Nintedanib ameliorates osteoarthritis in mice by inhibiting synovial inflammation and fibrosis caused by M1 polarization of synovial macrophages via the MAPK/PI3K-AKT pathway

Restoring tendon microenvironment in tendinopathy: Macrophage modulation and tendon regeneration with injectable tendon hydrogel and tendon-derived stem cells exosomes

Tendinopathy is a common musculoskeletal disorder in which a significant number of patients do not attain effective therapeutic outcomes. The extent of the inflammatory response and the dynamics of collagen synthesis metabolism are critical factors that influence the intrinsic self-repair capacity of tendons. However, the poor microenvironment within the tendon significantly impedes the self-repair process in tendinopathy. In this study, an injectable tendon-derived decellularized extracellular matrix (tdECM) hydrogel was utilized to treat tendinopathy. This hydrogel provides a more cytocompatible microenvironment while retaining certain bioactive factors of native tendon extracellular matrix (ECM), compared to collagen hydrogel. Notably, it was discovered for the first time that the tdECM hydrogel promotes M2 macrophage polarization, thereby exerting an anti-inflammatory effect in vivo. Furthermore, utilizing tdECM as a carrier for the sustained release of tendon-derived stem cells exosomes (TDSCs-Exos), our findings from both in vitro and in vivo studies indicate that the tdECM hydrogel, in conjunction with exosomes, demonstrated a pronounced synergistic enhancement in modulating inflammation, promoting M2 macrophage polarization, and facilitating tendon regeneration and repair efficacy. These results suggest its potential as a promising therapeutic strategy for tendon disorders.

Therapeutic effect of nintedanib in orbital fibroblasts in patients with Graves' orbitopathy

BACKGROUND

Nintedanib is a potent antifibrotic angiokinase inhibitor approved for various fibrotic lung diseases. Potential therapeutic efficacy of nintedanib in various inflammatory diseases is under investigation. In this study, we investigated the therapeutic effect of nintedanib on adipogenesis and fibrosis in orbital fibroblasts in patients with Graves' orbitopathy (GO).

METHODS

Primary orbital fibroblasts were cultured from orbital connective tissue of patients with GO and healthy controls. The cells were pretreated with nintedanib before stimulation with either interleukin (IL)-1β, transforming growth factor (TGF)-β, insulin-like growth factor-1, or IL-11. Fibrosis-related and intracellular signaling protein expressions were assessed using western blotting. Hyaluronan and procollagen concentrations were quantified using enzyme-linked immunosorbent assay. Adipogenesis was quantified by Oil Red O staining and the levels of adipogenic transcription factors were determined by Western blot.

RESULTS

TGF-β-induced fibronectin and collagen 1/3 protein expression was abrogated by nintedanib treatment. Nintedanib decreased the phosphorylation of signal transducer and activator of transcription 3, SMAD 2/3, Akt, c-Jun N-terminal kinase, and extracellular regulated protein kinase. Exposure to nintedanib hindered adipocyte differentiation and expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein α/β, adipocyte protein 2, adiponectin, and leptin. Additionally, nintedanib reduced hyaluronan and procollagen secretion.

CONCLUSIONS

Nintedanib suppressed profibrotic protein production, adipogenesis, and hyaluronan production in in vitro. These findings indicate the potential therapeutic efficacy of nintedanib in GO management.

Molecular features and diagnostic modeling of synovium- and IPFP-derived OA macrophages in the inflammatory microenvironment via scRNA-seq and machine learning

BACKGROUND

Osteoarthritis (OA) is the leading cause of degenerative joint disease, with total joint replacement as the only definitive cure. However, no disease-modifying therapy is currently available. Inflammation and fibrosis in the infrapatellar fat pad (IPFP) contribute to OA onset and progression. However, the cellular composition and molecular mechanisms in the IPFP microenvironment remain unclear. This study investigates the functions of OA-macrophages and their clinical significance.

METHODS

We analyzed single-cell RNA sequencing (scRNA-seq) data from normal and OA patients. Enrichment analysis revealed differences in biological pathways across cell types. Pseudotime and cell-cell communication analyses revealed the developmental trajectory and interactions of OA-macrophages with other cell types. Machine learning (ML) algorithms identified feature genes of OA-macrophages. An OAMGS diagnostic score was developed, and CIBERSORT was used to analyze immune infiltration and its association with immune cells. Rat OA and normal models were established, and feature gene expression was validated using immunofluorescence (IF) staining and quantitative reverse transcription PCR (RT-qPCR).

