Needleless in vivo gene transfer into muscles by jet injection in combination with electroporation

Previously, we have established an in vivo electroporation method for gene transfer into muscle by injection of DNA with a needle followed by electric pulse delivery using needle-type electrodes and proved that this method is effective for the systemic delivery of cytokines. To perform the needleless gene delivery, we combined jet injection of DNA with electroporation using plate-type electrodes. For delivery of beta-galactosidase- and enhanced green fluorescent protein (EGFP)-expressing plasmids into muscles, there was no significant difference between the previous needle-mediated method and the newly developed jet-injection method. When pCAGGS-IL-5 was introduced into tibialis anterior, quadricipital and back sural muscles by this new method, the serum IL-5 levels reached 3.4 +/- 0.9, 5.7 +/- 1.7 and 8.4 +/- 2.7 ng/ml at day 5, respectively. Although the peak values of IL-5 achieved by the jet-injection method in these muscles were lower than that of the highest value achieved by needle-mediated gene delivery into anterior tibial muscle, this new method could deliver plasmid into relatively large muscles with better efficiency than the needle-mediated method. Thus the jet-injection method provides a useful means of gene delivery into large muscles, which is essential for future use in human gene therapy.