In rodents and primates, the ability to generate new hippocampal cells declines with age. Scientists believed that a similar decline occurred in aging humans, also. Wrong!
While the New York researchers tempered their announcement with the caveat that "older individuals had less vascularization and maybe less ability of new neurons to make connections," they found that even the oldest brains they studied produced new brain cells.
The researchers autopsied hippocampi (a part of the brain used for emotion and cognition, and forming new memories) from 28 previously healthy individuals aged 14-79 who had died suddenly. This marks the first time researchers looked at newly formed neurons and the state of blood vessels within the human hippocampus soon after death! Study subjects were not cognitively impaired and had not suffered from depression or taken antidepressants, which the researchers previously found could negatively affect production of new brain cells.
"We found similar numbers of intermediate neural progenitors and thousands of immature neurons," they wrote. That said, healthy older adults do form fewer new blood vessels within the brain, and have a smaller pool of progenitor cells — constrained in their capacity to differentiate and self-renew.
The team leader writes that future research on the aging brain will continue to explore how neural cell proliferation, maturation, and survival are regulated.
As a neuroscience enthusiast / layperson, my main takeaway is that this is yet another indicator that dementia disorders may result more from lifestyle factors and disease, external factors. What do you think?
Maura Boldrini, Camille A. Fulmore, Alexandria N. Tartt, Laika R. Simeon, Ina Pavlova, Verica Poposka, Gorazd B. Rosoklija, Aleksandar Stankov, Victoria Arango, Andrew J. Dwork, René Hen, J. John Mann. Human Hippocampal Neurogenesis Persists throughout Aging. Cell Stem Cell, 2018; 22 (4): 589 DOI: 10.1016/j.stem.2018.03.015