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For the non-invasive treatment of rheumatoid arthritis (RA), a chondroitin sulfate C (CSC)-based dissolving microneedles (cMN) was prepared to deliver human adipose stem cell-derived extracellular vesicles (hASC-EV) into inflamed joints. Owing to their anti-inflammatory function, the hASC-EV-bearing cMN (EV@cMN) significantly suppressed activated fibroblast-like synoviocytes (aFLS) and M1 macrophages (M1), which are responsible for the progression of RA. In addition, EV@cMN facilitated the chondrogenic differentiation of bone marrow-derived stem cells. In mice with collagen-induced arthritis, EV@cMN efficiently delivered both hASC-EV and CSC to inflamed joints. Interestingly, pro-inflammatory cytokines in the inflamed joints were remarkably downregulated by the synergistic effect of CSC and hASC-EV. Consequently, as judged from the overall clinical score and joint swelling, EV@cMN showed an outstanding therapeutic effect, even comparable to the wild-type mice, without significant adverse effects. Overall, EV@cMN might have therapeutic potential for RA by efficiently delivering CSC and hASC-EV into the inflamed joints in a non-invasive manner. [Display omitted] • Macrophages and synoviocytes contribute significantly to the progression of rheumatoid arthritis. • Stem cell-derived extracellular vesicle (hASC-EV) inhibits M1 polarization of macrophages. • We discovered that chondroitin sulfate (CSC) reduces the invasiveness of synoviocytes. • Co-delivery of hASC-EV and CSC via microneedle effectively inhibits the progression of RA. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a systemic autoimmune disease driven by highly active autoantibody‐producing B cells. Activation of B cells is maintained within ectopic germinal centres found in affected joints. Fibroblast‐like synoviocytes (FLS) present in inflamed joints support B‐cell survival, activation, and differentiation. CD27+ memory B cells and naive B cells show very different responses to activation, particularly by CD40 ligand (CD40L). We show that FLS‐dependent activation of human B cells is dependent on interleukin‐6 (IL‐6) and CD40L. FLS have been shown to activate both naive and memory B cells. Whether the activating potential of FLS is different for naive and memory B cells has not been investigated. Our results suggest that FLS‐induced activation of B cells is dependent on IL‐6 and CD40L. While FLS are able to induce plasma cell differentiation, isotype switching, and antibody production in memory B cells, the ability of FLS to activate naive B cells is significantly lower. [ABSTRACT FROM AUTHOR]

The role of liver X receptors (LXR) in rheumatoid arthritis (RA) remains controversial. We studied the effect of LXR agonists on fibroblast‐like synoviocytes (FLS) from RA patients and the K/BxN arthritis model in LXRα and β double‐deficient (Nr1h2/3−/−) mice. Two synthetic LXR agonists, GW3965 and T0901317, were used to activate LXRs and investigate their effects on cell growth, proliferation and matrix metalloproteinases, and chemokine production in cultured FLS from RA patients. The murine model K/BxN serum transfer of inflammatory arthritis in Nr1h2/3−/− animals was used to investigate the role of LXRs on joint inflammation in vivo. LXR agonists inhibited the FLS proliferative capacity in response to TNF, the chemokine‐induced migration, the collagenase activity in FLS supernatant and FLS CXCL12 production. In the K/BxN mouse model, Nr1h2/3−/− animals showed aggravated arthritis, histological inflammation, and joint destruction, as well as an increase in synovial metalloproteases and expression of proinflammatory mediators such as IL‐1β and CCL2 in joints compared with wild type animals. Taken together, these data underscore the importance of LXRs in modulating the joint inflammatory response and highlight them as potential therapeutic targets in RA. [ABSTRACT FROM AUTHOR]

Background: Morinda officinalis iridoid glycosides (MOIG) showed potential benefits in the treatment of rheumatoid arthritis (RA), but their exact mechanism has yet to be explored. Purpose: To evaluate the effects of MOIG on RA, and explore the potential targets and molecular mechanism of MOIG in RA. Methods: The collagen-induced arthritis (CIA) rats were used to evaluate the effects of MOIG on RA. The proliferation, migration and invasion of fibroblast-like synoviocytes (FLSs) stimulated with or without tumor necrosis factor (TNF)-a were examined by CCK-8, wound healing and transwell assays, respectively. IF and WB were applied to investigate related mechanism in FLSs. The molecular docking, molecular dynamics simulation, CETSA and siRNA were used to analyze the interaction of MOIG with target. Finally, the adjuvant-induced arthritis (AA) mice model with gene knockdown was used to confirm the effect of MOIG on glycogen synthase kinase-3ß (GSK-3ß). Results: MOIG significantly alleviated the paw swelling and synovial hyperplasia in CIA rats. Moreover, MOIG suppressed proliferation, migration and invasion, the secretion of inflammatory factors, and the expression of adhesion related proteins in TNF-a-stimulated FLSs. MOIG also inhibited the activation of Janus activating kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappa-B (NF-κB) signaling pathway in FLSs. Interestingly, the plant metabolites in MOIG had a good affinity with GSK-3ß, and inhibition of GSK-3ß attenuated the effects of MOIG on FLSs. Knockdown GSK-3ß gene could inhibit the paw swelling and inflammatory indicators, decrease the arthritis score and synovial hyperplasia, reduce the phosphorylation of p65 and STAT3 in AA mice, thereby suppressing the NF-κB and STAT3 signaling activation, and MOIG treatment had no significant effects on AA mice with si-GSK-3ß. Conclusion: MOIG alleviates joint inflammation in RA through inhibition NF-κB and JAK2/STAT3 pathway via suppression of GSK-3ß in FLSs, which provides supports for MOIG as a promising therapeutic agent of RA. [ABSTRACT FROM AUTHOR]

Objective To investigate the regulatory effect of small interfering RNA (siRNA) silencing zinc finger protein A20 on pyroptosis of rheumatoid arthritis (RA) fibroblast-like synoviocytes (HFLS-RA). Methods Human FLS-RA cell line MH7A cells were cultivated, A20 siRNA silencing group was synthesized for knocking down the human A20 gene, and then specific A20 gene siRNA and siRNA-NC (negative control) were transfected into MH7A cells using liposome method. RT-qPCR was applied to detect the expression of NLRP3 and Caspase-1 mRNA in cells. The protein expression of NLRP3 and Caspase-1 was detected by Western blot, and IL-1β and IL-18 in cell culture medium were detected by ELISA method. Transmission electron microscopy (TEM) was used to detect pyroptosis. Results After A20 knockdown, the mRNA and expression of NLRP3 and Caspase-1 in MH7A cells in the siRNA-A20 group were significantly increased as compared with the siRNA-NC group (P＜0. 01). The concentration of IL-1β and IL-18 in the cell culture supernatant of the siRNA-A20 group was significantly increased compared with the siRNA-NC group (P＜0. 01). Compared with the siRNA-NC group, some cells in the siRNA-A20 group showed swollen and ruptured. The integrity of the cell membrane was also lost, and a large area of edema was present in the cell. In addition, a blurred depression of the local nuclear membrane was noted, while an increase in heterochromatin pyknosis was accompanied by their uneven distribution as well as their aggregation around the nuclear membrane. Conclusions Silencing of A20 gene with siRNA might promote NLRP3/Caspase-1 mediated pyroptosis in HFLS-RA, which lays an experimental foundation for new clinical treatment methods of RA. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by synovial hyperplasia, and fibroblast‐like synoviocytes (FLSs) constitute the majority of cells in the synovial tissue, playing a crucial role in the onset of RA. Dysregulation of FLSs function is a critical strategy in treating joint damage associated with RA. Non‐coding RNAs, a class of RNA molecules that do not encode proteins, participate in the development of various diseases. This article aims to review the progress in the study of long non‐coding RNAs, microRNAs, and circular RNAs in FLSs. Non‐coding RNAs are involved in the pathogenesis of RA, directly or indirectly regulating FLSs' proliferation, migration, invasion, apoptosis, and inflammatory responses. Furthermore, non‐coding RNAs also influence DNA methylation and osteogenic differentiation in FLSs. Therefore, non‐coding RNAs hold promise as biomarkers for diagnosing RA. Targeting non‐coding RNAs in FLSs locally represents a potential strategy for future therapies in RA. [ABSTRACT FROM AUTHOR]

