Presence of bone morphogenetic protein-7 (BMP7) during collagen-induced arthritis. Immunohistochemistry in the initial phase (a, b), with increasing severity (c-f), and in the destructive phase of collagen-induced arthritis (g, h) is shown. Severity scoring was done on sections stained with hematoxylin and eosin. Boxes indicate areas that are magnified in BMP7 stainings. Arrows indicate BMP7-positive cells in synovium, and arrowheads indicate BMP7-positive cells in articular cartilage. Asterisk indicates gradual clearing of the synovial lining layer. Bars = 200 μm (a, c, e, g), 50 μm (b, d), and 25 μm (f).