Attenuation of microRNA-1 derepresses the cytoskeleton regulatory protein twinfilin-1 to provoke cardiac hypertrophy

Spectroscopic characterization of the effect of mouse twinfilin-1 on actin filaments at different pH values

The effect of mammalian twinfilin-1 on the structure and dynamics of actin filaments were studied with steady state fluorescence spectroscopy, total internal reflection fluorescence microscopy and differential scanning calorimetry techniques. It was proved before that the eukaryotic budding yeast twinfilin-1 can efficiently bind and severe actin filaments in vitro at low pH values. In the present work steady-state anisotropy measurements revealed that twinfilin can bind efficiently to F-actin. Dilution-induced depolymerization assay proved that mammalian twinfilin-1 has an actin filament severing activity. This severing activity was more pronounced at low pH values. Total internal reflection fluorescence microscopy measurements could support the severing activity of mouse twinfilin-1. The average rate of depolymerization was more apparent at low pH values. The differential scanning calorimetry measurements demonstrated that mammalian twinfilin-1 could reduce the stiffness within the actin filaments before the detachment of the actin protomers. The structural and dynamic reorganization of actin can support the twinfilin-1 induced separation of actin protomers. The measured data indicated that mammalian twinfilin-1 was able to accelerate the monomers dissociation and/or sever the filaments effectively at low pH values. It was concluded that twinfilin-1 can affect the F-actin in biological processes or under stress situations when the pH is markedly under the physiological level.

Reversal of Phospholamban Inhibition of the Sarco(endo)plasmic Reticulum Ca2+-ATPase (SERCA) Using Short, Protein-interacting RNAs and Oligonucleotide Analogs

The sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) and phospholamban (PLN) complex regulates heart relaxation through its removal of cytosolic Ca²⁺ during diastole. Dysfunction of this complex has been related to many heart disorders and is therefore a key pharmacological target. There are currently no therapeutics that directly target either SERCA or PLN. It has been previously reported that single-stranded DNA binds PLN with strong affinity and relieves inhibition of SERCA in a length-dependent manner. In the current article, we demonstrate that RNAs and single-stranded oligonucleotide analogs, or xeno nucleic acids (XNAs), also bind PLN strongly (K_d <10 nm) and relieve inhibition of SERCA. Affinity for PLN is sequence-independent. Relief of PLN inhibition is length-dependent, allowing SERCA activity to be restored incrementally. The improved in vivo stability of XNAs offers more realistic pharmacological potential than DNA or RNA. We also found that microRNAs (miRNAs) 1 and 21 bind PLN strongly and relieve PLN inhibition of SERCA to a greater extent than a similar length random sequence RNA mixture. This may suggest that miR-1 and miR-21 have evolved to contain distinct sequence elements that are more effective at relieving PLN inhibition than random sequences.

MicroRNA-26a protects against cardiac hypertrophy via inhibiting GATA4 in rat model and cultured cardiomyocytes

Pathological cardiac hypertrophy is characterized by deleterious changes developed in cardiovascular diseases, whereas microRNAs (miRNAs) are involved in the mediation of cardiac hypertrophy. To investigate the role of microRNA-26a (miR-26a) in regulating cardiac hypertrophy and its functioning mechanisms, overexpression and suppression of miR‑26a via its mimic and inhibitor in a transverse abdominal aortic constriction (TAAC)-induced rat model and in angiotensin II (Ang II)-induced cardiomyocytes (CMs) was performed. In the rat model, the heart weight (HW) compared with the body weight (BW), the CM area, and expression of the hypertrophy‑associated factors, atrial natriuretic factor (ANF) and β‑myosin heavy chain (β‑MHC), were assessed. In CMs, the protein synthesis rate was determined using a leucine incorporation assay. Mutation of the GATA‑binding protein 4 (GATA4) 3'‑untranslated region (UTR) and overexpression of GATA4 were performed to confirm whether GATA4 is the target of miR‑26a. The results indicated that miR-26a was significantly downregulated in the heart tissue of the rat model, as well as in Ang II‑induced CMs (P<0.05). The TAAC-induced rat model exhibited a higher HW/BW ratio, a larger CM area, and higher expression levels of ANF and β‑MHC. CMs, upon Ang II treatment, also demonstrated a larger CM area, higher levels of ANF and β‑MHC, as well as accelerated protein synthesis. miR‑26a was not able to regulate GATA4 with mutations in the 3'‑UTR, indicating that GATA4 was the direct target of miR‑26a. Overexpression of GATA4 abrogated the inhibitory functions of miR‑26a in cardiac hypertrophy. Taken together, the present study suggested an anti‑hypertrophic role of miR‑26a in cardiac hypertrophy, possibly via inhibition of GATA4. These findings may be useful in terms of facilitating cardiac treatment, with potential therapeutic targets and strategies.

Role of microRNAs in Vascular Remodeling

Besides being involved in the gradual formation of blood vessels during embryonic development, vascular remodeling also contributes to the progression of various cardiovascular diseases, such as; myocardial infarction, heart failure, atherosclerosis, pulmonary artery hypertension, restenosis, aneurysm, etc. The integrated mechanisms; proliferation of medial smooth muscle cell, dysregulation of intimal endothelial cell, activation of adventitial fibroblast, inflammation of macrophage, and the participation of extracellular matrix proteins are important factors in vascular remodeling. In the recent studies, microRNAs (miRs) have been shown to be expressed in all of these cell-types and play important roles in the mechanisms of vascular remodeling. Therefore, some miRs may be involved in prevention and others in the aggravation of the vascular lesions. miRs are small, endogenous, conserved, single-stranded, non-coding RNAs; which degrade target RNAs or inhibit translation post-transcriptionally. In this paper, we reviewed the function and mechanisms of miRs, which are highly expressed in various cells types, especially endothelial and smooth muscle cells, which are closely involved in the process of vascular remodeling. We also assess the functions of these miRs in the hope that they may provide new possibilities of diagnosis and treatment choices for the related diseases.

Overview of MicroRNAs in Cardiac Hypertrophy, Fibrosis, and Apoptosis

MicroRNAs (miRNAs) are non-coding RNAs that play essential roles in modulating the gene expression in almost all biological events. In the past decade, the involvement of miRNAs in various cardiovascular disorders has been explored in numerous in vitro and in vivo studies. In this paper, studies focused upon the discovery of miRNAs, their target genes, and functionality are reviewed. The selected miRNAs discussed herein have regulatory effects on target gene expression as demonstrated by miRNA/3′ end untranslated region (3′UTR) interaction assay and/or gain/loss-of-function approaches. The listed miRNA entities are categorized according to the biological relevance of their target genes in relation to three cardiovascular pathologies, namely cardiac hypertrophy, fibrosis, and apoptosis. Furthermore, comparison across 86 studies identified several candidate miRNAs that might be of particular importance in the ontogenesis of cardiovascular diseases as they modulate the expression of clusters of target genes involved in the progression of multiple adverse cardiovascular events. This review illustrates the involvement of miRNAs in diverse biological signaling pathways and provides an overview of current understanding of, and progress of research into, of the roles of miRNAs in cardiovascular health and disease.

The effect of mouse twinfilin-1 on the structure and dynamics of monomeric actin

The effect of twinfilin-1 on the structure and dynamics of monomeric actin was investigated with fluorescence spectroscopy and differential scanning calorimetry experiments. Fluorescence anisotropy measurements proved that G-actin and twinfilin-1 could form a complex. Due to the formation of the complexes the dissociation of the nucleotide slowed down from the nucleotide-binding pocket of actin. Fluorescence quenching experiments showed that the accessibility of the actin bound ε-ATP decreased in the presence of twinfilin-1. Temperature dependent fluorescence resonance energy transfer and differential scanning calorimetry experiments revealed that the protein matrix of actin becomes more rigid and more heat resistant in the presence of twinfilin-1. The results suggest that the nucleotide binding cleft shifted into a more closed and stable conformational state of actin in the presence of twinfilin-1.

