Establishing clinical remission criteria for giant cell arteritis: Results of a Delphi exercise carried out by an expert panel of the Japan Research Committee of the Ministry of Health, Labour, and Welfare for Intractable Vasculitis.

OBJECTIVE: To develop a proposal for giant cell arteritis remission criteria in order to implement a treat-to-target algorithm. METHODS: A task force consisting of 10 rheumatologists, 3 cardiologists, 1 nephrologist, and 1 cardiac surgeon was established in the Large-vessel Vasculitis Group of the Japanese Research Committee of the Ministry of Health, Labour and Welfare for Intractable Vasculitis to conduct a Delphi survey of remission criteria for giant cell arteritis. The survey was circulated among the members over four reiterations with four face-to-face meetings. Items with a mean score of ≥4 were extracted as items for defining remission criteria. RESULTS: An initial literature review yielded a total of 117 candidate items for disease activity domains and treatment/comorbidity domains of remission criteria, of which 35 were extracted as disease activity domains (systematic symptoms, signs and symptoms of cranial and large-vessel area, inflammatory markers, and imaging findings). For the treatment/comorbidity domain, ≤5 mg/day of prednisolone 1 year after starting glucocorticoids was extracted. The definition of achievement of remission was the disappearance of active disease in the disease activity domain, normalization of inflammatory markers, and ≤5 mg/day of prednisolone. CONCLUSION: We developed proposals for remission criteria to guide the implementation of a treat-to-target algorithm for giant cell arteritis.

Influences of advanced age in rheumatoid arthritis: A multicentre ultrasonography cohort study.

OBJECTIVES: We aimed to evaluate the effects of age on clinical characteristics and outcomes in biologic or targeted synthetic disease-modifying antirheumatic drug (b/tsDMARD)-naïve patients with rheumatoid arthritis (RA). METHODS: We analysed the cases of 234 Japanese b/tsDMARD-naïve RA patients who underwent b/tsDMARD treatment in a multicentre ultrasound prospective observational cohort. We compared the clinical characteristics at baseline and outcomes at 12 months between those aged ≥60 years and those <60 years. RESULTS: Compared to the <60-year-old group (n = 78), the ≥60-year-old group (n = 156) had higher inflammatory marker values and ultrasound combined scores, especially wrist joints, at baseline. Age at baseline positively correlated significantly with the ultrasound scores at baseline; however, age was not a significant variable by the multiple regression analysis. The patients treated with different MOAs in the ≥60-year-old group had comparable outcomes and multiple regression analysis revealed that mechanism of action (MOA) was not a significant contributor to the Clinical Disease Activity Index at 12 months. CONCLUSIONS: RA patients with advanced age demonstrated distinctive clinical characteristics. The MOAs were not associated with clinical outcomes and ultrasound outcomes in RA patients with advanced age.

Association between the patterns of large-vessel lesions and treatment outcomes in patients with large-vessel giant cell arteritis.

OBJECTIVES: We aimed to identify associations between patterns of large-vessel lesions of large-vessel giant cell arteritis (LV-GCA) and treatment outcomes. METHODS: We extracted data on 68 newly diagnosed patients with LV-GCA from a retrospective, multi-centric, nationwide registry of GCA patients treated with glucocorticoids between 2007 and 2014. Patients with aortic lesions were identified based on the findings from contrast-enhanced computed tomography, magnetic resonance imaging, or positron emission tomography-computed tomography (Group 2, n = 49). Patients without aortic lesions were subdivided into LV-GCA with or without subclavian lesions defined as Group 1 (n = 9) or Group 3 (n = 10), respectively. The primary outcome evaluation was failure to achieve clinical remission by Week 24 and/or relapse within 104 weeks. RESULTS: The mean age and proportion of patients with cranial lesions and polymyalgia rheumatica in Group 2 were numerically lower than in the other two groups. Large-vessel lesions in Group 3 included carotid, pulmonary, renal, hepatic, or mesenteric lesions. The cumulative rate of poor treatment outcomes >2 years was 11.1%, 55.3%, and 88.0% in Groups 1, 2, and 3, respectively (by Kaplan-Meier analysis). The mean time to poor outcome was significantly different between the groups. CONCLUSIONS: Classification by subclavian and aortic lesions may be useful to determine treatment strategy.

Establishing clinical remission criteria and the framework of a treat-to-target algorithm for Takayasu arteritis: Results of a Delphi exercise carried out by an expert panel of the Japan Research Committee of the Ministry of Health, Labour and Welfare for intractable vasculitis.

