Role of miR-145 in cardiac myofibroblast differentiation

MiR-145-5p regulates hypoxia-induced inflammatory response and apoptosis in cardiomyocytes by targeting CD40

An increasing body of evidence indicates that inflammation and apoptosis are involved in the development of acute myocardial infarction (AMI). In this study, we sought to investigate the specific role and the underlying regulatory mechanism of miR-145-5p in myocardial ischemic injury. H9c2 cardiac cells were exposed to hypoxia to establish a model of myocardial hypoxic/ischemic injury. We found that miR-145-5p was notably down-regulated, while CD40 expression was highly elevated in H9c2 cells following exposure to acute hypoxia. Additionally, hypoxia markedly enhanced the inflammatory response, as reflected by an increase in the secretion of the cytokines IL-1β, TNF-α, and IL-6, whereas the introduction of miR-145-5p effectively suppressed inflammatory factor production triggered by hypoxia. Furthermore, we observed hypoxia stimulation significantly augmented apoptosis accompanied by a decrease in the expression of Bcl-2 and an increase in the expression of Bax, Caspase-3, and Caspase-9. However, augmentation of miR-145-5p led to a dramatic prevention of hypoxia-induced apoptosis. Importantly, we identified CD40 as a direct target of miR-145-5p. Interestingly, the depletion of CD40 with small interfering RNAs (siRNAs) apparently repressed the production of inflammatory cytokines and apoptosis in the setting of acute hypoxic treated. Taken together, these data demonstrated that miR-145-5p may function as a cardiac-protective molecule in myocardial ischemic injury by ameliorating inflammation and apoptosis via negative regulation of CD40. The study gives evidence that miR-145-5p provides an interesting strategy for protecting cardiomyocytes from hypoxia-induced inflammatory response and apoptosis.

MicroRNA-145 Modulates N6-Methyladenosine Levels by Targeting the 3'-Untranslated mRNA Region of the N6-Methyladenosine Binding YTH Domain Family 2 Protein

N⁶-Methyladenosine (m⁶A) is a prevalent modification present in the mRNAs of higher eukaryotes. YTH domain family 2 (YTHDF2), an m⁶A "reader" protein, can recognize mRNA m⁶A sites to mediate mRNA degradation. However, the regulatory mechanism of YTHDF2 is poorly understood. To this end, we investigated the post-transcriptional regulation of YTHDF2. Bioinformatics analysis suggested that the microRNA miR-145 might target the 3'-untranslated region (3'-UTR) of YTHDF2 mRNA. The levels of miR-145 were negatively correlated with those of YTHDF2 mRNA in clinical hepatocellular carcinoma (HCC) tissues, and immunohistochemical staining revealed that YTHDF2 was closely associated with malignancy of HCC. Interestingly, miR-145 decreased the luciferase activities of 3'-UTR of YTHDF2 mRNA. Mutation of predicted miR-145 binding sites in the 3'-UTR of YTHDF2 mRNA abolished the miR-145-induced decrease in luciferase activity. Overexpression of miR-145 dose-dependently down-regulated YTHDF2 expression in HCC cells at the levels of both mRNA and protein. Conversely, inhibition of miR-145 resulted in the up-regulation of YTHDF2 in the cells. Dot blot analysis and immunofluorescence staining revealed that the overexpression of miR-145 strongly increased m⁶A levels relative to those in control HCC cells, and this increase could be blocked by YTHDF2 overexpression. Moreover, miR-145 inhibition strongly decreased m⁶A levels, which were rescued by treatment with a small interfering RNA-based YTHDF2 knockdown. Thus, we conclude that miR-145 modulates m⁶A levels by targeting the 3'-UTR of YTHDF2 mRNA in HCC cells.

MicroRNAs in cardiovascular disease

PURPOSE OF REVIEW

Noncoding RNAs regulate many aspects of cardiovascular biology and are potential therapy targets. In this review, we summarize and highlight current discoveries in the field of microRNAs, a class of noncoding RNAs.

