Deconvolution of synovial myeloid cell subsets across pathotypes and role of COL3A1+ macrophages in rheumatoid arthritis remission.

Background: Monocyte/macrophage (Mo/Mp) is a critical cell population involved in immune modulation of rheumatoid synovitis (RA) across different pathotypes. This study aims to investigate the contribution of Mo/Mp clusters to RA activity, and the biological function of particular subtypes in RA remission. Methods: We integrated single-cell RNA sequencing datasets from 4 published and 1 in-house studies using Liger selected by comparison. We estimated the abundance of Mo/Mp subtypes in bulk RNA-seq data from the 81 patients of the Pathobiology of Early Arthritis Cohort (PEAC) using deconvolution analysis. Correlations between Mo/Mp subtypes and RA clinical metrics were assessed. A particular cell type was identified using multicolor immunofluorescence and flow cytometry in vivo and successfully induced from a cell line in vitro. Potential immune modulation function of it was performed using immunohistochemical staining, adhesion assay, and RT-qPCR. Results: We identified 8 Mo/Mp clusters. As a particular subtype among them, COL3A1+ Mp (CD68+, COL3A1+, ACTA2-) enriched in myeloid pathotype and negatively correlated with RA severity metrics in all pathotypes. Flow cytometry and multicolor immunofluorescence evidenced the enrichment and M2-like phenotype of COL3A1+ Mp in the myeloid pathotype. Further assays suggested that COL3A1+ Mp potentially attenuates RA severity via expressing anti-inflammatory cytokines, enhancing Mp adhesion, and forming a physical barrier at the synovial lining. Conclusion: This study reported unexplored associations between different pathologies and myeloid cell subtypes. We also identified a fibroblast-and-M2-like cluster named COL3A1+ Mp, which potentially contributes to synovial immune homeostasis. Targeting the development of COL3A1+ Mp may hold promise for inducing RA remission.

Macrophage-derived mir-100-5p orchestrates synovial proliferation and inflammation in rheumatoid arthritis through mTOR signaling.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by synovial inflammation, causing substantial disability and reducing life quality. While macrophages are widely appreciated as a master regulator in the inflammatory response of RA, the precise mechanisms underlying the regulation of proliferation and inflammation in RA-derived fibroblast-like synoviocytes (RA-FLS) remain elusive. Here, we provide extensive evidence to demonstrate that macrophage contributes to RA microenvironment remodeling by extracellular vesicles (sEVs) and downstream miR-100-5p/ mammalian target of rapamycin (mTOR) axis. RESULTS: We showed that bone marrow derived macrophage (BMDM) derived-sEVs (BMDM-sEVs) from collagen-induced arthritis (CIA) mice (cBMDM-sEVs) exhibited a notable increase in abundance compared with BMDM-sEVs from normal mice (nBMDM-sEVs). cBMDM-sEVs induced significant RA-FLS proliferation and potent inflammatory responses. Mechanistically, decreased levels of miR-100-5p were detected in cBMDM-sEVs compared with nBMDM-sEVs. miR-100-5p overexpression ameliorated RA-FLS proliferation and inflammation by targeting the mTOR pathway. Partial attenuation of the inflammatory effects induced by cBMDM-sEVs on RA-FLS was achieved through the introduction of an overexpression of miR-100-5p. CONCLUSIONS: Our work reveals the critical role of macrophages in exacerbating RA by facilitating the transfer of miR-100-5p-deficient sEVs to RA-FLS, and sheds light on novel disease mechanisms and provides potential therapeutic targets for RA interventions.

Lovastatin impairs cellular proliferation and enhances hyaluronic acid production in fibroblast-like synoviocytes.

