Bits of human brain tissue no larger than a pea are forcing scientists to think about questions as large as the nature of consciousness.
These clusters of living brain cells are popularly known as minibrains, though scientists prefer to call them cerebral organoids. At the moment, they remain extremely rudimentary versions of an actual human brain and are used primarily to study brain development and disorders like autism.
But minibrain research is progressing so quickly that scientists need to start thinking about the potential implications now, says Nita Farahany, a professor of law and philosophy at Duke University and the director of Duke Science and Society.
"Is it possible that an organoid far off in the future could develop something that looks like consciousness or any kind of sentience, the ability to feel something like pain," she says.
Farahaney and 16 other prominent scientists, ethicists and philosophers posed this question and many others in a commentary in this week's issue of the journal Nature.
Minibrains are usually created by transforming skin cells from a person into neural stem cells. These stem cells can grow into a range of structures like those found in the human brain, and even form networks of cells that communicate.
At the moment these lab-grown minibrains are limited to a few million cells and don't get much larger than a pea. In contrast, the human brain is thousands of times larger and contains about 85 billion cells.
"Right now they're pretty good proxies for being able to study how certain kinds of human neurons interact with each other and grow and develop over time," Farahany says. "But they are still far from what an actual human brain would look like."
Yet already, minibrains are helping scientists do remarkable things, Farahany says.
"If you're talking about something like schizophrenia or autism, if you want to model those things, it is difficult to do so with animal models and it is ethically impossible in many instances to do so with living humans," She says. But it is possible to grow a minibrain from cells with genetic mutations associated with like autism and watch how it develops.
Minibrain experiments also helped scientists figure out how the Zika virus interferes with normal brain development, Farahany says.
And just this month, a team at the Salk Institute in La Jolla, Calif., published evidence that a human minibrain transplanted into a mouse brain could develop functioning blood vessels. That would, in theory, allow scientists to grow much larger minibrains.
So it's clear the potential of the field is huge, Farahany says. But so are the ethical questions surrounding brain cells that live and grow outside the human body.
One area of concern involves the practice of transplanting human brain tissue into animals. That could eventually lead to, say, mice with exceptional mental abilities, Farahany says.
So now, she says, is when scientists and society needs to start asking questions like, "How comfortable are we with certain kinds of hybrids we're creating and does that change the way we regard those animals or the kinds of protections that should be afforded to them."
For example, researchers may need some guidance on what research rules apply to enhanced lab mouse, Farahany says. Do they assume it's like a typical lab mouse, which can be killed at the end of an experiment? Or do these mice enjoy the protections given to chimps, which are allowed to retire after their time in research is done?
The commentary doesn't offer answers to those questions, or any specific guidelines for research. Instead, it is intended as a way of guiding future discussions about minibrains and other efforts to replicate the functions of a human brain.
"This is really the time to get out ahead of these ethical issues before it becomes deeply problematic to proceed without having addressed them," Farahany says.
ARI SHAPIRO, HOST:
In the world of science, some tiny clusters of living human brain cells are raising big ethical questions. They're sometimes called minibrains. And as NPR's Jon Hamilton reports, they're allowing scientists to mimic aspects of the human brain in a Petri dish.
JON HAMILTON, BYLINE: In the lab, these minibrains still don't get much larger than a pea, and they contain only a few million cells. The human brain has about 85 billion. But Nita Farahany of Duke University says these bits of living tissue develop and get wired up a lot like actual brains. And she says they are helping scientists do remarkable things.
NITA FARAHANY: So if you're talking about something like schizophrenia or autism, if you want to model those things, it's difficult to do so with animal models, and it is ethically impossible to do so in many instances with living humans.
HAMILTON: But it is possible to grow a minibrain that models autism and watch how it develops. Farahany, who studies the legal and ethical implications of emerging technologies, says the potential of minibrains is mind-boggling. But she says so are some of the questions raised by creating these brain-like structures, which scientists prefer to call organoids.
FARAHANY: Is it possible that an organoid far off in the future could develop something that looks like consciousness or any kind of sentience, the ability to feel something like pain or experience anything?
HAMILTON: Farahany and 16 other prominent scientists, ethicists and philosophers summarized their thoughts in a commentary in the journal Nature. Farahany says one of their concerns involves the practice of transplanting human brain tissue into animals.
FARAHANY: How comfortable are we with certain kinds of hybrids that we're creating, and does that change the way we regard those animals or the kinds of protections that should be afforded to them?
HAMILTON: In other words, do we really want to create a mouse with exceptional mental abilities? And if we do, should it be treated like a typical lab mouse or more like a chimp? The commentary's authors don't try to answer those questions, and Farahany says there's no need to yet. She says that's because minibrains and related technologies are still in the very early stages.
FARAHANY: Right now they're pretty good proxies for being able to study how certain kinds of human neurons interact with each other and develop and grow over time. But they are still far away from what an actual human brain would look like.
HAMILTON: But the field is moving quickly. Just this month, the team at the Salk Institute in La Jolla showed that a human minibrain transplanted into a mouse brain developed functioning blood vessels. So Farahany says scientists and the rest of society need to start developing guidelines now.
FARAHANY: This is really the time to get out ahead of these ethical issues before it becomes deeply problematic, you know, to be able to proceed without having addressed them.
HAMILTON: She says minibrain research has so much potential to help people. It would be tragic to have it derailed by an ethical crisis. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.