A twinfilin-like protein coordinates karyokinesis by influencing mitotic spindle elongation and DNA replication in Leishmania

Twinfilin is an evolutionarily conserved actin-binding protein, which regulates actin-dynamics in eukaryotic cells. Homologs of this protein have been detected in the genome of various protozoan parasites causing diseases in human. However, very little is known about their core functions in these organisms. We show here that a twinfilin homolog in a human pathogen Leishmania, primarily localizes to the nucleolus and, to some extent, also in the basal body region. In the dividing cells, nucleolar twinfilin redistributes to the mitotic spindle and remains there partly associated with the spindle microtubules. We further show that approximately 50% depletion of this protein significantly retards the cell growth due to sluggish progression of S phase of the cell division cycle, owing to the delayed nuclear DNA synthesis. Interestingly, overexpression of this protein results in significantly increased length of the mitotic spindle in the dividing Leishmania cells, whereas, its depletion adversely affects spindle elongation and architecture. Our results indicate that twinfilin controls on one hand, the DNA synthesis and on the other, the mitotic spindle elongation, thus contributing to karyokinesis in Leishmania.

MicroRNA Signature and Cardiovascular Dysfunction

The worldwide increase in the prevalence of obesity and type 2 diabetes and the associated elevated risk of cardiovascular disease (CVD) has emphasized the need to seek new therapeutic targets to offset the negative impact on human health outcomes. In this regards, microRNAs (miRNAs), a class of small noncoding RNAs that mediate posttranscriptional gene silencing, have received considerable interest. miRNAs repress gene expression by their ability to pair with target sequences in the 3' untranslated region of the messenger RNA. miRNAs play a crucial role in the biogenesis and function of the cardiovascular system and are implicated as dynamic regulators of cardiac and vascular signaling and pathophysiology. Numerous miRNAs have been identified as novel biomarkers and potential therapeutic targets for CVD. In this review, we discuss the contribution of miRNAs to the regulation of CVD, their role in macrovascular/microvascular (dys)function, their potential as important biomarkers for the early detection of CVD, and, finally, as therapeutic targets.

Noncoding RNA as regulators of cardiac fibrosis: current insight and the road ahead

Cardiac fibrosis is an important pathological feature of cardiac remodeling in heart diseases. The molecular mechanisms of cardiac fibrosis are unknown. Genomic analyses estimated that many noncoding DNA regions generate noncoding RNAs (ncRNAs). ncRNAs have emerged as key molecular players in the regulation of gene expression in different biological processes. Recent studies have started to reveal the importance of ncRNAs in heart development and suggest also an involvement in cardiac fibrosis. These molecules are emerging as important regulators of cellular process. Here, we review particularly focuses on the involvement of two large families of ncRNAs, namely microRNAs (miRNAs) and long noncoding RNAs (LncRNAs) in the regulation of cardiac fibrosis. Furthermore, we review the functions and role of ncRNAs in cardiac biology and discuss these reports and the therapeutic potential of ncRNAs for cardiac fibrosis associated with fibroblast activation and proliferation.

MicroRNA-26a induces osteosarcoma cell growth and metastasis via the Wnt/β-catenin pathway

MicroRNAs (miRNAs/miRs) are a type of highly conserved, small non-coding RNA that are vital to the post-transcriptional regulation of gene expression via base pairing with target mRNA 3'-untranslated regions (3'-UTRs). Several studies have indicated that the abnormal expression of miRNAs occurs frequently in human osteosarcoma (OS). In the present study, the role of miR-26a in the progression and metastasis of OS was investigated using reverse transcription-quantitative polymerase chain reaction, a luciferase activity assay, cell viability assay, in vitro migration and invasion assays, transfection and western blot analysis. miR-26a was upregulated in OS tissues and cell lines, and the expression of miR-26a was indicated to affect the proliferation, migration and invasion of OS Saos-2 cells. At the molecular level, the results showed that glycogen synthase kinase-3β (GSK-3β) was identified as a target of miR-26a, and the ectopic expression of miR-26a inhibited GSK-3β by directly binding to the 3'-UTR. Therefore, the expression of miR-26a was negatively correlated with GSK-3β in the OS tissues. These data suggest that miR-26a is significant in the proliferation of human OS cells due to the direct regulation of Wnt/β-catenin signaling.

Diagnostic and prognostic value of circulating microRNAs in heart failure with preserved and reduced ejection fraction

microRNAs (miRNAs) are powerful regulators of posttranscriptional gene expression and play an important role in pathophysiological processes. Circulating miRNAs can be quantified in body liquids and are promising biomarkers in numerous diseases. In cardiovascular disease miRNAs have been proven to be reliable diagnostic biomarkers for different disease entities. In cardiac fibrosis (CF) and heart failure (HF) dysregulated circulating miRNAs have been identified, indicating their promising applicability as diagnostic biomarkers. Some miRNAs were successfully tested in risk stratification of HF implementing their potential use as prognostic biomarkers. In this respect miRNAs might soon be implemented in diagnostic clinical routine. In the young field of miRNA based research advances have been made in identifying miRNAs as potential targets for the treatment of experimental CF and HF. Promising study results suggest their potential future application as therapeutic agents in treatment of cardiovascular disease. This article summarizes the current state of the various aspects of miRNA research in the field of CF and HF with reduced ejection fraction as well as preserved ejection fraction. The review provides an overview of the application of circulating miRNAs as biomarkers in CF and HF and current approaches to therapeutically utilize miRNAs in this field of cardiovascular disease.

CDK6 mediates the effect of attenuation of miR-1 on provoking cardiomyocyte hypertrophy

MicroRNA-1 (miR-1) is approved involved in cardiac hypertrophy, but the underlying molecular mechanisms of miR-1 in cardiac hypertrophy are not well elucidated. The present study aimed to investigate the potential role of miR-1 in modulating CDKs-Rb pathway during cardiomyocyte hypertrophy. A rat model of hypertrophy was established with abdominal aortic constriction, and a cell model of hypertrophy was also achieved based on PE-promoted neonatal rat ventricular cardiomyocytes (NRVCs). We demonstrated that miR-1 expression was markedly decreased in hypertrophic myocardium and hypertrophic cardiomyocytes. Dual luciferase reporter assays revealed that miR-1 interacted with the 3'UTR of CDK6, and miR-1 was verified to inhibit CDK6 expression at the posttranscriptional level. CDK6 protein expression was observed increased in hypertrophic myocardium and hypertrophic cardiomyocytes. Morover, miR-1 mimic, in parallel to CDK6 siRNA, could inhibit PE-induced hypertrophy of NRVCs, with decreases in cell size, newly transcribed RNA, expressions of ANF and β-MHC, and the phosphorylated pRb. Taken together, our results reveal that derepression of CDK6 and activation of Rb pathway contributes to the effect of attenuation of miR-1 on provoking cardiomyocyte hypertrophy.

GTPase Activating Protein (Sh3 Domain) Binding Protein 1 Regulates the Processing of MicroRNA-1 during Cardiac Hypertrophy

Background

MicroRNAs (miR) are small, posttranscriptional regulators, expressed as part of a longer primary transcript, following which they undergo nuclear and cytoplasmic processing by Drosha and Dicer, respectively, to form the functional mature ~20mer that gets incorporated into the silencing complex. Others and we have shown that mature miR-1 levels decrease with pressure-induced cardiac hypertrophy, however, there is little or no change in the primary transcript encompassing miR-1 stem-loop, suggesting critical regulatory step in microRNA processing. The objective of this study was to investigate the underlying mechanisms regulating miR-1 expression in cardiomyocytes.

