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Belimumab is a therapeutic medication that inhibits the B-cell-activating factor (BAFF) used for systemic lupus erythematosus (SLE); however, the response sometimes varies among individuals, even when patients are stratified based on general clinical characteristics. Therefore, we focused on immunological phenotypic changes with belimumab, investigated their association with subsequent clinical courses, and sought to identify relevant immunological indicators to stratify patients who would benefit from belimumab. We assessed changes in B and T cell phenotypes, as well as BAFF-related factors, such as levels of BAFF and a proliferation-inducing ligand, and expression of three BAFF receptors: BAFF receptor (BAFF-R), B-cell maturation antigen (BCMA), transmembrane activator and cyclophilin ligand interactor (TACI), in 19 patients with SLE who were treated with belimumab before and 3 months after treatment. First, to visualize patterns in complex and diverse data, we summarized B cell changes such as subsets and BAFF receptor expressions into two axes, the first and second principal components (PC1 and PC2), and characterized broad phenotypic changes by cluster analysis. Next, we evaluated whether the B cell changes represented by PC1 and PC2 were associated with other concurrent phenotypic changes, baseline factors, and treatment response at 6 months. We found that lower PC2, indicating increased BAFF-R expression and decreased percentage of naïve B cells, was associated with a subsequent therapeutic response at 6 months (odds ratio 5.3, 95% confidence interval 1.2–24, p = .031). Furthermore, higher percentages of effector memory CD3+CD4+ T cells at baseline were associated with lower PC2 and therapeutic response. Further analysis revealed that increased PC1, as reflected by increased BCMA and TACI expression and an increase in the percentage of class-switched memory B cells, was associated with both T and B cell activation. Although belimumab is a B-cell targeted therapy, it can also influence T-cell phenotypes. Thus, early B cell changes could be used to predict treatment response, and their changes could be predicted from baseline T cell phenotypes, indicating the importance of B and T cell interactions.

We aimed to evaluate the utility of coagulation markers for the prediction of rapidly progressive interstitial lung disease (RP-ILD) in patients with dermatomyositis (DM). In this retrospective study, 29 patients with DM-associated ILD were analyzed. The number of patients with RP-ILD was 15 (52%). The baseline clinical and demographic data and laboratory markers were analyzed to identify predictive factors for RP-ILD.The univariate logistic regression analysis demonstrated that in addition to well-known laboratory markers, such as serum ferritin, KL-6, and lymphocyte counts, a prolonged activated partial thromboplastin time (aPTT) ratio at the time of DM-associated ILD diagnosis was useful for predicting RP-ILD. Moreover, the logistic regression model and receiver operating characteristic curve analysis showed that combinations of the aPTT ratio and well-known laboratory markers were significantly effective in predicting RP-ILD. This study suggested that an association between RP-ILD and the coagulation system exists.

Objectives: To identify the factors associated with the risk of diffuse alveolar hemorrhage (DAH) in patients with microscopic polyangiitis (MPA), focusing on other preexisting lung involvements such as interstitial lung disease (ILD) and airway disease.Methods: In this retrospective cohort study, we analyzed consecutive patients with myeloperoxidase-antineutrophil cytoplasmic antibody-positive MPA who had undergone chest computed tomography (CT) before starting treatment between 2006 and 2016. Patients who already had DAH at initial CT imaging were excluded. CT images were evaluated for the presence of ILD and airway disease. The association between preexisting lung involvements and the development of DAH was assessed using logistic regression models adjusted for various clinical characteristics.Results: We identified 113 patients (median age 72 years; median follow-up duration 39 months), and 27 (24%) of them developed DAH during the follow-up. Airway disease was identified in 41 (36%) patients and was independently associated with the development of DAH (adjusted odds ratio 6.86, 95% confidence interval 1.85-25.4). However, ILD identified in 45 (40%) patients was not associated with DAH.Conclusion: Our findings suggest that DAH in MPA occurs frequently in patients with airway disease. Attention to preexisting airway disease may help predict the development of DAH.

