Latest news with #neurogenesis
Yahoo
2 days ago
- Health
- Yahoo
Human brains keep growing neurons even in old age, study finds for first time
For decades, scientists believed the human brain stopped producing new neurons after childhood. This long-held view painted the adult brain as a fixed organ, incapable of generating fresh cells in the very region responsible for memory and learning. But a landmark new study turns that dogma on its head, offering the clearest evidence yet that adult humans continue to form new neurons well into the old age. A team of researchers from Karolinska Institutet in Sweden has identified and tracked the formation of new neurons in the hippocampus, a region critical for memory, learning, and emotional regulation. In 2013, a team of researchers led by Professor Jonas Frisén made headlines with a study showing that new neurons can form in the hippocampus of adult humans. They used carbon-14 dating in DNA extracted from brain tissue to pinpoint when individual cells were created, providing rare evidence of adult neurogenesis. But while the study proved that new neurons could exist, it did not answer where these neurons come from. Until now, scientists lacked direct proof that the neural progenitor cells were present and actively dividing in the adult human brain. 'We have now been able to identify these cells of origin, which confirms that there is an ongoing formation of neurons in the hippocampus of the adult brain,' said Frisén. In the new study, the team analyzed post-mortem brain tissue from individuals ranging in age from infancy to 78 years to discover that neural progenitor cells—precursors to fully developed neurons—not only exist in the adult brain but are also actively dividing. The study used advanced techniques like single-nucleus RNA sequencing to map gene activity in individual brain cell nuclei. Combined with flow cytometry and machine learning, the approach allowed researchers to identify various stages of neuronal development, ranging from stem-like cells to immature, still-dividing neurons. To visualize where these new neurons were forming, the scientists employed RNAscope and Xenium, two powerful spatial transcriptomics tools. These confirmed that the cell formation was happening in the dentate gyrus, a part of the hippocampus linked to learning, cognitive flexibility, and the encoding of new memories. The findings reveal that adult human neural progenitor cells closely resemble those seen in mice, pigs, and monkeys, though some gene activity patterns differ between species. What's especially intriguing is the variability between individuals. While some adults had abundant neural progenitor cells, others had very few, raising new questions about what factors might influence adult neurogenesis. 'This gives us an important piece of the puzzle in understanding how the human brain works and changes during life,' Frisén explained. 'Our research may also have implications for the development of regenerative treatments that stimulate neurogenesis in neurodegenerative and psychiatric disorders.' The findings could also pave the way for new regenerative therapies for neurodegenerative and psychiatric conditions, potentially helping to restore or enhance brain function by stimulating neuron formation in targeted ways. The groundbreaking study has been published in the journal Science.
Yahoo
3 days ago
- Health
- Yahoo
Proof That Adult Brains Make New Neurons Settles Scientific Controversy
For at least six decades, neuroscientists have been arguing over a big, foundational question: Do adult brains make new neurons? This process of 'neurogenesis' had been shown in other adult animals, but its evidence in humans was circumstantial—until now. Using a new technique, scientists have found newly formed neurons in the brains of adults as old as age 78—and, for the first time, have identified the other brain cells that birthed them. The results, published on Thursday in Science, are the first signs that cells with the capacity to turn into neurons, called neural precursor cells, exist in adult human brains. 'Now we have very strong evidence that the whole process is there in humans, from the precursor cells to the immature neurons,' says Gerd Kempermann, a neurobiologist at the Dresden University of Technology, who was not involved in the study. Throughout gestation, our brain churns out new neurons until it reaches the 100 billion we start life with, and that count declines as we age. As early as 1962, studies in rats had shown that neurogenesis continued throughout the animals' life. Others found that young neurons existed in adult human brains. But it was unclear whether these 'immature' neurons were truly new—or whether humans just start life with a collection of them, after which they slowly develop during adulthood. [Sign up for Today in Science, a free daily newsletter] One thing was clear from these studies: if adult neurogenesis happened anywhere, it was in the hippocampus, a deep-brain structure known for its role in memory processing and storage. But even in the human hippocampus, neuroscientists had not yet found the precursor cells that divide and develop to turn into new neurons. Researchers at the Karolinska Institute in Sweden had previously found immature neurons in the human brain. Marta Paterlini, a neuroscientist at the institute, and her colleagues, set out to pin down how those neurons came to be. Paterlini and her team took advantage of a new combination of techniques to examine immature neurons and neural precursor cells in the hippocampi of six young children, whose brain had been donated to science upon their death. From more than 100,000 cells, the researchers sequenced RNA—bits of genetic information used to carry out actions within each cell. These markers come together to form a sort of molecular fingerprint that can be used to predict a cell's stage of life. 