Plasma-Derived Exosomal Circular RNA hsa_circ_0005540 as a Novel Diagnostic Biomarker for Coronary Artery Disease

Non-Coding Ribonucleic Acids as Diagnostic and Therapeutic Targets in Cardiac Fibrosis

PURPOSE OF REVIEW

Cardiac fibrosis is a crucial juncture following cardiac injury and a precursor for many clinical heart disease manifestations. Epigenetic modulators, particularly non-coding RNAs (ncRNAs), are gaining prominence as diagnostic and therapeutic tools.

RECENT FINDINGS

miRNAs are short linear RNA molecules involved in post-transcriptional regulation; lncRNAs and circRNAs are RNA sequences greater than 200 nucleotides that also play roles in regulating gene expression through a variety of mechanisms including miRNA sponging, direct interaction with mRNA, providing protein scaffolding, and encoding their own products. NcRNAs have the capacity to regulate one another and form sophisticated regulatory networks. The individual roles and disease relevance of miRNAs, lncRNAs, and circRNAs to cardiac fibrosis have been increasingly well described, though the complexity of their interrelationships, regulatory dynamics, and context-specific roles needs further elucidation. This review provides an overview of select ncRNAs relevant in cardiac fibrosis as a surrogate for many cardiac disease states with a focus on crosstalk and regulatory networks, variable actions among different disease states, and the clinical implications thereof. Further, the clinical feasibility of diagnostic and therapeutic applications as well as the strategies underway to advance ncRNA theranostics is explored.

Progression in the Relationship between Exosome Production and Atherosclerosis

Atherosclerosis (AS) is the leading cause of cardiovascular disease, causing a major burden on patients as well as families and society. Exosomes generally refer to various lipid bilayer microvesicles originating from different cells that deliver various bioactive molecules to the recipient cells, exerting biological effects in cellular communication and thereby changing the internal environment of the body. The mechanisms of correlation between exosomes and the disease process of atherosclerosis have been recently clarified. Exosomes are rich in nucleic acid molecules and proteins. For example, the exosome miRNAs reportedly play important roles in the progression of atherosclerotic diseases. In this review, we focus on the composition of exosomes, the mechanism of their biogenesis and release, and the commonly used methods for exosome extraction. By summarizing the latest research progress on exosomes and atherosclerosis, we can explore the advances in the roles of exosomes in atherosclerosis to provide new ideas and targets for atherosclerosis prevention, diagnosis, and treatment.

Advances in the study of exosomes in cardiovascular diseases

BACKGROUND

Cardiovascular disease (CVD) has been the leading cause of death worldwide for many years. In recent years, exosomes have gained extensive attention in the cardiovascular system due to their excellent biocompatibility. Studies have extensively researched miRNAs in exosomes and found that they play critical roles in various physiological and pathological processes in the cardiovascular system. These processes include promoting or inhibiting inflammatory responses, promoting angiogenesis, participating in cell proliferation and migration, and promoting pathological progression such as fibrosis.

AIM OF REVIEW

This systematic review examines the role of exosomes in various cardiovascular diseases such as atherosclerosis, myocardial infarction, ischemia-reperfusion injury, heart failure and cardiomyopathy. It also presents the latest treatment and prevention methods utilizing exosomes. The study aims to provide new insights and approaches for preventing and treating cardiovascular diseases by exploring the relationship between exosomes and these conditions. Furthermore, the review emphasizes the potential clinical use of exosomes as biomarkers for diagnosing cardiovascular diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Exosomes are nanoscale vesicles surrounded by lipid bilayers that are secreted by most cells in the body. They are heterogeneous, varying in size and composition, with a diameter typically ranging from 40 to 160 nm. Exosomes serve as a means of information communication between cells, carrying various biologically active substances, including lipids, proteins, and small RNAs such as miRNAs and lncRNAs. As a result, they participate in both physiological and pathological processes within the body.

