Emerging functions of circular RNA in aging

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.

Role of the circRNA_34414/miR-6960a-5p/SIRT3 axis in postoperative delirium via CA1 Vglut1+ neurons in older mice

AIMS

Postoperative delirium (POD) is a common neurological complication in elderly patients after anesthesia/surgery. The main purpose of this study is to explore the effect of circRNA-targeted miRNA regulating SIRT3 on mitochondrial function through ceRNA mechanism under the surgical model of tibial fracture and to further explore the potential mechanism of postoperative delirium mediated by circRNA, so as to provide new ideas for clinical diagnosis and prevention of POD.

METHODS

The surgical model of tibial fracture under sevoflurane anesthesia caused acute delirium-like behavior in elderly mice. We observed that the decrease of SIRT3 and mitochondrial dysfunction was related to POD, and miRNA and circRNA (circRNA_34414) related to SIRT3 were further studied. Through luciferase and RAP, we observed that circRNA_34414, as a miRNA sponge, was involved in the regulation of SIRT3 expression.

RESULTS

Postoperative delirium in elderly mice showed decreased expression of hippocampal circRNA_34414, increased expression of miR-6960-5p, decreased expression of SIRT3, and impaired mitochondrial membrane potential. Overexpression of circRNA_34414, or knockdown of miR-6960-5p, or overexpression of SIRT3 in hippocampal CA1 glutamatergic neurons significantly upregulated hippocampal SIRT3 expression, increased mitochondrial membrane potential levels, and significantly ameliorated postoperative delirium in aged mice; CircRNA_34414 ameliorates postoperative delirium in mice, possibly by targeting miR-6960-5p to upregulate SIRT3.

CONCLUSIONS

CircRNA_34414 is involved in the improvement of postoperative delirium induced by anesthesia/surgery by upregulating SIRT3 via sponging miR-6960-5p.

Mediation of circ_0007142 on miR-128-3p/S100A14 pathway to stimulate the progression of cervical cancer

A previous study has confirmed the upregulation of circ_0007142 expression in CC. Here, we aimed to investigate the effect and mechanism of circ_0007142 in CC progression. The expression of circ_0007142, microRNA-128-3p (miR-128-3p), S100 calcium-binding protein A14 (S100A14), and epithelial mesenchymal transition (EMT)-related markers was measured by qRT-PCR and Western blot. Cell proliferative, migratory, and invasion abilities were evaluated using cell counting Kit-8, cell colony formation, 5-ethynyl-2'-deoxyuridine, and transwell assays, respectively. The interaction among circ_0007142, miR-128-3p and S100A14 was identified by dual-luciferase reporter and RNA immunoprecipitation assays. In vivo experiment was implemented to investigate the effect of circ_0007142 on tumor growth. CC tissues and cells displayed high expression of circ_0007142 and S100A14, and low expression of miR-128-3p in comparison to the controls. Knockdown of circ_0007142 resulted in the inhibition of cell proliferation, migration invasion, and EMT in vitro. In support, circ_0007142 deficiency hindered tumor growth and EMT in vivo. In rescue experiments, downregulation of miR-128-3p relieved circ_0007142 absence-mediated anticancer impacts. MiR-128-3p overexpression-induced inhibitory effects on cell growth and metastasis were attenuated by S100A14 overexpression. Importantly, circ_0007142 regulated S100A14 expression by sponging miR-128-3p. Circ_0007142 knockdown suppressed CC cell malignant behaviors by miR-128-3p/S100A14 pathway, providing a possible circRNA-targeted therapy for CC.

Optimal design of synthetic circular RNAs

Circular RNAs are an unusual class of single-stranded RNAs whose ends are covalently linked via back-splicing. Due to their versatility, the need to express circular RNAs in vivo and in vitro has increased. Efforts have been made to efficiently and precisely synthesize circular RNAs. However, a review on the optimization of the processes of circular RNA design, synthesis, and delivery is lacking. Our review highlights the multifaceted aspects considered when producing optimal circular RNAs and summarizes the available options for each step of exogenous circular RNA design and synthesis, including circularization strategies. Additionally, this review describes several potential applications of circular RNAs.

An epigenetic toolbox for conservation biologists

Ongoing climatic shifts and increasing anthropogenic pressures demand an efficient delineation of conservation units and accurate predictions of populations' resilience and adaptive potential. Molecular tools involving DNA sequencing are nowadays routinely used for these purposes. Yet, most of the existing tools focusing on sequence-level information have shortcomings in detecting signals of short-term ecological relevance. Epigenetic modifications carry valuable information to better link individuals, populations, and species to their environment. Here, we discuss a series of epigenetic monitoring tools that can be directly applied to various conservation contexts, complementing already existing molecular monitoring frameworks. Focusing on DNA sequence-based methods (e.g. DNA methylation, for which the applications are readily available), we demonstrate how (a) the identification of epi-biomarkers associated with age or infection can facilitate the determination of an individual's health status in wild populations; (b) whole epigenome analyses can identify signatures of selection linked to environmental conditions and facilitate estimating the adaptive potential of populations; and (c) epi-eDNA (epigenetic environmental DNA), an epigenetic-based conservation tool, presents a non-invasive sampling method to monitor biological information beyond the mere presence of individuals. Overall, our framework refines conservation strategies, ensuring a comprehensive understanding of species' adaptive potential and persistence on ecologically relevant timescales.

