Circular RNAs as Therapeutic Agents and Targets

Circular RNAs in laryngeal cancer

Laryngeal cancer remains a significant global health concern, with poor prognosis for advanced-stage disease highlighting the need for novel diagnostic, prognostic, and therapeutic approaches. Circular RNAs (circRNAs), a class of covalently closed non-coding RNAs, have emerged as important regulators of gene expression and cellular processes in various cancers, including laryngeal cancer. This review summarizes the current understanding of circRNAs in laryngeal cancer, covering their biogenesis, regulatory mechanisms, and potential clinical applications. We explore the diverse functions of circRNAs, including their roles as miRNA sponges, protein interactors, and direct mRNA regulators, and their influence on key cellular processes such as proliferation, invasion, and metastasis. The review highlights promising circRNAs as diagnostic and prognostic biomarkers, as well as potential therapeutic targets. We also outline current strategies for circRNA modulation, including suppression techniques like RNA interference and CRISPR/Cas systems, and overexpression methods using vectors and synthetic circRNAs.

Advancements in Omics and Breakthrough Gene Therapies: A Glimpse into the Future of Peripheral Artery Disease

Peripheral artery disease (PAD), a highly prevalent global disease, associates with significant morbidity and mortality in affected patients. Despite progress in endovascular and open revascularization techniques for advanced PAD, these interventions grapple with elevated rates of arterial restenosis and vein graft failure attributed to intimal hyperplasia (IH). Novel multiomics technologies, coupled with sophisticated analyses tools recently powered by advances in artificial intelligence, have enabled the study of atherosclerosis and IH with unprecedented single-cell and spatial precision. Numerous studies have pinpointed gene hubs regulating pivotal atherogenic and atheroprotective signaling pathways as potential therapeutic candidates. Leveraging advancements in viral and nonviral gene therapy (GT) platforms, gene editing technologies, and cutting-edge biomaterial reservoirs for delivery uniquely positions us to develop safe, efficient, and targeted GTs for PAD-related diseases. Gene therapies appear particularly fitting for ex vivo genetic engineering of IH-resistant vein grafts. This manuscript highlights currently available state-of-the-art multiomics approaches, explores promising GT-based candidates, and details GT delivery modalities employed by our laboratory and others to thwart mid-term vein graft failure caused by IH, as well as other PAD-related conditions. The potential clinical translation of these targeted GTs holds the promise to revolutionize PAD treatment, thereby enhancing patients' quality of life and life expectancy.

CircRNA and lncRNA-encoded peptide in diseases, an update review

Non-coding RNAs (ncRNAs), including circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs), are unique RNA molecules widely identified in the eukaryotic genome. Their dysregulation has been discovered and played key roles in the pathogenesis of numerous diseases, including various cancers. Previously considered devoid of protein-coding ability, recent research has revealed that a small number of open reading frames (ORFs) within these ncRNAs endow them with the potential for protein coding. These ncRNAs-derived peptides or proteins have been proven to regulate various physiological and pathological processes through diverse mechanisms. Their emerging roles in disease diagnosis and targeted therapy underscore their potential utility in clinical settings. This comprehensive review aims to provide a systematic overview of proteins or peptides encoded by lncRNAs and circRNAs, elucidate their production and functional mechanisms, and explore their promising applications in cancer diagnosis, disease prediction, and targeted therapy.

The role of circular RNA during the urological cancer metastasis: exploring regulatory mechanisms and potential therapeutic targets

Metastasis is a major contributor to treatment failure and death in urological cancers, representing an important biomedical challenge at present. Metastases form as a result of cancer cells leaving the primary site, entering the vasculature and lymphatic vessels, and colonizing clones elsewhere in the body. However, the specific regulatory mechanisms of action underlying the metastatic process of urological cancers remain incompletely elucidated. With the deepening of research, circular RNAs (circRNAs) have been found to not only play a significant role in tumor progression and prognosis but also show aberrant expression in various tumor metastases, consequently impacting tumor metastasis through multiple pathways. Therefore, circRNAs are emerging as potential tumor markers and treatment targets. This review summarizes the research progress on elucidating how circRNAs regulate the urological cancer invasion-metastasis cascade response and related processes, as well as their role in immune microenvironment remodeling and circRNA vaccines. This body of work highlights circRNA regulation as an emerging therapeutic target for urological cancers, which should motivate further specific research in this regard.

Circular RNA as a Biomarker for Diagnosis, Prognosis and Therapeutic Target in Acute and Chronic Lymphoid Leukemia

Circular RNAs (circRNAs) are single-stranded RNAs that have received much attention in recent years. CircRNAs lack a 5' head and a 3' poly-A tail. The structure of this type of RNAs make them resistant to digestion by exonucleases. CircRNAs are expressed in different cells and have various functions. The function of circRNAs is done by sponging miRNAs, changing gene expression, and protein production. The expression of circRNAs changes in different types of cancers, which causes changes in cell growth, proliferation, differentiation, and apoptosis. Changes in the expression of circRNAs can cause the invasion and progression of tumors. Studies have shown that changes in the expression of circRNAs can be seen in acute lymphoid leukemia (ALL) and chronic lymphoid leukemia (CLL). The conducted studies aim to identify circRNAs whose expression has changed in these leukemias and their more precise function so that these circRNAs can be identified as biomarkers, prediction of patient prognosis, and treatment targets for ALL and CLL patients. In this study, we review the studies conducted on the role and function of circRNAs in ALL and CLL patients. The results of the studies show that there is a possibility of using circRNAs as biomarkers in the identification and treatment of patients in the future.

Exploring the impact of circRNAs on cancer glycolysis: Insights into tumor progression and therapeutic strategies

Cancer cells exhibit altered metabolic pathways, prominently featuring enhanced glycolytic activity to sustain their rapid growth and proliferation. Dysregulation of glycolysis is a well-established hallmark of cancer and contributes to tumor progression and resistance to therapy. Increased glycolysis supplies the energy necessary for increased proliferation and creates an acidic milieu, which in turn encourages tumor cells' infiltration, metastasis, and chemoresistance. Circular RNAs (circRNAs) have emerged as pivotal players in diverse biological processes, including cancer development and metabolic reprogramming. The interplay between circRNAs and glycolysis is explored, illuminating how circRNAs regulate key glycolysis-associated genes and enzymes, thereby influencing tumor metabolic profiles. In this overview, we highlight the mechanisms by which circRNAs regulate glycolytic enzymes and modulate glycolysis. In addition, we discuss the clinical implications of dysregulated circRNAs in cancer glycolysis, including their potential use as diagnostic and prognostic biomarkers. All in all, in this overview, we provide the most recent findings on how circRNAs operate at the molecular level to control glycolysis in various types of cancer, including hepatocellular carcinoma (HCC), prostate cancer (PCa), colorectal cancer (CRC), cervical cancer (CC), glioma, non-small cell lung cancer (NSCLC), breast cancer, and gastric cancer (GC). In conclusion, this review provides a comprehensive overview of the significance of circRNAs in cancer glycolysis, shedding light on their intricate roles in tumor development and presenting innovative therapeutic avenues.

