Figure 3. Nampt gene silencing exacerbates MSC senescence. (A) Gene expression of Nampt in young EP MSCs (P3) after Nampt knockdown as demonstrated by RT-qPCR. (B) Protein levels of Nampt as detected by western blotting. (C) Senescent morphology (scale bar = 20 μm) and quantification. (D) Logarithmic proliferation in Nampt-deficient MSCs. (E) Cell population doubling time (PDT). (F) Detection of cell cycle and analysis of both S-phase fraction (SPF) and proliferation index (PI). (G) Osteogenic differentiation of MSCs (scale bar = 50 μm). (H) Adipogenic differentiation of MSCs (scale bar = 20 μm). (I) SA-β-gal staining (scale bar = 50 μm) and quantification. (J) Gene expression of senescence-related factor p16INK4a; n = 3 independent experiments. *P < 0.05, **P < 0.01.