We already know a lot about the human embryos’ first seven days after which they are implanted in the uterus. However, for years, scientists have struggled to study what happens after that. Until now, the record for in-vitro gestation was only nine days. But now two groups of scientists at the University of Cambridge and the Rockefeller University have been able to grow human embryos outside the uterus for up to 13 days.

Scientists Grow Human Embryos In Lab, Raise Ethical Issues

Researchers had to comply with the 14-day rule

They had to terminate their experiments before the 14th day mark to comply with international ethical standards. Both studies used a technique developed by Magdalena Zernicka-Goetz, a professor of stem cell biology at the University of Cambridge. Dr. Zernicka-Goetz had previously tested the technique on mice in 2014. It involves mimicking in the petri dish the entire process of an embryo’s implantation in the uterus.

The embryo is placed in a culture medium of hormones and growth factors in a petri dish, which also has a structure that the embryo can attach with. Findings of one study were published in the journal Nature, while another was published in the Nature Cell Biology. Had there been no 14-day red line, there is no telling how long the human embryos could have sustained outside the uterus.

Human embryos could ‘self-organize’

The 14-day rule was first proposed in 1979, and until now no study had come even close to broaching it. The latest studies show that it is possible to keep tracking embryos even after 14 days. The 14-day rule was established because on day-15 the symmetry of the human body starts taking shape. While the studies have raised ethical concerns, researchers argue that it is time to reconsider the decades-old rule.

Researchers found that embryonic development in humans is significantly different from that in other animals like mice. Another major finding was that embryos could self organize and begin the early development of body organs like heart, lungs without any cues from the mother. Ali Brivanlou, head of molecular embryology at the Rockefeller University, said, “That is counterintuitive to me.” Researchers thought there would be an exchange between the embryonic and maternal components before the next steps in the embryo’s development.