Ectopic RASGRP2 (CalDAG-GEFI) expression in rheumatoid synovium contributes to the development of destructive arthritis

Mechanism of berbamine-mediated DNA damage in synovial fibroblasts to alleviate rheumatoid arthritis

Rheumatoid arthritis (RA) is a common chronic autoimmune disease characterised by the proliferation and infiltration of fibroblast-like synoviocytes (FLS). However, pharmaceutical approaches to inhibit FLS in the treatment of RA are limited. Berbamine (BBM), a natural compound extracted from Phellodendron chinense Schneider, has demonstrated anti-tumour and anti-inflammatory effects. This study aimed to investigate the inhibitory effect of BBM on FLS in RA and to delineate the specific mechanisms involved, thereby proposing a novel therapeutic strategy for RA. Using the cell counting kit 8 assay and flow cytometry, we found that BBM reduced the proliferative ability of MH7A rheumatoid arthritis fibroblast-like synoviocytes by blocking the cell cycle and inducing apoptosis. In addition, BBM led to a decrease in the mitochondrial membrane potential and an increase in reactive oxygen species (ROS) and DNA damage. To explore the explicit mechanism of BBM, we used the ROS inhibitor N-acetyl-L-cysteine and the anti-apoptotic drug Z-VAD-FMK to rescue the effects of BBM. BBM effectively inhibited joint inflammation in RA cells in vivo. Regarding the safety confirmation, BBM does not damage the liver, spleen, and kidneys of collagen-induced arthritis mice. In summary, we found that the traditional Chinese medicine extract BBM alleviated RA by promoting ROS production and DNA damage in rheumatoid arthritis fibroblast-like synoviocytes providing new ideas for the clinical treatment of RA with traditional Chinese medicine.

Exploring the potential mechanism of action of Wutou-Guizhi decoction in the treatment of rheumatoid arthritis through network pharmacology analysis

As a widely recognized traditional Chinese medicine (TCM) decoction prescription in China, numerous studies have shown that Wutou-Guizhi decoction (WTGZD) exhibits significant therapeutic efficacy for Rheumatoid arthritis (RA). Nevertheless, the underlying molecular mechanisms have yet to be fully elucidated. This study aims to establish a database of active ingredients for WTGZD and identify RA-related target genes. The WTGZD-RA-Potential target gene network and protein-protein interaction network were constructed, followed by gene ontology (GO) analysis and functional enrichment analysis utilizing the Kyoto Encyclopedia of Genes and Genomes (KEGG). Cell proliferation was confirmed through CCK8 assay. Target gene identification was performed via real-time PCR using quantitative methods, and western blot analysis was conducted. In the course of this investigation, 95 active components of drugs and 34 targets associated with rheumatoid arthritis were identified. Through the utilization of network pharmacology analysis, we were able to identify a total of 17 essential active components of WTGZD and pinpoint 12 significant targets linked to rheumatoid arthritis (RA). Our findings suggest a consistent interaction between the key components of WTGZD and the critical targets associated with RA. Subsequent qPCR analysis revealed that stigmasterol, a principal constituent of WTGZD, exhibited inhibitory effects on the expression of various RA-related factors, such as TNF-α, IL-1β, MAPK8, MMP1, MMP3, and MMP9. Moreover, WTGZD effectively mitigated the increased protein expression of MMP-1 and MAPK8 induced by LPS stimulation, both of which are integral components of the IL-17 signaling pathway. These results suggest that WTGZD may play a significant role in the therapeutic intervention of rheumatoid arthritis by suppressing inflammatory immune responses.

NEDD4L-mediated RASGRP2 suppresses high-glucose and oxLDL-induced vascular endothelial cell dysfunctions by activating Rap1 and R-Ras

BACKGROUND

Ras guanyl-releasing protein 2 (RASGRP2) is an important regulator mediating endothelial cell function. However, whether RASGRP2 mediates diabetes mellitus (DM)-related atherosclerosis (AS) progression by regulating endothelial cell functions is unknown.

