Myogenic factors that regulate expression of muscle-specific microRNAs

A Dynamic Role of Mastermind-Like 1: A Journey Through the Main (Path)ways Between Development and Cancer

Major signaling pathways, such as Notch, Hedgehog (Hh), Wnt/β-catenin and Hippo, are targeted by a plethora of physiological and pathological stimuli, ultimately resulting in the modulation of genes that act coordinately to establish specific biological processes. Many biological programs are strictly controlled by the assembly of multiprotein complexes into the nucleus, where a regulated recruitment of specific transcription factors and coactivators on gene promoter region leads to different transcriptional outcomes. MAML1 results to be a versatile coactivator, able to set up synergistic interlinking with pivotal signaling cascades and able to coordinate the network of cross-talking pathways. Accordingly, despite its original identification as a component of the Notch signaling pathway, several recent reports suggest a more articulated role for MAML1 protein, showing that it is able to sustain/empower Wnt/β-catenin, Hh and Hippo pathways, in a Notch-independent manner. For this reason, MAML1 may be associated to a molecular “switch”, with the function to control the activation of major signaling pathways, triggering in this way critical biological processes during embryonic and post-natal life. In this review, we summarize the current knowledge about the pleiotropic role played by MAML proteins, in particular MAML1, and we recapitulate how it takes part actively in physiological and pathological signaling networks. On this point, we also discuss the contribution of MAML proteins to malignant transformation. Accordingly, genetic alterations or impaired expression of MAML proteins may lead to a deregulated crosstalk among the pathways, culminating in a series of pathological disorders, including cancer development. Given their central role, a better knowledge of the molecular mechanisms that regulate the interplay of MAML proteins with several signaling pathways involved in tumorigenesis may open up novel opportunities for an attractive molecular targeted anticancer therapy.

Role of microRNAs in myogenesis and their effects on meat quality in pig - A review

The demand for food is increasing day by day because of the increasing global population. Therefore, meat, the easiest and largely available source of protein, needs to be produced in large amounts with good quality. The pork industry is a significant shareholder in fulfilling the global meat demands. Notably, myogenesis- development of muscles during embryogenesis- is a complex mechanism which culminates in meat production. But the molecular mechanisms which govern the myogenesis are less known. The involvement of miRNAs in myogenesis and meat quality, which depends on factors such as myofiber composition and intramuscular fat contents which determine the meat color, flavor, juiciness, and water holding capacity, are being extrapolated to increase both the quantity and quality of pork. Various kinds of microRNAs (miRNAs), miR-1, miR-21, miR22, miR-27, miR-34, miR-127, miR-133, miR-143, miR-155, miR-199, miR-206, miR-208, miR-378, and miR-432 play important roles in pig skeletal muscle development. Further, the quality of meat also depends upon myofiber which is developed through the expression of different kinds of miRNAs at different stages. This review will focus on the mechanism of myogenesis, the role of miRNAs in myogenesis, and meat quality with a focus on the pig.

Influence of microRNAs and exosomes in muscle health and diseases

microRNAs are short, (18-22 nt) non-coding RNAs involved in important cellular processes due to their ability to regulate gene expression at the post-transcriptional level. Exosomes are small (50-200 nm) extracellular vesicles, naturally secreted from a variety of living cells and are believed to mediate cell-cell communication through multiple mechanisms, including uptake in destination cells. Circulating microRNAs and exosome-derived microRNAs can have key roles in regulating muscle cell development and differentiation. Several microRNAs are highly expressed in muscle and their regulation is important for myocyte homeostasis. Changes in muscle associated microRNA expression are associated with muscular diseases including muscular dystrophies, inflammatory myopathies, and congenital myopathies. In this review, we aim to highlight the biology of microRNAs and exosomes as well as their roles in muscle health and diseases. We also discuss the potential crosstalk between skeletal and cardiac muscle through exosomes and their contents.

MicroRNAs in Skeletal Muscle and Hints on Their Potential Role in Muscle Wasting During Cancer Cachexia

Cancer-associated cachexia is a heterogeneous, multifactorial syndrome characterized by systemic inflammation, unintentional weight loss, and profound alteration in body composition. The main feature of cancer cachexia is represented by the loss of skeletal muscle tissue, which may or may not be accompanied by significant adipose tissue wasting. Such phenotypic alteration occurs as the result of concomitant increased myofibril breakdown and reduced muscle protein synthesis, actively contributing to fatigue, worsening of quality of life, and refractoriness to chemotherapy. According to the classical view, this condition is primarily triggered by interactions between specific tumor-induced pro-inflammatory cytokines and their cognate receptors expressed on the myocyte membrane. This causes a shift in gene expression of muscle cells, eventually leading to a pronounced catabolic condition and cell death. More recent studies, however, have shown the involvement of regulatory non-coding RNAs in the outbreak of cancer cachexia. In particular, the role exerted by microRNAs is being widely addressed, and several mechanistic studies are in progress. In this review, we discuss the most recent findings concerning the role of microRNAs in triggering or exacerbating muscle wasting in cancer cachexia, while mentioning about possible roles played by long non-coding RNAs and ADAR-mediated miRNA modifications.

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.

The multifaceted roles of microRNAs in differentiation

MicroRNAs (miRNAs) are major drivers of cell fate specification and differentiation. The post-transcriptional regulation of key molecular factors by microRNAs contributes to the progression of embryonic and postembryonic development in several organisms. Following the discovery of lin-4 and let-7 in Caenorhabditis elegans and bantam microRNAs in Drosophila melanogaster, microRNAs have emerged as orchestrators of cellular differentiation and developmental timing. Spatiotemporal control of microRNAs and associated protein machinery can modulate microRNA activity. Additionally, adaptive modulation of microRNA expression and function in response to changing environmental conditions ensures that robust cell fate specification during development is maintained. Herein, we review the role of microRNAs in the regulation of differentiation during development.

Post-transcriptional regulation of MRTF-A by miRNAs during myogenic differentiation of myoblasts

The differentiation and regeneration of skeletal muscle from myoblasts to myotubes involves myogenic transcription factors, such as myocardin-related transcription factor A (MRTF-A) and serum response factor (SRF). In addition, post-transcriptional regulation by miRNAs is required during myogenesis. Here, we provide evidence for novel mechanisms regulating MRTF-A during myogenic differentiation. Endogenous MRTF-A protein abundance and activity decreased during C2C12 differentiation, which was attributable to miRNA-directed inhibition. Conversely, overexpression of MRTF-A impaired differentiation and myosin expression. Applying miRNA trapping by RNA affinity purification (miTRAP), we identified miRNAs which directly regulate MRTF-A via its 3′UTR, including miR-1a-3p, miR-206-3p, miR-24-3p and miR-486-5p. These miRNAs were upregulated during differentiation and specifically recruited to the 3′UTR of MRTF-A. Concomitantly, Ago2 recruitment to the MRTF-A 3′UTR was considerably increased, whereas Dicer1 depletion or 3′UTR deletion elevated MRTF-A and inhibited differentiation. MRTF-A protein expression was inhibited by ectopic miRNA expression in murine C2C12 and primary human myoblasts. 3′UTR reporter activity diminished upon differentiation or miRNA expression, whereas deletion of the predicted binding sites reversed these effects. Furthermore, TGF-β abolished MRTF-A reduction and decreased miR-486-5p expression. Our findings implicate miR-24-3p and miR-486-5p in the repression of MRTF-A and suggest a complex network of transcriptional and post-transcriptional mechanisms regulating myogenesis.

