1. ¹CNRS, UMR 8121, Laboratory of Vectorology and Gene Transfer, Institut Gustave-Roussy, Villejuif, France
2. ²Univ Paris-Sud, UMR 8121, Laboratory of Vectorology and Gene Transfer, Institut Gustave-Roussy, Villejuif, France
3. ³UMR7561 CNRS, Université de Nancy I, Vanduvre Lès Nancy, France
4. ⁴Biostatistics and Epidemiology Unit, Institut Gustave-Roussy, Villejuif, France

Correspondence: Dr LM Mir, Laboratory of Vectorology and Gene Transfer, UMR 8121 CNRS, Institut Gustave-Roussy, Université Paris XI, 39 rue Camille Desmoulins, F-94805 Villejuif Cédex, France. E-mail: luismir@igr.fr

Received 7 March 2006; Revised 7 June 2006; Accepted 7 June 2006; Published online 27 July 2006.

Abstract

The simple injection of DNA into muscles is known to result in the expression of the injected genes, even though at low and variable levels. We report that this variability in DNA expression is partly dependent on the injection speed. The acceleration of the injection speed from values around 2 l/s up to ones around 25 l/s (depending on the tissue) results in a significant increase in gene expression in skeletal muscle (280 times on an average) and in liver (50 times) and a nonsignificant sevenfold increase in tumors. Heparin, which inhibits the spontaneous uptake of the injected DNA, also inhibits the increases related to the injection speed. However, at the highest injection speed, this inhibition is not total because very fast injections provoke a direct permeabilization of the cells. This 'hydroporation' could be similar to the permeabilization found in the hydrodynamics method based on the fast intravascular injection of a huge volume of DNA. Neither the 'hydroporation' nor the heparin-inhibitable uptake mechanism induces histologically detectable lesions. There is a limited muscle cell stress independent of the injection speed. Heterogeneity in the injection speed might thus be an explanation for the variability in DNA expression after simple injection.