Synovial Macrophages Research Articles

Characterization of the single cell landscape in normal and osteoarthritic equine joints.

Osteoarthritis (OA) is a major source of pain and disability worldwide. Understanding of disease progression is evolving, but OA is increasingly thought to be a multifactorial disease in which the innate immune system plays a role in regulating and perpetuating low-grade inflammation. The aim of this study was to enhance our understanding of OA immunopathogenesis through characterization of the transcriptomic responses in OA joints, with the goal to facilitate the development of targeted therapies. Single-cell RNA sequencing (scRNA-seq) was completed on cells isolated from the synovial fluid of three normal and three OA equine joints. In addition to synovial fluid, scRNA-seq was also performed on synovium from one normal joint and one OA joint. Characterization of 28,639 cells isolated from normal and OA-affected equine synovial fluid revealed the composition to be entirely immune cells (CD45+) with 8 major populations and 26 subpopulations identified. In synovial fluid, we found myeloid cells (macrophage and dendritic cells) to be overrepresented and T cells (CD4 and CD8) to be underrepresented in OA relative to normal joints. Through subcluster and differential abundance analysis of T cells we further identified a relative overrepresentation of IL23R+ gamma-delta (γδ) T cells in OA-affected joints (a cell type we report to be enriched in gene signatures associated with T helper 17 mediated immunity). Analysis of an additional 17,690 cells (11 distinct cell type clusters) obtained from synovium of one horse led to the identification of an OA-associated reduction in the relative abundance of synovial macrophages, which contrasts with the increased relative abundance of macrophages in synovial fluid. Completion of cell-cell interaction analysis implicated myeloid cells in disease progression, suggesting that the myeloid-myeloid interactions were increased in OA-affected joints. Overall, this work provides key insights into the composition of equine synovial fluid and synovium in health and OA. The data generated in this study provides equine-specific cell type gene signatures which can be applied to future investigations. Furthermore, our analysis highlights the potential role of macrophages and IL23R+ γδ T cells in OA immunopathogenesis.

Exosomal microRNA-363 mediates the destructive effect of M1 macrophages on chondrocytes by repressing G3BP2

M1 polarization of synovial macrophages contributes to cartilage degeneration and osteoarthritis (OA) development. However, limited knowledge is available about how M1 macrophages affect the biological properties of chondrocytes. This study aimed to explore the role of exosomal microRNAs (miRs) released from M1 macrophages in modulating the proliferation and survival of chondrocytes. Through bioinformatic analysis and experimental validation, we indicated that miR-363 was selectively induced in M1 macrophages (CD68+CD80+) but not M2 macrophages (CD68+CD206+). The upregulation of miR-363 in M1 macrophages depended on the activation of STAT1 signaling. Clinically, OA patients had a significantly higher miR-363 level in synovial fluid than control individuals without OA. Functional studies revealed that inhibition of miR-363 blocked the M1 macrophage polarization induced by lipopolysaccharide and IFN-γ. Moreover, exosomal miR-363 released from M1 macrophages significantly suppressed the proliferation and survival and induced inflammatory gene expression in chondrocytes. G3BP2 was identified as a target gene for miR-363 and could be negatively regulated by miR-363. Knockdown of G3BP2 recapitulated the effect of miR-363 overexpression on chondrocytes. Most importantly, enforced expression of G3BP2 attenuated miR-363-induced apoptosis and inflammatory response in chondrocytes. In conclusion, miR-363 plays an indispensable role in M1 macrophage polarization and can be released from M1 macrophages via exosomes to cause chondrocyte injury and inflammation. The miR-363/G3BP2 axis may represent a promising target for the prevention of OA development.

