The design and synthesis of circular RNAs

Human and pathogen-encoded circular RNAs in viral infections: insights into functions and therapeutic opportunities

Circular RNAs (circRNAs) are emerging as important regulatory molecules in both host and viral systems, acting as microRNA sponges, protein decoys or scaffolds, and templates for protein translation. Host-derived circRNAs are increasingly recognized for their roles in immune responses, while virus-encoded circRNAs, especially those from DNA viruses, have been shown to modulate host cellular machinery to favor viral replication and immune evasion. Recently, RNA virus-encoded circRNAs were also discovered, but evidence suggests that they might be generated using a different mechanism compared to the circRNAs produced from the host and DNA viruses. This review highlights recent advances in our understanding of both host and virus-derived circRNAs, with a focus on their biological roles and contributions to pathogenesis. Furthermore, we discuss the potential of circRNAs as biomarkers and their application as therapeutic targets or scaffolds for RNA-based therapies. Understanding the roles of circRNAs in host-virus interactions offers novel insights into RNA biology and opens new avenues for therapeutic strategies against viral diseases and associated cancers.

Unveiling Pharmacogenomics Insights into Circular RNAs: Toward Precision Medicine in Cancer Therapy

Pharmacogenomics is revolutionizing precision medicine by enabling tailored therapeutic strategies based on an individual genetic and molecular profile. Circular RNAs (circRNAs), a distinct subclass of endogenous non-coding RNAs, have recently emerged as key regulators of drug resistance, tumor progression, and therapeutic responses. Their covalently closed circular structure provides exceptional stability and resistance to exonuclease degradation, positioning them as reliable biomarkers and novel therapeutic targets in cancer management. This review provides a comprehensive analysis of the interplay between circRNAs and pharmacogenomics, focusing on their role in modulating drug metabolism, therapeutic efficacy, and toxicity profiles. We examine how circRNA-mediated regulatory networks influence chemotherapy resistance, alter targeted therapy responses, and impact immunotherapy outcomes. Additionally, we discuss emerging experimental tools and bioinformatics techniques for studying circRNAs, including multi-omics integration, machine learning-driven biomarker discovery, and high-throughput sequencing technologies. Beyond their diagnostic potential, circRNAs are being actively explored as therapeutic agents and drug delivery vehicles. Recent advancements in circRNA-based vaccines, engineered CAR-T cells, and synthetic circRNA therapeutics highlight their transformative potential in oncology. Furthermore, we address the challenges of standardization, reproducibility, and clinical translation, emphasizing the need for rigorous biomarker validation and regulatory frameworks to facilitate their integration into clinical practice. By incorporating circRNA profiling into pharmacogenomic strategies, this review underscores a paradigm shift toward highly personalized cancer therapies. circRNAs hold immense potential to overcome drug resistance, enhance treatment efficacy, and optimize patient outcomes, marking a significant advancement in precision oncology.

The therapeutic potential of circular RNAs

Over the past decade, research into circular RNA (circRNA) has increased rapidly, and over the past few years, circRNA has emerged as a promising therapeutic platform. The regulatory functions of circRNAs, including their roles in templating protein translation and regulating protein and RNA functions, as well as their unique characteristics, such as increased stability and a favourable immunological profile compared with mRNAs, make them attractive candidates for RNA-based therapies. Here, we describe the properties of circRNAs, their therapeutic potential and technologies for their synthesis. We also discuss the prospects and challenges to be overcome to unlock the full potential of circRNAs as drugs.

Noncanonical circRNA biogenesis driven by alpha and gamma herpesviruses

Herpesviruses require the host transcriptional machinery, inducing significant changes in gene expression to prioritize viral transcripts. We examined alpha- and gamma-herpesvirus alterations to a type of alternative splicing, namely circular RNA (circRNA) synthesis. We developed "Circrnas in Host And viRuses anaLysis pIpEline" (CHARLIE) to facilitate viral profiling. This method identified thousands of back-splicing variants, including circRNA common to lytic and latent phases of infection. Ours is the first report of Herpes Simplex Virus-1 circRNAs, including species derived from ICP0 and the latency-associated transcript. We characterized back-splicing cis- and trans-elements, and found viral circRNAs resistant to spliceosome perturbation and lacking canonical splice donor-acceptors. Subsequent loss-of-function studies of host RNA ligases (RTCB, RLIG1) revealed instances of decreased viral back splicing. Using eCLIP and 4sU-Sequencing, we determined that the KSHV RNA-binding protein, ORF57, enhanced synthesis for a subset of viral and host circRNAs. Our work explores unique splicing mechanisms driven by lytic infection, and identifies a class of transcripts with the potential to function in replication, persistence, or tumorigenesis.

Engineered circular RNA-based DLL3-targeted CAR-T therapy for small cell lung cancer

PURPOSE

Circular RNA (circRNA) has emerged as a promising RNA therapeutic molecule due to its enhanced stability and prolonged protein expression compared to messenger RNA (mRNA). Using circRNA to construct transient Chimeric Antigen Receptor (CAR)-T cells can mitigate the limitations of conventional viral vector-based CAR-T approaches, such as complex process and long-term side effects.

METHODS

The study first reconfirmed the advantageous properties of circRNA, focusing on its stability and protein expression efficiency. Electroporation conditions were then optimized for the efficient delivery of circRNA into human primary T cells. Subsequently, a circRNA encoding the anti-Delta-like Ligand 3 (DLL3) CAR was constructed, and CAR-T cells were generated via electroporation. The efficacy of circRNA-based CAR-T cells was compared to mRNA-based CAR-T cells in both in vitro and in vivo models, including subcutaneous and orthotopic small cell lung cancer (SCLC) mouse models.

