MiRNA-21: a key to controlling the cardiac fibroblast compartment?

Total flavonoids from Smilax glabra Roxb blocks epithelial-mesenchymal transition and inhibits renal interstitial fibrosis by targeting miR-21/PTEN signaling

BACKGROUND

Smilax glabra Roxb, a traditional Chinese herb, has been widely used in folk medicine. The current study was performed to investigate the protective effect of S. glabra Roxb extract, pure total flavonoids from Smilax glabra Roxb (PTFS), on renal interstitial fibrosis (RIF) and its underlying mechanism.

METHODS

First, a surgical model of unilateral ureteral obstruction was established in rats to induce RIF. Then, rats were grouped and treated with PTFS at different concentration. Second, HK-2 cells underwent an epithelial-mesenchymal transition (EMT) by the addition of transforming growth factor-β1 (TGF-β1). Additionally, HK-2 cells after inducing for EMT were transfected with microRNA-21 (miR-21) mimic or inhibitor. These HK-2 cells were grouped and treated with PTFS at different concentration. Finally, real-time polymerase chain reaction and Western blot analysis were performed to detect the expression of possible signaling factor involved in RIF in renal tissues or HK-2 cells after PTFS treatment.

RESULTS

In vivo and in vitro experiments indicated that PTFS treatment could decrease the expression of α-smooth muscle actin (α-SMA; mesenchymal marker) and increase the expression of E-cadherin (epithelial marker) in both messenger RNA and protein level. Moreover, PTFS also attenuated the expression of TGF-β1/Smad signaling in both renal tissues and HK-2 cells that underwent EMT. Overexpression or inhibition of miR-21 in HK-2 cells activated or blocked the PI3K/Akt signaling via targeting phosphatase and tension homolog (PTEN), and then promoted or suppressed the progress of TGF-β1-induced EMT by regulating the expression of α-SMA and E-cadherin. Furthermore, PTFS treatment inhibited TGF-β1-induced EMT progress by blocking miR-21/PTEN/PI3K/Akt signaling.

CONCLUSION

PTFS has strong anti-EMT and antifibrosis effects both in vitro and in vivo. The mechanism underlying these effects may be related to inhibition of TGF-β1/Smad, and their downstream miR-21/PTEN signaling, leading to blocks of EMT process during RIF.

Cardiac remodeling and pre-eclampsia: an overview of microRNA expression patterns

Pre-eclampsia (PE) is strongly associated with heart failure (HF) later in life. During PE pregnancy, the left ventricle undergoes concentric remodeling which often persists after delivery. This aberrant remodeling can induce a molecular signature that can be evaluated in terms of microRNAs (miRNAs) and which may help to explain the associated increased risk of HF. For this review, we performed a literature search of PubMed (National Center for Biotechnology Information), identifying studies on miRNA expression in concentric remodeling and on miRNA expression in PE. The miRNA data were stratified based on origin (isolated from humans or animals and from tissue or the circulation) and both datasets compared in order to generate a list of miRNA expression patterns in concentric remodeling and in PE. The nine miRNAs identified in both concentric remodeling and PE-complicated pregnancy were: miR-1, miR-18, miR-21, miR-29b, miR-30, miR-125b, miR-181b, miR-195 and miR-499-5p. We found five of these miRNAs (miR-18, miR-21, miR-125b, miR-195 and miR-499-5p) to be upregulated in both PE pregnancy and cardiac remodeling and two (miR-1 and miR-30) to be downregulated in both; the remaining two miRNAs (miR-29b and miR-181b) showed upregulation during PE but downregulation in cardiac remodeling. This innovative approach may be a step towards finding relevant biomarkers for complicated pregnancy and elucidating their relationship with remote cardiovascular disease. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Calcific Aortic Valve Disease: Part 2-Morphomechanical Abnormalities, Gene Reexpression, and Gender Effects on Ventricular Hypertrophy and Its Reversibility

