Scientists are making real progress in developing therapies for heart damage. Here, EurekAlert reports on a study showing that human cord blood stem cells (HUBC) can repair heart attack damage in rats. "The HUCB stem cells were injected directly into the heart muscle of rats an hour after heart attacks were induced. After four months of recovery, the size of scar tissue left by dead heart muscle was approximately three times smaller in the HUCB treated rats than in the untreated rats. As a result, the heart's pumping capacity improved to near normal in the treated rats, after an initial decline, and was significantly greater than the cardiac function in the untreated rats with heart attacks." As the article notes, scientists are still trying to understand how stem cells work to repair damage in these types of therapies.