Results

Here we report that GTPase–activating protein (SH3 domain) binding protein 1 (G3bp1), an endoribonuclease regulates miR-1 processing in cardiomyocytes. G3bp1 is upregulated during cardiac hypertrophy and restricts miR-1 processing by binding to its consensus sequence in the pre-miR-1-2 stem-loop. In accordance, exogenous G3bp1 is sufficient to reduce miR-1 levels, along with derepression of miR-1 targets; General transcription factor IIB (Gtf2b), cyclin dependent factor 9 (Cdk9) and eukaryotic initiation factor 4E (Eif4e). While Cdk9 and Gtf2b are essential for transcription, Eif4e is required for translation. Thus, downregulation of miR-1 is necessary for increase in these molecules. Similar to miR-1 knockdown, G3bp1 overexpression is not sufficient for development of cardiac hypertrophy. Conversely, knockdown of G3bp1 in hypertrophying cardiomyocytes inhibited downregulation of miR-1 and upregulation of its targets along with restricted hypertrophy, suggesting that G3bp1 is necessary for development of cardiac hypertrophy. These results indicate that G3bp1-mediated inhibition of miR-1 processing with growth stimulation results in decrease in mature miR-1 and, thereby, an increase of its targets, which play fundamental roles in the development of hypertrophy.

Conclusion

G3bp1 posttranscriptionally regulates miRNA-1 processing in the heart, and G3bp1 mediated downregulation of mature miRNA-1 levels is required for the derepression of its targets and increase in gene expression during cardiac hypertrophy.

MicroRNA‑1 suppresses cardiac hypertrophy by targeting nuclear factor of activated T cells cytoplasmic 3

Cardiomyocyte hypertrophy is a threat to human health due to the probability of sudden heart failure‑induced mortality. Previous studies have demonstrated that nuclear factor of activated T cells cytoplasmic 3 (NFATC3) is important in the process of cardiomyocyte hypertrophy. However, the molecular mechanism underlying the alteration in the expression levels of NFATC3 during cardiomyocyte hypertrophy has remained to be fully elucidated. In order to shed light on the molecular mechanism, the present study employed several approaches, including the measurement of the cell surface area, analysis of the protein/DNA ratio, western blot analysis and a Luciferase reporter assay using isolated rat cardiomyocytes as model. The results showed that expression of microRNA‑1 (miR‑1) was reduced in patients diagnosed with cardiac hypertrophy and rat cardiomyocytes treated with pro‑hypertrophic stimuli. The increase in the expression of miR‑1 was able to inhibit the hypertrophic remodeling of cardiomyocytes. The suppression of miR‑1 was sufficient to induce cardiomyocyte hypertrophy, and further experiments confirmed that NFATC3 was a target of miR‑1 in cardiomyocytes. Forced expression of NFATC3 inhibited the protective activity of miR‑1 against hypertrophic stimuli in the cardiomyocytes. These findings provided clarification of the regulatory signaling pathway underlying cardiac hypertrophy, and provided evidence that targeting the miR‑1/NFATC3 pathway may be a promising strategy for the prevention and treatment of heart hypertrophy.

Platelet miRNAs and cardiovascular diseases

Activated platelets play a critical role in the acute complications of atherosclerosis that cause life-threatening ischemic events at late stages of the disease. The miRNAs are a novel class of small, non-coding RNAs that play a significant role in both inflammatory and cardiovascular diseases. The miRNAs are known to be present in platelets and exert important regulatory functions. Here we systematically examine the genes that are regulated by platelet miRNAs (miRNA-223,miRNA-126,miRNA-21, miRNA-24 and miRNA-197) and the association with cardiovascular disease risks. Platelet-secreted miRNAs could be novel biomarkers associated with cardiovascular diseases.

Mediated protective effect of electroacupuncture pretreatment by miR-214 on myocardial ischemia/reperfusion injury

Background

Electroacupuncture pretreatment plays a protective role in myocardial ischemia/reperfusion (I/R) injury and microRNAs (miRNAs) could act on various facets of cardiac function. However, the role of miRNAs in the cardioprotection by electroacupuncture pretreatment on myocardial I/R injury remains unknown. The purpose of the study was to examine whether miR-214 was involved in cardioprotection by electroacupuncture.

Methods

Using rat myocardial I/R model, we examined the role of electroacupuncture pretreatment in myocardial I/R injury and analyzed the changes in the expression of miR-214. In addition, I/R was simulated in vitro by performing oxygen-glucose deprivation (OGD) on H9c2 cell cultures, and the effect of electroacupuncture pretreatment on I/R injury as well as expressional level of miR-214 were examined in vitro. Furthermore, the miR-214 mimic was transfected into OGD-treated H9c2 cells, we analyzed the cell apoptosis, lactate dehydrogenase (LDH) and creatine kinase (CK) activities, intracellular free Ca²⁺ concentration ([Ca²⁺]i) as well as the relative protein levels of sodium/calcium exchanger 1(NCX1), BCL2-like 11 (BIM), calmodulin-dependent protein kinase IIδ (CaMKIIδ) and Cyclophilin D (CypD).

Results

The in vivo results revealed that compared with the I/R group, the electroacupuncture pretreatment group showed significant decreased myocardial infarct size, as well as the increased indices of the cardiac function, including heart rate, mean arterial pressure, left ventricular systolic pressure and maximal rate for left ventricular pressure rising and declining (±dp/dt max). In addition, electroacupuncture pretreatment could inhibit the elevation of LDH and CK activities induced by I/R injury. The quantitative PCR (qPCR) results demonstrated electroacupuncture pretreatment could provide cardioprotection against myocardial I/R injury in rats with miR-214 up-regulation. In the meanwhile, in vitro, electroacupuncture pretreatment protected H9c2 cells from OGD-induced injury. Transfection of miR-214 mimic showed protective effects on OGD-induced injury to H9c2 cells by reducing apoptosis, decreasing LDH and CK activities, rescuing the OGD-induced Ca²⁺ and down-regulating elevated protein levels of NCX1, BIM, CaMKIIδ and CypD.

Conclusions

Our findings firstly demonstrated that electroacupuncture pretreatment promotes the expression of miR-214 in myocardial I/R injury and miR-214 contributes to the protective effect of electroacupuncture on myocardial I/R injury.

Attenuation of microRNA-16 derepresses the cyclins D1, D2 and E1 to provoke cardiomyocyte hypertrophy

Cyclins/retinoblastoma protein (pRb) pathway participates in cardiomyocyte hypertrophy. MicroRNAs (miRNAs), the endogenous small non-coding RNAs, were recognized to play significant roles in cardiac hypertrophy. But, it remains unknown whether cyclin/Rb pathway is modulated by miRNAs during cardiac hypertrophy. This study investigates the potential role of microRNA-16 (miR-16) in modulating cyclin/Rb pathway during cardiomyocyte hypertrophy. An animal model of hypertrophy was established in a rat with abdominal aortic constriction (AAC), and in a mouse with transverse aortic constriction (TAC) and in a mouse with subcutaneous injection of phenylephrine (PE) respectively. In addition, a cell model of hypertrophy was also achieved based on PE-promoted neonatal rat ventricular cardiomyocyte and based on Ang-II-induced neonatal mouse ventricular cardiomyocyte respectively. We demonstrated that miR-16 expression was markedly decreased in hypertrophic myocardium and hypertrophic cardiomyocytes in rats and mice. Overexpression of miR-16 suppressed rat cardiac hypertrophy and hypertrophic phenotype of cultured cardiomyocytes, and inhibition of miR-16 induced a hypertrophic phenotype in cardiomyocytes. Expressions of cyclins D1, D2 and E1, and the phosphorylated pRb were increased in hypertrophic myocardium and hypertrophic cardiomyocytes, but could be reversed by enforced expression of miR-16. Cyclins D1, D2 and E1, not pRb, were further validated to be modulated post-transcriptionally by miR-16. In addition, the signal transducer and activator of transcription-3 and c-Myc were activated during myocardial hypertrophy, and inhibitions of them prevented miR-16 attenuation. Therefore, attenuation of miR-16 provoke cardiomyocyte hypertrophy via derepressing the cyclins D1, D2 and E1, and activating cyclin/Rb pathway, revealing that miR-16 might be a target to manage cardiac hypertrophy.

