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Michael Shelanski, MD, PhD |
There has been a lot of discussion about embryonic stem cell research lately. Has the debate left you with questions about the medical potential for control and cures for diseases like Parkinson's, diabetes, and Alzheimer's? Pathologist Michael Shelanski, MD, PhD, joined us on Sept. 22, 2004, to discuss what he and other researchers might find down the stem cell path.
MODERATOR: Welcome to WebMD Live, Dr. Shelanski. There has been a great deal of public discussion about stem cell research, but so much misinformation is floating around this subject. Can you give us a basic crash course on stem cell research? SHELANSKI: Stem cell research covers a very wide area, including stem cells on animals and research on stem cells from humans. A characteristic of a stem cell is that it is capable of giving rise over time to different types of cells; that is, it is a cell that has no characteristic of a kidney cell or a pancreas cell or a brain cell, but will, when put in the appropriate conditions, give rise to one or more of these types of cell. The thing that makes stem cells different is that they are cells that have no defined characteristics and that you can cause to grow in number. So if you start with one stem cell and keep it as a stem cell, over time you can have 10 cells or 10,000 cells. Then by providing the proper signals to those cells you can turn all 10,000 cells into a nerve, a kidney, or pancreas cell. From research in animals we can learn a great deal about the signals that are needed to do this, but the medical promise of the work lies in the possibility that you could use these cells in reparative or regenerative medicine; that is, you could take a heart that had a heart attack so part of it was dead or dying and you could then put the stem cells, in principle, into the heart to repair the heart. It would not be as good as new, but would be considerably less damaged. In humans you need to use human cells for this. You cannot put animal cells into humans because humans will reject the animal cells. The debate that is going on in the public today is over, if you will, a sub-issue of "How do we obtain stem cells?" and it is confused by the fact that the term "stem cell" does not have one single meaning; they all share this multipotential ability, but many people, by "stem cells," mean the very primitive cells taken from an embryo. In fact, you can obtain stem cells from the human umbilical cord; you can obtain them from the adult brain (although no one has obtained them from the human brain, but in principle you could do it), and you can obtain stem cells from the blood. Those people who object to stem cell research, for the most part, object to obtaining stem cells from human embryos. Many people who do not accept that work do not have a problem obtaining them from umbilical cord blood. The Catholic Church does not have a problem with stem cells obtained from umbilical cord blood. The issue comes that in working with embryonic stem cells is that you do sacrifice a very early embryo, and to some people that is completely acceptable, to some unacceptable, and the issue is not a scientific one. Other people might object to stem cells from blood or tissue, because in principle you could make an entire embryo from any stem cell, even an umbilical cord cell. Technologically it is difficult to do it, but theoretically it's possible.
Most scientists feel there is the possibility that they are different from other stem cells; they have greater potential, and if we do not investigate them we could miss the chance to proceed in curative or regenerative medicine, even though it's possible that a stem cell from a nonembryonic source might be able to do as well, but we do not know that. The limitation in access to embryonic stem cells is a bit like trying to fight a battle with one hand tied behind your back. You might find all the strength you need in one hand, but you might find the one hand won't do it. Nobody among responsible scientists is suggesting embryos be generated, be made, for the purpose of making embryonic stem cells. The interest has been largely in using the large number of banked or frozen embryos from the various in vitro fertilization programs to make the cells, taking the view these will never be children or people; they will either be discarded or, less likely, kept indefinitely in a freezer. Other people, including a small minority of scientists, either feel this use of an embryo for research is immoral to begin with or are afraid that this will encroach ultimately on the sanctity of life of children, late-term fetuses, and a whole scenario is postulated in which the child and fetus could be at risk, that we will not just stick to these excess embryos; we're going to want to encroach more on fetuses or generate more embryos for the purpose of medical therapy. The big issue is this is not a scientific question; this is a religious and a national policy question, but not scientific. There's no scientific answer except to say if we do not do the research it's very possible important treatments for Parkinson's, diabetes, ALS, and heart attacks will not be developed, or that they will be developed but developed in other countries where either they will not be available to Americans, either because they start with embryonic cells, or if they are available, they will be at extremely high cost. While the U.S. is doing little in stem cell research, other countries have made stem cell research a centerpiece of their research programs for the years to come. In the U.S., companies and universities that are not using government funds are also doing embryonic stem cell research, but most of the labs in the country have access to only a very limited number of cell lines. While I do not use any of these lines, there is some debate about how many of them are useful.
The opinions expressed herein are the guests' alone and have not been reviewed by a WebMD physician. |
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