RECENT FINDINGS

miRNAs regulate posttranscriptional gene expression and have been shown to control cardiac development, hypertrophy, fibrosis, and regeneration. Of note are the miRNAs that regulate cardiac contractility (for example, miR-25 and miR-22), cardiac regeneration (like miR-302-367 and miR99/100 families), and fibrosis (as miR-125b). Consistently with these roles of miRNAs, pharmacological intervention using anti-miRNA oligonucleotides (antagomirs or LNA-anti-miRs) has been shown to improve cardiac contractility and mitigate fibrosis, alleviating cardiac dysfunction in the setting of heart failure.

SUMMARY

miRNAs are crucial regulators of cardiac phenotype and have enthused both basic scientists and clinicians alike. With advancement of technology and better understanding of mechanisms governing miRNA deregulation, we are at the crossroads for deciphering miRNA function and modulating it for therapeutics.

Integrative analysis of miRNA and mRNA paired expression profiling of primary fibroblast derived from diabetic foot ulcers reveals multiple impaired cellular functions

Diabetic foot ulcers (DFUs) are one of the major complications of diabetes. Its molecular pathology remains poorly understood, impeding the development of effective treatments. Although it has been established that multiple cell types, including fibroblasts, keratinocytes, macrophages, and endothelial cells, all contribute to inhibition of healing, less is known regarding contributions of individual cell type. Thus, we generated primary fibroblasts from nonhealing DFUs and evaluated their cellular and molecular properties in comparison to nondiabetic foot fibroblasts (NFFs). Specifically, we analyzed both micro-RNA and mRNA expression profiles of primary DFU fibroblasts. Paired genomic analyses identified a total of 331 reciprocal miRNA-mRNA pairs including 21 miRNAs (FC > 2.0) along with 239 predicted target genes (FC > 1.5) that are significantly and differentially expressed. Of these, we focused on three miRNAs (miR-21-5p, miR-34a-5p, miR-145-5p) that were induced in DFU fibroblasts as most differentially regulated. The involvement of these microRNAs in wound healing was investigated by testing the expression of their downstream targets as well as by quantifying cellular behaviors in prospectively collected and generated cell lines from 15 patients (seven DFUF and eight NFF samples). We found large number of downstream targets of miR-21-5p, miR-34a-5p, miR-145-5p to be coordinately regulated in mRNA profiles, which was confirmed by quantitative real-time PCR. Pathway analysis on paired miRNA-mRNA profiles predicted inhibition of cell movement and cell proliferation, as well as activation of cell differentiation and senescence in DFU fibroblasts, which was confirmed by cellular assays. We concluded that induction of miR-21-5p, miR-34a-5p, miR-145-5p in DFU dermal fibroblasts plays an important role in impairing multiple cellular functions, thus contributing to overall inhibition of healing in DFUs.

Umbilical Cord-Derived Mesenchymal Stem Cell-Derived Exosomal MicroRNAs Suppress Myofibroblast Differentiation by Inhibiting the Transforming Growth Factor-β/SMAD2 Pathway During Wound Healing

: Excessive scar formation caused by myofibroblast aggregations is of great clinical importance during skin wound healing. Studies have shown that mesenchymal stem cells (MSCs) can promote skin regeneration, but whether MSCs contribute to scar formation remains undefined. We found that umbilical cord-derived MSCs (uMSCs) reduced scar formation and myofibroblast accumulation in a skin-defect mouse model. We found that these functions were mainly dependent on uMSC-derived exosomes (uMSC-Exos) and especially exosomal microRNAs. Through high-throughput RNA sequencing and functional analysis, we demonstrated that a group of uMSC-Exos enriched in specific microRNAs (miR-21, -23a, -125b, and -145) played key roles in suppressing myofibroblast formation by inhibiting the transforming growth factor-β2/SMAD2 pathway. Finally, using the strategy we established to block miRNAs inside the exosomes, we showed that these specific exosomal miRNAs were essential for the myofibroblast-suppressing and anti-scarring functions of uMSCs both in vitro and in vivo. Our study revealed a novel role of exosomal miRNAs in uMSC-mediated therapy, suggesting that the clinical application of uMSC-derived exosomes might represent a strategy to prevent scar formation during wound healing.

