ABSTRACT
BACKGROUND: The occlusive patch test developed for assessing topical retinoids activity in human skin has been extended as a short-term screening protocol for anti-ageing agents. In this model, biopsies are performed at the end of the occlusion period for morphological and immuno-histochemistry analysis. Multiphoton microscopy is a recent non-invasive imaging technique that combined with image processing tools allows the in vivo quantification of human skin modifications. OBJECTIVE: To validate with gold standards of anti-ageing that are retinoids, the relevance of multiphoton microscopy for kinetic and quantitative assessment in this model. METHODS: Twenty women, aged 50-65 years, were enrolled. Retinol 0.3% (RO) and Retinoic acid 0.025% (RA) were applied to the dorsal photo-damaged side of their forearm under occlusive patches for 12 days. A patch alone was applied to a third area as control. Evaluation was performed at day D0, D12 (end of treatment), D18 and D32 using multiphoton microscopy. Epidermal thickness, normalized area of the dermal-epidermal junction (DEJ) and melanin density were estimated using 3D image processing tools. RESULTS: Main significant results are: Epidermal thickening at D12, D18 and D32 with RO and at D12, D18 with RA vs. baseline and vs. CONTROL: Increased DEJ undulation at D32 with RO and at D12 with RA vs. baseline and vs. CONTROL: Decreased melanin content with RO (at D12 and D18 vs. baseline and at D32 vs. baseline and vs. control) and with RA (at D12 vs. baseline). CONCLUSIONS: This study shows that multiphoton microscopy associated to specific 3D image processing tools allows cutaneous effects induced by topical retinoids in this in vivo model to be non-invasively detected, quantified and followed over time. This innovative approach could be applied to the evaluation of other active compounds.
