miR-21 promotes fibrogenic epithelial-to-mesenchymal transition of epicardial mesothelial cells involving Programmed Cell Death 4 and Sprouty-1

Differential modulations of miRNAs in patients with systemic sclerosis-associated skeletal muscle loss

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune disease characterized by sustained vascular inflammation and progressive skin and internal organs fibrosis. Up to 22 % of SSc patients may manifest skeletal muscle impairment, which predicts worse clinical outcomes, including increased mortality, however, pathogenesis is still largely unclear and could be associated with modulation of circulating microRNAs (miRNAs). Aims of the present study were to evaluate differentially modulated miRNAs in SSc patients and to evaluate their association with changes in body composition(s) and with the clinical course and type of the disease.

METHODS

Circulating levels of miRNAs were detected by RT-qPCR. ELISA assay was performed to measure the TGF-β1 protein. Muscularity (FFMI kg/m2) and phase angle (PhA, °) were estimated by Bioelectrical Impedance Analysis.

RESULTS

We enrolled 47 SSc patients and 21 controls (C). We observed downregulation of miR-15b (p = 0.024), -21 (p < 0.001), -29a (p < 0.001), -29b (p = 0.007) and -133a (p < 0.001), whereas miR-206 (p < 0.001) and -486 (p < 0.001) were upregulated in SSc vs C. In SSc, miR-29b negatively correlates with TGF-β1 (r = -0.303, p = 0.046). MiR-206 was downregulated vs high FFMI (p = 0.040) in SSc with low FFMI, and miR-15b positively correlates with PhA (r = 0.356, p = 0.014). MiR-15b and -486 were modulated in early vs late nailfold capillaroscopy stage (p = 0.028 and p = 0.045, respectively). MiR-133a was higher in SSc with Scl70 v ACA subset of autoantibodies (p = 0.002).

CONCLUSIONS

In SSc patients, differential modulations of miRNAs involved in muscularity occur. The data obtained suggest that mechanisms other than disease-related malnutrition might be responsible for SSc-associated skeletal muscle loss.

miR-194-3p regulates epithelial-mesenchymal transition in embryonic epicardial cells via p120/β-catenin signaling

The epicardium is integral to cardiac development and facilitates endogenous heart regeneration and repair. While miR-194-3p is associated with cellular migration and invasion, its impact on epicardial cells remains uncharted. In this work we use gain-of-function and loss-of-function methodologies to investigate the function of miR-194-3p in cardiac development. We culture embryonic epicardial cells in vitro and subject them to transforming growth factor β (TGF-β) treatment to induce epithelial-mesenchymal transition (EMT) and monitor miR-194-3p expression. In addition, the effects of miR-194-3p mimics and inhibitors on epicardial cell development and changes in EMT are investigated. To validate the binding targets of miR-194-3p and its ability to recover the target gene-phenotype, we produce a mutant vector p120-catenin-3'UTR-MUT. In epicardial cells, TGF-β-induced EMT results in a notable overexpression of miR-194-3p. The administration of miR-194-3p mimics promotes EMT, which is correlated with elevated levels of mesenchymal markers. Conversely, miR-194-3p inhibitor attenuates EMT. Further investigations reveal a negative correlation between miR-194-3p and p120-catenin, which influences β-catenin level in the cell adhesion pathway. The suppression of EMT caused by the miR-194-3p inhibitor is balanced by silencing of p120-catenin. In conclusion, miR-194-3p directly targets p120-catenin and modulates its expression, which in turn alters β-catenin expression, critically influencing the EMT process in the embryonic epicardial cells via the cell adhesion mechanism.

Gallic acid attenuates metastatic potential of human colorectal cancer cells through the miR-1247-3p-modulated integrin/FAK axis

Colorectal cancer (CRC) exhibits highly metastatic potential even in the early stages of tumor progression. Gallic acid (GA), a common phenolic compound in plants, is known to possess potent antioxidant and anticancer activities, thereby inducing cell death or cell cycle arrest. However, whether GA reduces the invasiveness of CRC cells without inducing cell death remains unclear. Herein, we aimed to investigate the antimetastatic activity of low-dose GA on CRC cells and determine its underlying mechanism. Cell viability and tumorigenicity were analyzed by MTS, cell adhesion, and colony formation assay. Invasiveness was demonstrated using migration and invasion assays. Changes in protein phosphorylation and expression were assessed by Western blot. The involvement of microRNAs was validated by microarray analysis and anti-miR antagonist. Our findings showed that lower dose of GA (≤100 μM) did not affect cell viability but reduced the capabilities of colony formation, cell adhesion, and invasiveness in CRC cells. Cellularly, GA downregulated the cellular level of integrin αV/β3, talin-1, and tensin and diminished the phosphorylated FAK, paxillin, Src, and AKT in DLD-1 cells. Microarray results revealed that GA increased miR-1247-3p expression, and pretreatment of anti-miR antagonist against miR-1247-3p restored the GA-reduced integrin αV/β3 and the GA-inhibited paxillin activation in DLD-1 cells. Consistently, the in vivo xenograft model showed that GA administration inhibited tumor growth and liver metastasis derived from DLD-1 cells. Collectively, our findings indicated that GA inhibited the metastatic capabilities of CRC cells, which may result from the suppression of integrin/FAK axis mediated by miR1247-3p.

miRNAs in Heart Development and Disease

Cardiovascular diseases (CVD) are a group of disorders that affect the heart and blood vessels. They include conditions such as myocardial infarction, coronary artery disease, heart failure, arrhythmia, and congenital heart defects. CVDs are the leading cause of death worldwide. Therefore, new medical interventions that aim to prevent, treat, or manage CVDs are of prime importance. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the posttranscriptional level and play important roles in various biological processes, including cardiac development, function, and disease. Moreover, miRNAs can also act as biomarkers and therapeutic targets. In order to identify and characterize miRNAs and their target genes, scientists take advantage of computational tools such as bioinformatic algorithms, which can also assist in analyzing miRNA expression profiles, functions, and interactions in different cardiac conditions. Indeed, the combination of miRNA research and bioinformatic algorithms has opened new avenues for understanding and treating CVDs. In this review, we summarize the current knowledge on the roles of miRNAs in cardiac development and CVDs, discuss the challenges and opportunities, and provide some examples of recent bioinformatics for miRNA research in cardiovascular biology and medicine.

Inhibitory effect of microRNA-21 on pathways and mechanisms involved in cardiac fibrosis development

Cardiac fibrosis is a pivotal cardiovascular disease (CVD) process and represents a notable health concern worldwide. While the complex mechanisms underlying CVD have been widely investigated, recent research has highlighted microRNA-21's (miR-21) role in cardiac fibrosis pathogenesis. In this narrative review, we explore the molecular interactions, focusing on the role of miR-21 in contributing to cardiac fibrosis. Various signaling pathways, such as the RAAS, TGF-β, IL-6, IL-1, ERK, PI3K-Akt, and PTEN pathways, besides dysregulation in fibroblast activity, matrix metalloproteinases (MMPs), and tissue inhibitors of MMPs cause cardiac fibrosis. Besides, miR-21 in growth factor secretion, apoptosis, and endothelial-to-mesenchymal transition play crucial roles. miR-21 capacity regulatory function presents promising insights for cardiac fibrosis. Moreover, this review discusses numerous approaches to control miR-21 expression, including antisense oligonucleotides, anti-miR-21 compounds, and Notch signaling modulation, all novel methods of cardiac fibrosis inhibition. In summary, this narrative review aims to assess the molecular mechanisms of cardiac fibrosis and its essential miR-21 function.

