RESUMO
BACKGROUND: Non-ablative dermal remodeling and ablative skin resurfacing are currently well-established skin treatment modalities. Fractional laser was recently introduced as a new concept for laser skin rejuvenation, and is characterized by creation of a dense pattern of epidermal and dermal microthermal treatment zones (MTZs). However, the precise mechanisms of dermal remodeling by Er:glass fractional laser treatment are largely unknown. OBJECTIVE: The purpose of this study was to investigate the effect of 1,550 nm Er:glass fractional laser treatment on dermal collagen synthesis and expression of TGF-beta1, a potent cytokine involved in collagen synthesis. METHODS: We treated hairless mice with several power densities (5 W 5 mJ~20 W 20 mJ), and examined the tissue samples on days 1, 30, and 90 after treatment. We analyzed the penetrating depth of laser treatment by determining dermal response through assessment of type I collagen synthesis and TGF-beta1 expression by H&E, Masson-trichrome staining, western blot analysis and immunohistochemistry staining. RESULTS: We observed, through H&E staining, that increasing the pulse energy of fractional laser treatment correlated with increasing depth of MTZ. Also, fractional laser treatment increased type 1 collagen synthesis on days 30 and 90, energy dependently. Immunohistochemical study showed that fractional laser treatment increased expression of type I collagen and TGF-beta1, energy dependently, with TGF-beta1 expression peaking on day 1. In addition, according to western blot analysis, expressions of TGF-beta1 and type I collagen were up-regulated in an energy- dependent manner. CONCLUSION: Er:glass fractional laser induced dermal remodeling by up-regulation of TGF-beta1 and type I collagen synthesis, and may be a promising modality for skin rejuvenation.