The Therapeutic Potential and Role of miRNA, lncRNA, and circRNA in Osteoarthritis

Circ_0104873 promotes osteoarthritis progression via miR-875-5p/NOTCH3/Notch signaling pathway

Osteoarthritis (OA) is the most common joint disease with high prevalence and incidence. Increasing reports has indicated that circular RNAs (circRNAs) are implicated in OA progression. Nevertheless, the roles and functions of most circRNAs in OA remain to be elucidated. In this study, we emphatically discussed circ-IQGAP1 (circ_0104873) in OA. Firstly, we discovered that circ_0104873 was dramatically overexpressed during osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Several functional assays demonstrated that circ_0104873 inhibition repressed BMSCs proliferation and osteogenic differentiation. Moreover, mechanism assays also revealed that circ_0104873 sponged microRNA-875-5p (miR-875-5p) to up-regulate notch receptor 3 (NOTCH3), thereby activating the Notch signaling pathway. Rescue assays disclosed that circ_0104873 contributed to the development of OA via targeting miR-875-5p/NOTCH3 axis. In conclusion, circ_0104873 promoted the progression of OA by miR-875-5p/NOTCH3/Notch signaling pathway, which might provide a promising target for OA treatment.

PiRNA hsa_piR_019914 Promoted Chondrocyte Anabolic Metabolism By Inhibiting LDHA-Dependent ROS Production

OBJECTIVES

Osteoarthritis (OA) is the most common joint disease. The occurrence and progression of OA are regulated by epigenetics. A large number of studies have shown the important regulatory role of noncoding RNAs in joint diseases. As the largest class of noncoding small RNAs, the importance of piRNAs in many diseases, especially cancer, has been increasingly recognized. However, few studies have explored the role of piRNAs in OA. Our study showed that hsa_piR_019914 decreased significantly in OA. This study aimed to demonstrate the role of hsa_piR_019914 as a potential biological target of OA in chondrocytes.

DESIGN

The GEO database and bioinformatics analysis were used for a series of screenings, and the OA model using human articular chondrocytes (C28/I2 cells), SW1353 cells under inflammatory factor stimulation was used to determine that hsa_piR_019914 was significantly downregulated in OA. Overexpression or inhibition of hsa_piR_019914 in C28/I2 cells was achieved by transfecting mimics or inhibitors. The effect of hsa_piR_019914 on the biological function of chondrocytes was verified by qPCR, flow cytometry, and colony formation assays in vitro. The target gene of hsa_piR_019914, lactate dehydrogenase A (LDHA), was screened by small RNA sequencing and quantitative polymerase chain reaction (qPCR), LDHA was knocked out in C28/I2 cells by the transfection of siRNA LDHA, and the relationship between hsa_piR_019914, LDHA, and reactive oxygen species (ROS) production was verified by flow cytometry.

RESULTS

The piRNA hsa-piR-019914 was significantly downregulated in osteoarthritis (OA). Hsa-piR-019914 reduced inflammation-mediated chondrocyte apoptosis and maintained cell proliferation and clone formation in vitro. Hsa-piR-019914 reduced the production of LDHA-dependent ROS through targeted regulation of LDHA expression, maintained chondrocyte-specific gene expression of ACAN and COL2, and inhibited the gene expression of MMP3 and MMP13.

CONCLUSIONS

Collectively, this study showed that hsa_piR_019914 was negatively correlated with the expression of LDHA, which mediates ROS production. Under the stimulation of inflammatory factors, overexpression of hsa_piR_019914 had a protective effect on chondrocytes in vitro, and the absence of hsa_piR_019914 exacerbated the negative effect of inflammation on chondrocytes. Studies on piRNAs provide new therapeutic interventions for OA.

Identification of Key lncRNAs, circRNAs, and mRNAs in Osteoarthritis via Bioinformatics Analysis

Osteoarthritis (OA) is a common degenerative joint disorder that adversely affects the quality of life of patients. Identification of novel diagnostic biomarkers is pivotal for the early detection and prevention of OA. Dataset GSE185059 was selected from Gene Expression Omnibus database to obtain differentially expressed lncRNAs (DE-lncRNAs), mRNAs (DE-mRNAs), and circRNAs (DE-circRNAs) between OA and normal samples. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses as well as protein-protein interaction (PPI) network construction of DE-mRNAs were conducted. Hub genes were identified from PPI networks and validated by RT-qPCR. starBase database was utilized for predicting miRNAs binding with hub genes, selected DE-lncRNAs and DE-circRNAs, respectively. The competing endogenous RNA (ceRNA) networks were constructed. A total of 818 DE-mRNAs, 191 DE-lncRNAs, and 2053 DE-circRNAs were identified. The DE-mRNAs were significantly enriched in several inflammation-related GO terms and KEGG pathways such as positive regulation of cell-cell adhesion, TNF-alpha signaling pathway and NF-kappa B signaling pathway. Thirteen hub genes were identified, which were CFTR, GART, SMAD2, NCK1, TJP1, UBE2D1, EFTUD2, PRKACB, IL10, SNRPG, CHD4, RPS24, and SRSF6. OA-related DE-lncRNA/circRNA-miRNA-hub gene networks were constructed. We identified 13 hub genes and constructed the ceRNA networks related to OA, providing a theoretical basis for further research.

LncRNA AC005165.1 Alleviates IL-1β-Induced Osteoarthritis via miR-199a-3p/TXNIP Axis

Osteoarthritis (OA) is a chronic musculoskeletal disease and often causes impaired joint mobility and disability. Long noncoding RNAs (lncRNAs) play pivotal roles in OA development. This study was done to explore the role and mechanism of the lncRNA AC005165.1 in the cell model of interleukin-1β (IL)-1β-treated chondrocytes. This study recruited 20 surgically treated OA patients and 12 age- and gender-matched controls. Real-time reverse transcription quantitative polymerase chain reaction was used to examine the expression levels of AC005165.1, miR-199a-3p, and thioredoxin-interacting protein (TXNIP) in articular cartilage of patients and IL-1β-treated human chondrocytes. Cell viability and apoptosis were evaluated by cell counting kit-8 and flow cytometry assays, respectively. The protein levels of inflammatory cytokines were assessed by western blotting. Enzyme-linked immunosorbent assay was conducted to detect the concentrations of the inflammatory cytokines in chondrocytes. Luciferase reporter assay and Pearson's correlation analysis were used for analyzing the interaction and the correlation among AC005165.1, miR-199a-3p, and TXNIP. AC005165.1 expression was downregulated in cartilage of OA patients and chondrocytes treated with IL-1β, compared to that in the control groups. AC005165.1 knockdown increased apoptosis and aggravated inflammatory response in IL-1β-treated chondrocytes. AC005165.1 interacted with miR-199a-3p, and TXNIP was targeted by miR-199a-3p. In rescue assay, miR-199a-3p knockdown and TXNIP overexpression significantly reduced apoptosis and mitigated inflammatory response in IL-1β-treated chondrocytes with AC005165.1 knockdown. AC005165.1 knockdown promoted apoptosis and inflammatory response in IL-1β-treated chondrocytes via the miR-199a-3p/TXNIP axis.

circFOXK2 promotes the progression of osteoarthritis by regulating the miR-4640-5p/NOTCH2 axis

OBJECTIVES

Osteoarthritis (OA) is the most common age-related chronic and disabling joint disease, frequently causing pain and disability in the adult population. Given that there are no proven disease-modifying drugs for OA, it is urgent to gain a deeper understanding of OA pathogenesis. This study intended to uncover the circFOXK2 regulation in OA.

METHODS

First, an in vitro OA cell model was constructed by treating murine chondrocytes with interleukin (IL)-1β. Then, a series of functional assays were conducted to evaluate the effect of circFOXK2 on OA progression in murine chondrocytes. Bioinformatics analysis and mechanism investigations were performed to investigate the competitive endogenous ribonucleic acid (RNA) network of circFOXK2 in OA.

RESULTS

circFOXK2 is overexpressed in IL-1β-treated chondrocyte. We confirmed the cyclic structure and cytoplasmic distribution of circFOXK2. Functionally, circFOXK2 promotes chondrocyte apoptosis and extracellular matrix degradation but inhibits chondrocyte proliferation. Mechanically, circFOXK2 competitively binds to microRNA-4640-5p (miR-4640-5p) to enhance NOTCH2 expression in OA, affecting OA progression. Besides, circFOXK2 could motivate the NOTCH pathway to accelerate OA progression.

CONCLUSIONS

The circFOXK2/miR-4640-5p/NOTCH2 axis stimulates the NOTCH pathway to promote the transcription of inflammatory cytokines (IL33, IL17F, and IL6), consequently facilitating OA progression in murine chondrocytes.

Regulatory function and mechanism research for m6A modification WTAP via SUCLG2-AS1- miR-17-5p-JAK1 axis in AML

Acute myeloid leukemia (AML), characterized by the abnormal accumulation of immature marrow cells in the bone marrow, is a malignant tumor of the blood system. Currently, the pathogenesis of AML is not yet clear. Therefore, this study aims to explore the mechanisms underlying the development of AML. Firstly, we identified a competing endogenous RNA (ceRNA) SUCLG2-AS1-miR-17-5p-JAK1 axis through bioinformatics analysis. Overexpression of SUCLG2-AS1 inhibits proliferation, migration and invasion and promotes apoptosis of AML cells. Secondly, luciferase reporter assay and RIP assay validated that SUCLG2-AS1 functioned as ceRNA for sponging miR-17-5p, further leading to JAK1 underexpression. Additionally, the results of MeRIP-qPCR and m6A RNA methylation quantification indicted that SUCLG2-AS1(lncRNA) had higher levels of m6A RNA methylation compared with controls, and SUCLG2-AS1 is regulated by m6A modification of WTAP in AML cells. WTAP, one of the main regulatory components of m6A methyltransferase complexes, proved to be highly expressed in AML and elevated WTAP is associated with poor prognosis of AML patients. Taken together, the WTAP-SUCLG2-AS1-miR-17-5p-JAK1 axis played essential roles in the process of AML development, which provided a novel therapeutic target for AML.

