Apoptosis: a role in skin aging?

Prevailing theories view aging as an outcome of both programmed and stochastic events that occur over the lifetime of the individual. In this context, aging can be defined as a progressive decline in homeostasis and a period characterized by the inability of the organism to respond adaptively to stress. Apoptosis thus stands out as a potential key cellular process that may be affected during aging because apoptosis is both an important homeostatic mechanism and a protective cellular response to stress. In this paper we introduce the topic of apoptosis, its regulation, and its roles in epidermal homeostasis as a feature of normal keratinocyte differentiation and as a cellular endpoint of stress. To probe the question of whether apoptosis contributes to the process of skin aging, we present evidence for apoptotic dysregulation during aging in nonskin systems and discuss some findings suggesting that decreased efficiency of apoptosis may contribute to the alterations characteristic of intrinsic (chronologic) aging and extrinsic (photoaging) skin aging.