Study finds human brain cells continue to form into late adulthood

A study has shown that neurons or nerve cells continue to form well into late adulthood in the brain's hippocampus, which manages memory -- a finding that presents compelling new evidence about the human brain's adaptability.

Neurogenesis -- a process whereby new neurons are created -- is said to continue throughout one's life, even as the rate is considered to slow down with age.

However, researchers from Karonlinska Institutet in Sweden said the extent and significance of neurogenesis is still debated with no clear evidence of cells that precede new neurons -- or 'neural progenitor cells' -- actually existing and dividing in adults.

''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,'' Jonas Frisen, professor of stem cell research, Karolinska Institutet, who led the research published in the journal Science.

The team used carbon dating methods to analyse DNA from brain tissue, which made it possible to determine when the cells were formed. Tissue samples of people aged 0 to 78 were obtained from international biobanks, they said.

The results showed that cells that precede the forming of new neurons in adults are similar to those mice, pigs and monkeys, with differences in genes which are active.

The researchers also found large differences between individuals -- some adult humans had many neural progenitor cells, others hardly any at all.

Frisen added that the study is an ''important piece of the puzzle in understanding how the human brain works and changes during life'', with implications for developing regenerative treatments in neurodegenerative and psychiatric disorders.

A steady loss of neurons resulting in an impaired functioning and eventually cell death is said to drive neurodegenerative disorders, which affects the hippocampus, among other brain regions. Risks of the disorders are known to heighten with age.

For the study, the researchers used a method called 'single-nucleus RNA sequencing', which looks at activity of a gene in a cell's nucleus.

This was combined with machine learning (a type of AI) to discern varied stages of how neurons develop, from stem cells to immature neurons, many of which were in the division phase, the team said.

''We analysed the human hippocampus from birth through adulthood by single-nucleus RNA sequencing. We identified all neural progenitor cell stages in early childhood,'' they wrote.

''In adults, using antibodies against the proliferation marker Ki67 and machine learning algorithms, we found proliferating neural progenitor cells,'' the authors wrote.

''The results support the idea that adult neurogenesis occurs in the human hippocampus and add valuable insights of scientific and medical interest,'' the study said.

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