Role of miR-24, Furin, and Transforming Growth Factor-β1 Signal Pathway in Fibrosis After Cardiac Infarction

MicroRNAs and cardiac fibrosis: A comprehensive update on mechanisms and consequences

Fibrosis is a pathological wound-healing mechanism that results by the overactivation of fibroblasts. Fibrosis can become obstructive and deleterious during regeneration of various body tissues including cardiac muscle. This ultimately results in the development of cardiac fibrosis, characterized by an excessive buildup of extracellular matrix proteins. Thus, it could lead to arrhythmias and heart failure which creates a leading public health burden worldwide. MiRNAs are small non-coding RNAs with great potential for diagnostic and therapeutic purposes. Mounting evidence indicates that miRNAs are involved in the deregulation of tissue homeostasis during myocardial fibrosis. For instance, miRNAs that are implicated in the regulation of TGF-beta signaling pathway have been reported to be significantly altered in myocardial fibrosis. Accordingly, in this comprehensive review, we discuss and highlight recent available data on the role of miRNAs during myocardial fibrosis, providing valuable insights into the miRNA modulation of cardiac fibrosis and miRNAs targets that can be used in the future therapeutic interventions to cardiac fibrosis.

Regulation of SMAD Signaling Pathway by miRNAs Associated with Myocardial Fibrosis: In silico Analysis of Target Gene Networks

Hypertrophic cardiomyopathy (HCM) is a hereditary heart disease caused by mutations in the sarcomere genes, which is accompanied by myocardial fibrosis leading to progressive heart failure and arrhythmias. Recent studies suggest that the HCM development involves dysregulation of gene expression. Among the molecules involved in this process are microRNAs (miRNAs), which are short non-coding RNAs. Typically, one miRNA regulates several target genes post-transcriptionally, hence, it might be difficult to determine the role of a particular miRNA in the disease pathogenesis. In this study, using the PubMed database, we selected 15 miRNAs whose expression is associated with myocardial fibrosis, one of the critical pathological processes in HCM. We then used an earlier developed algorithm to search in silico for the signaling pathways regulated by these miRNAs and found that ten of them participate in the regulation of the TGF-β/SMAD signaling pathway. At the same time, among the SMAD signaling pathway genes, the target of the most identified miRNAs was the MYC gene, which is involved in the development of fibrosis in some tissues. In our earlier work, we found that the TGF-β/SMAD pathway is also regulated by a set of other miRNAs associated with the myocardial hypertrophy in HCM. The fact that two sets of miRNAs identified in two independent bioinformatic studies are involved in the regulation of the same signaling pathway indicates that the SMAD signaling cascade is indeed a key element in the regulation of pathological processes in HCM. The obtained data might contribute to understanding pathological processes underlying HCM development.

Versatile role of miR-24/24-1*/24-2* expression in cancer and other human diseases

MiRNAs (miRs) have been proven to be well-validated therapeutic targets. Emerging evidence has demonstrated that intricate, intrinsic and paradoxical functions of miRs are context-dependent because of their multiple upstream regulators, broad spectrum of downstream molecular targets and distinct expression in various tissues, organs and disease states. Targeted therapy has become an emerging field of research. One key for the development of successful miR-based/targeted therapy is to acquire integrated knowledge of its regulatory network and its association with disease phenotypes to identify critical nodes of the underlying pathogenesis. Herein, we systematically summarized the comprehensive role of miR-24-3p (miR-24), along with its passenger strands miR-24-1-5p* (miR-24-1) and miR-24-2-5p* (miR-24-2), emphasizing their microenvironment, intracellular targets, and associated gene networks and regulatory phenotypes in 18 different cancer types and 13 types of other disorders. MiR-24 targets and regulates numerous genes in various cancer types and enhances the expression of several oncogenes (e.g., cMyc, BCL2 and HIF1), which are challenging in terms of druggability. In contrast, several tumor suppressor proteins (p21 and p53) have been reported to be downregulated by miR-24. MiR-24 also regulates the cell cycle and is associated with numerous cancer hallmarks such as apoptosis, proliferation, metastasis, invasion, angiogenesis, autophagy, drug resistance and other diseases pathogenesis. Overall, miR-24 plays an emerging role in the diagnosis, prognosis and pathobiology of various diseases. MiR-24 is a potential target for targeted therapy in the era of precision medicine, which expands the landscape of targetable macromolecules, including undruggable proteins.

