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KMID : 0984920100120010079
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Journal of Skin Barrier Research
2010 Volume.12 No. 1 p.79 ~ p.84
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Skin Barrier in Aged Skin
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Park Hwa-Young
Choi Eung-Ho
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Abstract
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Epidermal permeability barrier function is normal in aged skin under basal conditions. However, aged skin barrier is disrupted more easily and repaired more slowly compared to young skin, which originate from an overall deficiency in all
key epidermal lipids (especially cholesterol), a decrease of stratum corneum (SC) intercellular lamellae and diminished
lamellar body secretion. Therefore aged skin is easily afflicted by inflammatory skin diseases, dry skin and eczema which
could be triggered or exacerbated by impaired barrier homeostasis. In advanced age (i.e., >75 years in human or >18-24
months in mice), a reduced epidermal lipid synthesis is the main cause of delayed barrier recovery. In contrast the defects of epidermal permeability barrier in moderately aged humans (50-80 years) or mice (12-15 months) are linked instead to defective SC acidity. In moderately aged skin, the abnormal epidermal acidification, in turn, is linked to decreased Na+/ H+ antiporter (NHE1) expression, which lead to increased SC pH. It results in defective SC lipid processing and then delayed maturation of SC lamellar membranes due to suboptimal activation of the pH-sensitive lipid processing enzyme, β-glucocerebrosidase. On the contrary, impaired SC integrity in moderately aged skin is due to increased pH-dependent activation of serine proteases, which leads to premature degradation of corneodesmosomes. In aged skin, basal epidermal calcium gradient is disturbed, which might result from a decrease of TRPV6. Diabetic skin has very similar barrier state to aged skin. Considering the defective epidermal lipid synthesis in advanced aged skin, moisturizer with appropriate lipid content would be beneficial in advanced aged skin. Application of the physiologic lipid mixture containing cholesterol, ceramides and free fatty acids, or a cholesterol-dominant mixture accelerates barrier recovery in advanced aged epidermis. For moderately aged skin, an exogenous acidification of the SC could be suggested. And some therapeutic implications are suggested for impaired epidermal calcium gradient in aged skin.
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KEYWORD
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Skin barrier, Aged skin, Skin pH, Physiologic Lipid mixture
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