Electroporation-facilitated delivery of plasmid DNA in skeletal muscle: Plasmid dependence of muscle damage and effect of poloxamer 188

Electroporation has been reported to facilitate naked DNA gene transfer in skeletal muscle, but has also been implicated in the pathogenesis of electr ical injuries. To assess the effects of electroporation on gene transfer, m ouse quadriceps muscles were injected with the luciferase reporter plasmid VR1255 and electroporated with caliper electrodes. Intramuscular luciferase expression was increased 10- to 70-fold by electroporation, depending on t he DNA dose and injection volume used. In the absence of plasmid DNA inject ion, electroporation of quadriceps muscles resulted in rapid elevations in serum creatine phosphokinase activity, but did not elicit visible muscle da mage. However, in muscles injected with plasmid DNA and electroporated, vis ible lesions consistently developed in the areas proximal to electrode plac ement when field strengths optimal for gene transfer (300 volts/cm) were ap plied. The development of muscle lesions was independent of plasmid transge ne expression and required the presence of plasmid in the muscle during ele ctroporation. Co-injection of poloxamer 188 (pluronic F68) with VR1255 subs tantially reduced elevations in serum creatine phosphokinase activity follo wing electroporation, but did not inhibit the development of muscle lesions . In non-electroporated muscles, co-injection of poloxamer 188 increased lu ciferase expression threefold. Poloxamer 188 may thus constitute a useful e xcipient for intramuscular delivery of naked DNA.