Change may allow scientists to grow human embryos longer

LONDON (AP) — New guidelines released Wednesday remove a decades-old barrier to stem cell research, recommending that researchers be allowed to grow human embryos longer under limited conditions.

The “14-day rule,” an international ethical standard that limits laboratory studies of human embryos, has been in place for decades and has been written into law in countries including Britain and Australia. Scientists previously have been required to destroy human embryos grown in a lab before they reach 14 days.

Some researchers have favored revising the rule to further study the development process while opponents say such experiments at any stage cross a moral boundary and it's unclear the change would advance research.

The original limit was arbitrary and prevented study of a critical period in embryo development — typically between 14 and 28 days, said Robin Lovell-Badge, a stem cell expert at London’s Crick Institute and chair of the group behind the new guidelines.

“We think a lot of congenital abnormalities are developing quite early during this period,” said Lovell-Badge. “By understanding these early stages better, it might allow us to adopt simple procedures to reduce the amount of suffering.”

The guidelines, last updated in 2016, were issued by the International Society for Stem Cell Research, whose standards are widely accepted by countries, medical journals and the research community. It didn't specify how much longer embryos could be grown.

For scientists in the U.K. to start making embryos beyond two weeks, the law regulating such research would need to be changed. Any relaxing of the rule would still need a “robust review” by national regulators, Lovell-Badge said.

It's “not a green light” for scientists to expand human embryo research, said Kathy Niakan of...