Orlando, Florida - Researchers said yesterday they had used gene therapy to grow new blood vessels in the legs of people with blocked arteries and said it was the first time gene therapy had worked successfully in humans. They injected DNA instructing the body to grow the new blood vessels into 10 people and were delighted to find most of the patients did indeed grow new arteries. "This is the first time that gene therapy has been proven to work," Dr Jeffrey Isner of St Elizabeth Medical Center and Tufts University School of Medicine in Boston, who worked on the study, said.