Background Haemophilic arthropathy (HA) may involve mainly the larger joints (target joint) presenting a spontaneous bleeding, haemarthrosis. Repeated bleeding episodes lead to synovitis implying synovial changes, cartilage and bone damages resulting in disability. The mechanisms and pathways of blood-induced damage in cartilage and bone are still not completely clear. Ultrasonography (US) is helpful to detect bone and cartilage alterations and synovitis. Power Doppler US (PDUS) may identify bleeding also in asymptomatic joints and is able to show different entity of haemarthrosis.
Objectives To investigate the expression tissue of molecules involved in bone remodelling (RANK/RANKL/OPG system) in synovial tissue from haemophilic patients (HP) with severe HA scored by sonographic score (US score).
Methods Synovial biopsies from 20 patients with HA and from 16 osteoarthritic (OA) patients, obtained during arthroplasty of the knee, were routinally processed for light microscopy. The severity of HA was evaluated according to a) US score, based on a semiquantitative method (score ranging from 0-21 with cut off>5), b) the World Federation of Haemophilia orthopaedic joint scale (WFH) and c) radiographic Petterson method. Synovial sections were stained with haematoxylin and eosin to evaluate pathological changes. The expression of RANK/RANK-L/OPG, involved in bone remodelling, was examined by immunohistochemistry. Moreover, levels of soluble RANKL and OPG in serum from 67 patients with HA and 30 healthy controls were measured by ELISA assay.
Results The mean sonographic score in HA patients >5 was 11. The mean WFH clinical score was 39.5 point (range:12-57). The mean Pettersson score was 10.4 points (range: 6-12).
Microscopically the synovium from patients with HA showed a large amount of intra- and extracellular haemosiderinic deposits. The lining layer showed mild proliferation and in the sublining area the vessels were characterized by thickened wall, due to a local and chronic inflammatory stimuli. A lower expression of OPG was found in HA synovium compared to OA. RANK and RANK-L positivity was strongly expressed in the lining and sublining both in HA and OA synovial tissue. Serum levels of sRANKL and OPG resulted lower than in controls.
Conclusions In HA synovial tissue, the elevation of RANK/RANKL and the reduction of OPG suggests an osteoclastic activation. Tissue expression of OPG correlates with serum level of this protein in HP and with severity of HA by US score.
Disclosure of Interest None Declared
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