Nobuyuki Asai

LRP4 third β-propeller domain mutations cause novel congenital myasthenia by compromising agrin-mediated MuSK signaling in a position-specific manner

Congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Using Sanger and exome sequencing in a CMS patient, we identified two heteroallelic mutations, p.Glu1233Lys and p.Arg1277His, in LRP4 coding for the postsynaptic low-density lipoprotein receptor-related protein 4. LRP4, expressed on the surface of the postsynaptic membrane of the neuromuscular junction, is a receptor for neurally secreted agrin, and LRP4 bound by agrin activates MuSK. Activated MuSK in concert with Dok-7 stimulates rapsyn to concentrate and anchor AChR on the postsynaptic membrane and interacts with other proteins implicated in the assembly and maintenance of the neuromuscular junction. LRP4 also functions as an inhibitor of Wnt/beta-catenin signaling. The identified mutations in LRP4 are located at the edge of its 3rd beta-propeller domain and decrease binding affinity of LRP4 for both MuSK and agrin. Mutations in the LRP4 3rd beta-propeller domain were previously reported to impair Wnt signaling and cause bone diseases including Cenani-Lenz syndactyly syndrome and sclerosteosis-2. By analyzing naturally occurring and artificially introduced mutations in the LRP4 3rd beta-propeller domain, we show that the edge of the domain regulates the MuSK signaling whereas its central cavity governs Wnt signaling. We conclude that LRP4 is a new CMS disease gene and that the 3rd beta propeller domain of LRP4 mediates the two signaling pathways in a position-specific manner.

Patient-reported outcomes as assessment tools and predictors of long-term prognosis: a 7-year follow-up study of patients with rheumatoid arthritis

Whether the Boolean‐based American College of Rheumatology/European League Against Rheumatism (EULAR) criteria for rheumatoid arthritis (RA) including patient‐reported outcome measures (PROMs) for remission are strict for use in daily clinical practice is controversial. This study aimed to clarify the differences in the remission status defined by the criteria, including and excluding PROMs, and to identify the baseline predictors of long‐term prognosis using 7‐year follow‐up data.

Importance of methotrexate therapy concomitant with tocilizumab treatment in achieving better clinical outcomes for rheumatoid arthritis patients with high disease activity: an observational cohort study

OBJECTIVE The purpose of this study was to identify the effects of concomitant use of MTX and baseline characteristics for remission in the treatment of RA with tocilizumab (TCZ) in daily clinical practice. METHODS A total of 240 RA patients who received TCZ were selected from the multicentre Tsurumai Biologics Communication Registry. Predictive baseline factors for remission [28-item DAS (DAS28) < 2.6] at 52 weeks were determined by logistic regression analysis. To confirm whether the associations varied by the level of baseline disease activity, we also assessed the model including the interaction term (each baseline variable × DAS28). RESULTS In total, 49.3% of the study participants used MTX with TCZ. Even after controlling for the baseline DAS28, shorter disease duration (≤3 year) [odds ratio (OR) 3.58 (95% CI 1.81, 7.07)], less structural damage [Steinbroker stage ≤II, OR 2.33 (95% CI 1.32, 4.12)] and concomitant prednisolone use [OR 0.38 (95% CI 0.21, 0.68)] showed significant predictive values for remission. Concomitant MTX use failed to show a significant association with remission, whereas a significant interaction was observed among concomitant MTX use × DAS28 (P = 0.006). In patients with high baseline disease activity (DAS28 > 5.1), concomitant MTX use was associated with increased odds for remission [adjusted OR for all baseline variables 2.54 (95% CI 1.11, 5.83)], while no association was indicated between them in patients with low to moderate baseline disease activity (DAS28 ≤ 5.1). CONCLUSION Concomitant MTX use is an important component of TCZ treatment for RA patients with high disease activity.

Longterm Efficacy and Safety of Abatacept in Patients with Rheumatoid Arthritis Treated in Routine Clinical Practice: Effect of Concomitant Methotrexate after 24 Weeks

