groups, PSL dose at 16 weeks, cumulative PSL dose until 16 weeks, and frequency of serious infections were significantly higher in the high miR-1 group as compared to the normal group (p = .025, .036, and .026, respectively).Conclusion: We propose serum miR-1 as a promising novel biomarker for predicting therapeutic response in PM/DM-ILD.

Disease-specific and glucocorticoid-responsive serum biomarkers for Duchenne Muscular Dystrophy

Extensive biomarker discoveries for DMD have occurred in the past 7 years, and a vast array of these biomarkers were confirmed in independent cohorts and across different laboratories. In these previous studies, glucocorticoids and age were two major confounding variables. In this new study, using SomaScan technology and focusing on a subset of young DMD patients who were not yet treated with glucocorticoids, we identified 108 elevated and 70 decreased proteins in DMD relative to age matched healthy controls (p value < 0.05 after adjusting for multiple testing). The majority of the elevated proteins were muscle centric followed by cell adhesion, extracellular matrix proteins and a few pro-inflammatory proteins. The majority of decreased proteins were of cell adhesion, however, some had to do with cell differentiation and growth factors. Subsequent treatment of this group of DMD patients with glucocorticoids affected two major groups of pharmacodynamic biomarkers. The first group consisted of 80 serum proteins that were not associated with DMD and either decreased or increased following treatment with glucocorticoids, and therefore were reflective of a broader effect of glucocorticoids. The second group consisted of 17 serum proteins that were associated with DMD and these tended to normalize under treatment, thus reflecting physiologic effects of glucocorticoid treatment in DMD. In summary, we have identified a variety of circulating protein biomarkers that reflect the complex nature of DMD pathogenesis and response to glucocorticoids.

Cross-sectional study into age-related pathology of mouse models for limb girdle muscular dystrophy types 2D and 2F

Limb girdle muscular dystrophy (LGMD) types 2D and 2F are caused by mutations in the genes encoding for α- and δ-sarcoglycan, respectively, leading to progressive muscle weakness. Mouse models exist for LGMD2D (Sgca-/-) and 2F (Sgcd-/-). In a previous natural history study, we described the pathology in these mice at 34 weeks of age. However, the development of muscle pathology at younger ages has not been fully characterised yet. We therefore performed a study into age-related changes in muscle function and pathology by examining mice at different ages. From 4 weeks of age onwards, male mice were subjected to functional tests and sacrificed at respectively 8, 16 or 24 weeks of age. Muscle histopathology and expression of genes involved in muscle pathology were analysed for several skeletal muscles, while miRNA levels were assessed in serum. In addition, for Sgcd-/- mice heart pathology was assessed. Muscle function showed a gradual decline in both Sgca-/- and Sgcd-/- mice. Respiratory function was also impaired at all examined timepoints. Already at 8 weeks of age, muscle pathology was prominent, and fibrotic, inflammatory and regenerative markers were elevated, which remained relatively constant with age. In addition, Sgcd-/- mice showed signs of cardiomyopathy from 16 weeks of age onwards. These results indicate that Sgca-/- and Sgcd-/- are relevant disease models for LGMD2D and 2F.

Differential MicroRNA expression following head-down tilt bed rest: implications for cardiovascular responses to microgravity

Head-down tilt bedrest (HDBR), an analog of spaceflight, elicits changes in cardiovascular function that adversely affect astronaut performance. It is therefore fundamental to elucidate the molecular regulators of these changes. Study aim was to determine if cardiovascular-related circulating microRNA (miRNA) are altered following HDBR and if they relate to changes in cardiac function and peak aerobic capacity. Eleven participants completed 30-days HDBR at an ambient CO2 of 0.5% (replicate the in-flight CO2 levels). Blood samples were obtained 3 days (BDC-3) prior to and immediately (R + 0) following HDBR. 44-targeted circulating miRNAs (c-miRNA) identified from published roles in cardiovascular structure/function were analyzed via RT-qPCR. Resting stroke volume was evaluated via ultrasonography. Peak oxygen uptake ( V ˙ O 2 peak ) was determined using a graded exercise test on an electronically braked cycle ergometer. Ten cardiovascular-related miRNA were significantly increased following HDBR. The differentially expressed c-miRNA were grouped into clusters according to their expression profile. Cluster A included c-miRNA that have been identified as regulators of cardiac function and hypertrophy (c-miRNA-133), atrial fibrillation and mitochondrial function (c-miRNA-1), skeletal muscle atrophy (c-miRNA-1), and vascular control (c-miRNA-155). Cluster B contained c-miRNA identified as regulators of cardiac hypertrophy (c-miRNA-30, -15), fibrosis (c-miRNA-22, -18), mitochondrial function (miRNA-181), and aerobic capacity (c-miRNA-20a). Following HDBR resting stroke volume was decreased and correlated with changes in c-miRNA-378a and -18a. V ˙ O 2 peak was decreased and correlated with changes c-miRNA-133. In conclusion, we found that HDBR induced a distinct and specific cardiovascular-related miRNA response, which were associated with changes in cardiac function and peak aerobic capacity.

