Association of methotrexate polyglutamates concentration with methotrexate efficacy and safety in patients with rheumatoid arthritis treated with predefined dose: results from the MIRACLE trial.

OBJECTIVES: The usefulness of methotrexate-polyglutamates (MTX-PGs) concentration for management of rheumatoid arthritis has been debated. We aimed to clarify the association of MTX-PGs concentration with efficacy and safety in MTX-naïve patients initiating MTX in a prospective interventional clinical trial. METHODS: The MIRACLE trial enrolled 300 MTX-naïve patients. Oral MTX was initiated and increased to the maximum tolerated dose by week 12. Patients who did not achieve remission according to the Simplified Disease Activity Index at week 24 were randomised to either the continued dose or reduced dose group and were started on subcutaneous adalimumab. We measured the concentrations of MTX-PGs in erythrocytes using liquid chromatography-tandem mass spectrometry and analysed the association of these concentrations with efficacy and safety. RESULTS: The mean concentration of total MTX-PGs increased with an increasing dose of MTX and continued to elevate for another 12 weeks after the dose was fixed. At week 24, the total MTX-PGs concentration was 110.5 (SD 43.8) nmol/L with MTX dose of 12.6 (3.0) mg/week (0.23 (0.07) mg/kg/week). During MTX monotherapy, the higher MTX-PGs concentration was an independent factor for lower disease activity; however, this association disappeared after adalimumab initiation in patients with continued MTX dose. Hepatotoxicity was related to the higher MTX-PGs concentration regardless of adalimumab use. The total MTX-PGs concentration was significantly elevated by lower estimated glomerular filtration rate, serum albumin and body mass index. CONCLUSIONS: The MIRACLE trial demonstrated that higher total MTX-PGs concentration in erythrocytes is related to the higher efficacy and lower safety of MTX. TRIAL REGISTRATION NUMBER: NCT03505008.

Effectiveness and safety of rituximab in severely relapsed antineutrophil cytoplasmic antibody-associated vasculitis: a retrospective analysis of a Japanese multicentre cohort from the J-CANVAS.

We aimed to clarify the long-term safety and efficacy of rituximab (RTX) as a remission induction therapy following severe relapse in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). We retrospectively collected the data of patients with severely relapsed AAV from a Japanese multicentre cohort. The primary exposure was RTX use; the primary outcome was complete remission (CR) proportions at week 24. Baseline characteristics were compared between the RTX and non-RTX groups. We performed multivariate logistic regression analysis and one-to-one propensity score matching analysis as a sensitivity analysis. Totally, 100 patients were enrolled: 52 in the RTX group and 48 in the non-RTX group. Baseline characteristics were comparable between the two groups, except for age, AAV subtype and ANCA serotype. The median age was 71 vs. 75 years, and the PR3-ANCA positivity rate was 44.2% vs. 18.8% in the RTX and non-RTX groups, respectively. No significant difference was observed in CR proportions at week 24 between the two groups (79.2% vs. 68.1%, p = 0.321), with an adjusted odds ratio of 1.27 (95% confidence interval [CI] 0.47-3.51). At week 48, CR proportions were significantly higher in the RTX group (91.7% vs. 64.9%, p = 0.005), with an adjusted odds ratio of 2.95 (95% CI 0.97-9.91). Serious infection rates were lower in the RTX group than in the non-RTX group, with no statistically significant difference. RTX was not superior to conventional immunosuppressive therapies at week 24 but showed significantly favourable results at week 48 for severely relapsed AAV.

A preliminary survey of rheumatologists on the management of late-onset rheumatoid arthritis in Japan.

Objectives We investigated the current perspectives regarding the management of late-onset rheumatoid arthritis (LORA) among rheumatologists in clinical practice. Methods This study was performed in October 2021, and included 65 rheumatologists certified by the Japan College of Rheumatology, who were administered questionnaires (including multiple choice and descriptive formulae) regarding the management of LORA. We aggregated and analyzed the responses. Results All 65 rheumatologists responded to the survey; 47 (72%) answered that >50% of newly diagnosed patients were aged ≥65 years, 42 (65%) answered that achievement of remission or low disease activity was the treatment goal, and 40 (62%) considered patient safety to be the highest priority. Most rheumatologists are concerned about the management of conditions other than RA, such as comorbidities, financial constraints, and life circumstances that interfere with standard or recommended treatment implementation. Conclusion This preliminary survey highlighted various rheumatologists' perspectives regarding the management of LORA.

