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MicroRNAs play an important role in myocardial diseases. MiR-133a regulates cardiac hypertrophy, while miR-29b is involved in cardiac fibrosis. The aim of this study was to evaluate whether miR-133a and miR-29b play a role in myocardial fibrosis caused by Angiotensin II (Ang II)-dependent hypertension. Sprague-Dawley rats were treated for 4 weeks with Ang II (200  ng/kg/min) or Ang II + irbesartan (50  mg/kg/day in drinking water), or saline by osmotic minipumps. At the end of the experimental period, cardiac miR-133a and miR-29b expression was measured by real-time PCR, and myocardial fibrosis was evaluated by morphometric analysis. A computer-based prediction algorithm led to the identification of collagen 1a1 (Col1A1) as a putative target of miR-133a. A reporter plasmid bearing the 3'-untranslated regions (UTRs) of Col1A1 mRNA was constructed and luciferase assay was performed. MiR-133a suppressed the activity of luciferase when the reporter gene was linked to a 3'-UTR segment of Col1A1 (P < 0.01). Mutation of miR-133a binding sites in the 3'-UTR of Col1A1 mRNA abolished miR-133a-mediated repression of reporter gene activity, showing that Col1A1 is a real target of miR-133a. In vivo, Ang II caused an increase in systolic blood pressure (P < 0.0001, tail cuff) and myocardial fibrosis in presence of a decrease in miR-133a (P < 0.01) and miR-29b (P < 0.01), and an increase in Col1A1 expression (P < 0.01). These effects were abolished by Ang II administration + irbesartan. These data demonstrate a relationship between miR-133a and Col1A1, suggesting that myocardial fibrosis occurring in Ang II-dependent hypertension is regulated by the down-regulation of miR-133a and miR-29b through the modulation of Col1A1 expression., (Copyright © 2011 Wiley Periodicals, Inc.)

MicroRNAs play important roles in many cellular and biological functions via the regulation of mRNA target translation. In the cardiovascular field, microRNAs are now acknowledged as fundamental in regulating the expression of genes that governs physiological and pathological myocardial adaptation to stress. Here, we review recent progress in the understanding of microRNA functions and their involvement in heart disease.

MicroRNAs (miRNAs) are endogenous, small ribonucleotides regulating the translation of target messenger RNAs that have been shown to be involved in orchestrating growth, development, function, and stress responses of various organs, including the heart. Muscle miRNAs are mainly controlled by a network of myogenic transcription factors, and throughout cardiac development they fine-tune regulatory protein levels in a spatiotemporal manner. Recent profiling studies revealed that miRNA expression patterns are derailed in both human cardiac disease and animal models of cardiac hypertrophy and failure. Modulation of miRNA expression in vitro as well as in vivo has revealed an important role of miRNAs in regulating heart function, particularly cardiac growth and conductance. Here, we overview the recent findings on miRNAs in cardiac development and disease and report the latest advances in the identification and validation of miRNA targets, which are important for a comprehensive understanding of cardiac miRNA function. Finally, we focus on the development and use of miRNA antagonists (antagomirs) to target miRNAs in vivo, which may translate into novel therapeutic strategies for heart disease in the future.

MicroRNA has been shown to be essential for correct cardiovascular development and physiology in a number of recent reports. Studies have also started to characterize the link between specific microRNAs and aspects of pathogenesis--such as chamber morphogenesis, conduction, and contraction--and between microRNA expression signatures and pathological cardiac phenotypes--such as hypertrophy, ischemic cardiomyopathy, dilated cardiomyopathy, and aortic stenosis. Congenital anomalies of the heart may also be associated with the dysregulation of specific microRNAs. Here we report on the latest findings.

The process of mitochondrial dynamics is emerging as a core player in cardiovascular homeostasis. This process refers to the co‐ordinated cycles of biogenesis, fusion, fission and degradation to which mitochondria constantly undergo to maintain their integrity, distribution and size. These mechanisms represent an early response to mitochondrial stress, confining organelle portions that are irreversibly damaged and preserving mitochondrial function. Accumulating evidence demonstrates that impairment in mitochondrial dynamics leads to myocardial damage and cardiac disease progression in a variety of disease models, including pressure overload, ischaemia/reperfusion and metabolic disturbance. These findings suggest that modulation of mitochondrial dynamics may be considered as a valid therapeutic strategy in cardiovascular diseases. In this review, we discuss the current evidence about the role of mitochondrial dynamics in cardiac pathophysiology, with a particular focus on the mechanisms underlying the development of cardiac hypertrophy and heart failure, metabolic and genetic cardiomyopathies, ischaemia/reperfusion injury, atherosclerosis and ischaemic stroke. LINKED ARTICLES: This article is part of a themed issue on Cellular metabolism and diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.10/issuetoc [ABSTRACT FROM AUTHOR]

