29 March 2021

After death, some brain cells become more active

The Back Page

While most brain cells start to degenerate after death, ‘zombie genes’ in glial cells come to life.

Medical researchers depend on post-mortem brain samples to study autism, schizophrenia and Alzheimer’s disease. But, to date, they’ve been working on the assumption that all cells start to degrade after death. 

That assumption is wrong, according to a new paper in Scientific Reports that compares “fresh” brain samples taken during surgery to post-mortem brain samples. 

By comparing these two samples, researchers at the University of Illinois Chicago in the US discovered that some brain cells become more active in the hours after the death of a patient.

The researchers found that 24 hours after death, around 80% of brain cells go quiet, with stable activity from the so-called “housekeeping genes” that provide basic cellular functions.

Another group of genes present in neurons that are involved in brain activities like memory, thinking and seizures rapidly degraded after death. 

But there was one type of brain cell that actually started to grow and increase their gene expression after death – inflammatory cells called glial cells.

These glial cells were growing and sprouting “long arm-like appendages” for many hours after death, according to the researchers.

“That glial cells enlarge after death isn’t too surprising given that they are inflammatory and their job is to clean things up after brain injuries like oxygen deprivation or stroke,” said Professor Jeffrey Loeb, the head of neurology and rehabilitation at the UIC College of Medicine and an author on the paper.

The activity of these “zombie” cells after death was quite important to consider when using post-mortem brain samples to study human brain disorders, he said. 

“Most studies assume that everything in the brain stops when the heart stops beating, but this is not so,” Professor Loeb said. 

“Our findings will be needed to interpret research on human brain tissues. We just haven’t quantified these changes until now.”

Scientific Reports 2021, 23 March

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