Figure 4. Delayed Senescence in DNP-Treated Fibroblasts Is Telomere Dependent.

(A) Telomere in-gel hybridisation of untreated (control) and DNP-treated MRC5. The size-weighted average of each peak is indicated by a white line. A λHindIII DNA digest is used as size marker (M).

(B) Average telomere (TRF) length in controls and DNP-treated MRC5 fibroblasts. Data are mean ± s.e.m. from quadruplicate gels. Solid line: linear regression, dotted lines: 95% confidence intervals. Differences between slopes are significant (2-tailed t test, p = 0.002).

(C) Telomere Q-FISH histograms of untreated (control) and DNP-treated MRC5 at the indicated PD. Medians are indicated by red bars and are at 6.0 arbitrary units (a.u.) (control PD 38), 1.3 a.u. (control PD 43), and 5.7 a.u. (DNP PD 45). Histograms of control PD 43 and DNP PD 45 are significantly different from each other according to a Mann-Whitney test (p-value < 2.2 × 10⁻¹⁶).

(D) ImmunoFISH of senescent DNP-treated cells at PD 50. γ-H2A.X–containing foci are shown in green and telomeres in red. The boxed area is shown as deconvoluted image at higher magnification at the right. Pixels that show significant co-localisation between foci and telomeres according to a Pearson correlation analysis are shown in white (indicated by arrows).