Adult Human Brains Do Not Produce New Neurons, Study Suggests (newatlas.com)

Rich Haridy reports via New Atlas: New research from scientists at UC San Francisco is challenging half a century of conventional wisdom by suggesting the human brain may cease producing new neurons beyond childhood. While the divisive study may prove a blow to some research aimed at birthing new neurons to battle neurodegenerative disorders, it offers a new perspective on how the human brain can adapt in later life without such a capability. The team generated its data by studying brain specimens of 59 subjects, from babies to the elderly. The strategy was to look for the presence of young neurons or dividing cells by using certain antibodies that bind to those cells of interest. The focus was on the hippocampus region of the brain, known to be crucial for memory, and a comprehensively studied area previously suggested to be a key location for neurogenesis. The results were fairly comprehensive. Young or immature neurons were identified in plentiful volumes in prenatal and newborn samples but the rate consistently declined over childhood. The oldest sample that immature neurons were found in was 13 years of age, and adult samples displayed no evidence of new neurons. The study has been published in the journal Nature.

Comments

Wrong.

[Qbertino]

The study found that certain indicators associated with the growth of cells in young mamals/people couldn't be found in grown-ups. This doesn't contradict the growth of cells in adult brains. The study isn't disputed as heavyly as the conclusions drawn are, but they are disputed.

Re:Wrong.

[macklin01]

There's a big difference between growth of cells (they get bigger) and proliferation of cells (they divide to create new cells), and so it's important to be careful. (I've been working on modeling both cell growth and cell division for a good while, mostly in cancer and a little in tissue engineering and synthetic biology. e.g., here.)

I looked at the study. They stained for Ki-67, the gold standard immunohistochemical marker for cell division. Cells that are actively cycling--in late G1, S, G2, and M phase, and a smidgen of G1 phase after division because Ki67 protein doesn't instantaneously degrade--stain positive for this marker. In particular, it is a nuclear marker, so the stain is localized to the cell nucleus, and the stain is very definitive. It's one of the easiest immunostains to do image processing on, because you can do nuclear segmentation, then analyze the colors in the segmented nuclei to see if they stained positive or negative for Ki-67.

And that Ki-67 marker was virtually non-existent in the region of interest in all the samples above 13 years old. See Figure 2. This is *the* universal gold standard marker for cell division used across pathology and experimental biology. So yes, the study indeed found no proliferating cells in the GCL. And then they used this "young neuronal cell" marker (DCX+PSA-NCAM+ cells) to further confirm what they already saw in Ki67.

Also, the Nature link is the *summary* of the paper, and not the actual paper. It's pretty common for the big journals to ask for a non-involved scientist in the same field to write a summary and commentary when a potentially controversial or significant paper comes out. Here's the actual paper.

Re:Wrong.

[macklin01]

No problem, and thanks for reading and replying.

I was confused on that, too, and neurobiology is pretty far from my regular work. Part of the problem is that there's a lot going on here: plasticity and differentiation (cell adaptations, transformations from one phenotype to another, differentiation, etc.), cell proliferation, tuning of connections, etc. It's a messy area with lots of new and sometimes contradictory data coming out.

From what I understand, there's a lot of plasticity in the brain as an adult: far more than was originally appreciated. I thought that we "knew" there were no new brain cells, and then we "knew" there were, and now we may "know" there aren't. That's the nature of evolving science, as others point out. And imprecise science communication--and imprecise English--doesn't help, either. Even biologists can get tripped up: we talk about tumor growth and cancer cell population growth, but we really primarily are talking about cell division there.

And there are all sorts of neat surprises. It was found that glial cells (a type of brain cell responsible for maintaining brain structure) can transdifferentiate into endothelial cells (which make blood vessels). See this PNAS paper and this one. This has all sorts of implications for gliomas and other brain cancers. And God only knows what other surprises are waiting to be found.

I suppose that's another reason they looked at the "new neuronal cell" marker: to see whether other cells could become new neuronal cells by transdifferentiation or other plastic processes. Biology is weird. :-)

Re:Thats' science!

[religionofpeas]

Actually, the studies were not done with eggs, but with high amounts of isolated cholesterol. And the cholesterol wasn't given to humans but to rabbits. Rabbits, who don't usually eat eggs or meat as part of their diet, are very bad at handling high amounts of cholesterol.