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

Curcumin alleviates renal fibrosis in chronic kidney disease by targeting the circ_0008925-related pathway

BACKGROUND

Curcumin has been shown to inhibit renal fibrosis, but whether curcumin mediates renal fibrosis progression by regulating the circular RNA (circRNA)-related pathway remain unclear.

METHODS

TGF-β1 was used to construct renal injury and fibrosis cell model. Cell growth was evaluated by cell counting kit 8 assay, EdU assay and flow cytometry. Fibrosis marker and interleukin 6 signal transducer (IL6ST) protein levels were measured using western bolt analysis. Inflammation factor concentrations were determined by ELISA. Circ_0008925, miR-204-5p and IL6ST expression was assessed by qRT-PCR. Unilateral ureteral obstruction (UUO) mice models were constructed to assess the role of curcumin in vivo.

RESULTS

Curcumin treatment alleviated TGF-β1-induced HK-2 cell apoptosis, inflammation and fibrosis in vitro, as well as relieved renal injury in UUO mice models in vivo. Circ_0008925 was highly expressed in TGF-β1-induced HK-2 cells and its expression was inhibited by curcumin. Circ_0008925 could sponge miR-204-5p to positively regulate IL6ST. The inhibition effect of curcumin on TGF-β1-induced HK-2 cell injury and fibrosis was reversed by circ_0008925 overexpression, miR-204-5p inhibitor or IL6ST upregulation. Besides, circ_0008925 knockdown inhibited TGF-β1-induced HK-2 cell injury and fibrosis by suppressing IL6ST expression.

CONCLUSION

Curcumin relieved renal fibrosis through regulating circ_0008925/miR-204-5p/IL6ST axis.

Circ_0035381 contributes to the progression of acute myeloid leukemia via regulating miR-186-5p/CDCA3 pathway

BACKGROUND

Circular RNAs (circRNAs) are involved in acute myeloid leukemia (AML) and may be useful for AML therapy. Herein, the project aimed to explore the functions and mechanisms of circ_0035381 in AML.

RESEARCH DESIGN AND METHODS

Circ_0035381, microRNA-186-5p (miR-186-5p), and cell division cycle associated 3 (CDCA3) expression were determined using quantitative real-time polymerase chain reaction (qRT-PCR) assay. Western blot assay was used to measure protein levels. 5'-ethynyl-2'-deoxyuridine (EdU) and flow cytometry were adopted to measure cell proliferation and apoptosis. Glucose consumption and lactate uptake were examined with commercial kits. The relationships between miR-186-5p and circ_0035381 or CDCA3 were validated using dual-luciferase reporter and RNA pull-down assays.

RESULTS

Circ_0035381 was increased in the AML subject and AML cell line. Circ_0035381 deficiency hindered the proliferation and glycolysis level and promoted apoptosis in the AML cell line. Circ_0035381 sponged miR-186-5p and miR-186-5p inhibition reversed the effect of circ_0035381 knockdown on AML cell progression. CDCA3 was the target gene of miR-186-5p. CDCA3 overexpression reversed circ_0035381 knockdown-mediated AML cell proliferation and glycolysis inhibition and apoptosis promotion.

CONCLUSIONS

Circ_0035381 promoted AML progression by elevating CDCA3 through sponging miR-186-5p, providing some clues for the diagnosis and treatment of AML.

Silencing circRNA-ZFAND6 induces trophoblast apoptosis by activating the mitochondrial pathway through the miR-575/SOD2 axis in unexplained recurrent spontaneous abortion

BACKGROUND

Unexplained recurrent spontaneous abortion (URSA) is a major problem in the field of human reproductive health. At present, several circRNAs have been reported to be differentially expressed and play an important biological function in pregnancy-related diseases. However, the role of circRNAs in URSA remains unclear.

METHODS

Levels of circRNA and miRNA were examined by RT-qPCR. The si-RNA and overexpression plasmid were respectively used to silence and overexpress circRNA-ZFAND6. We investigated the biological function of circRNA-ZFAND6 on trophoblasts through CCK8, EdU, Flow cytometric assay, Wound-healing assays and Transwell. Dual luciferase activity assay was conducted to identify the interaction between miR-575 and circRNA-ZFAND6.

RESULTS

We confirmed that circRNA-ZFAND6 was a stable circular RNA and was mostly localized in the cytoplasm. CircRNA-ZFAND6 was downregulated in placental villous tissues of URSA. CCK-8 and EdU assays showed that circRNA-ZFAND6 promoted the proliferation of HTR-8/SVneo cells. Flow cytometry and western blot assays prompted that circRNA-ZFAND6 obviously reduced cells apoptosis. Scratch wound healing and transwell assays revealed that circRNA-ZFAND6 had no effect on cell migration and invasion. CircRNA-ZFAND6 worked by adsorbing miR-575 through the ceRNA mechanism. MiR-575 can inhibit the proliferation and promote the apoptosis of HTR8/SVneo cells. SOD2 was identified as a direct target of miR-575 and was associated with mitochondrial apoptosis. Transmission electron microscopy, TMRM and ROS staining assays both suggested that circRNA-ZFAND6 affected mitochondrial apoptosis. Excessive trophoblast apoptosis was a key event to promote the development of URSA.

CONCLUSION

CircRNA-ZFAND6, which is low expressed in URSA and regulates the apoptosis of trophoblast cells, may affect the expression of SOD2 and thus affect mitochondrial apoptosis by regulating miR-575. This is closely related to the occurrence of URSA.

Comprehensive insights into circular RNAs, miRNAs, and lncRNAs as biomarkers in retinoblastoma

Retinoblastoma (RB) is a common and potentially lethal cancer that primarily affects young children worldwide, with survival rates significantly varying between high- and low-income countries. This review aims to identify essential diagnostic markers for early diagnosis by investigating the molecular pathways associated with RB. The prevalence of RB cases is notably concentrated in Asia and Africa, contributing to a global survival rate estimate of less than 30%. Current management strategies involve complex, individualized treatment plans that consider cultural nuances, genetic abnormalities, staging, and the availability of medical resources. Recent studies suggest that circular RNAs (circRNAs) may serve as predictive and diagnostic biomarkers in the etiology of RB. This review examines the roles of long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circRNAs in RB, with the goal of improving survival rates, particularly in low- and middle-income countries. A deeper understanding of the molecular pathways of RB may facilitate the development of personalized treatment plans and targeted therapies. Elevated expression of circRNAs has been observed in most patient cases, and studies indicate that reducing specific circRNA production can inhibit tumor cell development and progression. Investigating the roles and mechanisms of circular RNAs in RB holds promise for future treatment approaches.

Start small, think big: MicroRNAs in diabetes mellitus and relevant cardiorenal-liver metabolic health spectrum

Diabetes mellitus (DM), co-existing with metabolic disorder of cardio-renal-liver, is one of the most difficult problems in medicine that attracts global concern with high mortality. MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that negatively regulates gene expression and exerts active against a large proportion of the transcriptome, due to their high evolutionary conservation. Emerging evidence prove that miRNAs are involved in the pathogenesis of DM and associated metabolic disorders, manifested by their variable alteration in the blood, urine, tissues, or organs, principally contributing to modulate the interconnections between DM and cardio-renal-liver metabolism. Mechanistically, miRNAs regulate various biological processes, such as metabolism of insulin, lipid, glucose, inflammatory response, fibrosis, oxidative stress, apoptosis, and angiogenesis, etc. This review emphasizes the function of miRNAs and highlights the physiopathological regulation of miRNA in DM and related complications, especially the dysfunction of cardiovascular system, kidneys, and liver, with the aim of providing promising biomarkers for assisting early diagnosis of DM with cardio-renal-liver- specific metabolic disorders, as well as for the development of miRNA-targeting agents.

Regulatory effect and mechanism of CircSEC24A in IL-1β-induced osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized by articular cartilage degeneration and damage. Increasing circular RNAs (circRNAs) have been identified to participate in the pathogenesis of OA. Hsa_circ_0128006 (also known as circSEC24) was reported as an upregulated circRNA in OA tissues, but its biological role and underlying mechanism in OA are still to be discussed. circSEC24A and NAMPT expression levels were upregulated, and miR-515-5p was reduced in OA cartilage tissues and IL-1β-treated CHON-001 cells. The absence of circSEC24A overturned IL-1β-induced suppression of cell viability and promotion of oxidative stress, apoptosis, extracellular matrix (ECM) degradation, and inflammation in CHON-001 cells. Mechanistically, circSEC24A acted as a molecular sponge for miR-515-5p to affect NAMPT expression. CircSEC24A knockdown could attenuate IL-1β-triggered CHON-001 cell injury partly via the miR-515-5p/NAMPT axis, providing new insight into the underlying application of circSEC24A in OA treatment.

METTL3-mediated m6A modification of circSTAT6 modulates miR-188-3p/Beclin1 axis to promote osteogenic differentiation of mesenchymal stem cells

BACKGROUND

The role of N6-methyladenosine (m6A)-modified circRNAs in disease progression is of great significance. However, the specific impact of m6A modification of circSTAT6 on osteoporosis (OP) is still uncertain.

METHODS

The qRT-PCR was employed to assess the levels of METTL3, circSTAT6, miR-188-3p, and Beclin1. To investigate the interaction between miR-188-3p and circSTAT6 or Beclin, a dual-luciferase reporter assay was performed. To evaluate osteogenic differentiation in bone marrow mesenchymal stem cell (BMSC), western blot analysis was conducted to evaluate the protein expression of osteogenic markers, including ALP, OPN, and Runx2. In addition, alizarin red and alkaline phosphatase (ALP) staining assays were employed to assess osteogenesis.