Targeting Epigenetics and Non-coding RNAs in Myocardial Infarction: From Mechanisms to Therapeutics

Myocardial infarction (MI) is a complicated pathology triggered by numerous environmental and genetic factors. Understanding the effect of epigenetic regulation mechanisms on the cardiovascular disease would advance the field and promote prophylactic methods targeting epigenetic mechanisms. Genetic screening guides individualised MI therapies and surveillance. The present review reported the latest development on the epigenetic regulation of MI in terms of DNA methylation, histone modifications, and microRNA-dependent MI mechanisms and the novel therapies based on epigenetics.

MicroRNA-24 protects against myocardial ischemia-reperfusion injury via the NF-κB/TNF-α pathway

Acute myocardial infarction (AMI) is a form of cardiomyopathy in which a blocked coronary artery leads to an irreversible loss of cardiomyocytes due to inadequate blood and oxygen supply to the distal myocardium tissues, eventually leading to heart failure. Recently, studies have revealed that microRNA (miRNA/miR)-24 has diagnostic value in the pathogenesis of AMI by affecting multiple cell processes such as cell proliferation, differentiation and apoptosis. However, the specific mechanism of miR-24 in ischemia-reperfusion injury (IRI) after AMI remains to be fully elucidated. The present study aimed to investigate the effects and mechanisms of miR-24 in IRI. In vitro, the current study detected cellular apoptosis and apoptotic-related protein expression levels in the cardiomyocyte H9C2 cell line (negative control group, model group and miRNA group) via flow cytometry and western blot analysis. In the in vivo study, rats were randomly divided into sham, model and miRNA groups. The infarct area was observed using nitro blue tetrazolium staining, pathological changes of the myocardium were detected via hematoxylin and eosin staining and TUNEL staining was used to detect cardiomyocyte apoptosis. The expression levels of related proteins were evaluated via immunohistochemistry and western blot analysis. The in vitro and in vivo results demonstrated that miR-24 significantly inhibited cardiomyocyte apoptosis compared with the model group. Concurrently, the expression levels of proteins associated with the NF-κB/TNF-α pathway (NF-κB, caspase-3, Bax, Bcl-2, TNF-α, vascular cell adhesion molecule 1, intercellular adhesion molecule 1 and monocyte chemoattractant protein-1) in the miRNA group were significantly different from the model group (P<0.001). Compared with the model group, miR-24 significantly improved pathological damage and infarct size of rat myocardium. Overall, the present results suggested that miR-24 improves myocardial injury in rats by inhibiting the NF-κB/TNF-α pathway.

The association between plasma furin and cardiovascular events after acute myocardial infarction

Background

Furin is the key enzyme involved in the cleavage of pro-BNP and plays a critical role in the cardiovascular system through its involvement in lipid metabolism, blood pressure regulation and the formation of atheromatous plaques. NT-proBNP and recently, corin, also a key enzyme in the cleavage of pro-BNP, have been accepted as predictors of prognosis after acute myocardial infarction (AMI). This cohort study was conducted to investigate the relationship between plasma furin and the prognostic outcomes of AMI patients.

Methods

In total, 1100 AMI patients were enrolled in the study and their plasma furin concentrations were measured. The primary endpoint was major adverse cardiac events (MACE), a composite of cardiovascular (CV) death, non-fatal myocardial infarction (MI) and non-fatal stroke. The associations between plasma furin concentration and AMI outcomes were explored using Kaplan–Meier curves and multivariate Cox regression analysis.