RESULTS

OA-macrophages play a central role in inflammation and fibrosis, enhancing leukocyte recruitment, chondrocyte apoptosis, and angiogenesis. They interact with chondrocytes, endothelial cells, and fibroblasts via CXCL and NF-κB signaling. High-dimensional weighted gene co-expression network analysis (hdWGCNA) identified 352 module genes linked to OA-macrophages. Machine learning developed a four-gene-based OAMGS score that accurately identifies OA-macrophages, with an AUC of 1 in the discovery cohort and 0.990 in an external cohort. Gene expression was validated in the OA model using RT-qPCR and IF.

CONCLUSION

This study identifies a macrophage subcluster elevated in OA patients. OA-macrophages play an immunoregulatory role and may serve as diagnostic markers. The OAMGS score, based on four genes, provides an accurate diagnostic tool and potential therapeutic target for OA.

Kaempferol attenuates macrophage M1 polarization and liver fibrosis by inhibiting mitogen-activated protein kinase/nuclear factor κB signaling pathway

Chronic liver inflammation is a major cause of death in patients with liver fibrosis and cirrhosis, which pose a serious health threat worldwide, and there is no effective anti-hepatic fibrosis drug. Kaempferol (KA), a flavonoid polyphenol extracted from many edible plants and traditional Chinese medicine, has been reported to possess anti-inflammatory, antioxidant, and antitumor activities and has an ameliorating effect on liver fibrosis or other fibroproliferative diseases. However, the specific regulatory mechanism of KA-reversed macrophage M1 polarization is still obscure. This study aimed to investigate the protective effects of KA on carbon tetrachloride (CCl4)-induced liver fibrosis in mice through M1 polarization. C57BL/6 mice were intraperitoneally injected with CCl4 twice weekly to induce liver fibrosis. Male mice were randomly divided into 4 groups (n = 5): the oil group, the CCl4 group, the low-dose KA-treatment CCl4 group (50 mg/kg/day KA), and the high-dose KA-treatment CCl4 group (100 mg/kg/day KA). An equal amount of solvent was given to each group by intraperitoneal injection. The results indicated that KA decreased liver pathologic changes, hepatic macrophage recruitment, and serum alanine aminotransferase levels. Notably, it reduced the activation of M1-type macrophages in the liver. The expression of proinflammatory cytokines and genes associated with M1 macrophages, such as tumor necrosis factor-α, interleukin-6, interleukin-1β, and inducible nitric oxide synthase, was also decreased. The core targets, signaling pathways, and possible mechanisms related to the M1 polarization of KA were analyzed by network pharmacology and molecular docking. Further analysis revealed that KA regulated mitogen-activated protein kinase (MAPK)/nuclear factor κB (NF-κB) signaling pathways. Finally, the results indicated that KA regulates M1 macrophage activation by modulating the MAPK/NF-κB signaling pathways. This study revealed that KA ameliorated liver injury, inflammation, and fibrosis by inhibiting macrophage M1 polarization through the MAPK/NF-κB signaling pathway, highlighting KA as a potential novel agent for the prevention and treatment of liver fibrosis. SIGNIFICANCE STATEMENT: Chronic liver inflammation is a leading cause of mortality in patients with liver fibrosis and cirrhosis, presenting a significant global health threat. Kaempferol, as a traditional Chinese medicine, effectively suppresses M1 polarization of macrophages through the mitogen-activated protein kinase/nuclear factor κB signaling pathway, thereby ameliorating liver injury, inflammation, and fibrosis. These findings underscore the potential of kaempferol as an innovative therapeutic agent for the prevention and treatment of liver fibrosis.

