The role of circRNA derived from RUNX2 in the serum of osteoarthritis and its clinical value

Identification of osteoarthritis-characteristic genes and immunological micro-environment features through bioinformatics and machine learning-based approaches

BACKGROUND

Osteoarthritis (OA) is a multifaceted chronic joint disease characterized by complex mechanisms. It has a detrimental impact on the quality of life for individuals in the middle-aged and elderly population while also imposing a significant socioeconomic burden. At present, there remains a lack of comprehensive understanding regarding the pathophysiology of OA. The objective of this study was to examine the genes, functional pathways, and immune infiltration characteristics associated with the development and advancement of OA.

METHODS

The Gene Expression Omnibus (GEO) database was utilized to acquire gene expression profiles. The R software was employed to conduct the screening of differentially expressed genes (DEGs) and perform enrichment analysis on these genes. The OA-characteristic genes were identified using the Weighted Gene Co-expression Network Analysis (WGCNA) and the Lasso algorithm. In addition, the infiltration levels of immune cells in cartilage were assessed using single-sample gene set enrichment analysis (ssGSEA). Subsequently, a correlation analysis was conducted to examine the relationship between immune cells and the OA-characteristic genes.

RESULTS

A total of 80 DEGs were identified. As determined by functional enrichment, these DEGs were associated with chondrocyte metabolism, apoptosis, and inflammation. Three OA-characteristic genes were identified using WGCNA and the lasso algorithm, and their expression levels were then validated using the verification set. Finally, the analysis of immune cell infiltration revealed that T cells and B cells were primarily associated with OA. In addition, Tspan2, HtrA1 demonstrated a correlation with some of the infiltrating immune cells.

CONCLUSIONS

The findings of an extensive bioinformatics analysis revealed that OA is correlated with a variety of distinct genes, functional pathways, and processes involving immune cell infiltration. The present study has successfully identified characteristic genes and functional pathways that hold potential as biomarkers for guiding drug treatment and facilitating molecular-level research on OA.

CircRNA-mediated ceRNA mechanism in Osteoarthritis: special emphasis on circRNAs in exosomes and the crosstalk of circRNAs and RNA methylation

Osteoarthritis (OA) is an age-related joint disease with chronic inflammation, progressive articular cartilage destruction and subchondral bone sclerosis. CircRNAs (circRNAs) are a class of non-coding RNA with a circular structure that participate in a series of important pathophysiological processes of OA, especially its ceRNA mechanisms, and play an important role in OA. CircRNAs may be potential biomarkers for the diagnosis and prognosis of OA. Additionally, differentially expressed circRNAs were found in patients with OA, indicating that circRNAs are involved in the pathogenesis of OA. Experiments have shown that the intra-articular injection of modified circRNAs can effectively relieve OA. Exosomal circRNAs and methylated circRNAs also provide new ideas for the treatment of OA. Clarifying the important roles of circRNAs in OA will deepen people's understanding of the pathogenesis of OA. CircRNAs may be developed as new biomarkers or drug targets for the diagnosis of OA and provide new methods for the treatment of OA.

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.

Soluble biomarkers in osteoarthritis in 2022: year in review

OBJECTIVE

To review articles reporting on the development of soluble biomarkers in osteoarthritis (OA) over the past year.

DESIGN

Two literature searches were conducted using the PubMed database for articles published between April 1, 2021 and March 31, 2022. Two searches were done, one on soluble biomarkers and another on circulating non-coding RNAs in OA. Additional articles were hand-picked to highlight emerging biomarker trends in OA.

RESULTS

Of 348 publications retrieved, we included 20 articles with 3 that were hand-picked for the narrative synthesis. We review recent data on soluble biomarkers and circulating non-coding microRNAs in OA using the BIPED classification system. We highlight studies using proteomics to show that cartilage acidic protein 1 (CRTAC1) is a promising biomarker, helping diagnose and estimate severity in hand, hip, and knee OA. Subtle changes in the structure of glycosaminoglycans from the extracellular cartilage matrix were shown to discriminate OA from non-OA cartilage. C-reactive protein metabolite (CRPM) and collagen metabolites may help discriminate subsets of OA patients as well as disease progression. Additionally, physical activity may impact determination of biomarkers. We also report on circulating microRNAs, lncRNAs, and circRNAs in OA and their predictive accuracy in diagnosis and prognosis.