INTRODUCTION: Statins have demonstrated chondroprotective effects by reducing inflammation and mitigating extracellular matrix degradation. However, statins are also reported to be cytotoxic to several types of cells. Early-onset osteoarthritis (OA) is characterized by synovial inflammation, which adversely affects hyaluronan (HA) production in fibroblast-like synoviocytes (FLSs). Nevertheless, the precise effects of statins on the synovium remain unclear. METHODS: This study investigated the impact of lovastatin on human FLSs, and HA secretion-related genes, signaling pathways, and production were evaluated. RESULTS: The findings revealed that high doses of lovastatin (20 or 40 µM) decreased FLS viability and increased cell death. FLS proliferation ceased when cultured in a medium containing 5 or 10 µM lovastatin. mRNA expression analysis demonstrated that lovastatin (5 and 10 µM) upregulated the gene level of hyaluronan synthase 1 (HAS1), HAS2, and proteoglycan 4 (PRG4), but not HAS3. While the expression of multidrug resistance-associated protein 5 transporter gene remained unaffected, both inward-rectifying potassium channel and acid-sensing ion channel 3 were upregulated. Western blot further confirmed that lovastatin increased the production of HAS1 and PRG4, and activated the PKC-α, ERK1/2, and p38-MAPK signaling pathways. Additionally, lovastatin elevated intracellular cAMP levels and HA production in FLSs. CONCLUSION: Lovastatin impairs cellular proliferation but enhances HA production in human FLSs.

METTL3 knockdown suppresses RA-FLS activation through m6A-YTHDC2-mediated regulation of AMIGO2.

The dysregulation of N6-methyladenosine (m6A) on mRNAs is involved in the pathogenesis of rheumatoid arthritis (RA). Methyltransferase-like 3 (METTL3), serving as a central m6A methyltransferase, is highly expressed in macrophages, synovial tissues and RA fibroblast-like synoviocytes (RA-FLS) of RA patients. However, METTL3-mediated m6A modification on target mRNAs and the molecular mechanisms involved in RA-FLS remain poorly defined. Our research demonstrated that METTL3 knockdown decreased the proliferation, migratory and invasive abilities of RA-FLS. Notably, we identified the adhesion molecule with Ig like domain 2 (AMIGO2) as a probable downstream target of both METTL3 and YTH Domain Containing 2 (YTHDC2) in RA-FLS. We revealed that AMIGO2 augmented the activation of RA-FLS and can potentially reverse the phenotypic effects induced by the knockdown of either METTL3 or YTHDC2. Mechanistically, METTL3 knockdown decreased m6A modification in the 5'-untranslated region (5'UTR) of AMIGO2 mRNA, which diminished its interaction with YTHDC2 in RA-FLS. Our findings unveiled that silencing of METTL3 inhibited the proliferation and aggressive behaviors of RA-FLS by downregulating AMIGO2 expression in an m6A-YTHDC2 dependent mechanism, thereby underscoring the pivotal role of the METTL3-m6A-YTHDC2-AMIGO2 axis in modulating RA-FLS phenotypes.

Brucine alleviates fibroblast-like synoviocytes dysfunction and inflammation by regulating YY1 during rheumatoid arthritis.

Brucine is a weak alkaline indole alkaloid with wide pharmacological activities and has been identified to protect against rheumatoid arthritis (RA) process. Circular RNAs (circRNAs) are also reported to be involved in the pathogenesis of RA. Here, we aimed to probe the role and mechanism of Brucine and circ_0139658 in RA progression. The fibroblast-like synoviocytes of RA (RA-FLSs) were isolated for functional analysis. Cell proliferation, apoptosis, invasion, migration, as well as inflammatory response were evaluated by CCK-8 assay, EdU assay, flow cytometry, transwell assay, and ELISA analysis, respectively. qRT-PCR and western blotting analyses were utilized to measure the levels of genes and proteins. The binding between miR-653-5p and circ_0139658 or Yin Yang 1 (YY1), was verified using dual-luciferase reporter and RNA pull-down assays. Brucine suppressed the proliferation, migration, and invasion of RA-FLSs, and alleviated inflammation by reducing the release of pro-inflammatory factors and macrophage M1 polarization. RA-FLSs showed increased circ_0139658 and YY1 levels and decreased miR-653-5p levels. Circ_0139658 is directly bound to miR-653-5p to regulate YY1 expression. Brucine treatment suppressed circ_0139658 and YY1 expression but increased YY1 expression in RA-FLSs. Functionally, circ_0139658 overexpression reversed the suppressing effects of Brucine on RA-FLS dysfunction and inflammation. Moreover, circ_0139658 silencing alleviated the dysfunction and inflammation in RA-FLSs, which were reverted by YY1 overexpression. Brucine suppressed the proliferation, migration, invasion, and inflammation in RA-FLSs by decreasing YY1 via circ_0139658/miR-653-5p axis.

