Six months after being implanted, the human cell clusters not only survived, but also grew to occupy a third of the hemisphere of the rodent brain.
A group of scientists led by Sergiu Pasca, professor of psychiatry at the School of Medicine at Stanford University (USA), managed to create a kind of hybrid brain after implanting human cells in laboratory mice. The results of their experiment were published this October 12 in the journal Nature.
The specialists were able to influence the behavior of rodents, as well as deepen knowledge about diseases such as autism and epilepsy.
In the investigation, scientists used the method described by Pasca in 2015 to create brain cells using stem cells, which are capable of transforming into most types of cells in the human body. They multiplied these cells in laboratory dishes to form cell groups similar to the human cerebral cortex, called organoids.
Approximately two months later, the experts they grafted the organoids into the brains of mice, placing them in exactly the same sector of their brains to better observe the reaction. As a result, the animal cells moved into human tissue , is reported in a statement from Stanford University . The implanted organoids not only survived, but also grew to occupy a third of the brain hemisphere of the rodents, although six months earlier they were one-fifth of an inch.
In addition, the researchers observed that human neurons were six times larger than those of the unimplanted organoids. They also noticed that the neurons of the organoids established links with the brain structures of rodents, for example, with the thalamus, a deep region of the brain that transmits different sensory signals to the cortex.
On the other hand, the group of scientists managed to broaden their knowledge about Timothy’s syndrome, a rare congenital disease associated with autism and epilepsy. Specifically, they grafted an organoid generated from the skin cells of a patient with said disease in a brain sector of a mouse. In an area located on the other side of the brain, they transplanted an organoid derived from a healthy individual.
Five to six months later, observed substantial differences between the electrical activity on both sides, while the neurons of the organoid with Timothy syndrome were much smaller.
There is reaction!
As the organoids were placed in the sector of the brain that processes the information coming from the whiskers of animals, the specialists demonstrated that human neurons are activated when they receive signals from the mouse sense organs. Thus, by tickling the whiskers with air, the neurons became electrically active.
In another experiment, it was possible to control the behavior of rodents using human brain cells sensitive to light. Every time the animals wanted to drink water, the scientists used bursts of blue light to activate the human organoid tissue (water was only available after the light appeared). After two weeks, it was enough to press the light blue in the organoid and the animals began to run towards the water.