MyoD transcription factor induces myogenesis by inhibiting Twist-1 through miR-206

Aster glehni Extract, Including Caffeoylquinic Acids as the Main Constituents, Induces PPAR β/δ-Dependent Muscle-Type Change and Myogenesis in Apolipoprotein E Knockout Mice

To probe the functions of Aster glehni (AG) extract containing various caffeoylquinic acids on dyslipidemia, obesity, and skeletal muscle-related diseases focused on the roles of skeletal muscle, we measured the levels of biomarkers involved in oxidative phosphorylation and type change of skeletal muscle in C2C12 cells and skeletal muscle tissues from apolipoprotein E knockout (ApoE KO) mice. After AG extract treatment in cell and animal experiments, western blotting, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) were used to estimate the levels of proteins that participated in skeletal muscle type change and oxidative phosphorylation. AG extract elevated protein expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), phosphorylated 5'-AMP-activated protein kinase (p-AMPK), peroxisome proliferator-activated receptor beta/delta (PPARβ/δ), myoblast determination protein 1 (MyoD), and myoglobin in skeletal muscle tissues. Furthermore, it elevated the ATP concentration. However, protein expression of myostatin was decreased by AG treatment. In C2C12 cells, increments of MyoD, myoglobin, myosin, ATP-producing pathway, and differentiation degree by AG were dependent on PPARβ/δ and caffeoylquinic acids. AG extract can contribute to the amelioration of skeletal muscle inactivity and sarcopenia through myogenesis in skeletal muscle tissues from ApoE KO mice, and function of AG extract may be dependent on PPARβ/δ, and the main functional constituents of AG are trans-5-O-caffeoylquinic acid and 3,5-O-dicaffeoylquinic acid. In addition, in skeletal muscle, AG has potent efficacies against dyslipidemia and obesity through the increase of the type 1 muscle fiber content to produce more ATP by oxidative phosphorylation in skeletal muscle tissues from ApoE KO mice.

Idiopathic inflammatory myopathy and non-coding RNA

Idiopathic inflammatory myopathies (IIMs) are common autoimmune diseases that affect skeletal muscle quality and function. The lack of an early diagnosis and treatment can lead to irreversible muscle damage. Non-coding RNAs (ncRNAs) play an important role in inflammatory transfer, muscle regeneration, differentiation, and regulation of specific antibody levels and pain in IIMs. ncRNAs can be detected in blood and hair; therefore, ncRNAs detection has great potential for diagnosing, preventing, and treating IIMs in conjunction with other methods. However, the specific roles and mechanisms underlying the regulation of IIMs and their subtypes remain unclear. Here, we review the mechanisms by which micro RNAs and long non-coding RNA-messenger RNA networks regulate IIMs to provide a basis for ncRNAs use as diagnostic tools and therapeutic targets for IIMs.

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.

Age-Related Exosomal and Endogenous Expression Patterns of miR-1, miR-133a, miR-133b, and miR-206 in Skeletal Muscles

Skeletal muscle growth and maintenance depend on two tightly regulated processes, myogenesis and muscle regeneration. Both processes involve a series of crucial regulatory molecules including muscle-specific microRNAs, known as myomiRs. We recently showed that four myomiRs, miR-1, miR-133a, miR-133b, and miR-206, are encapsulated within muscle-derived exosomes and participate in local skeletal muscle communication. Although these four myomiRs have been extensively studied for their function in muscles, no information exists regarding their endogenous and exosomal levels across age. Here we aimed to identify any age-related changes in the endogenous and muscle-derived exosomal myomiR levels during acute skeletal muscle growth. The four endogenous and muscle-derived myomiRs were investigated in five skeletal muscles (extensor digitorum longus, soleus, tibialis anterior, gastrocnemius, and quadriceps) of 2-week–1-year-old wild-type male mice. The expression of miR-1, miR-133a, and miR-133b was found to increase rapidly until adolescence in all skeletal muscles, whereas during adulthood it remained relatively stable. By contrast, endogenous miR-206 levels were observed to decrease with age in all muscles, except for soleus. Differential expression of the four myomiRs is also inversely reflected on the production of two protein targets; serum response factor and connexin 43. Muscle-derived exosomal miR-1, miR-133a, and miR-133b levels were found to increase until the early adolescence, before reaching a plateau phase. Soleus was found to be the only skeletal muscle to release exosomes enriched in miR-206. In this study, we showed for the first time an in-depth longitudinal analysis of the endogenous and exosomal levels of the four myomiRs during skeletal muscle development. We showed that the endogenous expression and extracellular secretion of the four myomiRs are associated to the function and size of skeletal muscles as the mice age. Overall, our findings provide new insights for the myomiRs’ significant role in the first year of life in mice.

