From Mice to Men: An Evolutionary Conserved Breakdown of the Epidermal Calcium Gradient and Its Impact on the Cornified Envelope

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.

Abstract licence: CC BY

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