‘Zombie’ cells survive the death of the brain

In the hours after we die, certain cells in the human brain remain active. Some cells even increase their activity and grow to gargantuan proportions, according to a new study from the University of Illinois at Chicago.

In a newly published study in the journal Scientific Reports, UIC researchers analyzed gene expression in a new brain tissue – collected during routine brain surgery – at several times after removal to simulate the post-mortem time and death. They found that gene expression increased in some cells after death.

These ‘zombie genes’ – the ones that increased sensitivity after the post-mortem interval – were specific to one type of cell: inflammatory cells called glial cells. The researchers held that glial cells grow and explode long arm-like appendages for many hours after death.

These glial cells do not expand after death surprisingly because they are inflammatory and their job is to clear things up after a brain injury such as oxygen deficiency or stroke. “

Dr. Jeffrey Loeb, John S. Garvin Professor and head of neurology and rehabilitation at UIC College of Medicine and corresponding author

What matters, Loeb said, is the impact of this finding – most research studies that use postmortem human brain bones to rule out potential treatments and cures for disorders such as autism , schizophrenia and Alzheimer’s disease, describing the post-mortem gene expression. or cell activity.

“Most studies assume that everything in the brain stops when the heart stops beating, but this is not true,” Loeb said. “Our findings will be needed to study human brain bones. We have not yet measured these changes.”

Loeb and his team noted that the global pattern of gene expression in new human brain strains did not correspond to any of the published reports of postmortem brain gene expression from people without brain disorders or from people with multiple types of falls -brain order, from autism to Alzheimer’s.

“We decided to run a symbolic death test by looking at the expression of each human species, at times ranging from 0 to 24 hours, from a large, recently collected block of brain tissue that was allowed to sit at room temperature to temporarily reproduce the postmortem, “Loeb said.

Loeb and colleagues have a particular advantage when it comes to studying brain tension. Loeb is the director of UI NeuroRepository, a bank of human brain tissue from patients with brain disorders that has allowed material to be collected and stored for research either after death, or during labor -conventional care surgery to treat disorders such as epilepsy. For example, during some clinics for the treatment of epilepsy, epileptic brain tension is removed to help eliminate seizures. Not all of the material is required for pathology diagnosis, so some can be used for research. This is the tension that Loeb and colleagues analyzed in their research.

They found that about 80% of the genes studied remained relatively stable for 24 hours – the expression did not change much. These included genes often called housekeeping genes that provide basic cell functions and are commonly used in research studies to reveal the quality of the tumor. Another group of genes, which were known to be present in neurons and which have been shown to be closely involved in human brain activity such as memory, thinking and capture activity, were rapidly reduced in the brains. hours after death. These genes are important for researchers studying disorders such as schizophrenia and Alzheimer’s disease, Loeb said.

A third group of genes – the ‘zombie genes’ – increased the activity at the same time as the neuronal genes ramped down. The pattern of post-mortem changes peaked at about 12 hours.

“Our findings do not mean that we should discard human stress research programs, it simply means that researchers must pay attention to these genetic and cellular changes, and the reduce post-mortem time as much as possible to reduce the size of these. changes, “Loeb said.” The good news from our findings is that we now know which genes and cell types are stable, declining, and uplifting. time to better understand results from postmortem brain scans. “