Clinical Delivery of Circular RNA: Lessons Learned from RNA Drug Development

Circular RNAs in cancer: roles, mechanisms, and therapeutic potential across colorectal, gastric, liver, and lung carcinomas

The prominence of circular RNAs (circRNAs) has surged in cancer research due to their distinctive properties and impact on cancer development. This review delves into the role of circRNAs in four key cancer types: colorectal cancer (CRC), gastric cancer (GC), liver cancer (HCC), and lung cancer (LUAD). The focus lies on their potential as cancer biomarkers and drug targets. Our study analyses the reported circRNAs in the mentioned malignancies, examining their nature, functions, targets, origins, and contributions as tumor enhancers or suppressors. The approach involved assessing full-text reports on PMC, utilizing keywords such as "CircRNA" and "Cancer types," coupled with bioinformatics, experimental assays, or clinical investigations. Exclusions encompassed non-English publications, conference abstracts, letters, and expert opinions. The findings unveil 577 identified circRNAs across these cancer types: 124 in CRC, 177 in GC, 93 in HCC, and 183 in LUAD. Mechanistic insights into how circRNAs modulate gene expression in cancer are explored, particularly their interactions with microRNAs and RNA-binding proteins. Dysregulation of circRNAs across various cancers and their potential as diagnostic and prognostic indicators are synthesized. The exploration extends to the potential of targeting circRNAs as a novel cancer therapy strategy, either through inhibiting oncogenic circRNAs or reinstating tumor-suppressive ones. This article discusses the challenges and prospects in harnessing circRNAs for cancer diagnostics and therapies. These comprehensive analyses hold promise for advancing cancer research and fostering the development of innovative therapies and diagnostics.

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.

CircRNA-loaded DC vaccine in combination with low-dose gemcitabine induced potent anti-tumor immunity in pancreatic cancer model

Although promising, dendritic cell (DC) vaccines may not suffice to fully inhibit tumor progression alone, mainly due to the short expression time of the antigen in DC vaccines, immunosuppressive tumor microenvironment, and tumor antigenic modulation. Overcoming the limitations of DC vaccines is expected to further enhance their anti-tumor effects. In this study, we constructed a circRNA-loaded DC vaccine utilizing the inherent stability of circular RNA to enhance the expression level and duration of the antigen within the DC vaccine. Meanwhile we combined it with gemcitabine and validated their therapeutic efficacy in the Panc02 tumor model. We found that the use of DC vaccine alone can reach a tumor inhibition rate of 69%, and the effect was further enhanced when combined with gemcitabine, reaching a tumor inhibition rate of 89%. The combined treatment achieved a synergistic effect, which not only reduced immunosuppressive Tregs but also induced immunogenic cell death, leading to antigen spreading and reducing immune evasion caused by tumor antigenic modulation. As a result, the survival of the mice was significantly prolonged. Our research provides a promising approach for the clinical treatment of pancreatic cancer.

Advances in Evolved T7 RNA Polymerases for Expanding the Frontiers of Enzymatic Nucleic Acid Synthesis

In vitro RNA synthesis technologies are crucial in developing therapeutic RNA drugs, such as mRNA vaccines and RNA interference (RNAi) therapies. Enzymatic RNA synthesis, recognized for its sustainability and efficiency, enables the production of extensive RNA sequences under mild conditions. Among the enzymes utilized, T7 RNA polymerase is distinguished by its exceptional catalytic efficiency, enabling the precise and rapid transcription of RNA from DNA templates by recognizing the specific T7 promoter sequence. With the advancement in clinical applications of RNA-based drugs, there is an increasing demand for the synthesis of chemically modified RNAs that are stable and resistant to nuclease degradation. To this end, researchers have applied directed evolution to broaden the enzyme's substrate scope, enhancing its compatibility with non-canonical substrates and reducing the formation of by-products. This review summarizes the progress in engineering T7 RNA polymerase for these purposes and explores prospective developments in the field.

Advancing the next generation of cancer treatment with circular RNAs in CAR-T cell therapy

Chimeric Antigen Receptor T-cell (CAR-T) therapy has revolutionized the treatment of hematological malignancies. However, its effectiveness against solid tumors remains constrained by challenges such as T-cell exhaustion, limited persistence, and off-target effects. These challenges highlight critical gaps in current CAR-T cell therapeutic strategies, particularly for solid tumor applications. Circular RNAs (circRNAs) represent a transformative class of non-coding RNAs, known for their exceptional stability and precise regulatory functions, positioning them as promising candidates for enhancing next-generation CAR-T cell therapies. Notably, circRNAs can bridge the gap between preclinical research and clinical application by offering innovative solutions to overcome technical hurdles and improve therapeutic outcomes. Despite their potential, circRNAs remain underexplored in clinical application of CAR-T cell therapies for solid tumors, presenting a significant opportunity for innovation. The mechanisms through which circRNAs modulate CAR-T cell exhaustion, persistence, and tumor specificity are not yet fully understood, and technical challenges, such as achieving efficient and targeted circRNA delivery, which still need to be addressed. This review highlights the importance of integrating circRNAs into CAR-T cell therapy to enhance specificity, minimize off-target effects, and improve therapeutic durability. By emphasizing the innovative potential of circRNAs and identifying key research gaps, this review provides a roadmap for advancing CAR-T cell therapy and setting the stage for the next generation of personalized cancer treatments.

