美国国家公共电台 NPR Embryo Experiments Reveal Earliest Human Development, But Stir Ethical Debate（在线收听）

RACHEL MARTIN, HOST:

Scientists doing embryo research are facing some sensitive questions over a new generation of scientific experiments, questions like how long should scientists be allowed to keep human embryos alive in their labs to study them? And should entities that they create from stem cells resembling human embryos be treated the same way? NPR's health correspondent Rob Stein visited a lab that's at the forefront of this provocative research, and he brings us now the first of two reports.

ROB STEIN, BYLINE: So what are we going to see first?

ALI BRIVANLOU: A human embryo that is attached and grown for 13 days in a petri dish.

STEIN: Ali Brivanlou runs the lab at The Rockefeller University in midtown Manhattan.

So this is an embryo that - where you were able to keep it alive in the laboratory...

BRIVANLOU: Exactly.

STEIN: ...Up until day...

BRIVANLOU: Day 13.

STEIN: And had it been done before?

BRIVANLOU: Never.

STEIN: For decades, scientists thought the longest an embryo could survive outside the womb was only about half that long - only about a week tops. So this is the first time scientists can actually see living human embryos at this crucial stage of development and study them at a time when they're usually hidden in a woman's womb.

BRIVANLOU: And women don't even know they are pregnant at that stage, so it has always been a big black box.

STEIN: Brivanlou arranged for one of his colleagues to show me.

BRIVANLOU: I ask him to make sure that he has a real sample for you to see with your own eyes so that you can appreciate the beauty in their own glory. It's really one of the most beautiful things I have ever seen in my life.

STEIN: Brivanlou's colleague Gist Croft pulls out some samples. Turns out, he's going to show me several embryos, starting with one that's 12 days old.

GIST CROFT: So you can see this with the naked eye. In the middle of this well, if you look down, there's a little white speck that looks like a grain of sand or a piece of dust in this well right here. I don't know if you can - can you see that?

STEIN: Yeah, it looks like a tiny little white translucent dot.

CROFT: That's it.

STEIN: Croft carefully places it on a big microscope and pulls a heavy black curtain closed.

CROFT: Would you like to look through the microscope?

STEIN: Yeah.

BRIVANLOU: OK.

STEIN: Croft helps me bring the embryo into focus.

Oh, yeah, I can see...

CROFT: Better?

STEIN: I can see the - oh, wow. Wow, that's, like, kind of beautiful.

It is quite stunning. It looks like a fragile ball of overlapping bubbles that's sort of shimmering in a silvery light, but it's also a little, well, funny looking.

So that looks like a (laughter) well, I mean, it kind of just looks like a - kind of a translucent hairy ball actually.

CROFT: Yes.

STEIN: Croft and Brivanlou get excited that I noticed what looked like little hairs reaching out from all sides because that's exactly what scientists would expect embryos to do at this stage if they were in the womb - search for just the right spot to nestle in.

CROFT: They're doing the reaching out and attaching that they normally do into uterus cells, but here they're doing it onto plastic.

STEIN: Wow, so they're behaving like they would - this embryo is behaving like it would if it was actually in the womb.

CROFT: That's right. It's reproducing certain key features of what it's normally doing in the womb.

STEIN: Scientists thought embryos could only do that sort of thing if they were getting instructions from their mother's body about what to do next - not all alone in some plastic dish.

BRIVANLOU: The amazing thing is that it's doing its thing without any information from mom - completely unexpected to me. It just has all the information already in it. That was mind-blowing to me.

STEIN: The embryos also start pumping out hormones and start organizing themselves, all by themselves, to form the cells needed to create all the tissues and organs that make up the human body. So Brivanlou and his colleagues think they could learn lots of things by studying them that could help stop miscarriages, treat infertility, prevent birth defects.

BRIVANLOU: The only way to understand what goes wrong is to understand what happens normally or as normally as we can so we can prevent all of this.

STEIN: But that would mean studying embryos beyond 14 days and Brivanlou can't keep these embryos alive any longer to keep studying them. Why? Because of a rule that says scientists should not conduct experiments on human embryos that are more than 14 days old. So Brivanlou decided he had no choice but to pull the plug on these experiments.

BRIVANLOU: The decision about pulling the plug was probably the toughest decision I've made in my scientific career. It was sad for me. It was sad.

STEIN: The 14-day rule was adopted decades ago to avoid raising too many ethical questions. It's a guideline in the U.S. but law in some other countries. Fourteen days is when the central nervous system starts forming, starting with something called the primitive streak. It's also usually when an embryo can't split into twins anymore. So the idea is that's when it truly becomes an individual. But that was before anyone thought it would ever be possible to go beyond two weeks. So Brivanlou says it's time to rethink the 14-day rule.

BRIVANLOU: It's time to reopen that debate. This is the moment. I think we are here. It would be a travesty to decide that somehow ignorance is bliss.

STEIN: And Brivanlou's not alone. There's a big debate about this going on in the United States, Britain and other countries. Insoo Hyun is a bioethicist at the Case Western Reserve University. He points out that these are embryos that were donated for research by couples who were finished with infertility treatments.

INSOO HYUN: You have to realize that with these embryos they are being used for research. That decision has been made. Now, the question is how long can you study them before they have to be destroyed? So given that it has to be destroyed, some would argue that it's best to get as much information as possible scientifically from it before you destroy it.

STEIN: Now, some people think it's morally repugnant to use human embryos for any kind of research at any stage of their development. And lifting the 14-day rule, that would just make matters worse. But the idea of extending the 14-day rule even makes some people who support embryo research uncomfortable, especially without first coming up with another clear stopping point. Hank Greely is a bioethicist at Stanford.

HANK GREELY: Unless there was something really important we could learn from doing research with human embryos, I wouldn't allow research beyond 14 days because at some point experimentation with it seems to really draw into question whether we're using humans or things that are well along the path to humans purely as guinea pigs and purely as experimental animals.

STEIN: So as that debate continues, Brivanlou and his colleagues are trying something else. They're using stem cells to create things that resemble primitive human embryos in their lab, but that's controversial too. Rob Stein, NPR News, New York.

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