Skip to main content
Move the World.
Human Embryo

Lead image courtesy of Naomi Moris / University of Cambridge

Currently, scientists are only allowed to study human embryos for up to two weeks after fertilization — an international ethical standard known as the "14-day rule."

Now, European scientists say they have created an accurate model of a human embryo at days 18-21, offering researchers a peak into what's currently considered a "black box" in embryonic development — without violating any ethical guidelines.

A Human Embryo Model

Fourteen days after fertilization, a human embryo enters an important developmental stage known as "gastrulation."

During the gastrulation stage, the embryo begins forming three layers of cells that will eventually develop into all the major systems, including the brain and nervous system. At this point in development, many birth defects and genetic diseases begin emerging, and scientists suspect that studying it could help us better understand, treat, or prevent such disorders.

"Our model produces part of the blueprint of a human."

Alfonso Martinez-Arias

But ethical concerns about human experimentation have led international scientific bodies to forbid research on the developing human embryo during this stage.

To create a model of an embryo at this vital stage of development, researchers from the University of Cambridge and the Hubrecht Institute in the Netherlands started with embryonic stem cells.

After placing precise numbers of the stem cells into wells, the researchers treated them with chemicals. Those chemicals prompted the cells to spontaneously form into "gastruloids" — embryo-like 3D structures that lack the cells that would eventually form a brain.

According to the team's study, which was published in the journal Nature, their gastruloids stopped developing after three days, but at that point, they already resembled an 18 to 21 day old human embryo, complete with the trio of cell layers characteristic of gastrulation.

"This is a hugely exciting new model system, which will allow us to reveal and probe the processes of early human embryonic development in the lab for the first time," researcher Naomi Moris said in a news release.

human embryo

From left to right, the human embryo model at 24 hours, 48 hours, and 72 hours. The DNA is blue, the neural cells are magenta, and the mesodermal cells are green. Credit: Naomi Moris / University of Cambridge

Exploring Embryonic Development

In 2018, the team behind this study published research noting the similarities between mouse gastruloids and actual mouse embryos.

Gastruloids are easier to create in large numbers than real embryos, which must start with fertilizing an egg, so that discovery was a boon for embryonic development researchers.

But however similar mouse gastruloids are to mouse embryos, they are both still a far cry from humans', so researchers moved on to constructing human versions.

These human gastruloids aren't exactly a perfect model of a human embryo, either — as Rice University stem cell biologist Aryeh Warmflash, who wasn't involved in the study, told Science Magazine, they appear to have different patterns of gene expression.

Still, researchers now have their best model yet of a human embryo at a previously inaccessible stage of development. And because these cells could never form into an actual human embryo or survive in a womb, they don't violate ethical standards.

Now, the researchers plan to use their human embryo model to study standard embryonic development during gastrulation. They also plan to create gastruloids with specific mutations to study what happens when development goes awry.

"Our model produces part of the blueprint of a human," researcher Alfonso Martinez-Arias told Reuters. "It's exciting to witness the developmental processes that until now have been hidden from view — and from study."

We'd love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at [email protected].

Up Next

Science
A Regulatory Fight Is Brewing Over Experimental Stem Cell Therapies
A Regulatory Fight Is Brewing Over Experimental Stem Cell Therapies
Science
A Regulatory Fight Is Brewing Over Experimental Stem Cell Therapies
New proposed regulations from the FDA would effectively shut down private stem cell clinics in the U.S.
By Mike Riggs

New proposed regulations from the FDA would effectively shut down private stem cell clinics in the U.S.

Opinion
A Molecular Biologist Discusses the Morality of Genetic Engineering
A Molecular Biologist Discusses the Morality of Gene Editing
Opinion
A Molecular Biologist Discusses the Morality of Genetic Engineering
Molecular biologist Daisy Robinton speaks out on our moral imperative to solve some of humanity's greatest health threats.
By Daisy Robinton, Ph.D.

Molecular biologist Daisy Robinton speaks out on our moral imperative to solve some of humanity's greatest health threats.

Dispatches
A New Stem Cell Treatment Can Heal Burns, Bedsores, and Diabetic Ulcers
A New Stem Cell Treatment Can Heal Burns, Bedsores, and Diabetic Ulcers
Dispatches
A New Stem Cell Treatment Can Heal Burns, Bedsores, and Diabetic Ulcers
In addition to healing injuries, the approach could be useful for repairing skin damage, countering the effects of...

In addition to healing injuries, the approach could be useful for repairing skin damage, countering the effects of aging, and modeling skin cancer.

Superhuman
Stem Cells Give Paralyzed Man Movement
Stem Cells Give Paralyzed Man Movement
Watch Now
Superhuman
Stem Cells Give Paralyzed Man Movement
Could an injection of embryonic stem cells into the spinal cord reverse paralysis?
Watch Now

After a devastating car accident, Lucas Lindner was left almost completely paralyzed. But an injection of embryonic stem cells in his spinal cord has given him back almost complete function of his arms and hands.

Fertility
How GMO Zebrafish Could Inspire New Infertility Treatments
zebrafish  Infertility Treatments
Fertility
How GMO Zebrafish Could Inspire New Infertility Treatments
By genetically modifying zebrafish, researchers have discovered a sex hormone that could lead to future infertility treatments for humans.

By genetically modifying zebrafish, researchers have discovered a sex hormone that could lead to future infertility treatments for humans.

Future of Medicine
Stem Cell Research Breakthrough Opens Path to Growing Human Organs in Animals
Stem Cell Research
Future of Medicine
Stem Cell Research Breakthrough Opens Path to Growing Human Organs in Animals
New stem cell research has revealed a way to coax human cells to grow to maturity in mouse models, a major advance in the field.

New stem cell research has revealed a way to coax human cells to grow to maturity in mouse models, a major advance in the field.

Artificial Intelligence
Training a Home Robot To See — and Hear
Home Robot
Artificial Intelligence
Training a Home Robot To See — and Hear
Facebook's AI lab has released new tools for its embodied AI training platform, including one to train a home robot to respond to sounds.

Facebook's AI lab has released new tools for its embodied AI training platform, including one to train a home robot to respond to sounds.

Future of Health
Is the Future of Therapy… Virtual? A Look Into Virtual Reality Therapy
Is the Future of Therapy… Virtual? A Look Into Virtual Reality Therapy
Future of Health
Is the Future of Therapy… Virtual? A Look Into Virtual Reality Therapy
The immersive world of VR may have therapeutic benefits for people combating phobias, anxiety, and PTSD.
By Kaitlin Ugolik

The immersive world of VR may have therapeutic benefits for people combating phobias, anxiety, and PTSD.

Could Growing Vaccines in Plants Save Lives?
Could Growing Vaccines in Plants Save Lives?
Watch Now
Could Growing Vaccines in Plants Save Lives?
Vaccines for influenza, polio, smallpox, even Ebola have all be grown … in plants.
Watch Now

This flu season has been nasty in large part because the vaccine didn’t work as well as past versions. So scientists like Professor George Lomonossoff of the John Innes Centre are on the hunt for new ways to make better vaccines and think they might have found one -- by growing them in plants.