RESULTS

CircRNA-based CAR-T cells demonstrated superior efficacy against SCLC compared to mRNA-based CAR-T cells. In vitro experiments showed enhanced tumor-killing effects, while in vivo studies revealed complete elimination of human SCLC tumors in both subcutaneous and orthotopic mouse models. These results underscored the therapeutic advantages of circRNA in CAR-T cell therapy.

CONCLUSIONS

This study validated the feasibility of the circRNA-electroporation strategy in CAR-T cell therapy and offered a potentially effective approach for treating SCLC, highlighting the potential of circRNA-based technologies in advancing cell therapies.

Emerging roles of noncoding RNAs in cardiovascular pathophysiology

This review comprehensively examines the diverse roles of noncoding RNAs (ncRNAs) in the pathogenesis and treatment of cardiovascular disease (CVD), focusing on microRNA (miRNA), long noncoding RNA (lncRNA), piwi-interacting RNA (piRNA), small-interfering RNA (siRNA), circular RNA (circRNA), and vesicle-associated RNAs. These ncRNAs are integral regulators of key cellular processes, including gene expression, inflammation, and fibrosis, and they hold great potential as both diagnostic biomarkers and therapeutic targets. The review highlights novel insights into how these RNA species, particularly miRNAs, lncRNAs, and piRNAs, contribute to various CVDs such as hypertension, atherosclerosis, and myocardial infarction. In addition, it explores the emerging role of extracellular vesicles (EVs) in intercellular communication and their therapeutic potential in cardiovascular health. The review underscores the need for continued research into ncRNAs and RNA-based therapies, with a focus on advancing delivery systems and expanding personalized medicine approaches to improve cardiovascular outcomes.

Circular RNAs as key regulators in cancer hallmarks: New progress and therapeutic opportunities

Circular RNAs (circRNAs) have emerged as critical regulators in cancer biology, contributing to various cancer hallmarks, including cell proliferation, apoptosis, metastasis, and drug resistance. Defined by their covalently closed loop structure, circRNAs possess unique characteristics like high stability, abundance, and tissue-specific expression. These non-coding RNAs function through mechanisms such as miRNA sponging, interactions with RNA-binding proteins (RBPs), and modulating transcription and splicing. Advances in RNA sequencing and bioinformatics tools have enabled the identification and functional annotation of circRNAs across different cancer types. Clinically, circRNAs demonstrate high specificity and sensitivity in samples, offering potential as diagnostic and prognostic biomarkers. Additionally, therapeutic strategies involving circRNA mimics, inhibitors, and delivery systems are under investigation. However, their precise mechanisms remain unclear, and more clinical evidence is needed regarding their roles in cancer hallmarks. Understanding circRNAs will pave the way for novel diagnostic and therapeutic approaches, potentially improving patient outcomes.

Competing endogenous RNAs network and therapeutic implications: New horizons in disease research

Different diseases may arise from the dysregulation of non-coding RNAs (ncRNAs), which regulation is necessary for maintaining cellular homeostasis. ncRNAs are regulated by transcriptional, post-transcriptional, translational and post-translational processes. Post-transcriptional regulation of gene expression is carried out by microRNAs (miRNAs), a class of small ncRNA molecules, which can identify their target sites by a brief nucleotide sequence, known as the miRNA response element (MRE), present on the miRNA seed sequence and the target transcript. This binding between miRNAs and targets can regulate the gene expression through inhibition of translation or degradation of target messenger RNA (mRNA). The transcripts that share MREs can be involved in competition for the central miRNA pool, which could have an indirect impact on each other's regulation. This competition network is called competing endogenous RNAs network (ceRNET). Many ncRNAs, including circular RNA, pseudogene, and long non-coding RNA, as well as mRNA, a coding RNA transcript, make up ceRNET. These components play a crucial role in post-transcriptional regulation and are involved in the diagnosis and treatment of many pathological disorders. The mechanism of ceRNET and its essential components, as well as their therapeutic implications in different diseases such as cancer, diabetes mellitus, neurological, cardiovascular, hepatic and respiratory disorders were covered in this review.

CircGRB14 Inhibits Proliferation and Promotes Apoptosis of Granulosa Cells in Chicken Follicle Selection Through Sponging miR-12264-3p and miR-6660-3p

The development and selection of ovarian follicles are essential for continuous egg production in chickens. Non-coding RNAs, particularly circular RNAs (circRNAs), play a critical regulatory role in follicle selection, a process heavily involving granulosa cells (GCs). In this study, we analyzed circRNA expression profiles in small yellow follicles (SYFs) and large yellow follicles (LYFs) of Taihang chickens using RNA sequencing. We identified 14,586 circRNAs, with 57 showing differential expression (DE-circRNAs) between SYFs and LYFs. Functional enrichment analysis revealed that these DE-circRNAs are involved in key biological processes, including signal transduction, cell membrane formation, and nuclear enzymatic regulation. We focused on circGRB14, a circRNA derived from the growth factor receptor-bound protein 14 (GRB14) gene, as a potential regulator of follicle selection. Using qPCR, CCK-8 proliferation assays, and Annexin V/PI apoptosis analysis, we demonstrated that circGRB14 inhibits GC proliferation and promotes apoptosis. In contrast, miR-12264-3p and miR-6660-3p, validated as direct targets of circGRB14 via Dual-Luciferase Reporter assays, exhibited opposing effects by promoting GC proliferation and inhibiting apoptosis. These findings highlight the circGRB14-miR-12264-3p/miR-6660-3p axis as a key regulatory mechanism in GC dynamics during follicle selection. This study provides novel insights into the functional interplay between circRNAs and miRNAs in avian follicle development, offering potential targets for improving egg production in poultry.