RESULTS

The findings revealed that the downregulation of circSTAT6 was observed in OP. On the other hand, the overexpression of circSTAT6 was found to enhance the osteogenic differentiation of BMSC. In addition, the involvement of METTL3 in mediating m6A methylation of circSTAT6 was identified, which ultimately promoted osteogenesis. Furthermore, circSTAT6 functioned as an miR-188-3p sponge to regulate the expression of Beclin1. Further study revealed that the osteogenic-enhancing effect caused by circSTAT6 overexpression was counteracted by introducing a miR-188-3p mimic. Similarly, the osteogenic-promoting impact of the miR-188-3p inhibitor was reversed by suppressing Beclin1 expression.

CONCLUSIONS

The present study revealed, for the first time, that METTL3-mediated m6A modification of circSTAT6 regulated the miR-188-3p/Beclin1 axis to promote the osteogenic differentiation of BMSC. These findings offer a potential therapeutic target for the treatment of OP.

Functions and application of circRNAs in vascular aging and aging-related vascular diseases

Circular RNAs (circRNAs), constituting a novel class of endogenous non-coding RNAs generated through the reverse splicing of mRNA precursors, possess the capacity to regulate gene transcription and translation. Recently, the pivotal role of circRNAs in controlling vascular aging, as well as the pathogenesis and progression of aging-related vascular diseases, has garnered substantial attention. Vascular aging plays a crucial role in the increased morbidity and mortality of the elderly. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are crucial components of the intima and media layers of the vascular wall, respectively, and are closely involved in the mechanisms underlying vascular aging and aging-related vascular diseases. The review aims to provide a comprehensive exploration of the connection between circRNAs and vascular aging, as well as aging-related vascular diseases. Besides, circRNAs, as potential diagnostic markers or therapeutic targets for vascular aging and aging-related vascular diseases, will be discussed thoroughly, along with the challenges and limitations of their clinical application. Investigating the role and molecular mechanisms of circRNAs in vascular aging and aging-related vascular diseases will provide a novel insight into early diagnosis and therapy, and even effective prognosis assessment of these conditions.

Circular RNA contributes to gastric cancer by targeting Wnt family member 2B as a competing endogenous RNA

BACKGROUND

As a non-coding RNA molecule, circular RNAs (circRNAs) have significant specificity, and existing data suggest a close relationship between them and the prognosis of patients with gastric cancer (GC). However, this mechanism has no evidence yet. This article explores the functions of hsa_circRNA_102415 in the malignant behavior and potential downstream signaling of GC cells. The chosen approach is loss of signal and functional gain.

AIM

To investigate and analyze the relationship between hsa_circRNA_102415 and GC and explore its specific role. Results provide reference for other researchers to develop targeted treatment plans.

METHODS

The gene expression omnibus (GEO) database can be used to obtain the microarray dataset GSE83521. Data were analyzed using the GEO2R tool to identify differences in circRNAs between normal and GC samples. Quantitative real-time polymerase chain reaction was used to detect differentially expressed genes in GC tissue samples and adjacent cancer tissue samples. GC cells were transfected with small interfering-hsa_circRNA_104415 and plasmid DNA (pcDNA)-hsa_ircRNA_102415. Multiple detection methods, such as Transwell and cell counting kit 8, were used to evaluate cellular physiological activities, including cell invasion and proliferation. The relationship between Wnt family members 2B, microRNA (miR)-4529-5p, etc., including argonaute 2-RNA immunoprecipitation and luciferase reporter genes was analyzed. Rescue experiments were conducted to analyze and explore the relationship between the malignant behavior of GC cells and hsa_circRNA_102415.

RESULTS

GEO2R analysis confirmed that hsa_circRNA_102415 had significantly higher expression levels in disease tissues. hsa_circRNA_102415 and miR-4529-5p showed a negative correlation in disease cells, suggesting that hsa_circRNA_102415 upregulated WNT2B expression in GC cells as a competing endogenous RNA for miR-4529-5p. miR-4529-5p mimic or small interfering-WNT2B reversed the effects of pcDNA-hsa_circRNA_102415 or miR-4529-5p inhibitor on cell malignant functions.

CONCLUSION

miR-4529-5p was used to successfully activate the potential of WNT2B, clarify the role of hsa_circRNA_102415 in GC cells, and provide reference for other researchers to develop targeted treatment plans.

The involvement of circRNAs in molecular processes and their potential use in therapy and diagnostics for glioblastoma

Glioblastoma, a type of brain tumor, is well-known for its aggressive nature and can affect individuals of all ages. Glioblastoma continues to be a difficult cancer to manage because of various resistance mechanisms. The blood-brain barrier restricts the delivery of drugs, and the heterogeneity of tumors, along with overlapping signaling pathways, complicates its effective treatment. Patients diagnosed with glioblastoma typically survive for no more than 2 years. Innovative therapies and early diagnostic tools for glioblastoma are essential. Circular RNAs have emerged as significant contributors to glioblastoma, and influence cancer mechanisms such as cell growth, death, invasion, and resistance to treatment. The circRNAs presence makes them essential candidates for treatment and practical diagnostic tools for glioblastoma. This review highlights the therapeutic approaches and diagnostic potential of circRNAs and explores their role in the molecular mechanisms underlying glioblastoma.

Role of circRNAs in regulating cell death in cancer: a comprehensive review

Despite multiple diagnostic and therapeutic advances, including surgery, radiation therapy, and chemotherapy, cancer preserved its spot as a global health concern. Prompt cancer diagnosis, treatment, and prognosis depend on the discovery of new biomarkers and therapeutic strategies. Circular RNAs (circRNAs) are considered as a stable, conserved, abundant, and varied group of RNA molecules that perform multiple roles such as gene regulation. There is evidence that circRNAs interact with RNA-binding proteins, especially capturing miRNAs. An extensive amount of research has presented the substantial contribution of circRNAs in various types of cancer. To fully understand the linkage between circRNAs and cancer growth as a consequence of various cell death processes, including autophagy, ferroptosis, and apoptosis, more research is necessary. The expression of circRNAs could be controlled to limit the occurrence and growth of cancer, providing a more encouraging method of cancer treatment. Consequently, it is critical to understand how circRNAs affect various forms of cancer cell death and evaluate whether circRNAs could be used as targets to induce tumor death and increase the efficacy of chemotherapy. The current study aims to review and comprehend the effects that circular RNAs exert on cell apoptosis, autophagy, and ferroptosis in cancer to investigate potential cancer treatment targets.

SIRT1 in acute lung injury: unraveling its pleiotropic functions and therapeutic development prospects

Acute lung injury (ALI) is a continuum of lung changes caused by multiple lung injuries, often associated with severe complications and even death. In ALI, macrophages, alveolar epithelial cells and vascular endothelial cells in the lung are damaged to varying degrees and their function is impaired. Research in recent years has focused on the use of SIRT1 for the treatment of ALI. In this paper, we reviewed the role of SIRT1 in ALI in terms of its cellular and molecular mechanism, targeting of SIRT1 by non-coding RNAs and drug components, as well as pointing out the value of SIRT1 for clinical diagnosis and prognosis. Based on the current literature, SIRT1 exhibits diverse functionalities and possesses significant therapeutic potential. Targeting SIRT1 may provide new therapeutic ideas for the treatment of ALI.

Emerging roles of CircRNA-miRNA networks in cancer development and therapeutic response

The complex interplay of epigenetic factors is essential in regulating the hallmarks of cancer and orchestrating intricate molecular interactions during tumor progression. Circular RNAs (circRNAs), known for their covalently closed loop structures, are non-coding RNA molecules exceptionally resistant to enzymatic degradation, which enhances their stability and regulatory functions in cancer. Similarly, microRNAs (miRNAs) are endogenous non-coding RNAs with linear structures that regulate cellular biological processes akin to circRNAs. Both miRNAs and circRNAs exhibit aberrant expressions in various cancers. Notably, circRNAs can function as sponges for miRNAs, influencing their activity. The circRNA/miRNA interaction plays a pivotal role in the regulation of cancer progression, including in brain, gastrointestinal, gynecological, and urological cancers, influencing key processes such as proliferation, apoptosis, invasion, autophagy, epithelial-mesenchymal transition (EMT), and more. Additionally, this interaction impacts the response of tumor cells to radiotherapy and chemotherapy and contributes to immune evasion, a significant challenge in cancer therapy. Both circRNAs and miRNAs hold potential as biomarkers for cancer prognosis and diagnosis. In this review, we delve into the circRNA-miRNA circuit within human cancers, emphasizing their role in regulating cancer hallmarks and treatment responses. This discussion aims to provide insights for future research to better understand their functions and potentially guide targeted treatments for cancer patients using circRNA/miRNA-based strategies.

