Musculoskeletal ultrasound findings in adult-onset Still's disease: A case series.

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder of unknown etiology characterized by high spiking fever, salmon-like skin rash, arthritis, and elevated serum ferritin levels. Early detection of AOSD is remarkably difficult because of the lack of serologic biomarkers, nonspecific presentation, and rarity of the disease. Although arthralgia and arthritis are the most frequent symptoms and are correlated with health-related quality of life in patients with AOSD, the inflammatory changes associated with these symptoms have not been elucidated. We performed musculoskeletal ultrasound (MSKUS) in 11 patients between January 1, 2008 and July 31, 2023, seven of whom had abnormalities. MSKUS findings of those cases suggested that some patients with AOSD could present with tenosynovitis, tendonitis/peritendonitis, bursitis, and enthesitis along with synovitis. This case series demonstrate the diversity of inflammatory articular manifestations of AOSD identified by MSKUS.

Idiopathic multicentric Castleman disease-TAFRO after COVID-19: A case report.

TAFRO syndrome, a rare disease characterised by thrombocytopaenia, anasarca, fever, reticulin fibrosis, and organomegaly, is thought to be caused by hypercytokinaemia. It is a heterogeneous clinical entity, and a recent comprehensive international definition defined TAFRO syndrome with lymph node histopathology consistent with idiopathic multicentric Castleman disease (iMCD) as iMCD-TAFRO. Herein, we present a rare case of iMCD-TAFRO following coronavirus disease 2019 (COVID-19) infection. A 62-year-old Japanese woman, initially diagnosed with COVID-19, developed a persistent fever and fluid retention, prompting the diagnosis of iMCD-TAFRO. Following the initiation of prednisolone and cyclosporine, her symptoms gradually resolved. Therefore, we discuss the potential pathophysiological link between COVID-19 and iMCD-TAFRO, emphasising the role of cytokine storms. This case report highlights the importance of recognising the spectrum of inflammatory states after COVID-19 and differentiating iMCD-TAFRO after COVID-19 from the COVID-19 cytokine storm syndrome.

Subarachnoid Hemorrhaging with Multiple Cerebral Artery Stenoses after Initiating Remission Induction Therapy for Eosinophilic Granulomatosis with Polyangiitis: a Case Report.

We encountered a 64-year-old Japanese woman who developed subarachnoid hemorrhaging (SAH) with multiple cerebral artery stenoses during remission induction therapy for eosinophilic granulomatosis and polyangiitis (EGPA). The treatment involved intensified steroid pulse therapy and continued intravenous cyclophosphamide pulse therapy, which led to beneficial effects. Given the rarity of multiple EGPA-associated cerebral artery stenoses and SAH, it is crucial to differentiate them from other diseases. The mortality rate of EGPA complicated by intracranial hemorrhagic lesions, including SAH, is high. When headache is present at the onset of EGPA, the possibility of SAH must be considered.

Laser Capture Microscopy RNA Sequencing for Topological Mapping of Synovial Pathology During Rheumatoid Arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) is an autoimmune disease in which the joint lining or synovium becomes highly inflamed and majorly contributes to disease progression. Understanding pathogenic processes in RA synovium is critical for identifying therapeutic targets. We performed laser capture microscopy (LCM) followed by RNA sequencing (LCM-RNAseq) to study regional transcriptomes throughout RA synovium. METHODS: Synovial lining, sublining, and vessel samples were captured by LCM from seven patients with RA and seven patients with osteoarthritis (OA). RNAseq was performed on RNA extracted from captured tissue. Principal component analysis was performed on the sample set by disease state. Differential expression analysis was performed between disease states based on log2 fold change and q value parameters. Pathway analysis was performed using the Reactome Pathway Database on differentially expressed genes among disease states. Significantly enriched pathways in each synovial region were selected based on the false discovery rate. RESULTS: RA and OA transcriptomes were distinguishable by principal component analysis. Pairwise comparisons of synovial lining, sublining, and vessel samples between RA and OA revealed substantial differences in transcriptional patterns throughout the synovium. Hierarchical clustering of pathways based on significance revealed a pattern of association between biologic function and synovial topology. Analysis of pathways uniquely enriched in each region revealed distinct phenotypic abnormalities. As examples, RA lining samples were marked by anomalous immune cell signaling, RA sublining samples were marked by aberrant cell cycle, and RA vessel samples were marked by alterations in heme scavenging. CONCLUSION: LCM-RNAseq confirms reported transcriptional differences between the RA synovium and the OA synovium and provides evidence supporting a relationship between synovial topology and molecular anomalies in RA.