CONCLUSIONS

Biomarkers for routine use are still an unmet need in the OA clinical scenario. Emerging data and novel classes of biomarkers (i.e., non-coding RNAs) show promise. Although still requiring validation in multiple independent cohorts, the past year brought advances towards a ready-to-use, reproducible, cost-effective biomarker, namely CRTAC1, to better manage the OA patient.

The application of exosomes in the early diagnosis and treatment of osteoarthritis

With the increase in human lifespan and the aggravation of global aging, the incidence of osteoarthritis (OA) is increasing annually. To better manage and control the progression of OA, prompt diagnosis and treatment for early-stage OA are important. However, a sensitive diagnostic modality and therapy for early OA have not been well developed. The exosome is a class of extracellular vesicles containing bioactive substances, that can be delivered directly from original cells to neighboring cells to modulate cellular activities through intercellular communication. In recent years, exosomes have been considered important in the early diagnosis and treatment of OA. Synovial fluid exosome and its encapsulated substances, e.g., microRNA, lncRNA, and proteins, can not only distinguish OA stages but also prevent the progression of OA by directly targeting cartilage or indirectly modulating the immune microenvironment in the joints. In this mini-review, we include recent studies on the diagnostic and therapeutic modalities of exosomes and hope to provide a new direction for the early diagnosis and treatment of OA disease in the future.

Knockdown of Circ_0037658 Alleviates IL-1β-Induced Osteoarthritis Progression by Serving as a Sponge of miR-665 to Regulate ADAMTS5

Background: Osteoarthritis (OA) is a chronic musculoskeletal degeneration disease which brings great pain to patients and a tremendous burden on the world’s medical resources. Previous reports have indicated that circular RNAs (circRNAs) are involved in the pathogenesis of OA. The purpose of this study was to explore the role and mechanism of circ_0037658 in the OA cell model.

Methods: The content of interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α) was measured using enzyme-linked immunosorbent assay (ELISA). Cell proliferation ability and apoptosis were detected using Cell Counting Kit-8 (CCK-8), 5-ethynyl-2′-deoxyuridine (EDU), and flow cytometry assays. Western blot assay was used to measure the protein levels of Bcl-2-related X protein (Bax), cleaved-caspase-3, MMP13, Aggrecan, and ADAMTS5. The expression of circ_0037658, microRNA-665 (miR-665), and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) 5 was detected using real-time quantitative polymerase chain reaction (RT-qPCR). Dual-luciferase reporter assay and RNA Immunoprecipitation (RIP) assay were manipulated to analyze the relationships of circ_0037658, miR-665, and ADAMTS5.

Results: Human chondrocytes (CHON-001 cells) were treated with interleukin-1β (IL-1β) to establish an OA cell model. Circ_0037658 and ADAMTS5 levels were increased, and miR-665 was decreased in OA cartilage samples and IL-1β-treated chondrocyte cells. Moreover, circ_0037658 silencing promoted proliferation and impaired inflammation, apoptosis, and ECM degradation in IL-1β-treated CHON-001 cells. Mechanically, circ_0037658 acted as a sponge for miR-665 to regulate ADAMTS5 expression.

Conclusion: Circ_0037658 knockdown relieved IL-1β-triggered chondrocyte injury via regulating the miR-665/ADAMTS5 axis, promising an underlying therapeutic strategy for OA.