Progress and prospects of mRNA-based drugs in pre-clinical and clinical applications

In the last decade, messenger ribonucleic acid (mRNA)-based drugs have gained great interest in both immunotherapy and non-immunogenic applications. This surge in interest can be largely attributed to the demonstration of distinct advantages offered by various mRNA molecules, alongside the rapid advancements in nucleic acid delivery systems. It is noteworthy that the immunogenicity of mRNA drugs presents a double-edged sword. In the context of immunotherapy, extra supplementation of adjuvant is generally required for induction of robust immune responses. Conversely, in non-immunotherapeutic scenarios, immune activation is unwanted considering the host tolerability and high expression demand for mRNA-encoded functional proteins. Herein, mainly focused on the linear non-replicating mRNA, we overview the preclinical and clinical progress and prospects of mRNA medicines encompassing vaccines and other therapeutics. We also highlight the importance of focusing on the host-specific variations, including age, gender, pathological condition, and concurrent medication of individual patient, for maximized efficacy and safety upon mRNA administration. Furthermore, we deliberate on the potential challenges that mRNA drugs may encounter in the realm of disease treatment, the current endeavors of improvement, as well as the application prospects for future advancements. Overall, this review aims to present a comprehensive understanding of mRNA-based therapies while illuminating the prospective development and clinical application of mRNA drugs.

RNA Coating Promotes Peri-Implant Osseointegration

In addition to transmitting and carrying genetic information, RNA plays an important abiotic role in the world of nanomaterials. RNA is a natural polyanionic biomacromolecule, and its ability to promote osteogenesis by binding with other inorganic materials as an osteogenic induction agent was discovered only recently. However, whether it can promote osseointegration on implants has not been reported. Here, we investigated the effect of the RNA-containing coating materials on peri-implant osseointegration. Total RNA extracted from rat muscle tissue was used as an osteogenic induction agent, and hyaluronic acid (HA) was used to maintain its negative charge. In simulated body fluids (SBF), in vitro studies demonstrated that the resulting material encouraged calcium salt deposition. Cytological experiments showed that the RNA-containing coating induced greater cell adhesion and osteogenic differentiation in comparison to the control. The results of animal experiments showed that the RNA-containing coating had osteoinductive and bone conduction activities, which are beneficial for bone formation and osseointegration. Therefore, the RNA-containing coatings are useful for the surface modification of titanium implants to promote osseointegration.

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.

An insight into heat stress response and adaptive mechanism in cotton

The growing worldwide population is driving up demand for cotton fibers, but production is hampered by unpredictable temperature rises caused by shifting climatic conditions. Numerous research based on breeding and genomics have been conducted to increase the production of cotton in environments with high and low-temperature stress. High temperature (HT) is a major environmental stressor with global consequences, influencing several aspects of cotton plant growth and metabolism. Heat stress-induced physiological and biochemical changes are research topics, and molecular techniques are used to improve cotton plants' heat tolerance. To preserve internal balance, heat stress activates various stress-responsive processes, including repairing damaged proteins and membranes, through various molecular networks. Recent research has investigated the diverse reactions of cotton cultivars to temperature stress, indicating that cotton plant adaptation mechanisms include the accumulation of sugars, proline, phenolics, flavonoids, and heat shock proteins. To overcome the obstacles caused by heat stress, it is crucial to develop and choose heat-tolerant cotton cultivars. Food security and sustainable agriculture depend on the application of genetic, agronomic, and, biotechnological methods to lessen the impacts of heat stress on cotton crops. Cotton producers and the textile industry both benefit from increased heat tolerance. Future studies should examine the developmental responses of cotton at different growth stages, emphasize the significance of breeding heat-tolerant cultivars, and assess the biochemical, physiological, and molecular pathways involved in seed germination under high temperatures. In a nutshell, a concentrated effort is required to raise cotton's heat tolerance due to the rising global temperatures and the rise in the frequency of extreme weather occurrences. Furthermore, emerging advances in sequencing technologies have made major progress toward successfully se sequencing the complex cotton genome.

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.

Emerging Roles of ncRNAs in Type 2 Diabetes Mellitus: From Mechanisms to Drug Discovery

Type 2 diabetes mellitus (T2DM), a high-incidence chronic metabolic disorder, has emerged as a global health issue, where most patients need lifelong medication. Gaining insights into molecular mechanisms involved in T2DM development is expected to provide novel strategies for clinical prevention and treatment. Growing evidence validates that non-coding RNAs (ncRNAs) including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) function as crucial regulators in multiple biological processes of T2DM, inspiring various potential targets and drug candidates. In this review, we summarize the current understanding of ncRNA roles in T2DM and discuss the potential use of ncRNAs as targets and active molecules for drug discovery.

circCUL3 drives malignant progression of cervical cancer by activating autophagy through sponge miR-223-3p upregulation of ATG7

Circular RNA (circRNA) has emerged as a pivotal regulatory factor in cancer biology, yet its exact role in cervical cancer remains incompletely understood. In this study, we investigated the functional role of circCUL3 in cervical cancer and explored its potential as a therapeutic target. Functional gain and loss experiments were conducted in Hela and Siha cell lines to elucidate the biological functions of circCUL3 in cervical cancer. The results revealed that circCUL3 overexpression significantly enhanced cell viability, migration, and invasion while suppressing apoptosis, while circCUL3 knockout displayed the opposite effects. Mechanistically, we identified hsa-miR-223-3p as a target of circCUL3, with its expression being negatively regulated by circCUL3. Furthermore, we discovered that circCUL3 could sequester miR-223-3p, leading to the upregulation of ATG7 expression, and this was linked to the regulation of autophagy in cervical cancer cells. In vivo validation using a xenograft mouse model further supported our in vitro findings. Notably, we found that chloroquine (CQ), an autophagy inhibitor, restored miR-223-3p expression and counteracted the oncogenic effect of circCUL3 overexpression. In conclusion, circCUL3 potentially contributes to the malignant progression of cervical cancer by acting as a sponge for miR-223-3p, resulting in the upregulation of ATG7 and the activation of autophagy.