MicroRNAs and Long Non-coding RNAs in Genetic Diseases

Since the discovery and classification of non-coding RNAs, their roles have gained great attention. In this respect, microRNAs and long non-coding RNAs have been firmly demonstrated to be linked to regulation of gene expression and onset of human diseases, including rare genetic diseases; therefore they are suitable targets for therapeutic intervention. This issue, in the context of rare genetic diseases, is being considered by an increasing number of research groups and is of key interest to the health community. In the case of rare genetic diseases, the possibility of developing personalized therapy in precision medicine has attracted the attention of researchers and clinicians involved in developing "orphan medicinal products" and proposing these to the European Medicines Agency (EMA) and to the Food and Drug Administration (FDA) Office of Orphan Products Development (OOPD) in the United States. The major focuses of these activities are the evaluation and development of products (drugs, biologics, devices, or medical foods) considered to be promising for diagnosis and/or treatment of rare diseases or conditions, including rare genetic diseases. In an increasing number of rare genetic diseases, analysis of microRNAs and long non-coding RNAs has been proven a promising strategy. These diseases include, but are not limited to, Duchenne muscular dystrophy, cystic fibrosis, Rett syndrome, and β-thalassemia. In conclusion, a large number of approaches based on targeting microRNAs and long non-coding RNAs are expected in the field of molecular diagnosis and therapy, with a facilitated technological transfer in the case of rare genetic diseases, in virtue of the existing regulation concerning these diseases.

Phenotype-Specific Response of Circulating miRNAs Provides New Biomarkers of Slow or Fast Muscle Damage

Skeletal muscle is a heterogeneous tissue composed of a continuum of contracting fibers ranging from slow-type to fast-type fibers. Muscle damage is a frequent event and a susceptibility of fast-fibers to exercise-induced damage (EIMD) or statins toxicity has been reported. Biological markers of muscle damage such as creatine kinase (CK) are not fiber-type specific and new biomarkers are needed. Some microRNAs (miRNAs) are specific to the muscle tissue, can be found in the extracellular compartment and can rise in the plasma following muscle damage. Our aim was to identify whether a set of circulating miRNAs can be used as fiber-type specific biomarkers of muscle damage in a model of traumatic (crush) injuries induced either in the slow soleus (SOL) or in the fast extensor digitorum longus (EDL) muscles of rats. A subset of miRNAs composed of miR-1-3p, -133a-3p, -133b-3p, 206-3p, -208b-3p, 378a-3p, -434-3p, and -499-5p were measured by RT-PCR in non-injured SOL or EDL muscle and in the plasma of rats 12 h after damage induced to SOL or EDL. MiR-133b-3p, -378a-3p, and -434-3p were equally expressed both in SOL and EDL muscles. MiR-1-3-p and -133a-3p levels were higher in EDL compared to SOL (1.3- and 1.1-fold, respectively). Conversely, miR-206-3p, -208b-3p, and -499-5p were mainly expressed in SOL compared to EDL (7.4-, 35.4-, and 10.7-fold, respectively). In the plasma, miR-1-3p and -133a-3p were elevated following muscle damage compared to a control group, with no difference between SOL and EDL. MiR-133b-3p and -434-3p plasma levels were significantly higher in EDL compared to SOL (1.8- and 2.4-fold, respectively), while miR-378a-3p rose only in the EDL group. MiR-206-3p levels were elevated in SOL only (fourfold compared to EDL). Our results show that plasma miR-133b-3p and -434 are fast-fiber specific biomarkers, while miR-206-3p is a robust indicator of slow-fiber damage, opening new perspectives to monitor fiber-type selective muscle damage in research and clinic.