Cross talk between inflammation and coagulation plays important roles in acute or subacute progressive pulmonary fibrosis characterized by diffuse alveolar damage. Thrombomodulin is a physiological inhibitor of high-mobility group box 1 (HMGB1), and thrombin and may be effective for this condition. This study investigated the roles of HMGB1 and thrombin in the pathophysiology of bleomycin-induced pulmonary fibrosis and the efficacy of recombinant human soluble thrombomodulin (rhTM). Pulmonary fibrosis was induced in wild-type C57BL/6 mice by intratracheal instillation of bleomycin. We first assessed HMGB1, thrombin, transforming growth factor (TGF)-β1, and α-smooth muscle actin (SMA) levels in bronchoalveolar lavage fluid and lung tissue sections over time. Expression of HMGB1 and thrombin was elevated before that of TGF-β1 and α-SMA and remained high during the fibrotic phase after bleomycin instillation. We next examined whether in vitro stimulation with HMGB1 and thrombin induced expression of TGF-β1 and α-SMA in cultured alveolar macrophages and lung fibroblasts, respectively, by performing quantitative PCR, enzyme-linked immunosorbent assay, Western blot, and immunofluorescence analyses. HMGB1 and thrombin stimulation induced TGF-β1 production by alveolar macrophages, and thrombin stimulation also induced α-SMA expression in lung fibroblasts. Finally, we evaluated the effect of rhTM on bleomycin-induced pulmonary fibrosis. Compared with the vehicle control, both early and late-phase administration of rhTM suppressed the fibrotic process. Our results suggest that HMGB1 and thrombin were involved in the pathophysiology of pulmonary fibrosis via production of profibrotic proteins and that rhTM attenuated bleomycin-induced pulmonary fibrosis. rhTM may be a therapeutic option for acute or subacute pulmonary fibrosis.

Pulmonary fibrosis is a progressive disease with poor prognosis and limited therapeutic options. In this study, we evaluated the potential therapeutic effects of CG223, a novel inhibitor of bromodomain and extra-terminal motif (BET) proteins, on pulmonary fibrosis by focusing on the transforming growth factor-β1 (TGF-β1) pathway. In a murine model of bleomycin-induced pulmonary fibrosis, CG223 attenuated fibrosis while reducing the infiltration of inflammatory cells into the lungs. Fibroblasts expressing BRD4, a member of the BET protein family, were enriched in the tissue regions corresponding to bleomycin-induced fibrotic lesions. Additionally, pulmonary fibroblasts isolated from bleomycin-instilled mice showed a significantly increased association of BRD4 with the promoters of two pro-fibrotic genes linked to the entry into the TGF-β1 autocrine/paracrine loop, thrombospondin 1 (Thbs1) and integrin β3 (Itgb3), as well as with the promoter of a myofibroblast marker gene, actin alpha 2 (Acta2). Subsequent in vitro studies with murine primary lung fibroblasts showed that the mRNA induction of Thbs1, Itgb3, and Acta2 by TGF-β1 can be inhibited by CG223 in a dose-dependent manner. Taken together, CG223-induced BRD4 inhibition suppressed lung fibrogenesis by affecting multiple genes, including those involved in the triggering of the TGF-β1 autocrine/paracrine loop.

Allograft inflammatory factor-1 (AIF-1) is a protein expressed by macrophages infiltrating the area around the coronary arteries of rats with an ectopic cardiac allograft. Some studies have shown that expression of AIF-1 increased in a mouse model of trinitrobenzene sulfonic acid-induced acute colitis and in acute cellular rejection of human cardiac allografts. These results suggest that AIF-1 is related to acute inflammation. The current study used bleomycin-induced acute lung injury to analyze the expression of AIF-1 and to examine its function in acute lung injury. Results showed that AIF-1 was significantly expressed in lung macrophages and increased in bronchoalveolar lavage fluid from mice with bleomycin-induced acute lung injury in comparison to control mice. Recombinant AIF-1 increased the production of IL-6 and TNF-α from RAW264.7 (a mouse macrophage cell line) and primary lung fibroblasts, and it also increased the production of KC (CXCL1) from lung fibroblasts. These results suggest that AIF-1 plays an important role in the mechanism underlying acute lung injury.