Background: Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease. The fruits of Illicium verum, which is a medicinal and edible resource, have been shown to have anti-inflammatory properties. Methods: In this study, we investigated the effects of I. verum extracts (IVEs) on human RA fibroblasts-like synoviocytes (RA-FLS) by using a sensitive and selective ultra-high-performance liquid chromatography with high-definition mass spectrometry (UPLC-HDMS) method. We subsequently analyzed the metabolites produced after the incubation of cultured RA-FLS with IVEs. Results: IVEs inhibited the proliferation and suppressed the migration of RA-FLS, and reduced the levels of inflammatory factors including TNF-α and IL-6. Twenty differential metabolites responsible for the effects of IVEs were screened and annotated based on the UPLC-HDMS data by using a cell metabolomics approach. Discussion: Our findings suggest that treating RA-FLS with IVEs can regulate lipid and amino acid metabolism, indicating that this extract has the potential to modify the metabolic pathways that cause inflammation in RA. Conclusions: This might lead to novel therapeutic strategies for managing patients with RA. [ABSTRACT FROM AUTHOR]

Abstract Background Osteoarthritis (OA) is the most common motor system disease in older people, characterized by a high incidence and significant social and economic burden. Women have a higher risk of OA, more severe clinical symptoms, and a higher rate of disabilities than men. However, the pathogenesis of OA remains unclear. Therefore, we screened for differentially expressed genes (DEGs) in OA patients of different sex and searched for new targets that may be involved in regulating the development of OA. Methods The study compared the expression of DEGs in synovial fluid exosomes between male and female patients with OA through RNA sequencing combined with bioinformatics analysis using public data. To evaluate the screened DEGs, synovial tissue and fluid samples were obtained from patients with OA who underwent joint replacement surgery. SiRNA-mediated knockdown in vitro experiments were performed to investigate the role of glycoprotein membrane 6B (GPM6B). Meanwhile, GPM6B gene knockout mice were used to assess the in vivo pathological roles of GPM6B in OA. Results The results revealed that GPM6B is a potential target associated with OA. Immunofluorescence staining demonstrated that GPM6B was expressed in fibroblast-like synoviocytes (FLS) and macrophage-like synoviocytes in patients with OA. In vitro experiments confirmed that GPM6B knockdown can reduce the expression of inflammatory factors in primary FLS from patients with OA. Under inflammatory conditions, GPM6B knockdown can reduce the expression of matrix metalloproteinases as well as proliferation of FLS. In addition, using a destabilization of the medial meniscus-induced OA model, we revealed that GPM6B is associated with OA progression in mice. Conclusion Thus, we provided evidence that GPM6B act as a new target associated with OA.

Objective To investigate the regulatory effect of small interfering RNA (siRNA) silencing zinc finger protein A20 on pyroptosis of rheumatoid arthritis(RA) fibroblast-like synoviocytes (HFLS-RA). Methods Human FLS-RA cell line MH7A cells were cultivated, A20 siRNA silencing group was synthesized for knocking down the human A20 gene, and then specific A20 gene siRNA and siRNA-NC(negative control)were transfected into MH7A cells using liposome method. RT-qPCR was applied to detect the expression of NLRP3 and Caspase-1 mRNA in cells.The protein expression of NLRP3 and Caspase-1 was detected by Western blot, and IL-1β and IL-18 in cell culture medium were detected by ELISA method. Transmission electron microscopy (TEM) was used to detect pyroptosis. Results After A20 knockdown, the mRNA and expression of NLRP3 and Caspase-1 in MH7A cells in the siRNA-A20 group were significantly increased as compared with the siRNA-NC group(P＜0.01). The concentration of IL-1β and IL-18 in the cell culture supernatant of the siRNA-A20 group was significantly increased compared with the siRNA-NC group (P＜0.01). Compared with the siRNA-NC group, some cells in the siRNA-A20 group showed swollen and ruptured. The integrity of the cell membrane was also lost, and a large area of edema was present in the cell. In addition, a blurred depression of the local nuclear membrane was noted, while an increase in heterochromatin pyknosis was accompanied by their uneven distribution as well as their aggregation around the nuclear membrane. Conclusions Silencing of A20 gene with siRNA might promote NLRP3/Caspase-1 mediated pyroptosis in HFLS-RA, which lays an experimental foundation for new clinical treatment methods of RA.

Abstract The characteristic features of the rheumatoid arthritis (RA) microenvironment are synovial inflammation and hyperplasia. Therefore, there is a growing interest in developing a suitable therapeutic strategy for RA that targets the synovial macrophages and fibroblast-like synoviocytes (FLSs). In this study, we used graphene oxide quantum dots (GOQDs) for loading anti-arthritic sinomenine hydrochloride (SIN). By combining with hyaluronic acid (HA)-inserted hybrid membrane (RFM), we successfully constructed a new nanodrug system named HA@RFM@GP@SIN NPs for target therapy of inflammatory articular lesions. Mechanistic studies showed that this nanomedicine system was effective against RA by facilitating the transition of M1 to M2 macrophages and inhibiting the abnormal proliferation of FLSs in vitro. In vivo therapeutic potential investigation demonstrated its effects on macrophage polarization and synovial hyperplasia, ultimately preventing cartilage destruction and bone erosion in the preclinical models of adjuvant-induced arthritis and collagen-induced arthritis in rats. Metabolomics indicated that the anti-arthritic effects of HA@RFM@GP@SIN NPs were mainly associated with the regulation of steroid hormone biosynthesis, ovarian steroidogenesis, tryptophan metabolism, and tyrosine metabolism. More notably, transcriptomic analyses revealed that HA@RFM@GP@SIN NPs suppressed the cell cycle pathway while inducing the cell apoptosis pathway. Furthermore, protein validation revealed that HA@RFM@GP@SIN NPs disrupted the excessive growth of RAFLS by interfering with the PI3K/Akt/SGK/FoxO signaling cascade, resulting in a decline in cyclin B1 expression and the arrest of the G2 phase. Additionally, considering the favorable biocompatibility and biosafety, these multifunctional nanoparticles offer a promising therapeutic approach for patients with RA. Graphical abstract

Autoimmune diseases hold significant importance in the realm of medical research, prompting a thorough exploration of potential therapeutic interventions. One crucial aspect of this exploration involves understanding the intricate processes of histone acetylation and deacetylation. Histone acetylation, facilitated by histone acetyl transferases (HATs), is instrumental in rendering DNA transcriptionally active. Conversely, histone deacetylases (HDACs) are responsible for the removal of acetyl groups, influencing gene expression regulation. The upregulation of HDACs, observed in various cancers, has steered attention towards histone deacetylase inhibitors (HDACi) as promising anti-cancer agents. Beyond cancer, HDACi has demonstrated anti-inflammatory properties, prompting interest in their potential therapeutic applications for inflammatory diseases such as rheumatoid arthritis (RA). RA, characterized by the immune system erroneously attacking healthy cells, leads to joint inflammation. Recent studies suggest that HDACi could offer a viable therapeutic strategy for RA, with potential mechanisms including the inhibition of synovial tissue growth and suppression of pro-inflammatory cytokines. Furthermore, HDACi may exert protective effects on bone and cartilage, common targets in RA pathology. In-depth investigations through in vivo and histopathology studies contribute to the ongoing discourse on the therapeutic benefits of HDACis in the context of RA treatment. [ABSTRACT FROM AUTHOR]