METHODS

Human cardiac microvascular endothelial cells (HCMECs) were treated with high-glucose (HG) and oxidized low-density lipoprotein (oxLDL). The expression of RASGRP2 and neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) was examined by quantitative real-time PCR and western blot (WB). Cell viability, apoptosis, migration, angiogenesis were detected by CCK8 assay, flow cytometry, transwell assay and tube formation assay. ROS production and cell permeability were tested to assess cell function. Rap1 and R-Ras protein levels were examined using WB. The interaction between RASGRP2 and NEDD4L was confirmed by Co-IP assay and ubiquitination assay. Exosomes were isolated from adipose-derived MSC (ADMSC)-transfected RASGRP2 overexpression vector, and then co-cultured with HG + oxLDL-induced HCMECs.

RESULTS

RASGRP2 was lowly expressed in HG + oxLDL-induced HCMECs. RASGRP2 overexpression inhibited HG + oxLDL-induced HCMECs permeability, apoptosis and ROS production, while accelerated cell viability, migration and angiogenesis. NEDD4L could interact with RASGRP2 by ubiquitination, thus inhibiting RASGRP2 protein stability to degrade its expression. Functional experiments showed that NEDD4L knockdown suppressed HG + oxLDL-induced HCMECs dysfunction, while these effects were reversed by RASGRP2 downregulation. ADMSC-Exo overexpressed RASGRP2 could promote cell viability, migration and angiogenesis, while suppress permeability, apoptosis and ROS production in HG + oxLDL-induced HCMECs.

CONCLUSION

Our data showed that targeting NEDD4L/RASGRP2 axis or inducing RASGRP2-modified ADMSC-Exo might be the efficient strategy for alleviating DM-related AS.

MAGL inhibition relieves synovial inflammation and pain via regulating NOX4-Nrf2 redox balance in osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage injury, hyperplasia of bone and inflammatory lesions of synovium. Monoacylglycerol lipase (MAGL), a member of the α/β hydrolase superfamily, is involved in regulation of injury protection and immune-inflammation response. Autoinflammatory response of the synovium and the release of inflammatory mediators play critical roles in occurrence of early-stage OA. Fibroblast-like synoviocytes (FLSs) are resident mesenchymal cells of the synovial tissue. Considering that MAGL inhibition regulates the inflammatory signaling cascade, it is crucial to ascertain the biological effects and specific mechanisms of MAGL in alleviating inflammatory infiltration of OA FLSs. The aim of this study was to investigate the effect of MAGL on biological function in OA FLSs. Results from in vitro experiments showed that MAGL blockade not only effectively inhibited proliferation, invasion and migration of FLSs, but also downregulated expression of inflammatory-associated proteins. Sequencing results indicated that MAGL inhibition significantly suppressed NOX4-mediated oxidative stress, thus promoting Nrf2 nuclear accumulation and inhibiting generation of intracellular reactive oxygen species (ROS). Attenuation of NOX4 further alleviated redox dysplasia and ultimately improved tumor-like phenotypes, such as abnormal proliferation, migration and migration of FLSs. In vivo results corroborated this finding, with MAGL inhibition found to modulate pain and disease progression in an OA rat model. Collectively, these results indicate that MAGL administration is an ideal therapy treating OA.

Ageing and Osteoarthritis Synergically Affect Human Synoviocyte Cells: An In Vitro Study on Sex Differences

Osteoarthritis is a chronic inflammatory disease that affects all of the joints, especially those of the elderly. Aging is a natural and irreversible biological process implicated in the pathophysiology of many chronic diseases, such as osteoarthritis. Inflammation and oxidative stress are the main factors involved in osteoarthritis and aging, respectively, with the production of several pro-inflammatory cytokines such as Interleukin 1β (IL1β) and reactive oxygen species. The aim of the study was to set-up an in vitro model of osteoarthritis and aging, focusing on the sex differences by culturing male and female fibroblast-like synoviocytes (FLSs) with IL1β, hydrogen peroxide (H₂O₂), IL1β+H₂O₂ or a growth medium (control). IL1β+H₂O₂ reduced the cell viability and microwound healing potential, increased Caspase-3 expression and reactive oxygen species and IL6 production; IL1β increased IL6 production more than the other conditions did; H₂O₂ increased Caspase-3 expression and reactive oxygen species production; Klotho expression showed no differences among the treatments. The FLSs from female donors demonstrated a better response capacity in unfavorable conditions of inflammation and oxidative stress than those from the male donors did. This study developed culture conditions to mimic the aging and osteoarthritis microenvironment to evaluate the behavior of the FLSs which play a fundamental role in joint homeostasis, focusing on the sex-related aspects that are relevant in the osteoarthritis pathophysiology.

