Comparative study of the anti-aging effect of retinaldehyde alone or associated with pretocopheryl in a surviving human skin model submitted to ultraviolet A and B irradiation.

In the past few years, the cellular effects of ultraviolet (UV) irradiation induced on skin have become increasingly recognized. Indeed, it is now well known that UV irradiation induces structural and cellular changes in all the compartments of skin tissue. Our aim was to study the anti-aging efficacy of a cosmetic cream containing 0.05% retinaldehyde associated with an antioxidant such as pretocopheryl in comparison with a cream containing only 0.05% retinaldehyde. For this purpose, an ex vivo technique using human skin was used to approximate in vivo metabolic conditions. In this model, human skin was maintained alive by organ culture for 14 days and skin aging was simulated with UV irradiation. Creams were applied to the surface of the epidermis and were compared with nontreated skin. After 14 days, free radical modulation was analyzed by hydroperoxide dosage. Epidermal (laminin) and dermal changes (elastic fibers and collagen) were studied by a histological method. Moreover, to examine collagen synthesis, tritiated proline was added to the culture medium and its incorporation in the newly synthesized collagen was evaluated by Webster's method. The formula containing 0.05% retinaldehyde and pretocopheryl significantly decreased UV-generated free radicals. Repair of laminin, elastic fiber and collagen network was significant and the results were better than those obtained with retinaldehyde alone. An increase of collagen synthesis was also shown with the two creams.