Are rats with human brain cells still just rats?

That is a difficulty. The scientists behind this work argue that there is nothing truly human about these mice. Over the course of the study, the team tested mice to see if those with human cells were more intelligent or experienced more suffering than mice without organoid implants. They found no sign of human traits or behaviour.

But the whole point of transplanting human cells is to get some understanding of what happens in the human brain. So there is a trade-off here. Essentially, animals need to represent what happens in humans without becoming too human. And if the rats don’t exhibit any human behavior, can they really tell us much about human disease?

“The question is: What percentage of animal cells are needed in the brain to reduce animal behavior and see a different pattern of behavior?” ask Jeantine Lunshof, a philosopher and ethicist at the Wyss Institute for Biologically Inspired Engineering at Harvard University.

This raises another question. What will happen to us to accept that an animal is no longer a typical member of its own species? Much of the discussion on this topic focuses on the ethical status quo. Most people would agree that humans have a higher moral standing than other animals – and it is unacceptable to treat humans the same way we treat animals, even for research purposes. or in other contexts.

It can be difficult to pinpoint exactly what makes us special. but the consensus is that it has something to do with our brains, which are larger and more complex than the brains of other animals. It is our brain that allows us to think, feel, dream, rationalize, form social connections, plan for our future, and generally experience consciousness and perception. self aware. Could rodents with human brain cells have similar experiences?

That’s an important question for bioethicists like Julian Koplin at Monash University in Victoria, Australia. “If we’re talking about anthropomorphizing the brains of non-human animals…by introducing organic substances into the human brain and allowing them to integrate into the animal brain,” he said, “I think we It is necessary to start thinking about whether this might have a follow-up effect on the ethical status of the study animals. “

In the current study, the answer appears to be no. But that doesn’t mean we won’t see “humanized” or “enhanced” mice in the future, according to Koplin and other bioethicists who specialize in the field. .

We need to move carefully.

In this study, the scientists inserted organoids in the human brain into an area of ​​the brain of mice that helped them perceive their surroundings. But there’s no reason they couldn’t introduce the same organics into regions that play a role in perception or consciousness — which could result in higher cognitive enhancement.

Then the question arises how many rat brains are made up of human cells. The implantation of larger organoids might mean that the mouse is technically “more human” at the cellular level — but that’s not the point. What matters is how its mental state changes, if at all.

Mental changes aren’t just about how the rat’s mental state becomes “human”. “You can have an animal that thinks in a very different way from us, but is very sensitive to suffering, or is really intelligent in ways that we are not familiar with as humans,” Koplin said.

So far, we’ve focused on mice. But what if replacement organoids were introduced into the baby monkeys? Non-human primates have brains that look and function much more like ours, so they would be better models for studying human disease. But “it increases the likelihood that you will create a cloned primate,” says Julian Savulescu, a bioethicist at the National University of Singapore.

Savulescu is also interested in cloning. The cells that make up organoids contain a person’s DNA. What if a large portion of the monkey brain was made up of cells with an individual’s genetic code?

“If you put an advanced organoid into a developing primate, you can essentially create a clone of an existing human,” he said. “It’s not just anthropomorphic – it’s a copy of someone that already exists.” This will be the bottom of a slippery moral slope, says Savulescu.

There are many questions here, and few definitive answers. No one really knows how to measure the moral state, or when an animal with human cells becomes special — or even some new type of animal.

But it provides plenty of food for thought. To read more, check out these articles from Technology review of storage:

In this piece since 2016, Antonio Regalado describes the researchers’ efforts to grow 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 has blessed this kind of research. But the Vatican later denied the claim, calling it “completely baseless.”

A few years later, the same biologist went on to create embryos that were part human and part monkey, as reported by El Pais. Antonio explained Why is the study so controversial?

In this recent pieceHannah Thomasy discovers Eight technologies are helping us understand the mysteries of the human brain and how we form memories.

And you can read more about how our brains make up our minds In this piece from Lisa Feldman Barrett, introduced last year Mind problems.

From all over the web

Could an algorithm help people who choose to take their own lives? The founder of this nonprofit thinks so. (MIT Technology Review)

Smallpox cases in monkeys have been declining for several months now. But there are several ways things could go from here. (Nature)

Covid boosters have been approved for children under the age of 5 in the US. (Reuters)

Long covid is a long term problem. Nearly half of people who get sick with covid still have not fully recovered a few months later. (The New York Times)

Watch this game by Pong. And then realized that it was being played by brain cells in a dish. (Neuron)


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