Analysis of cell-specific promoters for viral gene therapy targeted at thevascular endothelium

The use of viral vectors for vascular gene therapy targeted at the endothel ium is limited by the promiscuous tropism of vectors and nonspecificity of viral promoters, resulting in high-level transgene expression in multiple t issues. To evaluate suitable endothelial cell (EC-specific promoters for va scular gene therapy, we directly compared the ability of the fins-like tyro sine kinase-1 (FLT-1), intercellular adhesion molecule-2 (ICAM-2), and von Willebrand factor (vWF) promoters to drive EC-restricted transcription afte r cloning into adenoviral vectors upstream of lacZ. Vastly different expres sion profiles were observed. Whereas both FLT-1 and ICAM-2 promoters genera ted transgene expression levels similar to cytomegalovirus in ECs in vitro, vWF expression levels were extremely low. Analysis of non-EC types reveale d that ICAM-2 but not FLT-1 evoked leaky transgene expression, thus identif ying FLT-1 as the most selective promoter. With an ex vivo human gene thera py model, the FLT-1 promoter demonstrated EC-specific transgene expression in intact human vein but no detectable expression from infected exposed smo oth muscle cells in EC-denuded vein. Furthermore, when adenoviruses were sy stemically administered to mice, the FLT-1 promoter demonstrated extremely low-level gene expression in the liver, the major target organ for adenovir al transduction in vivo. This study highlights the potential of using the F LT-1 promoter for local and systemic human gene therapy in hypertension and its complications.