Asiatic acid inhibits rheumatoid arthritis fibroblast-like synoviocyte growth through the Nrf2/HO-1/NF-κB signaling pathway.

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.

Metabolic changes in fibroblast-like synoviocytes in rheumatoid arthritis: state of the art review.

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.

LncRNA HOTTIP regulates TLR4 promoter methylation by recruiting H3K4 methyltransferase MLL1 to affect apoptosis and inflammatory response of fibroblast-like synoviocyte in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease, and the role of HOXA transcript at the distal tip (HOTTIP) in its pathogenesis remains underexplored. This study investigates the mechanism by which HOTTIP influences apoptosis and the inflammatory response of fibroblast-like synoviocytes (FLS). An RA mouse model was established, and clinical scores were analyzed. Pathological changes in synovial tissues, bone mineral density (BMD) of the paws, serum tartrate-resistant acid phosphatase (TRAP) activity, and TNF-α and IL-1ß levels were assessed. FLS were transfected, and cell proliferation and apoptosis were examined. The RNA-pull-down assay determined HOTTIP's interaction with mixed-lineage leukemia 1 (MLL1), while RNA immunoprecipitation assay measured HOTTIP expression pulled down by MLL1. The levels of MLL1 and toll-like receptor 4 (TLR4) after MLL1 overexpression based on HOTTIP silencing were determined. Chromatin immunoprecipitation (ChIP) was performed with H3K4me3 as an antibody, followed by the evaluation of TLR4 expression. HOTTIP expression was elevated in RA mouse synovial tissues. Inhibition of HOTTIP led to reduced clinical scores, inflammatory infiltration, synovial hyperplasia, TRAP activity, and TNF-α and IL-1ß levels, along with increased BMD. In vitro Interference with HOTTIP suppressed RA-FLS apoptosis and inflammation. HOTTIP upregulated TLR4 expression by recruiting MLL1 to facilitate TLR4 promoter methylation. MLL1 overexpression reversed HOTTIP silencing-mediated repression of RA-FLS apoptosis. Activation of H3K4 methylation counteracted HOTTIP knockout, ameliorating the inflammatory response. HOTTIP regulates TLR4 expression by recruiting MLL1, leading to TLR4 promoter methylation, thereby suppressing RA-FLS proliferation and inducing cell apoptosis and inflammatory response in RA.

LIGHT regulated gene expression in rheumatoid synovial fibroblasts.

BACKGROUND: Synovial hyperplasia caused by rheumatoid arthritis (RA), an autoimmune inflammatory disease, leads to the destruction of the articular cartilage and bone. A member of the tumor necrosis factor superfamily, Lymphotoxin-related inducible ligand that competes for glycoprotein D binding to herpes virus entry mediator on T cells (LIGHT) has been shown to correlate with the pathogenesis of RA. METHODS: We used cDNA microarray analysis to compare the expression of genes in rheumatoid fibroblast-like synoviocytes with and without LIGHT stimulation. RESULTS: Significant changes in gene expression (P-values < 0.05 and fold change ≥ 2.0) were associated mainly with biological function categories of glycoprotein, glycosylation site as N-linked, plasma membrane part, integral to plasma membrane, intrinsic to plasma membrane, signal, plasma membrane, signal peptide, alternative splicing, and topological domain as extracellular. CONCLUSIONS: Our results indicate that LIGHT may regulate the expression in RA-FLS of genes which are important in the differentiation of several cell types and in cellular functions.

