Microarray expression profile of circular RNAs in chronic thromboembolic pulmonary hypertension

Circular RNAs in human diseases

Circular RNAs (circRNAs) are a unique class of RNA molecules formed through back-splicing rather than linear splicing. As an emerging field in molecular biology, circRNAs have garnered significant attention due to their distinct structure and potential functional implications. A comprehensive understanding of circRNAs' functions and potential clinical applications remains elusive despite accumulating evidence of their involvement in disease pathogenesis. Recent research highlights their significant roles in various human diseases, but comprehensive reviews on their functions and applications remain scarce. This review provides an in-depth examination of circRNAs, focusing first on their involvement in non-neoplastic diseases such as respiratory, endocrine, metabolic, musculoskeletal, cardiovascular, and renal disorders. We then explore their roles in tumors, with particular emphasis on exosomal circular RNAs, which are crucial for cancer initiation, progression, and resistance to treatment. By detailing their biogenesis, functions, and impact on disease mechanisms, this review underscores the potential of circRNAs as diagnostic biomarkers and therapeutic targets. The review not only enhances our understanding of circRNAs' roles in specific diseases and tumor types but also highlights their potential as novel diagnostic and therapeutic tools, thereby paving the way for future clinical investigations and potential therapeutic interventions.

Levosimendan mediates the BMP/Smad axis through upregulation of circUSP34-targeted miR-1298 to alleviate pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a long-term disease that impacts approximately 1% of the world's population. Currently, levosimendan (Lev) is proposed for PH treatment. However, the mechanism of Lev in the treatment of PH is unknown.

METHODS

We used hypoxia-induced pulmonary artery smooth muscle cells (PASMCs) to establish a PH cell model. A number of cell biology methods were performed to assay alterations in cell proliferation, migration and apoptosis after Lev treatment. qRT-PCR and WB were performed to test the levels of circUSP34 and miR-1298, and BMP/Smad protein respectively. In addition, the regulatory relationship between circUSP34 or BMPR2 with miR-1298 was verified through the use of double luciferase as well as RIP assay. In addition, we explored the regulatory effect of Lev on the circUSP34/miR-1298/BMP/Smad axis using a rat PH model.

RESULTS

Our results demonstrate that Lev inhibited PASMCs cell proliferation, migration and promoted apoptosis exposed to hypoxia. In hypoxia-treated PASMCs, circUSP34 expression got downregulated while miR-1298 upregulated, whereas the addition with Lev resulted in upregulation of circUSP34 expression and downregulation of miR-1298 expression, indicating that circUSP34 can target and regulate miR-1298. In addition, miR-1298 targets and regulates the expression of BMPR2. In a rat PH model induced by hypoxia combined with SU5416, Lev upregulated circUSP34 targeting miR-1298-mediated BMP/Smad axis to alleviate the PH phenotype.

CONCLUSION

We have shown that Lev can be used as a therapeutic drug for PH patients, which works through the circUSP34/miR-1298/BMP/Smad axis to alleviate PH symptoms.

Circular RNA Expression of Peripheral Blood Mononuclear Cells Associated with Risk of Acute Exacerbation in Smoking Chronic Obstructive Pulmonary Disease

Purpose

Circular RNAs (circRNAs) are newly identified endogenous non-coding RNAs that function as crucial gene modulators in the development of several diseases. By assessing the expression levels of circRNAs in peripheral blood mononuclear cells (PBMCs) from patients with chronic obstructive pulmonary disease (COPD), this study attempted to find new biomarkers for COPD screening.

Patients and Methods

We confirmed altered circRNA expression in PBMCs of COPD (n=41) vs controls (n=29). Further analysis focused on the highest and lowest circRNA expression levels. The T-test is used to assess the statistical variances in circRNAs among COPD patients in the smoking and non-smoking cohorts. Additionally, among smokers, the Spearman correlation test assesses the association between circRNAs and clinical indicators.

Results

Two circRNAs, hsa_circ_0042590 and hsa_circ_0049875, that were highly upregulated and downregulated in PBMCs from COPD patients were identified and verified. Smokers with COPD had lower hsa_circ_0042590 and higher hsa_circ_0049875, in comparison to non-smokers. There was a significant correlation (r=0.52, P<0.01) between the number of acute exacerbations (AEs) that smokers with COPD experienced in the previous year and the following year (r=0.67, P<0.001). Moreover, hsa_circ_0049875 was connected to the quantity of AEs in the year prior (r=0.68, P<0.0001) as well as the year after (r=0.72, P<0.0001). AUC: 0.79, 95% CI: 0.1210-0.3209, P<0.0001) for hsa_circ_0049875 showed a strong diagnostic value for COPD, according to ROC curve analysis. Hsa_circ_0042590 showed a close second with an AUC of 0.83 and 95% CI: -0.1972--0.0739 (P <0.0001).

Conclusion

This research identified a strong correlation between smoking and hsa_circ_0049875 and hsa_circ_0042590 in COPD PBMCs. The number of AEs in the preceding and succeeding years was substantially linked with the existence of hsa_circ_0042590 and hsa_circ_0049875 in COPD patients who smoke. Additionally, according to our research, hsa_circ_0049875 and hsa_circ_0042590 may be valuable biomarkers for COPD diagnosis.

circNFXL1 Modulates the Kv2.1 Channel Function in Hypoxic Human Pulmonary Artery Smooth Muscle Cells via Sponging miR-29b-2-5p as a Competitive Endogenous RNA

ABSTRACT

Pulmonary arterial hypertension is characterized by abnormal pulmonary vasoconstriction and vascular remodeling caused by the dysregulation of K + channels in PA smooth muscle cells (PASMCs). However, how the K + channels are dysregulated is still unclear. Circular RNAs (circRNAs) are noncoding RNAs with a closed-loop structure capable of sponging microRNAs (miRs), thus regulating gene expression at the post-transcriptional level. Our previous studies have demonstrated the importance of one novel circRNA (hsa_circNFXL1_009, circNFXL1) in pulmonary arterial hypertension patients, playing as a critical regulator for K + channel activation in hypoxic human PASMCs (hPASMCs). Here, we explore the mechanisms underlying circNFXL1-regulated K + channel expression and functions in hypoxic hPASMCs. In cultured hPASMCs, the reduction of Kv current induced by hypoxia was significantly recovered by delivering exogenous circNFXL1. Moreover, luciferase, quantitative reverse transcription-quantitative polymerase chain reaction, western blot, and mutagenesis studies confirmed that circNFXL1 reversed hypoxia-induced inhibitory effects on the Kv2.1 channel via sponging hsa-miR-29b-2-5p (miR-29b-2). Furthermore, we found that circNFXL1 reversed the miR-29b-induced Kv2.1 channel dysfunction at the whole-cell and single-channel level in HEK cells using a patch-clamp. Finally, calcium imaging revealed that hypoxia also triggered a substantial rise in the cytosolic calcium concentration ([Ca2 + ]cyt) in hPASMCs, and this hypoxia-induced elevation of [Ca2 + ]cyt was reduced by circNFXL1 through miR-29b-2. These data suggested that circNFXL1-mediated regulation of the Kv2.1 channel activation and the related intracellular calcium concentration may contribute to the effects of hypoxic pulmonary vasoconstriction.

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.

The role of circular RNAs in pulmonary hypertension

Circular RNAs (circRNAs) are endogenous, covalently circularised, non-protein-coding RNAs generated from back-splicing. Most circRNAs are very stable, highly conserved, and expressed in a tissue-, cell- and developmental stage-specific manner. circRNAs play a significant role in various biological processes, such as regulation of gene expression and protein translation via sponging of microRNAs and binding with RNA-binding proteins. circRNAs have become a topic of great interest in research due to their close link with the development of various diseases. Their high stability, conservation and abundance in body fluids make them promising biomarkers for many diseases. A growing body of evidence suggests that aberrant expression of circRNAs and their targets plays a crucial role in pulmonary vascular remodelling and pulmonary arterial hypertension (group 1) as well as other forms (groups 3 and 4) of pulmonary hypertension (PH). Here we discuss the roles and molecular mechanisms of circRNAs in the pathogenesis of pulmonary vascular remodelling and PH. We also highlight the therapeutic and biomarker potential of circRNAs in PH.