Background Sphingosine-1-phosphate (S1P) is a biologically active phospholipid, which is derived from membrane lipid. It binds to the receptors, named S1P1–5, and regulates several signalling pathways involved in inflammation, cell survival, angiogenesis and cell migration. Concentration of S1P and expression of S1P receptors can vary according to local tissue conditions. RA is a chronic inflammatory disorder of joints and the concentration of S1P in synovial fluid is higher in RA patient than in OA patient. In vitro, S1P3 expression in RA synoviocyte is upregulated by TNFa treatment. On the other hand, it is not clarified whether S1P/S1P3 signalling pathway contributes to arthritis in RA. Objectives The objective of this study is to investigate the role of S1P/S1P3 signalling in inflammatory arthritis. Methods Collagen-induced arthritis (CIA) was induced by subcutaneous injection of bovine type II collagen emulsified in complete Freund’s adjuvant in wild-type (WT) or S1P3-knock-out (S1P3-KO) 7–9 week-old DBA/1J mice. Arthritis severity were evaluated by visual scoring and histological analysis. The severity was assessed over time by using the arthritis score, in which each paw was scored on a scale of 0–4 and the scores of all four paws were cumulated, resulting in a maximum possible score of 16 per mouse. For histopathological examination, mice were sacrificed on the 42nd day and the hindlimbs were removed and fixed in 4% buffered formaldehyde. Paraffin embedded sections of the knee joints stained with hematoxylin and eosin were systematically scanned in a microscope and scored based on cell infiltration, cartilage destruction and bone erosion parameters. S1P3 mRNA expression was examined by realtime PCR method with total RNA extracted from knee joint capsules of CIA or normal WT mice. Murine primary fibroblast like synoviocytes (FLS) were obtained from CIA mice. We examined S1P3 expression after TNFa treatment and measured cytokine produced after S1P treatment with or without TNFa pretreatment in FLS. Results S1P3 deficiency resulted in modest symptoms of arthritis and a significant reduction in synovial inflammation and bone erosions in histological analysis. S1P3 mRNA expression in knee joint capsule in CIA mice was about five times as high as that in normal mice. TNFa treatment upregulated S1P3 expression and S1P treatment enhanced IL-6 production in WT-FLS significantly. TNFa-priming enhanced S1P-induced IL-6 production, which is significantly higher in WT-FLS than in KO-FLS. This effect was not observed in MCP-1 production of WT-FLS. Conclusions S1P3-KO reduced severity of arthritis, inflammation and bone erosions in CIA. S1P3 mRNA was upregulated in inflamed joint capsule. S1P induces IL-6 production via S1P3 upregulation by TNFa in CIA-FLS. S1P3 inhibition could be a good target of the therapy for arthritis. References [1] Blaho VA and Hla T. An update on the biology of sphingosine 1-phosphate receptors. J Lipid Res55:1596–608. [2] Zhao C, Fernandes MJ, and Bourgoin SG, et al. Specific and overlapping sphingosine-1-phosphate receptor functions in human synoviocytes: impact of TNF-alpha. J Lipid Res49: 2323–37. Disclosure of Interest None declared

Allograft inflammatory factor-1 (AIF-1) is a protein expressed by macrophages infiltrating the area around the coronary arteries in a rat ectopic cardiac allograft model. We previously reported that AIF-1 is associated with the pathogenesis of rheumatoid arthritis and skin fibrosis in sclerodermatous graft-versus-host disease mice. Here, we used an animal model of bleomycin-induced lung fibrosis to analyze the expression of AIF-1 and examine its function in lung fibrosis. The results showed that AIF-1 was expressed on lung tissues, specifically macrophages, from mice with bleomycin-induced lung fibrosis. Recombinant AIF-1 increased the production of TGF-β which plays crucial roles in the mechanism of fibrosis by mouse macrophage cell line RAW264.7. Recombinant AIF-1 also increased both the proliferation and migration of lung fibroblasts compared with control group. These results suggest that AIF-1 plays an important role in the mechanism underlying lung fibrosis, and may provide an attractive new therapeutic target.