Brain Pathogenesis and Potential Therapeutic Strategies in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy that affects multiple systems including the muscle and heart. The mutant CTG expansion at the 3′-UTR of the DMPK gene causes the expression of toxic RNA that aggregate as nuclear foci. The foci then interfere with RNA-binding proteins, affecting hundreds of mis-spliced effector genes, leading to aberrant alternative splicing and loss of effector gene product functions, ultimately resulting in systemic disorders. In recent years, increasing clinical, imaging, and pathological evidence have indicated that DM1, though to a lesser extent, could also be recognized as true brain diseases, with more and more researchers dedicating to develop novel therapeutic tools dealing with it. In this review, we summarize the current advances in the pathogenesis and pathology of central nervous system (CNS) deficits in DM1, intervention measures currently being investigated are also highlighted, aiming to promote novel and cutting-edge therapeutic investigations.

Muscle-derived exosomes encapsulate myomiRs and are involved in local skeletal muscle tissue communication

Exosomes are extracellular vesicles that are released from most cell types encapsulating specific molecular cargo. Exosomes serve as mediators of cell-to-cell and tissue-to-tissue communications under normal and pathological conditions. It has been shown that exosomes carrying muscle-specific miRNAs, myomiRs, are secreted from skeletal muscle cells in vitro and are elevated in the blood of muscle disease patients. The aim of this study was to investigate the secretion of exosomes encapsulating the four myomiRs from skeletal muscle tissues and to assess their role in inter-tissue communication between neighboring skeletal muscles in vivo. We demonstrate, for the first time, that isolated, intact skeletal muscle tissues secrete exosomes encapsulating the four myomiRs, miR-1, miR-133a, miR-133b, and miR-206. Notably, we show that the sorting of the four myomiRs within exosomes varies between skeletal muscles of different muscle fiber-type composition. miR-133a and miR-133b downregulation in TA muscles caused a reduction of their levels in neighboring skeletal muscles and in serum exosomes. In conclusion, our results reveal that skeletal muscle-derived exosomes encapsulate the four myomiRs, some of which enter the blood, while a portion is used for the local communication between proximal muscle tissues. These findings provide important evidence regarding novel pathways implicated in skeletal muscle function.

Transcription factor forkhead box K1 regulates miR-32 expression and enhances cell proliferation in colorectal cancer