The role of circular RNAs in autoimmune diseases: Potential diagnostic biomarkers and therapeutic targets

With the emergence of high-quality sequencing technologies, further research on transcriptomes has become possible. Circular RNA (circRNA), a novel type of endogenous RNA molecule with a covalently closed circular structure through "back-splicing," is reported to be widely present in eukaryotic cells and participates mainly in regulating gene and protein expression in various ways. It is becoming a research hotspot in the non-coding RNA field. CircRNA shows close relation to several varieties of autoimmune diseases (AIDs) in both the physiological and pathological level and could potentially be used clinically in terms of diagnosis and treatment. Here, we focus on reviewing the importance of circRNA in various AIDs, with the aim of establishing new biomarkers and providing novel insights into understanding the role and functions of circRNA in AIDs. Specific signaling pathways of how circular RNAs are regulated in AIDs will also be illustrated in this review.

CircZMYM2 Alleviates TGF-β1-Induced Proliferation, Migration and Activation of Fibroblasts via Targeting miR-199b-5p/KLF13 Axis

Dysregulated circular RNAs (circRNAs) has been revealed to be involved in pulmonary fibrosis progression. Herein, this study focused on exploring the function and mechanism of circRNA Zinc Finger MYM-Type Containing 2 (circZMYM2) on idiopathic pulmonary fibrosis (IPF) using transforming growth factor (TGF)-β1-stimulated fibroblasts. Human fibroblast cell lines IMR-90 and HFL1 were stimulated with TGF-β1 to mimic fibrosis condition in vitro. Levels of genes and proteins were detected by qRT-PCR and western blotting. Cell proliferation and migration were analyzed using cell counting kit-8 assay, 5-Ethynyl-2'-deoxyuridine (EdU) and wound healing assays. The fibrosis progression was determined by the change of E-cadherin, α-smooth muscle actin (α-SMA), collagen type I α 1 (COL1A1) and collagen type III α 1 (COL3A1). The interaction between miR-199b-5p and circZMYM2 or KLF13 (Kruppel Like Factor 13) was analyzed using dual-luciferase reporter, RIP and RNA-pull-down assays. CircZMYM2 was decreased in TGF-β1-induced IMR-90 and HFL1 fibroblasts. Functionally, re-expression of circZMYM2 in IMR-90 and HFL1 cells could attenuate TGF-β1-evoked proliferation, migration and fibrosis in cells. Mechanistically, the circZMYM2/miR-199b-5p/KLF13 constituted a competing endogenous RNA (ceRNA). TGF-β1 reduced KLF13 expression and increased miR-199b-5p expression in IMR-90 and HFL1 cells. Further rescue experiments suggested that miR-199b-5p up-regulation or KLF13 knockdown reversed the anti-fibrotic effects of circZMYM2; moreover, silencing of miR-199b-5p exhibited anti-fibrotic effects, which was counteracted by KLF13 knockdown. CircZMYM2 had an anti-fibrotic effect that could suppress fibroblast activation via miR-199b-5p/KLF13 axis, pointing a novel perspective into the potential action pattern of circ_0022383 in IPF.

Inhibition of mmu_circ_0009303 improves metabolic dysfunction-associated steatotic liver disease by regulating lipid metabolism and oxidative stress

Circular RNAs (circRNAs) play an important role in regulating inflammation and oxidative stress during the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD); however, the underlying mechanism is unclear. This study aimed to determine the role of mmu_circ_0009303 in MASLD. We used a bioinformatics approach to identify potential targets and established an in vitro model of MASLD. Oil red O staining, cell transfection and dual-luciferase reporter assay were used to determine the role of mmu_circ_0009303. The results indicated that the mmu_circ_0009303 expression was significantly increased in the MASLD model both in vitro and in vivo and was associated with oxidative stress levels and inflammation. Moreover, bioinformatics analyses revealed that miRNA-182-5p and Foxo3 are targets of mmu_circ_0009303 and miRNA-182-5p, respectively. In the in vitro MASLD model, mmu_circ_0009303 promoted fat deposition in NCTC1469 cells, which was induced by free fatty acid (FFA) through the regulation of miRNA-182-5p/Foxo3. The expression of miRNA-182-5p and Forkhead box O3 (Foxo3) was associated with mmu_circ_0009303 expression in the liver of mice with MASLD, which was induced by a high-fat diet. Furthermore, mmu_circ_0009303 may be involved in regulating the expression of lipid metabolism-related regulatory proteins, such as CPT1A, SLC27A4, ACBD3, SREBP1, FAS, PPARα, and PPARγ. Taken together, mmu_circ_0009303 promotes oxidative stress, inflammation, and excessive fat accumulation in NCTC1469 cells induced by FFA through the regulation of miRNA-182-5p/Foxo3 and lipid metabolism-related regulatory proteins. These findings provide a potential target for the treatment of MASLD.

A Review on Circular RNA Translation and Its Implications in Disease

The mRNA vaccine has emerged as a powerful tool against viral infection during the coronavirus disease 2019 (COVID-19) pandemic. In the post-COVID-19 era, the applications of mRNA-based therapy continue to expand and evolve. Circular RNA (circRNA), long assumed to be a noncoding RNA, has been proven to be translatable and subsequently developed as a next-generation mRNA modality due to its higher stability and wider therapeutic window. Nonetheless, the studies of circRNA translation and its application in diseases still present numerous technical features and challenges. In this chapter, we provide a summary and discussion on the mechanisms of circRNA translation and its applications in medicine development, aiming to serve as a reference and inspiration for readers interested in circRNA-based therapy.

Non-coding RNAs in acute ischemic stroke: from brain to periphery

Acute ischemic stroke is a clinical emergency and a condition with high morbidity, mortality, and disability. Accurate predictive, diagnostic, and prognostic biomarkers and effective therapeutic targets for acute ischemic stroke remain undetermined. With innovations in high-throughput gene sequencing analysis, many aberrantly expressed non-coding RNAs (ncRNAs) in the brain and peripheral blood after acute ischemic stroke have been found in clinical samples and experimental models. Differentially expressed ncRNAs in the post-stroke brain were demonstrated to play vital roles in pathological processes, leading to neuroprotection or deterioration, thus ncRNAs can serve as therapeutic targets in acute ischemic stroke. Moreover, distinctly expressed ncRNAs in the peripheral blood can be used as biomarkers for acute ischemic stroke prediction, diagnosis, and prognosis. In particular, ncRNAs in peripheral immune cells were recently shown to be involved in the peripheral and brain immune response after acute ischemic stroke. In this review, we consolidate the latest progress of research into the roles of ncRNAs (microRNAs, long ncRNAs, and circular RNAs) in the pathological processes of acute ischemic stroke-induced brain damage, as well as the potential of these ncRNAs to act as biomarkers for acute ischemic stroke prediction, diagnosis, and prognosis. Findings from this review will provide novel ideas for the clinical application of ncRNAs in acute ischemic stroke.

CircCHSY1 protects hearts against ischaemia/reperfusion injury by enhancing heme oxygenase 1 expression via miR-24-3p

AIMS

Circular RNAs (circRNAs) are important players involved in a variety of physiological and pathological processes. However, their functions and mechanisms during myocardial ischaemic injury and protection remain largely unknown. We recently found significant alterations of many circRNAs including circCHSY1 following myocardial ischaemia/reperfusion (I/R) injury, whereas their exact functions are unclear. Here, we investigated the roles of circCHSY1 in the acute myocardial I/R injury and the potential mechanisms involved.

METHODS AND RESULTS

The expression of circCHSY1 was detected in cardiomyocytes from mouse, rat, and human embryonic stem cells (hESC-CMs). It was further up-regulated in mouse I/R (30 min/24 h) hearts, oxygen glucose deprivation/reperfusion (OGD/R, 6 h/2 h) primary neonatal rat ventricular cardiomyocytes (NRCMs) and OGD/R (48 h/2 h) hESC-CMs. Adenovirus-mediated circCHSY1 overexpression significantly decreased infarct size and lactate dehydrogenase (LDH) release in mouse I/R hearts. Consistently, circCHSY1 overexpression reduced the LDH release in the OGD/R NRCMs and hESC-CMs, improved cell viability, and preserved mitochondrial function in the OGD/R NRCMs, whereas there were no significant differences in cell viability and LDH release between the OGD/R NRCMs with and without small interfering RNA (siRNA)-mediated circCHSY1 knockdown. Mechanistically, circCHSY1 was detected to bind with miR-24-3p analysed by dual-luciferase assay and RNA pull-down assays. CircCHSY1 overexpression-mediated protective effects on cells and mitochondria in OGD/R NRCMs were reversed by the miR-24-3p mimic. Furthermore, dual-luciferase assay showed that miR-24-3p was directly bound to heme oxygenase 1 (HO1) via its 3'UTR. The protein level of HO1 was down-regulated by miR-24-3p mimic in OGD/R NRCMs but enhanced by the circCHSY1 overexpression in vitro and in vivo. Functionally, the HO1 knockdown by adenovirus in vivo and by siRNA in vitro eliminated cardioprotective effects of circCHSY1 overexpression.

CONCLUSION

CircCHSY1 is up-regulated following myocardial I/R injury. The higher level of circCHSY1 protects I/R hearts and cardiomyocytes. The protection of circCHSY1 is mediated through enhancement of the HO1 level, resulting in preserving mitochondrial homoeostasis via targeting miR-24-3p in cardiomyocytes. These findings suggest circCHSY1 as a protective factor.

