Analytical method to examine the effects of carbon dioxide lasers on skin: A study using wrinkles induced in hairless mice

Background and Objective: Investigation of the wrinkle smoothing process elicited by CO2 laser treatment is important for understanding the mechanism involved in their repair. Study Design/Materials and Methods: Hairless mice with wrinkles induced in their dorsal skin by long-term exposure to ultraviolet radiation in the wavelength range of 290-320 nm were treated with a CO2 laser. By using this model, we investigated the external appearance, histologic changes, and the mechanical properties of the skin during the wrinkle repair. Results: Laser treatment with an appropriate intensity caused wrinkles to smooth completely. In the healing process, reepithelialization and collagen tissue regeneration in the upper dermis was observed. However, marked changes in the skin were noted, such as increases in the collagen layer and in the skin thickness, and changes in the mechanical properties of the skin, despite the favorable external appearance. Conclusion: An abnormal state characterized by excessive collagen regeneration and other changes in the dermis occur concomitantly with wrinkle smoothing. Lasers Surg. Med. 28:348-354, 2001. (C) 2001 Wiley-Liss, Inc.