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.

Identification of serum exosomal lncRNAs and their potential regulation of characteristic genes of fibroblast-like synoviocytes in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a common autoimmune disease whose pathogenesis is poorly understand. Gaps in laboratory biomarkers cause a lack of clinically available strategies for the early diagnosis and treatment of RA. This study aims to identify serum exosomal lncRNAs as promising biomarkers and to unravel potential mechanisms by which they affect characteristic genes of fibroblast-like synoviocytes (FLSs) to induce RA malignant properties. RNA sequencing datasets of serum exosomes (GSE271161 and PRJNA911001) and FLSs (GSE103578, GSE122616, GSE128813, GSE181614 and GSE83147) were purposively mined. Visualization and functional enrichment of differentially expressed (DE) lncRNAs/protein-coding genes, screening of significant lncRNAs, and construction of competing endogenous RNAs (ceRNAs) and protein-protein interaction (PPI) network were carried out. Quantitative real-time PCR, receiver operating characteristic curve (ROC) and correlation analysis were conducted on the validation cohort. As a result, we screened a total of 131 serum exosomal DElncRNAs and 125 FLSs DEmRNAs, which were predominantly enriched in the proliferative, inflammatory and metabolic pathways. In-depth learning of DElncRNAs expression profiles was performed to identify models with better performance and lncRNAs with higher importance scores using 4 machine learning algorithms (SVM, KNN, RF, Logit), which led to the establishment of ceRNAs network linking serum exosomal lncRNAs and characteristic genes of FLSs. In short, we proposed that 4 RA-representative serum exosomal lncRNAs (DLEU2, FAM13A-AS1, MEG3 and SNHG15) may be applied as valuable indicators for laboratory tests, and their-mediated intercellular communication and ceRNAs network may regulate the characteristic genes of FLSs, thereby generating malignant phenotypes and adaptive synovial microenvironment in RA.

Apurinic/apyrimidinic endonuclease 1 alleviates inflammation in fibroblast-like synoviocytes from patients with rheumatoid arthritis.

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 α (TNF-α) 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-α/IL-17-stimulated RA FLS. Furthermore, APEX1 treatments attenuated TNF-α/IL-17-induced activation of p38 MAPK, NF-κB, and PI3K 110 δ signaling pathways. Similarly, APEX1 significantly diminished TNF-α/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-α/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.

Ultra-High-Performance Liquid Chromatography-High-Definition Mass Spectrometry-Based Metabolomics to Reveal the Potential Anti-Arthritic Effects of Illicium verum in Cultured Fibroblast-like Synoviocytes Derived from Rheumatoid Arthritis.

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.

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

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)-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-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-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-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.

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.

BACKGROUND: Rheumatoid 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. METHODS: We 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. RESULTS: Among 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)-1ß 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-1ß 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. CONCLUSION: QS-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.

PU.1 regulates osteoarthritis progression via CSF1R in synovial cells.

This study elucidates the molecular mechanisms driving osteoarthritis (OA) by focusing on the transcription factor PU.1's role in synovial cells, specifically macrophages and fibroblast-like synoviocytes (FLS). Analyzing OA-related synovial gene expression from the GEO database highlighted immune regulation pathways in OA. Using protein-protein interaction and the JASPAR database, we pinpointed essential genes in OA development. Synovial tissues from OA patients and controls revealed pronounced PU.1 and its target CSF1R presence. In a surgically induced OA mouse model with PU.1 and CSF1R knockdown, ChIP assays confirmed PU.1's binding to the CSF1R promoter. Dual luciferase reporter assays and immunohistochemistry validated PU.1's regulatory impact on CSF1R transcription. Combined analysis of microarrays GSE55235 and GSE206848 showed heightened PU.1 expression in OA, associated with immune regulation in macrophages. In vitro findings aligned with in vivo results, emphasizing PU.1's influence on macrophage polarization and FLS-induced inflammation. PU.1's direct activation of CSF1R transcription underpins its key role in OA progression. This research offers insights into OA's molecular basis, suggesting potential therapeutic targets.