Exosomal circRNAs: Novel biomarkers and therapeutic targets for urinary tumors

Exosomal circRNAs have emerged as promising biomarkers and therapeutic targets for urinary tumors. In this review, we explored the intricate role of exosomal circRNAs in urological cancers, focusing on their biological functions, dysregulation in tumors, and potential clinical applications. The review delves into the mechanisms by which exosomal circRNAs contribute to tumor progression and highlights their diagnostic and therapeutic implications. By synthesizing current research findings, we present a compelling case for the significance of exosomal circRNAs in the context of urinary tumors. Furthermore, the review discusses the challenges and opportunities associated with utilizing exosomal circRNAs as diagnostic tools and targeted therapeutic agents. There is a need for further research to elucidate the specific mechanisms of exosomal circRNA secretion and delivery, as well as to enhance the detection methods for clinical translational applications. Overall, this comprehensive review underscores the pivotal role of exosomal circRNAs in urinary tumors and underscores their potential as valuable biomarkers and therapeutic tools in the management of urological cancers.

Potential regulatory role of epigenetic modifications in aging-related heart failure

Heart failure (HF) is a serious clinical syndrome and a serious development or advanced stage of various heart diseases. Aging is an independent factor that causes pathological damage in cardiomyopathy and participates in the occurrence of HF at the molecular level by affecting mechanisms such as telomere shortening and mitochondrial dysfunction. Epigenetic changes have a significant impact on the aging process, and there is increasing evidence that genetic and epigenetic changes are key features of aging and aging-related diseases. Epigenetic modifications can affect genetic information by changing the chromatin state without changing the DNA sequence. Most of the genetic loci that are highly associated with cardiovascular diseases (CVD) are located in non-coding regions of the genome; therefore, the epigenetic mechanism of CVD has attracted much attention. In this review, we focus on the molecular mechanisms of HF during aging and epigenetic modifications mediating aging-related HF, emphasizing that epigenetic mechanisms play an important role in the pathogenesis of aging-related CVD and can be used as potential diagnostic and prognostic biomarkers, as well as therapeutic targets.

Circ-Bptf Ameliorates Learning and Memory Impairments via the miR-138-5p/p62 Axis in APP/PS1 Mice

Alzheimer's disease (AD) is a common age-associated progressive neurodegenerative disorder that is implicated in the aberrant regulation of numerous circular RNAs (circRNAs). Here, we reported that circ-Bptf, a conserved circRNA derived from the Bptf gene, showed an age-dependent decrease in the hippocampus of APP/PS1 mice. Overexpression of circ-Bptf significantly reversed dendritic spine loss and learning and memory impairment in APP/PS1 mice. Moreover, we found that circ-Bptf was predominantly localized to the cytoplasm and upregulated p62 expression by binding to miR-138-5p. Furthermore, the miR-138-5p mimics reversed the decreased expression of p62 induced by the silencing of circ-Bptf. Together, our findings suggested that circ-Bptf ameliorated learning and memory impairments via the miR-138-5p/p62 axis in APP/PS1 mice. It may act as a potential player in AD pathogenesis and therapy.

Adipose Tissue Exosome circ_sxc Mediates the Modulatory of Adiposomes on Brain Aging by Inhibiting Brain dme-miR-87-3p

Aging of the brain usually leads to the decline of neurological processes and is a major risk factor for various neurodegenerative diseases, including sleep disturbances and cognitive decline. Adipose tissue exosomes, as adipocyte-derived vesicles, may mediate the regulatory processes of adipose tissue on other organs, including the brain; however, the regulatory mechanisms remain unclear. We analyzed the sleep-wake behavior of young (10 days) and old (40 days) Drosophila and found that older Drosophila showed increased sleep fragmentation, which is similar to mammalian aging characteristics. To investigate the cross-tissue regulatory mechanisms of adiposity on brain aging, we extracted 10-day and 40-day Drosophila adipose tissue exosomes and identified circRNAs with age-dependent expression differences by RNA-seq and differential analysis. Furthermore, by combining data from 3 datasets of the GEO database (GSE130158, GSE24992, and GSE184559), circ_sxc that was significantly downregulated with age was finally screened out. Moreover, dme-miR-87-3p, a conserved target of circ_sxc, accumulates in the brain with age and exhibits inhibitory effects in predicted binding relationships with neuroreceptor ligand genes. In summary, the current study showed that the Drosophila brain could obtain circ_sxc by uptake of adipose tissue exosomes which crossed the blood-brain barrier. And circ_sxc suppressed brain miR-87-3p expression through sponge adsorption, which in turn regulated the expression of neurological receptor ligand proteins (5-HT1B, GABA-B-R1, Rdl, Rh7, qvr, NaCP60E) and ensured brain neuronal synaptic signaling normal function of synaptic signaling. However, with aging, this regulatory mechanism is dysregulated by the downregulation of the adipose exosome circ_sxc, which contributes to the brain exhibiting sleep disturbances and other "aging" features.

The Role of Circular RNAs in Male Infertility and Reproductive Cancers: A Narrative Review

Infertility is a global health problem affecting about 15% of all couples, of which 50% are due to male infertility. Although the etiology of infertility is known in most infertile men, idiopathic male infertility remains a challenge. Therefore, there is a need for novel diagnostic methods to detect the underlying mechanisms and develop appropriate therapies. Recent studies have focused on the role of non-coding RNAs (ncRNAs) in male infertility. Circular RNAs (CircRNAs), a type of ncRNAs, are found to play a key role in the development of some pathological conditions, including cardiovascular diseases, diabetes, cancers, autoimmune diseases, etc. Several studies have reported the presence of CircRNAs and their target genes in the human reproductive system. In addition, their expression in testicular tissues, sperm cells, and seminal fluid has been identified. Abnormal expression of CircRNAs has been associated with azoospermia and asthenozoospermia in infertile men. The present narrative review provides a brief description of the role of CircRNAs in spermatogenic cells, male infertility, and reproductive cancers. In addition, some CircRNAs have been identified as potential biomarkers for disease detection and treatment.

