Photo-pollution stress in skin: Traces of pollutants (PAH and particulate matter) impair redox homeostasis in keratinocytes exposed to UVA1.

Background: It is likely that skin is exposed to low concentrations of pollutants such as Polycyclic Aromatic Hydrocarbons (PAH) either through topical penetration by ultrafine particles or by systemic distribution. No precise estimation of pollutants in living skin is available, but literature has reported contamination of blood by PAH at concentrations in the nanomolar range. Some pollutants (PAH for example) are photo-reactive and phototoxic: sunlight and pollution might thus synergistically compromise skin health.

Evolution of the clonogenic potential of human epidermal stem/progenitor cells with age.

A number of clinical observations have indicated that the regenerative potential and overall function of the epidermis is modified with age. The epidermis becomes thinner, repairs itself less efficiently after wounding, and presents modified barrier function recovery. In addition, the dermal papillae fatten out with increasing age, suggesting a modification in the interaction between epidermal and dermal compartments.

Human side population keratinocytes exhibit long-term proliferative potential and a specific gene expression profile and can form a pluristratified epidermis.

The aim of the present study was to characterize human side population (SP) epidermal keratinocytes isolated from primary cell cultures. For that purpose, keratinocytes were isolated from normal adult breast skin samples and the Hoechst 33342 exclusion assay described for hematopoietic cells was adapted to keratinocytes. Three types of keratinocytes were studied: the SP, the main population (MP), and the unsorted initial population.