Advanced approaches of the use of circRNAs as a replacement for cancer therapy

Cancer is a broad name for a group of diseases in which abnormal cells grow out of control and are characterized by their complexity and recurrence. Although there has been progress in cancer therapy with the entry of precision medicine and immunotherapy, cancer incidence rates have increased globally. Non-coding RNAs in the form of circular RNAs (circRNAs) play crucial roles in the pathogenesis, clinical diagnosis, and therapy of different diseases, including cancer. According to recent studies, circRNAs appear to serve as accurate indicators and therapeutic targets for cancer treatment. However, circRNAs are promising candidates for cutting-edge cancer therapy because of their distinctive circular structure, stability, and wide range of capabilities; many challenges persist that decrease the applications of circRNA-based cancer therapeutics. Here, we explore the roles of circRNAs as a replacement for cancer therapy, highlight the main challenges facing circRNA-based cancer therapies, and discuss the key strategies to overcome these challenges to improve advanced innovative therapies based on circRNAs with long-term health effects.

A cis-acting ligase ribozyme generates circular RNA in vitro for ectopic protein functioning

Delivering synthetic protein-coding RNA bypassing the DNA stage for ectopic protein functioning is a novel therapeutic strategy. Joining the linear RNA head-to-tail covalently could be a state-of-the-art strategy for functioning longer. Here we enroll a cis-acting ligase ribozyme (RzL) to generate circular RNA (circRNA) in vitro for ectopic protein expression. The RNA circularization is confirmed by masking the 5' phosphate group, resisting exonuclease RNase R digestion, failing for further tailing, and sequencing the RT-PCR products of the joined region. Interestingly, one internal ribosome entry site (IRES) renders circRNA translation competent, but two IRES in cis, not trans, hamper the translation. The circRNA with highly potent in translation is conferred for antiviral functioning. Accompanying specific guided RNA, a circRNA expressing ribonuclease Cas13 shows excellent potential against the corresponding RNA virus, further extending circRNA functioning in its growing list of applications.

Advanced strategies of targeting circular RNAs as therapeutic approaches in colorectal cancer drug resistance

Colorectal cancer (CRC) stands second in terms of mortality and third among the highest prevalent kinds of cancer globally. CRC prevalence is rising in moderately and poorly developed regions and is greater in economically advanced regions. Despite breakthroughs in targeted therapy, resistance to chemotherapeutics remains a significant challenge in the long-term management of CRC. Circular RNAs (circRNAs) have been involved in growing cancer therapy resistance, particularly in CRC, according to an increasing number of studies in recent years. CircRNAs are one of the novel subclasses of non-coding RNAs, previously thought of as viroid. According to studies, circRNAs have been recommended as biological markers for therapeutic targets and diagnostic and prognostic purposes. That is particularly notable given that the expression of circRNAs has been linked to the hallmarks of CRC since they are responsible for drug resistance in CRC patients; thereby, circRNAs are significant for chemotherapy failure. Moreover, knowledge concerning circRNAs remains relatively unclear despite using all these advanced techniques. Here, in this study, we will go over the most recent published work to highlight the critical roles of circRNAs in CRC development and drug resistance and highlight the main strategies to overcome drug resistance to improve clinical outcomes.

New insights into the potential of exosomal circular RNAs in mediating cancer chemotherapy resistance and their clinical applications

Chemotherapy resistance typically leads to tumour recurrence and is a major obstacle to cancer treatment. Increasing numbers of circular RNAs (circRNAs) have been confirmed to be abnormally expressed in various tumours, where they participate in the malignant progression of tumours, and play important roles in regulating the sensitivity of tumours to chemotherapy drugs. As exosomes mediate intercellular communication, they are rich in circRNAs and exhibit a specific RNA cargo sorting mechanism. By carrying and delivering circRNAs, exosomes can promote the efflux of chemotherapeutic drugs and reduce intracellular drug concentrations in recipient cells, thus affecting the cell cycle, apoptosis, autophagy, angiogenesis, invasion and migration. The mechanisms that affect the phenotype of tumour stem cells, epithelial-mesenchymal transformation and DNA damage repair also mediate chemotherapy resistance in many tumours. Exosomal circRNAs are diagnostic biomarkers and potential therapeutic targets for reversing chemotherapy resistance in tumours. Currently, the rise of new fields, such as machine learning and artificial intelligence, and new technologies such as biosensors, multimolecular diagnostic systems and platforms based on circRNAs, as well as the application of exosome-based vaccines, has provided novel ideas for precision cancer treatment. In this review, the recent progress in understanding how exosomal circRNAs mediate tumour chemotherapy resistance is reviewed, and the potential of exosomal circRNAs in tumour diagnosis, treatment and immune regulation is discussed, providing new ideas for inhibiting tumour chemotherapy resistance.

Exploring circular RNAs as biomarkers for Parkinson's disease and their expression changes after aerobic exercise rehabilitation

Circular RNAs (circRNAs) are circularized single-stranded ribonucleic acids that interacts with DNA, RNA, and proteins to play critical roles in cell biology. CircRNAs regulate microRNA content, gene expression, and may code for specific peptides. Indeed, circRNAs are differentially expressed in neurodegenerative disorders like Parkinson's disease (PD), playing a potential role in the mechanisms of brain pathology. The RNA molecules with aberrant expression in the brain can cross the blood-brain barrier and reach the bloodstream, which enable their use as non-invasive PD disease biomarker. Promising targets with valuable discriminatory ability in combined circRNA signatures include MAPK9_circ_0001566, SLAIN1_circ_0000497, SLAIN2_circ_0126525, PSEN1_circ_0003848, circ_0004381, and circ_0017204. On the other hand, regular exercises are effective therapy for mitigating PD symptoms, promoting neuroprotective effects with epigenetic modulation. Aerobic exercises slow symptom progression in PD by improving motor control, ameliorating higher functions, and enhancing brain activity and neuropathology. These improvements are accompanied by changes circRNA expression, including hsa_circ_0001535 (circFAM13B) and hsa_circ_0000437 (circCORO1C). The sensitivity of current methods for detecting circulating circRNAs is considered a limitation. While amplification kits already exist for low-abundant microRNAs, similar kits are needed for circRNAs. Alternatively, the use of digital PCR can help overcome this constraint. The current review examines the potential use of circRNAs as non-invasive biomarkers of PD and to assess the effects of rehabilitation. Although circRNAs hold promise as targets for PD diagnosis and therapeutics, further validation is needed before their clinical implementation.