Silencing circSERPINE2 restrains mesenchymal stem cell senescence via the YBX3/PCNA/p21 axis

Increasing evidence indicates that circular RNAs (circRNAs) accumulate in aging tissues and nonproliferating cells due to their high stability. However, whether upregulation of circRNA expression mediates stem cell senescence and whether circRNAs can be targeted to alleviate aging-related disorders remain unclear. Here, RNA sequencing analysis of differentially expressed circRNAs in long-term-cultured mesenchymal stem cells (MSCs) revealed that circSERPINE2 expression was significantly increased in late passages. CircSERPINE2 small interfering RNA delayed MSC senescence and rejuvenated MSCs, while circSERPINE2 overexpression had the opposite effect. RNA pulldown followed by mass spectrometry revealed an interaction between circSERPINE2 and YBX3. CircSERPINE2 increased the affinity of YBX3 for ZO-1 through the CCAUC motif, resulting in the sequestration of YBX3 in the cytoplasm, inhibiting the association of YBX3 with the PCNA promoter and eventually affecting p21 ubiquitin-mediated degradation. In addition, our results demonstrated that senescence-related downregulation of EIF4A3 gave rise to circSERPINE2. In vivo, intra-articular injection of si-circSerpine2 restrained native joint-resident MSC senescence and cartilage degeneration in mice with aging-related osteoarthritis. Taken together, our findings provide strong evidence for a regulatory role for the circSERPINE2/YBX3/PCNA/p21 axis in MSC senescence and the therapeutic potential of si-circSERPINE2 in alleviating aging-associated syndromes, such as osteoarthritis.

Extracellular vesicles in gastric cancer: role of exosomal lncRNA and microRNA as diagnostic and therapeutic targets

Extracellular vesicles (EVs), including exosomes, play a crucial role in intercellular communication and have emerged as important mediators in the development and progression of gastric cancer. This review discusses the current understanding of the role of EVs, particularly exosomal lncRNA and microRNA, in gastric cancer and their potential as diagnostic and therapeutic targets. Exosomes are small membrane-bound particles secreted by both cancer cells and stromal cells within the tumor microenvironment. They contain various ncRNA and biomolecules, which can be transferred to recipient cells to promote tumor growth and metastasis. In this review, we highlighted the importance of exosomal lncRNA and microRNA in gastric cancer. Exosomal lncRNAs have been shown to regulate gene expression by interacting with transcription factors or chromatin-modifying enzymes, which regulate gene expression by binding to target mRNAs. We also discuss the potential use of exosomal lncRNAs and microRNAs as diagnostic biomarkers for gastric cancer. Exosomes can be isolated from various bodily fluids, including blood, urine, and saliva. They contain specific molecules that reflect the molecular characteristics of the tumor, making them promising candidates for non-invasive diagnostic tests. Finally, the potential of targeting exosomal lncRNAs and microRNAs as a therapeutic strategy for gastric cancer were reviewed as wee. Inhibition of specific molecules within exosomes has been shown to suppress tumor growth and metastasis in preclinical models. In conclusion, this review article provides an overview of the current understanding of the role of exosomal lncRNA and microRNA in gastric cancer. We suggest that further research into these molecules could lead to new diagnostic tools and therapeutic strategies for this deadly disease.

Highlighting functions of apoptosis and circular RNAs in colorectal cancer

Colorectal cancer (CRC) is known as one of the global problems that endangers the lives of thousands of people every year. Various treatments have been used to deal with this disease, but in some cases, they are not effective. Circular RNAs, as a novel class of noncoding RNAs, have different expression levels and various functions in cancer cells, such as gene regulation through microRNA sponging. They play an important role in various cellular processes, including differentiation, proliferation, invasion, and apoptosis. Changes in the process of apoptosis are closely related to the progression or inhibition of various malignancies. Induction of apoptosis in cancer cells is a promising target for tumor therapy. In this study, circRNAs were investigated as being central to the induction or inhibition of apoptosis in CRC. It is hoped that through targeted changes in the function of these biomolecules, better outcomes will be achieved in cancer treatment. Perhaps better outcomes for cancer treatment can be achieved by using new methods and modifying the expression of these nucleic acids. However, using this method may come with challenges and limitations.

Circular RNAs in gynecologic cancers: mechanisms and implications for chemotherapy resistance

Chemotherapy resistance remains a major challenge in the treatment of gynecologic malignancies. Increasing evidence suggests that circular RNAs (circRNAs) play a significant role in conferring chemoresistance in these cancers. In this review, we summarize the current understanding of the mechanisms by which circRNAs regulate chemotherapy sensitivity and resistance in gynecologic malignancies. We also discuss the potential clinical implications of these findings and highlight areas for future research. CircRNAs are a novel class of RNA molecules that are characterized by their unique circular structure, which confers increased stability and resistance to degradation by exonucleases. Recent studies have shown that circRNAs can act as miRNA sponges, sequestering miRNAs and preventing them from binding to their target mRNAs. This can lead to upregulation of genes involved in drug resistance pathways, ultimately resulting in decreased sensitivity to chemotherapy. We discuss several specific examples of circRNAs that have been implicated in chemoresistance in gynecologic cancers, including cervical cancer, ovarian cancer, and endometrial cancer. We also highlight the potential clinical applications of circRNA-based biomarkers for predicting chemotherapy response and guiding treatment decisions. Overall, this review provides a comprehensive overview of the current state of knowledge regarding the role of circRNAs in chemotherapy resistance in gynecologic malignancies. By elucidating the underlying mechanisms by which circRNAs regulate drug sensitivity, this work has important implications for improving patient outcomes and developing more effective therapeutic strategies for these challenging cancers.