Circular RNAs Regulate Vascular Remodelling in Pulmonary Hypertension

Circular RNAs (circRNAs) are a newly identified type of noncoding RNA molecule with a unique closed-loop structure. circRNAs are widely expressed in different tissues and developmental stages of many species, participating in many important pathophysiological processes and playing an important role in the occurrence and development of diseases. This article reviews the discovery, characteristics, formation, and biological function of circRNAs. The relationship between circRNAs and vascular remodelling, as well as the current status of research and potential application value in pulmonary hypertension (PH), is discussed to promote a better understanding of the role of circRNAs in PH. circRNAs are closely related to the remodelling of vascular endothelial cells and vascular smooth muscle cells. circRNAs have potential application prospects for in-depth research on the possible pathogenesis and mechanism of PH. Future research on the role of circRNAs in the pathogenesis and mechanism of PH will provide new insights and promote screening, diagnosis, prevention, and treatment of this disease.

New insights on circular RNAs and their potential applications as biomarkers, therapeutic agents, and preventive vaccines in viral infections: with a glance at SARS-CoV-2

The occurrence of viral infections and approaches to handling them are very challenging and require prompt diagnosis and timely treatment. Recently, genomic medicine approaches have come up with the discovery of the competing endogenous RNA (ceRNA) network, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) on the basis of gene silencing. CircRNAs, as a group of non-encoded RNAs, make a loop-like structure by back-splicing through 3' and 5' ends. They are stable, abundant, specific, and highly conserved and can be quickly generated at large scales in vitro. CircRNAs have the potential to contribute in several cellular processes in a way that some serve as microRNA sponges, cellular transporters, protein-binding RNAs, transcriptional regulators, and immune system modulators. CircRNAs can even play an important role in modulating antiviral immune responses. In the present review, circRNAs' biogenesis, function, and biomarker and therapeutic potential as well as their prospective applications as vaccines against viral infections such as SARS-CoV-2 are explained. By considering their unique properties, their potential to be used as novel vaccines, biomarkers, and a therapeutic approach appears possible.

The Landscape of Noncoding RNA in Pulmonary Hypertension

The transcriptome of pulmonary hypertension (PH) is complex and highly genetically heterogeneous, with noncoding RNA transcripts playing crucial roles. The majority of RNAs in the noncoding transcriptome are long noncoding RNAs (lncRNAs) with less circular RNAs (circRNAs), which are two characteristics gaining increasing attention in the forefront of RNA research field. These noncoding transcripts (especially lncRNAs and circRNAs) exert important regulatory functions in PH and emerge as potential disease biomarkers and therapeutic targets. Recent technological advancements have established great momentum for discovery and functional characterization of ncRNAs, which include broad transcriptome sequencing such as bulk RNA-sequence, single-cell and spatial transcriptomics, and RNA-protein/RNA interactions. In this review, we summarize the current research on the classification, biogenesis, and the biological functions and molecular mechanisms of these noncoding RNAs (ncRNAs) involved in the pulmonary vascular remodeling in PH. Furthermore, we highlight the utility and challenges of using these ncRNAs as biomarkers and therapeutics in PH.

Bioinformatic analysis of dysregulated circular RNAs in pediatric pulmonary hypertension linked congenital heart disease

BACKGROUND

Circular RNAs (circRNAs) may play important roles in the progression of pulmonary arterial hypertension. However, the potential roles they play in childhood pulmonary arterial hypertension associated congenital heart disease (CHD) progression remains unclear.

METHODS

Thirteen human plasma samples including eight from pulmonary arterial hypertension secondary to CHD patients and five from a control group were analyzed using the Arraystar Human circRNA array. The relative expression levels of five differentially expressed circRNAs in pulmonary arterial hypertension were detected using real-time polymerase chain reaction (PCR) analysis. In parallel, these levels were also taken on control samples from 32 CHD patients. We used miRanda and TargetScan software packages to predict potential microRNA (miRNA)targets, which were then combined into a circRNA-miRNA-messenger RNA (mRNA) network.

RESULTS

Twenty-seven circRNAs (three upregulated and 24 downregulated) were differentially expressed between the pulmonary arterial hypertension and control groups. Compared to control group levels, circ_003416 expression in the pulmonary arterial hypertension group was significantly downregulated, while circ_005372 expression, in contrast, was significantly upregulated. The differential expression of these circRNAs was mainly linked to variation in levels of oxidative phosphorylation and tight junction signaling.

CONCLUSIONS

We identified one overexpressed and one underexpressed circRNA in plasma samples from children with CHD associated pulmonary arterial hypertension. Bioinformatic analysis indicated these dysregulated circRNAs might be associated with the occurrence and regulation of pulmonary arterial hypertension.

Circular RNAs in pulmonary hypertension: Emerging biological concepts and potential mechanism

Circular RNAs (circRNAs) are endogenous RNAs with a covalently closed single-stranded transcript. They are a novel class of genomic regulators that are linked to many important development and disease processes and are being pursued as clinical and therapeutic targets. Using the most powerful RNA sequencing and bioinformatics techniques, a large number of circRNAs have been identified and further functional studies have been performed. It is known that circRNAs act as potential biomarkers, sponges for microRNAs (miRNAs) and RNA-binding proteins (RBPs), and regulators of mRNA transcription. They also participate in the translation of peptides or proteins. Many types of circRNAs are dysregulated in plasma or lung tissues, and they may be involved in regulating the proliferation and apoptosis of pulmonary artery endothelial cells (PAECs) and pulmonary artery smooth muscle cells (PASMCs), leading to pulmonary vascular remodeling in pulmonary hypertension (PH). One possible mechanism is that circRNAs can regulate the function of PAECs and PASMCs by acting as miRNA sponge. However, other potential mechanisms of action of circRNAs are still being actively explored in PH. This paper presents a systematic review of the biogenesis, biological characterization, relevant underlying functions, and future perspectives for studies of circRNAs in the pathogenesis of PH.

Non-Coding RNA Networks in Pulmonary Hypertension

Non-coding RNAs (ncRNAs) are involved in various cellular processes. There are several ncRNA classes, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). The detailed roles of these molecules in pulmonary hypertension (PH) remain unclear. We systematically collected and reviewed reports describing the functions of ncRNAs (miRNAs, lncRNAs, and circRNAs) in PH through database retrieval and manual literature reading. The characteristics of identified articles, especially the experimental methods, were carefully reviewed. Furthermore, regulatory networks were constructed using ncRNAs and their interacting RNAs or genes. These data were extracted from studies on pulmonary arterial smooth muscle cells, pulmonary artery endothelial cells, and pulmonary artery fibroblasts. We included 14 lncRNAs, 1 circRNA, 74 miRNAs, and 110 mRNAs in the constructed networks. Using these networks, herein, we describe the current knowledge on the role of ncRNAs in PH. Moreover, these networks actively provide an improved understanding of the roles of ncRNAs in PH. The results of this study are crucial for the clinical application of ncRNAs.

circ‑Grm1 promotes pulmonary artery smooth muscle cell proliferation and migration via suppression of GRM1 expression by FUS