Background: Temporomandibular joint osteoarthritis (TMJOA) is a degenerative cartilage disease. 17β‐estradiol (E2) aggravates the pathological process of TMJOA; however, the mechanisms of its action have not been elucidated. Thus, we investigate the influence of E2 on the cellular biological behaviors of synoviocytes and the molecular mechanisms. Methods: Primary fibroblast‐like synoviocytes (FLSs) isolated from rats were treated with TNF‐α to establish cell model, and phenotypes were evaluated using cell counting kit‐8, EdU, Tanswell, enzyme‐linked immunosorbent assay, and quantitative real‐time PCR (qPCR). The underlying mechanism of E2, FTO‐mediated NLRC5 m6A methylation, was assessed using microarray, methylated RNA immunoprecipitation, qPCR, and western blot. Moreover, TMJOA‐like rat model was established by intra‐articular injection of monosodium iodoacetate (MIA), and bone morphology and pathology were assessed using micro‐CT and H&E staining. Results: The results illustrated that E2 facilitated the proliferation, migration, invasion, and inflammation of TNF‐α‐treated FLSs. FTO expression was downregulated in TMJOA and was reduced by E2 in FLSs. Knockdown of FTO promoted m6A methylation of NLRC5 and enhanced NLRC5 stability by IGF2BP1 recognition. Moreover, E2 promoted TMJ pathology and condyle remodeling, and increased bone mineral density and trabecular bone volume fraction, which was rescued by NLRC5 knockdown. Conclusion: E2 promoted the progression of TMJOA. [ABSTRACT FROM AUTHOR]

The characteristic features of the rheumatoid arthritis (RA) microenvironment are synovial inflammation and hyperplasia. Therefore, there is a growing interest in developing a suitable therapeutic strategy for RA that targets the synovial macrophages and fibroblast-like synoviocytes (FLSs). In this study, we used graphene oxide quantum dots (GOQDs) for loading anti-arthritic sinomenine hydrochloride (SIN). By combining with hyaluronic acid (HA)-inserted hybrid membrane (RFM), we successfully constructed a new nanodrug system named HA@RFM@GP@SIN NPs for target therapy of inflammatory articular lesions. Mechanistic studies showed that this nanomedicine system was effective against RA by facilitating the transition of M1 to M2 macrophages and inhibiting the abnormal proliferation of FLSs in vitro. In vivo therapeutic potential investigation demonstrated its effects on macrophage polarization and synovial hyperplasia, ultimately preventing cartilage destruction and bone erosion in the preclinical models of adjuvant-induced arthritis and collagen-induced arthritis in rats. Metabolomics indicated that the anti-arthritic effects of HA@RFM@GP@SIN NPs were mainly associated with the regulation of steroid hormone biosynthesis, ovarian steroidogenesis, tryptophan metabolism, and tyrosine metabolism. More notably, transcriptomic analyses revealed that HA@RFM@GP@SIN NPs suppressed the cell cycle pathway while inducing the cell apoptosis pathway. Furthermore, protein validation revealed that HA@RFM@GP@SIN NPs disrupted the excessive growth of RAFLS by interfering with the PI3K/Akt/SGK/FoxO signaling cascade, resulting in a decline in cyclin B1 expression and the arrest of the G2 phase. Additionally, considering the favorable biocompatibility and biosafety, these multifunctional nanoparticles offer a promising therapeutic approach for patients with RA. [ABSTRACT FROM AUTHOR]

Abstract Background Rheumatoid arthritis (RA) is a chronic immune system disease with a high disability rate threatening the living quality of patients. Identifying potential biomarkers for RA is of necessity to improve the prevention and management of RA. Objectives This study focused on miR-146b-3p evaluating its clinical significance and revealing the underlying regulatory mechanisms. Materials and methods A total of 107 RA patients were enrolled, and both serum and synovial tissues were collected. Another 78 osteoarthritis patients (OA, providing synovial tissues), and 72 healthy individuals (providing serum samples) were enrolled as the control group. The expression of miR-146b-3p was analyzed by PCR and analyzed with ROC and Pearson correlation analyses evaluating its significance in diagnosis and development prediction of RA patients. In vitro, MH7A cells were treated with TNF-α. The regulation of cell proliferation, motility, and inflammation by miR-146b-3p was assessed by CCK8, Transwell, and ELISA assays. Results Significant upregulation of miR-146b-3p was observed in serum and synovial tissues of RA patients, which distinguished RA patients and were positively correlated with the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), anti-cyclic citrullinated peptide antibodies (anti-CCP), and rheumatoid factor (RF) of RA patients. TNF-α promoted the proliferation and motility of MH7A cells and induced significant inflammation in cells. Silencing miR-146b-3p alleviated the effect of TNF-α and negatively regulated the expression of HMGCR. The knockdown of HMGCR reversed the protective effect of miR-146b-3p silencing on TNF-α-stimulated MH7A cells. Conclusions Increased miR-146b-3p served as a biomarker for the diagnosis and severity of RA. Silencing miR-146b-3p could suppress TNF-α-induced excessive proliferation, motility, and inflammation via regulating HMGCR in MH7A cells.

Abstract Background Fibroblast-like synoviocytes (FLSs) are involved in osteoarthritis (OA) pathogenesis through pro-inflammatory cytokine production. TAK-242, a TLR4 blocker, has been found to have a significant impact on the gene expression profile of pro-inflammatory cytokines such as IL1-β, IL-6, TNF-α, and TLR4, as well as the phosphorylation of Ikβα, a regulator of the NF-κB signaling pathway, in OA-FLSs. This study aims to investigate this effect because TLR4 plays a crucial role in inflammatory responses. Materials and methods Ten OA patients’ synovial tissues were acquired, and isolated FLSs were cultured in DMEM in order to assess the effectiveness of TAK-242. The treated FLSs with TAK-242 and Lipopolysaccharides (LPS) were analyzed for the mRNA expression level of IL1-β, IL-6, TNF-α, and TLR4 levels by Real-Time PCR. Besides, we used western blot to assess the protein levels of Ikβα and pIkβα. Results The results represented that TAK-242 effectively suppressed the gene expression of inflammatory cytokines IL1-β, IL-6, TNF-α, and TLR4 which were overexpressed upon LPS treatment. Additionally, TAK-242 inhibited the phosphorylation of Ikβα which was increased by LPS treatment. Conclusion According to our results, TAK-242 shows promising inhibitory effects on TLR4-mediated inflammatory responses in OA-FLSs by targeting the NF-κB pathway. TLR4 inhibitors, such as TAK-242, may be useful therapeutic agents to reduce inflammation and its associated complications in OA patients, since traditional and biological treatments may not be adequate for all of them.

Abstract Background We aimed to investigate the development of synovial fibrosis in vitro and how the fibrosis can be halted. Synovial fibrosis causes joint stiffness in arthritic diseases. The pathway of the fibrotic growth factor, transforming growth factor-beta (TGF-β), has been associated with joint pain in osteoarthritis (OA) and with the fibroid phenotype of rheumatoid arthritis (RA). This suggests that synovial fibrosis, thus accumulation of extracellular matrix (ECM) proteins, plays a role in the clinical manifestations of the diseases. Improving our understanding of fibrotic development may aid in selecting appropriate treatments and development of drugs that can target synovial fibrosis. Methods We isolated primary fibroblast-like synoviocytes (FLS) from the synovial membrane of patients undergoing total knee replacement surgery. To investigate the development of synovial fibrosis, the FLS were cultured in a crowded in vitro model mimicking the ECM. TGF-β1 was used as the fibrotic initiator, the activin receptor-like kinase 5 inhibitor (ALK5i), the anti-fibrotic drug nintedanib, and the anti-inflammatory drug tofacitinib were used as fibrotic inhibitors. The ECM protein formation was quantified in the conditioned media using specific biomarkers of type I, III, and VI collagen formation and fibronectin turnover. Results The TGF-β stimulation inducted fibrogenesis by increasing the biomarkers of fibronectin turnover, type I, III, and VI collagen formation. ALK5i and nintedanib inhibited the TGF-β response across all biomarkers. Tofacitinib trended towards inhibiting TGF-β response with up to 78% inhibition. All the treatments preserved cell viability. Conclusion We have established an in vitro model for assessing fibrogenesis in primary FLS, which can be used to assess the anti-fibrotic effect of multiple drug types. Our study implies that synovial fibrosis can be induced by TGF-β, which additionally can be halted by both direct and indirect inhibition with anti-fibrotic substances. The anti-inflammatory drug tofacitinib also halted the fibrogenesis to some extent; thus, it may exert an anti-fibrotic effect.

