Simulated UV daylight is a relevant new tool for daily photoprotection studies.

Background: Dermal elastosis is considered the histological ‘gold standard’ for evaluation of skin photoaging, but the relation of the level of dermal elastosis to other histological indicators of photoaging is not clear. Objective: To investigate how various proposed histological measures of photoaging compare with the level of dermal elastosis. Methods: Prospective, community-based study in Southeast Queensland, Australia, among 89 participants aged 40–82 years. Quantitative histology was used to evaluate 8 biomarkers of photoaged skin, and associations between grades of dermal elastosis and each of the other 7 biomarkers were analysed using ordinal logistic regression models with proportional odds assumption, using histological grades of elastosis as the outcome. Results: Older age, male sex and high outdoor exposure levels were confirmed as predictors ofhigh levels of dermal elastosis. After adjustment for age and sex, the only significant positive association with increasing elastosis grades was the proportion of p53-positive cells. Epidermal thickness, interdigitation index proportion of surface covered with melanin (% Fontana-Masson staining) and glycosaminoglycan content were not associated with elastosis in either crude or adjusted models. Conclusions: Amonga range of suggested biomarkers of photoaged skin, only p53-positive cells appear to be strongly associated with the level of dermal elastosis.

Two double-blind studies versus vehicle were carried out to investigate the effects of a topically applied retinol plus vitamin C combination on epidermal and dermal compartments of aged or photoaged human skin. The two studies were performed on postmenopausal women who were selected for treatment based on the mild level of elastosis of their facial skin. At completion of treatment, skin biopsies were collected and processed for classical histology and immunohistochemistry. In the first study (aged skin), 8 volunteers applied the retinol- and vitamin C-containing preparation on the ventral side of one elbow and the vehicle on the other elbow twice daily for 3 months. After the 3-month treatment we observed histological changes mainly within the epidermis. The stratum corneum was thinner with a compact pattern, whereas the epidermal proliferation increased, resulting in a thickening of the viable epidermis. Moreover, the interdigitation index was increased. In the second study (photoaged skin), 11 volunteers were divided in two groups; one applied the retinol- and vitamin C-containing preparation and the other one the vehicle on their face twice daily for 6 months. Facial skin samples presented histologic hallmarks of photoaging, i.e. accumulation of elastotic material in the papillary dermis. After the 6-month topical treatment, the observed histological changes were mainly concentrated at the dermal level. Both treated and control groups showed the same distribution pattern of type I procollagen, however, the high level of type III procollagen originally observed in photoaged skin was reduced in the retinol- and vitamin C-treated group, resulting in a lower type III-to-type I procollagen ratio. Furthermore, a wide band of eosinophilic material just beneath the epidermis, devoid of oxytalan fibers and forming the ‘grenz zone’, appeared more frequently and was larger in the retinol- and vitamin C-treated group. In conclusion, our results show that repeated topical application of a preparation containing both retinol and vitamin C is able to reverse, at least in part, skin changes induced by both chronologic aging and photoaging.

Efficient daily UVR protection, as provided by a broad-spectrum daily-care product, is necessary to prevent the 'silent' sub-erythemal cumulative effects of UVR from inadvertent sun exposure.