Pulmonary arterial hypertension is a progressive and fatal disease. Recent studies suggest that circular RNA (circRNAs/circs) can regulate various biological processes, including cell proliferation. Therefore, it is possible that circRNA may have important roles in pulmonary artery smooth muscle cell proliferation in hypoxic pulmonary hypertension (HPH). The aim of the present study was to determine the role and mechanism of circRNA‑glutamate metabotropic receptor 1 (circ‑Grm1; mmu_circ_0001907) in pulmonary artery smooth muscle cell (PASMC) proliferation and migration in HPH. High‑throughput transcriptome sequencing was used to screen circRNAs and targeted genes involved in HPH. Cell Counting Kit‑8 (CCK‑8), 5‑ethynyl‑2‑deoxyuridine and wound healing assays were employed to assess cell viability and migration. Reverse transcription‑quantitative PCR and western blotting were used to detect target gene expression in different groups. Bioinformatical approaches were used to predict the interaction probabilities of circ‑Grm1 and Grm1 with FUS RNA binding protein (FUS). The interactions of circ‑Grm1, Grm1 and FUS were evaluated using RNA silencing and RNA immunoprecipitation assays. The results demonstrated that circ‑Grm1 was upregulated in hypoxic PASMCs. Further experiments revealed that the knockdown of circ‑Grm1 could suppress the proliferation and migration of hypoxic PASMCs. Transcriptome sequencing revealed that Grm1 could be the target gene of circ‑Grm1. It was found that circ‑Grm1 could competitively bind to FUS and consequently downregulate Grm1. Moreover, Grm1 could inhibit the function of circ‑Grm1 by promoting the proliferative and migratory abilities of hypoxic PASMCs. The results also demonstrated that circ‑Grm1 influenced the biological functions of PASMCs via the Rap1/ERK pathway by regulating Grm1. Overall, the current results suggested that circ‑Grm1 was associated with HPH and promoted the proliferation and migration of PASMCs via suppression of Grm1 expression through FUS.

Hsa_circ_0002062 Promotes the Proliferation of Pulmonary Artery Smooth Muscle Cells by Regulating the Hsa-miR-942-5p/CDK6 Signaling Pathway

Currently, new strategies for the diagnosis and treatment of hypoxia-induced pulmonary hypertension (HPH) are urgently required. The unique features of circRNAs have unveiled a novel perspective for understanding the biological mechanisms underlying HPH and the possibility for innovative strategies for treatment of HPH. CircRNAs function as competing endogenous RNAs (CeRNA) to sequester miRNAs and regulate the expression of target genes. This study aimed to explore the roles of hsa_circ_0002062 on the biological behaviors of pulmonary artery smooth muscle cells (PASMCs) in hypoxic conditions. A number of in vitro assays, such as RNA-binding protein immunoprecipitation (RIP), RNA pull-down, and dual-luciferase assays were performed to evaluate the interrelationship between hsa_circ_0002062, hsa-miR-942-5P, and CDK6. The potential physiological functions of hsa_circ_0002062, hsa-miR-942-5P, and CDK6 in hypoxic PASMCs were investigated through expression modulation. Our experiments demonstrated that hsa_circ_0002062 functions as a ceRNA, acts as a sponge for hsa-miR-942-5P, and consequently activates CDK6, which further promotes pulmonary vascular remodeling. Therefore, we speculate that hsa_circ_0002062 could serve as a candidate diagnostic biomarker and potential therapeutic target for HPH.

Research progress on biomarkers of pulmonary embolism

OBJECTIVES

To present a review on the traditional and new biomarkers of pulmonary embolism (PE).

DATA SOURCE

A systematic search has been carried out using keywords as PE, biomarker, diagnosis and risk stratification.

RESULTS

The results of this work have been structured into three parts: first, conventional biomarkers for vascular, cardiac and inflammation, including static markers and dynamic markers for measuring the time course; next, a review of new biomarkers in recent years, such as RNAs and markers obtained through proteomics and mass spectrometry; finally, use of new detection methods to directly detect the activity of existing markers, such as the determination of coagulation factor II and plasmin activities based on the proteolytic activation of an engineered zymogen.

CONCLUSIONS

This work summarized the characteristics of current traditional biomarkers for clinical diagnosis and risk stratification of PE, as well as a series of newly discovered biomarkers obtained through various clinical experimental methods.

Microarray Expression Profile and Analysis of Circular RNA Regulatory Network in Pulmonary Thromboembolism

Background

Pulmonary thromboembolism (PTE) is a common disease which may be a serious condition and has high mortality. Recently, it has been shown that circRNAs play an important role in the development of various diseases, including thromboembolic disease. However, circRNAs expression profiling is not clear in PTE, this study aims to identify the circRNAs expressed in PTE and to elucidate their possible role in pathophysiology of PTE.

Methods

A total of 5 patients with CTPA-confirmed PTE and 5 healthy controls were recruited for the present study. The circRNAs expression profile was analyzed by microarray.

Results

In total, 256 differentially expressed circRNAs (up 142, down114) and 1162 mRNA (up 446, down 716) were summarized by analyzing the circRNAs microarray data. The top 3 up-regulated and 3 down-regulated circRNAs were validated by Real-Time Polymerase Chain Reaction (qRT-PCR). Two differentially expressed circRNAs (hsa_circ_0000891, hsa_circ_0043506) were selected for further analysis. Finally, we construct a circRNA-miRNA-mRNA ceRNA network with a bioinformatic prediction tool. Pathway analysis shows that the enriched mRNAs targets take part in Protein processing in endoplasmic reticulum, Systemic lupus erythematosus, Endocytosis, Spliceosome, HTLV-I infection and Ubiquitin mediated proteolysis.

Conclusion

Our findings indicated that aberrantly expressed circRNAs (hsa_circ_0000891, hsa_circ_0043506) may be involved in the development of PTE.

Up-regulation of circRNA_0068481 promotes right ventricular hypertrophy in PAH patients via regulating miR-646/miR-570/miR-885

CircRNA‐0068481 and several miRNAs are important in the pathogenesis of right ventricular hypertrophy (VH), while the inhibition of eye absent transcriptional coactivator and phosphatase 3 (EYA3) was proved to reverse vascular remodelling in rats. In this study, we tried to study the diagnostic value and mechanistic role of circRNA_0068481 in the diagnosis of RVH in PAH patients. qPCR was done to measure circRNA‐0068481, miR‐646, miR‐750, miR‐885 and EYA3 mRNA expression. Luciferase assay was done to explore the regulatory relationship between circRNA‐0068481/EYA3 and the miRNAs. Western blot was done to measure EYA3 expression in AC16 cells. The expression of circRNA‐0068481, miR‐646 and miR‐570 showed a considerable capability to diagnose RVH in PAH patients. The luciferase activity of circRNA‐0068481 was remarkably suppressed by miR‐646, miR‐570 or miR‐885. The luciferase signal of EYA3 was also inhibited by miR‐646, miR‐570 and miR‐885. Up‐regulation of circRNA‐0068481 expression in AC16 significantly decreased miR‐646, miR‐570 and miR‐885 expression, and up‐regulated EYA3 expression, whereas circRNA‐0068481 down‐regulation significantly increased miR‐646, miR‐570 and miR‐885 expression, and repressed EYA3 expression. CircRNA_0068481 sponged several miRNAs including miR‐646, miR‐570 and miR‐885. These miRNAs were all found to target the expression of EYA3 mRNA, which is involved in the onset of right ventricular hypertrophy. Therefore, it can be concluded that the up‐regulation of circRNA_0068481 can predict the diagnosis of right ventricular hypertrophy in pulmonary arterial hypertension patients.