Bone destruction at inflamed joints is an important complication associated with rheumatoid arthritis (RA). Interleukin-10 (IL-10) may suppress not only inflammation but also induction of osteoclasts that play key roles in the bone destruction. If IL-10-producing osteoblast-like cells are induced from patient somatic cells and transplanted back into the destructive bone lesion, such therapy may promote bone remodeling by the cooperative effects of IL-10 and osteoblasts. We transduced mouse fibroblasts with genes for IL-10 and Runx2 that is a crucial transcription factor for osteoblast differentiation. The IL-10-producing induced osteoblast-like cells (IL-10-iOBs) strongly expressed osteoblast-specific genes and massively produced bone matrix that were mineralized by calcium phosphate in vitro and in vivo. Culture supernatant of IL-10-iOBs significantly suppressed induction of osteoclast from RANKL-stimulated Raw264.7 cells as well as LPS-induced production of inflammatory cytokine by macrophages. The IL-10-iOBs may be applicable to novel cell-based therapy against bone destruction associated with RA.

BackgroundSphingosine-1-phosphate receptor 3 (S1P3) is one of five receptors for sphingosine-1-phosphate (S1P). S1P/S1P3 signaling is involved in numerous physiological and pathological processes including bone metabolism, sepsis, cancer, and immunity. In rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLSs) are activated by several factors and promote abundant proinflammatory cytokine production and bone destruction. The aim of this study was to investigate whether S1P3 is associated with the development of autoimmune arthritis and the pathogenic function of FLSs.MethodsWild-type (WT) and S1P3 knockout (S1P3-KO) collagen-induced arthritis (CIA) mice were evaluated with respect to clinical and histological disease severity, along with the levels of anti-collagen antibodies and expression of tumor necrosis factor-α (TNFα) and interleukin-6 (IL-6). S1P3 expression in the synovium was analyzed by real-time reverse-transcription polymerase chain reaction (RT-PCR) and immunofluorescence staining. FLSs isolated from CIA mice were activated with TNFα and S1P3 expression was analyzed by real-time RT-PCR. The role of S1P/S1P3 signaling in activated and non-activated FLSs was investigated by measuring cell proliferation and cyto/chemokine production by real-time RT-PCR and/or enzyme-linked immunosorbent assay.ResultsClinical and histological scores, and synovial IL-6 expression were significantly lower in S1P3-KO mice with CIA than in WT mice. Arthritic synovia had higher S1P3 expression than intact synovia and FLSs in arthritic joints expressed S1P3 in vivo. Primary cultured FLSs produced IL-6 in a time-dependent manner in response to S1P stimulation and exhibited higher levels of S1P3 expression after activation with TNFα. S1P3-induced production of IL-6 and MMP-3 was increased in FLSs pre-activated with TNFα.ConclusionIn this study, we demonstrated that S1P3 expression is associated with the development of autoimmune arthritis via inflammation-induced increases in S1P/S1P3 signaling that increase production of IL-6 in FLSs. Inhibition of S1P/S1P3 signaling could open the door to the development of new therapies for RA.

Myeloid-derived suppressor cells (MDSCs) are of myeloid origin and are able to suppress T cell responses. The role of MDSCs in autoimmune diseases remains controversial, and little is known about the function of MDSCs in autoimmune arthritis. In this study, we clarify that MDSCs play crucial roles in the regulation of proinflammatory immune response in a collagen-induced arthritis (CIA) mouse model. MDSCs accumulated in the spleens of mice with CIA when arthritis severity peaked. These MDSCs inhibited the proliferation of CD4+ T cells and their differentiation into Th17 cells in vitro. Moreover, MDSCs inhibited the production of IFN-γ, IL-2, TNF-α, and IL-6 by CD4+ T cells in vitro, whereas they promoted the production of IL-10. Adoptive transfer of MDSCs reduced the severity of CIA in vivo, which was accompanied by a decrease in the number of CD4+ T cells and Th17 cells in the draining lymph nodes. However, depletion of MDSCs abrogated the spontaneous improvement of CIA. In conclusion, MDSCs in CIA suppress the progression of CIA by inhibiting the proinflammatory immune response of CD4+ T cells. These observations suggest that MDSCs play crucial roles in the regulation of autoimmune arthritis, which could be exploited in new cell-based therapies for human rheumatoid arthritis.