OCRClassifier: integrating statistical control chart into machine learning framework for better detecting open chromatin regions

Open chromatin regions (OCRs) play a crucial role in transcriptional regulation and gene expression. In recent years, there has been a growing interest in using plasma cell-free DNA (cfDNA) sequencing data to detect OCRs. By analyzing the characteristics of cfDNA fragments and their sequencing coverage, researchers can differentiate OCRs from non-OCRs. However, the presence of noise and variability in cfDNA-seq data poses challenges for the training data used in the noise-tolerance learning-based OCR estimation approach, as it contains numerous noisy labels that may impact the accuracy of the results. For current methods of detecting OCRs, they rely on statistical features derived from typical open and closed chromatin regions to determine whether a region is OCR or non-OCR. However, there are some atypical regions that exhibit statistical features that fall between the two categories, making it difficult to classify them definitively as either open or closed chromatin regions (CCRs). These regions should be considered as partially open chromatin regions (pOCRs). In this paper, we present OCRClassifier, a novel framework that combines control charts and machine learning to address the impact of high-proportion noisy labels in the training set and classify the chromatin open states into three classes accurately. Our method comprises two control charts. We first design a robust Hotelling T2 control chart and create new run rules to accurately identify reliable OCRs and CCRs within the initial training set. Then, we exclusively utilize the pure training set consisting of OCRs and CCRs to create and train a sensitized T2 control chart. This sensitized T2 control chart is specifically designed to accurately differentiate between the three categories of chromatin states: open, partially open, and closed. Experimental results demonstrate that under this framework, the model exhibits not only excellent performance in terms of three-class classification, but also higher accuracy and sensitivity in binary classification compared to the state-of-the-art models currently available.

Circular RNA LMBR1 inhibits bladder cancer progression by enhancing expression of the protein ALDH1A3

Background

Circular RNAs (circRNAs) have been identified as playing an integral role in the development of bladder cancer (BC). However, the mechanism by which circRNAs operate in the chemical carcinogenesis of BC remains unclear.

Methods

To explore this mechanism, we used RNA high-throughput sequencing to identify differentially expressed circRNA in bladder epithelial cells and chemically induced malignant transformed BC cells. Subsequently, in vitro experiments were conducted to investigate the biological function and molecular mechanism of circLMBR1 in BC. Finally, animal experiments were conducted to examine the clinical relevance of circLMBR1 in vivo.

Results

Our profiling of circular RNA expression during cellular malignant transformation induced by chemical carcinogens identified a subset of circRNAs associated with cell transformation. We verified that the expression of circLMBR1 in bladder epithelial malignant transformed cells was decreased compared with control cells, as well as in BC tissues and bladder cell lines. Furthermore, circLMBR1 was seen to inhibit the proliferation, invasion, and migration of BC cells both in vitro and in vivo. Mechanistically, circLMBR1 was found to exert its antitumor effect by binding to the protein ALDH1A3.

Conclusions

Our findings have revealed that circLMBR1 inhibits the progression of BC cells by binding to ALDH1A3 and upregulating its expression. As such, circLMBR1 serves as a promising predictor of BC and may provide a novel therapeutic target for the treatment of BC.

Circular RNA circ_0004630 promotes malignancy and glycolysis of nonsmall cell lung cancer by sponging microRNA-1208 and regulating leucine-rich repeat kinase 2 expression

Emerging evidence has discovered that circular RNAs play important regulators of nonsmall cell lung cancer (NSCLC), but the role and potential molecular mechanism of hsa_circ_100549 (circ_0004630) involved in NSCLC is poorly defined. In this study, circ_0004630, microRNA-1208 (miR-1208), and leucine-rich repeat kinase 2 (LRRK2) expression were detected using real-time quantitative polymerase chain reaction. Cell proliferation, colony formation, apoptosis, and invasion were assessed using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), 5-ethynyl-2'-deoxyuridine, colony formation, flow cytometry, and transwell assays. Protein levels of glucose transporter 1, Hexokinase 2, and LRRK2 were detected using western blot assay. Glucose consumption, lactate production, and adenosine triphosphate content were assessed using the corresponding kits. After predicting via bioinformatics software Circinteractome and Targetscan, the binding between miR-1208 and circ_0004630 or LRRK2 was verified by a dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assay. The xenograft tumor model analyzed the biological role circ_000460 on tumor growth in vivo. It was found that circ_0004630 and LRRK2 were increased, and miR-1208 was low expression in NSCLC tissues and cells. Functionally, the downregulation of circ_0004630 inhibited NSCLC cell proliferation, invasion, glycolysis, and accelerated apoptosis in vitro. In mechanism, circ_0004630 might work as a sponge of miR-1208 to modulate LRRK2 expression. In addition, DUXAP8 deficiency cured neuroblastoma tumor growth in vivo. In conclusion, circ_0004630 knockdown might suppress NSCLC cell proliferation, metastasis, and glycolysis partly by the miR-1208/LRRK2 axis. Our findings hinted at an important theoretical basis for further elucidating the pathogenesis of NSCLC and targeted therapy.

Hsa_circ_0072732 enhances sunitinib resistance of renal cell carcinoma by inhibiting ferroptosis

BACKGROUND

Renal cell carcinoma (RCC) is one of the most diagnosed urological malignancies with high mortality and increasing incidence. What's more, the sunitinib resistance undoubtedly increased the difficulties in RCC therapy. Circular RNAs (circRNAs) are a newly found type of non-coding RNAs with a special circular structure, and are found to participate in the occurrence development, chemoresistance, and prognosis of cancers. Ferroptosis regulates disease progression mainly via polyunsaturated fatty acid metabolism and glutamine catabolic pathways. The mechanism of circRNAs contributed to sunitinib resistance through ferroptosis has not been elucidated clearly.

MATERIALS AND METHODS

In our research, we identified a novel circRNA Hsa_circ_0072732 from circRNA datasets (GSE108735 and GSE100186). RNase R and Actinomycin D assays were used to detect the loop structure and stability of circRNAs. qRT-PCR and western blot were used for the detection of RNA and protein levels. CCK8 assays were used to detect proliferation and cell viability. Lipid peroxidation (MDA), and reactive oxygen species (ROS) were detected by indicted kits. Dual-luciferase reporter and RNA pull-down assays were used to detect the RNA interactions.

RESULTS

Our results showed that Hsa_circ_0072732 was highly expressed in RCC cells. Further investigations showed that the silence of Hsa_circ_0072732 could increase RCC sensitivity to sunitinib. Hsa_circ_0072732 contributed to sunitinib chemoresistance by impairing ferroptosis. Hsa_circ_0072732 exerts its function mainly by acting as sponges for miR-548b-3p and regulating the expression SLC7A11. Our research suggests that ferroptosis is involved in sunitinib resistance, and targeting ferroptosis is a promising way for RCC treatment.

CONCLUSION

Our research suggests Hsa_circ_0072732 enhanced renal cell carcinoma sunitinib resistance by inhibiting ferroptosis through miR-548b-3p/SLC7A11.

CircZNF609/miR-324-5p/voltage-dependent anion channel 1 axis promotes malignant progression of ovarian cancer cells

The dysregulation of circular RNAs (circRNAs) has been associated with OC development and progression. This study investigated the role of circZNF609 in ovarian cancer (OC) by analyzing its impact on cell proliferation, migration, and invasion. Initially, the study assessed the expression of circZNF609 in OC tissues and adjacent normal tissues. The results revealed elevated circZNF609 levels in OC tissues and cell lines, correlating with poor prognosis, lymph node metastasis, and advanced clinical stage. Subsequently, in vitro and in vivo experiments were conducted to elucidate the biological functions of circZNF609 in OC progression. The findings showed that the knockdown of circZNF609 resulted in reduced OC cell proliferation, migration, invasion, and tumor growth. Mechanistically, circZNF609 was identified to function as a sponge for miR-324-5p, thereby upregulating voltage-dependent anion channel 1 (VDAC1) expression and promoting OC progression. Our findings indicate that circZNF609 promotes OC via the miR-324-5p/VDAC1 axis, contributing to the therapeutic targeting of this disease.

Hsa_circ_0000423 promotes colorectal cancer EMT and immune escape by competitive adsorption of miR-369-3p mediating CCND1 expression

BACKGROUND

This investigation evaluated the mechanism of hsa_circ_0000423 in colorectal cancer (CRC).

METHODS

The hsa_circ_0000423 gene was identified by bioinformatics analyses of GEO circRNA microarrays, and its expression in CRC was investigated. Based on this, in vitro experiments were conducted. Assays with dual luciferase reporter and RIP were conducted to detect interactions between hsa_circ_0000423, miR-369-3p and CCND1. Cell proliferation was measured by MTT and colony formation assay assays, apoptosis was detected by flow cytometry, migration and invasion were detected by Transwell, and expression of EMT-related proteins was detected by Western Blot. SW480 cells and T cells were co-cultured to assess immune escape.

RESULTS

hsa_circ_0000423 and CCND1 were elevated in CRC while miR-369-3p was downregulated Silencing hsa_circ_0000423 resulted in reduced CCND1 expression by upregulating miR-369-3p. Overexpressing CCND1 or down-regulating miR-369-3p both interrupted the anti-tumor role of silencing hsa_circ_0000423 on CRC cells.

CONCLUSION

Hsa_circ_0000423 promotes CCND1 expression through competitive binding of miR-369-3p and promotes CRC cell development and immune escape.