Noncoding RNAs as epigenetic mediators of skeletal muscle regeneration

Skeletal muscle regeneration is a well-characterized biological process in which resident adult stem cells must undertake a series of cell-fate decisions to ensure efficient repair of the damaged muscle fibers while also maintaining the stem cell niche. Satellite cells, the main stem cell contributing to the repaired muscle fiber, are maintained in a quiescent state in healthy muscle. Upon injury, the satellite cells become activated, and proliferate to expand the muscle progenitor cell population before returning to the quiescent state or differentiating to become myofibers. Importantly, the determination of cell fate is controlled at the epigenetic level in response to environmental cues. In this review, we discuss our current understanding of the role played by noncoding RNAs (both miRNAs and long-noncoding RNAs) in the epigenetic control of muscle regeneration.

microRNAs and Cardiovascular Remodeling

Heart failure (HF) is associated with significant morbidity and mortality attributable largely to structural changes in the heart and with associated cardiac dysfunction. Remodeling is defined as alteration of the mass, dimensions, or shape of the heart (termed cardiac or ventricular remodeling) and vessels (vascular remodeling) in response to hemodynamic load and/or cardiovascular injury in association with neurohormonal activation. Remodeling may be described as physiologic or pathologic; alternatively, remodeling may be classified as adaptive or maladaptive. The importance of remodeling as a pathogenic mechanism has been controversial because factors leading to remodeling as well as the remodeling itself may be major determinants of patients' prognosis. The basic mechanisms of cardiovascular remodeling, and especially the roles of microRNAs in HF progression and vascular diseases, will be reviewed here.

Differential expression of microRNAs in ischemic heart disease

Recent studies provide evidence that ischemic preconditioning (IP) and ischemia/reperfusion (IR) injury lead to altered expression of microRNAs (miRNAs) that affect the survival and recovery of cardiomyocytes. These endogenous ∼22-nucleotide noncoding RNAs negatively regulate gene expression via degradation and translational inhibition of their target mRNAs. miRNAs are involved in differentiation, proliferation, electrical conduction, angiogenesis and apoptosis. These pathways can lead to physiological and pathological adaptations. This review intends to explore several facets of miRNA expression and the underlying mechanisms involved in IR injury, as well as IP as a cardioprotective strategy. In addition, we will investigate miRNA interaction with the renin-angiotensin system and the potential use of miRNAs in developing sensitive biomarkers for cardiovascular disease.

MicroRNA-1 in Cardiac Diseases and Cancers

MicroRNAs (miRs) are endogenous ≈22-nt non-coding RNAs that participate in the regulation of gene expression at post-transcriptional level. MiR-1 is one of the muscle-specific miRs, aberrant expression of miR-1 plays important roles in many physiological and pathological processes. In this review, we focus on the recent studies about miR-1 in cardiac diseases and cancers. The findings indicate that miR-1 may be a novel, important biomarker, and a potential therapeutic target in cardiac diseases and cancers.

RNA expression profiling of human iPSC-derived cardiomyocytes in a cardiac hypertrophy model

Cardiac hypertrophy is an independent risk factor for cardiovascular disease and heart failure. There is increasing evidence that microRNAs (miRNAs) play an important role in the regulation of messenger RNA (mRNA) and the pathogenesis of various cardiovascular diseases. However, the ability to comprehensively study cardiac hypertrophy on a gene regulatory level is impacted by the limited availability of human cardiomyocytes. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) offer the opportunity for disease modeling. Here we utilize a previously established invitro model of cardiac hypertrophy to interrogate the regulatory mechanism associated with the cardiac disease process. We perform miRNA sequencing and mRNA expression analysis on endothelin 1 (ET-1) stimulated hiPSC-CMs to describe associated RNA expression profiles. MicroRNA sequencing revealed over 250 known and 34 predicted novel miRNAs to be differentially expressed between ET-1 stimulated and unstimulated control hiPSC-CMs. Messenger RNA expression analysis identified 731 probe sets with significant differential expression. Computational target prediction on significant differentially expressed miRNAs and mRNAs identified nearly 2000 target pairs. A principal component analysis approach comparing the invitro data with human myocardial biopsies detected overlapping expression changes between the invitro samples and myocardial biopsies with Left Ventricular Hypertrophy. These results provide further insights into the complex RNA regulatory mechanism associated with cardiac hypertrophy.

miRNAs and lncRNAs in vascular injury and remodeling

Vascular injury, remodeling, as well as angiogenesis, are the leading causes of coronary or cerebrovascular disease. The blood vessel functional imbalance trends to induce atherosclerosis, hypertension, and pulmonary arterial hypertension. As several genes have been identified to be dynamically regulated during vascular injury and remodeling, it is becoming widely accepted that several types of non-coding RNA, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are involved in regulating the endothelial cell and vascular smooth muscle cell (VSMC) behaviors. Here, we review the progress of the extant studies on mechanistic, clinical and diagnostic implications of miRNAs and lncRNAs in vascular injury and remodeling, as well as angiogenesis, emphasizing the important roles of miRNAs and lncRNAs in vascular diseases. Furthermore, we introduce the interaction between miRNAs and lncRNAs, and highlight the mechanism through which lncRNAs are regulating the miRNA function. We envisage that continuous in-depth research of non-coding RNAs in vascular disease will have significant implications for the treatment of coronary or cerebrovascular diseases.

Relationship between downregulation of miRNAs and increase of oxidative stress in the development of diabetic cardiac dysfunction: junctin as a target protein of miR-1

Oxidative stress is involved in the etiology of diabetes-induced cardiac dysfunction while microRNAs (miRNAs) are known as regulators for genes involved in cardiac remodeling. However, a functional link between miRNAs and diabetes-induced cardiac dysfunction remains to be investigated. Here, we aimed to identify whether the expression levels of miRNAs are associated with oxidative stress/diabetic heart and if proteins responsible from contractile activity during diabetes might be directly modulated by miRNAs. Diabetic cardiomyopathy developed with streptozotocin, is characterized with marked changes in sarcomere and mitochondria, depressed left ventricular developed pressure, and a massive oxidative stress that is particularly evident in the heart. miRNA profiling was performed in freshly isolated left ventricular cells from diabetic rats. Using microarray analysis, we identified marked changes in the expression of 43 miRNAs (37 of them were downregulated while 6 miRNAs were upregulated) out of examined total of 351 miRNAs. Among them, 6 miRNAs were further validated by real-time PCR. The expression levels of miR-1, miR-499, miR-133a, and miR-133b were markedly depressed in the diabetic cardiomyocytes while miR-21 level increased and miR-16 level was unchanged. Notably, normalization of cardiac function and oxidant/antioxidant level after N-acetylcysteine (NAC)-treatment of diabetic rats resulted with a significant restoration in the expression levels of miR-499, miR-1, miR-133a, and miR-133b in the myocardium. Since changes in the level of muscle-specific miR-1 has been implicated in cardiac diseases and its specific molecular targets involved in its action, in part, associated with oxidative stress are limited, we first examined the protein levels of some SR-associated proteins such as junctin and triadin. Junctin but not triadin is markedly overexpressed in diabetic cardiomyocytes while its level was normalized in NAC-treated diabetics. Luciferase reporter assay showed that junctin is targetted by miR-1. Taken together, our data demonstrates that intervention with an antioxidant treatment for 4-week leads to significant cardioprotection against diabetes-induced injury, controlling oxidant/antioxidant level, which may directly control the levels of some miRNAs including miR-1 and its target protein junctin, which is involved in the development of diabetic cardiomyopathy.

Cardiac hypertrophy and dysfunction induced by overexpression of miR-214 in vivo

BACKGROUND

An increasing number of studies have demonstrated the critical role of microRNAs in the pathogenesis of cardiac hypertrophy and dysfunction. This study evaluated whether miR-214 plays a pivotal role in the development of cardiac hypertrophy and heart failure.