EIF4A3-Induced Exosomal circLRRC8A Alleviates Granulosa Cells Senescence Via the miR-125a-3p/NFE2L1 axis

Premature ovarian failure (POF) is an important cause of female infertility and seriously impacts the physical and psychological health of patients. Mesenchymal stromal cells-derived exosomes (MSCs-Exos) have an essential role in the treatment of reproductive disorders, particularly POF. However, the biological function and therapeutic mechanism of MSCs exosomal circRNAs in POF remain to be determined. Here, with bioinformatics analysis and functional assays, circLRRC8A was found to be downregulated in senescent granulosa cells (GCs) and acted as a crucial factor in MSCs-Exos for oxidative damage protection and anti-senescence of GCs in vitro and in vivo. Mechanistic investigations revealed that circLRRC8A served as an endogenous miR-125a-3p sponge to downregulate NFE2L1 expression. Moreover, eukaryotic initiation factor 4A3 (EIF4A3), acting as a pre-mRNA splicing factor, promoted circLRRC8A cyclization and expression by directly binding to the LRRC8A mRNA transcript. Notably, EIF4A3 silencing reduced circLRRC8A expression and attenuated the therapeutic effect of MSCs-Exos on oxidatively damaged GCs. This study demonstrates a new therapeutic pathway for cellular senescence protection against oxidative damage by delivering circLRRC8A-enriched exosomes through the circLRRC8A/miR-125a-3p/NFE2L1 axis and paves the way for the establishment of a cell-free therapeutic approach for POF. CircLRRC8A may be a promising circulating biomarker for diagnosis and prognosis and an exceptional candidate for further therapeutic exploration.

Roles of Aging, Circular RNAs, and RNA Editing in the Pathogenesis of Amyotrophic Lateral Sclerosis: Potential Biomarkers and Therapeutic Targets

Amyotrophic lateral sclerosis (ALS) is an incurable motor neuron disease caused by upper and lower motor neuron death. Despite advances in our understanding of ALS pathogenesis, effective treatment for this fatal disease remains elusive. As aging is a major risk factor for ALS, age-related molecular changes may provide clues for the development of new therapeutic strategies. Dysregulation of age-dependent RNA metabolism plays a pivotal role in the pathogenesis of ALS. In addition, failure of RNA editing at the glutamine/arginine (Q/R) site of GluA2 mRNA causes excitotoxicity due to excessive Ca²⁺ influx through Ca²⁺-permeable α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors, which is recognized as an underlying mechanism of motor neuron death in ALS. Circular RNAs (circRNAs), a circular form of cognate RNA generated by back-splicing, are abundant in the brain and accumulate with age. Hence, they are assumed to play a role in neurodegeneration. Emerging evidence has demonstrated that age-related dysregulation of RNA editing and changes in circRNA expression are involved in ALS pathogenesis. Herein, we review the potential associations between age-dependent changes in circRNAs and RNA editing, and discuss the possibility of developing new therapies and biomarkers for ALS based on age-related changes in circRNAs and dysregulation of RNA editing.

Exosomal circular RNAs: A chief culprit in cancer chemotherapy resistance

Chemotherapy is one of the primary treatments for malignant tumors. However, the acquired drug resistance hinders clinical efficacy and leads to treatment failure in most patients. Exosomes are cell-derived vesicles with a diameter of 30-150 nm carrying and delivering substances such as DNAs, RNAs, lipids, and proteins for cellular communication in tumor development. Circular RNAs (circRNAs) present covalently closed-loop RNA structures, which regulate tumor cell proliferation, apoptosis, and metastasis by controlling different genes and signaling pathways. CircRNAs are abundant and stably expressed in exosomes. Recent studies have shown that they play critical roles in chemotherapy resistance in various cancers. In this review, we summarized the origin of exosomes and discussed the regulation mechanism of exosomal circRNAs in cancer drug resistance.

hsa_circ_0136839 regulates the malignant phenotypes of nasopharyngeal carcinoma via the Wnt/β-catenin signaling pathway

With the development of RNA sequencing (RNA-seq) technology, circular RNA (circRNA), a new class of RNA, has received much attention in cancer research. However, information available on the biogenesis and functional value of circRNAs in nasopharyngeal carcinoma (NPC) is scarce. In the present study, we screened the circRNA profile of the NPC cell line C666-1 compared with that of the normal control NP69 by RNA-seq and identified a novel and relatively higher expressed circRNA, hsa_circ_0136839. Hsa_circ_0136839 was markedly downregulated in NPC tissues, as confirmed by quantitative reverse transcription polymerase chain reaction. Functional in vitro studies revealed that hsa_circ_0136839 knockdown in C666-1 cell notably promoted cell proliferation, migration, and invasion abilities, as well as affected cell cycle distribution with an S-phase arrest. However, hsa_circ_0136839 overexpression in CNE2 cells resulted in an opposite response. Mechanistically, we demonstrated that aberrant hsa_circ_0136839 expression might affect the malignant phenotypes of NPC cells by activating the wnt/β-catenin signaling pathway. Thus, our findings contribute to further the understanding of NPC pathogenesis and provide new ideas for NPC clinical diagnosis and treatment.

The role of tRNA-derived small RNAs in aging

Aging is characterized by a gradual decline in biological functions, leading to the increased probability of diseases and deaths in organisms. Previous studies have identified biological factors that modulate aging and lifespan, including non-coding RNAs (ncRNAs). Here, we review the relationship between aging and tRNA-derived small RNAs (tsRNAs), ncRNAs that are generated from the cleavage of tRNAs. We describe age-dependent changes in tsRNA levels and their functions in age-related diseases, such as cancer and neurodegenerative diseases. We also discuss the association of tsRNAs with aging-regulating processes, including mitochondrial respiration and reduced mRNA translation. We cover recent findings regarding the potential roles of tsRNAs in cellular senescence, a major cause of organismal aging. Overall, our review will provide useful information for understanding the roles of tsRNAs in aging and age-associated diseases. [BMB Reports 2023; 56(2): 49-55].

