It has long been established in mice that adult animals exhibit neurogenesis in the brain, the creation of new neurons that integrate into existing neural networks. There remains some debate over whether new neurons are created in the adult human brain, however, despite the consensus being that it would be unexpected to find that humans differ from mice in this way. Neurogenesis is thought to be essential to the function of learning and memory. That this process does occur would in principle make it easier to produce regenerative therapies that generate new neurons in the living brain to restore lost function. Establishing beyond doubt that this neurogenesis occurs in living humans brains has been challenging for a number of technical and logistical reasons. Nonetheless, progress has been made in establishing the necessary data.
The extent and significance of the formation of new neurons (neurogenesis) are still debated. There has been no clear evidence that the cells that precede new neurons, known as neural progenitor cells, actually exist and divide in adult humans. In a new study, the researchers combined several advanced methods to examine brain tissue from people aged 0 to 78 years from several international biobanks. They used a method called single-nucleus RNA sequencing, which analyses gene activity in individual cell nuclei, and flow cytometry to study cell properties.
By combining this with machine learning, they were able to identify different stages of neuronal development, from stem cells to immature neurons, many of which were in the division phase. To localise these cells, the researchers used two techniques that show where in the tissue different genes are active: RNAscope and Xenium. These methods confirmed that the newly formed cells were located in a specific area of the hippocampus called the dentate gyrus. This area is important for memory formation, learning, and cognitive flexibility.
The results show that the progenitors of adult neurons are similar to those of mice, pigs, and monkeys, but that there are some differences in which genes are active. There were also large variations between individuals - some adult humans had many neural progenitor cells, others hardly any at all. "Our research may also have implications for the development of regenerative treatments that stimulate neurogenesis in neurodegenerative and psychiatric disorders."
Link: https://news.ki.se/n...the-adult-brain
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