Histological findings of age-associated OA in wild-type (WT) and Col2-Ugcg−/− littermates. A, Histological findings of age-associated OA. Safranin-O (Saf-O) staining (top; knee joint), immunostaining of MMP-13 (middle; proximal tibia), and TUNEL staining (bottom; proximal tibia). Scale bars = 100 µm. B, Mankin score of WT and Col2-Ugcg−/− littermates (n = 10 per group). C, The percentage of MMP-13 positive staining cells in WT and Col2-Ugcg−/− littermates (n = 10 per group). D, The percentage of TUNEL-positive staining cells in WT and Col2-Ugcg−/− littermates (n = 10 per group). Data shown are mean ± SEM. * = P < 0.01.