The Integrative Regulatory Network of circRNA, microRNA, and mRNA in Atrial Fibrillation

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Progress of circRNA/lncRNA-miRNA-mRNA axis in atrial fibrillation

Atrial fibrillation (AF) is a prevalent arrhythmia that requires effective biomarkers and therapeutic targets for clinical management. In recent years, non-coding RNAs (ncRNAs) have emerged as key players in the pathogenesis of AF, particularly through the ceRNA (competitive endogenous RNA) mechanism. By acting as ceRNAs, ncRNAs can competitively bind to miRNAs and modulate the expression of target mRNAs, thereby influencing the biological behavior of AF. The ceRNA axis has shown promise as a diagnostic and prognostic biomarker for AF. This review provides a comprehensive overview of the roles of ncRNAs in the development and progression of AF, highlighting the intricate crosstalk between different ncRNAs in AF pathophysiology. Furthermore, we discuss the potential implications of targeting the circRNA/lncRNA-miRNA-mRNA axis for the diagnosis, prognosis, and therapeutic intervention of AF.

Circular RNAs in atrial fibrillation: From bioinformatics analysis of circRNA-miRNA-mRNA network to serum expression

Atrial fibrillation (AF) is a common arrhythmia in clinical practice, and its incidence is increasing year by year, which seriously affects the survival and prognosis of patients. In recent years, circRNAs has played an important role in the diagnosis and treatment of AF. The purpose of this study was to search for differentially expressed circRNAs(DEcircRNAs) in the serum of AF patients by analyzing the expression profile of existing chips, combining bioinformatics technology and in vitro experiments, and to explore the regulatory mechanism of circRNAs in the occurrence and development of AF. By using the AF datasets in the Gene expression omnibus (GEO) database, serum samples of patients with AF were collected, and the expression level of selected circRNAs was verified by qPCR. We found that the expression of four circRNAs was increased in the serum of patients with AF, suggesting that these four DEcircRNAs may be used as auxiliary diagnostic markers for AF. Bioinformatics predicts the related signaling pathways that differentially expressed genes may regulate in the occurrence and development of AF, providing a new theoretical basis for the molecular mechanism of the occurrence of atrial fibrillation and auxiliary diagnostic targets.

MiR-133b as a crucial regulator of TCS-induced cardiotoxicity via activating β-adrenergic receptor signaling pathway in zebrafish embryos

As a commonly used antibacterial agent in daily consumer products, triclosan (TCS) has attracted significant attention due to its potential environmental risks. In this study, we investigated the toxic effects of TCS exposure (1.4 μM) on heart development in zebrafish embryos. Our findings revealed that TCS exposure caused significant cardiac dysfunction, characterized by pericardial edema, malformations in the heart structure, and a slow heart rate. Additionally, TCS exposure induced oxidative damage and abnormal apoptosis in heart cells through the up-regulation of β-adrenergic receptor (β-AR) signaling pathway genes (adrb1, adrb2a, arrb2b), similar to the effects induced by β-AR agonists. Notably, the adverse effects of TCS exposure were alleviated by β-AR antagonists. Using high-throughput transcriptome miRNA sequencing and targeted miRNA screening, we focused on miR-133b, which targets adrb1 and was down-regulated by TCS exposure, as a potential contributor to TCS-induced cardiotoxicity. Inhibition of miR-133b produced similar toxic effects as TCS exposure, while overexpression of miR-133b down-regulated the β-AR signaling pathway and rescued heart defects caused by TCS. In summary, our findings provide new insights into the mechanisms underlying the cardiotoxic effects of TCS. We suggest that targeting the β-AR pathway and miR-133b may be effective strategies for pharmacotherapy in cardiotoxicity induced by environmental pollutants such as TCS.

Multiple targets related to mitochondrial function unveiled by metabolomics and proteomics profiles of hearts from atrial fibrillation patients

Background: The prominent mitochondrial metabolic changes of the atrium reportedly have significant impact on electrical signals and structural remodeling which play important roles in the occurrence and development of atrial fibrillation (AF). However, the mechanism is not completely known.

Objective: This study was aimed to explore the mitochondrial metabolism reprogrammed in AF patients by integrating metabolomics as well as proteomics of human atrium tissues.

Methods and Results: Left atrial tissue samples were harvested from 10 non-valvular AF patients and 10 matched samples from healthy donors for transplantation. In metabolomics analysis, 113 metabolites were upregulated and 10 metabolites were downregulated in AF, where multiple pathways related to mitochondrial energy metabolism were enriched. Correlation analysis between the differentially expressed proteins and metabolites identified several hub proteins related to mitochondrial function including Glycerol-3-phosphate dehydrogenase 2 (GPD2), Synemin (SYNM), Plectin (PLEC), with MCC score of 27, 17, 16, respectively, which have the most interactions with the dysregulated metabolites and ranked at the top in network string interactions scored by MCC method. All 330 differentially expressed proteins including 225 upregulated and 105 downregulated molecules were revealed and analyzed, which identified the downregulation of GPD2 (p = 0.02 and FC = 0.77), PLEC (p < 0.001 and FC = 0.71) and SYNM (p = 0.04 and FC = 0.76) in AF patients. Gene Set Variation Analysis (GSEA) showed mitochondrial metabolism-associated pathways including oxidative phosphorylation (NES: −1.73) and ATP biosynthetic process (NES: −2.29), were dramatically diversified in human AF. In GSVA, the expression levels of GPD2, PLEC, and SYNM were demonstrated to be associated with multiple metabolic pathways related to mitochondrial function (e.g., lipid metabolism and AMP activated protein kinase signaling) and cardiac structural and electrical remodeling (e.g., contractile fiber, ion homeostasis), which were proven vital in the development and maintenance of AF.

Conclusion: In all, this study provides new insights into understanding the mechanisms of AF progression, especially the reprogramming mitochondrial metabolism, and identifies several genes related to mitochondrial function as novel targets for AF, which may be involved in the occurrence and development of AF.

Insights into circular RNAs : Biogenesis, function and their regulatory roles in cardiovascular disease

As a distinctive member of the noncoding RNA family, circular RNAs (circRNAs) are generated from single-stranded, covalently closed structures and are ubiquitous in mammalian cells and tissues. Due to its atypical circular architecture, it was conventionally deemed insignificant dark matter for a prolonged duration. Nevertheless, studies conducted over the last decade have demonstrated that this abundant, structurally stable and tissue-specific RNA has been increasingly relevant in diverse diseases, including cancer, neurological disorders, diabetes mellitus and cardiovascular diseases (CVDs). Therefore, regulatory pathways controlled by circRNAs are widely involved in the occurrence and pathological processes of CVDs through their function as miRNA sponges, protein sponges and protein scaffolds. To better understand the role of circRNAs and their complex regulatory networks in CVDs, we summarize current knowledge of their biogenesis and function and the latest research on circRNAs in CVDs, with the hope of paving the way for the identification of promising biomarkers and therapeutic strategies for CVDs.

