Blau Syndrome With Delayed Cutaneous Manifestations: A Case Report.

ABSTRACT: Blau syndrome is a rare familial autoinflammatory disorder characterized by the triad of granulomatous dermatitis, polyarthritis, and uveitis. Blau syndrome exhibits an autosomal dominant inheritance pattern and can be caused by a gain-of-function mutation in nucleotide-binding oligomerization domain 2 (NOD2), a member of the NOD-like receptor family of pattern recognition receptors. Mutations in NOD2 cause upregulation of inflammatory cytokines and resultant autoinflammation. Because of the rarity of this condition and early onset of symptoms, Blau syndrome may be misdiagnosed as juvenile idiopathic arthritis. We present a case of a 37-year-old male patient with a long-documented history of juvenile idiopathic arthritis and uveitis, who developed an asymptomatic eruption of pink papules on the trunk and upper extremities. A biopsy demonstrated noncaseating, well-formed dermal granulomas with relatively sparse lymphocytic inflammation and Langerhans-type giant cells. Genetic testing confirmed a mutation in NOD2. Based on the patient's clinical history, histologic findings, genetic testing, the diagnosis of Blau syndrome was made.

A comprehensive analysis of biomarkers associated with synovitis and chondrocyte apoptosis in osteoarthritis.

Introduction: Osteoarthritis (OA) is a chronic disease with high morbidity and disability rates whose molecular mechanism remains unclear. This study sought to identify OA markers associated with synovitis and cartilage apoptosis by bioinformatics analysis. Methods: A total of five gene-expression profiles were selected from the Gene Expression Omnibus database. We combined the GEO with the GeneCards database and performed Gene Ontology and Kyoto Encyclopedia of Genes and Genome analyses; then, the least absolute shrinkage and selection operator (LASSO) algorithm was used to identify the characteristic genes, and a predictive risk score was established. We used the uniform manifold approximation and projection (UMAP) method to identify subtypes of OA patients, while the CytoHubba algorithm and GOSemSim R package were used to screen out hub genes. Next, an immunological assessment was performed using single-sample gene set enrichment analysis and CIBERSORTx. Results: A total of 56OA-related differential genes were selected, and 10 characteristic genes were identified by the LASSO algorithm. OA samples were classified into cluster 1 and cluster 2 subtypes byUMAP, and the clustering results showed that the characteristic genes were significantly different between these groups. MYOC, CYP4B1, P2RY14, ADIPOQ, PLIN1, MFAP5, and LYVE1 were highly expressed in cluster 2, and ANKHLRC15, CEMIP, GPR88, CSN1S1, TAC1, and SPP1 were highly expressed in cluster 1. Protein-protein interaction network analysis showed that MMP9, COL1A, and IGF1 were high nodes, and the differential genes affected the IL-17 pathway and tumor necrosis factor pathway. The GOSemSim R package showed that ADIPOQ, COL1A, and SPP1 are closely related to the function of 31 hub genes. In addition, it was determined that mmp9 and Fos interact with multiple transcription factors, and the ssGSEA and CIBERSORTx algorithms revealed significant differences in immune infiltration between the two OA subtypes. Finally, a qPCR experiment was performed to explore the important genes in rat cartilage and synovium tissues; the qPCR results showed that COL1A and IL-17A were both highly expressed in synovitis tissues and cartilage tissues of OA rats, which is consistent with the predicted results. Discussion: In the future, common therapeutic targets might be found forsimultaneous remissions of both phenotypes of OA.

Diagnostic value and immune infiltration characterization of YTHDF2 as a critical m6A regulator in osteoarthritic synovitis.

