Molecular mechanisms of skin ageing.

Cutaneous ageing is a complex biological phenomenon consisting of two components; intrinsic ageing, which is largely genetically determined and extrinsic ageing caused by environmental exposure, primarily UV light. In sun-exposed areas, these two processes are superimposed. The process of intrinsic skin ageing resembles that seen in most internal organs and is thought to involve decreased proliferative capacity leading to cellular senescence, and altered biosynthetic activity of skin derived cells. Extrinsic ageing, more commonly termed photoageing, also involves changes in cellular biosynthetic activity but leads to gross disorganisation of the dermal matrix. The molecular mechanisms underlying some of these changes are now beginning to be unravelled and are discussed. As these mechanisms are identified, further insights into the underlying processes of skin ageing should emerge and better strategies to prevent the undesirable effects of age on skin appearance should follow.