Histological evaluation of cartilage-protective effect of 4,5-diCQA against cartilage degradation in a DMM model. After sham or DMM surgery, rats received gavage of distilled water, 4,5-diCQA (5, 10, and 20 mg/kg bodyweight), or diclofenac sodium (10 mg/kg bodyweight) every other day for 2 weeks. (A) Protein levels of MMP-1, -3, and -13 were determined using Western blot analysis. α−Tubulin served as an internal control. (B) Quantitative data of (A) were analyzed using the ImageJ bundled with Java 1.8.0_172 software. n = 5 per group. Data are represented as mean ± SD of three independent experiments. ### p < 0.005 compared with sham group; ** p < 0.05, and *** p < 0.005 compared with the DMM-induced group. (C) Histological analysis of cartilage destruction was evaluated by Safranin O/Fast green staining. Black scale bars, 500 μm. White scale bars, 100 μm. (D) Osteoarthritis Research Society International (OARSI) advanced Osteoarthritis Cartilage Histopathology Assessment System. ANOVA and Dunnett tests were used to evaluate the significance of the results. ### p < 0.005 compared with sham group; ** p < 0.05, *** p < 0.005 compared with DMM group.