Fibroblast-like Synoviocytes Research Articles

Investigation of GPM6B as a novel therapeutic target in Osteoarthritis.

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. 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. 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. Thus, we provided evidence that GPM6B act as a new target associated with OA.

Collagen triple helix repeat-containing 1 protein: an emerging biomarker and its influence on the clinical and sonographic disease severity in Egyptian medicated female rheumatoid arthritis patients

BackgroundRheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease of synovial joints, with a multifactorial etiology. Collagen triple helix repeat-containing 1 protein (CTHRC1) is a biomarker produced by fibroblast-like synoviocytes, which was shown to be highly expressed in RA patients. The study aimed to measure serum CTHRC1 level in female RA patients currently on medical treatment and its influence on the clinical and sonographic severity of the disease.ResultsThe patients’ mean age was 43.39 ± 8.55 years and median RA disease duration of 5.5 (0.33–20) years. RA patients showed significantly higher serum CTHRC1 level [89.71 ng/ml (53.95–353.45)] in comparison to controls [87.38 ng/ml (44.47–110.3)] (U = 430, P = 0.014). Furthermore, higher serum CTHRC1 levels were recorded in seropositive versus seronegative patients (U = 76, P = 0.022) and in RA patients with severe disease activity compared to those with lower disease activity (H = 9.79, P = 0.007). Furthermore, serum CTHRC1 levels were lower in RA patients receiving biological therapy compared to those receiving conventional therapy; however, this difference did not reach statistical significance.Significant positive correlations were found between CTHRC1 and disease activity, acute-phase reactants, serological markers, functional assessment, fatigue, and erosions detected by ultrasound, while a significant negative correlation was recorded between CTHRC1 and duration of biologic intake (rs = − 0.45, P = 0.036). Furthermore, on multivariate linear regression analysis, serum CTHRC1 was the only significant predictor for higher disease activity (P = 0.028, B = 0.009, 95% CI 0.001 to 0.017).ConclusionRA patients showed higher CTHRC1 serum levels compared to healthy controls, especially those with seropositivity and highly active disease. Furthermore, it was positively associated with poor patient functional outcome, fatigability, and erosive findings by ultrasound, thus suggesting that serum CTHRC1 can be a good predictor for high RA disease activity and possibly severity. Moreover, biological therapy could influence serum CTHRC1 levels in these patients.

The Challenges of Local Intra-Articular Therapy

Fibroblast-like synoviocytes (FLSs) are among the main disease-driving players in most cases of monoarthritis (MonoA), oligoarthritis, and polyarthritis. In this review, we look at the characteristics and therapeutic challenges at the onset of arthritis and during follow-up management. In some cases, these forms of arthritis develop into autoimmune polyarthritis, such as rheumatoid arthritis (RA), whereas local eradication of the RA synovium could still be combined with systemic treatment using immunosuppressive agents. Currently, the outcomes of local synovectomies are well studied; however, there is still a lack of a comprehensive analysis of current local intra-articular treatments highlighting their advantages and disadvantages. Therefore, the aim of this study is to review local intra-articular therapy strategies. According to publications from the last decade on clinical studies focused on intra-articular treatment with anti-inflammatory molecules, a range of novel slow-acting forms of steroidal drugs for the local treatment of synovitis have been investigated. As pain is an essential symptom, caused by both inflammation and cartilage damage, various molecules acting on pain receptors are being investigated in clinical trials as potential targets for local intra-articular treatment. We also overview the new targets for local treatment, including surface markers and intracellular proteins, non-coding ribonucleic acids (RNAs), etc.