SIGNIFICANCE

Exosomes have been identified as a new type of major paracrine factor released by umbilical cord-derived mesenchymal stem cells (uMSCs). They have been reported to be an important mediator of cell-to-cell communication. However, it is still unclear precisely which molecule or group of molecules carried within MSC-derived exosomes can mediate myofibroblast functions, especially in the process of wound repair. The present study explored the functional roles of uMSC-exosomal microRNAs in the process of myofibroblast formation, which can cause excessive scarring. This is an unreported function of uMSC exosomes. Also, for the first time, the uMSC-exosomal microRNAs were examined by high-throughput sequencing, with a group of specific microRNAs (miR-21, miR-23a, miR-125b, and miR-145) found to play key roles in suppressing myofibroblast formation by inhibiting excess α-smooth muscle actin and collagen deposition associated with activity of the transforming growth factor-β/SMAD2 signaling pathway.

MicroRNA-145 inhibits hepatic stellate cell activation and proliferation by targeting ZEB2 through Wnt/β-catenin pathway

The activation of hepatic stellates cells (HSCs) is well believed to play a pivotal role in the development of liver fibrosis. MicroRNA-145 (miR-145) is known to suppress the progression of hepatocellular carcinoma, and is previously reported to be associated with Wnt/β-catenin pathway, but its role in the progression of hepatic fibrosis and activation of HSCs remains unknown and is warranted for investigation. In the present study, we found that the expression of miR-145 is significantly down-regulated in vivo in CCl4-induced mice liver fibrosis as well as in transforming growth factor-β1 (TGF-β1) induced HSC-T6 cell lines and human hepatic stellate cell line LX-2 in vitro. Furthermore, over-expression of miR-145 inhibited TGF-β1-induced the activation and proliferation of HSC-T6 cells in vitro. Mechanistically, we identified that zinc finger E-box-binding homeobox 2 (ZEB2), a key mediator of epithelial-to-mesenchymal transition, acted as a functional downstream target for miR-145. Interestingly, ZEB2 was shown to be involved in the TGF-β1-induced HSCs activation by regulating Wnt/β-catenin signaling pathway. Taken together, our results revealed the critical regulatory role of miR-145 in HSCs activation and implied miR-145 as a potential candidate for therapy of hepatic fibrosis by regulation of Wnt/β-catenin through targeting ZEB2.

Identifying circulating microRNAs as biomarkers of cardiovascular disease: a systematic review