Long non-coding RNA and circular RNA: new perspectives for molecular pathophysiology of atrial fibrillation

Many studies have demonstrated the association of atrial fibrillation (AF) with endogenous genetic regulatory mechanisms. These interactions could advance the understanding of the AF pathophysiological process, supporting the search for early biomarkers to improve diagnosis and disease monitoring. Among the endogenous genetic regulatory mechanisms, long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) have gained special attention, and studies have demonstrated their involvement in AF development and other AF-related diseases such as coronary artery disease and cardiomyopathy. This review describes the main experimental results reported by studies that analyzed the expression of lncRNAs and circRNAs in AF associated with miRNA or mRNA. The search was conducted in PubMed public database using the terms "lncRNA and atrial fibrillation" or "long ncRNA and atrial fibrillation" or "long non-coding RNA and atrial fibrillation" or "circular RNA and atrial fibrillation" or "circRNA and atrial fibrillation". There was no overlapping of lncRNA or circRNA among the studies, attributed to the different sample types, methods, species, and patient classification evaluated in these studies. Although the regulatory mechanisms in which these molecules are involved are not yet well understood, the studies analyzed show their importance in the pathophysiological process of AF, supporting the idea that lncRNAs and circRNAs are involved in miRNA or mRNA regulation in the molecular mechanism of this disease.

The Landscape of Circular RNAs in Cardiovascular Diseases

Cardiovascular disease (CVD) remains the leading cause of mortality globally. Circular RNAs (circRNAs) have attracted extensive attention for their roles in the physiological and pathological processes of various cardiovascular diseases (CVDs). In this review, we briefly describe the current understanding of circRNA biogenesis and functions and summarize recent significant findings regarding the roles of circRNAs in CVDs. These results provide a new theoretical basis for diagnosing and treating CVDs.

CircCAMTA1 facilitates atrial fibrosis by regulating the miR-214-3p/TGFBR1 axis in atrial fibrillation

Circular RNAs (circRNAs) have been shown to be associated with cardiac fibrosis. Atrial fibrosis is an important pathophysiological event in the progression of atrial fibrillation (AF). Although a novel circRNA calmodulin binding transcription activator 1 (circCAMTA1) has been reported to be related with the development of AF, the detailed molecular mechanisms remain largely unknown. In this study, we found that circCAMTA1 was upregulated in atrial muscle tissues of AF patients and angiotensin-II (Ang-II)-treated human atrial fibroblasts (HAFs). Moreover, circCAMTA1 expression was positively correlated with the expression of collagen (I and III) and α-SMA in atrial muscle tissues of AF patients. In vitro experiments, knockdown of circCAMTA1 significantly suppressed Ang-II-induced HAFs proliferation and reduced the expression of atrial fibrosis-associated genes, but overexpression of circCAMTA1 exhibited opposite results. In vivo experiments, circCAMTA1 knockdown ameliorated Ang-II-induced atrial fibrosis by reducing AF incidence, AF duration, and collagen synthesis. Functionally, circCAMTA1 facilitated Ang-II-induced atrial fibrosis in vitro and in vivo via downregulating the inhibitory effect of miR-214-3p on transforming growth factor β receptor 1 (TGFBR1) expression. In conclusions, circCAMTA1 knockdown alleviated atrial fibrosis through downregulating TGFBR1 expression intermediated by miR-214-3p in AF, suggesting circCAMTA1/miR-214-3p/TGFBR1 axis may be a novel therapeutic target for AF treatment in clinic.

The Function and Therapeutic Potential of Circular RNA in Cardiovascular Diseases

Circular RNA (circRNA) has a closed-loop structure, and its 3' and 5' ends are directly covalently connected by reverse splicing, which is more stable than linear RNA. CircRNAs usually possess microRNA (miRNA) binding sites, which can bind miRNAs and inhibit miRNA function. Many studies have shown that circRNAs are involved in the processes of cell senescence, proliferation and apoptosis and a series of signalling pathways, playing an important role in the prevention and treatment of diseases. CircRNAs are potential biological diagnostic markers and therapeutic targets for cardiovascular diseases (CVDs). To identify biomarkers and potential effective therapeutic targets without toxicity for heart disease, we summarize the biogenesis, biology, characterization and functions of circRNAs in CVDs, hoping that this information will shed new light on the prevention and treatment of CVDs.

Construction of atrial fibrillation-related circRNA/lncRNA-miRNA-mRNA regulatory network and analysis of potential biomarkers

BACKGROUND

The specific pathogenesis of atrial fibrillation (AF) remains unclear. In this study, we examined the expression of differential messenger RNAs (mRNAs), circular RNAs (circRNAs), and long-stranded noncoding RNAs (lncRNAs) from human peripheral blood mononuclear cells to initially construct a circRNA/lncRNA-miRNA-mRNA ceRNA regulatory network to explore the pathogenesis of AF and to screen for potential biomarkers.

METHODS

A total of four pairs of AF cases and healthy subjects were selected to detect differentially expressed mRNAs, circRNAs, and lncRNAs in peripheral blood mononuclear cells by microarray analysis. And 20 pairs of peripheral blood from AF patients and healthy subjects were selected for validation of mRNA, circRNA, and lncRNA by quantitative real-time PCR (qRT-PCR).The relevant ceRNA networks were constructed by GO and KEGG and correlation analysis.

RESULTS

The results showed that compared with healthy subjects, there were 813 differentially expressed mRNAs (DEmRNAs) in peripheral blood monocytes of AF, including 445 upregulated genes and 368 downregulated genes, 120 differentially expressed circRNAs (DEcircRNAs), including 65 upregulated and 55 downregulated, 912 differentially expressed lncRNAs (DElncRNAs), including 531 upregulated and 381 downregulated lncRNAs. GO and KEGG analysis of DERNA revealed the biological processes and pathways involved in AF. Based on microarray data and predicted miRNAs, a ceRNA network containing 34 mRNAs, 212 circRNAs, 108 lncRNAs, and 38 miRNAs was constructed.

CONCLUSION

We revealed a novel ceRNA network in AF and showed that downregulated XIST, circRNA_2773, and CADM1 were negatively correlated with miR-486-5p expression and had a potential targeting relationship with miR-486-5p.

Integrated Analysis of the microRNA–mRNA Network Predicts Potential Regulators of Atrial Fibrillation in Humans

Atrial fibrillation (AF) is a form of sustained cardiac arrhythmia and microRNAs (miRs) play crucial roles in the pathophysiology of AF. To identify novel miR–mRNA pairs, we performed RNA-seq from atrial biopsies of persistent AF patients and non-AF patients with normal sinus rhythm (SR). Differentially expressed miRs (11 down and 9 up) and mRNAs (95 up and 82 down) were identified and hierarchically clustered in a heat map. Subsequently, GO, KEGG, and GSEA analyses were run to identify deregulated pathways. Then, miR targets were predicted in the miRDB database, and a regulatory network of negatively correlated miR–mRNA pairs was constructed using Cytoscape. To select potential candidate genes from GSEA analysis, the top-50 enriched genes in GSEA were overlaid with predicted targets of differentially deregulated miRs. Further, the protein–protein interaction (PPI) network of enriched genes in GSEA was constructed, and subsequently, GO and canonical pathway analyses were run for genes in the PPI network. Our analyses showed that TNF-α, p53, EMT, and SYDECAN1 signaling were among the highly affected pathways in AF samples. SDC-1 (SYNDECAN-1) was the top-enriched gene in p53, EMT, and SYDECAN1 signaling. Consistently, SDC-1 mRNA and protein levels were significantly higher in atrial samples of AF patients. Among negatively correlated miRs, miR-302b-3p was experimentally validated to suppress SDC-1 transcript levels. Overall, our results suggested that the miR-302b-3p/SDC-1 axis may be involved in the pathogenesis of AF.