'It's not a matter of one marker defining active neurogenesis; it's the combination of many markers,' says Paterlini, who is co-lead author of the new study. After identifying these markers in young brains, the team then searched for those same signatures in 19 postmortem brains ranging from 13 to 78 years old. All of the brains contained immature neurons except one. The researchers also found neural precursor cells in each of the child brains and in 12 of the 19 adolescent and adult brains. Two adults stood out for having many more neural precursor cells and immature neurons than the rest. The younger of these two people had lived with epilepsy, which could potentially connect to the apparent abundance of neurogenesis. In mice, higher levels of neurogenesis can cause seizures, though the connection to epilepsy in humans is still unclear. The team suspects that neurogenesis happens in other parts of the adult brain, too. In mice, new neurons are regularly made in the olfactory bulb (a structure that processes smells) as well—but the same hasn't been shown in humans. Paterlini plans to investigate whether adult neurogenesis might happen there or elsewhere in the brain. Some research in mice suggests that disrupted neurogenesis is linked to Alzheimer's disease and depression. Learning more about how neurogenesis happens—and whether the process can be altered—could prove helpful for understanding a range of disorders and diseases, says the study's co-lead author Ionut Dumitru, a neuroscientist at the Karolinska Institute. With the question of adult neurogenesis resolved, scientists can begin learning more about what neurogenesis does in the brain and how it affects various disorders. 'This is an important paper because it should finally put this all to rest,' Kempermann says. 'And we can now concentrate on the question: How do these cells in the human contribute to brain function?'
Yahoo
3 days ago
- Health
- Yahoo
Can adults make new brain cells? New study may finally settle one of neuroscience's greatest debates
When you buy through links on our articles, Future and its syndication partners may earn a commission. Researchers say they have found clear evidence that the human brain can keep making new neurons well into adulthood, potentially settling decades of controversy. This new neuron growth, or "neurogenesis," takes place in the hippocampus, a critical part of the brain involved in learning, memory and emotions. "In short, our work puts to rest the long-standing debate about whether adult human brains can grow new neurons," co-lead study author Marta Paterlini, a researcher at the Karolinska Institute in Stockholm, told Live Science in an email. Other experts agree that the work makes a strong case for adult neurogenesis. While a single study does not constitute absolute proof, "this is strong evidence in support of the idea" that stem cells and precursors to new neurons exist and are proliferating in the adult human brain, said Dr. Rajiv Ratan, CEO of the Burke Neurological Institute at Weill Cornell Medicine, who was not involved in the study. "This is a perfect example of great science teeing up the ball for the clinical neuroscience community," he told Live Science. Related: Babies' brain activity changes dramatically before and after birth, groundbreaking study finds The researchers combined advanced techniques, including single-nucleus RNA sequencing and machine learning, to sort and examine brain tissue samples from international biobanks, they reported in a paper published July 3 in the journal Science. RNA, a cousin of DNA, reflects genes that are "switched on" inside cells, while machine learning is a type of artificial intelligence often used to crunch huge datasets. Since the 1960s, researchers have known that mice, rats and some nonhuman primates make new brain cells in the dentate gyrus, part of the hippocampus, throughout life. But getting quality brain tissue samples from adult humans is extremely challenging. "Human tissue comes from autopsies or surgeries, so how it's handled — how long before it's fixed in preservative, which chemicals are used, how thin the slices are — can hide those newborn cells," Paterlini said. Employing new technologies enabled the team to overcome this challenge. They analyzed more than 400,000 individual nuclei of hippocampus cells from 24 people, and in addition, looked at 10 other brains using other techniques. The brains came from people ages 0 to 78, including six children and four teens. Using two cutting-edge imaging methods, the team mapped where new cells sat in the tissue. They saw groups of dividing precursor cells sitting right next to the fully formed neurons, in the same spots where animal studies have shown that adult