Increased microRNA (miR)-32 expression in colorectal cancer (CRC) tissues enhances CRC cell proliferation, migration, invasion and attenuates CRC cell apoptosis by repressing the expression of phosphatase and tensin homolog (PTEN). Forkhead box K1 (FOXK1) was identified as a potential interacting transcription factor using DNA pull-down assays and mass spectrometry. The present study aimed to elucidate the role of FOXK1 in regulating miR-32 expression in CRC. The expressions of FOXK1, miR-32, transmembrane protein 245 gene (TMEM245) and PTEN were compared between CRC and normal colonic tissues. Levels of miR-32, TMEM245, PTEN and the proliferation and apoptosis of CRC cells were studied using FOXK1-overexpression or knockdown, or by simultaneously interfering with FOXK1 and miR-32 expression. Direct FOXK1 binding to the miR-32 promoter was verified using chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays. The results showed elevated FOXK1, miR-32 and TMEM245 expression, and significantly decreased PTEN expression in CRC, compared with normal colonic tissues. Correlations between the expressions of TMEM245 and miR-32, FOXK1 and miR-32, and FOXK1 and TMEM245 were positive and significant. FOXK1-knockdown led to decreased miR-32 and TMEM245 expression and increased PTEN expression, whereas FOXK1-overexpression had the opposite effect. Overexpressed FOXK1 promoted the malignancy of CRC cells in vitro by stimulating proliferation and reducing apoptosis; whereas FOXK1-depletion suppressed such malignancy and a miR-32 inhibitor partially reversed the effects of FOXK1. The results of ChIP and dual-luciferase reporter assays indicated that FOXK1 directly binds to the promoter of TMEM245/miR-32. Thus, the FOXK1-miR-32-PTEN signaling axis may play a crucial role in the pathogenesis and development of CRC.

Epigenetic modifications in muscle regeneration and progression of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a multisystemic disorder that affects 1:5000 boys. The severity of the phenotype varies dependent on the mutation site in the DMD gene and the resultant dystrophin expression profile. In skeletal muscle, dystrophin loss is associated with the disintegration of myofibers and their ineffective regeneration due to defective expansion and differentiation of the muscle stem cell pool. Some of these phenotypic alterations stem from the dystrophin absence-mediated serine-threonine protein kinase 2 (MARK2) misplacement/downregulation in activated muscle stem (satellite) cells and neuronal nitric oxide synthase loss in cells committed to myogenesis. Here, we trace changes in DNA methylation, histone modifications, and expression of regulatory noncoding RNAs during muscle regeneration, from the stage of satellite cells to myofibers. Furthermore, we describe the abrogation of these epigenetic regulatory processes due to changes in signal transduction in DMD and point to therapeutic treatments increasing the regenerative potential of diseased muscles based on this acquired knowledge.

The Biomarker Potential of miRNAs in Myotonic Dystrophy Type I

MicroRNAs (miRNAs) are mostly known for their gene regulation properties, but they also play an important role in intercellular signaling. This means that they can be found in bodily fluids, giving them excellent biomarker potential. Myotonic Dystrophy type I (DM1) is the most frequent autosomal dominant muscle dystrophy in adults, with an estimated prevalence of 1:8000. DM1 symptoms include muscle weakness, myotonia, respiratory failure, cardiac conduction defects, cataracts, and endocrine disturbances. Patients display heterogeneity in both age of onset and disease manifestation. No treatment or cure currently exists for DM1, which shows the necessity for a biomarker that can predict disease progression, providing the opportunity to implement preventative measures before symptoms arise. In the past two decades, extensive research has been conducted in the miRNA expression profiles of DM1 patients and their biomarker potential. Here we review the current state of the field with a tissue-specific focus, given the multi-systemic nature of DM1 and the intracellular signaling role of miRNAs.

Circulating Biomarkers in Muscular Dystrophies: Disease and Therapy Monitoring

Muscular dystrophies are a group of inherited disorders that primarily affect the muscle tissues. Across the muscular dystrophies, symptoms commonly compromise the quality of life in all areas of functioning. It is well noted that muscular dystrophies need reliable and measurable biomarkers that will monitor the progress of the disease and evaluate the potential therapeutic approaches. In this review, we analyze the current findings regarding the development of blood-based circulating biomarkers for different types of muscular dystrophies. We emphasize those muscular dystrophies that gained particular interest for the development of biomarkers, including Duchenne muscular dystrophy, Becker muscular dystrophy, myotonic dystrophy types 1 and 2, Ullrich congenital muscular dystrophy, congenital muscular dystrophy type 1A, Facioscapulohumeral muscular dystrophy, and limb-girdle muscular dystrophy types 2A, 2B, 2C, and 2D, recently renamed as limb-girdle muscular dystrophy R1 calpain3-related, R2 dysferlin-related, R5 γ-sarcoglycan-related, and R3 α-sarcoglycan-related. This review highlights the up-to-date progress in the development of biomarkers at the level of proteins, lipids, and metabolites, as well as microRNAs (miRNAs) that currently are the main potential biomarker candidates in muscular dystrophies.

