How to characterize skin barrier?

Evaluation of stratum corneum’s lipids restoration – dry skin

Epidermal differentiation triggers to the formation of dead cells, cornenocytes more or less cohesive. One of the main role of these cells is to regulate epidermis permeability.

The skin barrier is due to the accumulation of lipids (free fatty acids, cholesterol, ceramides) inside intercorneocytic spaces organized in stacks. This lipid matrix acts as a cement in the cell-cell cohesion and has a crucial role in protecting skin.

A nourishing cream, for example, provides feeding elements : it brings essentially lipids, absolutely crucial to the skin structure and its protection.

DermoMeca®’s solutions

DermoMeca® proposes to study a nourishing cream effect on structural and mechanical properties on stratum corneum.

We use Atomic Force Microscopy to visualize and characterize lipid matrix within the stratum corneum through skin explants. We will apply topically the nourishing cream on skin explants and then carry out cryo sections.

We will acquire high resolution images from cryosections. In the meantime, we will map adhesion and firmness properties of stratum corneum from the same area of it (Figure 1).

The lipid cement having specific adhesion properties, we will be able to quantify lipids amount in stratum corneum and so claim the nourishing effect. Cohesion forces might also be quantified with the firmness map (elastic modulus).

Evaluation skin barrier restoration – sensitive skin

Sensitive skin is an overreacting skin with many symptoms as redness, stinging, burning, itchiness, and discomfort after skin comes into contact with a particular ingredient or environmental trigger. This hyper-sensitivity is due to a lower tolerance threshold.

It might be explained according different factors :

• Inflammatory response after contact chemical products or even pollution, dust…
• Skin barrier alteration that triggers dehydration and worse, penetration of irritating agents.

DermoMeca®’s solutions

Recent studies at DermoMeca® has been showing that mechanical properties of corneocytes are important in the maintenance of skin barrier and are modified when this one is altered. This work proves that Atomic Force Microscopy with high resolution imaging and elastic modulus measurements are a suited approach to evaluate skin barrier function and structure of corneocyes, harvested by tape-stripping.

Figure 1 : Topographic images of corneocytes surfaces from healthy subjects (a and c) and from subject with AD (Atopic Dermatitis) skin (b and d). Image analysis allows to extract stiffness characteristics. Even though corneocytes surfaces seem to have a similar stiffness profiles (Rq, Ra and max), they are different about skewness (sk, h), the AD corneocytes having more asperities.

CONCLUSION

Our approach allows us to characterize corneocytes before and after treatment with a cream in order to prove its smoothing effect.