WOUND HEALING RESPONSE OF A FULL THICKNESS IN VITRO HUMAN SKIN EQUIVALENT (EPIDERM-FT™ 200) AFTER SOLAR UV-IRRADIATION.

Normal human epidermal keratinocytes (KC) and dermal fibroblasts (FB) were cultured to produce full-thickness skin equivalents with FB-containing dermal and stratified epidermal components and fully developed basement membrane at the dermal/epidermal junction (EpiDermFT 200). The wound healing response of EpiDermFT after solar UV-irradiation was compared to excised human skin. H&E stained paraffin sections of EpiDermFT showed a dose-dependent increase in apoptotic sunburn cells at 24 h post-irradiation. After 48 h, high dose (61 J/cm2, metal halide lamp) samples showed extensive epidermal damage and some dermal damage. At 72 h, sunburn cells still persisted in mid dose samples (40 J/cm2), which were thinner than controls (indicating decreased KC proliferation), but still without major epidermal damage. Epidermal destruction of high dose samples was nearly complete at 72 h with loss of dermal matrix also evident. However viable basal cells remained in some areas, with signs of proliferation and epidermal regeneration. Between days 5-7, substantial regeneration of the epidermis had occurred. Active MMP-1 protein in the culture media was also evaluated by ELISA. A 50% increase in MMP-1 was observed in irradiated samples at 24 h. By 48 h, mid-dose samples showed a 2-fold increase in active MMP-1 protein, while high dose samples showed a 3-fold increase. At 72 h, mid-dose sample MMP-1 protein was comparable to controls, while high dose sample activity remained elevated by 3-fold. Similar experiments were conducted with excised human skin. The response was similar to EpiDermFT. The earliest response was increased sunburn cell formation, with tissue thinning at 40 J/cm2 and extensive damage at 61 J/cm2. A viable, regenerative basal epidermal cell layer was also observed in the excised human skin at 72 h in high dose samples. These results show that the EpiDermFT human skin equivalent behaves similarly to excised human skin in terms of solar UV induced damage and wound healing. The model may thus prove useful for additional applications in dermal/epidermal wound healing phenomena.

Basement membrane, Collagenase (MMP) release, Cytokine release, Dermal phenomena, EFT-200 cultures, EpiDerm-FT, EpidermFT, IL-8, Immunohistochemistry, In vitro, Keratinocyte/fibroblast (KC/FB) interactions, MMP, Matrix metalloproteinase 1(MMP-1), Necrosis regeneration, Solar UV irradiation, Sunburn cell formation, Wound healing

UV light