Dysregulated NUB1 and Neddylation Enhances Rheumatoid Arthritis Fibroblast-Like Synoviocyte Inflammatory Responses.

OBJECTIVE: Fibroblast-like synoviocytes (FLS) contribute to the pathogenesis of rheumatoid arthritis (RA), in part due to activation of the proinflammatory transcription factor NF-κB. Neddylation is modulated by the negative regulator of ubiquitin-like protein (NUB) 1. We determined whether NUB1 and neddylation are aberrant in the models with RA FLS, thereby contributing to their aggressive phenotype. METHODS: Models with RA or osteoarthritis (OA) FLS were obtained from arthroplasty synovia. Real-time quantitative polymerase chain reaction and Western blot analysis assessed gene and protein expression, respectively. NUB1 was overexpressed using an expression vector. NF-κB activation was assessed by stimulating FLS with interleukin (IL)-1ß. Neddylation inhibitor (MLN4924) and proteasome inhibitor were used in migration and gene expression assays. MLN4924 was used in the model with K/BxN serum-transfer arthritis. RESULTS: Enhanced H3K27ac and H3K27me3 peaks were observed in the NUB1 promoter in the OA FLS compared with the RA FLS. NUB1 was constitutively expressed by FLS, but induction by IL-1ß was significantly greater in the OA FLS. The ratio of neddylated cullin (CUL) 1 to nonneddylated CUL1 was lower in the OA FLS than the RA FLS. NUB1 overexpression decreased NF-κB nuclear translocation and IL-6 messenger RNA (mRNA) in IL-1ß-stimulated the RA FLS. MLN4924 decreased CUL1 neddylation, NF-κB nuclear translocation, and IL-6 mRNA in IL-1ß-stimulated the RA FLS. MLN4924 significantly decreased arthritis severity in the model with K/BxN serum-transfer arthritis. CONCLUSION: CUL1 neddylation and NUB1 induction is dysregulated in the models with RA, which increases FLS activation. Inhibition of neddylation is an effective therapy in an animal model of arthritis. These data suggest that the neddylation system contributes to the pathogenesis of RA and that regulation of neddylation could be a novel therapeutic approach.

Myeloid-derived suppressor cell-derived osteoclasts with bone resorption capacity in the joints of arthritic SKG mice.

Background: Myeloid-derived suppressor cells (MDSCs) are heterogeneous immature myeloid cells with immunosuppressive functions. It is known that MDSCs are expanded at inflammatory sites after migrating from bone marrow (BM) or spleen (Sp). In chronic inflammatory diseases such as rheumatoid arthritis (RA), previous reports indicate that MDSCs are increased in BM and Sp, but detailed analysis of MDSCs in inflamed joints is very limited. Objective: The purpose of this study is to characterize the MDSCs in the joints of mice with autoimmune arthritis. Methods: We sorted CD11b+Gr1+ cells from joints (Jo), bone marrow (BM) and spleen (Sp) of SKG mice with zymosan (Zym)-induced arthritis and investigated differentially expressed genes (DEGs) by microarray analysis. Based on the identified DEGs, we assessed the suppressive function of CD11b+Gr1+ cells from each organ and their ability to differentiate into osteoclasts. Results: We identified MDSCs as CD11b+Gr1+ cells by flow cytometry and morphological analysis. Microarray analysis revealed that Jo-CD11b+Gr1+ cells had different characteristics compared with BM-CD11b+Gr1+ cells or Sp-CD11b+Gr1+ cells. Microarray and qPCR analysis showed that Jo-CD11b+Gr1+ cells strongly expressed immunosuppressive DEGs (Pdl1, Arg1, Egr2 and Egr3). Jo-CD11b+Gr1+ cells significantly suppressed CD4+ T cell proliferation and differentiation in vitro, which confirmed Jo-CD11b+Gr1+ cells as MDSCs. Microarray analysis also revealed that Jo-MDSCs strongly expressed DEGs of the NF-κB non-canonical pathway (Nfkb2 and Relb), which is relevant for osteoclast differentiation. In fact, Jo-MDSCs differentiated into osteoclasts in vitro and they had bone resorptive function. In addition, intra-articular injection of Jo-MDSCs promoted bone destruction. Conclusions: Jo-MDSCs possess a potential to differentiate into osteoclasts which promote bone resorption in inflamed joints, while they are immunosuppressive in vitro.

