In vitro 3D skin models for studying effects of cosmetic formulas or single actives after acute UV-damage
Ultraviolet-irradiation (UVR) is a fundamental elicitor of the premature skin aging process and predominantly responsible for cancerous transition of skin cells (1, 2). Today our knowledge about the molecular mechanisms of the UVR-induced premature skin aging process is quite passable but far from complete. A broad range of analytical clinical and in vitro methodologies (3, 4) enable correlated studies of photo-induced clinical signs, photo-activated molecular signaling as well as molecular and structural changes on tissue and cellular level possible (3, 5, 6). In this work, increasing doses of selective broadband UV/UV6, with a relevancy for human skin, were applied on in vitro reconstructed human skin equivalents (3D skin models). 3D skin models are composed out of a reconstructed multilayered and hornified epidermis on top of a living dermal equivalent (4, 7). Reconstructed skin equivalents were UV-irradiated. Tissue viability and secretion of pro-inflammatory Interleukin-6 were measured afterwards to characterize UVR-induced cellular stress. Post-UVR applied Resveratrol demonstrated a positive impact on irradiated 3D skin models after 48 hours. For testing actives or formulas for their effectiveness against mechanisms of acute photodamage and in consequence of premature skin aging, 3D skin models could probably used as an additional test platform to clinical UVR studies in future, which is free from ethical concerns (4).
Skin is most exposed to environmental sunlight, which is demonstrably involved in the development of human skin pathologies such as sunburn, autoimmunity, immunosuppression and cancer (1, 3). From the cosmetic point of view sun light induced skin damages that ultimately lead to visible signs of premature skin aging are particularly to stress (1, 8). The ultraviolet (UV) fraction of sunlight (200-400 nm) represents explicitly skin-toxic wavelengths, which can be class divided in UVC (200-280 nm), UVB (280-320 nm) and UVA (320-400 nm), (1, 8). However, UVC is quite effectively blocked by earth’s ozon-layer in the lower stratosphere but long-wave UVB and UVA irradiation reach earth surface and are well absorbed by unprotected human skin (1, 8). UVB is most effectively absorbed by cellular components of the epidermal keratinocytes, which form the most apical skin layers (1, 8). Inflammation, burns and immunosuppression are acute consequences of highly dosed UVB-irradiation, which eventually lead to skin cancer later on (1, 8). Long-wave UVA irradiation penetrates deeper into dermal structures and is also a proven cause for pathologic skin chan ...