Results

The results showed a slight increase in mean cTNT in patients with higher furin concentrations (P = 0.016). Over a median follow-up of 31 months, multivariate Cox regression analysis indicated that plasma furin was not significantly associated with MACE (HR 1.01; 95% CI 0.93–1.06; P = 0.807) after adjustment for potential conventional risk factors. However, plasma furin was associated with non-fatal MI (HR 1.09; 95% CI 1.01–1.17; P = 0.022) in the fully adjusted model. Subgroup analyses indicated no relationship between plasma furin and MACE in different subgroups.

Conclusions

This study found no association between plasma furin and risk of MACE. Thus, plasma furin may not be a useful predictor of poor prognosis after AMI. However, higher levels of plasma furin may be associated with a higher risk of recurrent non-fatal MI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02029-y.

MicroRNA Mimics or Inhibitors as Antiviral Therapeutic Approaches Against COVID-19

Coronaviruses, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for the coronavirus disease 2019 (COVID-19) pandemic, present a significant threat to human health by inflicting a wide variety of health complications and even death. While conventional therapeutics often involve administering small molecules to fight viral infections, small non-coding RNA sequences, known as microRNAs (miRNAs/miR-), may present a novel antiviral strategy. We can take advantage of their ability to modulate host-virus interactions through mediating RNA degradation or translational inhibition. Investigations into miRNA and SARS-CoV-2 interactions can reveal novel therapeutic approaches against this virus. The viral genomes of SARS-CoV-2, severe acute respiratory syndrome coronavirus (SARS-CoV), and Middle East respiratory syndrome coronavirus (MERS-CoV) were searched using the Nucleotide Basic Local Alignment Search Tool (BLASTn) for highly similar sequences, to identify potential binding sites for miRNAs hypothesized to play a role in SARS-CoV-2 infection. miRNAs that target angiotensin-converting enzyme 2 (ACE2), the receptor used by SARS-CoV-2 and SARS-CoV for host cell entry, were also predicted. Several relevant miRNAs were identified, and their potential roles in regulating SARS-CoV-2 infections were further assessed. Current treatment options for SARS-CoV-2 are limited and have not generated sufficient evidence on safety and efficacy for treating COVID-19. Therefore, by investigating the interactions between miRNAs and SARS-CoV-2, miRNA-based antiviral therapies, including miRNA mimics and inhibitors, may be developed as an alternative strategy to fight COVID-19.

MicroRNA‑331 inhibits isoproterenol‑induced expression of profibrotic genes in cardiac myofibroblasts via the TGFβ/smad3 signaling pathway

Cardiac fibrosis in the failing heart is modulated by activated myofibroblasts, and is a pathology marked by their deposition of extracellular matrix proteins. The TGFβ signaling pathway is important in stimulating fibrosis and therefore seems an attractive new target for anti-fibrotic therapy. The relationship between ncRNAs and TGFβ signaling pathway has been extensively studied. Here, we have provided several lines of evidence to prove that the fibrosis process could be regulated by miR-331 through targeting TGFβ signaling. First, bioinformatics analysis and dual luciferase assay validated a direct interaction between the miR-331 and TGFβ-R1 3'UTR sequence which results in the downregulation of TGFβ signaling pathway. Second, miR-331 expression was inversely related to the expression of a number of genes which are involved in extracellular matrix (ECM) production and deposition processes, both in the in vivo and in vitro fibrosis models. Third, in cultured mouse and human cardiac myofibroblasts (CMyoFbs) under ISO treatment, overexpression of miR-331 decreased the expression level of fibrosis-related genes. Consistently, western blot analysis confirmed that miR-331 overexpression ended in both Smad3 and Col1A1 protein level reduction in mouse cardiac myofibroblasts. Finally, flow cytometry analysis, cyclin D1 and D2 gene expression analysis, and wound-healing assay confirmed the inhibitory effect of miR-331 against cell proliferation and migration in ISO-treated cardiac myofibroblasts. Taken together, accumulative results showed that miR-331 reduced the level of fibrosis-related proteins in cardiac myofibroblasts culture via regulating TGFβ signaling pathway.