Extremely Low Frequency Magnetic Fields Induce mTOR and Hsa_Circ_100338 Expression Changes in Gastric Cancer and Normal Fibroblast Cell Lines

OBJECTIVE

Extremely low-frequency magnetic field (ELF-MF) exposure, as a targeted tumor therapy, presents several potential advantages. In this research, we investigated effects of different ELF-MF intensities on cell viability and expression levels of the mammalian target of rapamycin (mTOR) and hsa_circ_100338 in the normal fibroblast (Hu02) and human gastric adenocarcinoma (AGS) cell lines.

MATERIALS AND METHODS

In this experimental study, cell lines of AGS and Hu02, were cultured under the exposure of ELFMF with magnetic flux densities (MFDs) of 0.25, 0.5, 1 and 2 millitesla (mT) for 18 hours. The 3-(4, 5-dimethylthiazoyl-2- yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was used to evaluate the cell viability. Relative expression of mTOR and hsa_circ_100338 RNAs was estimated by quantitative real-time polymerase chain reaction (qRT-PCR) technique.

RESULTS

Viability of the normal cells was significantly increased at MFDs of 0.5, 1 and 2 mT, while viability of the tumor cells was significantly decreased at MFD of 0.25 and increased at MFD of 2 mT. Expression level of mTOR was significantly increased at the all applied MFDs in the normal cells, while it was significantly decreased at MFDs of 0.25 and 0.5mT in the tumor cells. MFDs of 1 and 2 mT in tumor cells inversely led to the increase in mTOR expression. hsa_circ_100338 was downregulated in MFD of 0.25 mT and then it was increased parallel to the increase of MFD in the normal and tumor cells.

CONCLUSION

Results of the present study indicated that ELF-MF at MFDs of 0.25 and 0.5 mT can lead to decrease in the both mTOR and hsa_circ_100338 expression levels. Given the role of mTOR in cell growth, proliferation and differentiation, in addition to the potential role of hsa_circ_100338 in metastasis, expression inhibition of these two genes could be a therapeutic target in cancer treatment.

Integrated Analysis of circRNA-miRNA-mRNA-Mediated Network and Its Potential Function in Atrial Fibrillation

Background

Atrial fibrillation (AF) is one of the most prevalent arrhythmias, characterized by a high risk of heart failure and embolic stroke. Competing endogenous RNA network has been reported to play an important role in cardiovascular diseases. The main objective of the present study was to construct a circRNA–miRNA–mRNA-mediated network and explore the potential function in AF.

Methods

The microarray data of circRNA, miRNA, and mRNA in AF were downloaded from the Gene Expression Omnibus database. The RobustRankAggreg method was used to screen the different expression circRNAs(DECs). Then the circRNA–miRNA–mRNA-mediated network was constructed by using the CircInteractome database and the miRWalk online tool. A quantitative real-time polymerase chain reaction was used to detect the circRNA expression level in plasma. The left atrial fibrosis was evaluated with the left atrial low voltage area (LVA) by using left atrial voltage matrix mapping.

Results

Three DECs (hsa_circRNA_102461, hsa_circRNA_103693, and hsa_circRNA_059880) and 4 miRNAs were screened. Then a circRNA–miRNA–mRNA-mediated network was constructed, which included 2 circRNAs, 4 miRNAs, and 83 genes. Furthermore, the plasma’s hsa_circ_0070391 expression level was confirmed to be upregulated and positively correlated with left atrial fibrosis in AF (r = 0.88, P < 0.001), whereas hsa_circ_0003935 was downregulated. Moreover, the ROC curve analysis revealed hsa_circ_0070391 and hsa_circ_0003935 could differentiate AF from the healthy controls with an AUC of 0.95 (95% sensitivity and 90% specificity) and 0.86 (70% sensitivity and 75% specificity), respectively. Finally, the free of atrial tachyarrhythmia rate was dramatically lower in the hsa_circ_0070391 high expression group than in the low expression group post catheter ablation (70.0 vs. 90.0%, p = 0.04).

Conclusion

This study provides a novel insight to further understand the AF pathogenesis from the perspective of the circRNA–miRNA–mRNA network, suggesting that plasma circRNAs could serve as a novel atrial fibrosis and prognosis biomarker for AF.

Construction of a circRNA-Mediated ceRNA Network Reveals Novel Biomarkers for Aortic Dissection

Background

Aortic dissection (AD) is a rare and lethal disorder with its genetic basis remains largely unknown. Many studies have confirmed that circRNAs play important roles in various physiological and pathological processes. However, the roles of circRNAs in AD are still unclear and need further investigation. The present study aimed to elucidate the underlying molecular mechanisms of circRNAs regulation in AD based on the circRNA-associated competing endogenous RNA (ceRNA) network.

Methods

Expression profiles of circRNAs (GSE97745), miRNAs (GSE92427), and mRNAs (GSE52093) were downloaded from Gene Expression Omnibus (GEO) databases, and the differentially expressed RNAs (DERNAs) were subsequently identified by bioinformatics analysis. CircRNA–miRNA–mRNA ceRNA network, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used to predict the potential functions of circRNA-associated ceRNA network. RNA was isolated from human arterial blood samples after which qRT-PCR was performed to confirm the DERNAs.

Results

We identified 14 (5 up-regulated and 9 down-regulated) differentially expressed circRNAs (DEcircRNAs), 17 (8 up-regulated and 9 down-regulated) differentially expressed miRNAs (DEmiRNAs) and 527 (297 up-regulated and 230 down-regulated) differentially expressed mRNAs (DEmRNAs) (adjusted P-value <0.05 and | log2FC | > 1.0). KEGG pathway analysis indicated that DEmRNAs were related to focal adhesion and extracellular matrix receptor interaction signaling pathways. Simultaneously, the present study constructed a ceRNA network based on 1 circRNAs (hsa_circRNA_082317), 1 miRNAs (hsa-miR-149-3p) and 10 mRNAs (MLEC, ENTPD7, SLC16A3, SLC7A8, TBC1D16, PAQR4, MAPK13, PIK3R2, ITGA5, SERPINA1). qRT-PCR demonstrated that hsa_circRNA_082317 and ITGA5 were significantly up-regulated, and hsa-miR-149-3p was dramatically down-regulated in AD (n = 3).

Conclusion

This is the first study to demonstrate the circRNA-associated ceRNA network is altered in AD, implying that circRNAs may play important roles in regulating the onset and progression and thus may serve as potential biomarkers for the diagnosis and treatment of AD.