Lactate-upregulated ARG2 expression induces cellular senescence in fibroblast-like synoviocytes of osteoarthritis via activating the mTOR/S6K1 signaling pathway.

Cellular senescence was implicated in the pathogenesis of age-related diseases such as osteoarthritis (OA). Increasing evidence suggests that alterations in the OA joint microenvironment play a crucial role in the pathogenesis of OA. This study aims to establish a clear link between the impact of accumulated lactate on the senescence of fibroblast-like synoviocytes (FLS) within the OA microenvironment. OA models and models with intra-articular injection of lactate were established in rat models, histological analyses were performed. Human OA-FLS treated with lactate was analyzed by mRNA sequencing, senescence related experiments and underlying signaling pathway activation were comprehensively evaluated. This study confirmed that OA models and lactate-injection models exhibited higher synovitis scores. Enrichment analyses indicated dysregulated cell cycle and cellular senescence pathways in OA-FLS treated with lactate. Lactate significantly up-regulated arginase 2 (ARG2) expression and promoted OA-FLS senescence, including G1/S arrest, increased reactive oxygen species and ß-galactosidase production, high expression of senescence-associated secretory phenotype factors, which could be attenuated by siRNA-Arg2. The ARG2-mTOR/S6K1 axis was identified as a potential signaling for lactate-induced OA-FLS senescence, and activated mTOR/S6K1 signaling could be reduced by siRNA-Arg2, rapamycin (mTOR inhibitor), and LY294002 (PI3K inhibitor). Our study provides novel targets and insights for OA therapies.

Chondroitin sulfate-based microneedles for transdermal delivery of stem cell-derived extracellular vesicles to treat rheumatoid arthritis.

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.

Eukaryotic translation initiation factor 6-mediated ribosome biogenesis promotes synovial aggression and inflammation by increasing the translation of SP1 in rheumatoid arthritis.

INTRODUCTION: Fibroblast-like synoviocytes (FLSs) play critical roles in synovial inflammation and aggression in rheumatoid arthritis (RA). Here, we explored the role of eukaryotic translation initiation factor 6 (eIF6) in regulating the biological behaviors of FLSs from patients with RA. METHODS: FLSs were isolated from the synovial tissues of RA patients. Gene expression was assessed via RT-qPCR, and protein expression was evaluated via Western blotting or immunohistochemistry. Proliferation and nascent peptide synthesis were evaluated via EdU incorporation and HPG labeling, respectively. Cell migration and invasion were observed via Transwell assays. Polysome profiling was conducted to analyze the distribution of ribosomes and combined mRNAs. The in vivo effect of eIF6 inhibition was evaluated in a collagen-induced arthritis (CIA) rat model. RESULTS: We found that eIF6 expression was elevated in FLSs and synovial tissues from RA patients compared to those from healthy controls and osteoarthritis patients. Knockdown of eIF6 inhibited the migration, invasion, inflammation, and proliferation of FLSs from patients with RA. Mechanistically, eIF6 knockdown downregulated ribosome biogenesis in FLSs from with RA, leading to a decrease in the proportion of polysome-associated specificity protein 1 (SP1) mRNA and a subsequent reduction in the translation initiation efficiency of SP1 mRNA. Thus, eIF6 controls SP1 expression through translation-mediated mechanisms. Interestingly, intra-articular eIF6 siRNA treatment attenuated symptoms and histological manifestations in CIA rats. CONCLUSIONS: Our findings suggest that an increase in synovial eIF6 might contribute to rheumatoid synovial inflammation and aggression and that targeting eIF6 may have therapeutic potential in RA patients.

17ß-estradiol promotes the progression of temporomandibular joint osteoarthritis by regulating the FTO/IGF2BP1/m6A-NLRC5 axis.

