The purpose of this study was to demonstrate the role of renin-angiotensin system (RAS)-related components, vascular endothelial growth factor (VEGF) and atrial metalloproteinase-13 (MMP-13) in synovial tissue and synovial fluid from patients with rheumatoid arthritis (RA) and osteoarthritis (OA).
Thirty-four patients with RA and 41 patients with OA were included in the study. Renin, angiotensin-converting enzyme (ACE), VEGF and MMP-13 protein levels in the synovial fluid were measured by enzyme-linked immunosorbent assay. Quantitative real-time polymerase chain reaction analysis, western blot analysis and immunohistochemistry were used to quantify renin, ACE, angiotensin type 1 and type 2 receptors, VEGF and MMP-13 in OA and RA. Additionally, the correlation was determined by Pearson's coefficient.
In synovial fluid, expression levels of renin, ACE, VEGF and MMP-13 in patients with RA were significantly higher than those in patients with OA. In synovial tissue, the RAS components VEGF and MMP-13 were also elevated in patients with RA. The results of immunohistochemistry in synovial tissue also showed that the RAS components VEGF and MMP-13 were significantly increased in patients with RA. Notably, the Pearson coefficient demonstrated that the levels of the RAS components were positively correlated with the expression of VEGF and MMP-13 in OA and RA.
The present results suggest that RAS-related components in RA and OA, including renin, ACE, angiotensin type 1 and type 2 receptors, are associated with increased expression of VEGF and play an important role in angiogenesis. Furthermore, there was a significant positive correlation between the expression of VEGF and MMP-13.