Structures of a natural circularly permuted group II intron reveal mechanisms of branching and backsplicing

Circularly permuted (CP) group II introns, identified in various bacteria phyla, swap domains D5 and D6 near the 5' end and have reversed splice sites (SSs), leading to backsplicing and circular RNA formation. In this study, we present multiple high-resolution cryo-electron microscopy structures of a natural CP group II intron from Comamonas testosteroni KF-1 (Cte 1), elucidating the molecular mechanisms of branching and backsplicing. During branching, the 5' SS is positioned by an auxiliary sequence (AUX)-enhanced interaction between the exon-binding site and intron-binding site (IBS) and stacks on the branch-site adenosine within D6, allowing the attacking 2'-OH group to coordinate with a metal ion in the active center. In backsplicing, the 3' SS is aligned with the branching step, leaving IBS in the active center, stabilized by base pairing with the AUX, which enables the free 3'-end hydroxyl group to directly attack the scissile phosphate of 3' SS. Furthermore, a groove in Cte 1 may stabilize the circular RNA. These findings highlight a conserved catalytic mechanism for canonical group II introns, albeit facilitated by the versatile AUX, opening avenues for designing potent ribozymes producing circular RNAs.

CircRNA hsa_circ_0004781 promoted cell proliferation by acting as a sponge for miR-9-5p and miR-338-3p and upregulating KLF5 and ADAM17 expression in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive types of solid tumor, and novel strategies must be developed for treating it. Previous studies predominantly utilized circular RNA (circRNA) expression plasmids incorporating Alu elements to facilitate the indirect expression of circRNA.

METHODS

Public databases and bioinformatics tools were used to identify hsa_circ_0004781 that is highly expressed in PDAC and its potential microRNA (miRNA) targets and corresponding mRNA targets. Real hsa_circ_0004781, which is identical to the native form of hsa_circ_0004781 without any exogenous sequences, was prepared through in vitro transcription by using a ribozyme and ion-pair reversed-phase high-performance liquid chromatography (IP-RP HPLC). The biological functions of hsa_circ_0004781 were evaluated using loss-of-function and gain-of-function approaches with circRNA expression plasmids and real hsa_circ_0004781.

RESULTS

Knockdown of hsa_circ_0004781 inhibited the proliferation and migration of PDAC cells, whereas its overexpression produced opposite effects. Hsa_circ_0004781 was identified as a sponge for miR-9-5p and miR-338-3p, and its expression was negatively correlated with that of these miRNAs. Among the targets of miR-9-5p and miR-338-3p, Kruppel-like factor 5 (KLF5) and a disintegrin and metalloproteinase domain 17 (ADAM17) were negatively correlated with survival in patients with PDAC and were inversely regulated by these miRNAs. Furthermore, real hsa_circ_0004781 exhibited the same effects as those of the circRNA expression plasmids.

CONCLUSIONS

This study is the first to use real circRNAs to validate results obtained using circRNA expression plasmids. The results suggest that hsa_circ_0004781 functions as an oncogene, promoting the proliferation of PDAC cells through the miR-9-5p/KLF5 and miR-338-3p/ADAM17 axes. Therefore, hsa_circ_0004781 might be a therapeutic target for PDAC.

Therapeutic application of circular RNA aptamers in a mouse model of psoriasis

Efforts to advance RNA aptamers as a new therapeutic modality have been limited by their susceptibility to degradation and immunogenicity. In a previous study, we demonstrated synthesized short double-stranded region-containing circular RNAs (ds-cRNAs) with minimal immunogenicity targeted to dsRNA-activated protein kinase R (PKR). Here we test the therapeutic potential of ds-cRNAs in a mouse model of imiquimod-induced psoriasis. We find that genetic supplementation of ds-cRNAs leads to inhibition of PKR, resulting in alleviation of downstream interferon-α and dsRNA signals and attenuation of psoriasis phenotypes. Delivery of ds-cRNAs by lipid nanoparticles to the spleen attenuates PKR activity in examined splenocytes, resulting in reduced epidermal thickness. These findings suggest that ds-cRNAs represent a promising approach to mitigate excessive PKR activation for therapeutic purposes.

Small circular RNAs as vaccines for cancer immunotherapy

Messenger RNA vaccines have shown strong prophylactic efficacy against viral infections. Here we show that antigen-encoding small circular RNAs (circRNAs) loaded in lipid nanoparticles elicit potent and durable T cell responses for robust tumour immunotherapy after subcutaneous injection in mice, particularly when combined with immune checkpoint inhibition. The small circRNA vaccines are highly stable and show low levels of activation of protein kinase R as well as low cytotoxicity, enabling long-lasting antigen translation (longer than 1 week in cells). Relative to large protein-encoding unmodified or modified mRNAs and circRNAs, small circRNA vaccines elicited up to 10-fold antigen-specific T cells in mice and accounted for 30-75% of the total peripheral CD8+ T cells over 6 months. Small circRNA vaccines encoding tumour-associated antigens, neoantigens and oncoviral or viral antigens elicited substantial CD8+ and CD4+ T cell responses in young adult mice and in immunosenescent aged mice. Combined with immune checkpoint inhibition, monovalent and multivalent circRNA vaccines reduced tumour-induced immunosuppression and inhibited poorly immunogenic mouse tumours, including melanoma resistant to immune checkpoint blockade.

Circular RNAs in cancer

Circular RNA (circRNA), a subtype of noncoding RNA, has emerged as a significant focus in RNA research due to its distinctive covalently closed loop structure. CircRNAs play pivotal roles in diverse physiological and pathological processes, functioning through mechanisms such as miRNAs or proteins sponging, regulation of splicing and gene expression, and serving as translation templates, particularly in the context of various cancers. The hallmarks of cancer comprise functional capabilities acquired during carcinogenesis and tumor progression, providing a conceptual framework that elucidates the nature of the malignant transformation. Although numerous studies have elucidated the role of circRNAs in the hallmarks of cancers, their functions in the development of chemoradiotherapy resistance remain unexplored and the clinical applications of circRNA-based translational therapeutics are still in their infancy. This review provides a comprehensive overview of circRNAs, covering their biogenesis, unique characteristics, functions, and turnover mechanisms. We also summarize the involvement of circRNAs in cancer hallmarks and their clinical relevance as biomarkers and therapeutic targets, especially in thyroid cancer (TC). Considering the potential of circRNAs as biomarkers and the fascination of circRNA-based therapeutics, the "Ying-Yang" dynamic regulations of circRNAs in TC warrant vastly dedicated investigations.