Fibroblast-like synoviocyte targeting antibodies are associated with failure to reach early and sustained remission or low disease activity after first-line therapy in rheumatoid arthritis

ObjectiveTo discover antibody biomarkers that can predict a lack of response to first-line therapy in rheumatoid arthritis (RA) patients.MethodsTwo RA cDNA phage display libraries were screened for novel antibodies in baseline RA sera from the Care in early RA (CareRA) trial, differentiating between patients who did or did not reach remission after first-line therapy (n=20 each). Antibody reactivity to identified University Hasselt (UH)-RA antigens was validated in baseline samples from 136 additional CareRA participants. The novel antibodies’ potential to predict failure to reach remission or low disease activity (LDA), according to the Disease Activity Score 28-joint C-reactive protein/erythrocyte sedimentation rate (DAS28CRP/ESR) and Clinical/Simplified Disease Activity Index (CDAI/SDAI), was studied by multivariate analyses. The presence of the antibody targets in RA synovial tissue and the fibroblast-like synoviocyte (FLS) cell line SW982 was determined by immunofluorescence.ResultsWe identified antibodies to 41 novel antigens. Antibodies against any of three antigens, UH-RA.305/318/329, discriminated between RA patients not reaching week (w)8 DAS28CRP remission and those that did (36% vs 13%,p=0.0031). In all patients, anti-UH-RA.305/318/329 antibody reactivity was associated with failure to reach week 8 DAS28CRP and DAS28ESR remission (OR 3.63,p=0.0031; OR 2.92,p=0.016; respectively), SDAI/CDAI sustained remission (OR 5.59,p=0.039 for both) and DAS28CRP and DAS28ESR sustained LDA (OR 3.7,p=0.009; OR 2.76,p=0.042; respectively). In rheumatoid factor/anti-citrullinated protein antibody (RF/ACPA) seronegative patients, these antibodies were strongly associated with failure to achieve week 8 DAS28CRP remission (OR 17.3,p=0.0029). Anti-UH-RA.305/329 antibodies were shown to target FLS in RA synovial tissue and SW982 cells.ConclusionWe identified three antibody biomarkers that are associated with failure to achieve remission/LDA after first-line RA therapy.

Sinulariolide Suppresses Inflammation of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis and Mitigates Collagen-Induced Arthritis Symptoms in Mice.

Rheumatoid arthritis (RA) is a systemic inflammatory disease characterized by active polyarthritis, which leads to functional loss and joint deformities. Natural compounds derived from marine organisms are considered valuable immune-modulating agents. This study aimed to assess the anti-inflammatory effect of sinulariolide, a soft coral-derived compound, on RA fibroblast-like synoviocytes and its therapeutic efficacy against collagen-induced arthritis (CIA). To determine the effects of sinulariolide on tumor necrosis factor-alpha (TNF-α)-induced inflammation, MH7A cells pre-treated with 10 ng/mL TNF-α for 24h were treated with sinulariolide. The effect of sinulariolide on proinflammatory cytokine expressions at both the mRNA and protein levels in the MH7A cells was assessed using real-time-polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA). Further, we analyzed the effect of sinulariolide on the activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways using Western blotting and the TransAM NF-κB p65 kit. To comprehensively evaluate the potential application of sinulariolide in the treatment of inflammatory diseases, we used a well-established collagen-induced arthritis (CIA) mouse model. We examined the tissue sections of the ankle joints of the mice, assessed synovial hyperplasia, inflammatory cell infiltration, and cartilage damage, and used ELISA to analyze changes in cytokine expression in the hind paw tissues. MH7A cells treated with sinulariolide showed a notable reduction in the expression of proinflammatory cytokines, which could be due to decreased activation of the MAPK and NF-kB pathways. Additionally, sinulariolide-treated mice showed significantly reduced joint swelling and lower clinical arthritis scores than those in the normal and control groups. Significant reductions in synovial hyperplasia, inflammatory cell infiltration, and cartilage damage were observed in the tissue sections of the ankle joints of the mice treated with sinulariolide. Furthermore, the expression of inflammatory cytokines in the hind paw tissue of the mice treated with sinulariolide was significantly decreased. Sinulariolide inhibited the progression of inflammation in MH7A cells. Sinulariolide treatment significantly reduced clinical arthritis symptoms and histological inflammatory responses in mice with CIA. Sinulariolide may serve as a potential therapeutic agent for RA.

