Identification of circular RNAs hsa_circ_0044235 in peripheral blood as novel biomarkers for rheumatoid arthritis

Dysregulated circular RNAs in rheumatoid arthritis: Cellular roles and clinical prospects

Rheumatoid arthritis (RA) is still a healthcare challenge, although current therapeutic strategies have substantially improved its clinical outcomes. The development of novel biomarkers and treatments can increase the likelihood of identification and disease remission in RA patients, especially for patients with seronegative RA and difficult-to-treat RA (D2T RA). Circular RNAs (circRNAs), a novel non-coding RNA species, have been reported to play crucial roles in various biological process of RA. The mechanistic functions of the dysregulated circRNAs in RA are primarily associated with miRNA sponging and regulating transcription. CircRNAs acting as miRNA sponges are further summarized by cell types, including fibroblast-like synoviocytes (FLSs), lymphocytes, macrophages, chondrocytes, and mesenchymal stem cells (MSCs)-/plasma-secreted exosomes. Besides, a description of dysregulated circRNAs in blood, synovial tissue and cartilage tissue suggests their diagnostic potential for RA. In addition, some directions for future research are provided to open the possibility that dysregulated cell- and tissue- specific circRNAs constituting a fresh reservoir of therapeutic targets, and biomarkers for diagnosis, predicting response to therapy, drug selection or patient stratification for RA.

Biosensors for autoimmune diseases

Diagnosis of autoimmune diseases (ADs) is usually based on symptoms and laboratory tests that measure the occurrence of serological and genetic biomarkers such as peptides, autoantibodies, and complement proteins. Early detection of AD is essential to reduce the severity of symptoms and organ damage as a result of progressive disease. Biosensors are tools that convert biochemical signals produced by molecular elements into optical, electrical, and other physical signals for analysis. In recent years, peptides, antigens, aptamers, autoantibodies, and other biomolecules have provided suitable diagnostic features for development of biosensors in detecting and follow up the diagnoses and treatment of diseases. This study reviews the introducing of different biomarkers in ADs with the novel vision to use of biosensor technology for research and development in this regard. Therefore, this study has the required innovation for using biosensor technology with more attention to electrochemical based biosensors to developing, targeting and designing the easy applicable and available diagnostic and response to treatment products using key biomolecules for ADs. It will help readers to understand the research trends of biosensors in ADs and further advance the development of this paramount field.

Circular RNA hsa_circ_0000467 promotes colorectal cancer progression by promoting eIF4A3-mediated c-Myc translation

BACKGROUND

Colorectal cancer (CRC) is the second most common malignant tumor worldwide, and its incidence rate increases annually. Early diagnosis and treatment are crucial for improving the prognosis of patients with colorectal cancer. Circular RNAs are noncoding RNAs with a closed-loop structure that play a significant role in tumor development. However, the role of circular RNAs in CRC is poorly understood.

METHODS

The circular RNA hsa_circ_0000467 was screened in CRC circRNA microarrays using a bioinformatics analysis, and the expression of hsa_circ_0000467 in CRC tissues was determined by in situ hybridization. The associations between the expression level of hsa_circ_0000467 and the clinical characteristics of CRC patients were evaluated. Then, the role of hsa_circ_0000467 in CRC growth and metastasis was assessed by CCK8 assay, EdU assay, plate colony formation assay, wound healing assay, and Transwell assay in vitro and in a mouse model of CRC in vivo. Proteomic analysis and western blotting were performed to investigate the effect of hsa_circ_0000467 on c-Myc signaling. Polysome profiling, RT‒qPCR and dual-luciferase reporter assays were performed to determine the effect of hsa_circ_0000467 on c-Myc translation. RNA pull-down, RNA immunoprecipitation (RIP) and immunofluorescence staining were performed to assess the effect of hsa_circ_0000467 on eIF4A3 distribution.

RESULTS

In this study, we found that the circular RNA hsa_circ_0000467 is highly expressed in colorectal cancer and is significantly correlated with poor prognosis in CRC patients. In vitro and in vivo experiments revealed that hsa_circ_0000467 promotes the growth and metastasis of colorectal cancer cells. Mechanistically, hsa_circ_0000467 binds eIF4A3 to suppress its nuclear translocation. In addition, it can also act as a scaffold molecule that binds eIF4A3 and c-Myc mRNA to form complexes in the cytoplasm, thereby promoting the translation of c-Myc. In turn, c-Myc upregulates its downstream targets, including the cell cycle-related factors cyclin D2 and CDK4 and the tight junction-related factor ZEB1, and downregulates E-cadherin, which ultimately promotes the growth and metastasis of CRC.

CONCLUSIONS

Our findings revealed that hsa_circRNA_0000467 plays a role in the progression of CRC by promoting eIF4A3-mediated c-Myc translation. This study provides a theoretical basis and molecular target for the diagnosis and treatment of CRC.

Functional analysis of a panel of molecular markers for diagnosis of systemic lupus erythematosus in rats

INTRODUCTION

Systemic lupus erythematosus (SLE) is a diverse autoimmune disease that arises from a combination of complex genetic factors and environmental influences. While circRNAs and miRNAs have recently been identified as promising biomarkers for disease diagnosis, their specific expression patterns, and clinical implications in SLE are not yet fully understood.

AIM OF THE WORK

The aim of the present study was to determine the role of a panel of noncoding-RNAs specifically circRNAs (circ-TubD1, circ-CDC27, and circ-Med14), along with miRNA (rno-miR-146a-5p) and mRNA (TRAF6), as novel minimally invasive diagnostic biomarkers for experimentally induced SLE. Additionally, the study involved an insilico bioinformatics analysis to explore potential pathways involved in the pathogenesis of SLE, aiming to enhance our understanding of the disease, enable early diagnosis, and facilitate improved treatment strategies.

MATERIALS AND METHODS

SLE was induced in rats using single IP injection of incomplete Freund's adjuvant (IFA). The Induction was confirmed by assessing the ANA and anti-ds DNA levels using ELSA technique. qPCR analysis was conducted to assess the expression of selected RNAs in sera collected from a group of 10 rats with induced SLE and a control group of 10 rats. In addition, bioinformatics and functional analysis were used to construct a circRNA-miRNA-mRNA network and to determine the potential function of these differentially expressed circRNAs.

RESULTS

SLE rats demonstrated significantly higher expression levels of circ-CDC27, circ-Med14, and rno-miR-146a-5p as well as TRAF6, with lower expression level of circ-TubD1 in sera of SLE rats relative to controls. ROC curve analysis indicated that all the selected non-coding RNAs could serve as potential early diagnostic markers for SLE. In addition, the expression level of circ-TubD1 was negatively correlated with rno-miR-146a-5p, however, rno-miR-146a-5p was positively correlated with TRAF6. Bioinformatic analysis revealed the incorporation of the circRNAs targeted genes in various immune system and neurodegeneration pathways.

CONCLUSIONS

Therefore, circRNAs; circ-TubD1, circ-CDC27, and circ-Med14, in addition to the miRNA (rno-miR-146a-5p) and mRNA (TRAF6) may be involved in the development of SLE and may have promising roles for future diagnosis and targeted 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.

Current situation and trend of non-coding RNA in rheumatoid arthritis: a review and bibliometric analysis

Background

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that affects multiple joints and has adverse effects on various organs throughout the body, often leading to a poor prognosis. Recent studies have shown significant progress in the research of non-coding RNAs (ncRNAs) in RA. Therefore, this study aims to comprehensively assess the current status and research trends of ncRNAs in RA through a bibliometric analysis.

Methods

This study retrieved articles relevant to ncRNAs and RA from the Science Citation Index Expanded Database of the Web of Science Core Collection between January 1st, 2003, and July 31st, 2023. The relevant articles were screened based on the inclusion criteria. VOSviewer and CiteSpace are utilized for bibliometric and visual analysis.

Results

A total of 1697 publications were included in this study, and there was a noticeable increase in annual publications from January 1st, 2003, to July 31st, 2023. China, the United States, and the United Kingdom were the most productive countries in this field, contributing to 43.81%, 13.09%, and 3.87% of the publications. Anhui Medical University and Lu Qianjin were identified as the most influential institution and author. Frontiers In Immunology stood out as the most prolific journal, while Arthritis & Rheumatology was the most co-cited journal. Additionally, the research related to "circular RNA", "oxidative stress", "proliferation", and "migration" have emerged as new hotspots in the field.

Conclusion

In this study, we have summarized the publication characteristics related to ncRNA and RA and identified the most productive countries, institutions, authors, journals, hot topics, and trends.

Circ-AMOTL1 enhances cardiac fibrosis through binding with EIF4A3 and stabilizing MARCKS expression in diabetic cardiomyopathy

OBJECTIVE

To evaluate the effects and possible mechanisms of circular RNAs (circRNAs) on diabetic myocardial fibrosis (DMF).

