For the first time, scientists have created mouse embryos in the lab without using eggs or sperm and watched them grow outside the womb. To achieve this feat, the researchers used nothing but stem cells and a spinner filled with shiny glass vials.
The experiment is a “game changer,” Alfonso Martinez Arias, a developmental biologist at Pompeu Fabra University in Barcelona who was not involved in the research, told the Washington Post (opens in a new tab).
“This is an important milestone in our understanding of how embryos are built,” he said.
The groundbreaking experiment, described in a report published Monday August 1 in the journal Cell (opens in a new tab), took place in a specially designed bioreactor that serves as an artificial womb for developing embryos. In the device, the embryos float in small beakers of nutrient-filled solution, and the beakers are all enclosed in a rotating cylinder that keeps them in constant motion. This movement simulates how some blood and nutrients flow to the placenta. The device also replicates the atmospheric pressure of a mouse 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 review Nature (opens in a new tab) in 2021, the team used this bioreactor to grow natural mouse embryos, which reached the 11th day of development in the device. “It really showed that mammalian embryos can develop outside of the womb – it’s not really about modeling or sending signals to the embryo but providing nutritional support,” Jacob said. Hanna, an embryonic stem cell biologist at Weizmann and lead author of both studies. told STAT News (opens in a new tab)
Related: “First complete models” of a human embryo made in the laboratory
After their initial success with natural embryos, the researchers wanted to try their hand at culturing lab-made embryos in the mechanical womb.
To do this, they applied a chemical treatment to mouse stem cells that “reset” them to a naïve state from which they could transform into any type of cell – heartliver, brain or otherwise. In a fraction of these naïve 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 needed to make the sac. vitelline. “We gave these two groups of cells a transient boost to give rise to extraembryonic tissues that support the developing embryo,” Hanna said in the release.
The scientists then placed these three groups of stem cells into the artificial womb to mix and mingle. The three flavors of cells soon came together to form clumps, but only about 50 out of 10,000 cell clumps continued to develop into embryo-like structures and those that only survived in the bioreactor for 8.5 days .
Over those 8.5 days — nearly half of a typical mouse pregnancy — the initially spherical embryos stretched and became cylindrical, as one would expect from natural embryos, STAT News reported. The beginnings of the power station the nervous system began to emerge on day 6 and quickly grew into a small wrinkly brain. By day 8, the embryos had developed intestinal tracts and small beating hearts that pushed blood stem cells through the newly formed vessels.
The shape of internal structures and the structure of genes in the synthetic embryos differed slightly from those found in natural mouse embryos, the team noted.
In follow-up experiments, the researchers plan to study the chemical signals that cause embryonic cells to become one type of tissue rather than another. What causes some stem cells to come together and form the neural tube while others eventually differentiate into cells that line the intestines?
“Our next challenge is to understand how stem cells know what to do – how they self-assemble into organs and find their way to their assigned locations inside an embryo,” Hanna said in the release. “And because our system, unlike a uterus, is transparent, it may prove useful in modeling birth and implantation defects in human embryos.”
In addition to serving as a research model, the artificial uterus could also one day serve as an incubator for cultured cells, tissues and organs for transplant procedures, he said.
“It’s just one step, but a very important step for us to be able to study early development,” Paul Tesar, a developmental biologist at Case Western Reserve University School of Medicine, who didn’t have not participated in the study. “We’re entering the realm of being able to generate an embryo from scratch, and potentially a living organism. That’s been a really notable change for the field.”
Of course, such research comes with heavy ethical considerations.
“The mouse is a jumping off point to think about how you want to approach this in humans,” Alex Meissner, a stem cell biologist at the Max Planck Institute for Molecular Genetics, told The Washington Post. “There’s no need to be alarmed or to panic, but…as we learn, it’s important to have the discussion side by side: how far do we want to go?
Originally posted on Live Science.
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