MicroRNAs and Long Non-Coding RNAs as Potential Candidates to Target Specific Motifs of SARS-CoV-2

The respiratory system is one of the most affected targets of SARS-CoV-2. Various therapies have been utilized to counter viral-induced inflammatory complications, with diverse success rates. Pending the distribution of an effective vaccine to the whole population and the achievement of "herd immunity", the discovery of novel specific therapies is to be considered a very important objective. Here, we report a computational study demonstrating the existence of target motifs in the SARS-CoV-2 genome suitable for specific binding with endogenous human micro and long non-coding RNAs (miRNAs and lncRNAs, respectively), which can, therefore, be considered a conceptual background for the development of miRNA-based drugs against COVID-19. The SARS-CoV-2 genome contains three motifs in the 5'UTR leader sequence recognized by selective nucleotides within the seed sequence of specific human miRNAs. The seed of 57 microRNAs contained a "GGG" motif that promoted leader sequence-recognition, primarily through offset-6mer sites able to promote microRNAs noncanonical binding to viral RNA. Similarly, lncRNA H19 binds to the 5'UTR of the viral genome and, more specifically, to the transcript of the viral gene Spike, which has a pivotal role in viral infection. Notably, some of the non-coding RNAs identified in our study as candidates for inhibiting SARS-CoV-2 gene expression have already been proposed against diverse viral infections, pulmonary arterial hypertension, and related diseases.

Pseudogenes in Cardiovascular Disease

Cardiovascular disease is the main disease that affects human life span. In recent years, the disease has been increasingly addressed at the molecular levels, for example, pseudogenes are now known to be involved in the pathogenesis and development of cardiovascular diseases. Pseudogenes are non-coding homologs of protein-coding genes and were once called “junk gene.” Since they are highly homologous to their functional parental genes, it is somewhat difficult to distinguish them. With the development of sequencing technology and bioinformatics, pseudogenes have become readily identifiable. Recent studies indicate that pseudogenes are closely related to cardiovascular diseases. This review provides an overview of pseudogenes and their roles in the pathogenesis of cardiovascular diseases. This new knowledge adds to our understanding of cardiovascular disease at the molecular level and will help develop new biomarkers and therapeutic approaches designed to prevent and treat the disease.

Integration of SNP Disease Association, eQTL, and Enrichment Analyses to Identify Risk SNPs and Susceptibility Genes in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a complex disease caused by the disturbance of genetic and environmental factors. Single-nucleotide polymorphisms (SNPs) play a vital role in the genetic dissection of complex diseases. In-depth analysis of SNP-related information could recognize disease-associated biomarkers and further uncover the genetic mechanism of complex diseases. Risk-related variants might act on the disease by affecting gene expression and gene function. Through integrating SNP disease association study and expression quantitative trait loci (eQTL) analysis, as well as functional enrichment of containing known causal genes, four risk SNPs and four corresponding susceptibility genes were identified utilizing next-generation sequencing (NGS) data of COPD. Of the four risk SNPs, one could be found in the SNPedia database that stored disease-related SNPs and has been linked to a disease in the literature. Four genes showed significant differences from the perspective of normal/disease or variant/nonvariant samples, as well as the high performance of sample classification. It is speculated that the four susceptibility genes could be used as biomarkers of COPD. Furthermore, three of our susceptibility genes have been confirmed in the literature to be associated with COPD. Among them, two genes had an impact on the significance of expression correlation of known causal genes they interact with, respectively. Overall, this research may present novel insights into the diagnosis and pathogenesis of COPD and susceptibility gene identification of other complex diseases.

Circulating Exosomal miRNAs as Novel Biomarkers for Stable Coronary Artery Disease

Exosomal miRNAs are currently being explored as a novel class of biomarkers in cardiovascular diseases. However, few reports have focused on the value of circulating exosomal miRNAs as biomarkers for stable coronary artery disease (SCAD). Here, we aimed to investigate whether miRNAs involved in cardiovascular diseases in circulating exosomes could serve as novel diagnostic biomarkers for SCAD. Firstly, the serum exosomes were isolated and purified by the ExoQuick reagent and identified by transmission electron microscopy, western blot, and nanoparticle tracking analysis. Then, the purified exosomes were quantified by measuring the exosome protein concentration and calculating the total protein amount. Next, eight miRNAs involved in cardiovascular diseases, miR-192-5p, miR-148b-3p, miR-125a-3p, miR-942-5p, miR-149-5p, miR-32-5p, miR-144-3p, and miR-142-5p, were quantified in circulating exosomes from the control group (n = 20) and the SCAD group (n = 20) by quantitative real-time polymerase chain reaction (qPCR). Finally, the gene targets of the differentially expressed miRNAs were predicted, and the functions and signaling pathways of these targets were analyzed using an online database. The isolated exosomes had a bilayer membrane with a diameter of about 100 nm and expressed exosomal markers including CD63, Tsg101, and Flotillin but negatively expressed Calnexin. Both the exosome protein concentration and total protein amount exhibited no significant differences between the two groups. The qPCR assay demonstrated that among the eight miRNAs, the expression levels of miR-942-5p, miR-149-5p, and miR-32-5p in the serum exosomes from the SCAD group were significantly higher than that from the control group. And the three miRNAs for SCAD diagnosis exhibited AUC values of 0.693, 0.702, and 0.691, respectively. GO categories and signaling pathways analysis showed that some of the predictive targets of these miRNAs were involved in the pathophysiology processes of SCAD. In conclusion, our findings suggest that serum exosomal miR-942-5p, miR-149-5p, and miR-32-5p may serve as potential diagnostic biomarkers for SCAD.

Possible immune regulation mechanisms for the progression of chronic thromboembolic pulmonary hypertension

PURPOSE

This study aimed to screen key genes significantly associated with chronic thromboembolic pulmonary hypertension (CTEPH) and predicted suitable drugs for the treatment of CTEPH from the perspective of immune cells.

METHODS

The dataset GSE130391 was used for this analysis. Differentially expressed genes (DEGs) between the CTEPH and control groups were screened. Abundance of infiltrating immune cells was analyzed and immune-related DEGs were identified. Next, the circular RNA (circRNA)-micro RNA (miRNA)-mRNA network was constructed, followed by functional enrichment analysis. Then, the protein-protein interaction (PPI) network was constructed and drug-gene interactions were predicted. Finally, miRNA and circRNA prediction results were verified by our previously published studies.

RESULTS

Five key immune cell-related DEGs [CD83 molecule (CD83), complement c5a receptor 1 (C5AR1), atypical chemokine receptor 1 (ACKR1), profilin 2 (PFN2), and solute carrier family 2 member 3 (SLC2A3)] were identified. Several circRNA-miRNA-mRNA interactions were obtained, including circ_0022342miR-503-5pSLC2A3 and circ_0002062miR-92b-3p/miR-92a-3pmannosidase alpha class 2A member 1 (MAN2A1). Immune cell for SLC2A3 was eosinophils and for MAN2A1 was regulatory T cells (Tregs). Additionally, Glufosfamide and Kifunensine might be suitable as candidate drugs for CTEPH treatment.

CONCLUSIONS

SLC2A3 and MAN2A1 may be important genes for the pathogenesis of CTEPH. Possible immune regulation mechanisms in CTEPH may be circ_0022342miR-503-5pSLC2A3 and circ_0002062miR-92b-3p/miR-92a-3pMAN2A1. These results may be helpful for the diagnosis and treatment of CTEPH from the perspective of immunology.

Regulation of circular RNAs act as ceRNA in a hypoxic pulmonary hypertension rat model

To explore potential critical genes and identify circular RNAs (circRNAs) that act as the competitive endogenous RNA (ceRNA) in a hypoxic pulmonary hypertension (HPH) rat model. Constructed rat model, and a bioinformatics method was used to analyse differentially expressed (DE) genes and construct a circRNA-miRNA-mRNA ceRNA regulatory network. Then, qRT-PCR was used to verify. The significant DEcircRNAs/DEmiRNAs/DEmRNAs was showed, and a ceRNA network with 8 DEcircRNAs, 9 DEmiRNAs and 46 DEmRNAs were constructed. The functional enrichment suggested the inflammatory response, NF-κB signalling, MAPK cascade and Toll-like receptor were associated with HPH. Further assessment confirmed that circ_002723, circ_008021, circ_016925 and circ_020581 could have a potential ceRNA mechanism by sponging miR-23a or miR-21 to control downstream target gene and be involved in the pathophysiology of HPH. The qRT-PCR validation results were consistent with the RNA-Seq results. This study revealed potentially important genes, pathways and ceRNA regulatory networks in HPH.

