VEGF is upregulated in synovial macrophages and synovial fibroblasts of RA patients, and cultured synovial cells can produce VEGF under hypoxia or with stimulation by IL-1, IL-6, IL-17, IL-18, prostaglandin, TGF-β, or CD40 ligation [10, 16, 41, 42]. Here, IL18 is linked to rheumatoid arthritis.