Neurotrophins and Skin Aging
Cutaneous aging is a complex biological phenomenon that consists of two superimposed components: intrinsic (true aging) and extrinsic (photoaging) aging. Intrinsic aging is largely genetically determined and represents an inevitable change attributable to the passage of time alone. It resembles aging that is seen in most internal organs, and its underlying mechanisms probably involve decreased proliferative capacity, leading to cellular senescence and altered biosynthetic activity of skin-derived cells. Intrinsic aging is manifested primarily by physiologic alterations with subtle but undoubtedly important consequences for both healthy and diseased skin. The morphologic changes of intrinsic aging include smoothing and thinning of the skin with exaggeration of the expression lines. The intrinsic rate of skin aging in any individual is dramatically influenced by personal and environmental factors, particularly the amount of exposure to ultraviolet light (UV), that is, intrinsic and extrinsic aging are superimposed processes. Extrinsic aging is caused by environmental exposure, primarily to UV. It is observed in the sun-exposed areas (photoaging) and is manifested by the presence of skin wrinkles, pigmented lesions, patchy hypopigmentations, and actinic keratoses. It involves changes in the cellular biosynthetic activity and usually leads to gross disorganization of the dermal matrix. Photodamage, which considerably accelerates the visible aging of skin, also greatly increases the risk of cutaneous neoplasia.
KeywordsNerve Growth Factor Human Keratinocytes Epidermal Keratinocytes Human Epidermal Keratinocytes Keratinocyte Proliferation
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