stem cells reside. "We didn't just see these dividing precursor cells in babies and young kids — we also found them in teenagers and adults," Paterlini said. "These include stem cells that can renew themselves and give rise to other brain cells." The newer technologies enabled the researchers to detect the new brain cells at various stages of development and conduct research that wouldn't have been possible a few years ago, Ratan added. The team also used fluorescent tags to mark the proliferating cells. This enabled them to build a machine learning algorithm that identified the cells that they knew would turn into neurogenic stem cells, based on past rodent studies. This was a "clever approach" for tackling the challenges of studying brain-cell formation in adolescents and adults, Ratan said. As expected, the brains of children produced more new brain cells than the brains of adolescents or adults did. Meanwhile, nine out of 14 adult brains analyzed with one technique showed signs of neurogenesis, while 10 out of 10 adult brains analyzed with a second technique bore new cells. Regarding the few brains with no new cells, Paterlini said it's too soon to draw conclusions about the disparity between adult brains with evidence of new cells and those without. RELATED STORIES —How much of your brain do you need to survive? —You're born with most of your neurons — but the brain makes some mysterious new ones in adulthood —Brain aging accelerates dramatically around age 44 — could ketone supplements help? Next, the researchers could explore whether the adults who produced new brain cells did so in response to a neurological disease, such as Alzheimer's, or whether adult neurogenesis is a sign of good brain health, said Dr. W. Taylor Kimberly, chief of neurocritical care at Massachusetts General Brigham, who was not involved in the study. "They were able to find these needles in a haystack," Kimberly told Live Science. "Once you detect them and learn about them and understand their regulation," scientists can research how to track the precursor cells through time and see how their presence relates to disease, he said. He envisioned comparing patients who have dementia to "super agers" who are cognitively resilient in old age. If the link between neurogenesis and disease can be uncovered, perhaps that could open the door to treatments. "Although the precise therapeutic strategies in humans are still under active research," Paterlini said, "the very fact that our adult brains can sprout new neurons transforms how we think about lifelong learning, recovery from injury and the untapped potential of neural plasticity."
Yahoo
3 days ago
- Health
- Yahoo
Even old brains can make new neurons, study suggests
Your body is constantly generating new cells. In your digestive tract, the colon's lining turns over every five to seven days. Your red blood cells replace themselves every few weeks, skin cells about once a month. But certain organs are a big exception. Contrary to popular belief, we are not biological Theseus' ships, reconstructing ourselves entirely from fresh building blocks every seven years. Most of your neurons, the cells that fast-track information across the brain, spine, and sensory organs, have the same lifespan as you do. Until the late 20th century, the prevailing view in neuroscience was that, past childhood, humans stop making neurons, brain-wide. What we have in adolescence, is what we get, and all we can do is lose cells or reorganize them. However, the latest research adds to a mounting body of evidence finding that the timeline of neuron generation isn't so clear-cut. In at least two parts of the brain, a subset of neuroscientists believe that neurons may continue to form throughout life–the hippocampus and the ventral striatum. In the hippocampus, a critical brain region for learning and memory, new cells emerge in some people into late adulthood, according to a study published July 3 in the journal Science. The findings tip the scales in a still-active debate over how our brains continue to develop throughout life. A better understanding of adult neurogenesis (the formation of new neurons), and a firm answer to if and where it occurs, could help improve treatments for neurological diseases as well as normal aging. [ Related: Scientists mapped every neuron of an adult animal's brain for the first time. ] Past research in rodents, pigs, and monkeys has shown that neurogenesis does happen in these other mammals, throughout life. Birds do it too. Yet based on other noted structural and developmental differences in the human brain, some scientists argue that our species is unique and lacks the lifelong neurogenesis that might interrupt complex, streamlined brain function. (New neurons may sound great, but too much activity and connectivity can cause chaos.) And it's difficult to get a clear answer. It's a major technical challenge to pin down new brain cells in humans because you can't readily see through living skulls at the cellular level. Researchers largely have to rely on scarce brain tissue collected via surgery on those with medical conditions like epilepsy or tissue donated by the deceased. With this new study, 'I think they used really strong tools,' Mercedes Paredes, a neurologist and developmental neuroscientist at University of