Novel Insights into the Molecular Mechanisms Governing Embryonic Epicardium Formation

The embryonic epicardium originates from the proepicardium, an extracardiac primordium constituted by a cluster of mesothelial cells. In early embryos, the embryonic epicardium is characterized by a squamous cell epithelium resting on the myocardium surface. Subsequently, it invades the subepicardial space and thereafter the embryonic myocardium by means of an epithelial-mesenchymal transition. Within the myocardium, epicardial-derived cells present multilineage potential, later differentiating into smooth muscle cells and contributing both to coronary vasculature and cardiac fibroblasts in the mature heart. Over the last decades, we have progressively increased our understanding of those cellular and molecular mechanisms driving proepicardial/embryonic epicardium formation. This study provides a state-of-the-art review of the transcriptional and emerging post-transcriptional mechanisms involved in the formation and differentiation of the embryonic epicardium.

MicroRNA Expression in Subretinal Fluid in Eyes Affected by Rhegmatogenous Retinal Detachment

Proliferative vitreoretinopathy (PVR) is an abnormal intraocular scarring process that can complicate cases of rhegmatogenous retinal detachment (RRD). Although previous studies have examined the relevance of microRNAs (miRNAs) in ophthalmic diseases, only a few studies have evaluated the expression profiles of microRNAs in subretinal fluid. We hypothesized that the expression profiles of specific miRNAs may change in response to RRD, in the subretinal fluid that is directly in contact with photoreceptors and the retinal pigment epithelium (RPE). We looked for a potential correlation between the expression of specific miRNAs in eyes with RRD and known clinical risk factors of PVR. A total of 24 patients (59 ± 11 years) who underwent scleral buckling procedure were enrolled in this prospective study. Twenty-four undiluted subretinal fluid samples were collected, RNA was isolated and qRT-PCR was performed to analyze the expression of 12 miRNAs. We found the existence of a positive association between the expression of miR-21 (p = 0.017, r = 0.515) and miR-34 (p = 0.030, r = 0.624) and the duration of symptoms related to retinal detachment. Moreover, the expression of miR-146a tended to decrease in patients who developed PVR. Subretinal fluid constitutes an intriguing biological matrix to evaluate the role of miRNAs leading to the development of PVR.

miR-21 promotes the fibrotic properties in oral mucosa through targeting PDCD4

Background/purpose

Oral submucous fibrosis (OSF) has been regarded as a premalignant disorder of oral cancer, and myofibroblasts are the main cells that are responsible for pathological fibrosis. Hence, elucidation of the molecular mechanism underlying myofibroblast activation is important to treat OSF. MicroRNA-21 (miR-21) is a well-known fibrosis non-coding RNA, and its role in the development of OSF remains largely unclear.

Materials and methods

Luciferase reporter assay was used to confirm the direct interaction between miR-21 and its target programmed cell death 4 (PDCD4). The expression level of PDCD4 in OSF was examined by qRT-PCR. Myofibroblast activities were assessed by collagen gel contraction and transwell migration assays.

Results

Our result validated the direct binding of miR-21 to PDCD4. We showed the expression of PDCD4 was downregulated in OSF specimens and negatively correlated with miR-21. Our results suggested that overexpression of PDCD4 in fibrotic buccal mucosal fibroblasts (fBMFs) mitigated the myofibroblast activities, including collagen gel contractility and migration capacity. Moreover, we showed miR-21 contributed to myofibroblast activation of BMFs through repression of PDCD4.

Conclusion

Our results suggest that the miR-21/PDCD4 axis mediates the myofibroblast activation of BMFs, and targeting this axis may exert an anti-fibrosis effect.

Interplay Between Non-Coding RNAs and Programmed Cell Death Proteins

Programmed cell death (PDCD) family of proteins includes at least 12 members, function of seven of them being more investigated. These members are PDCD1, PDCD2, PDCD4, PDCD5, PDCD6, PDCD7 and PDCD10. Consistent with the important roles of these proteins in the regulation of apoptosis, dysregulation of PDCDs is associated with diverse disorders ranging from intervertebral disc degeneration, amyotrophic lateral sclerosis, immune thrombocytopenia, type 1 diabetes, congenital hypothyroidism, Alzheimer’s disease to different types of cancers. More recently, the interaction between non-coding RNAs and different members of PDCD family is being discovered. In the current study, we described the functional interactions between PDCDs and two classes of non-coding RNAs, namely microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). miR-21 and miR-183 are two miRNAs whose interactions with PDCDs have been assessed in different contexts. The lncRNAs interaction with PDCDs is mainly assessed in the context of neoplasia indicating the role of MALAT1, MEG3, SNHG14 and LINC00473 in this process.

Post-Transcriptional Regulation of Molecular Determinants during Cardiogenesis

Cardiovascular development is initiated soon after gastrulation as bilateral precardiac mesoderm is progressively symmetrically determined at both sides of the developing embryo. The precardiac mesoderm subsequently fused at the embryonic midline constituting an embryonic linear heart tube. As development progress, the embryonic heart displays the first sign of left-right asymmetric morphology by the invariably rightward looping of the initial heart tube and prospective embryonic ventricular and atrial chambers emerged. As cardiac development progresses, the atrial and ventricular chambers enlarged and distinct left and right compartments emerge as consequence of the formation of the interatrial and interventricular septa, respectively. The last steps of cardiac morphogenesis are represented by the completion of atrial and ventricular septation, resulting in the configuration of a double circuitry with distinct systemic and pulmonary chambers, each of them with distinct inlets and outlets connections. Over the last decade, our understanding of the contribution of multiple growth factor signaling cascades such as Tgf-beta, Bmp and Wnt signaling as well as of transcriptional regulators to cardiac morphogenesis have greatly enlarged. Recently, a novel layer of complexity has emerged with the discovery of non-coding RNAs, particularly microRNAs and lncRNAs. Herein, we provide a state-of-the-art review of the contribution of non-coding RNAs during cardiac development. microRNAs and lncRNAs have been reported to functional modulate all stages of cardiac morphogenesis, spanning from lateral plate mesoderm formation to outflow tract septation, by modulating major growth factor signaling pathways as well as those transcriptional regulators involved in cardiac development.

Dynamic Changes in miR-21 Regulate Right Ventricular Dysfunction in Congenital Heart Disease-Related Pulmonary Arterial Hypertension

Right ventricular (RV) failure is a major cause of mortality in pulmonary arterial hypertension (PAH), but its mechanism remains largely unknown. MicroRNA-21 (miR-21) is involved in flow-mediated stress in the vasculature, but its effects on RV remodeling require investigations. Herein, we aim to study the mechanism of miR-21 in the early (compensated) and late (decompensated) phases of PAH-induced RV dysfunction. Using aorto-venous fistula (AVS) surgery, we established a rat model of PAH. To mimic the microenvironment of PAH, we treated cardiomyocytes with flow-mediated shear stress in 6 dyne for 3 and 8 h. To evaluate whether miR-21 could be a biomarker, we prospectively collected the sera of patients with congenital heart disease- (CHD) related PAH. Additionally, clinical, echocardiographic and right heart catheterization information was collected. The primary endpoint was hospitalization for decompensated heart failure (HF). It is of note that, despite an initial increase in miR-21 expression in hypertrophic RV post AVS, miR-21 expression decreased with RV dysfunction thereafter. Likewise, the activation of miR-21 in cardiomyocytes under shear stress at 3 h was downregulated at 6 h. The downregulated miR-21 at the late phase was associated with increased apoptosis in cardiomyocytes while miR-21 mimic rescued it. Among 76 CHD-induced PAH patients, 19 who were hospitalized for heart failure represented with a significantly lower expression of circulating miR-21. Collectively, our study revealed that the upregulation of miR-21 in the early phase (RV hypertrophy) and downregulation in the late phase (RV dysfunction) under PAH triggered a biphasic regulation of cardiac remodeling and cardiomyocyte apoptosis.

A microRNA-21-mediated SATB1/S100A9/NF-κB axis promotes chronic obstructive pulmonary disease pathogenesis

[Figure: see text].