Objective. Our study aimed to evaluate the longterm efficacy and safety of abatacept (ABA), and to explore factors that increase its longterm efficacy in patients with rheumatoid arthritis (RA) treated in routine clinical practice. Methods. There were 231 participants with RA treated with ABA who were prospectively registered in a Japanese multicenter registry. They were followed up for at least 52 weeks. Results. Mean age of the patients was 64.3 years, mean disease duration was 12.1 years, mean 28-joint Disease Activity Score (DAS28)-C-reactive protein was 4.49, and 48.5% of patients were concomitantly treated with methotrexate (MTX). Overall retention rate of ABA was 77.1% at 52 weeks; 14.8% of patients discontinued because of inadequate response and 3.5% because of adverse events. The proportion of patients achieving DAS28-defined low disease activity (LDA) significantly increased from baseline to 52 weeks (7.3% to 43.8%, p < 0.01); 40.9% of patients who did not achieve LDA at 24 weeks had more than 1 categorical improvement in DAS28-defined disease activity at 52 weeks. Multivariate logistic regression revealed concomitant MTX use to be an independent predictor of the categorical improvement in DAS28-defined disease activity from 24 to 52 weeks (adjusted OR 3.124, p = 0.010). Conclusion. In routine clinical practice, ABA demonstrated satisfactory clinical efficacy and safety in patients with established RA for 52 weeks. The clinical efficacy of ABA increased with time even after 24 weeks, and this was strongly influenced by concomitant MTX use. Our study provides valuable real-world findings on the longterm management of RA with ABA.

Drug retention rates of second biologic agents after switching from tumor necrosis factor inhibitors for rheumatoid arthritis in Japanese patients on low-dose methotrexate or without methotrexate

Abstract Objectives. The purpose of this study was to explore drug retention rates of second biologic agents after switching from tumor necrosis factor inhibitors (TNFi) in clinical practice in patients with rheumatoid arthritis (RA) on low-dose methotrexate (MTX) or without MTX. Methods. A total of 169 RA patients who had been withdrawn from first-course TNFi therapy and received a different TNFi or tocilizumab (TCZ) as a second biologic agent were selected from the Tsurumai Biologics Communication Registry, an observational cohort database. Retention rates of second biologic treatment were compared by the type of first TNFi and second biologic agents. Results. Eighty-six patients received first-course infliximab (IFX) or adalimumab (ADA) therapy, and 83 patients received first-course etanercept (ETN) therapy. The former group had a significantly higher retention rate (IFX, 81.1%; ADA, 83.3%) of the second biologic therapy compared to the latter (56.6%, p < 0.001, log-rank test). Drug retention rates of the second biologic agent after switching from IFX/ADA were significantly higher with ETN (90.0%) and TCZ (94.7%) than with ADA/IFX (59.3%). Drug retention rates of the second biologic agent after switching from ETN were significantly higher with TCZ (75.9%) than with ADA/IFX (46.3%). The differences were significant even after adjusting for baseline clinical variables using the Cox proportional hazards model. Conclusions. Drug retention rates of IFX and ADA after switching from the first TNFi were significantly lower compared to those of ETN and TCZ in patients on low-dose MTX or without MTX.

LRP4 induces extracellular matrix productions and facilitates chondrocyte differentiation

Endochondral ossification is an essential step for skeletal development, which requires chondrocyte differentiation in growth cartilage. The low-density lipoprotein receptor-related protein 4 (LRP4), a member of LDLR family, is an inhibitor for Wnt signaling, but its roles in chondrocyte differentiation remain to be investigated. Here we found by laser capture microdissection that LRP4 expression was induced during chondrocyte differentiation in growth plate. In order to address the roles, we overexpressed recombinant human LRP4 or knocked down endogenous LRP4 by lentivirus in mouse ATDC5 chondrocyte cells. We found that LRP4 induced gene expressions of extracellular matrix proteins of type II collagen (Col2a1), aggrecan (Acan), and type X collagen (Col10a1), as well as production of total proteoglycans in ATDC5 cells, whereas LRP4 knockdown had opposite effects. Interestingly, LRP4-knockdown reduced mRNA expression of Sox9, a master regulator for chondrogenesis, as well as Dkk1, an extracellular Wnt inhibitor. Analysis of Wnt signaling revealed that LRP4 blocked the Wnt/β-catenin signaling activity in ATDC5 cells. Finally, the reduction of these extracellular matrix productions by LRP4-knockdown was rescued by a β-catenin/TCF inhibitor, suggesting that LRP4 is an important regulator for extracellular matrix productions and chondrocyte differentiation by suppressing Wnt/β-catenin signaling.

Effects of Concomitant Methotrexate on Large Joint Replacement in Patients With Rheumatoid Arthritis Treated With Tumor Necrosis Factor Inhibitors: A Multicenter Retrospective Cohort Study in Japan

To determine the effects of concomitant methotrexate (MTX) on the incidence of large joint replacement resulting from the progression of large joint destruction in patients with rheumatoid arthritis (RA) treated with tumor necrosis factor (TNF) inhibitors.