Pivotal Role of TGF-β/Smad Signaling in Cardiac Fibrosis: Non-coding RNAs as Effectual Players

Unintended cardiac fibroblast proliferation in many pathophysiological heart conditions, known as cardiac fibrosis, results in pooling of extracellular matrix (ECM) proteins in the heart muscle. Transforming growth factor β (TGF-β) as a pivotal cytokine/growth factor stimulates fibroblasts and hastens ECM production in injured tissues. The TGF-β receptor is a heterodimeric receptor complex on the plasma membrane, made up from TGF-β type I, as well as type II receptors, giving rise to Smad2 and Smad3 transcription factors phosphorylation upon canonical signaling. Phosphorylated Smad2, Smad3, and cytoplasmic Smad4 intercommunicate to transfer the signal to the nucleus, culminating in provoked gene transcription. Additionally, TGF-β receptor complex activation starts up non-canonical signaling that lead to the mitogen-stimulated protein kinase cascade activation, inducing p38, JNK1/2 (c-Jun NH2-terminal kinase 1/2), and ERK1/2 (extracellular signal–regulated kinase 1/2) signaling. TGF-β not only activates fibroblasts and stimulates them to differentiate into myofibroblasts, which produce ECM proteins, but also promotes fibroblast proliferation. Non-coding RNAs (ncRNAs) are important regulators of numerous pathways along with cellular procedures. MicroRNAs and circular long ncRNAs, combined with long ncRNAs, are capable of affecting TGF-β/Smad signaling, leading to cardiac fibrosis. More comprehensive knowledge based on these processes may bring about new diagnostic and therapeutic approaches for different cardiac disorders.

Transplantation of Enterovirus 71 Virion Protein Particle Vaccine Protects Against Enterovirus 71 Infection in a Neonatal Mouse Model

Background

Enterovirus 71 (EV71) is the pathogen most likely to cause HFMD in young children (1–5 years old). A small number of virion protein (VP) vaccine candidates are considered as the protective molecules in EV71 models. This study aimed to observe comprehensive immunogenicity for a promising EV71 vaccine depending on VP1 in neonatal mouse EV71 models.

Material/Methods

VP1 was isolated from patients and associated peptides were synthesized. EV71 particles were inactivated and mixed with Freund’s complete adjuvant to prepare peptide vaccines. An EV71 vaccine was administered to establish the mouse model and the mice were infected with EV71. Hematoxylin and eosin staining was used to examine inflammatory response in EV71-infected neonatal mice. A semi-quantitative reverse transcription-polymerase chain reaction assay was performed to evaluate the levels of EV71 virus in skeletal muscle, small intestines, and brain tissues.

Results

Three peptides were selected from 20 VP1 peptides due to their exhibition of the highest immunogenicity. The peptide injection improved inflammation and decreased EV71 particle levels in muscle, small intestines, and brain tissues. The injection also decreased lesions in the small intestines of EV71-infected mice and protected brain tissues from the EV71 infection.

Conclusions

The present study confirmed the immuno-protective effects of VP1 vaccine transplantation in mice infected with EV71 virus. Our results provide valuable information that can be used in further studies investigating the specific mechanism of the anti-EV71 vaccine.

LncRNA MHRT Promotes Cardiac Fibrosis via miR-3185 Pathway Following Myocardial Infarction