The roles of microRNA in redox metabolism and exercise-mediated adaptation

MicroRNAs (miRs) are small regulatory RNA transcripts capable of post-transcriptional silencing of mRNA messages by entering a cellular bimolecular apparatus called RNA-induced silencing complex. miRs are involved in the regulation of cellular processes producing, eliminating or repairing the damage caused by reactive oxygen species, and they are active players in redox homeostasis. Increased mitochondrial biogenesis, function and hypertrophy of skeletal muscle are important adaptive responses to regular exercise. In the present review, we highlight some of the redox-sensitive regulatory roles of miRs.

Regulatory Role of the Transcription Factor Twist1 in Cancer-Associated Muscle Cachexia

Muscle cachexia is a catabolic response, usually takes place in various fatal diseases, such as sepsis, burn injury, and chronic kidney disease. Muscle cachexia is also a common co-morbidity seen in the vast majority of advanced cancer patients, often associated with low quality of life and death due to general organ dysfunction. The triggering events and underlying molecular mechanisms of muscle wasting are not yet clearly defined. Our recent study has shown that the ectopic expression of Twist1 in muscle progenitor cells is sufficient to drive muscle structural protein breakdown and attendant muscle atrophy, reminiscent of muscle cachexia. Intriguingly, muscle Twist1 expression is highly induced in cachectic muscles from several mouse models of pancreatic ductal adenocarcinoma (PDAC), raising the interesting possibility that Twist1 may mediate PDAC-driven muscle cachexia. Along these lines, both genetic and pharmacological inactivation of Twist1 function was highly significant at protecting against cancer cachexia, which translated into a significant survival benefit in the experimental PDAC animals. From a translational perspective, elevated expression of Twist1 is also detected in cancer patients with severe muscle wasting, implicating a role of Twist1 in cancer cachexia, and further providing a possible target for therapeutic attenuation of cachexia to improve cancer patient survival. In this article, we will briefly summarize how Twist1 acts as a master regulator of tumor-induced cachexia, and discuss the relevance of our findings to muscle wasting diseases in general. The mechanism of decreased muscle mass in various catabolic conditions is thought to rely on similar pathways, and, therefore, Twist1-induced cancer cachexia may benefit diverse groups of patients with clinical complications associated with loss of muscle mass and functions, beyond the expected benefits for cancer patients.

MicroRNA-Based Therapeutic Perspectives in Myotonic Dystrophy

Myotonic dystrophy involves two types of chronically debilitating rare neuromuscular diseases: type 1 (DM1) and type 2 (DM2). Both share similarities in molecular cause, clinical signs, and symptoms with DM2 patients usually displaying milder phenotypes. It is well documented that key clinical symptoms in DM are associated with a strong mis-regulation of RNA metabolism observed in patient’s cells. This mis-regulation is triggered by two leading DM-linked events: the sequestration of Muscleblind-like proteins (MBNL) and the mis-regulation of the CUGBP RNA-Binding Protein Elav-Like Family Member 1 (CELF1) that cause significant alterations to their important functions in RNA processing. It has been suggested that DM1 may be treatable through endogenous modulation of the expression of MBNL and CELF1 proteins. In this study, we analyzed the recent identification of the involvement of microRNA (miRNA) molecules in DM and focus on the modulation of these miRNAs to therapeutically restore normal MBNL or CELF1 function. We also discuss additional prospective miRNA targets, the use of miRNAs as disease biomarkers, and additional promising miRNA-based and miRNA-targeting drug development strategies. This review provides a unifying overview of the dispersed data on miRNA available in the context of DM.