Discovery of a novel role of tumor suppressor PDCD4 in stimulation of translation termination

Programmed cell death 4 protein (PDCD4) regulates many vital cell processes, although is classified as a tumor suppressor because it inhibits neoplastic transformation and tumor growth. For example, PCDC4 has been implicated in the regulation of transcription and mRNA translation. PDCD4 is known to inhibit translation initiation by binding to eukaryotic initiation factor 4A and elongation of oncogenic c- and A-myb mRNAs. Additionally, PDCD4 has been shown to interact with poly(A)-binding protein (PABP), which affects translation termination, although the significance of this interaction is not fully understood. Considering the interaction between PABP and PDCD4, we hypothesized that PDCD4 may also be involved in translation termination. Using in vitro translation systems, we revealed that PDCD4 directly activates translation termination. PDCD4 stimulates peptidyl-tRNA hydrolysis induced by a complex of eukaryotic release factors, eRF1-eRF3. Moreover, in combination with the PABP, which also stimulates peptide release, PDCD4 activity in translation termination increases. PDCD4 regulates translation termination by facilitating the binding of release factors to the ribosome, increasing the GTPase activity of eRF3, and dissociating eRF3 from the posttermination complex. Using a toe-printing assay, we determined the first stage at which PDCD4 functions-binding of release factors to the A-site of the ribosome. However, preventing binding of eRF3 with PABP, PDCD4 suppresses subsequent rounds of translation termination. Based on these data, we assumed that human PDCD4 controls protein synthesis during translation termination. The described mechanism of the activity of PDCD4 in translation termination provides a new insight into its functioning during suppression of protein biosynthesis.

MicroRNA roles in regeneration: Multiple lessons from zebrafish

MicroRNAs (miRNAs) are small noncoding RNAs with pivotal roles in the control of gene expression. By comparing the miRNA profiles of uninjured vs. regenerating tissues and structures, several studies have found that miRNAs are potentially involved in the regenerative process. By inducing miRNA overexpression or inhibition, elegant experiments have directed regenerative responses validating relevant miRNA-to-target interactions. The zebrafish (Danio rerio) has been the epicenter of regenerative research because of its exceptional capability to self-repair damaged tissues and body structures. In this review, we discuss recent discoveries that have improved our understanding of the impact of gene regulation mediated by miRNAs in the context of the regeneration of fins, heart, retina, and nervous tissue in zebrafish. We compiled what is known about the miRNA control of regeneration in these tissues and investigated the links among up-regulated and down-regulated miRNAs, their putative or validated targets, and the regenerative process. Finally, we briefly discuss the forthcoming prospects, highlighting directions and the potential for further development of this field.

LncRNA GAS5 Competitively Combined With miR-21 Regulates PTEN and Influences EMT of Peritoneal Mesothelial Cells via Wnt/β-Catenin Signaling Pathway

Objective

Epithelial-mesenchymal transition (EMT) is an important factor leading to peritoneal fibrosis (PF) in end-stage renal disease (ESRD) patients. The current research aimed to evaluate the effect of long non-coding RNA growth arrest-specific 5 (lncRNA GAS5) in human peritoneal mesothelial cells (HPMCs) EMT and explore the potential molecular mechanisms.

Materials and Methods

HPMCs were cultured under control conditions or with high glucose (HG). The cells were then treated with lncRNA GAS5, lncRNA GAS5 siRNA, with or without miR-21 inhibitor and PTEN transfection. Expression of lncRNA GAS5, miR-21, α-SMA, Vimentin, E-cadherin, phosphatase and tensin homolog deleted on chromosome ten (PTEN), Wnt3a, and β-catenin were measured by real time PCR and Western blotting. Bioinformatics analyses were used to test the specific binding sites between the 3' UTR of the PTEN gene, miR-21, and lncRNA GAS5. Rescue experiments were performed to confirm the lncRNA GAS5/miR-21/PTEN axis in HPMC EMT.

Results

We found that HG-induced EMT decreased lncRNA GAS5 and that overexpression of lncRNA GAS5 can attenuate EMT in HPMCs. In addition, lncRNA GAS5 regulated HG-induced EMT through miR-21/PTEN. Cotransfection of miR-21 inhibitors remarkably increased PTEN expression and attenuated EMT in lncRNA GAS5 knockdown HPMCs. Moreover, rescue experiments showed that overexpression of PTEN attenuated the EMT effects of lncRNA GAS5 siRNA in HPMCs. We also confirmed that the Wnt/β-catenin pathway was stimulated in lncRNA GAS5/miR-21/PTEN-mediated EMT.

Conclusion

Our research showed that lncRNA GAS5 competitively combined with miR-21 to regulate PTEN expression and influence EMT of HPMCs via the Wnt/β-catenin signaling pathway. This study provides novel evidence that lncRNA GAS5 may be a potential therapeutic target for HPMC EMT.

Bioengineering strategies to control epithelial-to-mesenchymal transition for studies of cardiac development and disease

Epithelial-to-mesenchymal transition (EMT) is a process that occurs in a wide range of tissues and environments, in response to numerous factors and conditions, and plays a critical role in development, disease, and regeneration. The process involves epithelia transitioning into a mobile state and becoming mesenchymal cells. The investigation of EMT processes has been important for understanding developmental biology and disease progression, enabling the advancement of treatment approaches for a variety of disorders such as cancer and myocardial infarction. More recently, tissue engineering efforts have also recognized the importance of controlling the EMT process. In this review, we provide an overview of the EMT process and the signaling pathways and factors that control it, followed by a discussion of bioengineering strategies to control EMT. Important biological, biomaterial, biochemical, and physical factors and properties that have been utilized to control EMT are described, as well as the studies that have investigated the modulation of EMT in tissue engineering and regenerative approaches in vivo, with a specific focus on the heart. Novel tools that can be used to characterize and assess EMT are discussed and finally, we close with a perspective on new bioengineering methods that have the potential to transform our ability to control EMT, ultimately leading to new therapies.

miR-200c-3p Regulates Epitelial-to-Mesenchymal Transition in Epicardial Mesothelial Cells by Targeting Epicardial Follistatin-Related Protein 1

Recent findings suggest that epithelial to mesenchymal transition (EMT), a key step during heart development, is involved in cardiac tissue repair following myocardial infarction (MI). MicroRNAs (miRNAs) act as key regulators in EMT processes; however, the mechanisms by which miRNAs target epicardial EMT remain largely unknown. Here, by using an in vitro model of epicardial EMT, we investigated the role of miRNAs as regulators of this process and their potential targets. EMT was induced in murine epicardial-mesothelial cells (EMCs) through TGF β1 treatment for 48, 72, and 96 h as indicated by the expression of EMT-related genes by qRT-PCR, WB, and immunofluorescence. Further, enhanced expression of stemness genes was also detected. Among several EMT-related miRNAs, miR-200c-3p expression resulted as the most strongly suppressed. Interestingly, we also found a significant upregulation of Follistatin-related protein 1 (FSTL1), a miR-200c predicted target already identified as a potent cardiogenic factor produced by epicardial cells that promotes regeneration following MI. Dual-luciferase reporter assay demonstrated that miR-200c-3p directly targeted the 3'-untranslated region of FSTL1 in EMCs. Consistently, WB analysis showed that knockdown of miR-200c-3p significantly increased FSTL1 expression, whereas overexpression of miR-200c-3p counteracted TGF β1-mediated FSTL1 upregulation. Importantly, FSTL1 silencing maintained epithelial features in EMCs, despite EMT induction by TGF β1, and attenuated EMT-associated traits, including migration and stemness. In conclusion, epicardial FSTL1, an important cardiogenic factor in its secreted form, induces EMT, stemness, and migration of EMCs in a miR-200c-3p dependent pathway.

