Altogether these results could become the basis to develop new approaches aiming to rebalance the skin microbiota, which is modified during the aging process.

UV irradiation is a major environmental factor causing skin dryness, aging and cancer. UVB in particular triggers cumulative DNA damage, oxidative stress and mitochondrial dysfunction. The objective of our study was to provide both qualitative and quantitative analysis of how mitochondria respond to UVB irradiation in normal human epidermal keratinocytes (NHEK) of healthy donors, with the rationale that monitoring mitochondrial shape will give an indication of cell population fitness and enable the screening of bioactive agents with UVB-protective properties. Our results show that NHEK undergo dose-dependent mitochondrial fragmentation after exposure to UVB. In order to obtain a quantitative measure of this phenomenon, we implemented a novel tool for automated quantification of mitochondrial morphology in live cells based on confocal microscopy and computational calculations of mitochondrial shape descriptors. This method was used to substantiate the effects on mitochondrial morphology of UVB irradiation and of knocking-down the mitochondrial fission-mediating GTPase Dynamin-related protein 1 (DRP1). Our data further indicate that all the major mitochondrial dynamic proteins are expressed in NHEK but that their level changes were stronger after mitochondrial uncoupler treatment than following UVB irradiation or DRP1 knock-down. Our system and procedures might be of interest for the identification of cosmetic or dermatologic UVB-protective agents.

BackgroundLine‐field confocal optical coherence tomography (LC‐OCT) is an imaging technique providing “optical biopsies” of the skin in real time and non‐invasively. At a center optical wavelength of 1.3 µm, this innovative technology can be applied to dermo‐cosmetic product development due to both high image resolution (~2 µm) and sufficient penetration (~0.5 mm). Nevertheless, the precise dermal area analyzed with LC‐OCT has never been identified. In this study, the objective was to compare LC‐OCT images with histological sections of the same area, in order to validate a new method for in vivo and non‐invasive quantification of superficial dermis thickness. Once validated, this standardized and quantitative method was used to assess age‐related changes of the superficial dermis.Materials and MethodsEx vivo LC‐OCT acquisitions and hematoxylin‐eosin‐safran staining were performed on a panel of four healthy Caucasian female volunteers. In vivo LC‐OCT study of skin aging was performed on a panel of 37 healthy Caucasian female divided into five different age‐groups.ResultsComparison with histological sections revealed that LC‐OCT images allow the visualization and the quantification of the superficial portion of papillary dermis. Applied to different age‐group of volunteers, LC‐OCT images show a constant decrease in this superficial dermis thickness with age.ConclusionsIn conclusion, we have introduced LC‐OCT as a novel technique for in vivo and non‐invasive evaluation of superficial dermis thickness. This approach could be used in the future to demonstrate visually and quantitatively the capacity of a dermo‐cosmetic active ingredient to renormalize the structural properties of the dermis.

No abstract

The LIP (Logarithmic Image Processing) framework is classically devoted to grayscale images. The aim of the present study is to extend this framework to color images. This new model is noted LIPC for LIP Color. It does not consist in applying the LIP Model to each channel R, G, B of a color image. We define the transmittance of color images in order to give a physical justification, on which will be based the definition of logarithmic operators like addition, subtraction and scalar multiplication, respectively noted in the LIPC : c , c and c . As for the classical LIP Model, the laws c and c define a vector space structure on the space of images which enables us to present notions requiring such a structure. For example, we define a color logarithmic interpolation by associating to a pair (F, G) of images the interval [F, G], set of barycenters of F and G. A new notion of color contrast is defined, which satisfies sub-additivity and homogeneity for scalar multiplication. This notion is proved to be efficient for edge detection. We note that the vector space structure opens the way to a lot of developments concerning the definition of metrics, norms, scalar products...and to transfer to LIPC gauges theory, duality theory... In this initial paper, we preferred insist on applications of the LIPC. For example, color prediction is presented and discussed as well as stabilization of images by dynamic range centring and enhancement of under-lighted images. Concerning the implementation of the LIPC operators and algorithms, informations are given on their execution time.