Microrna-221 and microrna-222 modulate differentiation and maturation of skeletal muscle cells

Analysis of microRNA Expression Profiles in Broiler Muscle Tissues by Feeding Different Levels of Guanidinoacetic Acid

The aim of this study was to explore the molecular mechanisms through which different levels of GAA affect chicken muscle development by influencing miRNA expression, to lay a theoretical foundation for the identification of key functional small RNAs related to poultry muscle development, and to provide new insights into the regulatory mechanisms of GAA on muscle development and meat quality in broilers. It provides a new theoretical basis for using GAA as a feed additive to improve feed performance. Small RNA sequencing technology was utilized to obtain the expression profiles of miRNA in the broiler pectoral muscle fed with different levels of GAA (0 g/kg, 1.2 g/kg and 3.6 g/kg). An analysis of differentially expressed miRNAs revealed 90 such miRNAs in the three combination comparisons, with gga-miR-130b-5p exhibiting significant differences across all three combinations. Furthermore, three of the differentially expressed miRNAs were performed by RT-qPCR verification, yielding results consistent with those obtained from small RNA sequencing. Target gene prediction, as well as the GO and KEGG enrichment analysis of differentially expressed miRNAs, indicated their involvement in muscle cell differentiation and other processes, particularly those associated with the MAPK signaling pathway. This study has, thus, provided valuable insights and resources for the further exploration of the miRNA molecular mechanism underlying the influence of guanidine acetic acid on broiler muscle development. Combined with previous studies and small RNA sequencing, adding 1.2 g/kg GAA to the diet can better promote the muscle development of broilers.

MicroRNA expression and oxidative stress markers in pectoral muscle of broiler chickens fed diets supplemented with phytobiotics composition

Phytobiotic compositions are commercially used in broiler production, mostly to improve general health and the production parameters. Moreover, some of their active substances may change the expression of miRNA in different tissues. Therefore, the purpose of this study was to evaluate the effect of the phytobiotic composition (PBC) containing white mustard, calamus, turmeric, and common ivy on production parameters, oxidative stress markers and expression of selected miRNAs in pectoral muscle of broiler chickens. The experiment was performed on broiler chickens fed the control diet (without PBC), and a diet supplemented with 60 or 100 mg/kg of PBC for 35 days. After the experiment, samples (blood and muscle) were collected for analyses. The analyzed production parameters included: feed conversion ratio, feed intake and body weight. There was no effect on growth performance of broiler chickens but feeding diet supplemented with 60 mg/kg phytobiotics significantly increased the expression of miR-30a-5p, miR-181a-5p, and miR-206, and decreased that of miR-99a-5p, miR-133a-5p, miR-142-5p, and miR-222 in pectoral muscle of chickens. The addition of 100 mg/kg phytobiotics significantly increased miR-99a-5p and miR-181a-5p expression, and caused down-regulation of the expression of miR-26a-5p and miR-30a-5p. Chickens fed diet supplemented with 100 mg/kg PBC had lower level of lipid peroxidation products in blood, while in the muscle tissue it was higher in birds fed a diet with the addition of 60 mg/kg as compared to the control group. The results suggest that this unique composition of phytobiotics does not affect productive traits but can change expression of miRNAs that are crucial for muscle physiology and pathology in broiler chickens. This additive may also protect against the oxidative stress but the effect is dose dependent.

Ageing at Molecular Level: Role of MicroRNAs

The progression of age triggers a vast number of diseases including cardiovascular, cancer, and neurodegenerative disorders. Regardless of our plentiful knowledge about age-related diseases, little is understood about molecular pathways that associate the ageing process with various diseases. Several cellular events like senescence, telomere dysfunction, alterations in protein processing, and regulation of gene expression are common between ageing and associated diseases. Accumulating information on the role of microRNAs (miRNAs) suggests targeting miRNAs can aid our understanding of the interplay between ageing and associated diseases. In the present chapter, we have attempted to explore the information available on the role of miRNAs in ageing of various tissues/organs and diseases and understand the molecular mechanism of ageing.

Extracellular vesicles and microRNAs are altered in response to exercise, insulin sensitivity and overweight

Extracellular vesicles induced by exercise have emerged as potential mediators of tissue crosstalk. Extracellular vesicles and their cargo miRNAs have been linked to dysglycemia and obesity in animal models, but their role in humans is unclear.

AIM

The aim of the study was to characterize the miRNA content in plasma extracellular vesicle isolates after acute and long-term exercise and to study associations between extracellular vesicle miRNAs, mRNA expression in skeletal muscle and adipose tissue, and cardiometabolic risk factors.

METHODS

Sedentary men with or without dysglycemia and overweight underwent an acute bicycle test and a 12-week exercise intervention with extensive metabolic phenotyping. Gene expression in m. vastus lateralis and subcutaneous adipose tissue was measured with RNA sequencing. Extracellular vesicles were purified from plasma with membrane affinity columns or size exclusion chromatography.

RESULTS

Extracellular vesicle miRNA profiling revealed a transient increase in the number of miRNAs after acute exercise. We identified miRNAs, such as miR-652-3p, that were associated to insulin sensitivity and adiposity. By performing explorative association analyses, we identified two miRNAs, miR-32-5p and miR-339-3p, that were strongly correlated to an adipose tissue macrophage signature.

CONCLUSION

Numerous miRNAs in plasma extracellular vesicle isolates were increased by exercise, and several miRNAs correlated to insulin sensitivity and adiposity. Our findings warrant future studies to characterize exercise-induced extracellular vesicles and cargo miRNA to clarify where exercise-induced extracellular vesicles originate from, and to determine whether they influence metabolic health or exercise adaptation.

MiR-223 Exclusively Impairs In Vitro Tumor Growth through IGF1R Modulation in Rhabdomyosarcoma of Adolescents and Young Adults

Adolescents and young adults (AYA) with rhabdomyosarcoma (RMS) form a subgroup of patients whose optimal clinical management and best possible access to care remain a challenge and whose survival rates lag behind that of children diagnosed with histologically similar tumors. A better understanding of tumor biology that differentiates children (PEDS-) from AYA-RMS could provide critical information and drive new initiatives to improve their final outcome. We investigated the functional role of miRNAs implicated in AYA-RMS development, as they have the potential to lead to discovery of new targets pathways for a more tailored treatment in these age groups of young RMS patients. MiR-223 and miR-486 were observed de-regulated in nine RMS tissues compared to their normal counterparts, yet only miR-223 replacement impaired proliferation and aggressiveness of AYA-RMS cell lines, while inducing apoptosis and determining cell cycle arrest. Interestingly, IGF1R resulted in the direct target of miR-223 in AYA-RMS cells, as demonstrated by IGF1R silencing. Our results highlight an exclusive functional role of miR-223 in AYA-RMS development and aggressiveness.

MicroRNA expression signature in the striated and smooth adductor muscles of Yesso scallop Patinopecten yessoensis

Increasing evidences point to the potential role of microRNAs (miRNAs) in muscle growth and development in animals. However, knowledge on the identity of miRNAs and their targets in molluscs remains largely unknown. Scallops have one large adductor muscle, composed of fast (striated) and slow (smooth) muscle types, which display great differences in muscle fibers, meat quality, cell types and molecular components. In the present study, we performed a comprehensive investigation of miRNA transcriptomes in fast and slow adductor muscles of Yesso scallop Patinopecten yessoensis. As a result, 47 differentially expressed miRNAs representing ten miRNA families were identified between the striated and smooth adductor muscles. The KEGG enrichment analysis of their target genes were mainly associated with amino acid metabolism, energy metabolism and glycan biosynthesis. The target genes of miR-133 and miR-71 were validated by the dual-luciferase reporter assays and miRNA antagomir treatment in vivo. The identification and functional validation of these different miRNAs in scallops will greatly help our understanding of miRNA regulatory mechanism that achieves the unique muscle phenotypes in scallops. The present findings provide the direct evidences for muscle-specific miRNAs involved in muscle growth and differentiation in molluscs.

