Scientists Create Mouse Embryos From Stem Cells

For the first time, scientists have created synthetic mouse embryos without using sperm or eggs, that managed to grow outside the womb. The embryos developed inside a specially designed bioreactor and were made up entirely of stem cells cultured in a petri dish. The breakthrough experiment was successfully conducted by the Weizmann Institute of Science in Israel and published Monday in Cell, marking the first time researchers have grown fully synthetic mouse embryos outside of the womb.

According to STAT, the research opens up new avenues of analysis to see how stem cells form various organs in developing embryos and how mutations cause developmental disease. It also raises profound questions on whether animals, including humans, might one day be cultured from stem cells in a lab.

“As soon as the science starts to move into a place where it’s feasible to go from a stem cell population in a petri dish all the way to organ development — which suggests one day it will be possible to go all the way to creating a living organism — it’s a pretty wild and remarkable time,” said Paul J. Tesar, professor of genetics and genome science at Case Western Reserve University School of Medicine who was not involved in the study.

Scientists have been struggling for decades to find ways to keep embryos viable outside the womb. Jacob Hanna, an embryonic stem cell biologist at Weizmann finally developed a mechanical uterus that helped natural mice embryos stay alive for up to 11 days, says STAT.

“That really showed that mammalian embryos can grow outside the uterus — it’s not really patterning or sending signals to the embryo so much as providing nutritional support,” said Hanna. The next step was determining whether stem cells could survive in their contraption. The team did manage to grow synthetic embryos to day 8.5, noting the beginning development of a well-shaped brain, a neural tube, and an intestinal tract, as well as a beating heart. The development was like that of normal mouse embryos, noted the researchers.

A full gestational time for a mouse is 20 days, and embryos that survived that long were a rarity. Only 50 of the 10,000 cellular clumps of stem cells organized into embryos and the rest failed to develop properly.

“This is just one step, but a very important step for us to be able to study early development,” said Tesar. “We’re crossing into the realm of being able to generate an embryo from scratch, and potentially a living organism. It’s been a really notable switch for the field. “

He says that the synthetic embryology revolution isn’t going to happen tomorrow. Humans have a much longer gestation period than mice, but the research has to start somewhere, and it usually starts with mice. He acknowledges that as the push for stem-celled embryos moves forward, there will always be an ethical issue.

“There will always be a grey area, but as scientists and society we need to come together to decide where the line is and define what is ethically acceptable,” he said. Hanna said he is not interested in synthetic embryos for reproductive purposes, but rather as a means to create organs and tissue for transplantation and to treat human diseases.

For example, if a leukemia patient needs a bone marrow transplant to survive, scientists could transform the patient’s own skin cells back into stem cells by growing them in the bioreactor. The result would be an army of bone marrow cells that could be given to the patient without having to wait for a donor.

“It’s early days but we are really opening up the field to explore the possibilities more seriously,” said Hanna. “We’re moving from science fiction to science.”