Non-coding RNAs: The key detectors and regulators in cardiovascular disease

Cardiovascular disease (CVD) is an important cause of disease-related death worldwide. One of its main pathological bases is imbalances in gene expression. Non-coding RNAs are a class of transcripts that do not encode proteins. They include microRNA (miRNA), long noncoding RNA (lncRNA) and circular RNA (circRNA). They have important biological functions such as regulating transcription and translation, as well as interacting with DNA, RNA, and proteins. They are also closely associated with pathological processes in CVD. This review will focus on the expression and function of miRNA, lncRNA, circRNA, as well as on their roles and molecular mechanisms in CVDs such as cardiac hypertrophy, heart failure, arrhythmia, myocardial infarction, atherosclerosis, rheumatic heart disease, myocardial fibrosis, pulmonary arterial hypertension. This review will outline concepts provide bases for early diagnosis and targeted treatment of CVDs.

Circular RNAs: Functions and Clinical Significance in Cardiovascular Disease

Cardiovascular disease (CVD) causes high morbidity and mortality worldwide. Accumulating research has indicated the possible roles played by circular RNAs (circRNAs) in the pathogenesis of CVD. CircRNAs are non-coding RNAs with covalently closed loop structures. CircRNAs can function by acting as miRNA sponges, RNA binding protein sponges, mRNA transcriptional regulators and templates for protein translation. The specific characteristics of circRNAs such as high stability, abundant distribution, and tissue- and developmental stage-specific expression make them potential biomarkers for the diagnosis and prognosis of CVD. In this paper, we systematically summarized the current knowledge regarding the biogenesis, biological properties and the action mechanisms of circRNAs, elucidated the roles played by circRNAs in the pathogenesis of CVD, and explored the diagnostic potential of circRNAs in CVD. With in-depth studies, an increasing number of molecular mechanisms underlying the participation of circRNAs in CVD may be elucidated, and the application of circRNAs in the clinical diagnosis and prevention of CVD may eventually be realized.

hsa_circNFXL1_009 modulates apoptosis, proliferation, migration, and potassium channel activation in pulmonary hypertension

In this study, we explored the circular RNA (circRNA) profile in pulmonary arterial hypertension (PAH) patients caused by chronic obstructive pulmonary disease (COPD) and the effects of hsa_circNFXL1_009 on abnormal proliferation, apoptosis, and migration of human pulmonary arterial smooth muscle cells (hPASMCs) driven by hypoxia. Using microarrays, we screened the circRNA profile in whole-blood samples from three pairs of subjects and found 158 dysregulated circRNAs in patients with PAH-COPD. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis further validated that hsa_circNFXL1_009 was dramatically downregulated with the highest area under a receiver operating characteristic curve (ROC) in 21 pairs of subjects. Consistently, exposure to hypoxia markedly reduced the hsa_circNFXL1_009 level in cultured hPASMCs. Delivery of exogenous hsa_circNFXL1_009 attenuated hypoxia-induced proliferation, apoptotic resistance, and migration of hPASMCs, as evidenced by immunocytochemistry, 5-ethynyl-2′-deoxyuridine incorporation, wound healing, and a TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling) assay. A luciferase assay showed that hsa_circNFXL1_009 directly sponged hsa-miR-29b-2-5p (miR-29b) and positively regulated the expression of voltage-gated potassium (K⁺) channel subfamily B member 1 (KCNB1) at the mRNA level. Using patch-clamp electrophysiology, we proved that overexpression of hsa_circNFXL1_009 promoted a whole-cell K⁺ current in hPASMCs. Taken together, these studies identify hsa_circNFXL1_009 as a key regulator of PAH, and it may be used as a potential therapeutic target for the treatment of PAH.

Circles in the heart and cardiovascular system

The combination of next-generation sequencing, advanced bioinformatics analysis, and molecular research has now established circular RNAs (circRNAs) as a heterogeneous group of non-coding RNA that is widely and abundantly expressed. CircRNAs are single-stranded RNA, covalently backspliced to form closed circular loops. Different models of back-splicing have been proposed, and mechanisms for circRNA function include sequestering microRNAs, direct interaction with proteins, regulation of transcription, and translation. Exploring the role of circRNAs in different disease settings, and understanding how they contribute to disease progression promises to provide valuable insight into potential novel therapeutic approaches. Here, we review the growing number of published research on circRNAs in the heart and cardiovascular system and summarize the circRNAs that have been implicated in disease.

LncRNAs and circular RNAs as endothelial cell messengers in hypertension: mechanism insights and therapeutic potential

Endothelial cells are major constituents in the vasculature, and they act as important players in vascular homeostasis via secretion/release of vasodilators and vasoconstrictors. In healthy arteries, endothelial cells play a key role in the regulation of vascular tone, cellular adhesion, and angiogenesis. A shift in the functions of the blood vessels toward vasoconstriction, proinflammatory state, oxidative stress and deficiency of nitric oxide (NO) might lead to endothelial dysfunction, a key event implicated in the pathophysiology of cardiovascular metabolic diseases, including diabetes, atherosclerosis, arterial hypertension and pulmonary arterial hypertension (PAH). Thus, reversibility of endothelial dysfunction may be beneficial for maintaining vascular homeostasis. In recent years, accumulative evidence has documented that noncoding RNAs (ncRNAs) are critically involved in endothelial homeostasis. Specifically, long noncoding RNAs (lncRNAs) and circular RNAs are highly expressed in endothelial cells where they serve as important mediators in normal endothelial functions. Dysregulation of lncRNAs and circular RNAs has been tightly associated with hypertension-related endothelial dysfunction. In this review, we will summarize the current progression and underlying mechanisms of lncRNA and circular RNA in endothelial cell biology under hypertensive conditions. We will also highlight their potential as biomarkers or therapeutic targets for hypertension and its associated endothelial dysfunction.

The up-regulated hsa-circRNA9102-5 may be a risk factor for essential hypertension

Background

The present study was aimed to investigate the expression levels of circular RNAs (circRNAs) in the peripheral blood of essential hypertension (EH) patients and healthy controls (HC). On this basis, we tried to explain the possible role of circRNAs in the progression of EH and their potential as diagnostic biomarkers of EH.

Methods

First, we analyzed the differentially expressed circRNAs in peripheral blood obtained from the finished microarray analysis and selected four circRNAs under strict standards. Then, quantitative real‐time polymerase chain reaction (qRT‐PCR) was performed to measure the expression levels of the selected circRNAs in a total of 192 blood samples, consisting of 96 HC and 96 diagnosed EH patients. Bioinformatics prediction of the target microRNAs (miRNAs) was performed for differentially expressed circRNAs, and the circulating vascular‐related miRNAs were selected for qRT‐PCR analysis to determine their expression levels.

Results

Hsa‐circRNA9102‐5 (11.7 ± 1.06 vs 12.13 ± 1.11, P = .007) was up‐regulated in the patients group which was diagnosed with EH, as compared to the HC group, and was involved in the regulation of EH by sponging hsa‐miR‐150‐5p. The area under the ROC curve (AUC) of the model was 0.620, using hsa‐circRNA9102‐5 as an independent predictor. Furthermore, the AUC was increased to 0.728 when hsa‐circRNA9102‐5 was combined with hsa‐miR‐150‐5p and multiple other factors, as a combined predictor.

