The effect of vascular endothelial growth factor on osteoclastogenesis in rheumatoid arthritis.

Hae-Rim Kim,Mi-La Cho,Kyoung-Woon Kim,Bo-Mi Kim,Sang-Heon Lee,Chih-Hsin Tang

doi:10.1371/journal.pone.0124909

Abstract

Vascular endothelial growth factor (VEGF) has angiogenic, inflammatory, and bone-destructive roles in rheumatoid arthritis (RA). We aimed to determine the unique role of VEGF in osteoclastogenesis in RA. VEGF-induced receptor activator of nuclear factor ҡB ligand (RANKL) expression was determined in RA synovial fibroblasts by real-time PCR, luciferase assays, and ELISA. Osteoclastogenesis in peripheral blood monocytes cultured with VEGF was assessed by determining the numbers of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells. Synovial fluid RANKL was correlated with VEGF concentration in the RA patients. VEGF stimulated the expression of RANKL in RA synovial fibroblasts. The RANKL promoter activity was upregulated by VEGF in the synovial fibroblasts transfected with RANKL-reporter plasmids. The VEGF-induced RANKL expression was decreased by the inhibition of both VEGF receptors (VEGFR) 1 and 2, Src, protein kinase C (PKC) and p38 MAPK. VEGF induced osteoclast differentiation from monocytes in the absence of RANKL and this was decreased by the inhibition of VEGFR1 and 2, Src, PKC and p38 MAPK. On coculturing with VEGF-prestimulated RA synovial fibroblasts, the monocytes differentiated into osteoclasts, and the osteoclastogenesis decreased by inhibition of Src and PKC pathways. VEGF plays dual roles on osteoclastogenesis in RA: direct induction of osteoclastogenesis from the precursors and stimulation of RANKL production in synovial fibroblasts, which is mediated by Src and PKC pathways. The axis of VEGF and RANKL could be a potential therapeutic target for RA-associated bone destruction.

Highlights

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by synovial inflammation and subsequent joint destruction [1, 2]
Expression of Vascular endothelial growth factor (VEGF) and receptor activator of nuclear factor-kappaB ligand (RANKL) in synovial fluids and synovial tissues of RA patients. Both VEGF and RANKL were overexpressed in the serum, synovial fluid, and synovial tissues of RA patients [9, 33]
A significant positive correlation was noted between VEGF and RANKL concentrations in the synovial fluid of 32 RA patients (r2 = 0.6, P < 0.001) (Fig 1A), while no such relationship was noted between their respective serum concentrations (Fig 1B)

Summary

Introduction

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by synovial inflammation and subsequent joint destruction [1, 2]. Angiogenesis plays an important role in the maintenance and progression of synovitis. This vascular process occurs during the early events of synovial proliferation, which promotes cartilage and bone destruction in later stages of RA. VEGF has proinflammatory and anti-apoptotic roles in RA pathogenesis [13]. It induces tumor necrosis factor (TNF)-α and interleukin (IL)-6 from synovial fluid mononuclear cells of RA patients [14]. Several inflammatory molecules such as TNF-α, IL-1β, IL-6, macrophage-migration inhibitory factor, IL-17, IL-18, prostaglandin, nitric oxide, and transforming growth factor (TGF)-β promote VEGF production by synovial fibroblasts [10, 15,16,17,18]. VEGF increases the survival of synovial fibroblasts in RA, protects the apoptotic death of synovial fibroblasts, and interacts with neuropilin-1 [19]

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