Fig. 4. KGF protects keratinocytes from UV-induced cell damage in vitro and in vivo. (A,B) Quiescent HaCaT cells were treated with KGF or vehicle 16 hours and 1 hour before irradiation with different doses of UVA (A) and UVB (B) as indicated. UV-irradiated cells were subjected to MTT assay 24 hours after irradiation. (C) The shaved back skin of transgenic mice expressing a dominant-negative FGFR2IIIb (tg) and their wild-type littermates (wt) was irradiated with 100 mJ/cm² UVB. One group of mice of each genotype received a subcutaneous injection of 10 µg KGF 24 hours before irradiation (n=8 for each genotype), whereas the control group (n=7 for each genotype) was only injected with the solvent (0.5% BSA in PBS). Representative histological pictures of each treatment group and genotype are depicted. The arrows indicate sunburn cells. E, epidermis; D, dermis; HF, hair follicle. (D) Apoptotic cells (arrows) were detected by TUNEL staining (green). Propidium iodide (PI) staining (red) was used to visualize the nuclei. The basement membrane is indicated with a dashed line. Four animals were used of each genotype for vehicle control and five animals of each genotype for KGF injections. Sunburn cells (E) or TUNEL-positive cells (F) were counted and their number per mm basement membrane was calculated. For quantitative analyses in E and F one section from each animal was analyzed; ten pictures were taken from each section. Results are mean ± s.d. For statistical analysis the Mann-Whitney U test was used. ^*P<0.05; ^***P<0.001.