Effectiveness of intravenous methylprednisolone pulse in patients with severe microscopic polyangiitis and granulomatosis with polyangiitis.

OBJECTIVES: To evaluate the effectiveness and safety of two different intravenous methylprednisolone (IVMP) pulse doses in patients with severe microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA). METHODS: We emulated a target trial using observational data from the nationwide registry in Japan. Patients with severe glomerulonephritis or diffuse alveolar haemorrhage were selected and pseudo-randomized into three groups using propensity score-based overlap weighting as follows: non-IVMP, IVMP 0.5 g/day and IVMP 1.0 g/day. The primary outcome was all-cause mortality, and the secondary outcomes were composite all-cause mortality and kidney failure, severe relapse and serious infection from 2 to 48 weeks after treatment initiation. To estimate the treatment effects, the Cox proportional hazard model and Fine-Gray subdistribution hazard model were used. RESULTS: In this emulated target trial, of 201 eligible patients (MPA, 175; GPA, 26), 6 (3%) died, 4 (2.0%) had kidney failure, 11 (5.5%) had severe relapse, and 40 (19.9%) had severe infections. Hazard ratios (HR) for IVMP 0.5 g/day and IVMP 1.0 g/day pulse groups compared with non-IVMP pulse were as follows: all-cause mortality 0.46 (95% CI: 0.07, 2.81) and 0.07 (95% CI: 0.01, 0.41), respectively; all-cause mortality/kidney failure 1.18 (95% CI: 0.26, 5.31) and 0.59 (95% CI: 0.08, 4.52), respectively; subdistribution HRs for severe relapse were 1.26 (95% CI: 0.12, 13.70) and 3.36 (95% CI: 0.49, 23.29), respectively; and for serious infection 1.88 (95% CI: 0.76, 4.65) and 0.94 (95% CI: 0.28, 3.13), respectively. CONCLUSION: IVMP 1.0 g/day pulse may improve 48-week mortality in patients with severe MPA/GPA.

The 2023 Guidelines for the management and treatment of glucocorticoid-induced osteoporosis.

INTRODUCTION: Although synthetic glucocorticoids (GCs) are commonly used to treat autoimmune and other diseases, GC induced osteoporosis (GIOP) which accounts for 25% of the adverse reactions, causes fractures in 30-50% of patients, and markedly decreases their quality of life. In 2014, the Japanese Society for Bone and Mineral Research (JSBMR) published the revised guidelines for the management and treatment of steroid-induced osteoporosis, providing the treatment criteria based on scores of risk factors, including previous fractures, age, GC doses, and bone mineral density, for patients aged ≥18 years who are receiving GC therapy or scheduled to receive GC therapy for ≥3 months. MATERIALS AND METHODS: The Committee on the revision of the guidelines for the management and treatment of GIOP of the JSBMR prepared 17 clinical questions (CQs) according to the GRADE approach and revised the guidelines for the management and treatment of GIOP through systematic reviews and consensus conferences using the Delphi method. RESULTS: Bisphosphonates (oral and injectable formulations), anti-RANKL antibody teriparatide, eldecalcitol, or selective estrogen receptor modulators are recommended for patients who has received or scheduled for GC therapy with risk factor scores of ≥3. It is recommended that osteoporosis medication is started concomitantly with the GC therapy for the prevention of fragility fractures in elderly patients. CONCLUSION: The 2023 guidelines for the management and treatment of GIOP was developed through systematic reviews and consensus conferences using the Delphi method.

Consensus statement on the management of late-onset rheumatoid arthritis.