The aim of the present study is to identify microRNAs (miRs) with high potential to be used as biomarkers in plasma and/or serum to clinically diagnose, or provide accurate prognosis for survival in, patients with atherosclerosis, coronary artery disease, and acute coronary syndrome (ACS). A systematic search of published original research yielded a total of 72 studies. After review of the risk of bias of the published studies, according to Cochrane Collaboration and the QUADUAS Group standards, 19 studies were selected. Overall 52 different miRs were reported. In particular, miR-133a/b (5 studies), miR-208a/b (6 studies), and miR-499 (7 studies) were well studied and found to be significant diagnostic and/or prognostic markers across different cardiovascular disease progression stages. miR-1 and miR-145b are potential biomarkers of ACS; miR-1 with higher sensitivity for all acute myocardial infarction (AMI), and miR-145 for STEMI and worse outcome of AMI. But when miRs were studied across different ACS study populations, patients had varying degrees of coronary stenosis, which was identified as an important confounder that limited the ability to quantitatively pool the study results. The identified miRs were found to regulate endothelial function and angiogenesis (miR-1, miR-133), vascular smooth muscle cell differentiation (miR-133, miR-145), communication between vascular smooth muscle and endothelial cell to stabilize plaques (miR-145), apoptosis (miR-1, miR-133, miR-499), cardiac myocyte differentiation (miR-1, miR-133, miR-145, miR-208, miR-499), and to repress cardiac hypertrophy (miR-133). Their role in these processes may be explained by regulation of shared RNA targets such as cyclin-dependent kinase inhibitor 1A (or p21), ETS proto-oncogene 1, fascin actin-bundling protein 1, hyperpolarization-activated cyclic nucleotide-gated potassium channel 4, insulin-like growth factor 1 receptor LIM and SH3 protein 1, purine nucleoside phosphorylase, and transgelin 2. These mechanistic data further support the clinical relevance of the identified miRs. miR-1, miR-133a/b, miR-145, miR-208a/b, and miR-499(a) in plasma and/or serum show some potential for diagnosis of cardiovascular disease. However, biased selection of miRs in most studies and unexplained contrasting results are major limitations of current miR research. Inconsistencies need to be addressed in order to definitively identify clinically useful miRs. Therefore, this paper presents important aspects to improve future miR research, including unbiased selection of miRs, standardization/normalization of reference miRs, adjustment for patient comorbidities and medication, and robust protocols of data-sharing plans that could prevent selective publication and selective reporting of miR research outcomes.

Mast cells promote proliferation and migration and inhibit differentiation of mesenchymal stem cells through PDGF

BACKGROUND

Mast cells (MCs) dynamically participate in wound healing after myocardial infarction (MI) by releasing cytokines. Indeed, MC-deficient mice undergo rapid left ventricular dilation post-MI. Mesenchymal stem cells (MSCs) are recruited to the injured region following an MI and have potential for cardiac repair. In the current study, we evaluate the effect of MCs on MSC proliferation and myogenic differentiation.

METHODS AND RESULTS

MCs were cultured from mouse bone marrow and MC granulate (MCG) was extracted from MCs via freeze-thaw cycles followed by filtration. α-SMA (smooth muscle actin) expression was examined as an indicator of myogenic differentiation. MSC/MC co-culture resulted in decreased MSC differentiation indicated by α-SMA suppression in MSCs. MCG also suppressed α-SMA expression and increased MSC migration and proliferation in a dose-dependent manner. Removal of MCG rescued α-SMA expression and MSC differentiation. Platelet derived growth factor (PDGF) receptor blockade using AG1296 also rescued MSC differentiation even after MCG treatment. Real-time PCR and Western blot showed that MCG exerted its effects on MSCs via downregulation of miR-145 and miR-143, downregulation of myocardin, upregulation of Klf4, and increased Erk and Elk1 phosphorylation.

CONCLUSIONS

MCs promote MSC proliferation and migration by suppressing their myogenic differentiation. MCs accomplish this via activation of the PDGF pathway, downregulation of miR-145/143, and modulation of the myocardin-Klf4 axis. These data suggest a potential role for MSC/MC interaction in the infarcted heart where MCs may inhibit MSCs from differentiation and promote their proliferation whereby increased cardiac MSC accumulation promotes eventual cardiac regeneration after MCs cease activity.

Expression of TGF-β1 and miRNA-145 in patients with diabetic foot ulcers

The aim of the present study was to investigate the expression levels of transforming growth factor (TGF)-β1 and microRNA (miRNA)-145 in patients with diabetic foot ulcers (DFUs). A total of 26 patients with DFUs requiring amputation were enrolled in the study between January 2013 and August 2014. In addition, 15 trauma patients undergoing amputation over the same time period were included as a control group. Samples were collected from the blood, the dorsalis pedis arteries and muscles of the amputated limbs. The expression levels of TGF-β1 mRNA and miRNA-145 in these samples was detected using reverse transcription-quantitative polymerase chain reaction. The expression levels of TGF-β1 protein were evaluated using western blot analysis. In comparison with the control, the protein and mRNA expression levels of TGF-β1 in the DFU patients was significantly higher in the serum and the dorsalis pedis arteries, and significantly lower in the muscles with ulcers. In contrast, the expression levels of miRNA-145 was significantly lower in the blood and the dorsalis pedis arteries, and significantly higher in the muscles with ulcers in DFU patients compared with the control. The results of the present study suggested that there exists an inverse correlation between the expression levels of miRNA-145 and TGF-β1 in patients with DFU; thus suggesting that miRNA-145 may regulate the expression of TGF-β1 in patients with DFUs.

