Skin owes its elasticity and its resistance to the different layers of tissue which constitute it: the epidermis, the dermis and the hypodermis. The epidermis, the skin’s outer layer, makes it waterproof and makes it resistant. It is mostly made up of keratin, a fibrous protein produced by keratinocytes, and melanin, the main cutaneous pigment, produced by melanocytes. As time passes, keratinocytes are renewed more slowly and their terminal differentiation slows down.
Fundamental changes take place in the dermis, the skin’s support structure, made up of 80% of elastin and collagen fibers, entirely enveloped in a gel made of glycoproteins. The main dermis cells, fibroblasts, are specialized in elastin and collagen fiber synthesis. Between 20 and 80 years of age, the fibroblast population – which ensures homeostasis of the synthesis, maturation and degradation of elastin and collagen fibers – is halved. The loss of fibroblasts causes an imbalance, which degrades the collagen and elastin fibers, and leads to diminished dermis elasticity and tonicity, and therefore the appearance of wrinkles.
Collagen fibers are distributed throughout the layers of the dermis. They are made of proteins, responsible for tissue cohesion and resistance. They are able to store water and contribute to skin hydration. A reduction in the quantity of collagen and/or a change in its quality cause the appearance of deep wrinkles.
Elastins are proteins arranged into fibers which are responsible for tissue elasticity and solidity. With age, elastin fibers become rarefied, and the skin thins and wrinkles.