Long-chain noncoding RNA (lncRNA) is a new class of molecular regulators in heart development and disease. However, the role of specific lncRNA in cardiac fibrosis remains to be fully explored. This study aimed to investigate the role and potential mechanism of lncRNA MHRT in myocardial fibrosis after myocardial infarction (MI).Cardiac fibroblasts (CFs) were isolated from a mouse model of MI. The expression levels of MHRT and miR-3185 in the hearts of MI and CFs mice treated with transforming growth factor beta 1 (TGF-β1) were analyzed by qRT-PCR. The collagen expression was assessed using qRT-PCR and Western blot. Cell proliferation was assessed by performing MTT and EdU assays. The direct interaction between lncRNA and miRNA was analyzed by luciferase assay, RNA-binding protein immunoprecipitation (RIP) assay, and RNA pull-down assay.The expression levels of MHRT were raised in MI and CFs mice treated with TGF-β1. Overexpression of MHRT promoted collagen production and CF proliferation, while silencing of MHRT showed the opposite effect. MiR-3185 was a target gene of MHRT. In addition, overexpression of MHRT reduced the expression levels of miR-3185, and siMHRT reversed the inhibitory effect of TGF-β1 on the expression of miR-3185. Overexpression of miR-3185 inhibited the upregulation of Col I and Col III induced by TGF-β1.MHRT promoted cardiac fibrosis after MI through miR-3185 and increased myocardial collagen deposition and promoted myocardial fibrosis.

Small Molecules with Big Impacts on Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. Although in recent years there has been a significant progress in the diagnosis, treatment, and prognosis of CVD, but due to their complex pathobiology, developing novel biomarkers and therapeutic interventions are still in need. MicroRNAs (miRNAs) are a fraction of non-coding RNAs that act as micro-regulators of gene expression. Mounting evidences over the last decade confirmed that microRNAs were deregulated in several CVDs and manipulating their expression could affect homeostasis, differentiation, and function of cardiovascular system. Here, we review the current knowledge concerning the roles of miRNAs in cardiovascular diseases with more details on cardiac remodeling, arrhythmias, and atherosclerosis. In addition, we discuss the latest findings on the potential therapeutic applications of miRNAs in cardiovascular diseases.

Long-term moderate intensity exercise alleviates myocardial fibrosis in type 2 diabetic rats via inhibitions of oxidative stress and TGF-β1/Smad pathway

Exercise has an effect on the reduction of myocardial fibrosis in diabetic rats as previously reported, in which oxidative stress and the TGF-β1/Smad signaling pathway may play key roles. There is little direct experimental evidence that exercise alleviates myocardial fibrosis in type 2 diabetes mellitus (T2DM). Here we established a type 2 diabetic model by using streptozotocin and a high-fat diet. Rats were divided into groups of normal control (NC), T2DM and T2DM plus exercise (T2DME). The T2DME group received further treadmill training at moderate intensity for 8 weeks. Histological and biochemical methods were used to detect the benefits of exercise to T2DM. Results showed that the weight of rats in the T2DM group dropped dramatically, along with significant increases in blood glucose, myocardial fibrosis and oxidative stress, associated with upregulated expression of factors of myocardial fibrosis, except Smad7. Exercise largely reversed T2DM-induced alterations in factors of myocardial fibrosis, including suppressing expression of MMP-2, CTGF, TGF-β1, p-Smad2 and p-Smad3, and increased expression of TIMP-1 and Smad7. Therefore, exercise might be considered an alternative therapeutic remedy for diabetic cardiomyopathy.

MicroRNA-24 attenuates vascular remodeling in diabetic rats through PI3K/Akt signaling pathway

BACKGROUND AND AIMS

The vascular remodeling plays a crucial role in pathogenesis of diabetic cardiovascular complications. In this study, we intended to explore the effects and potential mechanisms of microRNA-24 (miR-24) on vascular remodeling under diabetic conditions.