A Machine Learning Method for RNA-Small Molecule Binding Preference Prediction

The interaction between RNA and small molecules is crucial in various biological functions. Identifying molecules targeting RNA is essential for the inhibitor design and RNA-related studies. However, traditional methods focus on learning RNA sequence and secondary structure features and neglect small molecule characteristics, and resulting in poor performance on unknown small molecule testing. To overcome this limitation, we developed a double-layer stacking-based machine learning model called ZHMol-RLinter. This approach more effectively predicts RNA-small molecule binding preferences by learning RNA and small molecule features to capture their interaction information. ZHMol-RLinter also combines sequence and secondary structural features with structural geometric and physicochemical environment information to capture the specificity of RNA spatial conformations in recognizing small molecules. Our results demonstrate that ZHMol-RLinter has a success rate of 90.8% on the published RL98 testing set, representing a significant improvement over existing methods. Additionally, ZHMol-RLinter achieved a success rate of 77.1% on the unknown small molecule UNK96 testing set, showing substantial improvement over the existing methods. The evaluation of predicted structures confirms that ZHMol-RLinter is reliable and accurate for predicting RNA-small molecule binding preferences, even for challenging unknown small molecule testing. Predicting RNA-small molecule binding preferences can help in the understanding of RNA-small molecule interactions and promote the design of RNA-related drugs for biological and medical applications.

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.

Non-canonical translation in cancer: significance and therapeutic potential of non-canonical ORFs, m6A-modification, and circular RNAs

Translation is a decoding process that synthesizes proteins from RNA, typically mRNA. The conventional translation process consists of four stages: initiation, elongation, termination, and ribosome recycling. Precise control over the translation mechanism is crucial, as dysregulation in this process is often linked to human diseases such as cancer. Recent discoveries have unveiled translation mechanisms that extend beyond typical well-characterized components like the m7G cap, poly(A)-tail, or translation factors like eIFs. These mechanisms instead utilize atypical elements, such as non-canonical ORF, m6A-modification, and circular RNA, as key components for protein synthesis. Collectively, these mechanisms are classified as non-canonical translations. It is increasingly clear that non-canonical translation mechanisms significantly impact the various regulatory pathways of cancer, including proliferation, tumorigenicity, and the behavior of cancer stem cells. This review explores the involvement of a variety of non-canonical translation mechanisms in cancer biology and provides insights into potential therapeutic strategies for cancer treatment.

Current landscape of mRNA technologies and delivery systems for new modality therapeutics

Realizing the immense clinical potential of mRNA-based drugs will require continued development of methods to safely deliver the bioactive agents with high efficiency and without triggering side effects. In this regard, lipid nanoparticles have been successfully utilized to improve mRNA delivery and protect the cargo from extracellular degradation. Encapsulation in lipid nanoparticles was an essential factor in the successful clinical application of mRNA vaccines, which conclusively demonstrated the technology's potential to yield approved medicines. In this review, we begin by describing current advances in mRNA modifications, design of novel lipids and development of lipid nanoparticle components for mRNA-based drugs. Then, we summarize key points pertaining to preclinical and clinical development of mRNA therapeutics. Finally, we cover topics related to targeted delivery systems, including endosomal escape and targeting of immune cells, tumors and organs for use with mRNA vaccines and new treatment modalities for human diseases.

Biologic activity and treatment resistance to gastrointestinal cancer: the role of circular RNA in autophagy regulation

Circular RNAs (circRNAs) lack the 5'-end methylated guanine cap structure and 3' polyadenylate tail structure, classifying it as a non-coding RNA. With the extensive investigation of circRNA, its role in regulating cell death has garnered significant attention in recent years, establishing it as a recognized participant in cancer's biological processes. Autophagy, an essential pathway in programmed cell death (PCD), involves the formation of autophagosomes using lysosomes to degrade cellular contents under the regulation of various autophagy-related (ATG) genes. Numerous studies have demonstrated that circRNA can modulate the biological activity of cancer cells by influencing the autophagy pathway, exhibiting a dualistic role in suppressing or promoting carcinogenesis. In this review, we comprehensively analyze how autophagy-related circRNA impacts the progression of gastrointestinal cancer (GIC). Additionally, we discuss drug resistance phenomena associated with autophagy regulation in GIC. This review offers valuable insights into exploring potential biological targets for prognosis and treatment strategies related to GIC.