Circular RNAs in glioblastoma

Glioblastoma multiforme (GBM) is the most malignant and common form of brain cancer in adults. The molecular mechanisms underlying GBM progression and resistance are complex and poorly understood. Circular RNAs (circRNAs) are a new class of non-coding RNAsformed by covalently closed loopstructures with no free ends. Their circular structure makes them more stable than linear RNA and resistant to exonuclease degradation. In recent years, they have received significant attention due to their diverse functions in gene regulation and their association with various diseases, including cancer. Therefore, understanding the functions and applications of circRNAs is critical to developing targeted therapeutic interventions and advancing the field of glioblastoma cancer research. In this review, we summarized the main functions of circRNAs and their potential applications in the diagnosis, prognosis and targeted therapy of GBM.

EIF4A3-induced circ_0022382 promotes breast cancer cell progression through the let-7a-5p/PI3K/AKT/mTOR signaling pathway and SLC7A11 axis

Introduction

Breast cancer is one of the most common cancers in women and poses a serious threat to women's health. Circular RNAs (circRNAs) have been found to be specifically expressed in cancers and regulate the growth and death of tumor cells. The role of circRNAs in breast cancer remain unknown. In this study, we explored the impacts of circRNAs on the progression of breast cancer cells.

Methods

Using bioinformatics analysis, we screened out one up-regulated circRNA in breast cancer, and its function and regulatory mechanisms were confirmed by quantitative real-time PCR, cell counting kit-8 experiment, migration assay, dual luciferase reporter assay, Kyoto Encyclopedia of Genes and Genomes enrichment analysis, cell immunofluorescence, clone formation assay, scratch wound healing experiment, RNA immunoprecipitation and subcutaneous tumor-bearing experiments.

Results

Circ_0022382 was highly expressed in breast cancer cell lines MDA-MB-231, MCF-7 as well as breast cancer tissues, and promoted the proliferative and migratory capacity of breast cancer cells. In terms of regulatory mechanisms, circ_0022382 activated PI3K/AKT/mTOR signaling pathway and SLC7A11 by sponging let-7a-5p, while knockdown of circ_0022382 contributed to the occurrence of disulfidptosis. In addition, EIF4A3 promoted the expression of circ_0022382 in MDA-MB-231 and MCF-7. Consistently, knockdown of circ_0022382 inhibited the growth of breast cancer cells in vivo.

Discussion

Circ_0022382 and its related molecules may be effective targets for diagnosis or targeted therapy of breast cancer.

Expanding the Potential of Circular RNA (CircRNA) Vaccines: A Promising Therapeutic Approach

In recent years, circular RNAs (circRNAs) have garnered significant attention due to their unique structure and function, positioning them as promising candidates for next-generation vaccines. The circRNA vaccine, as an RNA vaccine, offers significant advantages in preventing infectious diseases by serving as a vector for protein expression through non-canonical translation. Notably, circRNA vaccines have demonstrated enduring antigenic expression and generate a larger percentage of neutralizing antibodies compared to mRNA vaccines administered at the same dosage. Furthermore, circRNA vaccines can elicit robust cellular and humoral immunity, indicating their potential for tumor vaccine development. However, certain challenges must be addressed to facilitate the widespread use of circRNA vaccines in both infectious disease prevention and tumor treatment. These challenges include the low efficiency of linear RNA circularization, the suboptimal targeting of delivery systems, and the assessment of potential side effects. This work aims to describe the characteristics and functions of circRNAs, elucidate the mechanism behind circRNA vaccines, and discuss their applications in the prevention of infectious diseases and the treatment of tumors, along with their potential future applications.

Circular RNAs: key players in tumor immune evasion

Immune responses against tumor antigens play a role in confining tumor growth. In response, cancer cells developed several mechanisms to bypass or defeat these anti-tumor immune responses-collectively referred to as "tumor immune evasion". Recent studies have shown that a group of non-coding RNAs, namely circRNAs affect several aspects of tumor immune evasion through regulation of activity of CD8 + T cells, regulatory T cells, natural killer cells, cytokine-induced killer cells or other immune cells. Understanding the role of circRNAs in this process facilitate design of novel therapies for enhancing the anti-tumor capacity of immune system. This review provides an outline of different roles of circRNAs in the tumor immune evasion.

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.

Recent progress in mRNA cancer vaccines

The research and development of messenger RNA (mRNA) cancer vaccines have gradually overcome numerous challenges through the application of personalized cancer antigens, structural optimization of mRNA, and the development of alternative RNA-based vectors and efficient targeted delivery vectors. Clinical trials are currently underway for various cancer vaccines that encode tumor-associated antigens (TAAs), tumor-specific antigens (TSAs), or immunomodulators. In this paper, we summarize the optimization of mRNA and the emergence of RNA-based expression vectors in cancer vaccines. We begin by reviewing the advancement and utilization of state-of-the-art targeted lipid nanoparticles (LNPs), followed by presenting the primary classifications and clinical applications of mRNA cancer vaccines. Collectively, mRNA vaccines are emerging as a central focus in cancer immunotherapy, offering the potential to address multiple challenges in cancer treatment, either as standalone therapies or in combination with current cancer treatments.