METHODS

In human tissues, miR-214 overexpression was determined to promote cardiac hypertrophy. We predicted miR-214 direct target by bioinformatics database and verifed it using luciferase dual reporting system. We silenced miR-214 using a specific antagomir in a pressure-overload mouse model of heart failure.

RESULTS

Analysis of transgenic mice with cardiomyocyte-specific overexpression of miR-214 indicated that their hearts were 21% heavier than wild-type hearts and expressed several biochemical and functional markers consistent with dilated cardiomyopathy. These findings include enlarged left ventricular internal diameters, wall thinning, reduced ejection fraction, fractional shortening, and an increased fetal gene expression. The enhancer of zeste homolog 2 (EZH2) was confirmed as a direct target of miR-214 in cardiomyocytes. In vivo silencing of miR-214 using a specific antagomir rescued cardiac EZH2 expression and prevented cardiac hypertrophy and dysfunction.

CONCLUSIONS

Taken together, these results suggest that miR-214 may induce pathologic cardiac hypertrophy in part by reducing EZH2 messenger RNA levels. MiR-214 may therefore be a potential therapeutic target for treating certain cardiac disease states.

Novel insights into miRNA in lung and heart inflammatory diseases

MicroRNAs (miRNAs) are noncoding regulatory sequences that govern posttranscriptional inhibition of genes through binding mainly at regulatory regions. The regulatory mechanism of miRNAs are influenced by complex crosstalk among single nucleotide polymorphisms (SNPs) within miRNA seed region and epigenetic modifications. Circulating miRNAs exhibit potential characteristics as stable biomarker. Functionally, miRNAs are involved in basic regulatory mechanisms of cells including inflammation. Thus, miRNA dysregulation, resulting in aberrant expression of a gene, is suggested to play an important role in disease susceptibility. This review focuses on the role of miRNA as diagnostic marker in pathogenesis of lung inflammatory diseases and in cardiac remodelling events during inflammation. From recent reports, In this context, the information about the models in which miRNAs expression were investigated including types of biological samples, as well as on the methods for miRNA validation and prediction/definition of their gene targets are emphasized in the review. Besides disease pathogenesis, promising role of miRNAs in early disease diagnosis and prognostication is also discussed. However, some miRNAs are also indicated with protective role. Thus, identifications and usage of such potential miRNAs as well as disruption of disease susceptible miRNAs using antagonists, antagomirs, are imperative and may provide a novel therapeutic approach towards combating the disease progression.

Establishment of lipofection for studying miRNA function in human adipocytes

miRNA dysregulation has recently been linked to human obesity and its related complications such as type 2 diabetes. In order to study miRNA function in human adipocytes, we aimed for the modulation of mature miRNA concentration in these cells. Adipocytes, however, tend to be resistant to transfection and there is often a need to resort to viral transduction or electroporation. Our objective therefore was to identify an efficient, non-viral transfection reagent capable of delivering small RNAs into these cells. To achieve this, we compared the efficiencies of three transfection agents, Lipofectamine 2000, ScreenFect A and BPEI 1.2 k in delivering fluorescent-labelled siRNA into human Simpson-Golabi-Behmel syndrome (SGBS) preadipocytes and adipocytes. Downregulation of a specific target gene in response to miRNA mimic overexpression was assayed in SGBS cells and also in ex vivo differentiated primary human adipocytes. Our results demonstrated that while all three transfection agents were able to internalize the oligos, only lipofection resulted in the efficient downregulation of a specific target gene both in SGBS cells and in primary human adipocytes. Lipofectamine 2000 outperformed ScreenFect A in preadipocytes, but in adipocytes the two reagents gave comparable results making ScreenFect A a notable new alternative for the gold standard Lipofectamine 2000.

Transplantation of human menstrual blood progenitor cells improves hyperglycemia by promoting endogenous progenitor differentiation in type 1 diabetic mice

Recently, a unique population of progenitor cells was isolated from human menstrual blood. The human menstrual blood progenitor cells (MBPCs) possess many advantages, such as the noninvasive acquisition procedure, broad multipotency, a higher proliferative rate, and low immunogenicity, and have attracted extensive attention in regenerative medicine. Preclinical studies to test the safety and efficacy of MBPCs have been underway in several animal models. However, relevant studies in type 1 diabetes mellitus (T1DM) have not yet been proceeded. Herein, we studied the therapeutic effect of MBPCs and the mechanism of β-cell regeneration after MBPC transplantation in the T1DM model. Intravenous injection of MBPCs can reverse hyperglycemia and weight loss, prolong lifespan, and increase insulin production in diabetic mice. Histological and immunohistochemistry analyses indicated that T1DM mice with MBPC transplantation recovered islet structures and increased the β-cell number. We further analyzed in vivo distribution of MBPCs and discovered that a majority of MBPCs migrated into damaged pancreas and located at the islet, duct, and exocrine tissue. MBPCs did not differentiate into insulin-producing cells, but enhanced neurogenin3 (ngn3) expression, which represented endocrine progenitors that were activated. Ngn3(+) cells were not only in the ductal epithelium, but also in the islet and exocrine tissue. We analyzed a series of genes associated with the embryonic mode of β-cell development by real-time polymerase chain reaction and the results showed that the levels of those gene expressions all increased after cell transplantation. According to the results, we concluded that MBPCs stimulated β-cell regeneration through promoting differentiation of endogenous progenitor cells.

In vitro and in vivo direct monitoring of miRNA-22 expression in isoproterenol-induced cardiac hypertrophy by bioluminescence imaging

PURPOSE

Growing evidence suggests that microRNAs (miRNAs) play key roles in cardiac hypertrophy. To measure the expression of endogenous miRNAs is very conducive to understanding the importance of miRNAs in cardiac hypertrophy. However, current methods to monitor endogenous miRNA levels, such as Northern blotting, quantitative real-time polymerase chain reaction (qRT-PCR), and microarrays cannot provide real-time information on miRNA biogenesis in vivo.

METHODS

We constructed a miRNA reporter imaging system to monitor miR-22 expression in isoproterenol-induced cardiac hypertrophy repetitively and noninvasively. There were three copies of the antisense of miR-22 (3×PT_miR-22) cloned into the 3' untranslated region (UTR) of the Gaussia luciferase (Gluc) reporter genes under the control of the cytomegalovirus (CMV) promoter in this miRNA reporter system (CMV/Gluc/3×PT_miR-22). CMV/firefly luciferase (Fluc) was used as a positive control for imaging of miR-22 expression. Meanwhile, quantifications of miR-22 in cardiomyocyte hypertrophy and in mouse cardiac hypertrophy induced by isoproterenol stimulation were measured by qRT-PCR. Furthermore, we used this miRNA reporter imaging system to appraise the antihypertrophic effect of antagomir-22 in vitro and in vivo.

RESULTS

The bioluminescence signals of the CMV/Gluc/3×PT_miR-22 were gradually decreased with prolongation of isoproterenol intervention in vitro and in vivo. Overexpression of miR-22 was observed in cardiac hypertrophy, and markedly administration of antagomir-22 could reverse the upregulation of miR-22 and its prohypertrophic effects. Furthermore, knockdown of miR-22 by antagomir-22 could markedly reverse the repressed Gluc activities in vitro and in vivo. However, the Fluc activity of CMV/Fluc was not affected with isoproterenol treatment.

CONCLUSION

This study elucidates the feasibility of using our constructed miRNA reporter imaging system to monitor the location and magnitude of expression levels of miR-22 in cardiac hypertrophy in vitro and in vivo.