Hidden liver-joint axis: HBV infection causes rheumatoid arthritis via TRAFD1 with imbalance of HBV X protein and trans-ferulic acid

ABSTRACT Background Liver metabolites are involved in the progression of rheumatoid arthritis (RA), indicating a connection between the liver and joints. However, the impact and mechanism of Hepatitis B virus (HBV), a hepatotropic virus, on RA are still unclear. Methods We investigated the correlation between HBV and RA using Mendelian randomization analysis. Single-cell transcriptome analysis was conducted to investigate changes in cell subtypes in synovial tissue of HBV-RA patients. Fibroblast-like synoviocytes (FLS) were used to create a cell model, and the transcriptome was examined to identify the key downstream molecules of FMT regulated by HBx. CIA model was constructed using HBV transgenic, HBx transgenic, and TRADF1 knockout mice to investigate the impact and mechanism of HBV on CIA. Results The results of our study revealed a significant positive correlation between HBV and RA. The functional studies identified a crucial role of fibroblast-myofibroblast transition (FMT) in the progression of RA. The results suggest that HBV-encoded HBx may promote FMT in RA by upregulating TRAFD1. Furthermore, trans-ferulic acid (TFA) was identified by screening for common metabolites in the liver, joints, and peripheral blood using the metabolome and WGCNA. Interestingly, we found that TFA ameliorated HBx-induced RA by suppressing TRAFD1 expression. Conclusions Our study demonstrates that hidden liver-joint axis, an imbalance between TFA and HBx, plays a critical role in HBV-induced RA, which could be a potential strategy for preventing RA development.

Hyaluronic acid modified prussian blue analogs/TiO₂ janus nanostructures through efficient charge separation to enhance photocatalytic-driven dual gas for achieve multimodal treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by the abnormal proliferation of fibroblast-like synoviocytes and changes in the joint synovium, including elevated reactive oxygen species, decreased pH, and reduced oxygen content. In this study, we synthesized a novel nanocomposite material, namely HA-PBA-TiO2 Janus nanocomposite, by in situ etching in prussian blue analogs doped with Co and Ni, followed by the growth of TiO2 nano-flowers and encapsulation in hyaluronic acid. When these janus nanoparticles diffused to the inflammatory sites of RA, they exhibited outstanding photocatalytic water-splitting ability under 660 nm laser irradiation, generating H2 and O2. This capability helps ameliorate the hypoxic microenvironment at RA inflammatory sites by eliminating reactive oxygen species (ROS) and enhancing antioxidation and oxygenation. Furthermore, owing to the doping of Co and Ni, HA-PBA-TiO2 exhibits photothermal conversion capability, which significant damage to FLS upon exposure to 660 nm laser irradiation, thereby controlling their aberrant proliferation. Through a series of in vitro and in vivo experiments, we validated the significant therapeutic efficacy of HA-PBA-TiO2 in treating RA, highlighting its broad prospects for application.

YTHDC1 Regulates the Migration, Invasion, Proliferation, and Apoptosis of Rheumatoid Fibroblast-Like Synoviocytes.

Rheumatoid arthritis (RA), a chronic autoimmune condition, is characterized by persistent synovial inflammation, bone degradation, and progressive joint deterioration. Despite considerable research efforts, the precise molecular mechanism underlying RA remains elusive. This investigation aims to elucidate the potential role and molecular mechanism of N6-methyladenosine (m6A) methylation regulators in the pathogenesis of RA. In this study, we employed bioinformatics tools to elucidate the association between RA and m6A modifications, aiming to identify potential biological markers. We extracted datasets GSE12021, GSE55235, and GSE55457 from the Gene Expression Omnibus (GEO) database for comprehensive analysis. Utilizing differential expression analysis, protein-protein interaction (PPI) analysis, and single-cell sequencing techniques, we identified pivotal hub genes implicated in the pathogenesis of RA. Subsequently, we assessed the correlation between these hub genes and the pathogenesis of RA using Gene Set Enrichment Analysis (GSEA). Both in vivo and in vitro experiments were performed to confirm the expression and functional roles of the identified key hub gene in RA. Differential expression analysis, PPI analysis, and single-cell analysis identified three key hub genes (YTHDC1, YTHDC2, and YTHDF2) associated with RA. GSEA results further revealed that these genes are enriched in pathways associated with inflammatory responses. Subsequent correlation analysis demonstrated a significant negative correlation between YTHDC1 expression and CD8+ T cell levels. Notably, the gene and protein expression levels of YTHDC1 and YTHDF2 were significantly reduced in the synovial tissue of RA patients. Furthermore, silencing YTHDC1 in fibroblast-like synoviocytes (FLSs) significantly inhibited their migration, invasion, proliferation, and induced apoptosis. YTHDC1 may potentially be involved in the pathogenesis of RA through its regulation of migration, invasion, proliferation, and apoptosis in FLSs.