The Role of the Microenvironment in Controlling the Fate of Bioprinted Stem Cells

The field of tissue engineering and regenerative medicine has made numerous advances in recent years in the arena of fabricating multifunctional, three-dimensional (3D) tissue constructs. This can be attributed to novel approaches in the bioprinting of stem cells. There are expansive options in bioprinting technology that have become more refined and specialized over the years, and stem cells address many limitations in cell source, expansion, and development of bioengineered tissue constructs. While bioprinted stem cells present an opportunity to replicate physiological microenvironments with precision, the future of this practice relies heavily on the optimization of the cellular microenvironment. To fabricate tissue constructs that are useful in replicating physiological conditions in laboratory settings, or in preparation for transplantation to a living host, the microenvironment must mimic conditions that allow bioprinted stem cells to proliferate, differentiate, and migrate. The advances of bioprinting stem cells and directing cell fate have the potential to provide feasible and translatable approach to creating complex tissues and organs. This review will examine the methods through which bioprinted stem cells are differentiated into desired cell lineages through biochemical, biological, and biomechanical techniques.

MicroRNAs as Biomarkers of Systemic Changes in Response to Endurance Exercise-A Comprehensive Review

Endurance sports have an unarguably beneficial influence on cardiovascular health and general fitness. Regular physical activity is considered one of the most powerful tools in the prevention of cardiovascular disease. MicroRNAs are small particles that regulate the post-transcription gene expression. Previous studies have shown that miRNAs might be promising biomarkers of the systemic changes in response to exercise, before they can be detected by standard imaging or laboratory methods. In this review, we focused on four important physiological processes involved in adaptive changes to various endurance exercises (namely, cardiac hypertrophy, cardiac myocyte damage, fibrosis, and inflammation). Moreover, we discussed miRNAs’ correlation with cardiopulmonary fitness parameter (VO_2max). After a detailed literature search, we found that miR-1, miR-133, miR-21, and miR-155 are crucial in adaptive response to exercise.

miR-324-5p Inhibits C2C12 cell Differentiation and Promotes Intramuscular Lipid Deposition through lncDUM and PM20D1

Skeletal muscle is an important metabolic organ of the body, and impaired skeletal muscle differentiation can result in a wide range of metabolic diseases. It has been shown that microRNAs (miRNAs) play an important role in skeletal muscle differentiation. The aim of this study was to investigate the role of mmu-miR-324-5p in the differentiation of C2C12 myoblasts and lipid droplet deposition in myotubes for future targeted therapies. We found that mmu-miR-324-5p was highly expressed in mouse skeletal muscle. Overexpression of miR-324-5p significantly inhibited C2C12 myoblast differentiation while promoting oleate-induced lipid accumulation and β-oxidation in C2C12 myoblasts. Conversely, inhibition of mmu-miR-324-5p promoted C2C12 myoblast differentiation and inhibited lipid deposition in myotubes. Mechanistically, mmu-miR-324-5p negatively regulated the expression of long non-coding Dum (lncDum) and peptidase M20 domain containing 1 (Pm20d1) in C2C12 myoblasts. Reduced lncDum expression was associated with a significant decrease in the expression of myogenesis-related genes. Knockdown of mmu-miR-324-5p increased the levels of lncDum and myogenesis-related gene expression. Following oleate-induced lipid deposition in C2C12 myoblasts, overexpression of mmu-miR-324-5p decreased the expression of Pm20d1 while increasing the expression of mitochondrial β-oxidation and long-chain fatty acid synthesis-related genes. In conclusion, we provide evidence that miR-324-5p inhibits C2C12 myoblast differentiation and promotes intramuscular lipid deposition by targeting lncDum and Pm20d1, respectively.

MicroRNAs: roles in cardiovascular development and disease

Cardiovascular diseases (CVDs) comprise a group of disorders ranging from peripheral artery, coronary artery, cardiac valve, cardiac muscle, and congenital heart diseases to arrhythmias and ultimately, heart failure. For all the advances in therapeutics, CVDs are still the leading cause of mortality the world over, hence the significance of a thorough understanding of CVDs at the molecular level. Disparities in the expressions of genes and microRNAs (miRNAs) play a crucial role in the determination of the fate of cellular pathways, which ultimately affect an organism's physiology. Indeed, miRNAs serve as the regulators of gene expressions in that they perform key functions both in several important cellular pathways and in the regulation of the onset of various diseases such as CVDs. Many miRNAs are expressed in embryonic, postnatal, and adult hearts; their aberrant expression or genetic deletion is associated with abnormal cardiac cell differentiation, disruption in heart development, and cardiac dysfunction. A substantial body of evidence implicates miRNAs in CVD development and suggests them as diagnostic biomarkers and intriguing therapeutic tools. The present review provides an overview of the history, biogenesis, and processing of miRNAs, as well as their function in the development, remodeling, and diseases of the heart.

miR-206 enforces a slow muscle phenotype

Striated muscle is a highly specialized collection of tissues with contractile properties that vary according to functional needs. Although muscle fiber types are established postnatally, lifelong plasticity facilitates stimulus-dependent adaptation. Functional adaptation requires molecular adaptation, which is partially provided by miRNA-mediated post-transcriptional regulation. miR-206 is a muscle-specific miRNA enriched in slow muscles. We investigated whether miR-206 drives the slow muscle phenotype or is merely an outcome. We found that miR-206 expression increases in both physiological (including female sex and endurance exercise) and pathological conditions (muscular dystrophy and adrenergic agonism) that promote a slow phenotype. Consistent with that observation, the slow soleus muscle of male miR-206-knockout mice displays a faster phenotype than wild-type mice. Moreover, left ventricles of male miR-206 knockout mice have a faster myosin profile, accompanied by dilation and systolic dysfunction. Thus, miR-206 appears to be necessary to enforce a slow skeletal and cardiac muscle phenotype and to play a key role in muscle sexual dimorphisms.

Downregulated miR-18b-5p triggers apoptosis by inhibition of calcium signaling and neuronal cell differentiation in transgenic SOD1 (G93A) mice and SOD1 (G17S and G86S) ALS patients

BACKGROUND

MicroRNAs (miRNAs) are endogenous non-coding RNAs that regulate gene expression at the post-transcriptional level and are key modulators in neurodegenerative diseases. Overexpressed miRNAs play an important role in ALS; however, the pathogenic mechanisms of deregulated miRNAs are still unclear.

