Biologie de la peau

Lamellar bodies/Odland bodies/membrane-coating granules/keratinosomes/cementsomes

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Lamellar bodies (also known as Odland bodies, membrane-coating granules, keratinosomes, and cementsomes) are tubular and/or ovoid-shaped membrane-bound secretory organelles of the epidermis . The classical view has been that the lamellar granules are produced as discrete granules in the upper stratum spinosum and in the stratum granulosum, probably from the Golgi apparatus, and then migrate to the cell surface of the granular layer cell, fuse with the plasma membrane, and extrude their contents at the SG–stratum corneum   interface. They contain not only pro-barrier lipids (glucosylceramides, phospholipids, and cholesterol) and their respective lipid processing enzymes (e.g., b-glucocerebrosidase, acidic sphingomyelinase, secretory phospholipase A2) . After extrusion in the intercorneocyte space, the extruded lipids will be modified by the action of the produced enzymes to generate ceramides, cholesterol, fatty acids, and cholesterol esters that form lamellae between the corneocytes and embedde the cornified envelope in a lipid envelope. This skin lipids are essential for the barrier function of the epidermisby limiting the transepidermal water loss. Lamellar bodies contain also proteases (stratum corneum chymotryptic enzyme  , cathepsin D, kalikrein KLK8, acid phosphatase, glycosidases, protease inhibitors) and others proteins including corneodesmosin   and b-defensin 2. Thus, lamellar bodies appear to be involved in barrier homeostasis, desquamation, formation of the cornified envelope and additionally antimicrobial defence.

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