BACKGROUND: N6-methyladenosine (m6A) is a universal RNA modification pattern regulated by multiple m6A regulators. In osteoarthritis (OA), m6A regulators influence disease progression by regulating cartilage degradation. However, the function of m6A regulators in synovial tissue remains unclear. In this work, we investigated the biological significance of m6A regulators in osteoarthritic synovitis. METHODS: Datasets were acquired from Gene Expression Omnibus. Differential analysis of merged data identified the differentially expressed m6A regulators. Machine learning models were used to evaluate genetic importance. To predict disease risk, a nomogram was constructed based on above m6A regulators. Cluster analysis divided the OA sample into different subgroups. Immune infiltration revealed the immune m6A regulators, which were validated using clinical samples. Eventually, a competing endogenous RNA (ceRNA) network was constructed. RESULTS: We acquired five differentially expressed m6A regulators and a random forest model. The nomogram accurately predicted disease risk. We identified 122 differentially expressed genes between two m6A subgroups. The analysis of immune infiltration showed that YTHDF2 was an immune-related m6A regulator closely related with macrophages. In clinical samples, the protein and mRNA contents of YTHDF2 were consistent with the results of bioinformatic analysis. The ceRNA network based on YTHDF2 revealed 75 lncRNA nodes and 19 miRNA nodes. CONCLUSION: YTHDF2 has a high diagnostic value in the synovitis of OA and significantly influences the immune status of patients. Hence, YTHDF2, a critical m6A regulator, may provide a biomarker for diagnosis and immune therapy of osteoarthritic synovitis.

Blau syndrome with NOD2 mutation in a 54-year-old man: A case report.

Blau syndrome (BS) is a rare genetic immune disease which commonly presents in childhood. Currently, the miss-rate of BS diagnosis is very high, and an effective clinical management of BS has not been well established. This case report depicts a 54-year-old male Chinese patient presenting with hand malformation, fever, skin rash and joint pain. His diagnosis was ultimately confirmed according to typical medical history and genetic analysis. This case report will further help clinicians to be aware of this rare clinical entity for correct diagnosis and proper treatment.

Type 2 diabetes and the risk of synovitis-tenosynovitis: a two-sample Mendelian randomization study.

Introduction: It has been shown that people with type 2 diabetes have a higher risk of synovitis and tenosynovitis, but previous studies were mainly observational, which may be biased and does not allow for a cause-and-effect relationship. Therefore, we conducted a two-sample Mendelian randomization (MR) study to investigate the causal relationship. Method: We obtained data on "type 2 diabetes" and "synovitis, tenosynovitis" from published large-scale genome-wide association studies (GWAS). The data were obtained from the FinnGen consortium and UK Biobank, both from European population samples. We used three methods to perform a two-sample MR analysis and also performed sensitivity analysis. Results: The results of all three MR methods we used for the analysis illustrated that T2DM increases the risk factor for the development of synovitis and tenosynovitis. Specifically, for the IVW method as the primary analysis outcome, OR = 1.0015 (95% CI, 1.0005 to 1.0026), P = 0.0047; for the MR Egger method as the supplementary analysis outcome, OR = 1.0032 (95% CI, 1.0007 to 1.0056), P = 0.0161; for the weighted median method, OR = 1.0022 (95% CI, 1.0008 to 1.0037), p = 0.0018. In addition, the results of our sensitivity analysis suggest the absence of heterogeneity and pleiotropy in our MR analysis. Conclusion: In conclusion, the results of our MR analysis suggest that T2DM is an independent risk factor for increased synovitis and tenosynovitis.

A Chinese girl of Blau syndrome with renal arteritis and a literature review.

BACKGROUND: Blau syndrome is a rare autoinflammatory disease caused by autosomal dominant mutations in the CARD15/NOD2 gene. Vascular involvement is a rare phenotype in Blau syndrome patients. In this study, we aimed to describe a 20-year- old Chinese girl with Blau syndrome complicated by renal arteritis. In addition, we summarized a literature review of published cases of vascular involvement in patients with Blau syndrome. CASE PRESENTATION: We describe a 20-year-old girl who was initially misdiagnosed with juvenile idiopathic arthritis (JIA) almost 15 years prior. In October 2019, she developed renal arteritis at the age of 17 years and was eventually diagnosed with Blau syndrome. A de-novo M513T mutation was found in her gene testing. A review of the literature on patients with Blau syndrome and vasculitis showed that a total of 18 cases were reported in the past 40 years. The vast majority of them were predominantly involved medium and large vessel arteritis. Of the 18 patients included in our literature review, 14 patients had aorto-arteritis, and 4 of them had renal artery involvement. Two patients presented with renal artery stenosis, 1with a sinus of Valsalva aneurysm, and 1 with retinal vasculitis. CONCLUSION: A detailed medical history inquiry and a careful physical examination are helpful for the early identification of Blau syndrome, especially for infant onset refractory JIA. Medium-and large-vessel arteritis is a rare clinical manifestation in Blau syndrome patients. Careful examination of the peripheral pulse and measurement of blood pressure at every regular visit may be helpful in the early identification of Blau syndrome-arteritis. Early diagnosis and appropriate treatment may prevent or delay the occurrence of severe symptoms in patients to improve the patient's quality of life.

