High-level expression of naked DNA delivered to rat liver via tail vein injection

• Published in: The journal of gene medicine Vol. 4; no. 3; pp. 333 - 341
• Main Authors: Maruyama, H., Higuchi, N., Nishikawa, Y., Kameda, S., Iino, N., Kazama, J. J., Takahashi, N., Sugawa, M., Hanawa, H., Tada, N., Miyazaki, J., Gejyo, F.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-05-2002; Wiley Periodicals Inc
• Subjects: Animals; Base Sequence; DNA - administration & dosage; DNA Primers; erythropoietin; Erythropoietin - genetics; Gene therapy; Genetic Vectors; hydrodynamics-based transfection; Immunohistochemistry; Lac Operon; liver; Liver - metabolism; Male; naked DNA; Plasmids; Polymerase Chain Reaction; rat; Rats; Rats, Wistar; Tail - blood supply; tail vein injection
• ISSN: 1099-498X; 1521-2254
• DOI: 10.1002/jgm.281

Background
High levels of foreign gene expression in mouse hepatocytes can be achieved by rapid tail vein injection of a large volume of a naked DNA solution, the ‘hydrodynamics‐based procedure’. Rats are more tolerant of the frequent phlebotomies required for monitoring blood parameters than mice, and thus are better for some biomedical research.
Methods
We tested this technique for the delivery of a therapeutic protein in normal rats, using a rat erythropoietin (Epo) expression plasmid vector, pCAGGS‐Epo.
Results
We obtained maximal Epo expression when the DNA solution was injected in a volume of 25 ml (approximately 100 ml/kg body weight) within 15 s. We observed a dose‐response relationship between serum Epo levels and the amount of injected DNA up to 800 µg. Using quantitative real‐time PCR, the vector‐derived Epo mRNA expression was mainly detected in the liver. When a lacZ expression plasmid was injected similarly, β‐galactosidase was exclusively detected in the liver, mainly in hepatocytes. Toxicity attributable to the technique was mild and transient, as assessed by histochemical analysis. Epo gene expression and erythropoiesis occurred with Epo gene transfer in a dose‐dependent manner, and persisted for at least 12 weeks, the last time point examined. Repeated administration of the plasmid DNA also effectively led to erythropoiesis.
Conclusions
These results demonstrate that gene transfer into the liver via rapid tail vein injection can easily be achieved in the rat, which is more than 10 times larger than the mouse, and has significant value for gene function analysis in rats. Copyright © 2002 John Wiley & Sons, Ltd.