Serum Galectin-3 Level in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-analysis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovial tissue transformation and fibroblast-like synoviocyte (FLS) proliferation. Galectin-3 is gaining attention as a diagnostic and prognostic biomarker for RA diagnosis. Elevated levels of Galectin-3 cause RA[1]FLSs to stimulate and generate proinflammatory agents, contributing to cartilage degradation and osteoclast formation. This systematic review and meta-analysis aimed to evaluate published evidence and support future investigation of Galectin-3 as an early biomarker for RA. A systematic search was performed through four databases, including PubMed, the Web of Science, Scopus, and Embase, to find the studies examining Galectin-3 in individuals with RA compared to healthy controls. The risk of bias was evaluated using the Newcastle-Ottawa Quality Assessment Scale. Random-effects meta-analysis comparing serum/plasma Galectin-3 levels between individuals with RA and healthy control groups was performed to determine the standardized mean differences (SMD) along with 95% confidence intervals. Following the initial search, studies went through screening. 12 studies, involving 773 patients with RA and 411 healthy controls, were included. Meta-analysis of the included studies revealed that individuals with RA had significantly higher levels of circulatory Galectin-3 compared to healthy control groups (SMD 0.957, 95% CI 0.393 to 1.520). Univariable meta-regression showed no significant association between age, publication year, sample size, or the male percentage with effect size. According to the results, Galectin-3 might be useful as a biomarker for RA. To support these findings, further investigations of Galectin-3 as a possible early biomarker of RA is necessary.

N-(4-methoxyphenyl) quinoline-8-sulfonamide reduces the inflammatory response of fibroblast-like synoviocytes by targeting receptor (calcitonin) activity modifying protein 1 in rheumatoid arthritis

BackgroundRheumatoid arthritis (RA) is characterized by chronic inflammation of the synovium of joints. Fibroblast-like synoviocytes (FLS) play an important role in RA pathogenesis. We aimed to investigate the effect of N-(4-methoxyphenyl) quinoline-8-sulfonamide (QS-3g) on the inflammatory response of FLS and explore the potential underlying mechanisms. MethodsWe screened and found that QS-3g exhibits the best anti-inflammatory response against FLS using the CCK8 assay. To investigate the therapeutic effects of QS-3g on K/BxN STA mice, we used H&E staining, immunofluorescence, immunohistochemistry, micro-CT, and other techniques. Additional investigations, including RNA-seq, molecular docking, and CETSA, revealed that QS-3g binds to RAMP1. ResultsAmong a series of 8-quinoline sulfonyl amide derivatives, QS-3g reduced the inflammatory response in TNF-α stimulated FLS, such as the release of interleukin (IL)-1β and IL-6. H&E staining and micro-CT showed that QS-3g inhibited synovial hypertrophy, inflammatory cell infiltration, and bone destruction. RNA-seq and CETSA analyses revealed the targeted inhibition of RAMP1 by QS-3g. Inhibition of RAMP1 expression could reduce IL-6 and IL-1β levels. Compared with RAMP1-si, combined administration of QS-3g and RAMP1-si reduced the TNF-α-induced inflammation in TNF-α stimulated FLS without statistically significant differences. Finally, the results of in vitro experiments showed that QS-3g could restore the balance of Gαi/Gαs by inhibiting Gαi and activating Gαs and up-regulate the expression of cAMP protein, thus inhibiting the RAMP1-mediated inflammatory response in FLS. ConclusionQS-3g could inhibit RAMP1 activity and mediate the Gαs/Gαi–cAMP pathway to reduce FLS inflammatory response. Therefore, QS-3g may serve as a novel anti-inflammatory compound for treating RA.