Extracellular vesicles from inflammatory-stimulated BMSCs ameliorate osteoarthritis via Rpl14 mediated synovial macrophage polarization

Bone marrow mesenchymal stem cells (BMSCs) and extracellular vesicles (EVs) were considered promising methods for the treatment of diverse diseases, including osteoarthritis (OA). However, the role of inflammatory-stimulated BMSCs driven EVs (iBMSC-EVs) in OA remains unclear. This study aims to investigate the potential function of iBMSC-EVs in ameliorating OA and its underlying molecular mechanism. In this study, EVs were isolated from inflammatory-stimulated BMSCs and destabilization of the medial meniscus (DMM) surgery was performed to induce knee OA model in mice. Micro-CT, H&E Staining, Safranin O-Fast Green Staining and immunofluorescence were used to examine the in vivo therapeutic effect of iBMSC-EVs on OA. Public single-cell RNA-seq data was downloaded and bulk RNA-seq data was acquired to identify critical genes promoted by iBMSC-EVs in macrophage polarization during OA. Real-time quantitative polymerase chain reaction (RT-qPCR), western blot, enzyme-linked immunosorbent assay (ELISA), cell counting kit-8 (CCK-8), transwell and scratch assays were used to further confirm the in vitro effect of iBMSC-EVs on macrophage polarization and chondrocyte proliferation, migration, as well as ECM anabolism and catabolism. In vivo experiments demonstrated that iBMSC-EVs could alleviate OA in mice and promote the reprogramming of M1 macrophages towards an M2 phenotype. RNA-Seq and scRNA-Seq analyses indicated that iBMSC-EVs altered the expression profiles of OA-related genes, with Rpl14 identified as a critical gene regulating macrophage reprogramming in OA. In vivo and in vitro experiments further confirmed that iBMSC-EVs, by downregulating Rpl14 expression, promoted M1 macrophage reprogramming to M2, facilitating chondrocyte proliferation and migration, inhibiting ECM degradation and ultimately alleviating OA progression. In conclusion, our data revealed the substantive role of iBMSC-EVs in ameliorating OA progression via Rpl14 mediated synovial macrophage polarization, presenting a promising therapeutic method for the treatment of OA.

Nanozyme-enhanced injectable hyaluronic acid-based hydrogel for the treatment of osteoarthritis

The progression of osteoarthritis (OA) is dramatically accelerated by excessive reactive oxygen species (ROS)-induced apoptosis of chondrocytes and the inflammatory response of synovial macrophages. In this study, we developed an injectable hydrogel with a catalase-mimicking nanozyme activity as a therapeutic agent for OA. In vitro experiments confirmed that the HA and peroxide-mimetic nanoenzyme-enhanced hydrogel, containing ε-polylysine/Mn1.8Co1.2O4 (ε-PLE/MnCoO) nanoparticles, continuously eliminated ROS and inflammatory cytokines while promoting the polarization of inflammatory macrophages (M1 phenotype) towards anti-inflammatory macrophages (M2 phenotype) in dysfunctional microenvironments. When used for intraarticular injections in OA models, the nanoenzyme-enhanced hydrogel effectively reduced oxidative stress by scavenging ROS and regulating the immune microenvironment. It resulted in a subsequent reduction in the expression of inflammatory factors, including MMP-13, TNF-α, IL-1β, and iNOS in both the synovium and joint fluid. Moreover, cartilage repair was enhanced by the promotion of COL-2 and SOX-9 expression in the cartilage tissue, whereas osteophyte formation in OA was reduced. This study introduced an innovative treatment strategy for the clinical management of OA, demonstrating its significant potential for application in treating OA.

Trained immunity of synovial macrophages is associated with exacerbated joint inflammation and damage after Staphylococcus aureus infection.

Investigate whether and which synoviocytes would acquire trained immunity characteristics that could exacerbate joint inflammation following a secondary Staphylococcus aureus infection. Lipopolysaccharide (LPS) and S. aureus were separately or double injected (21 days of interval) into the tibiofemoral joint cavity of male C57BL/6 mice. At different time points after these stimulations, mechanical nociception was analyzed followed by the analysis of signs of inflammation and damage in the affected joints. The trained immunity markers, including the glycolytic and mTOR pathway, were analyzed in whole tissue or isolated synoviocytes. A group of mice was treated with Rapamycin, an mTOR inhibitor before LPS or S. aureus stimulation. The double LPS - S. aureus hit promoted intense joint inflammation and damage compared to single joint stimulation, including markers in synoviocyte activation, production of proinflammatory cytokines, persistent nociception, and bone damage, despite not reducing the bacterial clearance. The double LPS - S. aureus hit joints increased the synovial macrophage population expressing CX3CR1 alongside triggering established epigenetic modifications associated with trained immunity events in these cells, such as the upregulation of the mTOR signaling pathway (p-mTOR and HIF1α) and the trimethylation of histone H3. Mice treated with Rapamycin presented reduced CX3CR1+ macrophage activation, joint inflammation, and bone damage. There is a trained immunity phenotype in CX3CR1+ synovial macrophages that contributes to the exacerbation of joint inflammation and damage during septic arthritis caused by S. aureus.