Circular RNAs in tumor immunity and immunotherapy

Circular RNAs (circRNAs) are unique noncoding RNAs that have a closed and stable loop structure generated through backsplicing. Due to their conservation, stability and tissue specificity, circRNAs can potentially be used as diagnostic indicators and therapeutic targets for certain tumors. Many studies have shown that circRNAs can act as microRNA (miRNA) sponges, and engage in interactions with proteins and translation templates to regulate gene expression and signal transduction, thereby participating in the occurrence and development of a variety of malignant tumors. Immunotherapy has revolutionized the treatment of cancer. Early researches have indicated that circRNAs are involved in regulating tumor immune microenvironment and antitumor immunity. CircRNAs may have the potential to be important targets for increasing sensitivity to immunotherapy and expanding the population of patients who benefit from cancer immunotherapy. However, few studies have investigated the correlation between circRNAs and tumor immunity. In this review, we summarize the current researches on circRNAs involved in antitumor immune regulation through different mechanisms and their potential value in increasing immunotherapy efficacy with the goal of providing new targets for cancer immunotherapy.

FGF18 encoding circular mRNA-LNP based on glycerolipid engineering of mesenchymal stem cells for efficient amelioration of osteoarthritis

Mesenchymal stem cells (MSCs) exhibit substantial potential for osteoarthritis (OA) therapy through cartilage regeneration, yet the realization of optimal therapeutic outcomes is hampered by their limited intrinsic reparative capacities. Herein, MSCs are engineered with circular mRNA (cmRNA) encoding fibroblast growth factor 18 (FGF18) encapsulated within lipid nanoparticles (LNP) derived from a glycerolipid to facilitate OA healing. A proprietary biodegradable and ionizable glycerolipid, TG6A, with branched tails and five ester bonds, forms LNP exhibiting above 9-fold and 41-fold higher EGFP protein expression in MSCs than commercial LNP from DLin-MC3-DMA and ALC-0315, respectively. The introduction of FGF18 not only augmented the proliferative capacity of MSCs but also upregulated the expression of chondrogenic genes and glycosaminoglycan (GAG) content. Additionally, FGF18 enhanced the production of proteoglycans and type II collagen in chondrocyte pellet cultures in a three-dimensional culture. In an OA rat model, transplantation with FGF18-engineered MSCs remarkably preserved cartilage integrity and facilitated functional repair of cartilage lesions, as evidenced by thicker cartilage layers, reduced histopathological scores, maintenance of zone structure, and incremental type II collagen and extracellular matrix (ECM) deposition. Taken together, our findings suggest that TG6A-based LNP loading with cmRNA for engineering MSCs present an innovative strategy to overcome the current limitations in OA treatment.

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.

The roles of circular RNAs in nerve injury and repair

Nerve injuries significantly impact the quality of life for patients, with severe cases posing life-threatening risks. A comprehensive understanding of the pathophysiological mechanisms underlying nerve injury is crucial to the development of effective strategies to promote nerve regeneration. Circular RNAs (circRNAs), a recently characterized class of RNAs distinguished by their covalently closed-loop structures, have been shown to play an important role in various biological processes. Numerous studies have highlighted the pivotal role of circRNAs in nerve regeneration, identifying them as potential therapeutic targets. This review aims to succinctly outline the latest advances in the role of circRNAs related to nerve injury repair and the underlying mechanisms, including peripheral nerve injury, traumatic brain injury, spinal cord injury, and neuropathic pain. Finally, we discuss the potential applications of circRNAs in drug development and consider the potential directions for future research in this field to provide insights into circRNAs in nerve injury repair.

mRNA Technology and Mucosal Immunization

Current mRNA vaccines are mainly administered via intramuscular injection, which induces good systemic immunity but limited mucosal immunity. Achieving mucosal immunity through mRNA vaccination could diminish pathogen replication at the entry site and reduce interhuman transmission. However, delivering mRNA vaccines to mucosae faces challenges like mRNA degradation, poor entry into cells, and reactogenicity. Encapsulating mRNA in extracellular vesicles may protect the mRNA and reduce reactogenicity, making mucosal mRNA vaccines possible. Plant-derived extracellular vesicles from edible fruits have been investigated as mRNA carriers. Studies in animals show that mRNA vehiculated in orange-derived extracellular vesicles can elicit both systemic and mucosal immune responses when administered by the oral, nasal, or intramuscular routes. Once lyophilized, these products show remarkable stability. The optimization of mRNA to improve translation efficiency, immunogenicity, reactogenicity, and stability can be obtained through adjustments of the 5'cap region, poly-A tail, codons selection, and the use of nucleoside analogues. Recent studies have also proposed self-amplifying RNA vaccines containing an RNA polymerase as well as circular mRNA constructs. Data from parenterally primed animals demonstrate the efficacy of nasal immunization with non-adjuvanted protein, and studies in humans indicate that the combination of a parenteral vaccine with the natural exposure of mucosae to the same antigen provides protection and reduces transmission. Hence, mucosal mRNA vaccination would be beneficial at least in organisms pre-treated with parenteral vaccines. This practice could have wide applications for the treatment of infectious diseases.

Prospects for the clinical application of exosomal circular RNA in squamous cell carcinoma

Squamous cell carcinoma (SCC) is a prevalent malignancy affecting multiple organs in the human body, including the oral cavity, esophagus, cervix, and skin. Given its significant incidence and mortality rates, researchers are actively seeking effective diagnostic and therapeutic strategies. In recent years, exosomes and their molecular cargo, particularly circular RNA (circRNA), have emerged as promising areas of investigation in SCC research. Exosomes are small vesicles released into the extracellular environment by cells that contain biomolecules that reflect the physiological state of the cell of origin. CircRNAs, known for their unique covalently closed loop structure and stability, have garnered special attention in oncology and are closely associated with tumorigenesis, progression, metastasis, and drug resistance. Interestingly, exosomal circRNAs have been identified as ideal biomarkers for noninvasive cancer diagnosis and prognosis assessment. This article reviews the progress in research on exosomal circRNAs, focusing on their expression patterns, functions, and potential applications as biomarkers in SCC, aiming to provide new insights and strategies for the diagnosis and treatment of SCC.