METHODS

We used an in vivo mice model of streptozotocin (STZ)-induced diabetes and conducted in vitro studies using cultured mouse cardiac fibroblast cells (CFs).

RESULTS

We found that the expression of circ-AMOTL1 was significantly upregulated in the myocardial tissue of diabetic mice compared to that in normal tissues. Inhibition of circ-AMOTL1 improved cardiac function in mice with type I diabetes and significantly repressed STZ-induced myocardial mesenchymal and perivascular fibrosis. In addition, silencing circ-AMOTL1 inhibited cell proliferation, decreased the expression levels of TGF-β1, collagen 1, collagen III, and α-SMA, and reduced the levels of ROS and NO in HG-treated CFs. Our data also indicated that silencing circ-AMOTL1 significantly reduced the expression of myristoylated alanine-rich C-kinase substrate (MARCKS). Finally, circ-AMOTL1 combined with the RNA-binding protein EIF4A3 to improve MARCKS stability. Moreover, co-transfection with si-circ-AMOTL1 and MARCKS reversed the effects of si-circ-AMOTL1 on cell proliferation, fibrotic marker proteins, and ROS and NO levels in vitro.

CONCLUSION

Our data suggest that circ-AMOTL1 plays a key role in STZ-induced DMF by modulating MARCKS, and that targeting circ-AMOTL1 may be a potential strategy to treat DMF.

Bioactive Molecules against Rheumatoid Arthritis by Suppressing Pyroptosis

Rheumatoid arthritis is an inflammatory disease, and pyroptosis is a form of death associated with an inflammatory response. Pyroptosis, which occurs in synovial and osteoblastic cells, can exacerbate the development of rheumatoid arthritis. The inhibition of pyroptosis of these cells can, therefore, clearly be used as a therapeutic strategy against rheumatoid arthritis. Here, we have summarized the current status of progress in the treatment of rheumatoid arthritis by targeting cellular pyroptosis. We have identified seven compounds, including a cyclic RNA, a microRNA, a peptide, and a cytokine (protein), that may influence the progression of rheumatoid arthritis by regulating the initiation of pyroptosis. All of these compounds have been shown to have anti-rheumatoid effects in vitro and/or in vivo and have the potential to be developed as anti-rheumatoid agents. These findings may help to accelerate the development of anti-rheumatoid arthritis drugs.

Can pyroptosis be a new target in rheumatoid arthritis treatment?

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease of undefined etiology, with persistent synovial inflammation and destruction of articular cartilage and bone. Current clinical drugs for RA mainly include non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, disease modifying anti-rheumatic drugs (DMARDs) and so on, which can relieve patients' joint symptoms. If we want to have a complete cure for RA, there are still some limitations of these drugs. Therefore, we need to explore new mechanisms of RA to prevent and treat RA radically. Pyroptosis is a newly discovered programmed cell death (PCD) in recent years, which is characterized by the appearance of holes in cell membranes, cell swelling and rupture, and the release of intracellular pro-inflammatory factors into the extracellular space, resulting in a strong inflammatory response. The nature of pyroptosis is pro-inflammatory, and whether it is participating in the development of RA has attracted a wide interest among scholars. This review describes the discovery and mechanism of pyroptosis, the main therapeutic strategies for RA, and the role of pyroptosis in the mechanism of RA development. From the perspective of pyroptosis, the study of new mechanisms of RA may provide a potential target for the treatment of RA and the development of new drugs in the clinics.

Fourier-transform infrared spectroscopy: a universal optical sensing technique with auspicious application prospects in the diagnosis and management of autoimmune diseases

Autoimmune diseases (AIDs) are poorly understood clinical syndromes due to breakdown of immune tolerance towards specific types of self-antigens. They are generally associated with an inflammatory response mediated by lymphocytes T, autoantibodies or both. Ultimately, chronic inflammation culminates in tissue damages and clinical manifestations. AIDs affect 5% of the world population, and they represent the main cause of fatality in young to middle-aged females. In addition, the chronic nature of AIDs has a devastating impact on the patient's quality of life. It also places a heavy burden on the health care system. Establishing a rapid and accurate diagnosis is considered vital for an ideal medical management of these autoimmune disorders. However, for some AIDs, this task might be challenging. Vibrational spectroscopies, and more particularly Fourier-transform infrared (FTIR) spectroscopy, have emerged as universal analytical techniques with promising applications in the diagnosis of various types of malignancies and metabolic and infectious diseases. The high sensitivity of these optical sensing techniques and their minimal requirements for test reagents qualify them to be ideal analytical techniques. The aim of the current review is to explore the potential applications of FTIR spectroscopy in the diagnosis and management of most common AIDs. It also aims to demonstrate how this technique has contributed to deciphering the biochemical and physiopathological aspects of these chronic inflammatory diseases. The advantages that can be offered by this optical sensing technique over the traditional and gold standard methods used in the diagnosis of these autoimmune disorders have also been extensively discussed.

Circular RNA in autoimmune diseases: special emphasis on regulation mechanism in RA and SLE

BACKGROUND

Autoimmune diseases are diseases caused by tissue damage caused by the body's immune response to autoantibodies. Circular RNAs (CircRNAs) are a kind of special endogenous non-coding RNA that play a biological role by regulating gene transcription.

METHODS

In this work, we searched the PubMed, Web of Science (SCIE), National Science and Technology Library (NSTL), and ScienceDirect Online (SDOL) databases to summarize the impact of circRNAs on autoimmune diseases, especially the results of circRNAs in rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).

RESULTS

The study on the function of circRNAs and autoimmune diseases further deepened our understanding of the development and pathogenesis of autoimmune diseases. CircRNAs may act as miRNA sponges to regulate biological processes and affect the occurrence and development of autoimmune diseases. CircRNAs are closely related to the pathogenesis of RA and SLE and may become potential biomarkers for the diagnosis and treatment of RA and SLE.

CONCLUSION

CircRNAs play an important role in the pathogenesis of RA, SLE and other autoimmune diseases, and are expected to provide new biomarkers for the diagnosis and treatment of autoimmune diseases. However, the function and mechanism of circRNAs in autoimmune diseases need more comprehensive research.

Implications and theragnostic potentials of circular RNAs in rheumatic diseases

Circular RNAs (circRNAs), a class of non-coding RNAs (ncRNAs), are highly stable and ubiquitous molecules that exhibit tissue-specific expression. Accumulating evidence has shown that aberrant expression of circRNAs can play a role in the pathogenesis of several diseases. Rheumatic diseases are a varied group of autoimmune and inflammatory disorders affecting mainly the musculoskeletal system. Notably, circRNAs, which are essential immune system gene modulators, are strongly linked to the occurrence and progression of autoimmune disorders. Here, we present and discuss the current findings concerning the roles, implications and theragnostic potentials of circRNAs in common rheumatic diseases, including ankylosing spondylitis (AS), osteoarthritis (OA), osteoporosis (OP), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Crohn's disease (CD), and gout. This review aims to provide new insights to support the development of novel diagnostic and therapeutic strategies for these disabling diseases.

Rheumatoid arthritis and non-coding RNAs; how to trigger inflammation

Rheumatoid arthritis (RA) is a systemic and chronic inflammatory disease categorized by continuous synovitis in the joints and systemic inflammatory responses that can cause lifelong disability. The major cause of RA is the dysregulation of the immune response. The development of RA disease includes multiplex association of several interleukins and cells, which leads to synovial cell growth, cartilage and bone damage. The primary stage of RA disease is related to the modification of both the innate and adaptive immune systems, which leads to the formation of autoantibodies. This process results in many damaged molecules and epitope spreading. Both the innate (e.g., dendritic cells, macrophages, and neutrophils) and acquired immune cells (e.g., T and B lymphocytes) will increase and continue the chronic inflammatory condition in the next stages of the RA disease. In recent years, non-coding RNAs have been proved as significant controllers of biological functions, especially immune cell expansion and reactions. Non-coding RNAs were primarily containing microRNA (miRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA). Various studies confirmed non-coding RNAs as hopeful markers for diagnosing and curing RA. This review will describe and cover existing knowledge about RA pathogenesis, which might be favorable for discovering possible ncRNA markers for RA.

Epigenetic Regulations in Autoimmunity and Cancer: from Basic Science to Translational Medicine

Epigenetics, as a discipline that aims to explain the differential expression of phenotypes arising from the same gene sequence and the heritability of epigenetic expression, has received much attention in medicine. Epigenetic mechanisms are constantly being discovered, including DNA methylation, histone modifications, noncoding RNAs and m6A. The immune system mainly achieves an immune response through the differentiation and functional expression of immune cells, in which epigenetic modification will have an important impact. Because of immune infiltration in the tumor microenvironment, immunotherapy has become a research hotspot in tumor therapy. Epigenetics plays an important role in autoimmune diseases and cancers through immunology. An increasing number of drugs targeting epigenetic mechanisms, such as DNA methyltransferase inhibitors, histone deacetylase inhibitors, and drug combinations, are being evaluated in clinical trials for the treatment of various cancers (including leukemia and osteosarcoma) and autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis). This review summarizes the progress of epigenetic regulation for cancers and autoimmune diseases to date, shedding light on potential therapeutic strategies.