Profile and Functional Prediction of Plasma Exosome-Derived CircRNAs From Acute Ischemic Stroke Patients

Stroke is one of the major causes of death and long-term disability, of which acute ischemic stroke (AIS) is the most common type. Although circular RNA (circRNA) expression profiles of AIS patients have been reported to be significantly altered in blood and peripheral blood mononuclear cells, the role of exosome-containing circRNAs after AIS is still unknown. Plasma exosomes from 10 AIS patients and 10 controls were isolated, and through microarray and bioinformatics analysis, the profile and putative function of circRNAs in the plasma exosomes were studied. A total of 198 circRNAs were differentially quantified (|log2 fold change| ≥ 1.00, p < 0.05) between AIS patients and controls. The levels of 12 candidate circRNAs were verified by qRT-PCR, and the quantities of 10 of these circRNAs were consistent with the data of microarray. The functions of host genes of differentially quantified circRNAs, including RNA and protein process, focal adhesion, and leukocyte transendothelial migration, were associated with the development of AIS. As a miRNA sponge, differentially quantified circRNAs had the potential to regulate pathways related to AIS, like PI3K-Akt, AMPK, and chemokine pathways. Of 198 differentially quantified circRNAs, 96 circRNAs possessing a strong translational ability could affect cellular structure and activity, like focal adhesion, tight junction, and endocytosis. Most differentially quantified circRNAs were predicted to bind to EIF4A3 and AGO2—two RNA-binding proteins (RBPs)—and to play a role in AIS. Moreover, four of ten circRNAs with verified levels by qRT-PCR (hsa_circ_0112036, hsa_circ_0066867, hsa_circ_0093708, and hsa_circ_0041685) were predicted to participate in processes of AIS, including PI3K-Akt, AMPK, and chemokine pathways as well as endocytosis, and to be potentially useful as diagnostic biomarkers for AIS. In conclusion, plasma exosome-derived circRNAs were significantly differentially quantified between AIS patients and controls and participated in the occurrence and progression of AIS by sponging miRNA/RBPs or translating into proteins, indicating that circRNAs from plasma exosomes could be crucial molecules in the pathogenesis of AIS and promising candidates as diagnostic biomarkers and therapeutic targets for the condition.

Epigenetic Mechanism and Therapeutic Implications of Atrial Fibrillation

Atrial fibrillation (AF) is the most common arrhythmia attacking 1. 5–2.0% of general population worldwide. It has a significant impact on morbidity and mortality globally and its prevalence increases exponentially with age. Therapies like catheter ablation or conventional antiarrhythmic drugs have not provided effective solution to the recurrence for AF over the past decades. Over 100 genetic loci have been discovered to be associated with AF by Genome-wide association studies (GWAS) but none has led to a therapy. Recently potential involvement of epigenetics (DNA methylation, histone modification, and non-coding RNAs) in the initiation and maintenance of AF has partly emerged as proof-of-concept in the mechanism and management of AF. Here we reviewed the epigenetic features involved in AF pathophysiology and provided an update of their implications in AF therapy.

Altered Expression of Transfer-RNA-Derived Small RNAs in Human With Rheumatic Heart Disease

Rheumatic heart disease (RHD) remains a severe public health problem in developing countries. Atrial fibrillation (AF) is a medical complication of RHD. Although the understanding of disease pathogenesis has advanced in recent years, the key questions need to be addressed. Transfer RNA–derived small RNAs (tsRNAs) are a novel type of short non-coding RNAs with potential regulatory functions in various physiological and pathological processes. The present study used tsRNAs sequencing to investigate the relationship between RHD and atrial fibrillation (AF). Three paired cardiac papillary muscles were taken from six rheumatic RHD patients with AF (3 cases) or without AF (3 cases) from January 2016 to January 2017 in Xiangya Hospital, Central South University. A total of 219 precisely matched tsRNAs were identified, and 77 tsRNAs (fold change > 2.0 and P < 0.05) were differently changed. Three tsRNAs (AS-tDR-001269, AS-tDR-001363, AS-tDR-006049) were randomly selected and confirmed by qRT-PCR. The results of qRT-PCR were consistent with tsRNAs sequencing, suggesting the tsRNAs sequencing was reliable. Subsequently, we predicted the target mRNAs of the three tsRNAs. Moreover, we verified the functions of tsRNAs targeting mRNAs in vitro. Finally, bioinformatics analysis indicated that the target genes were abundant in regulation of transcription, DNA binding, intracellular. Most of the genes were predicted to interplay with cytokine-cytokine receptor by KEGG analysis. Our findings uncover the pathological process of AF in RHD through tsRNAs sequencing. This research provides a new perspective for future research on elucidating the mechanism of AF in RHD and offers potential new candidates for the treatment and diagnosis.

The Construction and Comprehensive Analysis of a ceRNA Immunoregulatory Network and Tissue-Infiltrating Immune Cells in Atrial Fibrillation

Background

At present, the mechanisms behind atrial fibrillation (AF) pathogenesis are still unclear. We construct a ceRNA immunoregulatory network to further understand the mechanism of AF.

Methods

Four AF mRNA datasets from the Gene Expression Omnibus (GEO) database were integrated by SVA method. AF-related immune genes (AF-IRGs) were selected via combining ImmPort database with the genes in the module most associated with AF obtained by a weighted gene coexpression network analysis (WGCNA). Then, circRNA and miRNA expressions from the GEO database were extracted and mapped with related databases. Next, an immune-related circRNA-miRNA-mRNA ceRNA network was constructed and hub genes were filtered from a protein–protein interaction (PPI) network, and the differentially expressed (DE) hub genes in AF were further screened. Additionally, immune infiltration was investigated in AF by using CIBERSORT. Subsequently, the relationships between DE hub genes and AF-related infiltrating immune cells were performed by using Pearson correlation coefficients. Ulteriorly, the immune-cells-related ceRNA subnetwork in AF was built.

Results

A total of 95 AF-IRGs were detected, and an immune-related ceRNA network in AF was constructed with 12 circRNAs, 7 miRNAs and 50 mRNAs. The immune infiltration analysis indicated that a higher level of neutrophils, as well as a lower level of T cells regulatory (Tregs) and NK cells activated in AF. Four DE hub genes (CXCL12, IL7R, TNFSF13B, CD8A) were associated with Tregs or NK cells activated immune cells (P < 0.05). Tregs or NK cells activated immune cells-related ceRNA subnetwork including 5 circRNAs (has_circ_0001190, has_circ_0006725, has_circ_0079284, has_circ_0005299, and has_circ_0002103), 4 miRNAs (has-miR-198, has-miR-623, has-miR-1246, and has-miR-339-3p) and 4 DE hub genes was eventually constructed in AF.

Conclusion

Our results provide new insights into the molecular mechanisms governing AF progression from the perspective of immune-related ceRNA network.