Pulmonary artery smooth muscle cell HIF-1α regulates endothelin expression via microRNA-543

Pulmonary artery smooth muscle cells (PASMCs) express endothelin (ET-1), which modulates the pulmonary vascular response to hypoxia. Although cross-talk between hypoxia-inducible factor-1α (HIF-1α), an O₂-sensitive transcription factor, and ET-1 is established, the cell-specific relationship between HIF-1α and ET-1 expression remains incompletely understood. We tested the hypotheses that in PASMCs 1) HIF-1α expression constrains ET-1 expression, and 2) a specific microRNA (miRNA) links HIF-1α and ET-1 expression. In human (h)PASMCs, depletion of HIF-1α with siRNA increased ET-1 expression at both the mRNA and protein levels ( P < 0.01). In HIF-1α^-/- murine PASMCs, ET-1 gene and protein expression was increased ( P < 0.0001) compared with HIF-1α^+/+ cells. miRNA profiles were screened in hPASMCs transfected with siRNA-HIF-1α, and RNA hybridization was performed on the Agilent (Santa Clara, CA) human miRNA microarray. With HIF-1α depletion, miRNA-543 increased 2.4-fold ( P < 0.01). In hPASMCs, miRNA-543 overexpression increased ET-1 gene ( P < 0.01) and protein ( P < 0.01) expression, decreased TWIST gene expression ( P < 0.05), and increased ET-1 gene and protein expression, compared with nontargeting controls ( P < 0.01). Moreover, we evaluated low passage hPASMCs from control and patients with idiopathic pulmonary arterial hypertension (IPAH). Compared with controls, protein expression of HIF-1α and Twist-related protein-1 (TWIST1) was decreased ( P < 0.05), and miRNA-543 and ET-1 expression increased ( P < 0.001) in hPASMCs from patients with IPAH. Thus, in PASMCs, loss of HIF-1α increases miRNA-543, which decreases Twist expression, leading to an increase in PASMC ET-1 expression. This previously undescribed link between HIF-1α and ET-1 via miRNA-543 mediated Twist suppression represents another layer of molecular regulation that might determine pulmonary vascular tone.

Role of Exosomal MicroRNAs and myomiRs in the Development of Cancer Cachexia-Associated Muscle Wasting

Cachexia is a complex metabolic syndrome that promotes great weight loss, with marked muscle mass wasting. In the last years, many efforts have been directed to improve the understanding of the mechanisms involved in the disease. This syndrome is present in up to 80% of cancer patients and, despite its clinical relevance, is underdiagnosed. The orchestration of the molecular and biochemical disruptions observed in cachexia is paralleled by inflammation and the communication among the different body compartments, including the tumor and the skeletal muscle, is still not completely described. One of the mechanisms that may be involved in the transduction of the inflammatory signals and the activation of catabolic status in muscle is the participation of exosomes containing microRNAs (miRNAs) and muscle-specific miRNAs (myomiRs). Exosomes are nanovesicles, measuring from 30 to 100 µm, and able to carry miRNAs in the circulation, promoting cell–cell and tissue–tissue communication in an autocrine, paracrine, and endocrine manner. miRNAs transported in exosomes are preserved from degradation, while these nanoparticles deliver the cargo to specific cell targets, making communication more efficient. Several miRNAs are known to modulate inflammatory pathways, to induce metastasis, to mediate cancer aggressiveness and even to participate in the regulation of protein synthesis and degradation pathways in the skeletal muscle. The aim of this mini-review is to describe the present knowledge about the role of exosomal miRNAs and myomiRs in the induction of muscle mass wasting in cancer cachexia state and to explain which transcription factors, proteins, and pathways are regulated by these molecules.

