Human Neural Organoid Research Needs Better Regulation

In a 2022 study, scientists transplanted a cluster of human neurons into developing rat brains and discovered that these cells integrated and matured alongside rat neurons.¹ The researchers could even activate the human cells by touching the rats—which sounds like a scene from a science fiction movie.

“You tickle the rat whiskers, and the human cells fire,” said Henry (Hank) Greely, a bioethicist at Stanford University. “There’s a lot of weird stuff here.”

Human neural organoids are three-dimensional, self-assembling groups of neurons derived from induced pluripotent stem cells. Researchers commonly transplant them into the brains of non-human animals and use this combined model to study brain development as well as disorders, from autism to Zika virus infection.

Human Neural Organoid Research Moves Fast, and Its Regulation Must Keep Up

In the past decade, human neural organoid research has been moving at a “break-neck pace,” Greely said, but it lacks the legal and ethical guidelines that should accompany a field that is, according to Greely, “peculiarly ethically sensitive.”

“If [neural organoids] were human, we’ve got Institutional Review Boards; if they were animals, we’ve got the Institutional Animal Care and Use Committee—but they’re neither,” Greely said. “There’s no regulatory setup that’s looking at the organoids as organoids.”

In a recent Science article, Greely and his colleagues highlighted some of the legal and ethical concerns in the field and emphasized the need for better regulation as well as communication with the public.²

For the most part, Greely said, “people thought that this research seemed good and ethical and important for better understanding human brain conditions and relieving human suffering.” But there has also been some pushback.

At the Society for Neuroscience meeting in 2019, a group of researchers called Green Neuroscience Laboratory voiced their concern that the organoids might feel pain. Scientists don’t think that this is likely, Greely said, because the organoids are not complex or big enough—the largest neural organoids have about one or two million neurons (the average human brain has nearly 90 billion) and are about the size of a black peppercorn. But that’s not to say that as organoids grow in both size and complexity, this concern will stay as implausible. For now, though, Greely thinks that improving regulatory standards for donor consent and ensuring the welfare of animals that received the organoid transplant is more reasonable.

However, Greely does want to make sure that when people agree to let scientists use their cells for research, they fully understand how their cells may be used. It can create distrust in science and scientists if someone “finds out that their cells were used in research that they find scary or terrible or immoral,” he said. For example, the cells they donated could be integrated into a hybrid biocomputer, which is not an unrealistic fear.³

To get a grasp of the public’s thoughts on human neural organoids, John Evans, a bioethicist at the University of California, San Diego and a coauthor of the article, surveyed nearly 5,000 Americans in 2021.^4,5 He found that 38 percent of the survey participants believed that a neural organoid could share the thoughts of the individual who donated the cells from which the organoid was derived.

“We don’t think there’s any scientific plausibility to that, but it’s interesting that that’s what regular people think is a big issue,” Greely said. “I think it shows that scientists not only need to explain and communicate better, but also that they need to listen better to what other people say.”

A Group Effort to Close Regulatory Gaps in Human Neural Organoid Research

In 2024, Greely and 16 of his colleagues, who are coauthors of the article, met to try to come up with a set of ethical recommendations for researchers of human neural organoids. But instead, the group, which consisted of neuroscientists and bioethicists, wondered if they “have the knowledge, background, [and] the legitimacy to make these guidelines,” Greely shared.

This November, the panel will meet again, and this time, they are inviting “a wider range of voices,” said Greely. They hope to “bring together scientists, ethicists, patient advocates, and science communicators for an open conversation,” wrote Sergiu Pasca, a neuroscientist at Stanford University who will co-host the meeting with Greely, in an X post.

Greely hopes that the article could help provide background to those who are newer to the field as well as frame the group’s arguments on the need for an organization to oversee human neural organoid research. “We’re very happy that it’s published just before the meeting,” he said.

Greely added, “There are a lot of things we didn’t solve in last year’s meeting, and we don’t think we’re going to solve [them] in next week’s meeting, but maybe we can help set up a framework for watching, thinking, and acting in ways that try to have this technology used in beneficial ways and avoid dangerous activities.”