Q-switched 1064-nm dymium-doped yttrium aluminum garnet laser irradiation induces skin collagen synthesis by stimulating MAPKs pathway

The 1064-nm Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser is widely used in clinical practice. However, the effects of 1064-nm Q-switched Nd:YAG laser on skin collagen generation have not been fully elucidated. The objectives of the present study were to investigate whether the 1064-nm Q-switched Nd:YAG laser can be used for non-ablative rejuvenation and to explore the possible mechanism underlying the effects. Six-week-old SKH-1 hairless mice were irradiated by the 1064-nm Nd:YAG laser at fluences of 0, 0.5, 1, 1.5, and 2 J/cm(2), respectively. The contents of hydroxyproline and hydration were detected after laser irradiation. Moreover, hematoxylin-eosin (HE) staining was preformed to evaluate the dermal thickness. Immunofluorescence was used to detect the expressions of MMP-2 and TIMP-1 in the skin after laser irradiation. Furthermore, qRT-PCR was performed to determine the expressions of TGF-beta 1 and Smad3. In addition, the expressions of ERK1/2, p-ERK1/2, p38, p-p38, JNK, ERK5, and collagen were evaluated by Western blotting. The results indicated that the levels of hydroxyproline, hydration, and collagen were markedly increased; both the thickness of dermal was enhanced after low dose of laser treatment. Moreover, the expression of TIMP-1 was significantly increased, whereas the expression of MMP-2 was remarkably decreased after laser irradiation. Meanwhile, TGF-beta 1, Smad3, p-ERK1/2, p-P38, and JNK productions were significantly enhanced in irradiated group compared with the ones non-irradiated. Nevertheless, no significant changes were observed in the expression of ERK5 after irradiation. In summary, our study demonstrated that Q-switched 1064-nm Nd:YAG laser can induce collagen generation, at least in part, through activating TGF-beta 1/Smad3/MAPK signaling pathway.