The role of tRNA-derived small RNAs in aging

Aging is characterized by a gradual decline in biological functions, leading to the increased probability of diseases and deaths in organisms. Previous studies have identified biological factors that modulate aging and lifespan, including non-coding RNAs (ncRNAs). Here, we review the relationship between aging and tRNA-derived small RNAs (tsRNAs), ncRNAs that are generated from the cleavage of tRNAs. We describe age-dependent changes in tsRNA levels and their functions in age-related diseases, such as cancer and neurodegenerative diseases. We also discuss the association of tsRNAs with aging-regulating processes, including mitochondrial respiration and reduced mRNA translation. We cover recent findings regarding the potential roles of tsRNAs in cellular senescence, a major cause of organismal aging. Overall, our review will provide useful information for understanding the roles of tsRNAs in aging and age-associated diseases. [BMB Reports 2023; 56(2): 49-55].

Circ_0075960 targets the miR-202-5p/CTNND1 axis to promote the growth and migration of endometrial carcinoma cells via regulating Wnt/β-catenin signaling activity

BACKGROUND

Endometrial carcinoma (EC) is one of the most common malignant tumors of the female reproductive tract, involving multiple molecular alterations. Circular RNA (circRNA) dysregulation is frequently observed in EC tissues, suggesting the involvement of circRNA in EC development. We aimed to investigate the role of circ_0075960 in EC.

METHODS

Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot assays were applied for expression analysis. CCK-8, EdU, colony formation, flow cytometry and wound healing assays were employed for functional analysis. The predicted binding relationship between miR-202-5p and circ_0075960 or CTNND1 was validated by dual-luciferase reporter experiment. In vivo animal models were constructed in nude mice to verify the role of circ_0075960 in tumor growth.

RESULTS

Circ_0075960 and CTNND1 were upregulated, while miR-202-5p was downregulated in EC. Knockdown of circ_0075960 induced EC cell apoptosis, suppressed cell proliferation and migration, and repressed tumor growth in animal models. MiR-202-5p was targeted by circ_0075960 and it directly bound to CTNND1 3'UTR. The inhibition of circ_0075960 knockdown or miR-202-5p enrichment on EC cell proliferation and migration was reversed by miR-202-5p depletion or CTNND1 overexpression, respectively. Circ_0075960 targeted miR-202-5p to positively regulate CTNND1 expression. Moreover, circ_0075960 knockdown weakened the activity of Wnt/β-catenin signaling via targeting the miR-202-5p/CTNND1 axis.

CONCLUSION

Circ_0075960 targets the miR-202-5p/CTNND1 axis to modulate Wnt/β-catenin signaling activity, thus contributing to the malignant development of EC.

Circular RNAs: emerging players in brain aging and neurodegenerative diseases

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

Circ-Vps41 positively modulates Syp and its overexpression improves memory ability in aging mice

INTRODUCTION

Age is an established risk factor for neurodegenerative disorders. Aging-related cognitive decline is a common cause of memory impairment in aging individuals, in which hippocampal synaptic plasticity and hippocampus-dependent memory formation are damaged. Circular RNAs (circRNAs) have been reported in many cognitive disorders, but their role in aging-related memory impairment is unclear.Methods: In this study, we aimed to investigate the effects of circ-Vps41 on aging-related hippocampus-dependent memory impairment and explore the potential mechanisms. Here, D-galactose was used to produce a conventional aging model resulting in memory dysfunction.

RESULTS

Circ-Vps41 was significantly downregulated in D-galactose-induced aging in vitro and in vivo. The overexpression of circ-Vps41 could upregulate synaptophysin (Syp), thereby promoting the synaptic plasticity and alleviating cognitive impairment in aging mice. Mechanistically, we found that circ-Vps41 upregulated Syp expression by physically binding to miR-24-3p. Moreover, the miR-24-3p mimics reversed the circ-Vps41 overexpression-induced increase in Syp expression.

DISCUSSION

Overexpression of circ-Vps41 alleviated the synaptic plasticity and memory dysfunction via the miR-24-3p/Syp axis. These findings revealed circ-Vps41 regulatory network and provided new insights into its potential mechanisms for improving aging-related learning and memory impairment.

Pros and Cons of In Vitro Methods for Circular RNA Preparation

mRNA is gaining success as a new therapeutic agent and vaccine. However, mRNA has limitations in stability. To overcome the shortcomings of mRNA, circular RNA is emerging as a new modality. In this review, several current methods of manufacturing circular RNA in vitro are introduced and their advantages and disadvantages are reviewed. Furthermore, this study discusses which fields and directions of research and development are needed for the increase in the efficacy and productivity of circular RNA as a therapeutic agent and vaccine formulation.

Exportin 4 depletion leads to nuclear accumulation of a subset of circular RNAs

Numerous RNAs are exported from the nucleus, abnormalities of which lead to cellular complications and diseases. How thousands of circular RNAs (circRNAs) are exported from the nucleus remains elusive. Here, we provide lines of evidence to demonstrate a link between the conserved Exportin 4 (XPO4) and nuclear export of a subset of circRNAs in metazoans. Exonic circRNAs (ecircRNAs) with higher expression levels, larger length, and lower GC content are more sensitive to XPO4 deficiency. Cellular insufficiency of XPO4 leads to nuclear circRNA accumulation, circRNA:DNA (ciR-loop) formation, linear RNA:DNA (liR-loop) buildup, and DNA damage. DDX39 known to modulate circRNA export can resolve ciR-loop, and splicing factors involved in the biogenesis of circRNAs can also affect the levels of ciR-loop. Testis and brain are two organs with high abundance of circRNAs, and insufficient XPO4 levels are detrimental, as Xpo4 heterozygous mice display male infertility and neural phenotypes. Increased levels of ciR-loop, R-loop, and DNA damage along with decreased cell numbers are observed in testis and hippocampus of Xpo4 heterozygotes. This study sheds light on the understandings of mechanism of circRNA export and reveals the significance of efficient nuclear export of circRNAs in cellular physiology.