RNA technology and nanocarriers empowering in vivo chimeric antigen receptor therapy

The remarkable success of mRNA-based coronavirus 2019 (COVID-19) vaccines has propelled the advancement of nanomedicine, specifically in the realm of RNA technology and nanomaterial delivery systems. Notably, significant strides have been made in the development of RNA-based in vivo chimeric antigen receptor (CAR) therapy. In comparison to the conventional ex vivo CAR therapy, in vivo CAR therapy offers several benefits including simplified preparation, reduced costs, broad applicability and decreased potential for carcinogenic effects. This review summarises the RNA-based CAR constructs in in vivo CAR therapy, discusses the current applications of in vivo delivery vectors and outlines the immune cells edited with CAR molecules. We aim for the conveyed messages to contribute towards the advancement of in vivo CAR application.

The role of circRNAs in resistance to doxorubicin

Doxorubicin is an anthracyline recognized as an antitumor antibiotic agent. It is widely used in the chemotherapeutic regimens in different types of cancers. Resistance to doxorubicin is a major clinical obstacle and main cause of failure in cancer chemotherapy. Among different mechanisms involved in this process, the role of epigenetic factors has been highlighted. Circular RNAs (circRNAs) have a prominent role in this process. Here, we summarize the recent findings on the role of circRNAs in doxorubicin resistance, particularly in breast cancer and osteosarcoma and underscore their clinical application as potential biomarkers and therapeutic targets in this field. Recognition of the underlying mechanism of circRNAs involvement in doxorubicin resistance will expand our understanding of chemoresistance establishment and may provide a prospect to develop circRNA-based predictive biomarkers of chemotherapy or therapeutic strategies for cancer patients.

Development of hydrophobic tag purifying monophosphorylated RNA for chemical synthesis of capped mRNA and enzymatic synthesis of circular mRNA

We developed phosphorylation reagents with a nitrobenzyl hydrophobic tag and used them for 5'-phosphorylation of chemically or transcriptionally synthesized RNA. The capability of hydrophobic tags to synthesize 5'-monophosphorylated RNA was evaluated based on the yield of the desired oligonucleotides, stability of protecting groups during cleavage/deprotection, separation ability in reverse-phase HPLC (RP-HPLC), and deprotection efficiency after RP-HPLC purification. The results showed that a nitrobenzyl derivative with a tert-butyl group at the benzyl position was most suitable for RNA 5'-phosphorylation. Using the developed phosphorylation reagent, we chemically synthesized 5'-phosphorylated RNA and confirmed that it could be purified by RP-HPLC and the following deprotection. In addition, we demonstrated complete chemical synthesis of minimal mRNA by chemical capping of 5'-monophosphorylated RNA. Ribonucleoside 5'-monophosphates with hydrophobic protecting groups have also been developed and used as substrates to transcriptionally synthesize 5'-phosphorylated RNA with >1000 bases. From the mixture of the by-products and the desired RNA, only 5'-monophosphorylated RNA could be effectively isolated by RP-HPLC. Furthermore, monophosphorylated RNA can be converted into circular mRNA via RNA ligase-mediated cyclization. Circular mRNA expression of nanoluciferase in cultured cells and mice. These techniques are important for the production of chemically synthesized mRNA and circular mRNA.

Analytical Methods to Evaluate RNA Circularization Efficiency

Circular RNAs (circRNAs) have emerged as pivotal players in RNA therapeutics. Unlike linear counterparts, circRNAs possess a closed-loop structure, conferring them with enhanced stability and resistance to degradation. Ribozyme-based strategy stands out as the predominant method for synthetic circRNA production, by precisely cleaving and promoting the formation of a covalent circular structure. However, there is still a lack of analytical methods that can provide high-throughput and quantitative analysis to facilitate the circRNA vector engineering process. In the report, we detail analytical methods to characterize and evaluate ribozyme-based RNA circularization efficiency. Our approach will capture the attention of researchers interested in optimizing RNA circularization efficiency, as well as those focused on exploring key elements for ribozyme catalytic activity.

Synthetic circRNA therapeutics: innovations, strategies, and future horizons

Small molecule drugs are increasingly emerging as innovative and effective treatments for various diseases, with mRNA therapeutics being a notable representative. The success of COVID-19 vaccines has underscored the transformative potential of mRNA in RNA therapeutics. Within the RNA family, there is another unique type known as circRNA. This single-stranded closed-loop RNA molecule offers notable advantages over mRNA, including enhanced stability and prolonged protein expression, which may significantly impact therapeutic strategies. Furthermore, circRNA plays a pivotal role in the pathogenesis of various diseases, such as cancers, autoimmune disorders, and cardiovascular diseases, making it a promising clinical intervention target. Despite these benefits, the application of circRNA in clinical settings remains underexplored. This review provides a comprehensive overview of the current state of synthetic circRNA therapeutics, focusing on its synthesis, optimization, delivery, and diverse applications. It also addresses the challenges impeding the advancement of circRNA therapeutics from bench to bedside. By summarizing these aspects, the review aims to equip researchers with insights into the ongoing developments and future directions in circRNA therapeutics. Highlighting both the progress and the existing gaps in circRNA research, this review offers valuable perspectives for advancing the field and guiding future investigations.

Circular RNAs in Cardiovascular Diseases: Molecular Mechanisms, Therapeutic Advances, and Innovations

Circular RNAs (circRNAs) have emerged as promising therapeutic targets due to their unique covalently closed-loop structures and their regulatory roles in gene expression. Despite their potential, challenges in circRNA-based therapies include ensuring stability, tissue specificity, and efficient intracellular delivery. This review explores the implications of circRNAs in cardiovascular diseases (CVDs), providing an overview of their biogenesis, molecular mechanisms, and roles in disease pathology. In addition to discussing molecular features, this review highlights therapeutic advances, including small-molecule drugs targeting circRNAs, synthetic circRNA sponges, and innovations in drug delivery systems that enhance the effectiveness of these therapies. Finally, current challenges and future directions are addressed, emphasizing the need for continued research to fully unlock the therapeutic potential of circRNA-based strategies in cardiovascular medicine.

