Scientists Grew a Mouse Embryo Outside the Womb. Are Humans Next?

The mouse embryo grown 6 days outside the uterus.
  • In new research, scientists grew mouse embryos to half term in an artificial womb.
  • The milestone is equivalent to a human embryo at five weeks development.
  • Early pregnancy and implantation are very understudied because of ethics and logistics.

In a groundbreaking new study, Israeli scientists have grown mouse embryos in a fully artificial womb for about half of a mouse’s full gestational term.

The technology lets scientists study early embryos in detail for the first time, opening doors that come with several ethical questions. While this technology is unlikely to directly lead to lab-grown viable human fetuses, it could bring studies where embryos are grown to up to 40 days and then destroyed.

This new study, which appears in the journal Nature, builds on past research involving agitating jars (“the roller culture system”) with fertilized cells inside. In the experiment, Jacob Hanna of the Weizmann Institute of Science and his colleagues mixed human blood serum from umbilical cords into a spinning chamber filled with pressurized oxygen. They then put the fertilized mouse cells into the womb environment, where they survived for 11 or 12 days—the longest time frame to date.

Pressurized oxygen helps to feed the developing cells, pushing through with pressure where nature would build a circulatory system. The embryos eventually died because they grew too large for oxygen to penetrate without the help of the placental blood oxygen flow that embryos have in real wombs.

Twelve days represents about half a mouse’s natural full gestational term. Hanna tells MIT Technology Review he hopes this will lead to human embryo studies of up to 5-week-old embryos. In naturally occurring pregnancies, it’s almost impossible to study embryos without jeopardizing them in some way—the same way it’s very, very ethically difficult to study pregnant people under the traditional scientific method.

To demonstrate the wide-ranging research ramifications of their method, the scientists also experimented with specific stains, chemicals, and more to show the embryos could still grow in the spinning artificial womb

“This culture system is amenable to introducing a variety of embryonic perturbations and micro-manipulations that can be followed ex utero for up to six days. The ability to remove a mammalian embryo from the uterine environment and grow it normally in controlled conditions constitutes a powerful tool to characterize the effect of different perturbations on development during the period from gastrulation to organogenesis, that can be combined with genetic modification, chemical screens, tissue manipulation and microscopy methods.”

Developmentally, the 12-day-old mouse embryo, which is at “the hind limb formation stage,” is the same as the 5-week-old human fetus. As Technology Review points out, other researchers are actively studying ways to culture artificial human embryos by prompting human stem cells to divide and grow. But there are ethical questions that go both ways when it comes to studying embryos.

First, many critics consider the idea of implanting a so-called “artificial embryo” into a human womb to be extremely distasteful, and the practice is even illegal in some places. Trying to study this dynamic would be fraught, to say the least. Second, implanting a real embryo in an artificial womb to be studied up to 5 weeks, when the embryo would recognizably be human and have growing features, is a tough sell for many people.

But this research could help us put the two least ethically thorny situations together: an artificially cultivated embryo in an artificial womb, which scientists can manipulate and study up close without worrying about either a pregnant person or someone’s viable embryos. The idea isn’t very different from studying discarded 5-day-old embryos from in vitro fertilization, Hannah tells Technology Review.

Source: Popular Mechanics