You would think that once a man is dead, the body would do things; without the circulation of blood and air, the inner systems would run out quickly. But due to a strange biology oddity, there are things like the living dead – the living cells, at least, in a body made of dust.
Some cells in the human brain actually increase their activity after we die. These “zombie” cells increase their gene expression and boldly continue to try to perform their vital tasks, as if someone forgot to tell them that they are now redundant.
Neurologist Jeffrey Loeb of the University of Illinois and colleagues watched as these cells stubbornly sprout new tentacles and deal with hours after death.
“Most studies assume that everything in the brain stops when the heart stops beating, but it’s not,” Loeb said. Our findings will be needed to interpret research on human brain tissue. I just haven’t quantified these changes yet.
Much of the information we have about brain disorders, such as autism, Alzheimer’s, and schizophrenia, comes from experiments performed on brain tissues after death; this approach is essential in the search for treatments, because animal models for brain studies often fail to translate us back.
Usually, this work is done on tissues from people who died more than 12 hours ago. By comparing gene expression in fresh brain tissue (removed as part of epilepsy surgery in 20 patients) with the aforementioned brain samples from the deceased, Loeb and the team found striking differences that were not age-specific or disease-specific.
They used gene expression data, which they later corroborated by examining brain tissue histology, to understand changes in cell-specific activity over time from death to room temperature.
While most of the genetic activity remained stable for 24 hours, documented by the team, the neuronal cells and their genetic activity were rapidly depleted. But the most remarkable is the glial cells grown genetic expression and processes.
Cells come to life after the death of the human brain. (Dr. Jeffrey Loeb / UIC)
Although surprising at first, this actually makes a lot of sense, given that glial cells, such as microglia and waste-eating astrocytes, are put into action when things go wrong. And dying is as “wrong” as living things can be.
“Glial cells grow after death is not very surprising, given that they are inflammatory, and their job is to clean things up after brain damage, such as oxygen deprivation or stroke,” Loeb said.
The team then demonstrated that the RNA expressed by the genes does not change on its own within 24 hours of death, so any change in its amount must be due to the continuation of biological processes.
“The complete genetic expression of freshly isolated human brain samples allows an unprecedented view of the genomic complexity of the human brain, due to the preservation of so many different transcripts that are no longer present in postmortem tissues,” the researchers wrote in their paper.
This has huge implications for both past and present studies, which use brain tissue to understand diseases that involve immune responses – such as these “zombie” glial cells that swell as they unnecessarily devour pieces around them. the dying brain.
However, after 24 hours, these cells gave way and could no longer be distinguished from the degrading tissue surrounding them.
“Researchers need to take these genetic and cellular changes into account and reduce the post-mortem interval as much as possible to reduce the extent of these changes,” Loeb explained.
The good news from our findings is that we now know which genes and cell types are stable, which degrade, and which grow over time, so that the results of postmortem brain studies can be better understood.
Even in death, we biological entities are never completely static.
This research was published in Scientific reports.