In contrast to normal synovial tissue, rheumatoid synovium is hypoxic, and expresses the hypoxia-inducible transcription factors HIF-1α and HIF-2α which allow the transcription of genes involved in angiogenesis, inflammation, apoptosis and regulation of immune function. Hypoxia also stimulates osteoclast differentiation and causes a HIF-1α-dependent 3-fold increase in bone resorption. Angiopoietin-like 4 (ANGPTL4) is a hypoxia- and HIF-inducible pro-angiogenic adipokine that is induced in fibroblast-like synoviocytes in rheumatoid arthritis. This study sought to investigate whether ANGPTL4 is expressed in osteoclasts and other cells within rheumatoid synovial tissue, and to compare serum and synovial fluid levels of ANGPTL4 with those in normal controls and patients with osteoarthritis.
Ann rheum dis
73 Suppl 1