OBJECTIVES: To develop a proposal for remission criteria and a framework for a treat-to-target (T2T) algorithm for Takayasu arteritis (TAK). METHODS: A study group of the large-vessel vasculitis group of the Japanese Research Committee of the Ministry of Health, Labour and Welfare for Intractable Vasculitis consists of 10 rheumatologists, 5 cardiologists, 1 nephrologist, 1 vascular surgeon, 1 cardiac surgeon, and 2 paediatric rheumatologists. A Delphi survey of remission criteria items was circulated among the study group over four reiterations. To develop the T2T algorithm, the study group conducted four face-to-face meetings and two rounds of Delphi together with three patients. RESULTS: Initial literature review resulted in a list of 117 candidate items for remission criteria, of which 56 items with a mean score of ≥4 (0-5) were extracted including disease activity domains and treatment/comorbidity domains. The study group provided six overarching principles for the T2T algorithm, two recommendations on treatment goals, five on evaluation of disease activity and imaging findings including positron emission tomography-computed tomography, and two on treatment intensification. CONCLUSIONS: We developed a T2T algorithm and proposals for standardised remission criteria by means of a Delphi exercise. These will guide future evaluation of different TAK treatment regimens.

BAC-DROP: Rapid Digestion of Proteome Fractionated via Dissolvable Polyacrylamide Gel Electrophoresis and Its Application to Bottom-Up Proteomics Workflow.

The GeLC-MS workflow, which combines low-cost, easy-to-use sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (SDS-PAGE) with liquid chromatography-mass spectrometry (LC-MS), is very popular in current bottom-up proteomics. However, GeLC-MS requires that PAGE-separated proteins undergo overnight enzymatic digestion in a gel, resulting in more than 20 h of sample preparation for LC-MS. In this study, we overcame the limitations of GeLC-MS by developing a rapid digestion workflow for PAGE separation of proteins using N,N'-bis(acryloyl)cystamine (BAC) cross-linked gels that can be solubilized by reductive treatment. Making use of an established workflow called BAC-DROP (BAC-gel dissolution to digest PAGE-resolved objective proteins), crude proteome samples were fractionated based on molecular weight by BAC cross-linked PAGE. After fractionation, the gel fragments were reductively dissolved in under 5 min, and in-solution trypsin digestion of the protein released from the gel was completed in less than 1 h at 70 °C, equivalent to a 90-95% reduction in time compared to conventional in-gel trypsin digestion. The introduction of the BAC-DROP workflow to the MS assays for inflammatory biomarker CRP and viral marker HBsAg allowed for serum sample preparation to be completed in as little as 5 h, demonstrating successful marker quantification from a 0.5 µL sample of human serum.

PEPPI-MS: Polyacrylamide-Gel-Based Prefractionation for Analysis of Intact Proteoforms and Protein Complexes by Mass Spectrometry.

Prefractionation of complex mixtures of proteins derived from biological samples is indispensable for proteome analysis via top-down mass spectrometry (MS). Polyacrylamide gel electrophoresis (PAGE), which enables high-resolution protein separation based on molecular size, is a widely used technique in biochemical experiments and has the potential to be useful in sample fractionation for top-down MS analysis. However, the lack of a means to efficiently recover the separated proteins in-gel has always been a barrier to its use in sample prefractionation. In this study, we present a novel experimental workflow, called Passively Eluting Proteins from Polyacrylamide gels as Intact species for MS ("PEPPI-MS"), which allows top-down MS of PAGE-separated proteins. The optimization of Coomassie brilliant blue staining followed by the passive extraction step in the PEPPI-MS workflow enabled the efficient recovery of proteins, separated on commercial precast gels, from a wide range of molecular weight regions in under 10 min. Two-dimensional separation combining offline PEPPI-MS with online reversed-phase liquid chromatographic separation resulted in identification of over 1000 proteoforms recovered from the target region of the gel (≤50 kDa). Given the widespread availability and relatively low cost of traditional sodium dodecyl sulfate (SDS)-PAGE equipment, the PEPPI-MS workflow will be a powerful prefractionation strategy for top-down proteomics.

Human tolerogenic dendritic cells generated with protein kinase C inhibitor are optimal for functional regulatory T cell induction - A comparative study.