Association of large joint involvement at the start of biological disease-modifying antirheumatic drugs and Janus kinase inhibitors with disease activity and drug retention in patients with rheumatoid arthritis: The ANSWER cohort study.

AIM: To investigate the association of large joint involvement (LJI) with disease activity and drug retention in patients with rheumatoid arthritis (RA) who started receiving a biological disease-modifying antirheumatic drug or Janus kinase inhibitor. METHODS: Patients with RA from a Japanese multicenter observational registry were enrolled. Our definition of large joints included the shoulder, elbow, hip, knee, and ankle joints. Linear mixed-effects models were used to examine changes in the clinical disease activity index (CDAI) score at Week 24 as the primary outcome, and drug retention rates were compared between patients with and without LJI using Cox proportional hazards models. We examined the potential effect modifications of changes in the CDAI by baseline characteristics. RESULTS: Overall, 2507 treatment courses from 1721 patients were included (LJI, 1744; no LJI, 763). Although LJI was associated with significantly higher changes in CDAI from baseline at Week 24 (difference in change in CDAI: -5.84 [-6.65 to -5.03], p < .001), CDAI was significantly higher in patients with LJI over time. Retention rates were similar in both groups. The association of LJI with changes in disease activity was more prominent in patients with a short disease duration, negative anti-citrullinated peptide antibodies, and interleukin-6 receptor inhibitor (IL-6Ri) use. CONCLUSION: Although LJI was associated with a greater reduction in disease activity from baseline, higher disease activity at baseline was not offset over time in patients with LJI, demonstrating that LJI is an unfavorable predictor. An early treat-to-target strategy using an IL-6Ri may be beneficial for patients with LJI.

Trends of disease activity in Japanese patients over 75 years with rheumatoid arthritis from 2014 to 2021- the ANSWER cohort study.

OBJECTIVES: To investigate if disease activity among elderly RA patients over 75 years has changed over time in the real-world clinical setting. METHODS: Data from an observational multicentre registry of RA patients in Japan were analyzed. The primary outcome was to evaluate the changes in the proportion of very elderly RA patients (over 75 years) who achieved remission and low disease activity, from 2014 to 2021. The secondary outcome was to identify factors associated with remission and low disease activity by comparing demographic and clinical characteristics among the patients who had a study visit within the study period, using multivariate logistic regression. RESULTS: A total of 32 161 patient visits were identified from 2014 to 2021. The proportion of patients over 75 years increased from 16.5% to 26.9%, with biologics and targeted-synthetic disease modifying anti-rheumatic drugs (b/tsDMARDs) usage increasing and glucocorticoids usage decreasing, while conventional-synthetic DMARDs usage remained relatively stable. The proportion of RA patients over 75 years achieving remission and low disease activity significantly increased from 62.2% to 78.2% (p for trend < 0.001). A negative factor associated with achieving remission and low disease activity was glucocorticoid usage, seropositivity, and history of previous b/tsDMARDs use while MTX usage was associated positively, independent of other predictors. CONCLUSIONS: In our cohort, disease activity among very elderly RA patients has improved over time. The study suggests the importance of using a treat-to-target approach in very elderly RA patients to improve clinical outcomes.

Impact of anti-squamous cell carcinoma antigen antibodies on serum squamous cell carcinoma antigen levels measured by chemiluminescent immunoassay and chemiluminescent enzyme immunoassay.

OBJECTIVE: The serum squamous cell carcinoma antigen (SCCA) level is a well-known tumor marker for squamous cell carcinoma. In this study, we examined the impact of immunoglobulin (Ig)-bound macromolecular SCCA on serum SCCA levels measured by 2 different methods. METHODS: Seventy-five serum samples with an SCCA level >5.0 ng/mL as determined by a chemiluminescent immunoassay (CLIA) were also analyzed using a chemiluminescent enzyme immunoassay (CLEIA). The levels of IgG- and IgA-type anti-SCCA antibodies, which form immunoglobulins and macromolecules, respectively, were determined using an enzyme-linked immunosorbent assay. An absorption test was performed to confirm the presence of anti-SCCA antibodies. RESULTS: The correlation coefficient between the values measured by CLEIA and CLIA was 0.768. The ratio of SCCA levels measured by CLEIA to those measured by CLIA in 14 samples with IgG-type anti-SCCA antibodies was significantly lower than that in samples without these antibodies (P < .031). Absorption tests showed that SCCA levels measured by CLIA might be falsely high in samples with IgG-type anti-SCCA antibodies, probably due to reactions with SCCA1. CONCLUSION: The level of SCCA as measured by CLIA and CLEIA methods correlate well, but the presence of SCCA antibodies can affect the results of the CLIA method.

