During early development, human brain structure changes. Cells in our brain can divide, differentiate and take up new roles. But a study published in 2017 argues that this process is extremely rare or non-existent in the adult hippocampus. This suggests that there can be no neuron formation in an adult brain. Such a fact would indicate that brain-related pathology linked to aging can be due to a lack of neurogenesis. It is true that stem-cell pools in older individuals have been shown to be significantly lower.
On the other hand a newer study contradicts this claim.While stem-cell pools indeed appear to decline during aging, as well as neuroplasticity and angiogenesis, neural progenitor cells were found in “equal” levels in subjects of all ages.
Those two studies have focused on the dentate gyrus (DG) a part of the hippocampus where neurogenesis is most likely to occur. While certain areas appeared unaffected by age others were indeed affected.
The first study, the one claiming no neurogenesis in adults, used 59 human samples, while the second one used 28. Both studies used fairly similar techniques to obtain their results.
Immunohistochemistry was used to stain cells expressing factors indicating a proliferating or a non-proliferating state. Factors such as SOX1 and GCL were stained.
The results show that there needs to be more research done on this issue so that we can successfully identify target genes for treating age-related brain diseases. Aging has been for a long time the worst enemy for human health. Rejuvenating the human body by boosting regeneration and understanding stem-cells has been considered but we need to understand those mechanisms better.
The outcome of those studies may conclude that parts of the DG do exhibit neurogenesis even later in life while others don’t. Since this part of the brain has previously been associated with memory formation, this may explain a lot about dementia.
Sources: Human Hippocampal Neurogenesis Persists
throughout Aging, Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults, Neurogenesis in the human hippocampus declines sharply during infancy to extremely low levels in children and undetectable levels in the adult, NCS-1 in the Dentate Gyrus Promotes Exploration, Synaptic Plasticity, and Rapid Acquisition of Spatial Memory