Contribution of Palmitic Acid to Epidermal Morphogenesis and Lipid Barrier Formation in Human Skin Equivalents.

Arnout Mieremet,Gert Gooris,Abdoelwaheb El Ghalbzouri,Joke A Bouwstra,Andreea Nadaban,Walter Boiten,Richard Helder

doi:10.3390/ijms20236069

Abstract

The outermost barrier layer of the skin is the stratum corneum (SC), which consists of corneocytes embedded in a lipid matrix. Biosynthesis of barrier lipids occurs de novo in the epidermis or is performed with externally derived lipids. Hence, in vitro developed human skin equivalents (HSEs) are developed with culture medium that is supplemented with free fatty acids (FFAs). Nevertheless, the lipid barrier formation in HSEs remains altered compared to native human skin (NHS). The aim of this study is to decipher the role of medium supplemented saturated FFA palmitic acid (PA) on morphogenesis and lipid barrier formation in HSEs. Therefore, HSEs were developed with 100% (25 μM), 10%, or 1% PA. In HSEs supplemented with reduced PA level, the early differentiation was delayed and epidermal activation was increased. Nevertheless, a similar SC lipid composition in all HSEs was detected. Additionally, the lipid organization was comparable for lamellar and lateral organization, irrespective of PA concentration. As compared to NHS, the level of monounsaturated lipids was increased and the FFA to ceramide ratio was drastically reduced in HSEs. This study describes the crucial role of PA in epidermal morphogenesis and elucidates the role of PA in lipid barrier formation of HSEs.

Highlights

The human skin protects the body from desiccation and environmental challenges through the establishment of a multilayered barrier system
We showed that addition of the bioactive lipid palmitic acid (PA) to the culture medium of human skin equivalents (HSEs) supports a well-orchestrated epidermal morphogenesis
Irrespective of PA level in the culture medium, the stratum corneum (SC) lipid barrier composition and organization were similar. This indicates that the original level of PA was adequate and that the aberrant lipid barrier formation in HSEs is not

Summary

Introduction

The human skin protects the body from desiccation and environmental challenges through the establishment of a multilayered barrier system. The main physical barrier is formed by the outermost layer of the epidermis, which is the stratum corneum (SC). This SC consists of corneocytes embedded in a lipid matrix (Supplementary Figure S1a–c). Sophisticated in vitro tools which resemble native human skin (NHS) to a high extent are three-dimensional human skin equivalents (HSEs). These are widely applied in preclinical screenings and for research purposes to increase understanding of skin biology and epidermal barrier formation in healthy and diseased phenotypes [1,2,3,4,5,6]. HSEs mimic NHS in morphologic appearance, including the presence of distinguishable epidermal layers and formation of the SC [7,8,9]

Objectives

Methods

Conclusion