Melanosome transfer evaluation by quantitative measurement of Pmel 17 in human normal melanocyte-keratinocyte co-cultures: effect of an Alaria esculenta extract.

Numerous strategies have been proposed to evaluate melanosome transfer. Methods allowing quantitative measurements of this transfer in human normal cellular models, however, are very few and often require extremely specialized devices that are expensive and difficult to use. As a part of the melanosome-specific membrane-bound glycoprotein, Pmel 17 is released from the melanosome membrane by ectodomain shedding. We reasoned, therefore, that it should be possible to evaluate melanosome transfer by quantifying this "soluble" Pmel 17. The Pmel 17 ELISA assay developed permits a detection of 10 to 1000 ng/ml of this glycoprotein in human normal melanocyte-keratinocyte co-culture media. As expected, niacinamide, a well-known melanosome transfer inhibitor, significantly reduced the Pmel 17 quantities found in the culture media. This validated our experimental design. We then used our model to show that a whitening cosmetic active compound, i.e., an Alaria esculenta extract, can (at least in part) enable a significant decrease in the melanosome transfer to produce a lightening effect without affecting melanin production. This research provides a simple and efficient method to quantify melanosome transfer in a human normal co-culture model. It is a particularly useful tool with which to facilitate the development of new active whitening compounds.

In vivo vitiligo induction and therapy model: double-blind, randomized clinical trial.

In this study, we developed an in vivo vitiligo induction model to explore the underlying mechanisms leading to Koebner's phenomenon and to evaluate the efficacy of therapeutic strategies. The model consisted of 12 pigmented test regions on the back of generalized vitiligo patients that were exposed to three Koebner induction methods: cryotherapy, 755 nm laser therapy, and epidermal abrasion. In addition, four cream treatments (pimecrolimus, tacrolimus, steroid and placebo) were randomly applied. Koebnerization was efficiently induced by all three induction methods. In general, cryotherapy was the best method of Koebner induction, followed by 755 nm laser therapy and epidermal abrasion. Reproducible results were obtained, which showed enhanced depigmented surface areas and higher amounts of T lymphocytes in placebo-treated test zones compared to active treated areas. Tacrolimus and local steroids were better inhibitors of Koebner's process (P < 0.05) compared to pimecrolimus. Our in vivo vitiligo induction model is very informative to investigate vitiligo induction and to determine the efficacy of topical treatments in vitiligo. This proof of concept confirms the efficient comparison of head-to-head therapeutic strategies intra-individually in a standardized, specific and better timed way.