Fibroblast-like synoviocytes-derived exosomal circFTO deteriorates rheumatoid arthritis by enhancing N6-methyladenosine modification of SOX9 in chondrocytes.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic inflammatory disease that causes disability worldwide. Exosomes released by fibroblast-like synoviocytes in RA (RA-FLSs-Exos) play a role in the development of RA, and circular RNAs (circRNAs) are important for RA progression. This study aimed to investigate the molecular mechanisms underlying the effects of RA-FLSs-Exos in RA and identify the potential pathway responsible for these effects. METHODS: We initially conducted microarray analysis to identify dysregulated circRNAs in exosomes associated with RA. We then co-cultured isolated RA-FLSs-Exos with chondrocytes to examine their role in RA. In vivo experiments were performed using collagen-induced arthritis mouse models, and circFTO knockdown was achieved through intra-articular injection of AAV5 vectors. RESULTS: Our findings revealed increased expression of circFTO in both RA-FLSs-Exos and synovial tissues from patients with RA. Exosomal circFTO hindered chondrocyte proliferation, migration, and anabolism while promoting apoptosis and catabolism. Mechanistically, we discovered that circFTO facilitates the formation of methyltransferases complex to suppress SRY-related high-mobility group box 9 (SOX9) expression with assistance from YTH domain family 2 (YTHDF2) through an m6A-dependent mechanism. Furthermore, inhibition of circFTO improved symptoms of RA in vivo. CONCLUSION: Taken together, our study demonstrates that exosomal circFTO derived from FLSs contributes to the progression of RA by targeting SOX9. These findings highlight a promising target for treating RA.

FNDC4 reduces inflammation, proliferation, invasion and migration of rheumatoid synovial cells by inhibiting CCL2/ERK signaling.

BACKGROUND: Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic joint inflammation. Fibronectin type III domain-containing protein 4 (FNDC4) is a secretory factor that can regulate inflammatory diseases. However, the role of FNDC4 in RA has not been reported so far. METHODS: The expression of FNDC4 in synovial tissues of RA was analyzed by GEO database (GSE55235 dataset). Then, the expression of FNDC4 in RA fibroblast-like synoviocytes (RA-FLSs) was detected by RT-qPCR and western blot. After constructing FNDC4 overexpression plasmid, cell proliferation and apoptosis were detected. Wound healing and transwell assays were used to detect cell migration and invasion. Then we examined the expression of cytokines related to cell inflammation. Subsequently, the regulatory mechanism of FNDC4 was further discussed. We detected the expression of CCL2 and ERK signaling pathway related proteins downstream of FNDC4. Finally, the mechanism was discussed through the overexpression of FNDC4 and CCL2 and the addition of ERK pathway activator tBHQ. RESULTS: GEO database showed that FNDC4 expression decreased in synovial tissues of RA. FNDC4 expression was also decreased in RA-FLSs. Overexpression of FNDC4 inhibited the proliferation, invasion and migration of RA-FLSs whereas promoted the cellapoptosis. Overexpression of FNDC4 inhibited the release of inflammatory factors in RA-FLSs. The regulatory effect of FNDC4 is achieved by inhibiting the CCL2/ERK signaling pathway. CONCLUSION: FNDC4 reduces inflammation, proliferation, invasion and migration of RA-FLSs in RA by inhibiting CCL2/ERK signaling.

Nitazoxanide reduces inflammation and bone erosion in mice with collagen-induced arthritis via inhibiting the JAK2/STAT3 and NF-κB pathways in fibroblast-like synoviocytes.

Our recent study showed that Nitazoxanide (NTZ), an FDA-approved anti-parasitic drug, prevents ovariectomy-induced bone loss by inhibiting osteoclast activity. However, there have been no investigations to determine whether NTZ has preventive potential in other bone resorbing diseases, especially rheumatoid arthritis (RA). In this study, the primary RA fibroblast-like synoviocytes (RA-FLS) and collagen-induced arthritis (CIA) murine model were used to evaluate the effect of NTZ. The results showed that NTZ potently inhibited proliferation, migration and invasion capacity of RA-FLS in a dose dependent manner by restraining cell entry into S phases, without induction of cell apoptosis. NTZ obviously reduced spontaneous mRNA expression of IL-1ß, IL-6 and RANKL, as well as TNF-α-induced transcription of the IL-1ß, IL-6, and MMP9 genes. In terms of molecular mechanism, NTZ significantly inhibited the basal or TNF-α-induced activation of JAK2/STAT3 (T705) and NF-κB pathway, but not MAPK and STAT3 (S727) phosphorylation. Moreover, NTZ ameliorated synovial inflammation and bone erosion in CIA mice through reducing the production of inflammatory mediators and osteoclast formation, respectively. Collectively, our findings indicate that NTZ exhibits anti-inflammatory and anti-erosive effects both ex vivo and in vivo, which provides promising evidence for the therapeutic application of NTZ as a novel therapeutic agent for RA.

