writes "Researchers at Harvard University have been working towards a goal of replacing some types of heart surgery with injections of cells that would grow into blood vessels for damaged hearts. The cells that would be used are progenitor cells obtained from the blood or bone marrow, as opposed to stem cells that are obtained from human embryos. The research team was successful with their tests on growing heart blood vessels in mice. Joyce Bishoff, an associate professor of medicine at Harvard and senior author of the report, says, 'Our next goal down the line is to use them in humans.' She also notes that more studies need to be done on animals to see how these cells would react and behave with other types of tissues. A similar human experiment was done two years ago in Germany, during which a few people from a group of 75 heart attack victims were given injections of progenitor cells from their own bone marrow or blood. The report concluded that there were improved heart functions."
points out related coverage
with some more information at BBC News.