The human brain Store stem cells able to proliferate and mature potentially in neurons also in adulthood. This is the remarkable discovery of a study recently published on Science and conducted by researchers of the Karolinska Institute, who For the first time managed to demonstrate the presence of progenitors of neurons in the hippocampus (a region of the brain important especially for the memory and regulation of mood) also in adult brain. This discovery adds an important piece on one of the most debated puzzles of neuroscience: to demonstrate that the human brain is able to generate new neurons – a process called neurogenesis – also in adulthood.
How the progenitors of neurons were discovered: the study
Identifying progenitors of neurons In an adult human brain it is an extremely complex operation, comparable to recognize a specific star in the universe with the naked eye. To succeed in this company, researchers from the Karolinska Institute have analyzed 36 brains post-moral of individuals of age between 0 and 78 yearsusing some of the most modern techniques of molecular biology – like the sequencing of the angle of individual cell nuclei – combined with sophisticated algorithms of artificial intelligence and machine learning.
To orient themselves in this dark hunt, the researchers started from something known: the brain of rodentswhere we have known for some time that the neurogenesis in adulthood takes place inside the hippocampusa key region for the memory and regulation of emotions. Studying mice cells allowed the construction of a real “Identikit” of neuronal progenitorsidentifying characteristic molecules (specific RNAs) present only in these cells not only in rodents, but also in other species of mammals, including man. Using this sort of “Molecular label” The researchers managed to recognize the precursors of neurons also in the hipocampus of children from 0 to 5 yearsa period in which these cells are more abundant and easily identifiable than adulthood.
The identification of these cells in children has allowed scientists to study the characteristics and of train artificial intelligence software to recognize them also in the brains of teenagers and adults (from 13 to 78 years), where identifying them is considerably more complex due to the reduced number.
But Swedish researchers they didn’t stop there. Thanks to advanced techniques such as theRNA Scope And Xenium – which allow you to observe with very high resolution the Location of cells inside an intact brain tissue -They found that these neuronal precursors focus on a specific sub-region of the hippocampus call giro. This is where the cells are found collected in small groupskeeping the potential to divide and mature in new neurons Even in adulthood, albeit with reduced efficiency compared to children and with strong variations from individual to individual.
The impact of the new study on neuroscience
The idea that in the hippocampus of the adult human brain a form of neurogenesis can exist It is not a real news, but it is at the center of a bright debate In the neuroscience that has been going on for almost 30 years. Already in 1998, a study published on Nature Medicine he had provided the first tests That, as happens in many other species of mammals, even in the hippocampus of man, new neurons in adulthood could be born.
Since then, research groups from all over the world have tried to clarify the phenomenon, but the often contradictory results have repeatedly questioned its existence. In 2013, the same group of the Karolinska Institute had estimated, through an indirect method based onAnalysis of carbon levels-14that the human hippocampus could produce about 700 new neurons per day. Today, after more than a decade of studies, the researchers have added a fundamental piece – so far missing – to this intricate puzzle: identify and view convincingly in the adult hippocampus progenitor cells capable of proliferating and potentially maturing in neurons. An important test that strengthens the idea that the human brain is able to produce new neurons even in adulthood.
What he tells us (and above all what he does not tell us) this study
We immediately clarify an important point: if a neurogenesis in adulthood really exists – as they seem to indicate the results of this study – we must not imagine that it concerns the brain in its integrity. The Swedish researchers themselves, as reported in the article, they did not detect progenitor cells of neurons within other regions of the brain, such as the cerebral cortex. So, this phenomenon would be limited Only to the hippocampus, mainly within the region of giro. This is a necessary clarification, which however does not reduce the charm of this discovery.
For decades the adult human brain has imagined itself as a static systemequipped with a finite number of neurons, formed during development e intended to progressively reduce with the advance of age. This vision could now change, opening the way to the existence of possible mechanisms of neuroplasticity – The mechanism by which the brain forms or reorganizes its connections, important for learning, memory and for recovery from injuries – that we still ignore.
Even if the adult brain was able to generate new neurons, we do not yet know – and the study does not demonstrate – how and to what extent these new cells integrate into the hippocampus circuits. In other words, if neurogenesis in adulthood took place, his functional meaning In the human being it still remains cryptic. Some clues, however, comes from the studies conducted on rodents, in which hippocampal neurogenesis in adulthood has long been recognized as a potentially important mechanism for learning, memory and regulation of emotions.
This discovery therefore opens to New research prospects Sometimes to understand the role of neurogenesis also in the human brain and to clarify the possible involvement in some pathologies, such as Alzheimer’s, Parkinson’s disease, mood disorders and some forms of dementia, which affect the hippocampus cells, causing serious cognitive deficit. In short, the road to go is still long. But the starting point is undoubtedly promising.
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