THE CORNIFIED CELL ENVELOPE: AN IMPORTANT MARKER OF STRATUM CORNEUM MATURATION IN HEALTHY AND DRY SKIN

摘要

The cornified cell envelope (CE), formed by transglutaminase mediatedε-(γ-glutamyl)lysine cross-linking of specialised proteins is the most insoluble component of the terminally differentiated keratinocyte. Under normal Nomarski optics two types of CE are readily distinguishable: an irregularly shaped, readily deformed "fragile" envelope (CEf) which predominates in the deepest layers of the skin, and a polygonal "resilient" or "rigid" envelope (CEr) which represents over 80% of the CE population in the superficial layers. This distinct spatial distribution indicates a maturation of the CE from the fragile to the resilient morphology during stratum comeum maturation. In this study we have examined morphological and physical changes occurring in the CE during terminal differentiation. The proportion of CEf and CEr present in superficial samples of stratum corneum were readily distinguishable following staining with Tetramethylrhodamine isothiocyanate (TRITC) and showed significant body-site variation. The percentage of CEf was highest on samples recovered from exposed body-sites (back of hand>cheek>inner biceps) indicating that photodamage and other environmental trauma reduce or delay normal CE maturation. Soapinduced dryness resulted in a significant decrease in CE maturation coincidental with reduced desmosomal hydrolysis. Effective moisturisation of winter-induced dry skin enhanced CE maturation (33% increase in TRITC fluorescence, n=14 following four weeks treatment). Using a novel micro-manipulation instrument the force required (μN) to maximally deform individual CEf and CEr was compared. CEf recovered from deep stratum corneum were significantly weaker than CEr recovered from superficial layers. These studies indicate that the normal process of CE maturation is associated with an actual strengthening of this insoluble. protective structure and that the impairment of this process is associated with poor quality of the stratumcorneum.