METHODS

We aimed to assess the dysfunction of RNAs or miRNAs in fALS (SOD1 mutations). We compared the RNA-seq of subcellular fractions in NSC-34 WT (hSOD1) and MT (hSOD1 (G93A)) cells to find altered RNAs or miRNAs. We identified that Hif1α and Mef2c were upregulated, and Mctp1 and Rarb were downregulated in the cytoplasm of NSC-34 MT cells.

RESULTS

SOD1 mutations decreased the level of miR-18b-5p. Induced Hif1α which is the target for miR-18b increased Mef2c expression as a transcription factor. Mef2c upregulated miR-206 as a transcription factor. Inhibition of Mctp1 and Rarb which are targets of miR-206 induces intracellular Ca²⁺ levels and reduces cell differentiation, respectively. We confirmed that miR-18b-5p pathway was also observed in G93A Tg, fALS (G86S) patient, and iPSC-derived motor neurons from fALS (G17S) patient.

CONCLUSIONS

Our data indicate that SOD1 mutation decreases miR-18b-5p, which sequentially regulates Hif1α, Mef2c, miR-206, Mctp1 and Rarb in fALS-linked SOD1 mutation. These results provide new insights into the downregulation of miR-18b-5p dependent pathogenic mechanisms of ALS.

miR-206 family is important for mitochondrial and muscle function, but not essential for myogenesis in vitro

miR-206, miR-1a-1, and miR-1a-2 are induced during differentiation of skeletal myoblasts and promote myogenesis in vitro. miR-206 is required for skeletal muscle regeneration in vivo. Although this miRNA family is hypothesized to play an essential role in differentiation, a triple knock-out (tKO) of the three genes has not been done to test this hypothesis. We report that tKO C2C12 myoblasts generated using CRISPR/Cas9 method differentiate despite the expected derepression of the miRNA targets. Surprisingly, their mitochondrial function is diminished. tKO mice demonstrate partial embryonic lethality, most likely due to the role of miR-1a in cardiac muscle differentiation. Two tKO mice survive and grow normally to adulthood with smaller myofiber diameter, diminished physical performance, and an increase in PAX7 positive satellite cells. Thus, unlike other miRNAs important in other differentiation pathways, the miR-206 family is not absolutely essential for myogenesis and is instead a modulator of optimal differentiation of skeletal myoblasts.

miRNA-186 Improves Sepsis Induced Renal Injury Via PTEN/PI3K/AKT/P53 Pathway

Aim

The aim of this study is to explain the effects of miRNA-186 in renal injury induced by sepsis.

Methods

The Wistar rats were divided into 3 groups: the Sham group, Sepsis model group and the miRNA-186 group based on the model group; there were 9 rats in every group. The rat sepsis model was reproduced by cecal ligation and puncture (CLP). The rats of the miRNA-186 group were injected miRNA-186 from caudal vein. The rats of the difference group were killed after operation 24 h. The kidneys of the difference groups were taken for histopathological and cell apoptosis analysis by H&E and TUNEL assay. The relative protein expressions were measured by WB assay. miRNA-186 target to Phosphatase and tensin homologous protein (PTEN).

Results

Compared with the Sham group, the kidney histopathological and cell apoptosis rates of the model group were significantly damaged (P<0.05, respectively), however, the kidney histopathological and cell apoptosis rate of miRNA-186 group were significantly improved compared with the model group (P<0.05, respectively). The relative protein expressions were significantly different among 3 groups (P<0.05, respectively). The PTEN was the target of the miRNA-186.

Conclusion

miRNA-186 over-expression has effects that improve renal injury induced by sepsis via PTEN pathway.

MicroRNAs facilitate skeletal muscle maintenance and metabolic suppression in hibernating brown bears

Hibernating brown bears, Ursus arctos, undergo extended periods of inactivity and yet these large hibernators are resilient to muscle disuse atrophy. Physiological characteristics associated with atrophy resistance in bear muscle have been examined (e.g., muscle mechanics, neural activity) but roles for molecular signaling/regulatory mechanisms in the resistance to muscle wasting in bears still require investigation. Using quantitative reverse transcription PCR (RT-qPCR), the present study characterized the responses of 36 microRNAs linked with development, metabolism, and regeneration of skeletal muscle, in the vastus lateralis of brown bears comparing winter hibernating and summer active animals. Relative levels of mRNA of selected genes (mef2a, pax7, id2, prkaa1, and mstn) implicated upstream and downstream of the microRNAs were examined. Results indicated that hibernation elicited a myogenic microRNA, or "myomiR", response via MEF2A-mediated signaling. Upregulation of MEF2A-controlled miR-1 and miR-206 and respective downregulation of pax7 and id2 mRNA are suggestive of responses that promote skeletal muscle maintenance. Increased levels of metabolic microRNAs, such as miR-27, miR-29, and miR-33, may facilitate metabolic suppression during hibernation via mechanisms that decrease glucose uptake and fatty acid oxidation. This study identified myomiR-mediated mechanisms for the promotion of muscle regeneration, suppression of ubiquitin ligases, and resistance to muscle atrophy during hibernation mediated by observed increases in miR-206, miR-221, miR-31, miR-23a, and miR-29b. This was further supported by the downregulation of myomiRs associated with a muscle injury and inflammation (miR-199a and miR-223) during hibernation. The present study provides evidence of myomiR-mediated signaling pathways that are activated during hibernation to maintain skeletal muscle functionality in brown bears.

miR-206 knockout shows it is critical for myogenesis and directly regulates newly identified target mRNAs

The muscle specific miRNA, miR-206, is important for the process of myogenesis; however, studying the function of miR-206 in muscle development and differentiation still proves challenging because the complement of mRNA targets it regulates remains undefined. In addition, miR-206 shares close sequence similarity to miR-1, another muscle specific miRNA, making it hard to study the impact of miR-206 alone in cell culture models. Here we used CRISPR/Cas9 technology to knockout miR-206 in C2C12 muscle cells. We show that knocking out miR-206 significantly impairs and delays differentiation and myotube formation, revealing that miR-206 alone is important for myogenesis. In addition, we use an experimental affinity purification technique to identify new mRNA targets of miR-206 in C2C12 cells. We identified over one hundred mRNAs as putative miR-206 targets. Functional experiments on six of these targets indicate that Adam19, Bgn, Cbx5, Smarce1, and Spg20 are direct miR-206 targets in C2C12 cells. Our data show a unique and important role for miR-206 in myogenesis.

microRNA-mRNA network model in patients with achalasia

BACKGROUND

Achalasia is a rare idiopathic disease with a complex etio-pathogenesis still unknown. This study aimed to identify microRNA (miRNA)-mRNA regulatory networks underlying achalasia.

METHODS

The investigation was performed in tissue specimens from 11 patients and five controls using the microarray technology followed by an integrated bioinformatics analysis.

