Background Rheumatoid Arthritis (RA) is a chronic inflammatory autoimmune disease, affecting around 1% of the population, causing significant ill health, disability and increased mortality. The precise etiology of RA is not known, but both genetic and environmental influences play a role. Methotrexate (MTX) is the most commonly used disease modifying anti-rheumatic drug in the management of RA, however its mechanism of action has not been extensively studied.
Objectives The aim of this study is to determine the functional effect of MTX in the RA joint.
Methods Primary RA synovial fibroblasts (RASFC) were isolated from synovial biopsies obtained from patients undergoing arthroscopic examination. RASFC were cultured in the presence or absence of MTX (10-100uM) and cell migration, invasion, cytoskeletal rearrangement, viability, proliferation and pro-inflammatory cytokine expression were assessed by wound repair assays, transwell matrigel™ invasion chambers, F-actin immunofluorescent staining, MTT/ Crystal violet cell growth assay and ELISA respectively. In parallel, CD14+monocytes were isolated from peripheral blood mononuclear cells from RA patients both pre- and 12 weeks post-MTX therapy (n=5) and global methylation was assessed by a 5-methylcytosine DNA ELISA kit.
Results MTX (10-100uM) inhibited RASFC repopulation of the wound margins in comparison to vehicle control where migration across the wound was clearly evident (p<0.05). In parallel, MTX significantly decreased RASFC invasion (p<0.05) and altered cytoskeletal dynamics through inhibition of lamellopodia and filopodia formation, which are indicative of cell movement. Importantly, we determined that the effect of MTX on RASFC migration and invasion were independent of both cell viability and proliferation. Finally preliminary results demonstrated altered DNA methylation in CD14+ monocytes from RA patients at 3 months post MTX treatment.
Conclusions MTX inhibits RASFC migration, invasion and cytoskeletal re-arrangement, mechanisms which are critically involved in the pathogenesis of RA. Further preliminary data suggests that the effect of MTX on pro-inflammatory mechanisms in RA, maybe be mediated through alterations in epigenome.
Disclosure of Interest S. Cregan: None declared, K. Creevey: None declared, T. McGarry: None declared, C. Orr: None declared, D. Veale Grant/research support from: Abbvie, MSD, Pfizer, Roche, Consultant for: Pfizer, Roche, Speakers bureau: Abbott, MSD, Pfizer, Roche, U. Fearon: None declared, A. Wilson: None declared