Extracellular vesicles and their non-coding RNA cargos: Emerging players in cardiovascular disease

Extracellular vesicles (EVs), including exosomes, microvesicles and apoptotic bodies, have recently received attention as essential mechanisms for cell-to-cell communication in cardiovascular disease. EVs can be released from different types of cells, including endothelial cells, smooth muscle cells, cardiac cells, fibroblasts, platelets, adipocytes, immune cells and stem cells. Non-coding (nc)RNAs as EV cargos have recently been investigated in the cardiovascular system. Up- or downregulated ncRNAs in EVs have been shown to play a crucial role in various cardiovascular diseases. Communication via EV-derived ncRNAs can occur between cells of the same type and between different types of cells involved in the pathophysiology of cardiovascular disease. In the present review, we highlight the important aspects of diverse cell-derived EVs and their ncRNA cargos as disease mediators and potential therapeutic targets in atherosclerosis, coronary artery disease, ischaemic heart disease and cardiac fibrosis. In addition, we summarize the potential of EV-derived ncRNAs in the treatment of cardiovascular disease. Finally, we discuss the different methods for EV isolation and characterization. A better understanding of the specific role of EVs and their ncRNA cargos in the regulation of cardiovascular (dys)function will be of importance for the development of diagnostic and therapeutic tools for cardiovascular disease.

Unraveling the Intricate Roles of Exosomes in Cardiovascular Diseases: A Comprehensive Review of Physiological Significance and Pathological Implications

Exosomes, as potent intercellular communication tools, have garnered significant attention due to their unique cargo-carrying capabilities, which enable them to influence diverse physiological and pathological functions. Extensive research has illuminated the biogenesis, secretion, and functions of exosomes. These vesicles are secreted by cells in different states, exerting either protective or harmful biological functions. Emerging evidence highlights their role in cardiovascular disease (CVD) by mediating comprehensive interactions among diverse cell types. This review delves into the significant impacts of exosomes on CVD under stress and disease conditions, including coronary artery disease (CAD), myocardial infarction, heart failure, and other cardiomyopathies. Focusing on the cellular signaling and mechanisms, we explore how exosomes mediate multifaceted interactions, particularly contributing to endothelial dysfunction, oxidative stress, and apoptosis in CVD pathogenesis. Additionally, exosomes show great promise as biomarkers, reflecting differential expressions of NcRNAs (miRNAs, lncRNAs, and circRNAs), and as therapeutic carriers for targeted CVD treatment. However, the specific regulatory mechanisms governing exosomes in CVD remain incomplete, necessitating further exploration of their characteristics and roles in various CVD-related contexts. This comprehensive review aims to provide novel insights into the biological implications of exosomes in CVD and offer innovative perspectives on the diagnosis and treatment of CVD.

Recent Advances of Using Exosomes as Diagnostic Markers and Targeting Carriers for Cardiovascular Disease

Cardiovascular diseases (CVDs) are the leading cause of human death worldwide. Exosomes act as endogenous biological vectors; they possess advantages of low immunogenicity and low safety risks, also providing tissue selectivity, including the inherent targeting the to heart. Therefore, exosomes not only have been applied as biomarkers for diagnosis and therapeutic outcome confirmation but also showed potential as drug carriers for cardiovascular targeting delivery. This review aims to summarize the progress and challenges of exosomes as novel biomarkers, especially many novel exosomal noncoding RNAs (ncRNAs), and also provides an overview of the improved targeting functions of exosomes by unique engineered approaches, the latest developed administration methods, and the therapeutic effects of exosomes used as the biocarriers of medications for cardiovascular disease treatment. Also, the possible therapeutic mechanisms and the potentials for transferring exosomes to the clinic for CVD treatment are discussed. The advances, in vivo and in vitro applications, modifications, mechanisms, and challenges summarized in this review will provide a general understanding of this promising strategy for CVD treatment.