OBJECTIVES: Late-onset rheumatoid arthritis (LORA), which has been increasing in recent years, lacks evidence for initial treatment. Japanese rheumatology experts recognized this gap and addressed it by developing consensus statements on the first clinical application of LORA. METHODS: These statements were created following an introductory discussion about treatment fundamentals, which included a review of existing literature and cohort data. The steering committee created a draft, which was refined using a modified Delphi method that involved panel members reaching a consensus. The panel made decisions based on input from geriatric experts, clinical epidemiologists, guideline developers, patient groups, and the LORA Research Subcommittee of the Japan College of Rheumatology. RESULTS: The consensus identified four established facts, three basic approaches, and six expert opinions for managing LORA. Methotrexate was recommended as the primary treatment, with molecular-targeted agents being considered if treatment goals cannot be achieved. An emphasis was placed on assessing the lives of older patients due to challenges in risk management and methotrexate accessibility caused by comorbidities or cognitive decline. CONCLUSIONS: The experts substantiated and refined 13 statements for the initial treatment of LORA. To validate these claims, the next is to conduct a registry study focusing on new LORA cases.

Development of a nursing practice scale for rheumatoid arthritis treatment with biological disease-modifying anti-rheumatic drugs.

OBJECTIVE: The objective of the study was to develop a nursing practice scale for rheumatoid arthritis treatment with biological disease-modifying anti-rheumatic drugs. METHODS: An anonymous self-administered questionnaire survey was administered to 1826 nurses, 960 of whom were Certified Nurses by Japan Rheumatism Foundation (CNJRFs) and 866 were registered nurses (RNs). Using exploratory factor analysis, criterion validity, and known-groups technique, we assessed the reliability and validity of the self-created 19-item nursing practice scale to evaluate the care provided to patients with rheumatoid arthritis receiving biological disease-modifying anti-rheumatic drugs based on the nurse's role as clarified from a literature review of relevant studies. RESULTS: A total of 698 (38.4%) responses were collected from 407 CNJRFs and 291 RNs. Exploratory factor analysis was conducted on 18 items to examine three factors: 'nursing to enhance patients' capacity for self-care', 'nursing in which patients participate in decision-making', and 'nursing in which team medical care is promoted'. Cronbach's α was .95. The Spearman's coefficient was ρ = .738 for criterion validity. Using the known-groups technique, CNJRFs had higher total scale scores than RNs (P < .05). CONCLUSIONS: The results confirmed the reliability, criterion validity, and construct validity of the scale.

Optimal Dose of Intravenous Cyclophosphamide during remission induction therapy in ANCA-associated vasculitis: a retrospective cohort study of J-CANVAS.

OBJECTIVES: To identify the optimal dose of intravenous cyclophosphamide (IVCY) for induction therapy for anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). METHODS: We retrospectively assessed patients with AAV who received IVCY every 2-3 weeks during the remission induction phase. The associations of the IVCY dose with infection-free survival and relapse-free survival were analysed using a Cox regression model. We compared patients in three categories: very low-dose (VLD), low-dose (LD), and conventional dose (CD) (<7.5 mg/kg, 7.5-12.5 mg/kg, and >12.5 mg/kg, respectively). The non-linear association between IVCY dose and the outcomes were also evaluated. RESULTS: Of the 80 patients (median age 72 years), 12, 42, and 26 underwent the VLD, LD, and CD regimens, respectively, of whom 4, 3, and 7 developed infection or died. The adjusted hazard ratios for infection or death were 4.3 (95% confidence interval (CI) 0.94-19.8) for VLD and 5.1 (95% CI 1.21-21.3) for CD, compared with LD. We found the hazard ratio for infection or death increased when the initial IVCY dose exceeded 9 mg/kg. Relapse-free survival did not differ clearly. CONCLUSION: Low-dose IVCY (7.5-12.5 mg/kg) may result in fewer infections and similar relapse rates compared with the conventional regimen (>12.5 mg/kg).

Disseminated Mycobacterium abscessus infection with osteoarticular manifestations as an important differential diagnosis of inflammatory arthritis: A case report and literature review.

