Hepatic gene expression after direct DNA injection

The liver is an attractive target tissue for gene therapy. Current techniques which may be useful for in vivo hepatic gene delivery include viral vectors such as retroviruses, adenoviruses and adeno-associated viruses, and non-viral methods including liposome/DNA complexes, peptide/DNA complexes, dendrimer delivery and direct injection of DNA. While, previous studies have suggested that genes cannot be delivered to liver tissue by direct DNA injection, this review focuses on the factors that lead to significant gene expression in liver, as compared to other tissues, after direct injection of plasmid DNA. Several factors are discussed, including injection technique, DNA dose, DNA diluent and enhancement of transfected gene expression by dexamethasone administration. The current limitations and potential uses of direct DNA injection into liver are reviewed. Direct DNA injection is currently a reliable, reproducible and simple alternative for hepatic gene transduction that provides a tool for molecular research and may have future potential for therapeutic gene delivery.