Harmful effects of UVA on the structure and barrier function of engineered human cutaneous tissues

Purpose: To investigate the effects of a single UVA exposure on engineered human cutaneous tissues. Materials and methods: Skin equivalents (SE) were obtained by culturing keratinocytes on fibroblast-populated collagen gels; epidermal equivalents (EE) were obtained by seeding keratinocytes on non-populated collagen gels. After. maturation and differentiation of the epidermis, SE and EE were exposed to 50 or 100J/cm(2) UVA. Structural damage and total epidermal lipids were analysed and diffusion of radioactive oestradiol was monitored 24 and 72 h post-irradiation. Results: Twenty-four hours after UVA irradiation, a disorganization of the living epidermis is observed. UVA also significantly reduced the skin barrier function and led to an increase in phospholipid and in a decrease of ceramide levels. However, both the structure and thr barrier function of SE were recovered 72h post-irradiation, thereby suggesting that an intrinsic repair process might exist within the irradiated SE. Conclusion: This study provides a strong evidence that UVA radiation alters both the epidermal and dermal structures, the synthesis of epidermal lipids, and the permeability of the human skin.