A research team has succeeded in creating monkey embryos for the first time using stem cells instead of sperm and eggs. Some adult monkeys implanted in the uterus with these ‘synthetic embryos’ showed early signs of pregnancy. The study is the most advanced in terms of laboratory-grown primate embryos, and suggests that one day embryos may be created this way.
Susana Chuva de Sousa Lopes, a developmental biologist at Leiden University in the Netherlands, who was not involved in the study, said it was a “remarkable achievement”. say This is also the first time that a structure similar to an embryo has been artificially synthesized and transplanted into a monkey.
Zhen Liu’s research team at the Chinese Academy of Sciences in Shanghai, who conducted the study, used embryonic stem cells obtained from macaque monkey embryos. These embryonic stem cells, which have been cultured for several generations, can differentiate into almost any type of somatic cell, including cells that make up organs, blood, and the nervous system, given the right environment.
Embryos grown in the laboratory
The research team modified and improved the experimental conditions to allow the embryonic stem cells to mature further. After a few days, the cells began to develop in a way very similar to that of an embryo. The resultant mass of cells looks like a blastocyst, an early embryo, and is therefore called a ‘blastoid’.
The researchers cultured the blastocyst analogues in a petri dish for 7 days and then ran several experiments to see how similar they were to normal embryos. In one experiment, the researchers isolated individual cells of the blastocyst mimetic and determined which genes were expressed in each cell. They analyzed more than 6,000 cells each in this way.
As a result, stem cell-derived embryos and normal monkey embryos were found to be very similar. “The results of the analysis are very impressive,” said Chuva de Souza Lopes. These blastocyst analogues seemed to convert into beings that looked like real embryos. It’s amazing.”
Some blastocyst analogues have been cultured for up to 17 days. The researchers say the structures look a lot like a normal embryo, but other scientists not involved in the study say more evidence is needed to prove their similarity.
To see how much the blastocyst analogue actually resembles an embryo, the blastocyst analogue must be implanted into the uterus of a monkey to see if it develops. Therefore, the research team implanted 8 to 10 blastocyst analogues each on the 7th day of culture into the uterus of 8 adult female monkeys. The transplanted blastocyst analogues were then followed for 3 weeks.
The researchers believed that in three of them, blastocyst analogues successfully implanted and produced a yolk sac, one of the very early signs of pregnancy. These monkeys also had high levels of pregnancy hormones. In other words, it was the same result as a positive result on a pregnancy test.
Nicolas Rivron of the Austrian Academy of Sciences, who conducted a similar study in rats, says the high levels of pregnancy hormones are not surprising. Because developing embryos secrete pregnancy hormones regardless of maturing in the womb. Previously, as part of her research, Livron and her colleagues cultured human blastocyst analogues in a petri dish, which also tested positive when a pregnancy test was dipped into the dish.
However, the monkey blastocyst analogues stopped developing 20 days after implantation and eventually disintegrated and disappeared. Liu’s research team published their results in an international journal. <셀 스템 셀(Cell Stem Cell)>announced on Alfonso Martinez Arias, a developmental biologist at Pompeu Fabra University in Barcelona, Spain, says the results suggest that blastocyst analogues have not yet perfectly replicated normal embryos. For the time being, he added, “it’s clear that it won’t work.”
The cause of the problem may be related to the normal embryonic process in which an egg is fertilized by a sperm. According to Martinez Arias, blastocyst analogues made from stem cells can express genes in the same way as normal embryos, but may lack some important elements that come from eggs.
It is possible that the results would have been further advanced if the researchers had tested more individuals. Of the 484 blastocyst analogues on day 7 of development, only 5 ultimately survived on day 17. In addition, Chuvad Souza Lopes points out that intrauterine embryo transfer is tricky. “Embryo transfer is one of the most difficult factors in the pregnancy process, even in human in vitro fertilization (IVF),” she said. Maybe if you experiment with 100 monkeys, you could get two more pregnant,” she says.
But Martinez Arias says monkey lives are precious and such large-scale experiments are not ethical.
model embryo
This does not mean that blastocyst analogues are not useful. The blastocyst mimetic provides a good experimental model for what happens during the early stages of monkey embryonic development, and potentially the early stages of human embryonic development.
Researchers hope the monkey blastocyst analogue will help expand knowledge about the human embryo. Little is known about how the union of sperm and egg leads to the development of organs and nervous systems, and why development often fails. Regulations generally prohibit scientists from studying human embryos in the lab more than 14 days after fertilization. And recently published international guidelines emphasize that human blastocyst analogues should not be transplanted into humans or any other animal.
“It is not safe to transplant human blastocyst analogues into humans during human development studies,” Livron says. “We have to find an alternative,” he said. And non-human primates are helpful because they are the closest genetically related species to humans.”
Scientists hope that this type of research will lead to more knowledge about human pregnancy, including the causes of infertility and miscarriage. Since blastocyst analogues can be produced indefinitely, it is not necessary to harvest embryos from animals. Naomi Moris, who studies embryonic development at the Francis Crick Institute in London, says drugs could be tested on hundreds or thousands of blastocyst analogues to improve IVF technology.
A stem cell baby?
As technology advances, researchers will find ways to use stem cells to create more mature embryos, which may one day extend to fetuses or baby animals. “There seems to be a kind of competition in blastocyst analogues to see who will be the first to create something special,” says Martinez Arias.
Currently, there is no way to grow this blastocyst analogue into an embryo or baby monkey. But technology continues to advance. Morris says that although research on synthetic embryos started only five to 10 years ago, great progress has been made in the intervening years.
“Scientists are moving very nimble, and this field is advancing very quickly,” says Morris. “The law needs to keep up with the pace of technology development so that technology doesn’t advance too fast,” she says.
Martinez Arias said, “Maybe one day we can create monkey populations from blastocyst analogues? Maybe it will.” “But I don’t think that will happen for a while,” she added.
