Angiogenic circular RNAs: A new landscape in cardiovascular diseases

Research trends and hotspots of circular RNA in cardiovascular disease: A bibliometric analysis

From a global perspective, cardiovascular diseases (CVDs), the leading factor accounting for population mortality, and circRNAs, RNA molecules with stable closed-loop structures, have been proven to be closely related. The latent clinical value and the potential role of circRNAs in CVDs have been attracting increasing, active research interest, but bibliometric studies in this field are still lacking. Thus, in this study, we conducted a bibliometric analysis by using software such as VOSviewer, CiteSpace, Microsoft Excel, and the R package to determine the current research progress and hotspots and ultimately provide an overview of the development trends and future frontiers in this field. In our study, based on our search strategy, a total of 1206 publications published before July 31, 2023 were accessed from the WOSCC database. According to our findings, there is a notable increasing trend in global publications in the field of circRNA in CVDs. China was found to be the dominant country in terms of publication number, but a lack of high-quality articles was a significant fault. A cluster analysis on the co-cited references indicated that dilated cardiomyopathy, AMI, and cardiac hypertrophy are the greatest objects of concern. In contrast, a keywords analysis indicated that high importance has been ascribed to MI, abdominal aortic aneurysm, cell proliferation, and coronary artery diseases.

Circ-CIMIRC inhibition alleviates CIH-induced myocardial damage via FbxL4-mediated ubiquitination of PINK1

Obstructive sleep apnea (OSA) is a common sleep disordered breathing diseases that characterized by chronic intermittent hypoxia (CIH). This work aimed to explore the role of circ-CIMIRC in CIH-induced myocardial injury. CIH aggravated myocardial tissue damage in rats. Circ_CIMIRC overexpression promoted apoptosis and reduced the colocalization of Tom20 and Parkin and mitophagy in CIH-treated H9c2 cells. Additionally, FbxL4 interacted with PINK1, FbxL4 silencing reduced PINK1 ubiquitination in H9c2 cells. Two major ubiquitination sites (K319 and K433) were responsible for ubiquitination of PINK1. Circ_CIMIRC promoted FbxL4-mediated ubiquitination and degradation of PINK1. Furthermore, circ_CIMIRC inhibition alleviated the pathological damage, fibrosis and apoptosis of myocardial tissues, reduced oxidative stress in CIH rats. In conclusion, circ_CIMIRC silencing repressed FbxL4-mediated ubiquitination and degradation of PINK1 and then enhanced PINK1/Parkin-mediated mitophagy, thereby alleviating myocardial damage in CIH rats. Thus, circ_CIMIRC may be a potential strategy to alleviate CIH-induced myocardial damage.

Circular RNA 0016142 Knockdown Induces Ferroptosis in Hepatocellular Carcinoma Cells via Modulation of the MicroRNA-188-3p/Glutathione Peroxidase 4 Axis

Hepatocellular carcinoma (HCC) has high incidence and mortality rates, and it is characterized by invasiveness, poor prognosis, and limited treatment opportunities. The objective of our research was to assess the role of circ_0016142 in HCC. The ferroptosis inducer RSL3 and the iron chelator deferoxamine were used to treat cells to induce or inhibit ferroptosis, respectively, and cell viability and proliferation were assessed in Hep3B and HA22T cells by CCK8 and EdU assays, respectively. ROS, MDA, GSH, and Fe2+ levels were determined using commercial kits. RT-qPCR and western blotting were performed to determine the relative expression levels of entities of interest. Dual-luciferase reporter and RNA pull-down assays were performed to assess the relationship between circ_0016142/GPX4 and miR-188-3p. The results showed that circ_0016142/GPX4 was overexpressed, whereas miR-188-3p was downregulated in HCC. Circ_0016142 silencing reduced cell proliferation and GSH levels and increased ROS, MDA, and Fe2+ levels in HCC cells, and this was reversed by the miR-188-3p inhibitor. GPX4-overexpression abolished the effect of miR-188-3p mimic in HCC cells. In conclusion, circ_0016142 silencing suppressed HCC cell proliferation by inducing ferroptosis via the miR-188-3p/GPX4 axis.

Circular RNA CircACAP2 regulates temporomandibular joint osteoarthritis via miR-21-5p/PLAG1 axis

OBJECTIVES

The pathogenesis of temporomandibular joint osteoarthritis (TMJOA) remains not fully understood. Our previous studies demonstrated that miR-21-5p may participate in the TMJOA development and the interaction between circRNA-ACAP2 (CircACAP2) and miR-21-5p. Our present study aimed to explore the biological functions and regulatory mechanisms of CircACAP2 in TMJOA.