Loss of synovial tissue macrophage homeostasis precedes rheumatoid arthritis clinical onset.

This study performed an in-depth investigation into the myeloid cellular landscape in the synovium of patients with rheumatoid arthritis (RA), "individuals at risk" of RA, and healthy controls (HC). Flow cytometric analysis demonstrated the presence of a CD40-expressing CD206+CD163+ macrophage population dominating the inflamed RA synovium, associated with disease activity and treatment response. In-depth RNA sequencing and metabolic analysis demonstrated that this macrophage population is transcriptionally distinct, displaying unique inflammatory and tissue-resident gene signatures, has a stable bioenergetic profile, and regulates stromal cell responses. Single-cell RNA sequencing profiling of 67,908 RA and HC synovial tissue cells identified nine transcriptionally distinct macrophage clusters. IL-1B+CCL20+ and SPP1+MT2A+ are the principal macrophage clusters in RA synovium, displaying heightened CD40 gene expression, capable of shaping stromal cell responses, and are importantly enriched before disease onset. Combined, these findings identify the presence of an early pathogenic myeloid signature that shapes the RA joint microenvironment and represents a unique opportunity for early diagnosis and therapeutic intervention.

Low-Protein Diet Inhibits the Synovial Tissue Macrophage Pro-Inflammatory Polarization Via NRF2/SIRT3/SOD2/ROS Pathway in K/BxN Rheumatoid Arthritis Mice.

Rheumatoid arthritis (RA) is a chronic inflammatory disorder characterized by pain, swelling, stiffness, and impaired function. Attenuating inflammation is a crucial objective in RA management. Diet and nutrition are believed to influence RA symptomatology, with a low-protein diet being one potential nutritional strategy, although its underlying mechanisms remain to be fully elucidated. In this research, serum derived from arthritic transgenic K/BxN mice was administered to naive mice to establish a K/BxN rheumatoid arthritis model. Physiological assessments and histological staining were performed to evaluate joint pathology. (Enzyme-linked immunosorbent assay) ELISA was used to measure inflammatory cytokines. Flow cytometry and immunofluorescence were applied to characterize macrophage phenotypes. Transcriptomic analysis elucidated molecular pathways under the effect of a low-protein diet and verified by immunoblotting. Mitochondrial reactive oxygen species (ROS) was detected by Mito-SOX. Protein expression was silenced through the application of siRNA transfection. Our results indicate that a low-protein diet significantly alleviates disease symptoms and decreases pro-inflammatory cytokine levels in synovial fluid. Furthermore, this dietary intervention inhibits M1 macrophage polarization while promoting a shift towards the M2 phenotype. Transcriptomic analysis revealed that the beneficial effects of the low-protein diet in alleviating rheumatoid arthritis are closely linked to the NRF2 pathway. In vitro, low protein treatment can promote the activity of NRF2 via inhibiting the ubiquitin mediated proteolysis and activate the NRF2/SIRT3/SOD2 pathway to inhibit the production of ROS, which will further inhibit the M1 macrophage polarization. NRF2 knockdown can abolish the effects of low-protein treatment, indicating that the inhibition of M1 polarization and the anti-inflammatory response induced by low-protein treatment are dependent on NRF2. In summary, our findings propose that low-protein diet can inhibit synovial macrophage M1 polarization via activating NRF2/SIRT3/SOD2 pathway to reduce mitochondrial ROS production. This mechanism effectively decreases synovial inflammation and alleviates RA symptoms.

Proteoglycan 4 (Lubricin) and Regulation of Xanthine Oxidase in Synovial Macrophage as A Mechanism of Controlling Synovitis.

