Part-human part-mouse brain developed in science breakthrough
US neuroscientists successfully adapt mice with functioning human brain cells to test treatments for neurological conditions that only occur in humans.
Stock photo for illustration only, not from the actual event
- US neuroscientists successfully develop mice with functioning human brain cells integrated
- Aims to test treatments for complex conditions like epilepsy, autism, and cerebral palsy
- Researchers emphasize these are not mice that think like humans and followed strict ethics
- Human cells grew and connected with the mouse brain circuitry and spinal cord after six months
Neuroscientists in the United States have successfully adapted mice to house functioning human cells inside their brains. Published in the journal Nature, this significant research breakthrough aims to allow potential treatments for psychiatric and neurodevelopmental diseases that exclusively affect humans to be tested on laboratory rodents.
While the concept of mice possessing partially human brains may sound unconventional, the scientists explicitly clarified that these are not "mice that think like humans." The animals are genetically engineered and surgically altered so that portions of their brain tissue consist of human cells, carried out under independent ethical scrutiny.
Lead researcher Prof Sergiu Pașca from Stanford University explained in a press conference that psychiatry suffers from one of the lowest success rates for clinical trials. The Stanford team noted that for complex conditions including epilepsy, autism, and cerebral palsy, this approach has transformative potential because these disorders cannot be studied in normal mice since rodents do not develop certain brain diseases that humans experience.
Stock photo for illustration only, not from the actual event
Integrating human cells into animal models represents a major milestone bridging biotechnology and bioethics. Because the human brain features billions of cells and millions of interconnected circuits, studying human neurological disorders has historically faced severe biological limitations. The use of brain organoids derived from human skin cells serves as an essential bridge to replicate human cellular behavior within a living animal system.
The research process began by genetically engineering mice to develop almost none of their own cerebral cortex, the outer grey matter layer handling higher-level thinking, memory, and senses. Researchers then took human skin cells and reprogrammed them to grow into brain-like tissue pieces called organoids, which are collections of connected, living cells rather than whole brains.
When these organoids were implanted into the mouse brain, the cells divided and organized themselves into the animal's existing circuitry, connecting with the rest of the brain and spinal cord. Neuroscientist Dr Ilary Allodi from St Andrews University noted that scans of these human-mouse brains look a bit messy because normal cortex forms structured layers, but after a few months, the human cells began to look and function like the outer layer of the mouse brain.
Approximately six months following the surgery, scientists put the mice through basic behavioral tests by observing them move around a small table-top arena. Professor Pașca stated that they performed largely as normal mice did, though the study prompts reflection on what altering animal cognition entails.
"Here we have a new model that allows us to actually capture aspects of human brain function in a way that has not been possible before."
Prof Sergiu Pașca
Dr Ilary Allodi, who was not involved in the research, called the work very impressive, specifically pointing out that cell types exclusively found in human and primate brains spontaneously formed in the implanted mice. Meanwhile, Prof James Ainge from St Andrews University pointed out that while technically impressive, these mice could be of limited use partly due to ethical issues surrounding raising living human tissue in a mouse and what that means for the animal's experience.
Source: BBC Science & Environment
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