Roles of microRNAs in pressure overload- and ischemia-related myocardial remodeling

Cardiac remodeling, a term that spans maladaptation at the molecular, cellular, tissue and organ levels, is the key pathophysiological process that leads to heart failure (HF). In clinic, pressure overload and ischemia are the two most common reasons to induce cardiac remodeling and HF, which includes but is not limited to cardiac hypertrophy, fibrosis, and cardiomyocyte apoptosis. MicroRNAs (miRNAs) are endogenous, single-stranded, short non-coding RNAs. By imperfectly binding to the 3' untranslated region (UTR) of messenger RNAs (mRNAs), miRNAs are able to suppress target gene expression by promoting degradation or by inhibiting translation of the target mRNAs, thus playing an important role in a wide range of biologic processes. Growing evidence has indicated that miRNAs are aberrantly expressed in the cardiovascular system under experimental and clinical conditions with cardiac remodeling and HF. Clinically there is increasing evidence that miRNAs can act as diagnostic biomarker and even represent a novel therapeutic target in several cardiovascular disorders. This review provides an overview of several miRNAs' impacts in pressure-overload and ischemia-induced cardiac remodeling and HF.

Non-coding RNAs: the "dark matter" of cardiovascular pathophysiology

Large-scale analyses of mammalian transcriptomes have identified a significant number of different RNA molecules that are not translated into protein. In fact, the use of new sequencing technologies has identified that most of the genome is transcribed, producing a heterogeneous population of RNAs which do not encode for proteins (ncRNAs). Emerging data suggest that these transcripts influence the development of cardiovascular disease. The best characterized non-coding RNA family is represented by short highly conserved RNA molecules, termed microRNAs (miRNAs), which mediate a process of mRNA silencing through transcript degradation or translational repression. These microRNAs (miRNAs) are expressed in cardiovascular tissues and play key roles in many cardiovascular pathologies, such as coronary artery disease (CAD) and heart failure (HF). Potential links between other ncRNAs, like long non-coding RNA, and cardiovascular disease are intriguing but the functions of these transcripts are largely unknown. Thus, the functional characterization of ncRNAs is essential to improve the overall understanding of cellular processes involved in cardiovascular diseases in order to define new therapeutic strategies. This review outlines the current knowledge of the different ncRNA classes and summarizes their role in cardiovascular development and disease.

Breaking limitations of complex culture media: functional non-viral miRNA delivery into pharmaceutical production cell lines

MicroRNAs (miRNAs) are promising targets for cell engineering through modulation of crucial cellular pathways. An effective introduction of miRNAs into the cell is a prerequisite to reliably study microRNA function. Previously, non-viral delivery of nucleic acids has been demonstrated to be cell type as well as culture medium dependent. Due to their importance for biopharmaceutical research and manufacturing, Chinese hamster ovary (CHO) and Cevec's Amniocyte Production (CAP) cells were used as host cell lines to investigate transfection reagents with respect to successful delivery of small non-coding RNAs (ncRNAs) and their ability to allow for biological activity of miRNAs and small interfering RNAs (siRNAs) within the cell. In the present study, we screened numerous transfection reagents for their suitability to successfully deliver miRNA mimics into CHO DG44 and CAP cells. Our investigation revealed that the determination of transfection efficiency for a given transfection reagent alone is not sufficient to draw conclusions about its ability to maintain the functionality of the miRNA. We could show that independent from high transfection rates observed for several reagents only one was suitable for efficient introduction of functional miRNA mimics into cells cultured in complex protein production media. We provide evidence for the functionality of transferred ncRNAs by demonstrating siRNA-mediated changes in protein levels and cellular phenotype as well as decreased twinfilin-1 (twf-1) transcript levels by its upstream miR-1 regulator. Furthermore, the process could be shown to be scalable which has important implications for biotechnological applications.

Pivotal role of microRNAs in cardiac physiology and heart failure

Cardiac hypertrophy is a hallmark of heart failure (HF), a highly prevalent, debilitating and deadly condition in Western countries. Pronounced changes in molecular pathways governing cardiac physiology underlie hypertrophy and progression to HF. MicroRNAs, small nucleotide sequences that coordinate gene expression, may have a central role in orchestrating these changes since the hypertrophic and HF myocardium clearly shows disturbed microRNA profiles. Experimental interventions targeting miR disturbances have been shown beneficial in animal models of cardiac hypertrophy and HF. This short review discusses exciting potential diagnostic and therapeutic applications of microRNAs to cardiac hypertrophy and HF, highlighting the underlying molecular pathways.

miR-27b represses migration of mouse MSCs to burned margins and prolongs wound repair through silencing SDF-1a

Background

Interactions between stromal cell-derived factor-1α (SDF-1α) and its cognate receptor CXCR4 are crucial for the recruitment of mesenchymal stem cells (MSCs) from bone marrow (BM) reservoirs to damaged tissues for repair during alarm situations. MicroRNAs are differentially expressed in stem cell niches, suggesting a specialized role in stem cell regulation. Here, we gain insight into the molecular mechanisms involved in regulating SDF-1α.

Methods

MSCs from green fluorescent protein transgenic male mice were transfused to irradiated recipient female C57BL/6 mice, and skin burn model of bone marrow-chimeric mice were constructed. Six miRNAs with differential expression in burned murine skin tissue compared to normal skin tissue were identified using microarrays and bioinformatics. The expression of miR-27b and SDF-1α was examined in burned murine skin tissue using quantitative real-time PCR (qPCR) and immunohistochemistry (IHC), enzyme-linked immunosorbent assay (ELISA). The Correlation of miR-27b and SDF-1α expression was analyzed by Pearson analysis Correlation. miRNAs suppressed SDF-1α protein expression by binding directly to its 3′UTR using western blot and luciferase reporter assay. The importance of miRNAs in MSCs chemotaxis was further estimated by decreasing SDF-1α in vivo and in vitro.

Results

miR-23a, miR-27a and miR-27b expression was significantly lower in the burned skin than in the normal skin (p<0.05). We also found that several miRNAs suppressed SDF-1α protein expression, while just miR-27a and miR-27b directly bound to the SDF-1α 3′UTR. Moreover, the forced over-expression of miR-27a and miR-27b significantly reduced the directional migration of mMSCs in vitro. However, only miR-27b in burn wound margins significantly inhibited the mobilization of MSCs to the epidermis.

Conclusion

miR-27b may be a unique signature of the stem cell niche in burned mouse skin and can suppress the directional migration of mMSCs by targeting SDF-1α by binding directly to its 3′UTR.

Distinctive profile of IsomiR expression and novel microRNAs in rat heart left ventricle

MicroRNAs (miRNAs) are single-stranded non-coding RNAs that negatively regulate target gene expression through mRNA cleavage or translational repression. There is mounting evidence that they play critical roles in heart disease. The expression of known miRNAs in the heart has been studied at length by microarray and quantitative PCR but it is becoming evident that microRNA isoforms (isomiRs) are potentially physiologically important. It is well known that left ventricular (patho)physiology is influenced by transmural heterogeneity of cardiomyocyte phenotype, and this likely reflects underlying heterogeneity of gene expression. Given the significant role of miRNAs in regulating gene expression, knowledge of how the miRNA profile varies across the ventricular wall will be crucial to better understand the mechanisms governing transmural physiological heterogeneity. To determinine miRNA/isomiR expression profiles in the rat heart we investigated tissue from different locations across the left ventricular wall using deep sequencing. We detected significant quantities of 145 known rat miRNAs and 68 potential novel orthologs of known miRNAs, in mature, mature* and isomiR formation. Many isomiRs were detected at a higher frequency than their canonical sequence in miRBase and have different predicted targets. The most common miR-133a isomiR was more effective at targeting a construct containing a sequence from the gelsolin gene than was canonical miR-133a, as determined by dual-fluorescence assay. We identified a novel rat miR-1 homolog from a second miR-1 gene; and a novel rat miRNA similar to miR-676. We also cloned and sequenced the rat miR-486 gene which is not in miRBase (v18). Signalling pathways predicted to be targeted by the most highly detected miRNAs include Ubiquitin-mediated Proteolysis, Mitogen-Activated Protein Kinase, Regulation of Actin Cytoskeleton, Wnt signalling, Calcium Signalling, Gap junctions and Arrhythmogenic Right Ventricular Cardiomyopathy. Most miRNAs are not expressed in a gradient across the ventricular wall, with exceptions including miR-10b, miR-21, miR-99b and miR-486.

