SAT0038 SEMAPHORINS: FROM ANGIOGENESIS TO INFLAMMATION IN RHEUMATOID ARTHRITIS

Background Synovial neoangiogenesis is an early and crucial event to promote the development of the hyperplasic proliferative pathologic synovium in rheumatoid arthritis (RA). A recent microarray analysis of Endothelial cells (ECs) issued from patients with RA and matched controls has revealed a differential expression of semaphorin family in RA ECs, which is known to contribute to angiogenesis and autoimmunity/inflammation. Objectives Our aim was to study the potential implication of semaphorins in RA pathogenesis. Methods mRNA levels of class 3 and 4 Semaphorins (SEMA) SEMA3A, SEMA3E, SEMA4A and SEMA4E, as well as their receptors PlexinD1 (PLXND1) and Neuropillin-1 (NRP1), were measured by real-time quantitative PCR in RA (n = 15) and control (n = 15) ECs. Protein expression of these 4 semaphorins and their receptors was evaluated in ECs of 10 RA patients and controls by western blot, and in the synovial tissue of 10 RA patients and 5 controls by immunohistochemistry and immunofluorescence. Serum concentrations of these 4 semaphorins were measured by sandwich ELISA in a cohort of 130 patients with RA (85% women, mean age: 58 ± 12 years and mean disease duration: 11 ± 12 years) and 30 age- (56 ± 10 years) and sex- (82% women) matched controls. Results SEMA4A, SEMA3E and their receptors PLXND1 and NRP1 mRNA (Real time quantitative PCR) and protein (western blot analyses) levels were found to be markedly increased in RA ECs compared to control ECs. The expression of SEMA4A, SEMA3A, SEMA3E, PLXND1 and NRP1 was strikingly increased in the synovial tissue of patients with RA. Confocal microscopy with double labeling for CD31 confirmed the prominent endothelial expression of these class 3 and 4 semaphorins and their receptors. SEMA3A serum levels were significantly lower in RA compared to controls (13.93±5.69 vs. 18.29±6.69 ng/mL, P P = 0.041), SEMA4A (65922±27109 vs. 53189±25808 pg/ml, P = 0.010) and SEMA4D (3.59±3.39 vs. 1.90±3.95 ng/mL, P = 0.012) were significantly increased in patients with RA compared to controls. In patients with RA, SEMA3A, SEMA4A and SEMA 4D correlated with CRP levels (r=-0.36, P P P =0.001, respectively). SEMA4A and 4D correlated with the Disease Activity Score (DAS)-28, (r=0.27, P =0.006 and r=-0.23, P =0.020, respectively). SEMA3A, SEMA4A and SEMA4D also correlated with the Global OMERACT-EULAR Synovitis Score, reflecting the intensity of synovial vascularization measured by power Doppler ultrasound (r=-0.22, P = 0.023, r=0.21, P = 0.030 and r=-0.242, P = 0.013, respectively). In addition SEMA4A and SEMA3E correlated with serum levels of the angiogenic markers Tie-2, angiopoietin, Interleukin-8 and soluble Vascular Cell Adhesion Molecule. Conclusion Gene expression profiling of ECs identified semaphorins as potential biomarkers and therapeutic candidates in RA. Class 3 and 4 semaphorins are overexpressed in ECs, synovial vessels and the serum of patients with RA. They also correlated with validated markers of inflammation and angiogenesis. Thus, semaphorins might be novel and appealing EC-derived inflammatory and proangiogenic targets in RA. Disclosure of Interests Jerome Avouac Grant/research support from: research grant from Pfizer, Sonia Pezet: None declared, Eloise Vandebeuque: None declared, Yannick Allanore Grant/research support from: Inventiva, F Hoffman La-Roche, Sanofi, BMS, Pfizer, Consultant for: Actelion, Bayer, BMS, Boehringer, Roche, Sanofi