Pathogenesis of photoaging

This diagram demonstrates the effects of UV irradiation on the skin. UV radiations activate growth factor and cytokine receptors, which induce transcription factor AP-1, resulting in the upregulation of MMP genes. AP-1 also disturbs procollagen gene expression. The end results are dermal matrix breakdown and decreased collagen synthesis. The cumulative effect of repeated UV injury determines the clinical features seen in photoaged skin.