The 9p21.3 coronary artery disease risk locus drives vascular smooth muscle cells to an osteochondrogenic state

Genome-wide association studies have identified common genetic variants at ~400 human genomic loci linked to coronary artery disease (CAD) susceptibility. Among these genomic regions, the most impactful is the 9p21.3 CAD risk locus, which spans a 60 kb gene desert and encompasses ~80 SNPs in high linkage disequilibrium. Despite nearly two decades since its discovery, the functional mechanism of this genomic region remains incompletely resolved. To investigate the transcriptional gene programs mediated by 9p21.3 risk locus, we applied a model of induced pluripotent stem cells (iPSCs) from risk and non-risk donors at 9p21.3, as well as isogenic lines with a full haplotype deletion. Upon differentiation to vascular smooth muscle cells (VSMC), single-cell transcriptomic profiling demonstrated iPSC-VSMC phenotypes resembling those from native human coronary arteries, confirming the robustness of this model. Remarkably, our analyses revealed that VSMCs harboring the 9p21.3 risk haplotype preferentially adopt an osteochondrogenic state. Importantly, we identified LIMCH1 and CRABP1 as signature genes critical for defining this transcriptional program. Our study provides new insights into the mechanism at the 9p21.3 risk locus and defines its role in driving a disease-prone transcriptional state in VSMCs.

Engineering circular RNA for molecular and metabolic reprogramming

The role of messenger RNA (mRNA) in biological systems is extremely versatile. However, it's extremely short half-life poses a fundamental restriction on its application. Moreover, the translation efficiency of mRNA is also limited. On the contrary, circular RNAs, also known as circRNAs, are a common and stable form of RNA found in eukaryotic cells. These molecules are synthesized via back-splicing. Both synthetic circRNAs and certain endogenous circRNAs have the potential to encode proteins, hence suggesting the potential of circRNA as a gene expression machinery. Herein, we aim to summarize all engineering aspects that allow exogenous circular RNA (circRNA) to prolong the time that proteins are expressed from full-length RNA signals. This review presents a systematic engineering approach that have been devised to efficiently assemble circRNAs and evaluate several aspects that have an impact on protein production derived from. We have also reviewed how optimization of the key components of circRNAs, including the topology of vector, 5' and 3' untranslated sections, entrance site of the internal ribosome, and engineered aptamers could be efficiently impacting the translation machinery for molecular and metabolic reprogramming. Collectively, molecular and metabolic reprogramming present a novel way of regulating distinctive cellular features, for instance growth traits to neoplastic cells, and offer new possibilities for therapeutic inventions.

Circular RNA regulatory role in pathological cardiac remodelling

Cardiac remodelling involves structural, cellular and molecular alterations in the heart after injury, resulting in progressive loss of heart function and ultimately leading to heart failure. Circular RNAs (circRNAs) are a recently rediscovered class of non-coding RNAs that play regulatory roles in the pathogenesis of cardiovascular diseases, including heart failure. Thus, a more comprehensive understanding of the role of circRNAs in the processes governing cardiac remodelling may set the ground for the development of circRNA-based diagnostic and therapeutic strategies. In this review, the current knowledge about circRNA origin, conservation, characteristics and function is summarized. Bioinformatics and wet-lab methods used in circRNA research are discussed. The regulatory function of circRNAs in cardiac remodelling mechanisms such as cell death, cardiomyocyte hypertrophy, inflammation, fibrosis and metabolism is highlighted. Finally, key challenges and opportunities in circRNA research are discussed, and orientations for future work to address the pharmacological potential of circRNAs in heart failure are proposed.

CircMLH3 induces mononuclear macrophage pyroptosis in sepsis by sponging miR-590-3p to regulate TAK1 expression

Sepsis is a fatal syndrome characterized by uncontrolled systemic inflammatory responses. Circular RNAs (circRNAs) are involved in the modulation of various pathophysiological processes, but their potential role in sepsis has largely been unexplored. In this study, we observed differential expression of circMLH3 between healthy volunteers and septic patients, and revealed the value of circMLH3 for sepsis diagnosis and prognostic prediction. Interestingly, we discovered a correlation between the expression level of circMLH3 and the degree of pyroptosis, a critical mechanism contributing to uncontrolled inflammation in sepsis patients. Knocking down circMLH3 alleviated macrophage pyroptosis whereas overexpressing circMLH3 aggravated pyroptosis. circMLH3 regulated macrophage pyroptosis by sponging miR-590-3p and subsequently modulating TAK1 expression. Furthermore, we found that the miR-590-3p/TAK1 axis inhibited the activation of pro-caspase-1 and the NLRP3 inflammasome. miR-590-3p overexpression had a protective effect by reducing macrophage pyroptosis, thereby alleviating sepsis-induced lung injury and systemic inflammatory responses. In conclusion, our study elucidated the circMLH3/miR-590-3p/TAK1 signaling pathway and identified its role in regulating mononuclear macrophage pyroptosis, thus providing potential novel targets and strategies for sepsis diagnosis and therapy.

A therapeutical insight into the correlation between circRNAs and signaling pathways involved in cancer pathogenesis

Pre-messenger RNA molecules are back-spliced to create circular RNAs, which are non-coding RNA molecules. After a thorough investigation, it was discovered that these circRNAs have critical biological roles. CircRNAs have a variety of biological functions, including their ability to operate as microRNA sponges, interact with proteins to alter their stabilities and activities, and provide templates for the translation of proteins. Evidence supports a link between the emergence of numerous diseases, including various cancer types, and dysregulated circRNA expression. It is commonly known that a significant contributing element to cancer development is the disruption of numerous molecular pathways essential for preserving cellular and tissue homeostasis. The dysregulation of multiple biological processes is one of the hallmarks of cancer, and the molecular pathways linked to these processes are thought to be promising targets for therapeutic intervention. The biological and carcinogenic effects of circRNAs in the context of cancer are thoroughly reviewed in this article. Specifically, we highlight circRNAs' involvement in signal transduction pathways and their possible use as novel biomarkers for the early identification and prognosis of human cancer.

Engineering Synthetic circRNAs for Efficient CNS Expression

Circular RNAs (circRNAs) have recently emerged as a promising modality for gene and RNA-based therapies. They are more stable than their linear counterpart and can be designed for efficient expression in different cell and tissue types. In this chapter, we developed different backsplicing circRNA cassettes that can enable efficient gene expression in various cell and tissue types. Furthermore, we packaged cassettes encoding circRNAs into adeno-associated viral (AAV) vectors that can be delivered via intracerebroventricular (ICV) injections to achieve expression in murine brain tissue. We provide detailed methods for the design of backsplicing circRNAs, circRNA detection, and generation of AAV-circRNA vectors for CNS dosing and expression in mice.