CircRNA Regulation of T Cells in Cancer: Unraveling Potential Targets

T lymphocytes play a critical role in antitumor immunity, but their exhaustion poses a significant challenge for immune evasion by malignant cells. Circular RNAs (circRNAs), characterized by their covalently closed looped structure, have emerged as pivotal regulators within the neoplastic landscape. Recent studies have highlighted their multifaceted roles in cellular processes, including gene expression modulation and protein function regulation, which are often disrupted in cancer. In this review, we systematically explore the intricate interplay between circRNAs and T cell modulation within the tumor microenvironment. By dissecting the regulatory mechanisms through which circRNAs impact T cell exhaustion, we aim to uncover pathways crucial for immune evasion and T cell dysfunction. These insights can inform innovative immunotherapeutic strategies targeting circRNA-mediated molecular pathways. Additionally, we discuss the translational potential of circRNAs as biomarkers for therapeutic response prediction and as intervention targets. Our comprehensive analysis aims to enhance the understanding of immune evasion dynamics in the tumor microenvironment by facilitating the development of precision immunotherapy.

Advancing in vivo reprogramming with synthetic biology

Reprogramming cells will play a fundamental role in shaping the future of cell therapies by developing new strategies to engineer cells for improved performance and higher-order physiological functions. Approaches in synthetic biology harness cells' natural ability to sense diverse signals, integrate environmental inputs to make decisions, and execute complex behaviors based on the health of the organism or tissue. In this review, we highlight strategies in synthetic biology to reprogram cells, and discuss how recent approaches in the delivery of modified mRNA have created new opportunities to alter cell function in vivo. Finally, we discuss how combining concepts from synthetic biology and the delivery of mRNA in vivo could provide a platform for innovation to advance in vivo cellular reprogramming.

The role of circular RNAs in regulating resistance to cancer immunotherapy: mechanisms and implications

Cancer immunotherapy has rapidly transformed cancer treatment, yet resistance remains a significant hurdle, limiting its efficacy in many patients. Circular RNAs (circRNAs), a novel class of non-coding RNAs, have emerged as pivotal regulators of gene expression and cellular processes. Increasing evidence indicates their involvement in modulating resistance to cancer immunotherapy. Notably, certain circRNAs function as miRNA sponges or interact with proteins, influencing the expression of immune-related genes, including crucial immune checkpoint molecules. This, in turn, shapes the tumor microenvironment and significantly impacts the response to immunotherapy. In this comprehensive review, we explore the evolving role of circRNAs in orchestrating resistance to cancer immunotherapy, with a specific focus on their mechanisms in influencing immune checkpoint gene expression. Additionally, we underscore the potential of circRNAs as promising therapeutic targets to augment the effectiveness of cancer immunotherapy. Understanding the role of circRNAs in cancer immunotherapy resistance could contribute to the development of new therapeutic strategies to overcome resistance and improve patient outcomes.

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_0044235 regulates the development of osteoarthritis by the modulation of miR-375/PIK3R3 axis

BACKGROUND

Circular RNAs (circRNAs) play an important role in osteoarthritis (OA). However, the role of circRNA in OA is still unclear. Here, we explored the role and mechanism of circ_0044235 in OA.

METHODS

CHON-001 cells were treated with IL-1β to establish OA model in vitro. The levels of circ_0044235, miR-375 and phosphoinositide 3-kinase (PI3K) regulatory subunit 3 (PIK3R3) were detected by quantitative real-time PCR. Cell count kit-8 assay and flow cytometry assay were used to detect cell viability and apoptosis. The concentrations of inflammation factors were determined by enzyme-linked immunosorbent assay. Western blot was used to detect protein levels. The interaction between miR-375 and circ_0044235 or PIK3R3 was analyzed by dual-luciferase reporter assay and RNA immunoprecipitation assay.

RESULTS

Circ_0044235 was significantly decreased in OA cartilage tissue and IL-1β-treated CHON-001 cells. Overexpression of circ_0044235 promoted IL-1β-stimulated CHON-001 cell viability and inhibited apoptosis, inflammation, and extracellular matrix (ECM) degradation. In mechanism analysis, circ_0044235 could act as a sponge for miR-375 and positively regulate PIK3R3 expression. In addition, miR-375 ameliorated the effect of circ_0044235 overexpression on IL-1β-mediated CHON-001 cells injury. In addition, miR-375 inhibition mitigated IL-1β-induced CHON-001 cell injury, while PIK3R3 silencing restored the effect.

CONCLUSION

Circ_0044235 knockdown alleviated IL-1β-induced chondrocytes injury by regulating miR-375/PIK3R3 axis, confirming that circ_0044235 might be a potential target for OA treatment.

Strategies to reduce the risks of mRNA drug and vaccine toxicity

mRNA formulated with lipid nanoparticles is a transformative technology that has enabled the rapid development and administration of billions of coronavirus disease 2019 (COVID-19) vaccine doses worldwide. However, avoiding unacceptable toxicity with mRNA drugs and vaccines presents challenges. Lipid nanoparticle structural components, production methods, route of administration and proteins produced from complexed mRNAs all present toxicity concerns. Here, we discuss these concerns, specifically how cell tropism and tissue distribution of mRNA and lipid nanoparticles can lead to toxicity, and their possible reactogenicity. We focus on adverse events from mRNA applications for protein replacement and gene editing therapies as well as vaccines, tracing common biochemical and cellular pathways. The potential and limitations of existing models and tools used to screen for on-target efficacy and de-risk off-target toxicity, including in vivo and next-generation in vitro models, are also discussed.