This case report describes a 52-year-old immunocompromised man diagnosed with disseminated Mycobacterium abscessus complex (MABC) infection. The patient had a history of malignant lymphoma and presented with fever and polyarthritis that lasted 3 weeks. Upon initial evaluation, blood and synovial fluid cultures from the swollen joints were negative. Reactive arthritis or rheumatoid arthritis was suspected as the cause of inflammatory synovitis in multiple joints. Administration of prednisolone followed by an interleukin-6 inhibitor improved the fever, but polyarthritis persisted, and destruction of the left hip joint was observed. Two months later, M. abscessus was detected in a blood culture and right shoulder joint synovium, leading to a final diagnosis of disseminated MABC infection. The joint symptoms resolved with combined antimicrobial therapy using amikacin, azithromycin, and imipenem/cilastatin. To date, 12 cases of disseminated MABC infection with osteoarticular manifestations have been reported. A total of 13 cases, including the present case, were reviewed. Seven patients had bone involvements, five had joint involvement, and the remaining one had bursa involvement. All the cases with joint involvement, except for our case, presented with monoarthritis. MABC infection is diagnosed based on the demonstration of MABC itself. Clinicians should keep disseminated MABC infection in mind as a possible cause of persistent arthritis. As demonstrated in our case, multiple replicate cultures of blood or specimens from the affected sites may be needed to detect it.

Long-Term Prognosis of Antimelanoma Differentiation-Associated Gene 5-Positive Dermatomyositis With Interstitial Lung Disease.

OBJECTIVE: Antimelanoma differentiation-associated gene 5 (anti-MDA5)-positive dermatomyositis with interstitial lung disease (DM-ILD) progresses rapidly and has a poor prognosis. Previously, we reported the efficacy of a combination therapy comprising high-dose glucocorticoids (GCs), calcineurin inhibitors (CNIs), and intravenous cyclophosphamide (IV CYC) in a multicenter clinical trial (UMIN000014344). In the present study, we evaluated the long-term outcomes and effects of induction therapy on the maintenance of remission. METHODS: All participants from our previous trial were followed up for > 5 years. Seventy-three other patients with anti-MDA5-positive DM-ILD from our institute were retrospectively integrated into the previous trial for further analysis. Sixty-eight patients achieved remission and survived for > 6 months. Based on the induction treatment, we classified the patients into 2 groups: (1) group T (n = 56), with triple combination therapy (GCs, CNIs, and IV CYC), and (2) group C (n = 12), with monotherapy/dual therapy. The recurrence-free and drug-withdrawal rates of immunosuppressive agents were compared. RESULTS: The overall survival and recurrence-free survival rates at 5 years were 100% for the participants in the previous trial. The 5-year cumulative withdrawal rates for CNIs and GCs were 70% and 53%, respectively. In a comprehensive analysis, the recurrence-free rates in group T were higher than those in group C (90% vs 56%; P < 0.05). The drug-withdrawal rates of CNIs and GCs at 10 years in group T were also higher than those in group C (79% vs 0% and 43% vs 0%, respectively; P < 0.05). CONCLUSION: Triple combination therapy in the induction phase can reduce the risk of recurrence and facilitate drug withdrawal in anti-MDA5-positive DM-ILD.

Contribution of the factors to EuroQol 5 Dimensions in rheumatoid arthritis patients achieving low disease activity/remission with abatacept treatment: post-hoc subgroup analyses of the Japanese real-world observational "ORIGAMI" study.

OBJECTIVES: To address improvements in quality of life (QOL), we analysed the relative contributions of factors to EuroQol 5 Dimensions (EQ-5D) in abatacept-treated rheumatoid arthritis (RA) patients in the ORIGAMI study. METHODS: Patients who were evaluable for disease activity through to Week 52 in the ORIGAMI study were divided into those achieving Simplified Disease Activity Index-remission/low disease activity (remission/LDA; n=178) and patients with moderate/high disease activity (MDA/HDA; n=99). We compared the changes in EQ-5D and other outcomes through to Week 52. Focusing on the remission/LDA group, the contribution of each factor to the variance of EQ-5D at baseline and Week 52 was examined using analysis of variance. RESULTS: The remission/LDA group showed greater improvements than the MDA/HDA group in EQ-5D, Japanese Health Assessment Questionnaire, visual analogue scale for pain (Pain VAS), and patient global assessment (PtGA). In the remission/LDA group, factors significantly contributing to EQ-5D were sex, C-reactive protein, and Pain VAS at baseline, and PtGA and age at Week 52. CONCLUSIONS: In RA patients who achieved remission/LDA during abatacept treatment, PtGA and age at Week 52 contribute to the variance of EQ-5D, suggesting that identification of factors associated with PtGA may be important to address improvements of QOL.

Efficient detection of somatic UBA1 variants and clinical scoring system predicting patients with variants in VEXAS syndrome.

