In vivo electrotransfer of the cardiotrophin-1 gene into skeletal muscle slows down progression of motor neuron degeneration in pmn mice.

Among all vectors designed for gene therapy purposes, adenovirus appears to be the most efficient in vivo vehicle to transduce the broadest spectrum of cellular targets. However, the deleterious immunogenicity of this viral vector impedes its use in chronic diseases. Non-viral vectors, such as naked DNA, are attractive alternatives for safety and technical issues, such as scale-up production. Naked DNA injection, greatly improved when combined with electroporation, showed great potential in adult animals, especially when directed to the muscle. We have recently proven the therapeutic effect of a neonatal single intramuscular injection of a cardiotrophin-1 (CT-1)-encoding adenovirus in a hereditary disease mouse model of human motor neuron disease, the progressive motor neuronopathy (pmn) mutant. We now demonstrate that a single injection/electroporation of a CT-1-encoding plasmid in neonate pmn mice is almost as efficient as adenovirus-mediated gene transfer with respect to survival, muscular function and neuroprotection of the animals. Treated mice gain global weight, their mean lifespan is extended by 25%, all their electromyographic parameters are improved and myelinated axons of their phrenic nerves are protected. Moreover, we show that re-injection/electroporation leads to improvements in this neuroprotection. We therefore demonstrate for the first time the therapeutic efficacy of neonatal intramuscular DNA injection/electroporation in a murine model of a human hereditary disorder.