Recovery of pigmentation following selective photothermolysis in adult zebrafish skin: clinical implications for laser toning treatment of melasma

Abstract

In recent years, laser toning has gained popularity for the treatment of melasma, and tyrosinase inhibitors are conventionally used to prevent its recurrence after this treatment. The effectiveness of this treatment modality, however, is still questionable, and additional in vivo studies are needed to validate the method. In this study, we used adult zebrafish skin as an adult melanocyte regenerative system and examined the simulated human skin response to laser toning. Melanosomes regenerated after selective photothermolysis, and these organelles showed a bi-directional translocation pattern in accordance with the changes of intact melanosome patterns. Furthermore, a tyrosinase inhibitor, 1-phenyl-2-thiourea (PTU), completely blocked melanosome regeneration after laser irradiation, but this inhibitor failed to prevent melanosome regeneration after the medication was discontinued. Finally, arbutin and kojic acid, the commercially available tyrosinase inhibitors, slowed down but did not completely block melanosome regeneration. Based on these findings, we describe the limitations of laser toning treatment of melasma and the combined use of tyrosinase inhibitors. We suggest that melanosomes in adult zebrafish skin can be utilized for studying melanosome regeneration response to laser irradiation and for developing a system to assess the comparative efficacy of melanogenic regulatory compounds.

Key Words::

• laser
• melanosome
• photothermolysis
• tyrosinase
• zebrafish

Acknowledgment

The authors are grateful to Dr. Vincent J. Hearing at National Institutes of Health, Bethesda, MD, for providing antibodies for the study.

Declaration of interest: The authors have no conflicts of interest. The authors alone are responsible for the content and writing of the paper.