Circular RNAs Variously Participate in Coronary Atherogenesis

Over the past decade, numerous studies have shown that circular RNAs (circRNAs) play a significant role in coronary artery atherogenesis and other cardiovascular diseases. They belong to the class of non-coding RNAs and arise as a result of non-canonical splicing of premature RNA, which results in the formation of closed single-stranded circRNA molecules that lack 5'-end caps and 3'-end poly(A) tails. circRNAs have broad post-transcriptional regulatory activity. Acting as a sponge for miRNAs, circRNAs compete with mRNAs for binding to miRNAs, acting as competing endogenous RNAs. Numerous circRNAs are involved in the circRNA-miRNA-mRNA regulatory axes associated with the pathogenesis of cardiomyopathy, chronic heart failure, hypertension, atherosclerosis, and coronary artery disease. Recent studies have shown that сirc_0001445, circ_0000345, circ_0093887, сircSmoc1-2, and circ_0003423 are involved in the pathogenesis of coronary artery disease (CAD) with an atheroprotective effect, while circ_0002984, circ_0029589, circ_0124644, circ_0091822, and circ_0050486 possess a proatherogenic effect. With their high resistance to endonucleases, circRNAs are promising diagnostic biomarkers and therapeutic targets. This review aims to provide updated information on the involvement of atherogenesis-related circRNAs in the pathogenesis of CAD. We also discuss the main modern approaches to detecting and studying circRNA-miRNA-mRNA interactions, as well as the prospects for using circRNAs as biomarkers and therapeutic targets for the treatment of cardiovascular diseases.

Diagnostic value of circRNA in coronary heart disease: a meta-analysis

Aim: Studies have indicated that circRNAs have diagnostic value for coronary heart disease (CHD), but the efficacy varies greatly; therefore, a meta-analysis was conducted to assess the diagnostic value of circRNAs in CHD. Materials & methods: 16 studies with 3962 subjects (2239 cases and 1723 controls) were included by searching PubMed, Web of Science and MEDLINE. The pooled sensitivity and specificity, summary receiver operating characteristic and area under the curve, positive likelihood ratio and negative likelihood ratio were calculated. Results: The pooled area under the curve of circRNAs for the diagnosis of CHD was 0.80 (sensitivity and specificity were 0.77 and 0.68, respectively), and more indexes were calculated. Conclusion: circRNAs may be good biomarkers for diagnosing CHD.

Competing Endogenous RNA Regulatory Networks of hsa_circ_0126672 in Pathophysiology of Coronary Heart Disease

Coronary heart disease (CHD) is a global health concern, and its molecular origin is not fully elucidated. Dysregulation of ncRNAs has been linked to many metabolic and infectious diseases. This study aimed to explore the role of circRNAs in the pathogenesis of CHD and predicted a candidate circRNA that could be targeted for therapeutic approaches to the disease. circRNAs associated with CHD were identified and CHD gene expression profiles were obtained, and analyzed with GEO2R. In addition, differentially expressed miRNA target genes (miR-DEGs) were identified and subjected to functional enrichment analysis. Networks of circRNA/miRNA/mRNA and the miRNA/affected pathways were constructed. Furthermore, a miRNA/mRNA homology study was performed. We identified that hsa_circ_0126672 was strongly associated with the CHD pathology by competing for endogenous RNA (ceRNA) mechanisms. hsa_circ_0126672 characteristically sponges miR-145-5p, miR-186-5p, miR-548c-3p, miR-7-5p, miR-495-3p, miR-203a-3p, and miR-21. Up-regulation of has_circ_0126672 affected various CHD-related cellular functions, such as atherosclerosis, JAK/STAT, and Apelin signaling pathways. Our results also revealed a perfect and stable interaction for the hybrid of miR-145-5p with NOS1 and RPS6KB1. Finally, miR-145-5p had the highest degree of interaction with the validated small molecules. Henchashsa_circ_0126672 and target miRNAs, notably miR-145-5p, could be good candidates for the diagnosis and therapeutic approaches to CHD.

Analysis of the Research Hotspot of Exosomes in Cardiovascular Disease: A Bibliometric-based Literature Review

OBJECTIVE

To investigate the current status and development trend of research on exosomes in cardiovascular disease (CVD) using bibliometric analysis and to elucidate trending research topics.