This study identifies the evolutionarily conserved Exportin 4 as an essential regulator in the nuclear export of circRNAs. Defective circRNA export results in R-loop formation and DNA damage in cells, as well as testis and neurological defects in mice.

Identification of the circRNA–miRNA–mRNA regulatory network in osteoarthritis using bioinformatics analysis

Background: Osteoarthritis (OA) is a degenerative joint disease that seriously affects the quality of people. Unfortunately, the pathogenesis of OA has not been fully known. Therefore, this study aimed to construct a ceRNA regulatory network related to OA to explore the pathogenesis of OA.

Methods: Differentially expressed circRNAs (DEcircRNAs), microRNAs (DEmiRNAs), and mRNAs (DEmRNAs) were obtained from the Gene Expression Omnibus microarray data (GSE175959, GSE105027, and GSE169077). The miRNA response elements and target mRNAs were identified using bioinformatics approaches. Additionally, a circRNA–miRNA–mRNA network was established using Cytoscape version 3.8.0. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of mRNAs in the network were conducted to explore the possible mechanisms underlying OA development. Protein–protein interaction (PPI) analysis was performed to determine the hub genes. Based on the hub genes, a sub network was constructed using Cytoscape 3.8.0 version. Finally, connectivity map (CMap) and drug–gene interaction database (DGIdb) analyses were performed to identify the potential therapeutic targets for OA.

Results: Altogether, five DEcircRNAs, 89 DEmiRNAs, and 345 DEmRNAs were identified. Moreover, a circRNA–miRNA–mRNA network was established using three circRNAs, seven miRNAs, and 37 mRNAs. GO and KEGG analyses demonstrated that the mRNAs in the network could be related to the occurrence and development of OA. PPI analysis was performed and six key genes, namely serpin family H member 1 [SERPINH1], collagen type VIII alpha 2 chain [COL8A2], collagen type XV alpha 1 chain [COL15A1], collagen type VI alpha 3 chain [COL6A3], collagen type V alpha 1 chain [COL5A1], and collagen type XI alpha 1 chain [COL11A1], were identified. Furthermore, a circRNA–miRNA–hub gene subnetwork was established in accordance with two circRNAs (hsa_circ_0075320 and hsa_circ_0051428), two miRNAs (hsa-miR-6124 and hsa-miR-1207-5p), and six hub genes (COL11A1, SERPINH1, COL6A3, COL5A1, COL8A2, and COL15A1). Finally, three chemicals (noscapine, diazepam, and TG100-115) based on CMap analysis and two drugs (collagenase Clostridium histolyticum and ocriplasmin) based on DGIdb were discovered as potential treatment options for OA.

Conclusion: This study presents novel perspectives on the pathogenesis and treatment of OA based on circRNA-related competitive endogenous RNA regulatory networks.

Role of Circular RNAs in Pulmonary Fibrosis

Pulmonary fibrosis is a chronic progressive form of interstitial lung disease, characterized by the histopathological pattern of usual interstitial pneumonia. Apart from aberrant alterations of protein-coding genes, dysregulation of non-coding RNAs, including microRNAs, long non-coding RNAs, and circular RNAs (circRNAs), is crucial to the initiation and progression of pulmonary fibrosis. CircRNAs are single-stranded RNAs that form covalently closed loops without 5′ caps and 3′ tails. Different from canonical splicing of mRNA, they are produced from the back-splicing of precursor mRNAs and have unique biological functions, as well as potential biomedical implications. They function as important gene regulators through multiple actions, including sponging microRNAs and proteins, regulating transcription, and splicing, as well as protein-coding and translation in a cap-independent manner. This review comprehensively summarizes the alteration and functional role of circRNAs in pulmonary fibrosis, with a focus on the involvement of the circRNA in the context of cell-specific pathophysiology. In addition, we discuss the diagnostic and therapeutic potential of targeting circRNA and their regulatory pathway mediators, which may facilitate the translation of recent advances from bench to bedside in the future.

Non-coding RNAs in skin cancers:Biological roles and molecular mechanisms

Cutaneous malignancies, including basal cell carcinoma, cutaneous squamous cell carcinoma, and cutaneous melanoma, are common human tumors. The incidence of cutaneous malignancies is increasing worldwide, and the leading cause of death is malignant invasion and metastasis. The molecular biology of oncogenes has drawn researchers’ attention because of the potential for targeted therapies. Noncoding RNAs, including microRNAs, long noncoding RNAs, and circular RNAs, have been studied extensively in recent years. This review summarizes the aspects of noncoding RNAs related to the metastasis mechanism of skin malignancies. Continuous research may facilitate the identification of new therapeutic targets and help elucidate the mechanism of tumor metastasis, thus providing new opportunities to improve the survival rate of patients with skin malignancies.

Emerging Roles of Circ-ZNF609 in Multiple Human Diseases

Circular RNAs (circRNAs) are a special type of endogenous RNAs with extensive roles in multiple human diseases. They are formed by back-splicing of partial sequences of the parental precursor mRNAs. Unlike linear RNAs, their covalently closed loop structure without a 5′ cap and a 3′ polyadenylated tail confers on them high stability and they are difficult to be digested by RNase R. Increasing evidence has proved that aberrant expressions of many circRNAs are detected and that circRNAs exert essential biological functions in disease development and progression via acting as a molecular sponge of microRNA, interacting with proteins as decoys or scaffolds, or self-encoding small peptides. Circular RNA zinc finger protein 609 (circ-ZNF609) originates from exon2 of ZNF609, which is located at chromosome 15q22.31, and it has recently been proved that it can translate into a protein. Being aberrantly upregulated in various diseases, it could promote malignant progression of human tumors, as well as tumor cell proliferation, migration, and invasion. Here in this review, we concluded the biological functions and potential mechanisms of circ-ZNF609 in multiple diseases, which could be further explored as a targetable molecule in future accurate diagnosis and prognosis.

