NATURALS 21
White hibiscus and baobab extracts for global well-ageing
n Alexandra Jeanneau MS, Pascal Yvon PharmD, MBA - Alban Muller International, US
The skin is a complex organ both structurally and functionally. A healthy- looking skin is firm and elastic. Although the skin is incredibly durable, it is affected, like all other organ systems, by ageing. Skin changes are among the most visible signs of ageing. What is visible is highly related to what is happening under the skin, i.e. component assembly and physiology within the skin. Today, consumers embrace their age, but they want to age well, and they look for natural cosmetics to support wellbeing with well-ageing.
Skin structure and physiology in ageing Skin structure, physiology and barrier function The skin is the outermost layer of the body with an extensive surface. Its most important function is to form an effective barrier between the ‘inside’ and the ‘outside’ of the body. The skin barrier protects from external threats (infection agents, chemicals, allergens, etc.) and internally, helps to maintain homeostasis and protects from enhanced water loss.1 The skin barrier is formed by a high number of inter-related components.2 The skin consists of three layers: starting
with the epidermis, the outermost layer, followed by the dermis, and the subcutaneous layer or hypodermis. The epidermis is a stratified epithelium that undergoes continuous self-renewal from the basal layer up to the stratum corneum, where ultimate desquamation of the outermost cells from the skin surface occur.3 Epidermis is composed of four layers of keratinocytes in progressive stages of differentiation that culminates with the formation of the stratum corneum (SC). The dermis is a fibrous network of tissue that provides structure and resilience to the skin. It predominantly consists of the extracellular matrix, with components such as collagen and elastin fibres produced by fibroblasts; these proteins provide tensile, strength, support, and elasticity to the skin, respectively. Glycosaminoglycans (GAGs) along with collagen and elastin, are among
September 2020 Skin barrier EPIDERMIS Collagen DERMIS HYPODERMIS
Adipocyte Elastin Fibroblast Hyaluronic acid
Figure 1: Skin structure and key components.
the primary constituents of dermal skin and are responsible for conferring the outward appearance of the skin. These polysaccharides are macromolecules which are able to bind water up to 1,000 times their volume. There are four different GAGs according to their structure, including hyaluronic acid (HA). The subcutaneous layer, the hypodermis, is the thickest one of the skin and is primarily composed of adipocytes and connective tissue with the main function to store fat. Together with the other layers, it also provides strength, elasticity, and helps anchor the skin to muscles and bones. It also contributes significantly to the general appearance of the skin. While each layer has unique functions, it also works interdependently in upholding overall integrity of the skin (Fig 1).4 SC, outermost layer of the epidermis, is
a dynamic tissue comprised of about 60% structural proteins, 20% water, and 20% lipids.5
It is a multilayered tissue composed
of flattened enucleated mature cornified keratinocytes, the corneocytes, embedded in an intercellular matrix enriched in lipids (ceramides, cholesterol, and free fatty acids) that is crucial for the skin barrier function. This intercellular hydrophobic matrix plays a
major role in the watertightness of the SC. The corneocytes are loaded with keratin and surrounded by a highly insoluble cornified cell envelope (CE) composed of cross-linked proteins (major components include involucrin, loricrin, small proline-rich proteins SPRRs) as well as a covalently bound outer lipid envelope.6
The CE,
together with corneodesmosomes (“mechanical” junctions) confers stability and resistance on the SC layer. Although the SC is recognised as the most important physical barrier, the nucleated epidermal layers are also significant in barrier function, by preventing both excessive water loss and the entry of harmful substances into the skin. Underneath the SC is the stratum granulosum (SG), made of keratinocytes containing keratinosome and keratohyalin granules. These keratinocytes are tied together by specific cell-cell junctions called ‘tight junctions’ (TJs) which play an important role of the epidermal barrier by controlling the granules passage through the SC layer and create a dam to ions and solutes.4
If a molecule reaches the TJ from
outside to inside in case the SC barrier is impaired, it is likely to be stopped.1
Various TJ proteins have been identified and play PERSONAL CARE EUROPE
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