EPO promotes the progression of rheumatoid arthritis by inducing desialylation via increasing the expression of neuraminidase 3.

OBJECTIVE: Erythropoietin (EPO) known as an erythrocyte-stimulating factor is increased in patients with rheumatoid arthritis (RA). Nevertheless, the function of EPO in the process of RA and relative mechanism needs to be further clarified. METHODS: The level of EPO in serum and synovial fluid from patients with RA and healthy controls was determined by . Collagen-induced arthritis (CIA) mice were constructed to confirm the role of EPO on RA pathogenesis. Differentially expressed genes (DEGs) of EPO-treated fibroblast-like synoviocyte (FLS) were screened by transcriptome sequencing. The transcription factor of neuraminidase 3 (NEU3) of DEGs was verified by double luciferase reporting experiment, DNA pulldown, electrophoretic mobility shift assay and chromatin immunoprecipitation-quantitative PCR (qPCR) assay. RESULTS: The overexpression of EPO was confirmed in patients with RA, which was positively associated with Disease Activity Score 28-joint count. Additionally, EPO intervention could significantly aggravate the joint destruction in CIA models. The upregulation of NEU3 was screened and verified by transcriptome sequencing and qPCR in EPO-treated FLS, and signal transducer and activator of transcription 5 was screened and verified to be the specific transcription factor of NEU3. EPO upregulates NEU3 expression via activating the Janus kinase 2 (JAK2)-STAT5 signalling pathway through its receptor EPOR, thereby to promote the desialylation through enhancing the migration and invasion ability of FLS, which is verified by JAK2 inhibitor and NEU3 inhibitor. CONCLUSION: EPO, as a proinflammatory factor, accelerates the process of RA through transcriptional upregulation of the expression of NEU3 by JAK2/STAT5 pathway.

Synovial microenvironment-influenced mast cells promote the progression of rheumatoid arthritis.

Mast cells are phenotypically and functionally heterogeneous, and their state is possibly controlled by local microenvironment. Therefore, specific analyses are needed to understand whether mast cells function as powerful participants or dispensable bystanders in specific diseases. Here, we show that degranulation of mast cells in inflammatory synovial tissues of patients with rheumatoid arthritis (RA) is induced via MAS-related G protein-coupled receptor X2 (MRGPRX2), and the expression of MHC class II and costimulatory molecules on mast cells are upregulated. Collagen-induced arthritis mice treated with a combination of anti-IL-17A and cromolyn sodium, a mast cell membrane stabilizer, show significantly reduced clinical severity and decreased bone erosion. The findings of the present study suggest that synovial microenvironment-influenced mast cells contribute to disease progression and may provide a further mast cell-targeting therapy for RA.

Whether full-length IL-38 acts as a promoter or inhibitor in activating rheumatoid arthritis fibroblast-like synoviocytes depends on IL-1ß.

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-1ß. 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-1ß simultaneously, all experiments generated opposite results. Full-length IL-38 inhibited FLS function in the presence of IL-1ß. 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-1ß. The function of full-length IL-38 can be blocked by IL-1Ra and IL-36Ra.

ADAM8 silencing suppresses the migration and invasion of fibroblast-like synoviocytes via FSCN1/MAPK cascade in osteoarthritis.

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-1ß-induced FLSs. The in vitro results demonstrated that ADAM8 blockade inhibited the invasion and migration of IL-1ß-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.

circTldc1 increases Tldc1 expression by targeting miR-485-5p to promote fibroblast-like synoviocytes proliferation in collagen-induced arthritis.