Background Patients with glucocorticoid-induced osteoporosis (GIOP) are at very high risk of fracture, and patients with severe GIOP often experience fractures during treatment with bisphosphonates. Teriparatide (TPTD) is the only currently available anabolic agent expected to be effective for GIOP. Once-weekly TPTD decreased bone resorption marker with primary osteoporosis different from daily TPTD, but it has not yet been tested with GIOP. Objectives To evaluate the efficacy of once-weekly TPTD for patients with GIOP and inadequate response to bisphosphonates. Methods Patients with GIOP and collagen diseases treated with prednisolone for at least 6 months with inadequate responses to bisphosphonates were administered once-weekly TPTD. Bone density of the lumbar spine and femoral neck, measured as percent young adult mean (YAM); serum concentrations of cross-linked N-terminal telopeptides of type I collagen (NTx), bone alkaline phosphatase (BAP), and calcium; and FRAX were measured at baseline and 6, 12 and 18 months after starting TPTD. Results Of the 12 GIOP patients with collagen diseases enrolled, nine (seven females, two males; mean age 57.4 ± 11.1 years) completed treatment, including six with systemic lupus erythematosus, two with rheumatoid arthritis, and one with adult onset still disease. Only one new fracture event, a lumbar compression fracture, occurred during the study period, although seven patients experienced eight fracture events within 18 months before starting TPTD (p = 0.04). Lumbar spine YAM significantly improved at 18 months (p = 0.04), whereas femoral neck YAM did not (p = 0.477). Serum NTx, BAP, Ca, and FRAX were not significantly affected by TPTD treatment. Conclusions Once-weekly TPTD reduces fracture events and increases bone density of the lumbar spine of GIOP patients with inadequate response to bisphosphonates.

We report a case of rheumatoid vasculitis (RV) that responded well to abatacept, a cytotoxic T lymphocyte-associated antigen 4 (CTLA4)-immunoglobulin fusion protein. A 38-year-old woman developed RV despite treatment with methotrexate and tumor necrosis factor (TNF) inhibitors. The effects of steroid therapy, immunoabsorption plasmapheresis, and interleukin-6 inhibitor were insufficient, however, administration of abatacept rapidly improved her clinical symptoms with almost normalization of the immunological findings. This is the first published case report of the successful treatment of RV with abatacept.

Background Tocilizumab, anti-IL-6 receptor monoclonal antibody, is widely used for patients with rheumatoid arthritis. IL-6 is essential for production of C-reactive protein (CRP). Tocilizumab fully inhibit the production of CRP. Therefore, we have difficulty in objective assessment of infection and disease activity because the level of CRP is suppressed under tocilizumab therapy. The development of new biomarker alternative to CRP is needed for daily practice. Objectives To discover new biomarkers alternative to CRP under tocilizumab therapy for rheumatoid arthritis. Methods We registered patients with rheumatoid arthritis treated with tocilizumab. We collected serum samples from those patients at baseline, 4 weeks after the first tocilizumab administration when patient9s CRP level is almost normal, and 1 year later. And we measured CRP, ESR and clinical disease activity index (CDAI) score.Serum peptidomic analysis was conducted by newly-established one-step direct transfer technology (BLOTCHIP-MS analysis), a rapid quantitative technology for peptidomic analysis. All sample measurements were repeated four times. Statistical analyses of MS spectral data were conducted using ClinProTools version 2.2 (Bruker Daltonics). Results We registered 14 patients and their background is shown in Table 1. The levels of CRP were 1.16±0.99 mg/dl at baseline, 0.02±0.01 mg/dl at 4 weeks and 0.01±0.01mg/dl at 1 year, respectively. Their CDAI score were 22±9.2 at baseline, 15±8.9 at 4 weeks and 3±2.6 at 1 year, respectively. CRP titer decreased to almost normal level at 4 weeks regardless whether CDAI score did not fully decrease. We detect 6 biomarkers, named as PRSJ01 to PRSJ06, by the peptidomic analysis (Table 2). The AUC of diagnostic value of these markers is from 0.742 to 0.858. For example, the level of PRSJ06 significantly decreased 4 weeks (Wilcoxon singed-rank test, p=0.02) and 1 year (Wilcoxon singed-rank test, p=0.003) after first tocilizumab administration (Figure 1). and it was inversely-correlated with CDAI score. Conclusions We detect new disease activity biomarkers alternative to CRP under tocilizumab therapy for rheumatoid arthritis. It is useful for exact evaluation of disease activity and infection during tocilizumab therapy. Disclosure of Interest None declared