KEY RESULTS

One hundred and six miRNAs were significantly up-regulated and 64 were down-regulated in achalasia patients. The expression of the most 10 differential expressed miRNAs (miR-122-5p, miR-133a-3p, miR-504-5p, miR-187-3p, miR-133b, miR-200c-3p, miR-375, miR-200b-5p, miR-200b-3p, and miR203a) was confirmed by droplet digital PCR in an independent cohort. The interactions between the significant miRNAs and their targets uncovered 14 miRNA-mRNA interacting pairs with experimentally predicted genes (ie, FN1, ROCK2, DPYSL2), and 35 pairs with not experimentally target genes (ie, SULF1, MRVI1, PRKG1); all genes were involved in immune cell trafficking, skeletal and muscular system development, nervous system development macro-processes.

CONCLUSION & INFERENCES

The mRNA-miRNA regulatory networks described in this study provide new insights in the genetic background of the disease, suggesting further investigations in novel pathogenic mechanisms.

Chromatin accessibility is associated with the changed expression of miRNAs that target members of the Hippo pathway during myoblast differentiation

miRNAs reportedly participate in various biological processes, such as skeletal muscle proliferation and differentiation. However, the regulation of differentially expressed (DE) miRNAs and their function in myogenesis remain unclear. Herein, miRNA expression profiles and regulation during C2C12 differentiation were analyzed in relation to chromatin states by RNA-seq, ATAC-seq, and ChIP-seq. We identified 19 known and nine novel differentially expressed miRNAs at days 0, 1, 2, and 4. The expression of the differentially expressed miRNAs was related to the chromatin states of the 113 surrounding open chromatin regions defined by ATAC-seq peaks. Of these open chromatin regions, 44.25% were colocalized with MyoD/MyoG binding sites. The remainder of the above open chromatin regions were enriched with motifs of the myoblast-expressed AP-1 family, Ctcf, and Bach2 transcription factors (TFs). Additionally, the target genes of the above differentially expressed miRNAs were enriched primarily in muscle growth and development pathways, especially the Hippo signaling pathway. Moreover, via combining a loss-of-function assay with Q-PCR, western blotting, and immunofluorescence, we confirmed that the Hippo signaling pathway was responsible for C2C12 myoblast differentiation. Thus, our results showed that these differentially expressed miRNAs were regulated by chromatin states and affected muscle differentiation through the Hippo signaling pathway. Our findings provide new insights into the function of these differentially expressed miRNAs and the regulation of their expression during myoblast differentiation.

Circulating MyomiRs as Potential Biomarkers to Monitor Response to Nusinersen in Pediatric SMA Patients

Spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by mutations in survival motor neuron (SMN) 1 gene, resulting in a truncated SMN protein responsible for degeneration of brain stem and spinal motor neurons. The paralogous SMN2 gene partially compensates full-length SMN protein production, mitigating the phenotype. Antisense oligonucleotide nusinersen (Spinraza^®) enhances SMN2 gene expression. SMN is involved in RNA metabolism and biogenesis of microRNA (miRNA), key gene expression modulators, whose dysregulation contributes to neuromuscular diseases. They are stable in body fluids and may reflect distinct pathophysiological states, thus acting as promising biomarkers. Muscle-specific miRNAs (myomiRs) as biomarkers for clinical use in SMA have not been investigated yet. Here, we analyzed the expression of miR-133a, -133b, -206 and -1, in serum of 21 infantile SMA patients at baseline and after 6 months of nusinersen treatment, and correlated molecular data with response to therapy evaluated by the Hammersmith Functional Motor Scale Expanded (HFMSE). Our results demonstrate that myomiR serological levels decrease over disease course upon nusinersen treatment. Notably, miR-133a reduction predicted patients’ response to therapy. Our findings identify myomiRs as potential biomarkers to monitor disease progression and therapeutic response in SMA patients.

Evaluation of Vascular Endothelial Function in Young and Middle-Aged Women with Respect to a History of Pregnancy, Pregnancy-Related Complications, Classical Cardiovascular Risk Factors, and Epigenetics

The aim of the study was to examine the effect of previous pregnancies and classical cardiovascular risk factors on vascular endothelial function in a group of 264 young and middle-aged women 3 to 11 years postpartum. We examined microvascular functions by peripheral arterial tonometry and EndoPAT 2000 device with respect to a history of gestational hypertension, preeclampsia, fetal growth restriction, the severity of the disease with regard to the degree of clinical signs and delivery date. Besides, we compared Reactive Hyperemia Index (RHI) values and the prevalence of vascular endothelial dysfunction among the groups of women with normal and abnormal values of BMI, waist circumference, systolic and diastolic blood pressures, heart rate, total serum cholesterol levels, serum high-density lipoprotein cholesterol levels, serum low-density lipoprotein cholesterol levels, serum triglycerides levels, serum lipoprotein A levels, serum C-reactive protein levels, serum uric acid levels, and plasma homocysteine levels. Furthermore, we determined the effect of total number of pregnancies and total parity per woman, infertility and blood pressure treatment, presence of trombophilic gene mutations, current smoking of cigarettes, and current hormonal contraceptive use on the vascular endothelial function. We also examined the association between the vascular endothelial function and postpartum whole peripheral blood expression of microRNAs involved in pathogenesis of cardiovascular/cerebrovascular diseases (miR-1-3p, miR-16-5p, miR-17-5p, miR-20a-5p, miR-20b-5p, miR-21-5p, miR-23a-3p, miR-24-3p, miR-26a-5p, miR-29a-3p, miR-92a-3p, miR-100-5p, miR-103a-3p, miR-125b-5p, miR-126-3p, miR-130b-3p, miR-133a-3p, miR-143-3p, miR-145-5p, miR-146a-5p, miR-155-5p, miR-181a-5p, miR-195-5p, miR-199a-5p, miR-210-3p, miR-221-3p, miR-342-3p, miR-499a-5p, and miR-574-3p). A proportion of overweight women (17.94% and 20.59%) and women with central obesity (18.64% and 21.19%) had significantly lower RHI values at 10.0% false positive rate (FPR) both before and after adjustment of the data for the age of patients. At 10.0% FPR, a proportion of women with vascular endothelial dysfunction (RHI ≤ 1.67) was identified to have up-regulated expression profile of miR-1-3p (11.76%), miR-23a-3p (17.65%), and miR-499a-5p (18.82%) in whole peripheral blood. RHI values also negatively correlated with expression of miR-1-3p, miR-23a-3p, and miR-499a-5p in whole peripheral blood. Otherwise, no significant impact of other studied factors on vascular endothelial function was found. We suppose that screening of these particular microRNAs associated with vascular endothelial dysfunction may help to stratify a highly risky group of young and middle-aged women that would benefit from early implementation of primary prevention strategies. Nevertheless, it is obvious, that vascular endothelial dysfunction is just one out of multiple cardiovascular risk factors which has only a partial impact on abnormal expression of cardiovascular and cerebrovascular disease associated microRNAs in whole peripheral blood of young and middle-aged women.