The Living Scar--Cardiac Fibroblasts and the Injured Heart

Cardiac scars, often dubbed 'dead tissue', are very much alive, with heterocellular activity contributing to the maintenance of structural and mechanical integrity following heart injury. To form a scar, non-myocytes such as fibroblasts are recruited from intra- and extra-cardiac sources. Fibroblasts perform important autocrine and paracrine signaling functions. They also establish mechanical and, as is increasingly evident, electrical junctions with other cells. While fibroblasts were previously thought to act simply as electrical insulators, they may be electrically connected among themselves and, under some circumstances, to other cells including cardiomyocytes. A better understanding of these biophysical interactions will help to target scar structure and function, and will facilitate the development of novel therapies aimed at modifying scar properties for patient benefit.

Akt-dependent Girdin phosphorylation regulates repair processes after acute myocardial infarction

Myocardial infarction is a leading cause of death, and cardiac rupture following myocardial infarction leads to extremely poor prognostic feature. A large body of evidence suggests that Akt is involved in several cardiac diseases. We previously reported that Akt-mediated Girdin phosphorylation is essential for angiogenesis and neointima formation. The role of Girdin expression and phosphorylation in myocardial infarction, however, is not understood. Therefore, we employed Girdin-deficient mice and Girdin S1416A knock-in (Girdin(SA/SA)) mice, replacing the Akt phosphorylation site with alanine, to address this question. We found that Girdin was expressed and phosphorylated in cardiac fibroblasts in vitro and that its phosphorylation was crucial for the proliferation and migration of cardiac fibroblasts. In vivo, Girdin was localized in non-cardiomyocyte interstitial cells and phosphorylated in α-smooth muscle actin-positive cells, which are likely to be cardiac myofibroblasts. In an acute myocardial infarction model, Girdin(SA/SA) suppressed the accumulation and proliferation of cardiac myofibroblasts in the infarcted area. Furthermore, lower collagen deposition in Girdin(SA/SA) mice impaired cardiac repair and resulted in increased mortality attributed to cardiac rupture. These findings suggest an important role of Girdin phosphorylation at serine 1416 in cardiac repair after acute myocardial infarction and provide insights into the complex mechanism of cardiac rupture through the Akt/Girdin-mediated regulation of cardiac myofibroblasts.

Transforming growth factor-β-sphingosine kinase 1/S1P signaling upregulates microRNA-21 to promote fibrosis in renal tubular epithelial cells

Renal fibrosis is a progressive pathological change characterized by tubular cell apoptosis, tubulointerstitial fibroblast proliferation, and excessive deposition of extracellular matrix (ECM). miR-21 has been implicated in transforming growth factor-β (TGF-β)-stimulated tissue fibrosis. Recent studies showed that sphingosine kinase/sphingosine-1-phosphate (SphK/S1P) are also critical for TGF-β-stimulated tissue fibrosis; however, it is not clear whether SphK/S1P interacts with miR-21 or not. In this study, we hypothesized that SphK/S1P signaling is linked to upregulation of miR-21 by TGF-β. To verify this hypothesis, we first determined that miR-21 was highly expressed in renal tubular epithelial cells (TECs) stimulated with TGF-β by using qRT-PCR and Northern blotting. Simultaneously, inhibition of miR-21, mediated by the corresponding antimir, markedly decreased the expression and deposition of type I collagen, fibronectin (Fn), cysteine-rich protein 61 (CCN1), α-smooth muscle actin, and fibroblast-specific protein1 in TGF-β-treated TECs. ELISA and qRT-PCR were used to measure the S1P and SphK1 levels in TECs. S1P production was induced by TGF-β through activation of SphK1. Furthermore, it was observed that TGF-β-stimulated upregulation of miR-21 was abolished by SphK1 siRNA and was restored by the addition of exogenous S1P. Blocking S1PR2 also inhibited upregulation of miR-21. Additionally, miR-21 overexpression attenuated the repression of TGF-β-stimulated ECM deposition and epithelial-mesenchymal transition by SphK1 and S1PR2 siRNA. In summary, our study demonstrates a link between SphK1/S1P and TGF-β-induced miR-21 in renal TECs and may represent a novel therapeutic target in renal fibrosis.

