Stem cells from the amniotic sac that surrounds a fetus may someday be used to repair damage caused by a heart attack, Japanese researchers report. The work, so far only conducted in animals, raises the possibility of a non-controversial source of stem cells to treat not only heart disease but also many other conditions, said Dr. Shunichiro Miyoshi, an assistant professor in the cardiology department at the Keio University School of Medicine, and...