cqvip:Objective: To quantitatively examine the dynamics of molecular alterations in volved in dermal remodeling after carbon dioxide (CO2) laser resurfacing of phot odamaged human skin. Design: Serial in vivo biochemical analyses after laser therapy. Setting: Academic referral center, Department of Dermatology, University of Mich igan, Ann Arbor. Subjects: Volunteer sample of 28 adults, 48 to 76 years old, wi th clinically evident photodamage of the forearms. Intervention: Focal CO2 laser resurfacing of photodamaged forearms and serial biopsies at baseline and variou s times after treatment. Main Outcome Measures: Reverse transcriptase real-tim e polymerase chain reaction technology and immunohistochemistry were used to ass ess levels of type I and type III procollagens; matrix metalloproteinases (MMPs) 1, 3, 9, and 13; tropoelastin; fibrillin; primary cytokines interleukin 1β an d tumor necrosis factor α ; and profibrotic cytokine transforming growth factor β 1. Results: Production of type I procollagen and type III procollagen messen ger RNA peaked at 7.5 and 8.9 times baseline levels, respectively, 21 days after treatment and remained elevated for at least 6 months. Increases in messenger R NA levels of several cytokines (interleukin 1β , tumor necrosis factor a, and t ransforming growth factor β 1) preceded and/or accompanied changes in collagen levels. Marked increases in messenger RNA levels of MMP- 1 (39 130- fold), MMP - 3 (1041- fold), MMP- 9 (75- fold) , andMMP- 13 (767- fold)were noted. Le vels of fibrillin and tropoelastin rose in a delayed fashion several weeks after treatment. Conclusions: The biochemical changes seen after CO2 laser resurfacin g proceed through a well-organized and highly reproducible wound healing respo nse that results in marked alterations in dermal structure. These quantitative c hanges may serve as a means for comparison as other therapeutic modalitiesmeant to improve the appearance of photodamaged skin are evaluated.
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