OBJECTIVES: To efficiently detect somatic UBA1 variants and establish a clinical scoring system predicting patients with pathogenic variants in VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome. METHODS: Eighty-nine Japanese patients with clinically suspected VEXAS syndrome were recruited [81 males and 8 females; median onset age (IQR) 69.3 years (62.1-77.6)]. Peptide nucleic acid-clamping PCR (PNA-PCR), regular PCR targeting exon 3 clustering UBA1 variants, and subsequent Sanger sequencing were conducted for variant screening. Partitioning digital PCR (pdPCR) or targeted amplicon deep sequencing (TAS) was also performed to evaluate the variant allele frequency (VAF). We developed our clinical scoring system to predict UBA1 variant-positive and ­negative patients and assessed the diagnostic value of our system using receiver operating characteristic (ROC) curve analysis. RESULTS: Forty patients with reported pathogenic UBA1 variants (40/89, 44.9%) were identified, including a case having a variant with VAF of 1.7%, using a highly sensitive method. Our clinical scoring system considering >50 years of age, cutaneous lesions, lung involvement, chondritis, and macrocytic anaemia efficiently predicted patients with UBA1 variants (the area under the curve for the scoring total was 0.908). CONCLUSIONS: Genetic screening with the combination of regular PCR and PNA-PCR detected somatic UBA1 variants with high sensitivity and specificity. Our scoring system could efficiently predict patients with UBA1 variants.

Tumor Necrosis Factor and Interleukin-1ß Upregulate NRP2 Expression and Promote SARS-CoV-2 Proliferation.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), utilizes the host receptor angiotensin-converting enzyme 2 (ACE2) and the auxiliary receptor Neuropilin-1 (NRP1) to enter host cells. NRP1 has another isoform, NRP2, whose function in COVID-19 has seldom been reported. In addition, although patients with severe cases of COVID-19 often exhibit increased levels of proinflammatory cytokines, the relationship between these cytokines and SARS-CoV-2 proliferation remains unknown. The aim of this study is to clarify the roles of proinflammatory cytokines in Neuropilin expressions and in SARS-CoV-2 infection. To identify the expression patterns of NRP under inflamed and noninflamed conditions, next-generation sequencing (RNA-seq), immunohistochemistry, quantitative real-time PCR, and Western blotting were performed using primary cultured fibroblast-like synoviocytes, MH7A (immortalized cell line of human rheumatoid fibroblast-like synoviocytes), immortalized MRC5 (human embryonic lung fibroblast), and synovial tissues. To measure viral proliferative capacity, SARS-CoV-2 infection experiments were also performed. NRP2 was upregulated in inflamed tissues. Cytokine-stimulated human fibroblast cell lines, such as MH7A and immortalized MRC5, revealed that NRP2 expression increased with co-stimulation of tumor necrosis factor α (TNFα) and interleukin-1 beta (IL-1ß) and was suppressed with anti-TNFα antibody alone. TNFα and IL-1ß promoted SARS-CoV-2 proliferation and Spike protein binding. The viral proliferation coincided with the expression of NRP2, which was modulated through plasmid transfections. Our results revealed that proinflammatory cytokines, including TNFα, contribute to NRP2 upregulation and SARS-CoV-2 proliferation in host human cells.

Seasonal Influence on Development of Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A Retrospective Cohort Study Conducted at Multiple Institutions in Japan (J-CANVAS).

OBJECTIVE: To clarify seasonal and other environmental effects on the onset of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). METHODS: We enrolled patients with new-onset eosinophilic granulomatosis with polyangiitis (EGPA), microscopic polyangiitis (MPA), and granulomatosis with polyangiitis (GPA) registered in the database of a Japanese multicenter cohort study. We investigated the relationship between environmental factors and clinical characteristics. Seasons were divided into 4 (spring, summer, autumn, and winter), and the seasonal differences in AAV onset were analyzed using Pearson chi-square test, with an expected probability of 25% for each season. RESULTS: A total of 454 patients were enrolled, with a mean age of 70.9 years and a female proportion of 55.5%. Overall, 74, 291, and 89 patients were classified as having EGPA, MPA, and GPA, respectively. Positivity for myeloperoxidase (MPO)-ANCA and proteinase 3 (PR3)-ANCA was observed in 355 and 46 patients, respectively. Overall, the seasonality of AAV onset significantly deviated from the expected 25% for each season (P = 0.001), and its onset was less frequently observed in autumn. In ANCA serotypes, seasonality was significant in patients with MPO-ANCA (P < 0.001), but not in those with PR3-ANCA (P = 0.97). Additionally, rural residency of patients with AAV was associated with PR3-ANCA positivity and biopsy-proven pulmonary vasculitis. CONCLUSION: The onset of AAV was influenced by seasonal variations and was less frequently observed in autumn. In contrast, the occurrence of PR3-ANCA was triggered, not by season, but by rural residency.