In part 1, we considered cytomolecular mechanisms underlying calcific aortic valve disease (CAVD), hemodynamics, and adaptive feedbacks controlling pathological left ventricular hypertrophy provoked by ensuing aortic valvular stenosis (AVS). In part 2, we survey diverse signal transduction pathways that precede cellular/molecular mechanisms controlling hypertrophic gene expression by activation of specific transcription factors that induce sarcomere replication in-parallel. Such signaling pathways represent potential targets for therapeutic intervention and prevention of decompensation/failure. Hypertrophy provoking signals, in the form of dynamic stresses and ligand/effector molecules that bind to specific receptors to initiate the hypertrophy, are transcribed across the sarcolemma by several second messengers. They comprise intricate feedback mechanisms involving gene network cascades, specific signaling molecules encompassing G protein-coupled receptors and mechanotransducers, and myocardial stresses. Future multidisciplinary studies will characterize the adaptive/maladaptive nature of the AVS-induced hypertrophy, its gender- and individual patient-dependent peculiarities, and its response to surgical/medical interventions. They will herald more effective, precision medicine treatments.

Diverse microRNAs with convergent functions regulate tumorigenesis

MicroRNAs (miRNAs) regulate several biological processes, including tumorigenesis. In order to comprehend the roles of miRNAs in cancer, various screens were performed to investigate the changes in the expression levels of miRNAs that occur in different types of cancer. The present review focuses on the results of five recent screens, whereby a number of overlapping miRNAs were identified to be downregulated or differentially regulated, whereas no miRNAs were observed to be frequently upregulated. Furthermore, the majority of the miRNAs that were common to >1 screen were involved in signaling networks, including wingless-related integration site, receptor tyrosine kinase and transforming growth factor-β, or in cell cycle checkpoint control. The present review will discuss the aforementioned miRNAs implicated in cell cycle checkpoint control and signaling networks.

Downregulation of miR-21 is involved in direct actions of ursolic acid on the heart: implications for cardiac fibrosis and hypertrophy

PURPOSE

Myocardial fibrosis contributes to cardiac remodeling and loss of cardiac function in myocardial infarction and heart failure. This study used in vitro and in vivo models to examine the effects of ursolic acid (UA) on myocardial fibrosis and to explore its potential mechanism.

METHODS

Transverse aortic constriction (TAC) surgery was performed in mice to induce cardiac hypertrophy and fibrosis. UA was orally administered 1 week prior to TAC. Two weeks after TAC, myocardial pathology was detected using Masson's trichrome staining and transmission electron microscopy, and heart-to-body weight ratio was measured. For in vitro studies, cultured cardiac fibroblasts were treated with serum in the presence or absence of UA. The relative levels of miR-21 and p-ERK/ERK, collagen content and cell viability were measured.

RESULTS

Ursolic acid attenuated pathological cardiac hypertrophy and myocardial fibrosis in vivo induced by TAC. Downregulation of miR-21 and p-ERK/ERK were observed in myocardial fibroblasts treated with UA in a dose-dependent manner compared with the control group both in vitro and in vivo.

CONCLUSIONS

Our study demonstrates that UA can inhibit myocardial fibrosis both in vitro and in vivo, and the effects of UA on myocardial fibrosis may be due to the inhibition of miR-21/ERK signaling pathways.

A novel reciprocal loop between microRNA-21 and TGFβRIII is involved in cardiac fibrosis

Cardiac fibrosis is characterized by aberrant proliferation of cardiac fibroblasts and exaggerated deposition of extracellular matrix (ECM) in the myocardial interstitial, and ultimately impairs cardiac function. It is still controversial whether microRNA-21 (miR-21) participates in the process of cardiac fibrosis. Our previous study confirmed that transforming growth factor beta receptor III (TGFβRIII) is a negative regulator of TGF-β pathway. Here, we aimed to decipher the relationship between miR-21 and TGFβRIII in the pathogenic process of myocardial fibrosis. We found that TGF-β1 and miR-21 were up-regulated, whereas TGFβRIII was down-regulated in the border zone of mouse hearts in response to myocardial infarction. After transfection of miR-21 into cardiac fibroblasts, TGFβRIII expression was markedly reduced and collagen content was increased. And, luciferase results confirmed that TGFβRIII was a target of miR-21. It suggests that up-regulation of miR-21 could increase the collagen content and at least in part through inhibiting TGFβRIII. Conversely, we also confirmed that overexpression of TGFβRIII could inhibit the expression of miR-21 and reduce collagen production in fibroblasts. Further studies showed that overexpression of TGFβRIII could also deactivate TGF-β1 pathway by decreasing the expression of TGF-β1 and phosphorylated-Smad3 (p-Smad3). TGF-β1 has been proven as a positive regulator of miR-21. Taken together, we found a novel reciprocal loop between miR-21 and TGFβRIII in cardiac fibrosis caused by myocardial infarction in mice, and targeting this pathway could be a new strategy for the prevention and treatment of myocardial remodeling.

