Systematic evaluations of skin damage irradiated by an erbium:YAG laser: Histopathologic analysis, proteomic profiles, and cellular response

Background: The erbium:yttrium-aluminum-garnet (Er:YAG) laser is used for surgical resurfacing. It has ablative properties with water as its main chromophore. Objective: This study attempted to establish the cutaneous effect and cellular response to Er:YAG laser irradiation using different fluences (7.5 and 15J/cm²). Methods: Female nude mouse was used as the animal model in the study. Physiological parameters were examined and histology was evaluated at 4, 24 and 96. h after laser exposure. A proteomic analysis and immunoblotting were also used to determine the mechanisms of the laser's effect on the skin. Results: Both fluences were associated with a significant increase in transepidermal water loss (TEWL), erythema (a*), and the skin pH at 4 and 24h. In contrast, at 96h, the levels of these parameters had generally decreased to the baseline. The histology examined by light microscopy and transmission electron microscopy (TEM) showed vacuolization, hydropic degeneration and epidermal necrosis of laser-irradiated skin. The higher fluence (15J/cm²) exhibited more-severe disruption of the skin. Bulous and scarring were observed in skin treated with the higher fluence during the recovery period. p53 and p21 proteins were significantly activated in skin following exposure to the laser. However, proliferating cell nuclear antigen and cytokeratin expressions were downregulated by the low fluence (7.5J/cm²). Conclusion: Both proliferation and apoptosis occurred when the laser-irradiated the skin.