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US, UK scientists grow embryos in lab to 14 days, setting new mark

In what’s considered a landmark study among the scientific community, researchers in the United States and the United Kingdom have reportedly grown human embryos to 14 days old, the longest such record for lab-grown embryos to date.

Though the Petri dish-grown embryos likely could have lived longer than the charted 14 days, the scientists were forced to conclude the experiment because of a decades-old law prohibiting embryo research from lasting longer than two weeks. Despite the abrupt finish, the scientists’ breakthrough could potentially pave the way for womb-free reproduction, as well as an in-depth study of early human development.

For those unaware, the 14-day policy says that no donated IVF (in vitro fertilization) embryo can be lab-grown any longer than 14 days. Once this threshold is reached, the embryos must be destroyed to remain compliant with the international law. What’s significant about 14 days, according to Natureis that this is typically when an embryo’s primitive streak forms, that is, the point at which its biological individuation is guaranteed. Before the primitive streak, it has the ability to split into two separate embryos or fuse together, leading many scientists to reason that the primitive streak is when an embryo can be considered a being.

Closeup of an embryo on day 10 of development

Closeup of an embryo on day 10 of development

University of Cambridge

First proposed in 1979 by the Ethics Advisory Board of the U.S. Department of Health, Education, and Welfare, the international 14-day policy has been allowed to stand the test of time primarily because scientists were technologically incapable of breaching the 14-day limit. Until these recent experiments, the longest an in-lab embryo had grown stood at just nine days — however, most studies rarely lasted longer than seven days. Though parts of the scientific community have begun clamoring for an extension of the 14-day rule, it’s widely assumed any such move would be met with serious resistance, particularly from religious groups.

Related: Mice embryos can develop in space, Chinese scientists report

Politics (and ethics) aside, the recent breakthrough — published Wednesday in Nature and Nature Cell Biology — could be an absolute boon for the continued study of early human development, namely what occurs during an embryo’s critical first 14 days. During this time, an embryo goes through a significant growth phase that includes implantation into the wall of a woman’s uterus before forming into a collection of cells, which eventually grow into a baby. These 14 days also happen to be when a high number of pregnancy and developmental issues arise, though due to how early in the cycle this growth occurs, it’s incredibly difficult to study accurately.

This is precisely where lab-grown embryos can change the entire landscape of the study of human growth, and the scientists at the U.K.’s Cambridge University and New York’s Rockefeller University are at the forefront of this research. Additionally, expanded research could allow for the discovery of what leads to early-stage miscarriages and could potentially further the research of stem cells and their use in treating diseases.

“We can now, for the first time, study human development at this very critical stage of our lives, at the time of implantation,” said Cambridge lead researcher Magdalena Zernicka-Goetz. “To be able to culture embryos for a couple days longer would provide an enormous body of information, but it’s not for us now to decide whether we should do it or not. Rules are very useful, we would always adhere to them, and they should be set out by the wider community.”

The embryo's molecular signature

The embryo’s molecular signature

What particularly piqued the interest of the researchers was the embryo’s uncanny ability to execute its own development beyond when it would typically implant itself into a woman’s uterus. In other words, with absolutely no maternal input, the embryo self-organized in a completely artificial environment. A development of this nature caused Motherboard — frequent researcher into the realm of womb-free births — to put forth the idea that using an artificial womb to develop a baby to term might not be that far off.

“One day, under the right conditions, this means we might be able to grow a human to the point when it can be ‘born’ in a completely artificial environment,” wrote Motherboard writer Paul Tadich. “It also highlights the futility of the 14-day rule, in a new era where embryos can be grown past that artificial deadline.”

As Manchester University’s clinical embryology professor Daniel Brinson puts it, “this limit was chosen more than 20 years ago … there may be a case in the future to reconsider this.” With as much as there is to gain by the continued research of lab-grown embryos and the possibilities it presents beyond life-bearing, Cambridge and Rockefeller University’s incredible breakthrough will likely extend far beyond the lab in which the experiment was conducted.