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An 11-day-old human embryo tagged with fluorescent markers.


Studying embryos beyond 14 days? Not so fast, says one key U.K. expert

LONDON—It’s a looming question facing biologists, ethicists, and society as a whole: Should scientists be allowed to study embryos cultured in the lab beyond 14 days after fertilization? Perhaps in the future, but not just yet, one highly influential voice said at a meeting here today.

“It’s too soon,” said philosopher Mary Warnock, who chaired a committee in the 1980s that informed current regulations. “What we should do now is give people who do research the chance to exploit what they can find out between 5 and 14 days.” That will help build the case for what benefits might come from doing research on embryos older than 14 days, Warnock argued.

Currently, biologists in the United Kingdom and many other countries are not allowed to culture human embryos in the laboratory longer than 14 days. This never posed a constraint because it wasn’t possible to keep embryos alive longer than about a week anyway. But earlier this year, two teams succeeded in keeping embryos alive for 13 days, reigniting the debate about the legal limit. (Their work is among the finalists for the People’s Choice for Science’s Breakthrough of the Year.) Experts discussed the hopes and concerns of extending the limit at a daylong workshop held here today by the Progress Educational Trust, a nonprofit that promotes public understanding of embryology, human genetic research, and assisted reproduction.

An extension would certainly bring scientific gains, said Magdalena Zernicka‐Goetz, a developmental biologist at the University of Cambridge in the United Kingdom who led one of the teams that showed how to keep human embryos alive until day 13. After 2 weeks, when the embryo is a blastocyst, the basic organization of what will become the body begins, but under natural conditions, embryos of this age are embedded within maternal tissue and generally not accessible to researchers. By culturing them in the lab, researchers might be able to learn more about the origin of congenital heart defects, understand development of the central nervous system, or help improve stem cells for future therapies. “If we could extend beyond 14 days, it would really be a giant leap for science and society,” Zernicka‐Goetz said. “The question is when to do it.”

But Warnock urged caution. After her committee’s 1984 report, she noted, advocates for research spent 6 years explaining the potential benefits of embryo research before Parliament passed legislation to allow it. The benefits from research after 14 days would have to be “quite substantial” before it would be wise to lobby legislators, Warnock said, because there is a risk that opponents might convince Parliament to prohibit studies of human embryos altogether.

Warnock’s recommendation makes sense, says biochemist and physiologist Simon Fishel in Nottingham, U.K., president of CARE Fertility, the largest private in vitro fertilization provider in the United Kingdom. He is glad that another debate about the issue is coming up: The Nuffield Council on Bioethics, a prestigious independent think tank, will hold a workshop on 16 December and publish a brief report early next year, before deciding whether to research the question more fully. There should be reports from top academics as well as public discussions before Parliament steps in, Fishel tells ScienceInsider: “This is a process that should probably last 5 years.”