302 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS •' 3 E o 2 2 4 6 8 10 Weeks of UVB Irradiation Figure 5. Effects of temporary artificial groove production on wrinkle formation (artificial direction: parallel to the midline) using the back skin of hairless mice. Closed circles: UV-B irradiation after pro- duction of temporary wrinkles. Open circles: UV-B irradiation only. Closed triangles: production of tem- porary wrinkles after UV-B irradiation. Open squares: production of temporary wrinkles without UV-B irradiation. Closed squares: no treatment. Error bars represent one standard deviation about the mean. :. A' B :" C ' Figure 6. Photographs of mouse skin after ten weeks. (A) UV-B irradiation immediately after production of the artificial groove parallel to the midline. (B) Production of the artificial groove parallel to the midline immediately after UV-B irradiation. (C) Only the artificial groove was produced without UV-B irradiation. temporary groove was produced after UV-B irradiation, original wrinkling was slightly but significantly decreased compared with the UV-B irradiation-only group. There were no differences in original wrinkling in the group treated only by production of the temporary groove compared with age-matched controls. In the groups treated by UV-B irradiation after production of the temporary groove, artificial wrinkling was signifi-

SKIN MORPHOLOGY AND WRINKLE FORMATION 303 ? Figure 7. Photographs of skin impressions (replicas) after ten weeks. (A) UV-B irradiation immediately after production of the artificial groove parallel to the midline. (B) Production of the artificial groove parallel to the midline immediately after UV-B irradiation. (C) Only the artificial groove was produced without UV-B irradiation. cantly increased compared with all other groups. There were no differences in artificial wrinkling in the group treated by production of the temporary groove after UV-B irradiation compared with the group treated by production of the temporary groove only. In the group in which only the temporary groove was produced, artificial wrin- kling was significantly increased compared with age-matched controls. DISCUSSION We previously evaluated the effects of temporary skin fixation on wrinkle formation after 20 weeks of UV-B irradiation using the back skin of hairless mice, and suggested that both production of a temporary groove in the skin and UV-B irradiation are necessary for wrinkle formation (13). In this study, we examined the first ten-week period quan- titatively to determine how early wrinkle formation can occur, and we also studied the different effects of production of a temporary groove. Our results confirm that both the artificial temporary groove in the skin and UV-B irradiation immediately after--but not