Integrating analysis of circular RNA and mRNA expression profiles in doxorubicin induced cardiotoxicity mice

Doxorubicin (DOX)-induced cardiotoxicity impedes its clinical application, but the mechanisms have not been thoroughly elucidated. Based on circRNA and mRNA expression profiles, we illustrated RNA expression signature changes during DOX-induced cardiotoxicity; mechanism exploration and biomarkers screening were also conducted. Twelve mice were randomly divided into two groups, induction group was treated with doxorubicin, and the control group was given an equal quantity of saline. After the confirmation of myocardial injury in induction group, the heart tissues from both groups were isolated for RNA high-throughput sequencing. The expression profiles were compared between the two groups; a total of 295 mRNAs and 11 circRNAs were shown as biased expression in DOX-induced cardiotoxicity mouse hearts. The dysregulation of three circRNAs were validated by quantitative real-time PCR: mmu_circ_0015773, mmu_circ_0002106, and mmu_circ_001606. In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of the differentially expressed RNAs were performed; the results implied that DOX might cause cardiotoxicity by interfering hemoglobin-based oxygen delivery and DNA-associated signal pathways. We integrated the differential expressed mRNA and validated circRNAs by constructing a competing endogenous RNA (ceRNA) network, which indicated that the alteration of the three circRNAs could activate apoptosis process of myocardial cells. This study provided novel insight into the mechanisms of DOX induced cardiotoxicity, and potential biomarkers or therapeutic targets were also proposed.

Regulation of Mitochondrial Function by Noncoding RNAs in Heart Failure and Its Application in Diagnosis and Treatment

ABSTRACT

Heart failure (HF) is the terminal stage of multiple cardiovascular diseases. However, the pathogenesis of HF remains unclear and prompt; appropriate diagnosis and treatment of HF are crucial. Cardiomyocytes isolated from HF subjects frequently present mitochondrial impairment and dysfunction. Many studies have suggested that the regulation by noncoding RNAs (ncRNAs) of mitochondria can affect the occurrence and progression of HF. The regulation by ncRNAs of myocardial mitochondria during HF and the recent applications of ncRNAs in the diagnosis and treatment of HF are summarized in this review that is intended to gain keen insights into the mechanisms of HF and more effective treatments.

Circular RNA mmu_circ_0005019 inhibits fibrosis of cardiac fibroblasts and reverses electrical remodeling of cardiomyocytes

BACKGROUND

Circular RNA (circRNA) have been reported to play important roles in cardiovascular diseases including myocardial infarction and heart failure. However, the role of circRNA in atrial fibrillation (AF) has rarely been investigated. We recently found a circRNA hsa_circ_0099734 was significantly differentially expressed in the AF patients atrial tissues compared to paired control. We aim to investigate the functional role and molecular mechanisms of mmu_circ_0005019 which is the homologous circRNA in mice of hsa_circ_0099734 in AF.

METHODS

In order to investigate the effect of mmu_circ_0005019 on the proliferation, migration, differentiation into myofibroblasts and expression of collagen of cardiac fibroblasts, and the effect of mmu_circ_0005019 on the apoptosis and expression of Ito, INA and SK3 of cardiomyocytes, gain- and loss-of-function of cell models were established in mice cardiac fibroblasts and HL-1 atrial myocytes. Dual-luciferase reporter assays and RIP were performed to verify the binding effects between mmu_circ_0005019 and its target microRNA (miRNA).

RESULTS

In cardiac fibroblasts, mmu_circ_0005019 showed inhibitory effects on cell proliferation and migration. In cardiomyocytes, overexpression of mmu_circ_0005019 promoted Kcnd1, Scn5a and Kcnn3 expression. Knockdown of mmu_circ_0005019 inhibited the expression of Kcnd1, Kcnd3, Scn5a and Kcnn3. Mechanistically, mmu_circ_0005019 exerted biological functions by acting as a miR-499-5p sponge to regulate the expression of its target gene Kcnn3.

CONCLUSIONS

Our findings highlight mmu_circ_0005019 played a protective role in AF development and might serve as an attractive candidate target for AF treatment.

miR-455-5p regulates atrial fibrillation by targeting suppressor of cytokines signaling 3

Atrial fibrillation (AF) is a condition that heart beats quaveringly or irregularly, which causes blood clots, heart failure, stroke, and other heart-related complications. Therefore, early diagnosis and timely preventions are necessary for AF treatment. Compelling evidence indicated that microRNAs (miRNAs) become emerging biomarkers of AF; thus, we aimed to investigate the possibility of miR-455-5p as an AF marker to provide a new strategy for early diagnosis of AF. A minipump containing angiotensin II was implanted into mice to induce AF, and adeno-associated virus (AAV) carrying anti-miR-negative control (NC) or anti-miR-455-5p was injected into the pericardial space of mice respectively. Next, myocytes isolated from wild-type newborn mice were stimulated with angiotensin II and anti-miR-NC or anti-miR-455-5p mimic. The results showed that the expression of miR-455-5p was positively correlated with the severity of AF, and miR-455-5p mimic accelerated the progression of AF by directly binding to its target gene suppressor of cytokines signaling 3 (SOCS3), leading to the activation of signal transducer and activator of transcription 3 (STAT3) signaling pathway. On the contrary, inhibition of miR-455-5p expression effectively ameliorated AF. In conclusion, miR-455-5p might serve as a biomarker of AF.

Circular RNAs in Sudden Cardiac Death Related Diseases: Novel Biomarker for Clinical and Forensic Diagnosis

The prevention and diagnosis of sudden cardiac death (SCD) are among the most important keystones and challenges in clinical and forensic practice. However, the diagnostic value of the current biomarkers remains unresolved issues. Therefore, novel diagnostic biomarkers are urgently required to identify patients with early-stage cardiovascular diseases (CVD), and to assist in the postmortem diagnosis of SCD cases without typical cardiac damage. An increasing number of studies show that circular RNAs (circRNAs) have stable expressions in myocardial tissue, and their time- and tissue-specific expression levels might reflect the pathophysiological status of the heart, which makes them potential CVD biomarkers. In this article, we briefly introduced the biogenesis and functional characteristics of circRNAs. Moreover, we described the roles of circRNAs in multiple SCD-related diseases, including coronary artery disease (CAD), myocardial ischemia or infarction, arrhythmia, cardiomyopathy, and myocarditis, and discussed the application prospects and challenges of circRNAs as a novel biomarker in the clinical and forensic diagnosis of SCD.

Serum miR-222 is independently associated with atrial fibrillation in patients with degenerative valvular heart disease

Background

Inflammation is involved in the progression of degenerative valvular heart disease (DVHD). microRNA-222 (miR-222) contributes to inflammation-mediated vascular remodeling, but its involvement in DVHD in relation to atrial fibrillation (AF) is unknown. This study aimed to investigate the changes in miR-222, interleukin (IL)-6, high-sensitivity C-reactive protein (hs-CRP), and N-terminal pro-brain natriuretic peptide (NT-proBNP) in patients with DVHD complicated with AF.

Methods

This was a case control study of patients with DVHD who were hospitalized at the Geriatrics Department of the Affiliated Huai’an Hospital of Xuzhou Medical University between 01/2017 and 08/2018. The participants were grouped according to the presence of AF, and serum miR-222, IL-6, hs-CRP, and NT-proBNP levels were compared.