California, San Francisco, tells Popular Science. Paredes was not involved in the research, but has previously found contrasting results in her own lab. The new work, she says, is a 'good starting point' for applying novel methods to the brain and deciphering what types of cells are truly present. Other studies of potential adult neurogenesis have looked at protein and immune signatures in brain tissues to determine if, where, and how often new neurons are being formed. They've come to conflicting conclusions, with some (like Paredes' 2018 work) failing to identify the cells that other researchers report seeing. There've also been a few studies that rely on carbon dating to ascertain the age of neurons, which find young cells in adults. However, none of these methods have, so far, reliably pinpointed the stem cells or progenitors capable of yielding fresh neurons–leaving room for doubt. The new study seems to address this previously unresolved point. It's the 'missing link' of neurogenesis, Jonas Frisén, senior study author and a developmental biologist and stem cell researcher at Karolinska Institutet in Stockholm, tells Popular Science. To find that missing link, Frisén and his co-authors surveyed the scientific literature to compile a list of genes that are likely active in hippocampal neurogenesis. Then, they confirmed those gene markers (largely from animal studies) by comparing them to RNA sequences found in brain samples from six deceased, child and infant donors. Next, the team sequenced RNA from mitochondria in the brain tissue from 19 people between the ages of 13 and 78. They used three different machine learning algorithms to assess those sequences and identify likely intermediate, forming neural cells. The scientists validated their machine learning outputs by applying the same tools to datasets from mice and adult human cortex cells, and reported a false positive rate of just 0.37 all of their analyses, they identified 354 of cells out of hundreds of thousands across their 19 samples that appeared to be precursors to new neurons, including dozens of stem cells and neuroblasts from adults. The cells weren't distributed uniformly, only showing up in half the adolescent samples and five of the 14 adult samples. However, whether or not the cells were present didn't seem to wholly correlate with age or documented disease. One of the adults with the highest number of neurogenesis-related cells present was a 58-year-old with no known pathology, per the study.'We nailed down active neurogenesis in the adult human brain,' Marta Paterlini, a neuroscientist at Karolinska Institutet, tells Popular Science. She co-led the new work over eight years alongside her colleague Ionut Dumitru, who focused on the machine learning side. 'We are confident in our data,' Paterlini says. 'We would like to put an end to the controversy.' Still, not everyone in the field agrees that the cells identified in this study are indisputably emerging adult neurons. 'When I first heard about this study, I was excited. It's the sort of approach you would want to use to ID rare subtypes,' Shawn Sorrells, a neuroscientist at the University of Pittsburgh who co-authored the 2018 study with Paredes, tells Popular Science. But, after a closer look, he was 'disappointed by how few cells they found,' and in his view, there's an alternate potential explanation. 'The most likely conclusion is that the cells they are looking for are rare or nonexistent in most people. The other possibility is that the cells they claim are adult neural stem cells are associated with a disease process in these individuals or some other cell type altogether.' The human brain is full of cells that do divide and replicate throughout life called glial cells. These are the supportive and connective cells that enable neurons to do the job of conveying nerve signals. Glial cells are neurons' pit crew. It's possible that, in their efforts to identify neurons in progress, the study authors may have inadvertently included some glial stem cells in their analysis, Sorrells suggests. [ Related: New human brain atlas is the most detailed one we've seen yet. ] Both Sorrells and Paredes believe more research is needed to confirm the new study's conclusions. Direct, morphological comparisons between human and animal cells could boost the findings, says Paredes. Sorrells suggests we'll need more advanced brain imaging techniques to really resolve the issue. 'Following the same cells over time to see how they develop. That will be the best evidence for neurogenesis,' he explains, though notes that's currently not possible. And so, the science presses on. If, as the new research indicates, some healthy humans do continue to make neurons inside their hippocampuses for life, it could have major implications for psychiatric and neurodegenerative diseases like Alzheimers, where animal studies indicate a dearth of new cells plays a role. It could also aid in our ability to understand and maximize healthy aging and neuroplasticity, Frisén says. Perhaps down the line, adult neural stem cells could be used to help people recover after brain trauma, Paterlini suggests. 'The lab is working on regenerative medicine, so we will keep going on this.' And maybe all their effort will manage to change minds about how much human minds can change.