MiR-301a promotes embryonic stem cell differentiation to cardiomyocytes

BACKGROUND

Cardiovascular disease is the leading cause of death worldwide. Tissue repair after pathological injury in the heart remains a major challenge due to the limited regenerative ability of cardiomyocytes in adults. Stem cell-derived cardiomyocytes provide a promising source for the cell transplantation-based treatment of injured hearts.

AIM

To explore the function and mechanisms of miR-301a in regulating cardiomyocyte differentiation of mouse embryonic stem (mES) cells, and provide experimental evidence for applying miR-301a to the cardiomyocyte differentiation induction from stem cells.

METHODS

mES cells with or without overexpression of miR-301a were applied for all functional assays. The hanging drop technique was applied to form embryoid bodies from mES cells. Cardiac markers including GATA-4, TBX5, MEF2C, and α-actinin were used to determine cardiomyocyte differentiation from mES cells.

RESULTS

High expression of miR-301a was detected in the heart from late embryonic to neonatal mice. Overexpression of miR-301a in mES cells significantly induced the expression of cardiac transcription factors, thereby promoting cardiomyocyte differentiation and beating cardiomyocyte clone formation. PTEN is a target gene of miR-301a in cardiomyocytes. PTEN-regulated PI3K-AKT-mTOR-Stat3 signaling showed involvement in regulating miR-301a-promoted cardiomyocyte differentiation from mES cells.

CONCLUSION

MiR-301a is capable of promoting embryonic stem cell differentiation to cardiomyocytes.

Conditional Deletion of Dicer in Adult Mice Impairs Skeletal Muscle Regeneration

Skeletal muscle has a remarkable regenerative capacity, which is orchestrated by multiple processes, including the proliferation, fusion, and differentiation of the resident stem cells in muscle. MicroRNAs (miRNAs) are small noncoding RNAs that mediate the translational repression or degradation of mRNA to regulate diverse biological functions. Previous studies have suggested that several miRNAs play important roles in myoblast proliferation and differentiation in vitro. However, their potential roles in skeletal muscle regeneration in vivo have not been fully established. In this study, we generated a mouse in which the Dicer gene, which encodes an enzyme essential in miRNA processing, was knocked out in a tamoxifen-inducible way (iDicer KO mouse) and determined its regenerative potential after cardiotoxin-induced acute muscle injury. Dicer mRNA expression was significantly reduced in the tibialis anterior muscle of the iDicer KO mice, whereas the expression of muscle-enriched miRNAs was only slightly reduced in the Dicer-deficient muscles. After cardiotoxin injection, the iDicer KO mice showed impaired muscle regeneration. We also demonstrated that the number of PAX7⁺ cells, cell proliferation, and the myogenic differentiation capacity of the primary myoblasts did not differ between the wild-type and the iDicer KO mice. Taken together, these data demonstrate that Dicer is a critical factor for muscle regeneration in vivo.

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

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

Clinical value of non-coding RNAs in cardiovascular, pulmonary, and muscle diseases

Although a majority of the mammalian genome is transcribed to RNA, mounting evidence indicates that only a minor proportion of these transcriptional products are actually translated into proteins. Since the discovery of the first non-coding RNA (ncRNA) in the 1980s, the field has gone on to recognize ncRNAs as important molecular regulators of RNA activity and protein function, knowledge of which has stimulated the expansion of a scientific field that quests to understand the role of ncRNAs in cellular physiology, tissue homeostasis, and human disease. Although our knowledge of these molecules has significantly improved over the years, we have limited understanding of their precise functions, protein interacting partners, and tissue-specific activities. Adding to this complexity, it remains unknown exactly how many ncRNAs there are in existence. The increased use of high-throughput transcriptomics techniques has rapidly expanded the list of ncRNAs, which now includes classical ncRNAs (e.g., ribosomal RNAs and transfer RNAs), microRNAs, and long ncRNAs. In addition, splicing by-products of protein-coding genes and ncRNAs, so-called circular RNAs, are now being investigated. Because there is substantial heterogeneity in the functions of ncRNAs, we have summarized the present state of knowledge regarding the functions of ncRNAs in heart, lungs, and skeletal muscle. This review highlights the pathophysiologic relevance of these ncRNAs in the context of human cardiovascular, pulmonary, and muscle diseases.

The Expression and Functional Roles of miRNAs in Embryonic and Lineage-Specific Stem Cells

The discovery of small non-coding RNAs began an interesting era in cellular and molecular biology. To date, miRNAs are the best recognized non-coding RNAs for maintenance and differentiation of pluripotent stem cells including embryonic stem cells (ES), induced pluripotent stem cells (iPSC), and cancer stem cells. ES cells are defined by their ability to self-renew, teratoma formation, and to produce numerous types of differentiated cells. Dual capacity of ES cells for self-renewal and differentiation is controlled by specific interaction with the neighboring cells and intrinsic signaling pathways from the level of transcription to translation. The ES cells have been the suitable model for evaluating the function of non-coding RNAs and in specific miRNAs. So far, the general function of the miRNAs in ES cells has been assessed in mammalian and non-mammalian stem cells. Nowadays, the evolution of sequencing technology led to the discovery of numerous miRNAs in human and mouse ES cells that their expression levels significantly changes during proliferation and differentiation. Several miRNAs have been identified in ectoderm, mesoderm, and endoderm cells, as well. This review would focus on recent knowledge about the expression and functional roles of miRNAs in embryonic and lineage-specific stem cells. It also describes that miRNAs might have essential roles in orchestrating the Waddington's landscape structure during development.

Non-coding RNAs: key regulators of smooth muscle cell fate in vascular disease

The vascular smooth muscle cell (SMC) is one of the most plastic cells in the body. Understanding how non-coding RNAs (ncRNAs) regulate SMC cell-fate decision making in the vasculature has significantly enhanced our understanding of disease development, and opened up exciting new avenues for potential therapeutic applications. Recent studies on SMC physiology have in addition challenged our traditional view on their role and contribution to vascular disease, mainly in the setting of atherosclerosis as well as aneurysm disease, and restenosis after angioplasties. The impact of SMC behaviour on vascular disease is now recognized to be context dependent; SMC proliferation and migration can be harmful or beneficial, whereas their apoptosis, senescence, and switching into a more macrophage-like phenotype can promote inflammation and disease progression. This is in particular true for atherosclerosis-related diseases, where proliferation of SMCs was believed to promote lesion formation, but may also prevent plaque rupture by stabilizing the fibrous cap. Based on newer findings of genetic lineage tracing studies, it was revealed that SMC phenotypic switching can result in less-differentiated forms that lack classical SMC markers while exhibiting functions more related to macrophage-like cells. This switching can directly promote atherogenesis. The aim of this current review is to summarize and discuss how ncRNAs (mainly microRNAs and long ncRNAs) are involved in SMC plasticity, and how they directly affect vascular disease development and progression. Finally, we want to critically assess where potential future therapies could be useful to influence the burden of vascular diseases.