Therapeutic synthetic and natural materials for immunoengineering

Immunoengineering is a rapidly evolving field that has been driving innovations in manipulating immune system for new treatment tools and methods. The need for materials for immunoengineering applications has gained significant attention in recent years due to the growing demand for effective therapies that can target and regulate the immune system. Biologics and biomaterials are emerging as promising tools for controlling immune responses, and a wide variety of materials, including proteins, polymers, nanoparticles, and hydrogels, are being developed for this purpose. In this review article, we explore the different types of materials used in immunoengineering applications, their properties and design principles, and highlight the latest therapeutic materials advancements. Recent works in adjuvants, vaccines, immune tolerance, immunotherapy, and tissue models for immunoengineering studies are discussed.

The emerging role of non-coding RNAs in the Wnt/β-catenin signaling pathway in Prostate Cancer

Prostate cancer (PCa) is an important worldwide medical concern, necessitating a greater understanding of the molecular processes driving its development. The Wnt/-catenin signaling cascade is established as a central player in PCa pathogenesis, and recent research emphasizes the critical involvement of non-coding RNAs (ncRNAs) in this scenario. This in-depth study seeks to give a thorough examination of the complex relationship between ncRNAs and the Wnt/β-catenin system in PCa. NcRNAs, such as circular RNAs (circRNAs), long ncRNAs (lncRNAs), and microRNAs (miRNAs), have been recognized as essential regulators that modulate numerous facets of the Wnt/β-catenin network. MiRNAs have been recognized as targeting vital elements of the process, either enhancing or inhibiting signaling, depending on their specific roles and targets. LncRNAs participate in fine-tuning the Wnt/β-catenin network as a result of complicated interplay with both upstream and downstream elements. CircRNAs, despite being a relatively recent addition to the ncRNA family, have been implicated in PCa, influencing the Wnt/β-catenin cascade through diverse mechanisms. This article encompasses recent advances in our comprehension of specific ncRNAs that participate in the Wnt/β-catenin network, their functional roles, and clinical relevance in PCa. We investigate their use as screening and predictive indicators, and targets for treatment. Additionally, we delve into the interplay between Wnt/β-catenin and other signaling networks in PCa and the role of ncRNAs within this complex network. As we unveil the intricate regulatory functions of ncRNAs in the Wnt/β-catenin cascade in PCa, we gain valuable insights into the disease's pathogenesis. The implementation of these discoveries in practical applications holds promise for more precise diagnosis, prognosis, and targeted therapeutic approaches, ultimately enhancing the care of PCa patients. This comprehensive review underscores the evolving landscape of ncRNA research in PCa and the potential for innovative interventions in the battle against this formidable malignancy.

Hesperetin derivative 2a inhibits lipopolysaccharide-induced acute liver injury in mice via downregulation of circDcbld2

Acute liver injury (ALI) is a complex, life-threatening inflammatory liver disease, and persistent liver damage leads to rapid decline and even failure of liver function. However, the pathogenesis of ALI is still not fully understood, and no effective treatment has been discovered. Recent evidence shows that many circular RNAs (circRNAs) are associated with the occurrence of liver diseases. In this study we investigated the mechanisms of occurrence and development of ALI in lipopolysaccharide (LPS)-induced ALI mice. We found that expression of the circular RNA circDcbld2 was significantly elevated in the liver tissues of ALI mice and LPS-treated RAW264.7 cells. Knockdown of circDcbld2 markedly alleviates LPS-induced inflammatory responses in ALI mice and RAW264.7 cells. We designed and synthesized a series of hesperidin derivatives for circDcbld2, and found that hesperetin derivative 2a (HD-2a) at the concentrations of 2, 4, 8 μM effectively inhibited circDcbld2 expression in RAW264.7 cells. Administration of HD-2a (50, 100, 200 mg/kg. i.g., once 24 h in advance) effectively relieved LPS-induced liver dysfunction and inflammatory responses. RNA sequencing analysis revealed that the anti-inflammatory and hepatoprotective effects of HD-2a were mediated through downregulating circDcbld2 and suppressing the JAK2/STAT3 pathway. We conclude that HD-2a downregulates circDcbld2 to inhibit the JAK2/STAT3 pathway, thereby inhibiting the inflammatory responses in ALI. The results suggest that circDcbld2 may be a potential target for the prevention and treatment of ALI, and HD-2a may have potential as a drug for the treatment of ALI.

An introduction to RNA therapeutics and their potentials

RNA therapeutics is a biological term regarding the usage of RNA-based molecules for medical purposes. Thanks to the success of mRNA-vaccine production against COVID-19, RNA therapeutics has gained more and more attention and investigation from worldwide scientists. It is considered as one of the promising alternatives for conventional drugs. In this first chapter, we presented an overview of the history and perspectives of RNA therapeutics' development. This chapter also explained the underlying mechanisms of different RNA-based molecules, including antisense oligonucleotide, interfering RNA (iRNA), aptamer, and mRNA, from degrading mRNA to inactivating targeted protein. Although there are many advantages of RNA therapeutics, its challenges in designing RNA chemical structure and the delivery vehicle need to be discussed. We described advanced technologies in the development of drug delivery systems that are positively correlated to the efficacy of the drug. Our aim is to provide a general background of RNA therapeutics to the audience before introducing plenty of more detailed parts, including clinical applications in certain diseases in the following chapters of the "RNA therapeutics" book.

