Semaphorins: From Angiogenesis to Inflammation in Rheumatoid Arthritis

Abstract

Objective To study the potential role of semaphorins in the pathogenesis of rheumatoid arthritis (RA). Methods Microarray experiments were performed on Affymetrix GeneChip Human Exon 1.0 ST arrays in RA endothelial cells (ECs) and control ECs derived from circulating progenitors. Expression of class 3 and class 4 semaphorins and their receptors in the serum of RA patients and healthy controls was assessed by immunohistochemical analysis in synovial tissue and by enzyme‐linked immunosorbent assay. Results Microarray analysis revealed differential expression of class 3 and class 4 semaphorins and their receptors in RA ECs. Semaphorin 4A (SEMA4A), plexin D1, and neuropilin 1 messenger RNA (mRNA) levels were markedly increased in RA ECs by 1.75‐, 2.21‐, and 1.68‐fold, respectively. Stimulation with tumor necrosis factor (TNF) led to a 2‐fold increase in SEMA4A mRNA levels in RA ECs, and deficient SEMA4A expression modified RA EC angiogenic properties. Class 3 and class 4 semaphorins as well as their receptors were overexpressed in RA synovial tissue. A respective 1.30‐fold increase and 1.54‐fold increase in SEMA4A and SEMA3E, as well as a 24% decrease in SEMA3A, was observed in the serum of RA patients. Serum levels of SEMA4A, SEMA4D, and SEMA3A correlated with levels of inflammation and proangiogenic markers. In 2 independent cohorts of patients with low disease activity or with RA in remission, the presence of SEMA4A identified patients with residual disease activity. Conclusion Gene expression profiling of ECs identified class 3 and class 4 semaphorins as potential biomarkers and therapeutic candidates in RA, with confirmed overexpression in ECs, synovial vessels, and serum, and correlation with validated markers of inflammation and angiogenesis. Thus, semaphorins might be novel and appealing EC‐derived inflammatory and proangiogenic targets in RA.

Relevance of circulating Semaphorin 4A for rheumatoid arthritis progression and response to treatment

“…Patient samples: We considered our set of 130 patients with available SEMA4A serum concentrations at baseline, whose characteristics have previously been published [7]. Among these patients, 101 had at least one annual follow-up visit and were further included in this study.…”

“…Data collection: The detailed methods for the collection of clinical and biological data, as well as ultrasonography assessment have been previously reported [7]. RA disease activity was assessed at each visit by the Disease Activity Score based on the evaluation of 28 joints (DAS28) [8].…”

“…SEMA4A concentrations: Serum concentrations of SEMA4A have been previously measured in this cohort [7]. Increased SEMA4A concentrations were de ned as values >94 ng/mL since this cut-off value previously identi ed RA patients with an "in ammatory pro le" with an area under curve of 0.80 (P<0.001) [7].…”

“…The presence of erosions was assessed by systematic hand and foot x-rays. SEMA4A concentrations: Serum concentrations of SEMA4A have been measured by quantitative ELISAs (SEMA4A Coud-Clone Corp, Katy, TX), in the same location and conditions as the rst cohort, as previously described [7].…”

“…Increased SEMA4A concentrations have been detected in the serum, synovial uid, and synovial tissue of patients with RA [6]. In addition, we previously showed that SEMA4A serum levels correlated with multiple clinical, biological, and ultrasound markers of disease activity, including the Disease Activity Score (DAS)-28 and DAS28-CRP composite scores [7]. Following these promising results, our aims herein were to i) evaluate the merit of circulating SEMA4A to predict RA disease progression and ii) study its association with response to therapy.…”