Are rats with human brain cells still just rats?

It’s a tricky one. The scientists behind the work claim that there is nothing truly human about these rats. Throughout the study, the team examined the rats to see whether those with human cells were smarter, or suffered more, than rats that did not receive organoid transplants. They found no sign of human traits or behavior.

But the whole point of implanting human cells is to get some insight into what’s going on in the human brain. So there is a trade-off here. Essentially, the animals are supposed to represent what happens in humans without becoming too human themselves. And if the rats don’t show human behavior, can they really tell us so much about human disease?

“The question is, what percentage of animal cells would be needed in the brain to reduce animal behavior and see a different kind of behavior?” asks Jeantine Lunshof, a philosopher and ethicist at the Wyss Institute for Biologically Inspired Engineering at Harvard University.

This raises another question. What would it take to accept that an animal is no longer a typical member of its own species? Much of the discussion on this topic focuses on moral status. Most people agree that humans have a greater moral status than other animals – and that it is not acceptable to treat humans the same way we treat animals, both for research and in other contexts.

It can be difficult to determine exactly what it is that makes us special, but the consensus is that it has something to do with our brains, which are larger and more complex than those of other animals. It is our brains that allow us to think, feel, dream, rationalize, socialize, plan our future and, more generally, experience consciousness and self-awareness. Can rodents with human brain cells have the same experiences?

It’s an important question for bioethicists like Julian Koplin of Monash University in Victoria, Australia. “If we’re talking about humanizing the brains of non-human animals…by introducing organoids into the human brain and having them integrated into the brains of animals,” he says, “I think we should go consider whether this has any follow-up effect on the moral status of the test animal.”

In the current study, the answer seems to be no. But that doesn’t mean we won’t see “humanized” or “improved” rats in the future, according to Koplin and other bioethicists specializing in the field.

We must proceed with caution.

In this study, scientists placed organoids from the human brain in an area of ​​the rats’ brains that helps them sense their environment. But there’s no reason they couldn’t place the same organoids in regions that play a role in cognition or consciousness — which would make cognitive enhancement more likely.

Then there is the question of how much of the brains of rats consists of human cells. Transplanting larger organoids might mean the rat is technically more “human” at the cellular level, but that’s not what matters. What matters is how, if at all, the mental state changes.

The mental changes aren’t just about how “human” the rats’ mental states become, either. “Maybe you have an animal that thinks very differently than we do, but is acutely prone to suffering, or is really intelligent in ways that we as humans are unfamiliar with,” Koplin says.

So far, we’ve focused on rats. But what would happen if the organoids were put into baby monkeys instead? Non-human primates have brains that are much more like and work like ours, so they would be better models for studying human disease. But “it does raise the possibility that you will create a humanized primate,” said Julian Savulescu, a bioethicist at the National University of Singapore.

Savulescu is also concerned about cloning. The cells that make up organoids contain a person’s DNA. What would happen if much of a monkey’s brain were made up of cells containing an individual’s genetic code?

“If you were to introduce an advanced organoid into a developing primate, you could essentially create a clone of an existing individual,” he says. “It wouldn’t just be humanized, it would be a clone of someone who already exists.” This would be the bottom of an ethical slope, Savulescu says.

There are many questions here, and few definitive answers. No one really knows how to measure moral status, or the point at which animals with human cells become special — or even some kind of new animal.

But it gives a lot of food for thought. To read more, check out these articles from Technical reviews archive:

In this piece from 2016, Antonio Regalado describes the attempts of researchers to culture human organs in pigs and sheep. The goal here is to create new organs for people who need transplants.

A Spanish stem cell biologist told a reporter that the Pope had given his blessing to this kind of research. But the Vatican later disputed the claim, calling it “absolutely unfounded.”

A few years later, that same biologist went on to create embryos that are part human and part ape, as reported by El País. Antonio explained why the investigation was so controversial.

In this recent piece, Hannah Thomasy explores: eight technologies that help us understand the mysteries of the human brain and how we form memories.

And you can read more about how our brains make our minds in this piece by Lisa Feldman Barrett, which appeared in last year’s Mind issue.

from the web

Can an algorithm help people who choose to end their own lives? The founder of this non-profit thinks so. (MIT Technology Review)

The cases of monkey pox have been decreasing for a few months now. But there are several ways things can play out from here. (Nature)

In the US, Covid boosters are approved for children as young as five years old. (Reuters)

Long covid is an ongoing problem. Nearly half of those who get sick with Covid still have not fully recovered months later. (New York Times)

Check out this game of Pong. And then realize that it’s played by brain cells in a dish. (neuron)