Conclusions

The present results suggested that hsa‐circRNA9102‐5 may have played a crucial role in the development of EH by sponging hsa‐miR‐150‐5p, which showed great potential as a novel target.

Identification of candidate lncRNAs and circRNAs regulating WNT3/β-catenin signaling in essential hypertension

Mounting evidence suggests that noncoding RNAs (ncRNAs) contribute to the pathogenesis of cardiovascular diseases. However, their role in essential hypertension (EH) is still unclear. We therefore identified differentially expressed long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) in EH patients from a high-risk population group and constructed a competing endogenous RNA regulatory network that predicts interactions of potential diagnostic and therapeutic relevance between specific lncRNA/circRNA-microRNA-mRNA triplets. Our analysis identified two lncRNAs, transmembrane protein 183A pseudogene (LOC646616) and leucine aminopeptidase 3 pseudogene 2 (LAP3P2), and two circRNAs, hsa_circ_0039388 and hsa_circ_0038648, that are highly co-expressed with both wingless-type MMTV integration site family member 3 (WNT3) and calcium/calmodulin-dependent protein kinase II inhibitor 2 (CAMK2N2) mRNAs and also share common microRNA binding sites with these two transcripts. We also confirmed that a mutually regulated network composed of LOC646616/microRNA-637/WNT3 controls WNT3 expression and influences viability and invasive properties in human arterial smooth muscle cells in vitro. These findings highlight a novel ncRNA-based regulatory mechanism potentially driving WNT/β-catenin activation in EH, and suggest that the identified ncRNAs may represent useful biomarkers and therapeutic targets for this condition.

Circ-calm4 Serves as an miR-337-3p Sponge to Regulate Myo10 (Myosin 10) and Promote Pulmonary Artery Smooth Muscle Proliferation

Pulmonary artery smooth muscle cell proliferation is the pathological basis of pulmonary vascular remodeling in hypoxic pulmonary hypertension. Recent studies suggest that circular RNA (circRNA) can regulate various biological processes, including cell proliferation. Therefore, it is possible that circRNA may have important roles in pulmonary artery smooth muscle cell proliferation in hypoxic pulmonary hypertension. In the present study, we aimed to identify functional circRNAs and clarify their roles and mechanisms in pulmonary artery smooth muscle cell proliferation in pulmonary hypertension. RNA sequencing identified 67 circRNAs that were differentially expressed in hypoxic lung tissues of mice. Screening by bioinformatics and quantitative polymerase chain reaction revealed significant elevation of a circRNA derived from alternative splicing of the calmodulin 4 gene (designated circ-calm4). Notably, this circRNA absorbed miR-337-3p. We further identified Myo10 (myosin 10) as a target protein of miR-337-3p. miR-337-3p bound to the 3'-untranslated region of Myo10 mRNA, thereby attenuating the translation of Myo10. Using loss-of-function and gain-of-function approaches, we found that circ-calm4 regulated cell proliferation by regulating the cell cycle. Additionally, we verified the functions of miR-337-3p and Myo10 in hypoxic pulmonary artery smooth muscle. Our results suggested that the circ-calm4/miR-337-3p/Myo10 signal transduction axis modulated the proliferation of pulmonary artery smooth muscle cells at the molecular level, thus establishing potential targets for the early diagnosis and treatment of pulmonary hypertension.

Circular RNA circHUWE1 Is Upregulated and Promotes Cell Proliferation, Migration and Invasion in Colorectal Cancer by Sponging miR-486

Background

Emerging studies have revealed that circular RNAs (circRNAs) correlate with diverse diseases including cancers. However, little is known about the functions of circRNAs in colorectal cancer (CRC). In our previous research, downregulation of hsa_circ_0140388 (circHUEW1) has been detected in CRC tissues through high-throughput sequencing. However, the underlying mechanism by which circHUWE1 regulates the proliferation and apoptosis in CRC has not been investigated.

Materials and Methods

The levels of circHUWE1 in 58 pairs of CRC tissues and corresponding adjacent healthy tissues were detected by RT-qPCR. In addition, the effects of circHUWE1 on cell proliferation, apoptosis migration and invasion were evaluated by cell proliferation assays, flow cytometry, and transwell assays in HCT116 and SW480 cell lines respectively. Meanwhile, the dual-luciferase reporter system assay was used to explore the interaction between circHUWE1 and miR-486 (hsa-miR-486-5p).

Results

In this study, we demonstrate that the expression of circHUEW1 is upregulated in CRC tissues. High expression of circHUEW1 was significantly associated with lymphovascular invasion (P =0.036), lymph node metastasis (P =0.017), distant metastasis (P =0.024), and TNM stage (P =0.009). Moreover, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve was 0.732, which indicated that circHUWE1 could serve as a potential biomarker in the detection of CRC. Silencing circHUWE1 significantly inhibited the proliferation, migration and invasion capacity of CRC cells in vitro. Mechanistically, we demonstrated that circHUWE1 could sponge miR-486 and the downregulation of miR-486 could reverse the cancer suppressive effects caused by silencing circHUWE1.

Conclusion

In this study, our results revealed that circHUWE1 may be a potential therapeutic target and diagnostic biomarker for CRC.

mmu_circ_0000790 Is Involved in Pulmonary Vascular Remodeling in Mice with HPH via MicroRNA-374c-Mediated FOXC1

Recently, the identification of several circular RNAs (circRNAs) as vital regulators of microRNAs (miRNAs) underlines the increasing complexity of non-coding RNA (ncRNA)-mediated regulatory networks. This study aimed to explore the effects of mmu_circ_0000790 on the biological behaviors of pulmonary artery smooth muscle cells (PASMCs) in hypoxic pulmonary hypertension (HPH). The HPH mouse model and hypoxia-induced PASMC model were initially established, and the expression of mmu_circ_0000790 in the pulmonary vascular tissues and hypoxic PASMCs was determined using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). A series of in vitro experiments such as dual-luciferase, RNA pull-down, and RNA-binding protein immunoprecipitation (RIP) assays were conducted to evaluate the interactions among mmu_circ_0000790, microRNA-374c (miR-374c), and forkhead transcription factor 1 (FOXC1). The potential physiological functions of mmu_circ_0000790, miR-374c, and FOXC1 in hypoxic PASMCs were investigated through gain- and loss-of function approaches. Upregulated mmu_circ_0000790 was found in both the HPH-pulmonary vascular tissues and hypoxic PASMCs. Additionally, mmu_circ_0000790 could competitively bind to miR-374c and consequently upregulate the target gene of miR-374c, FOXC1. It was also observed that mmu_circ_0000790 induced proliferation and inhibited apoptosis of hypoxic PASMCs, which further promoted the pulmonary vascular remodeling in mice with HPH. Therefore, we speculate that mmu_circ_0000790 may serve as a prospective target for the treatment of patients with HPH.

Profiling of differentially expressed circular RNAs in peripheral blood mononuclear cells from Alzheimer's disease patients

Expression of circular RNA (circRNA), a class of noncoding RNAs that regulates gene expression, is altered in Alzheimer's disease. This study profiled differentially expressed circRNAs in peripheral blood mononuclear cells (PBMCs) from five patients with Alzheimer's disease compared to healthy controls using circRNA microarrays. We identified a total of 4060 differentially expressed circRNAs (1990 upregulated and 2070 downregulated) in Alzheimer's disease patients. Among these circRNAs, 10 randomly selected circRNAs were verified using qRT-PCR. The top 10 upregulated and downregulated circRNAs were used to predict their target miRNAs. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that these differentially expressed circRNAs were strongly associated with inflammation, metabolism, and immune responses, which are all risk factors for Alzheimer's disease. The circRNA-miRNA-mRNA network was most involved in the MAPK, mTOR, AMPK, and WNT signaling pathways in Alzheimer's disease. In conclusion, the current study demonstrated the importance of circRNAs in Alzheimer's disease development. Future studies will evaluate some of these circRNAs as biomarkers for early disease detection and to develop therapeutic strategies to clinically control Alzheimer's disease progression.