Non-coding RNAs in immunoregulation and autoimmunity: Technological advances and critical limitations

Immune cell function is critically dependent on precise control over transcriptional output from the genome. In this respect, integration of environmental signals that regulate gene expression, specifically by transcription factors, enhancer DNA elements, genome topography and non-coding RNAs (ncRNAs), are key components. The first three have been extensively investigated. Even though non-coding RNAs represent the vast majority of cellular RNA species, this class of RNA remains historically understudied. This is partly because of a lag in technological and bioinformatic innovations specifically capable of identifying and accurately measuring their expression. Nevertheless, recent progress in this domain has enabled a profusion of publications identifying novel sub-types of ncRNAs and studies directly addressing the function of ncRNAs in human health and disease. Many ncRNAs, including circular and enhancer RNAs, have now been demonstrated to play key functions in the regulation of immune cells and to show associations with immune-mediated diseases. Some ncRNAs may function as biomarkers of disease, aiding in diagnostics and in estimating response to treatment, while others may play a direct role in the pathogenesis of disease. Importantly, some are relatively stable and are amenable to therapeutic targeting, for example through gene therapy. Here, we provide an overview of ncRNAs and review technological advances that enable their study and hold substantial promise for the future. We provide context-specific examples by examining the associations of ncRNAs with four prototypical human autoimmune diseases, specifically rheumatoid arthritis, psoriasis, inflammatory bowel disease and multiple sclerosis. We anticipate that the utility and mechanistic roles of these ncRNAs in autoimmunity will be further elucidated in the near future.

Biomarkers (mRNAs and non-coding RNAs) for the diagnosis and prognosis of rheumatoid arthritis

In recent years, diagnostic and therapeutic approaches for rheumatoid arthritis (RA) have continued to improve. However, in the advanced stages of the disease, patients are unable to achieve long-term clinical remission and often suffer from systemic multi-organ damage and severe complications. Patients with RA usually have no overt clinical manifestations in the early stages, and by the time a definitive diagnosis is made, the disease is already at an advanced stage. RA is diagnosed clinically and with laboratory tests, including the blood markers C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) and the autoantibodies rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPA). However, the presence of RF and ACPA autoantibodies is associated with aggravated disease, joint damage, and increased mortality, and these autoantibodies have low specificity and sensitivity. The etiology of RA is unknown, with the pathogenesis involving multiple factors and clinical heterogeneity. The early diagnosis, subtype classification, and prognosis of RA remain challenging, and studies to develop minimally invasive or non-invasive biomarkers in the form of biofluid biopsies are becoming more common. Non-coding RNA (ncRNA) molecules are composed of long non-coding RNAs, small nucleolar RNAs, microRNAs, and circular RNAs, which play an essential role in disease onset and progression and can be used in the early diagnosis and prognosis of RA. In this review of the diagnostic and prognostic approaches to RA disease, we provide an overview of the current knowledge on the subject, focusing on recent advances in mRNA-ncRNA as diagnostic and prognostic biomarkers from the biofluid to the tissue level.

Circular RNAs: typical biomarkers for bone-related diseases

Bone is a connective tissue that has important functions in the human body. Cells and the extracellular matrix (ECM) are key components of bone and are closely related to bone-related diseases. However, the outcomes of conventional treatments for bone-related diseases are not promising, and hence it is necessary to elucidate the exact regulatory mechanisms of bone-related diseases and identify novel biomarkers for diagnosis and therapy. Circular RNAs (circRNAs) are single-stranded RNAs that form closed circular structures without a 5' cap or 3' tail and polycyclic adenylate tails. Due to their high stability, circRNAs have the potential to be typical biomarkers. Accumulating evidence suggests that circRNAs are involved in bone-related diseases, including osteoarthritis, osteoporosis, osteosarcoma, multiple myeloma, intervertebral disc degeneration, and rheumatoid arthritis. Herein, we summarize the recent research progress on the characteristics and functions of circRNAs, and highlight the regulatory mechanism of circRNAs in bone-related diseases.

Practical Significance of Biomarkers in Axial Spondyloarthritis: Updates on Diagnosis, Disease Activity, and Prognosis

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease that can lead to ankylosis by secondary ossification of inflammatory lesions, with progressive disability and a significant impact on quality of life. It is also a risk factor for the occurrence of comorbidities, especially cardiovascular diseases (CVDs), mood disorders, osteoporosis, and malignancies. Early diagnosis and treatment are needed to prevent or decrease functional decline and to improve the patient's prognosis. In respect of axSpA, there is an unmet need for biomarkers that can help to diagnose the disease, define disease activity and prognosis, and establish personalized treatment approaches. The aim of this review was to summarize the available information regarding the most promising biomarkers for axSpA. We classified and identified six core categories of biomarkers: (i) systemic markers of inflammation; (ii) molecules involved in bone homeostasis; (iii) HLA-B27 and newer genetic biomarkers; (iv) antibody-based biomarkers; (v) microbiome biomarkers; and (vi) miscellaneous biomarkers. Unfortunately, despite efforts to validate new biomarkers, few of them are used in clinical practice; however, we believe that these studies provide useful data that could aid in better disease management.

Circ_0088036 mediated progression and inflammation in fibroblast-like synoviocytes of rheumatoid arthritis by miR-1263/REL-activated NF-κB pathway

BACKGROUND

Rheumatoid arthritis (RA) is a common joint disease with abnormal development of human fibroblast-like synoviocytes (HFLS). Circular RNAs (circRNAs) have essential regulation in the disease progression, and this study was to explore the regulatory mechanism of circ_0088036 in RA.

METHODS

RNA expression analysis was performed through reverse transcription-quantitative polymerase chain reaction assay. Cell experiments were conducted by Cell Counting Kit-8 assay for cell viability, EdU (5-ethynyl-2'-deoxyuridine) assay for proliferation and flow cytometry for cell cycle or apoptosis. The protein detection was conducted using western blot. Enzyme-linked immunosorbent assay (ELISA) was used to examine the inflammatory cytokines. The binding identification was carried out through dual-luciferase reporter assay, RNA immunoprecipitation assay and pull-down assay.

RESULTS

The level of circ_0088036 RNA was significantly upregulated in sera and in HFLS cells of RA patients. Targeted silencing of circ_0088036 restrained proliferation, cell cycle progression and inflammatory reaction through promoted the apoptosis of HFLS-RA cells via inhibiting the NF-κB pathway. The miR-1263 was identified as a target of circ_0088036. MiR-1263 was found to be down-regulated in sera and in HFLS cells of RA patients. The regulatory effects of circ_0088036 on HFLS-RA cells were attributed to inhibit the miR-1263 level. REL is a susceptibility locus for certain autoimmune diseases. MiR-1263 directly targeted REL, which was discovered to be elevated in sera and HFLS cells of RA patients, and circ_0088036 interacted with miR-1263 to affect REL expression. Functionally, overexpression of miR-1263 suppressed the development of HFLS-RA by blocking the NF-κB pathway, and this phenomenon was reversed by the upregulation of REL.

CONCLUSION

These findings suggested that circ_0088036/miR-1263/REL/NF-κB pathway was involved in the functional development of HFLS-RA cells, indicating a novel molecular network in RA progression in vitro.

Expression profile of circRNA in peripheral blood mononuclear cells of patients with rheumatoid arthritis

Background

Circular RNAs (circRNAs) is a newly discovered non-coding RNA that can be used as biomarkers in clinical blood samples. This study aims to screen differentially expressed circular RNAs in PBMCs of patients with rheumatoid arthritis (RA) to determine new biomarkers for the diagnosis of RA.

Methods

The differentially expressed circRNAs in peripheral blood mononuclear cells (PBMCs) of 4 RA patients and 4 healthy participants were screened and analyzed by gene microarray technology. We then validated some of the differentially expressed circRNAs in PBMCs of 20 RA patients, 10 systemic lupus erythematosus (SLE) patients and 20 healthy participants using reverse transcription-quantitative polymerase chain reaction amplification (RT-qPCR). Spearman correlation test was performed to analyze the correlation between differentially expressed circRNAs and clinical variables in RA patients. Receiver operating characteristic (ROC) curves were calculated to evaluate the diagnostic value of circRNAs.

Results

Differential analysis obtained 149 circRNAs with significant up-regulated expression and 250 circRNAs with significant down-regulated expression, which predicted the miRNA targets and binding sites. Compared with SLE and health control group, hsa_circ_101328 was found to be a common gene with differential expression of RA. Besides, correlation analysis revealed significant correlation between hsa_circ_101328 and positive CRP. ROC curve analysis showed that hsa_circ_101328 has the potential of RA diagnosis.

Conclusion

We identified some dysregulated circRNAs in PBMCs from RA patients, and hsa_circ_101328 may be a novel and effective biomarker for early diagnosis of RA.