MicroRNA-24-3p promotes skeletal muscle differentiation and regeneration by regulating HMGA1

Numerous studies have established the critical roles of microRNAs in regulating post-transcriptional gene expression in diverse biological processes. Here, we report on the role and mechanism of miR-24-3p in skeletal muscle differentiation and regeneration. miR-24-3p promotes myoblast differentiation and skeletal muscle regeneration by directly targeting high mobility group AT-hook 1 (HMGA1) and regulating it and its direct downstream target, the inhibitor of differentiation 3 (ID3). miR-24-3p knockdown in neonatal mice increases PAX7-positive proliferating muscle stem cells (MuSCs) by derepressing Hmga1 and Id3. Similarly, inhibition of miR-24-3p in the tibialis anterior muscle prevents Hmga1 and Id3 downregulation and impairs regeneration. These findings provide evidence that the miR-24-3p/HMGA1/ID3 axis is required for MuSC differentiation and skeletal muscle regeneration in vivo.

UC.183, UC.110, and UC.84 Ultra-Conserved RNAs Are Mutually Exclusive with miR-221 and Are Engaged in the Cell Cycle Circuitry in Breast Cancer Cell Lines

In the human genome, there are about 600 ultra-conserved regions (UCRs), long DNA sequences extremely conserved in vertebrates. We performed a large-scale study to quantify transcribed UCR (T-UCR) and miRNA levels in over 6000 cancer and normal tissue samples to find possible correlation between these kinds of regulatory molecules. Our analysis evidenced several non-coding RNAs showing negative co-regulation with miRNAs; among them, we focused on miR-221 to investigate any relationship with its pivotal role in the cell cycle. We have chosen breast cancer as model, using two cell lines with different phenotypes to carry out in vitro treatments with siRNAs against T-UCRs. Our results demonstrate that the expression of uc.183, uc.110, and uc.84 T-UCRs is mutually exclusive with miR-221 and is engaged in the regulation of CDKN1B expression. In addition, tests with a set of anticancer drugs, including BYL719, AZD5363, AZD8055, AZD7762, and XL765, revealed the modulation of specific T-UCRs without alteration of miR-221 levels.

MiRNAs and Muscle Regeneration: Therapeutic Targets in Duchenne Muscular Dystrophy

microRNAs (miRNAs) are small non-coding RNAs required for the post-transcriptional control of gene expression. MicroRNAs play a critical role in modulating muscle regeneration and stem cell behavior. Muscle regeneration is affected in muscular dystrophies, and a critical point for the development of effective strategies for treating muscle disorders is optimizing approaches to target muscle stem cells in order to increase the ability to regenerate lost tissue. Within this framework, miRNAs are emerging as implicated in muscle stem cell response in neuromuscular disorders and new methodologies to regulate the expression of key microRNAs are coming up. In this review, we summarize recent advances highlighting the potential of miRNAs to be used in conjunction with gene replacement therapies, in order to improve muscle regeneration in the context of Duchenne Muscular Dystrophy (DMD).

microRNA-mRNA Profile of Skeletal Muscle Differentiation and Relevance to Congenital Myotonic Dystrophy

microRNAs (miRNAs) regulate messenger RNA (mRNA) abundance and translation during key developmental processes including muscle differentiation. Assessment of miRNA targets can provide insight into muscle biology and gene expression profiles altered by disease. mRNA and miRNA libraries were generated from C2C12 myoblasts during differentiation, and predicted miRNA targets were identified based on presence of miRNA binding sites and reciprocal expression. Seventeen miRNAs were differentially expressed at all time intervals (comparing days 0, 2, and 5) of differentiation. mRNA targets of differentially expressed miRNAs were enriched for functions related to calcium signaling and sarcomere formation. To evaluate this relationship in a disease state, we evaluated the miRNAs differentially expressed in human congenital myotonic dystrophy (CMD) myoblasts and compared with normal control. Seventy-four miRNAs were differentially expressed during healthy human myocyte maturation, of which only 12 were also up- or downregulated in CMD patient cells. The 62 miRNAs that were only differentially expressed in healthy cells were compared with differentiating C2C12 cells. Eighteen of the 62 were conserved in mouse and up- or down-regulated during mouse myoblast differentiation, and their C2C12 targets were enriched for functions related to muscle differentiation and contraction.

Functional Non-coding RNA During Embryonic Myogenesis and Postnatal Muscle Development and Disease

Skeletal muscle is a highly heterogeneous tissue that plays a crucial role in mammalian metabolism and motion maintenance. Myogenesis is a complex biological process that includes embryonic and postnatal development, which is regulated by specific signaling pathways and transcription factors. Various non-coding RNAs (ncRNAs) account for the majority of total RNA in cells and have an important regulatory role in myogenesis. In this review, we introduced the research progress in miRNAs, circRNAs, and lncRNAs related to embryonic and postnatal muscle development. We mainly focused on ncRNAs that regulate myoblast proliferation, differentiation, and postnatal muscle development through multiple mechanisms. Finally, challenges and future perspectives related to the identification and verification of functional ncRNAs are discussed. The identification and elucidation of ncRNAs related to myogenesis will enrich the myogenic regulatory network, and the effective application of ncRNAs will enhance the function of skeletal muscle.

Profiling of microRNA from skeletal muscle of Bandur sheep using RNA sequencing

MicroRNA profiling is a powerful approach for identifying key regulators of molecular functions which control skeletal muscle development, regeneration and function. Information on gene expression and the regulatory factors involved in myogenesis is very limited for Indian sheep. This study reports the identification and characterization of miRNAs from the skeletal muscles of Bandur sheep breed for the first time. Bandur is a consumer favoured, mutton type sheep of India, mainly distributed in Mandya district of Karnataka. Skeletal muscles from four animals of Bandur sheep of similar age, sex and reared under same management conditions were used for RNA sequencing. The total number of reads (15–36 bp) for each library of Bandur sheep ranged from 19,350,000 to 30,000,000. Highly expressed transcripts with an RPKM value of ≥1000 were observed to be 34%, whereas 38% transcripts exhibited RPKM between 100–1000 and 28% had RPKM <100 in Bandur sheep. A total of 110 known mature miRNAs could be identified on comparison with known human and bovine sequences. All the identified miRNAs represented 32 miRNA families and 44 clusters. A total of 499 novel miRNAs were discovered in Bandur sheep. The miRNAs identified in our study were enriched for functions namely cell proliferation, cell differentiation, osteogenesis, lipid metabolism, muscle development, adipocyte differentiation and stress response. Potential gene targets for the identified miRNAs were predicted. Most relevant target genes predicted in our study included MYO5A, SIN3B and NR2F2 which are mainly involved in myogenesis. This study provides information of miRNAs in the skeletal muscle tissue of Bandur sheep.

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.

Role of microRNA in muscle regeneration and diseases related to muscle dysfunction in atrophy, cachexia, osteoporosis, and osteoarthritis

MicroRNAs (miRNAs) are a class of small non-coding RNAs that have emerged as potential predictive, prognostic, and therapeutic biomarkers, relevant to many pathophysiological conditions including limb immobilization, osteoarthritis, sarcopenia, and cachexia. Impaired musculoskeletal homeostasis leads to distinct muscle atrophies. Understanding miRNA involvement in the molecular mechanisms underpinning conditions such as muscle wasting may be critical to developing new strategies to improve patient management. MicroRNAs are powerful post-transcriptional regulators of gene expression in muscle and, importantly, are also detectable in the circulation. MicroRNAs are established modulators of muscle satellite stem cell activation, proliferation, and differentiation, however, there have been limited human studies that investigate miRNAs in muscle wasting. This narrative review summarizes the current knowledge as to the role of miRNAs in the skeletal muscle differentiation and atrophy, synthesizing the findings of published data. Cite this article: Bone Joint Res 2020;9(11):798-807.

