This article is available online at http://www.jlr.org complex and specifi c architecture of the inter-corneocyte lipid matrix ( 2 ) composed of a mixture of ceramides, cholesterol, and long-chain fatty acids. Ultrastructural studies, using electron microscopy and diffraction techniques, have revealed that these lipids are organized in stacked bilayers that are predominantly parallel to the skin surface ( 3-5 ). Part of the lipids is covalently bound to the corneocytes whereas another part represents the "free lipids" removable by solvent extraction.X-ray diffraction is an excellent technique for studying the spatial organization of the intercellular matrix because the lipid molecules are highly ordered and oriented in a crystalline structure. This technique has provided a number of important results with regard to the SC structure. In particular, small-angle X-ray scattering (SAXS) gives information on the inter-bilayer distance in the multi-lamellar lipid structures, whereas the wide-angle X-ray scattering (WAXS) data contain information about the in-plane crystalline arrangement of lipids (lattice type).Most of the SAXS studies of human SC fi nd refl ections corresponding to ‫ف‬ 4.5 nm and ‫ف‬ 6.5 nm inter-bilayer spacings ( 4, 6, 7 ). Some studies have also detected a refl ection corresponding to a spacing of 11-13.5 nm ( 6, 8 ), referred to as the "long periodicity phase" ( 6 ). These data indicate that the SC lipid matrix has a complex organization into multiple sublayers or even phase-separated domains with different lamellar repeat distances.Similar complexity is found at the molecular level using WAXS, where two sets of peaks are found, corresponding to orthorhombic (peaks at 0.41 and 0.37 nm) and hexagonal (peak at 0.41 nm) packing of the lipid chains. In addition, a fraction of lipids might exist in a fl uid or amorphous state, which would then contribute to the broad band corresponding to an average distance of 0.46 nm. Abstract Lipid and protein components of the stratum corneum (SC) are organized in complex supramolecular arrangements. Exploring spatial relations between various possible substructures is important for understanding the barrier function of this uppermost layer of epidermis. Here, we report the fi rst study where micro-focus X-ray scattering was used for assessing fi ne structural variations of the human skin barrier with micrometer resolution. We found that the scattering profi les were unchanged when scanning in the direction parallel to the SC surface. Furthermore, small-angle scattering profi les did not change as a function of depth in the SC, confi rming that the lipid lamellar spacings remained the same throughout the SC. However, the wide-angle scattering data showed that the orthorhombic phase was more abundant in the middle layers of the SC, whereas the hexagonal phase dominated in the surface layers both at the external and the lowest part of the SC; i.e., the lipids were most tightly packed in the middle region of the SC. Taken together, our results demonstrate that micro...

The extracellular matrix of the dermis is a complex, dynamic system with the various dermal components undergoing individual physiologic changes as we age. Age-related changes in the physical properties of collagen were investigated in particular by measuring the effect of aging, most likely due to the accumulation of advanced glycation end product (AGE) cross-links, on the nanomechanical properties of the collagen fibril using atomic force microscope nano-indentation. An age-related decrease in the Young’s modulus of the transverse fibril was observed (from 8.11 to 4.19 GPa in young to old volunteers, respectively, P <0.001). It is proposed that this is due to a change in the fibril density caused by age-related differences in water retention within the fibrils. The new collagen–water interaction mechanism was verified by electronic structure calculations, showing it to be energetically feasible.

The hydration capacities of a biomimetic polymer, 2-methacryloyloxethylphosphorylcholine polymer (pMPC), alone and microencapsulated, in association with another well known hydrating polymer, Hyaluronic acid, were investigated in vitro on skin models and in vivo on volunteers by using confocal Raman microspectroscopy. The hydration impact and the relative water content in the Stratum corneum were calculated from the Raman spectra using the OH (water)/CH3 (protein) ratio. Moreover, the follow-up of the presence of pMPC through the Stratum corneum was possible with confocal Raman microspectroscopy, using a characteristic vibration of pMPC, different from that of the encapsulating material. From our in vitro measurements, the improved hydration of the Stratum corneum was confirmed by the use of the encapsulated form of pMPC, which was higher when combined with Hyaluronic acid. On the basis of these in vitro findings, we validated this trend in in vivo measurements on 26 volunteers, and found a good correlation with the in vitro results. Mechanical and ultrastructural studies have been carried out to demonstrate the positive effects of the pMPC on the Stratum corneum function, namely the interaction with lamellar lipids and the plasticizing effects, which are both supposed to spell out the moisturizing effect. This study demonstrates the efficiency of a original hydrating agent, pMPC, entrapped with Hyaluronic acid in a new type of microcapsules by the use of a novel tool developed for both in vitro and in vivo approaches. This indicates a new step to evaluate and improve new moisturizers in response to the cosmetics or dermatologic demands.

The in vitro and in vivo data demonstrate that based on its multiple interactions within human skin, LR2412 has potential to partially correct the signs of ageing in intrinsically and photoaged skin.

During the formation of the stratum corneum (SC) barrier, the extracellular spaces of viable epidermis, rich in glycans, are filled with a highly organized lipid matrix and the plasma membranes of keratinocytes are replaced by cornified lipid envelopes. These structures comprise cross‐linked proteins, including transmembrane glycoproteins and proteoglycans, covalently bound to a monolayer of cell surface ceramides. Little is known about the presence and distribution of glycans on the SC corneocytes despite their possible involvement in SC hydration, cohesion and desquamation. In this work, we visualized ultrastructurally and quantified the distribution of glycans on the surface of native and delipidated corneocytes. The cells were harvested at different depths of the SC, allowing us to define the relationship between the distribution of various glycans, proteoglycans and glycoproteins, and other changes occurring in SC. At the cell periphery, we found a correlation between the depth‐related alterations of corneodesmosome glycoproteins and α‐d‐mannosyl and N‐acetyl‐d‐glucosamine‐labelling patterns. Elimination of the terminal sugars, α‐linked fucose and α‐(2,3) linked sialic acid, was less abrupt, but also the initial extent of their peripheral distribution was overall lower than that of concanavalin A and wheat germ agglutinin lectin‐detected glycans. Diffuse labelling of heparan sulphate glycosaminoglycans disappeared completely from the outermost corneocytes, whereas that of several simple carbohydrates could be detected at all SC levels. Our results suggest that specific glycan distribution may participate in the progressive changes of SC, as it evolves from the SC compactum to the SC disjunctum, towards desquamation.

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