TIMECOURSE OF HEALING AFTER UV-INDUCED DAMAGE IN THE EPIDERM-FT IN VITRO HUMAN SKIN MODEL.

• TR Number: 651
• Keywords: Acantholysis, Basal cell proliferation, Cyclopyrimidine dimer, EFT-400, EpiDerm-FT, IL-8 release, Ki67, MMP-1 activity, Morphological analysis, Pyknotic nuclei, Skin healing , Solar stimulator, UV-induced damage, Wound healing

Solar ultraviolet (UV) radiation is known to have deleterious effects on human skin.  UVB (280-320 nm) and UVA (320-400 nm) segments of solar radiation have been shown to affect keratinocytes, the major cellular constituent of the epidermis, by causing direct DNA damage and/or indirect DNA damage and cytotoxicity through the formation of reactive oxygen species (1,2,3).  In the present study, a commercially available human skin equivalent (EpiDerm-FT) was compared to excised human skin to gain insight into the temporal UV-induced wound healing response of human epidermal tissue. A solar simulator was used to deliver a range of UVR doses to EpiDerm-FT and excised human skin.  UVR induced damage and healing over time was evaluated histologically in H&E stained paraffin sections.  DNA damage indicated by cyclopyrimidine dimer (CPD) formation was assessed by immunohistochemistry (IHC).  Cell proliferation during the healing process, as indicated by Ki67 expression, was also assessed by IHC. Finally, inflammatory mediator release (IL-8) and protease activity (MMP-1) in the culture medium was assessed by ELISA.