Fig. 2

Effects of selective tropomyosin-receptor-kinase A (TrkA) inhibitor AR786 on carrageenan-induced synovial inflammation and angiogenesis. Saline-treated control animals demonstrate normal synovial lining layer thickness/cellularity (a), macrophage infiltration (d) and endothelial cell (EC) proliferation (g). Four days after intra-articular injection of 2 % carrageenan there was an increase in synovial lining layer thickness/cellularity (b), macrophage infiltration (e) and endothelial cell (EC) proliferation (h). Following treatment with AR786 (c, f, i), synovial lining layer thickness/cellularity (c) and macrophage infiltration (f) were significantly reduced but not to saline control levels (a, d). EC proliferation was not significantly affected following treatment with AR786 (i). Photomicrographs show synovial lining (black arrows) and cellularity as indicated by haematoxylin and eosin staining (a–c), macrophages (purple/black) as delineated by immunoreactivity for CD68 (d–f) and EC (red) as delineated by immunoreactivity for CD31 (blue arrows), proliferating nuclei (black), as delineated by immunoreactivity for proliferating cell nuclear antigen (PCNA) (green arrows), and proliferating ECs (red arrows), which contain PCNA-immunoreactive nuclei (g–i). Bars = 100 μm