Tolerogenic dendritic cells (tDCs) are a promising therapeutic tool for specific induction of immunological tolerance. Human tDCs can be generated ex vivo using various compounds. However, the compound(s) most suitable for clinical application remain undefined. We compared the tolerogenic properties of tDCs treated with protein kinase C inhibitor (PKCI), dexamethasone, vitamin D3 (Vit D3), rapamycin (Rapa), interleukin (IL)-10, transforming growth factor (TGF)-ß, and a combination of peroxisome proliferator-activated receptor γ agonist and retinoic acid. All tDCs had a semi-mature DC phenotype. PKCI-, TGF-ß-, and Rapa-tDCs showed CCR7 expression and migration to CCL19, but other tDCs showed little or none. PKCI- and IL-10-tDCs induced functional regulatory T cells more strongly than other tDCs. The tolerogenic properties of all tDCs were stable against proinflammatory stimuli. Furthermore, PKCI-tDCs were generated from patients with rheumatoid arthritis and primary Sjögren's syndrome. Therefore, PKCI-tDCs showed the characteristics best suited for tolerance-inducing therapy.

Low complements and high titre of anti-Sm antibody as predictors of histopathologically proven silent lupus nephritis without abnormal urinalysis in patients with systemic lupus erythematosus.

OBJECTIVE: The aim of this study was to clarify the clinical characteristics and predictors of silent LN (SLN), a type of LN in SLE without abnormal urinalysis or renal impairment. METHODS: Of 182 patients who underwent renal biopsy, 48 did not present with abnormal urinalysis or renal impairment at the time of biopsy. The patients with LN (SLN group, n = 36) and those without LN (non-LN group, n = 12) were compared with respect to their baseline characteristics. Bivariate analysis comprised Fisher's exact test and the Mann-Whitney test, whereas multivariate analysis employed binomial logistic regression analysis. RESULTS: LN was histopathologically identified in 36 of 48 patients. According to the International Society of Nephrology/Renal Pathology Society classification, 72% of the SLN patients were classified as having class I/II, with a further 17% having class III/IV. Bivariate analyses indicated that platelet count, serum albumin, complement components (C3 and C4), complement haemolytic activity (CH50), anti-Sm antibody titre and anti-ribonucleoprotein antibody titre were significantly different between groups. Multivariate analysis indicated that CH50 and C3 titres were significantly lower in the SLN group, whereas anti-Sm antibody titre was significantly higher. The cut-off titre, calculated based on the receiver operating characteristic curve for CH50, was 33 U/ml, with a sensitivity and specificity of 89% and 83%, respectively. The cut-off titre for anti-Sm antibodies was 9 U/ml, with a sensitivity and specificity of 74% and 83%, respectively. CONCLUSION: Low titres of CH50 and C3 and a high titre of anti-Sm antibody were identified as predictors of SLN.

Protein kinase C inhibitor generates stable human tolerogenic dendritic cells.

Tolerogenic dendritic cells (DCs) are a promising tool for a specific form of cellular therapy whereby immunological tolerance can be induced in the context of transplantation and autoimmunity. From libraries of bioactive lipids, nuclear receptor ligands, and kinase inhibitors, we screened conventional protein kinase C inhibitors (PKCIs) bisindolylmaleimide I, Gö6983, and Ro32-0432 with strong tolerogenic potential. PKCI-treated human DCs were generated by subjecting them to a maturation process after differentiation of immature DCs. The PKCI-treated DCs had a semimature phenotype, showing high production of IL-10, and efficiently induced IL-10-producing T cells and functional Foxp3(+) regulatory T cells from naive CD4(+) T cells, thus eliciting a strong immunosuppressive function. They also showed CCR7 expression and sufficient capacity for migration toward CCR7 ligands. Additionally, PKCI-treated DCs were highly stable when exposed to inflammatory stimuli such as proinflammatory cytokines or LPS. Conventional PKCIs inhibited NF-κB activation of both the canonical and noncanonical pathways of DC maturation, thus suppressing the expression of costimulatory molecules and IL-12 production. High production of IL-10 in PKCI-treated DCs was due to not only an increase of intracellular cAMP, but also a synergistic effect of increased cAMP and NF-κB inhibition. Moreover, PKCI-treated mouse DCs that had properties similar to PKCI-treated human DCs prevented graft-versus-host disease in a murine model of acute graft-versus-host disease. Conventional PKCI-treated DCs may be useful for tolerance-inducing therapy, as they satisfy the required functional characteristics for clinical-grade tolerogenic DCs.