Role of the cGAS-STING pathway in systemic and organ-specific diseases

Cells are equipped with numerous sensors that recognize nucleic acids, which probably evolved for defence against viruses. Once triggered, these sensors stimulate the production of type I interferons and other cytokines that activate immune cells and promote an antiviral state. The evolutionary conserved enzyme cyclic GMP-AMP synthase (cGAS) is one of the most recently identified DNA sensors. Upon ligand engagement, cGAS dimerizes and synthesizes the dinucleotide second messenger 2',3'-cyclic GMP-AMP (cGAMP), which binds to the endoplasmic reticulum protein stimulator of interferon genes (STING) with high affinity, thereby unleashing an inflammatory response. cGAS-binding DNA is not restricted by sequence and must only be >45 nucleotides in length; therefore, cGAS can also be stimulated by self genomic or mitochondrial DNA. This broad specificity probably explains why the cGAS-STING pathway has been implicated in a number of autoinflammatory, autoimmune and neurodegenerative diseases; this pathway might also be activated during acute and chronic kidney injury. Therapeutic manipulation of the cGAS-STING pathway, using synthetic cyclic dinucleotides or inhibitors of cGAMP metabolism, promises to enhance immune responses in cancer or viral infections. By contrast, inhibitors of cGAS or STING might be useful in diseases in which this pro-inflammatory pathway is chronically activated.

Three-dimensional spatial transcriptomics uncovers cell type localizations in the human rheumatoid arthritis synovium

The inflamed rheumatic joint is a highly heterogeneous and complex tissue with dynamic recruitment and expansion of multiple cell types that interact in multifaceted ways within a localized area. Rheumatoid arthritis synovium has primarily been studied either by immunostaining or by molecular profiling after tissue homogenization. Here, we use Spatial Transcriptomics, where tissue-resident RNA is spatially labeled in situ with barcodes in a transcriptome-wide fashion, to study local tissue interactions at the site of chronic synovial inflammation. We report comprehensive spatial RNA-Seq data coupled to cell type-specific localization patterns at and around organized structures of infiltrating leukocyte cells in the synovium. Combining morphological features and high-throughput spatially resolved transcriptomics may be able to provide higher statistical power and more insights into monitoring disease severity and treatment-specific responses in seropositive and seronegative rheumatoid arthritis.

Network Pharmacology and Molecular Docking Study of the Chinese Miao Medicine Sidaxue in the Treatment of Rheumatoid Arthritis

Purpose

This study aimed to investigate the molecular mechanisms of Compound Sidaxue (SX), a prescription of Chinese Miao medicine, in treating rheumatoid arthritis (RA) using network pharmacology and in vivo experimental approaches.

Methods

Network pharmacology was adopted to detect the active components of four Traditional Chinese herbal medicine (TCM) of SX, and the key targets and signaling pathways in the treatment of RA were predicted, and the key components and targets were screened for molecular docking. The predicted targets and pathways were validated in bovine type II collagen and incomplete Freund’s adjuvant emulsifier-induced rat RA model.

Results

In this study, we identified 33 active components from SX, predicted to act on 44 RA-associated targets by network pharmacology. PPI network demonstrated that TNF-α, VEGF-A, IL-2, IL-6, AKT, PI3K, STAT1 may serve as the key targets of SX for the treatment of RA. The main functional pathways involving these key targets include PI3K-AKT signaling pathway, TNF signaling pathway, NF-κB signaling pathway. Molecular docking analysis found that the active components β-amyrin, cajanin, eleutheroside A have high affinity for TNF-α, VEGFA, IL-2, AKT, and PI3K, etc. SX can improve joint swelling in Collagen-induced arthritis (CIA) rats, reduce inflammatory cell infiltration and angiogenesis in joint synovial tissue, and down-regulate IL-2, IL-6, TNF-α, VEGF, PI3K, AKT, p-AKT, NF-κBp65, the expression of p-NF-κBp65, STAT1, and PTGS2 are used to control the exacerbation of inflammation and alleviate the proliferation of synovial pannus, and at the same time play the role of cartilage protection to achieve the effect of treating RA.

Conclusion

Through a network pharmacology approach and animal study, we predicted and validated the active compounds of SX and their potential targets for RA treatment. The results suggest that SX can markedly alleviate CIA rat by modulating the VEGF/PI3K/AKT signaling pathway, TNF-α signaling pathway, IL/NF-κB signaling pathway.