Results

There were fifty-two participants (28 males) in the DVHD with AF group, aged 60–80 years (73.0 ± 5.9 years). Sixty participants (31 males) were included in the DVHD without AF group, aged 60–80 years (71.9 ± 6.92 years). There were no significant differences in age, sex, body mass index, fasting blood glucose, triglycerides, cholesterol, and blood pressure between the two groups. The serum levels of miRNA-222, IL-6, hs-CRP, and NT-proBNP in DVHD patients were significantly higher in those with AF compared with the non-AF group (all P < 0.05). Correlation analyses revealed that IL-6, hs-CRP, and NT-proBNP levels were positively correlated with miR-222 levels in all patients (IL-6: r = 0.507, P < 0.01; hs-CRP: r = 0.390, P < 0.01; NT-proBNP: r = 0.509, P < 0.01).

Conclusions

Serum miR-222 was independently associated with AF in patients with DVHD.

Epigenetics in atrial fibrillation: A reappraisal

Atrial fibrillation (AF) is the most common cardiac arrhythmia and an important cause of morbidity and mortality globally. Atrial remodeling includes changes in ion channel expression and function, structural alterations, and neural remodeling, which create an arrhythmogenic milieu resulting in AF initiation and maintenance. Current therapeutic strategies for AF involving ablation and antiarrhythmic drugs are associated with relatively high recurrence and proarrhythmic side effects, respectively. Over the last 2 decades, in an effort to overcome these issues, research has sought to identify the genetic basis for AF thereby gaining insight into the regulatory mechanisms governing its pathophysiology. Despite identification of multiple gene loci associated with AF, thus far none has led to a therapy, indicating additional contributors to pathology. Recently, in the context of expanding knowledge of the epigenome (DNA methylation, histone modifications, and noncoding RNAs), its potential involvement in the onset and progression of AF pathophysiology has started to emerge. Probing the role of various epigenetic mechanisms that contribute to AF may improve our knowledge of this complex disease, identify potential therapeutic targets, and facilitate targeted therapies. Here, we provide a comprehensive review of growing epigenetic features involved in AF pathogenesis and summarize the emerging epigenomic targets for therapy that have been explored in preclinical models of AF.

Integrative Analysis Extracts a Core ceRNA Network of the Fetal Hippocampus With Down Syndrome

Accumulating evidence suggests that circular RNAs (circRNAs)-miRNA-mRNA ceRNA regulatory network-may play an important role in neurological disorders, such as Alzheimer's disease (AD). Interestingly, neuropathological changes that closely resemble AD have been found in nearly all Down syndrome (DS) cases > 35 years. However, few studies have reported circRNA transcriptional profiling in DS cases, which is caused by a chromosomal aberration of trisomy 21. Here, we characterized the expression profiles of circRNAs in the fetal hippocampus of DS patients (n = 8) and controls (n = 6) by using microarray. MiRNA, mRNA expression profiling of DS from our previous study and scRNA-seq data describing normal fetal hippocampus development (GEO) were also integrated into the analysis. The similarity between circRNAs/genes with traits/cell-types was calculated by weighted correlation network analysis (WGCNA). miRanda and miRWalk2 were used to predict ceRNA network interactions. We identified a total of 7,078 significantly differentially expressed (DE) circRNAs, including 2,637 upregulated and 4,441 downregulated genes, respectively. WGCNA obtained 15 hub circRNAs and 6 modules with cell type-specific expression patterns among scRNA-seq data. Finally, a core ceRNA network was constructed by 14 hub circRNAs, 17 DE miRNA targets and 245 DE mRNA targets with a cell type-specific expression pattern annotation. Known functional molecules in DS or neurodegeneration (e.g., miR-138, OLIG1, and TPM2) were also included in this network. Our findings are the first to delineate the landscape of circRNAs in DS and the first to effectively integrate ceRNA regulation with scRNA-seq data. These data may provide a valuable resource for further research on the molecular mechanisms or therapeutic targets underlying DS neuropathy.

Pilot Study on the Role of Circulating miRNAs for the Improvement of the Predictive Ability of the 2MACE Score in Patients with Atrial Fibrillation

Background. Atrial fibrillation (AF) increases the risk for stroke but also for non-stroke major adverse cardiovascular events (MACE). The 2MACE score was recently proposed to predict these events. Since the interest of microRNAs (miRNAs) in cardiovascular diseases is increasing, we aimed to investigate whether miRNA levels may improve the predictive performance of the 2MACE score. Methods. We included consecutive AF patients stable on vitamin K antagonist therapy. Blood samples were drawn at baseline and plasma expression of miRNAs was assessed. During a median of 7.6 (interquartile range (IQR) 5.4–8.0) years, the occurrence of any MACE (nonfatal myocardial infarction/cardiac revascularization and cardiovascular death) was recorded. Results. We conducted a miRNA expression analysis in plasma from 19 patients with and without cardiovascular events. The miRNAs selected (miR-22-3p, miR-107, and miR-146a-5p) were later measured in 166 patients (47% male, median age 77 (IQR 70–81) years) and all were associated with a higher risk of MACE. The addition of miR-107 and miR-146a-5p to the 2MACE score significantly increased the predictive performance (c-indexes: 0.759 vs. 0.694, p = 0.004), and the model with three miRNAs also improved the predictive performance compared to the original score (c-indexes: 0.762 vs. 0.694, p = 0.012). 2MACE models with the addition of miRNAs presented higher net benefit and potential clinical usefulness. Conclusions. Higher miR-22-3p andmiR-107 and lower miR-146a-5p levels were associated with a higher risk of MACE. The addition of these miRNAs to the 2MACE score significantly increased the predictive performance for MACE, which may aid to some extent in the decision-making process about risk stratification in AF.

Overexpression of circRNA circUCK2 Attenuates Cell Apoptosis in Cerebral Ischemia-Reperfusion Injury via miR-125b-5p/GDF11 Signaling

Circular RNAs (circRNAs) are expressed at high levels in the brain and are involved in various central nervous system diseases. However, the potential role of circRNAs in ischemic stroke-associated neuronal injury remains largely unknown. Herein, we uncovered the function and underlying mechanism of the circRNA UCK2 (circUCK2) in ischemia stroke. The oxygen-glucose deprivation model in HT-22 cells was used to mimic ischemia stroke in vitro. Neuronal viability and apoptosis were determined by Cell Counting Kit-8 (CCK-8) assays and TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling) staining, respectively. Middle cerebral artery occlusion was conducted to evaluate the function of circUCK2 in mice. The levels of circUCK2 were significantly decreased in brain tissues from a mouse model of focal cerebral ischemia and reperfusion. Upregulated circUCK2 levels significantly decreased infarct volumes, attenuated neuronal injury, and improved neurological deficits. circUCK2 reduced oxygen glucose deprivation (OGD)-induced cell apoptosis by regulating transforming growth factor β (TGF-β)/mothers against decapentaplegic homolog 3 (Smad3) signaling. Furthermore, circUCK2 functioned as an endogenous miR-125b-5p sponge to inhibit miR-125b-5p activity, resulting in an increase in growth differentiation factor 11 (GDF11) expression and a subsequent amelioration of neuronal injury. Consequently, these findings showed that the circUCK2/miR-125b-5p/GDF11 axis is an essential signaling pathway during ischemia stroke. Thus, the circRNA circUCK2 may serve as a potential target for novel treatment in patients with ischemic stroke.

