title: Laser induced collagen remodeling: a comparative study in vivo on mouse model.
abstract: OBJECTIVE
  Many lasers have claimed the clinical efficacy on skin rejuvenation. In this study, the mechanisms of laser induced collagen remodeling were explored systematically on a Kunming (KM) mouse model in vivo by comparing the different non-ablative laser effects using four different laser treatment modalities.
  
  
  METHODS
  The dorsal skin of KM mice was exposed by depilation before the laser treatments. Four laser treatment modalities were used: the 595-nm pulsed dye laser (PDL) (10 ms), 1,320-nm neodymium-yttrium-aluminum garnet (Nd:YAG) laser (0.35 ms), 1,064-nm Nd:YAG laser with Q-switched (5 ns), and long-pulsed (0.3 ms) mode. Each modality exposed one side of the mouse dorsal skin leaving the other side as the contralateral control. Then skin histology, fibroblast number, and the genesis of collagen type I and III were studied by comparing the treatment site and control site at 1 hour, 1 day, 1 week, 3 weeks, 4 weeks, and 8 weeks after laser treatment. Hydroxyproline content of the skin tissue was measured 4 weeks and 8 weeks after laser exposure.
  
  
  RESULTS
  All laser treatments led to marked improvements in dermal layer thickness and collagen fiber density, and the increase in fibroblast number and hydroxyproline content compared with their own controls. Collagen synthesis and remodeling induced by the Q-switched 1,064-nm laser was most effective 4 weeks after treatment, while there was no significant difference among the other three modalities. Among the new collagen genesis after the different laser treatments, collagen type III increased sharply after the Q-switched 1,064-nm laser treatment whereas more collagen type I was elicited by the other laser treatment modalities.
  
  
  CONCLUSIONS
  The efficacy of photo-mechanical effects in promoting more effectively the synthesis of collagen type III, whereas the photo-thermal effect favored more the formation of collagen type I.
authors.affiliation: Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Huaxu
authors.initials: H
authors.lastname: Liu
authors.forename: Yongyan
authors.initials: Y
authors.lastname: Dang
authors.forename: Zhan
authors.initials: Z
authors.lastname: Wang
authors.forename: Xinyu
authors.initials: X
authors.lastname: Chai
authors.forename: Qiushi
authors.initials: Q
authors.lastname: Ren
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D024042:Collagen Type I / Q000378:metabolism*; D024061:Collagen Type III / Q000378:metabolism*; D006909:Hydroxyproline / Q000378:metabolism; D053685:Laser Therapy / Q000379:methods*; D051379:Mice; D008815:Mice, Inbred Strains; D012867:Skin / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III; D006909:Hydroxyproline