The Human Skin Barrier Is Organized as Stacked Bilayers of Fully Extended Ceramides with Cholesterol Molecules Associated with the Ceramide Sphingoid Moiety

Iwai, Ichiro and Han, HongMei and den Hollander, Lianne and Svensson, Stina and Oefverstedt, Lars-Goeran and Anwar, Jamshed and Brewer, Jonathan and Bloksgaard, Maria and Laloeuf, Aurelie and Nosek, Daniel and Masich, Sergej and Bagatolli, Luis A. and Skoglund, Ulf and Norlen, Lars (2012) The Human Skin Barrier Is Organized as Stacked Bilayers of Fully Extended Ceramides with Cholesterol Molecules Associated with the Ceramide Sphingoid Moiety. Journal of Investigative Dermatology, 132 (9). pp. 2215-2225. ISSN 0022-202X

Abstract

The skin barrier is fundamental to terrestrial life and its evolution; it upholds homeostasis and protects against the environment. Skin barrier capacity is controlled by lipids that fill the extracellular space of the skin's surface layer-the stratum corneum. Here we report on the determination of the molecular organization of the skin's lipid matrix in situ, in its near-native state, using a methodological approach combining very high magnification cryo-electron microscopy (EM) of vitreous skin section defocus series, molecular modeling, and EM simulation. The lipids are organized in an arrangement not previously described in a biological system-stacked bilayers of fully extended ceramides (CERs) with cholesterol molecules associated with the CER sphingoid moiety. This arrangement rationalizes the skin's low permeability toward water and toward hydrophilic and lipophilic substances, as well as the skin barrier's robustness toward hydration and dehydration, environmental temperature and pressure changes, stretching, compression, bending, and shearing.