Clustering of phosphatase RPTPα promotes Src signaling and the arthritogenic action of synovial fibroblasts.

Receptor-type protein phosphatase α (RPTPα) promotes fibroblast-dependent arthritis and fibrosis, in part, by enhancing the activation of the kinase SRC. Synovial fibroblasts lining joint tissue mediate inflammation and tissue damage, and their infiltration into adjacent tissues promotes disease progression. RPTPα includes an ectodomain and two intracellular catalytic domains (D1 and D2) and, in cancer cells, undergoes inhibitory homodimerization, which is dependent on a D1 wedge motif. Through single-molecule localization and labeled molecule interaction microscopy of migrating synovial fibroblasts, we investigated the role of RPTPα dimerization in the activation of SRC, the migration of synovial fibroblasts, and joint damage in a mouse model of arthritis. RPTPα clustered with other RPTPα and with SRC molecules in the context of actin-rich structures. A known dimerization-impairing mutation in the wedge motif (P210L/P211L) and the deletion of the D2 domain reduced RPTPα-RPTPα clustering; however, it also unexpectedly reduced RPTPα-SRC association. The same mutations also reduced recruitment of RPTPα to actin-rich structures and inhibited SRC activation and cellular migration. An antibody against the RPTPα ectodomain that prevented the clustering of RPTPα also inhibited RPTPα-SRC association and SRC activation and attenuated fibroblast migration and joint damage in arthritic mice. A catalytically inactivating RPTPα-C469S mutation protected mice from arthritis and reduced SRC activation in synovial fibroblasts. We conclude that RPTPα clustering retains it to actin-rich structures to promote SRC-mediated fibroblast migration and can be modulated through the extracellular domain.

Effect of resolvin D5 on T cell differentiation and osteoclastogenesis analyzed by lipid mediator profiling in the experimental arthritis.

Resolvins, are specialized pro-resolving mediators (SPMs) derived from n-3 polyunsaturated fatty acids. They contribute actively to the resolution of inflammation, but little is known concerning their role in chronic inflammation, such as in rheumatoid arthritis (RA). Here, we performed lipid mediator (LM) profiling in tissues from the paws of SKG arthritic mice using lipid chromatography (LC)/mass spectrometry (MS)/MS-based LM metabololipidomics. We found elevated levels of SPMs including resolvin D5 (RvD5) in these tissues. Moreover, RvD5 levels were significantly correlated with arthritis disease activity. From experiments to assess the role of RvD5 in the pathology of RA, we concluded that RvD5 suppressed Th17 cell differentiation and facilitated regulatory T cell differentiation, as well as inhibiting CD4+ T cell proliferation. Furthermore, RvD5 attenuated osteoclast differentiation and interfered with osteoclastogenesis. Targeting the resolution of inflammation could be promising as a novel treatment for RA.

Treatment with an Anti-CX3CL1 Antibody Suppresses M1 Macrophage Infiltration in Interstitial Lung Disease in SKG Mice.

CX3C Motif Chemokine Ligand 1 (CX3CL1; fractalkine) has been implicated in the pathogenesis of rheumatoid arthritis (RA) and its inhibition was found to attenuate arthritis in mice as well as in a clinical trial. Therefore, we investigated the effects of an anti-CX3CL1 monoclonal antibody (mAb) on immune-mediated interstitial lung disease (ILD) in SKG mice, which exhibit similar pathological and clinical features to human RA-ILD. CX3CL1 and CX3C chemokine receptor 1 (CX3CR1), the receptor for CX3CL1, were both expressed in the fibroblastic foci of lung tissue and the number of bronchoalveolar fluid (BALF) cells was elevated in ILD in SKG mice. No significant changes were observed in lung fibrosis or the number of BALF cells by the treatment with anti-CX3CL1 mAb. However, significantly greater reductions were observed in the number of M1 macrophages than in M2 macrophages in the BALF of treated mice. Furthermore, CX3CR1 expression levels were significantly higher in M1 macrophages than in M2 macrophages. These results suggest the stronger inhibitory effects of the anti-CX3CL1 mAb treatment against the alveolar infiltration of M1 macrophages than M2 macrophages in ILD in SKG mice. Thus, the CX3CL1-CX3CR1 axis may be involved in the infiltration of inflammatory M1 macrophages in RA-ILD.