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.

MicroRNA-133a and Myocardial Infarction

Myocardial infarction (MI) is the leading cause of morbidity and mortality in the world. The infarcted heart displays typical cell death cascades characterized by a loss of cells and fibrotic scarring in the myocardium. Cardiac hypertrophy and fibrosis largely contribute to ventricular wall thickening and stiffening, altogether defining an adverse cardiac remodeling that ultimately leads to impaired cardiac function and subsequent heart failure. Finding a strategy to promote therapeutic, instead of detrimental, cardiac remodeling may pose as a potent MI treatment. Accumulating evidence shows that microRNAs (miRNAs) may play an essential role in cardiovascular diseases. In particular, microRNA-133a (miR-133a) is one of the most abundant miRNAs in the heart. Multiple studies have demonstrated that miR-133a participates in the early pathology of MI, as well as in subsequent cardiac remodeling. In this review, we summarize recent research progress highlighting the regulatory effects of miR-133a in ischemic myocardial diseases, such as inhibiting angiogenesis, apoptosis, fibrosis, hypertrophy, and inflammation, while promoting therapeutic cardiac remodeling. The goal is to elicit a critical discussion on the translational direction of miRNA-mediated treatments towards a safe and effective MI therapy.

Transient induction of Cdk9 in the early stage of differentiation is critical for myogenesis

Cdk9 is a serine-threonine protein kinase that has been recognized as a regulator of cardiac differentiation. Recently, we have reported that transient induction of Cdk9 using noncoding RNA targeting Cdk9 sequences results in efficient cardiac differentiation. Concerning Cdk9 regulatory roles, here, we proposed whether constant overexpression of Cdk9 might influence the differentiation of myoblast C2C12 cells into myotubes. We overexpressed Cdk9 in mouse myoblast C2C12 cells to investigate its regulatory roles on myogenic differentiation. Upon Cdk9 overexpression, the expression level of myogenic regulatory factors was determined. Moreover, the expression profile of three important myomiRs consist of miR 1, 133 and 206 was examined during the differentiation process. Although Cdk9 expression is necessary for inducing differentiation in the early stage of myogenesis, continuous Cdk9 expression inhibits differentiation by modulating myomiRs and myogenic gene expression. Our results indicate that the transient induction of Cdk9 in the early stage of differentiation is critical for myogenesis.

Aloe-emodin attenuates myocardial infarction and apoptosis via up-regulating miR-133 expression

Aloe-emodin (AE) is an anthraquinone derived from rhubarb and has a variety of pharmacological actions. However, the role of AE in regulating ischemic heart diseases is still unclear. The present study investigated the effect of AE on cardiac injuries induced by myocardial infarction (MI) in vivo and oxidative insults in vitro and explored the mechanisms involved. TUNEL and Flow cytometry were performed to measure cell apoptosis. Western blot analysis was employed to detect expression of Bcl-2, Bax and Caspase-3 proteins. Real-time PCR was used to quantify the microRNAs levels. Our data showed that AE protected neonatal rat ventricular myocytes (NRVMs) from hydrogen peroxide (H₂O₂) induced apoptosis and significantly inhibited H₂O₂-induced reactive oxygen species (ROS) elevation. Furthermore, AE treatment significantly reversed H₂O₂-induced upregulation of Bax/Bcl-2 and the loss of mitochondrial membrane potential. In vivo, AE treatment significantly reduced infarct size, ameliorated impaired cardiac function and obviously decreased cardiac apoptosis and oxidative stress in MI mice heart. Meanwhile, AE restored H₂O₂-induced downregulation of miR-133, and transfection with miR-133 inhibitor abolished the anti-apoptotic and anti-oxidative effects of AE. Moreover, AE prevented H₂O₂-induced increase in caspase-3 activity, which was diminished by application of miR-133 inhibitor. Our results indicate that AE protectes against myocardial infarction via the upregulation of miR-133, inhibition of ROS production and suppression of caspase-3 apoptotic signaling pathway.

Involvement of plasma miRNAs, muscle miRNAs and mitochondrial miRNAs in the pathophysiology of frailty

Frailty is a geriatric syndrome that leads not only to the loss of physical functions, but also to a generalized decline of the organism and a high risk of disability and dependency. Frailty's detection and management represent important goals for current gerontology. The advance in its rapid diagnosis could play a relevant role in taking measures to reduce the negative consequences it exerts on the body and to take preventive measures. microRNAs are the one of multiple epigenetic biomarkers that reflect functional changes in aged subject. In this review we analyze microRNAs as molecules involved in the control of the pathways leading to the development of frailty. miRNAs can be present in different body fluids, including plasma/serum and saliva, can be associated with organelles like the mitochondria, and can be expressed in tissues. Based on the multifactorial physiopathology of frailty, we analyzed here the microRNAs linked to "inflammaging" (inflamma-miRs), to musculoskeletal health (myomiRs), and microRNAs that can directly or indirectly affect the mitochondria (mitomiRs). Subsequently, we analyze those microRNAs that can be modified by physical exercise. In this review we will analyze the latest experimental studies carried out in animals, cell cultures, and human samples, with the aim to identify gaps in the research and in order to try to dazzle the information about the pathways regulated by each miRNA. Multiple studies revised here suggest that several miRs can be considered as possible markers of frailty, including miR-1, miR-21, miR-34a, miR-146a, miR-185, and miR-206, miR-223, among others. Normalization of miRNAs data and standardization of the protocols used for their measurement to avoid confounding variables influencing the results, are important to use miRNAs as disease biomarkers.

MiR-145 mediates cell morphology-regulated mesenchymal stem cell differentiation to smooth muscle cells

The use of biochemical signaling to derive smooth muscle cells (SMCs) from mesenchymal stem cells (MSCs) has been explored, but the induction of a fully functional SMC phenotype remains to be a major challenge. Cell morphology has been shown to regulate MSC differentiation into various lineages, including SMCs. We engineered substrates with microgrooves to induce cell elongation to study the mechanism underlying the MSC shape modulation in SMC differentiation. In comparison to those on flat substrates, MSCs cultured on engineered substrates were elongated with increased aspect ratios for both cell body and nucleus, as well as augmented cytoskeletal tensions. Biochemical studies indicated that the microgroove-elongated cells expressed significantly higher levels of SMC markers. MicroRNA analyses showed that up-regulation of miR-145 and the consequent repression of KLF4 in these elongated cells promoted MSC-to-SMC differentiation. Rho/ROCK inhibitions, which impair cytoskeletal tension, attenuated cell and nuclear elongations and disrupted the miR-145/KLF4 regulation for SMC differentiation. Furthermore, cell traction force measurements showed that miR-145 is essential for the functional contractility in the microgroove-induced SMC differentiation. Collectively, our findings demonstrate that, through a Rho-ROCK/miR-145/KLF4 pathway, the elongated cell shape serves as a decisive geometric cue to direct MSC differentiation into functional SMCs.