Abstract Fibroblast-like synoviocytes (FLSs) play a central role in RA pathogenesis and are the main cellular component in the inflamed synovium of patients with rheumatoid arthritis (RA). FLSs are emerging as promising new therapeutic targets in RA. However, fibroblasts perform many essential functions that are required for sustaining tissue homeostasis. Direct targeting of general fibroblast markers on FLSs is challenging because fibroblasts in other tissues might be altered and side effects such as reduced wound healing or fibrosis can occur. To date, no FLS-specific targeted therapies have been applied in the clinical management of RA. With the help of high-throughput technologies such as scRNA-seq in recent years, several specific pathogenic FLS subsets in RA have been identified. Understanding the characteristics of these pathogenic FLS clusters and the mechanisms that drive their differentiation can provide new insights into the development of novel FLS-targeting strategies for RA. Here, we discuss the pathogenic FLS subsets in RA that have been elucidated in recent years and potential strategies for targeting pathogenic FLSs.

Background: Rheumatoid arthritis (RA) is a chronic immune system disease with a high disability rate threatening the living quality of patients. Identifying potential biomarkers for RA is of necessity to improve the prevention and management of RA. Objectives: This study focused on miR-146b-3p evaluating its clinical significance and revealing the underlying regulatory mechanisms. Materials and methods: A total of 107 RA patients were enrolled, and both serum and synovial tissues were collected. Another 78 osteoarthritis patients (OA, providing synovial tissues), and 72 healthy individuals (providing serum samples) were enrolled as the control group. The expression of miR-146b-3p was analyzed by PCR and analyzed with ROC and Pearson correlation analyses evaluating its significance in diagnosis and development prediction of RA patients. In vitro, MH7A cells were treated with TNF-α. The regulation of cell proliferation, motility, and inflammation by miR-146b-3p was assessed by CCK8, Transwell, and ELISA assays. Results: Significant upregulation of miR-146b-3p was observed in serum and synovial tissues of RA patients, which distinguished RA patients and were positively correlated with the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), anti-cyclic citrullinated peptide antibodies (anti-CCP), and rheumatoid factor (RF) of RA patients. TNF-α promoted the proliferation and motility of MH7A cells and induced significant inflammation in cells. Silencing miR-146b-3p alleviated the effect of TNF-α and negatively regulated the expression of HMGCR. The knockdown of HMGCR reversed the protective effect of miR-146b-3p silencing on TNF-α-stimulated MH7A cells. Conclusions: Increased miR-146b-3p served as a biomarker for the diagnosis and severity of RA. Silencing miR-146b-3p could suppress TNF-α-induced excessive proliferation, motility, and inflammation via regulating HMGCR in MH7A cells. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is a common joint disorder characterized by the degeneration of cartilage and inflammation, affecting millions worldwide. The disease’s complex pathogenesis involves various cell types, such as chondrocytes, synovial cells, osteoblasts, and immune cells, contributing to the intricate interplay of factors leading to tissue degradation and pain. RNA interference (RNAi) therapy, particularly through the use of small interfering RNA (siRNA), emerges as a promising avenue for OA treatment due to its capacity for specific gene silencing. siRNA molecules can modulate post-transcriptional gene expression, targeting key pathways involved in cellular proliferation, apoptosis, senescence, autophagy, biomolecule secretion, inflammation, and bone remodeling. This review delves into the mechanisms by which siRNA targets various cell populations within the OA milieu, offering a comprehensive overview of the potential therapeutic benefits and challenges in clinical application. By summarizing the current advancements in siRNA delivery systems and therapeutic targets, we provide a solid theoretical foundation for the future development of novel siRNA-based strategies for OA diagnosis and treatment, paving the way for innovative and more effective approaches to managing this debilitating disease. [ABSTRACT FROM AUTHOR]

Objective: To determine the expression of small nucleolar RNA host gene 16( SNHG16) in fibroblast-like synoviocytes (FLS) of patients with rheumatoid arthritis (RA) and its role in the development of RA. Methods: RT-qPCR was performed to measure SNHG16, miR-182-5p and peroxisome proliferator-activated receptor gamma (PPARG) mRNA expression; dual-luciferase assay was performed to measure the interaction between SNHG16, miR-182-5p and PPARG mRNA; EdU and Transwell were performed to measure cell proliferation and invasion; Western blot was performed to measure PPARG protein level. Results: SNHG16 and PPARG mRNA expression were up-regulated and miR-182-5p expression was down-regulated in RA synovial tissue and human RA-FLS line (HFLS-RA). SNHG16 negatively targeted miR-182-5p expression and positively regulated PPARG (miR-182-5p target) expression. Silencing of SNHG16 inhibited the proliferation and invasion of HFLS-RA; down-regulation of miR-182-5p partially reversed the inhibitory effect of SNHG16 silencing on cell proliferation and invasion; overexpression of PPARG partially reversed the inhibitory effect of up-regulation of miR-182-5p on the proliferation and invasion of HFLS-RA. Conclusion: Silencing SNHG16 targeting miR-182-5p/PPARG axis inhibits the proliferation and invasion of HFLS-RA. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease characterised by the formation of a hyperplastic pannus, as well as cartilage and bone damage. The pathogenesis of RA is complex and involves broad interactions between various cells present in the inflamed synovium, including fibroblast-like synoviocytes (FLSs), macrophages, and T cells, among others. Under inflammatory conditions, these cells are activated, further enhancing inflammatory responses and angiogenesis and promoting bone and cartilage degradation. Novel treatment methods for RA are greatly needed, and mesenchymal stromal cells (MSCs) have been suggested as a promising new regenerative and immunomodulatory treatment. In this paper, we present the interactions between MSCs and RA-FLSs, and macrophages and T cells, and summarise studies examining the use of MSCs in preclinical and clinical RA studies. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is an enduring, progressive autoimmune disorder. Abnormal activation of fibroblast-like synoviocytes (FLSs) has been proposed as the initiating factor for inflammation of the synovium and bone destruction. Neutrophil extracellular traps (NETs), which are web-like structures composed of DNA, histones, and granule proteins, are involved in the development of RA in multiple aspects. Pyroptosis, gasdermin-mediated inflammatory programmed cell death, plays a vital function in the etiopathogenesis of RA. However, the exact mechanism underlying NETs-induced pyroptosis in FLSs of RA and its impact on cellular pathogenic behavior remain undefined. In this study, we demonstrated that gasdermin E (GSDME) expression was upregulated in RA plasma and synoviums, which was positively correlated with the elevated cell-free DNA (cfDNA) and citrullinated histone 3 (Cit H3) levels in the plasma. Additionally, in vitro experiments have shown that NETs triggered caspase 3/GSDME-mediated pyroptosis in RA-FLSs, characterized by decreased cell viability, cell membrane blebbing, and rupture, as well as increased levels of pyroptosis-related proteins and pro-inflammatory cytokines. Again, silencing GSDME significantly inhibited pyroptosis and suppressed the migration, invasion, and secretion of pro-inflammatory cytokines in RA-FLSs. Furthermore, we also found that the nuclear factor-kappa B (NF-κB) pathway, serving as an upstream mechanism, was involved in FLS pyroptosis. In conclusion, our investigation indicated that NETs could induce RA-FLS pyroptosis and facilitate phenotypic transformation through targeting the NF-κB/caspase 3/GSDME axis. This is the first to explore the crucial role of NETs-induced FLS pyroptosis in the progression of RA, providing novel targets for the clinical management of refractory RA. [ABSTRACT FROM AUTHOR]

