Abstract
Objective
Methotrexate is one of the most commonly used disease‐modifying antirheumatic drugs in the management of psoriatic arthritis (PsA). Despite the differences between the inflammation in PsA and rheumatoid arthritis (RA), the effects of methotrexate on the synovium have been described solely in RA. In this study, we sought to determine the effects of methotrexate on the inflammatory infiltrate and on cytokine and metalloproteinase gene expression in the synovium of PsA patients.
Methods
Ten patients with PsA (median duration 18 months) underwent arthroscopy and synovial biopsy of an inflamed knee before and after clinical improvement induced by methotrexate. Immunohistologic analysis was performed using antibodies to CD3, CD4, CD8, CD68, factor VIII, vascular cell adhesion molecule, E‐selectin, and intercellular adhesion molecule (ICAM). Matrix metalloproteinase 3 (MMP‐3) and tissue inhibitor of metalloproteinases 1 (TIMP‐1) messenger RNA (mRNA) were quantified by competitive reverse transcription–polymerase chain reaction (RT‐PCR). Interleukin‐1α (IL‐1α), IL‐1β, IL‐2, IL‐4, IL‐5, IL‐8, IL‐10, IL‐12p35, IL‐12p40, IL‐15, interferon‐γ (IFNγ), and tumor necrosis factor α (TNFα) mRNA expression was quantified by real‐time PCR.
Results
Patients received a median methotrexate dosage of 13.75 mg/week (range 7.5–15) for a median of 11.5 months (range 7–14 months). The Ritchie Articular Index, swollen joint count, and Disease Activity Score were significantly reduced. There was a decrease in all immunohistologic staining, although this was statistically significant only for CD3, CD4, CD8, CD68, E‐selectin, and ICAM. Despite clinical improvement in all patients, there was a residual T cell infiltrate in all synovial biopsy tissues. The synovial lining layer thickness, but not hypervascularity, was significantly reduced. There was also a significant reduction in MMP‐3, but not TIMP‐1, expression. Before treatment, PsA synovium was characterized by a predominant expression of the proinflammatory cytokines IL‐15, IFNγ, IL‐1β, and TNFα and the antiinflammatory cytokine IL‐10. Methotrexate reduced synovial IL‐1α, IL‐1β, IL‐8, IL‐10, IL‐15, IFNγ, and TNFα mRNA expression, but the effect was significant only for IL‐8.
Conclusion
Methotrexate produced a clinical response in PsA by reducing, but not abolishing, the inflammatory infiltrate, adhesion molecule expression, and MMP‐3 and proinflammatory cytokine gene expression, particularly IL‐8, in the synovium. Methotrexate did not reduce hypervascularity, which is a prominent differentiating feature of PsA synovium.