Laser induced collagen remodeling: A comparative study in vivo on mouse model

Abstract

Background and 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. Materials and 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-yttriumaluminum 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.

Immunohistochemical investigation of wound healing in response to fractional photothermolysis

“…This upregulation can promote chemotaxis for fibroblasts forming extracellular matrix and collagen, which may result in dermal remodeling or scar formation. 7,21,38,39,42,43,47 Types I and III procollagen mRNA levels peaked at day 21 after CO 2 -laser resurfacing of photodamaged human skin and remained elevated for at least six months. 40 During this dermal remodeling, younger patients seemed to form more new collagen compared with older patients with photodamaged skin 48 and denatured collagen appeared to be metabolized differently according to the depth of damage.…”

“…37 HSP47 expression is upregulated 4 -7 days post-laser intervention and is persistent over three months, 8,34,35,37 leading to increased procollagen and collagen I and III deposition. 40,42,43 Middle energy doses ͑of ϳ30 J / cm 2 ͒ and repeated treatments had the greatest effect on collagen formation, whereas higher energies ͑of ϳ50 J / cm 2 ͒ lead to marked ablative epidermal changes in porcine skin. 44 TGF␤ 1 and TGF␤ 2 40 are activated or induced by different lasers 1,6 2 days following laser irradiation, while TGF␤ 3 expression was increased after 14 days, concomitant with an increased inflammatory infiltrate.…”

A comparison of Q-switched 1064 nm Nd:YAG laser and intense pulsed light in the nonablative rejuvenation on rat model

“…Mature skin tissue is mainly consisted of type collagen, while type III collagen is a newly synthesized one. According to the study of Huaxu Liu, type ß collagen was mainly formed after being treated with Q-switched 1064 nm Nd:YAG laser (20). Our experiment detected the type III procoUagen mRNA expression at different times after the irradiation of two kinds of lights.…”

Effects of neodymium–yttrium–aluminum garnet (Nd:YAG) pulsed high-intensity laser therapy on full thickness wound healing in an experimental animal model

“…The main mechanism behind laser-tissue interaction of the long-pulsed Nd:YAG laser is photo-thermal effect, whereas that of the Q-switched Nd:YAG laser is the photo-mechanical effect. Unlike the long-pulsed Nd:YAG laser, the Q-switched Nd:YAG laser has very short pulse width, therefore a high level of energy can be quickly delivered into tissues and stimulate cellular metabolism with minimal temperature elevation (24,25). After irradiation with the appropriate amount of laser fluence (treated with 1.6 J/cm 2 ) of Q-switched Nd:YAG laser therapy, we observed significantly increased numbers of fibroblasts and collagen fibers, indicating that application of Q-switched Nd: YAG laser therapy promoted the synthesis of growth factors, thereby inducing a more rapid healing process.…”