There are few effective therapeutic strategies for temporomandibular joint osteoarthritis (TMJOA) due to the unclear pathology and mechanisms. We aimed to confirm the roles of GPX4 and ferroptosis in TMJOA progression. ELISA assay was hired to evaluate concentrations of ferroptosis‐related markers. The qRT‐PCR assay was hired to assess gene mRNA level. Western blot assay and immunohistochemistry were hired to verify the protein level. CCK‐8 assay was hired to detect cell viability. Human fibroblast‐like synoviocytes (FLSs) were cultured to confirm the effects of GPX4 and indicated inhibitors, and further verified the effects of GPX4 and ferroptosis inhibitors in TMJOA model rats. Markers of ferroptosis including 8‐hidroxy‐2‐deoxyguanosine (8‐OHdG) and iron were notably increased in TMJOA tissues and primary OA‐FLSs. However, the activity of the antioxidant system including the glutathione peroxidase activity, glutathione (GSH) contents, and glutathione/oxidized glutathione (GSH/GSSG) ratio was notably inhibited in TMJOA tissues, and the primary OA‐FLSs. Furthermore, the glutathione peroxidase 4 (GPX4) expression was down‐regulated in TMJOA tissues and primary OA‐FLSs. Animal and cell experiments have shown that ferroptosis inhibitors notably inhibited ferroptosis and promoted HLS survival as well as up‐regulated GPX4 expression. Also, GPX4 knockdown promoted ferroptosis and GPX4 overexpression inhibited ferroptosis. GPX4 also positively regulated cell survival which was the opposite with ferroptosis. In conclusion, GPX4 and ferroptosis regulated the progression of TMJOA. Targeting ferroptosis might be an effective therapeutic strategy for TMJOA patients in the clinic. [ABSTRACT FROM AUTHOR]

The severity of osteoarthritis (OA) and cartilage degeneration is highly associated with synovial inflammation. Although recent investigations have revealed a dysregulated crosstalk between fibroblast‐like synoviocytes (FLSs) and macrophages in the pathogenesis of synovitis, limited knowledge is available regarding the involvement of exosomes. Here, increased exosome secretion is observed in FLSs from OA patients. Notably, internalization of inflammatory FLS‐derived exosomes (inf‐exo) can enhance the M1 polarization of macrophages, which further induces an OA‐like phenotype in co‐cultured chondrocytes. Intra‐articular injection of inf‐exo induces synovitis and exacerbates OA progression in murine models. In addition, it is demonstrated that inf‐exo stimulation triggers the activation of glycolysis. Inhibition of glycolysis using 2‐DG successfully attenuates excessive M1 polarization triggered by inf‐exo. Mechanistically, HIF1A is identified as the determinant transcription factor, inhibition of which, both pharmacologically or genetically, relieves macrophage inflammation triggered by inf‐exo‐induced hyperglycolysis. Furthermore, in vivo administration of an HIF1A inhibitor alleviates experimental OA. The results provide novel insights into the involvement of FLS‐derived exosomes in OA pathogenesis, suggesting that inf‐exo‐induced macrophage dysfunction represents an attractive target for OA therapy. [ABSTRACT FROM AUTHOR]

Introduction: Apurinic/apyrimidinic endonuclease 1 (APEX1) is a protein with elevated expression in synovial fluids from rheumatoid arthritis (RA) patients. However, its role in RA pathogenesis remains unexplored. This study investigated the influence of APEX1 on inflammatory pathways in fibroblast-like synoviocytes (FLS) isolated from RA patients. Material and methods: FLS from RA patients (n = 5) were stimulated with recombinant tumor necrosis factor a (TNF-a) and interleukin (IL)-17. Subsequently, cells were treated with recombinant APEX1, and assessments were made on reactive oxygen species (ROS) production and mitochondrial membrane potential. Additionally, mRNA levels of IL-1 family members were quantified. Cell migration was evaluated through Transwell chamber assays, and levels of key secreted inflammatory cytokines were measured via enzyme-linked immunosorbent assay (ELISA). Results: The results demonstrated that APEX1 significantly reduced mitochondrial-specific ROS expression and restored mitochondrial membrane potential in TNF-a/IL-17-stimulated RA FLS. Furthermore, APEX1 treatments attenuated TNF-a/IL-17-induced activation of p38 MAPK, NF-κB, and PI3K 110d signaling pathways. Similarly, APEX1 significantly diminished TNF-a/IL-17-induced expression of inflammatory cytokines, including IL-1 family members, IL-6, IL-8, and vascular endothelial growth factor (VEGF). Notably, APEX1 downregulated cell migration of TNF-a/IL-17-treated RA FLS via inhibition of matrix metalloproteinase 3 (MMP3). Conclusions: These findings collectively underscore the role of APEX1 as a key mediator of cytokine-amplified migration, modulating ROS and MMP3 in RA FLS, thus supporting its potential as a therapeutic target in RA treatment. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a chronic and refractory autoimmune disease that primarily affects the synovium of diarthrodial joints. Inflammatory macrophages and fibroblast-like synoviocytes (FLS) in the synovial microenvironment produce pathogenic mediators such as cytokines and proteases that perpetuate immune-mediated inflammation and contribute to the destruction of cartilage and bone. Polydatin (PD), a natural active compound, has demonstrated potential anti-inflammatory and anti-arthritic effects. However, drug development and delivery of PD is still a great challenge owing to its low solubility, short half-life, and high dose requirement. In order to overcome these drawbacks, we developed a novel nanodrug system named HA-M@PB@Ag@PD NPs. This system is composed of hybrid membrane (M), hyaluronic acid (HA), Prussian blue nanoparticles (PB NPs), PD, and chitosan-silver (Chi-Ag). In vitro experiments demonstrated that HA-M@PB@Ag@PD NPs effectively cleared ROS, promoted the repolarization of inflammatory macrophages, and induced apoptosis of RA-FLS. Using a rat model of RA, HA-M@PB@Ag@PD NPs markedly suppressed joint inflammation, inhibited synovial hyperplasia, and protected joints against destruction of cartilage and bone. Moreover, HA-M@PB@Ag@PD NPs significantly improved the synovial microenvironment of arthritic rats by reducing the number of RA-FLS and inflammatory macrophages, and facilitating the repolarization of inflammatory macrophages.

Abstract Background Temporomandibular joint osteoarthritis (TMJOA) is a degenerative cartilage disease. 17β‐estradiol (E2) aggravates the pathological process of TMJOA; however, the mechanisms of its action have not been elucidated. Thus, we investigate the influence of E2 on the cellular biological behaviors of synoviocytes and the molecular mechanisms. Methods Primary fibroblast‐like synoviocytes (FLSs) isolated from rats were treated with TNF‐α to establish cell model, and phenotypes were evaluated using cell counting kit‐8, EdU, Tanswell, enzyme‐linked immunosorbent assay, and quantitative real‐time PCR (qPCR). The underlying mechanism of E2, FTO‐mediated NLRC5 m6A methylation, was assessed using microarray, methylated RNA immunoprecipitation, qPCR, and western blot. Moreover, TMJOA‐like rat model was established by intra‐articular injection of monosodium iodoacetate (MIA), and bone morphology and pathology were assessed using micro‐CT and H&E staining. Results The results illustrated that E2 facilitated the proliferation, migration, invasion, and inflammation of TNF‐α‐treated FLSs. FTO expression was downregulated in TMJOA and was reduced by E2 in FLSs. Knockdown of FTO promoted m6A methylation of NLRC5 and enhanced NLRC5 stability by IGF2BP1 recognition. Moreover, E2 promoted TMJ pathology and condyle remodeling, and increased bone mineral density and trabecular bone volume fraction, which was rescued by NLRC5 knockdown. Conclusion E2 promoted the progression of TMJOA.

Rheumatoid arthritis is a chronic inflammatory disease that shows characteristic diurnal variation in symptom severity, where joint resident fibroblast-like synoviocytes (FLS) act as important mediators of arthritis pathology. We investigate the role of FLS circadian clock function in directing rhythmic joint inflammation in a murine model of inflammatory arthritis. We demonstrate FLS time-of-day-dependent gene expression is attenuated in arthritic joints, except for a subset of disease-modifying genes. The deletion of essential clock gene Bmal1 in FLS reduced susceptibility to collagen-induced arthritis but did not impact symptomatic severity in affected mice. Notably, FLS Bmal1 deletion resulted in loss of diurnal expression of disease-modulating genes across the joint, and elevated production of MMP3, a prognostic marker of joint damage in inflammatory arthritis. This work identifies the FLS circadian clock as an influential driver of daily oscillations in joint inflammation, and a potential regulator of destructive pathology in chronic inflammatory arthritis.

