Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Methothrexate Directly Inhibits RANKL Expression and Osteoclasts Formation in Very Early Arthritis.

Revu,  Shankar, Neregard,  Petra, Afklint,  Erik, Irinel Catrina,  Anca

Objective:

Methotrexate (MTX) is one of the most widely used therapies in rheumatoid arthritis (RA). However, in the long term, patients treated with methotrexate may experience joint deterioration and subclinical inflammation even after clinical remission. Bone biology is governed by the RANKL/RANK/OPG system that determines the balance between bone formation by osteoblasts and bone resorbtion by osteoclasts. Herein we investigated MTX effects on the RANKL/RANK/OPG system in vivo and in vitro.

Methods:

16 patients with newly diagnosed RA (mean disease duration 1 week) were started on MTX 10 mg once a week and increased with 10 mg each week until a stable dose of 20 mg once a week was reached. Patients were naïve for other disease modifying anti rheumatic drugs. Synovial biopsies were obtained by needle arthroscopy at baseline and 8 weeks after initiation of therapy. X-ray of hands and feet were obtained at baseline and 1 year after diagnosis. Immunohistochemical analysis was performed to detect RANKL, RANK and OPG in the synovial biopsies. We further investigated the in vitro effect of MTX on synovial fluid derived mononuclear cells, SFMC (by immunohistochemistry), osteoblasts (by rtPCR and Western blot) and osteoclasts formation (tartrate-resistant acid phosphatase staining and dentine pit formation assay). Statistical analysis was performed using the Wilcoxon and Mann Whitney test when appropriate.

Results:

9 patients (56%) were responders to therapy according to EULAR criteria. 2 patients were having erosions at inclusion and 5 more developed erosions at 1 year follow-up in both the responder and non responder group. MTX treatment decreased synovial inflammation with a significant reduction of synovial cellularity. In parallel MTX decreased synovial RANK expression and the RANKL/OPG ratio, mainly in the subgroup of RA patients with no radiological progression at 1 year follow up. We confirmed the effect on RANK expression in SFMC cultured in vitro with MTX. A decrease of the RANKL/OPG ratio was also observed in cultured osteoblasts as demonstrated both at the mRNA and protein levels. MTX blocks osteoclastogenesis from PBMC despite presence of M-CSF and RANKL indicating that MTX directly inhibits osteoclastogenesis.

Conclusions:

MTX directly affects the RANKL/RANK/OPG system and inhibits osteoclasts formation providing an explanation for the bone-sparing effect of MTX observed in a subgroup of RA patients.

To cite this abstract, please use the following information:
Revu, Shankar, Neregard, Petra, Afklint, Erik, Irinel Catrina, Anca; Methothrexate Directly Inhibits RANKL Expression and Osteoclasts Formation in Very Early Arthritis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :394
DOI: 10.1002/art.28163

Abstract Supplement

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