Everyday our skin is subject to multiple aggressions: sun, cold, and bad weather, as well as other factors which damage the surface of our skin, causing dryness, chapping and rough skin.
Together these factors accelerate the ageing process. This phenomenon touches the entire family, from the youngest to the oldest, creating a need for skin care solutions that can be used by all members of the family. A need in line with today’s trend, which consists of reducing the current over-segmentation of cosmetic products. To develop suitable formulations, scientists need smart active ingredients that target precisely the skin reparation mechanism, without over-stimulating these natural mechanisms when there is no need. Gattefossé present an innovative cotton thistle extract, which acts on epidermal differentiation, helps the natural regeneration process and promotes cutaneous repair. A true solution adapted for both normal and damaged skins, resulting in healthier, smoother and more radiant appearance.
Cotton thistle (Onopordum acanthium) is a wild plant commonly known for its use for the treatment of burns. Emblem of Scotland, the cotton thistle grows in calcareous terrain and is found throughout Europe and also in more austral territories. Gattefossé’s new cotton thistle extract is a 100% natural ingredient, certified organic by Ecocert,1 yet preservative, glycol and mineral oil free, and not tested on animals.
The biological markers of cell differentiation
The stratum corneum, the external layer of the skin, plays an essential role in maintaining the skin integrity (barrier function). Its formation and its effective protective role result from a series of complex reactions involving the production of new keratinocytes and differentiation and migration of these new cells to the surface of the skin. Different factors can affect the skin barrier function:
• The ageing process, characterised by a decrease in the epidermal regeneration • Dermatological disorders (e.g. acne) or cutaneous injury (e.g. burns or wounds)
During the keratinocyte differentiation process, the synthesis of several proteins (Fig. 1), which play a critical role in providing the barrier function of the skin, can be detected and measured. The last steps of keratinocyte differentiation are characterised by the development of a highly resistant wall affixed to the internal face of the plasmic membrane. This cornified envelope is formed by the reticulation of specific proteins. The expression of these proteins, at the right time and in high concentrations, provides an indicator of enhanced cutaneous regeneration and therefore of better skin repair. Involucrin Involucrin is a protein specific to keratinocytes. It is synthesised during the early stages of cell differentiation within the stratum spinosum layer. This protein constitutes the major structural support of the insoluble cornified envelope. Loricrin It is also one of the major constituents of the cornified envelope. Loricrin is expressed in cells at the terminal differentiation stages. These two proteins are effective biological markers, identifying the stages of keratinocyte differentiation associated with skin regeneration and repair. Lympho-Epithelial Kazal-Type-related Inhibitor (LEKTI) LEKTI, is an inhibitor of serine-protease enzymes involved in the degradation of corneodesmosomes. It is expressed in the granular layer of the skin. The expression of LEKTI leads to improved cellular cohesion, and is essential for cutaneous repair, and to heal dry and damaged skin, resulting in better regeneration of the skin’s protective layer (Fig. 2).
Restructuring of the epidermal barrier
This study demonstrates the restructuring power of cotton thistle extract, when it is used for the treatment of damaged skin. Several human skin explants were artificially damaged by removal of the horny layer. The explants were then treated with a topical application of an emulsion containing 1.7% of cotton thistle extract. Two additional experiments were undertaken in parallel. A control using untreated skin explants (stripped of the horny layer), and a positive control using a product that is considered to be a market leader in skin moisturisation (dermopharmaceutical market). The study measures the expression of the biological markers of keratinocyte differentiation: involucrin, loricrin and LEKTI. Greater protein expression can be seen in the cotton thistle extract treated explants compared with the untreated explants (control) or those treated with the market reference product (positive control) (Fig. 3).
Smart action: targeted activity depending on the skin’s needs
By stimulating keratinocyte differentiation, cotton thistle extract efficiently helps reinforce the skin barrier effect, and thereby repair damaged or dry skin. For a family daily care, the challenge is to have a modulated action: to stimulate skin regeneration when needed and avoid over-expressing this mechanism in normal conditions. Hence, following the same test procedure, the activity of cotton thistle extract was assessed on normal undamaged skin explants. On normal skin, cotton thistle extract performs well (Fig. 4), and the results are comparable with the positive market reference (positive control) and, in general, slightly superior to the untreated explants (control). This shows that cotton thistle extract does not cause over-expression of the bio-marker proteins, which could be associated with negative effects when applied to undamaged skin. In normal skin, this active will help the natural regeneration process, reinforcing the protective barrier effect.
