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

Figure 3

Histological analysis of sagittal sections of PIP joints of normal and arthritic monkeys. (a–f) Hematoxylin and eosin- (H&E-) stained sections of controls (a, b) and in arthritis with moderate (c, d) and severe (e, f) joint destruction. (g–l) Immunolocalization of type II collagen in controls (g) and in arthritis with moderate (h) and severe (i) joint destruction, and immunostaining of CTX-II in controls (j) and in arthritis with moderate (k) and severe (l) joint destruction. In moderate joint destruction, the superficial layer of articular cartilage showed CTX-II positivity (black arrows, k), while the deeper layer had no CTX-II reactivity. Note the unstained layer of type II collagen and CTX-II (red arrowheads, h and k). In severe joint destruction, the deeper layer of the articular cartilage became positive for CTX-II (arrows, l). Note the partial destruction of the articular cartilage (arrow, i). AC, articular cartilage; ST, synovial tissue. Bars: (a), (c), (e): 650 μm, (b), (d), (f): 120 μm, (g), (i), (j), (l): 100 μm, and (h), (k): 50 μm.