Renin-angiotensin system components enriched in RA vs OA patients

Components of the renin-angiotensin system (RAS), such as renin, angiotensin-converting enzyme (ACE), matrix metalloproteinase-13 (MMP-13) and vascular endothelial growth factor (VEGF), are more elevated in the synovial fluid of patients with rheumatoid arthritis (RA) than with osteoarthritis (OA), a recent study has shown.

The study included 34 RA (mean age, 54.11±4.08 years) and 41 OA (mean age, 67.09±3.92 years) patients. Enzyme-linked immunosorbent assays were used to measure the levels of ACE, VEGF, renin and MMP-13 in synovial fluid samples. Quantitative real-time polymerase chain reaction, along with western blot analysis and immunohistochemistry, was used to quantify expression of pertinent receptors.

Expression levels of renin, as well as ACE and its type 1 and 2 receptors, were significantly enriched in RA vs OA patients (p<0.05 for mRNA and protein). The same was true for VEGF and MMP-13 expression (p<0.05).

This enrichment was also reflected in the concentration of the markers in synovial fluid samples. Renin, for example, was present in much higher levels in RA than in OA patients (13.36±4.72 vs 4.81±1.98 pg/mL; p<0.001), as was ACE (50.79±15.30 vs 26.26±10.15 ng/mL; p<0.001). MMP-13 (412.72±145.31 vs 154.58±66.91 pg/mL; p<0.001) and VEGF (600.06±90.98 vs 224.99±73.09 pg/mL; p<0.001) were similarly more concentrated in RA synovial fluid.

“These results suggest that RAS-related components and MMP-13 may be therapeutic targets for inhibiting angiogenesis and may be new strategies for the treatment of RA and OA,” said researchers.