Antagonism between splicing and microprocessor complex dictates the serum-induced processing of lnc-MIRHG for efficient cell cycle reentry

Cellular quiescence and cell cycle reentry regulate vital biological processes such as cellular development and tissue homeostasis and are controlled by precise regulation of gene expression. The roles of long noncoding RNAs (lncRNAs) during these processes remain to be elucidated. By performing genome-wide transcriptome analyses, we identify differential expression of several hundreds of lncRNAs, including a significant number of the less-characterized class of microRNA-host-gene (MIRHG) lncRNAs or lnc-MIRHGs, during cellular quiescence and cell cycle reentry in human diploid fibroblasts. We observe that MIR222HG lncRNA displays serum-stimulated RNA processing due to enhanced splicing of the host nascent pri-MIR222HG transcript. The pre-mRNA splicing factor SRSF1 negatively regulates the microprocessor-catalyzed cleavage of pri-miR-222, thereby increasing the cellular pool of the mature MIR222HG Association of SRSF1 to pri-MIR222HG, including to a mini-exon, which partially overlaps with the primary miR-222 precursor, promotes serum-stimulated splicing over microRNA processing of MIR222HG Further, we observe that the increased levels of spliced MIR222HG in serum-stimulated cells promote the cell cycle reentry post quiescence in a microRNA-independent manner. MIR222HG interacts with DNM3OS, another lncRNA whose expression is elevated upon serum-stimulation, and promotes cell cycle reentry. The double-stranded RNA binding protein ILF3/2 complex facilitates MIR222HG:DNM3OS RNP complex assembly, thereby promoting DNM3OS RNA stability. Our study identifies a novel mechanism whereby competition between the splicing and microprocessor machinery modulates the serum-induced RNA processing of MIR222HG, which dictates cell cycle reentry.

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.

Differential expression of miRNAs in skeletal muscles of Indian sheep with diverse carcass and muscle traits

The study presents the miRNA profiles of two Indian sheep populations with divergent carcass and muscle traits. The RNA sequencing of longissimus thoracis muscles from the two populations revealed a total of 400 known miRNAs. Myomirs or miRNAs specific to skeletal muscles identified in our data included oar-miR-1, oar-miR-133b, oar-miR-206 and oar-miR-486. Comparison of the two populations led to identification of 100 differentially expressed miRNAs (p < 0.05). A total of 45 miRNAs exhibited a log₂ fold change of ≥ ( ±) 3.0. Gene Ontology analysis revealed cell proliferation, epithelial to mesenchymal transition, apoptosis, immune response and cell differentiation as the most significant functions of the differentially expressed miRNAs. The differential expression of some miRNAs was validated by qRT-PCR analysis. Enriched pathways included metabolism of proteins and lipids, PI3K-Akt, EGFR and cellular response to stress. The microRNA-gene interaction network revealed miR-21, miR-155, miR-143, miR-221 and miR-23a as the nodal miRNAs, with multiple targets. MicroRNA-21 formed the focal point of the network with 42 interactions. The hub miRNAs identified in our study form putative regulatory candidates for future research on meat quality traits in Indian sheep. Our results provide insight into the biological pathways and regulatory molecules implicated in muscling traits of sheep.

MicroRNA‑23a‑5p mediates the proliferation and differentiation of C2C12 myoblasts

Skeletal myogenesis is a highly ordered and complex biological process that is mediated by numerous regulatory factors. In previous studies, it has been demonstrated that microRNAs (miRs) and long non-coding RNAs (lncRNAs) serve key roles in skeletal myogenesis. The present study showed that the expression levels of miR-23a-5p showed a dynamic change from decrease to increase during C2C12 myoblast proliferation and differentiation. Functional analysis using 5-ethynyl-2′-deoxyuridine proliferation and Cell Counting Kit-8 detection assays indicated that overexpression of miR-23a-5p significantly promoted C2C12 myoblast proliferation compared with the negative control. In addition, in C2C12 myoblasts transfected with miR-23a-5p mimics, increased expression levels of regulators associated with cell proliferation (Cyclin E, CCND1 and Cyclin B) were observed compared with the negative control. By contrast, overexpression of miR-23a-5p decreased the expression levels of specific-myogenesis factors (MyoD, MyoG and Myf5) and decreased C2C12 myoblast differentiation. Luciferase activity assays indicated that miR-23a-5p suppressed the luciferase activity of lncDum. Further analysis demonstrated that miR-23a-5p not only showed an opposite expression level pattern compared with lncDum, which was first increased and then decreased, but also had an opposite effect on the proliferation and differentiation of C2C12 myoblasts compared with lncDum which inhibited cell proliferation and promoted cell differentiation. Taken together, these results indicated that miR-23a-5p may mediate the proliferation and differentiation of C2C12 myoblasts, which may be involved in lncDum regulation.

Bidirectional regulation of genistein on the proliferation and differentiation of C2C12 myoblasts

Genistein is a widely studied phytoestrogen. The effects of genistein on myoblasts were reported long ago, but the conclusions are controversial. In this study, we evaluated the effects of different concentrations of genistein on C2C12 myoblasts. Genistein treatment promoted myoblast proliferation in a dose-dependent manner in the concentration range of 0-2 µM/L, reaching its maximum effect at 2 µM/L. Proliferation then declined, and a concentration higher than 20 µM/L showed significant inhibition. In addition, genistein treatment promoted myoblast differentiation at a dose of 10 µM/L. However, at treatment concentrations higher than 10 µM/L, the effect on myoblast differentiation was rapidly inhibited as the concentration increased. Genistein treatment also down-regulated the expression of miR-222, resulting in increased expression of its target genes, MyoG, MyoD, and ERα and thereby promoting myoblast differentiation. Our results suggest that genistein has a dose-dependent and bidirectional regulation effect on myoblast proliferation and differentiation. We also found that genistein is a miRNA inducer, and it specifically affects the expression of miR-222 to regulate myoblast differentiation.

MiRNA Profiling in Pectoral Muscle Throughout Pre- to Post-Natal Stages of Chicken Development

MicroRNA (miRNA) is known to be an important regulator of muscle growth and development. The regulation of microRNA on the skeletal muscle phenotype of animals is mainly achieved by regulating the proliferation and differentiation of myoblasts. In this study, we sequenced a total of 60 samples from 15 developing stages of the pectoral muscle and five other tissues at 300 days of Tibetan chicken. We characterized the expression patterns of miRNAs across muscle developmental stages, and found that the chicken growth and development stage was divided into early-embryonic and late-embryonic as well as postnatal stages. We identified 81 and 21 DE-miRNAs by comparing the miRNA profiles of pectoral muscle of three broad periods and different tissues, respectively; and 271 miRNAs showed time-course patterns. Their potential targets were predicted and used for functional enrichment to understand their regulatory functions. Significantly, GgmiRNA-454 is a time-dependent and tissue-differential expression miRNA. In order to elucidate the role of gga-miRNA-454 in the differentiation of myoblasts, we cultured chicken myoblasts in vitro. The results show that although gga-miRNA-454-3p initiates increase and thereafter decrease during the chicken myoblasts differentiation, it had no effect on primary myoblasts proliferation. Furthermore, we confirm that gga-miRNA-454 inhibits myoblast differentiation by targeting the myotube-associated protein SBF2.

Transcriptome Characterization of Repressed Embryonic Myogenesis Due to Maternal Calorie Restriction

Fetal malnutrition decreases skeletal myofiber number and muscle mass in neonatal mammals, which increases the risk of developing obesity and diabetes in adult life. However, the associated molecular mechanisms remain unclear. Here, we investigated how the nutrient (calorie) availability affects embryonic myogenesis using a porcine model. Sows were given a normal or calorie restricted diet, following which skeletal muscle was harvested from the fetuses at 35, 55, and 90 days of gestation (dg) and used for histochemical analysis and high-throughput sequencing. We observed abrupt repression of primary myofiber formation following maternal calorie restriction (MCR). Transcriptome profiling of prenatal muscles revealed that critical genes and muscle-specific miRNAs associated with increased proliferation and myoblast differentiation were downregulated during MCR-induced repression of myogenesis. Moreover, we identified several novel miRNA-mRNA interactions through an integrative analysis of their expression profiles, devising a putative molecular network involved in the regulation of myogenesis. Interestingly, NC_010454.3_1179 was identified as a novel myogenic miRNA that can base-pair with sequences in the 3'-UTR of myogenic differentiation protein 1 (MyoD1). And we found that this UTR inhibited the expression of a linked reporter gene encoding a key myogenic regulatory factor, resulting in suppression of myogenesis. Our results greatly increase our understanding of the mechanisms underlying the nutrient-modulated myogenesis, and may also serve as a valuable resource for further investigation of fundamental developmental processes or assist in rational target selection ameliorating repressed myogenesis under fetal malnutrition.

