Fig. 4.

Accelerated senescence and increased expression of SMAD4 in Werner syndrome fibroblasts. a SMAD4 levels were quantified in serially passaged normal skin fibroblasts, 82-6, and Werner skin fibroblasts, 78-85. p indicates passage number. Fold induction of SMAD4 mRNA was quantified by real-time PCR. b Growth curves represent population doubling times of 78-85 Werner cells or 82-6 normal fibroblasts cells at the indicated passage numbers. c Percentage of SA-β-gal positive cells in 78-85 Werner cells. d Relative mRNA expression of IL-6, STAT1, and IFNγ by real-time-PCR in Werner cells at the passage numbers indicated. *denotes statistical significance (*p < 0.05, ** < 0.01). Error bars represent SEM