METHODS

Research articles on exosomes in CVD published up to April 2022 were retrieved from the Web of Science database. Data were organized using Microsoft Office Excel 2019. CiteSpace 6.1 and VOSviewer 1.6.18 were used for bibliometric analysis and result visualization.

RESULTS

Overall, 256 original research publications containing 190 fundamental research publications and 66 clinical research publications were included. "Extracellular vesicle" was the most frequent research keyword, followed by "microrna," "apoptosis," and "angiogenesis." Most publications were from China (187, 73.05%), followed by the United States (57, 22.27%), the United Kingdom (7, 2.73%), and Japan (7, 2.73%). A systematic review of the publications revealed that myocardial infarction and stroke were the most popular topics and that exosomes and their contents, such as microRNAs (miRNAs), play positive roles in neuroprotection, inhibition of autophagy and apoptosis, promotion of angiogenesis, and protection of cardiomyocytes.

CONCLUSION

Research on exosomes in CVD has attracted considerable attention, with China having the most published studies. Fundamental research has focused on CVD pathogenesis; exosomes regulate the progression of CVD through biological processes, such as the inflammatory response, autophagy, and apoptosis. Clinical research has focused on biomarkers for CVD; studies on using miRNAs in exosomes as disease markers for diagnosis could become a future trend.

Exosomal circular RNAs: Biogenesis, effect, and application in cardiovascular diseases

As natural nanoparticles, exosomes regulate a wide range of biological processes via modulation of its components, including circular RNAs (circRNAs). CircRNAs are a novel class of closed-loop single-stranded RNAs with a wide distribution, and play diverse biological roles. Due to its stability in exosomes, exosomal circRNAs serve as biomarkers, pathogenic regulators and exert therapeutic potentials in some cardiovascular diseases, including atherosclerosis, acute coronary syndrome, ischemia/reperfusion injury, heart failure, and peripheral artery disease. In this review, we detailed the current knowledge on the biogenesis and functions of exosomes, circRNAs, and exosomal circRNAs, as well as their involvement in these cardiovascular diseases, providing novel insights into the diagnosis and treatment of these diseases.

Advances in detecting N6-methyladenosine modification in circRNAs

Circular RNAs (circRNAs) are a class of noncoding RNAs with covalently single-stranded closed loop structures derived from back-splicing event of linear precursor mRNAs (pre-mRNAs). N6-methyladenosine (m⁶A), the most abundant epigenetic modification in eukaryotic RNAs, has been shown to play a crucial role in regulating the fate and biological function of circRNAs, and thus affecting various physiological and pathological processes. Accurate identification of m⁶A modification in circRNAs is an essential step to fully elucidate the crosstalk between m⁶A and circRNAs. In recent years, the rapid development of high-throughput sequencing technology and bioinformatic methodology has propelled the establishment of a multitude of approaches to detect circRNAs and m⁶A modification, including in vitro-based and in silico methods. Based on this, the research community has started on a new journey to develop methods for identification of m⁶A modification in circRNAs. In this review, we provide a comprehensive review and evaluation of the existing methods responsible for detecting circRNAs, m⁶A modification, and especially, m⁶A modification in circRNAs, which mainly focused on those developed based on high-throughput technologies and methodology of bioinformatics. This handy reference can help researchers figure out towards which direction this field will go.

The role of circRNAs in the regulation of myocardial angiogenesis in coronary heart disease

During myocardial ischemia, timely reperfusion is critical to limit infarct area and the overall loss of cardiac contractile function. New treatment strategies need to be developed for patients who are neither able to receive interventional treatment nor suitable for surgical blood transport reconstruction surgery. Therapeutic angiogenesis is a promising approach that can be used to guide new treatment strategies. The goal of these therapies is to form new blood vessels or promote the maturation of existing vasculature systems, bypassing blocked arteries to maintain organ perfusion, thereby relieving symptoms and preventing the remodeling of bad organs. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), have been attracted much attention for their roles in various physiological and pathological processes. There is growing evidence that ncRNAs, especially circRNAs, play an important role in the regulation of cardiomyopathy angiogenesis due to its diversity of functions. Therefore, this article reviews the role and mechanisms of circRNA in myocardial angiogenesis to better understand the role of circRNAs in myocardial angiogenesis, which may provide useful insights and new revelations for the research field of identifying diagnostic markers and therapeutic approaches for the treatment of coronary artery disease.