CircIRAK3 exerts negative feedback regulation on inflammation by binding to HNRNP U and destabilizing proinflammatory cytokine mRNA in osteoarthritis and chondrogenesis

Osteoarthritis (OA) is the most prevalent age-related and degenerative joint disease with limited treatment options. Previous studies have identified the therapeutic effects of mesenchymal stem cells (MSCs) therapy. Nevertheless, chronic inflammation impedes MSCs therapeutic effect. There have been reports suggesting that circular RNAs (circRNAs) are involved in OA and chondrogenesis. The combination of MSCs and circRNAs in therapies appears to be a promising option. In this study, we identified circIRAK3 as a significant regulator in cartilage degeneration and chondrogenesis through high-throughput sequencing analyses. We observed increased circIRAK3 in OA cartilage and during MSCs chondrogenesis. Knockdown of circIRAK3 resulted in excessive apoptosis, inhibited proliferation, and degradation of chondrocytes, along with the inhibition of MSCs chondrogenesis. Mechanistically, circIRAK3 bound to HNRNP U and competitively prevented its binding to IL-1β, TNFα, and IL6 mRNA, thereby promoting mRNA degradation. Notably, circIRAK3 expression in plasma increased with higher OARSI scores. Intra-articular injection of adeno-associated virus-circIRAK3 delayed cartilage degeneration and reduced inflammation in DMM mouse model. Our study highlights a compensatory regulation network of circIRAK3 in chondrocytes in response to inflammation. CircIRAK3 has the potential to serve as a new therapeutic target for OA. Furthermore, therapies targeting circIRAK3 combined with MSCs hold promise.

MicroRNA-34a-5p promotes the progression of osteoarthritis secondary to developmental dysplasia of the hip by restraining SESN2-induced autophagy

Osteoarthritis (OA), a late-stage complication of developmental dysplasia of the hip (DDH), is a key factor leading to further degeneration of joint function. Studies have shown that Sestrin2 (SESN2) is a positive regulator in protecting articular cartilage from degradation. However, the regulatory effects of SESN2 on DDH-OA and its upstream regulators remain obscure. Here, we first identified that the expression of SESN2 significantly decreased in the cartilage of DDH-OA samples, with an expression trend negatively correlated with OA severity. Using RNA sequencing, we identified that the upregulation of miR-34a-5p may be an important factor for the decrease in SESN2 expression. Further exploring the regulation mechanism of miR-34a-5p/SESN2 is of great significance for understanding the mechanism of DDH occurrence and development. Mechanistically, we showed that miR-34a-5p could significantly inhibit the expression of SESN2, thereby promoting the activity of the mTOR signaling pathway. We also found that miR-34a-5p significantly inhibited SESN2-induced autophagy, thereby suppressing the proliferation and migration of chondrocytes. We further validated that knocking down miR-34a-5p in vivo resulted in a significant increase in SESN2 expression and autophagy activity in DDH-OA cartilage. Our study suggests that miR-34a-5p is a negative regulator of DDH-OA, and may provide a new target for the prevention of DDH-OA.

Long non-coding RNA KCNQ10T1/miR-19a-3p/SMAD5 axis promotes osteogenic differentiation of mouse bone mesenchymal stem cells

BACKGROUND

Bone fracture is a common orthopedic disease that needs over 3 months to recover. Promoting the osteogenic differentiation of bone mesenchymal stem cells (BMSCs) is beneficial for fracture healing. Therefore, this research aimed to study the roles of long non-coding RNA (lncRNA) KCNQ10T1 in osteogenic differentiation of BMSCs.

METHODS

BMSCs were treated with osteogenic medium and assessed by CCK-8 and flow cytometry assays. Alkaline phosphatase (ALP) staining, alizarin red staining (ARS), as well as concentration of osteoblast markers were measured to evaluate osteogenic differentiation of BMSCs. Western blot was employed to detect proteins; while, qRT-PCR was for mRNA levels. Additionally, targeted relationships between KCNQ10T1 and miR-19a-3p, as well as miR-19a-3p and SMAD5 were verified by dual luciferase reporter gene assay along with RNA pull-down method.

RESULTS

Upregulation of KCNQ10T1 promoted the ALP staining and ARS intensity, increased the cell viability and decreased the apoptosis rate of BMSCs. Besides, KCNQ10T1 overexpression increased the ALP, OPG, OCN and OPN protein levels. KCNQ10T1 sponges miR-19a-3p, which targets Smad5. Upregulated miR-19a-3p reversed the overexpressed KCNQ10T1-induced effects, and depletion of SMAD5 reversed the miR-19a-3p inhibitor-induced effects on osteogenic medium-treated BMSCs.

CONCLUSIONS

Upregulation of KCNQ10T1 promoted osteogenic differentiation of BMSCs through miR-19a-3p/SMAD5 axis in bone fracture.

Biomaterial-Based Gene Delivery: Advanced Tools for Enhanced Cartilage Regeneration

Gene therapy has emerged as a promising and innovative approach in cartilage regeneration. Integrating biomaterials into gene therapy offers a unique opportunity to enhance gene delivery efficiency, optimize gene expression dynamics, modulate immune responses, and promote tissue regeneration. Despite the rapid progress in biomaterial-based gene delivery, there remains a deficiency of comprehensive discussions on recent advances and their specific application in cartilage regeneration. Therefore, this review aims to provide a thorough overview of various categories of biomaterials employed in gene delivery, including both viral and non-viral vectors, with discussing their distinct advantages and limitations. Furthermore, the diverse strategies employed in gene therapy are discussed and summarized, such as the utilization of growth factors, anti-inflammatory cytokines, and chondrogenic genes. Additionally, we highlights the significant challenges that hinder biomaterial-based gene delivery in cartilage regeneration, including immune response modulation, gene delivery efficiency, and the sustainability of long-term gene expression. By elucidating the functional properties of biomaterials-based gene therapy and their pivotal roles in cartilage regeneration, this review aims to enhance further advances in the design of sophisticated gene delivery systems for improved cartilage regeneration outcomes.

TMT quantitative proteomics reveals key proteins relevant to microRNA-1-mediated regulation in osteoarthritis

Osteoarthritis (OA) is the second-commonest arthritis, but pathogenic and regulatory mechanisms underlying OA remain incompletely understood. Here, we aimed to identify the mechanisms associated with microRNA-1 (miR-1) treatment of OA in rodent OA models using a proteomic approach. First, N = 18 Sprague Dawley (SD) rats underwent sham surgery (n = 6) or ACL transection (n = 12), followed at an interval of one week by randomization of the ACL transection group to intra-articular administration of either 50 µL placebo (control group) or miR-1 agomir, a mimic of endogenous miR-1 (experimental group). After allowing for eight weeks of remodeling, articular cartilage tissue was harvested and immunohistochemically stained for the presence of MMP-13. Second, N = 30 Col2a1-cre-ERT2 /GFPf1/fl -RFP-miR-1 transgenic mice were randomized to intra-articular administration of either placebo (control group, N = 15) or tamoxifen, an inducer of miR-1 expression (experimental group, N = 15), before undergoing surgical disruption of the medial meniscus (DMM) after an interval of five days. After allowing for eight weeks of remodeling, articular cartilage tissue was harvested and underwent differential proteomic analysis. Specifically, tandem mass tagging (TMT) quantitative proteomic analysis was employed to identify inter-group differentially-expressed proteins (DEP), and selected DEPs were validated using real-time quantitative polymerase chain reaction (RT-qPCR) technology. Immunohistochemically-detected MMP-13 expression was significantly lower in the experimental rat group, and proteomic analyses of mouse tissue homogenate demonstrated that of 3526 identified proteins, 345 were differentially expressed (relative up- and down-regulation) in the experimental group. Proteins Fn1, P4ha1, P4ha2, Acan, F2, Col3a1, Fga, Rps29, Rpl34, and Fgg were the *top ten most-connected proteins, implying that miR-1 may regulate an expression network involving these proteins. Of these ten proteins, three were selected for further validation by RT-qPCR: the transcript of Fn1, known to be associated with OA, exhibited relative upregulation in the experimental group, whereas the transcripts of P4ha1 and Acan exhibited relative downregulation. These proteins may thus represent key miR-1 targets during OA-regulatory mechanisms, and may provide additional insights regarding therapeutic mechanisms of miR-1 in context of OA.

Paeoniflorin shows chondroprotective effects under IL-1β stress by regulating circ-PREX1/miR-140-3p/WNT5B axis

BACKGROUND

Osteoarthritis (OA) is a chronic and degenerative bone and joint disease, and paeoniflorin shows anti-arthritis role in OA. This study planned to investigate the mechanism related to chondroprotective role of paeoniflorin in OA.

METHODS

Real-time quantitative PCR and western blotting were performed to measure expression levels of circ-PREX1, microRNA (miR)-140-3p, Wingless-type MMTV integration site family, member 5B (WNT5B), B cell lymphoma (Bcl)-2, and Bcl-2 Associated X Protein (Bax). MTT assay, EdU assay, flow cytometry and enzyme-linked immunosorbent assay evaluated cell viability, proliferation, apoptosis and inflammatory response, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation assay identified the relationship among circ-PREX1, miR-140-3p, and WNT5B.

