Scientists use stem cells to model pre-embryos.

Using human stem cells, scientists are developing a structure that replicates the pre-embryo and may act as a substitute for the real one.

They say the “blastoids” provide an effective, ethical way to study human development and advance biological discoveries in fertility and contraceptives.

Details of the latest attempt were given in the journal Nature on Thursday. The structures are not embryos, but scientists have not allowed them to grow for the past two weeks in defiance of long-standing moral 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. Nicholas Reveron, a researcher at the Austrian Academy of Sciences and one of the authors of the Nature Paper, said that these models are “an excellent alternative” to human embryos for research, partly because of the need to obtain donated embryos. And it’s hard to manipulate the lab.

“It’s extremely difficult to use human embryos to discover any molecules, genes, principles that could allow us to better understand evolution and make biomedical discoveries,” Reverend said.

But laboratory-made stand-ins can be made, modified and studied in large numbers, and will complement fetal research.

“It illuminates the possibilities for scientific and biomedical discoveries,” he said. For example, what researchers learn while 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 blastide, said Magdalena Zarnika Goetz, a stem cell biologist at Cambridge University, who was not included in the latest study. But “every step is important,” to improve performance as researchers try to master the model.

To make blastoids, Revron and his colleagues used two different types of stem cells: either stem cells from pre-established cell lines or reprogrammed stem cells from adult cells such as skin cells. No new embryonic cell lines have been developed for research.

In the future, reprogrammed stem cells from adult cells are likely to become the new standard in research, but now it is important to establish embryonic cell lines because they are “still the ultimate reference,” he said. He said that blastocysts were cultured separately so that they could be compared to laboratory structures.

Studies have shown that blastoids reliably replicate important stages of early fetal development. When they came in contact with the cells of the uterine lining that were stimulated by hormones, they were almost half connected and began to grow as the blastoists did.

After 13 days, the researchers stopped their growth and analyzed the cells, Reverend said. At the time, he said, the collection of cells did not reflect a 13-day-old fetus. They were not growing enough and were not being organized.

He said ethical concerns also arose: for decades, researchers have been guided by the “14-day rule” on growing embryos in the laboratory. Earlier this year, the International Society for Stem Cell Research recommended relaxation of the principle in limited circumstances.

Revron, a member of the working group that updated the Society’s guidelines, said that blasticides were not subject to the same rules, but pointed out that they should never be transmitted to any animal or human. Should.

“It’s very clear that blastoids are not embryos … and if they are not, then why would we apply the 14-day rule to these structures?” They said. Nevertheless, they decided to stop “for the sake of transparency and to make sure that people understand things well.”

Dr. Barbara Goulder, editor-in-chief of the Catholic Medical Association’s journal The Linear Quarterly, says the development of blastoids shows “how science progresses.” But, he said, the problem is that fetal cell lines remain standard in science.

“Ethical issues will remain as long as they have nothing to do with the stem cells obtained from the aborted fetus and as long as we have to connect a set of stem cell lines to those that are embryonic stem cells,” he said. Are taken from, “he said. .

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