Towards Understanding the Role of the Glycosylation of Proteins Present in Extracellular Vesicles in Urinary Tract Diseases: Contributions to Cancer and Beyond

Extracellular vesicles (EVs) are a population of nanoscale particles surrounded by a phospholipid bilayer, enabling intercellular transfer of bioactive molecules. Once released from the parental cell, EVs can be found in most biological fluids in the human body and can be isolated from them. For this reason, EVs have significant diagnostic potential and can serve as an excellent source of circulating disease biomarkers. Protein glycosylation plays a key role in many biological processes, and aberrant glycosylation is a hallmark of various diseases. EVs have been shown to carry multiple glycoproteins, but little is known about the specific biological roles of these glycoproteins in the context of EVs. Moreover, specific changes in EV glycosylation have been described for several diseases, including cancers and metabolic, cardiovascular, neurological or kidney diseases. Urine is the richest source of EVs, providing almost unlimited (in terms of volume) opportunities for non-invasive EV isolation. Recent studies have also revealed a pathological link between urinary EV glycosylation and urological cancers, as well as other pathologies of the urinary tract. In this review, we discuss recent research advances in this field and the diagnostic/prognostic potential of urinary EV glycosylation. In addition, we summarize common methods for isolating EVs from urine and techniques used to study their glycosylation.

Circular RNA circ_0022707 impedes the progression of preeclampsia via the miR-3135b/GHR/PI3K/Akt axis

Preeclampsia (PE) is a severe pregnancy complication linked to maternal and fetal health, yet its underlying causes and pathogenesis remain elusive. Circular RNA (circRNA), a form of non-coding RNA, is implicated in the progression of PE; nevertheless, the specific mechanism is not fully elucidated. This study aimed to identify and validate circRNAs that are pivotal in the pathophysiology of PE. Firstly, we constructed a ceRNA network using datasets from the GEO database and identified circ_0022707 as our study target. Then, using qRT-PCR analysis, we validated that circ_0022707 was downregulated in preeclamptic placentas compared to those of normal pregnant women. In situ hybridization assays revealed that circ_0022707 existed in placental villous trophoblast cells. Additionally, Pearson correlation analysis revealed a negative relationship between the expression of circ_0022707 and PE-related indicators (systolic and diastolic blood pressure, along with 24-h proteinuria levels). Furthermore, gain-of-function experiments confirmed that circ_0022707 could promote trophoblast cell proliferation and cell cycle progression while suppressing apoptosis. In vivo experiments using a preeclampsia-like mouse model also demonstrated that circ_0022707 administration could mitigate preeclampsia-like symptoms. Mechanistically, we confirmed that circ_0022707 functions through the miR-3135b/GHR/PI3K/Akt pathway in trophoblast cells. Overall, our study has provided insight into the important function of circ_002707 in the development of PE, enhancing our understanding of the disease's mechanism and proposing a viable therapeutic strategy for PE.

CircVIRMA enhances cell malignant behavior by governing the miR-452-5p/CREBRF pathway in cervical cancer

Our current study aimed to investigate the role and mechanism of circVIRMA in cervical cancer (CC) progression. CircVIRMA, microRNA-452-5p (miR-452-5p) and CREB3 regulatory factor (CREBRF) mRNA levels were examined in CC via quantitative real-time PCR (qRT-PCR). The protein level of CREBRF in CC was checked by Western blot. Cell Counting Kit-8 (CCK-8), colony formation, 5-Ethynyl-2'-deoxyuridine (EdU) staining, cell cycle, flow cytometry and transwell assays were conducted to estimate the effects of circVIRMA on malignant phenotypes of CC tumors. Western blot was used to measure related marker protein levels. The interaction between miR-452-5p and circVIRMA or CREBRF was predicted by bioinformatics analysis and verified by dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays. Xenograft assay was used to assess the effect of circVIRMA on tumor growth in vivo. Immunohistochemistry (IHC) assay was performed to detect Ki-67 expression in tissues of mice. CircVIRMA and CREBRF levels were upregulated, while miR-452-5p was downregulated in CC tissues and cells. CircVIRMA silencing restrained CC cell proliferation, migration and invasion whereas induced apoptosis in vitro. In addition circVIRMA knockdown markedly attenuated xenograft tumor growth in vivo. circVIRMA was an efficient molecular sponge for miR-452-5p, and negatively regulated miR-452-5p expression. circVIRMA regulated CREBRF expression to modulate CC progression via miR-452-5p. MiR-452-5p downregulation reversed the effects of circVIRMA knockdown on CC progression. MiR-452-5p directly targeted CREBRF, and CREBRF overexpression partly restored the impact of miR-452-5p mimics on CC progression. circVIRMA mediated CC progression via regulating miR-452-5p/CREBRF axis, providing a novel therapeutic target for CC treatment.

CircROBO1 knockdown improves the radiosensitivity of hepatocellular carcinoma by regulating RAD21

INTRODUCTION AND OBJECTIVES

Radioresistance is a common problem in the treatment of many cancers, including hepatocellular carcinoma (HCC). Previous studies have shown that circROBO1 is highly expressed in HCC tissues and acts as a cancer promoter to accelerate the malignant progression of HCC. However, the role and mechanism of circROBO1 in HCC radioresistance remain unclear.

MATERIALS AND METHODS

CircROBO1, microRNA (miR)-136-5p and RAD21 expression levels were analyzed by quantitative real-time PCR. Cell function and radioresistance were evaluated by colony formation assay, cell counting kit 8 assay, EdU assay and flow cytometry. Protein expression was determined using western blot analysis. RNA interaction was analyzed by dual-luciferase reporter assay and RNA pull-down assay. In vivo experiments were performed by constructing mice xenograft models.

RESULTS

CircROBO1 was highly expressed in HCC, and its knockdown inhibited HCC cell proliferation and promoted apoptosis to enhance cell radiosensitivity. On the mechanism, circROBO1 could serve as miR-136-5p sponge to positively regulate RAD21. MiR-136-5p inhibitor or RAD21 overexpression reversed the regulation of circROBO1 knockdown on the radiosensitivity of HCC cells. Also, circROBO1 interference improved the radiosensitivity of HCC tumors in vivo.

CONCLUSIONS

CircROBO1 might be a promising target for treating HCC radioresistance.

Unlocking the potential of extracellular vesicle circRNAs in breast cancer: From molecular mechanisms to therapeutic horizons

Breast cancer remains the leading cause of cancer-related morbidity and mortality among women worldwide, underscoring the urgent need for novel diagnostic and therapeutic strategies. This review explores the emerging roles of circular RNAs (circRNAs) within extracellular vesicles (exosomes) in breast cancer. circRNAs, known for their stability and tissue-specific expression, are aberrantly expressed in breast cancer and regulate critical cellular processes such as proliferation, migration, and apoptosis, positioning them as promising biomarkers. Exosomes facilitate intercellular communication by delivering circRNAs, reflecting the physiological and pathological state of their source cells. This review highlights the multifaceted roles of exosomal circRNAs in promoting tumor growth, metastasis, and drug resistance through their modulation of tumor metabolism, the tumor microenvironment, and immune responses. In particular, we emphasize their contributions to chemotherapy resistance and their potential as both diagnostic markers and therapeutic targets. By synthesizing current research, this review provides novel insights into the clinical applications of exosomal circRNAs, offering a foundation for future studies aimed at improving breast cancer management through non-invasive diagnostics and targeted therapies.

CircRNA Arf3 suppresses glomerular mesangial cell proliferation and fibrosis in diabetic nephropathy via miR-107-3p/Tmbim6 axis

Diabetic nephropathy (DN) is one of microvascular complication associated with diabetes. Circular RNAs (circRNAs) have been shown to be involved in DN pathogenesis. Hence, this work aimed to explore the role and mechanism of circ_Arf3 in DN. Mouse mesangial cells (MCs) cultured in high glucose (HG) condition were used for functional analysis. Cell proliferation was determined using 5-ethynyl-2'-deoxyuridine (EdU) and cell counting kit-8 assays. Western blotting was used to measure the levels of proliferation indicator PCNA and fibrosis-related proteins α-smooth muscle actin (α-SMA), collagen I (Col I), fibronectin (FN), and collagen IV (Col IV). The binding interaction between miR-107-3p and circ_Arf3 or Tmbim6 (transmembrane BAX inhibitor motif containing 6) was confirmed using dual-luciferase reporter and pull-down assays. Circ_Arf3 is a stable circRNA, and the expression of circ_Arf3 was decreased after HG treatment in MCs. Functionally, ectopic overexpression of circ_Arf3 protected against HG-induced proliferation and elevation of fibrosis-related proteins in MCs. Mechanistically, circ_Arf3 directly bound to miR-107-3p, and Tmbim6 was a target of miR-107-3p. Further rescue assay showed miR-107-3p reversed the protective action of circ_Arf3 on MCs function under HG condition. Moreover, inhibition of miR-107-3p suppressed HG-induced proliferation and fibrosis, which were attenuated by Tmbim6 knockdown in MCs. CircRNA Arf3 could suppress HG-evoked mesangial cell proliferation and fibrosis via miR-107-3p/Tmbim6 axis, indicating the potential involvement of this axis in DN progression.

Circ_0000099/miR-223-3p/CTGF Regulates the Growth, Metastasis, and EMT Processes in TGF-β2-Stimulated Human Lens Epithelial Cells

PURPOSE

Posterior capsule opacification (PCO) is the major complication of visual impairment after cataract surgery. Circular RNAs (circRNAs) are involved in the development of many diseases. The purpose of this study was to explore the role and molecular mechanism of circ_0000099 in PCO.