Identification of Circular RNA-MicroRNA-Messenger RNA Regulatory Network in Atrial Fibrillation by Integrated Analysis

BACKGROUND

Circular RNA (circRNA) is a noncoding RNA that forms a closed-loop structure, and its abnormal expression may cause disease. We aimed to find potential network for circRNA-related competitive endogenous RNA (ceRNA) in atrial fibrillation (AF).

METHODS

The circRNA, miRNA, and mRNA expression profiles in the heart tissue from AF patients were retrieved from the Gene Expression Omnibus database and analyzed comprehensively. Differentially expressed circRNAs (DEcircRNAs), differentially expressed miRNAs (DEmiRNAs), and differentially expressed mRNAs (DEmRNAs) were identified, followed by the establishment of DEcircRNA-DEmiRNA-DEmRNA regulatory network. Functional annotation analysis of host gene of DEcircRNAs and DEmRNAs in ceRNA regulatory network was performed. In vitro experiment and electronic validation were used to validate the expression of DEcircRNAs, DEmiRNAs, and DEmRNAs.

RESULTS

A total of 1611 DEcircRNAs, 51 DEmiRNAs, and 1250 DEmRNAs were identified in AF. The DEcircRNA-DEmiRNA-DEmRNA network contained 62 circRNAs, 14 miRNAs, and 728 mRNAs. Among which, two ceRNA regulatory pairs of hsa-circRNA-100053-hsa-miR-455-5p-TRPV1 and hsa-circRNA-005843-hsa-miR-188-5p-SPON1 were identified. In addition, six miRNA-mRNA regulatory pairs including hsa-miR-34c-5p-INMT, hsa-miR-1253-DDIT4L, hsa-miR-508-5p-SMOC2, hsa-miR-943-ACTA1, hsa-miR-338-3p-WIPI1, and hsa-miR-199a-3p-RAP1GAP2 were also obtained. MTOR was a significantly enriched signaling pathway of host gene of DEcircRNAs. In addition, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy, and hypertrophic cardiomyopathy were remarkably enriched signaling pathways of DEmRNAs in DEcircRNA-DEmiRNA-DEmRNA regulatory network. The expression validation of hsa-circRNA-402565, hsa-miR-34c-5p, hsa-miR-188-5p, SPON1, DDIT4L, SMOC2, and WIPI1 was consistent with the integrated analysis.

CONCLUSION

We speculated that hsa-circRNA-100053-hsa-miR-455-5p-TRPV1 and hsa-circRNA-005843-hsa-miR-188-5p-SPON1 interaction pairs may be involved in AF.

Rapid Development of Targeting circRNAs in Cardiovascular Diseases

Circular RNAs (circRNAs) are circularized, single-stranded RNAs that are covalently linked. With their abundance in tissues and developmental stage-specific expression, circRNAs participate in a variety of physiological and pathological processes. In this review, we discuss the development of circRNAs used as biomarkers and therapeutic targets for cardiovascular diseases (CVDs), focusing on recent discoveries and applications of exosomal circRNAs that highlight opportunities and challenges. Some studies have identified a spectrum of circRNAs that are differentially expressed in CVDs, while other studies further manipulated specific circRNA expression and showed an ameliorated pathogenic state such as ischemic injury, hypertrophy, and cardiac fibrosis. Studies and applications of circRNAs are being rapidly developed. We expect to see clinical use of circRNAs as biomarkers and targets for disease treatment in the near future.

Epigenetic and Transcriptional Networks Underlying Atrial Fibrillation

Genome-wide association studies have uncovered over a 100 genetic loci associated with atrial fibrillation (AF), the most common arrhythmia. Many of the top AF-associated loci harbor key cardiac transcription factors, including PITX2, TBX5, PRRX1, and ZFHX3. Moreover, the vast majority of the AF-associated variants lie within noncoding regions of the genome where causal variants affect gene expression by altering the activity of transcription factors and the epigenetic state of chromatin. In this review, we discuss a transcriptional regulatory network model for AF defined by effector genes in Genome-wide association studies loci. We describe the current state of the field regarding the identification and function of AF-relevant gene regulatory networks, including variant regulatory elements, dose-sensitive transcription factor functionality, target genes, and epigenetic states. We illustrate how altered transcriptional networks may impact cardiomyocyte function and ionic currents that impact AF risk. Last, we identify the need for improved tools to identify and functionally test transcriptional components to define the links between genetic variation, epigenetic gene regulation, and atrial function.

Circular RNA in Diseased Heart

Heart disease remains the leading cause of death globally and leads to tremendous socio-economic burden. Despite advances in the field of cardiovascular research, novel theranostics are still in urgent need. Remarkable progress has been made in understanding aberrant protein interactions and signaling pathways in the diseased heart, but less is known regarding epigenetic regulation. Non-coding RNAs have emerged as important regulators of cardiac function and have been implicated in disease. While significant progress has been made in understanding the roles of microRNAs and long non-coding RNAs, the functional roles of circular RNAs are less explored. Recent studies have provided ample evidence supporting their roles in multiple physiological processes including regulating the function of the heart. Compared with other RNAs, circular RNAs exhibit higher stability and more versatile functional modes: including sponging microRNAs, scaffolding proteins, regulating transcription, and even encoding small regulatory peptides. These characteristics make circular RNAs promising candidates for the development of diagnostic tools and therapies for heart disease. In this review, we will discuss the biogenesis of circular RNAs and provide an update of their functional implications in heart disease, with an emphasis on heart failure and arrhythmias.

Preclinical and Clinical Development of Noncoding RNA Therapeutics for Cardiovascular Disease

RNA modulation has become a promising therapeutic approach for the treatment of several types of disease. The emerging field of noncoding RNA-based therapies has now come to the attention of cardiovascular research, in which it could provide valuable advancements in comparison to current pharmacotherapy such as small molecule drugs or antibodies. In this review, we focus on noncoding RNA-based studies conducted mainly in large-animal models, including pigs, rabbits, dogs, and nonhuman primates. The obstacles and promises of targeting long noncoding RNAs and circRNAs as therapeutic modalities in humans are specifically discussed. We also describe novel ex vivo methods based on human cells and tissues, such as engineered heart tissues and living myocardial slices that could help bridging the gap between in vivo models and clinical applications in the future. Finally, we summarize antisense oligonucleotide drugs that have already been approved by the Food and Drug Administration for targeting mRNAs and discuss the progress of noncoding RNA-based drugs in clinical trials. Additional factors, such as drug chemistry, drug formulations, different routes of administration, and the advantages of RNA-based drugs, are also included in the present review. Recently, first therapeutic miRNA-based inhibitory strategies have been tested in heart failure patients as well as healthy volunteers to study effects on wound healing (NCT04045405; NCT03603431). In summary, a combination of novel therapeutic RNA targets, large-animal models, ex vivo studies with human cells/tissues, and new delivery techniques will likely lead to significant progress in the development of noncoding RNA-based next-generation therapeutics for cardiovascular disease.