Differentially expressed circulating miRNAs in postmenopausal osteoporosis: a meta-analysis

MicroRNAs (miRNAs) have been proven to play a crucial role in postmenopausal osteoporosis (PMO), and studies on their diagnostic value have been increasing. In our study, we aim to identify the key miRNAs in the PMO that might be potential biomarkers. A comprehensive systematic literature search was conducted by searching PubMed, Web of Science, Embase and Cochrane Library databases. In the total of 16 independent miRNA expression studies which contained 327 PMO patients and 328 postmenopausal (PM) healthy control samples, miRNAs were evaluated by using robust rank aggregation (RRA) method. A statistically significant meta-signature of up-regulated hsa-miR-133a-3p (P = 1.38e-03) was determined. Then bioinformatics analysis to recruit putative target genes prediction of hsa-miR-133a-3p and pathway enrichment analysis to reveal what biological processes this miRNA may affect were conducted. It was indicated that pathways were commonly associated with adrenergic signaling in cardiomyocytes, adherens junction, PI3K-Akt signaling pathway and AMPK signaling pathway. Furthermore, STRING and Cytoscape tools were used to visualize the interactions between target genes of hsa-miR-133a-3p. Six genes were detected as hub genes among 576 targets which were CDC42, RHOA, EGFR, VAMP2, PIK3R2 and FN1. After Kyoto Encyclopedia of Genes and Genomes pathway analysis, it was detected that these hub genes were mostly enriched in signaling pathways and cancer. In this meta-analysis, it is stated that circulating hsa-miR-133a-3p may serve as a potential non-invasive biomarker and therapeutic target in PMO.

A miR-206 regulated gene landscape enhances mammary epithelial differentiation

miR‐206 is known to suppress breast cancer. However, while it is expressed in mammary stem cells, its function in such nontumor cells is not well understood. Here, we explore the role of miR‐206 in undifferentiated, stem‐like mammary cells using the murine mammary differentiation model HC11, genome‐wide gene expression analysis, and functional assays. We describe the miR‐206‐regulated gene landscape and propose a network whereby miR‐206 suppresses tumor development. We functionally demonstrate that miR‐206 in nontumor stem‐like cells induces a G1–S cell cycle arrest, and reduces colony formation and epithelial‐to‐mesenchymal transition markers. Finally, we show that addition of miR‐206 accelerates the mammary differentiation process along with related accumulation of lipids. We conclude that miR‐206 impacts a network of signaling pathways, and acts as a regulator of proliferation, stemness, and mammary cell differentiation in nontumor stem‐like mammary cells. Our study provides a broad insight into the breast cancer suppressive functions of miR‐206.

Small molecules with big roles in microRNA chemical biology and microRNA-targeted therapeutics

MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression. Aberrant miRNA expression or function have close links with various human diseases. Therefore, therapeutic treatments with disease-associated miRNAs as targets are emerging. However, the intracellular miRNA networks are extremely complicated and poorly understood, which thus hinder the development of miRNA-targeted therapeutics. Small molecules that are able to regulate endogenous miRNAs hold great potential in both elucidation of miRNA networks and treatment of miRNA-related diseases. Herein, we summarize current strategies for discovery of small molecule modifiers of miRNAs, and we highlight aspects of miRNA cellular biology elucidated by using these small molecules and miRNA-targeted therapeutics realized by these small molecules. We envision that this area will expand dramatically in the near future and will ultimately contribute to a better understanding of miRNA-involved cellular processes and development of therapeutic agents for miRNA-associated diseases.

MicroRNA-133b regulates the growth and migration of vascular smooth muscle cells by targeting matrix metallopeptidase 9

Atherosclerosis is a systemic disease affecting the whole arterial tree of the human body, and it is the leading cause of cardiovascular diseases.Vascular smooth muscle cells (VSMCs) have been identified to play a key role in the development of atherosclerosis. MicroRNAs (miRNAs) are a group of endogenous small non-coding RNAs, and they play a critical role in many biological processes including regulating cell proliferation, migration and apoptosis. However, till now, the expression and role of miR-133b in atherosclerosis remain largely unknown. Therefore, our purpose was to investigate the expression and role of miR-133b in atherosclerosis and to explore the underlying mechanism. The results showed that miR-133b was down-regulated in the blood and vascular plaque tissues of rabbits with atherosclerosis. Matrix metallopeptidase 9 (MMP-9) was a direct target of miR-133b. In addition, our data indicated that miR-133b mimic could significantly inhibit rVSMC cell proliferation activity, migration ability and induce cell apoptosis compared with the control group, and all these effects were reversed by MMP-9-plasmid. Taken together, these findings highlight an important role for miR-133b/MMP-9 axis in atherosclerosis. And miR-133b might be a valuable clinical marker and therapeutic target for atherosclerosis.

A microRNA-inducible CRISPR-Cas9 platform serves as a microRNA sensor and cell-type-specific genome regulation tool

microRNAs (miRNAs) are small noncoding RNAs that play important regulatory roles in plants, animals and viruses. Measuring miRNA activity in vivo remains a big challenge. Here, using an miRNA-mediated single guide RNA (sgRNA)-releasing strategy and dCas9-VPR to drive a transgene red fluorescent protein, we create an miRNA sensor that can faithfully measure miRNA activity at cellular levels and use it to monitor differentiation status of stem cells. Furthermore, by designing sgRNAs to target endogenous loci, we adapted this system to control the expression of endogenous genes or mutate specific DNA bases upon induction by cell-type-specific miRNAs. Finally, by miRNA sensor library screening, we discover a previously undefined layer of heterogeneity associated with miR-21a activity in mouse embryonic stem cells. Together, these results highlight the utility of an miRNA-induced CRISPR-Cas9 system as miRNA sensors and cell-type-specific genome regulation tools.

Distal-less homeobox 3, a negative regulator of myogenesis, is downregulated by microRNA-133

Distal-less homeobox 3 (Dlx3), a member of the Dlx family of homeobox proteins, is a transcriptional activator of runt-related transcription factor 2 (Runx2) during osteogenic differentiation. It has been demonstrated that forced expression of Runx2 induces an osteogenic program and ectopic calcification in muscles. Therefore, it would be reasonable to predict that Dlx3 also affects myogenic differentiation. The relationship between Dlx3 and myogenesis, however, remains poorly understood. Therefore, in this study, the role and regulation of Dlx3 during myogenic differentiation were investigated. Expression level of Dlx3 was downregulated in human mesenchymal stem cells (MSCs), mouse MSCs, and C2C12 cells cultured in myogenic medium. Dlx3 level was inversely correlated with myogenic differentiation 1 and the muscle-specific microRNA, microRNA-133 (miR-133). The expression level of Runx2 was closely regulated by Dlx3 even under myogenic conditions. Overexpression of Dlx3 markedly downregulated expression levels of myogenic transcription factors and myotube formation in C2C12 cells, whereas Dlx3 knockdown enhanced myogenic differentiation. The Dlx3 3'-untranslated region (3'-UTR) has two potential binding sites for miR-133. Luciferase reporter assays demonstrated that Dlx3 is a direct target of miR-133a and miR-133b, and that the two target sites are redundantly active. Taken together, these results suggest that Dlx3 is a negative regulator of myogenic differentiation and that miR-133a and miR-133b enhance myogenic differentiation, partly through inhibition of Dlx3 expression via direct targeting of the Dlx3 3'-UTR.