Soluble guanylate cyclase stimulator reduced the gastrointestinal fibrosis in bleomycin-induced mouse model of systemic sclerosis.

BACKGROUND: Systemic sclerosis (SSc) is a chronic autoimmune-mediated connective tissue disorder. Although the etiology of the disease remains undetermined, SSc is characterized by fibrosis and proliferative vascular lesions of the skin and internal organs. SSc involves the gastrointestinal tract in more than 90 % of patients. Soluble guanylate cyclase (sGC) stimulator is used to treat pulmonary artery hypertension (PAH) and has been shown to inhibit experimental skin fibrosis. METHODS: Female C57BL/6J mice were treated with BLM or normal saline by subcutaneous implantation of osmotic minipump. These mice were sacrificed on day 28 or day 42. Gastrointestinal pathologies were examined by Masson Trichrome staining. The expression of fibrosis-related genes in gastrointestinal tract was analyzed by real-time PCR, and the levels of collagen in the tissue were measured by Sircol collagen assay. To evaluate peristaltic movement, the small intestinal transport (ITR%) was calculated as [dyeing distance × (duodenum - appendix)] - 1 × 100 (%). We treated BLM-treated mice with sGC stimulator or DMSO orally and analyzed them on day 42. RESULTS: Histological examination revealed that fibrosis from lamina propria to muscularis mucosa in the esophagus was significantly increased in BLM-treated mice, suggesting that BLM induces esophageal hyperproliferative and prefibrotic response in C57BL/6J mice. In addition, the gene expression levels of Col3a1, CCN2, MMP-2, MMP-9, TIMP-1, and TIMP-2 in the esophagus were significantly increased in BLM-treated mice. More severe hyperproliferative and prefibrotic response was observed in the mice sacrificed on day 42 than the mice sacrificed on day 28. The ITR% was found to be significantly lower in BLM-treated mice, suggesting that gastrointestinal peristaltic movement was reduced in BLM-treated mice. Furthermore, we demonstrated that sGC stimulator treatment significantly reduced hyperproliferative and prefibrotic response of esophagus and intestine in BLM-treated mice, by histological examination and Sircol collagen assay. CONCLUSIONS: These findings suggest that BLM induces gastrointestinal hyperproliferative and prefibrotic response in C57BL/6J mice, and treatment with sGC stimulator improves the BLM-induced gastrointestinal lesion.

Subjective well-being among rheumatoid arthritis patients.

AIM: Subjective well-being (SWB) is a psychological construct that is synonymous with happiness. Many variables including age, sex, income, employment, and marital status are related to SWB. Health is also an important determinant of SWB that can be adversely affected in patients with chronic conditions such as rheumatoid arthritis (RA). In this study, we evaluate the SWB of RA patients and compare it with that of healthy controls. METHODS: We obtained the original dataset from the "Quality of Life Survey, 2013", which was conducted by the Economic and Social Research Institute, Cabinet Office, Government of Japan. In this survey, SWB was determined by asking participants to rate their happiness between 0 (very unhappy) and 10 (very happy). The survey also included a 56-point questionnaire regarding well-being-related variables. This questionnaire was administered to RA patients recruited from Kobe University Hospital, and clinical and treatment data were simultaneously collected. RESULTS: Multivariate analysis revealed that RA patients with high or moderate disease activity had SWB scores that were similar to those of controls. However, the SWB scores of RA patients in remission or with low disease activity were higher than those of controls (P = .013). SWB was associated with household income, self-assessment of living costs, self-assessment of health, depression/ anxiety, and social connection. CONCLUSIONS: For RA patients, achieving the therapeutic target can result in better SWB than that of healthy controls. Financial status, self-assessment of health, psychological stress, and social network are also important determinants for the SWB of RA patients.

Tofacitinib facilitates the expansion of myeloid-derived suppressor cells and ameliorates interstitial lung disease in SKG mice.

