Genetic targeting of endothelial populations for therapeutic applications

Abstract

1046

We have identified a transgenic enhancer cassette derived from cadherin 5 (VE-cadherin, VECAD) gene that directs gene expression in a subset of bone marrow cells that include endothelial cell progenitors (BMD-ECP). In the present report we describe the creation and initial characterization of a family of lentiviral expression cassettes using the VECAD genetic element. Preliminary studies with VEcad-GFP lentiviral vectors indicated utility in marking a variety of endothelial cell types, including those from large and small blood vessels and from arterial and venous vessels. Expression in non-endothelial cells was not detected. A second family of cad5 promoter vectors was created to carry hsv thymidine kinase (hsvTK). hsvTK is widely used in gene therapy vectors because of its specific ability to convert the prodrug gancyclovir into a cytotoxic thymidine analog p-gancyclovir. VEcad-hsvTK infected endothelial cells displayed high levels of killing in response to treatment with gancyclovir. Killing was both dose and time dependent and was restricted to endothelial targets. In vitro experiments with a variety of endothelial and non endothelial cell lines indicated that killing by gancyclovir was EC specific and required both the presence VEcad-hsvTK lentivirus and gancylovir. Experiments are currently underway to test the efficacy and specificity of this approach for in vivo labeling and tracking of BMD-ECP in mice.