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. 2008 Apr;19(4):1346–1353. doi: 10.1091/mbc.E07-10-1041

Figure 1.

Figure 1.

Low doses of UVB irradiation induce cellular senescence only in keratinocytes containing functional IGF-1 receptors. Normal human keratinocytes were grown in EpiLife Complete media [(+)IGF-1R, A and B] or EpiLife NoIn media [(−)IGF-1R, C and D] for 24 h. At that time, keratinocytes were irradiated with 0 (A and C) or 100 (B and D) J/m2 UVB. Eighteen hours after irradiation, the media on all of the dishes was replaced with EpiLife Complete media. Seventy-two hours after irradiation, the keratinocytes were assayed for the expression of senescence-associated β-galactosidase. (A–D) Photomicrographs of keratinocyte cultures stained for the presence of senescence-associated β-galactosidase activity (positive cells are blue). (E) Compiled percentage of senescent cells from each culture condition. Error bars indicate the SEM; the asterisk indicates significant difference between irradiated (+)IGF-1R and (−)IGF-1R keratinocyte percentages (p < 0.01; t test). The data represent three independent assays.