Disease activity early in treatment as a predictor of future low disease activity in RA patients treated with iguratimod

Objectives. This retrospective observational study aimed to examine the efficacy of iguratimod with and without concomitant methotrexate (MTX) and to estimate the adequate observational period for predicting low disease activity (LDA) achievement at 24 weeks in patients with rheumatoid arthritis (RA). Methods. All patients treated with iguratimod were registered in a Japanese multicenter registry. Multivariate analyses were performed to identify predictive factors for LDA achievement at 24 weeks. Receiver operating characteristic (ROC) curve analyses were performed to estimate the association of 28-joint disease activity score based on erythrocyte sedimentation rate (DAS28-ESR) at each time point with achievement of LDA at 24 weeks and determine a cut-off for DAS28-ESR. Results. A total of 123 patients were treated with iguratimod with (n = 65) or without (n = 58) MTX. Iguratimod therapy resulted in significant clinical improvement in both groups. Multivariate analysis revealed that DAS28-ESR at each time point was an independent significant predictor of LDA achievement at 24 weeks. Cut-off values of DAS28-ESR at 12 weeks based on ROC curves were 3.2 and 3.6 in patients with and without MTX, respectively. Conclusions. Iguratimod was effective in RA patients in clinical practice. Our results suggest that 12 weeks may be a sufficient period to judge the medium-term efficacy of iguratimod in patients treated with and without MTX.

Concomitant Methotrexate Protects Against Total Knee Arthroplasty in Patients with Rheumatoid Arthritis Treated with Tumor Necrosis Factor Inhibitors

Objective. To determine the effects of concomitant methotrexate (MTX) on the incidence of total knee arthroplasty (TKA) resulting from the progression of joint destruction in patients with rheumatoid arthritis (RA) during longterm treatment with tumor necrosis factor (TNF) inhibitors. Methods. A total of 155 patients with RA (310 knee joints) received TNF inhibitors at our institute between May 1, 2001, and May 31, 2008. A total of 111 symptomatic (tender and/or swollen) knee joints in 68 patients were retrospectively studied over the course of a minimum of 5 years of followup. The median (interquartile range) followup period was 8.1 (7.0–9.3) years. All data were analyzed using the knee joint as the statistical unit of analysis. TKA during treatment with TNF inhibitors was used as the outcome variable in predictive analyses. The cumulative incidence of TKA was compared by concomitant or no MTX use (MTX±). Results. There were 79 subjects (71%) who received concomitant MTX. According to Kaplan-Meier estimates, the cumulative incidence of TKA for the MTX+ group was significantly lower than that for the MTX− group (24% vs 45% at 5 yrs, respectively, p = 0.035). Multivariate analysis using the Cox proportional hazards model revealed that concomitant MTX (HR 0.44, 95% CI 0.22–0.89), Larsen grade (HR 2.93, 95% CI 1.94–4.41), and older age at baseline (HR 1.04, 95% CI 1.01–1.08) were independent predictors of TKA. Conclusion. Concomitant MTX reduces the incidence of TKA by 56% in patients with RA during longterm treatment with TNF inhibitors.

Clinical effectiveness and long-term retention of abatacept in elderly rheumatoid arthritis patients: Results from a multicenter registry system

Abstract Objective: To study the clinical effectiveness and long-term retention rate of abatacept (ABA) in elderly rheumatoid arthritis (RA) patients in daily clinical practice. Methods: A retrospective cohort study was performed using data from a multicenter registry. Our study population comprised 500 consecutive RA patients treated with ABA. We compared clinical effectiveness and ABA retention rates between the Young (≤62 years), Middle (62 to 72 years), and Elderly (≥72 years) groups. We also performed separate examinations to identify predictive factors for ABA discontinuation in those with versus those without concomitant methotrexate (MTX) treatment. Results: Mean age was 52.7 years in the Young group, 67.7 years in the Middle group, and 78.1 years in the Elderly group. No significant group-dependent differences were found in mean DAS28 score, categorical distribution of DAS28, and EULAR response rate across the 52 weeks. The ABA retention rates at three years as determined by the Kaplan–Meier method were similar in all three groups. Patient age was not a significant predictor of ABA discontinuation due to adverse events in patients with concomitant MTX; however, it was found to be a significant predictor for those who did not use MTX (Cox hazard model). Conclusion: ABA would be a reasonable treatment option for elderly RA patients from the viewpoints of both clinical effectiveness and long-term retention. However, physicians should watch carefully for any serious adverse reactions in elderly RA patients with intolerance to MTX.