Neuroscientists: Mysterious 'Zombie' Cells Discovered in the Human Brain After Death

You would think once human beings are dead, their body would stop doing normal things; without air and blood circulation, the internal organs would be fast depleted. But as a result of a weird quirk of biology, there are some things known as the living dead. At least, living cells inside a done and dusted body.

(Photo : Getty Images)

The Zombie Cells 

Actually, the activity of some cells that reside inside the human brain increases after we die. These 'zombie' cells increase the expression of their genes and boldly continue trying to perform their normal tasks as if someone failed to tell them that they are now redundant.

Neurologist from the University of Illinois, Jeffrey Loeb, and co-workers observed as these cells stubbornly developed new tentacles and employed themselves with tasks for hours after death.
Loeb said: "Most findings have the assumption that everything in the human brain ceases immediately the heart stops beating, but it does not work that way, our studies will be needed to explain research on human brain tissues. We just have not figured these changes out until now."

Most of the information we possessed on brain disorders like Alzheimer's, schizophrenia and autism, arises from experiments done on human brain tissues after death. This method is vital in the lookout for treatments, as animals used for brain studies continuously fail to interpret back to us.

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Matching Gene Expression in Fresh Tissues 

This work is usually conducted on tissues from people who have died over 12 hours ago. By matching gene expression in fresh human brain tissues (taken away from 20 patients as part of epilepsy surgery) to earlier mentioned brain samples from dead people. Loeb and colleagues discovered clear differences which were not disease nor age-specific. 

They made use of data on gene expression, which they later authenticated by examining the histology of the brain tissue, to know the specific cell activity changes across time since death, at ambient temperature.

While some gene activity stayed stable for the 24 hours the team reported, neuronal cells and their gene activity immediately decreased. Though most remarkably, glial cells increased gene processes and gene expression.

At first, it was surprising but it actually makes a lot of sense. Given glial cells, such as astrocytes and waste-eating microglia are brought together when things go wrong. And demise is just as 'wrong' as living things can go.

(Photo : Mart production)

Glial Cells Expand After Death 

Jeffrey Loeb said that glial cells that expand after death are not too surprising given that they are exposed and their task is to clean things up after injuries to the brain such as stroke or deprivation of oxygen.

The team then explained that the Ribonucleic acid (RNA) expressed by genes does not change by itself within 24 hours after death, so any changes in its amount must surely be as a result of the continuation of biological processes. 

However, after 24 hours, these cells also pass away and can no longer be distinguished from the degrading tissue that enclosed them. 

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