MATERIALS AND METHODS

The differential expression pattern of CircACAP2 in OA and normal tissues or cells was detected. CircACAP2 biological functions experiments were performed in chondrocytes by overexpression and interference techniques. The interaction of CircACAP2 with miR-21-5p and downstream target mRNA, polymorphic adenoma gene 1 (PLAG1), was predicted by bioinformatic databases and then demonstrated by dual-luciferase reporter assay. The biological role of CircACAP2 in TMJOA was investigated and validated in a mouse model.

RESULTS

The expression level of CircACAP2 was markedly reduced in OA cartilage and directly related to chondrocyte proliferation and apoptosis as well as ECM metabolism in the cartilage. CircACAP2 functioned in chondrocytes via targeting miR-21-5p and PLAG1. Overexpressing of CircACAP2 alleviated TMJOA in mouse models.

CONCLUSIONS

The present study unveiled that CircACAP2/miR-21-5p/PLAG1 axis may play an important regulatory role in TMJOA progression, which may highlight a potentially effective intervention and therapeutic strategy for the treatment of TMJOA.

HNEAP Regulates Necroptosis of Cardiomyocytes by Suppressing the m5 C Methylation of Atf7 mRNA

PIWI-interacting RNAs (piRNAs) are highly expressed in various cardiovascular diseases. However, their role in cardiomyocyte death caused by ischemia/reperfusion (I/R) injury, especially necroptosis, remains elusive. In this study, a heart necroptosis-associated piRNA (HNEAP) is found that regulates cardiomyocyte necroptosis by targeting DNA methyltransferase 1 (DNMT1)-mediated 5-methylcytosine (m5 C) methylation of the activating transcription factor 7 (Atf7) mRNA transcript. HNEAP expression level is significantly elevated in hypoxia/reoxygenation (H/R)-exposed cardiomyocytes and I/R-injured mouse hearts. Loss of HNEAP inhibited cardiomyocyte necroptosis and ameliorated cardiac function in mice. Mechanistically, HNEAP directly interacts with DNMT1 and attenuates m5 C methylation of the Atf7 mRNA transcript, which increases Atf7 expression level. ATF7 can further downregulate the transcription of Chmp2a, an inhibitor of necroptosis, resulting in the reduction of Chmp2a level and the progression of cardiomyocyte necroptosis. The findings reveal that piRNA-mediated m5 C methylation is involved in the regulation of cardiomyocyte necroptosis. Thus, the HNEAP-DNMT1-ATF7-CHMP2A axis may be a potential target for attenuating cardiac injury caused by necroptosis in ischemic heart disease.

The Function and Therapeutic Potential of Circular RNA in Cardiovascular Diseases

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

New insights into circRNA and its mechanisms in angiogenesis regulation in ischemic stroke: a biomarker and therapeutic target

Ischemic stroke accounts for about 71% of strokes worldwide. Due to limited recommended therapeutics for ischemic stroke, more attention is focused on angiogenesis in ischemic stroke. Not long after ischemic stroke, angiogenesis arises and is vital for the prognosis. Various pro-angiogenic, anti-angiogenic factors and their downstream pathways engage in angiogenesis regulation. CircRNAs are differentially expressed after ischemic stroke. Up to now, circRNAs have been found to exert many functions in regulating apoptosis, autophagy, proliferation, and differentiation of neurons and neural stem cells mainly as miRNAs sponges or proteins decoy. Thus, many circRNAs are considered promising biomarkers or therapeutic targets for ischemic stroke. Besides, circRNAs participate in the modulation of endothelial-mesenchymal transition and blood-brain barrier maintenance. Moreover, circRNAs play significant roles in endothelial dysfunction concerning inflammation responses, apoptosis, proliferation, and migration. They correlate with many angiogenesis-related signaling pathways and genes via the circRNA/miRNA/mRNA network. Novel insights into circRNAs significance in angiogenesis regulation in ischemic stroke could be provided for further researches on the clinical application of circRNAs in ischemic stroke.

