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. 2013 Oct 23;3:3022. doi: 10.1038/srep03022

Figure 3. Sirt6 is required for chondrocyte proliferation.

Figure 3

(a) Histomorphometric analysis of proximal tibia growth plates from the Sirt6−/− and WT littermate mice confirmed a reduction of approximately 20–30% in the thickness of the proliferating zone and the hypertrophic zone. Also, there were fewer cells per column in the proliferative zone and hypertrophic zone in Sirt6−/− mice (b). (c) The percentage of the hypertrophic zone volume occupied by ECM was reduced in Sirt6−/− growth plates. (d) TUNEL staining of P14 WT and Sirt6−/− mouse femur sections. The number of apoptotic cells was similar between Sirt6−/− and WT. (e), (f) PCNA immunohistochemistry of P14 WT (e) and Sirt6−/− (f) mouse tibia sections. There are fewer PCNA-positive (brown) proliferative chondrocytes in the growth plates of Sirt6−/− P14 pups. (g), (h) Sirt6 siRNA reduced cyclin D1 and cyclin D2 expression in primary epiphyseal chondrocytes (g) and ATDC5 cells (h). (i) Transient overexpression of Sirt6 in ATDC5 cells increased cyclin D1 and cyclin D2 mRNA. Values represent the mean ± SD of 3 samples per group. *; p < 0.05. Magnification is indicated in the figure.