TOPICS > Science

Embryonic Stem Cell Tests

October 17, 2005 at 12:00 AM EDT


JEFFREY BROWN: Embryonic stem cells are considered potentially powerful tools for treating and even curing some diseases. But they’ve also raised many ethical and religious concerns. Yesterday in the journal, Nature, scientists reported two new techniques for creating stem cells, aimed at addressing these concerns, and, perhaps, changing the terms of the debate.

Here to tell us about all this is our health correspondent, Susan Dentzer. Our health unit is a partnership with the Robert Wood Johnson Foundation. Susan, start by reminding us why the current method of producing stem cells is so controversial.

SUSAN DENTZER: Well, stem cell research opponents have one overriding objection, which is they say that human embryos should be accorded the highest moral status that life begins at conception and therefore tampering with embryos is violating their moral status. But in addition they are specifically concerned about two commonly used techniques in embryonic stem cell research: One is that to simply get at embryonic stem cells you have to go into a several-day-old embryo called a blastocyst, take out what’s known as the inner cell mass to get at the stem cells and in that process you destroy the embryo. So they object to that.

The second thing they object to is an area of research that is sometimes called therapeutic cloning, sometimes called somatic cell nuclear transfer. And this is the notion that you could engineer some embryonic stem cells that were a genetic match to a particular adult individual or even a child. Essentially what is done is you take a woman’s egg, you strip out the nucleus. You take the nucleus of a skin cell, for example, from another person, put that back in, create in effect what could be construed as an embryo, derive stem cells from that, and then those are a genetic match.

What people object to is if you can create an embryo this way, if you can, in effect, clone an embryo, you might also be able to clone a human being, and because that’s considered morally reprehensible by many, they object to this area of therapeutic cloning research that could eventually lead to stem cell creation too.

JEFFREY BROWN: Okay. So these two new techniques were intended to get at both of those concerns. Let’s talk about the first one. It was done by researchers at Advanced Cell Technology, a biotech firm. What were they able to do?

SUSAN DENTZER: Exactly right. What they did was take on this notion of you have to destroy the embryo in order to get the stem cells. They borrowed a technique that is used commonly — if you’re concerned that a couple might be carriers of a genetic disease you can do what’s called pre-implantation genetic diagnosis.

You can actually create their future child in an embryo state in an IVF lab and then you can actually extract a cell, examine that to see whether there’s a genetic problem and then decide what to do from there. They took that same technique; they created an embryo. When they got to just the eight cell stage — only a couple of days old — they plucked out a single cell and from that single cell they developed several lines of stem cells.

JEFFREY BROWN: This work is done on – this is done on mice.

SUSAN DENTZER: Yes. It’s important to say above all this was done on mice. The important point here is that the embryo, the seven cells left went on to survive. So this was done as a way of calming the objection that the embryo would have to be destroyed in the process. As you say, it was done on mice; mice are pretty good stand-ins though for human cells at this stage in particular. So the theory is this probably could be done with human cells as well.

JEFFREY BROWN: So, but what are the problems and concerns that are still raised? There are practical issues I suppose because it was done on mice.

SUSAN DENTZER: It was done on mice. So first it would have to be replicated with human cells. And of course at the moment it would not be possible to do that with federal funding. It could be done and probably is going to be done very soon with human cells outside of the federal funding context.

But an additional concern, some people say, well, maybe this isn’t the way out of an ethical box after all because some people surmise, well, maybe this one single cell that you just plucked out and turned into stem cells maybe that could also grow into an embryo and go on to develop into a human being.

So maybe rather than getting rid of this ethical problem, maybe you’ve created another ethical problem in that you’ve created another potential embryo that you’re still going to destroy and make into stem cells. So it’s not clear some people say that this gets us out of an ethical box.

JEFFREY BROWN: All right. And then the second study was reported by a team at the Whitehead Institute for Biomedical Research in Cambridge. And this one goes to the second issue you raised which concerns cloning.

SUSAN DENTZER: Yes, indeed. And, in fact what this paper did was pick up on a suggestion that was made by members of the president’s Bioethics Council, in particular a Stanford physician named William Hurlbut who said if you’re going to proceed this therapeutic cloning but you want to make sure that you don’t create cloned human beings in the process, maybe what you could do is once you took this new construct that some people call an embryo maybe you can do something that would keep it from developing it into a human being. You can manipulate a gene.

And, in fact, that’s exactly what these scientists at Whitehead and MIT did. They tinkered with a gene that basically leads an embryo to implant into a uterus. And they essentially manipulate it in such a way so that this altered embryo could not be implanted into a uterus and develop into a human being saying in effect, look, there is a way we can do this genetically. We can keep these cloned embryos if you want to call them embryos from turning into human beings. And we can protect that and in fact many believe we should keep that from happening because of the uncertainties of what could happen with cloned human beings.

JEFFREY BROWN: Now, Dr. Hurlbut called this a non-embryonic entity but I also saw that not everyone agreed there too.


JEFFREY BROWN: So not all the ethical issues were addressed.

SUSAN DENTZER: Absolutely right. Some people say, you know, this now has the capability — we clone animals this way all the time. So if you have created, in fact, an animal embryo, if you did the same thing with human cells, why would that not be an embryo too? They believe that that is also, in effect, a violation of the superior moral status that should be accorded embryos.

Hurlbut and others say, wait a minute, this would not be an embryo; this would be an altered product. Some people call this a nuclear transfer product. It would be created not for the purpose of going into personhood, evolving into personhood but rather specifically to generate stem cells.

And, of course the value of genetically matched stem cells theoretically is that some day if you developed organs and tissues out of these genetically matched cells and transferred them back into the human being to which they were a genetic match, maybe the body wouldn’t reject them. So they argue that that’s a very important path we should pursue and perhaps even that has a known ethical basis in its own right.

JEFFREY BROWN: We just have a minute but I want to ask you because all this comes as there is legislation being debated in Congress to loosen some of the restrictions that the president put on funding. How do these new findings fit into that?

SUSAN DENTZER: Well, it’s completely unclear whether they make a difference one way or the other. Some proponents of embryonic stem cell research say, “see, we can get our way out of these ethical conundrums, therefore, let’s go ahead.” Others as we’ve said say, “no, we still have many ethical conundrums that they didn’t change things a wit.” So we’re going to have to see how things play out. The Senate is scheduled to take or I shouldn’t say scheduled but may take up legislation looking at loosening the federal funding restrictions sometime this year or next year.

We’ll have to see how the scientific evidence that we’ve just heard about plays into the debate at that time.

JEFFREY BROWN: Science and politics, of course, still tied together.

SUSAN DENTZER: Very much so.

JEFFREY BROWN: Okay. Susan, thanks a lot.