RNA-binding proteins and translation control in angiogenesis

Tissue vascularization through the process of angiogenesis ensures adequate oxygen and nutrient supply during development and regeneration. The complex morphogenetic events involved in new blood vessel formation are orchestrated by a tightly regulated crosstalk between extra and intracellular factors. In this context, RNA-binding protein (RBP) activity and protein translation play fundamental roles during the cellular responses triggered by particular environmental cues. A solid body of work has demonstrated that key RBPs (such as HuR, TIS11 proteins, hnRNPs, NF90, QKIs and YB1) are implicated in both physiological and pathological angiogenesis. These RBPs are critical for the metabolism of messenger (m)RNAs encoding angiogenic modulators and, importantly, strong evidence suggests that RBP-mRNA interactions can be altered in disease. Lesser known, but not less important, the mechanistic aspects of protein synthesis can also regulate the generation of new vessels. In this review, we outline the key findings demonstrating the implications of RBP-mediated RNA regulation and translation control in angiogenesis. Furthermore, we highlight how these mechanisms of post-transcriptional control of gene expression have led to promising therapeutic strategies aimed at targeting undesired blood vessel formation.

CircCERS6 Suppresses the Development of Epithelial Ovarian Cancer Through Mediating miR-630/RASSF8

Accumulating evidence have demonstrated that circular RNAs (circRNAs) exert important roles in tumor initiation and progression. Nevertheless, the role and mechanism of circRNA ceramide synthase 6 (circCERS6) in epithelial ovarian cancer (EOC) remain to be clarified. Using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot assay, we measured RNA and protein expression. We analyzed the effects of circCERS6/microRNA-630 (miR-630)/Ras-association domain family member 8 (RASSF8) axis in cell proliferation, migration, and invasion by 5-Ethynyl-2'-deoxyuridine (EdU) assay, colony formation assay, scratch test, and transwell assay. Using RNA-pull down assay and dual-luciferase reporter assay, the interaction between miR-630 and circCERS6 or RASSF8 was verified. The in vivo role of circCERS6 in tumor growth was analyzed using xenograft mice model. CircCERS6 expression was markedly reduced in EOC tissues and cell lines. CircCERS6 overexpression hampered the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of EOC cells. CircCERS6 directly interacted with miR-630. miR-630 expression was up-regulated in EOC tissues and cell lines. CircCERS6 overexpression-induced anti-tumor effects in EOC were largely reversed by the overexpression of miR-630. RASSF8 was a direct target of miR-630. RASSF8 level was decreased in EOC tissues and cell lines. CircCERS6 up-regulated RASSF8 expression by acting as a molecular sponge for miR-630 in EOC cells. CircCERS6 overexpression-mediated suppressive effects in EOC cells were largely overturned by the silence of RASSF8. CircCERS6 overexpression blocked tumor growth in vivo. CircCERS6 overexpression hampered the proliferation, migration, invasion, and EMT of EOC cells by up-regulating RASSF8 via sponging miR-630.

N6-Methyladenosine Modification Opens a New Chapter in Circular RNA Biology

As the most abundant internal modification in eukaryotic cells, N6-methyladenosine (m6A) in mRNA has shown widespread regulatory roles in a variety of physiological processes and disease progressions. Circular RNAs (circRNAs) are a class of covalently closed circular RNA molecules and play an essential role in the pathogenesis of various diseases. Recently, accumulating evidence has shown that m6A modification is widely existed in circRNAs and found its key biological functions in regulating circRNA metabolism, including biogenesis, translation, degradation and cellular localization. Through regulating circRNAs, studies have shown the important roles of m6A modification in circRNAs during immunity and multiple diseases, which represents a new layer of control in physiological processes and disease progressions. In this review, we focused on the roles played by m6A in circRNA metabolism, summarized the regulatory mechanisms of m6A-modified circRNAs in immunity and diseases, and discussed the current challenges to study m6A modification in circRNAs and the possible future directions, providing a comprehensive insight into understanding m6A modification of circRNAs in RNA epigenetics.

Factors Affecting the Re-Endothelialization of Endothelial Progenitor Cell

The vascular endothelium, which plays an essential role in maintaining the normal shape and function of blood vessels, is a natural barrier between the circulating blood and the vascular wall tissue. The endothelial damage can cause vascular lesions, such as atherosclerosis and restenosis. After the vascular intima injury, the body starts the endothelial repair (re-endothelialization) to inhibit the neointimal hyperplasia. Endothelial progenitor cell is the precursor of endothelial cells and plays an important role in the vascular re-endothelialization. However, re-endothelialization is inevitably affected in vivo and in vitro by factors, which can be divided into two types, namely, promotion and inhibition, and act on different links of the vascular re-endothelialization. This article reviews these factors and related mechanisms.

Association study of hsa_circ_0001946, hsa-miR-7-5p and PARP1 in coronary atherosclerotic heart disease

BACKGROUND

Our previous work identified an aberrant expression of hsa_circ_0001946 in coronary atherosclerotic heart disease (CHD). Here we aimed to verify the role of hsa_circ_0001946 as a biomarker for CHD, and explore the clues of its downstream regulation.