Circ_0088036 facilitates the proliferation and inflammation and inhibits the apoptosis of fibroblast-like synoviocytes through targeting miR-326/FZD4 axis in rheumatoid arthritis

BACKGROUND

The function and pathological significance of circular RNAs (circRNAs) in autoimmune diseases, such as rheumatoid arthritis (RA), are barely known. Here, we explored the role of circ_0088036 in RA progression and its associated mechanism.

METHODS

The synovial lining layer tissues of RA patients and non-RA control patients were collected for clinical study in vivo, and tumour necrosis factor α (TNF-α)-induced RA-fibroblast-like synoviocytes (RA-FLSs) were used for the experiments in vitro. Cell proliferation was assessed by Cell Counting Kit 8 (CCK8) assay and flow cytometry. Cell apoptosis was analyzed by flow cytometry. Enzyme-linked immunosorbent assay (ELISA) was conducted to analyze the release of pro-inflammatory cytokines. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the target interaction between microRNA-326 (miR-326) and circ_0088036 or frizzled class receptor 4 (FZD4).

RESULTS

Circ_0088036 expression was elevated in the synovial lining layer tissues of RA patients and TNF-α-treated RA-FLSs. Circ_0088036 interference largely reversed TNF-α-induced proliferation and inflammation in RA-FLSs. The interaction between circ_0088036 and miR-326 was verified, and miR-326 silencing largely reversed circ_0088036 knockdown-mediated effects in TNF-α-treated RA-FLSs. MiR-326 bound to the 3' untranslated region (3'UTR) of FZD4 in RA-FLSs. FZD4 overexpression largely diminished miR-326 accumulation-mediated influences in TNF-α-treated RA-FLSs. Circ_0088036 could up-regulate FZD4 by sponging miR-326 in RA-FLSs.

CONCLUSION

Circ_0088036 contributed to TNF-α-induced RA progression partly by targeting miR-326/FZD4 signalling.

Circular RNA circ_0130438 suppresses TNF-α-induced proliferation, migration, invasion and inflammation in human fibroblast-like MH7A synoviocytes by regulating miR-130a-3p/KLF9 axis

BACKGROUND

Circular RNAs (circRNAs) can play a critical role in rheumatoid arthritis (RA) pathogenesis by involving gene regulation by competing for shared microRNAs (miRNAs), a family of small noncoding RNAs. MiR-130a-3p is a disease-related miRNA and Kruppel-like factor 9 (KLF9) is a zinc finger transcription factor, which are involved in RA pathogenesis. Here, we identified the action of circRNA circ_0130438 in regulating fibroblast-like synoviocytes (FLSs) stimulated by tumor necrosis factor α (TNF-α).

METHODS

The direct relationship between miR-130a-3p and circRNA circ_0130438 or KLF9 was predicted by bioinformatics analysis and examined by a dual-luciferase reporter or RNA immunoprecipitation (RIP) assay. CircRNA circ_0130438, miR-130a-3p and KLF9 factor expression levels were gauged by a quantitative real-time PCR (qRT-PCR) or a western blot method. Cell proliferation ability was analyzed by a 5-Ethynyl-2'-Deoxyuridine (EdU) staining assay. The transwell assay was used to evaluate cell migration and invasion capacities. The production levels of interleukin-1β (IL)-1β, IL-6 and IL-8 were assessed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The level of circRNA circ_0130438 was reduced in RA tissues (P = 0.0001) and FLSs isolated from RA tissues (P = 0.0001) compared with corresponding normal controls. Exposure of human fibroblast-like MH7A synoviocytes to TNF-α suppressed circRNA circ_0130438 expression (P < 0.0001). In contrast, the elevated expression of circRNA circ_0130438 suppressed the TNF-α-induced proliferation (P = 0.0047) and migration (P = 0.0023) of MH7A cells, as well as their pro-inflammatory cytokines (IL-1β, IL-6 and IL-8) production (P < 0.0001, P < 0.0001 and P < 0.0001). The circRNA circ_0130438 contained a miR-130a-3p binding site. Furthermore, the increase of miR-130-3p in TNF-α-stimulated MH7A cells reversed the effects of circRNA circ_0130438 elevation on cell proliferation (P = 0.0006), migration (P = 0.0406) and pro-inflammatory cytokines (IL-1β, IL-6 and IL-8) production (P = 0.0036, P < 0.0001 and P = 0.0004), indicating that miR-130a-3p was a functional mediator of circRNA circ_0130438 regulation. We also documented that KLF9 was a direct target and downstream effector of miR-130a-3p. Importantly, circRNA circ_0130438 enhanced KLF9 expression (P < 0.0001) in TNF-α-stimulated MH7A cells by functioning as a competing endogenous RNA (ceRNA) for miR-130a-3p (P = 0.0004).

CONCLUSION

Our findings demonstrate that the elevated expression of circRNA circ_0130438 suppresses TNF-α-induced migration, proliferation and pro-inflammatory cytokines (IL-1β, IL-6 and IL-8) production of human MH7A cells by enhancing KLF9 expression by operating as a ceRNA for miR-130a-3p.

VHPKQHR Peptide Modified Ultrasmall Paramagnetic Iron Oxide Nanoparticles Targeting Rheumatoid Arthritis for T1-Weighted Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) could be the ideal diagnostic modality for early rheumatoid arthritis (RA). Vascular cell adhesion molecule-1 (VCAM-1) is highly expressed in synovial locations in patients with RA, which could be a potential target protein for RA diagnosis. The peptide VHPKQHR (VHP) has a high affinity to VCAM-1. To make the contrast agent to target RA at an early stage, we used VHP and ultrasmall paramagnetic iron oxide (USPIO) to synthesize UVHP (U stands for USPIO) through a chemical reaction with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The size of UVHP was 6.7 nm; the potential was −27.7 mV, and the r₂/r₁ value was 1.73. Cytotoxicity assay exhibited that the cell survival rate was higher than 80% at even high concentrations of UVHP (Fe concentration 200 µg/mL), which showed the UVHP has low toxicity. Compared with no TNF-α stimulation, VCAM-1 expression was increased nearly 3-fold when mouse aortic endothelial cells (MAECs) were stimulated with 50 ng/mL TNF-α; cellular Fe uptake was increased very significantly with increasing UVHP concentration under TNF-α treatment; cellular Fe content was 17 times higher under UVHP with Fe concentration 200 µg/mL treating MAECs. These results indicate that UVHP can target overexpression of VCAM-1 at the cellular level. RA mice models were constructed with adjuvant-induced arthritis. In vivo MRI and biodistribution results show that the signal intensity of knee joints was increased significantly and Fe accumulation in RA model mice compared with normal wild-type mice after injecting UVHP 24 h. These results suggest that we have synthesized a simple, low-cost, and less toxic contrast agent UVHP, which targeted VCAM-1 for early-stage RA diagnosis and generates high contrast in T₁-weighted MRI.

Functional Interactions Between lncRNAs/circRNAs and miRNAs: Insights Into Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases that affect synovitis, bone, cartilage, and joint. RA leads to bone and cartilage damage and extra-articular disorders. However, the pathogenesis of RA is still unclear, and the lack of effective early diagnosis and treatment causes severe disability, and ultimately, early death. Accumulating evidence revealed that the regulatory network that includes long non-coding RNAs (lncRNAs)/circular RNAs (circRNAs), micro RNAs (miRNAs), and messenger RNAs (mRNA) plays important roles in regulating the pathological and physiological processes in RA. lncRNAs/circRNAs act as the miRNA sponge and competitively bind to miRNA to regulate the expression mRNA in synovial tissue, FLS, and PBMC, participate in the regulation of proliferation, apoptosis, invasion, and inflammatory response. Thereby providing new strategies for its diagnosis and treatment. In this review, we comprehensively summarized the regulatory mechanisms of lncRNA/circRNA-miRNA-mRNA network and the potential roles of non-coding RNAs as biomarkers and therapeutic targets for the diagnosis and treatment of RA.

The potential of using blood circular RNA as liquid biopsy biomarker for human diseases

Circular RNA (circRNA) is a novel class of single-stranded RNAs with a closed loop structure. The majority of circRNAs are formed by a back-splicing process in pre-mRNA splicing. Their expression is dynamically regulated and shows spatiotemporal patterns among cell types, tissues and developmental stages. CircRNAs have important biological functions in many physiological processes, and their aberrant expression is implicated in many human diseases. Due to their high stability, circRNAs are becoming promising biomarkers in many human diseases, such as cardiovascular diseases, autoimmune diseases and human cancers. In this review, we focus on the translational potential of using human blood circRNAs as liquid biopsy biomarkers for human diseases. We highlight their abundant expression, essential biological functions and significant correlations to human diseases in various components of peripheral blood, including whole blood, blood cells and extracellular vesicles. In addition, we summarize the current knowledge of blood circRNA biomarkers for disease diagnosis or prognosis.

