Microbeam X-ray diffraction study of lipid structure in stratum corneum of human skin.

Richard G. Haverkamp,Naoto Yagi,Koki Aoyama,Noboru Ohta

doi:10.1371/journal.pone.0233131

Richard G. Haverkamp, Naoto Yagi + Show 2 more

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https://doi.org/10.1371/journal.pone.0233131

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Abstract

Human skin, not previously frozen, was studied by small-angle X-ray diffraction. The samples were folded so that a 6μm X-ray beam passed through the top layer of skin, stratum corneum. Diffraction patterns recorded with this method consisted of peaks at about q = 0.5, 1.0 and 1.4 nm-1 in the direction perpendicular to the skin surface more clearly than in previous studies. These peaks are interpreted to arise from lipids between corneocytes. A simple unit of a linear electron density profile with three minima was used to account for the observed intensity profiles. Combinations of calculated diffraction from models with one, two and three units accounted for the major part of the observed diffraction pattern, showing the diversity in the structure of the intercellular lipids.

Highlights

The top layer of human skin, stratum corneum (SC), serves as a barrier which protects human body from dehydration and penetration of unwanted substances
We demonstrated that the obtained diffraction pattern can be analyzed with a simple model based on the tri-lamellar structure
Orange arcs represent the intercellular lipid layers that run approximately parallel to the skin surface

Summary

Introduction

The top layer of human skin, stratum corneum (SC), serves as a barrier which protects human body from dehydration and penetration of unwanted substances. The barrier function is considered to mostly depend on the lipids that fill the gap of less than 50 nm wide Several lipid molecules, such as ceramides and sphingolipids, are arranged in a lamellar structure with their long axes lying across the gap. Many studies on the intercellular lipid structure have been carried out using electron microscopy, electron diffraction and X-ray diffraction. In X-ray diffraction experiments, SC samples were often separated from skin by trypsin digestion [2,3,4,5] and investigated as whole SC. This method allows control of hydration and temperature and helps identify origins of diffraction peaks [2, 4, 5].

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