CircSEC24A promotes IL-1β-induced apoptosis and inflammation in chondrocytes by regulating miR-142-5p/SOX5 axis

Circular RNAs and inflammation: Epigenetic regulators with diagnostic role

Circular RNAs (circRNAs) are a group of transcripts generally known to be non-coding transcripts, but occasionally producing short peptides. Circ_Ttc3/miR-148a, circ_TLK1/miR-106a-5p, circ_VMA21/miR-9-3p, circ_0068,888/miR-21-5p, circ_VMA21/miR-199a-5p, circ_AFF2/miR-375, circ_0008360/miR-135b-5p and circ-FBXW7/miR-216a-3p are examples of circRNA/miRNA pairs that contribute in the pathogenesis of immune-related conditions. CircRNAs have been found to regulate function of immune system and participate in the pathophysiology of immune-related disorders. In the current study, we searched PubMed and Google Scholar databases until July 2022 with the key words "circRNA" OR "circular RNA" AND "inflammation". Then, we assessed the abstract of retrieved articles to include original articles that assessed contribution of circRNAs in the pathoetiology of inflammation and related disorders. Finally, we went through the main texts of the articles and tabulated the available information. Therefore, the current study summarizes the role of circRNAs in the pathoetiology of sepsis, atherosclerosis, rheumatoid arthritis and osteoarthritis, immune-related cardiovascular, pulmonary, gastrointestinal and nervous system disorders.

CircRNAs in osteoarthritis: research status and prospect

Osteoarthritis (OA) is the most common joint disease globally, and its progression is irreversible. The mechanism of osteoarthritis is not fully understood. Research on the molecular biological mechanism of OA is deepening, among which epigenetics, especially noncoding RNA, is an emerging hotspot. CircRNA is a unique circular noncoding RNA not degraded by RNase R, so it is a possible clinical target and biomarker. Many studies have found that circRNAs play an essential role in the progression of OA, including extracellular matrix metabolism, autophagy, apoptosis, the proliferation of chondrocytes, inflammation, oxidative stress, cartilage development, and chondrogenic differentiation. Differential expression of circRNAs was also observed in the synovium and subchondral bone in the OA joint. In terms of mechanism, existing studies have mainly found that circRNA adsorbs miRNA through the ceRNA mechanism, and a few studies have found that circRNA can serve as a scaffold for protein reactions. In terms of clinical transformation, circRNAs are considered promising biomarkers, but no large cohort has tested their diagnostic value. Meanwhile, some studies have used circRNAs loaded in extracellular vesicles for OA precision medicine. However, there are still many problems to be solved in the research, such as the role of circRNA in different OA stages or OA subtypes, the construction of animal models of circRNA knockout, and more research on the mechanism of circRNA. In general, circRNAs have a regulatory role in OA and have particular clinical potential, but further studies are needed in the future.

Role of circular RNAs in osteoarthritis: update on pathogenesis and therapeutics

Osteoarthritis (OA) is a common and crippling joint disease characterized by cartilage degeneration, subchondral bone sclerosis, and synovitis. The main clinical manifestations of OA are chronic joint pain and impaired mobility, which seriously affect patient's quality of life. Circular RNAs (circRNAs) are noncoding RNAs that are widely discovered in eukaryotic cells. Unlike standard linear RNAs, circRNAs form a covalently closed continuous loop structure without a 5' or 3' polarity. Various experiments in recent years have confirmed that numerous circRNAs appear to be differentially expressed in OA cartilage and synovium. And they are closely associated with various pathological progressions in OA, such as extracellular matrix degradation, chondrocyte apoptosis, and inflammation. In this review, we briefly described the biogenesis, characterization, and functions of circRNAs. And we focused on the relationships between circRNAs and OA progression. At last, we further discussed the prospects of clinical applications of circRNAs in OA, with the expectation to provide feasible directions for OA diagnosis and treatment.

