Scientists use human 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” offer an efficient and ethical way to study human development and pursue biomedical discoveries in fertility and contraception.

The last effort was detailed on Thursday in the journal Nature. The structures are not embryos, but scientists nevertheless did not allow them to grow beyond two weeks out of respect for long-standing ethical guidelines.

A blastoid is a model for a blastocyst, a ball of cells that forms within a week of fertilization and is about the width of a hair. Nicolas Rivron, a researcher at the Austrian Academy of Sciences and one of the authors of the Nature article, said the models are “a fantastic alternative” to human embryos for research, in part because the donated embryos are difficult to obtain and handle in the laboratory.

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

But laboratory-created replacements can be made, modified and studied in large numbers, and would complement embryonic research, he said.

“It unleashes the potential for scientific and biomedical discoveries,” he said. For example, what researchers learn from studying blastoids could be used to develop contraceptives that do not contain hormones.

This is not the first time that scientists have created a human blastoid, noted Magdalena Zernicka-Goetz, an expert in stem cell biology at the University of Cambridge who was not involved in the latest study. But “every step is important,” improving efficiency as researchers try to master the model, she said.

To create the blastoids, Rivron and his colleagues used two different types of stem cells: either embryonic stem cells from already established cell lines, or stem cells reprogrammed from adult cells, such as skin cells. No new embryonic cell line has been created for the research.

In the future, reprogrammed stem cells from adult cells will likely become the new standard in research, he said, but established embryonic cell lines are now needed because they “remain the gold standard”. He said the blastocysts were cultured separately to compare them side-by-side with structures created in the lab.

The study showed that the blastoids reliably mimicked key phases of early embryo development. When brought into contact with cells in the lining of the uterus that had been stimulated by hormones, about half attached themselves to them and began to grow the same way blastocysts would.

Rivron said the researchers stopped growing after 13 days and analyzed the cells. At this point, he said, the cell collection did not reflect a 13-day-old embryo; they weren’t growing enough or organizing as well.

He said ethical concerns also came into play: For decades, a “14-day rule” on the growth of embryos in the lab has guided researchers. Earlier this year, the International Society for Stem Cell Research recommended relaxing the rule in limited circumstances.

Rivron, who is part of the task force that updated the company’s guidelines, said blastoids are not subject to the same rule, but stressed that the guidelines say they should never be transferred. in an animal or a human.

“It is very clear that blastoids are not embryos… and if they are not, then why would we apply the 14 day rule to these structures? he said. Nevertheless, they decided to stop “for the sake of transparency and to make sure that things are very well understood by the public”.

Dr Barbara Golder, editor of The Linacre Quarterly, the journal of the Catholic Medical Association, said the development of blastoids shows “how science progresses.” But, she said, it’s problematic that embryonic cell lines remain the norm in science.

“The ethical issues will exist as long as there is a link with stem cells derived from an aborted fetus and as long as we have to correlate a set of stem cell lines with those derived from embryonic stem cells,” he said. she declared. .

” Previous

Next ”

Related stories