Skin lipids

Abstract

Synopsis Concepts regarding the structure and function of the stratum corneum (SC) have changed from that of a tough film of loosely adherent cells to that of a two-compartment system of protein-enriched cells embedded in intercellular lipids. The two-compartment arrangement enlarged the role of epidermal lipids from that of the plasticizing component of the SC to that of the epidermal barrier governing water-holding properties as well as take-up of water, the differences in permeability of topically applied lipophilic and hydrophilic agents as well as cohesion and desquamation of the SC. Barrier properties of SC are dependent largely on the intactness of the lipid lamellae that surround the corneocytes. The pliability of the SC depends on a correct balance of lipids, hygroscopic water-soluble substances and water. Mammalian differentiation involves characteristic changes in lipid composition consistent with the requirements for waterproofing. There is a progressive depletion of phospholipids and glycosphingolipids with enrichment in ceramides, cholesterol, free fatty acids, and small amounts of other polar (e.g. cholesterol sulphate) and non-polar species (e.g. hydrocarbons, cholesterol esters, triglycerides). The sphingolipids account for the most lipid by weight and are presumed to be of major importance for the water-retaining properties of the epidermal barrier. Decrease of sphingolipid content occurs in aged skin. Deficiency of essential fatty acids leads to enhanced transdermal water transport in addition to dryness and scaliness of the skin. A mixture of both saturated and unsaturated fatty acids produces the optimal barrier to water loss from the SC. The balance between solid crystal and liquid crystalline phases in epidermal lipids is determined by the degree of fatty acid unsaturation and the amount of water.

Comparative investigation of human stratum corneum ceramides

“…This feature is attributed mainly to the amount and composition of the intercellular lipid matrix in the stratum corneum (SC), which consists mainly of ceramides, free fatty acids, and sterols (5)(6)(7). Since alterations of barrier lipid composition are known to result in a functional impairment of the skin barrier or to delay barrier repair (8)(9)(10), different types of healthy human skin and skin diseases have been previously investigated for possible changes in overall barrier lipid composition (10)(11)(12)(13).…”

PRELIMINARY COMMUNICATION Occlusive power evaluation of O/W/O multiple emulsions on gelatin support cells

“…To differentiate the secondary surfactant quantity, we added a subscript number to the second slash (outermost phase). The multiple emulsions were named O/W/ (1) O and O/W/ (2) O.…”

“…The essential function of the stratum corneum [1][2][3][4], is to defend the body against dehydration, as well as against chemical and biological attack. The vital factor for this defence is the lipid part of the stratum corneum, which constitutes approximately 10% of its dry mass.…”

Separation and identification of ceramides in the human stratum corneum by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry and electrospray multiple-stage mass spectrometry profiling

“…Important structural components of the skin barrier are the lipids of the stratum corneum [5], which comprise 10 % of the dry solids content [6]. Because the barrier function of the skin depends substantially on the amount and composition of the intracellular lipid matrix [7,8], changes in lipid cornposition, and especially in the sphingolipids in the straturn corneum, are of utmost importance [9,10]. This is true both cosmetically and medically, because deficiencies in lipid composition and metabolism can result in skin defects [11,12].…”