The Difference Between Embryonic, Adult Stem Cells
ROBERT SIEGEL, host:
With adult stem cell research and embryonic stem cell research at odds with each other, we figured it's time for a primer on stem cells and the two different approaches. So we have turned to Dr. Zach Hall. He used to be head of the National Institute for Neurological Disorders and Stroke at NIH, and he was president of the California Institute of Regenerative Medicine - that's California's state-funded stem cell research facility.
Welcome to the program, Dr. Hall.
Dr. ZACH HALL (Former Director, National Institute of Neurological Disorders and Stroke, National Institutes of Health): Thank you very much. I'm glad to be here.
SIEGEL: And first, stem cell research, why are we talking about this? Why is it so important?
Dr. HALL: Stem cell research has captured the imagination of the public and of scientists alike. Its object is to use cells that are grown in dishes to replace cells in our body that have been damaged or lost through disease, like Alzheimer's or Parkinson's or diabetes. It's almost a science-fiction idea that if you could just grow cells in a dish and replace them, what a wonderful thing this would be.
SIEGEL: Let's talk about embryonic stem cells that would be - it's the most controversial source of these cells. What is so promising about working with them, and how do we get them?
Dr. HALL: Embryonic stem cells are particularly useful for this purpose for two reasons. They come from very early-stage embryos that have been discarded. The cells are taken out and grown in a dish, and the two remarkable properties are, number one, they can multiply almost indefinitely, so you can get very large numbers of them.
Number two, they are unspecialized cells, but under appropriate conditions, they can form all the specialized cells in our body - nerve cells, heart cells, muscle cells, kidney cells - that could then be used to replace damaged cells in our bodies.
SIEGEL: Now, adult stem cells have the political advantage of not violating the interests of those who oppose working with embryos or oppose abortion. To what extent are they as promising for medical research, and to what extent are they limited?
Dr. HALL: So during development, some of the early stage stem cells remain in the body in various tissues as adult stem cells, however, they've changed their properties slightly. They're very rare, but they can be isolated. And the two features that I mentioned are both less prominent in adult stem cells. That is they don't grow very well in culture. So it's very hard to make very many of them.
And number two, their ability to make other specialized cells is highly restricted. For example, an adult stem cell in the bone marrow makes up all of our blood cells. It's important because it replaces blood cells in our body as they're lost. It cannot, however, make muscle or nerve or other kinds of specialized cells.
So these cells are useful. They're used in bone marrow transplants, for example, but they are limited in number and their potential for other kinds of diseases is very restricted.
SIEGEL: Given a potential application of stem cells would assume, I would imagine, what kind of cells are needed, why would the variegation of the adult stem cells be a disadvantage in that case? Because you would know you had either wanted nerve cells or other tissues. Wouldn't the adult stem cell specialization therefore not be a problem?
Dr. HALL: It might not be, but we have to find that out. And the problem is we can't get very many of those cells. And what we want to do is to compare cells from various sources for particular diseases. In each case, you want to say, now, where are the cells that provide the best replacement? It might be adult stem cells. You're right. It might be embryonic stem cells. But I think we don't know, and in particular cases, it might very well be different.
So I think we need to wait and see. We need to explore all avenues, and we - I feel we very much need the power of federal funds behind this work to move it forward.
SIEGEL: Dr. Hall, thank you very much for talking with us.
Dr. HALL: Thank you. I've enjoyed the conversation.
SIEGEL: That's Dr. Zach Hall who spoke to us from Jackson Hole, Wyoming.