Figure 2. Proximal tibia growth plates from 2-week-old mice were stained with HE (X40 a, e; X100 b, f) and safranin O (X40 c, g; X100 d, h).

(a), (b), (e), (f) A reduction in the thickness of the proliferating zone (PZ) and hypertrophic zone (HZ) was observed in the Sirt6−/− growth plates, whereas resting zone (RZ) thickness was increased. (c), (d), (g), (h) Safranin O staining indicated delayed ossification of secondary ossification center (*) in Sirt6−/− mice. Primary spongiosa formation (#) was also markedly reduced in Sirt6−/− mice. Also, proteoglycan expression was sparsely observed in the hypertrophic zone of Sirt6−/− mice (d), (h). Magnification is indicated in the figure.