Effects of miRNA-145 on airway smooth muscle cells function

The pathological changes of airway smooth muscle (ASM) contribute to airway remodeling during asthma. Here, we investigated the effect of miR-145 on ASM function. We found that miR-145 was aberrantly more highly expressed in ASM cells exposed to cytokine stimulation that mimic the airway conditions of patients with asthma. Repression of miR-145 resulted in decreased ASM cell proliferation and migration in a dose-dependent manner and down-regulation of type I collagen and contractile protein MHC in ASM cells. qRT-PCR and Western blot analysis demonstrated that miR-145 negatively regulated the expression of downstream target Krüppel-like factor 4 (KLF4) protein, and overexpression of KLF4 attenuated the effects of miR-145 on ASM cells. Further studies showed that KLF4 significantly up-regulated the expression of p21 and down-regulated matrix metalloproteinase (MMP-2 and MMP-9). In conclusion, miR-145 overexpression in ASM cells significantly inhibited KLF4, and subsequently affected downstream p21, MMP-2, and MMP-9 expressions, eventually leading to enhanced proliferation and migration of ASM cells in vitro.

Potential application of miRNAs as diagnostic and therapeutic tools in chronic pancreatitis

Chronic pancreatitis (CP) is a progressive inflammatory disease typified by end-stage fibrosis. This disease can also increase the risk of pancreatic cancer. The associated diagnosis, pain and other complications further add to the burden of disease management. In recent years, significant progress has been achieved in identifying miRNAs and their physiological functions, including mRNA repression and protein expression control. Given the extensive effort made on miRNA research, a close correlation has been discovered between certain types of miRNAs and disease progression, particularly for tissue fibrosis. Designing miRNA-related tools for disease diagnosis and therapeutic treatments presents a novel and potential research frontier. In the current review, we discuss various miRNAs closely interacting with CP, as well as the possible development of targeted miRNA therapies in managing this disease.

Lipid nanoparticle delivery of a microRNA-145 inhibitor improves experimental pulmonary hypertension

Therapies that exploit RNA interference (RNAi) hold great potential for improving disease outcomes. However, there are several challenges that limit the application of RNAi therapeutics. One of the most important challenges is effective delivery of oligonucleotides to target cells and reduced delivery to non-target cells. We have previously developed a functionalized cationic lipopolyamine (Star:Star-mPEG-550) for in vivo delivery of siRNA to pulmonary vascular cells. This optimized lipid formulation enhances the retention of siRNA in mouse lungs and achieves significant knockdown of target gene expression for at least 10days following a single intravenous injection. Although this suggests great potential for developing lung-directed RNAi-based therapies, the application of Star:Star-mPEG mediated delivery of RNAi based therapies for pulmonary vascular diseases such as pulmonary arterial hypertension (PAH) remains unknown. We identified differential expression of several microRNAs known to regulate cell proliferation, cell survival and cell fate that are associated with development of PAH, including increased expression of microRNA-145 (miR-145). Here we test the hypothesis that Star:Star-mPEG mediated delivery of an antisense oligonucleotide against miR-145 (antimiR-145) will improve established PAH in rats. We performed a series of experiments testing the in vivo distribution, toxicity, and efficacy of Star:Star-mPEG mediated delivery of antimiR-145 in rats with Sugen-5416/hypoxia induced PAH. We showed that after subchronic therapy of three intravenous injections over 5weeks at 2mg/kg, antimiR-145 accumulated in rat lung tissue and reduced expression of endogenous miR-145. Using a novel in situ hybridization approach, we demonstrated substantial distribution of antimiR-145 in the lungs as well as the liver, kidney, and spleen. We assessed toxic effects of Star:Star-mPEG/antimiR-145 with serial complete blood counts of leukocytes and serum metabolic panels, gross pathology, and histopathology and did not detect significant off-target effects. AntimiR-145 reduced the degree of pulmonary arteriopathy, reduced the severity of pulmonary hypertension, and reduced the degree of cardiac dysfunction. The results establish effective and low toxicity of lung delivery of a miRNA-145 inhibitor using functionalized cationic lipopolyamine nanoparticles to repair pulmonary arteriopathy and improve cardiac function in rats with severe PAH.