Methotrexate promotes the release of granulocyte–macrophage colony-stimulating factor from rheumatoid arthritis fibroblast-like synoviocytes via autocrine interleukin-1 signaling

BackgroundActivated fibroblast-like synoviocytes (FLS) are drivers of synovitis and structural joint damage in rheumatoid arthritis (RA). Despite the use of disease-modifying drugs, only about 50% of RA patients reach remission in real-world settings. We used an unbiased approach to investigate the effects of standard-of-care methotrexate (MTX) and a Janus kinase inhibitor, tofacitinib (TOFA), on gene expression in RA-FLS, in order to identify untargeted disease mediators.MethodsPrimary RA-FLS were activated by stimulation with interleukin-1β (IL-1β) or platelet-derived growth factor + IL-1β in the presence or absence of MTX or TOFA, with or without additional inhibitors. Co-cultures of synovial cells were performed in direct and indirect systems. Cells were collected for RNA sequencing or qPCR, and supernatants were analyzed for protein concentrations.ResultsSix thousand three hundred fifty genes were differentially expressed, the majority being upregulated, in MTX-treated activated RA-FLS and 970 genes, the majority being downregulated, in TOFA-treated samples. Pathway analysis showed that MTX had largest effects on ‘Molecular mechanisms of cancer’ and TOFA on ‘Interferon signaling’. Targeted analysis of disease-associated genes revealed that MTX increased the expression of cell cycle-regulating genes but also of pro-inflammatory mediators like IL-1α (IL1A) and granulocyte–macrophage colony-stimulating factor, GM-CSF (CSF2). The MTX-promoted expression of CSF2 in activated RA-FLS peaked at 48 h, could be mediated via either NF-κB or AP-1 transcription factors, and was abrogated by IL-1 inhibitors (IRAK4 inhibitor and anakinra). In a co-culture setting, MTX-treatment of activated RA-FLS induced IL1B expression in macrophages.ConclusionsMTX treatment induces secretion of IL-1 from activated RA-FLS which by autocrine signaling augments their release of GM-CSF. This unexpected effect of MTX might contribute to the persistence of synovitis.

Morinda officinalis iridoid glycosides, as an inhibitor of GSK-3β, alleviates rheumatoid arthritis through inhibition of NF-κB and JAK2/STAT3 pathway.

Morinda officinalis iridoid glycosides (MOIG) showed potential benefits in the treatment of rheumatoid arthritis (RA), but their exact mechanism has yet to be explored. To evaluate the effects of MOIG on RA, and explore the potential targets and molecular mechanism of MOIG in RA. 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)-α 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-3β (GSK-3β). 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-α-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-3β, and inhibition of GSK-3β attenuated the effects of MOIG on FLSs. Knockdown GSK-3β 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-3β. MOIG alleviates joint inflammation in RA through inhibition NF-κB and JAK2/STAT3 pathway via suppression of GSK-3β in FLSs, which provides supports for MOIG as a promising therapeutic agent of RA.

Bone-protective effects of neutralizing angiopoietin-like protein 4 monoclonal antibody in rheumatoid arthritis