RESULTS

IL-1β highly induced apoptosis rate, Bax expression and TNF-α product, accompanied with decreased cell viability, cell proliferation and IL-10 secretion, whereas these effects were partially reversed after paeoniflorin pretreatment. Expression of circ-PREX1 was upregulated and miR-140-3p was downregulated in cartilage tissues of patients with knee OA (KOA) and IL-1β-induced human chondrocytes (C28/I2). Circ-PREX1 overexpression and miR-140-3p silencing attenuated the suppressive effect of paeoniflorin in IL-1β-induced C28/I2 cells. Furthermore, miR-140-3p was negatively regulated by circ-PREX1. WNT5B was a downstream target of miR-140-3p and could be modulated by the circ-PREX1/miR-140-3p pathway in IL-1β-induced C28/I2 cells.

CONCLUSION

Paeoniflorin might protect human chondrocytes from IL-1β-induced inflammatory injury via circ-PREX1-miR-140-3p-WNT5B pathway, suggesting a potential preventative agent and a novel target for the treatment of KOA.

Heterogeneous graph framework for predicting the association between lncRNA and disease and case on uterine fibroid

Long non-coding RNAs (lncRNAs) play crucial regulatory roles in various cellular processes, including gene expression, chromatin remodeling, and protein localization. Dysregulation of lncRNAs has been linked to several diseases, making it essential to understand their functions in disease mechanisms and therapeutic strategies. However, traditional experimental methods for studying lncRNA function are time-consuming, expensive, and offer limited insights. In recent years, computational methods have emerged as valuable tools for predicting lncRNA functions and their associations with diseases. However, many existing methods focus on constructing separate networks for lncRNA and disease similarity, resulting in information loss and insufficient processing capacity for isolated nodes. To address this, we developed 'RGLD' by combining Random Walk with restarting (RWR), Graph Neural Network (GNN), and Graph Attention Networks (GAT) to predict lncRNA-disease associations in a heterogeneous network. RGLD achieved an impressive AUC of 0.88, outperforming other methods. It can also predict novel associations between lncRNAs and diseases. RGLD identified HOTAIR, MEG3, and PVT1 as lncRNAs associated with uterine fibroids. Biological experiments directly or indirectly verified the involvement of these three lncRNAs in uterine fibroids, validating the accuracy of RGLD's predictions. Furthermore, we extensively discussed the functions of the target genes regulated by these lncRNAs in uterine fibroids, providing evidence for their role in the development and progression of the disease.

Enhancement of the therapeutic efficacy of mesenchymal stem cell-derived exosomes in osteoarthritis

Osteoarthritis (OA), a common joint disorder with articular cartilage degradation as the main pathological change, is the major source of pain and disability worldwide. Despite current treatments, the overall treatment outcome is unsatisfactory. Thus, patients with severe OA often require joint replacement surgery. In recent years, mesenchymal stem cells (MSCs) have emerged as a promising therapeutic option for preclinical and clinical palliation of OA. MSC-derived exosomes (MSC-Exos) carrying bioactive molecules of the parental cells, including non-coding RNAs (ncRNAs) and proteins, have demonstrated a significant impact on the modulation of various physiological behaviors of cells in the joint cavity, making them promising candidates for cell-free therapy for OA. This review provides a comprehensive overview of the biosynthesis and composition of MSC-Exos and their mechanisms of action in OA. We also discussed the potential of MSC-Exos as a therapeutic tool for modulating intercellular communication in OA. Additionally, we explored bioengineering approaches to enhance MSC-Exos' therapeutic potential, which may help to overcome challenges and achieve clinically meaningful OA therapies.

Senescence-responsive miR-33-5p promotes chondrocyte senescence and osteoarthritis progression by targeting SIRT6

Osteoarthritis (OA) is a prevalent disease among elderly individuals that is caused by cartilage degeneration. Chondrocyte senescence involved in the development of OA, and antisenescence therapies have been proposed for OA treatment. In our study, we identified the role of a microRNA, miR-33-5p, in promoting chondrocyte senescence and OA progression. miR-33-5p expression was upregulated under senescence conditions. miR-33-5p-mimic transfection can induce cellular senescence, while transfection of a miR-33-5p-inhibitor in chondrocytes alleviated senescence induced by IL-1β. Moreover, SIRT6 expression was downregulated under IL-1β treatment, and could be restored by miR-33-5p-inhibitor transfection. Luciferase assays revealed that miR-33-5p targeted the SIRT6 mRNA 3' UTR. In addition, SIRT6 mRNA expression showed negative correlations with senescence and OA degree in human cartilage. Bioinformatic analysis also confirmed the pro-senescence effect of miR-33-5p. Furthermore, periodic intraarticular injection of agomiR-33-5p induced cartilage loss and OA-like cartilage changes. To conclude, we revealed the pro-senescence and cartilage-destructive effect of miR-33-5p, whose expression was elevated under various senescence conditions, and showed that SIRT6 was one of its targets. Therefore, miR-33-5p is a potential therapeutic target for treating OA.

The Protective Effect of Selenium Nanoparticles in Osteoarthritis: In vitro and in vivo Studies

Introduction

Osteoarthritis (OA) is a common chronic joint disease characterized by articular cartilage degeneration. OA usually manifests as joint pain, limited mobility, and joint effusion. Currently, the primary OA treatment is non-steroidal anti-inflammatory drugs (NSAIDs). Although they can alleviate the disease's clinical symptoms and signs, the drugs have some side effects. Selenium nanoparticles (SeNPs) may be an alternative to relieve OA symptoms.

Materials and Results

We confirmed the anti-inflammatory effect of selenium nanoparticles (SeNPs) in vitro and in vivo experiments for OA disease in this study. In vitro experiments, we found that SeNPs could significantly reduce the expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), the major inflammatory factors, and had significant anti-inflammatory and anti-arthritic effects. SeNPs can inhibit reactive oxygen species (ROS) production and increased glutathione peroxidase (GPx) activity in interleukin-1beta (IL-1β)-stimulated cells. Additionally, SeNPs down-regulated matrix metalloproteinase-13 (MMP-13) and thrombospondin motifs 5 (ADAMTS-5) expressions, while up-regulated type II collagen (COL-2) and aggrecan (ACAN) expressions stimulated by IL-1β. The findings also indicated that SeNPs may exert their effects through suppressing the NF-κB p65 and p38/MAPK pathways. In vivo experiments, the prevention of OA development brought on by SeNPs was demonstrated using a DMM model.

Discussion

Our results suggest that SeNPs may be a potential anti-inflammatory agent for treating OA.

Analysis of the regulatory role of miR-34a-5p/PLCD3 in the progression of osteoarthritis

Osteoarthritis is a heterogeneous disease with a complex etiology. However, there is no effective treatment strategy at present. The purpose of this study was to explore the miRNA‒mRNA regulatory network and molecular mechanism that regulate the progression of osteoarthritis. In this article, we downloaded datasets (GSE55457, GSE82107, GSE143514 and GSE55235) from Gene Expression Omnibus (GEO) to screen differentially expressed mRNAs in osteoarthritis. Then, through weighted gene coexpression network (WGCNA), functional enrichment, protein‒protein interaction (PPI) network, miRNA‒mRNA coexpression network, ROC curve, and immune infiltration analyses and qPCR, the mRNA PLCD3, which was highly expressed in osteoarthritis and had clinical predictive value, was screened. We found that PLCD3 directly targets miR-34a-5p through DIANA and dual-luciferase experiments. The expression levels of PLCD3 and miR-34a-5p were negatively correlated. In addition, CCK-8 and wound healing assays showed that the miR-34a-5p mimic inhibited hFLS-OA cell proliferation and promoted hFLS-OA cell migration. PLCD3 overexpression showed the opposite trend. Western blotting further found that overexpression of miR-34a-5p reduced the protein expression levels of p-PI3K and p-AKT, while overexpression of PLCD3 showed the opposite trend. In addition, combined with the effect of the PI3K/AKT pathway inhibitor BIO (IC50 = 5.95 μM), the results showed that overexpression of miR-34a-5p increased the inhibitory effects of BIO on p-PI3K and p-AKT protein expression, while overexpression of PLCD3 significantly reversed these inhibitory effects. Overall, the miR-34a-5p/PLCD3 axis may mediate the PI3K/AKT pathway in regulating cartilage homeostasis in synovial osteoarthritis. These data indicate that miR-34a-5p/PLCD3 may be a new prognostic factor in the pathology of synovial osteoarthritis.

LncRNA AC006064.4-201 serves as a novel molecular marker in alleviating cartilage senescence and protecting against osteoarthritis by destabilizing CDKN1B mRNA via interacting with PTBP1

BACKGROUND

Osteoarthritis (OA) is the most prevalent age-related disease in the world. Chondrocytes undergo an age-dependent decline in their proliferation and synthetic capacity, which is the main cause of OA development. However, the intrinsic mechanism of chondrocyte senescence is still unclear. This study aimed to investigate the role of a novel long non-coding RNA (lncRNA), AC006064.4-201 in the regulation of chondrocyte senescence and OA progression and to elucidate the underlying molecular mechanisms.

METHODS

The function of AC006064.4-201 in chondrocytes was assessed using western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), immunofluorescence (IF) and β-galactosidase staining. The interaction between AC006064.4-201 and polypyrimidine tract-binding protein 1 (PTBP1), as well as cyclin-dependent kinase inhibitor 1B (CDKN1B), was evaluated using RPD-MS, fluorescence in situ hybridization (FISH), RNA immunoprecipitation (RIP) and RNA pull-down assays. Mice models were used to investigate the role of AC006064.4-201 in post-traumatic and age-related OA in vivo.