BACKGROUND: Temporomandibular joint osteoarthritis (TMJOA) is a degenerative cartilage disease. 17ß-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.

Modulation of the K/BxN arthritis mouse model and the effector functions of human fibroblast-like synoviocytes by liver X receptors.

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 ß 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-1ß 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.

Gastrodin Ameliorates the Inflammation, Oxidative Stress, and Extracellular Matrix Degradation of IL-1ß-Mediated Fibroblast-Like Synoviocytes via Suppressing the Gremlin-1/NF-κB Pathway.

BACKGROUND: Synovial inflammation plays a crucial role in osteoarthritis (OA). Gastrodin (GAS), an active ingredient derived from the Gastrodia elata Blume rhizome, possesses antioxidant and anti-inflammatory pharmacological effects. This research aimed to evaluate the function and molecular mechanism of GAS on human fibroblast-like synoviocytes of osteoarthritis (HFLS-OA) induced by interleukin (IL)-1ß. METHODS: The impact of GAS on the viability of IL-1ß-treated HFLS-OA cells was assessed using the cell counting kit-8 (CCK-8). Quantitative real-time reverse transcription PCR (qRT-PCR) was employed to detect changes in IL-8, IL-6, monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor (TNF)-α, and Gremlin-1 mRNA expression in each group. Corresponding kits were utilized to measure the catalase (CAT) and superoxide dismutase (SOD) activities, as well as the nitric oxide (NO) level. Western blot analysis was conducted to examine the expression of extracellular matrix degradation-associated proteins and nuclear factor kappa-B (NF-κB) pathway-correlated proteins in each group. RESULTS: GAS significantly promoted the proliferation of IL-1ß-induced HFLS-OA cells and concurrently down-regulated Gremlin-1 mRNA expression (p < 0.05). Through the down-regulation of Gremlin-1 expression, GAS exhibited the following effects: decreased IL-8, IL-6, and TNF-α mRNA expression, as well as NO levels (p < 0.05); increased SOD and CAT activities (p < 0.05); down-regulated matrix metallopeptidase 13 (MMP-13) and MMP-1 protein expression levels (p < 0.01); and up-regulated collagen II protein expression level (p < 0.01) in IL-1ß-treated HFLS-OA cells. Additionally, GAS decreased phospho-inhibitory kappa B (p-IκB)/IκB, phospho-inhibitory kappa B kinase (p-IKK)/IKK, and p-p65/p65 ratios in IL-1ß-induced HFLS-OA cells by inhibiting Gremlin-1 expression (p < 0.01). CONCLUSION: GAS demonstrates a positive impact on inflammation, oxidative stress, and extracellular matrix degradation in IL-1ß-mediated HFLS-OA cells. This effect is achieved by suppressing Gremlin-1 expression and reducing NF-κB pathway activity.

[MMPs/pH synergically responsive XTS-Prussian blue nanoparticles inhibiting proliferation and migration of RAFLS assisted with laser irradiation].