Despite recent advances, rheumatoid arthritis (RA) patients remain refractory to therapy. Dysregulated overproduction of angiopoietin-like 4 protein (ANGPTL4) is thought to be contributed to the disease development. ANGPTL4 was initially identified as a regulator of lipid metabolism, which is hydrolyzed to N-terminal (nANGPTL4) and C-terminal (cANGPTL4) fragments in vivo. cANGPTL4 is involved in several non-lipid-related processes, including angiogenesis and inflammation. The present study revealed that the level of ANGPTL4 was markedly elevated in the sera and synovial tissues from patients with RA versus controls. The administration of a neutralizing antibody against cANGPTL4 (anti-cANGPTL4 Ab) resulted in the inhibition of inflammatory processes and bone loss in animal models of collagen-induced arthritis (CIA) and adjuvant-induced arthritis (AIA). Transcriptomic and proteomic profiling of synovial tissues from AIA model indicated that the anti-cANGPTL4 Ab inhibited fibroblast-like synoviocytes (FLS) immigration and inflammatory-induced osteoclastogenesis. Mechanistically, the anti-cANGPTL4 Ab has been shown to inhibit TNF-α-induced inflammatory cascades in RA-FLS through the sirtuin 1/nuclear factor-κB signaling pathway. Moreover, the anti-cANGPTL4 Ab was found to block FLS invasion- and immigration-induced osteoclast activation. Collectively, these findings identify ANGPTL4 as a prospective biomarker for the diagnosis of RA, and targeting cANGPTL4 may represent a potential therapeutic strategy.

The role of non-coding RNAs in fibroblast-like synoviocytes in rheumatoid arthritis.

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.

Another Notch in the Belt of Rheumatoid Arthritis.

Notch ligands and receptors, including JAG1/2, DLL1/4, and Notch1/3, are enriched on macrophages (MΦs), fibroblast-like synoviocytes (FLS), and/or endothelial cells in rheumatoid arthritis (RA) compared with normal synovial tissues (ST). Power Doppler ultrasound-guided ST studies reveal that the Notch family is highly involved in early active RA, especially during neovascularization. In contrast, the Notch family is not implicated during the erosive stage, evidenced by their lack of correlation with radiographic damage in RA ST. Toll-like receptors and tumor necrosis factor (TNF) are the common inducers of Notch expression in RA MΦs, FLS, and endothelial cells. Among Notch ligands, JAG1 and/or DLL4 are most inducible by inflammatory responses in RA MΦs or endothelial cells and transactivate their receptors on RA FLS. TNF plays a central role on Notch ligands, as anti-TNF good responders display JAG1/2 and DLL1/4 transcriptional downregulation in RA ST myeloid cells. In in vitro studies, TNF increases Notch3 expression in MΦs, which is further amplified by RA FLS addition. Specific disease-modifying antirheumatic drugs reduced JAG1 and Notch3 expression in MΦ and RA FLS cocultures. Organoids containing FLS and endothelial cells have increased expression of JAG1 and Notch3. Nonetheless, Methotrexate, interleukin-6 receptor (IL-6R) antibodies, and B cell blockers are mostly ineffective at decreasing Notch family expression. NF-κB, MAPK, and AKT pathways are involved in Notch signaling, whereas JAK/STATs are not. Although Notch blockade has been effective in RA preclinical studies, its small molecule inhibitors have failed in phase Iand II studies, suggesting that alternative strategies may be required to intercept their function.

SPHK2 Knockdown Inhibits the Proliferation and Migration of Fibroblast-Like Synoviocytes Through the IL-17 Signaling Pathway in Osteoarthritis.

Synovial inflammation is vital for the progression of osteoarthritis (OA). The objective of this study was to explore the effects and potential molecular mechanisms of sphingosine kinase 2 (SPHK2) on the proliferation and migration of fibroblast-like synoviocytes (FLS). A TNF-α-stimulated FLS model and a papain-induced OA rat model were constructed. The functions of SPHK2 knockdown in OA were explored by a series of in vivo and in vitro assays.Downstream target genes of SPHK2 were investigated using transcriptome sequencing and validated by reverse transcription quantitative PCR (RT-qPCR). The effects of the SPHK2/IL-17 signaling pathway on inflammation, proliferation, and migration of OA-FLS were investigated using the IL-17 pathway inhibitor (secukinumab) and the activator (rhIL-17A). TNF-α stimulation promoted SPHK2 expression at mRNA and protein levels in OA-FLS. SPHK2 knockdown reduced IL-1β, IL-6, MMP-2, MMP-9, cyclinD1, and PCNA levels and suppressed proliferation and migration of OA-FLS. SPHK2 knockdown alleviated cartilage damage and synovial inflammation in the OA rat model. LRRIQ3, H4C8, CXCL1, CABP4, COL23A1, and PROK2 expression levels were regulated by SPHK2. SPHK2 knockdown inhibited the protein levels of IL-17A, IL-17RA, and Act1. The IL-17 pathway inhibitor secukinumab enhanced the inhibitory effect of SPHK2 knockdown on the proliferation and migration of OA-FLS, while the IL-17 pathway activator rhIL-17A exerted the opposite effect. SPHK2 knockdown inhibits proliferation and migration of OA-FLS by blocking the IL-17 pathway, which provides a novel approach to the OA treatment.