[Pulmonary Nocardiosis due to Nocardia asiatica in a Patient with ANCA-associated Vasculitis].

Nocardia asiatica is a rare causative organism responsible for opportunistic infection, and was first reported by Kageyama et al. in 2004. We report herein on a very rare case of N. asiatica infection in a 76-year old male patient with ANCA-associated vasculitis and a history of pulmonary tuberculosis. The patient developed pulmonary nocardiosis due to N. asiatica while receiving glucocorticoid therapy. Chest computed tomography demonstrated multiple granules and cavity formation mainly in the left lower lobe. From the images, we suspected opportunistic infection, possibly pulmonary tuberculosis or pulmonary damage due to ANCA-associated vasculitis. Nocardia sp. was detected from a bronchoalveolar lavage culture and N. asiatica was identified by 16S ribosomal DNA gene sequencing. Cranial magnetic resonance imaging revealed no abnormality. Administration of Doripenem (1.5g/day) and sulfamethoxazole-trimethoprim (4g/day) was started, and the patient's clinical and imaging findings promptly improved. Thereafter, he received sulfamethoxazole-trimethoprim (2g/day) and prednisolone (10 mg/day) as maintenance therapy for ANCA-associated vasculitis for more than one year, and there has since been no recurrence of the Nocardia infection.

Assessment of Musculoskeletal Ultrasound of Rheumatoid Arthritis.

Musculoskeletal ultrasound (MSUS) is a valuable tool that is used in outpatient clinics or at the bedside to assess multiple joint sites, including small joints. It provides detailed images of structures commonly observed in rheumatoid arthritis (RA), such as synovitis, tenosynovitis, bone erosions, cartilage damage, and synovial fluid accumulation. MSUS is frequently used in the management of RA and provides more objective information for an early diagnosis and disease activity assessment through imaging findings.

Design an Intervention Study.

Randomized controlled trials are commonly designed to compare the effectiveness of treatments in rheumatoid arthritis (RA). In a clinical trial (intervention study), researchers apply interventions or preventive services to patients and examine outcomes. Clinical trial design consists of the following categories: choice of intervention and control, selection of patients, informed consent, baseline measurement, bank specimens, randomized allocation and blinding, and outcome measurements. Here, we discuss the design of clinical trials for RA.

Assessment of Disease Activity, Structural Damage, and Function in Rheumatoid Arthritis.

The primary goal in the treatment of rheumatoid arthritis (RA) is to control disease activity, prevent structural damage in joints, and normalize function. Therefore, reliable tools are needed to disease activity, physical function, and radiographic progression in RA. We herein describe methods recently used to assess RA.

The impact of glucocorticoid use on the outcomes of rheumatoid arthritis in a multicenter ultrasound cohort study.

OBJECTIVE: Glucocorticoids are effective in treating rheumatoid arthritis (RA) when used appropriately considering the balance of the risks and benefits, especially at low doses. We aimed to evaluate the response of biologic and targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) in patients having already been treated with glucocorticoids. METHODS: We reviewed RA patients treated with b/tsDMARDs in a prospective multicenter ultrasound cohort study. We compared the differences in the clinical characteristics at baseline and outcomes at 12 months between the two groups having been treated with and without glucocorticoids at baseline. The differences in the clinical characteristics and the treatments were balanced by the inverse probability weighting (IPW) with the propensity score. RESULTS: Of 307 patients with RA, 160 patients were treated with glucocorticoids at baseline. The median dose of glucocorticoids was equivalent to 5.0 mg/day of prednisolone. Significant differences were in age and concomitant methotrexate use, composite measures for the disease activity, and the ultrasound grayscale score at baseline. Patients treated with glucocorticoids had less frequent remissions defined by composite measures and ultrasound findings than those treated without glucocorticoids. These significant differences in the achievement of remissions remained robust even after adjusting differences in the clinical characteristics and the treatments between the two groups by IPW. CONCLUSION: RA patients treated with glucocorticoids had a higher disease activity at baseline and a poorer response to treatments with b/tsDMARDs than those without glucocorticoids. The states of patients requiring glucocorticoids might be associated with the poor response to the b/tsDMARDs.

A case of clinically amyopathic dermatomyositis that was refractory to intensive immunosuppressive therapy including tofacitinib, but successfully treated with plasma exchange therapy.