Identification of Circular RNAs Circ_0005008 and Circ_0005198 in Plasma as Novel Biomarkers for New-Onset Rheumatoid Arthritis

The progression of autoimmune diseases is affected by the differential expression of circular RNAs (circRNAs). However, in the plasma from rheumatoid arthritis (RA), circRNAs have an uncertain role. Herein, microarray analysis was used to determine the plasma expression profile of circRNAs from new-onset patients with RA and healthy controls (HCs). CircRNA expression was verified using quantitative real-time reverse transcription PCR. The correlation between clinical variables and circRNA expression was assessed using Spearman's correlation test. The diagnostic value of plasma circRNAs was evaluated using receiver operating characteristic (ROC) curves. Circ_0005008 and circ_0005198 were confirmed to be elevated significantly in plasma samples from new-onset patients with RA compared with those from HCs and from patients with systemic lupus erythematosus. Among these new-onset patients with RA, we found that the levels of circ_0005008 and circ_0005198 correlated positively with the severity of disease, including the rheumatoid factor, C-reactive protein, the erythrocyte sedimentation rate, and the disease activity score in 28 joints (DAS28). However, their expression levels did not correlate with anti-cyclic citrullinated peptide antibodies. Analysis using ROC curves implied that circ_0005008 and circ_0005198 have significant value in the diagnosis of RA. In addition, we found that compared with that in osteoarthritis fibroblast-like synoviocytes (OA-FLSs), circ_0005198 expression was enhanced in RA-FLSs and correlated positively with DAS28. The level of the miRNA target of circ_0005198, miR-4778-3p, was identified as significantly decreased in RA-FLSs, and the expression levels of circ_0005198 and miR-4778-3p correlated significantly and negatively. The results suggested that in new-onset patients with RA, plasma circ_0005008 and circ_0005198 levels are associated with disease activity and represent possible RA biomarkers.

Advance in circular RNA modulation effects of heart failure

CircRNA (circular RNA) is a kind of closed circular structure of noncoding RNA molecules without 5′ hat structure and 3′ polyA, mainly located in the cytoplasm or stored in exosomes. It is not affected by RNA exonuclease, so it's stable and hard to be degraded. Proved to be widespread in a variety of eukaryotes, most circRNAs are cyclized by exons, some are lasso structures formed by intron cyclization. Recently, circRNAs have been demonstrated to play crucial roles in cardiomyocyte hypertrophy, fibrosis, autophagy and apoptosis, participating in the development of heart failure. There is increasing evidence that circRNAs may be a novel target for the treatment of heart failure.

Correlations between autoantibodies and the ATR-FTIR spectra of sera from rheumatoid arthritis patients

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases worldwide. Due to high heterogeneity in disease manifestation, accurate and fast diagnosis of RA is difficult. This study analyzed the potential relationship between the infrared (IR) spectra obtained by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and the presence of autoantibodies and antibodies against urease in sera. Additionally, the wave number of the IR spectrum that enabled the best differentiation between patients and healthy blood donors was investigated. Using a mathematical model involving principal component analysis and discriminant analysis, it was shown that the presence of anti-citrullinated protein antibody, rheumatoid factor, anti-neutrophil cytoplasmic antibodies, and anti-nuclear antibodies correlated significantly with the wave numbers in the IR spectra of the tested sera. The most interesting findings derived from determination of the best predictors for distinguishing RA. Characteristic features included an increased reaction with urease mimicking peptides and a correspondence with particular nucleic acid bands. Taken together, the results demonstrated the potential application of ATR-FTIR in the study of RA and identified potential novel markers of the disease.

Circular RNA circ_0008360 Inhibits the Proliferation, Migration, and Inflammation and Promotes Apoptosis of Fibroblast-Like Synoviocytes by Regulating miR-135b-5p/HDAC4 Axis in Rheumatoid Arthritis

Circular RNAs (circRNAs) have been demonstrated to play crucial roles in the development and progression of many diseases, including rheumatoid arthritis (RA). However, the functions and molecular mechanism of circ_0008360 in RA remain unclear. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to determine the expression of circ_0008360, microRNA-135b-5p (miR-135b-5p), and histone deacetylase 4 (HDAC4). Cell Counting Kit-8 (CCK-8) assay, wound healing assay, and flow cytometry analysis were performed to assess cell proliferation, migration, and apoptosis, respectively. Inflammatory response was evaluated by enzyme-linked immunosorbent assay (ELISA). The interaction between miR-135b-5p and circ_0008360 or HDAC4 was predicted by bioinformatics analysis and verified by dual-luciferase reporter and RNA Immunoprecipitation (RIP) and RNA pull-down assays. Western blot assay was used to detect the protein expression of HDAC4 and proliferating cell nuclear antigen (PCNA). The expression of circ_0008360 was downregulated in RA synovial tissues and RA fibroblast-like synoviocytes (RA-FLSs). Circ_0008360 suppressed the proliferation, migration, and inflammation and promoted apoptosis of RA-FLSs, and circ_0008360 knockdown showed opposite effects. Moreover, miR-135b-5p was a direct target of circ_0008360, and miR-135b-5p could reverse the effects of circ_0008360 on proliferation, migration, inflammation, and apoptosis in RA-FLSs. Furthermore, HDAC4 was a downstream target of miR-135b-5p, and miR-135b-5p accelerated the proliferation, migration, and inflammation and suppressed apoptosis of RA-FLSs by targeting HDAC4. In addition, circ_0008360 positively regulated HDAC4 expression by sponging miR-135b-5p. Circ_0008360 inhibited the proliferation, migration, and inflammation and facilitated apoptosis of RA-FLSs by sponging miR-135b-5p and upregulating HDAC4, providing a potential target for prevention and treatment of RA.

Circ_0085289 Alleviates the Progression of Periodontitis by Regulating let-7f-5p/SOCS6 Pathway

Periodontitis is a common chronic inflammation that often occurs in adults. Circular RNAs (circRNAs) play a vital role in inflammation-related diseases. However, the role and potential basis of hsa_circ_0085289 in periodontitis remain unknown. Periodontal ligament cells (PDLCs) were exposed to lipopolysaccharide (LPS) to mimic periodontitis. The levels of circ_0085289, let-7f-5p, and suppressor of cytokine signaling 6 (SOCS6) were determined using qRT-PCR and western blot. The release of inflammatory cytokines was measured via enzyme-linked immunosorbent assay (ELISA). Cell viability and apoptosis were determined using Cell Counting Kit-8, flow cytometry, Caspase-3 Assay Kit, and western blot assays. The association between let-7f-5p and circ_0085289/SOCS6 was validated via dual-luciferase reporter, RNA pull-down, and RIP assays. Circ_0085289 and SOCS6 levels were reduced, and let-7f-5p level was increased in periodontitis patients and LPS-treated PDLCs. LPS stimulation caused PDLC injury and circ_0085289 downregulation. Moreover, circ_0085289 upregulation or let-7f-5p downregulation diminished LPS-triggered PDLC injury. Besides, circ_0085289 promoted SOCS6 expression by absorbing let-7f-5p. Circ_0085289 alleviated LPS-stimulated PDLC injury via targeting let-7f-5p. Moreover, let-7f-5p targeted SOCS6 to affect LPS-resulted PDLC injury. Circ_0085289 alleviated PDLC injury induced by LPS stimulation via modulating let-7f-5p/SOCS6 axis, suggesting a promising biomarker for periodontitis treatment.

Hsa_circ_0044235 regulates the pyroptosis of rheumatoid arthritis via MiR-135b-5p-SIRT1 axis

Studies have found that cell pyroptosis is involved in the occurrence and development of rheumatoid arthritis (RA). Hsa_circ_0044235 has been found to be significantly low-expressed in RA patients. The purpose of this research was to reveal the regulatory mechanism of hsa_circ_0044235 in the pyroptosis pathway of RA. Serum expressions of hsa_circ_0044235 and SIRT were detected by RT-qPCR, and the relationship of the two genes was analyzed by Pearson. Next, a collagen-induced arthritis (CIA) mouse model was constructed to examine the effect of hsa_circ_0044235 on knee joint injury. The number of apoptotic cells and the level of inflammatory cytokines in synovial tissue were detected by TUNEL and ELISA. Fibroblast-like synoviocytes (FLSs) were extracted as in vitro study subject. Functional assays including flow cytometry and immunofluorescence staining, molecular experiments including RT-qPCR, Western blot and dual luciferase assay, and bioinformatics analysis were performed to analyze the mechanism of hsa_circ_0044235 in pyroptosis in FLSs. Hsa_circ_0044235 and SIRT1 expressions were suppressed in RA patients and the two were positively correlated. Overexpressed hsa_circ_0044235 attenuated joint inflammation, cell apoptosis, and joint damage, reduced foot pad thickness, clinical case scores, inhibited the NLRP3-mediated pyroptosis pathway but promoted SIRT1 expression in CIA mice. Overexpressed hsa_circ_0044235 inhibited caspase-1 content and the NLRP3-mediated pyroptosis pathway. Moreover, hsa_circ_0044235 promoted SIRT1 expression by sponging miR-135b-5p in FLSs. Additionally, the effect of overexpressed hsa_circ_0044235 on FLSs was reversed by miR-135b-5p mimic and siSIRT1, while the effect of siSIRT1 was reversed by miR-135b-5p inhibitor. Hsa_circ_0044235 regulated NLRP3-mediated pyroptosis through miR-135b-5p-SIRT1 axis to regulate the development of RA.

