This project aims at improving the circulation in ischemic tissues by gene transfer of VEGF and related factors. The first part of the project deals with mouse studies in which ischemia is induced in the leg and viral vectors containing VEGF and other factors are attributed to the ischemic area. Visualization and quantification of the formation of collateral vessels and evaluation of increased blood flow are the first objectives. Subsequently, the way of application and involvement of different cell types is evaluated. Clinical studies are prepared. The studies are done at TNO Prevention and Health (TNO-PG) and Leiden University Medical Centre (LUMC) in the context of the tripartite angiogenesis program of VUMC - LUMC -TNO-PG.