308nm Excimer Laser Induced Experimental Hyperpigmentation On The Skin Of Brownish Guinea Pigs

OBJECTIVE To research the experimental hyperpigmentation induced by 308-nm excimer lasers on the skin of brownish guinea pigs and provide experimental evidence for treating vitiligo with 308nm excimer laser.METHODS 10 healthy brwnish guinea pigs were used in this experiment. We select 4 isolated areas on the back of each guinea pigs as control group, low dosage group, moderate dosage group and high dosage group. Each tested group was treated with different dosages of excimer lasers for 2 or 3 times a week, and the subsequent dose is determined as follows: 100 mJ/cm~2 increment if there is no erythema after the initial treatment, 50 mJ/cm~2 increment if there is erythema lasting for less than 24 hours, and no increment if there is erythema lasting for 24 hours or more. If symptomatic erythema (burning, pain) or blistering developed, treatment was withheld until resolution, and then the dose was decreased by 50 mJ/cm~2. Nothing is treated on control group. Efficacy was evaluated at the end of experiment via Fontana-Masson stain, Imokawa's stain and immunohistochemistry method.RESULTS All the guinea pigs had completed the study. Transient erythema and slight desquamating were noticed on some guinea pigs ,which can be controled by decrease the dosage or stop the treatment for several days. Experimental hyperpigmentation can be observed on each test groups while all the untreated areas (controls) remain unchanged. HE stain shows a proliferation on the epidermic cells in the test groups, which correspond to morphological changes caused by ultraviolet on normal epidermic cells. The differences among the 4 groups are proved to be of statistical significances (P<0.05) by either visual evaluation, Fontana-Masson stain or Imokawa's stain. Immunohistochemistry stain shows the number of NOS in the skin tissue tend to be increase after the treatment of excimer lasers. No depigmentation caused by over-irradiation was noticed in the whole experiment.CONCLUSION 308-nm excimer lasers can induce experimental hyperpigmentation on the skin of healthy brownish guinea pigs and there might be a dose-effect relationship between the dosage and pigmental diagree.