The Role of Extracellular Non-coding RNAs in Atherosclerosis

Atherosclerosis (AS) is a complex chronic inflammatory disease that leads to myocardial infarction, stroke, and disabling peripheral artery disease. Non-coding RNAs (ncRNAs) directly participate in various physiological processes and exhibit a wide range of biological functions. The present review discusses how different ncRNAs participate in the process of AS in various carrier forms. We focused on the role and potential mechanisms of extracellular ncRNAs in AS and examined their potential implications for clinical treatment.

Extracellular Circular RNAs Act as Novel First Messengers Mediating Cell Cross-Talk in Ischemic Cardiac Injury and Myocardial Remodeling

Myocardial infarction (MI) causes most of the mortality worldwide. Coronary obstruction-caused myocardial ischemic injury leads to permanent loss of the myocardium. Subsequent compensatory myocardial remodeling and heart failure would result in arrhythmia and even sudden death. The molecular mechanisms of these pathological processes remain to be thoroughly revealed. Circular RNAs (circRNAs) are special types of non-coding RNAs which can durably regulate gene expression and modulate cell fate. They had been reported to mediate ischemic myocardial injury and myocardial remodeling. circRNAs can be loaded into extracellular vesicles and released into extracellular space. More recently, it was uncovered that the extracellular circRNAs can regulate intercellular communications, similar to "first messengers." The cross-talk mediated by extracellular circRNAs had been demonstrated to play important roles in pathological processes. Here, we would like to review the modulation of extracellular circRNAs in ischemic myocardial injury and myocardial remodeling. We believe the extracellular circRNAs can bring new strategies of MI treatment.

Competing endogenous RNA network mediated by circ_3205 in SARS-CoV-2 infected cells

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a new member of the Betacoronaviridae family, responsible for the recent pandemic outbreak of COVID-19. To start exploring the molecular events that follow host cell infection, we queried VirusCircBase and identified a circular RNA (circRNA) predicted to be synthesized by SARS-CoV-2, circ_3205, which we used to probe: (i) a training cohort comprised of two pools of cells from three nasopharyngeal swabs of SARS-CoV-2 infected (positive) or uninfected (negative, UCs) individuals; (ii) a validation cohort made up of 12 positive and 3 negative samples. The expression of circRNAs, miRNAs and miRNA targets was assayed through real-time PCR. CircRNA-miRNA interactions were predicted by TarpMiR, Analysis of Common Targets for circular RNAs (ACT), and STarMir tools. Enrichment of the biological processes and the list of predicted miRNA targets were retrieved from DIANA miRPath v3.0. Our results showed that the predicted SARS-CoV-2 circ_3205 was expressed only in positive samples and its amount positively correlated with that of SARS-CoV-2 Spike (S) mRNA and the viral load (r values = 0.80952 and 0.84867, Spearman's correlation test, respectively). Human (hsa) miR-298 was predicted to interact with circ_3205 by all three predictive tools. KCNMB4 and PRKCE were predicted as hsa-miR-298 targets. Interestingly, the function of both is correlated with blood coagulation and immune response. KCNMB4 and PRKCE mRNAs were upregulated in positive samples as compared to UCs (6 and 8.1-fold, p values = 0.049 and 0.02, Student's t test, respectively) and their expression positively correlated with that of circ_3205 (r values = 0.6 and 0.25, Spearman's correlation test, respectively). We propose that our results convincingly suggest that circ_3205 is a circRNA synthesized by SARS-CoV-2 upon host cell infection and that it may behave as a competitive endogenous RNA (ceRNA), sponging hsa-miR-298 and contributing to the upregulation of KCNMB4 and PRKCE mRNAs.