Shared Molecular Mechanisms between Atherosclerosis and Periodontitis by Analyzing the Transcriptomic Alterations of Peripheral Blood Monocytes

OBJECTIVE

This study investigated the nature of shared transcriptomic alterations in PBMs from periodontitis and atherosclerosis to unravel molecular mechanisms underpinning their association.

METHODS

Gene expression data from PBMs from patients with periodontitis and those with atherosclerosis were each downloaded from the GEO database. Differentially expressed genes (DEGs) in periodontitis and atherosclerosis were identified through differential gene expression analysis. The disease-related known genes related to periodontitis and atherosclerosis each were downloaded from the DisGeNET database. A Venn diagram was constructed to identify crosstalk genes from four categories: DEGs expressed in periodontitis, periodontitis-related known genes, DEGs expressed in atherosclerosis, and atherosclerosis-related known genes. A weighted gene coexpression network analysis (WGCNA) was performed to identify significant coexpression modules, and then, coexpressed gene interaction networks belonging to each significant module were constructed to identify the core crosstalk genes.

RESULTS

Functional enrichment analysis of significant modules obtained by WGCNA analysis showed that several pathways might play the critical crosstalk role in linking both diseases, including bacterial invasion of epithelial cells, platelet activation, and Mitogen-Activated Protein Kinases (MAPK) signaling. By constructing the gene interaction network of significant modules, the core crosstalk genes in each module were identified and included: for GSE23746 dataset, RASGRP2 in the blue module and VAMP7 and SNX3 in the green module, as well as HMGB1 and SUMO1 in the turquoise module were identified; for GSE61490 dataset, SEC61G, PSMB2, SELPLG, and FIBP in the turquoise module were identified.

CONCLUSION

Exploration of available transcriptomic datasets revealed core crosstalk genes (RASGRP2, VAMP7, SNX3, HMGB1, SUMO1, SEC61G, PSMB2, SELPLG, and FIBP) and significant pathways (bacterial invasion of epithelial cells, platelet activation, and MAPK signaling) as top candidate molecular linkage mechanisms between atherosclerosis and periodontitis.

The Role of RASGRP2 in Vascular Endothelial Cells-A Mini Review

RAS guanyl nucleotide-releasing proteins (RASGRPs) are important proteins that act as guanine nucleotide exchange factors, which activate small GTPases and function as molecular switches for intracellular signals. The RASGRP family is composed of RASGRP1-4 proteins and activates the small GTPases, RAS and RAP. Among them, RASGRP2 has different characteristics from other RASGRPs in that it targets small GTPases and its localizations are different. Many studies related to RASGRP2 have been reported in cells of the blood cell lineage. Furthermore, RASGRP2 has also been reported to be associated with Huntington's disease, tumors, and rheumatoid arthritis. In addition, we also recently reported RASGRP2 expression in vascular endothelial cells, and clarified the involvement of xenopus Rasgrp2 in the vasculogenesis process and multiple signaling pathways of RASGRP2 in human vascular endothelial cells with stable expression of RASGRP2. Therefore, this article outlines the existing knowledge of RASGRP2 and focuses on its expression and role in vascular endothelial cells, and suggests that RASGRP2 functions as a protective factor for maintaining healthy blood vessels.

Treatment of rheumatoid arthritis by phototherapy: advances and perspectives

Rheumatoid arthritis (RA) is an inflammatory disease that is prevalent worldwide and seriously threatens human health. Though traditional drug therapy can alleviate RA symptoms and slow progression, high dosage and frequent administration would cause unfavorable side effects. Phototherapy including photodynamic therapy (PDT) and photothermal therapy (PTT) has demonstrated distinctive potential in RA treatment. Under light irradiation, phototherapy can convert light into heat, or generate ROS, to promote necrosis or apoptosis of RA inflammatory cells, thus reducing the concentration of related inflammatory factors and relieving the symptoms of RA. In this review, we will summarize the development in the application of phototherapy in the treatment of rheumatoid arthritis.

