Did you know, a few hours after we die, certain cells of a human brain still remain active? In fact, according to new research conducted at the University of Illinois Chicago, some of the cells of a dead brain increase their activities quite heavily and grow in humongous size. Spooky! Just like in a zombie movie, right? Well, let’s find more about it.
In the journal Scientific Reports, a newly published study states that the UIC researchers have analyzed gene expression in fresh brain tissue (collected during routine brain surgery) multiple times after removal. They have explained that this is done in order to simulate the post-mortem interval and death. Surprisingly, the researchers have found that some cells actually have increased gene expression after death. Fascinating!
So, these ‘zombie cells’ which have increased gene expressions after the post-mortem interval, had a specific type. All these cells were inflammatory cells called glial cells. According to the researchers, the glial cells grow and sprout long arm-like appendages for many hours after the human brain is dead.
The head of neurology and rehabilitation at the UIC College of Medicine, Dr Jeffrey Loeb states, “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.” Jeffrey is also a corresponding author on the paper of this new study on cells. He emphasized that the implications of this discovery are significant. Most research studies which include the post-mortem of human brain tissues to find treatments and potential cures for several disorders (autism, schizophrenia and Alzheimer’s disease), do not account for the post-mortem gene expression or cell activity such as this.
“Most studies assume that everything in the brain stops when the heart stops beating, but this is not so,” Loeb said adding, “Our findings will be needed to interpret research on human brain tissues. We just haven’t quantified these changes until now.”
The team of researchers including Loeb noticed that the global pattern of gene expression in fresh human brain cells didn’t match any of the previously published reports of postmortem brain gene expression. This was neither found from people without neurological disorders nor from people with a wide variety of neurological disorders, ranging from autism to Alzheimer’s.
“We decided to run a simulated death experiment by looking at the expression of all human genes, at time points from 0 to 24 hours, from a large block of recently collected brain tissues, which were allowed to sit at room temperature to replicate the postmortem interval,” Loeb added.
The reason why these researchers are way ahead of others in studying brain tissues is that Loeb is the director of the UI NeuroRepository. It’s literally a bank of human brain tissues from patients with neurological disorders who have given prior consent to have their tissue collected and stored for research either after they die. In fact, they have permission to study brain cells during standard of care surgery to treat disorders such as epilepsy. For example, epileptic brain tissue is required during certain surgeries to treat epilepsy in order to eliminate seizures. Now, not all of the tissue acquired is needed for pathological diagnosis. So, some can be used for research. This is the type of tissue that Loeb and colleagues analyzed in their research which gave prominent results.
Further research revealed that about 80% of the genes that were analyzed, remained relatively stable for 24 hours including the genes known as housekeeping genes. These genes have such names since they provide basic cellular functions and are often used in common research studies. The second group found in the neurons are heavily involved in human brain activities (memory, thinking) rapidly degrade within hours after death. According to Loeb, these neuronal genes are vital for researchers since they help them study disorders like schizophrenia and Alzheimer’s disease.
Now, the third group, the ‘zombie cells’ rapidly increase their activities right after the neuronal genes start to wear down. “Our findings don’t mean that we should throw away human tissue research programs, it just means that researchers need to take into account these genetic and cellular changes, and reduce the post-mortem interval as much as possible to reduce the magnitude of these changes,” Loeb said. According to him, the pattern of the post-mortem changes reaches sky high during the 12th-hour mark.
The article concluded with Loeb summarizing that the good news from the findings is now they know the exact nature of the specific genes and cells. They know which would degrade first, which would have increased activities over time. This will help in understanding the postmortem brain studies more efficiently.
THE CO-AUTHORS OF THE PAPER: Fabien Datchet, Tibor Valyi-Nagy, Kunwar Narayan, Anna Serafini and Gayatri Mohapatra of UIC; James Brown and Susan Celniker of Lawrence Berkeley National Laboratory; Nathan Boley of the University of California, Berkeley; and Thomas Gingeras of Cold Spring Harbor Laboratory.
SOURCE MATERIAL: The University of Illinois at Chicago. Writer: Sharon Parmet.