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Angiogenesis is an essential event in the development of synovial inflammation in rheumatoid arthritis (RA). The aim of the current study was to investigate the expression of vasohibin-1, a novel endothelium-derived vascular endothelial growth factor (VEGF)-inducible angiogenesis inhibitor, in the RA synovium, and to test the effect of inflammatory cytokines on the expression of vasohibin-1 by RA synovial fibroblasts (RASFs). Synovial tissue samples were obtained at surgery from patients with osteoarthritis (OA) and RA, and subjected to immunohistochemistry to investigate the expression and distribution of vasohibin-1 relevant to the degree of synovial inflammation. In an in vitro analysis, RASFs were used to examine the expression of vasohibin-1 and VEGF mRNA by real-time PCR after stimulation with VEGF or inflammatory cytokines under normoxic or hypoxic conditions. The immunohistochemical results showed that vasohibin-1 was expressed in synovial lining cells, endothelial cells, and synovial fibroblasts. In synovial tissue, there was a significant correlation between the expression of vasohibin-1 and histological inflammation score (p0.002, r0.842). In vitro, stimulation with VEGF induced the expression of vasohibin-1 mRNA in RASFs under normoxic conditions, and stimulation with cytokines induced vasohibin-1 mRNA expression under a hypoxic condition. These results suggest that vasohibin-1 was expressed in RA synovial tissue and might be regulated by inflammatory cytokines.
Acta Medica Okayama
Okayama University Medical School
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