METHODS

The hsa_circ_0001946 expression in CHD patients (n = 120) and controls (n = 120) were confirmed with qRT-PCR. CircBank and miRDB were used for target analysis in silico. Spearman correlation test was performed to infer potential interrelationships among the nucleic acid molecular biomarkers, and their predictive abilities were examined using receiver operating characteristic (ROC) curves.

RESULTS

Hsa_circ_0001946 was validated to be significantly up-regulated in the peripheral blood mononuclear cells of CHD patients, and revealed as an independent indicator of increased CHD risk (odds ratio: 2.364; 95% confidence interval [CI]: 1.765-3.165) after adjusting for confounding factors. Hsa-miR-7-5p was found to own the largest number of binding sites in has_circ_0001946 sequence, and among its targets predicted, the poly ADP-ribose polymerase 1 (PARP1) has been implicated in the pathophysiology of CHD. Spearman analysis indicated negative correlations of hsa-miR-7-5p with hsa_circ_0001946 and PARP1, respectively; while hsa_circ_0001946 was positively correlated with PARP1. The prediction accuracy of hsa_circ_0001946 in CHD was evaluated, showing an area under the ROC curve of 0.897 (95% CI: 0.791-0.961), which could further increase to 0.957 (95% CI: 0.870-0.992) upon a combination of hsa-miR-7-5p and PARP1.

CONCLUSION

The present work demonstrated the predictive power of hsa_circ_0001946, hsa-miR-7-5p and PARP1 as combined biomarkers for CHD, and suggests a regulatory axis they consisted might contribute to the CHD development.

Extracellular Vesicle miRNAs in the Promotion of Cardiac Neovascularisation

Cardiovascular disease (CVD) is the leading cause of mortality worldwide claiming almost 17. 9 million deaths annually. A primary cause is atherosclerosis within the coronary arteries, which restricts blood flow to the heart muscle resulting in myocardial infarction (MI) and cardiac cell death. Despite substantial progress in the management of coronary heart disease (CHD), there is still a significant number of patients developing chronic heart failure post-MI. Recent research has been focused on promoting neovascularisation post-MI with the ultimate goal being to reduce the extent of injury and improve function in the failing myocardium. Cardiac cell transplantation studies in pre-clinical models have shown improvement in cardiac function; nonetheless, poor retention of the cells has indicated a paracrine mechanism for the observed improvement. Cell communication in a paracrine manner is controlled by various mechanisms, including extracellular vesicles (EVs). EVs have emerged as novel regulators of intercellular communication, by transferring molecules able to influence molecular pathways in the recipient cell. Several studies have demonstrated the ability of EVs to stimulate angiogenesis by transferring microRNA (miRNA, miR) molecules to endothelial cells (ECs). In this review, we describe the process of neovascularisation and current developments in modulating neovascularisation in the heart using miRNAs and EV-bound miRNAs. Furthermore, we critically evaluate methods used in cell culture, EV isolation and administration.

CircRNA circ_0072995 promotes the progression of epithelial ovarian cancer by modulating miR-147a/CDK6 axis

BACKGROUND

Increasing evidence has indicated that circular RNAs (circRNAs) play vital roles in modulating tumor progression. However, regulatory roles and underlying mechanisms of circRNA circ_0072995 in epithelial ovarian cancer (EOC) are not well characterized.

RESULTS

Circ_0072995 was up regulated in EOC afflicted tissues and cell lines (HO8910 and A2780), and was mainly located in the cytoplasm. The expression of circ_0072995 was associated with the pathological grade of EOC for respective patients. Functional experiments revealed that circ_0072995 promoted EOC cell proliferation, migration, induced apoptosis, as well as enhanced tumorigenesis in vivo. Mechanistic analyses indicated that circ_0072995 may have acted as a sponge of miR-147a such as to relieve repressive effects of miR-147a upon its target CDK6.

CONCLUSIONS

Our results revealed that circ_0072995 promoted EOC progression through the circ_0072995/miR-147a/CDK6 axis and may represent a strategy for treatment of EOC afflicted patients.

METHODS

Expression of circ_0072995 was evaluated in 40 EOC tissue samples and cell lines by qRT-PCR. The location of circ_0072995 was determined via nuclear-cytoplasmic fractionation. A series of functional experiments facilitated determinations of effects of circ_0072995 on EOC progression in vitro, and in vivo. Underlying mechanisms and influence of circ_0072995 on EOC were confirmed by bioinformatic analyses, luciferase reporter assays, qRT-PCR, and Western blotting.