PracticeUpdate Conference Series: IID 2018

Concanamycin A and ammonium chloride were able to reverse the inhibition of melanogenesis induced by vitamin C and its derivatives by further alkalizing melanosomes. Dr. Lei concluded that vitamin C and its derivatives were found to inhibit tyrosinase activity and melanogenesis. This inhibition was likely due to the acidification of melanosomes. The finding provides a promising strategy for screening of depigmenting agents through acidification of melanosomes and reversible inhibition of tyrosinase. A chromometer in a 3D epidermal model containing functional melanocytes M ichael Bachelor, PhD, of MatTek Corporation in Ashland, Massachusetts, explained that considerable interest has arisen in evaluating effects on skin pigmentation using treatment with new materials, skin care formulations, and as side effects induced by medication. A convenient way to screen such effects employs the MelanoDerm tissue model, a highly differentiated, three-dimen- sional tissue culture model of human epidermis. The model contains normal human melanocytes and keratinocytes. Use of this in vitro model can provide valuable in vitro data as an early screening tool prior to costly clinical trials. Dr. Bachelor and colleagues evaluated pigmentation over 2–3 weeks using a tristimulus chromometer to measure brightness in

MelanoDerm tissue produced with normal human melanocytes from black, Asian, or Caucasian donors. In parallel to measurements taken with the chromometer, total melanin content of tissues was also quantified. Over time, cultures became increasingly pigmented with retention of normal epithelial morphology, with the expected pig- mentation level of donor tissue, that is, black, Asian, or Caucasian, when cultured in media containing α melanocyte-stimulating hormone and β fibroblast growth factor. Several over-the-counter skin lightening products were also evaluated in cultures containing normal human melanocytes from black donors. Over the 2–3 week treatment period, control cultures became increasingly pigmented while tissues treated topically with cos- metic skin-lightening agents containing tyrosinase inhibitors such as kojic acid and magnesium ascorbyl phosphate remained distinctly lighter than control cultures. After 14 days in culture, total melanin content was found to cor- relate inversely with surface reflectance. Dr. Bachelor concluded that the results suggested that the model is useful for evaluating effects on melanogenesis, skin lightening, and other pigmentation phenomena of skin in vitro. In particular, the results highlight two distinct endpoints, total melanin content and skin color measurement, that can be used to evaluate skin pigmentation in vitro.

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IID 2018 • PRACTICEUPDATE CONFERENCE SERIES 17