miR-145 Contributes to Hypertrophic Scarring of the Skin by Inducing Myofibroblast Activity

Hyperthrophic scarring of the skin is caused by excessive activity of skin myofibroblasts after wound healing and often leads to functional and/or aesthetic disturbance with significant impairment of patient quality of life. MicroRNA (miRNA) gene therapies have recently been proposed for complex processes such as fibrosis and scarring. In this study, we focused on the role of miR-145 in skin scarring and its influence in myofibroblast function. Our data showed not only a threefold increase of miR-145 levels in skin hypertrophic scar tissue but also in transforming growth factor β1 (TGF-β1)-induced skin myofibroblasts compared with healthy skin or nontreated fibroblasts (p < 0.001). Consistent with the upregulation of miR-145 induced by TGF-β1 stimulation of fibroblasts, the expression of Kruppel-like factor 4 (KLF4) was decreased by 50% and α-smooth muscle actin (α-SMA) protein expression showed a threefold increase. Both could be reversed by miR-145 inhibition (p < 0.05). Restoration of KLF4 levels equally abrogated TGF-β1-induced α-SMA expression. These data demonstrate that TGF-β1 induces miR-145 expression in fibroblasts, which in turn inhibits KLF4, a known inhibitor of α-SMA, hence upregulating α-SMA expression. Furthermore, treatment of myofibroblasts with a miR-145 inhibitor strongly decreased their α-1 type I collagen expression, TGF-β1 secretion, contractile force generation and migration. These data demonstrate that upregulation of miR-145 plays an important role in the differentiation and function of skin myofibroblasts. Additionally, inhibition of miR-145 significantly reduces skin myofibroblast activity. Taken together, these results suggest that miR-145 is a promising therapeutic target to prevent or reduce hypertrophic scarring of the skin.

Sodium tanshinone IIA sulfonate attenuates the transforming growth factor-β1-induced differentiation of atrial fibroblasts into myofibroblasts in vitro

The differentiation of atrial fibroblasts into myofibroblasts is a critical event in atrial fibrosis. One of the most important factors in atrial fibroblast differentiation is transforming growth factor-β1 (TGF-β1). Accumulating evidence indicates that sodium tanshinone IIA sulfonate (STS) possesses antifibrotic properties. In this study, we therefore investigated whether STS attenuates the TGF-β1‑induced differentiation of atrial fibroblasts. TGF-β1 enhanced collagen production, collagen synthesis and the expression of collagen type I and III, as shown by hydroxyproline assay, collagen synthesis assay and western blot analysis, respectively. In addition, as shown by immunohistochemistry and western blot analysis, TGF-β1 enhanced the expression of α-smooth muscle actin (α-SMA), which is the hallmark of myofibroblast differentiation. These responses were attenuated by treatment with STS. In addition, STS suppressed the TGF-β1‑induced expression of phosphorylated (p)Smad/pSmad3 expression and nuclear translocation. Furthermore, STS suppressed extracellular signal-regulated kinase (ERK) phosphorylation. In conclusion, the current study demonstrates that STS exerts antifibrotic effects by modulating atrial fibroblast differentiation through ERK phosphorylation and the Smad pathway.