Elevated serum circ_0068481 levels as a potential diagnostic and prognostic indicator in idiopathic pulmonary arterial hypertension

Circular RNAs have continuous, stable, and covalently closed circular structures and are not easily degraded by nucleases, thus they are ideal serum biomarkers for detecting diseases. However, research is still lacking on circular RNAs as diagnostic and prognostic markers for idiopathic pulmonary arterial hypertension. This study investigated the potential role of serum circ_0068481 levels in idiopathic pulmonary arterial hypertension diagnosis and prognosis. This prospective cohort study enrolled 82 patients with idiopathic pulmonary arterial hypertension between January 2016 and July 2018 at Guangdong Provincial People's Hospital. Serum circ_0068481 levels were measured using quantitative reverse transcription-polymerase chain reaction. Baseline data, including clinical background, hemodynamic variables, and biochemical variables, were collected. Receiver operating characteristic curves were used to investigate diagnostic effect, the Kaplan-Meier method was used to estimate survival rates, and univariate analysis of prognostic factors was performed with a Cox proportional hazard model. We found that serum circ_0068481 expression levels were significantly higher in patients with idiopathic pulmonary arterial hypertension and had higher sensitivity and specificity for predicting idiopathic pulmonary arterial hypertension. Additionally, we found that circ_0068481 expression correlated significantly with heart function, 6-min walk distance, serum N-terminal pro-B-type natriuretic peptide, serum H2S, the 6th World Symposium on Pulmonary Hypertension risk stratification, right heart failure, and patient death. Moreover, serum circ_0068481 levels were elevated in patients with idiopathic pulmonary arterial hypertension and right heart failure and were able to predict right heart failure. Serum circ_0068481 levels were also elevated in patients who died with idiopathic pulmonary arterial hypertension and were able to predict poorer clinical outcomes. Circ_0068481 is a novel and noninvasive biomarker for diagnosing idiopathic pulmonary arterial hypertension and predicting poor clinical outcome in patients with idiopathic pulmonary arterial hypertension.

Expression of microRNA-514a-5p and its biological function in experimental pulmonary thromboembolism

It is difficult to diagnose pulmonary thromboembolism (PTE) in clinical practice. While microRNAs (miRNAs) have been widely investigated as biomarkers for various diseases, their value as biomarkers for PTE remains largely unknown. In the present study, 83 miRNAs showed altered expression in an intermediate-risk PTE group when compared with their expression in a low-risk PTE group as detected by miRNA microarray analysis. After reviewing those data, hsa-miR-514a-5p was selected as a potential biomarker for PTE progression. Disordered myocardial fibroblast arrangements, broadened intercellular spaces, diapedesis of erythrocytes, and lower numbers of nuclei in the right ventricular wall were observed in rats in a PTE model group when compared to rats in a normal saline (NS) group. Furthermore, hyperexpression of miR-514a-5p exacerbated the morphological characteristics of lung and right ventricular tissues, and caused increased RVHI and lung index values, as well as increased BNP and NT-pro-BNP levels in the PTE model rats, possibly by downregulating Chordin-like 1 (CHRDL1) expression. These results suggest that MiR-514a-5p helps to exasperate PTE development by promoting several aspects of PTE pathology, including inflammation, lung injury, and right ventricular hypertrophy by targeting CHRDL1.

Circular RNA hsa_circ_0016070 Is Associated with Pulmonary Arterial Hypertension by Promoting PASMC Proliferation

Noncoding RNAs play an important role in the pathogenesis of pulmonary arterial hypertension (PAH). In this study, we investigated the roles of hsa_circ_0016070, miR-942, and CCND1 in PAH. circRNA microarray was used to search circRNAs involved in PAH, whereas real-time PCR and western blot analysis were performed to detect miR-942 and CCND1 expression in different groups. In addition, the effect of miR-942 on CCND1 expression, as well as the effect of hsa_circ_0016070 on the expression of miR-942 and CCND1, was also studied using real-time PCR and western blot analysis. Moreover, MTT assay and flow cytometry were used to detect the effect of hsa _circ_0016070 on cell proliferation and cell cycle. According to the results of circRNA microarray analysis, hsa _circ_0016070 was identified to be associated with the risk of PAH in chronic obstructive pulmonary disease (COPD) patients. The miR-942 level in the COPD(+) PAH(+) group was much lower than that in the COPD(+) PAH(−) group, while the CCND1 level in the COPD(+) PAH(+) group was much higher. CCND1 was identified as a candidate target gene of miR-942, and the luciferase assay showed that the luciferase activity of wild-type CCND1 3′ UTR was inhibited by miR-942 mimics. In addition, hsa _circ_0016070 reduced miR-942 expression and enhanced CCND1 expression. Furthermore, hsa _circ_0016070 evidently increased cell viability and decreased the number of cells arrested in the G1/G0 phase. In summary, the results of this study suggested that hsa_circ_0016070 was associated with vascular remodeling in PAH by promoting the proliferation of pulmonary artery smooth muscle cells (PASMCs) via the miR-942/CCND1. Accordingly, has_circ_0016070 might be used as a novel biomarker in the diagnosis and treatment of PAH.

Circular RNAs in hypertension: challenges and clinical promise

Hypertension (HT), or high blood pressure (BP), is a chronic disease that is common among populations worldwide. The occurrence of HT is one of the leading causes of cardiovascular morbidity and mortality in adults. Although multiple studies have stressed the multifactorial and multigenic nature of HT, uncertainties about its etiology persist, and current diagnostic biomarkers can explain only a small part of the phenotypic variance of BP. Hence, the search for novel biomarkers that enable early disease prevention and guided therapy is warranted. Regulatory circRNAs have emerged as the newest player in HT-related gene networks and hold promise for improving the accuracy of diagnosis. These RNAs are genome products that are formed through back-splicing of specific regions of pre-mRNAs. Evidence suggests that these RNA species are involved in various metabolic diseases. Recent studies have revealed that aberrant expression of circRNAs is relevant to the occurrence and development of HT. Accordingly, circRNAs are proposed as a new generation of predictive biomarkers and potential therapeutic targets for different forms of HT, including pulmonary hypertension and preeclampsia. This paper presents an overview of the findings from current research focusing on the emerging role of circRNAs in the pathogenesis of hypertension. Furthermore, some of the challenges encountered by circRNA studies are highlighted, and perspectives are provided on the future of research in this area.

Changing expression profiles of mRNA, lncRNA, circRNA, and miRNA in lung tissue reveal the pathophysiological of bronchopulmonary dysplasia (BPD) in mouse model

New perinatal care technologies have improved the survival rate of preterm neonates, but the prevalence of bronchopulmonary dysplasia (BPD), one of the most intractable problems in neonatal intensive care unit (NICU), remains unchanged. In present study, high-throughput sequencing (HTS) was performed to detect the expression profiles of long noncoding RNAs (lncRNAs), messenger RNAs (mRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs) in hyperoxia-induced BPD mouse model. Significant differentially expressed RNAs were selected and clustered between the BPD group and the control group. The results revealed that expressions of 1778 lncRNAs, 1240 mRNAs, 97 circRNAs, and 201 miRNAs were significantly altered in the BPD group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed to predict the potential functions of differentially expressed RNAs. lncRNA-mRNA and circRNA-miRNA coexpression networks were constructed to detect their association with the pathogenesis of BPD. Our study provides a systematic perspective on the potential function of RNAs during BPD.

