Scientists writing in the upcoming issue of the journal Nature say experiments in mice show that a special sort of cell that we all carry around in our blood and bone marrow can rebuild damaged hearts, and probably other organs as well. This ScienCentral News video report (at right) has all the details.

The end of a controversy?

For years, scientists believed that only fetal stem cells had this capability, leading to efforts to reverse a federal ban on funding research using embryos. Fetal stem cell research hit another snag recently, when it was reported in the New England Journal of Medicine (NEJM) that fetal cells implanted in the brains of Parkinson’s disease patients not only showed less improvement than had been hoped for, but also caused additional severe side effects—uncontrollable writhing and jerking—a year after the procedure.

Now the Nature paper and other research has many persuaded that adult stem cells are both scientifically and ethically superior.

"The benefit of working with adult stem cells, of course, is that you avoid all of the political and religious controversy," says Donald Orlic at the National Institutes of Health’s Human Genome Research Institute. "You’re working with adult stem cells, which all of us possess—we don’t have to depend upon a donor source. They can be harvested, the method for harvesting adult stem cells is going to improve, and the capability of working with these stem cells and regenerating various organs is obviously going to improve. So I would say that while many people had looked to embryonic stem cells as a kind of a cure for many disorders, I think that a lot of attention now deservedly should shift to adult stem cells."

Human clinical studies are probably at least three or four years away though, according to Orlic. The finding that bone marrow stem cells are able to reprogram themselves to produce cardiac muscle and vessels rather than blood cells is "totally unexpected," he says. "What we have is an empirical finding, but we can’t explain it—we’re only grateful that it worked. We have to find out the triggers for that reprogramming."

Another problem is that there is no way to predict what might happen to the organs being treated in the several years after the procedure. An analysis of the Parkinson’s/fetal cell study in NEJM points out that "one of the most important lessons from this study is that one year of follow-up is not sufficient for an evaluation of nerve-cell transplantation. Neural plasticity works at mysteriously different rates, so long-term outcome must be evaluated."

"I don’t think this is the kind of a thing that can be rushed into," says Orlic. "I think we want to be very cautious. Optimistic, but cautious."