Overview of Skin Aging and Photoaging

Yolanda Rosi Helfrich, MD; Dana L. Sachs, MD; John J. Voorhees, MD


Dermatology Nursing. 2008;20(3):177-183. 

In This Article

Mechanism of Skin Aging

Generally, the molecular changes of photoaging are considered to be an augmentation and amplification of the molecular changes associated with chronologic skin aging (Fisher et al., 2002). In aged skin, there is elevation of AP-1 as compared to young skin (Chung et al., 2000). MMP activity is also increased in aged human skin, and is associated with increased levels of degraded collagen (4-fold higher in aged vs. young subjects ) (Fisher et al., 2002). In addition, synthesis of types I and III procollagen is reduced in aged human skin (Varani et al., 2000). The combination of increased breakdown of collagen and decreased synthesis of new collagen results in an overall decrease in collagen levels in the dermis. These molecular changes in chronologically aged skin resemble the changes associated with photoaging. This supports the notion that photoaging is superimposed upon and amplifies the changes associated with chronologic skin aging.

Chronologic aging is thought to result from a combination of forces. Generation of ROS is thought to play a major role. The free radical theory of aging proposes that aging results from accumulation of oxidative damage over a lifetime due to excess ROS, which result from aerobic metabolism (Hensley & Floyd, 2002). ROS generation is increased in aged skin. As discussed previously, ROS generation is a key step in molecular pathways which eventually lead to increased collagen breakdown. This free radical theory of aging gives a good explanation of the molecular changes associated with chronologic aging.


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