Hyperplasia and migration of fibroblast-like synoviocytes (FLSs) are the key drivers in the pathogenesis of rheumatoid arthritis (RA) and joint destruction. Abundant Yes-associated protein (YAP), which is a powerful transcription co-activator for proliferative genes, was observed in the nucleus of inflammatory FLSs with unknown upstream mechanisms. Using Gene Expression Omnibus database analysis, it was found that Salvador homolog-1 (SAV1), the pivotal negative regulator of the Hippo-YAP pathway, was slightly downregulated in RA synovium. However, SAV1 protein expression is extremely reduced. Subsequently, it was revealed that SAV1 is phosphorylated, ubiquitinated, and degraded by interacting with an important serine-threonine kinase, G protein-coupled receptor (GPCR) kinase 2 (GRK2), which was predominately upregulated by GPCR activation induced by ligands such as prostaglandin E2 (PGE2) in RA. This process further contributes to the decreased phosphorylation, nuclear translocation, and transcriptional potency of YAP, and leads to aberrant FLSs proliferation. Genetic depletion of GRK2 or inhibition of GRK2 by paroxetine rescued SAV1 expression and restored YAP phosphorylation and finally inhibited RA FLSs proliferation and migration. Similarly, paroxetine treatment effectively reduced the abnormal proliferation of FLSs in a rat model of collagen-induced arthritis which was accompanied by a significant improvement in clinical manifestations. Collectively, these results elucidate the significance of GRK2 regulation of Hippo-YAP signaling in FLSs proliferation and migration and the potential application of GRK2 inhibition in the treatment of FLSs-driven joint destruction in RA.

Abstract Objective Osteoarthritis (OA) is a degenerative joint disease that affects elderly populations worldwide, causing pain and disability. Alteration of the fibroblast-like synoviocytes (FLSs) phenotype leads to an imbalance in the synovial inflammatory microenvironment, which accelerates the progression of OA. Despite this knowledge, the specific molecular mechanisms of the synovium that affect OA are still unclear. Methods Both in vitro and in vivo experiments were undertaken to explore the role of ADAM8 playing in the synovial inflammatory of OA. A small interfering RNA (siRNA) was targeting ADAM8 to intervene. High-throughput sequencing was also used. Results Our sequencing analysis revealed significant upregulation of the MAPK signaling cascade and ADAM8 gene expression in IL-1β-induced FLSs. The in vitro results demonstrated that ADAM8 blockade inhibited the invasion and migration of IL-1β-induced FLSs, while also suppressing the expression of related matrix metallomatrix proteinases (MMPs). Furthermore, our study revealed that inhibiting ADAM8 weakened the inflammatory protein secretion and MAPK signaling networks in FLSs. Mechanically, it revealed that inhibiting ADAM8 had a significant effect on the expression of migration-related signaling proteins, specifically FSCN1. When siADAM8 was combined with BDP-13176, a FSCN1 inhibitor, the migration and invasion of FLSs was further inhibited. These results suggest that FSCN1 is a crucial downstream factor of ADAM8 in regulating the biological phenotypes of FLSs. The in vivo experiments demonstrated that ADAM8 inhibition effectively reduced synoviocytes inflammation and alleviated the progression of OA in rats. Conclusions ADAM8 could be a promising therapeutic target for treating OA by targeting synovial inflammation.

Fibroblast-like synoviocytes (FLS) are important components of the synovial membrane. They can contribute to joint damage through crosstalk with inflammatory cells and direct actions on tissue damage pathways in rheumatoid arthritis (RA). Recent evidence suggests that, compared with FLS in normal synovial tissue, FLS in RA synovial tissue exhibits significant differences in metabolism. Recent metabolomic studies have demonstrated that metabolic changes, including those in glucose, lipid, and amino acid metabolism, exist before synovitis onset. These changes may be a result of increased biosynthesis and energy requirements during the early phases of the disease. Activated T cells and some cytokines contribute to the conversion of FLS into cells with metabolic abnormalities and pro-inflammatory phenotypes. This conversion may be one of the potential mechanisms behind altered FLS metabolism. Targeting metabolism can inhibit FLS proliferation, providing relief to patients with RA. In this review, we aimed to summarize the evidence of metabolic changes in FLS in RA, analyze the mechanisms of these metabolic alterations, and assess their effect on RA phenotype. Finally, we aimed to summarize the advances and challenges faced in targeting FLS metabolism as a promising therapeutic strategy for RA in the future. [ABSTRACT FROM AUTHOR]

Asiatic acid (AA) is generally recognized in the treatment of various diseases and has significant advantages in the treatment of various inflammatory diseases. The treatment of rheumatoid arthritis (RA) with AA is a completely new entry point. RA is a complex autoimmune inflammatory disease, and despite the involvement of different immune and nonimmune cells in the pathogenesis of RA, fibroblast‐like synoviocytes (FLS) play a crucial role in the progression of the disease. si‐Nrf2 was transfected in RA‐FLS and the cells were treated with AA. MTT assay and colony formation assay were used to detect the effect of AA on the viability and formation of clones of RA‐FLS, respectively. Moreover, the apoptosis of RA‐FLS was observed by Hoechst 33342 staining and flow cytometry. Western blot was applied to measure the expression of the Nrf2/HO‐1/NF‐κB signaling pathway‐related proteins. Compared with the control group, RA‐FLS proliferation, and clone formation were significantly inhibited by the increase of AA concentration, and further experiments showed that AA‐induced apoptosis of RA‐FLS. In addition, AA activated the Nrf2/HO‐1 pathway to inhibit NF‐κB protein expression. However, the knockdown of Nrf2 significantly offsets the effects of AA on the proliferation, apoptosis, and Nrf2/HO‐1/NF‐κB signaling pathway of RA‐FLS cells. AA can treat RA by inhibiting the proliferation and inducing the apoptosis of RA‐FLS. The mechanism may be related to the activation of the Nrf2/HO‐1/NF‐κB pathway. [ABSTRACT FROM AUTHOR]

Background: Mammalian STE20-like kinase 1 (MST1) is involved in the occurrence of cancer and autoimmune diseases by regulating cell proliferation, differentiation, apoptosis and other functions. However, its role and downstream targets in rheumatoid arthritis (RA) remain unclear. Methods: The model of RA fibroblast-like synoviocytes (RA-FLSs) overexpressing MST1 was constructed by lentiviral transfection in vitro and analyzed the effects of MST1 on apoptosis, migration, invasion, and inflammation of RA-FLSs. The effect of MST1 on joint synovial membrane inflammation and bone destruction was observed in vivo by establishing a rat model of arthritis with complete Freund's adjuvant. Results: MST1 is down-regulated in RA-FLSs, and up-regulation of MST1 inhibits the survival, migration, invasion and inflammation of RA-FLSs. Mechanistically, MST1 inhibits SIRT3/mTOR-signaling pathway, inducing decreased mitochondrial autophagy and increased mitochondrial fission, resulting in mitochondrial morphological abnormalities and dysfunction, and ultimately increased apoptosis. We have observed that activation of MST1 alleviates synovial inflammation and bone erosion in vivo. Conclusions: MST1 reduces the survival, migration, invasion and inflammation of FLSs by inhibiting the SIRT3/mTOR axis to reduce mitochondrial autophagy and promote mitochondrial division, thereby achieving the potential role of relieving rheumatoid arthritis. [ABSTRACT FROM AUTHOR]

