Expression patterns of Tie2 mRNA and protein. 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 rabbit antihuman Tie2 polyclonal antibody from Santa Cruz Biotechnology (Santa Cruz, CA, USA). (a) Synovial tissue from a patient with rheumatoid arthritis showing positive staining for Tie2. (b) Positive staining for Tie2 in osteoarthritis synovial tissue. (c) Tie2 staining is absent in normal synovial tissue. (a), (b) and (c) Original magnification × 200. (d) Immunohistochemistry of synovial tissues from normal (NL) subjects (n = 11) and those with rheumatoid arthritis (RA) (n = 15) and osteoarthritis (OA) (n = 11). The bars represent mean ± SE. (e) Tie2 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). (f) Western blot analysis of Tie2 in synovial tissues from RA, OA, RA fibroblasts and human microvascular endothelial cells (Endo) using the goat antihuman antibody from R&D Systems (Minneapolis, MN, USA). Lining, synovial tissue lining cell layer; Mac, subsynovial macrophages; Endo, vascular endothelium; Sm, vascular smooth muscle cells; Lymph, lymphocytes. *P < 0.05.