Advances in the design and delivery of RNA vaccines for infectious diseases

RNA medicines represent a paradigm shift in treatment and prevention of critical diseases of global significance, e.g., infectious diseases. The highly successful messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were developed at record speed during the coronavirus disease 2019 pandemic. A consequence of this is exceptionally shortened vaccine development times, which in combination with adaptability makes the RNA vaccine technology highly attractive against infectious diseases and for pandemic preparedness. Here, we review state of the art in the design and delivery of RNA vaccines for infectious diseases based on different RNA modalities, including linear mRNA, self-amplifying RNA, trans-amplifying RNA, and circular RNA. We provide an overview of the clinical pipeline of RNA vaccines for infectious diseases, and present analytical procedures, which are paramount for characterizing quality attributes and guaranteeing their quality, and we discuss future perspectives for using RNA vaccines to combat pathogens beyond SARS-CoV-2.

Role of exosomal non‑coding RNAs in ovarian cancer (Review)

Ovarian cancer (OC) is a common gynecological disease with a high mortality rate worldwide due to its insidious nature and undetectability at an early stage. The standard treatment, combining platinum‑based chemotherapy with cytoreductive surgery, has suboptimal results. Therefore, early diagnosis of OC is crucial. All cell types secrete extracellular vesicles, particularly exosomes. Exosomes, which contain lipids, proteins, DNA and non‑coding RNAs (ncRNAs), are novel methods of intercellular communication that participate in tumor development and progression. ncRNAs are categorized by size into long ncRNAs (lncRNAs) and small ncRNAs (sncRNAs). sncRNAs further include transfer RNAs, small nucleolar RNAs, PIWI‑interacting RNAs and microRNAs (miRNAs). miRNAs inhibit protein translation and promote messenger RNA (mRNA) cleavage to suppress gene expression. By sponging downstream miRNAs, lncRNAs and circular RNAs can regulate target gene expression, thereby weakening the interactions between miRNAs and mRNAs. Exosomes and exosomal ncRNAs, commonly present in human biological fluids, are promising biomarkers for OC. The present article aimed to review the potential role of exosomal ncRNAs in the diagnosis and prognosis of OC by summarizing the characteristics, processes, roles and isolation methods of exosomes and exosomal ncRNAs.

Circular RNA oligonucleotides: enzymatic synthesis and scaffolding for nanoconstruction

We report the efficient synthesis of monomeric circular RNAs (circRNAs) in the size range of 16-44 nt with a novel DNA dumbbell splinting plus T4 DNA ligation strategy. Such a DNA dumbbell splinting strategy was developed by one group among ours recently for near-quantitative conversion of short linear DNAs into monomeric circular ones. Furthermore, using the 44 nt circRNA as scaffold strands, we constructed hybrid RNA:DNA and pure RNA:RNA double crossover tiles and their assemblies of nucleic acid nanotubes and flat arrays.

Circular RNAs: Novel Players in Cancer Mechanisms and Therapeutic Strategies

Circular RNAs (circRNAs) are a novel class of noncoding RNAs that have emerged as pivotal players in gene regulation. Our understanding of circRNAs has greatly expanded over the last decade, with studies elucidating their biology and exploring their therapeutic applications. In this review, we provide an overview of the current understanding of circRNA biogenesis, outline their mechanisms of action in cancer, and assess their clinical potential as biomarkers. Furthermore, we discuss circRNAs as a potential therapeutic strategy, including recent advances in circRNA production and translation, along with proof-of-concept preclinical studies of cancer vaccines.

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.

In Vitro Self-Circularization Methods Based on Self-Splicing Ribozyme

In vitro circular RNA (circRNA) preparation methods have been gaining a lot of attention recently as several reports suggest that circRNAs are more stable, with better performances in cells and in vivo, than linear RNAs in various biomedical applications. Self-splicing ribozymes are considered a major in vitro circRNA generation method for biomedical applications due to their simplicity and efficiency in the circularization of the gene of interest. This review summarizes, updates, and discusses the recently developed self-circularization methods based on the self-splicing ribozyme, such as group I and II intron ribozymes, and the pros and cons of each method in preparing circRNA in vitro.

Advances in Engineering Circular RNA Vaccines

Engineered circular RNAs (circRNAs) are a class of single-stranded RNAs with head-to-tail covalently linked structures that integrate open reading frames (ORFs) and internal ribosome entry sites (IRESs) with the function of coding and expressing proteins. Compared to mRNA vaccines, circRNA vaccines offer a more improved method that is safe, stable, and simple to manufacture. With the rapid revelation of the biological functions of circRNA and the success of Severe Acute Respiratory Coronavirus Type II (SARS-CoV-2) mRNA vaccines, biopharmaceutical companies and researchers around the globe are attempting to develop more stable circRNA vaccines for illness prevention and treatment. Nevertheless, research on circRNA vaccines is still in its infancy, and more work and assessment are needed for their synthesis, delivery, and use. In this review, based on the current understanding of the molecular biological properties and immunotherapeutic mechanisms of circRNA, we summarize the current preparation methods of circRNA vaccines, including design, synthesis, purification, and identification. We discuss their delivery strategies and summarize the challenges facing the clinical application of circRNAs to provide references for circRNA vaccine-related research.

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.

Bibliometric Analysis of Global Research on Circular RNA: Current Status and Future Directions

Circular RNAs (circRNAs) have gained significant attention in recent years. This bibliometric analysis aimed to provide insights into the current state and future trends of global circRNA research. The scientific output on circRNAs from 2010 to 2022 was retrieved from the Web of Science Core Collection with circRNA-related terms as the subjects. Key bibliometric indicators were calculated and evaluated using CiteSpace. A total of 7385 studies on circRNAs were identified. The output and citation number have increased rapidly after 2015. China, the USA, and Germany were top three publishing countries. Currently, circCDR1as, circHIPK3, circPVT1, circSHPRH, and circZNF609 are the most studied circRNAs; and all are related to cancer. The theme of research have shifted from transcript, exon circularization and miRNA sponge topics to the transcriptome, tumor suppressor, and biomarkers, indicating that research interests have evolved from basic to applied research. CircRNAs will continue to be a highly active research area in the near future. From the current understanding of circRNA characterization and regulatory mechanisms as miRNA sponges in cancer, future directions may examine potential diagnostic and therapeutic roles of circRNAs in cancers or the function and mechanism of circRNAs in other diseases.