RESULTS

Our research revealed that AC006064.4-201 was downregulated in senescent and degenerated human cartilage, which could alleviate senescence and regulate metabolism in chondrocytes. Mechanically, AC006064.4-201 directly interacts with PTBP1 and blocks the binding between PTBP1 and CDKN1B mRNA, thereby destabilizing CDKN1B mRNA and decreasing the translation of CDKN1B. The in vivo experiments were consistent with the results of the in vitro experiments.

CONCLUSIONS

The AC006064.4-201/PTBP1/CDKN1B axis plays an important role in OA development and provides new molecular markers for the early diagnosis and treatment of OA in the future. Schematic diagram of AC006064.4-201 mechanism. A schematic diagram of the mechanism underlying the effect of AC006064.4-201.

Circ_0108942 Regulates the Progression of Breast Cancer by Regulating the MiR-1178-3p/TMED3 Axis

BACKGROUND

Breast cancer (BC) has posed a fatal threat to women's lives and the search for new methods of diagnosis and treatment is an important way to break the bottleneck of high mortality in BC. Circular RNAs (circRNAs) have been confirmed to be aberrantly expressed in several types of cancers, and this study is intended to elucidate the role and mechanism of circ_0108942 in BC.

MATERIALS AND METHODS

The levels of circ_0108942, microRNA-1178-3p (miR-1178-3p), and transmembrane p24 trafficking protein 3 (TMED3) were measured using real-time quantitative polymerase chain reaction (RT-qPCR) or western blot. Meanwhile, the cell proliferation, migration, invasion, angiopoiesis, and apoptosis were analyzed using 5-ethynyl-2'-deoxyuridine (EdU), transwell, tubule formation, and flow cytometry assays. Protein levels were determined by western blot. In addition, we used dual-luciferase reporter and RNA pull-down assays to identify the interplay between miR-1178-3p and circ_0108942 or TMED3. Lastly, the impact of circ_0108942 on the growth of BC tumors in vivo was analyzed by xenograft models.

RESULTS

Circ_0108942 and TMED3 were notably upregulated in BC, and the miR-1178-3p was downregulated. Functionally, silencing circ_0108942 suppressed cell proliferation, migration, invasion and promoted apoptosis in BC cells. In mechanism, circ_0108942 regulated TMED3 expression by sponging miR-1178-3p. Meanwhile, circ_0108942 knockdown also greatly constrained tumor growth in vivo.

CONCLUSION

Circ_0108942 boosted BC progression by regulating miR-1178-3p and thus upregulating TMED3.

Circular RNA SLTM as a miR-421-competing endogenous RNA to mediate HMGB2 expression stimulates apoptosis and inflammation in arthritic chondrocytes

Osteoarthritis (OA) is the most common age-related joint disease characterized by chronic inflammation, progressive articular cartilage destruction, and subchondral sclerosis. Accumulating evidence suggests that circular RNAs (circRNAs) play key roles in OA, but the function of circSLTM in OA remains greatly unknown. Therefore, this study focused on interleukin-1β (IL-1β)-treated primary human chondrocytes as well as a rat model to investigate the expression pattern and functional role of circSLTM in OA in vitro and in vivo. CircSLTM and high mobility group protein B2 (HMGB2) were upregulated in IL-1β-induced chondrocytes, whereas miR-421 was downregulated. Knockdown of circSLTM or overexpression of miR-421 ameliorated IL-1β-induced chondrocyte apoptosis and inflammation. The regulatory relationship between circSLTM and miR-421, as well as that between miR-421 and HMGB2, was predicted by bioinformatics and then verified by the RNA immunoprecipitation experiment and dual-luciferase reporter gene assay. Furthermore, silencing of circSLTM increased cartilage destruction and decreased cartilage tissue apoptosis rate and inflammation in a rat model of OA. Taken together, our findings demonstrate the fundamental role of circSLTM in OA progression and provide a potential molecular target for OA therapy.

Mechanism of immune infiltration in synovial tissue of osteoarthritis: a gene expression-based study

BACKGROUND

Osteoarthritis is a chronic degenerative joint disease, and increasing evidences suggest that the pathogenic mechanism involves immune system and inflammation.

AIMS

The aim of current study was to uncover hub genes linked to immune infiltration in osteoarthritis synovial tissue using comprehensive bioinformatics analysis and experimental confirmation.

METHODS

Multiple microarray datasets (GSE55457, GSE55235, GSE12021 and GSE1919) for osteoarthritis in Gene Expression Omnibus database were downloaded for analysis. Differentially expressed genes (DEGs) were identified using Limma package in R software, and immune infiltration was evaluated by CIBERSORT algorithm. Then weighted gene co-expression network analysis (WGCNA) was performed to uncover immune infiltration-associated gene modules. Protein-protein interaction (PPI) network was constructed to select the hub genes, and the tissue distribution of these genes was analyzed using BioGPS database. Finally, the expression pattern of these genes was confirmed by RT-qPCR using clinical samples.

RESULTS

Totally 181 DEGs between osteoarthritis and normal control were screened. Macrophages, mast cells, memory CD4 T cells and B cells accounted for the majority of immune cell composition in synovial tissue. Osteoarthritis synovial showed high abundance of infiltrating resting mast cells, B cells memory and plasma cells. WGCNA screened 93 DEGs related to osteoarthritis immune infiltration. These genes were involved in TNF signaling pathway, IL-17 signaling pathway, response to steroid hormone, glucocorticoid and corticosteroid. Ten hub genes including MYC, JUN, DUSP1, NFKBIA, VEGFA, ATF3, IL-6, PTGS2, IL1B and SOCS3 were selected by using PPI network. Among them, four genes (MYC, JUN, DUSP1 and NFKBIA) specifically expressed in immune system were identified and clinical samples revealed consistent change of these four genes in synovial tissue retrieved from patients with osteoarthritis.

CONCLUSION

A 4-gene-based diagnostic model was developed, which had well predictive performance in osteoarthritis. MYC, JUN, DUSP1 and NFKBIA might be biomarkers and potential therapeutic targets in osteoarthritis.

Research progress on the role and mechanism of miR-671 in bone metabolism and bone-related diseases

Bone metabolism consists of bone formation and resorption and maintains a dynamic balance in vivo. When bone homeostasis is broken, it can manifest as osteoarthritis (OA), rheumatoid arthritis (RA), osteosarcoma (OS), etc. MiR-671, an important class of non-coding nucleotide sequences in vivo, is regulated by lncRNA and regulates bone metabolism balance by regulating downstream target proteins and activating various signaling pathways. Based on the structure and primary function of miR-671, this paper summarizes the effect and mechanism of miR-671 in bone-related inflammation and cancer diseases, and prospects the application possibility of miR-671, providing reference information for targeted therapy of bone-related disorders.

LncRNA RNA XIST binding to GATA1 contributes to rheumatoid arthritis through its effects on proliferation of synovial fibroblasts and angiogenesis via regulation of CCN6

This study explored the role of the long non-coding RNA (lncRNA) XIST (X-inactive specific transcript) as a driver of RA pathogenesis, with a particular focus on the ability of this lncRNA to interact with GATA1 and CCN6. The GSE83147and GSE181614 datasets were downloaded for analysis. XIST and CCN6 expression were assessed in synovial fibroblasts (SFs) and in both normal cartilage samples and those from RA patients, with the relationship between XIST and CCN6 additionally being examined. XIST and CCN6 were respectively knocked down or overexpressed in SFs to establish their regulatory roles in these cells in the context of RA. Further studies of the regulatory interplay between XIST, GATA1, and CCN6 were then performed through RNA immunoprecipitation, RNA pull-down, gain-of-function, loss-of-function, and luciferase reporter assays. In addition, RA model rats were established and used to measure the production of TNF-α, IL-6, and IL-8 and to subject tissues from these animals to histopathological examination. RA patient synovial tissues and SFs exhibited XIST and CCN6 upregulation. The knockdown of XIST suppressed SF migratory, proliferative, invasive, and angiogenic activity, while CCN6 knockdown partially reversed the ability of XIST to influence these phenotypic outcomes in vitro and in vivo. XIST bound to GATA1 within SFs, thus promoting enhanced CCN6 transcription. Knocking down XIST alleviated RA-related pathological damage, synovial injury, and inflammatory response induction in rats. The binding of XIST to GATA1 leads to CCN6 upregulation, driving RA pathogenesis by altering SF proliferation and angiogenic activity, suggesting that this pathway may represent a viable target for therapeutic intervention.

