Research on conditions like autism and schizophrenia often involves clusters of human cells called brain organoids. These pea-sized bits of neural tissue model human brain development. They also make some people uneasy, in part because the brain is so closely tied to our sense of self. So experts met in California this fall to discuss how scientists and society should proceed. NPR's Jon Hamilton was there and filed this report.
JON HAMILTON, BYLINE: The event was hosted by Dr. Sergiu Pasca, whose lab at Stanford University has used organoids to develop a potential treatment for a rare cause of autism and epilepsy. He says the approach allows scientists to study brain cells and circuits that don't exist in animals.
SERGIU PASCA: For the first time, we have this ability to really work with human neurons and human glial cells and ask questions about these really mysterious disorders of the brain.
HAMILTON: That ability comes with some big questions, though. Should human organoids be placed in an animal's brain? Can organoids feel pain? Can they become conscious? And who, if anyone, should regulate this research? Pasca himself has grappled with these questions as his lab recreated a human pain pathway and transplanted a human organoid into the brain of a rat.
PASCA: Of course, there are issues of ethics and societal implications and religious views that have to be taken into consideration.
HAMILTON: So Pasca invited a group of scientists, ethicists, patient advocates and journalists to Asilomar on the Monterey Peninsula. Fifty years ago, another group met here to hash out the first ethical guidelines for genetic engineering. Pasca had more modest expectations for the two-day organoid event.
PASCA: Our goal really for this meeting was to just bring everybody together across all these fields, including in terms of how do we communicate this type of science to the public and start really identifying what are some of the issues and start brainstorming.
HAMILTON: That happened in formal sessions, coffee breaks and even walks on the beach. And participants brought widely varying perspectives. Scientists and patient advocates emphasized the need to find cures quickly. Bioethicists favored guardrails to make sure people consent before their cells are made into organoids and to discourage efforts to enhance the brains of animals or humans. There was consensus, though, on the need to keep the public informed. Alta Charo, a bioethicist at the University of Wisconsin Madison, says people have one overarching question for scientists in this field.
ALTA CHARO: How far along are they in building organoids that can actually recapitulate something that we associate with human capacities? Have we reached a point where we're worried?
HAMILTON: Not yet, probably, but Charo says the prospect seems closer now that scientists are linking multiple organoids to create more brain-like structures called assembloids. Pasca's team, for example, has built a network of four organoids to model the pathway that carries pain signals to the brain. Charo says that sounds disturbing unless you know that this network of cells lacks the circuitry to feel pain.
CHARO: The mere existence of the pain pathway, I think, is enough to give a public perception problem that the organoid or the assembloid is suffering. And yet, if the pathway that allows for this emotional aversion doesn't exist, then there's no suffering.
HAMILTON: And no ethical issue for now. But Charo says it's best for researchers and regulators to try to get ahead of issues like that.
CHARO: Do you build guidelines, build restrictions, build regulations around a perception problem, or do you wait until there's an actual problem?
HAMILTON: Several participants faulted the media for glossing over the current limits on what organoids can do and for describing them as mini brains. Dr. Guo-li Ming of the University of Pennsylvania says this has led some people to misunderstand the science.
GUO-LI MING: They believe there's some sort of brains growing in the Petri dish. That's definitely, I think, harmful in the long run.
HAMILTON: And decidedly not the case. Ming says one remedy is for scientists to say more about how organoid research is helping people with life-threatening diseases. For instance, her lab is working to customize brain cancer treatment using organoids derived from a patient's own tumor cells.
MING: We do have a good model for this personalized treatment. For example, we can test different treatment in vitro before giving them to patients.
HAMILTON: That way, cancer patients only get drugs shown to work on their specific tumor. Ming also thinks it's too soon to worry about organoids becoming conscious.
MING: At this moment, we are far from really mimicking the brain activity in real human beings.
HAMILTON: Even so, Ming says she's in favor of placing limits on what scientists should do.
MING: We definitely need some guidelines because people - they do have some concerns given the potential implications of this brain organoids.
HAMILTON: Similar concerns hovered around stem cells more than 20 years ago. Insoo Hyun, an ethicist at the Museum of Science in Boston, says, back then, the fear was neural stem cells might give animals human-like cognitive abilities. It turned out those cells didn't do well in another creature's brain. But Hyun says organoids, which start out as stem cells, can thrive in animal brains and even integrate with their circuitry.
INSOO HYUN: So what used to be a very hot issue has now come back in full force with the organoid approach because that really does get you the kind of scenarios that people were very concerned about back in the day.
HAMILTON: Hyun was part of a group that worked on organoid guidelines for the International Society for Stem Cell Research. That was several years ago, he says, when the need for oversight seemed less pressing.
HYUN: We kind of had a let's-wait-and-see attitude to see where the research progresses to then recommend what oversight might look like. We've gotten to that point rather quickly now in 2025, early 2026.
HAMILTON: Hyun's immediate concern is protecting research animals from organoid experiments that could cause suffering. But in the long term, he says, it may take guidelines and government oversight to ensure that organoid research doesn't harm or horrify people.
HYUN: The promise is definitely there, but we are talking about an organ that is at the seed of human consciousness. It's the seed of personality and who we are. So it's reasonable for people to be especially careful with the kind of experiments we're doing in this area of the body.
HAMILTON: The Asilomar conference suggests many scientists know that and want help navigating this new scientific frontier.
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