title: Molecular mechanisms of nonablative fractionated laser resurfacing.
abstract: BACKGROUND
  Nonablative fractionated laser resurfacing improves the texture of treated skin, but little is known about the molecular mechanisms that underlie clinical improvements.
  
  
  OBJECTIVE
  We sought to examine and quantify the time course and magnitude of dermal matrix changes that occur in response to nonablative fractionated laser resurfacing, with the dual goals of better understanding the molecular mechanisms that underlie clinical improvements and of gaining knowledge that will enable evidence-based treatment parameter optimization.
  
  
  METHODS
  Twenty patients (mean age 58 years) with photodamaged skin were focally treated on dorsal forearms with a nonablative fractionated laser. Serial skin samples were obtained at baseline and at various times after treatment. Biopsies were examined with real-time polymerase chain reaction technology and immunohistochemical techniques.
  
  
  RESULTS
  Laser treatment resulted in an initial inflammatory response as indicated by statistically significant induction of proinflammatory cytokines (interleukin-1β and tumour necrosis factor-α). This was followed by substantial increases in levels of several matrix metalloproteinases and later by significant induction of type I collagen. Dermal remodelling was noted with both low and high microbeam energy treatment parameters.
  
  
  CONCLUSIONS
  Nonablative fractionated laser resurfacing induces a well-organized wound-healing response that leads to substantial dermal remodelling and collagen induction. Surprisingly, only minimal differences were observed between lower and higher microbeam energy settings. These data suggest that lower microbeam energy/higher microbeam density treatment parameters, which are generally better tolerated by patients, may yield dermal changes similar to those that result from higher microbeam energy/lower microbeam density treatment parameters.
authors.affiliation: Department of Dermatology, University of Michigan Medical School, Ann Arbor, MI 48109-0314, USA. jorringe@umich.edu
authors.forename: J S
authors.initials: JS
authors.lastname: Orringer
authors.forename: L
authors.initials: L
authors.lastname: Rittié
authors.forename: D
authors.initials: D
authors.lastname: Baker
authors.forename: J J
authors.initials: JJ
authors.lastname: Voorhees
authors.forename: G
authors.initials: G
authors.lastname: Fisher
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D024042:Collagen Type I / Q000096:biosynthesis / Q000235:genetics; D024061:Collagen Type III / Q000096:biosynthesis / Q000235:genetics; D062109:Dermatologic Surgical Procedures; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008875:Middle Aged; D012867:Skin / Q000378:metabolism / Q000473:pathology; D015595:Skin Aging; D012879:Skin Physiological Phenomena; D014945:Wound Healing / Q000502:physiology*; D055815:Young Adult
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III; D020782:Matrix Metalloproteinases