BACKGROUND: Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a sometimes life-threatening complication in RA patients. SKG mice develop not only arthritis but also an ILD resembling RA-ILD. We previously reported that tofacitinib, a JAK inhibitor, facilitates the expansion of myeloid-derived suppressor cells (MDSCs) and ameliorates arthritis in SKG mice. The aim of this study was to elucidate the effect of tofacitinib on the ILD in SKG mice. METHODS: We assessed the effect of tofacitinib on the zymosan (Zym)-induced ILD in SKG mice histologically and examined the cells infiltrating the lung by flow cytometry. The effects of lung MDSCs on T cell proliferation and Th17 cell differentiation were assessed in vitro. We also evaluated the effects of tofacitinib on MDSCs and dendritic cells in vitro. RESULTS: Tofacitinib significantly suppressed the progression of ILD compared to the control SKG mice. The MDSCs were increased, while Th17 cells, group 1 innate lymphoid cells (ILC1s), and GM-CSF+ILCs were decreased in the lungs of tofacitinib-treated mice. MDSCs isolated from the inflamed lungs suppressed T cell proliferation and Th17 cell differentiation in vitro. Tofacitinib promoted MDSC expansion and suppressed bone marrow-derived dendritic cell (BMDC) differentiation in vitro. CONCLUSION: Tofacitinib facilitates the expansion of MDSCs in the lung and ameliorates ILD in SKG mice.

Additive effects of inhibiting both mTOR and glutamine metabolism on the arthritis in SKG mice.

Glutamine metabolism and the mechanistic target of rapamycin (mTOR) pathway are activated cooperatively in the differentiation and activation of inflammatory immune cells. But the combined inhibition of both pathways was rarely investigated. This study investigated how inhibiting both glutamine metabolism with 6-diazo-5-oxo-L-norleucine (DON) and mTOR with rapamycin affects immune cells and the arthritis in a mouse model. We revealed that rapamycin and DON additively suppressed CD4+ T cell proliferation, and both of them inhibited Th17 cell differentiation. While DON inhibited the differentiation of dendritic cells and macrophages and facilitated that of Ly6G+ granulocytic (G)-MDSCs more strongly than did rapamycin, G-MDSCs treated with rapamycin but not DON suppressed CD4+ T cell proliferation in vitro. The combination of rapamycin and DON significantly suppressed the arthritis in SKG mice more strongly than did each monotherapy in vivo. The numbers of CD4+ T and Th17 cells in the spleen were lowest in mice treated with the combination therapy. Thus, combined treatment with rapamycin and DON additively ameliorated the arthritis in SKG mice, possibly by suppressing CD4+ T cell proliferation and Th17 differentiation. These results suggest the combination of rapamycin and DON may be a potential novel therapy for arthritis.

Acute Pulmonary Hypertension Crisis after Adalimumab Reduction in Rheumatoid Vasculitis.

Rheumatoid vasculitis is a rare etiology for pulmonary hypertension (PH) in patients with connective tissue disease. We encountered a case of acute PH crisis in a case with rheumatoid vasculitis eight months after undergoing adalimumab reduction. Since no repetition of arthralgia occurred after the adalimumab reduction, we decided to not increase the dose of adalimumab. However, hemodynamic collapse thereafter developed and even though steroid pulse therapy was administered, the patient nevertheless died. The autopsy showed clusters of acute and chronic inflammation around the remodeled pulmonary arteries along with micro-thrombi in the vessel lumen. We should consider the possibility of critical worsening of PH as a phenotype of vasculitis related to immunosuppressive therapy reduction.

Myeloid-derived suppressor cells in non-neoplastic inflamed organs.

BACKGROUND: Myeloid-derived suppressor cells (MDSCs) are a highly heterogeneous population of immature myeloid cells with immunosuppressive function. Although their function in tumor-bearing conditions is well studied, less is known about the role of MDSCs in various organs under non-neoplastic inflammatory conditions. MAIN BODY: MDSCs are divided into two subpopulations, G-MDSCs and M-MDSCs, and their distribution varies between organs. MDSCs negatively control inflammation in inflamed organs such as the lungs, joints, liver, kidneys, intestines, central nervous system (CNS), and eyes by suppressing T cells and myeloid cells. MDSCs also regulate fibrosis in the lungs, liver, and kidneys and help repair CNS injuries. MDSCs in organs are plastic and can differentiate into osteoclasts and tolerogenic dendritic cells according to the microenvironment under non-neoplastic inflammatory conditions. CONCLUSION: This article summarizes recent findings about MDSCs under inflammatory conditions, especially with respect to their function and differentiation in specific organs.