Context-specific effects of sequence elements on subcellular localization of linear and circular RNAs

Long RNAs vary extensively in their post-transcriptional fates, and this variation is attributed in part to short sequence elements. We used massively parallel RNA assays to study how sequences derived from noncoding RNAs influence the subcellular localization and stability of circular and linear RNAs, including spliced and unspliced forms. We find that the effects of sequence elements strongly depend on the host RNA context, with limited overlap between sequences that drive nuclear enrichment of linear and circular RNAs. Binding of specific RNA binding proteins underpins some of these differences-SRSF1 binding leads to nuclear enrichment of circular RNAs; SAFB binding is associated with nuclear enrichment of predominantly unspliced linear RNAs; and IGF2BP1 promotes export of linear spliced RNA molecules. The post-transcriptional fate of long RNAs is thus dictated by combinatorial contributions of specific sequence elements, of splicing, and of the presence of the terminal features unique to linear RNAs.

Epigenetic modifications in spinal ligament aging

Spinal stenosis is a common degenerative spine disorder in the aged population and the spinal ligament aging is a main contributor to this chronic disease. However, the underlying mechanisms of spinal ligament aging remain unclear. Epigenetics is the study of heritable and reversible changes in the function of a gene or genome that occur without any alteration in the primary DNA sequence. Epigenetic alterations have been demonstrated to play crucial roles in age-related diseases and conditions, and they are recently studied as biomarkers and therapeutic targets in the field of cancer research. The main epigenetic modifications, including DNA methylation alteration, histone modifications as well as dysregulated noncoding RNA modulation, have all been implicated in spinal ligament aging diseases. DNA methylation modulates the expression of critical genes including WNT5A, GDNF, ACSM5, miR-497 and miR-195 during spinal ligament degeneration. Histone modifications widely affect gene expression and obvious histone modification abnormalities have been found in spinal ligament aging. MicroRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) exert crucial regulating effects on spinal ligament aging conditions via targeting various osteogenic or fibrogenic differentiation related genes. To our knowledge, there is no systematic review yet to summarize the involvement of epigenetic mechanisms of spinal ligament aging in degenerative spinal diseases. In this study, we systematically discussed the different epigenetic modifications and their potential functions in spinal ligament aging process.

Recent Advances in Epigenetics of Age-Related Kidney Diseases

Renal aging has attracted increasing attention in today’s aging society, as elderly people with advanced age are more susceptible to various kidney disorders such as acute kidney injury (AKI) and chronic kidney disease (CKD). There is no clear-cut universal mechanism for identifying age-related kidney diseases, and therefore, they pose a considerable medical and public health challenge. Epigenetics refers to the study of heritable modifications in the regulation of gene expression that do not require changes in the underlying genomic DNA sequence. A variety of epigenetic modifiers such as histone deacetylases (HDAC) inhibitors and DNA methyltransferase (DNMT) inhibitors have been proposed as potential biomarkers and therapeutic targets in numerous fields including cardiovascular diseases, immune system disease, nervous system diseases, and neoplasms. Accumulating evidence in recent years indicates that epigenetic modifications have been implicated in renal aging. However, no previous systematic review has been performed to systematically generalize the relationship between epigenetics and age-related kidney diseases. In this review, we aim to summarize the recent advances in epigenetic mechanisms of age-related kidney diseases as well as discuss the application of epigenetic modifiers as potential biomarkers and therapeutic targets in the field of age-related kidney diseases. In summary, the main types of epigenetic processes including DNA methylation, histone modifications, non-coding RNA (ncRNA) modulation have all been implicated in the progression of age-related kidney diseases, and therapeutic targeting of these processes will yield novel therapeutic strategies for the prevention and/or treatment of age-related kidney diseases.

Spatiotemporal Regulation of Circular RNA Expression during Liver Development of Chinese Indigenous Ningxiang Pigs

BACKGROUND

There have been many studies on the relationship between circRNAs and fat deposition. Although the liver is a central organ for fat metabolism, there are few reports on the relationship between circRNAs in the liver and fat deposition.

METHODS

In this study, we systematically analyzed circular RNAs in the liver of Ningxiang pigs, at four time points after birth (30 days, 90 days, 150 days and 210 days).

RESULTS

A total of 3705 circRNAs were coexpressed in four time periods were found, and KEGG analysis showed that the significantly upregulated pathways were mainly enriched in lipid metabolism and amino acid metabolism, while significantly downregulated pathways were mainly related to signal transduction, such as ECM-receptor interaction, MAPK signaling pathway, etc. Short time-series expression miner (STEM) analysis showed multiple model spectra that were significantly enriched over time in the liver. By constructing a competing endogenous RNA (ceRNA) regulatory network, 9187 pairs of networks related to the change in development time were screened.

CONCLUSIONS

The expression profiles of circRNAs in Ningxiang pig liver were revealed at different development periods, and it was determined that there is differential coexpression. Through enrichment analysis of these circRNAs, it was revealed that host genes were involved in metabolism-related signaling pathways and fatty acid anabolism. Through STEM analysis, many circRNAs involved in fat metabolism, transport, and deposition pathways were screened, and the first circRNA-miRNA-mRNA regulation network map in Ningxiang pig liver was constructed. The highly expressed circRNAs related to fat deposition were verified and were consistent with RNA-Seq results.