METHODS

SRA01/04 cells were treated with TGF-β2 to establish a PCO cell model. The expression of circ_0000099, miR-223-3p, and connective tissue growth factor (CTGF) mRNA was determined by real-time quantitative polymerase chain reaction (qRT-PCR). Western blot assay was used to analyze the protein expression. Cell proliferation, migration, and invasion were analyzed by (4-5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), 5-ethynyl-2 '-Deoxyuridine (EdU), transwell, and wound healing tests. The circ_0000099/miR-223-3p/CTGF relationship was verified by dual luciferase reporter gene and RNA binding protein immunoprecipitation (RIP) assays.

RESULTS

TGF-β2 treatment promoted SRA01/04 cell proliferation invasion, migration, and EMT. Circ_0000099 expression was increased in POC patients and TGF-β2-treated SRA01/04 cells.Knockdown of circ_0000099 suppressed TGF-β2-induced proliferation, invasion, migration, and EMT in SRA01/04 cells. miR-223-3p was identified as the target of circ_0000099, and miR-223-3p inhibitor might partly abolish the repression of circ_0000099 silencing on TGF-β2-triggered SRA01/04 cell disorders. MiR-223-3p directly targeted CTGF. Knockdown of CTGF suppressed TGF-β2-induced SRA01/04 cell injury. Circ_0000099 can regulate CTGF expression by targeting miR-223-3p.

CONCLUSIONS

Circ_0000099 silencing might relieve TGF-2-induced SRA01/04 cell injury by the miR-223-3p/CTGF axis, providing new avenues for the prevention and treatment of PCO.

Role of circular RNAs in preeclampsia (Review)

Preeclampsia (PE) is a hypertensive disorder of pregnancy characterized by new-onset hypertension and proteinuria after 20 weeks of gestation, which affects 3-8% of pregnant individuals worldwide each year. Prevention, diagnosis and treatment of PE are some of the most important problems faced by obstetrics. There is growing evidence that circular RNAs (circRNAs) are involved in the pathogenesis of PE. The present review summarizes the research progress of circRNAs and then describes the expression patterns of circRNAs in PE and their functional mechanisms affecting PE development. The role of circRNAs as biomarkers for the diagnosis of PE, and the research status of circRNAs in PE are summarized in the hope of finding novel strategies for the prevention and treatment of PE.

Biomarkers and diagnostic significance of non-coding RNAs in extracellular vesicles of pathologic pregnancy

Intercellular communication is an important mechanism for the development and maintenance of normal biological processes in all organs, including the female reproductive system. Extracellular vesicles, as important carriers of intercellular communication, contain a variety of biologically active molecules, such as mRNAs, miRNAs, lncRNAs, and circRNAs, which are involved in cell-to-cell exchanges as well as in many physiological and pathological processes in the body. Compared with biomarkers found in tissues or body fluids, extracellular vesicles show better stability due to the presence of their envelope membrane which prevents the degradation of the RNA message in their vesicles. Therefore, the genomic and proteomic information contained in extracellular vesicles can serve as important markers and potential therapeutic targets for female reproductive system-related diseases or placental function. Moreover, changes in the expression of non-coding RNAs (mainly miRNAs, lncRNAs, and circRNAs) in maternal extracellular vesicles can accurately and promptly reflect the progress of female reproductive system diseases. The aim of this review is to collect information on different types of non-coding RNAs with key molecular carriers in female pathologic pregnancies (preeclampsia and recurrent spontaneous abortion), so as to explore the relevant molecular mechanisms in female pathologic pregnancies and provide a theoretical basis for clinical research on the pathogenesis and therapeutic approaches of reproductive system diseases. The current state of the art of exosome isolation and extraction is also summarized.

Molecular significance of circRNAs in malignant lymphoproliferative disorders: pathogenesis and novel biomarkers or therapeutic targets

Recent studies have shown that circular RNAs (CircRNAs) have the novel functions and molecular mechanisms in the pathogenesis of malignant diseases. CircRNAs have been found to be associated with the occurrence and development of lymphoproliferative diseases, impacting on lymphocyte proliferation. This article provides a review of the pathogenesis of circRNAs in malignant lymphoproliferative disorders, focusing on conditions such as acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), and lymphoma. Additionally, it discusses the potential value of circRNAs as novel biomarkers or therapeutic targets in these disorders.

Hsa_circ_0000825 promotes the progression of laryngeal squamous cell carcinoma by sponging miR-766 and interacting with ELAVL1

Emerging evidence suggests that circular RNAs (circRNAs) are involved in the regulation of tumourigenesis and progression of a variety of malignant tumours. In this study, we aimed to identify laryngeal squamous cell carcinoma (LSCC)-specific circRNAs and explore their biological functions and underlying molecular mechanisms. Employing microarray and qRT-PCR, hsa_circ_0000825 was found to be significantly increased in LSCC tissues versus para-cancerous tissues. High hsa_circ_0000825 expression was positively associated with advanced clinical stages, lymph node metastasis, and poor survival. Furthermore, the overexpression of hsa_circ_0000825 in TU177 and AMC-HN-8 cells promoted cell proliferation. Transwell assays showed enhanced migration and invasion of TU177 and AMC-HN-8 cells upon overexpression of hsa_circ_0000825. Conversely, the knockdown of hsa_circ_0000825 had the opposite effect. Xenograft tumours in BALB/c nude mice derived from hsa_circ_0000825-overexpressed TU177 cells showed greater volume and weight than those derived from control TU177 cells. Mechanistically, nuclear-cytoplasmic fractionation assay confirmed that hsa_circ_0000825 was mainly located in the cytoplasm of TU177 and AMC-HN-8 cells. The AGO2-RNA immunoprecipitation (RIP) assay revealed that hsa_circ_0000825 was significantly enriched in the AGO2-precipitated complex in both TU177 and AMC-HN-8 cells, suggesting that this circRNA may function via a competitive endogenous RNA (ceRNA) mechanism. Next, bioinformatics analysis, biotinylated-oligo pull-down assay and dual-luciferase reporter assay verified that miR-766 could be sponged by hsa_circ_0000825 and also target 3'UTR of HOXD10 mRNA. Moreover, miR-766 was shown to be involved in the pro-oncogenic effect of hsa_circ_0000825. This occurred via the mediation of hsa_circ_0000825-enhanced HOXD10 mRNA by the ceRNA mechanism in TU177 and AMC-HN-8 cells. Besides, RNA-binding protein (RBP) ELAVL1 interacted with hsa_circ_0000825 in TU177 and AMC-HN-8 cells, as revealed through bioinformatics analysis, biotinylated-oligo pull-down assays, and RIP assays. ELAVL1 knockdown decreased cell proliferation by 38 % and 34 % in hsa_circ_0000825-overexpressed TU177 and AMC-HN-8 cells (P < 0.05). Similarly, ELAVL1 was involved in the pro-migration and pro-invasion effects of hsa_circ_0000825 overexpression. In addition, comprehensive analysis of mRNA-seq in hsa_circ_0000825-overexpressed TU177 cells, as well as catRAPID and TCGA databases, suggested that ITGB2, HOXD10, and MTCL1 might be crucial downstream target mRNAs of ELAVL1 in LSCC, participating in the hsa_circ_0000825-ELAVL1 axis pro-oncogenic effect. Taken together, hsa_circ_0000825 plays a pro-oncogenic role in LSCC via the miR-766/HOXD10 axis and ELAVL1 and may serve as a promising specific biomarker and therapeutic target for LSCC.

Circ_0084653 promotes the tumor progression and immune escape in triple-negative breast cancer via the deubiquitination of MYC and upregulation of SOX5

The role of circular RNAs (circRNAs) in cancers is gaining more and more attention, yet related reporters are limited. In triple-negative breast cancer (TNBC), circRNA circ_0084653 originated from COP9 signalosome subunit 5 (COPS5), and COPS5 has been validated to be upregulated in breast cancer before. In our research, COPS5 was also upregulated in TNBC cells, and knockdown of it repressed cell proliferation, invasion, EMT, stemness and PDL-1 protein expression but increased T-cell percentage. Further, circ_0084653 was an aberrantly upregulated circRNA in TNBC cells, and similarly, circ_0084653 silence inhibited TNBC development. Besides, circ_0084653 expression was distributed in both cytoplasm and nucleus. COPS5 overexpression partially rescued the suppressing effects of circ_0084653 depletion in TNBC. Subsequently, circ_0084653 triggered deubiquitination of MYC, the upstream transcription factor of COPS5, via recruiting ubiquitin specific peptidase 36 (USP36). Moreover, circ_0084653 served as the sponge of miR-1323 to release the expression the target gene SRY-box transcription factor 5 (SOX5). SOX5 upregulation completely remedied the inhibiting influence of circ_0084653 downregulation in TNBC. Meanwhile, transcription factor SOX5 activated transcriptionally circ_0084653. To sum up, SOX5-induced circ_0084653 promotes TNBC via the deubiquitination of USP36, which may provide some fresh ideas for TNBC-related molecular mechanisms.