Repairing care for severe epidermal damage
The repairing performance of cotton thistle extract has been evaluated in a model of severe epidermal damage. Human skin explants were treated with UVB irradiation (10 J/cm2) to simulate burned skin. The repairing performance can be estimated by measuring the formation of a neo-epidermis under the burned surface or around the edges of the wound, corresponding to the early stages of epidermal reparation. Skin explants were treated by topical application of a formulation (aqueous gel) containing 1.7% of cotton thistle extract or by a pharmaceutical market reference containing a purified extract of Centella asiatica (CAP) rich in madecassoside and asiaticoside.
• In burned but untreated skin explants (Fig. 5b), the UVB-induced cellular damage can be seen clearly: numerous keratinocytes with pycnotic nucleus and perinuclear edema. There are very few keratinocytes with normal morphological features.• In skin explants treated with CAP (Fig. 5c), the cellular morphology of the explants is similar to the control, although a moderate number of normal keratinocytes can be observed in the basal layer. • In explants treated with cotton thistle extract (Fig. 5d), many more normal keratinocytes can be seen in the basal layer with many fewer cells presenting with damaged pycnotic nucleus.
Results around the edges of the wound Analysis of the edges of the wound is even more revealing since it represents the starting point of the skin reparation process.
• In CAP-treated explants (Fig. 6a) the edges of the wound show keratinocytes with normal morphology in addition to a weak and moderated growth bud. • In cotton thistle extract-treated explants (Fig. 6b) keratinocytes are normal and well-stratified. Furthermore, a clear and thick growth bud can be seen indicating that a strong skin reparation response is being mounted.
In severely damaged skin, cotton thistle extract stimulates the processes of cutaneous repair.
In vivo evaluation of the repairing effect of the cutaneous barrier
The cutaneous barrier acts as a regulator of skin water balance. Damage to this barrier can lead to destabilisation of the skin’s water exchange regulation system, resulting in an increase in the loss of water from the skin into the external environment. The integrity of the cutaneous barrier can be assessed using a method which precisely measures Trans Epidermal Water Loss (TEWL). The repairing action of cotton thistle extract in the skin’s cutaneous barrier was tested in vivo on skin damaged by stripping, using the TEWL test. A cotton thistle extract formulation (gel-cream containing 2% cotton thistle extract) was tested in parallel with a positive control consisting of a market reference containing madecassoside, well known for its repairing performance (dermopharmaceutical market). The two test products were applied once a day for five days (from D0 to D4) on sections of skin damaged by stripping. TEWL assessments were performed on a daily basis before application of the test product (Fig. 7). From the first application and on a daily basis, cotton thistle extract improves water balance regulation. The prevention of water loss indicates epidermal repair and good restoration of the cutaneous barrier effect following skin damage.
By stimulating keratinocyte differentiation, cotton thistle extract acts quickly to repair damaged skin.
• Good cellular differentiation and cell proliferation are essential for the reconstruction of the natural barrier of the skin and to repair skin damaged by burning, lesions or trauma. • Dermo-protecting effects also benefit dry skin. The cohesion of the cutaneous barrier is strengthened, stabilising and regulating skin hydration, which maintains the flexibility and softness of the skin. • Smart Action makes cotton thistle extract a perfect natural active for all the family
Cotton thistle extract is ideal for use at 2% in skin care products for:
• Anti-ageing and moisturisers for mature skin• Post-operative/dermatological skin treatment (peeling, dermabrasion) • Dry and/or atopic skin • Sun burn treatments • Face and body care for damaged skin (acne, cut, chapping)
Cotton thistle extract is created using eco-responsible sourcing and has Organic certification. It is an ideal active for organic and natural skin care products meeting customers’ demand for performance and responsible purchasing.
1 Ecological and organic cosmetic certified by Ecocert SAS – BP 47 – F32600 L’Isle Jourdain-France.
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