Long Non-coding RNA Therapeutics: Recent Advances and Challenges

The discovery of the roles of RNA other than just as a messenger, such as a ribozyme, and regulatory RNAs, such as microRNA and long noncoding RNAs, is fascinating. RNA is now recognized as an important regulator involved in practically every biological process. Research in the field of non-coding RNAs, specifically microRNAs (miRNAs) and long non-coding RNAs (LncRNAs) have developed immensely over the years. Recent studies identified diverse RNAs, including non-coding RNAs such as LncRNA and their various modes of action in the cells. These RNAs are anticipated to be key targets for the treatment of various diseases since they control a broad array of biological pathways. LncRNA-targeted drug platform delivers the pharmaceutical industry a myriad of opportunities and has the potential to modulate diseases at the genetic level while also overcoming the limitations of inconsistent proteins. This article focuses on the recent advancement as well as the major challenges in the field and describes the various RNA-based therapeutics that alter the quality of healthcare for many diseases and bring personalized medicines to fruition. The article also summarizes RNA-based therapeutics that are undergoing testing in clinical trials or have been granted FDA approval.

circRNA-MSR regulates the expression of FBXO21 to inhibit chondrocyte autophagy by targeting miR-761 in osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease and is the most prevalent and disabling form of arthritis worldwide. Autophagy plays a vital role in OA. This study aimed to explore whether covalently closed circular RNA MSR (circRNA-MSR) could affect the F-box Only Protein 21 (FBXO21) expression by targeting microRNA-761 (miR-761), thereby affecting the autophagy in OA chondrocytes. Clinical OA tissues were collected, and circRNA-MSR, miR-761, and FBXO21 expressions were detected via quantitative real-time polymerase chain reaction (qRT-PCR). An in vitro OA model was constructed by treating C28/I2 cells with LPS and treating them with overexpression or knockdown vector of circRNA-MSR, miR-761, and FBXO21, and autophagy inhibitor 3-MA. Fluorescence in situ hybridization (FISH) determined the location of circRNA-MSR and miR-761. Dual-luciferase assay assessed circRNA-MSR and miR-761, along with the bindings of miR-761 and FBXO21. Cell viability was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. LC3 II/I, p62 and beclin 1 expressions were detected via the western blot. circRNA-MSR and FBXO21 levels were elevated in OA, but miR-761 level was inhibited. Suppressing circRNA-MSR promoted the autophagy of LPS-treated cells. circRNA-MSR could bind to miR-761 and inhibit its expression. MiR-761 inhibition reversed the promoted autophagy caused by circRNA-MSR knockdown in LPS-treated C28/I2 cells. Moreover, miR-761 could target FBXO21 and inhibit its expression. FBXO21 overexpression reversed the increased autophagy caused by miR-761 overexpression in LPS-treated C28/I2 cells. circRNA-MSR could affect FBXO21 level via targeting miR-761, thereby repressing autophagy in OA chondrocytes, providing a new target and strategy for OA treatment.

MiR-19b-3p Attenuates Chondrocytes Injury by Inhibiting MAPK/NF-Κb Axis via Targeting SOCS1

In this study, miR-19b-3p was downregulated in osteoarthritic cartilage tissues and IL-1β-stimulated primary chondrocytes, and miR-19b-3p overexpression reversed the inhibitory effect of IL-1β on cell viability, the promotion effects of apoptosis, inflammatory factor secretion and extracellular matrix degradation, whereas the opposite effect was observed with miR-19b-3p inhibitor. Moreover, SOCS1 is a target gene of miR-19b-3p. Furthermore, SOCS1 overexpression enhanced cell injury compared with IL-1β alone treatment, whereas knockdown of SOCS1 restored cell damage caused by IL-1β. Further studies revealed that miR-19b-3p promoted chondrocyte injury repair by suppressing SOCS1 expression, and we found that was mediated by blocking the MAPK/NF-κB axis. Taken together, our findings may provide a new therapeutic strategy for osteoarthritis.

The therapeutic effect and mechanism of melatonin on osteoarthritis: From the perspective of non-coding RNAs

Osteoarthritis (OA) is a slowly progressing and irreversible joint disease. The existing non-surgical treatment can only delay its progress, making the early treatment of OA a research hotspot in recent years. Melatonin, a neurohormone mainly secreted by the pineal gland, has a variety of regulatory functions in different organs, and numerous studies have confirmed its therapeutic effect on OA. Non-coding RNAs (ncRNAs) constitute the majority of the human transcribed genome. Various ncRNAs show significant differentially expressed between healthy people and OA patients. ncRNAs play diverse roles in many cellular processes and have been implicated in many pathological conditions, especially OA. Interestingly, the latest research found a close interaction between ncRNAs and melatonin in regulating the pathogenesis of OA. This review discusses the current understanding of the melatonin-mediated modulation of ncRNAs in the early stage of OA. We also delineate the potential link between rhythm genes and ncRNAs in chondrocytes. This review will serve as a solid foundation to formulate ideas for future mechanistic studies on the therapeutic potential of melatonin and ncRNAs in OA and better explore the emerging functions of the ncRNAs.

Long Noncoding RNA P53 Upregulated Regulator of P53 Levels Promotes Osteogenic Differentiation in Osteoporosis Progression Through Sponging miR-135a-5p

This study aimed to explore the expression of long noncoding RNA p53 upregulated regulator of P53 levels (lncRNA PURPL) and microRNA (miR)-135a-5p in osteoporosis and their role in osteogenic differentiation. The relationship between lncRNA PURPL and miR-135a-5p was confirmed by Star-Base and luciferase reporter assay. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) assay was used to detect lncRNA PURPL and miR-135a-5p expression. RT-qPCR and western blot analysis were used to measure osteogenic markers expression. Alkaline phosphatase (ALP) activity was also determined. Results indicated that lncRNA PURPL binds to miR-135a-5p. lncRNA PURPL expression was decreased and miR-135a-5p expression was increased in patients with osteoporosis. In the process of osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs), the expression levels of osteoblast markers including RUNX family transcription factor 2 (Runx2), ALP and Osterix, and ALP activity were significantly increased. Besides, lncRNA PURPL was improved, while miR-135a-5p was down-regulated during the osteogenic differentiation of hBMSCs. Moreover, lncRNA PURPL-siRNA significantly decreased the expression of ALP, Runx2 and Osterix, and reduced ALP activity in hBMSCs subjected to osteogenic induction, while all of these effects were reversed by miR-135a-5p inhibitor. In conclusion, lncRNA PURPL/miR-135a-5p may be a new axis for osteoporosis treatment.

LncRNA TM1-3P Regulates Proliferation, Apoptosis and Inflammation of Fibroblasts in Osteoarthritis through miR-144-3p/ONECUT2 Axis

OBJECTIVE

This study explores LncRNA TM1-3P effects on the proliferation, apoptosis, and inflammatory response of fibroblasts in osteoarthritis (OA) and its underlying mechanism.

METHODS

Bioinformatics was performed to analyze OA disease-related genes, miRNA profiles, and function. The targeted regulation of LncRNA TM1-3P and miR-144-3p, ONECUT2 and miR-144-3p were analyzed by dual luciferase reporter gene assay, RNA Binding Protein Immunoprecipitation (RIP), and RNA pull down. Histopathological morphology of the knee joint was observed by hematoxylin-eosin (HE) and Annona Red O/Fast Green. The expressions of mRNAs and proteins were detected by RT-qPCR, Western blot, and immunohistochemistry. Unpaired T test was used between groups, and the one-way analysis of variance of repeated measurement data was applied for multi-group comparison, following Tukey's post-test.

RESULTS

ONECUT2 and Smurf2 genes were significantly elevated in the osteoarthritis group compared with the normal group (P < 0.001, P < 0.001). Expressions of ONECUT2 and LncRNA TM1-3P were increased, and expression of miR-144-3p was decreased in interleukin (IL)-1β-induced human fibroblast synovial cells (hFSCs) (mRNA: 1.06 ± 0.24 vs. 3.29 ± 0.73, proteins: 0.22 ± 0.03 vs. 0.46 ± 0.22, 1.23 ± 0.22 vs. 3.76 ± 0.73, 1.06 ± 0.25 vs. 0.37 ± 0.13, P < 0.01, P < 0.001, P < 0.01, P < 0.05). Overexpression of miR-144-3p down-regulated the ONECUT2 expression, reduced cell proliferation, promoted apoptosis in hFSCs induced by IL-1β (mRNA: 0.89 ± 0.14 vs. 0.15 ± 0.01, P < 0.05; proteins: 0.46 ± 0.01 vs. 0.23 ± 0.01, P < 0.001; CCK8: 1.88 ± 0.07 vs. 1.65 ± 0.07; P < 0.05; EDU: 55.82 ± 1.44 vs 40.57 ± 2.24, P < 0.05; apoptosis: 10.57 ± 0.79 vs 16.36 ± 0.35, P < 0.0001). Overexpression of LncRNA TM1-3P up-regulated the expression of ONECUT2, promoted cell proliferation, and inhibited apoptosis (mRNA: 0.9 ± 0.09 vs 1.94 ± 0.12, P < 0.05; proteins: 0.61 ± 0.05 vs 0.76 ± 0.03, P > 0.05; CCK8: 2.07 ± 0.05 vs 2.47 ± 0.06; P < 0.01; EDU: 52.67 ± 1.17 vs 60.06 ± 3.24, P < 0.05; apoptosis: 10.57 ± 0.79 vs 16.36 ± 0.35, P < 0.001), which were reversed by the overexpression of miR-144-3p treatment (mRNA: 1.82 ± 0.07 vs 0.31 ± 0.07, P < 0.0001; proteins: 0.74 ± 0.02 vs 0.35 ± 0.01, P < 0.01; CCK8: 2.41 ± 0.01 vs 1.67 ± 0.02; P < 0.0001; EDU: 66.85 ± 2.86 vs 44.68 ± 1.97, P < 0.0001; apoptosis: 7.19 ± 0.19 vs 13.36 ± 0.53, P < 0.0001). Silencing LncRNA TM1-3P attenuated the injury of knee joint tissue, down-regulated the expression of ONECUT2, Smurf2, IL-1β, IL-6, TNF-α, and improved the expression of Rap1 in rats (0.71 ± 0.04 vs 0.48 ± 0.02, 0.68 ± 0.06 vs 0.36 ± 0.02, 0.74 ± 0.03 vs 0.49 ± 0.04, 0.78 ± 0.01 vs 0.54 ± 0.03, 0.68 ± 0.02 vs 0.4 ± 0.04, 0.24 ± 0.01 vs 0.4 ± 0.03, P < 0.05, P < 0.05, P < 0.05, P < 0.01, P < 0.01, P < 0.05).