Cardiac Development: A Glimpse on Its Translational Contributions

Cardiac development is a complex developmental process that is initiated soon after gastrulation, as two sets of precardiac mesodermal precursors are symmetrically located and subsequently fused at the embryonic midline forming the cardiac straight tube. Thereafter, the cardiac straight tube invariably bends to the right, configuring the first sign of morphological left–right asymmetry and soon thereafter the atrial and ventricular chambers are formed, expanded and progressively septated. As a consequence of all these morphogenetic processes, the fetal heart acquired a four-chambered structure having distinct inlet and outlet connections and a specialized conduction system capable of directing the electrical impulse within the fully formed heart. Over the last decades, our understanding of the morphogenetic, cellular, and molecular pathways involved in cardiac development has exponentially grown. Multiples aspects of the initial discoveries during heart formation has served as guiding tools to understand the etiology of cardiac congenital anomalies and adult cardiac pathology, as well as to enlighten novels approaches to heal the damaged heart. In this review we provide an overview of the complex cellular and molecular pathways driving heart morphogenesis and how those discoveries have provided new roads into the genetic, clinical and therapeutic management of the diseased hearts.

The Cell Type-Specific Functions of miR-21 in Cardiovascular Diseases

Cardiovascular diseases are one of the prime reasons for disability and death worldwide. Diseases and conditions, such as hypoxia, pressure overload, infection, and hyperglycemia, might initiate cardiac remodeling and dysfunction by inducing hypertrophy or apoptosis in cardiomyocytes and by promoting proliferation in cardiac fibroblasts. In the vascular system, injuries decrease the endothelial nitric oxide levels and affect the phenotype of vascular smooth muscle cells. Understanding the underlying mechanisms will be helpful for the development of a precise therapeutic approach. Various microRNAs are involved in mediating multiple pathological and physiological processes in the heart. A cardiac enriched microRNA, miR-21, which is essential for cardiac homeostasis, has been demonstrated to act as a cell–cell messenger with diverse functions. This review describes the cell type–specific functions of miR-21 in different cardiovascular diseases and its prospects in clinical therapy.

miR-21 mediates nickel nanoparticle-induced pulmonary injury and fibrosis

We and other groups have demonstrated that exposure to nickel nanoparticles (Nano-Ni) results in severe and persistent lung inflammation and fibrosis, but the underlying mechanisms remain unclear. Here, we propose that miR-21 may play an important role in Nano-Ni-induced lung inflammation, injury, and fibrosis. Our dose- and time-response studies demonstrated that exposure of C57BL/6J (WT) mice to Nano-Ni resulted in upregulation of miR-21, proinflammatory cytokines, and profibrotic mediators. Histologically, exposure to Nano-Ni caused severe pulmonary inflammation and fibrosis. Based on the dose- and time-response studies, we chose a dose of 50 µg of Nano-Ni per mouse to compare the effects of Nano-Ni on WT with those on miR-21 KO mouse lungs. At day 3 post-exposure, Nano-Ni caused severe acute lung inflammation and injury that were reflected by increased neutrophil count, CXCL1/KC level, LDH activity, total protein concentration, MMP-2/9 protein levels and activities, and proinflammatory cytokines in the BALF or lung tissues from WT mice, which were confirmed histologically. Although Nano-Ni had similar effects on miR-21 KO mice, the above-mentioned levels were significantly lower than those in WT mice. Histologically, lungs from WT mice exposed to Nano-Ni had infiltration of a large number of polymorphonuclear (PMN) cells and macrophages in the alveolar space and interstitial tissues. However, exposure of miR-21 KO mice to Nano-Ni only caused mild acute lung inflammation and injury. At day 42 post-exposure, Nano-Ni caused extensive pulmonary fibrosis and chronic inflammation in the WT mouse lungs. However, exposure of miR-21 KO mice to Nano-Ni only caused mild lung fibrosis and chronic lung inflammation. Our results also showed that exposure to Nano-Ni caused upregulation of TGF-β1, phospho-Smad2, COL1A1, and COL3A1 in both WT and miR-21 KO mouse lungs. However, levels were significantly lower in miR-21 KO mice than in WT mice, except TGF-β1, which was similar in both kinds of mice. Decreased expression of Smad7 was observed in WT mouse lungs, but not in miR-21 KO mice. Our results demonstrated that knocking out miR-21 ameliorated Nano-Ni-induced pulmonary inflammation, injury, and fibrosis, suggesting the important role of miR-21 in Nano-Ni-induced pulmonary toxicity.

Circulating microRNA in Heart Failure - Practical Guidebook to Clinical Application

Heart failure (HF) remains a major cause of death and disability worldwide. Currently, B-type natriuretic peptide and N-terminal pro-brain natriuretic peptide are diagnostic biomarkers used in HF. Although very sensitive, they are not specific enough and do not allow the prediction or early diagnosis of HF. Many ongoing studies focus on determining the underlying cause and understanding the mechanisms of HF on the cellular level. MicroRNAs (miRNAs) are non-coding RNAs which control the majority of cellular processes and therefore are considered to have a potential clinical application in HF. In this review, we aim to provide synthesized information about miRNAs associated with ejection fraction, HF etiology, diagnosis, and prognosis, as well as outline therapeutic application of miRNAs in HF. Further, we discuss methodological challenges associated with the analysis of miRNAs and provide recommendations for defining a study population, collecting blood samples, and selecting detection methods to study miRNAs in a reliable and reproducible way. This review is intended to be an accessible tool for clinicians interested in the field of miRNAs and HF.

MiR-195 enhances cardiomyogenic differentiation of the proepicardium/septum transversum by Smurf1 and Foxp1 modulation

Cardiovascular development is a complex developmental process in which multiple cell lineages are involved, namely the deployment of first and second heart fields. Beside the contribution of these cardiogenic fields, extracardiac inputs to the developing heart are provided by the migrating cardiac neural crest cells and the proepicardial derived cells. The proepicardium (PE) is a transitory cauliflower-like structure located between the cardiac and hepatic primordia. The PE is constituted by an internal mesenchymal component surrounded by an external epithelial lining. With development, cells derived from the proepicardium migrate to the neighboring embryonic heart and progressive cover the most external surface, leading to the formation of the embryonic epicardium. Experimental evidence in chicken have nicely demonstrated that epicardial derived cells can distinctly contribute to fibroblasts, endothelial and smooth muscle cells. Surprisingly, isolation of the developing PE anlage and ex vivo culturing spontaneously lead to differentiation into beating cardiomyocytes, a process that is enhanced by Bmp but halted by Fgf administration. In this study we provide a comprehensive characterization of the developmental expression profile of multiple microRNAs during epicardial development in chicken. Subsequently, we identified that miR-125, miR-146, miR-195 and miR-223 selectively enhance cardiomyogenesis both in the PE/ST explants as well as in the embryonic epicardium, a Smurf1- and Foxp1-driven process. In addition we identified three novel long non-coding RNAs with enhanced expression in the PE/ST, that are complementary regulated by Bmp and Fgf administration and well as by microRNAs that selectively promote cardiomyogenesis, supporting a pivotal role of these long non coding RNAs in microRNA-mediated cardiomyogenesis of the PE/ST cells.

Prevention of heart failure with preserved ejection fraction (HFpEF): reexamining microRNA-21 inhibition in the era of oligonucleotide-based therapeutics

Heart failure with preserved ejection fraction (HFpEF) accounts for 50% of cases of heart failure, which is the most common cause of hospitalization in US patients over the age of 65. HFpEF pathogenesis is increasingly believed to be due to pathological hypertrophy and fibrosis of the myocardium that may be a result of systemic inflammation from comorbid conditions such as hypertension, diabetes mellitus, chronic obstructive pulmonary disease, anemia, chronic kidney disease and others. It is believed that oxidative stress triggers a process of pathological hypertrophy and fibrosis in cardiac endothelial cells, which leads to increased left ventricle filling pressures and, eventually, symptoms of heart failure. Numerous recent major clinical trials that have examined various therapies aimed at improving mortality in HFpEF have emerged empty-handed and thus the search for effective management strategies continues. Over the last several years, there have been many new developments in the field of antisense oligonucleotide-based therapeutics, which involves using noncoding nucleic acid particles such as microRNA and small interfering RNA to repress the expression of specific messenger RNA. In this article, we review the concept of using oligonucleotide-based therapeutics to prevent or treat HFpEF by targeting a specific microRNA that has been implicated in the pathogenesis of myocardial fibrosis and hypertrophy, microRNA-21 (miR-21). We review the various evidence that implicates miR-21 in the process of myocardial fibrosis and discuss recent attempts to use antimiR-21 compounds to prevent fibrosis. We also discuss proposed methods for screening patients at high risk for HFpEF for diastolic dysfunction in order to determine which patients.

