Figure 5. DNA damage induces an aging phenotype by downregulation of SIRT1. Cell culture medium of UdRPCs was supplemented with 1μM of resveratrol and or 30 μg/ml of bleomycin for 24h. Phosphorylation of H2A.X was monitored by immunofluorescence-based expression analysis (A) (scale bars: 100 μm). mRNA expression of SIRT1, ATM, P16 and SIX2 was determined by quantitative real time PCR (B). Relative protein expression normalized to ß-ACTIN for SIRT1, AKT and GSK3ß and relative protein phosphorylation for AKT, GSK3β and pH2A.X was detected by Western blotting (C).