Clinically amyopathic dermatomyositis (CADM) patients often develop rapidly progressive interstitial lung disease (RP-ILD). A high level of anti-melanoma differentiation-associated gene 5 antibodies (anti-MDA5 Ab) before treatment is associated with RP-ILD development, a poor treatment response, and poor survival. The prognosis of CADM patients remains poor due to ILD even with combined intensive immunosuppressive therapy. Recently, several additional therapies, including tofacitinib (TOF) and plasma exchange (PE) therapy, have been reported to be effective. We herein report a case of CADM-ILD with a high level of anti-MDA5 Ab that was refractory to combined intensive immunosuppressive therapy including TOF, but successfully treated with PE. The following are possible reasons why TOF was ineffective: (1) cytokines that were not suppressed by TOF played an important role in RP-ILD; (2) TOF was administered later than previously reported; and (3) TOF did not suppress pathological substances such as antibodies. On the other hand, PE removes cytokines and various pathological substances. Therefore, PE may be a more reasonable additional therapy for intractable CADM-ILD.

Giant Cell Arteritis Presenting with Ptosis and Diplopia.

Giant cell arteritis (GCA) is vasculitis of large-sized vessels that can lead to vision loss. We herein report a rare case of GCA accompanied by ptosis and diplopia as early symptoms, which were caused by third nerve palsy. A 78-year-old man presented with fever, right temporal headache, right eyelid ptosis, and diplopia. GCA was confirmed by a temporal artery biopsy. The symptoms disappeared after a slight delay following the administration of prednisolone. Unlike vision loss, ptosis and diplopia are considered to be reversible and responsive to treatment. GCA should not be ruled out if patients exhibit these ophthalmic symptoms.

The hearing prognosis of otitis media with ANCA-associated vasculitis.

OBJECTIVE: The concept of otitis media with ANCA-associated vasculitis (OMAAV) was recently proposed by the study group of the Japan Otological Society. However, information remains limited regarding the hearing outcome of OMAAV. Thus, we investigated this issue in this study. METHODS: We retrospectively examined 50 ears from 32 patients diagnosed with OMAAV at our hospital between 2010 and 2019. We collected the results of pure tone audiometry (PTA) at diagnosis and changes in PTA threshold after treatment, serological findings including ANCA type, titer, soluble interleukin-2 receptor (sIL2R), and C-reactive protein, organs involved at initial diagnosis, treatment, and disease relapse from medical records. According to the hearing outcome, patients were divided into two groups: good prognosis and poor prognosis groups. We investigated the clinical features, treatment, and changes in PTA between the groups. RESULTS: Age, sex, ANCA negativity, and the use of intravenous cyclophosphamide (IVCY) were significantly related to hearing prognosis of OMAAV, while other organs involved at diagnosis, serological findings, and relapse rate were not significantly associated with hearing outcome. Hearing level at diagnosis was significantly better in good prognosis group, while air-bone gap (ABG) was not significantly different between the groups. The air conduction (AC), bone conduction (BC), and ABG were significantly improved in the good prognosis group. However, ABG was not improved in the poor prognosis group, while AC and BC were significantly improved. The AC hearing level at diagnosis (58.5 dB) and hearing gain at 2 weeks after treatment (12.5 dB) were suggested as good indicators for predicting the hearing outcome of OMAAV. CONCLUSION: Younger age, male sex, shorter period from onset to diagnosis, the use of IVCY, and better hearing threshold at diagnosis were the good prognostic factors of the hearing outcome of OMAAV. These results suggest that earlier diagnosis of OMAAV might be needed for better hearing outcome, and the use of IVCY may be recommended for the treatment of OMAAV patients.

Usefulness of tissue inhibitor of metalloproteinase 1 as a predictor of sustained remission in patients with antineutrophil cytoplasmic antibody-associated vasculitis.

