Scientists have cultured monkey embryos in the lab long enough to observe the onset of organogenesis and development of the nervous system, which is difficult to observe in embryos growing in the womb. Stone. The embryo is 25 days old and may be the oldest primate embryo cultured outside the womb.
An independent team described their findings in a separate paper. cell May 11th.
“This is very impressive,” says developmental biologist Magdalena Zernika Goetz of Caltech Pasadena, who was not involved in the study. “It will bring a lot of new insights.”
Transition to 3D
Few things are more difficult than keeping lab-grown embryos alive for more than a few weeks. Most of the time it’s just a mixed bag of cells in a dish. So far, both teams have successfully grown monkey blastocysts (spheres of dividing cells) in Petri dishes for up to 20 days. After that point, all embryos had disintegrated and were unable to see further stages of development, such as the nervous system and early signs of organogenesis.
But in a new study, researchers cultured monkey embryos in tiny vials of culture medium that allowed them to grow in three dimensions, just like they do in the womb. Both teams persuaded the embryos to survive 25 days after fertilization. Both authors and outside scientists Nature I knew about old primate embryos grown in the lab.
Observe how organs are formed
Wang Hongmei, a developmental biologist at the National Key Laboratory of Stem Cell and Reproductive Biology at the Chinese Academy of Sciences in Beijing, and his team obtained egg cells from female cynomolgus monkeys (Cynomolgus monkey) and fertilized in the lab with sperm collected from the corresponding male. After 1 week, the resulting blastocysts were placed in gel-like material in small cylindrical containers and observed for growth for 25 days.
About two weeks after fertilization, more than half of the embryos developed a scutellum, a flat mass of cells. These discs eventually formed her three major cell layers of the body: endoderm, mesoderm, and ectoderm. Lab-grown embryos also showed genetic characteristics similar to those seen in natural monkey embryos within the same time period.
By day 20, embryos have developed a neural plate, one of the early features of the nervous system. As in a natural embryo, the plates thickened and bent into tubes that formed the basis of the brain and spine. Wang and her team also identified cells that eventually become motor neurons. Insights gleaned from lab-grown embryos will help researchers better understand the development of early primate embryos, Wang said.
where blood is born
In a second study, developmental biologist Tao Tang of Kunming University of Science and Technology in Yunnan, China, and colleagues also generated blastocysts from cynomolgus monkey eggs and sperm. However, they used two different types of cell culture to provide the embryos with strong mechanical support and added glucose to provide energy as they grew.
Similar to Wang’s work, most of the cells in cultured monkey embryos were of the same type as those normally found in natural embryos 18 to 25 days after fertilization. By examining embryonic mesodermal cells, Tan and colleagues found that some differentiated into cardiomyocytes, while others matured into cells lining blood and lymph vessels. The researchers also identified cells that develop into connective tissue and cells that form the basis of the digestive system.
The researchers also found signs that blood cells and their components are beginning to form within the yolk sac that nourishes the embryo. “We were deeply impressed,” Tan says. These blood cells are “almost impossible to obtain during human fetal development.”
Naomi Morris, a developmental biologist at the University of Cambridge, UK, said the study represents an important step in developing ways to keep embryos longer outside the womb than previously possible. . But she warns that there is still a long way to go before the embryos grown in her lab look and behave like the real thing. “They still look a little different than what we’re expecting. [them] To study these stages,” says Morris, who was not involved in the study. “There is definitely room for improvement.”
This article is reprinted with permission and was first published May 11, 2023.