METHODS AND RESULTS

MiR-24 recombinant adenovirus (Ad-miR-24-GFP) was used to induce miR-24 overexpression either in carotid arteries or high glucose (HG)-induced vascular smooth muscle cells (VSMCs). Cell proliferation was analyzed using CCK-8 method. Cell migration was examined using wound-healing and transwell assay. mRNA and protein expressions of critical factors were, respectively, measured by real-time PCR and western blot as follows: qRT-PCR for the levels of miR-24, PIK3R1; western blot for the protein levels of PI3K (p85α), Akt, p-Akt, mTOR, p-mTOR, 4E-BP1, p-4E-BP1, p70s6k, p-p70s6k, MMP 2, MMP 9, collagen Ⅰ, as well as collagen Ⅲ. Carotid arteries in diabetic rats suffered balloon injury were harvested and examined by HE, immunohistochemical and Masson trichrome staining. The expression of miR-24 was decreased in HG-stimulated VSMCs and balloon-injured carotid arteries of diabetic rats, accompanied by increased mRNA expression of PIK3R1. The up-regulation of miR-24 suppressed VSMCs proliferation, migration, collagen deposition not only induced by HG in vitro, but also in balloon-injured diabetic rats, which were related to inactivation of PI3K/Akt signaling pathway.

CONCLUSION

The up-regulation of miR-24 significantly attenuated vascular remodeling both in balloon-injured diabetic rats and HG-stimulated VSMCs via suppression of proliferation, migration and collagen deposition by acting on PIK3R1 gene that modulated the PI3K/Akt/mTOR axes.

Induced pluripotent stem cell-conditional medium inhibits H9C2 cardiomyocytes apoptosis via autophagy flux and Wnt/β-catenin pathway

Induced pluripotent stem cell‐derived conditioned medium (iPS‐CM) could improve cell viability in many types of cells and may be a better alternative for the treatment of myocardial infarction. This study aimed to examine the influence of iPS‐CM on anti‐apoptosis and the proliferation of H9C2 cardiomyocytes and investigate the underlying mechanisms. H9C2 cardiomyocytes were exposed to 200 μmol/L hydrogen peroxide (H₂O₂) for 24 hours with or without pre‐treatment with iPS‐CM. The ratio of apoptotic cells, the loss of mitochondrial membrane potential (△Ψm) and the levels of intracellular reactive oxygen species were analysed by flow cytometric analysis. The expression levels of BCL‐2 and BAX proteins were analysed by Western blot. Cell proliferation was assessed using cell cycle and EdU staining assays. To study cell senescence, senescence‐associated β‐galactosidase (SA‐β‐gal) staining was conducted. The levels of malondialdehyde, superoxide dismutase and glutathione were also quantified using commercially available enzymatic kits. The results showed that iPS‐CM containing basic fibroblast growth factor significantly reduced H₂O₂‐induced H9C2 cardiomyocyte apoptosis by activating the autophagy flux pathway, promoted cardiomyocyte proliferation by up‐regulating the Wnt/β‐catenin pathway and inhibited oxidative stress and cell senescence. In conclusion, iPS‐CM effectively enhanced the cell viability of H9C2 cardiomyocytes and could potentially be used to inhibit cardiomyocytes apoptosis to treat myocardial infarction in the future.

Effects of microRNA-24 targeting C-myc on apoptosis, proliferation, and cytokine expressions in chondrocytes of rats with osteoarthritis via MAPK signaling pathway

To investigate whether microRNA-24 (miR-24) targeting C-myc affects chondrocytes of rats with osteoarthritis (OA) via the MAPK signaling pathway. Thirty rats were assigned as a sham group and an OA group (established as OA rat models by cutting the anterior cruciate ligaments and removing 1/3 medial meniscus). TUNEL staining and immunohistochemistry were conducted for cell apoptosis index (AI) and positive expression rate of C-myc protein. Enzyme-linked immuno sorbent assay (ELISA) was carried out for serum level of IL-1β and TNF-α. Primary chondrocytes were assigned into the blank, negative control (NC), miR-24 mimics, miR-24 inhibitors, siRNA-C-myc, and miR-24 inhibitors+siRNA-C-myc groups. The expressions of miR-24, C-myc, p38, ERK, JNK, IL-1β, and TNF-α in tissues and cells were detected using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and Western blotting. CCK8 assay and flow cytometry were performed for cell proliferation and apoptosis. The OA group showed higher IL-1β, TNF-α, AI, and C-myc than the sham group. C-myc is a target gene of miR-24. Compared with the blank group, the miR-24 mimics and siRNA-C-myc groups showed reduced expression of C-myc, IL-1β, TNF-α, p38, p-p38, ERK, p-ERK, JNK, and p-JNK, apoptosis rate yet increased cell proliferation; however, the miR-24 inhibitors group exhibited an opposite trend. The miR-24 inhibitors+siRNA-C-myc group presented a same tendency compared to the siRNA-C-myc group. Upregulated miR-24 downregulates C-myc could suppress apoptosis and promote proliferation of chondrocytes to prevent the occurrence and subsequent progression of OA via inactivating the MAPK signaling pathway.

