Erythropoietin secretion and physiological effect in mouse after intramuscular plasmid DNA electrotransfer

Background Direct intramuscular plasmid DNA injection has recently been pro posed for erythropoietin therapy, as an alternative to either systemic inje ction of recombinant erythropoietin or the use of viral vectors for erythro poietin gene transfer. However, direct intramuscular plasmid injection has so far been hampered by low efficiency and high interindividual variability . Method We explored the use of a new method termed 'intramuscular electrotra nsfer' for erythropoietin gene expression in the mouse. This method is base d on intramuscular plasmid injection followed by application of appropriate electric pulses. Results Intramuscular plasmid electrotransfer in mouse leg led to an increa se of approximately 10- to 100- fold in circulating murine erythropoietin l evel, as compared to naked DNA alone. Using electrotransfer, as little as 1 mu g of an erythropoietin encoding plasmid was sufficient to induce an inc rease in mouse hematocrit, from 47% up to 80%. This hematocrit increase was stable for at least two months. Moreover, interindividual hematocrit varia bility was markedly reduced by electrotransfer, as compared with naked DNA injection. Conclusion In vivo electrotransfer appears to be a convenient method for ob taining high erythropoietin expression in mice, and it could also be used f or the expression of other secreted therapeutic proteins. Copyright (C) 199 9 John Wiley & Sons, Ltd.