Uptake of exogenous DNA via the skin

Easy accessibility makes the skin extremely attractive for therapeutic gene transfer, but this feature may be equally responsible for inadvertent DNA uptake. Therefore we studied lacZ reporter gene expression after epicutaneo us and intracutaneous administration of naked DNA, lipofection and transfer rinfection to intact, tape-stripped, and wound-healing skin of hairless mic e. Gold particles coated with 1 mu g pCMVnlslacZ were inoculated with a gen e gun as a positive control. P-Galactosidase expression by skin cells, i.e. , keratinocytes of the upper epithelial layers and single cells in the uppe r dermis, determined by X-Cal histochemistry was not observed except after ballistic gene transfer. By polymerase chain reaction we detected lacZ DNA after skin bombardment up to 4 weeks. After intracutaneous and epicutaneous application to normal and tape-stripped skin of the various delivery syste ms lacZ DNA was detectable up to 1 week. Epicutaneous application of the de livery systems to wounded skin resulted in lacZ DNA detectability up to 48 h only. Reverse-transcriptase polymerase chain reaction indicated transcrip tion of the reporter gene after particle bombardment and intracutaneous inj ection, up to 48 h, but not after epicutaneous application of either delive ry system. The possibility of inadvertent uptake of exogeneous DNA by intac t and tape-stripped skin is evidenced by the detection of reporter gene DNA after epicutaneous application of naked DNA and DNA complexed to cationic lipids or transferrin-polylysine (transferrinfection). However, the effects of the presence and persistence of foreign genes in the target cells are n ot clear yet.