Osteoclasts are multinucleated giant cells responsible for bone resorption. Various mediators involved in osteoclast differentiation have been investigated as possible therapeutic targets for osteoporosis and rheumatoid arthritis (RA). Although transforming growth factor beta1 (TGFβ1) has been described as one such multifunctional cytokine essential for bone remodeling, its effect on osteoclastogenesis remains controversial. Therefore, we sought to examine the effect of TGFβ1 on osteoclast generation induced by receptor activator of nuclear factor (NF)-κB ligand (RANKL) in humans. Peripheral blood monocytes, isolated using magnetic bead sorting, were cultured with macrophage-colony stimulating factor (M-CSF) or RANKL with or without TGFβ1. Tartrate-resistant acid phosphatase (TRAP) staining, as well as bone resorption assays, revealed that TGFβ1 suppressed RANKL-mediated human osteoclast development. Real-time reverse transcription PCR and Western blotting revealed that TGFβ1 reduced the gene and protein expression of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), the master regulator of osteoclast differentiation, respectively. Luciferase assays indicated that TGFβ1 inhibited the NF-κB p65-stimulated promoter activity of NFATc1. Immunofluorescence analysis demonstrated that TGFβ1 abrogated RANKL-induced nuclear translocation of p65. Thus, TGFβ1 regulates human RANKL-induced osteoclastogenesis via downregulation of NFATc1 by blocking nuclear translocation of NF-κB, suggesting that TGFβ1 may be a potential therapeutic target for RA.

Cytotoxic T lymphocyte antigen-4-immunoglobulin (CTLA-4-Ig) exerts anti-rheumatic action via negative regulation of the co-stimulation process between antigen-presenting cells and T cells. CTLA-4-Ig also binds to CD80/CD86 on monocytes of osteoclast precursors. However, little is known about the effect of CTLA-4-Ig on osteoclastogenesis in rheumatoid arthritis (RA). In this study we evaluated the effects of CTLA-4-Ig on osteoclast generation from human blood monocytes (PBM) and rheumatoid synovial fluid monocytes (RSFM). Highly purified monocytes were cultured with receptor activator of nuclear factor kappa-B ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) in the presence of CTLA-4-Ig. CTLA-4-Ig inhibited RANKL-induced osteoclast generation in PBM and RSFM, as determined by tartrate-resistant acid phosphatase (TRAP) staining and bone resorption assay using osteo assay surface plates. In addition, CTLA-4-Ig reduced the gene and protein expressions of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) and cathepsin K during osteoclastogenesis. Furthermore, CTLA-4-Ig significantly inhibited cell proliferation during osteoclastogenesis. Interestingly, the gene expression of indoleamine 2,3-dioxygenase-1, an inducer of apoptosis, was enhanced by CTLA-4-Ig. We next examined the effect of tumour necrosis factor (TNF)-α, a major inflammatory cytokine in rheumatoid synovium, on the expression of CD80 and CD86 by flow cytometric analysis. TNF-α potently induced the surface expression of CD80, which is known to have much higher affinity to CTLA-4-Ig than CD86, and this induction was observed at mRNA levels. Interestingly, freshly prepared rheumatoid synovial monocytes also expressed CD80 as much as TNF-α-treated PBM. Furthermore, TNF-α enhanced CTLA-4-Ig-induced inhibition of osteoclastogenesis and cell proliferation. Taken together, the TNF-α-induced CD80 may augment CTLA-4-Ig-induced inhibition of osteoclastogenesis, suggesting that CTLA-4-Ig potently inhibits osteoclast differentiation and protects bone destruction in rheumatoid inflamed joints.

