1. ¹Bristol Heart Institute, University of Bristol, Bristol, UK
2. ²Leiden/Amsterdam Center for Drug Research, Leiden University, Leiden, The Netherlands

Correspondence: Dr SJ White, Bristol Heart Institute, University of Bristol, Level 7 Bristol Royal Infirmary, Bristol BS2 8HW, UK. E-mail: steve.white@bris.ac.uk

³Current address: Kingswood Court, London, UK

Received 2 May 2007; Revised 1 September 2007; Accepted 8 October 2007; Published online 8 November 2007.

Abstract

Increasing the level and duration of transgene expression and restricting expression to vascular cells are important goals for clinically useful gene therapy vectors. We evaluated several promoters, enhancers and introns in endothelial, smooth muscle and liver cells in tissue culture and in vivo, comparing local delivery to the carotid artery with intravenous delivery to the liver. A 1800-bp fragment of the oxidized LDL receptor (LOX-1) promoter showed highest in vivo activity in the carotid artery, achieving 39% the activity of the reference cytomegalovirus promoter, with 188-fold greater specificity for carotid artery over liver. An enhancer from the Tie2 gene in combination with the intracellular adhesion molecule-2 promoter improved endothelial specificity of plasmid vectors, increased the expression from adenoviral vectors in cultured endothelial cells and doubled the specificity for carotid artery over liver in vivo. Adding a short intron to expression cassettes increased expression in both endothelial and smooth muscle cells in vitro; however, the eNOS enhancer failed to consistently increase the expression or endothelial specificity of the vector. In conclusion, elements from the LOX-1 promoter and Tie2 enhancer together with an intron can be used to improve vectors for vascular gene transfer.