Yi Zheng / University of Michigan, Ann Arbor
Scientists have invented a device that can quickly produce a large number of living entities that are very similar to very primitive human embryos.
Researchers welcomed the development, which is described Wednesday in the journal Nature as an important advance in studying the earliest days of human embryonic development. But it also raises questions about where to draw the line when it comes to producing "synthetic" human life.
Other researchers have previously created synthetic embryos, also called embryoids. These units are manufactured by coaxing human stem cells to form structures found in very early human embryos. The research has raised questions about how similar to complete embryos they could and should be allowed to become.
The new work continues with such research by creating a method that can quickly generate relatively large number of embryoids.
"This new system allows us to achieve superior efficiency in generating these human embryonic-like structures," said Jianping Fu, associate professor of biomedical engineering at the University of Michigan at Ann Arbor, who led the research.
Fu calls the step "an exciting new milestone for this emerging field" that should significantly improve researchers' ability to study early human development.
"Such human embryonic structures have much potential to open what we call the so-called black box for human development," says Fu's.
He refers to the first few weeks after a sperm fertilizes an egg, when the embryo is inside a woman's body and difficult to study. A long-standing guideline prevents researchers from conducting research on embryos in their laboratories in addition to 14 days of development for ethical reasons.
Fu says that the ability to produce a large number of embryoids, which are not covered by the 14-day guideline, will hopefully provide researchers with new insights into important health problems, including how to prevent birth defects and miscarriages. In addition, researchers can use the embryoids to screen drugs to determine if the drugs are safe for pregnant women to take.
"Such research can lead to very good," says Fu.
Other researchers agree
"It is a great advance in the knowledge of early human development," says Ali Brivanlou, an embryologist at Rockefeller University in New York. "We open windows to aspects of development that we have never seen before. This knowledge is truly the holy grail of human embryology."
Other scientists and bioethicists agree. But they also warn that Fu's research raises sensitive issues.
"This team must be very careful not to model all aspects of the developing human embryo so that they can avoid the worry that this embryo model may one day become a child if you put it in the uterus, says Insoo Hyun, a bioethicist at Case Western Reserve University and Harvard Medical School.
Because of such concerns, Fu says he has deliberately made embryoids that are not complete models of complete human embryos. part of the human embryo – the core of the early human embryo, "says Fu. They lack key structures, such as the early stages of the placenta and" egg yolk ", which nourish the embryo yon.
"I understand that there may be people sensitive when you see that you can massively produce organized embryonic structures. People will be worried. I understand that. I guess we push the limit, Fu says.
Yi Zheng / University of Michigan, Ann Arbor
"But I want to make 100% clear that we have no intention of trying to create a synthetic structure [that] looks like a complete human embryo," says Fu. "We have no intention of doing that."
Others praised Fu's strategy and said it would be very problematic to move on.
"It would be a very early kind of Frankenstein model, right? – take different parts and sew them together to try to create an organism," says Daniel Sulmasy, a bioethicist at Georgetown University.
"If anyone tried to do that and it was even in the earliest stages of embryonic development, and they then tried to let it develop further, that would be a problem, "says Sulmasy.
The unit Fu created is a thin silicone square. The plate contains four Researchers place stem cells – either human embryonic stem cells or induced pluripotent stem cells, which can be made from adult cells – into the device, and then add adjacent well chemicals that stimulate cells to grow key structures in human embryos] . can produce about a dozen embryoids in just a few days, says Fu, which allows researchers to produce your hundreds of structures using many of the devices simultaneously.
Time-lapse video shows human stem cells forming "embryoids" containing key structures for very early human embryos.
The rapid advances in embryoid creation have prompted the International Society for Stem Cell Research to begin a review of its guidelines.
"If these embryo models cease to be complete and are built to have all components of natural embryos, they should be covered by the same 14-day rule that limits research with natural human embryos," Hyun says. "That's another reason why avoid modeling the whole thing at once. "