The role of the immune system in osteoarthritis: mechanisms, challenges and future directions

Osteoarthritis (OA) is a chronic joint disease that has long been considered a simple wear-and-tear condition. Over the past decade, research has revealed that various inflammatory features of OA, such as low-grade peripheral inflammation and synovitis, contribute substantially to the pathophysiology of the disease. Technological advances in the past 5 years have revealed a large diversity of innate and adaptive immune cells in the joints, particularly in the synovium and infrapatellar fat pad. Notably, the presence of synovial lymphoid structures, circulating autoantibodies and alterations in memory T cell and B cell populations have been documented in OA. These data indicate a potential contribution of self-reactivity to the disease pathogenesis, blurring the often narrow and inaccurate line between chronic inflammatory and autoimmune diseases. The diverse immune changes associated with OA pathogenesis can vary across disease phenotypes, and a better characterization of their underlying molecular endotypes will be key to stratifying patients, designing novel therapeutic approaches and ultimately ameliorating treatment allocation. Furthermore, examining both articular and systemic alterations, including changes in the gut-joint axis and microbial dysbiosis, could open up novel avenues for OA management.

Low intensity pulsed ultrasound alleviates synovial fibrosis in osteoarthritis via the PI3K/AKT pathway

Previous studies have reported that low-intensity pulsed ultrasound (LIPUS) can alleviate cartilage degradation in osteoarthritis (OA). However, the functions and mechanisms of LIPUS in synovial fibrosis with OA require further study. To investigate the role of the PI3K/AKT signaling pathway in synovial fibrosis and in LIPUS treatment in synovial fibrosis, a TGF-β stimulated rat FLS cell model and a rat OA animal model based on anterior cruciate ligament transection (ACLT) and partial medial meniscectomy (MMx) were used. The results revealed that LIPUS delayed the progression of OA. Masson staining revealed that LIPUS reduced the collagen deposition of synovial tissue in OA rats. Correspondingly, immunofluorescence demonstrated that LIPUS significantly downregulated the expression of α-SMA, Col1a1 and Col3a1 in OA rats. Moreover, TGF-β stimulation upregulated fibrosis markers at the mRNA and protein levels in FLS, as well as increased phosphorylation-dependent activation of the PI3K/Akt pathway. 740Y-P was found to promote the fibrotic change of FLS induced by TGF-β, but LY294002 reduced its expression. However, LIPUS inhibits the fibrotic change and activation of the PI3K/Akt pathway in FLS under stimulation of TGF-β. In conclusion, LIPUS alleviates synovial fibrosis by blocking the PI3K/AKT pathway.

Gentiopicroside ameliorates synovial inflammation and fibrosis in KOA rats by modulating the HMGB1-mediated PI3K/AKT signaling axis

BACKGROUND

Knee osteoarthritis (KOA) is a degenerative joint disease characterized by synovial inflammation and fibrosis. Gentiopicroside (GPS), one of the main active ingredients of Gentiana macrophylla, is widely used in anti-inflammatory and anti-fibrotic therapies. However, the exact mechanism by which GPS treats synovial inflammation and fibrosis in KOA remains unclear.

METHODS

Fibroblast-like synoviocytes (FLSs) were stimulated with lipopolysaccharide (LPS) to induce inflammation and fibrosis, and CCK-8 was performed to determine the viability of GPS-treated FLSs, using immunofluorescence to examine the expression of P-PI3K and P-AKT, confocal microscopy was used to identify intracellular HMGB1 translocation. The KOA rat model was established by anterior cruciate ligament transection (ACLT) and subsequently subjected to GPS intervention. Inflammatory cytokines (TNF-α, IL-1β, and IL-6), fibrosis-related indicators (TGF-β, collagen I, TIMP1, and α-SMA), and HMGB1/PI3K/AKT signaling axis-related proteins and gene expression of fibroblast-like synoviocytes and synovial tissues were detected by Western blotting and real-time PCR. The histopathology of the synovium of the rats was assessed using Hematoxylin-eosin (HE), Sirius Red, and Masson staining. Immunohistochemistry was performed to detect the expression of HMGB1, P-PI3K, and P-AKT.

RESULTS

The present study revealed that GPS intervention significantly ameliorated inflammation and fibrosis in LPS-stimulated FLSs and KOA rat synovium. Immunofluorescence demonstrated that GPS inhibited the release of HMGB1 from the nucleus. Furthermore, GPS intervention down-regulates the levels of proteins and gene associated with the HMGB1/PI3K/AKT signaling pathway.

CONCLUSION

GPS ameliorated synovial inflammation and fibrosis in KOA rats, which may involve HMGB1-mediated activation of the PI3K/AKT signaling axis.