Influence of physical exercise on microRNAs in skeletal muscle regeneration, aging and diseases

Skeletal muscle is a dynamic tissue with remarkable plasticity and its growth and regeneration are highly organized, with the activation of specific transcription factors, proliferative pathways and cytokines. The decline of skeletal muscle tissue with age, is one of the most important causes of functional loss of independence in older adults. Maintaining skeletal muscle function throughout the lifespan is a prerequisite for good health and independent living.

Physical activity represents one of the most effective preventive agents for muscle decay in aging.

Several studies have underlined the importance of microRNAs (miRNAs) in the control of myogenesis and of skeletal muscle regeneration and function.

In this review, we reported an overview and recent advances about the role of miRNAs expressed in the skeletal muscle, miRNAs regulation by exercise in skeletal muscle, the consequences of different physical exercise training modalities in the skeletal muscle miRNA profile, their regulation under pathological conditions and the role of miRNAs in age-related muscle wasting.

Specific miRNAs appear to be involved in response to different types of exercise and therefore to play an important role in muscle fiber identity and myofiber gene expression in adults and elder population.

Understanding the roles and regulation of skeletal muscle miRNAs during muscle regeneration may result in new therapeutic approaches in aging or diseases with impaired muscle function or re-growth.

Circulating myomiRs: a new class of biomarkers to monitor skeletal muscle in physiology and medicine

MicroRNAs (miRNA) are small non-coding RNAs that target mRNAs and are consequently involved in the post-transcriptional regulation of gene expression. Some miRNAs are ubiquitously expressed in tissue, while others are tissue-specific or tissue-enriched. miRNAs can be released by cells and are found in various biofluids, including serum and plasma. Thus, measuring miRNAs in the circulation may provide information on the originating tissue or cells. MyomiRs are described as striated muscle-specific or muscle-enriched miRNAs. Their circulating levels can be measured and have been proposed to be new biomarkers of physiological and pathological muscle processes. The aims of this review are to summarize the current knowledge of circulating myomiRs, to identify the types of information they can provide about skeletal muscle, and to determine how to apply that information in the fields of research and medicine.

Biomarkers of Duchenne muscular dystrophy: current findings

Numerous biomarkers have been unveiled in the rapidly evolving biomarker discovery field, with an aim to improve the clinical management of disorders. In rare diseases, such as Duchenne muscular dystrophy, this endeavor has created a wealth of knowledge that, if effectively exploited, will benefit affected individuals, with respect to health care, therapy, improved quality of life and increased life expectancy. The most promising findings and molecular biomarkers are inspected in this review, with an aim to provide an overview of currently known biomarkers and the technological developments used. Biomarkers as cells, genetic variations, miRNAs, proteins, lipids and/or metabolites indicative of disease severity, progression and treatment response have the potential to improve development and approval of therapies, clinical management of DMD and patients’ life quality. We highlight the complexity of translating research results to clinical use, emphasizing the need for biomarkers, fit for purpose and describe the challenges associated with qualifying biomarkers for clinical applications.

Serum miRNAs miR-23a, 206, and 499 as Potential Biomarkers for Skeletal Muscle Atrophy

Muscle biopsy has long been expected to be replaced by noninvasive biomarkers with diagnostic value and prognostic applications for muscle atrophy. Growing evidence suggests that circulating microRNAs (miRNAs) could act as biomarkers for numerous pathophysiological statuses. In the present study, our results showed that the serum levels of six muscle-specific miRNAs (miR-1/23a/133/206/208b/499) were all elevated in unloading induced mice. The medium levels of these six muscle-specific miRNAs were all elevated in starvation induced atrophic C2C12 myotubes. Moreover, the serum levels of miR-23a/206/499 were induced in participants after 45 days of head-down bed rest (HDBR). The levels of miR-23a/206/499 were positively correlated with the ratio of soleus volume loss in HDBR participants, indicating that they might represent the process of muscle loss. In conclusion, our results demonstrated that circulating miRNAs could serve as useful biochemical and molecular indicators for muscle atrophy diagnosis and disease progression.