The mouse embryo seemed completely normal. All his organs were developing as expected, along with his organs and circulatory system and nervous system. His small heart was beating in a normal beat of 170 minutes per minute.
But these embryos were not growing in the mother’s rat. This was the first time such an accomplishment has been accomplished inside an artificial uterus, scientists reported on Wednesday.
The experiments, at the Weisman Institute of Science in Israel, were intended to help scientists understand how mammals develop and how gene mutations, nutrients, and environmental conditions can affect the fetus. But the work may one day raise deeper questions about whether other animals, even humans, should be cultured outside the living womb.
In a study Published in the journal Nature, Dr. Jacob Hanna described removing the embryos from the mice’s uterus at five days’ gestation and growing them for six more days in the artificial womb.
At that time, the fetus was about half its development; The entire gestation period is about 20 days. A human at this stage of development will be called a fetus. To this day, Drs. Hanna and her colleagues have developed more than 1,000 embryos in this way.
“This is a truly remarkable achievement,” said Paul Tesar, a developmental biologist at Case Western Reserve University School of Medicine.
Alexander Meisner, director of genome regulation at the Max Planck Institute for Molecular Genetics in Berlin, said that “this is very surprising” and that the study was “a major milestone”.
But researchers have already moved on to what investigators described in the paper. In an interview, Drs. Hanna said that he and his colleagues had taken the fertilized eggs – on day 0 of development – from the oviducts of female mice just after fertilization – and had developed them into an artificial uterus for 11 days.
Until now, researchers were able to fertilize eggs from mammals in the laboratory and grow them for only a short time. The fetus required a living fetus. Dr. “The uterus of placental mammals has a lock,” Taser said.
This prevented scientists from answering fundamental questions about the early stages of development.
Dr. “The sacred grave of developmental biology is to understand how a single cell, a fertilized egg, can make all the specific types of cells in the human body and grow into 40 trillion cells,” said Taser. “Since the beginning of time, researchers have been trying to develop ways to answer this question.”
The only way to study the development of tissues and organs was to turn to species such as insects, frogs, and flies that do not require a uterus, or to remove embryos from the uterus of experimental animals at different times, Snapshot As such provide a glimpse of development. Compared to the video.
What was needed was a way to get inside the uterus, to see and recreate the development in mammals as it happened. Dr. For Hanna, this means developing an artificial uterus.
He spent seven years developing a two-part system consisting of an incubator, nutrients and a ventilation system. The embryos of the mice are placed in glass vials inside the incubators, where they float in a special nutrient fluid.
The vials are attached to a wheel that rotates slowly so the embryos do not attach to the wall, where they deform and die. Incubators are connected to a ventilation machine that delivers oxygen and carbon dioxide to the embryo, controlling the concentration of those gases, as well as the gas pressure and flow rate.
On the 11th day of development – more than half through a mouse pregnancy – Drs. Hanna and his colleagues examined the size of the embryo, only apple seeds, and compared them to those developing in the uterus of living mice. Laboratory embryos were similar, scientists found.
By that time, however, lab-developed fetuses had grown too large to survive without a blood supply. They had a placenta and a yolk sack, but the nutrient solution fed to them through diffusion was not sufficient.
Dr. Hannah said in an interview that creating a barrier is the next goal. He is considering using an enriched nutrient solution or an artificial blood supply that binds to the embryo’s invertebrates.
Meanwhile, experiments are considered. The ability to keep the fetus alive and develop half during pregnancy is “a gold mine for us,” Drs. Hanna said.
Artificial insemination may allow researchers to learn more about why abortion ends in conception or why fertilized eggs fail to implant. This opens a new window on how gene mutations or deletions affect fetal development. Researchers may be able to move individual cells to their final locations.
The work is “a success,” said Magdalena Zernica-Goetz, a professor of biology and biological engineering at Caltech. This “opens the door to a new era of developmental studies in experimental mouse models.”
A recent development provides another opportunity. Researchers have created mouse embryos directly from mouse fibroblasts – connective tissue cells – to form an initial embryo without starting with a fertilized egg.
Dr. Combine that development with Hanna’s work, and “you no longer need mice to study the development of mouse embryos,” Dr. Meisner said. Scientists may be able to make all the embryos they need from connective tissue.
If scientists can make embryos without fertilizing eggs and study their development without the uterus, Drs. “You can get away with embryonic destruction,” Meisner said. Mouse eggs will not need to be fertilized to destroy them only during study.
But the work may eventually go beyond mice. Two other papers Published in nature In this report on Wednesday, an attempt has been made to have a near edge of making human embryos in this way. Of course, Drs. The creation of a human embryo is years away – if it is allowed, Meisner said. For now, scientists generally avoid studying human embryos beyond 14 days after fertilization.
In future, Drs. “It is not unreasonable that we may have the ability to give birth to human embryos completely outside the uterus by fertilization,” Tesser said.
Of course, the suggestion of this science fiction scenario is also bound to frighten many people. But these are the early days, without any assurance that the human fetus can ever fully develop outside the womb.
Even they may assume, Drs. “Is it fair that there is a question for moralists, regulators and society,” said Taser.