Skin-targeted gene transfer using in vivo electroporation

The skin is an important target for gene transfer because of its easy accessibility. Using plasmid DNA expressing rat erythropoietin (pCAGGS-Epo) as the vector, we previously demonstrated long-term Epo delivery in rats by muscle-targeted gene transfer using in vivo electroporation. Here we examined whether this electroporation approach could be applied to gene delivery in rat skin. To optimize gene transfer, we tested the efficiency of skin-targeted Epo gene transfer with three types of electrodes at three different electrode voltages. Each rat was injected intradermally with a total of 800 mug of pCAGGS-Epo, in the abdominal area. Plate-and-fork-type electrodes were effective for Epo delivery by skin-targeted gene transfer at low voltages (12-24 V). The vector-derived Epo mRNA was expressed only at the DNA injection site. The Epo gene was expressed in a dose-dependent manner, the expression persisted for 7 weeks, and hematocrit levels were increased for 11 weeks. Skin injection with pCAGGS-lacZ showed lacZ gene expression in the epidermis on day 1 after injection and in the subcutaneous muscle layer on day 7. Slight skin damage due to the gene transfer procedure was evident on day 1, but absent by day 7. These results demonstrate that skin-targeted pCAGGS-Epo transfer by in vivo electroporation at low voltage is a useful procedure for the short-term delivery of Epo.