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Hydrating the Stratum Corneum With Ceremides
By: Christine Heathman
Posted: September 24, 2010, from the October 2010 issue of Skin Inc. magazine.
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Lipids in the intercellular spaces of the SC provide the permeability barrier of the skin. Corneocytes are held together by attachments called desmosomes. The lipids between them help to conserve moisture because it is difficult for water to pass through them.4
For the skin to sustain balance, it is important to understand what occurs in this tiny SC ecosystem. According to Proksch’s study, “Lipid synthesis occurs in the keratinocytes in all nucleated layers of the epidermis.”2 The study also states that these newly synthesized lipids are then delivered by lamellar bodies to the interstices of the SC during critical epidermal differentiation.2
The disruption of barrier function by topical fatty acid removal, such as through the use of cleansers, pretreatment of peels, masks and other constituents during professional spa treatments—particularly peeling, microdermabrasion, ultrasound and other therapies or medical modalities that impact the SC environment—results in an increase in the synthesis of free fatty acids, sphingolipids and cholesterol in the living layers of the epidermis, leading to barrier repair. This is the natural course of reproduction to replace the lipid loss. Because ceramides are a lipid family available in high concentrations in the cell membrane, it subscribes to this logic. Ceramides can act as signaling molecules that help regulate differentiation proliferation, the apoptosis of cells and programmed cell death.5 Given this physiological fact, ceramide replacement is important for the balance of the SC ecosystem to overcome the impact of lipid loss.
Studies clearly demonstrate that three key lipids—cholesterol, free fatty acids and ceramides—are required for the permeability barrier to maintain skin health, and these lipids must be supplied together in a proper proportion for normal barrier recovery. All three lipids have different chemical compositions and different functions throughout the body. Nine different types of ceramides exist in the SC and they account for up to 50% of the lipids in the SC.6 The lipid layer provides a firm, smooth structure that coheases cells together and maintains the moisture-retention ability of the skin. Application of a ceramide-rich serum used as the final step of a skin care treatment or as an integral part of a client’s home care regimen can be a major point of difference in a results-oriented skin recovery outcome.
The crucial role of ceramides in the skin’s barrier function is still being researched, as well as how these natural interstitial substances are important in managing conditions of the skin that are unbalanced.5 The bottom line is ceramides are the major lipid constituent of lamellar sheets present in the intercellular spaces of the SC, according to “Penetration and Growth of DPPC/DHPC Bicelles Inside the Stratum Corneum of the Skin” by L. Barbosa-Barros, et al.7 “These lamellar sheets are thought to provide the barrier property of the epidermis,” states the study “Ceramides and skin function,” by L Coderch, et al.8 The dead cells form this compound system, and the lamellae are the skin’s actual barrier against the hostile environment of UV rays, bacteria, chemicals and other substances.