Synovial effusion and synovial fluid biomarkers in psoriatic arthritis to assess intraarticular tumor necrosis factor-α blockade in the knee joint.

Introduction: Evaluation of synovial effusion (SE), synovial fluid (SF) and synovial tissue (ST) biomarkers in relation to disease activity indexes to assess the response to intraarticular (IA) tumor necrosis factor (TNF)-α blockers in psoriatic arthritis (PsA). Methods: Systemic and local disease activity indexes (disease activity score [DAS]; the Ritchie articular index [mRAI], erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP); Thompson articular [THOMP] and joint articular [KJAI]-Index ) and ST samples were assessed at baseline, throughout treatment, and during the follow-up in 14 patients affected with PsA who underwent IA injections (0.5 ml - 12.5 mg) in the knee joint of etanercept (E) or placebo (P) once every two weeks for a ten week period. Total SF white blood cell (WBC) counts (WBC/ μl) and SF cytokine/chemokine (CK/CCK) levels were measured before IA-E at baseline, after IA-E, and as long as there were adequate amounts of SF for knee aspiration (post). Characterization of synovial mononuclear cell infiltration and synovial vessels was carried out in 8/14 knees by staining serial sections of synovial tissue biopsies for CD45, CD3, CD68, CD31 and CD105. Results: At baseline, CRP and/or ESR were significantly correlated with SF-CK (IL-1β, IL-1Ra, IL-6, IL-8) and CCK (CCL2, CCL3 and CCL4). Post-IA injections, there was a decrease in SE in the knees in which aspiration following IA-E injection was possible as well as a significant reduction in SF WBC/μl and in SF-CK (TNF-α, IL- 1β, IL-1Ra, IL-6 and IL-22). Pre- and post- IAE injections, there were significant correlations between ST markers and SF-CK (IL-1β with CD45; IL-1β and IL-6 with CD31) and between SF-CCK (CCL4 and CCL3 with CD3). At the end of the study, there was a significant reduction in disease activity indexes (CRP, DAS, RAI, THOMP, KJAI) as well as in the ST markers (CD45; CD3).