Joint Degradation in a Monkey Model of Collagen-Induced Arthritis: Role of Cathepsin K Based on Biochemical Markers and Histological Evaluation

Figure 4

TRAP and ALPase staining and immunolocalization of cathepsin K in sagittal sections of PIP joints. TRAP staining in controls (a) and in arthritis with moderate (b) and severe (c) joint destruction. Immunolocalization of cathepsin K in controls (d) and in arthritis with moderate (e) and severe (f) joint destruction. In moderate joint destruction, the immunolocalization of cathepsin K was observed in osteoclast, cells in synovial tissue (arrows, e) and chondrocytes (arrowheads, e). In severe joint destruction, the immunolocalization of cathepsin K was observed in osteoclast (black arrows, f) and cells in connective tissue near articular joint (red arrows, f). ALPase staining in controls (g) and in arthritis with moderate (h) and severe (i) joint destruction. Black arrows, strongly cathepsin K-positive osteoclast; AC, articular cartilage; ST, synovial tissue; OC, osteoclasts. Bars: (a)–(c): 120 μm, (d)–(f): 100 μm, and (g)–(i): 300 μm.