Upregulation of Circulating Cardiomyocyte-Enriched miR-1 and miR-133 Associate with the Risk of Coronary Artery Disease in Type 2 Diabetes Patients and Serve as Potential Biomarkers

Circulating miRNAs are increasingly suggested as clinical biomarker for diseases. We evaluated the expression of circulating cardiomyocyte-enriched miR-1 and miR-133 by real-time PCR in blood from patients with type 2 diabetes (T2D) without and with coronary artery disease (CAD) and healthy controls, investigated their association with the risk of CAD risk and their potential as biomarkers. The two miRNAs were upregulated in patients with T2D and CAD compared with controls, associated with CAD risk and remained significant after adjustment for multiple confounders. LDL-C was a positive predictor for miR-1 and miR-133, and mean blood pressure was also a positive predictor for miR-133. Both miRNAs strongly distinguished CAD from controls. miR-1 significantly distinguished CAD from T2D with higher diagnostic ability than miR-133, whereas the miR-1/miR-133 combination improved the diagnostic value. Upregulation of circulating miR-1 and miR-133 associate with the risk of CAD in T2D patients and may serve as diagnostic biomarkers.

Dysregulation of microRNA metabolism in motor neuron diseases: Novel biomarkers and potential therapeutics

In the last 15 years, several classes of small regulatory RNAs have been identified, uncovering the widespread impact of non-coding elements in the human genome on cell homeostasis and human diseases. MicroRNAs (miRNAs) are a family of small, non-coding RNAs, which exert silencing of mRNA targets in a sequence-dependent fashion. Many miRNAs are specifically expressed in the central nervous system, where they display roles in differentiation, neuronal survival, neuronal plasticity and learning. On the other hand, deregulated miRNA/mRNA expression networks are deeply involved in neurodegeneration. Recent findings suggest a role for miRNAs in the pathogenesis of motor neuron diseases. In particular, cell-specific changes in miRNA profile are involved in the motor neuron disease phenotype and might be implicated in their selective vulnerability. Exploitation of noncoding RNAs, in particular miRNAs, for therapeutic strategies is being assessed for implementing current therapies. In this regard, the neuroprotective potential of certain miRNAs could represent a promising potential tool to improve therapies for motor-neuron diseases. This review focuses on emerging roles of miRNAs in motor neuron diseases and on their impact on neuron life-span and integrity.

gga-mir-133a-3p Regulates Myoblasts Proliferation and Differentiation by Targeting PRRX1

Non-coding RNAs play a regulatory role in the growth and development of skeletal muscle. Our previous study suggested that gga-mir-133a-3p was a potential candidate for regulating myoblast proliferation and differentiation in skeletal muscle. The purpose of our study was to reveal the regulatory mechanism of gga-mir-133a-3p in the proliferation and differentiation of chicken myoblasts. Through the detection of cell proliferation activity, cell cycle progression and EdU, we found that gga-mir-133a-3p can significantly inhibit the proliferation of myoblasts. In the process of myogenic differentiation, gga-mir-133a-3p is up-regulated, while gga-mir-133a-3p can significantly promote the up-regulation of differentiation-related muscle-derived factors, indicating that gga-mir-133a-3p can promote the differentiation of myoblasts. Validation at the transcriptional level and protein level proved that gga-mir-133a-3p can inhibit the expression of PRRX1, and the dual-luciferase assay also showed their direct targeting relationship. Correspondingly, PRRX1 can significantly promote myoblast proliferation and inhibit myoblast differentiation. In our study, we confirmed that gga-mir-133a-3p participates in the regulation of proliferation and differentiation of myoblasts by targeting PRRX1.

Potential Role of MicroRNA in the Anabolic Capacity of Skeletal Muscle With Aging

Age-induced loss of skeletal muscle mass and function, termed sarcopenia, may be the result of diminished response to anabolic stimulation. This review will explore the hypothesis that alterations in the expression of microRNA with aging contributes to reduced muscle plasticity resulting in impaired skeletal muscle adaptations to exercise-induced anabolic stimulation.

Guanidinoacetic Acid Regulates Myogenic Differentiation and Muscle Growth Through miR-133a-3p and miR-1a-3p Co-mediated Akt/mTOR/S6K Signaling Pathway

Guanidinoacetic acid (GAA), an amino acid derivative that is endogenous to animal tissues including muscle and nerve, has been reported to enhance muscular performance. MicroRNA (miRNA) is a post-transcriptional regulator that plays a key role in nutrient-mediated myogenesis. However, the effects of GAA on myogenic differentiation and skeletal muscle growth, and the potential regulatory mechanisms of miRNA in these processes have not been elucidated. In this study, we investigated the effects of GAA on proliferation, differentiation, and growth in C2C12 cells and mice. The results showed that GAA markedly inhibited the proliferation of myoblasts, along with the down-regulation of cyclin D1 (CCND1) and cyclin dependent kinase 4 (CDK4) mRNA expression, and the upregulation of cyclin dependent kinase inhibitor 1A (P21) mRNA expression. We also demonstrated that GAA treatment stimulated myogenic differentiation 1 (MyoD) and myogenin (MyoG) mRNA expression, resulting in an increase in the myotube fusion rate. Meanwhile, GAA supplementation promoted myotube growth through increase in total myosin heavy chain (MyHC) protein level, myotubes thickness and gastrocnemius muscle cross-sectional area. Furthermore, small RNA sequencing revealed that a total of eight miRNAs, including miR-133a-3p and miR-1a-3p cluster, showed differential expression after GAA supplementation. To further study the function of miR-133a-3p and miR-1a-3p in GAA-induced skeletal muscle growth, we transfected miR-133a-3p and miR-1a-3p mimics into myotube, which also induced muscle growth. Through bioinformatics and a dual-luciferase reporter system, the target genes of miR-133a-3p and miR-1a-3p were determined. These two miRNAs were shown to modulate the Akt/mTOR/S6K signaling pathway by restraining target gene expression. Taken together, these findings suggest that GAA supplementation can promote myoblast differentiation and skeletal muscle growth through miR-133a-3p- and miR-1a-3p-induced activation of the AKT/mTOR/S6K signaling pathway.