Evaluation of circulating miR-16-5p and miR-223-5p in association with musculoskeletal ultrasonography seven-joint score in the assessment of rheumatoid arthritis activity.

Rheumatoid arthritis (RA) is characterized by ongoing joint destruction. MicroRNAs (miRs) are blood-based biomarkers linked to RA pathogenesis. The musculoskeletal ultrasonography seven-joint score (US7) is an objective tool to assess RA activity. We aimed to evaluate miR-223 and miR-16 roles in monitoring RA activity and to investigate if there is a link between their plasma levels and US7 score. This study enrolled 76 RA patients classified according to Disease Activity Score 28-joint count with erythrocyte sediment rate (DAS28-ESR) to inactive cases (n = 38) and active cases (n = 38). Each patient's joint was scored for synovial proliferation (gray-scale ultrasound 'GSUS7') and vascularization (power Doppler ultrasound 'PDUS7'). Real-time quantitative PCR was used to measure the expression levels of miR-16 and miR-223 in plasma. When compared to inactive group, the active group revealed significant upregulation of miR-16 and miR-223, (P = 0.001 and P = 0.02, respectively). miR-16 and miR-223 levels were correlated with synovitis PDUS7 (r = 0.34, p < 0.01 and r= 0.25, P = 0.03, respectively). miR-16 was also positively correlated with synovitis GSUS7 (r= 0.42, p < 0.001). miR-223 upregulation discriminated active from inactive RA patients at AUC = 0.64, with 76% sensitivity and 50% specificity at cutoff > 2.8-fold change), whereas miR-16 distinguished the two groups at AUC = 0.78 with 87% sensitivity and 53% specificity at cutoff >38.27-fold change. In conclusion, upregulated miR-16 may have more potential to serve as activity biomarkers than miR-223 in RA. The miR-16 level was linked to synovitis GSUS7 and synovitis PDUS7 changes but miR-223 only linked to synovitis PDUS.

Incomplete penetrance of NOD2 C483W mutation underlining Blau syndrome.

BACKGROUND: Blau syndrome (BS) is a rare autoinflammatory disorder with NOD2 gain-of-function mutation and characterized by autoactivation of the NFκB pathway. Classically considered a disease of high penetrance, reports on NOD2 mutations underlining BS with incomplete penetrance is limited. CASE PRESENTATION: The proband is a 9-year-old girl presented with brownish annular infiltrative plaques and symmetric boggy polyarthritis over bilateral wrists and ankles. Her skin biopsy revealed noncaseating granulomas inflammation with multinucleated giant cells. A novel C483W NOD2 mutation was identify in the proband and her asymptomatic father. Functional examinations including autoactivation of the NFκB pathway demonstrated by in vitro HEK293T NOD2 overexpression test as well as intracellular staining of phosphorylated-NFκB in patient's CD11b+ cells were consistent with BS. CONCLUSIONS: We reported a novel C483W NOD2 mutation underlining BS with incomplete penetrance. Moreover, a phosphorylated-NFκB intracellular staining assay of CD11b+ was proposed to assist functional evaluation of NFκB autoactivation in patient with BS.

lncRNA-mediated synovitis in rheumatoid arthritis: A perspective for biomarker development.

Long noncoding RNAs (lncRNAs) are a regulatory class of noncoding RNAs with a wide range of activities such as transcriptional and post-transcriptional regulations. Emerging evidence has demonstrated that various lncRNAs contribute to the initiation and progression of Rheumatoid Arthritis (RA) through distinctive mechanisms. The present study reviews the recent findings on lncRNA role in RA development. It focuses on the involvement of different lncRNAs in the main steps of RA pathogenesis including T cell activation, cytokine dysregulation, fibroblast-like synoviocyte (FLS) activation and joint destruction. Besides, it discusses the current findings on RA diagnosis and the potential of lncRNAs as diagnostic, prognostic and predictive biomarkers in Rheumatology clinic.

Contribution of MicroRNA-27b-3p to Synovial Fibrotic Responses in Knee Osteoarthritis.

