Comeocyte envelope

Dry skin is further characterized by structural changes in comeocyte envelope (CE) as a result of reduced transglutaminase activity. The enzyme is responsible for the transformation of a soft or fragile envelope into a rigid one. Fragile corneocyte envelopes predominate in dry skin.9... 

White, S.H., Mirejovsky, D., and King, G.I., Structure of lamellar domains and comeocyte envelopes of murine stratum corneum an X-ray diffraction study, Biochemistry, 27, 3725, 1988. 

Figure 5 Murine stratum comeum normal full thickness. Powder diffraction patterns obtained from mouse SC at 25°C. The upper figure shows the small-angle lamellar pattern produced by the intercellular lipid domains, with a repeat period of 131 2 A. The lower figure shows the wide-angle pattern produced by the lipid alkyl chains and the comeocyte envelope. See text. (Data from White et al., 1988.)...

The typical properties assigned to cosmetic products include skin moisturization, emolhency and spreadability and coadjuvants to help maintain skin pliability and softness (57). Moisturization is usually considered to be simply occlusivity and humectancy. The role of cosmetics, especially lipid cosmetics besides moisturization, has expanded to multiple effects such as modulation of barrier function, increasing comeodesmolysis and facilitating comeocyte envelope maturation. Specific examples of lipids of interest are listed in Table 2. Examples of lipids used in cosmetics include products derived from olive oil, shea butter oil, mango kernel oil, borage oil, nut oils, and palm and coconut oils. 

The presence of these crystalline lamellae between the comeocytes and the impermeable comeocyte envelope that forces drugs to diffuse through the... 

S. H. White. D. Mirejnvsky, and G. I. King. Structure of lamellar lipid domain. and comeocytes envelopes of murine. stratum comeum. An x-ray diffraction study. Biochetnisiry 27 (1988) 3725-3732,... 

Swartzendruber, D.C., et al. 1987. Evidence that the comeocyte has a chemically bound lipid envelope. J Invest Dermatol 88 709. 

The barrier properties of human skin have long been an area of multidisciplinary research. Skin is one of the most difficult biological barriers to penetrate and traverse, primarily due to the presence of the stratum corneum. The stratum cor-neum is composed of comeocytes laid in a brick-and-mortar arrangement with layers of lipid. The corneocytes are partially dehydrated, anuclear, metabolically active cells completely filled with bundles of keratin with a thick and insoluble envelope replacing the cell membrane [29]. The primary lipids in the stratum corneum are ceramides, free sterols, free fatty acids and triglycerides [30], which form lamellar lipid sheets between the corneocytes. These unique structural features of the stratum comeum provide an excellent barrier to the penetration of most molecules, particularly large, hydrophilic molecules such as ASOs. 

The stratum comeum is usefully thought of as a brick wall , with the fully differentiated comeocytes comprising the bricks , embedded in the mortar created by the intercellular lipids. A layer of lipid covalently bound to the comified envelope of the comeocyte contributes to this exquisite organization. The intercellular lipids of the stratum comeum include no phosphohpids, comprising an approximately equimolar mixture of ceramides, cholesterol and free fatty acids. These non-polar and somewhat rigid components of the stratum comeum s cement play a critical role in barrier function. On average, there are about 20 cell layers in the stratum comeum, each of which is about 0.5 fim in thickness. Yet, the architecture of the membrane is such that this very thin structure limits, under normal conditions, the passive loss of water across the entire skin surface to only about 250 mL per day, a volume easily replaced in order to maintain homeostasis. 

Lazo ND, Meine JG, Downing DT (1995) Lipids are covalently attached to rigid comeocyte protein envelope existing predominantly as beta-sheets a solid state nuclear magnetic resonance study. J Invest Dermatol 105 296-300... 

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