Time and dose-related ultraviolet B damage in viable pig skin explants held in a newly developed organ culture system

For facilitating photochemical and toxicological studies an ex vivo skin mo del was developed in our laboratory using skin from domestic pigs, The mode l comprised the use of a complete skin piece, including the dermis and stra tum corneum, of bigger areas to make future topical applications easier. Fu lly differentiated skin explants (5 x 50 mm, thickness 5 mm) were irradiate d with ultraviolet B (UVB; 1-10 kJ/m(2); 6 W/m(2)). Directly thereafter the y were brought in culture (Dulbeccos modified Eagles medium containing hydr ocortisone; air/liquid interface) for a maximum of 144 h, In nonirradiated skin explants, signs of tissue degeneration were observed after 48 h in cul ture (hematoxylin and eosin, light microscope). However, keratinocytes, iso lated enzymatically (thermolysin and trypsin) at different time intervals i n culture from nonirradiated skin explants showed negligible loss in viabil ity (trypan blue exclusion) and increased apoptosis (terminal deoxynucleoti dyl transferase-mediated deoxy uridine triphosphatase nick end labeling ass ay) for up to 72 h, Explants irradiated with a single dose of UVB showed a clear and reproducible dose- and time-dependent tissue degeneration, loss i n keratinocyte viability and increase in apoptosis compared with nonirradia ted explants at the same time interval. In conclusion, the presently design ed ex vivo pig skin model can be a useful and cheap tool for future investi gations of short-term UV-induced effects in combination with phototoxic and photoprotective compounds.