360° hydration approach for moisturising treatment

The SC provides a highly efficient barrier against water loss.4 Everyday conditions like cold, wind, air conditioning, the use of soap, and other factors are the main cause of hydration disruption in the SC resulting in noticeable scaling, itching, damaged skin, and a general unhealthy look. The skin protects us against the environment and regulates water exchange. It is comprised of the functional layers: epidermis, dermis, and subcutaneous fat.1 Epidermis is the outermost layer of the skin and it is comprised of four layers: basal, spinous, granular and the outermost cornified layer or SC.5 Water content is also affected by internal factors, such as the natural moisturising factor, certain proteins involved in water transport and the effects of the natural ageing process that decrease SC hydration. The hydrophilic nature of the migrated keratinocytes from the epidermal basal layer to the SC (called corneocytes) together with the hydrophobic environment found in the extracellular domains of the lower SC are the main reason to impede free water diffusion. Taking into account the great and continuous water exchange among the SC, the underlying epidermal living cells and the atmosphere, there is an important and constant water flux, which depends on adequate SC conditions and integrity. Glycosaminoglycans (GAGs) are relevant elements involved in hydration that must be considered. These macromolecules can be found in the extracellular matrix (ECM), which is a 3D fibre network that acts like a structural support. They are composed of a variable number of repeated disaccharide units, which form long, linear and negatively charged heterogeneous polysaccharides, considered as highly hydrophilic. Fibroblasts and keratinocytes produce hyaluronic acid (HA), which is a GAG found in the skin as a main constituent of the ECM. The hydrophilic chains of HA attract water into the tissue and retain it, causing an osmotic swelling pressure that contributes to the physical properties of the tissue and to a plumping effect when HA gets deep into the dermis.6 Due to its excellent water retention capacity, HA is able to maintain the extracellular space and facilitate the transport of ion solutes and nutrients. Skin contains about 50% of the total HA in a given organism but its level decreases year by year, resulting in dermal dehydration and wrinkle formation, processes accelerated by free radicals. Among inner agents, aquaporins are a family of hydrophobic and small integral membrane proteins that act as water selective pores, facilitating water transport along a favourable osmotic gradient.7 One of these 13 homologous protein types found in mammals acts like a water channel, conducting water molecules inside and outside the cell, while another type known as aquaglyceroporins can exceptionally transport other molecules as well.7 Aquaporin 3 (AQP3) is the most abundant aquaglyceroporin in the human epidermis, being responsible for facilitating the transportation of water, glycerol and other solutes like urea through membranes. This aquaglyceroporin provides a short water circuit between the base of the epidermis and the SC, maintains constant water content and prevents the formation of a continuous water gradient across the epidermis below the SC, but its expression decreases with sun exposure and through ageing.7,8 Lipotec proposes a 360° hydration approach in order to prevent skin dehydration in the short and long term. The proposal involves a combination of three cosmetic active ingredients which decrease SC water loss, retain water molecules and improve water transport within the skin, offering an integral dehydration protection. Lipomoist Series are molecular films containing a submicrodispersion of heteropolysaccharides obtained by microfluidising techniques. Molecular films are very thin monolayer functional films that spread very well on the epidermis, forming a protective film that helps to prevent water loss and acts as a controlled delivery system. Their particular rheology enables the extension of monolayers of functional ingredients on the skin, which are very easily absorbed by the SC. Lipomoist-2013 is a molecular film that forms a moisturising protective film on the skin confering a pleasant and fresh feeling. Intertidal rocky shores are highly dynamic systems exposed to a combination of harsh factors. Therefore, their intertidal inhabitants may produce exopolysaccharides (EPSs) to protect themselves. Hyadisine (INCI name: Pseudoalteromonas Exopolysaccharides) is an EPS obtained through biotechnology by fermentation of a marine bacterial strain that belongs to the genus Pseudoalteromonas sp. It was collected from a colony of mussels in the Douarnenez bay (Brittany department, France). During high tides, these mussels are covered with water and gradually become exposed to desiccation and other environmental drastic changes at low tide. One of the main monomers of this EPS is glucuronic acid, which is also in HA, so they were thought to have similar cosmetic properties. The third active ingredient is a hexapeptide of natural amino acids, named Diffuporine (INCI name: Acetyl Hexapeptide-37). It was identified by a combinatorial chemistry approach by screening the peptide library with a reporter gene assay, which monitored luminescence released by cells that express the luciferase-AQP3 promoter construct when in contact with the luciferase substrate. This hexapeptide proved to increase human AQP3 mRNA levels thus enhancing AQP3 expression in the skin. As a result, it was hypothesised that it could improve the water flux from the basal layer to the SC providing hydration to the skin.

Materials and methods

Hydration effect of the molecular film
The moisturising effect induced by the molecular film was quantified by corneometry. A panel of 20 healthy female volunteers, aged 34 to 69, applied a gel containing 7% of the active ingredient on half of the face and a placebo cream on the other half, twice a day for 20 days. Readings of three different spots of the treated area were recorded. Measurements of the degree of hydration were performed at the beginning of the treatment, and after 24 hours and 20 days.