Human brain cells implanted in rats to study mental disorders

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Human brain cells implanted in rats to study mental disorders

Rat-human hybrid brains offer new possibilities, but raise many ethical questions. implantation-brain-rat.jpg” media=”(min-width: 0px) and (max-width: 99999px)”/>

Human brain cells were implanted in rats to study psychiatric disorders

Scientists have succeeded in implanting human brain cells in young rats to better study complex psychiatric disorders, such as schizophrenia, and possibly even experiment with treatments, according to a study published in the journal Nature .

It is very difficult to study mental disorders because animals do not experience them in the same way as humans, who for their part cannot make sense of them. #x27;object of in vivo experiments.

Scientists are already practicing cultures, in Petri dishes, of human brain tissue from stem cells. But in the lab, neurons don't grow to the size they would in a real human brain, says Sergiu Pasca, professor of psychiatry and behavioral sciences at Stanford University in the US and lead author work.

Furthermore, these tissues being cultured outside the human body, they do not make it possible to study the symptoms resulting from a defect in their operation.

The parade involves implanting a human brain organoid, a miniature, simplified version of the organ, into the brains of young rats. Age is important because the brain of an adult animal stops developing, which would have affected the integration of human cells.

By transplanting them into a young animal, we have found that the organoids can become quite large and vascularized and therefore be supplied by the rat's bloodstream, to the point of occupying approximately one-third of the rat's brain hemisphere. the animal, explains Professor Pasca.

The researchers tested the correct implantation of the organoids by blowing a breath of air on the whiskers of the rat, which x27; is translated into electrical activity in human-derived neurons – a sign that they were performing their role as receptors well with a stimulus.

They then wanted to know if these neurons could transmit a signal to the rat's body. To do this, they implanted organoids previously modified in the laboratory to react to blue light. They then trained the rats to drink from a cannula of water when that blue light stimulated the organoids via a cable connected to their brains. The maneuver proved effective within two weeks.

The team finally used their new technique with organoids from patients with a genetic disease, Timothy syndrome. She observed that in the rat brain, these organoids grew more slowly and had a lower activity than organoids from healthy patients.

This technique could ultimately be used to test new drugs, according to two scientists who were not involved in the study, but commented on its findings in Nature.

It takes our ability to study the development, evolution and disease of the human brain into uncharted territory, write Gray Camp, of the Swiss Roche Institute for Translational Bioengineering, and Barbara Treutlein, of the Swiss Institute for Translational Bioengineering. Zurich University of Technology (ETH).

The technique raises ethical questions, including the extent to which the implantation of human brain tissue into an animal can change its inner nature.

Professor Pasca ruled out such a risk for the rat, because of the great rapidity with which its brain develops compared to that of a human. He called the functioning of a rat cortex, which would not have time to deeply integrate human-derived neurons, a natural barrier.

Such a barrier, on the other hand, could not exist in species closer to humans, according to Professor Pasca, opposed to the use of this method in primates.

It emphasizes the moral imperative of being able to better study and possibly treat psychiatric disorders, while taking into account the proximity to humans of the animal model used.

Human psychiatric disorders are very largely unique to humans. That's why we're going to have to think very carefully […] about how hard we want to work on some of these models, he says.

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