OBJECTIVE: Synovial fibrosis contributes to osteoarthritis (OA) pathology, but the underlying mechanisms remain unknown. We have observed increased microRNA-27b-3p (miR-27b-3p) levels in synovial fluid of patients with late-stage radiographic knee OA. Here, we investigated the contribution of miR-27b-3p to synovial fibrosis in patients with severe knee OA and in a mouse model of knee OA. METHODS: We stained synovium sections obtained from patients with radiographic knee OA scored according to the Kellgren/Lawrence scale and mice that underwent destabilization of the medial meniscus (DMM) for miR-27b-3p using in situ hybridization. We examined the effects of intraarticular injection of miR-27b-3p mimic into naive mouse knee joints and intraarticular injection of a miR-27b-3p inhibitor into mouse knee joints after DMM. We performed transfection with miR-27b-3p mimic and miR-27b-3p inhibitor in human OA fibroblast-like synoviocytes (FLS) using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) array, RNA sequencing, RT-qPCR, Western blotting, immunofluorescence, and migration assays. RESULTS: We observed increased miR-27b-3p expression in the synovium from patients with knee OA and in mice with DMM-induced arthritis. Injection of the miR-27b-3p mimic in mouse knee joints induced a synovial fibrosis-like phenotype, increased synovitis scores, and increased COL1A1 and α-smooth muscle actin (α-SMA) expression. In the mouse model of DMM-induced arthritis, injection of the miR-27b-3p inhibitor decreased α-SMA but did not change COL1A1 expression levels or synovitis scores. Transfection with the miR-27b-3p mimic in human OA FLS induced profibrotic responses, including increased migration and expression of key extracellular matrix (ECM) genes, but transfection with the miR-27b-3p inhibitor had the opposite effects. RNA sequencing identified a PPARG/ADAMTS8 signaling axis regulated by miR-27b-3p in OA FLS. Human OA FLS transfected with miR-27b-3p mimic and then treated with the PPARG agonist rosiglitazone or with ADAMTS8 small interfering RNA exhibited altered expression of select ECM genes. CONCLUSION: Our findings demonstrate that miR-27b-3p has a key role in ECM regulation associated with synovial fibrosis during OA.

Identification of SCRG1 as a Potential Therapeutic Target for Human Synovial Inflammation.

Synovial inflammation of joint tissue is the most important cause of tissue damage, joint destruction, and disability and is associated with higher morbidity or mortality. Therefore, this study aims to identify key genes in osteoarthritis synovitis tissue to increase our understanding of the underlying mechanisms of osteoarthritis and identify new therapeutic targets. Five GEO datasets with a total of 41 normal synovial membrane tissues and 45 osteoarthritis synovial membrane samples were used for analysis, and seven common differential genes were identified. The classification model constructed by LASSO analysis showed that six genes including CDKN1A, FOSB, STMN2, SLC2A3, TAC, and SCRG1 can be used as biomarkers of osteoarthritis, and the SCRG1 gene shows importance in osteoarthritis. Furthermore, drug database enrichment found that these six DEGs may be the drug targets of synovitis in osteoarthritis, and Valproic Acid CTD 00006977 may be a potential targeted therapeutic drug of SCRG1. Spearman correlation analysis was performed on the SCRG1 gene, and 27 genes with consistent expression were obtained. Functional analysis showed that 27 genes were mainly involved in metabolism, complement, antigen presentation, apoptosis, and regulation of immune pathways. The co-regulatory network of TFs-miRNA suggested that the SCRG1 gene may be regulated by hsa-miR-363-3p miRNA. In conclusion, SCRG1, as a diagnostic marker of osteoarthritis, co-regulates immune-related pathways through the interaction of related proteins, playing an important role in the occurrence and development of osteoarthritis, which may be a novel drug target.

Potential Benefits of TNF Targeting Therapy in Blau Syndrome, a NOD2-Associated Systemic Autoinflammatory Granulomatosis.

