Previously, we showed that rodent muscle has the ability to take up and express plasmid genes injected intramuscularly. This study now demonstrates that nonhuman primate muscle also has this ability to express injected plasmids. A scaled-up version of the standard large preparation of plasmid DNA allowed several tens of milligrams of CCC plasmid DNA to be relatively easily produced and administered to monkeys. After the injection of the E. coli beta-galactosidase reporter gene in pRSVLac-Z, foreign gene expression was localized to both type I and type II myofibers. The luciferase reporter gene in pRSVL was used to quantify the amount of expression. The multiple implantation of plasmid DNA pellets was more efficient in expressing luciferase than the injection of DNA in normal saline. Luciferase activity persisted for at least 4 months after injection. However, the luciferase expression was considerably less than that in rodents. Preliminary studies explored why expression was less in monkeys. Of particular interest was the increased thickness of the perimysium of monkeys as compared to that in rodents. This increased connective tissue may decrease delivery of the plasmid DNA to the myofibers. Anti-nuclear or anti-DNA antibodies were not observed, even after repetitive DNA administrations, and no adverse effects were observed in any of the monkeys.

We have previously demonstrated that the particle bombardment method for gene transfer (Accell) provides a new means for transfection of various cell types in culture. In this study we evaluate its application to rat brain systems. Using a luciferase (luc) gene as a reporter, we obtained high levels of transient gene expression in primary cultures of fetal brain tissue. Reduced but significant levels were also detected in adult brain primary cultures. Both neuron and glial cells were transfected using this technique. The transient gene expression level obtained with Accell was at least 100-fold higher than that obtained with three other gene transfer methods. The relative strengths of four cellular and seven viral promoters were also evaluated in these cultures. In vivo gene expression was studied using freshly excised and bombarded fetal brain tissues which were immediately transplanted into caudate or intracortical brain tissues of adult host animals. Assays showed that luciferase activity was present in transplants for up to two months following gene transfer. In vitro and in vivo expression of a rat tyrosine hydroxylase (TH) gene, a candidate gene for treatment of Parkinson's disease, was also detected in this rat brain system. Our results suggest that the particle bombardment gene transfer technology can be employed as an effective method for ex vivo gene transfer into brain tissues.

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