Smriti Mallapaty
nature.com
Originally posted 11 Sept 24
Here is an excerpt:
Science accelerates
Meanwhile, the science keeps moving at such a pace that regulators have a lot to keep up with. In June 2024, the ISSCR announced that it had set up a working group to assess the state of the science and review earlier guidelines, in light of the models published since 2021.
In 2023, around half a dozen teams described models that recapitulate the development of embryos just after implantation. Two models in particular were widely covered by the media — one by Magdalena Zernicka-Goetz, a developmental biologist at the California Institute for Technology in Pasadena, and one by Jacob Hanna, a stem-cell biologist at the Weizmann Institute of Science in Rehovot, Israel. They were described as complete post-implantation models, but that title has been hotly debated.
“These are not complete models,” says Rivron. The one by Zernicka-Goetz’s group7 doesn’t have cells that behave like trophoblasts, which provide nutrition for the embryo — and although Hanna’s8 does contain a trophoblast-like layer, it isn’t as organized as the real thing, say researchers.
“It’s almost like a beauty contest — whose ‘model’ looked better,” says Jianping Fu, a bioengineer at the University of Michigan in Ann Arbor. “There’s a lot of excitement, but at the same time, there’s some hype in the field right now.”
Some researchers question the value of chasing a complete model. It’s a “pretty exquisite balancing act”, says Hyun. Researchers want models to resemble an embryo closely enough that they provide real insight into human development but not so closely that they can’t tell the difference between the two, and so risk restrictions to their work. “You want to skate as close to the edge as possible, without falling over,” he says.
Some researchers try to avoid this ethical dilemma by intentionally introducing changes to their embryo models that would make it impossible for the model to result in an organism. For example, Hanna has started working on models in which genes involved in brain and heart development have been inactivated. He has inferred from discussions with Christian and Jewish leaders in his community that an embryo model lacking brain or heart tissue would not be considered a form of person.
The info is here.
Here are some thoughts:
Scientists have made significant strides in developing sophisticated "embryo models" using stem cells that closely mimic aspects of early human development. These models present exciting opportunities to explore critical areas such as embryo development, infertility, and disease prevention, while also raising important ethical questions. Key advancements include the creation of "blastoids," which resemble early embryos at the blastocyst stage, as well as models that capture post-implantation development and gastrulation. Additionally, researchers have developed organ-specific models, such as those representing the neural tube and somites, which are crucial for understanding organogenesis.
The potential applications of these models are vast, including studying the causes of early pregnancy loss, improving the success rates of in vitro fertilization (IVF), testing drug safety, and producing blood stem cells for transplants. However, the rapid advancement of this field has led to ongoing challenges related to ethical and regulatory considerations, such as defining the distinction between embryos and embryo models, establishing limits on culturing duration, and imposing restrictions on implantation into animals or humans. As the field continues to progress, there is a pressing need for ongoing ethical guidance and oversight, as well as public engagement and transparency to address societal concerns.