Background Multitarget therapy for lupus nephritis which was reported by Bao et al. 1 is hopeful treatment option for refractory systemic lupus erythematosus (SLE). However, there are few studies about multitarget therapy with combination of prednisolone (PSL), purine synthesis inhibitor and calcineurin inhibitor for SLE. Objectives The aim of this study is to evaluate efficacy and safety of multitarget therapy with combination of PSL, mizoribine (MZR) and tacrolimus (TAC) as induction or add-on therapy for refractory SLE with or without lupus nephritis. Methods We retrospectively studied 26 SLE patients treated with multitarget therapy in our department from April 2009 to December 2013. The mean age was 44.5 years old and 23 patients were female. They were divided into two groups; (A) 10 patients who were initially treated with this therapy as induction, and (B) 16 patients who were additionally treated with this therapy due to minor flares or difficulty in reducing PSL dose. We evaluated efficacy and safety of this combination strategy as (A) induction therapy and (B) add-on therapy respectively. Results (A) Five of 10 patients had lupus nephritis (2 were class IV and 3 were class IV+V). Three of 10 stopped this therapy due to severe adverse events within 12 months. Other 2 patients stopped this therapy due to preparation for pregnancy. Among nephritis patients, complete renal response rate at 6 months was 75%. The mean SLE disease activity index (SLEDAI) was reduced from 25 at baseline to 7.5 at 6 months. In all non-nephritis patients, their symptoms or blood examination data were improved. The mean SLEDAI was reduced from 14.4 at baseline to 2.4 at 6 months. (B) Five of 16 patients had lupus nephritis. One patient stopped this therapy due to preparation for pregnancy. The mean PSL dose was reduced from 14.8mg/day at baseline to 9.2mg/day at 12 months. The mean SLEDAI was reduced from 6.5 at baseline to 2.7 at 12 months. In all 26 patients, adverse events were 28 cases in the observation period. Most of these were mild infections. Three severe adverse events were observed. These were hypertrophic cardiomyopathy due to interaction of TAC and clarithromycin, nocardial soft tissue abscess and cryptococcal meningitis. All three patients who experienced severe adverse events were over 65 years old. Conclusions The combination use of PSL, MZR and TAC is effective as induction therapy and as add-on therapy for refractory SLE regardless of having lupus nephritis. However, elderly patients tend to suffer from sever adverse events. References Bao H et al: Successful treatment of class V+IV lupus nephritis with multitarget therapy, J Am Soc Nephrol 19; 2001-2010, 2008 Disclosure of Interest Y. Kukida Grant/research support: Astellas Pharma Inc. Asahi Kasei Pharma Corp., T. Kida: None declared, T. Inoue: None declared, Y. Isoda: None declared, T. Sagawa: None declared, R. Ishigaki: None declared, A. Kasahara: None declared, A. Nakabayashi: None declared, K. Fujioka: None declared, H. Nagahara: None declared, W. Fujii: None declared, K. Murakami: None declared, T. Seno: None declared, A. Yamamoto Grant/research support: Astellas Pharma Inc. Asahi Kasei Pharma Corp., M. Kohno Grant/research support: Astellas Pharma Inc. Asahi Kasei Pharma Corp., Y. Kawahito Grant/research support: Astellas Pharma Inc. Asahi Kasei Pharma Corp. DOI 10.1136/annrheumdis-2014-eular.3186