Twist promotes angiogenesis in pancreatic cancer by targeting miR-497/VEGFA axis

Angiogenesis is a critical step in the growth and dissemination of malignant diseases, including pancreatic cancer. Twist has been shown to stimulate angiogenesis in the tumor site. However, whether Twist contributes to angiogenesis in pancreatic cancer remains unknown. In this paper, we found that the expression of Twist was significantly increased in human pancreatic cancer cell lines and pancreatic cancer specimens. It is also closely engaged to adverse clinical feature, diminished survival and angiogenesis in pancreatic cancer patients. The up-regulation of Twist was found to be promoting cell growth, invasion and tubule formation of human umbilical vein endothelial cells (HUVECs) in vitro. By contrast, the silencing of Twist inhibited orthotopic xenograft tumor growth, metastasis and angiogenesis. Subsequent investigations disclosed that Twist was regulated by miR-497 directly, leading to the increased level of Vascular Endothelial Growth Factor-A (VEGFA). Moreover, gain-of-function and loss-of-function studies demonstrated that miR-497 could suppress the pro-proliferative, angiogenic and metastatic ability of pancreatic cancer cells. The ectopic expression of VEGFA obviously abrogated the anti-angiogenic effect induced by Twist knockdown, whereas the silencing of VEGFA markedly rescued the pro-angiogenic effect of Twist. By analyzing the expression levels of miR-497, Twist was found inversely correlated with miR-497 in pancreatic cancer tissues, and a positive correlation was found between Twist and VEGFA levels in pancreatic cancer specimens. In conclusion, our results suggested that the Twist/miR-497/VEGFA axis is significantly correlated with metastasis and angiogenesis in pancreatic cancer.

Emerging role of extracellular vesicles in musculoskeletal diseases

Research into the biology of extracellular vesicles (EVs), including exosomes and microvesicles, has expanded significantly with advances in EV isolation techniques, a better understanding of the surface markers that characterize exosomes and microvesicles, and greater information derived from -omics approaches on the proteins, lipids, mRNAs, and microRNAs (miRNAs) transported by EVs. We have recently discovered a role for exosome-derived miRNAs in age-related bone loss and osteoarthritis, two conditions that impose a significant public health burden on the aging global population. Previous work has also revealed multiple roles for EVs and their miRNAs in muscle regeneration and congenital myopathies. Thus, EVs appear to be involved in a number of degenerative conditions that impact the musculoskeletal system, indicating that the musculoskeletal system is an excellent model for investigating the role of EVs in tissue maintenance and repair. This review highlights the role of EVs in bone, skeletal muscle, and joint health, including both normal tissue metabolism as well as tissue injury repair and regeneration. A consistent theme that emerges from study of musculoskeletal EVs is that various miRNAs appear to mediate a number of key pathological processes. These findings point to a potential therapeutic opportunity to target EV-derived miRNAs as a strategy for improving musculoskeletal function.

DNMT3B in vitro knocking-down is able to reverse embryonal rhabdomyosarcoma cell phenotype through inhibition of proliferation and induction of myogenic differentiation

Aberrant DNA methylation has been frequently observed in many human cancers, including rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children. To date, the expression and function of the de novo DNA methyltransferase (DNMT) 3B in RMS have not yet been investigated. Our study show for the first time a significant up-regulation of DNMT3B levels in 14 RMS tumour samples and 4 RMS cell lines in comparison to normal skeletal muscle. Transfection of RD and TE671 cells, two in vitro models of embryonal RMS (ERMS), with a synthetic DNMT3B siRNA decreased cell proliferation by arresting cell cycle at G1 phase, as demonstrated by the reduced expression of Cyclin B1, Cyclin D1 and Cyclin E2, and by the concomitant up-regulation of the checkpoint regulators p21 and p27. DNMT3B depletion also impaired RB phosphorylation status and decreased migratory capacity and clonogenic potential. Interestingly, DNMT3B knock-down was able to commit ERMS cells towards myogenic terminal differentiation, as confirmed by the acquisition of a myogenic-like phenotype and by the increased expression of the myogenic markers MYOD1, Myogenin and MyHC. Finally, inhibition of MEK/ERK signalling by U0126 resulted in a reduction of DNMT3B protein, giving evidence that DNMT3B is a down-stream molecule of this oncogenic pathway.Taken together, our data indicate that altered expression of DNMT3B plays a key role in ERMS development since its silencing is able to reverse cell cancer phenotype by rescuing myogenic program. Epigenetic therapy, by targeting the DNA methylation machinery, may represent a novel therapeutic strategy against RMS.

