Perhaps the biggest question rests on how embryonic these stem cell-derived structures are. For some scientists, it’s a catch-22 situation. If blastoids are too similar to embryos, many believe that research with them should be restricted in the same way that we control work with human embryos.
But if they don’t look enough like embryos, then there’s no point in using them for research, says Chuva de Sousa Lopes. “Right now, it’s so hard to understand how close they are or how different they are,” he says.
Scientists tend to look at the size and shape of the structures, and what genes their cells express, to figure out how similar they are to typical embryos. But there are other important aspects to consider.
“We first need to agree on what an embryo is,” says Naomi Moris, a developmental biologist at the Crick Institute in London. “Is it that which is only generated from the fusion of a sperm and an egg? It has something to do with the types of cells you have, or the [shape] of the structure?”
Perhaps it has more to do with the potential of the structure. A human embryo could become a person. Human blastoids cannot become people. However.
As technology advances, it seems increasingly likely that one day, embryos derived from stem cells could become living animals. “In theory, if you have all the right cell types … they could go further,” says Rossant. “Never say never.”
As we define blastoids and other embryo-like structures, now is the time to start regulating how we grow and study them. Rossant is one of many scientists I spoke with who agree that, given the embryonic appearance of these structures, they should probably be subject to the same rules and regulations that cover research on normal embryos.
“The big risk is that … if we had a rogue player who went really fast [with human cells]and developed something that caused a public reaction,” says Moris.