Osteoarthritis year in review: genetics, genomics and epigenetics

This "year in review" provides a summary of the research findings on the topic of genetics, genomics and epigenetics for osteoarthritis (OA) between Mar 2021-Apr 2022. A search routine of the literature in PubMed for the keyword, osteoarthritis, together with topics on genetics, genomics, epigenetics, polymorphism, DNA methylation, noncoding RNA, lncRNA, proteomics, and single cell RNA sequencing, returned key research articles and relevant reviews. Following filtering of duplicates across search routines, 695 unique research articles and 112 reviews were identified. We manually curated these articles and selected 90 as references for this review. However, we were unable to refer to all these articles, and only used selected articles to highlight key outcomes and trends. The trend in genetics is on the meta-analysis of existing cohorts with comparable genetic and phenotype characterisation of OA; in particular, clear definition of endophenotypes to enhance the genetic power. Further, many researchers are realizing the power of big data and multi-omics approaches to gain molecular insights for OA, and this has opened innovative approaches to include transcriptomics and epigenetics data as quantitative trait loci (QTLs). Given that most of the genetic loci for OA are not located within coding regions of genes, implying the impact is likely to be on gene regulation, epigenetics is a hot topic, and there is a surge in studies relating to the role of miRNA and long non-coding RNA on cartilage biology and pathology. The findings are exciting and new insights are provided in this review to summarize a year of research and the road map to capture all new innovations to achieve the desired goal in OA prevention and treatment.

Silencing of circ-NT5C2 retards the progression of IL-1β-induced osteoarthritis in an in vitro cell model by targeting the miR-142-5p/NAMPT axis

Osteoarthritis (OA) is a degenerative disease that occurs mostly in the elderly, and its specific pathogenesis is still unknown, but recent studies have found that circular RNA generally display aberrant expression in OA. Our study explored the expression characteristics and mechanism of action of circ-NT5C2 in OA. Circ-NT5C2, microRNA-142-5p (miR-142-5p), and nicotinamide phosphoribosyltransferase (NAMPT) mRNA levels were measured using RT-qPCR. Western blot was employed to assess the protein level of NAMPT and extracellular matrix (ECM) production-related markers. The viability, proliferation, apoptosis and inflammation were examined using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, 5-ethynyl-2'-deoxyuridine (EdU) assay, flow cytometry, and enzyme-linked immunosorbent assay, respectively. Relationship between miR-142-5p and circ-NT5C2 or NAMPT was demonstrated by dual-luciferase reporter system and RNA immunoprecipitation assay. We reported that circ-NT5C2 and NAMPT were greatly upregulated, and miR-142-5p level was constrained in OA tissues and in a cell model. Circ-NT5C2 silencing alleviated IL-1β-induced inhibitory effects on chondrocyte proliferation and ECM generation, meanwhile the promotional role of IL-1β on chondrocyte apoptosis and inflammation was also weakened. The targeting relationship of miR-142-5p with either circ-NT5C2 or NAMPT was confirmed. Knockdown of miR-142-5p reversed the suppressive effects of circ-NT5C2 silencing on the OA progression in vitro, and NAMPT overexpression also attenuated the effects of miR-142-5p upregulation in an OA cell model. Collectively, circ-NT5C2 accelerated the OA process by targeting the miR-142-5p/NAMPT axis. This study provides valuable information to find a better treatment for OA.

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.

A Novel Circular RNA CircRFX3 Serves as a Sponge for MicroRNA-587 in Promoting Glioblastoma Progression via Regulating PDIA3

An increasing number of studies have indicated that circular RNAs (circRNAs) participate in the progression of numerous tumors. However, the functions of circRNAs in glioblastoma (GBM) remain largely unknown. In this study, we focused on a novel circRNA (hsa_circRFX3_003) that was spliced from RFX3, which we named circRFX3. We confirmed that the expression of circRFX3 was substantially increased in GBM cell lines and clinical GBM tissues. The results of a series of overexpression and knockdown assays indicated that circRFX3 could boost the proliferation, invasion, and migration of GBM cells. By performing dual-luciferase reporter gene and RNA pull-down assays, we verified that circRFX3 could sponge microRNA-587 (miR-587) to exercise its function as a competing endogenous RNA (ceRNA) in the development of GBM. In addition, PDIA3 was proven to be a downstream target of miR-587 and to regulate the Wnt/β-catenin pathway. In conclusion, circRFX3 could act as a cancer-promoting circRNA to boost the development of GBM and regulate the miR-587/PDIA3/β-catenin axis. This study might provide a novel target for the treatment of GBM with molecular therapy.

