August 16, 2002
By Erica Heilman
Last year, scientific researchers and pro-life groups waited for a presidential verdict on the future of embryonic stem cell research. On August 9, 2001, they got their verdict. President Bush announced that federal funds could be used only to study currently existing stem cell lines extracted from human embryos, and that no tax money would be spent to develop new stem cell lines using cells derived from embryos. Soon after, the National Institutes of Health determined that although the presidential ruling prohibited federal funding of research using new embryonic stem cell lines, research of this type could continue, provided the work was paid for with private money.
Embryonic stem cell research has long been a political hot potato. But in order to fully understand the ethical and political implications surrounding this issue, it is important to first understand the science. What makes stem cells so special? And how do these elusive cells stand to revolutionize the practice of medicine?
Below, hematologist Dr. Robert Marcus, of Addenbrooke's Hospital in Cambridge, UK, introduces us to the power and potential of the human stem cell.
First, what are stem cells, and where are they found?
DR. ROBERT MARCUS: Stem cells are the basic seed cells of the body. In the same way that seeds turn into flowers, stem cells turn into the mature cells that perform the functions of all the organs and tissues in the body.
What is the difference between adult stem cells and embryonic stem cells?
Stem cells derived from early embryos are "totipotent," which means that they can become any cell type in the body. After all, people start out as a single fertilized egg. That single cell begins a process of cell division that results in all the different cells of the body.
As the embryo grows into a fetus and then a baby, the potentiality, or the flexibility of those stem cells, diminishes. We're not certain yet whether adult stem cells, or cord blood cells, which are also rich in stem cells, will be flexible enough to repair brain cells, for example, or heart muscle cells. That's why there is major interest in embryonic stem cells.
In your opinion, do embryonic stem cells play a central role in the
development of new cell therapies?
I think it's quite possible. In the UK there have been two centers designated for embryonic stem cell banks, suggesting that we are beginning to recognize their potential. Now we don't know of course whether they will fulfill that potential, but I think that those stem cell banks will be very valuable indeed.
Do you think that stem cell therapy is going to become viable in the
Stem cell transplantation has already proven successful in leukemia, where we use it to restore blood production after high-dose chemotherapy. We have been doing this for twenty years.
And as we continue to get a clearer understanding of stem cell biology, we are beginning to see how stem cells derived from marrow cells or blood cells or embryonic cells might be used to repair damaged hearts or brains. I think that's potentially very exciting. When it will happen is not certain. I think it could be between five and ten years away. But I might be too pessimistic there.
Do you think that we should be cautious in our progress?
I do. I think that in terms of gene transfer, which is a process of inserting genetic material into the stem cells to try and treat genetic disease, we should be cautious. We should be cautious with hybridization experiments, and with cloning as well. Any time you transfer genes within the cloning process, or change the genetic material within a cell, there may be defects introduced into a natural organ or species development. I think I would be quite cautious there.
But in terms of differentiating embryonic stem cells and adult stem cells into different kinds of cells -- liver, heart, lung, brain -- I would be less cautious there. I think the potential for damage or danger is much more limited.
Dr Robert Marcus is Consultant Hematologist at Addenbrooke's Hospital,
Cambridge, UK and Director of the East Anglia Bone Marrow Transplant Unit
Copyright 2002 Healthology, Inc.