Circulating exosomal hsa_circRNA_0039480 is highly expressed in gestational diabetes mellitus and may be served as a biomarker for early diagnosis of GDM

Background

Gestational diabetes mellitus (GDM) seriously affects the health of mothers and babies, and there are still no effective early diagnostic markers. Therefore, it is necessary to find diagnostic biomarkers for screening GDM in early pregnancy. Circular RNA (circRNA) is more stable than linear RNA, and can be encapsulated in exosomes and participate in the pathological process of various diseases, which makes it a better candidate biomarker for various diseases. In this study, we attempted to identify the exosomal circRNA biomarkers for detecting early GDM.

Methods

We performed microarray analysis to compare the plasma exosomal circRNA expression profiles of three GDM patients 48 h before and 48 h after delivery. The repeatability of the expression of circRNAs were randomly validated by RT-PCR analysis. Pearson correlation analysis was applied to evaluate the correlation between circRNAs and OGTT level. ROC curve was established to assess the diagnostic value of circRNAs for GDM at different stages.

Results

Plasma exosomal hsa_circRNA_0039480 and hsa_circRNA_0026497 were highly expressed in GDM patients before delivery (P < 0.05). The hsa_circRNA_0039480 expression was higher for GDM group than NGT group at different stages, and was also positively correlated with OGTT during the second trimester (P < 0.05). The expression of hsa_circRNA_0026497 was higher for GDM group during the third, and second trimesters. And there was a strong correlation between two circRNAs in GDM patients during the first-trimester (r = 0.496, P = 0.014). Hsa_circRNA_0039480 showed significant diagnostic value in the first, second, and third trimesters of pregnancy (AUC = 0.704, P = 0.005; AUC = 0.898, P < 0.001 and AUC = 0.698, P = 0.001, respectively). Notably, the combination of hsa_circRNA_0039480 and hsa_circRNA_0026497 exhibited promising discriminative effect on GDM in the first trimesters (AUC = 0.754, P < 0.001).

Conclusion

Plasma exosomal hsa_cirRNA_0039480 is highly expressed in GDM patients at different stages and may be served as a candidate biomarker for early detection of GDM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03195-5.

Diagnostic value of circRNAs as effective biomarkers in human cardiovascular disease: an updated meta-analysis

Background: A growing body of literature has demonstrated that circular RNAs (circRNAs) are the potential biomarkers in human cardiovascular disease (CVD). Therefore, a meta-analysis based on current studies was accomplished to appraise the role of circRNAs in the diagnostic of CVD patients. Methods: Studies before October 30, 2021, were searched using PubMed, EMBASE, the Web of Science, and Cochrane Library. The diagnostic odds ratio (DOR) with a confidence interval (CI) of 95% was used to investigate the associations between circRNAs and CVDs. Results: A total of 27 eligible articles were selected, including 47 studies, with 6833 participants meeting the criteria standard constrain. The pooled overall sensitivity and specificity for circRNAs expression profile in differentiating CVD patients from controls (non-CVDs or healthy subjects) were 0.81 (95%CI 0.78-0.83) and 0.74 (95%CI 0.68-0.78), respectively; the overall positive likelihood ratio was 3.1 (95%CI 2.5-3.7); the negative likelihood ratio was 0.26 (95%CI 0.22-0.31); the overall diagnostic odds ratio corresponding to an area under the curve of 0.85 (95%CI 0.81-0.88) was 12 (95%CI 9-16). Subgroup analysis indicated that the serum rather than blood has higher diagnostic accuracy. Likewise, meta-regression analysis demonstrated that the specimen, detection method, sample size, and publication year were the main sources of heterogeneity. Sensitivity analysis and Deeks' funnel plot revealed that our results are relatively robust. Conclusions: Our evidence-based analysis results suggested that circRNAs provide higher diagnostic accuracy in the prediction of CVDs. Thus, circRNAs might be potential biomarkers in CVDs.

