Cellular characteristics of NS and S HDFs following UV exposure.

(A)Normal or non-senescent (NS) and senescent (S) HDFs were irradiated with UVA (7.5 J/cm2) or UVB (0.25 J/cm2). The extent of senescence-associated β-galactosidase (SA-β-Gal) staining after UV irradiation was observed. Scale bar = 50 μm. (B, C) Immunofluorescence analysis of γ-H2AX foci formation was performed by confocal microscopy. DAPI (blue), γ-H2AX foci (red), and merge images are shown. Scale bar = 10 μm. The graph shows the number of γ-H2AX foci per cell. The data represent the mean ± SEM of three independent sets of experiments.