MicroRNA miR145 regulates TGFBR2 expression and matrix synthesis in vascular smooth muscle cells

RATIONALE

MicroRNA miR145 has been implicated in vascular smooth muscle cell differentiation, but its mechanisms of action and downstream targets have not been fully defined.

OBJECTIVE

Here, we sought to explore and define the mechanisms of miR145 function in smooth muscle cells.

METHODS AND RESULTS

Using a combination of cell culture assays and in vivo mouse models to modulate miR145, we characterized its downstream actions on smooth muscle phenotypes. Our results show that the miR-143/145 gene cluster is induced in smooth muscle cells by coculture with endothelial cells. Endothelial cell-induced expression of miR-143/145 is augmented by Notch signaling and accordingly expression is reduced in Notch receptor-deficient cells. Screens to identify miR145-regulated genes revealed that the transforming growth factor (TGF)-β pathway has a significantly high number of putative target genes, and we show that TGFβ receptor II is a direct target of miR145. Extracellular matrix genes that are regulated by TGFβ receptor II were attenuated by miR145 overexpression, and miR145 mutant mice exhibit an increase in extracellular matrix synthesis. Furthermore, activation of TGFβ signaling via angiotensin II infusion revealed a pronounced fibrotic response in the absence of miR145.

CONCLUSIONS

These data demonstrate a specific role for miR145 in the regulation of matrix gene expression in smooth muscle cells and suggest that miR145 acts to suppress TGFβ-dependent extracellular matrix accumulation and fibrosis, while promoting TGFβ-induced smooth muscle cell differentiation. Our findings offer evidence to explain how TGFβ signaling exhibits distinct downstream actions via its regulation by a specific microRNA.

Harnessing the Therapeutic Potential of MicroRNAs for Cardiovascular Disease

Cardiovascular diseases are one of the most common causes of death in humans and are responsible for billions of dollars in health care expenditures. As the molecular basis of cardiac diseases continues to be explored, there remains the hope for identification of more effective therapeutics. MicroRNAs (miRNAs) are recognized as important regulators of numerous biological pathways and stress responses, including those found in cardiovascular diseases. MicroRNA signatures of cardiovascular diseases can provide targets for miRNA adjustment and offer the possibility of changing gene and protein expression to treat certain pathologies. These adjustments can be conferred using advances in oligonucleotide delivery methods, which can target single miRNAs, families of miRNAs, and certain tissue types. In this review, we will discuss the use of miRNAs in vivo and recent advances in their use for cardiovascular disease in mammalian models.

Helicobacter pylori infection: host immune response, implications on gene expression and microRNAs

Helicobacter pylori (H. pylori) infection is the most common bacterial infection worldwide. Persistent infection of the gastric mucosa leads to inflammatory processes and may remain silent for decades or progress causing more severe diseases, such as gastric adenocarcinoma. The clinical consequences of H. pylori infection are determined by multiple factors, including host genetic predisposition, gene regulation, environmental factors and heterogeneity of H. pylori virulence factors. After decades of studies of this successful relationship between pathogen and human host, various mechanisms have been elucidated. In this review, we have made an introduction on H. pylori infection and its virulence factors, and focused mainly on modulation of host immune response triggered by bacteria, changes in the pattern of gene expression in H. pylori-infected gastric mucosa, with activation of gene transcription involved in defense mechanisms, inflammatory and immunological response, cell proliferation and apoptosis. We also highlighted the role of bacteria eradication on gene expression levels. In addition, we addressed the recent involvement of different microRNAs in precancerous lesions, gastric cancer, and inflammatory processes induced by bacteria. New discoveries in this field may allow a better understanding of the role of major factors involved in the pathogenic mechanisms of H. pylori.