Gizmodo
3 days ago
- Health
- Gizmodo
New Research Debunks Myth That Brain Cells Stop Growing After Childhood
You've probably heard the old canard that new brain cells simply stop forming as we become adults. But research out today is the latest to show that this isn't really true. Scientists in Sweden led the study, published Thursday in Science. They found abundant signs of neural stem cells growing in the hippocampus of adult brains. The findings reveal more about the human brain as we get older, the researchers say, and also hint at potential new ways to treat neurological disorders. 'We've found clear evidence that the human brain keeps making new nerve cells well into adulthood,' study co-author Marta Paterlini, a neuroscientist at the Karolinska Institute in Stockholm, told Gizmodo. This Is What Your Brain Looks Like When You Solve a Problem This isn't the first paper to chip away at the idea of new neurons ceasing to form in adulthood (a concept not to be confused with general brain development, which does seem to reach maturity around age 30). In 2013, study researcher Jonas Frisén and his team at the Karolinska Institute concluded that substantial neuron growth—also known as neurogenesis—occurs throughout our lives, albeit with a slight decline as we become elderly. But there's still some debate ongoing among scientists. In spring 2018, for instance, two different studies of neurogenesis published a month apart came to the exact opposite conclusion. The researchers were hoping to settle one particular aspect of human neurogenesis in adults. If we do keep growing new neurons as we age, then we should be able to spot the cells that eventually mature into neurons, neural progenitor cells, growing and dividing inside the adult brain. To look for these cells, the team analyzed brain tissue samples from people between the ages of 0 and 78 using relatively new advanced methods. These methods allowed them to figure out the characteristics of brain cells on an individual level and to track the genes being expressed by a single cell's nucleus. All told, the researchers examined more than 400,000 individual cell nuclei from these samples. And as hoped, they found these progenitor cells along various stages of development in adult brains, including cells just about to divide. They also pinpointed the location within the hippocampus where the new cells appeared to originate: the dentate gyrus, a brain region critical to helping us form certain types of memory. 'We saw groups of dividing precursors sitting right next to the fully formed nerve cells, in the same spots where animal studies have shown adult stem cells live,' said Paterlini, a senior scientist at the Frisén lab. 'In short, our work puts to rest the long-standing debate about whether adult human brains can grow new neurons.' Something Strange Happens to Brains During a Marathon The findings, as is often true in science, foster more questions in need of an answer. Our adult precursor cells seem to have different patterns of gene activity compared to the cells found in pigs, mice, and other mammals with clear evidence of adult neurogenesis, for instance. The researchers also found that some adults' brains were filled with these growing precursors, while others had relatively few. These differences—combined with the team's earlier research showing that adult neurogenesis slows down over time—may help explain people's varying risk of neurological or psychological conditions, the authors say. And likewise, finding a safe way to improve the adult brain's existing ability to grow new cells could help treat these conditions or improve people's recovery from serious head injuries. 'Although precise therapeutic strategies for humans are still being researched, the simple fact that our adult brains can generate new neurons radically changes the way we view lifelong learning, recovery from injury, and the untapped potential of neuronal plasticity,' said Paterlini. There's plenty more to be learned about how our brains change over time. The team is planning to investigate other likely hotspots of neurogenesis in the adult brain, such as the wall of the lateral ventricles (c-shaped cavities found in each of the brain's cerebral hemispheres) and nearby regions. But we can be fairly certain that our neurons keep on growing and replacing themselves into adulthood—at least for some of us.