Hyperplasia and migration of fibroblast-like synoviocytes (FLSs) are the key drivers in the pathogenesis of rheumatoid arthritis (RA) and joint destruction. Abundant Yes-associated protein (YAP), which is a powerful transcription co-activator for proliferative genes, was observed in the nucleus of inflammatory FLSs with unknown upstream mechanisms. Using Gene Expression Omnibus database analysis, it was found that Salvador homolog-1 (SAV1), the pivotal negative regulator of the Hippo-YAP pathway, was slightly downregulated in RA synovium. However, SAV1 protein expression is extremely reduced. Subsequently, it was revealed that SAV1 is phosphorylated, ubiquitinated, and degraded by interacting with an important serine-threonine kinase, G protein-coupled receptor (GPCR) kinase 2 (GRK2), which was predominately upregulated by GPCR activation induced by ligands such as prostaglandin E 2 (PGE 2) in RA. This process further contributes to the decreased phosphorylation, nuclear translocation, and transcriptional potency of YAP, and leads to aberrant FLSs proliferation. Genetic depletion of GRK2 or inhibition of GRK2 by paroxetine rescued SAV1 expression and restored YAP phosphorylation and finally inhibited RA FLSs proliferation and migration. Similarly, paroxetine treatment effectively reduced the abnormal proliferation of FLSs in a rat model of collagen-induced arthritis which was accompanied by a significant improvement in clinical manifestations. Collectively, these results elucidate the significance of GRK2 regulation of Hippo-YAP signaling in FLSs proliferation and migration and the potential application of GRK2 inhibition in the treatment of FLSs-driven joint destruction in RA. The interaction of GRK2 promotes the phosphorylation, ubiquitination, and degradation of SAV1, which enhances YAP nuclear translocation and downstream gene expression, and finally promotes the proliferation and migration of FLSs. [Display omitted] [ABSTRACT FROM AUTHOR]

Circular RNAs (circRNAs) play functional roles in rheumatoid arthritis (RA) progression. Fibroblast‐like synoviocytes (RASFs) are the main effectors in RA development. In this study, we explored the function and mechanism of circ_0008410 in RASFs. qRT‐PCR was used to detect the expression of circ_0008410, microRNA‐149‐5p (miR‐149‐5p), and homeodomain‐interacting protein kinase 2 (HIPK2). Cell counting kit‐8, EdU assay, flow cytometry, and transwell assay were performed to evaluate cell proliferation, apoptosis, migration, and invasion. Western blot measured the protein levels of related markers and HIPK2. The levels of IL‐1β, TNF‐α, and IL‐6 were tested by corresponding ELISA kits and Western blot. The combination between miR‐149‐5p and circ_0008410 or HIPK2 was detected by dual‐luciferase reporter assay or RNA immunoprecipitation (RIP) assay. Our data showed that circ_0008410 and HIPK2 were elevated, while miR‐149‐5p was downregulated in RA synovial tissues and RASFs. Circ_0008410 promoted RASF proliferation, migration, invasion, and inflammation while inhibiting apoptosis. MiR‐149‐5p was a target of circ_0008410, and its overexpression could reverse the promoting effects of circ_0008410 on RASF dysfunction. Moreover, miR‐149‐5p could target HIPK2 to suppress RASF proliferation, migration, invasion, and inflammation. Collectively, circ_0008410 promoted RASF dysfunction via miR‐149‐5p/HIPK2, which might provide a potential target for RA therapy. [ABSTRACT FROM AUTHOR]

Objective To observe the expression changes of lymphatic vessel endothelial receptor-1（LYVE1)+ macrophages in the synovial tissues of patients with rheumatoid arthritis （RA） and their inhibitory effects on migration, invasion, and fibroblast-to-myofibroblast transformation （FMT). Methods Immunofluorescence staining was used to qualita‐ tively and quantitatively detect LYVE1 and CD68 in synovial tissues of 45 RA patients and 45 osteoarthritis （OA） pa‐ tients. Human monocytic leukemia THP-1 cells in the logarithmic growth phase were treated with LYVE1 overexpression lentivirus in the culture medium, and LYVE1-expressing THP-1 cells were obtained after 48 h of cultivation. These cells were induced with 100 ng/mL phorbol 12-myristate 13-acetate （PMA） for 48 h to obtain LYVE1+ macrophages. Another portion of THP-1 cells were induced by only 100 ng/mL PMA for 48 h to obtain LYVE1- macrophages. Human rheumatoid arthritis fibroblasts MH7A in the logarithmic growth phase were divided into theLYVE1+ macrophage group and LYVE1- macrophage group, which were added withLYVE1+ macrophages and LYVE1- macrophages, separately. In addition, the cells containing only medium were set as the blank control group. Scratch experiment was performed to observe the migration ability of cells in each group. MH7A cells were divided into groups A, B, and C, which were added withLYVE1+ macrophages, LYVE1- macrophages, and only culture medium, respectively. Transwell invasion experiment was conducted to observe the invasion ability of cells in each group. MH7A cells were divided into the group one, group two, and the blank control group, which were added withLYVE1+ macrophages, LYVE1- macrophages, and only culture medium, respectively. Real-time quantitative PCR was used to detect the mRNA expression of FMT-related genes （COL1A1, fibronectin, α-SMA） in MH7A cells after 48 h of culture. Results The expression locations of LYVE1 and CD68 in the synovial tissues of RA and OA patients overlapped. The relative expression levels of LYVE1 in the synovial tissues of RA and OA patients were 0. 319±0. 033 and 1. 000±0. 159, respectively, with statistically significant difference between these two groups （both P<0. 05). Compared with the LYVE1- macrophage group and the blank control group, theLYVE1+ macro‐ phage group had lower cell scratch healing at 24 and 48 h of cultivation （all P<0. 05). Compared with groups B and C, the number of transmembrane cells in the group A was smaller at 24 h of cultivation （P<0. 05). Compared with groups two and the blank control group, the relative expression levels of COL1A1 mRNA, fibronectin mRNA, and α-SMA mRNA in the group one were lower at 48 h of cultivation （all P<0. 05). ConclusionLYVE1+ macrophages are underexpressed in the synovial tissues of RA patients, andLYVE1+ macrophages can inhibit the migration, invasion, and FMT. [ABSTRACT FROM AUTHOR]

Aim: Rheumatoid arthritis (RA) inflicts chronic joint inflammation, leading to cartilage damage and potential disability. This study delves into the impact of fat mass and obesity‐associated protein (FTO) on the invasion and migration of fibroblast‐like synoviocytes (FLSs) in RA, aiming to identify a novel target for RA treatment. Methods: RA‐FLSs and control‐FLSs from RA patients and healthy controls were isolated and cultured. An FTO overexpression vector was constructed and transfected into RA‐FLSs, with subsequent measurement of FTO, miR‐126‐5p, and FOXO3 expression levels using quantitative real‐time polymerase chain reaction or western blot assays. The proliferation, invasion, and migration capabilities of RA‐FLSs were assessed. The total m6A modification of cellular mRNA was quantified. The interaction between m6A and DiGeorge syndrome critical region 8 (DGCR8) on pri‐miR‐126‐5p was evaluated using methylated RNA immunoprecipitation. The binding relationship between miR‐126‐5p and FOXO3 3′UTR sequence was verified. Results: FTO was downregulated in RA‐FLSs. FTO overexpression inhibited the invasion and migration of RA‐FLSs. FTO reduced the m6A modification level of pri‐miR‐126‐5p in RA‐FLSs, inhibiting miR‐126‐5p expression by reducing the binding of DGCR8 to pri‐miR‐126‐5p. miR‐126‐5p targeted and inhibited FOXO3 expression. Overexpression of miR‐126‐5p or FOXO3 knockdown could partially reverse FTO overexpression's inhibitory effect on the invasion and migration of RA‐FLSs. Conclusion: FTO overexpression curtailed miR‐126‐5p by diminishing the m6A modification level of pri‐miR‐126‐5p, subsequently enhancing FOXO3 expression and restraining the invasion and migration of RA‐FLSs. [ABSTRACT FROM AUTHOR]

The interplay between immune cells/macrophages and fibroblast‐like synoviocytes (FLSs) plays a pivotal role in initiating synovitis; however, their involvement in metabolic disorders, including diabetic osteoarthritis (DOA), is largely unknown. In this study, single‐cell RNA sequencing (scRNA‐seq) is employed to investigate the synovial cell composition of DOA. A significant enrichment of activated macrophages within eight distinct synovial cell clusters is found in DOA synovium. Moreover, it is demonstrated that increased glycolysis in FLSs is a key driver for DOA patients' synovial macrophage infiltration and polarization. In addition, the yes‐associated protein 1 (YAP1)/thioredoxin‐interacting protein (TXNIP) signaling axis is demonstrated to play a crucial role in regulating glucose transporter 1 (GLUT1)‐dependent glycolysis in FLSs, thereby controlling the expression of a series of adhesion molecules such as intercellular adhesion molecule‐1 (ICAM‐1) which may subsequently fine‐tune the infiltration of M1‐polarized synovial macrophages in DOA patients and db/db diabetic OA mice. For treatment, M1 macrophage membrane‐camouflaged Verteporfin (Vt)‐loaded PLGA nanoparticles (MVPs) are developed to ameliorate DOA progression by regulating the YAP1/TXNIP signaling axis, thus suppressing the synovial glycolysis and the infiltration of M1‐polarized macrophages. The results provide several novel insights into the pathogenesis of DOA and offer a promising treatment approach for DOA. [ABSTRACT FROM AUTHOR]