Potential clinical biomarkers in rheumatoid arthritis with an omic approach

Objective

To aid in the selection of the most suitable therapeutic option in patients with diagnosis of rheumatoid arthritis according to the phase of disease, through the review of articles that identify omics biological markers.

Methods

A systematic review in PubMed/Medline databases was performed. We searched articles from August 2014 to September 2019, in English and Spanish, filtered by title and full text; and using the terms "Biomarkers" AND “Rheumatoid arthritis".

Results

This article supplies an exhaustive review from research of objective measurement, omics biomarkers and how disease activity appraise decrease unpredictability in treatment determinations, and finally, economic, and clinical outcomes of treatment options by biomarkers’ potential influence. A total of 122 articles were included. Only 92 met the established criteria for review purposes and 17 relevant references about the topic were included as well. Therefore, it was possible to identify 196 potential clinical biomarkers: 22 non-omics, 20 epigenomics, 33 genomics, 21 transcriptomics, 78 proteomics, 4 glycomics, 1 lipidomics and 17 metabolomics.

Conclusion

A biomarker is a measurable indicator of some, biochemical, physiological, or morphological condition; evaluable at a molecular, biochemical, or cellular level. Biomarkers work as indicators of physiological or pathological processes, or as a result of a therapeutic management. In the last five years, new biomarkers have been identified, especially the omics, which are those that proceed from the investigation of genes (genomics), metabolites (metabolomics), and proteins (proteomics). These biomarkers contribute to the physician choosing the best therapeutic option in patients with rheumatoid arthritis.

Circular RNAs hsa-circ0000175 and hsa-circ0044235 in plasma are novel biomarkers for new-onset rheumatoid arthritis

Circular RNAs (circRNAs) are a class of non-coding RNAs that could serve as potential molecular markers for disease diagnosis. However, the role of circRNAs in plasma from new-onset rheumatoid arthritis (RA) has not been extensively investigated. In this study, the expression of hsa-circ0000175 and hsa-circ0044235 in plasma from RA patients, healthy controls (HCs), systemic lupus erythematosus (SLE) patients, osteoarthritis (OA), and undiagnosed arthritis (UA) patients were determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Correlation analysis was used to assess the correlation of the two circRNAs and clinical variables of RA. The receiver operating characteristic (ROC) curves were created to evaluate the diagnostic value and multivariate analysis (logistic regression) was performed to analyse the risk factors. We confirmed that hsa-circ0000175 was significantly elevated in plasma from patients with new-onset RA compared with HC and patients with new-onset SLE, but significantly was reduced when compared with OA + UA patients. Hsa-circ0044235 was found to be significantly decreased in plasma from patients with new-onset RA compared with HC and OA + UA patients, but was significantly increased compared with SLE patients. The expression of plasma hsa-circ0000175 in new-onset RA patients was associated with platelet count (PLT), plateletcrit (PCT), and platelet large cell ratio (PLR), the expression of plasma hsa-circ0044235 new-onset RA patients was associated with swollen joint count (SJC), painful joint count (PJC), and disease activity score 28 (DAS28). ROC curve analysis suggested that the combination of hsa-circ0000175 and hsa-circ0044235 has some value in the diagnosis of new-onset RA from HC, patients with SLE and patients with OA + UA. The logistic regression analysis revealed that the expression of hsa-circ0000175 and hsa-circ0044235 in plasma were risk factors for RA. This study suggests that the combination of plasma hsa-circ0000175 and hsa-circ0044235 improves the diagnostic accuracy for new-onset RA. Moreover, the expression levels of plasma hsa-circ0000175 and hsa-circ0044235 were associated with disease activity and severity of RA.

CircASH2L facilitates tumor-like biologic behaviours and inflammation of fibroblast-like synoviocytes via miR-129-5p/HIPK2 axis in rheumatoid arthritis

Background

Previous study showed that circular RNA Absent-Small-Homeotic-2--Like protein (circASH2L) was higher in rheumatoid arthritis (RA) patients. However, the roles and mechanisms of circASH2L in RA progression remain unclear.

Methods

Levels analysis was conducted using western blot and qRT-PCR. The proliferation, apoptosis, cell cycle progression, migration, invasiveness, and inflammation of RA fibroblast-like synoviocytes (RA-FLSs) were determined via MTT, flow cytometry, western blot, transwell, and ELISA assays.

Results

CircASH2L knockdown in RA-FLSs suppressed cell proliferative, migratory, and invasive capacities, triggered cell cycle arrest, promoted apoptosis, and inhibited inflammation. Mechanistically, circASH2L targeted miR-129-5p, and repression of miR-129-5p abolished the functions of circASH2L silencing on the growth, motility, and inflammation of RA-FLSs. Besides, miR-129-5p was found to directly target HIPK2, and suppressed the tumor-like biologic behaviors and inflammation of RA-FLSs via regulating HIPK2. Importantly, we proved that circASH2L could modulate HIPK2 expression via miR-129-5p.

Conclusion

CircASH2L promoted RA-FLS growth, motility, and inflammation through miR-129-5p/HIPK2 axis.

Circular RNAs: Expression, localization, and therapeutic potentials

Circular RNAs (circRNAs) are RNAs with a unique circular structure that is generated from back-splicing processes. These circular molecules were discovered more than 40 years ago but failed to raise scientific interest until lately. Increasing studies have found that these circular RNAs might not just be byproducts of the splicing process but possess important regulatory functions through different cellular events. Most circular RNAs are currently being studied in the field of cancer, and many of them have been confirmed to be involved in the process of tumorigenesis. However, many circular RNAs are implicated in the developmental stages of diseases other than cancer. In this review, we focus on discussing the role of circular RNAs in non-cancer diseases, especially in cardiovascular diseases. Following the summary of the life cycle of circRNAs, we provide input on studying circRNA-protein interactions based on our experience, which modulate protein translocation. Furthermore, we outline the potential of circRNAs to be potent biomarkers, effective therapeutic targets, and potential treatments in cardiovascular diseases as well as other non-cancer fields.

Promising diagnostic and therapeutic circRNAs for skeletal and chondral disorders

Circular RNAs (circRNAs) belong to a highly conserved subtype of non-coding RNAs, produced by the back-splicing of specific regions of pre-mRNA. CircRNAs have wide-ranging effects on eukaryotic physiology and pathology by acting as transcription regulators, miRNA sponges, protein sponges, and templates for translation. Skeletal and chondral disorders are the leading causes of pain and disability, especially for elders, affecting hundreds of millions of people worldwide. Plenty of evidence have shown that circRNAs are dysregulated and play vital roles in the occurrence and progression of skeletal and chondral disorders. Herein, we systematically summarize the emerging roles and underlying molecular mechanisms of hub circRNAs in the pathogenesis of several representative skeletal and chondral disorders. Our findings may provide further insight into the mechanistic details of the role of circRNA in bone or cartilage metabolism, and highlight the promising application of circRNAs in serving as potential diagnostic or therapeutic targets for the prevention and treatment of skeletal and chondral disorders.

Current Status of Functional Studies on Circular RNAs in Rheumatoid Arthritis and Their Potential Role as Diagnostic Biomarkers

Circular RNAs (circRNAs), a new class of endogenous non-coding RNAs (ncRNAs), are highly stable and exhibit tissue-specific expression. Accumulating evidence has indicated that circRNAs play crucial roles in the development and progression of multiple diseases. Notably, circRNAs, important epigenetic modulators of gene expression in inflammation and autoimmune regulation, have a close association with the pathogenesis of rheumatoid arthritis (RA). RA, one of the most common systemic autoimmune diseases, is characterized by synovial hyperplasia and inflammation, and cartilage and bone destruction. Here, we focus on the roles of circRNAs in macrophage, synovial tissues, fibroblast-like synoviocytes (FLSs), and cartilage tissues in pathogenesis and progression of RA, highlighting the potential of circRNAs in the blood as diagnostic biomarkers, and aiming at providing new insights into the diagnosis and therapy of this disease.

