Abstract
In previous publications, we could establish that a hallmark of human skin aging is the breakdown of the epidermal calcium gradient. This redistribution of calcium has many implications, including a restructuring of the cornified envelope, a reduced epidermal barrier function, a change in lipid composition, a reduced skin hydration, and an increased skin pH. Especially the age-dependent change in the cornified envelope composition was solely studied in human foreskin samples. The aim of this study was to confirm that this effect is neither restricted to UV-protected skin area nor limited to a specific sex. In addition, we wanted to show that the collapse of the epidermal calcium gradient is not only a hallmark of human skin aging, but is also evolutionarily conserved in mammals. By using such techniques as IHC, Western blot analysis, and RT-PCR, we could demonstrate the following: (1) A change in the epidermal calcium gradient is in fact the most important sign of epidermal aging in mammals (as shown in female human eyelids and mouse skin samples of the external ear-shell); (2) The disturbed calcium homeostasis affects the expression and crosslinking of most cornified-envelope-specific genes such as loricrin and filaggrin. In this way, we could establish that the age-dependent altered composition of the cornified envelope is a typical sign of skin aging not only in humans, but in mice, too. This makes the mouse an important model organism to study these changes.
Highlights
The epidermis is the main protective barrier against the surrounding environment in most vertebrate organisms
To check if the breakdown of the epidermal calcium gradient is a general hallmark of Toskin check if the breakdown thea certain epidermal gradient is insex, fact10aeyelids generalfrom hallmark of human aging and not specificoffor skincalcium area or for a specific females human skin aging and not specific for a certain skin area or for a specific sex, eyelids from females were analyzed that were obtained after a blepharoplasty
In the course of this project we could demonstrate that the collapse of the epidermal calcium gradient is a general hallmark of aging skin in mammals
Summary
The epidermis is the main protective barrier against the surrounding environment in most vertebrate organisms. In mammals, this barrier consists of several key elements such as specific proteins, lipids, and a low skin pH. The first two components are known as the “brick and mortar” of the epidermis In this model, the “bricks” are dead corneocytes that are filled with a large protein complex that is known as the cornified envelope (CE). The space between the dead cells is filled with lipids that form the “mortar” [1] These lipids are mainly ω-OH-ceramides that are attached to the cornified envelope via ester bonds [2]. The key component in Cosmetics 2018, 5, 35; doi:10.3390/cosmetics5020035 www.mdpi.com/journal/cosmetics
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