Melatonin ameliorates renal fibroblast-myofibroblast transdifferentiation and renal fibrosis through miR-21-5p regulation

Fibroblast‐myofibroblast transdifferentiation (FMT) is widely recognized as the major pathological feature of renal fibrosis. Although melatonin has exerted antifibrogenic activity in many diseases, its role in renal FMT remains unclear. In the present study, the aim was to explore the effect of melatonin on renal FMT and the underlying mechanisms. We established the transforming growth factor (TGF)‐β1 stimulated rat renal fibroblast cells (NRK‐49F) model in vitro and unilateral ureteral obstruction (UUO) mice model in vivo. We assessed levels of α‐smooth muscle actin (α‐SMA), col1a1 and fibronectin, STAT3 and AP‐1, as well as miR‐21‐5p and its target genes (Spry1, PTEN, Smurf2 and PDCD4). We found that melatonin reduced the expression of α‐SMA, col1a1 and fibronectin, as well as the formation of α‐SMA filament in TGF‐β1‐treated NRK‐49F cells. Meanwhile, melatonin inhibited STAT3 phosphorylation, down‐regulated miR‐21‐5p expression, and up‐regulated Spry1 and PTEN expression. Moreover, miR‐21‐5p mimics partially antagonized the anti‐fibrotic effect of melatonin. For animal experiments, the results revealed that melatonin remarkably ameliorated UUO‐induced renal fibrosis, attenuated the expression of miR‐21‐5p and pro‐fibrotic proteins and elevated Spry1 and PTEN expression. Nevertheless, agomir of miR‐21‐5p blocked the renoprotective effect of melatonin in UUO mice. These results indicated that melatonin could alleviate TGF‐β1‐induced renal FMT and UUO‐induced renal fibrosis through down‐regulation of miR‐21‐5p. Regulation of miR‐21‐5p/PTEN and/or miR‐21‐5p/Spry1 signal might be involved in the anti‐fibrotic effect of melatonin in the kidneys of UUO mice.

Non-ischemic dilated cardiomyopathy and cardiac fibrosis

Cardiac fibrosis is associated with non-ischemic dilated cardiomyopathy, increasing its morbidity and mortality. Cardiac fibroblast is the keystone of fibrogenesis, being activated by numerous cellular and humoral factors. Macrophages, CD4+ and CD8+ T cells, mast cells, and endothelial cells stimulate fibrogenesis directly by activating cardiac fibroblasts and indirectly by synthetizing various profibrotic molecules. The synthesis of type 1 and type 3 collagen, fibronectin, and α-smooth muscle actin is rendered by various mechanisms like transforming growth factor-beta/small mothers against decapentaplegic pathway, renin angiotensin system, and estrogens, which in turn alter the extracellular matrix. Investigating the underlying mechanisms will allow the development of diagnostic and prognostic tools and discover novel specific therapies. Serum biomarkers aid in the diagnosis and tracking of cardiac fibrosis progression. The diagnostic gold standard is cardiac magnetic resonance with gadolinium administration that allows quantification of cardiac fibrosis either by late gadolinium enhancement assessment or by T1 mapping. Therefore, the goal is to stop and even reverse cardiac fibrosis by developing specific therapies that directly target fibrogenesis, in addition to the drugs used to treat heart failure. Cardiac resynchronization therapy had shown to revert myocardial remodeling and to reduce cardiac fibrosis. The purpose of this review is to provide an overview of currently available data.

Dietary delphinidin inhibits human colorectal cancer metastasis associating with upregulation of miR-204-3p and suppression of the integrin/FAK axis

Delphinidin is a flavonoid belonging to dietary anthocyanidin family that has been reported to possess diverse anti-tumoral activities. However, the effects of delphinidin on colorectal cancer (CRC) cells and the underlying mechanisms are not fully understood. Thus, we aimed to investigate the anti-cancer activity of delphinidin in CRC cells and the underlying molecular mechanisms. The effects of delphinidin on the viability, metastatic characteristics, signaling, and microRNA (miR) profile of human CRC cell lines used were analyzed. In vivo metastasis was also evaluated using xenograft animal models. Our findings showed that delphinidin (<100 μM) inhibited the colony formation of DLD-1, SW480, and SW620 cells, but non-significantly affected cell viability. Delphinidin also suppressed the migratory ability and invasiveness of the tested CRC cell lines, downregulated integrin αV/β3 expression, inhibited focal adhesion kinase (FAK)/Src/paxillin signaling, and interfered with cytoskeletal construction. Analysis of the miR expression profile revealed a number of miRs, particularly miR-204-3p, that were significantly upregulated and downregulated by delphinidin. Abolishing the expression of one upregulated miR, miR-204-3p, with an antagomir restored delphinidin-mediated inhibition of cell migration and invasiveness in DLD-1 cells as well as the αV/β3-integrin/FAK/Src axis. Delphinidin also inhibited the lung metastasis of DLD-1 cells in the xenograft animal model. Collectively, these results indicate that the migration and invasion of CRC cells are inhibited by delphinidin, and the mechanism may involve the upregulation of miR-204-3p and consequent suppression of the αV/β3-integrin/FAK axis. These findings suggest that delphinidin exerts anti-metastatic effects in CRC cells by inhibiting integrin/FAK signaling and indicate that miR-204-3p may play an important role in CRC metastasis.

Connecting sex differences, estrogen signaling, and microRNAs in cardiac fibrosis

Sex differences are evident in the pathophysiology of heart failure (HF). Progression of HF is promoted by cardiac fibrosis and no fibrosis-specific therapies are currently available. The fibrotic response is mediated by cardiac fibroblasts (CFs), and a central event is their phenotypic transition to pro-fibrotic myofibroblasts. These myofibroblasts may arise from various cellular origins including resident CFs and epicardial and endothelial cells. Both female subjects in clinical studies and female animals in experimental studies generally present less cardiac fibrosis compared with males. This difference is at least partially considered attributable to the ovarian hormone 17β-estradiol (E2). E2 signals via estrogen receptors to regulate genes are involved in the fibrotic response and myofibroblast transition. Besides protein-coding genes, E2 also regulates transcription of microRNA that modulate cardiac fibrosis. Sex dimorphism, E2, and miRNAs form multi-level regulatory networks in the pathophysiology of cardiac fibrosis, and the mechanism of these networks is not yet fully deciphered. Therefore, this review is aimed at summarizing current knowledge on sex differences, E2, and estrogen receptors in cardiac fibrosis, emphasizing on microRNAs and myofibroblast origins. KEY MESSAGES: • E2 and ERs regulate cardiac fibroblast function. • E2 and ERs may distinctly affect male and female cardiac fibrosis pathophysiology. • Sex, E2, and miRNAs form multi-level regulatory networks in cardiac fibrosis. • Sex-dimorphic and E2-regulated miRNAs affect mesenchymal transition.

