Synovial fluid macrophages are capable of osteoclast formation and resorption

• Published in: The Journal of pathology Vol. 208; no. 1; pp. 35 - 43
• Main Authors: Adamopoulos, IE, Sabokbar, A, Wordsworth, BP, Carr, A, Ferguson, DJ, Athanasou, NA
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2006; Wiley
• Subjects: Aged; Arthritis, Rheumatoid - immunology; Arthritis, Rheumatoid - physiopathology; Biological and medical sciences; Bone Resorption - immunology; Bone Resorption - physiopathology; Carrier Proteins - immunology; Carrier Proteins - physiology; Cell Differentiation - immunology; Cell Differentiation - physiology; Cells, Cultured; Chondrocalcinosis - immunology; Chondrocalcinosis - physiopathology; Diseases of the osteoarticular system; Female; Humans; Interleukin-1 - immunology; Interleukin-1 - physiology; Investigative techniques, diagnostic techniques (general aspects); Knee Joint - immunology; Knee Joint - physiopathology; Lipopolysaccharide Receptors - immunology; macrophages; Macrophages - immunology; Macrophages - physiology; Male; Medical sciences; Membrane Glycoproteins - immunology; Membrane Glycoproteins - physiology; Middle Aged; Osteoarthritis; Osteoarthritis, Knee - immunology; Osteoarthritis, Knee - physiopathology; osteoclasts; Osteoclasts - immunology; Osteoclasts - physiology; Osteogenesis - immunology; Osteogenesis - physiology; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Phenotype; pyrophosphate; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; rheumatoid arthritis; synovial fluid; Synovial Fluid - immunology; Synovial Fluid - physiology; Tumor Necrosis Factor-alpha - immunology; Tumor Necrosis Factor-alpha - physiology; Diseases of the osteoarticular system; Resorption; pyrophosphate; Autoimmune disease; Inflammatory joint disease; Osteoclast; Osteoarticular system; Synovial fluid; Anatomic pathology; Chronic; macrophages; Rheumatoid arthritis; osteoclasts; Arthropathy; Degenerative disease; Bone; Osteoarthritis; Macrophage
• ISSN: 0022-3417; 1096-9896
• DOI: 10.1002/path.1891

To determine whether synovial fluid (SF) macrophages isolated from the SF of osteoarthritis (OA), rheumatoid arthritis (RA) and pyrophosphate arthropathy (PPA) joints are capable of osteoclast formation, and to investigate the cellular and humoral factors required for this to occur, SF macrophages (CD14+) were isolated from the knee joint SF from patients with OA, RA and PPA and cultured for up to 14 days with macrophage‐colony stimulating factor (M‐CSF) and soluble receptor activator for nuclear factor‐κB ligand (RANKL) or tumour‐necrosis factor‐α (TNFα) and interleukin‐1α (IL‐1α). Osteoclast differentiation was assessed by expression of tartrate‐resistant acid phosphatase (TRAP) and vitronectin receptor (VNR), F‐actin ring formation and lacunar resorption. Osteoclast formation and lacunar resorption was seen in RANKL‐treated cultures of SF macrophages isolated from OA, RA and PPA joints with the largest amount of resorption noted in RA and PPA SF macrophage cultures. In TNFα/IL‐1α‐treated RA and PPA SF macrophage cultures, osteoclasts capable of lacunar resorption were also formed. Lacunar resorption was more extensive in RANKL than TNFα/IL‐1α‐treated cultures. These findings indicate that SF macrophages are capable of differentiating into mature osteoclasts capable of lacunar resorption. M‐CSF in combination with RANKL or TNFα/IL‐1α was required for osteoclast formation. As inflammatory synovial fluids contain an increase in the number of macrophages and an increase in the amounts of RANKL, TNFα and IL‐1α, these findings suggest that one means whereby bone erosions may form in rheumatoid or crystal arthritis is by differentiation of synovial fluid macrophages into osteoclasts. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.