Comprehensive characterization of the structure and properties of human stratum corneum relating to barrier function and skin hydration: modulation by a moisturizer formulation.

The stratum corneum (SC) is key in the maintenance of the biomechanical barrier and hydration of skin. Our previous investigations showed beneficial effects of a combination of emollients on water capture and retention and protein and lipid organization, all of which are linked to dryness and dry skin damage. Here, we show how a formulation containing an emollient combination ("Trio") and its basal formulation (placebo) impacted the descriptors of SC hydration in SC layers. Only the Trio formulation-not its placebo formulation-modified SC biomechanical drying stress behaviour and imparted a high capacity to protect it from dehydration. This was in accordance with findings at the molecular level using Raman analyses and at the structural level using cryo-scanning electron microscopy (SEM). After topical application, only the Trio formulation profoundly increased lateral packing of lipids and their compactness. Cryo-SEM showed that, unlike the placebo formulation, the Trio formulation prevented the water loss when applied before the dehydration process. In conclusion, these studies demonstrate that stresses in the SC due to dehydration can be alleviated using a formulation containing emollients that interact with the SC lipid components.

IL-1ß induces thymic stromal lymphopoietin and an atopic dermatitis-like phenotype in reconstructed healthy human epidermis.

Atopic dermatitis (AD) is a common skin inflammatory disease characterized by the production of thymic stromal lymphopoietin (TSLP) and marked TH 2 polarization. Recent studies suggest that IL-1ß contributes to the development of AD skin inflammation. Here, we have investigated the impact of IL-1ß signalling on the epidermal homeostasis of both healthy subjects and AD patients [with functional filaggrin (FLG) alleles], with particular attention to TSLP production and keratinocyte differentiation. In healthy reconstructed human epidermis (RHE), IL-1ß promoted (i) robust secretion of TSLP in an NF-κB-dependent manner and (ii) a significant decrease in the expression of filaggrin and other proteins of the epidermal differentiation complex. These effects were prevented by treatment of RHE with the anti-IL-1ß mAb canakinumab and by the IL-1 receptor antagonist anakinra. Interestingly, RHE generated from AD donors behaved like that of healthy individuals and showed comparable responses to IL-1ß signals. Collectively, our results suggest that IL-1ß may be an early key mediator for the acquisition of an AD phenotype through induction of TSLP and alteration of the epidermal homeostasis. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.