Synovial macrophages (SMs) are important effectors of joint health and disease. A novel Cx3CR1 + TREM2 + SM population expressing the tight junction protein claudin-5, was recently discovered in synovial lining. Ablation of these SMs was associated with onset of arthritis. Proteoglycan 4 (PRG4) is a mucinous glycoprotein that fulfills lubricating and homeostatic roles in the joint. The aim of this work is to study the role of PRG4 in modulating synovitis in the context of SM homeostasis and assess the contribution of xanthine oxidase (XO)-hypoxia inducible factor alpha (HIF-1α) axis to this regulation. We used Prg4 FrlioxP/FrtloxP ;R26 FlPoER/+ , a novel transgenic mouse, where the Prg4 Frt allele normally expresses the PRG4 protein and was designed to flank the first two exons of Prg4 with a flippase recognition target and "LOXP" sites. Inducing flippase activity with tamoxifen (TAM) inactivates the Frt allele and thus creates a conditional knockout state. We studied anti-inflammatory SMs and XO by quantitative immunohistochemistry, isolated RNA and studied immune pathway activations by multiplexed assays and isolated SMs and studied PRG4 signaling dysfunction in relation to glycolytic switching due to pro-inflammatory activation. Prg4 inactivated mice were treated with oral febuxostat, a specific XO inhibitor, and quantification of Cx3CR1 + TREM2 + SMs, XO immunostaining and synovitis assessment were conducted. Prg4 inactivation induced Cx3CR1 + TREM2 + SM loss (p < 0.001) and upregulated glycolysis and innate immune pathways in the synovium. In isolated SMs, Xdh (p < 0.01) and Hif1a (p < 0.05) were upregulated. Pro-inflammatory activation of SMs was evident by enhanced glycolytic flux and XO-generated reactive oxygen species (ROS). Febuxostat reduced glycolytic flux (p < 0.001) and HIF-1α levels (p < 0.0001) in SMs. Febuxostat also reduced systemic inflammation (p < 0.001), synovial hyperplasia (p < 0.001) and preserved Cx3CR1 + TREM2 + SMs (p < 0.0001) in synovia of Prg4 inactivated mice. PRG4 is a biologically significant modulator of synovial homeostasis via inhibition of XO expression and downstream HIF-1a activation. PRG4 signaling is anti-inflammatory and promotes synovial homeostasis in chronic synovitis, where direct XO inhibition is potentially therapeutic in chronic synovitis.

An injectable thermosensitive hydrogel delivering M2 macrophage-derived exosomes alleviates osteoarthritis by promoting synovial lymphangiogenesis

Osteoarthritis (OA) is a prevalent chronic degenerative disease affecting millions worldwide, with current treatment measures lacking efficacy in slowing disease progression. The synovial lymphatic system (SLS) has emerged as a crucial player in OA pathogenesis, with compromised drainage function contributing to disease advancement. Lymphatic endothelial cells (LECs) within the SLS are influenced by synovial macrophages, whose precise impact on LEC function remains unclear. Exosomes released by macrophages may serve as mediators of this interaction, with potential implications for OA progression. Here, we propose that polarized macrophages modulate LEC activity via exosome release in synovial tissue, with M2 macrophage-derived exosomes (M2Exo) promoting LEC proliferation, migration, and lymphangiogenesis, potentially offering a therapeutic avenue for OA. Moreover, we developed an injectable thermosensitive hydrogel with the characteristic of sustained release of M2Exo for alleviating OA. The hydrogel was prepared by dynamically linking hyaluronic acid (HA) and Pluronic F-127 and loading M2Exo, termed as M2Exo loaded HP hydrogel. The in vitro and in vivo experiments showed that M2Exo loaded HP hydrogel exhibits a controlled release profile of exosomes, thereby efficaciously fostering synovial lymphangiogenesis and enhancing synovial lymphatic drainage functionality under OA conditions, thus alleviating OA progression, and providing promising insights into OA therapeutic strategies. Statement of significanceOsteoarthritis (OA) is a widespread degenerative disease with limited effective treatments to halt its progression. This research highlights the critical role of the synovial lymphatic system (SLS) in OA, focusing on how macrophage-derived exosomes influence lymphatic endothelial cell (LEC) function. We propose that M2 macrophage-derived exosomes (M2Exo) enhance LEC activity, promoting lymphangiogenesis, and offering a therapeutic approach for OA. Furthermore, we developed an injectable thermosensitive hydrogel (M2Exo loaded HP hydrogel) for sustained M2Exo release. Our in vitro and in vivo experiments demonstrate that this hydrogel supports synovial lymphangiogenesis and improves lymphatic drainage, effectively alleviating OA progression. This study presents significant advancements in OA therapy, offering new insights into its management.

