Identification of the fate and regenerative mechanism of zebrafish melanocyte progenitor cells and melanocytes after laser‐induced pigment ablation

Background and Objectives Lasers are known to be the most effective treatment modality for pigmentary skin diseases. However, melanocytes and melanin pigment often recur or leave post‐inflammatory hyperpigmentation after the laser procedure. Studies have reported on the role of progenitor cells in pigment cell regeneration, which can be constantly replenished through mitosis. However, the response of unpigmented melanocyte progenitor cells to laser treatment is poorly understood. In this study, we used adult zebrafish skin as the melanocyte regenerative system and examined the response of melanocyte progenitor cells to laser photothermolysis. Materials and Methods The two groups of adult zebrafish were irradiated with 1064 nm wavelength laser system of Q‐switched neodymium:yttrium–aluminum–garnet (Nd:YAG) laser with 0.3 or 0.7 J·cm−2. We compared the regeneration of pigment at different energy levels by measuring new melanocyte counts and pigment area. We traced and quantitatively compared the melanocyte lineage cells by immunohistochemical staining using specific markers such as sox10, mitfa, and dct during the regeneration process. Three repetitive laser ablations were also held to test the postinflammatory hyperpigmentation. Results After the laser ablation of melanocytes, most of the new melanocytes appeared between Days 5 and 10. In high‐energy irradiation of 0.7 J·cm−2, the unpigmented mitfa‐expressing cells showed significant decrease (p