Potential Clinical Applications of Exosomal Circular RNAs: More than Diagnosis

Exosomes are small vesicles derived from cells used as cell-to-cell communication goods in numerous diseases including tumorigenesis, neurological diseases, cardiovascular diseases and other diseases. Circular RNAs (circRNAs) are an innovative constituent of non-coding endogenous RNAs generated through backsplicing, catalyzed by RNA polymerase Ⅱ. These non-coding RNAs have been suggested to control gene expression through miRNA sponging, RNA-binding protein regulation and translational capabilities. Genome-wide RNA sequence analyses observed that circRNAs were stably improved in exosomes in association to parental cells. Little attention has been dedicated to exosomal circRNAs (exo-circRNAs). However, research has demonstrated that exo-circRNAs may have important regulatory functions because of their stability in cells and within exosomes. If well understood, the precise roles and mechanisms of exo-circRNAs might surge the impending clinical applications of these molecules as markers in the identification, prediction and treatment of various diseases. In this review, we outline recent findings regarding exo-circRNAs which includes their functions and highlights their potential applications and therapeutic targets in human diseases.

Insights into circular RNAs: their biogenesis, detection, and emerging role in cardiovascular disease

Circular RNAs (circRNAs) are an evolutionarily conserved form of noncoding RNA with covalently closed loop structures. Initial studies established a functional role for circRNAs as potent microRNA sponges and many other studies have focussed solely on this. However, the biological functions of most circRNAs are still undetermined and other functional roles are gaining traction. These include protein sponges and regulators, and coding for proteins with an alternative mechanism of translation, potentially opening up a whole new transcriptome. The first step to gaining insight into circRNA function is accurate identification and various software platforms have been developed. Specialized detection software has now evolved into whole bioinformatics pipelines that can be used for detection, de novo identification, functional prediction, and validation of circRNAs. However, few cardiovascular circRNA studies have utilized these tools. This review summarizes current knowledge of circRNA biogenesis, bioinformatic detection tools and the emerging role of circRNAs in cardiovascular disease.

The Emerging Role of Long Non-coding RNAs and Circular RNAs in Coronary Artery Disease

Coronary artery disease (CAD) is a common disorder caused by atherosclerotic processes in the coronary arteries. This condition results from abnormal interactions between numerous cell types in the artery walls. The main participating factors in this process are accumulation of lipid deposits, endothelial cell dysfunction, macrophage induction, and changes in smooth muscle cells. Several lines of evidence underscore participation of long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) in the pathogenesis of CAD. Several lncRNAs such as H19, ANRIL, MIAT, lnc-DC, IFNG-AS1, and LEF1-AS1 have been shown to be up-regulated in the biological materials obtained from CAD patients. On the other hand, Gas5, Chast, HULC, DICER1-AS1, and MEG3 have been down-regulated in CAD patients. Meanwhile, a number of circRNAs have been demonstrated to influence function of endothelial cells or vascular smooth muscle cells, thus contributing to the pathogenesis of CAD. In the current review, we summarize the function of lncRNAs and circRNAs in the development and progression of CAD.

Exosomes in atherosclerosis: performers, bystanders, biomarkers, and therapeutic targets

Exosomes are nanosized lipid vesicles originating from the endosomal system that carry many macromolecules from their parental cells and play important roles in intercellular communication. The functions and underlying mechanisms of exosomes in atherosclerosis have recently been intensively studied. In this review, we briefly introduce exosome biology and then focus on advances in the roles of exosomes in atherosclerosis, specifically exosomal changes associated with atherosclerosis, their cellular origins and potential functional cargos, and their detailed impacts on recipient cells. We also discuss the potential of exosomes as biomarkers and drug carriers for managing atherosclerosis.

