Scientists in the earliest stages of development created hollow cells that looked like human embryos. The artificial embryos, called ‘blastoids’, can allow scientists to study early human development, infertility and pregnancy loss without experimenting on real embryos.
Two separate research groups created these model embryos in different ways, and each published their results on March 17 in the journal Nature Portfolio.
A research group start with adult skin cells, which they have genetically reprogrammed to look like embryonic cells, according to a statement. The researchers then grew these modified cells over a 3D scaffold that led them into a spherical shape. The resulting structure mimics a human blastocyst, a structure that usually contains several hundred cells and forms about four days after a sperm cell fertilizes an egg, and later implants in the uterine wall, Nature News reported.
The second research group start with human stem selle, which includes both embryonic stem cells and stem cells derived from adult skin tissue known as ‘induced pluripotent stem cells’, reports Nature News. The team treated the stem cells with specific chemicals, known as growth factors, to attract them in the form of a blastocyst.
Related: Inside life science: once on a stem cell
Both teams showed that their homemade blastocysts behaved in the same way as the real ones, in that they formed hollow spheres and contained three different cell types that eventually formed different body parts, as blastocysts do, Nature reports. In addition, the spheres can be “implanted” in a plastic sheet that stood in the uterine wall of man.
Despite these similarities, no model recreates a human embryo perfectly, and based on evidence from similar mouse models, the spheres are unlikely to develop beyond the blastocyst stage. Evidence suggests that mouse blastoids, when implanted in a mouse uterus, cannot properly differentiate into additional cell types, possibly due to how their gene expression differs from true blastocysts, according to a 2019 report in the journal Development cell.
“I would consider it a major advancement in the field,” said Jianping Fu, a professor of mechanical engineering at the University of Michigan, Ann Arbor. told NPR. “It really is the first complete model of a human embryo.”
“With this technique we can create hundreds of these structures. It will enable us to increase our understanding of very early human development,” said José Polo, a developmental biologist at Monash University in Australia and the senior author of the first study, told NPR. “We think it will be very important.”
However, the experiments raise serious ethical questions.
“I’m sure it makes someone morally serious nervous when people start creating structures in a petri dish that are so close to being early human,” Daniel Sulmasy, a bioethicist at Georgetown University, told NPR. “The more they push the envelope, the more nervous I think someone would try to create people in a test tube.”
The International Society for Stem Cell Research (ISSCR) has from now on a guideline that places time limits on human embryo experiments in the laboratory, limiting it to 14 days, Nature reports. This cap is intended to prevent the embryo from becoming past a point where its cells begin to differentiate into complex structures; during human pregnancy, the implanted blastosis would form a ‘primitive streak’ by Day 14, which is a sign of a shift toward this differentiation. Both research teams adhered to this rule in the new blastoid experiments.
The ISSCR plans to issue updated guidelines in May 2021 on embryo-like structures, such as these blastoids, according to Nature.
In a report published in February 2020, the association said that such models would “have great potential benefits for understanding early human development, for biomedical science and for reducing the use of animals and human embryos in research.” for the ethical conduct of this line of work is currently not well defined, ”according to the statement from Monash University.
Meanwhile, the U.S. National Institutes of Health (NIH) will “continue to consider applications on a case-by-case basis,” according to a statement issued March 11 by Carrie Wolinetz, the NIH director of science policy.
Originally published on Live Science.