Encapsulating In Vitro Transcribed circRNA into Lipid Nanoparticles Via Microfluidic Mixing

This chapter serves as a guide for researchers embarking on circular RNA-based translational studies. It provides a foundation for the successful encapsulation of circular RNA into lipid nanoparticles (LNPs) and facilitates progress in this emerging field. Crucial scientific methods and techniques involved in the formulation process, particle characterization, and downstream processing of circ-LNPs are covered. The production of in vitro transcribed circular RNA-containing LNPs based on a commercially available lipid mix is provided, in addition to the fundamentals for successful encapsulation based on lipid mixes composed of single components. Furthermore, the transfection and validation protocols for the identification of a functional and potentially therapeutic circRNA candidate for initial in vitro verification, before subsequent LNP studies, are explained.

Exploring the interplay between PARP1 and circRNA biogenesis and function

PARP1 (poly-ADP-ribose polymerase 1) is a multidomain protein with a flexible and self-folding structure that allows it to interact with a wide range of biomolecules, including nucleic acids and target proteins. PARP1 interacts with its target molecules either covalently via PARylation or non-covalently through its PAR moieties induced by auto-PARylation. These diverse interactions allow PARP1 to participate in complex regulatory circuits and cellular functions. Although the most studied PARP1-mediated functions are associated with DNA repair and cellular stress response, subsequent discoveries have revealed additional biological functions. Based on these findings, PARP1 is now recognized as a major modulator of gene expression. Several discoveries show that this multifunctional protein has been intimately connected to several steps of mRNA biogenesis, from transcription initiation to mRNA splicing, polyadenylation, export, and translation of mRNA to proteins. Nevertheless, our understanding of PARP1's involvement in the biogenesis of both coding and noncoding RNA, notably circular RNA (circRNA), remains restricted. In this review, we outline the possible roles of PARP1 in circRNA biogenesis. A full examination of the regulatory roles of PARP1 in nuclear processes with an emphasis on circRNA may reveal new avenues to control dysregulation implicated in the pathogenesis of several diseases such as neurodegenerative disorders and cancers. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Processing > Splicing Regulation/Alternative Splicing.

The circular RNA Rap1b promotes Hoxa5 transcription by recruiting Kat7 and leading to increased Fam3a expression, which inhibits neuronal apoptosis in acute ischemic stroke

Circular RNAs can regulate the development and progression of ischemic cerebral disease. However, it remains unclear whether they play a role in acute ischemic stroke. To investigate the role of the circular RNA Rap1b (circRap1b) in acute ischemic stroke, in this study we established an in vitro model of acute ischemia and hypoxia by subjecting HT22 cells to oxygen and glucose deprivation and a mouse model of acute ischemia and hypoxia by occluding the right carotid artery. We found that circRap1b expression was remarkably down-regulated in the hippocampal tissue of the mouse model and in the HT22 cell model. In addition, Hoxa5 expression was strongly up-regulated in response to circRap1b overexpression. Hoxa5 expression was low in the hippocampus of a mouse model of acute ischemia and in HT22-AIS cells, and inhibited HT22-AIS cell apoptosis. Importantly, we found that circRap1b promoted Hoxa5 transcription by recruiting the acetyltransferase Kat7 to induce H3K14ac modification in the Hoxa5 promoter region. Hoxa5 regulated neuronal apoptosis by activating transcription of Fam3a, a neuronal apoptosis-related protein. These results suggest that circRap1b regulates Hoxa5 transcription and expression, and subsequently Fam3a expression, ultimately inhibiting cell apoptosis. Lastly, we explored the potential clinical relevance of circRap1b and Hoxa5 in vivo. Taken together, these findings demonstrate the mechanism by which circRap1b inhibits neuronal apoptosis in acute ischemic stroke.

Current Approaches to Epigenetic Therapy

Epigenetic therapy is a promising tool for the treatment of a wide range of diseases. Several fundamental epigenetic approaches have been proposed. Firstly, the use of small molecules as epigenetic effectors, as the most developed pharmacological method, has contributed to the introduction of a number of drugs into clinical practice. Secondly, various innovative epigenetic approaches based on dCas9 and the use of small non-coding RNAs as therapeutic agents are also under extensive research. In this review, we present the current state of research in the field of epigenetic therapy, considering the prospects for its application and possible limitations.

RNA-RNA competitive interactions: a molecular civil war ruling cell physiology and diseases

The idea that proteins are the main determining factors in the functioning of cells and organisms, and their dysfunctions are the first cause of pathologies, has been predominant in biology and biomedicine until recently. This protein-centered view was too simplistic and failed to explain the physiological and pathological complexity of the cell. About 80% of the human genome is dynamically and pervasively transcribed, mostly as non-protein-coding RNAs (ncRNAs), which competitively interact with each other and with coding RNAs generating a complex RNA network regulating RNA processing, stability, and translation and, accordingly, fine-tuning the gene expression of the cells. Qualitative and quantitative dysregulations of RNA-RNA interaction networks are strongly involved in the onset and progression of many pathologies, including cancers and degenerative diseases. This review will summarize the RNA species involved in the competitive endogenous RNA network, their mechanisms of action, and involvement in pathological phenotypes. Moreover, it will give an overview of the most advanced experimental and computational methods to dissect and rebuild RNA networks.

Progress in circRNA-Targeted Therapy in Experimental Parkinson's Disease

Circular RNAs (circRNAs) are single-stranded RNA molecules often circularized by backsplicing. Growing evidence implicates circRNAs in the underlying mechanisms of various diseases, such as Alzheimer's and Parkinson's disease (PD)-the first and second most prevalent neurodegenerative disorders. In this sense, circSNCA, circHIPK2, circHIPK3, and circSLC8A1 are circRNAs that have been related to the neurodegenerative process of PD. Gain-of-function and loss-of-function studies on circRNAs have shed light on their roles in the pathobiology of various diseases. Gain-of-function approaches typically employ viral or non-viral vectors that hyperexpress RNA sequences capable of circularizing to form the specific circRNA under investigation. In contrast, loss-of-function studies utilize CRISPR/Cas systems, antisense oligonucleotides (ASOs), or RNAi techniques to knock down the target circRNA. The role of aberrantly expressed circRNAs in brain pathology has raised a critical question: could circRNAs serve as viable targets for neuroprotective treatments? Translating any oligonucleotide-based therapy, including those targeting circRNAs, involves developing adequate brain delivery systems, minimizing off-target effects, and addressing the high costs of treatment. Nonetheless, RNAi-based FDA-approved drugs have entered the market, and circRNAs have attracted significant attention and investment from major pharmaceutical companies. Spanning from bench to bedside, circRNAs present a vast opportunity in biotechnology for oligonucleotide-based therapies designed to slow or even halt the progression of neurodegenerative diseases.