Pleiotropic microRNA-21 in pulmonary remodeling: novel insights for molecular mechanism and present advancements

MicroRNA-21 (miR-21), probably one of the most studied miRNAs to date, is found pleiotropic in various biological events. Its emerging role in pulmonary remodeling has attracted extensive attention. This review summarizes the genomic information of its primary transcript and various transcriptional regulations on its promoter. In addition, the role of miR-21 in pulmonary remodeling related signaling such as transforming growth factor β (TGF-β), bone morphogenetic protein (BMP), epidermal growth factor receptor (EGFR) and Notch signaling is discussed. Various validated miR-21 target genes participate in controlling of the overactive cell accumulation, smooth muscle contraction, inflammatory stress (trigger for lung epithelium damage), extracellular matrix deposition and hypoxia-induced disorders. Moreover, we focus on its particular implication in events including inflammatory stress-driven epithelium damage, epithelial-to-mesenchymal transition (EMT), transdifferentiation of fibroblasts into myofibroblasts, hypoxia stimuli and ROS response, as well as some other pulmonary remodeling related events such as overactive fibroblast (myofibroblast) accumulation, extracellular matrix deposition, and angiogenesis. Here, we summarize the strong potential of miR-21 in pulmonary remodeling and provide novel clues for further research in this area.

MiRNA-21 functions in ionizing radiation-induced epithelium-to-mesenchymal transition (EMT) by downregulating PTEN

Radiation-induced pulmonary fibrosis (RIPF) results from thoracic radiotherapy and severely limits the use of radiotherapy. Recent studies suggest that epithelium-to-mesenchymal transition (EMT) contributes to pulmonary fibrosis. Although miRNA dysregulation participates in a variety of pathophysiologic processes, their roles in fibrotic lung diseases and EMT are unclear. In this study, we aimed to identify key miRNAs involved in this process using a mouse model of RIPF previously established by irradiation with a single dose (20 Gy) of ⁶⁰Co γ-rays. At 2-weeks post-irradiation, a set of significantly upregulated miRNAs was identified in lung tissue by miRNA array analysis. This included miR-21, which has been reported to contribute to the pulmonary fibrotic response induced by stereotactic body radiotherapy. Here, we showed that miR-21 expression increased in parallel with EMT progression in the lungs of irradiated mice. Ectopic miR-21 expression promoted EMT progression in lung epithelial cells. Furthermore, downregulation of miR-21 expression by transfection of its inhibitor inhibited ionizing radiation (IR)-induced EMT. Knockdown of PTEN, which is the functional target of miR-21, reversed the attenuation of IR-induced EMT mediated by miR-21 downregulation. Radiation treatment decreased PTEN expression and increased Akt phosphorylation; these effects were abolished by the miR-21 inhibitor. MiR-21 overexpression in lung epithelial cell also downregulated PTEN expression and upregulated Akt phosphorylation. In conclusion, we have demonstrated that miR-21 functions as a key regulator of IR-induced EMT in lung epithelial cells via the PTEN/Akt pathway. Targeting miR-21 is implicated as a novel therapeutic strategy for the prevention of RIPF.

MicroRNA-21 contributes to high glucose-induced fibrosis in peritoneal mesothelial cells in rat models by activation of the Ras-MAPK signaling pathway via Sprouty-1

Peritoneal fibrosis remains to be one of the most severe causes of failure in continuous peritoneal dialysis. The current study cultured peritoneal mesothelial cells in high glucose to stimulate the environment of peritoneal fibrosis model in rats, and investigate whether microRNA-21 (miR-21) targeting Sprouty-1 affects high glucose-induced fibrosis in peritoneal mesothelial cells via the rennin angiotensin system (Ras)-mitogen-activated protein kinase (MAPK) signaling pathway, as well as potential mechanisms. Peritoneal tissues in fibrosis rats were collected to extract peritoneal mesothelial cells, which, after in vitro culture, were transfected with a series of mimic or inhibitor of miR-21, or the small interfering RNA (siRNA) against Sprouty-1. Reverse-transcription quantitative polymerase chain reaction and western blot analyses were performed to determine the levels of related genes or proteins. MTT assay and flow cytometry were conducted to observe the cell viability and cell apoptosis of peritoneal mesothelial cells. Dual-luciferase reporter gene assay revealed that Sprouty-1 is the target gene of miR-21. Peritoneal fibrosis manifested with elevated miR-21, extracellular-signal-regulated kinase (ERK), c-Jun NH2-terminal protein kinase (JNK), RAS and p38MAPK but reduced Sprouty-1. Cells transfected with miR-21 mimic exhibited decreased Sprouty-1 expressions, but increased levels of ERK, JNK, RAS, and p38MAPK. As for cellular process, miR-21 mimic or siRNA against Sprouty-1 exposure reduced cell viability, which resulted in more cells arrested at the G1 stage, and induced apoptosis. In contrast, miR-21 inhibitor exposure was observed to have induced effects on peritoneal mesothelial cells. These key findings provide evidence that miR-21 inhibits Sprouty-1 to promote the progression of fibrosis in peritoneal mesothelial cells by activating the Ras-MAPK signaling pathway.

Role of miRNA-21/PTEN on the high glucose-induced EMT in human mesothelial peritoneal cells

OBJECTIVE

To explore the effects of miRNA-21/phosphatase and tensin homolog (PTEN) on the high glucose-stimulated epithelial-to-mesenchymal transition (EMT) in human peritoneal mesothelial cells (HPMCs).

METHODS

HPMCs were cultured under control conditions, or with high glucose (HG), HG with miRNA-21 mimic or a miRNA-21 inhibitor. Expression of miRNA-21, α-smooth muscle actin, >fibronectin, E-cadherin and PTEN were measured by real time PCR, Western blotting and immunofluorescence staining.

RESULTS

Compared with the control, HG induced the EMT, as shown by upregulation of α-smooth muscle actin and >fibronectin, and downregulation of E-cadherin. We also found that HG upregulated miRNA-21 expression and downregulated PTEN expression; the miRNA-21 inhibitor attenuated the HG-induced EMT in HPMCs by targeting PTEN; the miRNA-21 mimic increased the HG-induced EMT in HPMCs by targeting PTEN.

CONCLUSIONS

This study demonstrated that miRNA-21 played a vital role in the HG-induced EMT by targeting PTEN in HPMCs.

Expanding the horizons of microRNA bioinformatics

MicroRNA regulation of key biological and developmental pathways is a rapidly expanding area of research, accompanied by vast amounts of experimental data. This data, however, is not widely available in bioinformatic resources, making it difficult for researchers to find and analyze microRNA-related experimental data and define further research projects. We are addressing this problem by providing two new bioinformatics data sets that contain experimentally verified functional information for mammalian microRNAs involved in cardiovascular-relevant, and other, processes. To date, our resource provides over 4400 Gene Ontology annotations associated with over 500 microRNAs from human, mouse, and rat and over 2400 experimentally validated microRNA:target interactions. We illustrate how this resource can be used to create microRNA-focused interaction networks with a biological context using the known biological role of microRNAs and the mRNAs they regulate, enabling discovery of associations between gene products, biological pathways and, ultimately, diseases. This data will be crucial in advancing the field of microRNA bioinformatics and will establish consistent data sets for reproducible functional analysis of microRNAs across all biological research areas.

Functional Role of Non-Coding RNAs during Epithelial-To-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is a key biological process involved in a multitude of developmental and pathological events. It is characterized by the progressive loss of cell-to-cell contacts and actin cytoskeletal rearrangements, leading to filopodia formation and the progressive up-regulation of a mesenchymal gene expression pattern enabling cell migration. Epithelial-to-mesenchymal transition is already observed in early embryonic stages such as gastrulation, when the epiblast undergoes an EMT process and therefore leads to the formation of the third embryonic layer, the mesoderm. Epithelial-to-mesenchymal transition is pivotal in multiple embryonic processes, such as for example during cardiovascular system development, as valve primordia are formed and the cardiac jelly is progressively invaded by endocardium-derived mesenchyme or as the external cardiac cell layer is established, i.e., the epicardium and cells detached migrate into the embryonic myocardial to form the cardiac fibrous skeleton and the coronary vasculature. Strikingly, the most important biological event in which EMT is pivotal is cancer development and metastasis. Over the last years, understanding of the transcriptional regulatory networks involved in EMT has greatly advanced. Several transcriptional factors such as Snail, Slug, Twist, Zeb1 and Zeb2 have been reported to play fundamental roles in EMT, leading in most cases to transcriptional repression of cell⁻cell interacting proteins such as ZO-1 and cadherins and activation of cytoskeletal markers such as vimentin. In recent years, a fundamental role for non-coding RNAs, particularly microRNAs and more recently long non-coding RNAs, has been identified in normal tissue development and homeostasis as well as in several oncogenic processes. In this study, we will provide a state-of-the-art review of the functional roles of non-coding RNAs, particularly microRNAs, in epithelial-to-mesenchymal transition in both developmental and pathological EMT.