Serum hsa_circ_0087776 as a new oncologic marker for the joint diagnosis of multiple myeloma

Multiple myeloma (MM) is a hematologic malignancy caused by abnormal proliferation of bone marrow plasma cells, which lacks diagnostic markers and has a general prognosis. At present, the understanding of its pathogenesis provides the basis for the combined diagnosis and new targeted therapy of the disease. In this study, quantitative real-time PCR was used to detect 136 MM patients and 74 healthy controls, and the clinical application value of hsa_circ_0087776 as a new tumor marker and combined diagnosis was evaluated. The results showed that the expression of hsa_circ_0087776 was significantly lower in serum of MM patients (P-value < 0.0001), and the expression was consistent in MM cells. In the analysis of clinicopathological parameters, it was found that there were significant statistical differences with MM stage and renal injury. In addition, it significantly increased the sensitivity with ALB, β₂-MG joint diagnosis, to provide a basis for diagnosis, improve the prognosis of the disease, improve the survival of patients and quality of life. These studies suggest that hsa_circ_0087776 can be used as a new oncology marker for the combined diagnosis of MM.

Impact statement: Various evidences have shown that the role of circRNA in the occurrence and development of diseases is potentially unknown and untapped. Therefore, it has a broad prospect to find circRNA specifically expressed in MM patients for combined diagnosis and targeted therapy of MM. However, MM lacks such specific tumor markers. Therefore, the discovery of new specific tumor markers for combined diagnosis is an important milestone in the development of medical history. In the research, we founded hsa_circ_0087776 can be used as a new oncology marker for combined diagnosis of MM.

CircSEC24A upregulates TGFBR2 expression to accelerate pancreatic cancer proliferation and migration via sponging to miR-606

Background

Circular RNA (circRNA), producing by special selective splicing, was widely expressed in the cytoplasm of eukaryotic cells as a newly non-coding RNAs. It played different roles in a variety of diseases including cancer and performed different functions. Nonetheless, reports on the specific function of circRNA in pancreatic cancer (PC) were still rarely so far. In particular, the role of circSEC24A in PC remains unclear.

Methods

Real-time fluorescent quantitative PCR was used to evaluate the expression level of circSEC24A in pancreatic cancer tissues and cell lines. Furthermore, we used some functional experiments, such as EDU and Transwell assays, to explore the effects of circSEC24A on the proliferation and invasiveness of pancreatic cancer. Finally, the corresponding relationship among circSEC24A, miR-606 and TGFBR2 was explored by dual luciferase reporter and other mechanism studies.

Results

The expression of circSEC24A in both pancreatic cancer tissues and cell lines was evidently up-regulated. Furthermore, knockdown of circSEC24A significantly inhibited the proliferative, migration and invasive capacity of pancreatic cancer cells, whereas miR-606 inhibitor obviously counteracted these effects. Further study confirmed that circSEC24A alleviated suppression on target TGFBR2 expression by directly sponging miR-606 and then influenced the tumorigenesis of pancreatic cancer.

Conclusions

These findings indicated that the progression of pancreatic cancer can be driven by circSEC24A influencing miR-606/TGFBR2 axis. Therefore, circSEC24A might be used as a critical biomarker influencing the early diagnosis and prognosis of pancreatic cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02392-y.

The Role and Clinical Potentials of Circular RNAs in Prostate Cancer

Globally, prostate cancer (PCa) is the second most commonly diagnosed cancer in men globally. Early diagnosis may help in promoting survival in the affected patients. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) which have been found to show extensive dysregulation in a handful of human diseases including cancers. Progressions in RNA identification techniques have provided a vast number of circRNAs exhibiting either up-regulation or down-regulation in PCa tissues compared to normal adjacent tissues. The mechanism of action is not clear for most of dysregulated circRNAs. Among them, function of a number of newly identified dysregulated circRNAs have been assessed in PCa cells. Increase in cell proliferation, migration, invasion, and metastasis have been reported for up-regulated circRNAs which suggest their role as oncogenes. On the other hand, down-regulated circRNAs have shown tumor suppressing actions in experimental studies. Furthermore, in a majority of studies, circRNAs have been found to sponge microRNAs (miRNAs), negatively regulating expression or activity of the downstream miRNAs. Additionally, they have been identified in interaction with regulatory proteins. This axis consequently regulates a signaling pathway, a tumor suppressor, or an oncogene. Easy, quick, and reliable detection of circRNAs in human body fluids also suggests their potentials as biomarker candidates for diagnosis and prediction of prognosis in PCa patients. In this review, we have discussed the role and potentials of a number of dysregulated circRNAs in PCa.