Quantification of macrophage activity in knee synovial tissue using [18F]FEPPA positron emission tomography

ObjectiveInflammation in knee osteoarthritis (OA) is mediated primarily by synovial tissue macrophages, but non-invasive measurement of macrophage activity in vivo is a challenge. Activated macrophages markedly increase expression of the translocator protein (TSPO). In the context of other diseases TSPO-PET using the [18F]FEPPA tracer (binding to TSPO) has been reported to be an effective method for imaging macrophages in vivo. The goal of this study was to validate the use of [18F]FEPPA PET radiotracer to accurately measure macrophage activation in knee synovial tissue. DesignTen participants with late-stage OA scheduled for knee replacement surgery were recruited. Prior to surgery, 5 of the participants underwent a clinical [18F]FEPPA PET/MRI scan and the standard uptake value (SUV) in the suprapatellar synovial region was calculated. Suprapatellar synovial tissue samples were collected from all participants at the time of surgery and were imaged ex vivo with [18F]FEPPA autoradiography. Tracer uptake was compared to TSPO antibody immunostaining in serial tissue sections. The correlation between the [18F]FEPPA uptake and gold standard TSPO fluorescent intensity was measured. RESULTSThe autoradiography [18F]FEPPA signal in the synovial lining was correlated with the TSPO signal in the. lining macrophages measured by immunohistochemistry (r = 0.81, p = 0.0040, CI [0.37, 0.95]). Similarly, PET/MRI scans demonstrated similar correlation between SUV in synovial tissues in vivo and in situ TSPO signal in lining macrophages {r = 0.90, p = 0.083, CI [0.086, 0.99]) Conclusion[18F]FEPPA uptake in knee synovial tissue is strongly correlated to the expression of TSPO in synovial lining macrophages, suggesting that clinical [18F]FEPPA PET/MRI may be a valid measure of true macrophage activity in synovial tissues in knee OA. [18F]FEPPA may be an effective tool to assess macrophage activation both ex vivo and in vivo, and should be investigated further to assess its performance and measurement properties in different clinical contexts of knee OA including disease states and responses to treatment.

An HFD negatively influences both joint and liver health in rabbits with and without an enzymatically-induced model of arthritis

Osteoarthritis (OA) is a common arthritis types in animals that causes persistent pain and reduces quality of life. Although a high-fat diet (HFD) is widely believed to induce obesity and have adverse effects on the body, the connection between HFD and joint health is not well understood. Therefore, in this study, 32 healthy male New Zealand rabbits were randomly divided into four groups: healthy rabbits fed a standard diet (NDG, n=8) or an HFD (HDG, n=8), rabbits fed a standard diet (OAG, n=8) and an HFD (HOG, n=8), and arthritis was induced by intra-articular enzyme injection. After 12 weeks of HFD feeding, articular cartilage, synovium, and subchondral bone were isolated and collected. Joint tissue damage was evaluated using histopathological and imaging tests. The results showed that there was no significant difference in body weight between rabbits fed a normal diet and those fed an HFD. However, the HFD led to an increase in joint injuries in both induced and non-induced arthritis rabbits. Specifically, the HFD induced lipid metabolism disorders and liver damage in vivo, significantly elevating the levels of serum inflammatory cytokines and bone metabolism markers. Moreover, HFD exacerbated articular cartilage damage in the joints and increased the accumulation of inflammatory cells in synovial tissue, resulting in a notable increase in synovial macrophages and inflammatory cytokines. Additionally, HFD accelerated the bone resorption process in subchondral bone, leading to the destruction of bone mass and subchondral bone microstructure. In summary, the results of this study indicate that an HFD can cause histological damage to the articular cartilage, synovium, and subchondral bone in rabbits, exacerbating arthritis in pre-existing joint damage. Notably, weight is not the primary factor in this effect.