Hsa_circ_0056558 regulates cyclin-dependent kinase 6 by sponging microRNA-1290 to suppress the proliferation and differentiation in ankylosing spondylitis

The aims of this study was to investigate the influences of hsa_circ_0056558/miR-1290/CDK6 axis in ankylosing spondylitis (AS). The differentially expressed has_circ_0056558 and miR-1290 in AS tissue were analysed based on RNA-seq data and microarray data, respectively. qRT-PCR was performed for detection of relative expression levels of hsa_circ_0056558, miR-1290, CDK6, osteogenic differentiation markers (Runx2 and Osterix) and other inflammatory factors (TNF-α, IL-1β, and IL-6). Western blotting analysis was conducted to test the protein levels of CDK6, osteogenic differentiation markers (Runx2 and Osterix), and PI3K/AKT/NF-κB pathway-associated proteins. CCK8 assay and flow cytometry were conducted to determine cell proliferation and cell apoptotic ability, respectively. Targeted relationships were predicted by bioinformatic analysis and verified by dual-luciferase reporter assay. The differentiation of fibroblast cells was analysed by alkaline phosphatase (ALP) activity assay. Our findings revealed that the expression levels of both circ_0056558 and CDK6 in AS tissue were significantly higher than that in normal samples. Besides, hsa_circ_0056558 could suppress cell proliferation and differentiation by facilitating CDK6 expression and suppressing miR-1290 expression in AS. Over-expression of miR-1290 negatively regulated CDK6 expression to enhance cell proliferation. The protein levels of p-AKT, p-NF-κB p65, and p-IκBα were promoted by hsa_circ_0056558 or CDK6 over-expression while suppressed by miR-1290 up-regulation. In conclusion, our study demonstrated that hsa_circ_0056558 and CDK6 suppressed cell proliferation and differentiation while enhanced cell apoptosis by competitive binding to miR-1290 in AS, which might be possibly achieved by PI3K/AKT/NF-κB pathway, providing us novel therapeutic strategy for AS.

Emerging roles of circular RNAs in systemic lupus erythematosus

Circular RNAs (circRNAs) are a class of non-coding RNAs with covalently closed single-stranded structures lacking 5'-3' polarity and a polyadenine tail. Over recent years, a growing body of studies have been conducted to explore the roles of circRNAs in human diseases. Systemic lupus erythematosus (SLE) is a severe autoimmune disorder characterized by the presence of autoantibodies and excessive inflammation, which impact multiple organs. Recent advances have begun to shed light on the roles of circRNAs in SLE, providing fresh insights into the pathogenesis of SLE and the latent capacity for translation into clinical applications. Here, we briefly introduce these "star molecules" and summarize their roles in SLE. In addition, we outline the limitations of the current studies and raise prospects for future research.

Current Understanding of Circular RNAs in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a common and potentially fatal autoimmune disease that affects multiple organs. To date, its etiology and pathogenesis remains elusive. Circular RNAs (circRNAs) are a novel class of endogenous non-coding RNAs with covalently closed loop structure. Growing evidence has demonstrated that circRNAs may play an essential role in regulation of gene expression and transcription by acting as microRNA (miRNA) sponges, impacting cell survival and proliferation by interacting with RNA binding proteins (RBPs), and strengthening mRNA stability by forming RNA-protein complexes duplex structures. The expression patterns of circRNAs exhibit tissue-specific and pathogenesis-related manner. CircRNAs have implicated in the development of multiple autoimmune diseases, including SLE. In this review, we summarize the characteristics, biogenesis, and potential functions of circRNAs, its impact on immune responses and highlight current understanding of circRNAs in the pathogenesis of SLE.

Circular RNAs in Toxicology

Circular RNAs (circRNAs) are a type of closed, long, non-coding RNAs, which have attracted significant attention in recent years. CircRNAs exhibit unique functions and are characterized by stable expression in various tissues across different species. Because the identification of circRNA in plant viroids in 1976, numerous studies have been conducted to elucidate its generation as well as expression under normal and disease conditions. The rapid development of research focused on the roles of circRNAs as biomarkers in diseases such as cancers has led to increased interests in evaluating the effects of toxicants on the human genetics from a toxicological perspective. Notably, increasing amounts of chemicals are generated in the environment; however, their toxic features and interactions with the human body, particularly from the epigenetic viewpoint, remain largely unknown. Considering the unique features of circRNAs as potential prognostic biomarkers as well as their roles in evaluating health risks following exposure to toxicants, the aim of this review was to assess the latest progress in the research concerning circRNA, to address the role of the circRNA-miRNA-mRNA axis in diseases and processes occurring after exposure to toxic compounds. Another goal was to identify the gaps in understanding the interactions between toxic compounds and circRNAs as potential biomarkers. The review presents general information about circRNA (ie, biogenesis and functions) and provides insights into newly discovered exosome-contained circRNA. The roles of circRNAs as potential biomarkers are also explored. A comprehensive review of the available literature on the role of circRNA in toxicological research (ie, chemical carcinogenesis, respiratory toxicology, neurotoxicology, and other unclassified toxicological categories) is included.

Expression and clinical significance of circular RNAs related to immunity and inflammation in patients with rheumatoid arthritis

The aim of this study was to investigate the changes in and clinical significance of circular RNAs (circRNAs) expression related to immunity and inflammation in patients with rheumatoid arthritis (RA). We analyzed the circRNAs related to immunity and inflammation in peripheral blood mononuclear cells (PBMCs) from three RA patients and three healthy controls using high-throughput sequencing and bioinformatics analysis. Subsequently, four differentially expressed circRNAs were verified by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). We selected hsa_circ_0003353 for functional phenotype analysis in fibroblast-like synoviocytes (FLS) according to correlation tests and logistic regression analysis. The results identified and verified the expression of circRNAs (0003353, 0005732, 0072428, 0091685) that were significantly changed in PBMCs from RA patients. ROC analysis suggested that these circRNAs have significant value in RA diagnosis. Spearman analysis revealed that significant relationships between these circRNAs and clinical indicators as well as SPP. The logistic regression analysis showed that clinical indicators and SPP were risk factors for hsa_circ_0003353 expression, which is worthy of further investigation. As predicted, hsa_circ_0003353 had significantly higher expression in RA-FLS. The cell proliferation, migration, invasion, apoptosis, and inflammatory cytokine production of RA-FLS showed significant alterations after hsa_circ_0003353 suppression and overexpression. Our results indicate that hsa_circ_0003353 may play an essential role in promoting immunity, inflammation, synovial invasion, and joint destruction and that hsa_circ_0003353 may act as a biomarker of RA.

Circ_0000396 inhibits rheumatoid arthritis synovial fibroblast growth and inflammatory response via miR-203/HBP1 axis

Background

Circ_0000396 was found to be down-regulated in the rheumatoid arthritis (RA) patients and had a high diagnostic value. However, the function and mechanisms underlying circ_0000396 in RA progression remain unclear.

Methods

The expression of circ_0000396, microRNA (miR)-203 and HMG-box transcription factor 1 (HBP1) was detected using qRT-PCR and western blot. The proliferative and apoptotic capabilities of rheumatoid arthritis synovial fibroblasts (RASFs) were measured by colony formation, CCK-8, flow cytometry and western blot assays, respectively. The levels of interleukins (IL)-6, IL-1β, IL-8 and tumor necrosis factor-α (TNF-α) were detected using enzyme-linked immunosorbent assay (ELISA). The target correlations between miR-203 and circ_0000396 or HBP1 were validated using pull-down and dual-luciferase reporter assay.

Results

Circ_0000396 was decreased in RA synovial tissues and RASFs, and overexpression of circ_0000396 suppressed cell proliferation, induced cell apoptosis and reduced the release of inflammatory cytokine IL-6, IL-1β, IL-8 and TNF-α in RASFs, while circ_0000396 deletion functioned oppositely. MiR-203 was confirmed to be a target of circ_0000396, and miR-203 reversed the protective effects of circ_0000396 on the dysfunction and inflammation of RASFs. HBP1 was a target of miR-203, and silencing miR-203 inhibited RASFs malignant changes by regulating HBP1. In addition, circ_0000396 could regulate HBP1 by sponging miR-203, and HBP1 decrease attenuated the effects of circ_0000396 on RASF growth and inflammation.

Conclusion

Circ_0000396 inhibited the growth and inflammation in RASFs by regulating miR-203/HBP1 axis, providing a potential therapeutic target for RA.

Differential Profile of Plasma Circular RNAs in Type 1 Diabetes Mellitus

BACKGROUND

No currently available biomarkers or treatment regimens fully meet therapeutic needs of type 1 diabetes mellitus (T1DM). Circular RNA (circRNA) is a recently identified class of stable noncoding RNA that have been documented as potential biomarkers for various diseases. Our objective was to identify and analyze plasma circRNAs altered in T1DM.

METHODS

We used microarray to screen differentially expressed plasma circRNAs in patients with new onset T1DM (n=3) and age-/gender-matched healthy controls (n=3). Then, we selected six candidates with highest fold-change and validated them by quantitative real-time polymerase chain reaction in independent human cohort samples (n=12). Bioinformatic tools were adopted to predict putative microRNAs (miRNAs) sponged by these validated circRNAs and their downstream messenger RNAs (mRNAs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to gain further insights into T1DM pathogenesis.