Exosomal circTGFBR2 promotes hepatocellular carcinoma progression via enhancing ATG5 mediated protective autophagy

Exosomes contribute substantially to the communication between tumor cells and normal cells. Benefiting from the stable structure, circular RNAs (circRNAs) are believed to serve an important function in exosome-mediated intercellular communication. Here, we focused on circRNAs enriched in starvation-stressed hepatocytic exosomes and further investigated their function and mechanism in hepatocellular carcinoma (HCC) progression. Differentially expressed circRNAs in exosomes were identified by RNA sequencing, and circTGFBR2 was identified and chosen for further study. The molecular mechanism of circTGFBR2 in HCC was demonstrated by RNA pulldown, RIP, dual-luciferase reporter assays, rescue experiments and tumor xenograft assay both in vitro and vivo. We confirmed exosomes with enriched circTGFBR2 led to an upregulated resistance of HCC cells to starvation stress. Mechanistically, circTGFBR2 delivered into HCC cells via exosomes serves as a competing endogenous RNA by binding miR-205-5p to facilitate ATG5 expression and enhance autophagy in HCC cells, resulting in resistance to starvation. Thus, we revealed that circTGFBR2 is a novel tumor promoter circRNA in hepatocytic exosomes and promotes HCC progression by enhancing ATG5-mediated protective autophagy via the circTGFBR2/miR-205-5p/ATG5 axis, which may be a potential therapeutic target for HCC.

Exosomal circRNA: emerging insights into cancer progression and clinical application potential

Exosomal circRNA serves a novel genetic information molecule, facilitating communication between tumor cells and microenvironmental cells, such as immune cells, fibroblasts, and other components, thereby regulating critical aspects of cancer progression including immune escape, tumor angiogenesis, metabolism, drug resistance, proliferation and metastasis. Interestingly, microenvironment cells have new findings in influencing tumor progression and immune escape mediated by the release of exosomal circRNA. Given the intrinsic stability, abundance, and broad distribution of exosomal circRNAs, they represent excellent diagnostic and prognostic biomarkers for liquid biopsy. Moreover, artificially synthesized circRNAs may open up new possibilities for cancer therapy, potentially bolstered by nanoparticles or plant exosome delivery strategies. In this review, we summarize the functions and underlying mechanisms of tumor cell and non-tumor cell-derived exosomal circRNAs in cancer progression, with a special focus on their roles in tumor immunity and metabolism. Finally, we examine the potential application of exosomal circRNAs as diagnostic biomarkers and therapeutic targets, highlighting their promise for clinical use.

Characterization of cell-type specific circular RNAs associated with colorectal cancer metastasis

Colorectal cancer (CRC) is the most common gastrointestinal malignancy and a leading cause of cancer deaths in the United States. More than half of CRC patients develop metastatic disease (mCRC) with an average 5-year survival rate of 13%. Circular RNAs (circRNAs) have recently emerged as important tumorigenesis regulators; however, their role in mCRC progression remains poorly characterized. Further, little is known about their cell-type specificity to elucidate their functions in the tumor microenvironment (TME). To address this, we performed total RNA sequencing (RNA-seq) on 30 matched normal, primary and metastatic samples from 14 mCRC patients. Additionally, five CRC cell lines were sequenced to construct a circRNA catalog in CRC. We detected 47 869 circRNAs, with 51% previously unannotated in CRC and 14% novel candidates when compared to existing circRNA databases. We identified 362 circRNAs differentially expressed in primary and/or metastatic tissues, termed circular RNAs associated with metastasis (CRAMS). We performed cell-type deconvolution using published single-cell RNA-seq datasets and applied a non-negative least squares statistical model to estimate cell-type specific circRNA expression. This predicted 667 circRNAs as exclusively expressed in a single cell type. Collectively, this serves as a valuable resource, TMECircDB (accessible at https://www.maherlab.com/tmecircdb-overview), for functional characterization of circRNAs in mCRC, specifically in the TME.

Tactics targeting circular mRNA biosynthesis

Faced with the development of mRNA technology in the field of medicine and vaccine, circular mRNA (circmRNA) becomes a strong alternative to mRNA for its circular secondary structure and higher stability. At present, the synthesis of circmRNAs has been realized by ligating linear mRNA precursors and is limited by poor efficiency. To solve this challenge, this study started with ribozyme catalysis and enzymatic reaction to explore different circmRNA biosynthesis strategies. In terms of ribozyme method, by screening different group I intron self-splicing system sequences, the sequence from thymidylate synthase (Td) gene of phage T4 showed the highest ligation efficiency. In terms of enzyme method, with the help of 20-bp homologous arm, T4 Rnl 2 was determined as the ligation method with the highest ligation efficiency. By comparing the two ligation methods, the expression level of circmRNA ligated by T4 Rnl 2 was 86% higher than that ligated by Td ribozyme. Based on these ligation methods, the screening results of internal ribosome entry site (IRES) sequences showed that mud crab dicistrovirus IRES was an IRES sequence with high ribosome binding ability and could be widely used in circmRNAs for efficient and stable translation in mammalian cells. These results should provide positive guidance for the industrial production of circmRNAs and the development of mRNA vaccines. Eventually, circmRNAs could widely function in the field of biomedicine.

The Emerging Value of Circular Noncoding RNA Research in Cancer Diagnosis and Treatment

Circular RNAs (circRNA) are a recently described class of RNA molecules that have attracted substantial attention as new components of disease mechanisms and as potential biomarkers in multiple diseases, including cancer. CircRNAs are often highly conserved and exhibit developmental stage- and disease-specific expression. Several studies have reported circRNA expression patterns that are associated with specific cancer types and with patient prognosis. Here, we overview the active registered clinical trials that investigate the value of circRNAs as cancer biomarkers and discuss the potential of circRNAs in clinical cancer care. Taken together, circRNAs are actively being investigated as diagnostic, predictive, and prognostic biomarkers, and their potential to serve as therapeutic intervention points motivates ongoing translational and clinical research.

An in silico study to find potential effective circRNAs in the progression of Huntington's disease

Objectives

Huntington's disease (HD) is identified as a progressive genetic disorder caused by a mutation in the Huntington gene. Although the pathogenesis of this disease has not been fully understood, investigations have demonstrated the role of various genes and non-coding RNAs in the disease progression. In this study, we aimed to discover the potential promising circRNAs which can bind to miRNAs of HD.

Materials and Methods

We used several bioinformatics tools such as ENCORI, Cytoscape, circBase, Knime, and Enrichr to collect possible circRNAs and then evaluate their connections with target miRNAs to reach this goal. We also found the probable relationship between parental genes of these circRNAs and the disease progress.