Blau syndrome is a systemic autoinflammatory granulomatous disease caused by mutations in the nucleotide-binding oligomerization domain 2 (NOD2) gene. NOD2 is an intracellular pathogen recognition receptor. Upon binding to muramyl dipeptide (MDP), NOD2 activates the NF-κB pathway, leading to the upregulation of proinflammatory cytokines. Clinical manifestations of Blau syndrome appear in patients before the age of four. Skin manifestations resolve spontaneously in some cases; however, joint and eye manifestations are progressive, and lead to serious complications, such as joint contracture and blindness. Currently, there is no specific curative treatment for the disease. Administration of high-dose oral steroids can improve clinical manifestations; however, treatments is difficult to maintain due to the severity of the side effects, especially in children. While several new therapies have been reported, including JAK inhibitors, anti-IL-6 and anti-IL-1 therapies, anti-TNF therapy plays a central role in the treatment of Blau syndrome. We recently performed an ex vivo study, using peripheral blood and induced pluripotent stem cells from patients. This study demonstrated that abnormal cytokine expression in macrophages from untreated patients requires IFNγ stimulation, and that anti-TNF treatment corrects the abnormalities associated with Blau syndrome, even in the presence of IFNγ. Therefore, although the molecular mechanisms by which the genetic mutations in NOD2 lead to granuloma formation remain unclear, it is possible that prior exposure to TNFα combined with IFNγ stimulation may provide the impetus for the clinical manifestations of Blau syndrome.

Monogenic disorders as mimics of juvenile idiopathic arthritis.

BACKGROUND: Juvenile idiopathic arthritis is the most common chronic rheumatic disease of childhood. The term JIA encompasses a heterogenous group of diseases. The variability in phenotype of patients affected by the disease means it is not uncommon for mimics of JIA to be misdiagnosed. CASE PRESENTATION: We present four cases who were treated in single tertiary rheumatology centre for JIA who were subsequently diagnosed with a rare monogenic disease. All four patients shared the unifying features of presenting in early childhood and subsequently suffered with refractory disease, not amenable to usual standards of treatment. Multicentric Carpotarsal Osteolysis Syndrome and Camptodactyly-arthropathy-coxa vara-pericarditis syndrome are non-inflammatory conditions and patients typically present with arthropathy, normal inflammatory markers and atypical radiological features. Blau syndrome is an autosomal dominant condition and patients will typically have symmetrical joint involvement with a strong family history of arthritis, signifying the genetic aetiology. CONCLUSIONS: We share our learning from these cases to add to the growing portfolio of JIA mimics and to highlight when to consider an alternative diagnosis. In cases of refractory disease and diagnostic uncertainty further imaging and genetic testing can play a crucial role in establishing the aetiology. In all of these cases the correct diagnosis was made due to careful, longitudinal clinical phenotyping and a close working relationship between rheumatology, radiology and clinical genetics; highlighting the importance of the multidisciplinary team in managing complex patients.

Pentraxin 3 regulated by miR-224-5p modulates macrophage reprogramming and exacerbates osteoarthritis associated synovitis by targeting CD32.

Emerging evidence has shown an imbalance in M1/M2 macrophage polarization to play an essential role in osteoarthritis (OA) progression. However, the underlying mechanistic basis for this polarization is unknown. RNA sequencing of OA M1-polarized macrophages found highly expressed levels of pentraxin 3 (PTX3), suggesting a role for PTX3 in OA occurrence and development. Herein, PTX3 was found to be increased in the synovium and articular cartilage of OA patients and OA mice. Intra-articular injection of PTX3 aggravated, while PTX3 neutralization reversed synovitis and cartilage degeneration. No metabolic disorder or proteoglycan loss were observed in cartilage explants when treated with PTX3 alone. However, cartilage explants exhibited an OA phenotype when treated with culture supernatants of macrophages stimulated with PTX3, suggesting that PTX3 did not have a direct effect on chondrocytes. Therefore, the OA anti-chondrogenic effects of PTX3 are primarily mediated through macrophages. Mechanistically, PTX3 was upregulated by miR-224-5p deficiency, which activated the p65/NF-κB pathway to promote M1 macrophage polarization by targeting CD32. CD32 was expressed by macrophages, that when stimulated with PTX3, secreted abundant pro-inflammation cytokines that induced severe articular cartilage damage. The paracrine interaction between macrophages and chondrocytes produced a feedback loop that enhanced synovitis and cartilage damage. The findings of this study identified a functional pathway important to OA development. Blockade of this pathway and PTX3 may prevent and treat OA.

Lef1 ablation alleviates cartilage mineralization following posttraumatic osteoarthritis induction.