Noncoding RNAs in the Glycolysis of Ovarian Cancer

Energy metabolism reprogramming is the characteristic feature of tumors. The tumorigenesis, metastasis, and drug resistance of ovarian cancer (OC) is dependent on energy metabolism. Even under adequate oxygen conditions, OC cells tend to convert glucose to lactate, and glycolysis can rapidly produce ATP to meet their metabolic energy needs. Non-coding RNAs (ncRNAs) interact directly with DNA, RNA, and proteins to function as an essential regulatory in gene expression and tumor pathology. Studies have shown that ncRNAs regulate the process of glycolysis by interacting with the predominant glycolysis enzyme and cellular signaling pathway, participating in tumorigenesis and progression. This review summarizes the mechanism of ncRNAs regulation in glycolysis in OC and investigates potential therapeutic targets.

m6A hypomethylation of DNMT3B regulated by ALKBH5 promotes intervertebral disc degeneration via E4F1 deficiency

BACKGROUND

The intervertebral disc (IVD) degeneration is the leading cause of low back pain, which accounts for a main cause of disability. N6-methyladenosine (m6A) is the most abundant internal modification in eukaryotic messenger RNAs and is involved in various diseases and cellular processes by modulating mRNA fate. However, the critical role of m6A regulation in IVD degeneration remains unclear. Nucleus pulposus cell (NPC) senescence is critical for the progression of IVD degeneration. Here, we uncovered the role and explored the regulatory mechanism of m6A in NPC senescence during IVD degeneration.

METHODS

Identification of NPC senescence during IVD degeneration was based on the analysis of tissue samples and the cellular model. ALKBH5 upregulation inducing cellular senescence was confirmed by functional experiments in vivo and in vitro. ChIP-qPCR and DNA-Pulldown were used to reveal increased ALKBH5 was regulated by KDM4A-mediated H3K9me3. Furthermore, Me-RIP-seq was performed to identify m6A hypomethylation of DNMT3B transcripts in senescent NPCs. Stability analysis showed that DNMT3B expression was enhanced for less YTHDF2 recognition and increased DNMT3B promoted NPC senescence and IVD degeneration via E4F1 methylation by in vivo and in vitro analyses.

RESULTS

Expression of ALKBH5 is enhanced during IVD degeneration and NPC senescence, due to decreased KDM4A-mediated H3K9me3 modification. Functionally, ALKBH5 causes NPC senescence by demethylating DNMT3B transcripts and in turn promoting its expression via less YTHDF2 recognition and following degradation due to transcript hypomethylation in vitro and in vivo. Increased DNMT3B promotes the development of IVD degeneration and NPC senescence, mechanistically by methylating CpG islands of E4F1 at the promoter region and thus restraining its transcription and expression.

CONCLUSIONS

Collectively, our findings reveal an epigenetic interplay mechanism in NPC senescence and IVD degeneration, presenting a critical pro-senescence role of ALKBH5 and m6A hypomethylation, highlighting the therapeutic potential of targeting the m6A/DNMT3B/E4F1 axis for treating IVD degeneration.

MicroRNAs, Long Non-Coding RNAs, and Circular RNAs in the Redox Control of Cell Senescence

Cell senescence is critical in diverse aspects of organism life. It is involved in tissue development and homeostasis, as well as in tumor suppression. Consequently, it is tightly integrated with basic physiological processes during life. On the other hand, senescence is gradually being considered as a major contributor of organismal aging and age-related diseases. Increased oxidative stress is one of the main risk factors for cellular damages, and thus a driver of senescence. In fact, there is an intimate link between cell senescence and response to different types of cellular stress. Oxidative stress occurs when the production of reactive oxygen species/reactive nitrogen species (ROS/RNS) is not adequately detoxified by the antioxidant defense systems. Non-coding RNAs are endogenous transcripts that govern gene regulatory networks, thus impacting both physiological and pathological events. Among these molecules, microRNAs, long non-coding RNAs, and more recently circular RNAs are considered crucial mediators of almost all cellular processes, including those implicated in oxidative stress responses. Here, we will describe recent data on the link between ROS/RNS-induced senescence and the current knowledge on the role of non-coding RNAs in the senescence program.

Epigenetic Regulation of Cellular Senescence

Senescence is a complex cellular stress response that abolishes proliferative capacity and generates a unique secretory pattern that is implicated in organismal aging and age-related disease. How a cell transitions to a senescent state is multifactorial and often requires transcriptional regulation of multiple genes. Epigenetic alterations to DNA and chromatin are powerful regulators of genome architecture and gene expression, and they play a crucial role in mediating the induction and maintenance of senescence. This review will highlight the changes in chromatin, DNA methylation, and histone alterations that establish and maintain cellular senescence, alongside the specific epigenetic regulation of the senescence-associated secretory phenotype (SASP).

Research progress of circRNAs in chemotherapy resistance of digestive system neoplasms

Circular RNAs (circRNAs) are a novel class of noncoding RNA molecules with a unique closed continuous loop structure. CircRNAs are abundant in eukaryotic cells, have unique stability and tissue specificity, and can play a biological regulatory role at various levels, such as transcriptional and posttranscriptional levels. Accumulating evidence indicates that circRNAs play critical roles in tumor genesis, development, and chemotherapy. Chemotherapy is a primary type of intervention for most cancers, but its therapeutic efficacy is usually retarded by intrinsic and acquired resistance. CircRNAs regulate tumor chemoresistance through various molecular mechanisms, such as affecting apoptosis, promoting drug transportation, promoting DNA repair, promoting epithelial-mesenchymal transformation, regulating the characteristics of tumor stem cells, and affecting autophagy. This review summarizes the recent progress and mechanisms of circRNAs in cancer cell resistance to chemotherapy.

Age-dependent upregulation of Y RNAs in Caenorhabditis elegans

Y RNA is a conserved small non-coding RNA whose functions in aging remain unknown. Here, we sought to determine the role of C. elegans Y RNA homologs, CeY RNA (CeY) and stem-bulge RNAs (sbRNAs), in aging. We found that the levels of CeY and sbRNAs generally increased during aging. We showed that CeY was downregulated by oxidative and thermal stresses, whereas several sbRNAs were upregulated by oxidative stress. We did not observe lifespan phenotypes by mutations in CeY-coding yrn-1. Future research under various genetic and environmental conditions is required to further evaluate the role of Y RNA in C. elegans aging.