RESUMO
BACKGROUND: The treatment of facial rhytides has traditionally centered around methods that involve removal of the epidermis and superficial dermis, encouraging the production of a new epidermis with collagenesis and remodelling. But all of the resurfacing techniques lead to postoperative complications such as oozing, bleeding, infections, "downtime" as the skin begins to reepithelialize, and the occasional incidence of posttreatment, postinflammatory pigmentary changes. 1320nm and 1064nm wavelengths are nonspecifically absorbed in the human dermis and are unique for its significant horizontal scattering. These wavelengths, when used for localized facial areas, have been shown to produce new collagen formation and improvement in the quality of treated skin. OBJECTIVE: The purpose of this study was to examine the effect of 1320nm Nd: YAG laser and long-pulsed 1064nm Nd: YAG laser irradiation on hairless mouse skin and rat skin. METHODS: In this study, the effect of 1320nm Nd: YAG laser and long-pulsed 1064nm Nd: YAG laser irradiation were examined by Hematoxylin and eosin (H&E) stain, Masson's trichrome stain, immunohistochemical stain for type I collagen and dot-blot hybridization for alpha1(I) procollagen mRNA. RESULTS: In the H&E stain, Masson's trichrome stain, and immunohistochemical stain of the hairless mouse skin, the number of collagen fibers with a greater density of fibers increased, compared to the non-irradiated controls on both the 1320nm Nd: YAG laser and the long-pulsed 1064nm Nd: YAG laser. In the dot-blot hybridization in the hairless mouse, levels of alpha1(I) procollagen mRNA were increased 3.0-fold, 4.8-fold and 5.2-fold at each 1 week, 4 weeks and 12 weeks after irradiation in 1320nm Nd: YAG laser and 1.8-fold and 2.1-fold at each 4 weeks and 12 weeks after irradiation in long-pulsed 1064nm Nd: YAG laser, compared to the non-irradiated controls. But in the 1320nm Nd: YAG laser irradiation on the rat, there is no significant change in the number and density of collagen fibers, compared to the non- irradiated controls. CONCLUSION: These results indicate that the 1320nm Nd: YAG laser and the long-pulsed 1064nm Nd: YAG laser may be a powerful up-regulator of collagen synthesis through significant dermal damage and the 1320nm Nd: YAG laser is better than the long-pulsed 1064nm Nd: YAG laser for collagen synthesis. Therefore, the 1320nm Nd: YAG laser can be more effective clinically than the long-pulsed 1064nm Nd: YAG laser for the treatment of photodamaged skin.