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.

CircRNA knockdown based on antisense strategies

Circular RNAs (circRNAs) are a type of noncoding RNA that are formed by back-splicing from eukaryotic protein-coding genes. The most frequently reported and well-characterized function of circRNAs is their ability to act as molecular decoys, most often as miRNA and protein sponges. However, the functions of most circRNAs still need to be better understood. To more fully understand the biological relevance of validated circRNAs, knockdown functional analyses can be performed using antisense oligonucleotides, RNA interference (RNAi) experiments (e.g., targeting back-splicing junction sites), the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas)-9 system (e.g., generating circRNA-specific knockouts), and CRISPR-Cas13 technology to effectively target circRNAs without affecting host genes. In this review, I summarize the feasibility and effectiveness of circRNA knockdown through antisense strategies for investigating the biological roles of circRNAs in cultured cells and animal models.

N6-methyladenosine-modified circ_0006168 promotes epithelial mesenchymal transition via miR-384/STAT3/Snail axis in esophageal squamous cell carcinoma

Circular RNAs (circRNAs) are involved in the pathogenesis of esophageal squamous cell carcinoma (ESCC). This study aimed to explore the mechanisms of aberrant expression and functions of circ_0006168 in ESCC. In this study, real-time qPCR and fluorescence in situ hybridization (FISH) are adopted to estimate the expression and localization of circ_0006168 in cancer tissues and cells. Methylated RNA immunoprecipitation (MeRIP) was performed to detect the N6-methyladenosine (m6A) modification of circ_0006168. Gain- and loss-of-functions of circ_0006168 were performed to identify its role in ESCC progression. RNA-binding protein immunoprecipitation (RIP) was used to detect the interaction of circ_0006168 with IGF2BP2. Luciferase reporter assay and RIP are used to confirm the circ_0006168/miR-384/STAT3 ceRNA network. Our results showed that the expression of circ_0006168 was upregulated in ESCC tissues and cells. METTL3-mediated m6A modification increased the expression of circ_0006168 via IGF2BP2-dependent way in TE-1 cells. Circ_0006168 promoted cell proliferation, migration, invasion, cell cycle progression and inhibited cell apoptosis, while knockdown of circ_0006168 had the reverse effects. Mechanistically, circ_0006168 acted its functions via miR-384/STAT3/Snail axis in TE-1 cells. In conclusion, circ_0006168 is upregulated in ESCC and m6A methylation increased its expression via IGF2BP2. CircRNA_0006168 promotes cell migration, invasion by regulating EMT via miR-384/STAT3/Snail axis in ESCC.

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.

Potential therapeutic applications of circular RNA in acute kidney injury

Acute kidney injury (AKI) is a common clinical syndrome characterized by a rapid deterioration in renal function, manifested by a significant increase in creatinine and a sharp decrease in urine output. The incidence of morbidity and mortality associated with AKI is on the rise, with most patients progressing to chronic kidney disease or end-stage renal disease. Treatment options for patients with AKI remain limited. Circular RNA (circRNA) is a wide and diverse class of non-coding RNAs that are present in a variety of organisms and are involved in gene expression regulation. Studies have shown that circRNA acts as a competing RNA, is involved in disease occurrence and development, and has potential as a disease diagnostic and prognostic marker. CircRNA is involved in the regulation of important biological processes, including apoptosis, oxidative stress, and inflammation. This study reviews the current status and progress of circRNA research in the context of AKI.

Potential therapeutic strategy for cancer: Multi-dimensional cross-talk between circRNAs and parental genes

In many ways, circular RNAs (circRNAs) have been demonstrated to be crucial in the onset and advancement of cancer throughout the last ten years and have become a new focus of intense research in the field of RNAs. Accumulating studies have demonstrated that circRNAs can regulate parental gene expression via a variety of biological pathways. Furthermore, research into the complex interactions between circRNAs and their parental genes will shed light on their biological roles and open up new avenues for circRNAs' potential clinical translational uses. However, to date, multi-dimensional cross-talk between circRNAs and parental genes have not been systematically elucidated. Particularly intriguing is circRNA's exploration of tumor targeting, and potential therapeutic uses based on the parental gene regulation perspective. Here, we discuss their biogenesis, take a fresh look at the molecular mechanisms through which circRNAs control the expression of their parental genes in cancer. We further highlight We further highlight the latest circRNA clinical translational applications, including prognostic diagnostic markers, cancer vaccines, gDNA, and so on. Demonstrating the potential benefits and future applications of circRNA therapy.

Circ_0003945: an emerging biomarker and therapeutic target for human diseases

Due to the rapid development of RNA sequencing techniques, a circular non-coding RNA (ncRNA) known as circular RNAs (circRNAs) has gradually come into focus. As a distinguished member of the circRNA family, circ_0003945 has garnered attention for its aberrant expression and biochemical functions in human diseases. Subsequent studies have revealed that circ_0003945 could regulate tumor cells proliferation, migration, invasion, apoptosis, autophagy, angiogenesis, drug resistance, and radio resistance through the molecular mechanism of competitive endogenous RNA (ceRNA) during tumorigenesis. The expression of circ_0003945 is frequently associated with some clinical parameters and implies a poorer prognosis in the majority of cancers. In non-malignant conditions, circ_0003945 also holds considerable importance in diseases pathogenesis. This review aims to recapitulate molecular mechanism of circ_0003945 and elucidates its potential as a diagnostic and therapeutic target in neoplasms and other diseases.