Rheumatoid arthritis(RA) is a condition in which the joints are in a weakly acidic environment. In RA, RA fibroblastlike synoviocytes( RAFLS) in the joints become abnormally activated and secrete a large amount of matrix metalloproteinases(MMPs), and the receptor protein CD44 on the cell membrane is specifically upregulated. Xuetongsu(XTS), an active ingredient in the Tujia ethnomedicine Xuetong, is known to inhibit the proliferation of RAFLS. However, its development and utilization have been limited due to poor targeting ability. A biomimetic XTS-Prussian blue nanoparticles(PB NPs) drug delivery system called THMPX NPs which can target CD44 was constructed in this study. The surface of THMPX NPs was modified with hyaluronic acid(HA) and a long chain of triglycerol monostearate(TGMS) and 3-aminobenzeneboronic acid(PBA)(PBA-TGMS). The overexpressed MMPs and H+ in inflammatory RAFLS can synergistically cleave the PBA-TGMS on the surface of the nanoparticles, exposing HA to interact with CD44. This allows THMPX NPs to accumulate highly in RAFLS, and upon near-infrared light irradiation, generate heat and release XTS, thereby inhibiting the proliferation and migration of RAFLS. Characterization revealed that THMPX NPs were uniform cubes with a diameter of(190. 3±4. 7) nm and an average potential of(-15. 3± 2. 3) m V. Upon near-infrared light irradiation for 5 min, the temperature of THMPX NPs reached 41. 5 ℃, indicating MMPs and H+-triggered drug release. Safety assessments showed that THMPX NPs had a hemolysis rate of less than 4% and exhibited no cytotoxicity against normal RAW264. 7 and human fibroblast-like synoviocytes(HFLS). In vitro uptake experiments demonstrated the significant targeting ability of THMPX NPs to RAFLS. Free radical scavenging experiments revealed excellent free radical clearance capacity of THMPX NPs, capable of removing reactive oxygen species in RAFLS. Cell counting kit-8 and scratch assays demonstrated that THMPX NPs significantly suppressed the viability and migratory ability of RAFLS. This study provides insights into the development of innovative nanoscale targeted drugs from traditional ethnic medicines for RA treatment.

Acetyl-11-keto-ß-boswellic acid restrains the progression of synovitis in osteoarthritis via the Nrf2/HO-1 pathway.

Synovial inflammation plays a key role in osteoarthritis (OA) pathogenesis. Fibroblast-like synoviocytes (FLSs) represent a distinct cell subpopulation within the synovium, and their unique phenotypic alterations are considered significant contributors to inflammation and fibrotic responses. The underlying mechanism by which acetyl-11-keto-ß-boswellic acid (AKBA) modulates FLS activation remains unclear. This study aims to assess the beneficial effects of AKBA through both in vitro and in vivo investigations. Network pharmacology evaluation is used to identify potential targets of AKBA in OA. We evaluate the effects of AKBA on FLSs activation in vitro and the regulatory role of AKBA on the Nrf2/HO-1 signaling pathway. ML385 (an Nrf2 inhibitor) is used to verify the binding of AKBA to its target in FLSs. We validate the in vivo efficacy of AKBA in alleviating OA using anterior cruciate ligament transection and destabilization of the medial meniscus (ACLT+DMM) in a rat model. Network pharmacological analysis reveals the potential effect of AKBA on OA. AKBA effectively attenuates lipopolysaccharide (LPS)-induced abnormal migration and invasion and the production of inflammatory mediators, matrix metalloproteinases (MMPs), and reactive oxygen species (ROS) in FLSs, contributing to the restoration of the synovial microenvironment. After treatment with ML385, the effect of AKBA on FLSs is reversed. In vivo studies demonstrate that AKBA mitigates synovial inflammation and fibrotic responses induced by ACLT+DMM in rats via activation of the Nrf2/HO-1 axis. AKBA exhibits theoretical potential for alleviating OA progression through the Nrf2/HO-1 pathway and represents a viable therapeutic candidate for this patient population.

Graphene oxide quantum dots-loaded sinomenine hydrochloride nanocomplexes for effective treatment of rheumatoid arthritis via inducing macrophage repolarization and arresting abnormal proliferation of fibroblast-like synoviocytes.

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.

Fibroblast-like synoviocytes orchestrate daily rhythmic inflammation in arthritis.

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.

Pyroptosis-related crosstalk in osteoarthritis: Macrophages, fibroblast-like synoviocytes and chondrocytes.

