For the first time, scientists created mouse embryos in the lab without using any eggs or sperm and watched them grow outside the womb. To achieve this feat, the researchers used only stem cells and a spinning apparatus filled with shiny glass vials.
The experiment is a “game changer,” Alfonso Martinez Arias, an evolutionary biologist at the Pompeu Fabra University in Barcelona who was not involved in the research, said. He told the Washington Post (Opens in a new tab).
“This is a milestone in our understanding of how embryos build themselves,” he said.
The hacking experience described in a report published Monday (August 1) in the Journal cell (Opens in a new tab), in a bioreactor specifically designed to serve as an artificial womb for developing embryos. Inside the device, embryos float in small cups of nutrient-filled solution, and all the cups are locked into a rotating cylinder that keeps them in constant motion. This movement mimics how the blood Nutrients flow to the placenta. The device also replicates the atmospheric pressure of a mouse’s uterus, according to A statement (Opens in a new tab) from the Weizmann Institute of Science in Israel, where the research was conducted.
In a previous experience described in the journal temper nature (Opens in a new tab) In 2021, the team used this bioreactor to grow normal mouse embryos, which had reached day 11 of development in the device. “It really showed that mammalian embryos can grow outside the womb – they don’t actually form or send signals to the fetus as much as they provide nutritional support,” said Jacob Hanna, a Weizmann embryonic stem cell biologist and senior author of the two studies, Stat News said (Opens in a new tab)
Related: The first complete models of a human embryo made in a laboratory
After their initial success with normal embryos, the researchers wanted to try their hand at growing lab-made embryos in a mechanical womb.
To do this, they applied chemotherapy to stem cells in mice that “reset” them to a naive state in which they can turn into any type of cell – heartliver, brain or something else. In a small portion of these naive cells, the team applied additional treatments to turn on genes needed to make the placenta, and in a third group of cells they applied treatments to turn on genes to make the yolk sac. “We gave these two groups of cells a transient impulse to form tissue outside the embryo that sustains fetal growth,” Hanna said in the statement.
Then the scientists placed these three groups of stem cells in the artificial womb to mix and mingle. The three flavors of cells quickly came together to form clumps, but only about 50 out of 10,000 cell clumps continued to develop into embryo-like structures and those only survived in the bioreactor for 8.5 days.
Over the course of those 8.5 days — or about half of a typical mouse pregnancy — primary spherical embryos stretched and became cylindrical, as would be expected of normal embryos, STAT News reports. The beginnings of the central Nervous system It started appearing by the sixth day and quickly resulted in a wrinkled little brain. By day 8, the fetuses had developed intestinal ducts and small beating hearts that propel blood stem cells through the newly formed vessels.
The team noted that the shape of the internal structures and the gene structure in the artificial embryos differed slightly from those in normal mouse embryos.
In follow-up experiments, the researchers plan to study the chemical signals that drive embryonic cells to become one type of tissue over another. What drives some stem cells to assemble and form a neural tube while others end up differentiating into the cells that line the intestines?
“The next challenge is to understand how stem cells know what to do — and how they self-assemble into organs and find their way to their designated places within the fetus,” Hanna said in the statement. “And because our system, unlike the uterus, is transparent, it may be useful for modeling birth defects and implanting human embryos.”
In addition to being a research model, he said, the artificial uterus could one day serve as an incubator for transplanted cells, tissues and organs to perform transplants.
“This is just one step, but it’s a very important step for us to be able to study early evolution,” Paul Tesar, an evolutionary biologist at Case Western Reserve University School of Medicine who was not involved in the study, told STAT News. “We’re crossing into the realm of being able to generate an embryo from scratch, possibly a living organism. It was really a remarkable shift in the field.”
Of course, such research comes with heavy ethical considerations.
“The mouse is a starting point for thinking about how one would like to approach this in humans,” Alex Messner, a stem cell biologist at the Max Planck Institute for Molecular Genetics, told The Washington Post. “You don’t have to get upset or panic, but…as we know, it’s important to have a parallel discussion: How far do we want to take it?”
Originally published on Live Science.