The Brain Seems To Shift Between Ages 50 And 75

A previous study has suggested that our brains are technically in their adolescent phase until about 32, with the adulthood section running ’til about 66.

But a new paper published in Science found that the brain seems to undergo sweeping changes in how its genome is regulated, starting in midlife.

Study author Nathan Zemke, Director of Single-cell Genomics at the Centre for Epigenomics at UC San Diego, described the finding as “a major step forward in understanding how aging reshapes the human genome in brain cells”.

In this research, scientists used single-cell analyses involving samples from participants’ hippocampi (the parts of the brain linked to learning and memory) to look at their gene regulation and genome organisation.

They chose people of different ages.

Genome regulation refers to how the genes already in your body are expressed. Changes in gene expression can lead to changes, including diseases and altered tissue and organs.

In this study, researchers noticed a sharp decline in microglia – immune cells that can help to protect the brain – between about 50 and 75. These cells seemed to be replaced by something similar to the immune cells typically seen in our blood.

The replacements seemed to have stronger inflammatory signals than our original microglia – and researchers think this might be linked to chronic inflammation in older brains.

Dr Bing Ren, the study’s corresponding author, said: “Microglia are critical for maintaining brain homeostasis.

“When these cells fail to perform their housekeeping duties, toxic materials accumulate that can trigger inflammatory processes that may contribute to neurodegenerative diseases”.

Additionally, older brains seemed to have fewer cells that protect the blood-brain barrier. That might mean ageing minds are more susceptible to exposure to potentially harmful substances in our blood.

And the physical structure of the three-dimensional genome seemed to erode, too, potentially leaving people more liable to develop unwanted changes.

Zemke said this was a good reason to study gene regulation in order to help us better understand the mechanisms behind ageing.

And co-corresponding author of the study, Dr Xiangmin Xu, shared: “Importantly, this study reveals that aging is not simply a gradual decline, but involves coordinated and dynamic remodeling of immune, vascular, and neuronal systems.

“These findings open the door to identifying new therapeutic targets aimed at preserving circuit integrity and brain function across the lifespan”.