MicroRNA-127-3p regulates myoblast proliferation by targeting Sept7

OBJECTIVE

MicroRNAs (miRNAs) are highly conserved, endogenous small RNAs that regulate gene expression at the post-transcriptional level. miR-127 plays an essential role in myogenic differentiation in vivo and in vitro. However, it is not clear whether miR-127-3p affects myogenic cell proliferation.

METHODS

The detailed function of miR-127-3p in proliferative C2C12 cell lines and further identified its regulatory mechanism by qRT-PCR, western blot, flow cytometry analysis and luciferase reporter assay.

RESULTS

Overexpression of miR-127-3p significantly inhibited proliferation of C2C12 cells and vice versa. Sept7 was a target gene of miR-127-3p using dual-luciferase reporter assay, qRT-PCR, and western blotting. The RNA interference analysis, in which Sept7 was downregulated, showed that Sept7 significantly promoted the proliferation of C2C12 cells. Besides, the expression level of Sept7 was detected analysis in muscle cells and tissues.

CONCLUSIONS

These findings reveal that miR-127-3p regulates myoblast proliferation by targeting Sept7.

Genetic deletion of microRNA biogenesis in muscle cells reveals a hierarchical non-clustered network that controls focal adhesion signaling during muscle regeneration

OBJECTIVE

Decreased muscle mass is a major contributor to age-related morbidity, and strategies to improve muscle regeneration during ageing are urgently needed. Our aim was to identify the subset of relevant microRNAs (miRNAs) that partake in critical aspects of muscle cell differentiation, irrespective of computational predictions, genomic clustering or differential expression of the miRNAs.

METHODS

miRNA biogenesis was deleted in primary myoblasts using a tamoxifen-inducible CreLox system and combined with an add-back miRNA library screen. RNA-seq experiments, cellular signalling events, and glycogen synthesis, along with miRNA inhibitors, were performed in human primary myoblasts. Muscle regeneration in young and aged mice was assessed using the cardiotoxin (CTX) model.

RESULTS

We identified a hierarchical non-clustered miRNA network consisting of highly (miR-29a), moderately (let-7) and mildly active (miR-125b, miR-199a, miR-221) miRNAs that cooperate by directly targeting members of the focal adhesion complex. Through RNA-seq experiments comparing single versus combinatorial inhibition of the miRNAs, we uncovered a fundamental feature of this network, that miRNA activity inversely correlates to miRNA cooperativity. During myoblast differentiation, combinatorial inhibition of the five miRNAs increased activation of focal adhesion kinase (FAK), AKT, and p38 mitogen-activated protein kinase (MAPK), and improved myotube formation and insulin-dependent glycogen synthesis. Moreover, antagonizing the miRNA network in vivo following CTX-induced muscle regeneration enhanced muscle mass and myofiber formation in young and aged mice.

CONCLUSION

Our results provide novel insights into the dynamics of miRNA cooperativity and identify a miRNA network as therapeutic target for impaired focal adhesion signalling and muscle regeneration during ageing.

Mechanism and Functions of Identified miRNAs in Poultry Skeletal Muscle Development – A Review

Development of the skeletal muscle goes through several complex processes regulated by numerous genetic factors. Although much efforts have been made to understand the mechanisms involved in increased muscle yield, little work is done about the miRNAs and candidate genes that are involved in the skeletal muscle development in poultry. Comprehensive research of candidate genes and single nucleotide related to poultry muscle growth is yet to be experimentally unraveled. However, over a few periods, studies in miRNA have disclosed that they actively participate in muscle formation, differentiation, and determination in poultry. Specifically, miR-1, miR-133, and miR-206 influence tissue development, and they are highly expressed in the skeletal muscles. Candidate genes such as CEBPB, MUSTN1, MSTN, IGF1, FOXO3, mTOR, and NFKB1, have also been identified to express in the poultry skeletal muscles development. However, further researches, analysis, and comprehensive studies should be made on the various miRNAs and gene regulatory factors that influence the skeletal muscle development in poultry. The objective of this review is to summarize recent knowledge in miRNAs and their mode of action as well as transcription and candidate genes identified to regulate poultry skeletal muscle development.

Mechanosensitive MiRs regulated by anabolic and catabolic loading of human cartilage

OBJECTIVE

Elucidation of whether miRs are involved in mechanotransduction pathways by which cartilage is maintained or disturbed has a particular importance in our understanding of osteoarthritis (OA) pathophysiology. The aim was to investigate whether mechanical loading influences global miR-expression in human chondrocytes and to identify mechanosensitive miRs responding to beneficial and non-beneficial loading regimes as potential to obtain valuable diagnostic or therapeutic targets to advance OA-treatment.

METHOD

Mature tissue-engineered human cartilage was subjected to two distinct loading regimes either stimulating or suppressing proteoglycan-synthesis, before global miR microarray analysis. Promising candidate miRs were selected, re-evaluated by qRT-PCR and tested for expression in human healthy vs OA cartilage samples.

RESULTS

After anabolic loading, miR microarray profiling revealed minor changes in miR-expression while catabolic stimulation produced a significant regulation of 80 miRs with a clear separation of control and compressed samples by hierarchical clustering. Cross-testing of selected miRs revealed that miR-221, miR-6872-3p, miR-6723-5p were upregulated by both loading conditions while others (miR-199b-5p, miR-1229-5p, miR-1275, miR-4459, miR-6891-5p, miR-7150) responded specifically after catabolic loading. Mechanosensitivity of miR-221 correlated with pERK1/2-activation induced by both loading conditions. The miR-response to loading was transient and a constitutive deregulation of mechano-miRs in OA vs healthy articular cartilage was not observed.

CONCLUSIONS

MiRs with broader vs narrower mechanosensitivity were discovered and the first group of mechanosensitive miRs characteristic for non-beneficial loading was defined that may shape the proteome differentially when cartilage tissue is disturbed. The findings prompt future investigations into miR-relevance for mechano-responsive pathways and the corresponding miR-target molecules.

Adult stem cells at work: regenerating skeletal muscle

Skeletal muscle regeneration is a finely tuned process involving the activation of various cellular and molecular processes. Satellite cells, the stem cells of skeletal muscle, are indispensable for skeletal muscle regeneration. Their functionality is critically modulated by intrinsic signaling pathways as well as by interactions with the stem cell niche. Here, we discuss the properties of satellite cells, including heterogeneity regarding gene expression and/or their phenotypic traits and the contribution of satellite cells to skeletal muscle regeneration. We also summarize the process of regeneration with a specific emphasis on signaling pathways, cytoskeletal rearrangements, the importance of miRNAs, and the contribution of non-satellite cells such as immune cells, fibro-adipogenic progenitor cells, and PW1-positive/Pax7-negative interstitial cells.

Integrative microRNA-mRNA Analysis of Muscle Tissues in Qianhua Mutton Merino and Small Tail Han Sheep Reveals Key Roles for oar-miR-655-3p and oar-miR-381-5p

The Qianhua Mutton Merino (QHMM) is a new variety of sheep (Ovis aries) with improved meat performance compared with the traditional Small Tail Han (STH) sheep variety. We recently reported the transcriptome profiling of longissimus muscle tissues between QHMM and STH sheep. In the present study, we aimed to evaluate key micro (mi)RNA-mRNA networks associated with sheep muscle growth and development. We used miRNA sequencing to obtain longissimus muscle miRNA profiles from QHMM and STH sheep. We identified a total of 153 known sheep miRNAs, of which 4 were differentially expressed (DE) between the 2 sheep varieties. We combined these results with mRNA library data to build an miRNA-mRNA network, including 26 target genes of the 4 DE miRNAs. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that 26 target genes were significantly enriched in 86 biological processes, including muscle organogenesis, myoblast migration, cell proliferation, and adipose tissue development, and in 9 metabolic pathways, including carbohydrate, nucleotide, and amino acid metabolic pathways. oar-miR-655-3p and its target gene ACSM3 and oar-miR-381-5p and its target gene ABAT were selected for subsequent analysis based on GO and KEGG analyses. The binding sites of oar-miR-655-3p with ACSM3 and oar-miR-381-5p with ABAT were validated by a dual-luciferase reporter gene detection system. This represents the first integrative analysis of miRNA-mRNA networks in QHMM and STH muscles and suggests that DE miRNAs, especially oar-miR-655-3p and oar-miR-381-5p, play crucial roles in muscle growth and development.