Molecular Research in Chronic Thromboembolic Pulmonary Hypertension

Chronic Thromboembolic Pulmonary Hypertension (CTEPH) is a debilitating disease, for which the underlying pathophysiological mechanisms have yet to be fully elucidated. Occurrence of a pulmonary embolism (PE) is a major risk factor for the development of CTEPH, with non-resolution of the thrombus being considered the main cause of CTEPH. Polymorphisms in the α-chain of fibrinogen have been linked to resistance to fibrinolysis in CTEPH patients, and could be responsible for development and disease progression. However, it is likely that additional genetic predisposition, as well as genetic and molecular alterations occurring as a consequence of tissue remodeling in the pulmonary arteries following a persistent PE, also play an important role in CTEPH. This review summarises the current knowledge regarding genetic differences between CTEPH patients and controls (with or without pulmonary hypertension). Mutations in BMPR2, differential gene and microRNA expression, and the transcription factor FoxO1 have been suggested to be involved in the processes underlying the development of CTEPH. While these studies provide the first indications regarding important dysregulated pathways in CTEPH (e.g., TGF-β and PI3K signaling), additional in-depth investigations are required to fully understand the complex processes leading to CTEPH.

Circular RNAs in Vascular Functions and Diseases

Vascular disease is one of the top five causes of death and affects a variety of other diseases, such as heart, nervous system, and metabolic disorders. Vascular dysfunction is a hallmark of ischemia, cancer, and inflammatory diseases and can accelerate the progression of diseases. Circular RNAs (circRNAs) are a new type of noncoding RNAs with covalent bond ring structure, which have been reported to be abnormally expressed in many human diseases. circRNAs regulate gene expression through the sponging of microRNAs (miRNAs) and can also be used as disease biomarkers. Here we will summarize the functions of circRNAs in vascular diseases, including vascular dysfunction, atherosclerosis, diabetes mellitus-related retinal vascular dysfunction, chronic thromboembolic pulmonary hypertension, carotid atherosclerotic disease, hepatic vascular invasion in hepatocellular carcinoma, aortic aneurysm, coronary artery disease, and type 2 diabetes mellitus.

Circular RNAs: a rising star in respiratory diseases

Circular RNAs (CircRNAs), as a new class of non-coding RNA molecules that, unlike linear RNAs, have covalently closed loop structures from the ligation of exons, introns, or both. CircRNAs are widely expressed in various organisms in a specie-, tissue-, disease- and developmental stage-specific manner, and have been demonstrated to play a vital role in the pathogenesis and progression of human diseases. An increasing number of recent studies has revealed that circRNAs are intensively associated with different respiratory diseases, including lung cancer, acute respiratory distress syndrome, pulmonary hypertension, pulmonary tuberculosis, and silicosis. However, to the best of our knowledge, there has been no systematic review of studies on the role of circRNAs in respiratory diseases. In this review, we elaborate on the biogenesis, functions, and identification of circRNAs and focus particularly on the potential implications of circRNAs in respiratory diseases.

Circular RNAs as Potential Theranostics in the Cardiovascular System

Cardiovascular diseases (CVDs) represent the largest contributor to mortality worldwide. Identification of novel therapeutic targets and biomarkers for CVDs is urgently needed. Circular RNAs (circRNAs) are endogenous, abundant, and stable non-coding RNAs formed by back-splicing events. Their role as regulators of gene expression has been increasingly reported. Notably, circRNAs mediate essential physiological and pathological processes in the cardiovascular system. Our first aim, therefore, is to summarize recent advances in the role of circRNAs in cardiac development as well as in pathogenesis of various CVDs. Because circRNAs are stable in circulation and their dynamic changes may reflect different disease stages, they are considered ideal biomarkers. Therefore, our second aim is to review studies that have identified circulating circRNAs as biomarkers for CVDs. Finally, we discuss the shortage of functional studies and the limitations of available clinical studies and provide future perspectives.

Dysregulated circRNAs in plasma from active tuberculosis patients

Endogenous circular RNAs (circRNAs) have been reported in various diseases. However, their role in active TB remains unknown. The study was aimed to determine plasma circRNA expression profile to characterize potential biomarker and improve our understanding of active TB pathogenesis. CircRNA expression profiles were screened by circRNA microarrays in active TB plasma samples. Dysregulated circRNAs were then verified by qRT-PCR. CircRNA targets were predicted based on analysis of circRNA-miRNA-mRNA interaction. GO and KEGG pathway analyses were used to predict the function of circRNA. ROC curve was calculated to evaluate diagnostic value for active TB. A total of 75 circRNAs were significantly dysregulated in active TB plasma. By further validation, hsa_circRNA_103571 exhibited significant decrease in active TB patients and showed potential interaction with active TB-related miRNAs such as miR-29a and miR-16. Bioinformatics analysis revealed that hsa_circRNA_103571 was primarily involved in ras signalling pathway, regulation of actin cytoskeleton, T- and B-cell receptor signalling pathway. ROC curve analysis suggested that hsa_circRNA_103571 had significant value for active TB diagnosis. Circulating circRNA dysregulation may play a role in active TB pathogenesis. Hsa_circRNA_103571 may be served as a potential biomarker for active TB diagnosis, and hsa_circRNA_103571-miRNA-mRNA interaction may provide some novel mechanism for active TB.

Characteristics of circular RNA expression in lung tissues from mice with hypoxia‑induced pulmonary hypertension

Pulmonary hypertension (PH) is a life-threatening lung disease, characterized by an increase in pulmonary arterial pressure caused by vasoconstriction and vascular remodeling. The pathogenesis of PH is not fully understood, and there is a lack of potential biomarkers for the diagnosis and treatment of patients with PH. Non-coding RNAs with a characteristic covalently closed loop structure, termed circular RNAs (circRNAs), are present in a number of pulmonary diseases. To the best of our knowledge, the present study is the first to use microarray analysis to determine the expression profile of circRNAs in lung tissues from mice with hypoxia-induced PH. In total, 23 significantly upregulated and 41 significantly down-regulated circRNAs were identified. Of these, 12 differentially expressed circRNAs were selected for further validation using reverse transcription-quantitative polymerase chain reaction. Putative microRNAs (miRNAs) that bind to the dysregulated circRNAs were predicted. Subsequently, bioinformatics tools were used to construct circRNA-miRNA-mRNA networks for the two most promising circRNAs, namely mmu_circRNA_004592 and mmu_circRNA_018351. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of target genes of the dysregulated circRNAs revealed that these dysregulated circRNAs may serve an important role in the pathogenesis of hypoxia-induced PH. Therefore, these dysregulated circRNAs are candidate diagnostic biomarkers and potential therapeutic targets for PH.

Circular RNA and its mechanisms in disease: From the bench to the clinic

The emerging recognition of the functional roles of circular RNAs (circRNAs) has given rise to a new perspective regarding our understanding of cellular physiology and disease pathogenesis. Unlike linear RNAs, circRNAs are covalently closed continuous loops that act as gene regulators in mammals, and their sequence composition determines the mode of circRNA biogenesis. The availability and integrated use of advanced genome analysis platforms have allowed the identification of a large number of these molecules. Their high abundance, stability and evolutionary conservation among species endow circRNAs with numerous potential functions, such as acting as microRNA (miRNA) sponges or binding to RNA-associated proteins to form RNA-protein complexes that regulate gene transcription. Moreover, circRNAs have been shown to be expressed in a tissue-specific manner and in pathological conditions, which has stimulated significant interest in their role in human disease and cancer. In this concise review, we outline the characteristics, functions and mechanisms of action of circRNAs as well as their involvement in different diseases. Although their exact roles and mechanisms of gene regulation remain to be clarified, circRNAs have potential applications as disease biomarkers and novel therapeutic targets.