About a third of heart disease patients undergoing angioplasty to open up blocked arteries develop complications and even new blockages caused by stents-the tiny metal scaffolds inserted to hold the arteries open. Now researchers at the Children's Hospital of Philadelphia have developed a way to shield arteries from such complications using the stents themselves to deliver beneficial genes to the body. In contrast to other methods of gene therapy, which use viruses as carriers, this new approach depends on coating the stents with a biodegradable polymer containing therapeutic genes. In recent experiments, researchers inserted the coated stents into pigs' arteries and observed the polymer degrade, releasing genes into the arterial-wall cells. Once inside the cells, the genes began producing specific proteins. According to head researcher Robert Levy, the team is screening various candidate genes to find one that would not only protect blood vessels but also treat underlying heart disease. They hope to start human clinical trials within three years.