Nonprotein-coding RNAs in Fetal Alcohol Spectrum Disorders

Early developmental exposure to ethanol, a known teratogen, can result in a range of neurodevelopmental disorders, collectively referred to as Fetal Alcohol Spectrum Disorders (FASDs). Changes in the environment, including exposure to teratogens, can result in long term alterations to the epigenetic landscape of a cell, thereby altering gene expression. Noncoding RNAs (ncRNAs) can affect transcription and translation of networks of genes. ncRNAs are dynamically expressed during development and have been identified as a target of alcohol. ncRNAs therefore make for attractive targets for novel therapeutics to address the developmental deficits associated with FASDs.

Programmed cell death 4 overexpression enhances sensitivity to cisplatin via the JNK/c-Jun signaling pathway in bladder cancer

The aim of the present study was to evaluate the effects of programmed cell death 4 (PDCD4) on cell proliferation and apoptosis, and to elucidate the potential role of the Jun N-terminal kinase (JNK)/c-Jun pathway in human bladder cancer (BCa) cells. Mixed BCa cells were transfected with plasmids containing PDCD4 (PDCD4-pcDNA3). The sensitivity to cisplatin was analyzed using cell viability, invasion/migration, apoptosis, flow cytometry, wound healing and Transwell assays at different transfection times. Furthermore, epithelial-to-mesenchymal transition (EMT) markers were detected by immunofluorescence staining, and the protein expression of c-Jun, and phosphorylated Jun N-terminal kinase (p-JNK) and c-Jun (p-c-Jun, Ser-73) were also tested using western blotting. It was observed that BCa cell proliferation and invasion and tumor growth were significantly inhibited, whereas apoptosis was enhanced in PDCD4-transfected cells treated with cisplatin compared with controls. Moreover, the western blotting and immunofluorescence results demonstrated that PDCD4 upregulated the expression of epithelial cell markers, but downregulated the expression of mesenchymal cell markers. Furthermore, overexpression of PDCD4 reduced the protein levels of p-JNK and p-c-Jun. Taken together, the findings of the present study indicate that PDCD4 enhances the sensitivity of BCa cells to cisplatin, partially via regulation of the JNK/c-Jun pathway, and reverses EMT. In conclusion, the results of the present study suggested that PDCD4, a nuclear/cytoplasmic shuttling protein with multiple functions, plays an important role in the development and progression of human BCa.

Cardiac repair by epicardial EMT: Current targets and a potential role for the primary cilium

Despite therapeutic advances that have prolonged life, myocardial infarction (MI) remains a leading cause of death worldwide and imparts a significant economic burden. The advancement of treatments to improve cardiac repair post-MI requires the discovery of new targeted treatment strategies. Recent studies have highlighted the importance of the epicardial covering of the heart in both cardiac development and lower vertebrate cardiac regeneration. The epicardium serves as a source of cardiac cells including smooth muscle cells, endothelial cells and cardiac fibroblasts. Mammalian adult epicardial cells are typically quiescent. However, the fetal genetic program is reactivated post-MI, and epicardial epithelial-to-mesenchymal transition (EMT) occurs as an inherent mechanism to support neovascularization and cardiac healing. Unfortunately, endogenous EMT is not enough to encourage sufficient repair. Recent developments in our understanding of the mechanisms supporting the EMT process has led to a number of studies directed at augmenting epicardial EMT post-MI. With a focus on the role of the primary cilium, this review outlines the newly demonstrated mechanisms supporting EMT, the role of epicardial EMT in cardiac development, and promising advances in augmenting epicardial EMT as potential therapeutics to support cardiac repair post-MI.

Noncoding RNAs in Heart Failure

Heart failure is a major contributor to the healthcare burden and mortality worldwide. Current treatment strategies are able to slow down the transition of healthy heart into the failing one; nevertheless better understanding of the complex genetic regulation of maladaptive remodeling in the failing heart is essential for new drug discovery. Noncoding RNAs are key epigenetic regulators of cardiac gene expression and thus significantly influence cardiac homeostasis and functions.In this chapter we will discuss characteristics of noncoding RNAs, especially miRNAs, long noncoding RNAs, and circular RNAs, and review recent evidences proving their profound involvement during different stages of heart failure progression. Several open questions still prevent the extensive use of noncoding RNA-modulating therapies in clinics; yet they are becoming an attractive target to define novel regulatory mechanisms in the heart. In-depth study of their interaction with gene networks will refine our current view of heart failure and revolutionize the drug development in coming years.

KH-type splicing regulatory protein is involved in esophageal squamous cell carcinoma progression

KH-type splicing regulatory protein (KHSRP) is a multifunctional RNA-binding protein, which is involved in several post-transcriptional aspects of RNA metabolism, including microRNA (miRNA) biogenesis. It affects distinct cell functions in different tissues and can have an impact on various pathological conditions. In the present study, we investigated the oncogenic functions of KHSRP and their underlying mechanisms in the pathogenesis of esophageal squamous cell carcinoma (ESCC). KHSRP expression levels were elevated in ESCC tumors when compared with those in non-tumorous tissues by immunohistochemistry, and cytoplasmic KHSRP overexpression was found to be an independent prognosticator for worse overall survival in a cohort of 104 patients with ESCC. KHSRP knockdown inhibited growth, migration, and invasion of ESCC cells. KHSRP knockdown also inhibited the maturation of cancer-associated miRNAs, such as miR-21, miR-130b, and miR-301, and induced the expression of their target mRNAs, such as BMP6, PDCD4, and TIMP3, resulting in the inhibition of epithelial-to-mesenchymal transition. Our findings uncover a novel oncogenic function of KHSRP in esophageal tumorigenesis and implicate its use as a marker for prognostic evaluation and as a putative therapeutic target in ESCC.

Bone marrow mesenchymal stem cell-derived vascular endothelial growth factor attenuates cardiac apoptosis via regulation of cardiac miRNA-23a and miRNA-92a in a rat model of myocardial infarction

Bone marrow-mesenchymal stem cell (BM-MSC) therapy improves the recovery of cardiac function after myocardial infarction (MI); however, the underlying molecular mechanisms are not completely understood. Recent studies have shown that microRNAs (miRNAs) modulate the pathophysiology of cardiovascular diseases. Here, we investigated the mechanisms underlying the effects of BM-MSC-derived paracrine factors and cardiac miRNAs on myocardial regeneration after MI. In our study, MI was induced by permanent ligation of the left anterior descending (LAD) coronary artery. BM-MSCs transplanted in infarcted rats significantly downregulated the expression of miRNA-23a and miRNA-92a and inhibited apoptosis in the myocardium. An in vitro experiment showed that supernatant from BM-MSCs cultured under hypoxia contained higher levels of vascular endothelial growth factor (VEGF) than that from BM-MSCs under normoxia. In addition, inhibition of miRNA-23a and miRNA-92a reduced cardiac apoptosis. Moreover, the VEGF-containing BM-MSC supernatant inhibited miRNA-23a and miRNA-92a expression and reduced apoptotic signaling in cardiomyocytes under hypoxia. These effects were inhibited when the supernatant was treated with neutralizing antibodies against VEGF. Our results indicate that the paracrine factor, VEGF, derived from transplanted BM-MSCs, regulated the expression of miRNAs such as miRNA-23a and miRNA-92a and exerted anti-apoptotic effects in cardiomyocytes after MI.