Circular RNA hsa_circ_0004277 contributes to malignant phenotype of colorectal cancer by sponging miR-512-5p to upregulate the expression of PTMA

In recent years, extensive reports have been published concerning the molecular mechanism underlying the occurrence and progression of colorectal cancer. Circular RNAs (circRNAs) have been identified as important modulators in the biological processes of colorectal cancer. Microarray analysis unveiled that differential circ-0004277 expression was identified in tissue samples of colorectal cancer. High circ-0004277 expression was then verified in tissue samples and cell lines of colorectal cancer via qRT-PCR. Kaplan-Meier analysis was used for identifying the association between circ-0004277 expression and the overall survival rate of colorectal cancer patients. A relationship existed between higher circ-0004277 expression and decreased overall survival rate of colorectal cancer patients. From a functional perspective, circ-0004277 knockdown accelerated cell apoptosis and restrained cell proliferation of colorectal cancer. From mechanistic perspective, circ-0004277 upregulated PTMA by sponging miR-512-5p. Rescue assay was used for verifying the roles of the circ-0004277-miR-512-5p-PTMA axis. Both miR-512-5p and PTMA participated in circ-0004277-mediated colorectal cancer cell proliferation based on experiments. In summary, our study showed that circ-0004277 promoted the proliferation of colorectal cancer cells as a miR-512-5p sponge to upregulate the PTMA expression.

Genome-wide profiling reveals atrial fibrillation-related circular RNAs in atrial appendages

Atrial fibrillation (AF) is an abnormal heart rhythm characterized by rapid and irregular beating of the atria. The non-coding RNAs (ncRNAs) have attracted much attention of AF researchers, as they play a critical role in the transcriptional and post-transcriptional regulation, which could greatly benefit the interpretation of the pathogenesis of AF. However, circRNAs, as a special member of the ncRNAs, and their role in the pathogenesis of AF is less understood. In the present study, we detected a total of 14,215 circRNAs in AF patients and healthy controls. Differential expression analysis of these circRNAs revealed 20 upregulated and 3 downregulated circRNAs, which were differentially expressed in both left and right atrial appendages. The association analysis of the AF-related circRNAs and their parental genes revealed that hsa_circ_0003965 had significantly negative correlation with its parental gene TMEM245 (PCC = -0.51), suggesting that the dysregulation of hsa_circ_0003965 was not regulated by the transcription of its parental gene, but could be associated with glucagon signaling pathway. The competing endogenous RNA (ceRNA) network analysis revealed two upregulated genes, IFNG and GDF7, and one downregulated gene, BMP7, all of which were involved in TGF-beta signaling pathway, which further suggested that these circRNAs, namely hsa_circ_0000075 and hsa_circ_0082096, participated in the AF pathogenesis via TGF-beta signaling pathway. Consistently, TGF-beta signaling pathway was a well-recognized player for its association with atrial fibrosis in AF. In summary, we aimed to discover and provide key circRNAs involved in AF for AF-related researchers, which had the potential to greatly improve our understanding of the underlying mechanism behind circRNAs and AF.

CircRNA expression profile and functional analysis in testicular tissue of patients with non-obstructive azoospermia

BACKGROUND

Non-obstructive azoospermia (NOA) is a multifactorial disorder whose molecular basis remains largely unknown. Circular RNAs (CircRNAs), a novel class of endogenous RNAs, have been recognized to play important roles in many biological processes. However, little is known about the expression patterns and functions of circRNAs in human testes involved in NOA.

METHODS

In this study, the testicular circRNA expression profile were explored in NOA patients and the controls by high-throughput circRNA microarray. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to confirm the microarray data. Bioinformatics analyses including the circRNA/miRNA/mRNA interaction network, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were used to predict the functions of differentially expressed circRNAs.

RESULTS

A total of 368 differentially down-regulated and 526 up-regulated circRNAs were detected in NOA patients. These findings have been verified by qRT-PCR on 6 selected circRNAs. Among these differentially expressed circRNAs, the hsa_circRNA_0023313 was obviously up-regulated in testicular tissue of NOA patients. The most likely potential target miRNA for hsa_circRNA_0023313 include hsa-miR-520d-3p, hsa-miR-373-3p, hsa-miR-372-3p, hsa-miR-302c-3p and hsa-miR-130b-5p. Function analysis indicated that hsa_circRNA_0023313 was ubiquitin-protein transferase activity and chromatin binding. KEGG analysis revealed that the top five pathways related to hsa_circRNA_0023313 were endocytosis, meiosis, FoxO signaling pathway, ubiquitin mediated proteolysis and AMPK signaling pathway.

CONCLUSIONS

This is the first report that the testicular circRNA expression profile is altered in NOA patients indicating circRNAs might play important roles in regulating spermatogenesis and be potential biomarkers for the diagnosis and treatment of NOA.

Identification of Long Non-Coding RNA and Circular RNA Expression Profiles in Atrial Fibrillation

BACKGROUND

Long non-coding RNA (lncRNA) and circular RNA (circRNA) have both been found to play important roles in cardiovascular diseases, including myocardial infarction, heart failure, and atherosclerosis. However, the role of lncRNA and circRNA in atrial fibrillation (AF) has rarely been investigated. This study aimed to identify lncRNA and circRNA expression profiles in AF patients.

METHODS

Atrial tissues from seven patients with AF and seven matched controls were collected. The lncRNA and circRNA expression profiles of atrial tissues were identified using Hiseq/Proton RNA sequencing. Validation was performed by reverse transcription quantitative real-time PCR (qRT-PCR) on 35 pairs of AF patients and controls. Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed. A competing endogenous RNA (ceRNA) network was constructed.

RESULTS

A total of 557 lncRNAs and 280 circRNAs were significantly differentially expressed with fold change >1.5 (p<0.05). An lncRNA Voltage Dependent Anion Channel 2 Pseudogene 2 (VDAC2P2) and two circRNAs chr13_41887361_41865736_-21625 and chr13_100368574_100301460_-67114 were validated, using qRT-PCR, to have significantly different expression levels. GO and KEGG pathway analysis showed that some pathways such as ribosome and chromatin modification, Rap1 signalling and cardiac muscle contraction were involved in the pathogenesis of AF. Competing endogenous RNAs were predicted based on constructional network analysis. The LncRNA-miRNA-mRNA and circRNA-miRNA-mRNA networks were constructed by co-expressing lncRNA/circRNA and mRNAs, which were competitively combined with miRNAs.

CONCLUSION

This study characterised lncRNA and circRNA expression and their interaction with mRNA and miRNA in AF.

Revealing new landscape of cardiovascular disease through circular RNA-miRNA-mRNA axis

Non-coding RNA (ncRNA) is a kind of RNA, produced by genomic transcription and does not encode protein, but can regulate the function of genes, thus widely regulating pathological and physiological processes. The dynamic balance of the reticular structure between them is needed to regulate the homeostasis, the abnormal regulation of one of them may lead to the occurrence of the disease. CircRNA is mainly involved in the evolution of CVD through sponge-like regulation of miRNAs, subsequently regulating miRNAs and their targets, mRNA functions. The role of circRNA-miRNA-mRNA axis in pathogenesis of cardiovascular diseases has been recently reported and highlighted. In this review, the emerging roles of circRNA-miRNA-mRNA axis in cardiovascular pathophysiology and regulation were discussed, with a novel focus on cardioprotective network activities of the circRNA.