Scientists use stem cells to create models of pre-embryos

Scientists are using human stem cells to create a structure that mimics a pre-embryo and can serve as a research alternative to a real one.

They say these "blastoids" provide an efficient, ethical way to study human development and pursue biomedical discoveries in fertility and contraception.

The latest effort was detailed on Dec. 2 in the journal Nature. The structures aren't embryos, but scientists nevertheless didn't let them grow past two weeks in deference to longstanding ethical guidelines.

A blastoid is a model for a blastocyst, a ball of cells that form within a week of fertilization and are about the width of a hair. Nicolas Rivron, a researcher at the Austrian Academy of Sciences and one of the authors of the Nature paper, said the models are "a fantastic alternative" to human embryos for research, partly because donated embryos are hard to obtain and manipulate in the lab.

"It is extremely difficult to use such human embryos to discover any molecules, genes, principles that might allow us to better understand development and also make biomedical discoveries," Rivron said.

But lab-created stand-ins can be made, altered and studied in big numbers, and would complement embryonic research, he said.

"This unleashes the potential for scientific and biomedical discoveries," he said. For example, what researchers learn studying blastoids could be used to develop contraceptives that don't include hormones.

It's not the first time scientists have created a human blastoid, noted Magdalena Zernicka-Goetz, an expert in stem cell biology at the University of Cambridge who wasn't involved in the latest study. But "every single step is significant," improving efficiency as researchers try to master the model, she said.<...