At the heart of programming: the role of micro-RNAs

Epidemiological and experimental observations tend to prove that environment, lifestyle or nutritional challenges influence heart functions together with genetic factors. Furthermore, when occurring during sensitive windows of heart development, these environmental challenges can induce an 'altered programming' of heart development and shape the future heart disease risk. In the etiology of heart diseases driven by environmental challenges, epigenetics has been highlighted as an underlying mechanism, constituting a bridge between environment and heart health. In particular, micro-RNAs which are involved in each step of heart development and functions seem to play a crucial role in the unfavorable programming of heart diseases. This review describes the latest advances in micro-RNA research in heart diseases driven by early exposure to challenges and discusses the use of micro-RNAs as potential targets in the reversal of the pathophysiology.

miR-24 and miR-122 Negatively Regulate the Transforming Growth Factor-β/Smad Signaling Pathway in Skeletal Muscle Fibrosis

Fibrosis is common after skeletal muscle injury, undermining tissue regeneration and function. The mechanism underlying skeletal muscle fibrosis remains unveiled. Transforming growth factor-β/Smad signaling pathway is supposed to play a pivotal role. However, how microRNAs interact with transforming growth factor-β/Smad-related muscle fibrosis remains unclear. We showed that microRNA (miR)-24-3p and miR-122-5p declined in skeletal muscle fibrosis, which was a consequence of transforming growth factor-β. Upregulating Smad4 suppressed two microRNAs, whereas inhibiting Smad4 elevated microRNAs. Luciferase reporter assay and chromatin immunoprecipitation confirmed that Smad4 directly inhibited two microRNAs. On the other hand, overexpression of these two miRs retarded fibrotic process. We further identified that Smad2 was a direct target of miR-24-3p, whereas miR-122-5p targeted transforming growth factor-β receptor-II. Both targets were important participants in transforming growth factor-β/Smad signaling. Taken together, a positive feedback loop in transforming growth factor-β/Smad4 signaling pathway in skeletal muscle fibrosis was identified. Transforming growth factor-β/Smad axis could be downregulated by microRNAs. This effect, however, was suppressed by Smad4, the downstream of transforming growth factor-β.

Molecular Pathogenesis of Chlamydia Disease Complications: Epithelial-Mesenchymal Transition and Fibrosis

The reproductive system complications of genital chlamydial infection include fallopian tube fibrosis and tubal factor infertility. However, the molecular pathogenesis of these complications remains poorly understood. The induction of pathogenic epithelial-mesenchymal transition (EMT) through microRNA (miRNA) dysregulation was recently proposed as the pathogenic basis of chlamydial complications. Focusing on fibrogenesis, we investigated the hypothesis that chlamydia-induced fibrosis is caused by EMT-driven generation of myofibroblasts, the effector cells of fibrosis that produce excessive extracellular matrix (ECM) proteins. The results revealed that the targets of a major category of altered miRNAs during chlamydial infection are key components of the pathophysiological process of fibrogenesis; these target molecules include collagen types I, III, and IV, transforming growth factor β (TGF-β), TGF-β receptor 1 (TGF-βR1), connective tissue growth factor (CTGF), E-cadherin, SRY-box 7 (SOX7), and NFAT (nuclear factor of activated T cells) kinase dual-specificity tyrosine (Y) phosphorylation-regulated kinase 1a (Dyrk1a). Chlamydial induction of EMT resulted in the generation of α-smooth muscle actin (α-SMA)-positive myofibroblasts that produced ECM proteins, including collagen types I and III and fibronectin. Furthermore, the inhibition of EMT prevented the generation of myofibroblasts and production of ECM proteins during chlamydial infection. These findings may provide useful avenues for targeting EMT or specific components of the EMT pathways as a therapeutic intervention strategy to prevent chlamydia-related complications.