Effective synthesis of circRNA via a thermostable T7 RNA polymerase variant as the catalyst

Introduction

Circular RNAs (circRNAs) are endogenous noncoding RNAs (ncRNAs) with transcriptional lengths ranging from hundreds to thousands. circRNAs have attracted attention owing to their stable structure and ability to treat complicated diseases. Our objective was to create a one-step reaction for circRNA synthesis using wild-type T7 RNA polymerase as the catalyst. However, T7 RNA polymerase is thermally unstable, and we streamlined circRNA synthesis via consensus and folding free energy calculations for hotspot selection. Because of the thermal instability, the permuted intron and exon (PIE) method for circRNA synthesis is conducted via tandem catalysis with a transcription reaction at a low temperature and linear RNA precursor cyclization at a high temperature.

Methods

To streamline the process, a multisite mutant T7 RNA polymerase (S430P, N433T, S633P, F849I, F880Y, and G788A) with significantly improved thermostability was constructed, and G788A was used.

Results

The resulting mutant exhibited stable activity at 45°C for over an hour, enabling the implementation of a one-pot transcription and cyclization reaction. The simplified circRNA production process demonstrated an efficiency comparable to that of the conventional two-step reaction, with a cyclization rate exceeding 95% and reduced production of immunostimulatory dsRNA byproducts.

Role of circular RNAs and gut microbiome in gastrointestinal cancers and therapeutic targets

Gastrointestinal cancers are a huge worldwide health concern, which includes a wide variety of digestive tract cancers. Circular RNAs (circRNAs), a kind of non-coding RNA (ncRNAs), are a family of single-stranded, covalently closed RNAs that have become recognized as crucial gene expression regulators, having an impact on several cellular functions in cancer biology. The gut microbiome, which consists of several different bacteria, actively contributes to the regulation of host immunity, inflammation, and metabolism. CircRNAs and the gut microbiome interact significantly to greatly affect the growth of GI cancer. Several studies focus on the complex functions of circRNAs and the gut microbiota in GI cancers, including esophageal cancer, colorectal cancer, gastric cancer, hepatocellular cancer, and pancreatic cancer. It also emphasizes how changed circRNA expression profiles and gut microbiota affect pathways connected to malignancy as well as how circRNAs affect hallmarks of gastrointestinal cancers. Furthermore, circRNAs and gut microbiota have been recommended as biological markers for therapeutic targets as well as diagnostic and prognostic purposes. Targeting circRNAs and the gut microbiota for the treatment of gastrointestinal cancers is also being continued to study. Despite significant initiatives, the connection between circRNAs and the gut microbiota and the emergence of gastrointestinal cancers remains poorly understood. In this study, we will go over the most recent studies to emphasize the key roles of circRNAs and gut microbiota in gastrointestinal cancer progression and therapeutic options. In order to create effective therapies and plan for the future gastrointestinal therapy, it is important to comprehend the functions and mechanisms of circRNAs and the gut microbiota.

Highly efficient cellular expression of circular mRNA enables prolonged protein expression

A major problem with mRNA therapeutics is that mRNA is usually degraded within a few hours after entering the cytosol. New approaches for in vitro synthesis of circular mRNA have allowed increased levels and duration of protein synthesis from mRNA therapeutics due to the long half-life of circular mRNA. However, it remains difficult to genetically encode circular mRNAs in mammalian cells. Here, we describe the adaptation of the Tornado (Twister-optimized RNA for durable overexpression) system to achieve in-cell synthesis of circular mRNAs. We screen different promoters and internal ribosomal entry sites (IRESs) and identify combinations that result in high levels of circular mRNA and protein expression. We show that these circular mRNAs can be packaged into virus-like particles (VLPs), thus enabling prolonged protein expression. Overall, these data describe a platform for synthesis of circular mRNAs and how these circular mRNAs can improve VLP therapeutics.

Regulation of Angiogenesis by Non-Coding RNAs in Cancer

Non-coding RNAs, including microRNAs, long non-coding RNAs, and circular RNAs, have been identified as crucial regulators of various biological processes through epigenetic regulation, transcriptional regulation, and post-transcriptional regulation. Growing evidence suggests that dysregulation and activation of non-coding RNAs are closely associated with tumor angiogenesis, a process essential for tumor growth and metastasis and a major contributor to cancer-related mortality. Therefore, understanding the molecular mechanisms underlying tumor angiogenesis is of utmost importance. Numerous studies have documented the involvement of different types of non-coding RNAs in the regulation of angiogenesis. This review provides an overview of how non-coding RNAs regulate tumor angiogenesis. Additionally, we discuss emerging strategies that exploit non-coding RNAs for anti-angiogenic therapy in cancer treatment. Ultimately, this review underscores the crucial role played by non-coding RNAs in tumor angiogenesis and highlights their potential as therapeutic targets for anti-angiogenic interventions against cancer.

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.

Biogenesis and Function of circRNAs in Pulmonary Fibrosis

Pulmonary fibrosis is a class of fibrosing interstitial lung diseases caused by many pathogenic factors inside and outside the lung, with unknown mechanisms and without effective treatment. Therefore, a comprehensive understanding of the molecular mechanism implicated in pulmonary fibrosis pathogenesis is urgently needed to develop new and effective measures. Although circRNAs have been widely acknowledged as new contributors to the occurrence and development of diseases, only a small number of circRNAs have been functionally characterized in pulmonary fibrosis. Here, we systematically review the biogenesis and functions of circRNAs and focus on how circRNAs participate in pulmonary fibrogenesis by influencing various cell fates. Meanwhile, we analyze the current exploration of circRNAs as a diagnostic biomarker, vaccine, and therapeutic target in pulmonary fibrosis and objectively discuss the challenges of circRNA- based therapy for pulmonary fibrosis. We hope that the review of the implication of circRNAs will provide new insights into the development circRNA-based approaches to treat pulmonary fibrosis.