PdZn/CoSA‐NC Nanozymes with Highly Efficient SOD/CAT Activities for Treatment of Osteoarthritis via Regulating Immune Microenvironment

AbstractInflammatory infiltration of synovial M1 macrophages, high levels of ROS, and NO exacerbate osteoarthritis (OA) progression. The PdZn/CoSA‐NC nanozymes, which are highly ordered PdZn intermetallic nanoparticles loaded with Co single atom N‐doped carbon‐rich in multi‐level pores, in an attempt to serve as SOD and CAT mimicking nanozymes for OA therapy is designed. The PdZn/CoSA‐NC nanozymes' high electron transfer and dual active site sufficient exposure enhances free radical adsorption and lower reaction energies, accelerating SOD‐like, CAT‐like, and GPx‐like catalyzed reactions, outperforming CoSA‐NC and PdZn/NC alone. Furthermore, PdZn/CoSA‐NC nanozymes exhibit favorable biocompatibility, reduce synovial macrophage oxidative stress in OA, alleviate hypoxia, restore mitochondrial function, regulate energy metabolism, increase antioxidant factors, and reduce inflammatory factors, thus effectively mitigating the progression of OA. Mechanistically, PdZn/CoSA‐NC nanozymes downregulate M1‐type phenotypic markers like IL‐1β by regulating purine metabolism. The PdZn/CoSA‐NC nanozymes offer a novel approach to treating oxidative stress‐related inflammatory diseases.

Injectable porous microspheres for articular cartilage regeneration through in situ stem cell recruitment and macrophage polarization

In situ mesenchymal stem cells (MSCs) regenerative therapy holds promising potential for treating osteoarthritis. However, MSCs engraftment and intra-articular inflammation limit the therapeutic efficacy of this approach. This study introduces porous microspheres (PMs) composed of aldehyde-modified poly(lactic-co-glycolic acid), that encapsulate platelet derived growth factor-AB and kartogenin. Metformin (Met) is also incorporated onto the microsphere through a Schiff base reaction to create PMs@Met. In vitro, in vivo and ex experiments revealed that PMs@Met can be injected into the joint cavity, effectively recruiting endogenous MSCs in situ. This approach creates a favorable environment for MSCs proliferation. It also controls the intra-articular inflammatory environment by modulating the polarization of synovial macrophages, ultimately promoting cartilage repair. In summary, our study presents an innovative tissue engineering strategy for the treatment of osteoarthritis-induced articular cartilage injuries. Statement of significanceCell therapy using autologous mesenchymal stem cells (MSCs) has potential to slow the progression of osteoarthritis (OA). Nonetheless, there are some disadvantages to adopting in situ MSCs therapy, including difficulties with MSC engraftment into cartilage-deficient regions, the effect of intra-articular inflammation on MSC therapeutic efficacy, and attaining selective chondrogenic MSC differentiation. We created injectable PLGA microspheres (PMs) that were loaded with PDGF-AB and KGN. Metformin was bonded to the surface of microspheres using a Schiff base reaction. The microspheres can recruit intra-articular MSCs and encourage their development into chondrocytes. The microspheres actively modulate the inflammatory joint environment by altering synovial macrophage polarization, thereby supporting MSCs in effective cartilage treatment. To summarize, microspheres hold great potential in the treatment of OA.

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.Graphical abstract

Bioinspired nanozyme-reinforced hydrogels with free radical scavenging capability for treating temporomandibular joint osteoarthritis

Temporomandibular joint osteoarthritis (TMJ-OA) is usually caused by increased friction at the joint interface, excessive release of inflammatory factors and catabolic enzymes, and free radical accumulation, which can lead to accelerated degradation and damage of cartilage. In this study, we develop a biological metabolism-inspired injectable hydrogel crosslinking by hydrazide modified hyaluronic acid (HA-HYD), aldehyde modified hyaluronic acid (HA-ALD), and ε-polylysine coated catalase-mimic nanozyme (mesoporous manganese cobalt oxide). Herein, this nanozyme-reinforced hydrogel with outstanding and durable reactive oxygen species (ROS) depletion capability and biocompatibility can alleviate the oxidative stress microenvironment, improve cell viability and proliferation, as well as up-regulate chondrogenic related gene expression and cartilage matrix formation of chondrocytes in vitro. Intra-articular administration of this engineered hydrogel can effectively scavenge endogenous over-expressed ROS to ameliorate the harsh microenvironment in the cavity of TMJ-OA. The nanozyme-reinforced hydrogel reduced proinflammatory cytokines (TNF-α, IL-1β, and IL-6) and enhance anti-inflammatory cytokines (IL-10) expression, induced polarization of synovial macrophages towards M2 phenotype, alleviated structural damage to the cartilage and subchondral bone of the condyle, thus reducing cartilage matrix destruction and protect cartilage in osteoarthritis. In summary, the bioinspired nanozyme-reinforced hydrogels might be used as a promising ROS scavenger for treatment of TMJ-OA.

