Fig. 3

Elevated COX-2 activity in subchondral bone in spontaneous OA. a Immunohistochemical staining for COX-2 (brown) in the subchondral bone of STR/ORT and CBA mice at 2, 4, and 6 months of age. Scale bars, 50 μm. b Quantitative analysis of COX-2⁺ cells (per mm²) in the subchondral bone of STR/ORT and CBA mice. N = 5 mice in each group from three independent experiments. c Western blot analysis of COX-2 protein expression in osteocytes isolated from the subchondral bone of STR/ORT and CBA mice at 4 months of age. d PGE2 levels in the medium used to culture osteocytes isolated from the subchondral bone of 4-month-old STR/ORT and CBA mice. N = 5 mice in each group from three independent experiments. e Serum PGE2 levels in 4-month-old STR/ORT and CBA mice. N = 5 mice in each group from three independent experiments. f and g Immunohistochemical staining f and quantitative analysis g of COX-2⁺ cells (brown) in the subchondral bone of C57BL/6 mice 30 days after sham operation or anterior cruciate ligament transection (ACLT) surgery. Scale bar, 50 μm. N = 5 mice in each group from three independent experiments. h and i Immunohistochemical staining h and quantitative analysis i of COX-2⁺ cells (brown) in the articular cartilage of STR/ORT and CBA mice at 4 months of age. Scale bars, 50 μm. N = 5 mice in each group from three independent experiments. j and k Immunohistochemical staining j and quantitative analysis k of COX-2⁺ cells (brown) in the synovial membrane of STR/ORT and CBA mice at 4 months of age. Scale bars, 50 μm. N = 5 mice in each group from three independent experiments. l Quantitative analysis of mechanical allodynia in 4-month-old STR/ORT and CBA mice, as measured by the foot-lift response frequency to stimulation with a 0.008-g von Frey filament. N = 5 mice in each group from three independent experiments. All data are shown as the mean ± standard deviation. *P < 0.05. Statistical significance was determined by Student’s t-test