Ultrasound-mediated delivery (USMD) of novel therapeutic agents in the presence of
microbubbles is a potentially safe and effective method for gene therapy offering many desired characteristics, such as low toxicity, potential for repeated treatment, and organ specificity. In this study, we tested the capability of USMD to improve gene expression in mice livers using
glycogen storage disease Type Ia as a model disease under systemic administration of naked plasmid
DNA. Image-guided
therapeutic ultrasound was used in two studies to provide
therapeutic ultrasound to mice livers. In the first study, involving wild-type mice, control animals received naked plasmid
DNA (pG6Pase 150 μg) via the tail vein, followed by an infusion of
microbubbles; the treated animals additionally received
therapeutic ultrasound (1 MHz). Following the procedure, the animals were left to recover and were subsequently euthanized after 2 d and liver samples were extracted. Reverse transcription polymerase chain reaction (RT-PCR) assays were performed on the samples to quantify
mRNA expression. In addition, Western blot assays of FLAG-tagged
glucose-6-phosphatase (G6Pase) were performed to evaluate
protein expression. Ultrasound-exposed animals showed a 4-fold increase in G6Pase
RNA in the liver, in comparison with control animals. Furthermore, results from Western blot analysis demonstrated a 2-fold increased
protein expression in ultrasound-exposed animals after two days ( p < 0.05). A second pilot study was performed with G6Pase knockout mice, and the animals were monitored for correction of
hypoglycemia over a period of 3 weeks before tissue analysis. The RT-PCR assays of samples from these animals demonstrated increased G6Pase
RNA in the liver following ultrasound treatment. These results demonstrate that USMD can increase gene expression of systemically injected naked pDNA in the liver and also provide insight into the development of realistic approaches that can be translated into clinical practice.