AIM: To observe how total flavonoids of Pterocarya hupehensis Skan （PHSTF） affects the migration and invasion of human rheumatoid fibroblast-like synoviocyte line MH7A. METHODS: The MH7A cells were divided into control group（ without any treatment）, low-, medium- and high-dose（ 6. 25, 12. 5 and 25 mg/L, respectively） PHSTF groups, phosphatidylinositol 3-kinase（ PI3K） inhibitor 740Y-P（ 10 μmol/L） group, and 740Y-P（ 10 μmol/L）+high-dose （25 mg/L） PHSTF group. The viability of the MH7A cells was determined by CCK-8 assay, while the migration and invasion were assessed by scratch and Transwell assays. The protein levels of matrix metalloproteinase-2 （MMP-2）, MMP-9, PI3K, p-PI3K, AKT and p-AKT were detected by Western blot. RESULTS: Compared with control group, the cell viability in PHSTF treatment groups was reduced （P<0. 05）, the cell wound healing area was significantly decreased （P< 0. 01）, migratory and invasive cells in the lower chamber were significantly reduced （P<0. 01）, and the protein expression of MMP-2 and MMP-9 and the ratios of p-PI3K/PI3K and pAKT/AKT were decreased（ P<0. 01）. Compared with highdose PHSTF group, the addition of PI3K/AKT pathway agonist 740Y-P significantly increased the migration and invasion ability of MH7A cells （P<0. 01） and elevated the protein expression of MMP-2 and MMP-9 and the ratios of p-PI3K/PI3K and pAKT/AKT （P<0. 01） under the treatment with PHSTF. CONCLUSION: Total flavonoids of Pterocarya hupehensis Skan could inhibit the migration and invasion of MH7A cells by regulating the PI3K/AKT signaling pathway. [ABSTRACT FROM AUTHOR]

Aim: IL‐38 is a recently discovered inflammatory factor that belongs to the IL‐1 family and has full‐length and truncated forms. Clinical findings demonstrated that serum IL‐38 levels in people with infectious and autoimmune diseases are significantly different from those in healthy people, but the form remains unclear. We are keenly interested in learning more about the regulatory role of full‐length IL‐38 in rheumatoid arthritis (RA), a classic autoimmune disease. Methods: RA‐fibroblast‐like synoviocytes (RA‐FLS) were isolated from six RA patients and stimulated with full‐length IL‐38 to observe IL‐6 and IL‐8 secretion. Then, the migration and invasion functions of FLS were assessed. Next, the protein expressions of the MAPK, NF‐κB, and JAK pathways were evaluated. In addition, we examined the effect of full‐length IL‐38 on FLS functions in the presence of IL‐1β. The function of FLS affected by full‐length IL‐38 was also examined after blocking IL‐1 and IL‐36 receptors. Results: The functions of FLS were activated after the cells were stimulated with full‐length IL‐38. IL‐6 and IL‐8 levels increased with an increase in the full‐length IL‐38 concentration, and full‐length IL‐38 induced the acceleration of FLS migration and invasion functions. In addition, the levels of proteins in the MAPK signaling pathway increased after stimulation with full‐length IL‐38 and depended on its concentration. However, when the FLS were stimulated by IL‐38 and IL‐1β simultaneously, all experiments generated opposite results. Full‐length IL‐38 inhibited FLS function in the presence of IL‐1β. IL‐1R and IL‐36R blockers terminated all effects of full‐length IL‐38 on RA‐FLS. Conclusion: Full‐length IL‐38 activates FLS functions and acts as a promoter in RA, whereas it inhibits FLS functions and acts as an inhibitor of RA in the presence of IL‐1β. The function of full‐length IL‐38 can be blocked by IL‐1Ra and IL‐36Ra. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis is an autoimmune disease characterized by synovium hyperplasia and bone destruction. Macrophage extracellular traps are released from macrophages under various stimuli and may generate stable autoantigen–DNA complexes, as well as aggravate autoantibody generation and autoimmune responses. We aimed to investigate the role of macrophage extracellular traps on the biologic behaviors of rheumatoid arthritis fibroblast-like synoviocytes. Synovial tissues and fibroblast-like synoviocytes were obtained from patients with rheumatoid arthritis. Extracellular traps in synovium and synovial fluids were detected by immunofluorescence, immunohistochemistry, and SYTOX Green staining. Cell viability, migration, invasion, and cytokine expression of rheumatoid arthritis fibroblast-like synoviocytes were assessed by CCK-8, wound-healing assay, Transwell assays, and quantitative real-time polymerase chain reaction, respectively. RNA sequencing analysis was performed to explore the underlying mechanism, and Western blot was used to validate the active signaling pathways. We found that extracellular trap formation was abundant in rheumatoid arthritis and positively correlated to anti-CCP. Rheumatoid arthritis fibroblast-like synoviocytes stimulated with purified macrophage extracellular traps demonstrated the obvious promotion in tumor-like biologic behaviors. The DNA sensor cGAS in rheumatoid arthritis fibroblast-like synoviocytes was activated after macrophage extracellular trap stimuli. RNA sequencing revealed that differential genes were significantly enriched in the PI3K/Akt signaling pathway, and cGAS inhibitor RU.521 effectively reversed the promotion of tumor-like biologic behaviors in macrophage extracellular trap–treated rheumatoid arthritis fibroblast-like synoviocytes and downregulated the PI3K/Akt activation. In summary, our study demonstrates that macrophage extracellular traps promote the pathogenically biological behaviors of rheumatoid arthritis fibroblast-like synoviocytes through cGAS-mediated activation of the PI3K/Akt signaling pathway. These findings provide a novel insight into the pathogenesis of rheumatoid arthritis and the mechanisms of macrophages in modulating rheumatoid arthritis fibroblast-like synoviocyte tumor-like behaviors. [ABSTRACT FROM AUTHOR]

Background: Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to progressive joint damage. Circular RNA (circRNA) can regulate the inflammatory response of fibroblast-like synoviocytes (FLSs) in RA, influencing the disease progression. Paeoniflorin (PF) is the main active ingredient extracted from Paeonia lactiflora and is known for its anti-inflammatory effect. This study aims to explore the potential mechanisms by which hsa_circ_009012 and PF regulate the inflammatory response in RA. Methods: RNA expression of hsa_circ_009012, has-microRNA-1286 (miR-1286), toll-like receptor 4 (TLR4), NOD-like receptor thermal protein domain associated protein 3 (NLRP3) was assessed by real-time quantitative polymerase chain reaction (RT-qPCR) or western blotting (WB). Cell inflammation markers (TNF-α, IL-1β, IL-6) were assessed by RT-qPCR and immunofluorescence (IF). Counting Kit-8 (CCK-8) assay, flow cytometry, and transwell assay were utilized to test cell viability, cell cycle distribution, and migration. Results: Hsa_circ_009012 was highly expressed in RA-FLS. Hsa_circ_009012 over-expression facilitated the inflammation in RA-FLS and was closely associated with the miR-1286/TLR4 axis. Paeoniflorin inhibited inflammation and the expression of hsa_circ_009012 and TLR4, while upregulating the expression of miR-1286 in RA-FLS. Moreover, the upregulation of hsa_circ_009012 reversed the repressive effect of paeoniflorin on RA-FLS progression. Conclusion: Paeoniflorin inhibits the inflammation of RA-FLS via mediating the hsa_circ_009012/miR-1286/TLR4/NLRP3 axis.