Development of a novel rabbit model for femoroacetabular impingement through surgically induced acetabular overcoverage

There is a lack of validated small animal models for femoroacetabular impingement (FAI) that induce intra-articular lesions and cause osteoarthritis (OA) progression. The gene expression profile of articular cartilage in patients with FAI has not been characterized in animal studies. The purpose of this study is to describe a novel rabbit model for FAI with validated induction of intra-articular lesions and OA progression and to characterize the gene expression pattern in impinged cartilage using this model. Thirty 6-month-old New Zealand White rabbits underwent unilateral endobutton implant placement at the acetabular rim to surgically create overcoverage. Radiological assessment confirmed secure placement of endobutton at the acetabular rim for all operated hips with a mean alteration in lateral center-edge angle (ΔLCEA) of 16.2 ± 6.6°. Gross inspection revealed secondary cartilage injuries in the anterosuperior region of the femoral head for the operated hips. Cartilage injuries were shown to exacerbate with increased impingement duration, as demonstrated by the modified Outerbridge scores and Mankin scores. Immunostaining and quantitative real-time polymerase chain reaction revealed elevated expression of inflammatory, anabolic and catabolic genes in impinged cartilage. RNA sequencing analysis of cartilage tissue revealed a distinct transcriptome profile and identified C-KIT, CD86, and CD68 as central markers. Our study confirmed that the novel rabbit FAI model created acetabular overcoverage and produced articular cartilage injury at the impingement zone. Cartilage from the impingement zone demonstrated a heightened metabolic state, corroborating with the gene expression pattern observed in patients with FAI.

Analysis of the potential biological mechanisms of geniposide on renal fibrosis by network pharmacology and experimental verification

BACKGROUND

Renal fibrosis is crucial in the progression of chronic kidney disease (CKD) to end-stage renal failure. Geniposide, an iridoid glycoside, has shown therapeutic potential in acute kidney injury, diabetic nephropathy, and atherosclerosis. The aim of this study was to investigate the role of geniposide in renal fibrosis and its underlying mechanisms.

METHODS

The network pharmacology and molecular docking methods were used to identify potential targets and pathways of geniposide for treating renal fibrosis. In vivo, the unilateral ureteral obstruction (UUO) mouse model was treated with geniposide. In vitro, TGF-β1-stimulated human renal tubular epithelial (HK-2) cells were applied for validation. HE, PAS, Masson, and immunohistochemistry staining were performed to evaluate its effects on the kidneys of UUO mice. RT-qPCR and western blotting were used to detect the expression of hub genes and signaling pathways.

RESULTS

101 overlapping genes were identified, with the top 10 including AKT1, MMP9, GAPDH, BCL2, TNF, CASP3, SRC, EGFR, IL-1β, and STAT1. GO analysis suggested that these key targets were mainly involved in cell proliferation and apoptosis. KEGG analysis revealed that the PI3K/AKT, MAPK, and Rap1 signaling pathways were associated with geniposide against renal fibrosis. Molecular docking suggested a strong binding affinity of geniposide to the hub genes. In vivo experiments showed that geniposide ameliorated kidney injury and fibrosis, and inhibited the mRNA levels of AKT1, MMP9, BCL2, and TNF. In addition, geniposide inhibited the activation of the PI3K/AKT signaling pathway, thereby suppressing renal fibrosis in UUO mice and TGF-β1-induced HK-2 cells.

CONCLUSIONS

Geniposide can attenuate renal fibrosis by inhibiting the PI3K/AKT pathway, suggesting its potential as a therapeutic agent for renal fibrosis.

Novel Clinical Insights into the Pathogenesis of Posttraumatic Elbow Stiffness: An Expression Profile Analysis of Contracted Joint Capsule in Human

Background

Posttraumatic elbow stiffness is a complex complication with two characteristics of capsular contracture and heterotopic ossification. Currently, genomic mechanisms and pathogenesis of posttraumatic elbow stiffness remain inadequately understood. This study aims to identify differentially expressed genes (DEGs) and elucidate molecular networks of posttraumatic elbow stiffness, providing novel insights into disease mechanisms at transcriptome level.

