To study living cells, scientists grow inspecial containers cell cultures. They are in a nutrient medium that allows them to grow and divide. However, cells grown separately are different from those that grow in an organ and interact with neighboring cells. Therefore, scientists came up with the idea of growing organelles - a complex of cells that form a semblance of any part of a real organ. In organelles, cells are able to receive signals from other cells, as well as send their own signals. However, as we discussed earlier in the article on the “artificial” brain, cells of complex organs, such as the brain, were not suitable for studying cells until recently. This is due to the fact that neurons in organelles do not have certain properties that they have in the living brain. But American scientists figured out how to solve this problem - they transplanted an organoid with human cells into the brains of newborn rats. The result surprised even the researchers themselves.
Rat brain transplant
Scientists have introduced an organoid into the somatosensoryregion of the rat cerebral cortex. This part of the brain is able to respond to impulses from vibrissae, that is, tactile long and coarse hair (mustache). When the whiskers vibrate, the brain recognizes them. As researchers report in the journal Nature, after the introduction of an organoid from human cells into the brain of a rat, it began to grow actively. In three months, it increased nine times, as a result of which it was about a third of the cortex of one of the hemispheres. It developed as one unit with the brain of rats. However, the rat neurons did not add volume to the organoid.
What is the advantage of growing an organoid directly inbrain? First of all, he eats better. In addition, they received signals from other cells that influenced their development. Obviously, due to this, the neurons in the transplanted organoid were 6 times larger than during this period in the organoid, which develops by itself. In addition, they were more complex - they had more branches and synapses.
How the human brain worked together with the brain of a rat
What happened to the rat itself after the transplanthuman brain (organoid)? Of course, she did not turn into a person, like a dog in the famous novel by Mikhail Bulgakov. However, according to the researchers, the cells differed in maturity. Their electrophysiological properties were more similar to real brain cells. And they also established connections not only between their own cells, that is, the cells of the organoid, but also the neurons of the brain of rats.
When the vibrissae reacted to the puff of air,human neurons responded to these impulses. But, most interestingly, human neurons influenced the behavior of rodents. The organoid has been modified so that its neurons can respond to flashes of light.
When neurons in the rat brain were stimulated with light,the animal received a portion of water. Then, when the neurons of the organoid showed activity, but the rat was not given water, she herself began to look for it, that is, a reflex developed. Has a rat become smarter with a human brain? According to the researchers, tests that assessed mental activity, the animal passed in the same way as ordinary rats.
An electroencephalogram and other studies of the brain did not show any significant abnormalities. Although, scientists assumed that such deviations should be, because part of the brain was still someone else's.
Why did a rat get a human brain transplant?
What is the practical use of transplanted into the brainorganoid? This technology, obviously, will help to study in detail various neuropsychiatric diseases, as well as genetic mutations. In their experiment, the researchers transplanted one of the rats into an organoid that contained neurons with Timothy's syndrome, a genetic disease that affects brain development.
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As a result, the organoid really developed fromanomalies. For example, processes-dendrites turned out to be simpler than in a healthy organoid. I must say that human neurons have tried to transplant into the brain of rodents before. However, these were precisely neurons grown in cell culture, and not a whole organoid. Perhaps because of this, they took root well and behaved more naturally.