Objective: Activin A is known to be highly expressed in rheumatoid synovium. In the present study, we investigated the effect of inflammatory cytokines on activin A production and its role in rheumatoid inflammation using freshly prepared rheumatoid synovial cells (fresh-RSC). Methods: Fresh-RSC from patients with rheumatoid arthritis were obtained and stimulated with multiple cytokines for activin A production. Gene expression levels of activin A and inflammatory cytokines were determined by quantitative PCR (qPCR) analysis. An enzyme-linked immunosorbent assay (ELISA) was used to measure activin A and CXCL10 in culture supernatants. The osteoclasts generated from human peripheral monocytes by RANKL stimulation were identified by tartrate-resistant acid phosphatase staining and bone resorption assay using Osteo plate. The expression levels of NFATc1 and cathepsin K, critical intracellular proteins for osteoclastogenesis, were determined by Western blotting. Results: Activin A production in fresh-RSC was markedly enhanced by the synergistic effect of TGF-β₁ with inflammatory cytokines, including TNFα, IL-1β, and IL-6. Activin A inhibited TNFα-induced CXCL10, an important chemoattractant for pathogen-activated T cells and monocytes of osteoclast precursors, but it did not affect the expression of inflammatory cytokines and chemokines. In addition, activin A directly inhibited the expression of NFATc1 and cathepsin K, as well as osteoclast formation in human samples. Conclusion: Our data indicated that TGF-β₁ is involved in the expression of activin A at inflamed joints. Activin A mainly exerts an anti-inflammatory action, which prevents joint damage via the regulation of CXCL10 and osteoclastogenesis.

Severe digital ischemia (SDI), which presents with digital ulcers, necrosis, or gangrene, has been reported to be a rare manifestation of anti‐aminoacyl transfer RNA synthetase (ARS) antibody‐positive polymyositis/dermatomyositis or anti‐synthetase syndrome. A retrospective study was conducted between 2009 and 2020 at our department to investigate the clinical features of anti‐ARS antibody‐positive patients with SDI and identify their predictors. A total of 46 patients who were positive for anti‐ARS antibody were included, four of whom (8.7%) presented with SDI. The characteristics of the patients with SDI were as follows: the median age was 74 years, with 75% being female; anti‐Jo–1 antibody, Raynaud's phenomenon, interstitial lung disease, and myositis were observed in two (50%), four (100%), four (100%), and three patients (75%), respectively. Next, we reviewed the literature of anti‐ARS antibody‐positive patients with SDI and investigated the predictors of SDI by analyzing a total of 51 patients, including the previously reported five patients with SDI. Multivariable analyses revealed that Raynaud's phenomenon and myositis independently predicted the development of SDI in patients with anti‐ARS antibody. In conclusion, digital ulcers, necrosis, or gangrene seem to be more common presentations in our study, and Raynaud's phenomenon and myositis can predict the complications of SDI in anti‐ARS antibody‐positive patients.

Objectives This study aimed to quantify nailfold capillary (NFC) abnormalities in anti-melanoma differentiation-associated gene 5 (MDA5)-positive dermatomyositis (DM) patients and to evaluate the association with clinical parameters, including serum biomarkers. In addition, we aimed to clarify the period leading to remission of NFC abnormalities during immunosuppressive treatment in patients with DM. Methods A prospective observational study was conducted including patients (n = 10) who first visited Hiroshima University Hospital and were diagnosed with DM or clinically amyopathic dermatomyositis (CADM) with anti-MDA5 antibodies. We compared the NFC abnormalities detected by nailfold-video capillaroscopy (NVC), physical findings, blood tests, respiratory function tests, and vascular-related growth factors measured using a LEGENDplexTM Multi-Analyte Flow Assay Kit. Results NFC abnormalities improved in all patients from 2–17 weeks after the initiation of immunosuppressive treatment. The NVC scores were inversely correlated with anti-MDA5 antibody titres at baseline. NVC scores and forced vital capacity (FVC) were positively correlated. Baseline with macrophage colony-stimulating factor (M-CSF) and stem cell factor (SCF) was correlated with anti-MDA-5 titres. Conclusion Our study suggests that NVC scores and disease activity are inversely correlated before treatment. Vascular-related growth factors, such as M-CSF and SCF, may be associated with the disease mechanism in patients with anti-MDA5 antibody-positive DM.

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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.

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