Methods

Global transcriptome sequencing was conducted on six capsular samples from individuals with posttraumatic elbow stiffness and three control capsular samples from individuals with elbow fractures. Differentially expressed genes (DEGs), microRNAs, and long non-coding RNAs (LncRNAs) were identified and analyzed. Functional enrichment analysis was performed, and the associated protein-protein interaction (PPI) network was constructed. MicroRNAs targeting these DEGs were identified, and transcription factors (TFs) targeting DEGs were predicted using the ENCODE database. Finally, key DEGs were validated by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

A total of 4909 DEGs associated with protein-coding, LncRNA and microRNA were detected, including 2124 upregulated and 2785 downregulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the DEGs were significantly enriched in 36 signaling pathways, notably involving inflammatory responses and extracellular matrix (ECM) receptor interactions. The protein-protein interaction (PPI) network analysis highlighted genes such as SPP1, IBSP, MMP13 and MYO1A as having higher degrees of connectivity. Key microRNAs (hsa-miR-186-5p, hsa-miR-515-5p, and hsa-miR-590-3p) and transcription factors (TFDP1 and STAT3) were predicted to be implicated in the pathogenesis of posttraumatic elbow stiffness through the microRNA-transcription factor regulatory network analysis.

Conclusion

The study provided insights into the molecular mechanisms underlying the changes in the contracted capsules associated with posttraumatic elbow stiffness. Hub genes including SPP1, IBSP, MMP13, and MYO1A, key microRNAs (has-miR-186-5p, has-miR-515-5p, hsa-miR-590-3p) and TFs (TFDP1 and STAT3) may serve as prognostic and therapeutic targets of posttraumatic elbow stiffness, and provide a new idea for the future research direction of clinical treatment.

Identification of ZNF652 as a Diagnostic and Therapeutic Target in Osteoarthritis Using Machine Learning

Purpose

Osteoarthritis (OA) is the most common degenerative joint disease. However, its etiology remains largely unknown. Zinc Finger Protein 652 (ZNF652) is a transcription factor implicated in various biological processes. Nevertheless, its role in OA has not been elucidated.

Methods

The search term "osteoarthritis" was utilized to procure transcriptome data relating to OA patients and healthy people from the Gene Expression Omnibus (GEO) database. Then a screening process was initiated to identify differentially expressed genes (DEGs). The DEGs were discerned using three distinct machine learning methods. The accuracy of these DEGs in diagnosing OA was evaluated using the Receiver Operating Characteristic (ROC) Curve. A competitive endogenous RNA (ceRNA) visualization network was established to delve into potential regulatory targets. The ZNF652 expression was confirmed in the cartilage of OA rats using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blotting (WB) and analyzed using an independent t-test.

Results

ZNF652 was identified as a DEG and exhibited the highest diagnostic value for OA according to the ROC analysis. The GO and KEGG enrichment analyses suggest that ZNF652 plays a vital role in OA development through processes including nitric oxide anabolism, macrophage proliferation, immune response, and the PI3K/Akt and the MAPK signaling pathways. The increased expression of ZNF652 in OA was validated in qRT-PCR (1.193 ± 0.005 vs 1.000 ± 0.005, p < 0.001) and WB (0.981 ± 0.055 vs 0.856 ± 0.026, p = 0.012) analysis.

Conclusion

ZNF652 was found to be related to OA pathogenesis and can potentially serve as a diagnostic and therapeutic target of OA. The underlying mechanism is that ZNF652 was related to nitric oxide anabolism, macrophage proliferation, various signaling pathways, and immune cells and their functions in OA. Nevertheless, the findings need to be confirmed in clinical trials and the molecular mechanism requires further study.

Deciphering the Role of LncRNAs in Osteoarthritis: Inflammatory Pathways Unveiled

Long non-coding RNA (LncRNA), with transcripts over 200 nucleotides in length, play critical roles in numerous biological functions and have emerged as significant players in the pathogenesis of osteoarthritis (OA), an inflammatory condition traditionally viewed as a degenerative joint disease. This review comprehensively examines the influence of LncRNA on the inflammatory processes driving OA progression, focusing on their role in regulating gene expression, cellular activities, and inflammatory pathways. Notably, LncRNAs such as MALAT1, H19, and HOTAIR are upregulated in OA and exacerbate the inflammatory milieu by modulating key signaling pathways like NF-κB, TGF-β/SMAD, and Wnt/β-catenin. Conversely, LncRNA like MEG3 and GAS5, which are downregulated in OA, show potential in dampening inflammatory responses and protecting against cartilage degradation by influencing miRNA interactions and cytokine production. By enhancing our understanding of LncRNA' roles in OA inflammation, we can better leverage them as potential biomarkers for the disease and develop innovative therapeutic strategies for OA management. This paper aims to delineate the mechanisms by which LncRNA influence inflammatory responses in OA and propose them as novel targets for therapeutic intervention.

