In VivoGene Transfer and Expression in Rat Stomach by Submucosal Injection of Plasmid DNA

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Abstract
Gastrointestinal nonepithelial tissue is a useful target for in vivo gene transfer. The aim of this study was to investigate whether gene transfer into this organ could be achieved by submucosal injection of plasmid DNA. Plasmid DNA carrying either the firefly luciferase or Escherichia coli LacZ reporter gene was injected directly into the gastric submucosa of adult rats. Gene expression was characterized by quantitative luciferase assay and qualitative in situ β-galactosidase (β-Gal) staining. Luciferase activity was detected as early as 1 day after injection, increased markedly at 2 days, and then decreased. Some of the rats showed detectable levels of luciferase expression at 14 and 21 days postinjection. Histochemical staining for β-Gal demonstrated that expression of the recombinant genes was localized in smooth muscle cells of the muscularis mucosae and the muscular layer and mesenchymal cells in the lamina propria. Our results indicate that gene transfer into the gastrointestinal tract can be achieved by simple needle insertion of naked plasmid DNA into the submucosa. In this study, we demonstrate successful gene transfer into rat stomach following submucosal injection of plasmid DNA. Gene expression in the stomach was observed at levels similar to those seen in the control striated muscle and persisted substantially for 7 days. Expression of the recombinant gene mainly occurred in smooth muscle cells of the muscularis mucosae and the muscular layer. Our results extend previous observations for naked DNA expression in skeletal muscle and cardiac muscle and suggest that the capability to take up and express naked DNA is a general property of all types of myocytes, but the kinetics of DNA expression substantially differ among myocyte types.