Abstract
Q-switched ruby laser is widely used in therapy of cutaneous pigmented cells. Its pulses cause selective damage to melanin granules in cutaneous pigmented cells. However, the mechanism of selective destruction of pigmented cells has not been well described. Therfore, using Mexican hairless dog descendants, we studied the histological changes after 25-ns, Q-switched ruby laser irradiation. Gross observation and light microscopy were performed. With radiant exposures of 1.5J/cm2 or greater, immediate whitening appeared, and depigmentation continued until repigmentation occured in day 28. Disruption of melanin granules was seen immediately by light microscopy. Over the next seven days, epidermal necrosis was followed by regeneration of depigmented epidermis. 28 days after irradiation, melanin garanules appeared in hair follicles and basal cell layer. By 16 weeks, melanin pigmentation had returned. The style of regeneration of melanin granules coincided with the one of human's Neavus Spilus. This study suggested the posibility of Mexican hairless dog descendants' skin as a model of epidermal pigmented lesion in human.