Recent research progress of circular RNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an extremely heterogeneous malignant tumor with a high morbidity and mortality. Circular RNAs (circRNAs) are noncoding RNAs with high stability, organ/tissue/cell-specific expression and are conserved across species. Accumulating evidence suggested that circRNAs play crucial roles as microRNA sponges, protein sponges, scaffolds, recruiters and could even polypeptide encoders. Many studies have since revealed that circRNAs were aberrantly expressed in HCC and acted as crucial modulators of HCC carcinogenesis and progression. Furthermore, circRNAs have also been identified as potential diagnostic and prognostic biomarkers for HCC. In this review, we thoroughly outline and evaluate the function of circRNAs in HCC development, with an emphasis on the specific molecular pathways by which they participated in the formation and progression of HCC, and we address their potential for serving as clinical biomarkers in HCC.

Recent advances in nano- and micro-scale carrier systems for controlled delivery of vaccines

Vaccines provide substantial safety against infectious diseases, saving millions of lives each year. The recent COVID-19 pandemic highlighted the importance of vaccination in providing mass-scale immunization against outbreaks. However, the delivery of vaccines imposes a unique set of challenges due to their large molecular size and low room temperature stability. Advanced biomaterials and delivery systems such as nano- and mciro-scale carriers are becoming critical components for successful vaccine development. In this review, we provide an updated overview of recent advances in the development of nano- and micro-scale carriers for controlled delivery of vaccines, focusing on carriers compatible with nucleic acid-based vaccines and therapeutics that emerged amid the recent pandemic. We start by detailing nano-scale delivery systems, focusing on nanoparticles, then move on to microscale systems including hydrogels, microparticles, and 3D printed microneedle patches. Additionally, we delve into emerging methods that move beyond traditional needle-based applications utilizing innovative delivery systems. Future challenges for clinical translation and manufacturing in this rapidly advancing field are also discussed.

CircRNA in ocular neovascular diseases: Fundamental mechanism and clinical potential

Ocular neovascular disease (OND), characterized by the aberrant formation of immature blood vessels, is the leading cause of vision impairment and blindness. It is important to find effective ways to diagnose and treat these diseases. Circular RNA (circRNA) is a group of endogenous non-coding RNA that play a crucial role in regulating different biological processes. Due to their close association with ocular disease and angiogenesis, circRNAs have become a hotspot in OND research. In this review, we intensively investigate the possibility of using circRNAs in the management of ONDs. In general, angiogenesis is divided into five phases. On the basis of these five steps, we describe the potential of using circRNAs by introducing how they regulate angiogenesis. Subsequently, the interactions between circRNAs and ONDs, including pterygium, corneal neovascularization, age-related macular degeneration, diabetic retinopathy, and retinopathy of prematurity, are analyzed in detail. We also introduce the potential use of circRNAs as OND diagnostic biomarkers. Finally, we summarize the prospects of using circRNAs as a potential strategy in OND management. The gaps in recent research are also pointed out with the purpose of promoting the introduction of circRNAs into clinical applications.

Unlocking the role of non-coding RNAs in prostate cancer progression: exploring the interplay with the Wnt signaling pathway

Prostate cancer (PCa) is one of the most common cancers in males, exhibiting a wide spectrum of clinical manifestations that pose challenges in its diagnosis and treatment. The Wnt signaling pathway, a conserved and complex pathway, is crucial for embryonic development, tissue homeostasis, and various physiological processes. Apart from the classical Wnt/β-catenin signaling pathway, there exist multiple non-classical Wnt signaling pathways, including the Wnt/PCP and Wnt/Ca2+ pathways. Non-coding RNAs (ncRNAs) are involved in the occurrence and development of PCa and the response to PCa treatment. ncRNAs are known to execute diverse regulatory roles in cellular processes, despite their inability to encode proteins. Among them, microRNAs, long non-coding RNAs, and circular RNAs play key roles in the regulation of the Wnt signaling pathway in PCa. Aberrant expression of these ncRNAs and dysregulation of the Wnt signaling pathway are one of the causes of cell proliferation, apoptosis, invasion, migration, and angiogenesis in PCa. Moreover, these ncRNAs affect the characteristics of PCa cells and hold promise as diagnostic and prognostic biomarkers. Herein, we summarize the role of ncRNAs in the regulation of the Wnt signaling pathway during the development of PCa. Additionally, we present an overview of the current progress in research on the correlation between these molecules and clinical features of the disease to provide novel insights and strategies for the treatment of PCa.