Systematic review of the osteogenic effect of rare earth nanomaterials and the underlying mechanisms

Rare earth nanomaterials (RE NMs), which are based on rare earth elements, have emerged as remarkable biomaterials for use in bone regeneration. The effects of RE NMs on osteogenesis, such as promoting the osteogenic differentiation of mesenchymal stem cells, have been investigated. However, the contributions of the properties of RE NMs to bone regeneration and their interactions with various cell types during osteogenesis have not been reviewed. Here, we review the crucial roles of the physicochemical and biological properties of RE NMs and focus on their osteogenic mechanisms. RE NMs directly promote the proliferation, adhesion, migration, and osteogenic differentiation of mesenchymal stem cells. They also increase collagen secretion and mineralization to accelerate osteogenesis. Furthermore, RE NMs inhibit osteoclast formation and regulate the immune environment by modulating macrophages and promote angiogenesis by inducing hypoxia in endothelial cells. These effects create a microenvironment that is conducive to bone formation. This review will help researchers overcome current limitations to take full advantage of the osteogenic benefits of RE NMs and will suggest a potential approach for further osteogenesis research.

Conformationally regulated "nanozyme-like" cerium oxide with multiple free radical scavenging activities for osteoimmunology modulation and vascularized osseointegration

Given post-operative aseptic loosening in orthopedic disease treatment, osteointegration occurs at the bone-implant interface as a holistic process, including immunoregulation (e.g., macrophage polarization), angiogenesis and osteogenesis in sequence. In order to achieve early rapid and satisfactory osseointegration, different nano-shaped (nanocone, nanopolyhedron and nanoflower abbr. NC, NP & NF) cerium oxide (CeO2-x) coatings, endowed with "nanozyme-like" activities for multiple free radical elimination and osteoimmunology regulation, were hydrothermally synthesized on titanium alloy (TC4). In vitro cell experiments showed that nano-CeO2-x coated TC4 not only induced polarization of RAW264.7 cells toward M2 phenotype, but also promoted angiogenesis and vascularization of endothelial cells along with differentiation and mineralization of osteogenic precursor cells. Improvements in M2-polarized macrophage, angiogenesis, and bone regeneration were further confirmed in a rat femoral condyle model. Among the above three nano-morphologies, NF exhibited the best osseoinetegration. RNA sequencing and mechanism exploration suggested that the inhibition of PI3K-AKT signaling pathway was essential for immunomodulatory capacity of NF. In conclusion, it provided promising insights into the immunomodulatory exploitation of orthopedic implants.

Immunomodulatory effects of curcumin on macrophage polarization in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by synovial inflammation, cartilage destruction, pannus formation and bone erosion. Various immune cells, including macrophages, are involved in RA pathogenesis. The heterogeneity and plasticity of macrophages render them pivotal regulators of both the induction and resolution of the inflammatory response. Predominantly, two different phenotypes of macrophages have been identified: classically activated M1 macrophages exacerbate inflammation via the production of cytokines, chemokines and other inflammatory mediators, while alternatively activated M2 macrophages inhibit inflammation and facilitate tissue repair. An imbalance in the M1/M2 macrophage ratio is critical during the initiation and progression of RA. Macrophage polarization is modulated by various transcription factors, epigenetic elements and metabolic reprogramming. Curcumin, an active component of turmeric, exhibits potent immunomodulatory effects and is administered in the treatment of multiple autoimmune diseases, including RA. The regulation of macrophage polarization and subsequent cytokine production as well as macrophage migration is involved in the mechanisms underlying the therapeutic effect of curcumin on RA. In this review, we summarize the underlying mechanisms by which curcumin modulates macrophage function and polarization in the context of RA to provide evidence for the clinical application of curcumin in RA treatment.