Results

According to the data collected, more than 370 thousand circRNA-miRNA interactions were found for 57 target miRNAs. Several of circRNAs were spliced out of parental genes involved in the etiology of HD. Some of them need to be further investigated to elucidate their role in this neurodegenerative disease.

Conclusion

This in silico investigation highlights the potential role of circRNAs in the progression of HD and opens up new horizons for drug discovery as well as diagnostic approaches for the disease.

CircRNA_0075723 protects against pneumonia-induced sepsis through inhibiting macrophage pyroptosis by sponging miR-155-5p and regulating SHIP1 expression

Introduction

Circular RNAs (circRNAs) have been linked to regulate macrophage polarization and subsequent inflammation in sepsis. However, the underlying mechanism and the function of circRNAs in macrophage pyroptosis in pneumonia-induced sepsis are still unknown.

Methods

In this study, we screened the differentially expressed circRNAs among the healthy individuals, pneumonia patients without sepsis and pneumonia-induced sepsis patients in the plasma by RNA sequencing (RNA-seq). Then we evaluated macrophage pyroptosis in sepsis patients and in vitro LPS/nigericin activated THP-1 cells. The lentiviral recombinant vector for circ_0075723 overexpression (OE-circ_0075723) and circ_0075723 silence (sh-circ_0075723) were constructed and transfected into THP-1 cells to explore the potential mechanism of circ_0075723 involved in LPS/nigericin induced macrophage pyroptosis.

Results

We found circ_0075723, a novel circRNA that was significantly downregulated in pneumonia-induced sepsis patients compared to pneumonia patients without sepsis and healthy individuals. Meanwhile, pneumonia-induced sepsis patients exhibited activation of NLRP3 inflammasome and production of the pyroptosis-associated pro-inflammatory cytokines IL-1β and IL-18. circ_0075723 inhibited macrophage pyroptosis via sponging miR-155-5p which promoted SHIP1 expression directly. Besides, we found that circ_0075723 in macrophages promoted VE-cadherin expression in endothelial cells through inhibiting the release of NLRP3 inflammasome-related cytokines, IL-1β and IL-18, and protects endothelial cell integrity.

Discussion

Our findings propose a unique approach wherein circ_0075723 suppresses macrophage pyroptosis and inflammation in pneumonia-induced sepsis via sponging with miR-155-5p and promoting SHIP1 expression. These findings indicate that circRNAs could be used as possible potential diagnostic and therapeutic targets for pneumonia-induced sepsis.

Circular RNAs: emerging players in brain aging and neurodegenerative diseases

Brain aging is closely related to neurodegenerative diseases. Circular RNAs (circRNAs) are a type of conserved RNAs with covalently closed continuous loops. Emerging evidence has shown that circRNAs are implicated in the biology of brain aging and the pathology of age-related neurodegenerative diseases. Here, we summarize current studies on circRNAs associated with brain aging and neurodegenerative diseases by discussing their expression features, pathophysiological roles, and mechanisms of action. We also discuss the potential challenges of circRNA-based therapy against brain aging and neurodegenerative diseases, as well as their potential as diagnostic biomarkers of neurodegenerative diseases. The review provides insights into current progress in the functions of circRNAs in the process of brain aging and neurodegenerative diseases. © 2022 The Pathological Society of Great Britain and Ireland.

Knockdown of Circular RNAs Using LNA-Modified Antisense Oligonucleotides

Circular RNAs (circRNAs) constitute an abundant class of covalently closed noncoding RNA molecules that are formed by backsplicing from eukaryotic protein-coding genes. Recent studies have shown that circRNAs can act as microRNA or protein decoys, as well as transcriptional regulators. However, the functions of most circRNAs are still poorly understood. Because circRNA sequences overlap with their linear parent transcripts, depleting specific circRNAs without affecting host gene expression remains a challenge. In this study, we assessed the utility of LNA-modified antisense oligonucleotides (ASOs) to knock down circRNAs for loss-of-function studies. We found that, while most RNase H-dependent gapmer ASOs mediate effective knockdown of their target circRNAs, some gapmers reduce the levels of the linear parent transcript. The circRNA targeting specificity can be enhanced using design-optimized gapmer ASOs, which display potent and specific circRNA knockdown with a minimal effect on the host genes. In summary, our results demonstrate that LNA-modified ASOs complementary to backsplice-junction sequences mediate robust knockdown of circRNAs in vitro and, thus, represent a useful tool to explore the biological roles of circRNAs in loss-of-function studies in cultured cells and animal models.

mRNA COVID-19 Vaccines-Facts and Hypotheses on Fragmentation and Encapsulation

BACKGROUND

The adventure of the mRNA vaccine began thirty years ago in the context of influenza. This consisted in encapsulating the mRNA coding for a viral protein in a lipid particle. We show how the mRNA encoding S protein has been modified for that purpose in the context of the anti-SARS-CoV-2 vaccination.

RESULTS

by using data coming from genetic and epidemiologic databases, we show the theoretical possibility of fragmentation of this mRNA into small RNA sequences capable of inhibiting important bio-syntheses such as the production of beta-globin.

DISCUSSION

we discuss two aspects related to mRNA vaccine: (i) the plausibility of mRNA fragmentation, and (ii) the role of liposomal nanoparticles (LNPs) used in the vaccine and their impact on mRNA biodistribution.

CONCLUSION

we insist on the need to develop lipid nanoparticles allowing personalized administration of vaccines and avoiding adverse effects due to mRNA fragmentation and inefficient biodistribution. Hence, we recommend (i) adapting the mRNA of vaccines to the least mutated virus proteins and (ii) personalizing its administration to the categories of chronic patients at risk most likely to suffer from adverse effects.

Noncoding RNA therapeutics for substance use disorder

Although noncoding RNAs (ncRNAs) have been shown to regulate maladaptive neuroadaptations that drive compulsive drug use, ncRNA-targeting therapeutics for substance use disorder (SUD) have yet to be clinically tested. Recent advances in RNA-based drugs have improved many therapeutic issues related to immune response, specificity, and delivery, leading to multiple successful clinical trials for other diseases. As the need for safe and effective treatments for SUD continues to grow, novel nucleic acid-based therapeutics represent an appealing approach to target ncRNA mechanisms in SUD. Here, we review ncRNA processes implicated in SUD, discuss recent therapeutic approaches for targeting ncRNAs, and highlight potential opportunities and challenges of ncRNA-targeting therapeutics for SUD.