Simultaneous miRNA and mRNA Transcriptome Profiling of Differentiating Equine Satellite Cells Treated with Gamma-Oryzanol and Exposed to Hydrogen Peroxide

Gamma-oryzanol (GO) is a popular supplement for performance horses, dogs, and humans. Previous studies indicated that GO supplementation decreases creatine kinase activity and lactate level after exercise and may affect oxidative stress in Thoroughbred horses. GO may change genes expression in equine satellite cells (ESC). The purpose of this study was to evaluate the effect of GO on miRNA, gene expression, oxidative stress, and cell damage and viability in differentiating ESC pretreated with hydrogen peroxide (H₂O₂). ESCs were obtained from a young horse’s skeletal muscle. ESCs were pre-incubated with GO (24 h) and then exposed to H₂O₂ for one hour. For the microRNA and gene expression assessment, the microarray technique was used. Identified miRNAs and genes were validated using real time-quantitative polymerase chain reaction. Several tests related to cell viability, cell damage, and oxidative stress were performed. The microarray analysis revealed differences in 17 miRNAs and 202 genes between GO-treated and control ESC. The tests related to apoptosis, cell viability, and oxidative stress showed that GO affects these processes to varying degrees. Our results suggest that GO can change miRNA and gene expression and may impact the processes involved in tissue repairing after an injury.

The Role of MicroRNAs in Patients with Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a serious neurodegenerative disease that affects motor neurons and leads to death within 2 to 3 years after the first symptoms manifest. MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression in fundamental cellular processes and, post-transcriptionally, the translation levels of target mRNA transcripts. We searched PubMed for studies that examined miRNAs in ALS patients and attempted to group the results in order to find the strongest miRNA candidate for servings as an ALS biomarker. The studies on humans so far have been diverse, yielding considerably heterogeneous results, as they were performed on a wide variety of tissues and subjects. Among the miRNAs that were found consistently deregulated are miR-206, miR-133, miR-149, and miR-338-3p. Additively, the deregulation of some specific miRNAs seems to compose a miRNA expression profile that is specific for ALS. More research is required in order for the scientific community to reach a consensus.

Circulatory exosomal miRNA following intense exercise is unrelated to muscle and plasma miRNA abundances

MicroRNAs (miRNAs) regulate gene expression via transcript degradation and translational inhibition, and they may also function as long distance signaling molecules. Circulatory miRNAs are either protein-bound or packaged within vesicles (exosomes). Ten young men (24.6 ± 4.0 yr) underwent a single bout of high-intensity interval cycling exercise. Vastus lateralis biopsies and plasma were collected immediately before and after exercise, as well as 4 h following the exercise bout. Twenty-nine miRNAs previously reported to be regulated by acute exercise were assessed within muscle, venous plasma, and enriched circulatory exosomes via qRT-PCR. Of the 29 targeted miRNAs, 11 were altered in muscle, 8 in plasma, and 9 in the exosome fraction. Although changes in muscle and plasma expression were bidirectional, all regulated exosomal miRNAs increased following exercise. Three miRNAs were altered in all three sample pools (miR-1-3p, -16-5p, and -222-3p), three in both muscle and plasma (miR-21-5p, -134-3p, and -107), three in both muscle and exosomes (miR-23a-3p, -208a-3p, and -150-5p), and three in both plasma and exosomes (miR-486-5p, -126-3p, and -378a-5p). There was a marked discrepancy between the observed alterations between sample pools. A subset of exosomal miRNAs increased in abundance following exercise, suggesting an exercise-induced release of exosomes enriched in specific miRNAs. The uniqueness of the exosomal miRNA response suggests its relevance as a sample pool that needs to be further explored in better understanding biological functions.

MicroRNA profiling associated with muscle growth in modern broilers compared to an unselected chicken breed

Background

Genetically selected modern broiler chickens have acquired outstanding production efficiency through rapid growth and improved feed efficiency compared to unselected chicken breeds. Recently, we analyzed the transcriptome of breast muscle tissues obtained from modern pedigree male (PeM) broilers (rapid growth and higher efficiency) and foundational Barred Plymouth Rock (BPR) chickens (slow growth and poorer efficiency). This study was designed to investigate microRNAs that play role in rapid growth of the breast muscles in modern broiler chickens.

Results

In this study, differential abundance of microRNA (miRNA) was analyzed in breast muscle of PeM and BPR chickens and the results were integrated with differentially expressed (DE) mRNA in the same tissues. A total of 994 miRNA were identified in PeM and BPR chicken lines from the initial analysis of small RNA sequencing data. After filtering and statistical analyses, the results showed miR-2131-5p, miR-221-5p, miR-126-3p, miR-146b-5p, miR-10a-5p, let-7b, miR-125b-5p, and miR-146c-5p up-regulated whereas miR-206 down-regulated in PeM compared to BPR breast muscle. Based on inhibitory regulations of miRNAs on the mRNA abundance, our computational analysis using miRDB, an online software, predicated that 118 down-regulated mRNAs may be targeted by the up-regulated miRNAs, while 35 up-regulated mRNAs appear to be due to a down-regulated miRNA (i.e., miR-206). Functional network analyses of target genes of DE miRNAs showed their involvement in calcium signaling, axonal guidance signaling, and NRF2-mediated oxidative stress response pathways suggesting their involvement in breast muscle growth in chickens.

Conclusion

From the integrated analyses of differentially expressed miRNA-mRNA data, we were able to identify breast muscle specific miRNAs and their target genes whose concerted actions can contribute to rapid growth and higher feed efficiency in modern broiler chickens. This study provides foundation data for elucidating molecular mechanisms that govern muscle growth in chickens.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5061-7) contains supplementary material, which is available to authorized users.

MiR-139 promotes differentiation of bovine skeletal muscle-derived satellite cells by regulating DHFR gene expression

MicroRNAs play an important regulatory role in the proliferation and differentiation of skeletal muscle-derived satellite cells (MDSCs). In particular, miR-139 can inhibit tumor cell proliferation and invasion, and its expression is down-regulated during C2C12 myoblast differentiation. The aim of this study was thus to examine the effect and potential mechanism of miR-139 in bovine MDSCs. The expression of miR-139 was found to be significantly increased during bovine MDSC differentiation by stem-loop reverse transcription-polymerase chain reaction amplification. Statistical analysis of the myotube fusion rate was done through immunofluorescence detection of desmin, and western blotting was used to measure the change in protein expression of the muscle differentiation marker genes MYOG and MYH3. The results showed that the miR-139 mimic could enhance the differentiation of bovine MDSCs, whereas the inhibitor had the opposite effect. By using the dual-luciferase reporter system, miR-139 was found to target the 3'-untranslated region of the dihydrofolate reductase (DHFR) gene and regulate its expression. In addition, the expression of miR-139 was found to be regulated by its host gene phosphodiesterase 2A (PDE2A) via inhibition of the latter by CRISPR interference (CRISPRi). Overall, our findings indicate that miR-139 plays an important role in regulating the differentiation of bovine MDSCs.

High-throughput analysis of the RNA-induced silencing complex in myotonic dystrophy type 1 patients identifies the dysregulation of miR-29c and its target ASB2

Myotonic dystrophy type 1 (DM1) is a multi-systemic disorder caused by abnormally expanded stretches of CTG DNA triplets in the DMPK gene, leading to mutated-transcript RNA-toxicity. MicroRNAs (miRNAs) are short non-coding RNAs that, after maturation, are loaded onto the RISC effector complex that destabilizes target mRNAs and represses their translation. In DM1 muscle biopsies not only the expression, but also the intracellular localization of specific miRNAs is disrupted, leading to the dysregulation of the relevant mRNA targets. To investigate the functional alterations of the miRNA/target interactions in DM1, we analyzed by RNA-sequencing the RISC-associated RNAs in skeletal muscle biopsies derived from DM1 patients and matched controls. The mRNAs found deregulated in DM1 biopsies were involved in pathways and functions relevant for the disease, such as energetic metabolism, calcium signaling, muscle contraction and p53-dependent apoptosis. Bioinformatic analysis of the miRNA/mRNA interactions based on the RISC enrichment profiles, identified 24 miRNA/mRNA correlations. Following validation in 21 independent samples, we focused on the couple miR-29c/ASB2 because of the role of miR-29c in fibrosis (a feature of late-stage DM1 patients) and of ASB2 in the regulation of muscle mass. Luciferase reporter assay confirmed the direct interaction between miR-29c and ASB2. Moreover, decreased miR-29c and increased ASB2 levels were verified also in immortalized myogenic cells and primary fibroblasts, derived from biopsies of DM1 patients and controls. CRISPR/Cas9-mediated deletion of CTG expansions rescued normal miR-29c and ASB2 levels, indicating a direct link between the mutant repeats and the miRNA/target expression. In conclusion, functionally relevant miRNA/mRNA interactions were identified in skeletal muscles of DM1 patients, highlighting the dysfunction of miR-29c and ASB2.