Biomarkers in patients with myocardial fibrosis

Myocardial fibrosis is observed in many cardiovascular diseases including hypertension, heart failure and cardiomyopathy. Myocardial fibrosis has been proved to be reversible and treatable only under timely intervention, which makes early detection and assessment of fibrosis crucial. Aside from tissue biopsy as the gold standard for the diagnosis of myocardial fibrosis, circulating biomarkers have been adopted as noninvasive assessment of this lesion. Dysregulated collagen deposition is thought to be the major cause of myocardial fibrosis. Collagens, procollagens, TGF-β, TIMP, galectin-3, and microRNAs are thought to be indicators of myocardial fibrosis. In this review, we summarize the molecules that are frequently used as biomarkers in diagnosis of cardiac fibrosis. Mechanisms of fibrosis that they take part in are also introduced.

Knockdown of MicroRNA-122 Protects H9c2 Cardiomyocytes from Hypoxia-Induced Apoptosis and Promotes Autophagy

BACKGROUND Acute myocardial infarction (AMI) is a severe disease causing heart failure and sudden death. Studies indicate that microRNAs (miRNAs) are involved in the pathophysiology of AMI. In the present study, we carefully explored the effects of miR-122 on myocardial hypoxia injury and its possible underlying mechanism. MATERIAL AND METHODS miR-122 expression was analyzed in H9c2 cardiomyocytes after being transfected with miR-122 mimic, ASO-miR-122, or negative control. Cell viability and apoptosis were investigated by CCK-8 assays and flow cytometry analysis, respectively. Cell migration was analyzed using wound-healing assays. Western blotting was performed to analyze the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN)/phosphatidylinositol 3-hydroxy kinase (PI3K)/AKT and LC3-II/LC3-I. RESULTS Hypoxia exposure significantly inhibited H9c2 cell viability (P<0.01). miR-122 overexpression promoted the hypoxia-induced H9c2 cell proliferation and migration loss (P<0.05), and cell apoptosis was increased (P<0.05). miR-122 knockdown enhanced cell viability and decreased cell apoptosis (P<0.05). Knockdown of miR-122 enhanced PTEN/PI3K/AKT activation and cell autophagy. Overexpression of miR-122 inhibited the PTEN/PI3K/AKT pathway and cell autophagy pathway. CONCLUSIONS The expression of miR-122 is involved in hypoxia-induced H9c2 cardiomyocyte injury. Knockdown of miR-122 protects H9c2 cells from hypoxia-induced apoptosis and enhances cell viability.

The Role of MicroRNAs in Myocardial Infarction: From Molecular Mechanism to Clinical Application

MicroRNAs (miRNAs) are a class of small single-stranded and highly conserved non-coding RNAs, which are closely linked to cardiac disorders such as myocardial infarction (MI), cardiomyocyte hypertrophy, and heart failure. A growing number of studies have demonstrated that miRNAs determine the fate of the heart by regulating cardiac cell death and regeneration after MI. A deep understanding of the pathophysiology of miRNA dependent regulatory pathways in these processes is required. The role of miRNAs as diagnostic, prognostic, and therapeutic targets also needs to be explored in order to utilize them in clinical settings. This review summarizes the role of miRNAs in myocardial infarction and focuses mainly on their influence on cardiomyocyte regeneration and cell death including apoptosis, necrosis, and autophagy. In addition, the targets of pro- and anti-MI miRNAs are comparatively described. In particular, the possibilities of miRNA-based diagnostic and therapeutic strategies for myocardial infarction are discussed in this review.