CONCLUSION

LncRNA TM1-3P improved inflammation and damage of knee joints in OA rats through miR-144-3p/ONECUT2 axis, providing a new theoretical basis for gene therapy of OA.

Current understanding of MSC-derived exosomes in the management of knee osteoarthritis

Mesenchymal stem cell-derived exosomes (MSC-Exos) have been utilized as medicinal agents or as delivery vehicles in cartilage injuries and cartilage-based diseases. Given the ongoing emergence of evidence on the effector mechanisms and methods of the utility of the MSC-Exos in knee osteoarthritis, a comprehensive review of the current evidence is the need of the hour. Hence, in this article, we review the current understanding of the role of MSC-Exos in the management of knee osteoarthritis in view of their classification, characterization, biogenesis, mechanism of action, pathways involved in their therapeutic action, in-vitro evidence on cartilage regeneration, in-vivo evidence in OA knee models and recent advances in using MSC-Exos to better streamline future research from bench to bedside for OA knee.

CircPRKCH modulates extracellular matrix formation and metabolism by regulating the miR-145/HGF axis in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a chronic degenerative joint disease. Extracellular matrix (ECM) degradation is essential for OA progression. Previous studies have shown that circular RNAs (circRNAs) are involved in the pathological process of OA. CircPRKCH has been shown to be upregulated in OA chondrocytes. The present study was aimed to explore the roles of circPRKCH in vivo and in vitro models of OA and its underlying molecular mechanisms.

METHODS

IL-1β-induced chondrocytes and mice injected with monosodium iodoacetate were used as OA models in vitro and in vivo, respectively. RT-qPCR was performed to measure the expression of circPRKCH, miR-145, and HGF in cartilage tissues and chondrocytes. The interaction between miR-145 and circPRKCH or HGF was verified by a dual-luciferase reporter assay. Chondrocyte apoptosis, viability, and ECM-related proteins were examined by flow cytometry, MTT assay, and Western blotting, respectively. Histopathological changes were detected by HE and Safranin O-fast green staining.

RESULTS

The expression of circPRKCH and HGF was increased in OA cartilage tissues and IL-1β-treated chondrocytes, while miR-145 expression was decreased. IL-1β induced chondrocyte apoptosis and ECM degradation in chondrocytes. Moreover, circPRKCH promoted HGF expression and activated HGF/c-MET by directly binding to miR-145. miR-145 knockdown or HGF overexpression significantly reversed circPRKCH knockdown-mediated inhibition of apoptosis and ECM degradation in IL-1β-induced chondrocytes. Besides, miR-145 overexpression alleviated IL-1β-induced chondrocyte apoptosis and ECM degradation by inhibiting HGF/c-MET. Finally, circPRKCH knockdown reduced ECM degradation by regulating the miR-145/HGF axis in an experimental OA model in mice.

CONCLUSION

Our study demonstrated that circPRKCH promoted chondrocyte apoptosis and ECM degradation via the miR-145/HGF axis in OA, which may provide a novel target for OA treatment.

Advances of circRNA-miRNA-mRNA regulatory network in cerebral ischemia/reperfusion injury

Ischemic stroke (IS) is the most common type of stroke, and its pathophysiological process is more complex. In recent years, the key regulatory roles of non-coding RNA (miRNA, circRNA) and mRNA in the development of IS have attracted more attention. In the process of cerebral ischemia/reperfusion injury, circRNA can regulate nerves, blood vessels and immune system through miRNA/mRNA axis, so as to affect the neurovascular unit of IS. The combination of these noncoding RNAs and mRNAs can be used as non-invasive biomarkers and therapeutic tools for IS diagnosis, prognosis and brain injury. Therefore, it is very important to study the potential molecular mechanism, activation pathway and treatment methods of circRNA/miRNA/mRNA network in IS. This review will focus on the latest progress of circRNA/miRNA/mRNA regulatory network, we have also included some circRNAs, which does not mediate through a miRNA, so we also include circRNA -mRNA network. And explore the application prospect of these RNAs as potential therapeutic targets in the prevention and treatment of IS.

PCB153 suppressed autophagy via PI3K/Akt/mTOR and RICTOR/Akt/mTOR signaling by the upregulation of microRNA-155 in rat primary chondrocytes

Polychlorinated biphenyls (PCBs) are a typical type of persistent organic pollutant. PCB exposure is associated to the occurrence and development of osteoarthritis (OA); however, the involved mechanisms have yet to be elucidated. Here, we investigated the pro-osteoarthritic effect of 2, 2', 4, 4', 5, 5'-hexachlorobiphenyl (PCB153), and the involvement of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) and the RICTOR/Akt/mTOR signaling pathways. PCB153 of 20 and 30 μM increased the expression of MMP13 and decreased the expression of type II collagen, in a concentration-dependent manner. PCB153 treatment reduced the expression of Beclin 1 and LC3B, but increased the expression of p62 by upregulating miR-155 levels. PCB153 treatment activated the PI3K/Akt/mTOR signaling pathway by upregulating miR-155 levels. RICTOR was involved in activating the Akt/mTOR signaling pathway, and was also regulated by miR-155. In conclusion, PCB153 could promote the degradation of the extracellular matrix of chondrocytes by upregulating miR-155 via a mechanism related to the activation of the PI3K/Akt/mTOR and RICTOR/Akt/mTOR signaling pathway, which suppressed autophagy and facilitated the development of OA. MiR-155 may represent potential therapeutic targets to alleviate the development of OA.

RNA binding proteins in osteoarthritis

Osteoarthritis (OA) is a common chronic degenerative joint disease worldwide. The pathological features of OA are the erosion of articular cartilage, subchondral bone sclerosis, synovitis, and metabolic disorder. Its progression is characterized by aberrant expression of genes involved in inflammation, proliferation, and metabolism of chondrocytes. Effective therapeutic strategies are limited, as mechanisms underlying OA pathophysiology remain unclear. Significant research efforts are ongoing to elucidate the complex molecular mechanisms underlying OA focused on gene transcription. However, posttranscriptional alterations also play significant function in inflammation and metabolic changes related diseases. RNA binding proteins (RBPs) have been recognized as important regulators in posttranscriptional regulation. RBPs regulate RNA subcellular localization, stability, and translational efficiency by binding to their target mRNAs, thereby controlling their protein expression. However, their role in OA is less clear. Identifying RBPs in OA is of great importance to better understand OA pathophysiology and to figure out potential targets for OA treatment. Hence, in this manuscript, we summarize the recent knowledge on the role of dysregulated RBPs in OA and hope it will provide new insight for OA study and targeted treatment.

Exosomes rewire the cartilage microenvironment in osteoarthritis: from intercellular communication to therapeutic strategies

Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by cartilage loss and accounts for a major source of pain and disability worldwide. However, effective strategies for cartilage repair are lacking, and patients with advanced OA usually need joint replacement. Better comprehending OA pathogenesis may lead to transformative therapeutics. Recently studies have reported that exosomes act as a new means of cell-to-cell communication by delivering multiple bioactive molecules to create a particular microenvironment that tunes cartilage behavior. Specifically, exosome cargos, such as noncoding RNAs (ncRNAs) and proteins, play a crucial role in OA progression by regulating the proliferation, apoptosis, autophagy, and inflammatory response of joint cells, rendering them promising candidates for OA monitoring and treatment. This review systematically summarizes the current insight regarding the biogenesis and function of exosomes and their potential as therapeutic tools targeting cell-to-cell communication in OA, suggesting new realms to improve OA management.

Circular RNA MELK Promotes Chondrocyte Apoptosis and Inhibits Autophagy in Osteoarthritis by Regulating MYD88/NF-κB Signaling Axis through MicroRNA-497-5p

Osteoarthritis (OA) is a rheumatic disease and its pathogenesis involves the dysregulation of noncoding RNAs. Therefore, the regulatory mechanism of circular RNA MELK (circMELK) was specified in this work. OA human cartilage tissue was collected, and circMELK, miR-497-5p, and myeloid differentiation factor 88 (MYD88) expression were examined. Human chondrocytes were stimulated with interleukin- (IL-) 1β and interfered with vectors altering circMELK, miR-497-5p, and MyD88 expression to observe their effects on cell viability, cell cycle and apoptosis, autophagy, and inflammation. The binding relationship between RNAs was verified. The data presented that OA cartilage tissues presented raised circMELK and MYD88 and inhibited miR-497-5p expression. IL-1β suppressed cell viability, prevented cell cycle, and induced apoptosis, autophagy, and inflammation of chondrocytes. Functionally, IL-1β-induced changes of chondrocytes could be attenuated by suppressing circMELK or overexpressing miR-497-5p. circMELK acted as a sponge of miR-497-5p while miR-497-5p was a regulator of MYD88. MYD88 restricted the effect of overexpressing miR-497-5p on IL-1β-stimulated chondrocytes. MYD88 triggered nuclear factor-kappaB (NF-κB) pathway activation. Shortly, CircMELK promotes chondrocyte apoptosis and inhibits autophagy in OA by regulating MYD88/NF-κB signaling axis through miR-497-5p. Our study proposes a new molecular mechanism for the development of OA.