Effects of microRNAs on skeletal muscle development

MicroRNAs (miRNAs) are small (about 22 nucleotides) noncoding RNAs, which were highly conserved among mammals. They have ushered in a new era in molecular biology over twenty years. They can negatively regulate gene expression at the posttranscriptional level through the principle of complementary base pairing with the 3' untranslated region (UTR) of their target mRNAs and induce their degradation. They involve in tissue morphogenesis, cellular processes like apoptosis, and major signaling pathways. Previous studies have promoted our understanding that miRNAs play an important role in myogenesis and have a big impact on muscle mass, muscle fiber type and muscle diseases. Many researchers have provided evidence of the involvement of muscle-specific and enriched miRNAs in the individual stages of skeletal muscle development as well as of their significant influence on muscle metabolism during quiescence, proliferation, differentiation and regeneration. Here, we focus on the microRNAs that related to the development of skeletal muscle. For example, some microRNAs are upregulated in differentiated skeletal muscle and can promote differentiation, like, miR-1, miR-24, miR-26a, miR-181 and miR-206. However, some microRNAs highly expressed in proliferating myoblasts, downregulated in differentiated and could inhibit differentiation, like MiR-221 and miR-222. Some others not only promote skeletal muscle proliferation, but also promote differentiation, like miR-214. Studying the miRNAs' regulatory mechanisms in skeletal development will help us know more about the knowledge of miRNAs in muscle developmental biology and make us learn more about involved signal pathway.

miR-487b-3p Suppresses the Proliferation and Differentiation of Myoblasts by Targeting IRS1 in Skeletal Muscle Myogenesis

MicroRNAs are endogenous, small non-coding RNAs that can play critical gene-regulatory roles during skeletal muscle development and are highly conserved. miR-487b-3p is expressed in muscle, and the detailed mechanism by which it regulates myoblast proliferation and differentiation has not been explored. Here, we found that miR-487b-3p expression was significantly higher in goat muscle tissues than in other tissues and was higher in fetal goat muscle tissues than in mature goat tissues, suggesting that miR-487b-3p has an important effect on skeletal muscle myogenesis. Functional studies showed that miR-487b-3p overexpression significantly suppressed C2C12 myoblast proliferation and differentiation, which was accompanied by the down-regulation of functional genes related to proliferation (MyoD, Pax7 and PCNA) and differentiation (Myf5, MyoG and Mef2c), whereas the inhibition of miR-487b-3p accelerated C2C12 myoblast proliferation and differentiation and was accompanied by the up-regulation of functional genes. Using Target-Scan and David, we found that miR-487b-3p targeted the 3'-UTR of IRS1, an essential regulator in the PI3K/Akt and MAPK/Erk pathways. We then confirmed the targeting of IRS1 by miR-487b-3p using dual-luciferase assays, RT-qPCR and western blotting. Furthermore, IRS1 silencing markedly inhibited proliferation and differentiation in cultured C2C12 myoblasts, confirming the important role of IRS1 in myogenesis. These results reveal an IRS1-mediated regulatory link between miR-487b-3p and the PI3K/Akt and MAPK/Erk pathways during skeletal muscle myogenesis.

Characterization of miRNA transcriptome profiles related to breast muscle development and intramuscular fat deposition in chickens

Studies of the miRNA expression profiles associated with the postnatal late development of skeletal muscle and IMF deposition are lacking in chicken. Here, we evaluated the patterns of muscle fiber growth and IMF deposition in breast muscle in the Chinese domestic breed called Gushi chicken, where we constructed four small RNA libraries from breast muscle tissues at 6, 14, 22, and 30 weeks. A total of 388 known miRNAs and 31 novel miRNAs were identified based on four small RNA libraries. Comparative analysis identified 92 significant differentially expressed (SDE) miRNAs based on six combinations. KEGG pathway analysis for the SDE miRNAs showed that metabolic pathways such as glycolysis and biosynthesis of amino acids were significantly enriched before 22 weeks, and pathways such as biosynthesis of unsaturated fatty acids and fatty acid elongation were significantly enriched after 22 weeks. This trend was consistent with the patterns of breast muscle fiber growth and IMF deposition in Gushi chickens. We also constructed miRNA-mRNA interaction networks related to breast muscle development and IMF deposition. The results showed that miRNAs such as gga-miR-1a-3p, and gga-miR-133a-5p may play important roles in breast muscle development, and miRNAs such as gga-miR-103-3p, and gga-miR-138-2-3p may have key roles in IMF deposition. This study determined the dynamic miRNA transcriptome in breast muscle tissue for the first time in Gushi chickens. The results provide a valuable resource for investigating the post-transcriptional regulation mechanisms during postnatal late development of breast muscle and IMF deposition and for evaluating the muscular disease.

Effect of β-hydroxy-β-methylbutyrate on miRNA expression in differentiating equine satellite cells exposed to hydrogen peroxide

Background

Skeletal muscle injury activates satellite cells to initiate processes of proliferation, differentiation, and hypertrophy in order to regenerate muscle fibers. The number of microRNAs and their target genes are engaged in satellite cell activation. β-Hydroxy-β-methylbutyrate (HMB) is known to prevent exercise-induced muscle damage. The purpose of this study was to evaluate the effect of HMB on miRNA and relevant target gene expression in differentiating equine satellite cells exposed to H₂O₂. We hypothesized that HMB may regulate satellite cell activity, proliferation, and differentiation, hence attenuate the pathological processes induced during an in vitro model of H₂O₂-related injury by changing the expression of miRNAs.

Methods

Equine satellite cells (ESC) were isolated from the samples of skeletal muscle collected from young horses. ESC were treated with HMB (24 h) and then exposed to H₂O₂ (1 h). For the microRNA and gene expression assessment microarrays, technique was used. Identified miRNAs and genes were validated using real-time qPCR. Cell viability, oxidative stress, and cell damage were measured using colorimetric method and flow cytometry.

Results

Analysis of miRNA and gene profile in differentiating ESC pre-incubated with HMB and then exposed to H₂O₂ revealed difference in the expression of 27 miRNAs and 4740 genes, of which 344 were potential target genes for identified miRNAs. Special attention was focused on differentially expressed miRNAs and their target genes involved in processes related to skeletal muscle injury. Western blot analysis showed protein protection in HMB-pre-treated group compared to control. The viability test confirmed that HMB enhanced cell survival after the hydrogen peroxide exposition.

Conclusions

Our results suggest that ESC pre-incubated with HMB and exposed to H₂O₂ could affect expression on miRNA levels responsible for skeletal muscle development, cell proliferation and differentiation, and activation of tissue repair after injury. Enrichment analyses for targeted genes revealed that a large group of genes was associated with the regulation of signaling pathways crucial for muscle tissue development, protein metabolism, muscle injury, and regeneration, as well as with oxidative stress response.