Long chikungunya? An overview to immunopathology of persistent arthralgia

Chikungunya fever (CF) is caused by an arbovirus whose manifestations are extremely diverse, and it has evolved with significant severity in recent years. The clinical signs triggered by the Chikungunya virus are similar to those of other arboviruses. Generally, fever starts abruptly and reaches high levels, followed by severe polyarthralgia and myalgia, as well as an erythematous or petechial maculopapular rash, varying in severity and extent. Around 40% to 60% of affected individuals report persistent arthralgia, which can last from months to years. The symptoms of CF mainly represent the tissue tropism of the virus rather than the immunopathogenesis triggered by the host's immune system. The main mechanisms associated with arthralgia have been linked to an increase in T helper type 17 cells and a consequent increase in receptor activator of nuclear factor kappa-Β ligand and bone resorption. This review suggests that persistent arthralgia results from the presence of viral antigens post-infection and the constant activation of signaling lymphocytic activation molecule family member 7 in synovial macrophages, leading to local infiltration of CD4+ T cells, which sustains the inflammatory process in the joints through the secretion of pro-inflammatory cytokines. The term "long chikungunya" was used in this review to refer to persistent arthralgia since, due to its manifestation over long periods after the end of the viral infection, this clinical condition seems to be characterized more as a sequel than as a symptom, given that there is no active infection involved.

Inflammation dynamically regulates steroid hormone metabolism and action within macrophages in rheumatoid arthritis

RationaleIn inflammatory diseases such as rheumatoid arthritis (RA), steroid metabolism is a central component mediating the actions of immuno-modulatory glucocorticoids and sex steroids. However, the regulation and function of cellular steroid metabolism within key leukocyte populations such as macrophages remain poorly defined. In this study, the inflammatory regulation of global steroid metabolism was assessed in RA macrophages. MethodsBulk RNA-seq data from RA synovial macrophages was used to assess transcripts encoding key enzymes in steroid metabolism and signalling. Changes in metabolism were assessed in synovial fluids, correlated to measures of disease activity and functionally validated in primary macrophage cultures. ResultsRNA-seq revealed a unique pattern of differentially expressed genes, including changes in genes encoding the enzymes 11β-HSD1, SRD5A1, AKR1C2 and AKR1C3. These correlated with disease activity, favouring increased glucocorticoid and androgen levels. Synovial fluid 11β-HSD1 activity correlated with local inflammatory mediators (TNFα, IL-6, IL-17), whilst 11β-HSD1, SRD5A1 and AKR1C3 activity correlated with systemic measures of disease and patient pain (ESR, DAS28 ESR, global disease activity). Changes in enzyme activity were evident in inflammatory activated macrophages in vitro and revealed a novel androgen activating role for 11β-HSD1. Together, increased glucocorticoids and androgens were able to suppress inflammation in macrophages and fibroblast-like-synoviocytes. ConclusionsThis study underscores the significant increase in androgen and glucocorticoid activation within inflammatory polarized macrophages of the synovium, contributing to local suppression of inflammation. The diminished profile of inactive steroid precursors in postmenopausal women may contribute to disturbances in this process, leading to increased disease incidence and severity.

Exosomes derived from miR-146a-overexpressing fibroblast-like synoviocytes in cartilage degradation and macrophage M1 polarization: a novel protective agent for osteoarthritis?

