527 Long-term melatonin treatment stimulates melanin production as well as melanocyte dendricity and proliferation in human epidermis ex vivo

Abstract

The pigmentary activities of the neurohormone, melatonin, have long fascinated dermatologists. Yet, cell culture reports are contradictory, and it remains unclear how melatonin alters melanocyte physiology in human epidermis. Thus, we have asked in healthy, organ-cultured, full-thickness human eyelid skin whether melatonin stimulates/inhibits melanin production by epidermal melanocytes that operate within their natural skin habitat. By assessing melanin content, tyrosinase activity in situ, melanocyte number, proliferation, and dendricity (gp100/Ki-67 IF), we show here that, after 3 days of organ culture, 200ug/mL melatonin initially reduces the epidermal melanin content, but without affecting tyrosinase activity or melanocyte proliferation/number (no significant changes seen for 100ug/mL).