Scientists Report Breakthrough in Growing Embryos in Vitro

Scientists have reported they have grown human embryos in vitro for 12 to 13 days, significantly longer than the previous record of nine days.

If scientists are able to conduct experiments on embryos past 14 days, they may be able to "study all aspects of early human development with unprecedented precision," according to commentators on the two breakthrough studies published today in Nature and Nature Cell Biology.

Two groups of researchers were able to get embryos to grow for 12 days and 13 days, respectively. Both groups used similar cutting-edge technology in which chemicals and a special medium mimicked a human womb so that the embryos would continue to develop, researchers said.

Part of technology involved creating a method that allowed the embryo to attach in a manner similar to that way it would in the womb. The breakthrough technology also raises ethical questions that were highlighted in an accompanying commentary.

Many countries currently restrict experiments on embryos to the first 14 days. Additionally, the International Society for Stem Cell Research has issued guidelines advising researchers across the globe to stick with this 14-day window. The authors of the commentary point out that experiments reaching close to the 14-day rule may mean medical officials will eventually revise this guideline.

"The 14-day rule was never intended to be a bright line denoting the onset of moral status in human embryos," the authors wrote. "Rather, it is a public-policy tool designed to carve out a space for scientific inquiry and simultaneously show respect for the diverse views on human-embryo research."

The 14-days limit was set due to how an embryo develops, according to the commentary. After approximately two weeks, the embryo starts to develop more distinct structures that will usually develop into a fetus and placenta. The authors note that the timeline was picked to be sensitive to the different views on when "a human embryo obtains sufficient moral status that research on it should be prohibited."

Arthur Caplan, a bioethicist and head of the Division of Medical Ethics at New York University Langone Medical Center, said the breakthroughs means the medical community will have to re-evaluate what is ethical when it comes to experimentation on embryos.

"What is that entity?" asked Caplan, who was not involved in these studies. "Many people believe that it is a full person from conception, but it will renew that debate."

Caplan pointed out that medical officials will have to grapple with the fact that embryonic experimentation past 14 days could lead to important results that help many pregnancies in the future.

"How far can you go with embryo research and how far can you go with editing the genes of embryos to repair them?" Caplan told ABC News. "All of this is in play in the same time."