Electrogene transfer (EGT) of plasmid DNA into skeletal muscle is a promising strategy for the treatment of muscle disorders and for the systemic secretion of therapeutic proteins. We report here that preinjecting hyaluronidase (HYAse) significantly increases the gene transfer efficiency of muscle EGT. Three constructs encoding mouse erythropoietin (pCMV/mEPO), secreted alkaline phosphatase (pCMV/SeAP), and luciferase (pGGluc) were electroinjected intramuscularly in BALB/c mice and rabbits with and without HYAse pre-treatment. Preinjection 1 or 4 hr before EGT increased EPO gene expression by about 5-fold in mice and maintained higher gene expression than plasmid EGT alone. A similar increment in gene expression was observed on pretreatment with HYAse and electroinjection of pCMV/mEPO into rabbit tibialis muscle. The increment of gene expression in rabbits reached 17-fold on injection of plasmid pCMV/SeAP and 24-fold with plasmid pGGluc. Injection of a plasmid encoding β-galactosidase (pCMV/βgal/NLS) and subsequent staining with 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside indicated that HYAse increased the tissue area involved in gene expression. No irreversible tissue damage was observed on histological analysis of treated muscles. HYAse is used in a variety of clinical applications, and thus the combination of HYAse pretreatment and muscle EGT may constitute an efficient gene transfer method to achieve therapeutic levels of gene expression.
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