Abnormalities in the function of fibroblast-like synoviocytes (FLSs) are crucial factors leading to joint damage of rheumatoid arthritis. In recent years, the role of circular RNA (circRNA) in RA has gradually been revealed. However, the functional regulation of FLSs mediated by circRNA and its potential mechanisms remain unclear. In this study, we elucidated the expression profile of circRNA in FLSs, as well as the role and molecular mechanisms of circTldc1. Through sequencing and validation experiments on primary FLSs derived from collagen-induced arthritis (CIA) rats, we found that circTldc1 can promote FLSs proliferation and exacerbate CIA-induced joint damage. The data revealed that circTldc1's parent gene, Tldc1, is homologous to human Tldc1, and circTldc1 is located in the cytoplasm of FLSs, belonging to the exonic circRNA category. The results from bioinformatics analysis, molecular experiments on FLSs (manipulating circTldc1 expression in vitro), and animal experiments (local regulation of circTldc1 expression in vivo) collectively confirmed that circTldc1 promotes Tldc1 expression by targeting miR-485-5p. High expression of Tldc1 further enhances FLSs proliferation and inflammatory responses, thereby worsening joint damage in CIA rats. High expression of circTldc1 and its parent gene Tldc1 may serve as biomarkers for RA. Local regulation of circTldc1 and Tldc1 gene levels in the joint cavity may represent a potential strategy to improve joint damage and inflammation in RA.

Targeting YAP1-regulated Glycolysis in Fibroblast-Like Synoviocytes Impairs Macrophage Infiltration to Ameliorate Diabetic Osteoarthritis Progression.

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.

Anethole mitigates H2 O2 -induced inflammation in HIG-82 synoviocytes by suppressing the aquaporin 1 expression and activating the protein kinase A pathway.

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease affecting approximately 1% of the global population, with a higher prevalence in women than in men. Chronic inflammation and oxidative stress play pivotal roles in the pathogenesis of RA. Anethole, a prominent compound derived from fennel (Foeniculum vulgare), possesses a spectrum of therapeutic properties, including anti-arthritic, anti-inflammatory, antioxidant, and tumor-suppressive effects. However, its specific impact on RA remains underexplored. This study sought to uncover the potential therapeutic value of anethole in treating RA by employing an H2 O2 -induced inflammation model with HIG-82 synovial cells. Our results demonstrated that exposure to H2 O2 induced the inflammation and apoptosis in these cells. Remarkably, anethole treatment effectively countered these inflammatory and apoptotic processes triggered by H2 O2 . Moreover, we identified the aquaporin 1 (AQP1) and protein kinase A (PKA) pathway as critical regulators of inflammation and apoptosis. H2 O2 stimulation led to an increase in the AQP1 expression and a decrease in p-PKA-C, contributing to cartilage degradation. Conversely, anethole not only downregulated the AQP1 expression but also activated the PKA pathway, effectively suppressing cell inflammation and apoptosis. Furthermore, anethole also inhibited the enzymes responsible for cartilage degradation. In summary, our findings highlight the potential of anethole as a therapeutic agent for mitigating H2 O2 -induced inflammation and apoptosis in synovial cells, offering promising prospects for future RA treatments.

PTEN-mediated FOXO signaling affects autophagy, migration and invasion of rheumatoid arthritis fibroblast-like synoviocytes.

Rheumatoid arthritis (RA) is a chronic, progressive, systemic autoimmune disease. Among them, abnormal proliferation, migration and vascularization of fibroblast-like synoviocytes (FLS) are the main pathological basis of persistent synovitis and bone destruction in RA. In the current study, we attempted to find effective molecular mechanisms for the treatment of RA by investigating RA-FLS. Firstly, the study was conducted to identify the potential target gene PTEN and its related signaling pathway through bioinformatics analysis. Subsequently, the target gene PTEN overexpression was regulated by cell transfection. The expression of FOXO signaling factors and autophagy-related proteins were detected by western blotting assay. Cell proliferation was measured by CCK-8 and EdU assays. Inflammation level was detected by ELISA. Cell migration and invasion were detected using wound healing assay and transwell chamber assay, respectively. Cell apoptosis was detected using flow cytometry. The results showed that overexpression of PTEN activated FOXO1 signaling in RA-FLS, and regulated autophagy, proliferation, invasion, migration, and the levels of pro-inflammatory factors in the disease. In conclusion, PTEN might provide an effective therapeutic strategy for rheumatoid arthritis by mediating the FOXO1 signaling pathway.