The pathogenesis of osteoarthritis (OA) involves a multifaceted interplay of inflammatory processes. The initiation of pyroptosis involves the secretion of pro-inflammatory cytokines and has been identified as a critical factor in regulating the development of OA. Upon initiation of pyroptosis, a multitude of inflammatory mediators are released and can be disseminated throughout the synovial fluid within the joint cavity, thereby facilitating intercellular communication across the entire joint. The main cellular components of joints include chondrocytes (CC), fibroblast-like synoviocytes (FLS) and macrophages (MC). Investigating their interplay can enhance our understanding of OA pathogenesis. Therefore, we comprehensively examine the mechanisms underlying pyroptosis and specifically investigate the intercellular interactions associated with pyroptosis among these three cell types, thereby elucidating their collective contribution to the progression of OA. We propose the concept of ' CC-FLS-MC pyroptosis-related crosstalk', describe the various pathways of pyroptotic interactions among these three cell types, and focus on recent advances in intervening pyroptosis in these three cell types for treating OA. We hope this will provide a possible direction for diversification of treatment for OA. The Translational potential of this article. The present study introduces the concept of 'MC-FLS-CC pyroptosis-related crosstalk' and provides an overview of the mechanisms underlying pyroptosis, as well as the pathways through which it affects MC, FLS, and CC. In addition, the role of regulation of these three types of cellular pyroptosis in OA has also been concerned. This review offers novel insights into the interplay between these cell types, with the aim of providing a promising avenue for diversified management of OA.

Synoviocytes assist in modulating the effect of Ross River virus infection in micromass-cultured primary human chondrocytes.

Introduction. Ross River virus (RRV) is a mosquito-borne virus prevalent in Australia and the islands of the South Pacific, where it causes an arthritogenic illness with a hallmark feature of severe joint pain. The joint space is a unique microenvironment that contains cartilage and synovial fluid. Chondrocytes and synoviocytes are crucial components of the joint space and are known targets of RRV infection.Hypothesis/Gap statement. Understanding the relationship between synoviocytes and chondrocytes during RRV infection will provide further insights into RRV-induced joint pathology.Methodology. To better understand the unique dynamics of these cells during RRV infection, we used primary chondrocytes cultured in physiologically relevant micromasses. We then directly infected micromass chondrocytes or infected primary fibroblast-like synoviocytes (FLS), co-cultured with micromass chondrocytes. Micromass cultures and supernatants were collected and analysed for viral load with a PCR array of target genes known to play a role in arthritis.Results. We show that RRV through direct or secondary infection in micromass chondrocytes modulates the expression of cellular factors that likely contribute to joint inflammation and disease pathology, as well as symptoms such as pain. More importantly, while we show that RRV can infect micromass-cultured chondrocytes via FLS infection, FLS themselves affect the regulation of cellular genes known to contribute to arthritis.Conclusion. Single-cell culture systems lack the complexity of in vivo systems, and understanding the interaction between cell populations is crucial for deciphering disease pathology, including for the development of effective therapeutic strategies.

FTO-mediated RNA m6A methylation regulates synovial aggression and inflammation in rheumatoid arthritis.

Fibroblast-like synoviocytes (FLS) plays an important role in synovial inflammation and joint damage in rheumatoid arthritis (RA). As the most abundant mRNA modification, N6-methyladenosine (m6A) is involved in the development of various diseases; however, its role in RA remains to be defined. In this study, we reported the elevated expression of the m6A demethylase fat mass and obesity-associated protein (FTO) in FLS and synovium from RA patients. Functionally, FTO knockdown or treatment with FB23-2, an inhibitor of the mRNA m6A demethylase FTO, inhibited the migration, invasion and inflammatory response of RA FLS, however, FTO-overexpressed RA FLS exhibited increased migration, invasion and inflammatory response. We further demonstrated that FTO promoted ADAMTS15 mRNA stability in an m6A-IGF2BP1 dependent manner. Notably, the severity of arthritis was significantly reduced in CIA mice with FB23-2 administration or CIA rats with intra-articular injection of FTO shRNA. Our results illustrate the contribution of FTO-mediated m6A modification to joint damage and inflammation in RA and suggest that FTO might be a potential therapeutic target in RA.