Background Recent reports demonstrated that somatic cells such as fibroblasts can be directly reprogrammed into other cell types including neurons and cardiomyocytes by introducing critical transcription factors involved in the differentiation of the corresponding cell lineages 1,2 . Such procedures in combination with co-transduction of a particular gene may allow creation of the cells with desired functions. If patient specific osteoblasts can be induced and engineered to produce IL-10, autologous transplantation of such cells may suppress inflammation and bone destruction in rheumatoid arthritis by modulating immune responses and osteoclast development. Objectives To generate IL-10-producing mouse osteoblast-like cells from fibroblasts, and estimate potential effect of the cell supernatants on osteoclast differentiation. Methods Various combinations of transcription factors were transduced into mouse embryonic fibroblasts (MEFs) with retroviral vectors and the efficiency of conversion into osteoblast-like cells were estimated by alizarine red S staining. IL-10 gene was also transduced to the cells that received the most effective combination of the transcription factors, and resultant cells were characterized by qRT-PCR, alkaline phosphatase staining, and alizarine red S staining. IL-10 production was measured by qRT-PCR and ELISA. The supernatant was added to a mouse macrophage cell line Raw264.7 cells that were induced to differentiate into osteoclasts by an addition of RANKL. Results MEFs were successfully induced to massively produce bone matrix that were mineralized by calcium phosphate. Co-transduction of the IL-10 gene by means of a retrovirus vector resulted in establishment of osteoblasts that produced IL-10 at a significant level. The culture supernatant of the cells significantly suppressed osteoclast differentiation from Raw264.7 cells. Conclusions IL-10-secreting osteoblasts were successfully generated from fibroblasts by direct reprogramming procedures. The cells may be useful in novel cell-based therapy against RA in the future. References Ieda, M. et al.: Cell, 142: 375-386, 2010. Vierbuchen T.: Nature, 463: 1035-1041, 2010. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.2247

Background Myeloid-derived suppressor cells (MDSCs) are of myeloid origin and are able to suppress T cell responses. MDSCs are characterized by the co-expression of the myeloid differentiation antigens Gr-1 and CD11b in mice (1). MDSCs in cancer have been studied in detail and are known to play roles in tumor associated immune suppression. However, the roles of MDSCs in autoimmune disease remain controversial and little is known about MDSCs in autoimmune arthritis. Objectives We investigate the roles of MDSCs in autoimmune arthritis using collagen-induced arthritis (CIA) mouse models. Methods We determined the number of Gr-1 + CD11b + MDSCs in the spleens of CIA mice by flow cytometry. Next, we isolated MDSCs from CIA mice by magnetic cell sorting and cultured with CD4 + T cells to analyze the functions of MDSCs. We investigated the proliferation of CD4 + T cells by CFSE dye dilution assay and estimated cytokine levels produced by CD4 + T cells using ELISA. Furthermore, we investigated CD4 + T cell differentiation into Th17 cells by flow cytometry. Finally, we performed adoptive transfer of MDSCs into CIA mice and investigated the severity of arthritis. Results MDSCs significantly accumulated in the spleens of mice with CIA when arthritis severity peaked. These MDSCs inhibited CD4 + T cell proliferation and differentiation into Th17 cells. Moreover, MDSCs inhibited the production of IFNγ, IL-2, TNFα, and IL-6 by CD4 + T cells in vitro , whereas they promoted the production of IL-10. Adoptive transfer of MDSCs reduced both clinical (Image A) and histological arthritis scores (Image B) in vivo , which was accompanied by a decrease in the number of CD4 + T cells and Th17 cells in the draining lymph nodes. Image/graph Conclusions MDSCs in CIA suppress the progression of CIA by inhibiting the pro-inflammatory immune response of CD4 + T cells. These observations suggest that MDSCs play crucial roles in the regulation of autoimmune arthritis, which could be exploited in new cell-based therapies for human rheumatoid arthritis (RA). References Gabrilovich, D. I., and S. Nagaraj. 2009. Myeloid-derived suppressor cells as regulators of the immune system. Nat. Rev. Immunol. 9: 162-174. Disclosure of Interest None Declared