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Scientists Reach Breakthrough in Cloning Monkey Embryos

November 15, 2007 at 6:25 PM EDT
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JIM LEHRER: Now, a development in stem cell research. Scientists say they have extracted embryonic stem cells from cloned monkey embryos. It’s the first time that method has been successful with primates.

Our health correspondent, Susan Dentzer, has more on this.

Susan, welcome.

SUSAN DENTZER, NewsHour Health Correspondent: Thanks, Jim.

JIM LEHRER: First of all, who are the scientists, and where did they do their work?

SUSAN DENTZER: Jim, this is a team from Oregon Health and Science University. They’re at the Oregon Primate Research Center, and they do research on primates, basically monkeys and apes.

JIM LEHRER: All right, now, what exactly have they done in this case?

SUSAN DENTZER: What they did was something that people have dreamed about doing for a long time, essentially taking an adult cell and turning back the clock, turning it into an embryonic cell that produces stem cells. And as we know, these are the cells that develop into any of the organs and tissues in the body.

And so what they did was they took a skin cell from an adult, 9-year-old adult male rhesus monkey named Semos — he’s named after a character in a “Planet of the Apes” movie. They took the skin cell. They took the nucleus of that cell, which has the nuclear DNA, the instructions for the cell. They stripped out that nucleus.

Then, they took an egg cell from a very different female monkey, took the nucleus out of that, and you were left with the rest of the cell, which was the mitochondrial DNA. They took the nucleus from Semos. They stuck it into the rest of the egg cell.

And, voila, you get a clone, in effect, of Semos, because what the cell — what you end up with is the cell with all of the nuclear content, the DNA nuclear content that Semos had. So, in effect, that creates an embryo.

They then let that embryo grow for about five days to what’s called the blastocyst stage. They then destroy the embryo and removed…

JIM LEHRER: Killed the embryos…

SUSAN DENTZER: … killed it — in effect, by pulling out the embryonic stem cells, you destroy the embryo. Then they took those stem cells. They were able to create two so-called lines of stem cells. And then they allowed those cells to differentiate into different kinds of cells, in one case, heart muscle cells and, in another case, neurons, nerve cells, showing that they could actually create these embryonic stem cells and differentiate them into higher orders of cells.

Cloning primate stem cells

JIM LEHRER: And this had never been done with primates before?

SUSAN DENTZER: Never with this high order a mammal, specifically in this case primates, a monkey. It has only been done in mice. Now, several years ago, South Korean researchers claimed that they had done this with human cells, but that essentially turned out to be fraudulent. They did not actually...

JIM LEHRER: They just made it up.

SUSAN DENTZER: Well, they didn't actually clone an embryo, and they didn't actually derive stem cells from a cloned embryo, so it was exposed as a fraud. And ever since then, people have been trying to get back and prove that you really could do this. We don't have that proof yet in humans, but we do have it in this very high order mammal now, a rhesus monkey.

JIM LEHRER: Just for the record, because of the South Korea thing, before we move on, there is no question about fraudulent operation here, correct?

SUSAN DENTZER: No, not at all. They were able to prove -- they shipped their results, in effect, off to another research team, an independent research team, that was able to establish that, yes, indeed, the nuclear DNA came from Semos and, yes, indeed, the rest from it came from this female monkey. And they also performed some other tests to prove that they achieved what they said they had achieved.

Possibilities of stem cell research

Susan Dentzer
This proves that one can do this, turn back the clock, create embryonic stem cells that are genetically identical to the adult mammal that you clone.

JIM LEHRER: In a nutshell, why is this important? What's the significance of having done this?

SUSAN DENTZER: This proves that one can do this, turn back the clock, create embryonic stem cells that are genetically identical to the adult mammal that you clone. And the reason that's important is that, in the future, if we're able to generate therapies -- you know, you have a damaged heart. We want to transfer in new heart cells. Maybe we want to grow them from embryonic stem cells.

But we'd love them if they were a genetic match to you, because then your body wouldn't reject them the way you might reject, say, a foreign organ that's transplanted into your body. So this shows that we can do that in theory, with so-called proof of concept in monkeys. And if we can do it in monkeys, the odds are very, very good and the researchers are quite confident they'll be able to do this in human beings.

JIM LEHRER: Are they now going to, in fact, do that?

SUSAN DENTZER: They are not going to specifically, but other teams around the world are very much trying to do that. This team is, instead, going to do things still in primates.

They are going to, for example, take some of these stem cells and grow them into a certain other kind of cell, transfer those back into Semos, do a kind of a transplant back into him, and see what happens, and other kinds of experiments like that.

Goals of embryo development

Susan Dentzer
[What] the fight is over: Are you going to do this research in humans going forward? Is it ethically responsible to do that? Or is it worth the cost, given that it might result in therapies that could help very, very many sick people down the line?

JIM LEHRER: The bottom line here is, the goal of all of this kind of research and experimentation is aimed eventually at humans, correct?

SUSAN DENTZER: Absolutely, absolutely. People want to do two things. First of all, we want to study human disease. And one way to do that, for example, we could take someone who had a genetic condition, create stem cells genetically identical to that person, and then watch those cells develop and say, "What happens? What goes wrong in the body process?"

And then, also, potentially down the line, these therapies, transferring in cells, tissues, organs that would be genetically identical.

JIM LEHRER: Finally, how does this development fit into the ongoing social policy debate about stem cell research?

SUSAN DENTZER: Well, for proponents, it's very exciting, because it does show that it's quite likely this could be done in humans one day. For the opponents, it's equally terrifying for the same reason, because it might be able to be done in humans.

And, again, the opponents believe that destroying a human embryo in order to derive the stem cells is morally reprehensible and should not be done. This research could not be done now on humans, human cells, with federal funding because of the restrictions that the president put in place in 2001.

And that's what the fight is over: Are you going to do this research in humans going forward? Is it ethically responsible to do that? Or is it worth the cost, given that it might result in therapies that could help very, very many sick people down the line?

JIM LEHRER: OK. Susan, thank you very much.

SUSAN DENTZER: Thanks, Jim.