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Briefing and Opinion
July 15, 2005

Unique Potential of Stem Cells

Geneticist Dr. Janet Rowley is a professor in the Department of Genetics at the University of Chicago and a member of the President's Council of Bioethics.

Janet Rowley

Q: What is a stem cell?

JANET ROWLEY: A stem cell is a very primitive cell that can differentiate into many different kinds of cells. You figure that our body is made up of 200 different tissues. They all came initially from an egg that was fertilized by a sperm. So the cells early on have the possibility of turning into any one of those 200 tissues. It's those very early cells that are stem cells.

Q: How does the stem cell know what to become? A muscle or a bone cell, for example?

ROWLEY: That's a very complicated question that we can't answer in great detail at the present time. But it's very clear that the stem cells get messages from the cells that are right next door. And it is the interaction of the cell's own genetic program with messages that it gets that turns it into a muscle cell or a pancreas cell. All of developmental biology is focused on trying to answer that question.

Q: Is that why researchers are so interested in having access to embryonic stem cells? Because they are so fundamental to the question of how we become what we are?

ROWLEY: That's only part of it, because you can ask and answer many of those questions in other species. So much of the work has been done in the fruit fly or in some very simple worms. If you want to ask more complicated questions, then you go to the mouse. The challenge is that human embryonic stem cells, if we knew all of the right things to do with them, could also then be used to treat patients with disease and that's what makes them so important.

Q: What diseases are we talking about?

ROWLEY: There are a number. I think that one of the ones that we may be most successful with early on is going to be juvenile diabetes. In individuals with this form of diabetes, their own cells, their own lymphocytes attack the cells in the pancreas that make insulin and kill those cells so that the patient then has to use insulin for the rest of their life. If we could figure out a strategy to replace those cells making insulin then that would be the cure or go a long way to cure that disease. One can think of Parkinson's Disease, as well in such a category.

Q: You would take the stem cells and train them to become the cells in the pancreas that make insulin, then implant them into the patient who is suffering from diabetes and the problem would be solved?

ROWLEY: That is right. Except that we still have to worry about how are we also going to get rid of the lymphocytes that killed the patient's own cells that made insulin. But that's a separate problem, removed from the critical problem of how do we figure out how to make those cells into the specialized cells in the pancreas? So that's a real challenge.

Q: Can umbilical cord blood stem cells and adult stem cells offer the same opportunities to researchers that embryonic stem cells do?

ROWLEY: Scientists who have specialized in working with adult stem cells say that the adult stem cells do not have the same potential to differentiate into multiple tissues. They certainly can differentiate into many, many tissues but probably not all. The other problem is they have a finite lifespan. All of our cells in the body will divide a certain number of times and then they die. If you use adult stem cells, they already have divided quite a number of times. And so that if you put them into a younger individual, they are going to die before the individual will die.

Q: But what about the umbilical cord blood stem cells? Do they offer better potential than the adult stem cells do?

ROWLEY: At the present time, umbilical cord blood stem cells have not been able to differentiate into other types of cells than blood cells and so they would have an even more limited potential than some of the cells that have been used from adults.

Q: Some suggest there is a sizeable minority in the American public who simply think that embryonic stem-cell research is wrong. How do you bear that in mind as a working researcher?

ROWLEY: This is what we go through in the President's Council all the time, individuals who believe that using embryos for research is murder. There is no way of discussing and changing their points of view. Scientists can make every effort to persuade the general public that, in fact, they realize that there have to be guidelines on how they do research. For instance, if you were going to use eggs from women who donate them, that they not be paid so there not be an incentive for them to do this. Or that embryos that are donated have to be donated with informed consent from both of the donors, the egg donor and the sperm donor if it's a couple.

Q: If you had five minutes with the president, one on one, to try to change his mind, on the subject of stem-cell research, what would you say to him?

ROWLEY: You certainly have the respect that is due to human embryos. At the same time, I think you have major respect due to individuals who have serious diseases. It is important to the American people to try to see if, with proper support, some aspects of human embryonic stem-cell therapy can really come to fruition. The possibility of doing major good should balance the possibility of using the embryos. Moreover, these embryos are going to be thawed out and thrown away. They can't be kept indefinitely in freezers. You are wasting what is, in my view, a very valuable resource.

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