Poster presentation, P32

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

Multiphoton microscopy of pigmented reconstructed epidermis: assessment of 3D pigmentation modulation

In situ imaging methods based on Multiphoton Microscopy (MMP) were developed to assess the effects of molecules used to modulate epidermal melanin content. MMP is a non invasive optical imaging technique that allows the three dimensional (3 D) structures of skin to be investigated, even at a sub-cellular resolution. It provides complementary information namely two-photon excited fluorescence (2PEF) and Second Harmonic Generation (SHG). 2PEF signals are emitted by skin endogenous chromophores such as NADP(H), flavins, keratin, melanin or elastin, whereas SHG signals are specific to dense and ordered macromolecular structures such as fibrillar collagen. Here, MMP allowed a non-invasive analysis of the 3 D distribution of melanin at different levels in epidermis, thanks to melanin endogenous fluorescence. First, use of different pigmented reconstructed epidermises showed that MMP could discriminate “in vitro phototypes”, i.e. phototypes II, IV and VI. Second, the efficacy of a whitening compound was tested on pigmented reconstructed epidermises and recorded MMP images were analyzed with specifically-developed software combined with statistical analysis. A significant decrease in epidermal melanin was demonstrated in samples treated with the whitening compound. In this study, MMP appeared to be a relevant methodology to visualize and quantify the 3 D distribution of melanin in epidermis which makes it a promising new diagnostic tool to characterize and evaluate whitening compounds.

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