Messenger RNA chromatographic purification: advances and challenges

Messenger RNA (mRNA) technologies have shown great potential in prophylactic vaccines and therapeutic medicines due to their adaptability, rapidity, efficacy, and safety. The purity of mRNA determines the efficacy and safety of mRNA drugs. Though chromatographic technologies are currently employed in mRNA purification, they are facing challenges, mainly arising from the large size, relatively simple chemical composition, instability, and high resemblance of by-products to the target mRNA. In this review, we will first make a comprehensive analysis of physiochemical properties differences between mRNA and proteins, then the major challenges facing in mRNA purification and general considerations are highlighted. A detailed summary of the state-of-arts in mRNA chromatographic purification will be provided, which are mainly classified into physicochemical property-based (size, charge, and hydrophobicity) and chemical structure-based (phosphate backbone, bases, cap structure, and poly A tail) technologies. Efforts in eliminating dsRNA byproducts via post in vitro transcript (IVT) purification and by manipulating the IVT process to reduce the generation of dsRNA are highlighted. Finally, a brief summary of the current status of chromatographic purification of the emerging circular mRNA (circRNA) is provided. We hope this review will provide some useful guidance for the Quality by Design (QbD) of mRNA downstream process development.

Circular RNA vaccine in disease prevention and treatment

CircRNAs are a class of single-stranded RNAs with covalently linked head-to-tail topology. In the decades since its initial discovery, their biogenesis, regulation, and function have rapidly disclosed, permitting a better understanding and adoption of them as new tools for medical applications. With the development of biotechnology and molecular medicine, artificial circRNAs have been engineered as a novel class of vaccines for disease treatment and prevention. Unlike the linear mRNA vaccine which applications were limited by its instability, inefficiency, and innate immunogenicity, circRNA vaccine which incorporate internal ribosome entry sites (IRESs) and open reading frame (ORF) provides an improved approach to RNA-based vaccination with safety, stability, simplicity of manufacture, and scalability. However, circRNA vaccines are at an early stage, and their optimization, delivery and applications require further development and evaluation. In this review, we comprehensively describe circRNA vaccine, including their history and superiority. We also summarize and discuss the current methodological research for circRNA vaccine preparation, including their design, synthesis, and purification. Finally, we highlight the delivery options of circRNA vaccine and its potential applications in diseases treatment and prevention. Considering their unique high stability, low immunogenicity, protein/peptide-coding capacity and special closed-loop construction, circRNA vaccine, and circRNA-based therapeutic platforms may have superior application prospects in a broad range of diseases.

Lipid nanoparticle-based mRNA delivery systems for cancer immunotherapy

Cancer immunotherapy, which harnesses the power of the immune system, has shown immense promise in the fight against malignancies. Messenger RNA (mRNA) stands as a versatile instrument in this context, with its capacity to encode tumor-associated antigens (TAAs), immune cell receptors, cytokines, and antibodies. Nevertheless, the inherent structural instability of mRNA requires the development of effective delivery systems. Lipid nanoparticles (LNPs) have emerged as significant candidates for mRNA delivery in cancer immunotherapy, providing both protection to the mRNA and enhanced intracellular delivery efficiency. In this review, we offer a comprehensive summary of the recent advancements in LNP-based mRNA delivery systems, with a focus on strategies for optimizing the design and delivery of mRNA-encoded therapeutics in cancer treatment. Furthermore, we delve into the challenges encountered in this field and contemplate future perspectives, aiming to improve the safety and efficacy of LNP-based mRNA cancer immunotherapies.

Advancements of in vitro transcribed mRNA (IVT mRNA) to enable translation into the clinics

The accelerated progress and approval of two mRNA-based vaccines to address the SARS-CoV-2 virus were unprecedented. This record-setting feat was made possible through the solid foundation of research on in vitro transcribed mRNA (IVT mRNA) which could be utilized as a therapeutic modality. Through decades of thorough research to overcome barriers to implementation, mRNA-based vaccines or therapeutics offer many advantages to rapidly address a broad range of applications including infectious diseases, cancers, and gene editing. Here, we describe the advances that have supported the adoption of IVT mRNA in the clinics, including optimization of the IVT mRNA structural components, synthesis, and lastly concluding with different classes of IVT RNA. Continuing interest in driving IVT mRNA technology will enable a safer and more efficacious therapeutic modality to address emerging and existing diseases.

Circular RNAs in hepatocellular carcinoma: biogenesis, function, and pathology

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Both genetic and environmental factors through a multitude of underlying molecular mechanisms participate in the pathogenesis of HCC. Recently, numerous studies have shown that circular RNAs (circRNAs), an emerging class of non-coding RNAs characterized by the presence of covalent bonds linking 3' and 5' ends, play an important role in the initiation and progression of cancers, including HCC. In this review, we outline the current status of the field of circRNAs, with an emphasis on the functions and mechanisms of circRNAs in HCC and its microenvironment. We also summarize and discuss recent advances of circRNAs as biomarkers and therapeutic targets. These efforts are anticipated to throw new insights into future perspectives about circRNAs in basic, translational and clinical research, eventually advancing the diagnosis, prevention and treatment of HCC.

Non-coding RNAs in renal cell carcinoma: Implications for drug resistance

Renal cell carcinoma (RCC) represents a malignant tumor of the urinary system. Individuals with early-stage RCC could be cured by surgical treatment, but a considerable number of cases of advanced RCC progress to drug resistance. Recently, numerous reports have demonstrated that a variety of non-coding RNAs (ncRNAs) contribute to tumor occurrence and development. ncRNAs can act as oncogenic or tumor suppressor genes to regulate proliferation, migration, drug resistance and other processes in RCC cells through a variety of signaling pathways. Considering the lack of treatment options for advanced RCC after drug resistance, ncRNAs may be a good choice as biomarkers of drug resistance in RCC and targets to overcome drug resistance. In this review, we discussed the effects of ncRNAs on drug resistance in RCC and the great potential of ncRNAs as a biomarker of or a new therapeutic method in RCC.