January 16, 2021

The Niche

Trusted stem cell blog & resources

Aging: can we grow new brain cells as adults?

Can we humans grow healthy new brain cells as adults and during later aging?

The answer to this question is a big deal because it could have major impact on aging. Those hoped-for new brain cells could keep our brains functionally younger. Who doesn’t want to slow down the aging of their brain, right? Slowing down aging of the brain via new cell growth more broadly would have major impacts on society.

Cell Stem Cell Boldrini, et al., 2018, new brain cells
Cell Stem Cell Boldrini, et al., 2018, Part of Figure 1

Researchers have gone back and forth on this over years.

Fairly long ago, it was thought the answer was definitely “No, we humans can’t grow new brain cells”, but in the last few decades a loose consensus has emerged that in fact the answer is, “Yes, to some degree.”

A recent Nature paper, however, said “No” again. It challenged that “Yes” by directly arguing we don’t make new brain cells. Neuroscientists who study this stuff generally reacted skeptically. The paper’s title was, “Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults.”

Yet an even newer paper,this time in Cell Stem Cell that is Boldrini, et al. argues “Yes” and goes further to say, in fact, that we adults and even older adults can grow brain cells just about as well as the younger folks. This paper’s title pretty much directly contradicts the above one as it says, “Human Hippocampal Neurogenesis Persists throughout Aging.”

So who’s right and who’s wrong?

My gut feeling is that there is adult human neurogenesis and there are stem cell populations in adults and even fairly aged humans.

It’s really hard to conclusively prove a negative thing in science like the claim that there’s no neurogenesis in adult brains. I bet the team recently arguing no detectable new neurogenesis used methods that simply didn’t detect it. It’s much harder to dismiss the findings in the newer paper (and in many past ones) showing adult human hippocampal neurogenesis and the presence of stem/precursor cells. See part of Boldrini Figure 1 above showing evidence of neural progenitor/stem cells in the adult brain. The data in that paper are clear.

Still, this new paper arguing for sizable levels of stem cell activity in the adult human brain found some effects of aging on the brain and that neural precursor numbers in older adults are somewhat lower than say teenagers.

People are more generally really wanting their brains to stay robust as they age. I’ve covered brain aging in the past on this blog and efforts to counteract it, mainly via stem cell-related efforts such as exosomes, which were the focus of a paper I was fairly skeptical about some months back. Some people also think that stem cell transplants or infusions of young blood might fight brain aging, but those are somewhat wilder ideas.

I’m hopeful that there are real ways eventually found to keep our brains healthy and even producing more new, healthy cells and stem cells as we add on the decades. The debate over adult human brain stem cells might continue in years to come, but most people I know think there is some neurogenesis going on even as we age, which provides hope for the aging human brain.

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