Phenotype Diversity of Macrophages in Osteoarthritis: Implications for Development of Macrophage Modulating Therapies

Chronic inflammation is implicated in numerous human pathologies. In particular, low-grade inflammation is currently recognized as an important mechanism of osteoarthritis (OA), at least in some patients. Among the signs of the inflammatory process are elevated macrophage numbers detected in the OA synovium compared to healthy controls. High macrophage counts also correlate with clinical symptoms of the disease. Macrophages are central players in the development of chronic inflammation, pain, cartilage destruction, and bone remodeling. However, macrophages are also involved in tissue repair and remodeling, including cartilage. Therefore, reduction of macrophage content in the joints correlates with deleterious effects in OA models. Macrophage population is heterogeneous and dynamic, with phenotype transitions being induced by a variety of stimuli. In order to effectively use the macrophage inflammatory circuit for treatment of OA, it is important to understand macrophage heterogeneity and interactions with surrounding cells and tissues in the joint. In this review, we discuss functional phenotypes of macrophages and specific targeting approaches relevant for OA treatment development.

Phloridzin Reveals New Treatment Strategies for Liver Fibrosis

Liver fibrosis is an urgent public health problem which is difficult to resolve. However, various drugs for the treatment of liver fibrosis in clinical practice have their own problems during use. In this study, we used phloridzin to treat hepatic fibrosis in the CCl4-induced C57/BL6N mouse model, which was extracted from lychee core, a traditional Chinese medicine. The therapeutic effect was evaluated by biochemical index detections and ultrasound detection. Furthermore, in order to determine the mechanism of phloridzin in the treatment of liver fibrosis, we performed high-throughput sequencing of mRNA and lncRNA in different groups of liver tissues. The results showed that compared with the model group, the phloridzin-treated groups revealed a significant decrease in collagen deposition and decreased levels of serum alanine aminotransferase, aspartate aminotransferase, laminin, and hyaluronic acid. GO and KEGG pathway enrichment analysis of the differential mRNAs was performed and revealed that phloridzin mainly affects cell ferroptosis. Gene co-expression analysis showed that the target genes of lncRNA were obvious in cell components such as focal adhesions, intercellular adhesion, and cell–substrate junctions and in metabolic pathways such as carbon metabolism. These results showed that phloridizin can effectively treat liver fibrosis, and the mechanism may involve ferroptosis, carbon metabolism, and related changes in biomechanics.

Quercetin and Osteoarthritis: A Mechanistic Review on the Present Documents

BACKGROUND

Osteoarthritis (OA), as one of the chronic debilitating conditions, affects 15% of people globally and is linked with serious problems, such as cardiovascular diseases, metabolic syndrome, and autoimmune inflammatory disorders. The current therapeutic options for this disease include nonsteroidal anti-inflammatory drugs, surgery, gene therapy, intrasynovial gel injection, and warm needle penetration. However, these approaches may be accompanied by considerable side effects, high costs, and some limitations for patients. Thus, using an alternative way is needed.

SUMMARY

Presently, natural compounds based-therapies, like flavonoids, have acquired much attention in the current era. One of the compounds belonging to the flavonoid family is quercetin, and its therapeutic effects on disorders related to joints and cartilage have been addressed in vivo and in vitro studies.

KEY MESSAGES

In this review, we summarized evidence indicating its curative capacity against OA with a mechanistic insight.

Novel insights into the interaction between N6-methyladenosine methylation and noncoding RNAs in musculoskeletal disorders

BACKGROUND

Musculoskeletal disorder (MSD) are a class of inflammatory and degener-ative diseases, but the precise molecular mechanisms are still poorly understood. Noncoding RNA (ncRNA) N6-methyladenosine (m6A) modification plays an essential role in the pathophysiological process of MSD. This review summarized the interaction be-tween m6A RNA methylation and ncRNAs in the molecular regulatory mechanism of MSD. It provides a new perspective for the pathophysiological mechanism and ncRNA m6A targeted therapy of MSD.

METHODS

A comprehensive search of databases was conducted with musculoskeletal disorders, noncoding RNA, N6-methyladenosine, intervertebral disc degeneration, oste-oporosis, osteosarcoma, osteoarthritis, skeletal muscle, bone, and cartilage as the key-words. Then, summarized all the relevant articles.

RESULTS

Intervertebral disc degeneration (IDD), osteoporosis (OP), osteosarcoma (OS), and osteoarthritis (OA) are common MSDs that affect muscle, bone, cartilage, and joint, leading to limited movement, pain, and disability. However, the precise pathogenesis remains unclear, and no effective treatment and drug is available at present. Numerous studies confirmed that the mutual regulation between m6A and ncRNAs (i.e., microRNAs, long ncRNAs, and circular RNAs) was found in MSD, m6A modification can regulate ncRNAs, and ncRNAs can also target m6A regulators. ncRNA m6A modification plays an essential role in the pathophysiological process of MSDs by regulating the homeostasis of skeletal muscle, bone, and cartilage.

CONCLUSION

m6A interacts with ncRNAs to regulate multiple biological processes and plays important roles in IDD, OP, OS, and OA. These studies provide new insights into the pathophysiological mechanism of MSD and targeting m6A-modified ncRNAs may be a promising therapy approach.

CircCDK14 ameliorates interleukin-1β-induced chondrocyte damage by the miR-1183/KLF5 pathway in osteoarthritis

BACKGROUND

The pathogenesis of osteoarthritis (OA), an endemic and debilitating disease, remains unclear. The study aimed to reveal the role of circular RNA cyclin dependent kinase 14 (circCDK14) in OA development and the underlying mechanism.

METHODS

Human chondrocytes were stimulated by 10 ng/mL interleukin-1β (IL-1β) to mimic OA cell model. The RNA expression of circCDK14, microRNA-1183 (miR-1183) and kruppel like factor 5 (KLF5) was checked through quantitative real-time polymerase chain reaction. Western blot was employed to detect protein expression. Cell viability, proliferation and apoptosis were investigated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine and flow cytometry analysis, respectively. Starbase online database was performed to identify the interaction between miR-1183 and circCDK14 or KLF5. Exosomes were isolated by differential centrifugation and identified by transmission electron microscopy, nanoparticle tracking analysis and western blot analysis.

RESULTS

CircCDK14 and KLF5 expression were significantly decreased, while miR-1183 was increased in OA cartilage tissues and IL-1β-treated chondrocytes in comparison with controls. CircCDK14 overexpression attenuated the inhibitory effect of IL-1β treatment on cell proliferation and the promoting effects on cell apoptosis and extracellular matrix degradation. Additionally, miR-1183 was targeted by circCDK14, and miR-1183 mimics reversed circCDK14-mediated actions in IL-1β-treated chondrocytes. The knockdown of KLF5, a target mRNA of miR-1183, also rescued the effects of miR-1183 inhibitors in IL-1β-induced chondrocytes. Moreover, circCDK14 could induce KLF5 expression by interacting with miR-1183. Further, exosomal circCDK14 had a high diagnostic value in OA.

CONCLUSION

CircCDK14 reintroduction assuaged IL-1β-caused chondrocyte damage by the miR-1183/KLF5 pathway, providing a diagnostic biomarker 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.

N6-methyladenosine (m6A) methyltransferase METTL3-mediated LINC00680 accelerates osteoarthritis through m6A/SIRT1 manner

Increasing evidence suggest the biological roles of N⁶-methyladenosine (m⁶A) and long noncoding RNAs (lncRNAs) in the bone disease, especially osteoarthritis (OA). However, the interaction of m⁶A and lncRNA in osteoarthritis is still unclear. Here, we found that a m⁶A-related lncRNA LINC00680 upregulated in the OA tissue and IL-1β-induced isolated primary chondrocytes. Functionally, in IL-1β-induced chondrocytes, silencing of LINC00680 recovered the proliferation and repressed the extracellular matrix (ECM) degradation. Mechanistically, m⁶A methyltransferase METTL3 combined tithe the m⁶A site of LINC00680 to up-regulate its expression. Moreover, LINC00680 interacted with SIRT1 mRNA through binding at m⁶A site on SIRT1 mRNA 3'-UTR, thereby enhancing the stability of SIRT1 mRNA. Overall, these findings exhibited a role of LINC00680/m⁶A/SIRT1 mRNA complex in chondrocytes. Taken together, the present study intends to uncover the mechanism by which METTL3-mediated LINC00680 accelerates OA progression, which may provide novel insight for OA.

microRNA-4701-5p protects against interleukin-1β induced human chondrocyte CHON-001 cells injury via modulating HMGA1

Background

miRNA-4701-5p has been reported to be a vital regulator in many diseases, including rheumatoid arthritis, and miRNA-4701-5p is evidenced to be participated in synovial invasion and joint destruction. In our report, we investigated the roles of miRNA-4701-5p in osteoarthritis (OA) and analyzed the molecular mechanism.

Methods

Interleukin-1β (IL-1β) was applied for stimulating human chondrocyte CHON-001 cells to establish an OA injury model. mRNA levels and protein expression were measured using qRT-PCR and western blot assay, respectively. The proliferation ability and cytotoxicity of CHON-001 cells were checked using MTT assay and lactate dehydrogenase activity. The inflammation of chondrocytes was accessed by the secretion levels of interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor (TNF)-α. The apoptosis of chondrocytes was determined by flow cytometry assay. Bioinformatics software Starbase v2.0 analyzed the functional binding sites between miRNA-4701-5p and HMGA1 and the interaction was further confirmed using dual luciferase reporter analysis. Results: miRNA-4701-5p was down-regulated in the IL-1β-stimulated chondrocytes and HMGA1 directly targeted miRNA-4701-5p. Up-regulation of miRNA-4701-5p could alleviate IL-1β-treated CHON-001 cells inflammation and apoptosis, and reversed the cell proliferation decrease and cytotoxicity increase after IL-1β treatment. Nevertheless, all the roles of miRNA-4701-5p overexpression in CHON-001 cells could be reversed by HMGA1 up-regulation.