Emerging Roles of Extracellular Vesicles Derived Non-Coding RNAs in the Cardiovascular System

Cardiovascular disease is the leading cause of morbidity and mortality all over the world. Emerging evidence emphasize the importance of extracellular vesicles (EVs) in the cell to cell communication in the cardiovascular system which is majorly mediated through non-coding RNA cargo. Advancement in sequencing technologies revealed a major proportion of human genome is composed of non-coding RNAs viz., miRNAs, lncRNAs, tRNAs, snoRNAs, piRNAs and rRNAs. However, our understanding of the role of ncRNAs-containing EVs in cardiovascular health and disease is still in its infancy. This book chapter provides a comprehensive update on our understanding on the role of EVs derived ncRNAs in the cardiovascular pathophysiology and their therapeutic potential.

Circulating Circular RNAs: Novel Biomarkers for Heart Failure

Heart failure (HF) is a serious, chronic disease, causing significant ill health and high mortality worldwide. The current clinical strategies emphasize reducing the transition from a healthy to a failing heart despite the shift in the clinical goal from healing to disease prevention. Recent research advancements on noncoding RNAs (ncRNAs) have demonstrated that circular RNAs (circRNAs) are significant therapeutic targets in HF. Previous studies have highlighted the potential applicability of circRNAs in the diagnosis and treatment of diseases. However, less is known regarding the potential benefits of circRNAs as novel diagnostic and treatment biomarkers for HF. In the present study, we summarize the current developments and achievements associated with the use of circRNAs as HF biomarkers. We also discuss future research directions regarding HF diagnosis and treatment.

The Role of Exosomal Non-Coding RNAs in Coronary Artery Disease

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality worldwide. Atherosclerosis (AS) is a major cause of CVD. Oxidative stress, endothelial dysfunction, and inflammation are key factors involved in the development and progression of AS. Exosomes are nano-sized vesicles secreted into the extracellular space by most types of cells, and are ideal substances for the transmission and integration of signals between cells. Cells can selectively encapsulate biologically active substances, such as lipids, proteins and RNA in exosomes and act through paracrine mechanisms. Non-coding RNAs (ncRNAs) are important for communication between cells. They can reach the recipient cells through exosomes, causing phenotypic changes and playing a molecular regulatory role in cell function. Elucidating their molecular mechanisms can help identify therapeutic targets or strategies for CVD. Coronary artery disease (CAD) is the most important disease in CVD. Here, we review the role and the regulatory mechanism of exosomal ncRNAs in the pathophysiology of CAD, as well as the potential contribution of exosomal ncRNA to diagnosis and treatment of CAD.

Non-Coding RNAs as Blood-Based Biomarkers in Cardiovascular Disease

In 2020, cardiovascular diseases (CVDs) remain a leading cause of mortality and morbidity, contributing to the burden of the already overloaded health system. Late or incorrect diagnosis of patients with CVDs compromises treatment efficiency and patient's outcome. Diagnosis of CVDs could be facilitated by detection of blood-based biomarkers that reliably reflect the current condition of the heart. In the last decade, non-coding RNAs (ncRNAs) present on human biofluids including serum, plasma, and blood have been reported as potential biomarkers for CVDs. This paper reviews recent studies that focus on the use of ncRNAs as biomarkers of CVDs.

Exosomes in Nephropathies: A Rich Source of Novel Biomarkers

The biomarkers commonly utilized in diagnostic evaluations of kidney disease suffer from low sensitivity, especially in the early stages of renal damage. On the other hand, obtaining a renal biopsy to augment clinical decision making can lead to potentially serious complications. In order to overcome the shortcomings of currently available diagnostic tools, recent studies suggest that exosomes, cell-secreted extracellular vesicles containing a large array of active molecules to facilitate cell-to-cell communication, may represent a rich source of novel disease biomarkers. Because of their endocytic origin, exosomes carry markers typical for their parent cells, which could permit the localization of biochemical cellular alterations in specific kidney compartments. Different types of exosomes can be isolated from noninvasively obtained biofluids; however, in the context of kidney disease, evidence has emerged on the role of urinary exosomes in the diagnostic and predictive modeling of renal pathology. The current review summarizes the potential application of exosomes in the detection of acute and chronic inflammatory, metabolic, degenerative, and genetic renal diseases.