Signalling and putative therapeutic molecules on the regulation of synoviocyte signalling in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by symmetrical and chronic polyarthritis. Fibroblast-like synoviocytes are mainly involved in joint inflammation and cartilage and bone destruction by inflammatory cytokines and matrix-degrading enzymes in RA. Approaches that induce various cellular growth alterations of synoviocytes are considered as potential strategies for treating RA. However, since synoviocytes play a critical role in RA, the mechanism and hyperplastic modulation of synoviocytes and their motility need to be addressed. In this review, we focus on the alteration of synoviocyte signalling and cell fate provided by signalling proteins, various antioxidant molecules, enzymes, compounds, clinical candidates, to understand the pathology of the synoviocytes, and finally to achieve developed therapeutic strategies of RA.

Cite this article: Bone Joint Res 2021;10(4):285–297.

Anti-Rheumatic Properties of Gentiopicroside Are Associated With Suppression of ROS-NF-κB-NLRP3 Axis in Fibroblast-Like Synoviocytes and NF-κB Pathway in Adjuvant-Induced Arthritis

Rheumatoid arthritis (RA) is among the most prevalent forms of autoimmunity. Gentiopicroside (Gent) is an iridoid glucoside derived from the Gentiana Macrophylla Pall which is used in traditional Chinese medicine to treat RA. The present study was designed to explore the ability of Gent to combat RA and to explore the molecular basis for such anti-RA activity both in vitro using tumor necrosis factor alpha (TNF-α)-stimulated human RA fibroblast-like synoviocytes (RA-FLS) and in vivo using a rat adjuvant-induced arthritis (AIA) model. We found that Gent was able to significantly reduce the swelling of joints and arthritic index scores, with corresponding reductions in synovial inflammatory cell infiltration, synovial hyperplasia, and bone erosion in treated AIA rats. Importantly, Gent 200 mg/kg reduced thymus index in AIA rats, but had no effect on spleen index and body weight, it revealed that Gent was relatively safe at the dose we chose. We further found that Gent was able to suppress the TNF-α-induced proliferation and migration of RA-FLS cells. This suppression was attributed to the ability of Gent to block NOD-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC), and caspase-1, thereby disrupting the activation of the NLRP3 inflammasome. Consistent with such suppression, Gent led to a significant decrease in IL-1β secretion by treated cells. Furthermore, this reduction in NLRP3 inflammasome activation was also associated with decreases in the activation of nuclear factor (NF-κB), the production of reactive oxygen species (ROS), and the expression of inflammatory IL-6. Together these findings indicate that Gent can suppress the ROS-NF-κB-NLRP3 axis to alleviate RA symptoms.

Hypoxia/reoxygenation activates the JNK pathway and accelerates synovial senescence

Hypoxia/reoxygenation (H/R) may play an important role via senescence in the mechanism of osteoarthritis (OA) development. The synovial membrane is highly sensitive to H/R due to its oxygen consumption feature. Excessive mechanical loads and oxidative stress caused by H/R induce a senescence-associated secretory phenotype (SASP), which is related to the development of OA. The aim of the present study was to investigate the differences of SASP manifestation in synovial tissue masses between tissues from healthy controls and patients with OA. The present study used tumor necrosis factor-α (TNF-α) to pre-treat synovial tissue and fibroblast-like synoviocytes (FLS) to observe the effect of inflammatory cytokines on the synovial membrane before H/R. It was determined that H/R increased interleukin (IL)-1β and IL-6 expression levels in TNF-α-induced cell culture supernatants, increased the proportion of SA-β-gal staining, and increased the expression levels of high mobility group box 1, caspase-8, p16, p21, matrix metalloproteinase (MMP)-3 and MMP-13 in the synovium. Furthermore, H/R opened the mitochondrial permeability transition pore, caused the loss of mitochondrial membrane potential (ΔΨm) and increased the release of reactive oxygen species (ROS). Moreover, H/R caused the expansion of the mitochondrial matrix and rupture of the mitochondrial extracorporeal membrane, with a decrease in the number of cristae. In addition, H/R induced activation of the JNK signaling pathway in FLS to induce cell senescence. Thus, the present results indicated that H/R may cause inflammation and escalate synovial inflammation induced by TNF-α, which may lead to the pathogenesis of OA by increasing changes in synovial SASP and activating the JNK signaling pathway. Therefore, further studies expanding on the understanding of the pathogenesis of H/R etiology in OA are required.