Cartilage mineralization is a tightly controlled process, imperative for skeletal growth and fracture repair. However, in osteoarthritis (OA), cartilage mineralization may impact the joint range of motion, inflict pain, and increase chances for joint effusion. Here we attempt to understand the link between inflammation and cartilage mineralization by targeting Sirtuin 1 (SIRT1) and lymphoid enhancer binding factor 1 (LEF1), both reported to have contrasting effects on cartilage. We find that inflammatory-dependent cleavage of SIRT1 or its cartilage-specific genetic ablation, directly enhanced LEF1 expression accompanied by a catabolic response. Applying a posttraumatic OA (PTOA) model to cartilage-specific Sirt1 nulls displayed severe OA, which was accompanied by synovitis, meniscal mineralization, and osteophyte formation of the lateral joint compartment. Alternatively, cartilage-specific Lef1 nulls presented reduced lateral mineralization, OA severity, and local pain. Differential gene expression analysis revealed that Lef1 ablation reduced nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and Toll-like receptor (Tlr) pathways, while enhancing SRY-Box transcription factor 9 (Sox9) and cartilaginous extracellular matrix genes. The results support a link between inflammation and Lef1-dependent cartilage mineralization, mediated by the inactivation of Sirt1. By ablating Lef1 in a PTOA model, the structural and pain-related phenotypes of OA were reduced, in part, by preventing cartilage mineralization of the lateral joint compartment, partially manifested by meniscal tissue mineralization. Overall, these data provide a molecular axis to link between inflammation and cartilage in a PTOA model.

Defining imaging sub-phenotypes of psoriatic arthritis: integrative analysis of imaging data and gene expression in a PsA patient cohort.

OBJECTIVES: To define imaging sub-phenotypes in patients with PsA; determine their association with whole blood gene expression and identify biological pathways characterizing the sub-phenotypes. METHODS: Fifty-five patients with PsA ready to initiate treatment for active disease were prospectively recruited. We performed musculoskeletal ultrasound assessment of the extent of inflammation in the following domains: synovitis, peritenonitis, tenosynovitis and enthesitis. Peripheral whole blood was profiled with RNAseq, and gene expression data were obtained. First, unsupervised cluster analysis was performed to define imaging sub-phenotypes that reflected the predominant tissue involved. Subsequently, principal component analysis was used to determine the association between imaging-defined sub-phenotypes and peripheral blood gene expression profile. Pathway enrichment analysis was performed to identify underlying mechanisms that characterize individual sub-phenotypes. RESULTS: Cluster analysis revealed three imaging sub-phenotypes: (i) synovitis predominant [n = 31 (56%)]; (ii) enthesitis predominant [n = 13 (24%)]; (iii) peritenonitis predominant [n = 11 (20%)]. The peritenonitis-predominant sub-phenotype had the most severe clinical joint involvement, whereas the enthesitis-predominant sub-phenotype had the highest tender entheseal count. Unsupervised clustering of gene expression data identified three sub-phenotypes that partially overlapped with the imaging sub-phenotypes suggesting biological and clinical relevance of these sub-phenotypes. We therefore characterized enriched differential pathways, which included: immune system (innate system, B cells and neutrophil degranulation), complement system, platelet activation and coagulation function. CONCLUSIONS: We identified three sub-phenotypes based on the predominant tissue involved in patients with active PsA. Distinct biological pathways may underlie these imaging sub-phenotypes seen in PsA, suggesting their biological and clinical importance.

Matrix metalloproteinase-13 is fully activated by neutrophil elastase and inactivates its serpin inhibitor, alpha-1 antitrypsin: Implications for osteoarthritis.

