Photodynamic therapy inhibits melanogenesis through paracrine effects by keratinocytes and fibroblasts

Summary

Photodynamic therapy (PDT) is a treatment option for skin cancer and premalignant skin diseases and exhibits rejuvenation effects, including reducing fine wrinkles and whitening, on aged skin. In the present study, we investigated the mechanism underlying the whitening effects of PDT on melanocytes in vitro and in vivo. Exposure of melanocytes to PDT in vitro reduced their melanin content and tyrosinase activity without, however, affecting cell survival. Interestingly, melanogenesis was also inhibited by exposing melanocytes to conditioned media of PDT-treated keratinocytes or dermal fibroblasts. This paracrine effect was likely due to a decreased release of melanocyte-stimulating cytokines such as Kit ligand and hepatocyte growth factor from these cells. Furthermore, we observed that PDT reduced mottled hyperpigmentation of photoaged patient skin in vivo, highlighting the clinical importance of skin whitening by PDT.

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