BACKGROUND: We previously identified tissue inhibitor of metalloproteinase 1 (TIMP-1) as a biomarker of disease activity that distinguished mildly or highly active antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) from remission 6 months after the initiation of remission-induction therapy. In the present study, we investigated whether TIMP-1 is clinically useful as a predictor of relapse and sustained remission in AAV patients with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) during maintenance therapy. METHODS: The relationship between serum TIMP-1 levels and clinical outcomes in AAV patients receiving maintenance therapy was assessed using the follow-up data of a Japanese large-cohort study (the RemIT-JAV-RPGN study) and data collected from AAV patients on maintenance therapy in our hospital (the MAAV-EU study). RESULTS: In the RemIT-JAV RPGN study, serum levels of TIMP-1 were significantly higher in mildly active AAV patients with MPA and GPA 6 months after the initiation of remission-induction therapy than in patients in remission. Regarding maintenance therapy, elevated levels of TIMP-1 in patients in remission were associated with relapse and/or difficulty reducing the glucocorticoid dosage after 6 to 12 months. In the MAAV-EU study, serum levels of TIMP-1 were elevated in relapsed patients 6 months before relapse, earlier than the increase in serum levels of CRP. Analyses of both studies revealed that approximately 30% of patients in remission with a serum TIMP-1 level ≥ 150 ng/mL relapsed after 6 to 12 months, while the majority of patients with a TIMP-1 level < 150 ng/mL sustained remission for at least 12 months. CONCLUSION: We herein demonstrated that TIMP-1 is more useful as a predictive biomarker of sustained remission than as a predictor of relapse in maintenance therapy for AAV. TIMP-1 levels < 150 ng/mL are important for the long-term maintenance of remission and may be an indicator for the tapering or cessation of treatment.

The association between ear involvement and clinical features and prognosis in ANCA-associated vasculitis.

OBJECTIVE: The concept of otitis media with ANCA-associated vasculitis (OMAAV) was recently proposed by the study group of the Japan Otological Society. However, little is known about the effect of ear involvement on the clinical features and prognosis of AAV. We investigate this issue in this study. METHODS: We retrospectively examined 36 patients diagnosed with OMAAV and 44 patients diagnosed with AAV without ear involvement (non-OMAAV) at Ehime University Hospital from 2013 to 2018. We collected serological findings including ANCA type and titer, C-reactive protein (CRP), serum creatinine level, organ involved at initial diagnosis, treatment, remission, disease relapse, and mortality from medical records. We investigated whether clinical features and outcomes differed between the OMAAV and non-OMAAV groups. RESULTS: Age, ANCA titer, and CRP at initial diagnosis were not significantly different between the two groups, and the rate of intravenous cyclophosphamide (IVCY) use also did not differ. The proportions of patients with concurrent eye involvement, facial palsy (FP), and hypertrophic pachymeningitis (HCP) were significantly higher in the OMAAV than in the non-OMAAV group (p = 0.005, 0.005 and 0.049, respectively), while both renal and peripheral nerve involvement were significantly less common in OMAAV patients (p = 0.04). Among the 30 patients with renal involvement, serum creatinine level at diagnosis was significantly lower in the OMAAV group (p = 0.04). The mortality rate was 8.3% in OMAAV and 6.8% in non-OMAAV cases, but this difference was not significant. The rate of relapse was 33.3% in OMAAV and 13.6% in non-OMAAV cases; this difference was significant (p = 0.04). CONCLUSIONS: Serological measurements of disease activity did not differ between the groups. Eye involvement, FP, and HCP, however, were significantly more common in AAV with ear involvement. In addition, renal involvement was less common and renal impairment was milder in AAV with ear involvement. These findings can be considered clinical features. The relapse rate was significantly higher in AAV with ear involvement.

The interaction of monocytes with rheumatoid synovial cells is a key step in LIGHT-mediated inflammatory bone destruction.

Formation of osteoclasts and consequent joint destruction are hallmarks of rheumatoid arthritis (RA). Here we show that LIGHT, a member of the tumour necrosis factor (TNF) superfamily, induced the differentiation into tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs) of CD14(+) monocytes cocultured with nurse-like cells isolated from RA synovium, but not of freshly isolated CD14(+) monocytes. Receptor activator of nuclear factor-kappaB ligand (RANKL) enhanced this LIGHT-induced generation of TRAP-positive MNCs. The MNCs showed the phenotypical and functional characteristics of osteoclasts; they showed the expression of osteoclast markers such as cathepsin K, actin-ring formation, and the ability to resorb bone. Moreover, the MNCs expressed both matrix metalloproteinase 9 (MMP-9) and MMP-12, but the latter was not expressed in osteoclasts induced from CD14(+) monocytes by RANKL. Immunohistochemical analysis showed that the MMP-12-producing MNCs were present in the erosive areas of joints in RA, but not in the affected joints of osteoarthritic patients. These findings suggested that LIGHT might be involved in the progression of inflammatory bone destruction in RA, and that osteoclast progenitors might become competent for LIGHT-mediated osteoclastogenesis via interactions with synoviocyte-like nurse-like cells.