Matrix metalloproteinase-13 (MMP-13) is a uniquely important collagenase that promotes the irreversible destruction of cartilage collagen in osteoarthritis (OA). Collagenase activation is a key control point for cartilage breakdown to occur, yet our understanding of the proteinases involved in this process is limited. Neutrophil elastase (NE) is a well-described proteoglycan-degrading enzyme which is historically associated with inflammatory arthritis, but more recent evidence suggests a potential role in OA. In this study, we investigated the effect of neutrophil elastase on OA cartilage collagen destruction and collagenase activation. Neutrophil elastase induced significant collagen destruction from human OA cartilage ex vivo, in an MMP-dependent manner. In vitro, neutrophil elastase directly and robustly activated pro-MMP-13, and N-terminal sequencing identified cleavage close to the cysteine switch at 72 MKKPR, ultimately resulting in the fully active form with the neo-N terminus of 85 YNVFP. Mole-per-mole, activation was more potent than by MMP-3, a classical collagenase activator. Elastase was detectable in human OA synovial fluid and OA synovia which displayed histologically graded evidence of synovitis. Bioinformatic analyses demonstrated that, compared with other tissues, control cartilage exhibited remarkably high transcript levels of the major elastase inhibitor, (AAT) alpha-1 antitrypsin (gene name SERPINA1), but these were reduced in OA. AAT was located predominantly in superficial cartilage zones, and staining enhanced in regions of cartilage damage. Finally, active MMP-13 specifically inactivated AAT by removal of the serine proteinase cleavage/inhibition site. Taken together, this study identifies elastase as a novel activator of pro-MMP-13 that has relevance for cartilage collagen destruction in OA patients with synovitis.

Anti-TNF treatment corrects IFN-γ-dependent proinflammatory signatures in Blau syndrome patient-derived macrophages.

BACKGROUND: Blau syndrome (BS) is an autoinflammatory disease associated with mutations in nucleotide-binding oligomerization domain 2. Although treatments with anti-TNF agents have been reported to be effective, the underlying molecular mechanisms remain unclear. OBJECTIVE: We aimed to elucidate the mechanisms of autoinflammation in patients with BS and to clarify how anti-TNF treatment controls the disease phenotype at the cellular level in clinical samples. METHODS: Macrophages were differentiated from monocytes of 7 BS patients, and global transcriptional profiles of 5 patients were analyzed with or without IFN-γ stimulation. Macrophages were also generated from BS-specific induced pluripotent stem cells (iPSCs), and their transcriptome was examined for comparison. RESULTS: Aberrant inflammatory responses were observed upon IFN-γ stimulation in macrophages from untreated BS patients, but not in those from patients treated with anti-TNF. iPSC-derived macrophages carrying a disease-associated mutation also showed IFN-γ-dependent accelerated inflammatory responses. Comparisons of peripheral blood- and iPSC-derived macrophages revealed the upregulation of nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) targets in unstimulated macrophages as a common feature. CONCLUSIONS: IFN-γ stimulation is one of the key signals driving aberrant inflammatory responses in BS-associated macrophages. However, long-term treatment with anti-TNF agents ameliorates such abnormalities even in the presence of IFN-γ stimulation. Our data thus suggest that preexposure to TNF or functionally similar cytokines inducing NF-κB-driven proinflammatory signaling during macrophage development is a prerequisite for accelerated inflammatory responses upon IFN-γ stimulation in BS.

MicroRNA-106b overexpression suppresses synovial inflammation and alleviates synovial damage in patients with rheumatoid arthritis.

OBJECTIVES: To explore the effect of miR-106b on synovial inflammation and damage in rheumatoid arthritis (RA) patients and further to investigate its possible mechanism. METHODS: Quantitative real-time polymerase chain reaction, immunofluorescence, in situ hybridization, and immunohistochemistry assay were used to verify the levels of miR-106b and cytokines. Pearson's correlation analysis was conducted to examine bivariate relationship between miR-106b and cytokines or receptor activator of nuclear factor-κ B ligand (RANKL). Following the isolation of fibroblast-like synoviocytes (FLS), the cultured cells were separately transfected with or without miR-106b mimic. Thereafter, cell proliferation, invasion and migration were measured by Cell Counting Kit-8 assay and Transwell assay, respectively. Furthermore, concentration and expression of cytokines were separately detected by enzyme-linked immunosorbent assay and Western blot. RESULTS: Compared with osteoarthritis, RA patients had a lower level of miR-106b and higher levels of RANKL, tumour necrosis factor-a (TNF-a), and interleukin-6 (IL-6). The relative transcription of miR-106b level was negatively correlated to TNF-a, IL-6, and RNKAL levels in both patients (all P < 0.05). Furthermore, miR-106b overexpression suppressed cell proliferation, migration, and invasion capacity of RA-FLS. CONCLUSIONS: miR-106b overexpression suppresses synovial inflammation and alleviates synovial damage; thus, it may be served as a potential therapeutic target for RA patients.