Small non-coding RNA therapeutics for cardiovascular disease

Novel bio-therapeutic agents that harness the properties of small, non-coding nucleic acids hold great promise for clinical applications. These include antisense oligonucleotides that inhibit messenger RNAs, microRNAs (miRNAs), or long non-coding RNAs; positive effectors of the miRNA pathway (short interfering RNAs and miRNA mimics); or small RNAs that target proteins (i.e. aptamers). These new therapies also offer exciting opportunities for cardiovascular diseases and promise to move the field towards more precise approaches based on disease mechanisms. There have been substantial advances in developing chemical modifications to improve the in vivo pharmacological properties of antisense oligonucleotides and reduce their immunogenicity. Carrier methods (e.g. RNA conjugates, polymers, and lipoplexes) that enhance cellular uptake of RNA therapeutics and stability against degradation by intracellular nucleases are also transforming the field. A number of small non-coding RNA therapies for cardiovascular indications are now approved. Moreover, there is a large pipeline of therapies in clinical development and an even larger list of putative therapies emerging from pre-clinical studies. Progress in this area is reviewed herein along with the hurdles that need to be overcome to allow a broader clinical translation.

Circular RNAs in diabetes and its complications: Current knowledge and future prospects

A novel class of non-coding RNA transcripts called circular RNAs (circRNAs) have been the subject of significant recent studies. Accumulating evidence points that circRNAs play an important role in the cellular processes, inflammatory expression, and immune responses through sponging miRNA, binding, or translating in proteins. Studies have found that circRNAs are involved in the physiologic and pathologic processes of diabetes. There has been an increased focus on the relevance of between abnormal circRNA expression and the development and progression of various types of diabetes and diabetes-related diseases. These circRNAs not only serve as promising diagnostic and prognostic molecular biomarkers, but also have important biological roles in islet cells, diabetes, and its complications. In addition, many circRNA signaling pathways have been found to regulate the occurrence and development of diabetes. Here we comprehensively review and discuss recent advances in our understanding of the physiologic function and regulatory mechanisms of circRNAs on pancreatic islet cells, different subtypes in diabetes, and diabetic complications.

circRNA422 enhanced osteogenic differentiation of bone marrow mesenchymal stem cells during early osseointegration through the SP7/LRP5 axis

Circular RNAs (circRNAs) play an important role in biological activities, especially in regulating osteogenic differentiation of stem cells. However, no studies have reported the role of circRNAs in early osseointegration. Here we identified a new circRNA, circRNA422, from rat bone marrow mesenchymal stem cells (BMSCs) cultured on sandblasted, large-grit, acid-etched titanium surfaces. The results showed that circRNA422 significantly enhanced osteogenic differentiation of BMSCs with increased expression levels of alkaline phosphatase, the SP7 transcription factor (SP7/osterix), and lipoprotein receptor-related protein 5 (LRP5). Silencing of circRNA422 had opposite effects. There were two SP7 binding sites on the LRP5 promoter, indicating a direct regulatory relationship between SP7 and LRP5. circRNA422 could regulate early osseointegration in in vivo experiments. These findings revealed an important function of circRNA422 during early osseointegration. Therefore, circRNA422 may be a potential therapeutic target for enhancing implant osseointegration.

Transcription factor Nrf2 binds to circRNAPIBF1 to regulate SOD2 in lung adenocarcinoma progression

Emerging evidence indicates that circular RNAs (circRNAs) play important roles in disease development, especially in cancers. Analysis of circRNA expression microarrays from the Gene Expression Omnibus database revealed that circPIBF1 was highly upregulated in lung adenocarcinoma (LUAD). The main aim of this study was to probe the function of circPIBF1 in pyroptosis of LUAD cells and the signal transduction pathways involved. CircPIBF1 was significantly overexpressed in LUAD and was related to the dismal prognosis of patients with LUAD. CircPIBF1 could bind to nuclear factor erythroid 2-related factor 2 (Nrf2), which further promoted the expression of superoxide dismutase 2 (SOD2). In addition, Nrf2 was also observed to recruit histone acetyltransferase E1A binding protein p300 (EP300) to enhance H3K27ac modification of SOD2, thus modulating the Nrf2-Keap1 signaling pathway. Moreover, we found that knockdown of circPIBF1 significantly suppressed the expression of SOD2 in cells and LUAD cell growth, while enhanced the expression of pyroptosis-related factors, which were further reversed by overexpression of SOD2 or EP300. Collectively, our findings suggest a direct involvement of circPIBF1 in pyroptosis-related LUAD carcinogenesis and implicate a role of Nrf2/EP300/SOD2 signaling in this process.

Circular RNAs in Acute Kidney Injury: Roles in Pathophysiology and Implications for Clinical Management

Acute kidney injury (AKI) is a common clinical condition, results in patient morbidity and mortality, and incurs considerable health care costs. Sepsis, ischaemia-reperfusion injury (IRI) and drug nephrotoxicity are the leading causes. Mounting evidence suggests that perturbations in circular RNAs (circRNAs) are observed in AKI of various aetiologies, and have pathogenic significance. Aberrant circRNA expressions can cause altered intracellular signalling, exaggerated oxidative stress, increased cellular apoptosis, excess inflammation, and tissue injury in AKI due to sepsis or IRI. While circRNAs are dysregulated in drug-induced AKI, their roles in pathogenesis are less well-characterised. CircRNAs also show potential for clinical application in diagnosis, prognostication, monitoring, and treatment. Prospective observational studies are needed to investigate the role of circRNAs in the clinical management of AKI, with special focus on the safety of therapeutic interventions targeting circRNAs and the avoidance of untoward off-target effects.

Non-Coding RNAs and Oral Cancer: Small Molecules With Big Functions

Oral cancer remains a major public concern with considerable socioeconomic impact in the world. Despite substantial advancements have been made in treating oral cancer, the five-year survival rate for oral cancer remained undesirable, and the molecular mechanisms underlying OSCC carcinogenesis have not been fully understood. Noncoding RNAs (ncRNAs) include transfer RNAs (tRNAs), as well as small RNAs such as microRNAs, and the long ncRNAs such as HOTAIR are a large segment of the transcriptome that do not have apparent protein-coding roles, but they have been verified to play important roles in diverse biological processes, including cancer cell development. Cell death, such as apoptosis, necrosis, and autophagy, plays a vital role in the progression of cancer. A better understanding of the regulatory relationships between ncRNAs and these various types of cancer cell death is therefore urgently required. The occurrence and development of oral cancer can be controlled by increasing or decreasing the expression of ncRNAs, a method which confers broad prospects for oral cancer treatment. Therefore, it is urgent for us to understand the influence of ncRNAs on the development of different modes of oral tumor death, and to evaluate whether ncRNAs have the potential to be used as biological targets for inducing cell death and recurrence of chemotherapy. The purpose of this review is to describe the impact of ncRNAs on cell apoptosis and autophagy in oral cancer in order to explore potential targets for oral cancer therapy.