miR-21 Promotes Fibrogenesis in Peritoneal Dialysis

Peritoneal dialysis (PD) is a life-saving form of renal replacement therapy for those with end-stage kidney disease. Mesothelial cells (MCs) line the peritoneal cavity and help define peritoneal response to treatment-associated injury, a major reason for treatment failure. miRNAs are important regulators, but their roles in peritoneal fibrosis are largely unknown. In this study, miR-21 was one of the most abundant miRNAs in primary MCs, and was up-regulated by the profibrotic cytokine transforming growth factor-β1 and in PD effluent-derived MCs exhibiting mesenchymal phenotypic change. Increased miR-21 was found in peritoneal membrane biopsy specimens from PD patients compared to healthy controls (PD biocompatible, 5.86×, P = 0.0001; PD conventional, 7.09×, P < 0.0001, n = 11 per group). In PD effluent from a cohort of 230 patients, miR-21 was higher in those receiving the therapy long-term compared to new starters (n = 230, miR-21 3.26×, P = 0.001) and associated with icodextrin use (R = 0.52; 95% CI, 0.20-0.84), peritonitis count (R = 0.16; 95% CI, 0.03-0.29), and dialysate cytokines. miR-21 down-regulated programmed cell death 4 and programmed cell death 4 protein was decreased in peritoneal membrane biopsy specimens from PD patients compared to healthy controls. New miR-21 targets were identified that may be important during PD fibrogenesis. These data identify miR-21 as an important effector of fibrosis in the peritoneal membrane, and a promising biomarker in the dialysis effluent for membrane change in patients receiving PD.

More than Just a Simple Cardiac Envelope; Cellular Contributions of the Epicardium

The adult pumping heart is formed by distinct tissue layers. From inside to outside, the heart is composed by an internal endothelial layer, dubbed the endocardium, a thick myocardial component which supports the pumping capacity of the heart and exteriorly covered by a thin mesothelial layer named the epicardium. Cardiac insults such as coronary artery obstruction lead to ischemia and thus to an irreversible damage of the myocardial layer, provoking in many cases heart failure and death. Thus, searching for new pathways to regenerate the myocardium is an urgent biomedical need. Interestingly, the capacity of heart regeneration is present in other species, ranging from fishes to neonatal mammals. In this context, several lines of evidences demonstrated a key regulatory role for the epicardial layer. In this manuscript, we provide a state-of-the-art review on the developmental process leading to the formation of the epicardium, the distinct pathways controlling epicardial precursor cell specification and determination and current evidences on the regenerative potential of the epicardium to heal the injured heart.

Downregulation of Lnc-Spry1 mediates TGF-β-induced epithelial-mesenchymal transition by transcriptional and posttranscriptional regulatory mechanisms

Long non-coding RNAs (lncRNAs) are a class of regulatory genes that participate in a wide range of biological processes, including proliferation, differentiation and development, as well as in a broad spectrum of diseases. Although the role of lncRNAs in TGF-β-induced epithelial-to-mesenchymal transition (EMT) has been well established, little is known about the role of lncRNAs as immediate-early regulators of EMT. Here lnc-Spry1 is identified as an immediate-early regulator of EMT that is downregulated by TGF-β. It is also found that knockdown of lnc-Spry1 promotes a mesenchymal-like phenotype and results in increased cell migration and invasion. In addition, it is shown that lnc-Spry1 depletion preferentially affects the expression of TGF-β-regulated gene targets. Moreover, lnc-Spry1 associates with U2AF65 splicing factor, suggesting a role in alternative splicing. Depletion of lnc-Spry1 induces, as TGF-β, isoform switching of fibroblast growth factor receptors, resulting in FGF-2-sensitive cells. Taken together, these results show that lnc-Spry1 could act as an early mediator of TGF-β signaling and reveal different roles for a lncRNA in modulating transcriptional and posttranscriptional gene expression.

EMT: 2016

The significant parallels between cell plasticity during embryonic development and carcinoma progression have helped us understand the importance of the epithelial-mesenchymal transition (EMT) in human disease. Our expanding knowledge of EMT has led to a clarification of the EMT program as a set of multiple and dynamic transitional states between the epithelial and mesenchymal phenotypes, as opposed to a process involving a single binary decision. EMT and its intermediate states have recently been identified as crucial drivers of organ fibrosis and tumor progression, although there is some need for caution when interpreting its contribution to metastatic colonization. Here, we discuss the current state-of-the-art and latest findings regarding the concept of cellular plasticity and heterogeneity in EMT. We raise some of the questions pending and identify the challenges faced in this fast-moving field.

MicroRNAs-mediated epithelial-mesenchymal transition in fibrotic diseases

MicroRNAs (miRNAs), a large family of small and highly conserved non-coding RNAs, regulate gene expression through translational repression or mRNA degradation. Aberrant expression of miRNAs underlies a spectrum of diseases including organ fibrosis. Recent evidence suggests that miRNAs contribute to organ fibrosis through mediating epithelial-mesenchymal transition (EMT). Alleviation of EMT has been proposed as a promising strategy against fibrotic diseases given the key role of EMT in fibrosis. miRNAs impact the expression of specific ligands, receptors, and signaling pathways, thus modulating EMT and consequently influencing fibrosis. This review summarizes the current knowledge concerning how miRNAs regulate EMT and highlights the specific roles that miRNAs-regulated EMT plays in fibrotic diseases as diverse as pulmonary fibrosis, hepatic fibrosis, renal fibrosis and cardiac fibrosis. It is desirable that a more comprehensive understanding of the functions of miRNAs-regulated EMT will facilitate the development of novel diagnostic and therapeutic strategies for various debilitating organ fibrosis.

The role of microRNAs in heart failure

MicroRNAs are small non-coding RNA molecules that regulate gene expression by inhibiting mRNA translation and/or inducing mRNA degradation. In the past decade, many in vitro and in vivo studies have explored the involvement of microRNAs in various cardiovascular diseases. In this paper, studies focused upon the target genes and functionality of miRNAs in the pathophysiological processes of heart failure are reviewed. The selected miRNAs are categorized according to the biological relevance of their target genes in relation to four cardiovascular pathologies, namely angiogenesis, cardiac hypertrophy, fibrosis and apoptosis. This review illustrates the involvement of miRNAs in different biological signaling pathways and provides an overview of current understanding of the roles of miRNAs in cardiovascular health and diseases. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

Leukemia inhibitory factor promotes EMT through STAT3-dependent miR-21 induction

Leukemia inhibitory factor (LIF) is a multi-function cytokine. Its role in cancer is not well-understood. Recent studies including ours show that LIF is frequently overexpressed in many types of human tumors and promotes the progression and metastasis of tumors. However, the underlying mechanism of LIF's promoting effects on tumor progression and metastasis is poorly defined. Epithelial-mesenchymal transition (EMT) plays an important role in tumor metastasis. This study reports that LIF promotes EMT in human tumor cells. Overexpression of LIF promotes tumor cells to acquire mesenchymal features, including morphological changes of cells from epithelial-like to mesenchymal-like, increased expression levels of mesenchymal markers and decreased expression of epithelial markers. Knockdown of endogenous LIF reverses EMT in cancer cells. We further identified that LIF induces the expression of microRNA-21 (miR-21), which in turn mediates the promoting effect of LIF on EMT. LIF induces miR-21 expression through the activation of STAT3. Importantly, blocking miR-21 function greatly abolished the promoting effect of LIF on EMT and the migration ability of cancer cells. Taken together, results from this study identified an important function and a novel underlying mechanism of LIF in EMT and tumor metastasis.