Micro-RNAs (miRNAs) are a class of small non-coding RNAs, recently emerged as a post-transcriptional regulator having a key role in various cardiac pathologies. Among them, cardiac fibrosis that occurs as a result from an imbalance of extracellular matrix proteins turnover and is a highly debilitating process that eventually lead to organ dysfunction. An emerging theme on is that miRNAs participate in feedback loop with transcription factors that regulate their transcription. NF-κB, a key transcription factor regulator controls a series of gene program in various cardiac diseases through positive and negative feedback mechanism. But, NF-κB mediated miRNA regulation in cardiac fibrosis remains obscure. Bioinformatics analysis revealed that miR-26a has targets collagen I and CTGF and possesses putative NF-κB binding element in its promoter region. Here, we show that inhibition of NF-κB in cardiac fibroblast restores miR-26a expression, attenuating collagen I, and CTGF gene expression in the presence of Ang II, conferring a feedback regulatory mechanism in cardiac fibrosis. The target genes for miR-26a were confirmed using 3′-UTR luciferase reporter assays for collagen I and CTGF genes. Using NF-κB reporter assays, we determine that miR-26a overexpression inhibits NF-κB activity. Finally, we show that miR-26a expression is restored along with the attenuation of collagen I and CTGF genes in cardiac specific IkBa triple mutant transgenic mice (preventing NF-κB activation) subjected to 4 weeks transverse aortic banding (TAC), compared to wild type (WT) mice. The data indicate a potential role of miR-26a in cardiac fibrosis and, offer novel therapeutic intervention. J. Cell. Physiol. 228: 1433-1442, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Growing evidence indicates that microRNAs (miRNAs) are involved in a variety of basic biological processes, including cell proliferation, apoptosis, stress response, hematopoesis, and oncogenesis. In fact, bioinformatic analysis predicts that each miRNA may regulate hundreds of targets, suggesting that miRNAs may play roles in almost every biological pathway. Information from recent studies indicate that miRNAs are involved in the regulation of cardiac development and pathophysiology. Notably, knockout of miRNA-1 was associated with cardiac defects, including regulation of cardiac morphogenesis, electrical conduction, and cell cycle control. Our group has identified a critical role of miRNA-1 and miRNA-133 in determining cardiac hypertrophy and has shown an inverse correlation of expression with cardiac hypertrophy, in vitro, in murine models and in human disease states associated with cardiac hypertrophy. Remarkably, in vivo experiments with a single infusion of antagomir-133 oligonucleotide, a small cholesterol-conjugated RNA sequence suppressing endogenous miRNA, induced marked and sustained cardiac hypertrophy. Shedding light on the role of this new class of RNA molecules in heart physiology and pathology may reveal possible future therapeutic applications for the treatment of heart diseases. [ABSTRACT FROM AUTHOR]

Growing evidence indicates that microRNAs (miRNAs or miRs) are involved in basic cell functions and oncogenesis. Here we report that miR-133 has a critical role in determining cardiomyocyte hypertrophy. We observed decreased expression of both miR-133 and miR-1, which belong to the same transcriptional unit, in mouse and human models of cardiac hypertrophy. In vitro overexpression of miR-133 or miR-1 inhibited cardiac hypertrophy. In contrast, suppression of miR-133 by 'decoy' sequences induced hypertrophy, which was more pronounced than that after stimulation with conventional inducers of hypertrophy. In vivo inhibition of miR-133 by a single infusion of an antagomir caused marked and sustained cardiac hypertrophy. We identified specific targets of miR-133: RhoA, a GDP-GTP exchange protein regulating cardiac hypertrophy; Cdc42, a signal transduction kinase implicated in hypertrophy; and Nelf-A/WHSC2, a nuclear factor involved in cardiogenesis. Our data show that miR-133, and possibly miR-1, are key regulators of cardiac hypertrophy, suggesting their therapeutic application in heart disease. [ABSTRACT FROM AUTHOR]

Abstract: Heart failure (HF) is a syndrome caused by diminished heart function that arises from pathologies like hypertension, infarction, and diabetes. Neurohormonal, cardiorenal and cardiocirculatory models have been developed to explain HF but they have not provided sufficient understanding for the elaboration of therapies to conquer the syndrome. In fact, even though progress has been made in improving survival, HF remains a frequent cause of hospitalization and death. Since in most forms of HF, development of the disorder is associated with an alteration of cardiomyocyte structure, perceived as an increase in heart mass due to cell hypertrophy, effort is being directed to address hypertrophy as a therapeutic target. Here, we outline recent understanding of two gene-silencing regulatory mechanisms underlying cardiomyocyte hypertrophy, i.e., transcriptional control by HDACs, and post-transcriptional control by microRNAs. [Copyright &y& Elsevier]