Conclusions

miRNA-4701-5p could alleviate the inflammatory injury of IL-1β-treated CHON-001 cells via down-regulating HMGA1, indicating that miRNA-4701-5p/HMGA1 is a promising therapeutic target for OA.

Long non-coding PRNCR1 regulates the proliferation and apoptosis of synoviocytes in osteoarthritis by sponging miR-377-3p

Background

LncRNA PRNCR1 has been reported to be involved in LPS-induced inflammation, which contributes to osteoarthritis (OA). We predicted that miR-377-3p could bind to PRNCR1.MiR-377-3p can suppress OA development. We therefore analyzed the potential interaction between them in OA.

Methods

Expression of miR-377-3p and PRNCR1 in both OA (n = 40) and control (n = 40) samples were analyzed by RT-qPCR. MiR-377-3p or PRNCR1 were overexpressed in synoviocytes to explore their potential interaction. The subcellular location of PRNCR1 was analyzed by nuclear fractionation assay. The direct interaction between miR-377-3p and PRNCR1 was analyzed by RNA-pull down assay. The proliferation and apoptosis of synoviocytes were analyzed by BrdU and apoptosis assay, respectively.

Results

PRNCR1 was overexpressed in OA, while miR-377-3p was downexpressed in OA. PRNCR1 was detected in the cytoplasm and directly interacted with miR-377-3p. Interestingly, overexpression of PRNCR1 and miR-377-3p showed no regulatory role in each other’s expression. LPS treatment increased PRNCR1 expression and decreased miR-377-3p expression. PRNCR1 overexpression decreased LPS-induced synoviocyte proliferation and increased LPS-induced synoviocyte apoptosis. MiR-377-3p played opposite roles in cell proliferation and apoptosis. Moreover, PRNCR1 suppressed the role of miR-377-3p.

Conclusions

Therefore, PRNCR1 is was detected in cytoplasm and regulates synoviocyte proliferation and apoptosis in OA by sponging miR-377-3p.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03035-2.

The Application of Extracellular Vesicles Mediated miRNAs in Osteoarthritis: Current Knowledge and Perspective

Osteoarthritis (OA) is a whole joint disease characterized by synovitis, cartilage destruction, and subchondral bone sclerosis and cyst. Despite decades’ study, effective treatment is rare for this chronic disease. Extracellular vesicles (EVs), including exosomes, microvesicles, and apoptosis bodies, are nano-sized vesicles with a cargo containing biologically active agents, such as nucleic acids, lipids, and proteins. As a group of short non-coding RNAs, microRNAs (miRNAs) can be delivered by parental cells secreted EVs. Negatively regulate the target mRNAs at the posttranscriptional level and regulate gene expression in recipient cells without modifying gene sequence. Recently, most studies focused on the function of EVs mediated miRNAs in the pathophysiological process of OA. However, all kinds of EVs specific and OA specific factors might influence the administration of EVs-miRNAs, especially the precise quantitative management. As a result, the flourishing of current research about EVs in the laboratory might not promote the relevant clinical transformation in OA treatment. In this review, we reviewed the present application of EVs-miRNAs in the therapeutic of OA and further analyzed the potential factors that might influence its application. Further progress in the quantitative management of EVs-miRNAs would accelerate the clinical transformation of miRNAs enriched EVs in the OA field.

Knockdown of circ-PRKCH alleviates IL-1β-treated chondrocyte cell phenotypic changes through modulating miR-502-5p/ADAMTS5 axis

BACKGROUND

Osteoarthritis (OA) is a common joint disease characterized by progressive cartilage degradation. Circular RNAs (circRNAs) are involved in the initiation and development of OA. This study aimed to explore the potential role and mechanism of circRNA protein kinase C eta (circ-PRKCH) in OA.

METHODS

A total of 30 cartilage specimens were collected from OA patients or normal subjects. Human chondrocytes (CHON-001) were stimulated with interleukin-1β (IL-1β) to establish an in vitro OA model. The expression levels of circ-PRKCH, microRNA-502-5p (miR-502-5p) and circ-PRKCH or A disintegrin and metalloproteases metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS5) in cartilage specimens and IL-1β-treated chondrocytes were detected by quantitative real-time PCR or Western blot, and their correlation in OA cartilage specimens was analysed by Spearman's correlation coefficient. The targeted relationship between miR-502-5p and circ-PRKCH or ADAMTS5 was verified by dual-luciferase reporter assay and RNA Immunoprecipitation (RIP) assay. Cell Counting Kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EDU), flow cytometry, wound healing and enzyme-linked immunosorbent assay (ELISA) assays were applied to evaluate cell proliferation, apoptosis, migration and inflammatory response in IL-1β-treated chondrocytes. Exosomes were identified by transmission electron microscope (TEM) and Western blot.

RESULTS

Circ-PRKCH and ADAMTS5 expression levels were up-regulated, while miR-502-5p expression was down-regulated in OA cartilage tissues and IL-1β-treated chondrocytes. Depletion of circ-PRKCH relieved IL-1β-treated chondrocyte cell phenotypic changes by promoting cell proliferation and migration, as well as inhibiting apoptosis and inflammatory response. Mechanically, circ-PRKCH acted as a sponge for miR-502-5p to regulate ADAMTS5 expression, thereby contributing to IL-1β-treated chondrocyte cell phenotypic changes. Moreover, exosomes derived from IL-1β-treated chondrocytes could transfer circ-PRKCH across cells.

CONCLUSION

Circ-PRKCH contributed to IL-1β-treated cell phenotypic changes in chondrocytes via modulating miR-502-5p/ADAMTS5 pathway, which might provide a promising biomarker for OA treatment.

Circ_0043947 contributes to interleukin 1β-induced injury in chondrocytes by sponging miR-671-5p to up-regulate RTN3 expression in osteoarthritis pathology

Objective

Osteoarthritis (OA) is a chronic joint disease featured by articular cartilage degeneration and damage. Accumulating evidence have demonstrated the pivotal regulatory roles of circular RNAs in OA pathology. However, the role of circ_0043947 in OA progression and its associated mechanism remain largely unknown.

Methods

The expression of RNA and protein was determined by reverse transcription-quantitative polymerase chain reaction and Western blot assay. Cell viability was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation was analyzed by 5-Ethynyl-2′-deoxyuridine (EdU) assay and flow cytometry. Cell apoptosis was assessed by flow cytometry. Enzyme linked immunosorbent assay was conducted to analyze the release of pro-inflammatory cytokines. Dual-luciferase reporter assay and RNA immunoprecipitation assay were performed to confirm the target interaction between microRNA-671-5p (miR-671-5p) and circ_0043947 or reticulon 3 (RTN3).

Results

Interleukin 1β (IL-1β) stimulation up-regulated the expression of circ_0043947 in chondrocytes. IL-1β treatment restrained the viability and proliferation and induced the apoptosis, extracellular matrix degradation and inflammatory response of chondrocytes partly by up-regulating circ_0043947. Circ_0043947 interacted with miR-671-5p, and miR-671-5p silencing largely reversed circ_0043947 knockdown-mediated protective effects in IL-1β-induced chondrocytes. miR-671-5p interacted with the 3′ untranslated region (3′UTR) of RTN3. miR-671-5p overexpression attenuated IL-1β-induced injury in chondrocytes, and these protective effects were largely overturned by the overexpression of RTN3. Circ_0043947 acted as a molecular sponge for miR-671-5p to up-regulate RTN3 level in chondrocytes.

Conclusion

Circ_0043947 silencing alleviated IL-1β-induced injury in chondrocytes by targeting miR-671-5p/RTN3 axis.

Circ-LRP1B functions as a competing endogenous RNA to regulate proliferation, apoptosis and oxidative stress of LPS-induced human C28/I2 chondrocytes

Circular RNAs (circRNAs) are crucial for the pathogenesis of human diseases, including osteoarthritis (OA). Here, we set to elucidate the biological action of circ-LRP1B in OA pathogenesis. Human C28/I2 chondrocytes were stimulated by lipopolysaccharide (LPS). Circ-LRP1B, nuclear factor, erythroid 2 like 1 (NRF1) and microRNA (miR)-34a-5p were quantified by quantitative real-time PCR (qRT-PCR) or immunoblotting. Cell viability, proliferation, and apoptosis abilities were gauged by MTT, 5-Ethynyl-2'-Deoxyuridine (EdU) staining, and flow cytometry assays, respectively. Direct relationship between miR-34a-5p and circ-LRP1B or NRF1 was validated by RNA pull-down and dual-luciferase reporter assays. Circ-LRP1B was found to be underexpressed in OA cartilage and LPS-stimulated C28/I2 chondrocytes. Enforced expression of circ-LRP1B promoted cell proliferation, and repressed apoptosis and oxidative stress, as well as impacted OA-specific hallmarks expression of LPS-stimulated C28/I2 cells. NRF1 was identified as a downstream effector of circ-LRP1B function. Moreover, NRF1 was identified as a miR-34a-5p target in LPS-stimulated C28/I2 cells. Circ-LRP1B acted as a competing endogenous RNA (ceRNA) for miR-34a-5p to involve the post-transcriptional regulation of NRF1 expression. Furthermore, the effects of circ-LRP1B overexpression partly depended on the reduction of available miR-34a-5p. These findings demonstrate that circ-LRP1B functions as a ceRNA to regulate the proliferation, apoptosis and oxidative stress of LPS-stimulated human C28/I2 chondrocytes by miR-34a-5p/NRF1 network.