CD11b+Gr-1dim Tolerogenic Dendritic Cell-Like Cells Are Expanded in Interstitial Lung Disease in SKG Mice.

OBJECTIVE: SKG mice develop interstitial lung disease (ILD) resembling rheumatoid arthritis-associated ILD in humans. The aim of this study was to clarify the mechanism underlying the lung pathology by analyzing lung-infiltrating cells in SKG mice with ILD. METHODS: We assessed the severity of zymosan A (ZyA)-induced ILD in SKG mice histologically, and we examined lung-infiltrating cells by flow cytometry. Total lung cells and isolated monocytic myeloid-derived suppressor cells (MDSCs) were cultured in vitro with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4. The proliferation of 5,6-carboxyfluorescein diacetate N-succinimidyl ester-labeled naive T cells cocultured with isolated CD11b+Gr-1dim cells and MDSCs was evaluated by flow cytometry. CD11b+Gr-1dim cells were adoptively transferred to ZyA-treated SKG mice. RESULTS: MDSCs, Th17 cells, and group 1 and 3 innate lymphoid cells (ILC1s and ILC3s) were increased in the lungs; the proportion of these cells varied with ILD severity. In this process, we found that a unique cell population, CD11b+Gr-1dim cells, was expanded in the severely inflamed lungs. Approximately half of the CD11b+Gr-1dim cells expressed CD11c. CD11b+Gr-1dim cells were induced from monocytic MDSCs with GM-CSF in vitro and were considered tolerogenic because they suppressed T cell proliferation. These CD11b+Gr-1dim cells have never been described previously, and we termed them CD11b+Gr-1dim tolerogenic dendritic cell (DC)-like cells. Th17 cells, ILC1s, and ILC3s in the inflamed lung produced GM-CSF, which may have expanded CD11b+Gr-1dim tolerogenic DC-like cells in vivo. Furthermore, adoptive transfer of CD11b+Gr-1dim tolerogenic DC-like cells significantly suppressed progression of ILD in SKG mice. CONCLUSION: We identified unique suppressive myeloid cells that were differentiated from monocytic MDSCs in SKG mice with ILD, and we termed them CD11b+Gr-1dim tolerogenic DC-like cells.

Glutaminase 1 plays a key role in the cell growth of fibroblast-like synoviocytes in rheumatoid arthritis.

BACKGROUND: The recent findings of cancer-specific metabolic changes, including increased glucose and glutamine consumption, have provided new therapeutic targets for consideration. Fibroblast-like synoviocytes (FLS) from rheumatoid arthritis (RA) patients exhibit several tumor cell-like characteristics; however, the role of glucose and glutamine metabolism in the aberrant proliferation of these cells is unclear. Here, we evaluated the role of these metabolic pathways in RA-FLS proliferation and in autoimmune arthritis in SKG mice. METHODS: The expression of glycolysis- or glutaminolysis-related enzymes was evaluated by real-time polymerase chain reaction (PCR) and Western blotting, and the intracellular metabolites were evaluated by metabolomic analyses. The effects of glucose or glutamine on RA-FLS cell growth were investigated using glucose- or glutamine-free medium. Glutaminase (GLS)1 small interfering RNA (siRNA) and the GLS1 inhibitor compound 968 were used to inhibit GLS1 in RA-FLS, and compound 968 was used to study the effect of GLS1 inhibition in zymosan A-injected SKG mice. RESULTS: GLS1 expression was increased in RA-FLS, and metabolomic analyses revealed that glutamine metabolism was increased in RA-FLS. RA-FLS proliferation was reduced under glutamine-deprived, but not glucose-deprived, conditions. Cell growth of RA-FLS was inhibited by GLS1 siRNA transfection or GLS1 inhibitor treatment. Treating RA-FLS with either interleukin-17 or platelet-derived growth factor resulted in increased GLS1 levels. Compound 968 ameliorated the autoimmune arthritis and decreased the number of Ki-67-positive synovial cells in SKG mice. CONCLUSIONS: Our results suggested that glutamine metabolism is involved in the pathogenesis of RA and that GLS1 plays an important role in regulating RA-FLS proliferation, and may be a novel therapeutic target for RA.