Ion Current-Based Proteomic Profiling for Understanding the Inhibitory Effect of Tumor Necrosis Factor Alpha on Myogenic Differentiation

Despite a demonstrated role for TNF-α in promoting muscle wasting and cachexia, the associated molecular mechanisms and signaling pathways of myoblast differentiation dysregulated by TNF-α remain poorly understood. This study presents well-controlled proteomic profiling as a means to investigate the mechanisms of TNF-α-regulated myogenic differentiation. Primary human muscle precursor cells (MPCs) cultured in growth medium (GM), differentiation medium (DM) to induce myogenic differentiation, and DM with 20 ng/mL of TNF-α (n = 5/group) were comparatively analyzed by an ion current-based quantitative platform consisting of reproducible sample preparation/on-pellet digestion, a long-column nano-LC separation, and ion current-based differential analysis. The inhibition of myogenic differentiation by TNF-α was confirmed by reduced formation of multinucleated myotubes and the recovered expression of altered myogenic proteins such as MYOD and myogenin during myogenic differentiation. Functional analysis and validation by immunoassay analysis suggested that the cooperation of NF-κB and STAT proteins is responsible for dysregulated differentiation in MPCs by TNF-α treatment. Increased MHC class I components such as HLA-A, HLA-B, HLA-C, and beta-2-microglobulin were also observed in cultures in DM treated with TNF-α. Interestingly, inhibition of the cholesterol biosynthesis pathway during myogenic differentiation induced by serum starvation was not recovered by TNF-α treatment, which combined with previous reports, implies that this process may be an early event of myogenesis. This finding could lay the foundation for the potential use of statins in modulating myogenesis through cholesterol, for example, in stem cell-based myocardial infarction treatment, where differentiation of myoblasts and stem cells into force-generating mature muscle cells is a key step to the therapeutic capacity. In conclusion, the landscapes of altered transcription regulators, metabolic processes, and signaling pathways in MPCs are revealed in the regulation of myogenic differentiation by TNF-α, which is valuable for myogenic cellular therapeutics.

Key transcription factors in the differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells that represent a promising source for regenerative medicine. MSCs are capable of osteogenic, chondrogenic, adipogenic and myogenic differentiation. Efficacy of differentiated MSCs to regenerate cells in the injured tissues requires the ability to maintain the differentiation toward the desired cell fate. Since MSCs represent an attractive source for autologous transplantation, cellular and molecular signaling pathways and micro-environmental changes have been studied in order to understand the role of cytokines, chemokines, and transcription factors on the differentiation of MSCs. The differentiation of MSC into a mesenchymal lineage is genetically manipulated and promoted by specific transcription factors associated with a particular cell lineage. Recent studies have explored the integration of transcription factors, including Runx2, Sox9, PPARγ, MyoD, GATA4, and GATA6 in the differentiation of MSCs. Therefore, the overexpression of a single transcription factor in MSCs may promote trans-differentiation into specific cell lineage, which can be used for treatment of some diseases. In this review, we critically discussed and evaluated the role of transcription factors and related signaling pathways that affect the differentiation of MSCs toward adipocytes, chondrocytes, osteocytes, skeletal muscle cells, cardiomyocytes, and smooth muscle cells.