Human embryo the size of a poppy seed offers rare insight into early development

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The donation of a tiny human embryo the size of a poppy seed has given scientists extremely rare insight into an early stage in human development that has long been difficult to study, the Associated Press reported. The embryo was in its third week after fertilization, a period that practical and ethical concerns made difficult to examine.

A woman who terminated her pregnancy donated a single 16-19 day old embryo to European researchers. Most women don’t know they’re pregnant so soon after conception, and global rules in place for decades until recently prohibit labs from growing human embryos beyond 14 days, the report reported. AP.

Since these factors make it difficult for scientists to access embryos at this stage of development, the rare donation provided researchers with a unique chance to examine it. A study published Wednesday by Nature detailed a process called “gastrulation,” which begins about 14 days after fertilization and lasts a little over a week.

Shankar Srinivas, an expert in developmental biology at the University of Oxford, was the study’s lead investigator, collaborating with researchers in the UK and Germany. He described gastrulation as “a process by which you have this kind of explosion of cell diversity.”

“It is during gastrulation that different cells emerge, but they also begin to position themselves in different places to form the body so that they can perform their functions and form the right organs,” Srinivas said.

This stage of development in humans has never been fully mapped before, according to officials at the University of Oxford.

For more Associated Press reporting, see below.

Research published in the journal Nature provides rare insight into an early stage in human development. This image from the University of Oxford shows a human embryo 16-19 days after fertilization.
University of Oxford via AP

For decades the so-called “14-day rule” on the growth of embryos in the laboratory has guided researchers, some places, including the UK, have enshrined it in law. Others, including the United States, have accepted it as the standard guiding scientists and regulators.

Earlier this year, the International Society for Stem Cell Research recommended relaxing the rule and allowing researchers to grow embryos in the last two weeks under limited circumstances and after a difficult review process. . But the rule remains the law in the UK

This research was not subject to the law because the embryo was not cultured in the laboratory. But it’s an example of the types of things scientists expect to learn more about if the rules are relaxed. Researchers have discovered various types of cells, including red blood cells and “primordial germ cells” that give rise to eggs or sperm. But they didn’t see any neurons, Srinivas said, which means embryos aren’t equipped at this stage to sense their surroundings.

The authors said they hope their work will not only shed light on this stage of development, but will also help scientists learn from nature how to turn stem cells into particular types of cells that can be used to help heal damage or disease. diseases.

Robin Lovell-Badge, a stem cell expert at the Francis Crick Institute in London who chaired the group behind the guidelines, said being able to grow human embryos beyond 14 days “would be extremely important for understanding not only how we normally develop but how things go wrong. “

It is very common for embryos to fail during gastrulation or soon after, he said. “If things go even slightly wrong, you end up with birth defects, or the embryo miscarries.”

Dr Daniel Sulmasy, director of the Kennedy Institute of Ethics at Georgetown University, said that “those of us who are morally conservative” have always thought the 14 day rule is somewhat arbitrary, “but at least it was a certain recognition of the humanity of the embryo. “

With the new recommendation, there will be more research on older embryos, he said. “Part of what science does is always trying to move forward and learn new things. And that continues to be a pressure. But just the fact that we can do something is not enough. to say we have to do it. “

Oxford Researcher
Shankar Srinivas, an expert in developmental biology at the University of Oxford, was the lead investigator in a study examining an early stage in human development that has long been difficult to examine. Honorands and senior members of the university participate in the annual Encaenia ceremony in Oxford, west London on September 22, 2021.
Tolga Akmen / AFP via Getty Images


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