CircVCAN promotes glioma progression through the miR-488-3p/MEF2C-JAGGED1 axis

Gliomas are the most prevalent primary malignant brain tumors worldwide. Growing evidences indicate that circular RNAs (circRNAs) play an important role in the regulation of biological behavior of tumors. We aimed to investigate the role and mechanism of circVCAN in glioma. RNase R treatment was utilized to assess the cyclic properties of circVCAN. CircVCAN, miR-488-3p, and myocyte enhancer factor 2C (MEF2C) levels in glioma tissues and cells were detected by reverse transcription real-time polymerase chain reaction (RT-qPCR), and the localization of them in glioma cells was determined with fluorescence in situ hybridization. Furthermore, a variety of biologically functional assessments were used to validate the role of circVCAN in glioma. The regulatory mechanisms of circVCAN, miR-488-3p, and MEF2C were further confirmed by double luciferase reporter gene assay, RNA immunoprecipitation and RNA pull-down assay, and the binding of MEF2C to JAGGED1 was revealed by chromatin immunoprecipitation. Additionally, a xenograft tumor model was constructed to demonstrate the effect of circVCAN on tumor growth in vivo. Our results indicated that circVCAN was more stable than its linear RNA and was significantly upregulated in gliomas. CircVCAN overexpression stimulated glioma cells to proliferate and metastasize, but circVCAN silencing exerted the opposite effect. Meanwhile, silencing circVCAN inhibited tumor growth in vivo. Moreover, we found that circVCAN interacted with miR-488-3p to regulate MEF2C expression, and miR-488-3p inhibition or MEF2C overexpression reversed the inhibitory effect on malignant bio-behaviors mediated by circVCAN knockdown in glioma cells. MEF2C promoted the transcription of JAGGED1, and circVCAN knockdown reduced the binding between MEF2C and JAGGED1. Collectively, circVCAN is a carcinogenic circRNA in glioma, and the circVCAN/miR-488-3p/MEF2C-JAGGED1 axis could serve as a potential target for the management of glioma.

Mucin 1 expression is regulated by hsa_circ_0055054/microRNA‑122‑5p and promotes hepatocellular carcinoma development

The abnormal expression of mucin 1 (MUC1) is a major cause of poor prognosis in patients with hepatocellular carcinoma (HCC). Competitive endogenous RNA demonstrates a novel regulatory mechanism that can affect the biological behavior of tumors. In the present study, the regulatory functions of hsa_circ_0055054 as well as those of microRNA (miR/miRNA) 122-5p on MUC1 expression and its role in HCC cell proliferation, migration and invasion, were evaluated. MUC1 expression was assessed using western blotting and reverse transcription-quantitative PCR. The phenotypic functions of the HCC cell lines were evaluated following MUC1 knockdown using Cell Counting Kit-8, wound healing and Transwell assays. Bioinformatics tools were used to identify specific miRNAs and circular (circ)RNAs that interact with and can regulate MUC1. The stability of circRNAs was assessed using a Ribonuclease R assay. The binding of circRNA/miRNA/MUC1 was assessed using dual-luciferase reporter assays and cellular function tests. Finally, in vivo experiments were performed using animal models. The results demonstrated that in MHCC97L cells, MUC1 and hsa_circ_0055054 were expressed at high levels while miR-122-5p was downregulated. The proliferation, migration and invasion of MHCC97L cells were suppressed by low MUC1 expression. hsa_circ_0055054 knockdown or miR-122-5p overexpression both led to a decrease in MUC1 expression. In MHCC97L cells with a low MUC1 expression caused by hsa_circ_0055054 knockdown, miR-122-5p inhibition resulted in the increased proliferation, migration and invasion of MHCC97L cells. In combination, the results of the present study indicate that hsa_circ_0055054 knockdown in MHCC97L cells leads to an increased expression of miR-122-5p and decreased expression of MUC1, which results in the inhibition of MHCC97L cell proliferation, migration and invasion.

Circulating exosomal circRNA-miRNA-mRNA network in a familial partial lipodystrophy type 3 family with a novel PPARG frameshift mutation c.418dup

Familial partial lipodystrophy 3 (FPLD3) is a rare genetic disorder caused by loss-of-function mutations in the PPARG gene, characterized by a selective absence of subcutaneous fat and associated metabolic complications. However, the molecular mechanisms of FPLD3 remain unclear. In this study, we recruited a 17-yr-old Chinese female with FPLD3 and her family, identifying a novel PPARG frameshift mutation (exon 4: c.418dup: p.R140Kfs*7) that truncates the PPARγ protein at the seventh amino acid, significantly expanding the genetic landscape of FPLD3. By performing next-generation sequencing of circular RNAs (circRNAs), microRNAs (miRNAs), and mRNAs in plasma exosomes, we discovered 59 circRNAs, 57 miRNAs, and 299 mRNAs were significantly altered in the mutation carriers compared with the healthy controls. Integration analysis highlighted that the circ_0001597-miR-671-5p pair and 18 mRNAs might be incorporated into the metabolic regulatory networks of the FPLD3 induced by the novel PPARG mutation. Functional annotation suggested that these genes were significantly enriched in glucose- and lipid metabolism-related pathways. Among the circRNA-miRNA-mRNA network, we identified two critical regulators, early growth response-1 (EGR1), a key transcription factor known for its role in insulin signaling pathways and lipid metabolism, and 1-acylglycerol-3-phosphate O-acyltransferase 3 (AGPAT3), which gets involved in the biosynthesis of triglycerides and lipolysis. Circ_0001597 regulates the expression of these genes through miR-671-5p, potentially contributing to the pathophysiology of FPLD3. Overall, this study clarified a circulating exosomal circRNA-miRNA-mRNA network in a FPLD3 family with a novel PPARG mutation, providing evidence for exploring promising biomarkers and developing novel therapeutic strategies for this rare genetic disorder.NEW & NOTEWORTHY Through the establishment of a ceRNA regulatory networks in a novel PPARG frameshift mutation c.418dup-induced FPLD3 pedigree, this study reveals that circ_0001597 may contribute to the pathophysiology of FPLD3 by sequestering miR-671-5p to regulate the expression of EGR1 and AGPAT3, pivotal genes situated in the triglyceride (TG) synthesis and lipolysis pathways. Current findings expand our molecular understanding of adipose tissue dysfunction, providing potential blood biomarkers and therapeutic avenues for lipodystrophy and associated metabolic complications.

Adipocytes promote metastasis of breast cancer by attenuating the FOXO1 effects and regulating copper homeostasis

BACKGROUND

Obesity and the forkhead box O1(FOXO1) affect the survival of breast cancer patients, but the underlying mechanism remains unclear. We aimed to investigate the role of FOXO1 in obesity-associated-breast cancer.

METHODS

We screened 383 breast disease patients from the first affiliated hospital with Nanjing Medical University in 2020. We performed wound healing, transwell, matrigel assays to assess the metastatic ability of cancer cells. We adopted mRNAs sequencing to select the differentially expressed transcripts in breast cancer. We applied immunohistochemistry, western blot, tissue microarrays to assess the level of FOXO1 and epithelial-mesenchymal transition (EMT) pathways. We conducted bioinformatic analysis to investigate interactions between FOXO1 and miR-135b. We used fluorescence in situ hybridization, RT-qPCR to confirm the characteristics of circCNIH4. We conducted luciferase reporter assay, rescue experiments to investigate interactions between circCNIH4 and miR-135b.

RESULTS

Obesity was positively correlated with the incidence and progression of breast cancer. Adipocytes enhanced the migration of breast cancer and attenuated the effects of FOXO1. MiR-135b was a binding gene of FOXO1 and was regulated by circCNIH4. CircCNIH4 exhibited antitumor activity in vitro and in vivo.

CONCLUSION

Adipocytes might accelerate the progression of breast cancer by modulating FOXO1/miR-135b/ circCNIH4 /EMT axis and regulating copper homeostasis.

Downregulation of circ-RAPGEF5 inhibits colorectal cancer progression by reducing the expression of polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3)

BACKGROUND

Circular RNA (circRNA) plays a crucial role in the pathogenesis and progression of colorectal cancer (CRC). However, the current understanding of the emerging function and mechanism of circ-RAPGEF5 in CRC remains poorly understood.

METHODS

We first evaluated the expression level of circ-RAPGEF5 in CRC tissues and cells by quantitative real-time polymerase chain reaction (qRT-PCR). Then, we analyzed cell proliferation (EdU and colony formation assay), migration (cell wound healing assay), invasion (transwell assay), and apoptosis (flow cytometry assay). To further elucidate the mechanism of circ-RAPGEF5 in CRC, bioinformatics tools, Dual-luciferase reporter assay, Ago2 RNA immunoprecipitation assay, and RNA pull-down assay were employed. Moreover, we established a CRC transplantation tumor model to evaluate the effect of circ-RAPGEF5 on tumor growth in vivo.

RESULTS

circ-RAPGEF5 was significantly upregulated in CRC tissues and CRC cells. Furthermore, the downregulation of circ-RAPGEF5 restrained CRC cell proliferation, migration, and invasion, and promoted cell apoptosis in vitro. Mechanistically, circ-RAPGEF5 accelerated the malignant behaviors of CRC cells by sponging miR-545-5p, which targeted polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3). In addition, we revealed that circ-RAPGEF5 silence curbed tumor growth in vivo.

CONCLUSION

These findings revealed that circ-RAPGEF5 played an oncogenic role through the miR-545-5p/GALNT3 axis in CRC progression, providing potential therapeutic targets for the treatment of CRC.

