Direct gene transfer into the mouse heart

Direct injection of plasmid DNA into the myocardium of several species has been shown to be useful for studying cardiac gene expression. However, despite a better understanding of mouse genetics and the availability of several disease models in mice, gene injection with plasmid DNA into the mouse heart has not been reported. In this study, we demonstrate a simple and reproducible method for gene transfer into the mouse heart via direct injection of plasmid DNA. A firefly luciferase gene, driven by the RSV promoter, was used to quantitatively determine the spatial and temporal characteristics of gene transfer. Luciferase gene expression was stable for 8 weeks and showed a dose-dependent response over a range of 0.3-3 mu g of input DNA. Inter-animal variability was low and gene expression was restricted to the left ventricle, near the site of injection. This method was also demonstrated to be suitable for detecting the expression of structural genes under the control of cellular promoters. Immunohistochemistry was used to detect the expression of an epitope-tagged myosin heavy chain driven by a rat a-myosin heavy chain promoter. Thus, naked DNA injection into the mouse heart results in a highly reproducible expression of constructs with either viral or cellular promoters. It is a relatively inexpensive and efficient means of studying cardiac gene regulation in vivo and a useful tool for screening the potential transgenes before generating transgenic mice. (C) 1997 Academic Press Limited.