Association between hypogammaglobulinaemia and severe infections during induction therapy in ANCA-associated vasculitis: from J-CANVAS study.

OBJECTIVES: To investigate the association between decreased serum IgG levels caused by remission-induction immunosuppressive therapy of antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and the development of severe infections. METHODS: We conducted a retrospective cohort study of patients with new-onset or severe relapsing AAV enrolled in the J-CANVAS registry, which was established at 24 referral sites in Japan. The minimum serum IgG levels up to 24 weeks and the incidence of severe infection up to 48 weeks after treatment initiation were evaluated. After multiple imputations for all explanatory variables, we performed the multivariate analysis using a Fine-Gray model to assess the association between low IgG (the minimum IgG levels <500 mg/dl) and severe infections. In addition, the association was expressed as a restricted cubic spline (RCS) and analysed by treatment subgroups. RESULTS: Of 657 included patients (microscopic polyangiitis, 392; granulomatosis with polyangiitis, 139; eosinophilic granulomatosis with polyangiitis, 126), 111 (16.9%) developed severe infections. The minimum serum IgG levels were measured in 510 patients, of whom 77 (15.1%) had low IgG. After multiple imputations, the confounder-adjusted hazard ratio of low IgG for the incidence of severe infections was 1.75 (95% confidence interval: 1.03-3.00). The RCS revealed a U-shaped association between serum IgG levels and the incidence of severe infection with serum IgG 946 mg/dl as the lowest point. Subgroup analysis showed no obvious heterogeneity between treatment regimens. CONCLUSION: Regardless of treatment regimens, low IgG after remission-induction treatment was associated with the development of severe infections up to 48 weeks after treatment initiation.

Expression of factor XIII originating from synovial fibroblasts and macrophages induced by interleukin-6 signaling.

BACKGROUND: Blood coagulation factor XIII (FXIII) promotes cross-linking between fibrin molecules at the final stage of the blood coagulation cascade. However, its expression in cells or tissues and function, particularly factor XIII subunit B (FXIII-B), remains controversial. Hemorrhagic FXIII deficiency following anti-interleukin-6 (IL-6) receptor antibody treatment has been reported in patients with rheumatoid arthritis (RA). Patients receiving this biologics have reduced FXIII activity when compared to the activity in those treated with other biologics. The relationship between pro-inflammatory cytokines and FXIII expression remains unknown. METHODS: To investigate the expression pattern of FXIII in synovial tissues, immunohistochemistry, RT-qPCR, and western blotting were performed. FXIII-A expressed monocyte-derived macrophages were treated with recombinant IL-6 and anti-IL-6 receptor antibody. RNA sequencing of FXIII-B-overexpressing cells was performed to clarify the function of FXIII-B. RESULTS: The immunohistochemical analysis of synovial tissues revealed that factor XIII subunit A (FXIII-A) was expressed in M2 macrophages, and FXIII-B was expressed in fibroblast-like synoviocytes. IL-6 stimulation upregulated FXIII-A expression in IL-4-induced monocyte-derived macrophages, and the anti-IL-6 receptor antibody suppressed FXIII-A expression. FXIII-B was more abundantly secreted in the supernatant of fibroblast-like synoviocytes compared with that of other cells. RNA sequencing showed that FXIII-B elevated the expression of genes associated with anti-apoptotic molecules and chemokines. CONCLUSIONS: Our findings highlight that synovial tissue is one of the sources of FXIII production. We also have demonstrated IL-6-dependent FXIII-A expression and the novel potential functions of FXIII-B.