Circular RNAs in tuberculosis and lung cancer

This review signifies the role of circular RNAs (circRNAs) in tuberculosis (TB) and lung cancer (LC), focusing on pathogenesis, diagnosis, and treatment. CircRNAs, a newly discovered type of non-coding RNA, have emerged as key regulators of gene expression and promising biomarkers in various bodily fluids due to their stability. The current review discusses circRNA biogenesis, highlighting their RNase-R resistance due to their loop forming structure, making them effective biomarkers. It details their roles in gene regulation, including splicing, transcription control, and miRNA interactions, and their impact on cellular processes and diseases. For LC, the review identifies circRNA dysregulation affecting cell growth, motility, and survival, and their potential as therapeutic targets and biomarkers. In TB, it addresses circRNAs' influence on host anti-TB immune responses, proposing their use as early diagnostic markers. The paper also explores the interplay between TB and LC, emphasizing circRNAs as dual biosignatures, and the necessity for differential diagnosis. It concludes that no single circRNA biomarker is universally applicable for both TB and LC. Ultimately, the review highlights the pivotal role of circRNAs in TB and LC, encouraging further research in biomarker identification and therapeutic development concomitant for both diseases.

N6-methyladenosine modification of circMARK2 enhances cytoplasmic export and stabilizes LIN28B, contributing to the progression of Wilms tumor

BACKGROUND

The potential involvement of circular RNAs (circRNAs) and N6-methyladenosine (m6A) modification in the progression of Wilms tumor (WT) has not been fully elucidated. This study investigates the regulatory mechanisms and clinical significance of m6A-modified circMARK2 and its role in WT progression.

METHODS

We identified dysregulated circRNAs through deep sequencing and validated their expression by qRT-PCR in WT tissues. The biological functions of circMARK2 were assessed using clone formation, transwell migration, and orthotopic animal models. To dissect the underlying mechanisms, we employed RNA immunoprecipitation, RNA pull-down, dual-luciferase reporter assays, Western blotting, and immunofluorescence and immunohistochemical staining.

RESULTS

CircMARK2, upregulated in WT tissues, was found to be m6A-modified and promoted cytoplasmic export. It facilitated WT progression by stabilizing LIN28B mRNA through the circMARK2/IGF2BP2 interaction. In vitro and in vivo studies demonstrated that circMARK2 enhances the malignant behavior of WT cells. Clinically, higher circMARK2 levels in tumor tissues of WT patients were linked to increased tumor aggressiveness and reduced survival rates.

CONCLUSIONS

Our study provides the first comprehensive evidence that m6A-modified circMARK2 contributes to WT progression by enhancing LIN28B mRNA stability, promoting cellular aggressiveness. CircMARK2 emerges as a potential biomarker for prognosis and a promising target for therapeutic intervention in WT, underscoring the clinical relevance of m6A modification in pediatric renal cancer.

CircTrim37 Ameliorates Intracerebral Hemorrhage Outcomes by Modulating Microglial Polarization via the miR-30c-5p/SOCS3 Axis

Circular RNAs (circRNAs) have been progressively recognized as critical regulators in the pathology and pathophysiology of central nervous system disease. However, the potential role of circRNAs in intracerebral hemorrhage (ICH) is still largely unclear. Here, we demonstrate that circTrim37 expression was significantly upregulated at 3 days after ICH by circular RNA microarray and qPCR assays. Overexpression of circTrim37 could significantly ameliorate brain injury volume, brain edema, neurologic deficits, and inflammation in vivo after ICH. CircTrim37 promotes M2 polarization while restrains M1 polarization in vitro. Furthermore, circTrim37 acts as an endogenous sponge for miR-30c-5p, thereby inhibiting miR-30c-5p activity, leading to the upregulation of SOCS3 and making the balance of microglial response towards an M2 phenotype. Taken together, our results indicate the participation of circTrim37 and its coupling mechanism in ICH and provide a novel therapeutic target for ICH.

MicroRNA-409: Molecular functions and clinical applications in cancer

Late diagnosis is one of the main reasons for high mortality rates in cancer patients. Therefore, investigating the molecular mechanisms involved in tumor progression can improve the cancer diagnosis in the early stages of the tumor progression. MicroRNAs (miRNAs) have important roles in regulation of cell growth, proliferation, metabolism, and migration. Since, deregulation of miR-409 has been reported in a wide range of cancers, in the present review, we investigated the molecular mechanisms of miR-409 during tumor progression and invasion. It has been shown that miR-409 functions as a tumor suppressor in different tumor types. MiR-409 can reduce tumor cell proliferation, growth, and migration by regulation of signaling pathways, cellular metabolism, transcription factors, and cellular adhesion. This review can be an effective step in introducing miR-409 as a non-invasive marker in cancer patients.

Subcellular localization of circular RNAs: Where and why

Localization of RNAs at specific subcellular locations regulating various local cellular events has gained much attention recently. Like most other classes of RNAs, the function of newly discovered circular RNAs (circRNAs) is predominantly determined by their association with different cellular factors in the cell. CircRNAs function as transcriptional and posttranscriptional regulators of gene expression by interacting with transcription factors, splicing regulators, RNA-binding proteins, and microRNAs or by translating into functional polypeptides. Hence, studying their subcellular localization to assess their function is essential. The discovery of more than a million circRNA and increasing evidence of their involvement in development and diseases require a thorough analysis of their subcellular localization linking to their biological functions. Here, we summarize current knowledge of circRNA localization in cells and extracellular vesicles, factors regulating their subcellular localization, and the implications of circRNA localization on their cellular functions. Given the discovery of many circRNAs in all life forms and their implications in pathophysiology, we discuss the challenges in studying circRNA localization and the opportunities for unlocking the mystery of circRNA functions.

Identification and characterization of Varicella Zoster Virus circular RNA in lytic infection

This study investigates the role of circular RNAs (circRNAs) in the context of Varicella-Zoster Virus (VZV) lytic infection. We employ two sequencing technologies, short-read sequencing and long-read sequencing, following RNase R treatment on VZV-infected neuroblastoma cells to identify and characterize both cellular and viral circRNAs. Our large scanning analysis identifies and subsequent experiments confirm 200 VZV circRNAs. Moreover, we discover numerous VZV latency-associated transcripts (VLTs)-like circRNAs (circVLTslytic), which contain multiple exons and different isoforms within the same back-splicing breakpoint. To understand the functional significance of these circVLTslytic, we utilize the Bacteria Artificial Chromosome system to disrupt the expression of viral circRNAs in genomic DNA location. We reveal that the sequence flanking circVLTs' 5' splice donor plays a pivotal role as a cis-acting element in the formation of circVLTslytic. The circVLTslytic is dispensable for VZV replication, but the mutation downstream of circVLTslytic exon 5 leads to increased acyclovir sensitivity in VZV infection models. This suggests that circVLTslytic may have a role in modulating the sensitivity to antiviral treatment. The findings shed new insight into the regulation of cellular and viral transcription during VZV lytic infection, emphasizing the intricate interplay between circRNAs and viral processes.

Three-layer heterogeneous network based on the integration of CircRNA information for MiRNA-disease association prediction

Increasing research has shown that the abnormal expression of microRNA (miRNA) is associated with many complex diseases. However, biological experiments have many limitations in identifying the potential disease-miRNA associations. Therefore, we developed a computational model of Three-Layer Heterogeneous Network based on the Integration of CircRNA information for MiRNA-Disease Association prediction (TLHNICMDA). In the model, a disease-miRNA-circRNA heterogeneous network is built by known disease-miRNA associations, known miRNA-circRNA interactions, disease similarity, miRNA similarity, and circRNA similarity. Then, the potential disease-miRNA associations are identified by an update algorithm based on the global network. Finally, based on global and local leave-one-out cross validation (LOOCV), the values of AUCs in TLHNICMDA are 0.8795 and 0.7774. Moreover, the mean and standard deviation of AUC in 5-fold cross-validations is 0.8777+/-0.0010. Especially, the two types of case studies illustrated the usefulness of TLHNICMDA in predicting disease-miRNA interactions.

CircWHSC1 (CircNSD2): A Novel Circular RNA in Multiple Cancers

Circular RNAs (circRNAs) are a type of non-coding RNA (ncRNA) that possesses a unique single-stranded circular structure. They are primarily formed through alternative splicing of pre-mRNA (messenger RNA). The primary biological function of circRNAs is to regulate gene expression at both the transcriptional and post-transcriptional levels. Recent studies have increasingly demonstrated a close association between the dysregulation of circRNAs and the progression of diverse cancers, where they can function as either tumor suppressors or oncogenes. circWHSC1 (circNSD2) is a circular ncRNA that originates from the first 2 exons of the Wolf-Hirschhorn syndrome candidate gene (WHSC1). As Chen 2019 discovery that circWHSC1 (circNSD2) functions as a sponge for miRNAs and promotes cancer, this circRNA has garnered significant interest among researchers. circWHSC1 (circNSD2) has been found to be up-regulated in various malignant tumors, including nasopharyngeal carcinoma, lung cancer, breast cancer, liver cancer, colorectal cancer, ovarian cancer, cervical cancer, and endometrial cancer. It exerts its effects on cancer by either inhibiting or promoting the expression of related genes through direct or indirect pathways, ultimately affecting cancer proliferation, invasion, and prognosis. This article provides a comprehensive review and discussion of the biological roles of circWHSC1 (circNSD2) and its target genes in various cancers, as well as the latest research progress on related molecular biological regulatory mechanisms. Furthermore, the potential significance of circWHSC1 (circNSD2) in future clinical applications and transformations is thoroughly analyzed and discussed.