Fig. 3

Comparison of histological and immunohistochemical analyses on knee OA between the No-Ex and Ex groups. A, B Safranin-O staining on the cartilage surface in the tibial plateau and synovium in the No-Ex and Ex groups. C High magnification of the rectangular area in A (No-Ex). D High magnification of the rectangular area of B (Ex). The remaining articular cartridge was observed in the anterior tibial plateau in the Ex group. However, posterior cartilage in the tibial plateau was degenerated in both groups. E The modified Mankin score. F The OARSI score. G The osteophyte formation score. H The synovial lining cell layer score. I Immunoreactivities of collagen type II- and MMP-13 positive chondrocytes in the remaining cartilage of the tibial plateau. High magnification panels show immune-positive cells (black arrow head) for collagen type II- and MMP-13-positive chondrocytes. J MCP-1 and TNF-α positive cells (arrow) in the posterior synovium (semi-serial section of the No-Ex and Ex groups, corresponding to * and + , respectively). K The number of collagen type II-positive chondrocytes. L The number of MMP-13 positive-chondrocytes. M The percentage of MCP-1-positive cell areas in the synovium. N The percentage of TNF-α-positive cell areas in the synovium. Animals in the No-Ex group were equivalent to 9-month-old SAMP8. Data are expressed as the means ± 95% CI. *p < 0.05, **p < 0.01, ***p < 0.001. Scale bars = 500 μm (A, B), 100 μm (C, D), 50 μm (I, J), and 25 μm (high magnification panels of I) (n = 6–10 for both groups)