Figure 5. Nampt regulation on MSC senescence is linked to the NAD+–Sirt1 signaling pathway. (A, B, C) Intracellular NAD+ content (A) NAD+/ NADH ratio (B) and Sirt1 deacetylase activity (C) were measured when Nampt was suppressed by either FK866 treatment or gene silencing. (D, E, F) Effect of Nampt overexpression on intracellular NAD+ content (D) and NAD+/ NADH ratio (E), as well as Sirt1 deacetylase activity (F); n = 3 independent experiments. *P < 0.05, **P < 0.01.