Dynamic Regulation of Circulating microRNAs During Acute Exercise and Long-Term Exercise Training in Basketball Athletes

Emerging evidence indicates the beneficial effects of physical exercise on human health, which depends on the intensity, training time, exercise type, environmental factors, and the personal health status. Conventional biomarkers provide limited insight into the exercise-induced adaptive processes. Circulating microRNAs (miRNAs, miRs) are dynamically regulated in response to acute exhaustive exercise and sustained rowing, running and cycling exercises. However, circulating miRNAs in response to long-term basketball exercise remains unknown. Here, we enrolled 10 basketball athletes who will attend a basketball season for 3 months. Specifically, circulating miRNAs which were involved in angiogenesis, inflammation and enriched in muscle and/or cardiac tissues were analyzed at baseline, immediately following acute exhaustive exercise and after 3-month basketball matches in competitive male basketball athletes. Circulating miR-208b was decreased and miR-221 was increased after 3-month basketball exercise, while circulating miR-221, miR-21, miR-146a, and miR-210 were reduced at post-acute exercise. The change of miR-146a (baseline vs. post-acute exercise) showed linear correlations with baseline levels of cardiac marker CKMB and the changes of inflammation marker Hs-CRP (baseline vs. post-acute exercise). Besides, linear correlation was observed between miR-208b changes (baseline vs. after long-term exercise) and AT VO₂ (baseline). The changes of miR-221 (baseline vs. after long-term exercise) were significantly correlated with AT VO₂, peak work load and CK (after 3-month basketball matches). Although further studies are needed, present findings set the stage for defining circulating miRNAs as biomarkers and suggesting their physiological roles in long-term exercise training induced cardiovascular adaptation.

Exciting perspectives for Translational Myology in the Abstracts of the 2018Spring PaduaMuscleDays: Giovanni Salviati Memorial - Chapter IV - Abstracts of March 17, 2018

Myologists working in Padua (Italy) were able to continue a half-century tradition of studies of skeletal muscles, that started with a research on fever, specifically if and how skeletal muscle contribute to it by burning bacterial toxin. Beside main publications in high-impact-factor journals by Padua myologists, I hope to convince readers (and myself) of the relevance of the editing Basic and Applied Myology (BAM), retitled from 2010 European Journal of Translational Myology (EJTM), of the institution of the Interdepartmental Research Center of Myology of the University of Padova (CIR-Myo), and of a long series of International Conferences organized in Euganei Hills and Padova, that is, the PaduaMuscleDays. The 2018Spring PaduaMuscleDays (2018SpPMD), were held in Euganei Hills and Padua (Italy), in March 14-17, and were dedicated to Giovanni Salviati. The main event of the “Giovanni Salviati Memorial”, was held in the Aula Guariento, Accademia Galileiana di Scienze, Lettere ed Arti of Padua to honor a beloved friend and excellent scientist 20 years after his premature passing. Using the words of Prof. Nicola Rizzuto, we all share his believe that Giovanni “will be remembered not only for his talent and originality as a biochemist, but also for his unassuming and humanistic personality, a rare quality in highly successful people like Giovanni. The best way to remember such a person is to gather pupils and colleagues, who shared with him the same scientific interests and ask them to discuss recent advances in their own fields, just as Giovanni have liked to do”. Since Giovanni’s friends sent many abstracts still influenced by their previous collaboration with him, all the Sessions of the 2018SpPMD reflect both to the research aims of Giovanni Salviati and the traditional topics of the PaduaMuscleDays, that is, basics and applications of physical, molecular and cellular strategies to maintain or recover functions of skeletal muscles. The translational researches summarized in the 2018SpPMD Abstracts are at the appropriate high level to attract endorsement of Ethical Committees, the interest of International Granting Agencies and approval for publication in top quality international journals. The abstracts of the presentations of the March 16, 2018 Padua Muscle Day and those of the remaining Posters are listed in this chapter IV. The Author Index of the 2018Spring PaduaMuscleDays follows at page 78.

Breed-dependent microRNA expression in the primary culture of skeletal muscle cells subjected to myogenic differentiation

Background

Skeletal muscle in livestock develops into meat, an important source of protein and other nutrients for human consumption. The muscle is largely composed of a fixed number of multinucleated myofibers determined during late gestation and remains constant postnatally. A population of postnatal muscle stem cells, called satellite cells, gives rise to myoblast cells that can fuse with the existing myofibers, thus increasing their size. This requires a delicate balance of transcription and growth factors and specific microRNA (miRNA) expressed by satellite cells and their supporting cells from the muscle stem cell niche. The role of transcription and growth factors in bovine myogenesis is well-characterized; however, very little is known about the miRNA activity during this process. We have hypothesized that the expression of miRNA can vary between primary cultures of skeletal muscle cells isolated from the semitendinosus muscles of different cattle breeds and subjected to myogenic differentiation.

Results

After a 6-day myogenic differentiation of cells isolated from the muscles of the examined cattle breeds, we found statistically significant differences in the number of myotubes between Hereford (HER)/Limousine (LIM) beef breeds and the Holstein-Friesian (HF) dairy breed (p ≤ 0.001). The microarray analysis revealed differences in the expression of 23 miRNA among the aforementioned primary cultures. On the basis of a functional analysis, we assigned 9 miRNA as molecules responsible for differentiation progression (miR-1, -128a, -133a, -133b, -139, -206, -222, -486, and -503). The target gene prediction and functional analysis revealed 59 miRNA-related genes belonging to the muscle organ development process.

Conclusion

The number of myotubes and the miRNA expression in the primary cultures of skeletal muscle cells derived from the semitendinosus muscles of the HER/LIM beef cattle breeds and the HF dairy breed vary when cells are subjected to myogenic differentiation. The net effect of the identified miRNA and their target gene action should be considered the result of the breed-dependent activity of satellite cells and muscle stem cell niche cells and their mutual interactions, which putatively can be engaged in the formation of a larger number of myotubes in beef cattle-related cells (HER/LIM) during in vitro myogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4492-5) contains supplementary material, which is available to authorized users.

Regulatory Role of MicroRNAs in Muscle Atrophy during Exercise Intervention

Skeletal muscle comprising approximately 40% of body weight is highly important for locomotion and metabolic homeostasis. The growth and regeneration of skeletal muscle are highly organized processes; thus, it is not surprising to reveal certain complexity during these regulatory processes. Recently, a large number of evidence indicate that microRNAs can result in obvious impacts on growth, regeneration and metabolism of skeletal muscle. In this review, recent research achievements of microRNAs in regulating myogenesis, atrophy and aging during exercise intervention are discussed, which will provide the guidance for developing potential applications of microRNAs in health promotion and rehabilitation of sports injuries.

PAX3-FOXO1 drives miR-486-5p and represses miR-221 contributing to pathogenesis of alveolar rhabdomyosarcoma

Rhabdomyosarcoma is the most common soft-tissue sarcoma in childhood and histologically resembles developing skeletal muscle. Alveolar rhabdomyosarcoma (ARMS) is an aggressive subtype with a higher rate of metastasis and poorer prognosis. The majority of ARMS tumors (80%) harbor a PAX3-FOXO1 or less commonly a PAX7-FOXO1 fusion gene. The presence of either the PAX3-FOXO1 or PAX7-FOXO1 fusion gene foretells a poorer prognosis resulting in clinical re-classification as either fusion-positive (FP-RMS) or fusion-negative RMS (FN-RMS). The PAX3/7-FOXO1 fusion genes result in the production of a rogue transcription factors that drive FP-RMS pathogenesis and block myogenic differentiation. Despite knowing the molecular driver of FP-RMS, targeted therapies have yet to make an impact for patients, highlighting the need for a greater understanding of the molecular consequences of PAX3-FOXO1 and its target genes including microRNAs. Here we show FP-RMS patient-derived xenografts and cell lines display a distinct microRNA expression pattern. We utilized both loss- and gain-of function approaches in human cell lines with knockdown of PAX3-FOXO1 in FP-RMS cell lines and expression of PAX3-FOXO1 in human myoblasts and identified microRNAs both positively and negatively regulated by the PAX3-FOXO1 fusion protein. We demonstrate PAX3-FOXO1 represses miR-221/222 that functions as a tumor suppressing microRNA through the negative regulation of CCND2, CDK6, and ERBB3. In contrast, miR-486-5p is transcriptionally activated by PAX3-FOXO1 and promotes FP-RMS proliferation, invasion, and clonogenic growth. Inhibition of miR-486-5p in FP-RMS xenografts decreased tumor growth, illustrating a proof of principle for future therapeutic intervention. Therefore, PAX3-FOXO1 regulates key microRNAs that may represent novel therapeutic vulnerabilities in FP-RMS.