RESULTS

We identified 68 differentially expressed circRNAs, with 61 and seven being up- and downregulated respectively. Four of the six selected candidates were successfully validated. Curations of their predicted interacting miRNAs revealed critical roles in inflammation and pathogenesis of autoimmune disorders. Functional relations were visualized by a circRNA-miRNA-mRNA network. GO and KEGG analyses identified multiple inflammation-related processes that could be potentially associated with T1DM pathogenesis, including cytokine-cytokine receptor interaction, inflammatory mediator regulation of transient receptor potential channels and leukocyte activation involved in immune response.

CONCLUSION

Our study report, for the first time, a profile of differentially expressed plasma circRNAs in new onset T1DM. Further in silico annotations and bioinformatics analyses supported future application of circRNAs as novel biomarkers of T1DM.

Circular RNAs: Promising Biomarkers for Age-related Diseases

Aging is a complex biological process closely linked with the occurrence and development of age-related diseases. Despite recent advances in lifestyle management and drug therapy, the late diagnosis of these diseases causes severe complications, usually resulting in death and consequently impacting social economies. Therefore, the identification of reliable biomarkers and the creation of effective treatment alternatives for age-related diseases are needed. Circular RNAs (circRNAs) are a novel class of RNA molecules that form covalently closed loops capable of regulating gene expression at multiple levels. Several studies have reported the emerging functional roles of circRNAs in various conditions, providing new perspectives regarding cellular physiology and disease pathology. Notably, accumulating evidence demonstrates the involvement of circRNAs in the regulation of age-related pathologies, including cardio-cerebrovascular disease, neurodegenerative disease, cancer, diabetes, rheumatoid arthritis, and osteoporosis. Therefore, the association of circRNAs with these age-related pathologies highlights their potential as diagnostic biomarkers and therapeutic targets for better disease management. Here, we review the biogenesis and function of circRNAs, with a special focus on their regulatory roles in aging-related pathologies, as well as discuss their potential as biological biomarkers and therapeutic targets for these diseases.

Emerging roles of circular RNAs in innate immunity

The proper function of the innate immune system depends on an intricate network of regulation that promotes effective responses to pathogens while avoiding autoimmunity. Circular RNAs (circRNAs), a class of RNAs that lack 5' and 3' ends, have emerged as key actors in these networks. Recent studies have demonstrated that endogenous circRNAs in eukaryotes regulate the activation of innate immune proteins and cells through diverse modes of action. Some DNA viruses also encode circRNAs, and foreign circRNAs have been found to stimulate an innate immune response. This review summarizes recent investigations that reveal the critical roles that circRNAs play in innate immunity and points to future areas of study in this emerging field.

Expression and clinical significance of circular RNA hsa_circ_0079787 in the peripheral blood of patients with axial spondyloarthritis

Axial spondyloarthritis (AxSpA) is a chronic rheumatic disease involving the axial skeleton. Recent evidence suggested that certain circular RNAs (circRNAs) have a crucial role in rheumatic diseases. However, the functions of circRNAs in AxSpA have remained largely elusive. The present study identified the utility of the circRNA Homo sapiens (hsa)_circ_0079787 as a potential biomarker for AxSpA. A total of 5 circRNAs (hsa_circ_0002715, hsa_circ_0001947, hsa_circ_0079787, hsa_circ_0000367 and hsa_circ_0035197) were determined in the peripheral blood of 46 patients with AxSpA, 46 patients with systemic lupus erythematosus (SLE) and 25 healthy controls (HC) by reverse transcription‑quantitative PCR analysis. The detailed clinical history of each patient was recorded and the correlations between these circRNAs and clinical characteristics were analyzed. Furthermore, receiver operating characteristic (ROC) curves were constructed to evaluate the diagnostic value of hsa_circ_0079787 and other factors for AxSpA. Of the 5 selected circRNAs, the expression of hsa_circ_0079787 was indicated to be significantly reduced in the peripheral blood of patients with AxSpA as compared with the levels in HCs and patients with SLE. The peripheral blood levels of hsa_circ_0079787 in patients with AxSpA were negatively correlated with the Bath Ankylosing Spondylitis Disease Activity Index and positively correlated with the platelet count (PLT) and the lymphocyte‑to‑monocyte ratio. In addition, the expression of peripheral blood hsa_circ_0079787 in male patients with AxSpA was negatively correlated with the mean platelet volume (MPV) and positively correlated with the plateletcrit (PCT). ROC curve analysis suggested that hsa_circ_0079787 and the combination of hsa_circ_0079787‑PLT‑MPV‑PCT had a significant diagnostic value for AxSpA. hsa_circ_0079787 and the combination of hsa_circ_0079787‑PLT‑MPV‑PCT was also able to differentiate between patients with AxSpA and those with SLE. In conclusion, peripheral‑blood hsa_circ_0079787 and the combination of hsa_circ_0079787‑PLT‑MPV‑PCT may provide improved diagnostic accuracy for AxSpA. In addition, the levels of hsa_circ_0079787 in the peripheral blood were correlated with disease activity and severity of AxSpA.

CircRNA_09505 aggravates inflammation and joint damage in collagen-induced arthritis mice via miR-6089/AKT1/NF-κB axis

A number of circular RNAs (circRNAs) have been implicated in rheumatoid arthritis (RA) pathogenesis; however, little is known about their function and hidden molecular mechanism in immune and inflammation regulation. We investigated the role and the underlying mechanism of circRNA_09505 in RA in this study. Real-time PCR and fluorescence in situ hybridization (FISH) are adopted to estimate the quantitative expression and localization of circRNA_09505 in macrophages. The altering effect of circRNA_09505 on inflammation is investigated in vitro and in vivo by use of macrophage cell models and collagen-induced arthritis (CIA) mice. Luciferase reporter assay and RNA-binding protein immunoprecipitation (RIP) are used to confirm the circRNA_09505/miR-6089 ceRNA network predicted by bioinformatics analysis. Compared with controls, the expression of circRNA_09505 is upregulated in peripheral blood mononuclear cells (PBMCs) from patients with RA. The proliferation and cell cycle are significantly promoted when circRNA_09505 is upregulated in macrophages, whereas knockdown of circRNA_09505 inhibits macrophage proliferation and cell- cycle progression. Besides, circRNA_09505 can act as a miRNA sponge for miR-6089 in macrophages, and promote the production of TNF-α, IL-6, and IL-12 through ceRNA mechanism. Moreover, AKT1 is a direct target of miR-6089. CircRNA_09505 can promote AKT1 expression by acting as a miR-6089 sponge via IκBα/NF-κB signaling pathway in macrophages. Most interestingly, knockdown of circRNA_09505 significantly alleviates arthritis and inflammation in vivo in CIA mice. These data support the hypothesis that circRNA_09505 can function as a miR-6089 sponge and regulate inflammation via miR-6089/AKT1/NF-κB axis in CIA mice.

Comprehensive Analysis of Differentially Expressed Circular RNAs in Patients with Senile Osteoporotic Vertebral Compression Fracture

Aim

Circular RNAs (circRNAs) have been found to contribute to the regulation of many diseases and are abundantly expressed in various organisms. The present study is aimed at systematically characterizing the circRNA expression profiles in patients with senile osteoporotic vertebral compression fracture (OVCF) and predicting the potential functions of the regulatory networks correlated with these differentially expressed circRNAs.

Methods

The circRNA expression profile in patients with senile OVCF was explored by using RNA sequencing. The prediction of the enriched signaling pathways and circRNA-miRNA networks was conducted by bioinformatics analysis. Real-time quantitative PCR was used to validate the selected differentially expressed circRNAs from 20 patients with senile OVCF relative to 20 matched healthy controls.

Results

A total of 884 differentially expressed circRNAs were identified, of which 554 were upregulated and 330 were downregulated. The top 15 signaling pathways associated with these differentially expressed circRNAs were predicted. The result of qRT-PCR of the selected circRNAs was consistent with RNA sequencing.

Conclusions

CircRNAs are differentially expressed in patients with senile OVCF, which might contribute to the pathophysiological mechanism of senile osteoporosis.

New Insight of Circular RNAs in Human Musculoskeletal Diseases

Circular RNAs (circRNAs), a novel group of noncoding RNAs, are present in most eukaryotic cells. Different from messenger RNAs, circRNAs have a covalently closed single-stranded stable structure and often act in cell type and tissue-specific manners, indicating that they can be used as biomarkers. With the advance of high-throughput RNA sequencing technology and bioinformatics, a large number of circRNAs have been identified in association with musculoskeletal diseases, but the functions of most circRNAs have not been clarified. circRNAs regulate biological processes by adsorbing microRNA as "sponges," binding to proteins, acting as transcriptional regulators, and participating in translation of proteins. In this study, we discuss the latest understanding of biogenesis and gene regulatory mechanisms of circRNAs with special emphasis on new targets for musculoskeletal disease diagnosis and clinical treatment.