Pathological changes in the articular cartilage (AC) and synovium are major manifestations of osteoarthritis (OA) and are strongly associated with pain and functional limitations. Exosome-derived microRNAs (miRNAs) are crucial regulatory factors in intercellular communication and can influence the progression of OA by participating in the degradation of chondrocytes and the phenotypic transformation in the polarization of synovial macrophages. However, the specific relationships and pathways of action of exosomal miRNAs in the pathological progression of OA in both cartilage and synovium remain unclear. This study evaluates the effects of fibroblast-like synoviocyte (FLS)-derived exosomes (FLS-Exos), influenced by miR-146a, on AC degradation and synovial macrophage polarization. We investigated the targeted relationship between miR-146a and TRAF6, both in vivo and in vitro, along with the involvement of the NF-κB signaling pathway. The expression of miR-146a in the synovial exosomes of OA rats was significantly higher than in healthy rats. In vitro, the upregulation of miR-146a reduced chondrocyte apoptosis, whereas its downregulation had the opposite effect. In vivo, exosomes derived from miR-146a-overexpressing FLSs (miR-146a-FLS-Exos) reduced AC injury and chondrocyte apoptosis in OA. Furthermore, synovial proliferation was reduced, and the polarization of synovial macrophages shifted from M1 to M2. Mechanistically, the expression of TRAF6 was inhibited by targeting miR-146a, thereby modulating the Toll-like receptor 4/TRAF6/NF-κB pathway in the innate immune response. These findings suggest that miR-146a, mediated through FLS-Exos, may alleviate OA progression by modulating cartilage degradation and macrophage polarization, implicating the NF-κB pathway in the innate immune response. These insights highlight the therapeutic potential of miR-146a as a protective agent in OA, underscoring the importance of exosomal miRNAs in the pathogenesis and potential treatment of the disease.

Extracellular vesicles from senescent mesenchymal stromal cells are defective and cannot prevent osteoarthritis

Age is the most important risk factor in degenerative diseases such as osteoarthritis (OA), which is associated with the accumulation of senescent cells in the joints. Here, we aimed to assess the impact of senescence on the therapeutic properties of extracellular vesicles (EVs) from human fat mesenchymal stromal cells (ASCs) in OA. We generated a model of DNA damage-induced senescence in ASCs using etoposide and characterized EVs isolated from their conditioned medium (CM). Senescent ASCs (S-ASCs) produced 3-fold more EVs (S-EVs) with a slightly bigger size and that contain 2-fold less total RNA. Coculture experiments showed that S-ASCs were as efficient as healthy ASCs (H-ASCs) in improving the phenotype of OA chondrocytes cultured in resting conditions but were defective when chondrocytes were proliferating. S-EVs were also impaired in their capacity to polarize synovial macrophages towards an anti-inflammatory phenotype. A differential protein cargo mainly related to inflammation and senescence was detected in S-EVs and H-EVs. Using the collagenase-induced OA model, we found that contrary to H-EVs, S-EVs could not protect mice from cartilage damage and joint calcifications, and were less efficient in protecting subchondral bone degradation. In addition, S-EVs induced a pro-catabolic and pro-inflammatory gene signature in the joints of mice shortly after injection, while H-EVs decreased hypertrophic, catabolic and inflammatory pathways. In conclusion, S-EVs are functionally impaired and cannot protect mice from developing OA.

Degrasyn alleviates osteoarthritis by blocking macrophagic pyroptosis via suppressing NLRP3/GSDMD signaling pathway and protecting chondrocytes

Synovitis and cartilage destruction are crucial characteristics of osteoarthritis (OA). Inflammatory cytokines, such as IL-1β, are secreted by synovial macrophages, leading to cartilage destruction. Pyroptosis is a lytic form of programmed cell death, which could be triggered by the NLRP3 inflammasome of macrophages. Pyroptosis promotes the secretion of IL-1β and is supposed as a potential biomarker for OA. However, the function of Pyroptosis and NLRP3 inflammasome and its regulatory mechanism for activation is unclear in OA. In this study, we found that Degrasyn could alleviate the GSDMD-mediated pyroptosis of macrophages and the release of IL-1β, caspase-1, and LDH. Furthermore, it selectively impedes the form of ASC oligomer and speckle to effectively suppress the NLRP3 inflammasome during its assembly phase. Notably, Degrasyn exhibited potential chondroprotective effects in a co-culture system. Additionally, these results also indicate that Degrasyn mitigates synovitis and cartilage damage in a murine model of destabilization of the medial meniscus (DMM)-induced OA. In summary, Degrasyn emerges as a promising pharmaceutical agent for synovitis, paving the way for innovative therapeutic approaches to OA. Our findings underscore the potential of Degrasyn as a viable candidate for OA therapeutics, demonstrating its ability to regulate pyroptosis and NLRP3 inflammasome activation.