Measurement of Skin Pigmentation Using a Chromameter in a 3-Dimensional Epidermal Model Containing Functional Melanocytes

Cosmetic or skin care pharmaceutical formulations augment skin pigmentation either for the intended purpose of skin lightening or as an off-target effect.   A convenient way to screen such effects utilizes the MelanoDerm tissue model, a highly differentiated, three-dimensional tissue culture model of human epidermis containing normal human melanocytes and keratinocytes.  Use of this model can provide valuable in vitro data as an early screening tool prior to the commencement of costly clinical trials.  In this study, pigmentation was evaluated over the course of 2-3 weeks using a tristimulus chromometer to measure brightness (L*) in MelanoDerm tissue produced with normal human melanocytes from Black, Asian, or Caucasian donors.  In parallel to measurements taken with the chromameter, total melanin content of tissues was also quantified.  Over time, cultures became increasingly pigmented with retention of normal epithelial morphology with the expected pigmentation level of the donor tissue, i.e. Black>Asian>Caucasian when cultured in media containing alpha-MSH and beta-FGF.  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 cosmetic skin lightening agents containing tyosinase inhibitors such as kojic acid and magnesium ascorbyl phosphate remained distinctly lighter when compared to control cultures.  After 14 days in culture, total melanin content was found to inversely correlate with surface reflectance (L*).  The results described herein suggest that this model is useful for evaluating effects on melanogenesis, skin lightening, and other pigmentation phenomena of skin in vitro.  In particular, this study highlights two distinct endpoints, total melanin content and skin color measurement that can be used to evaluate skin pigmentation in vitro.

MelanoDerm, Fontana-Masson, Lvalues, skin color, MEL-300-A, MEL-300-B, MEL-300-C, EPI-100-LLMM, EPI-100-NMM-113, chromameter, Konica Minolta spectrometer, handheld spectrometer, Solvable, melanin assay

Kojic acid, 1,3 butanediol, spot remover