Morphological Changes in Epidermal Lipids in AD
The stratum corneum represents a multicellular vertically stacked layer of cells embedded within a hydrophobic extracellular matrix. This matrix is derived from the secretion of lipid precursors and lipid hydrolases, both of which are secreted from lamellar bodies in the stratum granulosum. These hydrolases cleave the precursors to form essential and non-essential fatty acids, cholesterol, and at least 10 different ceramides, which self-organize into multilayered lamellar bilayers between the corneocytes ("bricks"), resulting in the formation of watertight "mortar", thus, maintaining skin hydration. In physiological balance, the approximate proportions of the lipid component are predominantly composed of 50% ceramides, 25% cholesterol, and 10–20% free fatty acids. In atopic dermatitis, there is a decrease in all three key lipids, especially ceramides, which are found in both lesional and non-lesional skin. A lipid imbalance and inadequate amounts of ceramides contribute to defective formation of the corneocyte lipid envelope and lipid mortar, which correlates with increased TEWL and enhanced barrier permeability.
Skin Therapy Letter. 2012;17(7) © 2012 SkinCareGuide.com