Non-ablative collagen remodeling initiated by different laser effects: A comparative study on mouse model

Many lasers have claimed the clinical efficacy on skin rejuvenation. Systematic and comparative studies are needed to compare different laser effects and probe into the mechanism of laser skin rejuvenation. We performed this study to compare collagen remodeling with different laser effects on mice model in vivo. After depilation, the back skin of KM mice was used for the study. The 595nm pulsed dye laser (10ms), 1320nm Nd:YAG laser(350 μs), 1064nm Q-switched (5ns) and long-pulsed Nd:YAG(0.3ms) lasers were applied based on optimal tissue reaction fluence test to irradiate one side of the mice back and leave the other side as the control. Then the collagen remodelling was evaluated at 0, 1, 7, 21, 30 and 60 days, with biophysical parameters' measurements, histological and biochemical examination. All lasers applied showed a statistical improvement in skin elasticity, dermal thickness and synthesis of hydroxyproline compared with their own controls. The Q-switched 1064-nm laser resulted in greater improvement of skin elasticity, dermal thickness, and higher synthesis of hydroxyproline than the other lasers after two months of treatments, while there was no significant difference among the 595nm, 1320nm and long-pulsed 1064nm lasers. Collagen type III increased markedly after the Q-switched 1064-nm laser treatment whereas more collagen type I was elicited by the 1320-nm laser.