Some scientific controversy exists over whether the brains of adult humans are capable of growing new brain cells. In fact, previous research has suggested that the adult brain is hard-wired and unable to grow new neurons.
Now in a new study, published in the journal Cell Stem Cell, researchers show for the first time that healthy older men and women can generate just as many new brain cells as their younger counterparts. The findings suggest that many senior citizens may be more cognitively and emotionally intact than commonly believed.
“We found that older people have similar ability to make thousands of hippocampal new neurons from progenitor cells as younger people do,” said lead author Dr. Maura Boldrini, associate professor of neurobiology at Columbia University.
“We also found equivalent volumes of the hippocampus (a brain structure used for emotion and cognition) across ages. Nevertheless, older individuals had less vascularization and maybe less ability of new neurons to make connections.”
The research team from Columbia University and New York State Psychiatric Institute looked at the brains of 28 previously healthy cadavers aged 14-79 who had died suddenly. This is the first time researchers have analyzed newly formed neurons and the state of blood vessels within the entire human hippocampus soon after death.
The researchers had predetermined that the study subjects had no cognitive impairments and had not suffered from depression or taken antidepressants, which Boldrini and colleagues had previously found could affect the production of new brain cells.
Previous studies have shown that, in rodents and primates, the ability to generate new hippocampal cells declines with age. A declining production of neurons and an overall shrinking of the dentate gyrus — part of the hippocampus thought to help form new episodic memories — was believed to occur in aging humans as well.
However, the researchers found that even the oldest brains they studied produced new brain cells.
“We found similar numbers of intermediate neural progenitors and thousands of immature neurons,” they wrote. However, older individuals do form fewer new blood vessels within brain structures and possess a smaller pool of progenitor cells (descendants of stem cells that are less able to differentiate and self-renew).
Boldrini hypothesized that reduced cognitive-emotional resilience in old age may be caused by this smaller pool of neural stem cells, the decline in vascularization, and reduced cell-to-cell connectivity within the hippocampus.
“It is possible that ongoing hippocampal neurogenesis sustains human-specific cognitive function throughout life and that declines may be linked to compromised cognitive-emotional resilience,” she said.
Boldrini says that future studies on the aging brain will continue to investigate how neural cell proliferation, maturation, and survival are regulated by hormones, transcription factors, and other inter-cellular pathways.
Source: Cell Press