[pchealth] Humans can make new brain cells into their 90s, scientists discover | Science | The Guardian

Lawrence London lfljvenaura at gmail.com
Mon Mar 25 23:55:50 EDT 2019

Humans can make new brain cells into their 90s, scientists discover |
Science | The Guardian

Humans can make new brain cells into their 90s, scientists discover

Study may help diagnose and identify people at risk of developing
Alzheimer’s much earlier

Ian Sample <https://www.theguardian.com/profile/iansample> Science editor
@iansample <https://twitter.com/iansample>

Mon 25 Mar 2019 12.19 EDT Last modified on Mon 25 Mar 2019 16.35 EDT


[image: Brain tissue.]
microscopic view shows tissue from the dentate gyrus, part of the
hippocampus, of a man who died at 68. He had a healthy brain at time of
death. On the picture, fresh brain cells are in red and mature ones in
blue. Photograph: CSIC via Nature

Humans can make fresh brain cells until they are well into their 90s, but
the production of new neurons falls in those with Alzheimer’s, even when
the disease has recently taken hold, scientists have found.

The findings may help doctors to diagnose Alzheimer’s at an earlier stage,
and identify those most at risk who may benefit from exercise and other
interventions that could boost the production of new brain cells.

The work is the latest on an issue that has divided neuroscientists for
decades, with some arguing humans have their full quota of brain cells by
the time they reach adulthood <https://www.nature.com/articles/nature25975>,
and others claiming fresh neurons continue to be made into old age

In research that may help settle the matter, scientists in Spain ran a
battery of tests on brain tissue donated by 13 individuals who died aged 43
to 87. All were neurologically healthy before their deaths.
New drug raises hopes of reversing memory loss in old age
Read more

María Llorens-Martín, a neuroscientist at the Autonomous University of
Madrid and the senior scientist on the study, found while the healthy
brains contained newborn neurons, the number declined steadily with age.
Between the ages of 40 and 70, the number of fresh neurons spotted in the
part of the brain studied fell from about 40,000 to 30,000 per cubic

The new cells were born in the part of the brain called the dentate gyrus.
It is a part of the hippocampus which plays a central role in learning,
memory, mood and emotion. The gradual reduction in new brain cells appeared
to go hand-in-hand with the cognitive decline that comes with old age. It
suggests that in middle age about 300 fewer neurons per cubic millimetre
are made in the dentate gyrus with each advancing year.

The study, published in the journal Nature Medicine
<https://www.nature.com/articles/s41591-019-0375-9>, suggests that part of
the reason scientists disagree on whether or not adult brains make fresh
neurons is that different tests and tissue processing give different
results. “In the same brains we can detect lots of immature neurons or no
immature neurons depending on the processing of the tissue,” said
[image: A brain scan of a patient with Alzheimer’s disease.]
A brain scan of a patient with Alzheimer’s disease. Photograph: BSIP/UIG
via Getty Images

Having studied healthy brain tissue, the scientists went on to look at the
brains of people who had been diagnosed with Alzheimer’s before death. This
time, the researchers analysed brain tissue from 45 patients aged 52 to 97.
All had fresh brain cells in the dentate gyrus, including the 97-year old,
the oldest person in which “neurogenesis” has yet been seen.

But while the Alzheimer’s patients showed evidence of new brain cell
formation, there were stark differences with the healthy brains. Even in
the earliest stages of the disease, their brains only had between half and
three quarters as many fresh neurons as the healthy ones.

“This is very important for the Alzheimer’s disease field because the
number of cells you detect in healthy subjects is always higher than the
number detected in Alzheimer’s disease patients, regardless of their age,”
Llorens-Martín said. “It suggests that some independent mechanism,
different from physiological ageing, might drive this decreasing number of
new neurons.” She said the research was only possible because of the
generosity of the individuals who donated their brains to science.
Humans produce new brain cells throughout their lives, say researchers
Read more

She said brain scans might one day be able to detect newly-formed brain
cells and so diagnose Alzheimer’s in its earliest stages. If studies on
rodents are any guide, people most at risk of the disease could potentially
benefit from exercise, socialising and cognitive stimulation.

Sandrine Thuret, the head of the neurogenesis and mental health laboratory
at King’s College London, said the paper was “extremely timely” and
provided “another strong piece of evidence that neurogenesis is occurring
in the adult human hippocampus”.

Thuret said Alzheimer’s disease would not be cured by restoring
neurogenesis once it had already been affected and diagnosed. But she added
there was potential in using neurogenesis as a marker for Alzheimer’s
before it took hold. “If you could just prevent or delay onset of cognitive
symptoms of Alzheimer’s for a few years by maintaining neurogenesis, it
would be fantastic,” she said.
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