Study of the mechanism of fibroblast-like synoviocytes-derived exosomes inducing macrophages M1 polarization and CD8+T cells immune regulation ferroptosis and autophagy in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects the joints. The pathogenesis of RA is complex, involving membrane lipid antioxidant systems, oxidative stress, and lipid peroxidation. In this study, it was found that cysteine dioxygenase 1 (CDO1) is significantly upregulated in RA fibroblast-like synoviocytes (RA-FLS) and that exosomes derived from these RA-FLS deliver CDO1 to promote M1 polarization of macrophages, thus facilitating RA progression. In the immune microenvironment, CD8+T cells play a role in immune regulation by producing cytokines such as interferon gamma (IFNγ) in various diseases. The results of this study suggested that in RA-FLS, CD8+T cells deliver IFNγ, which not only inhibits the viability of RA-FLS but also affects glutathione (GSH) through CDO1, regulating the GPX4 antioxidant signaling pathway to promote ferroptosis and autophagy in cells. It was also discovered that IFNγ enhances the expression of TRI69, ubiquitinates and degrades FSP1, thereby forming a cooperative regulation process of GPX4 and FSP1 in ferroptosis. These findings provide a new direction for the treatment of RA.

Amentoflavone Induces Ferroptosis to Alleviate Proliferation, Migration, Invasion and Inflammation in Rheumatoid Arthritis Fibroblast-like Synoviocytes by Inhibiting PIN1.

Rheumatoid arthritis (RA) is a systemic autoimmune disease that is prevalent worldwide and seriously threatens human health. RA-fibroblast-like synoviocytes (FLS) play important roles in almost all aspects of RA progression. This study aimed to study the effect of Amentoflavone (AMF), a polyphenol compound derived from extracts of Selaginella tamariscina, on the abnormal biological behaviors of RA-FLS. The immortalized human RA-FLS cell line (MH7A) was treated with AMF or transfected with small interfering RNAs (siRNAs) targeting peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1). Then, cell viability was detected by CCK-8 assay. EDU staining, wound healing and transwell assays were employed to measure the capacities of MH7A cell proliferation, migration and invasion. The levels of inflammatory factors were assessed using ELISA kits. Additionally, ferroptosis was analyzed by detecting Fe2+ content, lipid reactive oxygen species (ROS) level and expression of ferroptosis-related proteins. Pull-down assay was employed to verify the targeted binding of AMF to PIN1. Further, PIN1 overexpression or ferroptosis inhibitor Ferrostatin-1 (Fer-1) addition was conducted to elucidate the regulatory mechanism of AMF on PIN1 and ferroptosis. Results revealed that AMF intervention or PIN1 knockdown inhibited the proliferation, migration, invasion and inflammation in MH7A cells. AMF facilitated lipid peroxidation and ferroptosis in MH7A cells. Moreover, AMF targeted inhibition of PIN1 expression, and PIN1 overexpression restored the promoting effect of AMF on lipid peroxidation and ferroptosis in MH7A cells. Besides, Fer-1 reversed the impacts of AMF on the abnormal biological behaviors of MH7A cells. In summary, AMF induced ferroptosis to inhibit the proliferation, migration, invasion and inflammation in RA-FLS by inhibiting PIN1, providing a promising candidate for RA treatment.

