Molecular mechanisms of cutaneous aging: connective tissue alterations in the dermis.

Cutaneous aging is a complex biological phenomenon consisting of two distinct components, (a) the intrinsic, genetically determined degenerative aging processes and (b) extrinsic aging due to exposure to the environment, also known as "photoaging". These two processes are superimposed in the sun-exposed areas of skin, with profound effects on the biology of cellular and structural elements of the skin. This overview summarizes our current understanding of the mechanisms of innate versus extrinsic aging with emphasis on connective tissue alterations, primarily collagen and the elastic fiber network. We also introduce a novel transgenic mouse model, expressing a human elastin promoter-reporter gene construct, suitable for studies on biology and preventive pharmacology of the cutaneous aging.