Expression pattern of angiopoietin-2 (Ang-2) mRNA and protein in synovial tissues. The double arrowhead denotes subsynovial macrophages, the single arrowhead denotes vascular endothelium and the double headed arrows denote vascular smooth muscle cells. The immunohistochemistry was performed with a goat antihuman Ang-2 polyclonal antibody from Santa Cruz Biotechnology (Santa Cruz, CA, USA). (a) Synovial tissue from a patient with rheumatoid arthritis showing positive staining for Ang-2. (b) Positive staining for Ang-2 in osteoarthritis synovial tissue. (c) Ang-2 staining is absent in normal synovial tissue. (a), (b) and (c) Original magnification × 226. (d) Immunohistochemistry of synovial tissues from normal (NL) subjects (n = 7) and those with rheumatoid arthritis (RA) (n = 11) and osteoarthritis (OA) (n = 12). The bars represent mean ± SE. (e) Ang-2 mRNA levels in synovial tissue (ST) and RA fibroblasts (Fib) were quantified using real-time reverse transcription-PCR and normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Bars represent the mean ± SE (n = 3). Lining, synovial tissue lining cell layer; Mac, subsynovial macrophages; Endo, vascular endothelium; Sm, vascular smooth muscle cells. *P < 0.05.