Transient MicroRNA Expression Enhances Myogenic Potential of Mouse Embryonic Stem Cells

MicroRNAs (miRNAs) are known regulators of various cellular processes, including pluripotency and differentiation of embryonic stem cells (ESCs). We analyzed differentiation of two ESC lines-D3 and B8, and observed significant differences in the expression of miRNAs and genes involved in pluripotency and differentiation. We also examined if transient miRNA overexpression could serve as a sufficient impulse modulating differentiation of mouse ESCs. ESCs were transfected with miRNA Mimics and differentiated in embryoid bodies and embryoid body outgrowths. miRNAs involved in differentiation of mesodermal lineages, such as miR145 and miR181, as well as miRNAs regulating myogenesis (MyomiRs)-miR1, miR133a, miR133b, and miR206 were tested. Using such approach, we proved that transient overexpression of molecules selected by us modulated differentiation of mouse ESCs. Increase in miR145 levels upregulated Pax3, Pax7, Myod1, Myog, and MyHC2, while miR181 triggered the expression of such crucial myogenic factors as Myf5 and MyHC2. As a result, the ability of ESCs to initiate myogenic differentiation and form myotubes was enhanced. Premature expression of MyomiRs had, however, an adverse effect on myogenic differentiation of ESCs. Stem Cells 2018;36:655-670.

Integrated Analyses Reveal Overexpressed Notch1 Promoting Porcine Satellite Cells' Proliferation through Regulating the Cell Cycle

Notch signaling as a conserved cell fate regulator is involved in the regulation of cell quiescence, proliferation, differentiation and postnatal tissue regeneration. However, how Notch signaling regulates porcine satellite cells (PSCs) has not been elucidated. We stably transfected Notch1 intracellular domain (N1ICD) into PSCs to analyze the gene expression profile and miRNA-seq. The analysis of the gene expression profile identified 295 differentially-expressed genes (DEGs) in proliferating-N1ICD PSCs (P-N1ICD) and nine DEGs on differentiating-N1ICD PSCs (D-N1ICD), compared with that in control groups (P-Control and D-Control, respectively). Analyzing the underlying function of DEGs showed that most of the upregulated DEGs enriched in P-N1ICD PSCs are related to the cell cycle. Forty-four and 12 known differentially-expressed miRNAs (DEMs) were identified in the P-N1ICD PSCs and D-N1ICD PSCs group, respectively. Furthermore, we constructed the gene-miRNA network of the DEGs and DEMs. In P-N1ICD PSCs, miR-125a, miR-125b, miR-10a-5p, ssc-miR-214, miR-423 and miR-149 are downregulated hub miRNAs, whose corresponding hub genes are marker of proliferation Ki-67 (MKI67) and nuclear receptor binding SET domain protein 2 (WHSC1). By contrast, miR-27a, miR-146a-5p and miR-221-3p are upregulated hub miRNAs, whose hub genes are RUNX1 translocation partner 1 (RUNX1T1) and fibroblast growth factor 2 (FGF2). All the hub miRNAs and genes are associated with cell proliferation. Quantitative RT-PCR results are consistent with the gene expression profile and miRNA-seq results. The results of our study provide valuable information for understanding the molecular mechanisms underlying Notch signaling in PSCs and skeletal muscle development.

Inducible microRNA-122 modulates RIG-I signaling pathway via targeting DAK in miiuy croaker after poly(I:C) stimulation

MicroRNA-122 (miR-122) was originally identified in mouse and then lots of researches on miR-122 had been performed in mammals. However, the functional study of miR-122 were restricted in fish. In miiuy croaker, miR-122 is sensitive to poly(I:C) stimulation. In this study, a combination of bioinformatics and experimental techniques were used to investigate the functions of miR-122. DAK is a putative target gene of miR-122 which was predicted by bioinformatics, and further the luciferase reporter assays were used to confirm the target sites in DAK 3'untranslated region. The inhibiting effect of miR-122 mimics or pre-miR-122 on DAK presented the dose and time dependent manners, and the pre-miR-122 showed stronger inhibiting effect on DAK than the miR-122 mimics. Therefore, the miR-122 participate in regulating RIG-I-like receptors signaling pathway via inhibiting DAK which is the inhibitors of MDA5. The expression of miR-122 and DAK showed negative relationship in both miiuy croaker spleen and macrophages, which imply that miR-122 may regulate DAK at the post-transcriptional level. These results will enhance our understanding about the regulation of miRNAs on immune response in fish.

miR-221 modulates skeletal muscle satellite cells proliferation and differentiation

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules, which play important roles in animals by targeting mRNA transcripts for translational repression. Many recent studies have shown that miRNAs are involved in the control of muscle development. In this study, the expression levels of miR-221 in different tissues and during rabbit skeletal muscle satellite cells (SMSCs) differentiation were detected. Gene ontology term enrichment was used to predict the potential biological roles of miR-221. A synthetic miR-221 mimic and a miR-221 inhibitor were used to investigate the functions of miR-221 during SMSCs proliferation and differentiation to further verify the functions of miR-221 in muscle development. In this report, we compared the expression levels of miR-221 in different tissues. The expression levels of miR-221 were upregulated after the induction of differentiation, and then were gradually downregulated during SMSCs differentiation. Overexpression of miR-221 promoted SMSCs proliferation, whereas inhibiting expression restrained proliferation in the EdU and CCK-8 assays. In addition, overexpression of miR-221 led to a decline in the expression levels of the differentiation marker genes MyoG and MHC. miR-221 overexpression suppressed SMSCs myotube formation. On the contrary, inhibition of miR-221 promoted myotube formation. Our data showed that miR-221 increased SMSCs proliferation and decreased differentiation.

A Noninvasive In Vitro Monitoring System Reporting Skeletal Muscle Differentiation

Monitoring of cell differentiation is a crucial aspect of cell-based therapeutic strategies depending on tissue maturation. In this study, we have developed a noninvasive reporter system to trace murine skeletal muscle differentiation. Either a secreted bioluminescent reporter (Metridia luciferase) or a fluorescent reporter (green fluorescent protein [GFP]) was placed under the control of the truncated muscle creatine kinase (MCK) basal promoter enhanced by variable numbers of upstream MCK E-boxes. The engineered pE3MCK vector, coding a triple tandem of E-Boxes and the truncated MCK promoter, showed twentyfold higher levels of luciferase activation compared with a Cytomegalovirus (CMV) promoter. This newly developed reporter system allowed noninvasive monitoring of myogenic differentiation in a straining bioreactor. Additionally, binding sequences of endogenous microRNAs (miRNAs; seed sequences) that are known to be downregulated in myogenesis were ligated as complementary seed sequences into the reporter vector to reduce nonspecific signal background. The insertion of seed sequences improved the signal-to-noise ratio up to 25% compared with pE3MCK. Due to the highly specific, fast, and convenient expression analysis for cells undergoing myogenic differentiation, this reporter system provides a powerful tool for application in skeletal muscle tissue engineering.

Characterization of miRNA and their target gene during chicken embryo skeletal muscle development

MicroRNAs (miRNAs) are non-coding RNAs that regulate mRNA expression by degradation or translational inhibition. We investigated the underlying molecular mechanisms of skeletal muscle development based on differentially expressed genes and miRNAs. We compared mRNA and miRNA from chicken skeletal muscle at embryonic day E11, E16 and one day post-hatch (P1). The interaction networks were constructed, according to target prediction results and integration analysis of up-regulated genes with down regulated miRNAs or down-regulated genes with up-regulated miRNAs with |log2fold change| ≥ 1.75, P < 0.005. The miRNA-mRNA integration analysis showed high number of mRNAs regulated by a few number of miRNAs. In the E11_VS_E16, comparison group we identified biological processes including muscle maintenance, myoblast proliferation and muscle thin filament formation. The E11_VS_P1 group comparison included negative regulation of axon extension, sarcomere organization, and cell redox homeostasis and kinase inhibitor activity. The E16_VS_P1 comparison group contained genes for the negative regulation of anti-apoptosis and axon extension as well as glomerular basement membrane development. Functional in vitro assays indicated that over expression of miR-222a and miR-126–5p in DF-1 cells significantly reduced the mRNA levels of the target genes CPEB3 and FGFR3, respectively. These integrated analyses provide several candidates for future studies concerning miRNAs-target function on regulation of embryonic muscle development and growth.