miR-30a downregulation aggravates pressure overload-induced cardiomyocyte hypertrophy

miRNAs play an important role in the pathogenesis of cardiac hypertrophy and dysfunction. However, little is known about how miR-30a regulates cardiomyocyte hypertrophy. In the study, Male C57BL/6 mice were subjected to thoracic aortic constriction, and hearts were harvested at 3 weeks. We assayed miR-30a expression level by real-time PCR and defined the molecular mechanisms of miR-30a-mediated cardiomyocyte hypertrophy. We found that myocardial expression of miR-30a was decreased in mouse models of hypertrophy and in H9c2 cells treated with phenylephrine. MiR-30a inhibition markedly increased mRNA expression of cardiac hypertrophy markers such as atrial natriuretic factor and brain natriuretic peptide in H9c2, and cell size was increased after miR-30a inhibitor treatment. Downregulated miR-30a activated autophagy by inhibiting beclin-1 expression in H9c2 cell. More important, autophagy inhibition suppressed miR-30a inhibitor-induced cardiomyocyte hypertrophy. Together, our data demonstrated that downregulated miR-30a aggravates pressure overload-induced cardiomyocyte hypertrophy by activating autophagy, thus offering a new target for the therapy of cardiomyocyte hypertrophy.

Therapeutic cardiac-targeted delivery of miR-1 reverses pressure overload-induced cardiac hypertrophy and attenuates pathological remodeling

Background

MicroRNAs (miRNAs) play a key role in the development of heart failure, and recent studies have shown that the muscle‐specific miR‐1 is a key regulator of cardiac hypertrophy. We tested the hypothesis that chronic restoration of miR‐1 gene expression in vivo will regress hypertrophy and protect against adverse cardiac remodeling induced by pressure overload.

Methods and Results

Cardiac hypertrophy was induced by left ventricular pressure overload in male Sprague‐Dawley rats subjected to ascending aortic stenosis. When the hypertrophy was established at 2 weeks after surgery, the animals were randomized to receive either an adeno‐associated virus expressing miR‐1 (AAV9.miR‐1) or green fluorescent protein (GFP) as control (AAV9.GFP) via a single‐bolus tail‐vein injection. Administration of miR‐1 regressed cardiac hypertrophy (left ventricular posterior wall thickness,; 2.32±0.08 versus 2.75±0.07 mm, P<0.001) and (left ventricular septum wall thickness, 2.23±0.06 versus 2.54±0.10 mm, P<0.05) and halted the disease progression compared with control‐treated animals, as assessed by echocardiography (fractional shortening, 37.60±5.01% versus 70.68±2.93%, P<0.05) and hemodynamic analyses (end‐systolic pressure volume relationship/effective arterial elastance, 1.87±0.46 versus 0.96±0.38, P<0.05) after 7 weeks of treatment. Additionally, miR‐1 replacement therapy lead to a marked reduction of myocardial fibrosis, an improvement in calcium handling, inhibition of apoptosis, and inactivation of the mitogen‐activated protein kinase signaling pathways, suggesting a favorable effect on preventing the maladaptive ventricular remodeling. We also identified and validated a novel bona fide target of miR‐1, Fibullin‐2 (Fbln2), a secreted protein implicated in extracellular matrix remodeling.

Conclusions

Taken together, our findings suggest that restoration of miR‐1 gene expression is a potential novel therapeutic strategy to reverse pressure‐induced cardiac hypertrophy and prevent maladaptive cardiac remodeling.

A cardiac-enriched microRNA, miR-378, blocks cardiac hypertrophy by targeting Ras signaling

Understanding the regulation of cardiomyocyte growth is crucial for the management of adverse ventricular remodeling and heart failure. MicroRNA-378 (miR-378) is a newly described member of the cardiac-enriched miRNAs, which is expressed only in cardiac myocytes and not in cardiac fibroblasts. We have previously shown that miR-378 regulates cardiac growth during the postnatal period by direct targeting of IGF1R (Knezevic, I., Patel, A., Sundaresan, N. R., Gupta, M. P., Solaro, R. J., Nagalingam, R. S., and Gupta, M. (2012) J. Biol. Chem. 287, 12913-12926). Here, we report that miR-378 is an endogenous negative regulator of cardiac hypertrophy, and its levels are down-regulated during hypertrophic growth of the heart and during heart failure. In primary cultures of cardiomyocytes, overexpression of miR-378 blocked phenylephrine (PE)-stimulated Ras activity and also prevented activation of two major growth-promoting signaling pathways, PI3K-AKT and Raf1-MEK1-ERK1/2, acting downstream of Ras signaling. Overexpression of miR-378 suppressed PE-induced phosphorylation of S6 ribosomal kinase, pERK1/2, pAKT, pGSK-3β, and nuclear accumulation of NFAT. There was also suppression of the fetal gene program that was induced by PE. Experiments carried out to delineate the mechanism behind the suppression of Ras, led us to identify Grb2, an upstream component of Ras signaling, as a bona fide direct target of miR-378-mediated regulation. Deficiency of miR-378 alone was sufficient to induce fetal gene expression, which was prevented by knocking down Grb2 expression and blocking Ras activation, thus suggesting that miR-378 interferes with Ras activation by targeting Grb2. Our study demonstrates that miR-378 is an endogenous negative regulator of Ras signaling and cardiac hypertrophy and its deficiency contributes to the development of cardiac hypertrophy.

Revisiting the timing hypothesis: biomarkers that define the therapeutic window of estrogen for stroke

Significantly extended life expectancy coupled with contemporary sedentary lifestyles and poor nutrition has created a global epidemic of cardiovascular disease and stroke. For women, this issue is complicated by the discrepant outcomes of hormone therapy (HT) for stroke incidence and severity as well as the therapeutic complications for stroke associated with advancing age. Here we propose that the impact of estrogen therapy cannot be considered in isolation, but should include age-related changes in endocrine, immune, and nucleic acid mediators that collaborate with estrogen to produce neuroprotective effects commonly seen in younger, healthier demographics. Due to their role as modulators of ischemic cell death, the post-stroke inflammatory response, and neuronal survival and regeneration, this review proposes that Insulin-like Growth Factor (IGF)-1, Vitamin D, and discrete members of the family of non-coding RNA peptides called microRNAs (miRNAs) may be crucial biochemical markers that help determine the neuroprotective "window" of HT. Specifically, IGF-1 confers neuroprotection in concert with, and independently of, estrogen and failure of the insulin/IGF-1 axis is associated with metabolic disturbances that increase the risk for stroke. Vitamin D and miRNAs regulate and complement IGF-1 mediated function and neuroprotective efficacy via modulation of IGF-1 availability and neural stem cell and immune cell proliferation, differentiation and secretions. Together, age-related decline of these factors differentially affects stroke risk, severity, and outcome, and may provide a novel therapeutic adjunct to traditional HT practices.

Mutual antagonism between IP(3)RII and miRNA-133a regulates calcium signals and cardiac hypertrophy

Inositol 1,4,5'-triphosphate receptor II (IP(3)RII) calcium channel expression is increased in both hypertrophic failing human myocardium and experimentally induced models of the disease. The ectopic calcium released from these receptors induces pro-hypertrophic gene expression and may promote arrhythmias. Here, we show that IP(3)RII expression was constitutively restrained by the muscle-specific miRNA, miR-133a. During the hypertrophic response to pressure overload or neurohormonal stimuli, miR-133a down-regulation permitted IP(3)RII levels to increase, instigating pro-hypertrophic calcium signaling and concomitant pathological remodeling. Using a combination of in vivo and in vitro approaches, we demonstrated that IP(3)-induced calcium release (IICR) initiated the hypertrophy-associated decrease in miR-133a. In this manner, hypertrophic stimuli that engage IICR set a feed-forward mechanism in motion whereby IICR decreased miR-133a expression, further augmenting IP(3)RII levels and therefore pro-hypertrophic calcium release. Consequently, IICR can be considered as both an initiating event and a driving force for pathological remodeling.