The Role of MicroRNAs and Stem cells in Rheumatoid Arthritis: A Therapeutic and Diagnostic Approach.

In autoimmune illnesses like Rheumatoid Arthritis (RA), the synovium is constantly inflamed, and joints are ruptured. It is becoming increasingly clear that stem cells, especially notably mesenchymal stem cells (MSCs) and microRNAs (miRNAs), play important roles in the onset and amelioration of RA. There is mounting evidence from both animal and human studies that suggests a potentially safe and effective method to treat RA and other intractable diseases by reducing chronic inflammation and spurring tissue regeneration through the transplantation of multipotent adult stem cells, such as mesenchymal stromal/stem cells. To control gene expression, which impacts immune cell differentiation and inflammatory pathways, microRNAs (miRNAs) are crucial, even though MSCs can self-renew and modify inflammatory reactions. The pathophysiology of RA is marked by the dysregulation of immunological responses and the proliferation of fibroblast-like synoviocytes, which are linked to the aberrant expression of specific microRNAs (miRNAs). This study mainly aims to examine the therapeutic implications of these microRNAs (miRNAs) in relation to RA, as they can function as diagnostic and prognostic indicators. This study explores the functions of microRNAs (miRNAs) and stem cells in rheumatoid arthritis (RA), drawing attention to the relevance of these biological processes and the potential for creating novel therapeutic strategies to improve patient outcomes.

Diminished expression of the ubiquitin-proteasome system in early treatment-naïve patients with rheumatoid arthritis and concomitant type 2 diabetes may be linked to IL-1 pathway hyper-activity; results from PEAC cohort

ObjectiveBased on the recent evidence of IL-1 inhibition in patients with rheumatoid arthritis (RA) and concomitant type 2 diabetes (T2D), we evaluated the synovial tissue expression of IL-1 related genes in relationship to the ubiquitin–proteasome system and the effects of insulin on ubiquitinated proteins in fibroblast-like synoviocytes (FLSs).MethodsThe synovial expression of IL-1 pathway genes was compared in early (< 1 year) treatment-naïve RA patients with T2D (RA/T2D n = 16) and age- and sex-matched RA patients without T2D (n = 16), enrolled in the Pathobiology of Early Arthritis Cohort (PEAC). The synovial expression of ubiquitin in macrophages and synovial lining fibroblasts was also assessed by Immunohistochemistry/immunofluorescence and correlated with synovial pathotypes. Finally, FLSs from RA patients (n = 5) were isolated and treated with human insulin (200 and 500 nM) and ubiquitinated proteins were assessed by western blot.ResultsSynovial tissues of RA/T2D patients were characterised by a consistent reduced expression of ubiquitin–proteasome genes. More specifically, ubiquitin genes (UBB, UBC, and UBA52) and genes codifying proteasome subunits (PSMA2, PSMA6, PSMA7, PSMB1, PSMB3, PSMB4, PSMB6, PSMB8, PSMB9, PSMB10, PSMC1, PSMD9, PSME1, and PSME2) were significantly lower in RA/T2D patients. On the contrary, genes regulating fibroblast functions (FGF7, FGF10, FRS2, FGFR3, and SOS1), and genes linked to IL-1 pathway hyper-activity (APP, IRAK2, and OSMR) were upregulated in RA/T2D. Immunohistochemistry showed a significant reduction of the percentage of ubiquitin-positive cells in synovial tissues of RA/T2D patients. Ubiquitin-positive cells were also increased in patients with a lympho-myeloid pathotype compared to diffuse myeloid or pauci-immune-fibroid. Finally, in vitro experiments showed a reduction of ubiquitinated proteins in RA-FLSs treated with a high concentration of insulin (500 nM).ConclusionsA different IL-1 pathway gene expression was observed in the synovial tissues of early treatment-naïve RA/T2D patients, linked to decreased expression of the ubiquitin–proteasome system. These findings may provide a mechanistic explanation of the observed clinical benefits of IL-1 inhibition in patients with RA and concomitant T2D.