The effect of etanercept on osteoclast precursor frequency and enhancing bone marrow oedema in patients with psoriatic arthritis

Abstract
Objective: The frequency of osteoclast precursors (OCPF) and the presence of bone marrow oedema (BMO) are potential response biomarkers in psoriatic arthritis (PsA). Previous studies suggest a central role for tumour necrosis factor (TNF) in the formation of osteoclast precursors. To better understand this association, the effect of etanercept on OCPF and BMO was analysed in PsA patients with erosive arthritis. Methods: A total of 20 PsA patients with active erosive PsA were enrolled. Etanercept was administered twice weekly for 24 weeks. OCPF was measured and clinical assessments were performed at baseline, 2, 12 and 24 weeks. Gadolinium enhanced MR images were obtained at baseline and 24 weeks. Results: Significant improvements in joint score (pConclusion: The rapid decline in OCPF and overall improvement in BMO after anti-TNFα therapy provides one mechanism to explain the anti-erosive effects of TNF blockade in PsA. Persistence of BMO after etanercept treatment, despite a marked clinical response, was unexpected, and suggests ongoing subchondral inflammation or altered remodelling in PsA bone.