MicroRNAs Are Involved in End-Organ Damage During Hypertension

Even in the new millennium, arterial hypertension remains a serious condition, with considerable morbidity and mortality worldwide. Crucial in managing the disease is not only lowering arterial blood pressure but also preventing or treating the typical end-organ damage caused by long-lasting and inadequately treated hypertension. In the past decade, it has been shown that microRNAs (miRs) are involved in several hypertension-related pathologies, such as cardiac hypertrophy and fibrosis, hypertensive heart failure, renal fibrosis, kidney failure, and, to a lesser extent, eye disease and hemorrhagic stroke. Whereas others extensively reviewed the role of miRs in atherosclerosis and vascular disease, this review focuses on their role in target organ damage during arterial hypertension. We emphasize the involvement of miRs in pathological end-organ remodeling processes and try to demonstrate some common miR signatures in distinct end organs. Hence, we aimed to provide proof of arterial hypertension being a systemic disease, similar to diabetes mellitus or metabolic syndrome. Furthermore, miRs that act on one particular process in different end organs are interesting therapeutic targets. Some future perspectives in miR research are highlighted with respect to novel therapeutic strategies in the cardiovascular field.

Hypoxia induces downregulation of soluble guanylyl cyclase β1 by miR-34c-5p

Soluble guanylyl cyclase (sGC) is the principal receptor for nitric oxide (NO) and crucial for the control of various physiological functions. The β1 subunit of sGC is obligatory for the biological stability and activity of the sGC heterodimer. MicroRNAs (miRNAs) are important regulators of gene expression and exert great influences on diverse biological activities. The aim of the present study was to determine whether or not the expression of sGCβ1 is specifically regulated by miRNAs. We report that miR-34c-5p directly targets sGCβ1 under hypoxia. Bioinformatics analysis of the sGCβ1 3'-untranslated region (3'-UTR) revealed a putative binding site for miR-34b-5p and miR-34c-5p, but only miR-34c-5p inhibited luciferase activity through interaction with sGCβ1 3'-UTR in HEK293T cells. Site-directed mutagenesis of the putative miR-34c-5p binding site abolished the negative regulation of luciferase expression. Overexpression of miR-34c-5p repressed the expression of sGCβ1 in stable cell lines, which was reversed by miR-34c-5p-specific sponge. Inoculation of mouse lung tissues in vitro with lentivirus bearing miR-34c-5p significantly decreased both the expression of sGCβ1 and NO-stimulated sGC activity, which was also rescued by miR-34c-5p-specific sponge. Furthermore, we identified the putative Sp1-binding site in the promoter region of miR-34c-5p. Luciferase reporter constructs revealed that Sp1 directly binds to the wild-type promoter of miR-34c-5p, which was confirmed by chromatin immunoprecipitation. In summary, these findings reveal that miR-34c-5p directly regulates sGCβ1 expression, and they identify the key transcription factor Sp1 that governs miR-34c-5p expression during hypoxia.

Global microRNA profiling of the mouse ventricles during development of severe hypertrophic cardiomyopathy and heart failure

MicroRNAs (miRNAs) regulate post-transcriptional gene expression during development and disease. We have determined the miRNA expression levels of early- and end-stage hypertrophic cardiomyopathy (HCM) in a severe, transgenic mouse model of the disease. Five miRNAs were differentially expressed at an early stage of HCM development. Time-course analysis revealed that decreased expression of miR-1 and miR-133a commences at a pre-disease stage, and precedes upregulation of target genes causal of cardiac hypertrophy and extracellular matrix remodelling, suggesting a role for miR-1 and miR-133a in early disease development. At end-stage HCM, 16 miRNA are dysregulated to form an expression profile resembling that of other forms of cardiac hypertrophy, suggesting common responses. Analysis of the mRNA transcriptome revealed that miRNAs potentially target 15.7% upregulated and 4.8% downregulated mRNAs at end-stage HCM, and regulate mRNAs associated with cardiac hypertrophy and electrophysiology, calcium signalling, fibrosis, and the TGF-β signalling pathway. Collectively, these results define the miRNA expression signatures during development and progression of severe HCM and highlight critical miRNA regulated gene networks that are involved in disease pathogenesis.

Up-regulation of miR-26a promotes apoptosis of hypoxic rat neonatal cardiomyocytes by repressing GSK-3β protein expression

Myocardial ischemia is the major cause of morbidity and mortality due to cardiovascular diseases. This disease is a severe stress condition that causes extensive biochemical changes which trigger cardiac cell death. Stress conditions such as deprivation of glucose and oxygen activate the endoplasmic reticulum in the cytoplasm of cells, including cardiomyocytes, to generate and propagate apoptotic signals in response to these conditions. microRNAs (miRNAs) are a class of small non-coding RNAs that mediate posttranscriptional gene silencing. The miRNAs play important roles in regulating cardiac physiological and pathological events such as hypertrophy, apoptosis, and heart failure. However, the roles of miRNAs in reactive oxygen species (ROS)-mediated injury on cardiomyocytes are uncertain. In this study, we identified at the apoptotic concentration of H(2)O(2), miR-26a expression was increased. To determine the potential roles of miR-26a in H(2)O(2)-mediated cardiac apoptosis, miR-26a expression was regulated by a miR-26a or an anti-miR-26a. Overexpression of miR-26a increased apoptosis as determined by upregulation of Annexin V/PI positive cell population, caspase-3 activity and expression of pro-apoptotic signal molecules, whereas inhibition of miR-26a reduced apoptosis. We identified GSK3B as a direct downstream target of miR-26a. Furthermore, miR-26a attenuated viability and increased caspase-3 activity in normal cardiomyocytes. This study demonstrates that miR-26a promotes ROS-induced apoptosis in cardiomyocytes. Thus, miR-26a affects ROS-mediated gene regulation and cellular injury response.

Overexpression of microRNA-1 impairs cardiac contractile function by damaging sarcomere assembly

AIMS

The purpose of the present study was to evaluate the effects of overexpression of microRNA-1 (miR-1) on cardiac contractile function and the potential molecular mechanisms.

METHODS AND RESULTS

Transgenic (Tg) mice (C57BL/6) for cardiac-specific overexpression of miR-1 driven by the α-myosin heavy chain promoter were generated and identified by real-time reverse-transcription polymerase chain reaction with left ventricular samples. We found an age-dependent decrease in the heart function in Tg mice by pressure-volume loop analysis. Histological analysis and electron microscopy displayed short sarcomeres with the loss of the clear zone and H-zone as well as myofibril fragmentation and deliquescence in Tg mice. Further studies demonstrated miR-1 post-transcriptionally down-regulated the expression of calmodulin (CaM) and cardiac myosin light chain kinase (cMLCK) proteins by targeting the 3'UTRs of MYLK3, CALM1, and CALM2 genes, leading to decreased phosphorylations of myosin light chain 2v (MLC2v) and cardiac myosin binding protein-C (cMyBP-C). Knockdown of miR-1 by locked nucleic acid-modified anti-miR-1 antisense (LNA-antimiR-1) mitigated the adverse changes of cardiac function associated with overexpression of miR-1.

CONCLUSION

miR-1 induces adverse structural remodelling to impair cardiac contractile function. Targeting cMLCK and CaM likely underlies the detrimental effects of miR-1 on structural components of muscles related to the contractile machinery. Our study provides the first evidence that miRNAs cause adverse structural remodelling of the heart.