009 Skin aging and photoaging effects can be quantified in vivo by fluoresence excitation spectroscopy

Fluoresence excitation spectroscopy of skin is a noninvasive method for objective evaluations of skin aging and photoaging. Fluoresence bands in the UV have been assigned to tryptophan moieties, pepsin digestible collagen cross-links (PDCCL), collagenase digestible collagen cross-links (CDCCL) and elastin cross-links. We have studied the dependence of these bands to aging and photoaging in the hairless mouse model and in humans. In the mouse, gluorescence of the tryptophan moieties decreases linearly with age, while the fluorescence band due to PDCCL increases linearly with age. In contrast, chronically UVB exposed mice showed an increase in the tryptophan band and a dramatic reduction of the PDCCL band compared to age-matched controls. The same phenomena were observed on mouse skin immediately after UVA exposure. The dependence of fluorescence of human facial skin with aging was studied in a large population sample (> 500 people in total) ages 15–70 at five geographic locations. Similar to the mouse model we observed a decrease in the tryptophan fluorescence signal, which is probably related to the reduction of the cell turnover rate with aging. Furthermore, observed increases in the fluorescence signals corresponding to collagen and elastin cross-links with aging may be attributed to chronic accumulation of cross-links in these long-lived molecules. The fluorescence ratio of the elastin cross-links signal to that of tryptophan moieties correlates strongly with age and is independent of geographical region and seasonal effects. The same fluorescence ratio has been used to monitor the antiaging effects of retinol treatment.