Myocardial and circulating levels of microRNA-21 reflect left ventricular fibrosis in aortic stenosis patients

BACKGROUND

Various human cardiovascular pathophysiological conditions associate aberrant expression of microRNAs (miRNAs) and circulating miRNAs are emerging as promising biomarkers. In mice, myocardial miR-21 overexpression is related to cardiac fibrosis elicited by pressure overload. This study was designed to determine the role of myocardial and plasmatic miR-21 in the maladaptive remodeling of the extracellular matrix induced by pressure overload in aortic stenosis (AS) patients and the clinical value of miR-21 as a biomarker for pathological myocardial fibrosis.

METHODS

In left ventricular biopsies from 75 AS patients and 32 surgical controls, we quantified the myocardial transcript levels of miR-21, miR-21-targets and ECM- and TGF-β-signaling-related elements. miR-21 plasma levels were determined in 25 healthy volunteers and in AS patients. In situ hybridization of miR-21 was performed in myocardial sections.

RESULTS

The myocardial and plasma levels of miR-21 were significantly higher in the AS patients compared with the controls and correlated directly with the echocardiographic mean transvalvular gradients. miR-21 overexpression was confined to interstitial cells and absent in cardiomyocytes. Using bootstrap validated multiple linear regression, the variance in myocardial collagen expression was predicted by myocardial miR-21 (70% of collagen variance) or plasma miR-21 (52% of collagen variance), together with the miR-21 targets RECK and PDCD4, and effectors of TGF-ß signaling.

CONCLUSIONS

Our results support the role of miR-21 as a regulator of the fibrotic process that occurs in response to pressure overload in AS patients and underscore the value of circulating miR-21 as a biomarker for myocardial fibrosis.

MicroRNAs in cardiac hypertrophy: angels or devils

MicroRNAs (miRNAs) are short noncoding RNA molecules that can regulate gene expression via affecting mRNA stability or translation efficiency. miRNAs mediate many important cellular processes and emerge as a newly discovered regulator of gene expression. In cardiac hypertrophy, miRNAs expression is aberrantly altered. Some of these miRNAs can promote cardiac hypertrophy, whereas others can inhibit the process. In this review, we summarize the up- and downregulated miRNAs during cardiac hypertrophy and discuss about their roles in cardiac hypertrophy. The studies on miRNAs shed new light on the mechanism of cardiac hypertrophy and suggest that they may be promising therapeutic targets in tackling cardiac hypertrophy.

MicroRNAs and the regulation of fibrosis

MicroRNAs (miRNAs) are small, noncoding RNAs of 18-25 nucleotides that are generally believed to either block the translation or induce the degradation of target mRNA. miRNAs have been shown to play fundamental roles in diverse biological and pathological processes, including cell proliferation, differentiation, apoptosis and carcinogenesis. Fibrosis results from an imbalance in the turnover of extracellular matrix molecules and is a highly debilitating process that can eventually lead to organ dysfunction. A growing body of evidence suggests that miRNAs participate in the fibrotic process in a number of organs including the heart, kidney, liver and lung. In this review, we summarize our current understanding of the role of miRNAs in the development of tissue fibrosis and their potential as novel drug targets.

microRNAs in heart disease: putative novel therapeutic targets?

microRNAs (miRs) are short, approximately 22-nucleotide-long non-coding RNAs involved in the control of gene expression. They guide ribonucleoprotein complexes that effect translational repression or messenger RNA degradation to targeted messenger RNAs. miRs were initially thought to be peculiar to the developmental regulation of the nematode worm, in which they were first described in 1993. Since then, hundreds of different miRs have been reported in diverse organisms, and many have been implicated in the regulation of physiological processes of adult animals. Of importance, misexpression of miRs has been uncovered as a pathogenic mechanism in several diseases. Here, we first outline the biogenesis and mechanism of action of miRs, and then discuss their relevance to heart biology, pathology, and medicine.