Next RNA Therapeutics: The Mine of Non-Coding

The growing knowledge on several classes of non-coding RNAs (ncRNAs) and their different functional roles has aroused great interest in the scientific community. Beyond the Central Dogma of Biology, it is clearly known that not all RNAs code for protein products, and they exert a broader repertoire of biological functions. As described in this review, ncRNAs participate in gene expression regulation both at transcriptional and post-transcriptional levels and represent critical elements driving and controlling pathophysiological processes in multicellular organisms. For this reason, in recent years, a great boost was given to ncRNA-based strategies with potential therapeutic abilities, and nowadays, the use of RNA molecules is experimentally validated and actually exploited in clinics to counteract several diseases. In this review, we summarize the principal classes of therapeutic ncRNA molecules that are potentially implied in disease onset and progression, which are already used in clinics or under clinical trials, highlighting the advantages and the need for a targeted therapeutic strategy design. Furthermore, we discuss the benefits and the limits of RNA therapeutics and the ongoing development of delivery strategies to limit the off-target effects and to increase the translational application.

Novel insights into the role of circular RNAs in Parkinson disease: An emerging renaissance in the management of neurodegenerative diseases

Parkinson's disease (PD), as a debilitating neurodegenerative disease, particularly affects the elderly population, and is clinically identified by resting tremor, rigidity, and bradykinesia. Pathophysiologically, PD is characterized by an early loss of dopaminergic neurons in the Substantia nigra pars compacta, accompanied by the extensive aggregation of alpha-synuclein (α-Syn) in the form of Lewy bodies. The onset of PD has been reported to be influenced by multiple biological molecules. In this context, circular RNAs (circRNAs), as tissue-specific noncoding RNAs with closed structures, have been recently demonstrated to involve in a set of PD's pathogenic processes. These RNA molecules can either up- or downregulate the expression of α-Syn, as well as moderating its accumulation through different regulatory mechanisms, in which targeting microRNAs (miRNAs) is considered the most common pathway. Since circRNAs have prominent structural and biological characteristics, they could also be considered as promising candidates for PD diagnosis and treatment. Unfortunately, PD has become a global health concern, and a large number of its pathogenic processes are still unclear; thus, it is crucial to elucidate the ambiguous aspects of PD pathophysiology to improve the efficiency of diagnostic and therapeutic strategies. In line with this fact, the current review aims to highlight the interplay between circRNAs and PD pathogenesis, and then discusses the diagnostic and therapeutic potential of circRNAs in PD progression. This study will thus be the first of its kind reviewing the relationship between circRNAs and PD.

Past, Present and Future: The Relationship Between Circular RNA and Immunity

The immune system has evolved since the birth of humans. However, immune-related diseases have not yet been overcome due to the lack of expected indicators and targeting specificity of current medical technology, subjecting patients to very uncomfortable physical and mental experiences and high medical costs. Therefore, the requirements for treatments with higher specificity and indicative ability are raised. Fortunately, the discovery of and continuous research investigating circular RNAs (circRNAs) represent a promising method among numerous methods. Although circRNAs wear regarded as metabolic wastes when discovered, as a type of noncoding RNA (ncRNA) with a ring structure and wide distribution range in the human body, circRNAs shine brilliantly in medical research by virtue of their special nature and structure-determined functions, such as high stability, wide distribution, high detection sensitivity, acceptable reproducibility and individual differences. Based on research investigating the role of circRNAs in immunity, we systematically discuss the hotspots of the roles of circRNAs in immune-related diseases, including expression profile analyses, potential biomarker research, ncRNA axis/network construction, impacts on phenotypes, therapeutic target seeking, maintenance of nucleic acid stability and protein binding research. In addition, we summarize the current situation of and problems associated with circRNAs in immune research, highlight the applications and prospects of circRNAs in the treatment of immune-related diseases, and provide new insight into future directions and new strategies for laboratory research and clinical applications.

Deciphering the RNA universe in sperm in its role as a vertical information carrier

The inheritance of neurophysiologic and neuropsychologic complex diseases can only partly be explained by the Mendelian concept of genetic inheritance. Previous research showed that both psychological disorders like post-traumatic stress disorder and metabolic diseases are more prevalent in the progeny of affected parents. This could suggest an epigenetic mode of transmission. Human studies give first insight into the scope of intergenerational influence of stressors but are limited in exploring the underlying mechanisms. Animal models have elucidated the mechanistic underpinnings of epigenetic transmission. In this review, we summarize progress on the mechanisms of paternal intergenerational transmission by means of sperm RNA in mouse models. We discuss relevant details for the modelling of RNA-mediated transmission, point towards currently unanswered questions and propose experimental considerations for tackling these questions.

Synthetic Circular miR-21 Sponge as Tool for Lung Cancer Treatment

Lung cancer is the most common cancer in the world and several miRNAs are associated with it. MiRNA sponges are presented as tools to inhibit miRNAs. We designed a system to capture miRNAs based on circular RNAs (circRNA). To demonstrate its usefulness, we chose miR-21, which is upregulated and implicated in lung cancer. We constructed a miR-21 sponge and inserted it into a vector that facilitates circular RNA production (Circ-21) to study its effect on growth, colony formation, and migration in lung cancer cell lines and multicellular tumor spheroids (MTS). Circ-21 induced a significant and time-dependent decrease in the growth of A549 and LL2 cells, but not in L132 cells. Furthermore, A549 and LL2 cells transfected with Circ-21 showed a lower number of colonies and migration than L132. Similar findings were seen in A549 and LL2 Circ-21 MTS, which showed a significant decrease in volume growth, but not in L132 Circ-21 MTS. Based on this, the miR-21 circular sponge may suppress the processes of tumorigenesis and progression. Therefore, our system based on circular sponges seems to be effective, as a tool for the capture of other miRNAs.

Novel insights into the interaction between N6-methyladenosine modification and circular RNA

As the most prevalent type of RNA modification in eukaryotes, N6-methyladenosine (m⁶A) can modulate RNA fates such as processing, splicing, maturation, export, stability, translation, and degradation. Circular RNAs (circRNAs), a novel type of non-coding RNA (ncRNAs) characterized by a covalently closed loop structure, play an essential role in various physiological and pathological processes. Extensive studies have revealed that m⁶A modification is widespread in circRNAs and influences their biogenesis and functions. Intriguingly, circRNAs can affect m⁶A modification by regulating m⁶A regulatory proteins. In this review, we summarize the characteristics and biological functions of m⁶A and circRNAs and focus on recent advances in the interaction of m⁶A modification and circRNAs. In addition, the potential clinical applications of m⁶A modification and circRNAs in diagnosis and therapeutic targets are discussed.