The Application of circRNA-016901 in Improving the Diagnostic Accuracy of Osteoarthritis

In clinical practice, osteoarthritis (OA) is frequently misdiagnosed as rheumatoid arthritis (RA) and osteonecrosis (ON), leading to wrong treatment and disease progression. Circular RNA- (circRNA-) 016901 affects the recovery of irradiation-induced injury in the bone, while its role in OA is unclear. This study is aimed at exploring the role of circRNA-016901 in improving the diagnostic accuracy of OA. The present study included patients with OA (n = 80), patients with RA (n = 80), patients with ON (n = 80), and healthy controls (HCs, n = 80) to collect plasma samples before and after treatment. RT-qPCR was performed to detect RNA accumulation of circRNA-016901 in plasma samples from all participants. The role of plasma expression of circRNA-016901 in predicting OA was studied with ROC curve analysis. Association between plasma expression of circRNA-016901 and patients' clinical features was analyzed with the chi-squared test. Compared to HCs, increased accumulation of circRNA-016901 was only observed in the OA group, but not in the RA and ON groups before treatment. OA patients were effectively separated from the RA, ON, and HC groups using plasma expression of circRNA-016901 before treatment as a biomarker. Plasma expression of circRNA-016901 was closely associated with OA patients' disease severity. After treatment, decreased plasma expression levels of circRNA-016901 were only observed in OA patients, while no alteration in plasma circRNA-016901 accumulation was observed in the RA and ON groups. In conclusion, circRNA-016901 is accumulated to high levels in OA and may be applied to improve the diagnostic accuracy of OA.

Circ_0005526 contributes to interleukin-1β-induced chondrocyte injury in osteoarthritis via upregulating transcription factor 4 by interacting with miR-142-5p

Circular RNAs (circRNAs) can regulate the progression of osteoarthritis (OA) via serving as competing endogenous RNAs (ceRNAs). This work was performed for functional research of circ_0005526 in Interleukin-1β (IL-1β)-induced OA injury. Circ_0005526, microRNA-142-5p (miR-142-5p) or transcription factor 4 (TCF4) expression was measured via reverse transcription-quantitative polymerase chain reaction assay. Cell analysis was performed by Cell Counting Kit-8 assay for cell viability, EdU assay for cell proliferation and flow cytometry for cell apoptosis. The protein level detection was conducted using western blot. Target analysis was carried out via dual-luciferase reporter assay and RNA pull-down assay. Circ_0005526 was upregulated in OA cartilage tissues and IL-1β-exposed chondrocyte cells. IL-1β inhibited cell viability and proliferation but enhanced cell apoptosis and inflammation, then these damages were attenuated after downregulation of circ_0005526. Circ_0005526 interacted with miR-142-5p, and circ_0005526 knockdown suppressed IL-1β-induced OA progression through upregulating miR-142-5p. TCF4 was regulated by circ_0005526 via targeting miR-142-5p. The function of circ_0005526 was also achieved by upregulation of TCF4. These results unraveled that circ_0005526 promoted IL-1β-induced chondrocyte injury in OA via suppressing miR-142-5p binding to TCF4.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

The role of circRNA derived from RUNX2 in the serum of osteoarthritis and its clinical value

Background

Circular RNA (circRNA) has been shown to affect the pathological process of osteoarthritis (OA) and is expected to become a potential marker for disease diagnosis. This study aimed to investigate the association between circRNA derived from the gene of runt‐related transcription factor 2 (RUNX2) and OA risk.

Methods

The expression profile of RUNX2‐derived circRNAs in serum of OA patients was detected. Then, the cytological localization of screened differential circRNAs was studied. Luciferase (LUC) reporter assay was used to identify the microRNA (miRNA) sponge capacity of the circRNAs. Bioinformatics analysis was used to construct the functional pathway of this circRNA‐miRNAs network. And then, the diagnostic value of RUNX2‐derived circRNAs in OA was evaluated.

Results

RUNX2‐derived hsa_circ_0005526 (circ_RUNX2) is significantly highly expressed in OA serum and mainly located in the cytoplasm within the cartilage cell by sponging multiple miRNAs (miR‐498, miR‐924, miR‐361‐3p, and miR‐665). Bioinformatics analysis showed ECM‐receptor interaction pathway ranked the most significant pathway of circ_RUNX2‐miRNAs regulatory network in KEGG database. The ROC curve showed that there may be good diagnostic value of serum circ_RUNX2 in OA.

Conclusion

RUNX2‐derived circ_RUNX2 may be involved in OA development via ECM‐receptor interaction pathways and may be used as potential clinical indicator of OA.