RasGRP2 Structure, Function and Genetic Variants in Platelet Pathophysiology

RasGRP2 is calcium and diacylglycerol-regulated guanine nucleotide exchange factor I that activates Rap1, which is an essential signaling-knot in "inside-out" αIIbβ3 integrin activation in platelets. Inherited platelet function disorder caused by variants of RASGRP2 represents a new congenital bleeding disorder referred to as platelet-type bleeding disorder-18 (BDPLT18). We review here the structure of RasGRP2 and its functions in the pathophysiology of platelets and of the other cellular types that express it. We will also examine the different pathogenic variants reported so far as well as strategies for the diagnosis and management of patients with BDPLT18.

MicroRNA-9 ameliorates destructive arthritis through down-regulation of NF-κB1-RANKL pathway in fibroblast-like synoviocytes

We investigated the effect of miR-9 on fibroblast-like synoviocytes (FLS) from RA patients and animal arthritis model. The binding of miR-9 to NF-κB1 3'UTR was analyzed by luciferase reporter assay and immunoprecipitation. ChIP assay and luciferase promoter assay were performed to identify the binding of NF-κB1 to RANKL promoter and its activity. FLS were treated with miR-9/anti-miR-9 to evaluate cell proliferation and the expression of RANKL. Therapeutic effect of intra-articular miR-9 was evaluated in type-II collagen-induced arthritis in rats. miR-9 bound to the 3'-UTR of NF-κB1 and downregulated NF-κB1. NF-κB1 bound to RANKL promoter and increased the promoter activity of RANKL. RANKL was downregulated by miR-9. Proliferation of FLS was increased by miR-9 inhibitor. miR-9 dampened experimental arthritis by lowering inflammatory state, reducing RANKL and osteoclasts formation. Our findings revealed miR-9-NF-κB1-RANKL pathway in RA-FLS, further, miR-9 ameliorated inflammatory arthritis in vivo which propose therapeutic implications of miR- 9 in RA.

The inhibition of Bax activation-induced apoptosis by RasGRP2 via R-Ras-PI3K-Akt signaling pathway in the endothelial cells

Apoptosis of endothelial cells is a very important event in various diseases and angiogenesis. We recently reported that ras guanyl nucleotide releasing protein 2 (RasGRP2), which is a guanine nucleotide exchange factor, was expressed in the human umbilical vein endothelial cells (HUVECs) and that Rap1 activation by its overexpression inhibited apoptosis by suppressing tumor necrosis factor-α induced-reactive oxygen species (ROS) production. However, other signaling pathways and roles of RasGRP2 not mediated via Rap1 are not well understood. Therefore, we compared the Mock (M) and the RasGRP2-stable overexpression (R) immortalized HUVECs using BAM7 and anisomycin, which are apoptosis inducers. BAM7 and anisomycin induced apoptosis without causing ROS production, and such apoptosis was significantly increased in M cells, but not in R cells. RasGRP2 suppressed BAM7- and anisomycin-induced apoptosis, but not via the Rap1 pathway as observed using Rap1 knockdown. Furthermore, RasGRP2 activated not only Rap1 but also R-Ras, and suppressed apoptosis by activating R-Ras-phosphoinositide 3-kinase (PI3K)-Akt signaling pathway. The phosphorylation of Akt by RasGRP2 inhibited Bax translocation by promoting translocation of hexokinase-2 (HK-2) from cytoplasm to mitochondria. Taken together, it was suggested that RasGRP2 suppresses the Bax activation-induced apoptosis by promoting HK-2 translocation to mitochondria via R-Ras-PI3K-Akt signaling pathway.

MicroRNA-21-5p are involved in apoptosis and invasion of fibroblast-like synoviocytes through PTEN/PI3K/AKT signal

The function of microRNA-21-5p (miR-21) in fibroblast-like synoviocytes in RA was still unclear. In our study, we used tumor necrosis factor alpha (TNFα) (10 ng/ml) to mimic RA-FLSs and we found that normal FLS stimulated with TNFα caused the increasing expression of miR-21, a disintegrin and metalloproteinase with thrombospondin motifs 5 and matrix metalloproteinase 3, which were in accord with RA-FLSs changes. Our data showed that miR-21 overexpression significantly increased cell invasion and decreased apoptosis in FLSs. Knockdown of miR-21 in FLSs causes the opposite result. However, miR-21 may not affect the proliferation of FLSs. Meanwhile, we showed that miR-21 activated the PI3K/AKT signaling pathway to participate in RA by inhibiting PTEN expression. Taken together, our results suggested that miR-21 may play a positive role in RA and may be a promising new therapeutic target for RA.