In the world of cell physiology, cells that can’t die, but are unable to function normally, have been referred to as “Zombie cells.” These are old, worn out cells that are seen in several age-related diseases—such as Alzheimer’s Disease (AD), traumatic brain injury, and more.
These stressed out, toxic Zombie cells were first seen in Alzheimer’s disease during a recent study, conducted at the University of Texas, Health Science Center at San Antonio. The study was published in the journal, Aging Cell, on August 20Th, 2018.
The researchers discovered a link between tau tangles in the brain—thought to be a hallmark symptom of Alzheimer’s disease—and senescent (stressed out, old) cells. This type of cellular stress, noted in the senescent cells, has also been implicated in cancer. But, this is the first time the Zombie cells were associated with Alzheimer’s disease.
Zombie Cells
When a cell becomes senescent, it can continue surviving, but does not function properly. The reason these abnormal cells have been deemed “Zombie cells” is that they release substances that kill adjacent cells. “When cells enter this stage, they change their genetic programming and become pro-inflammatory and toxic,” said study author Miranda E. Orr, Ph.D., at the South Texas Veterans Health Care System. “Their existence means the death of surrounding tissue.”
According to Darren Baker, a Mayo Clinic molecular biologist and senior study author, “Senescent cells are known to accumulate with advancing natural age and at sites related to diseases of aging, including osteoarthritis; atherosclerosis; and neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. In prior studies, we have found that elimination of senescent cells from naturally aged mice extends their healthy life span.”
USC Study of Zombie Cells
Researchers at the University of Southern California (USC) performed a study to examine the gene mutation that occurs as Zombie cells interrupt the normal DNA cell division cycle—causing severe damage to the chromosomes of the cell, while concurrently allowing the cell to continue to divide.
The researchers discovered what they referred to as “a mess,” with cells having damaged chromosomes, sometimes connected to other cells with ultra-fine DNA bridges. The state of the Zombie cells was described as appearing like “a hot pizza,” with abnormal strings of DNA (cheese) draping between the separate pieces Next, the most damaged portion of the DNA—the micronuclei—was observed rejoining the parent nuclei, while importing its mutations into healthy cells.
The mutations found in the USC study were linked with cancer in mice, and micronuclei, are oftentimes associated with human cancer cells.
Removing Zombie Cells
In a more recent study at Mayo Clinic, scientists were able to decrease the number of senescent cells, which, in turn, lowered the amount of tau protein aggregation, as well as diminishing death of cells in the brain (neurons) and, ultimately lowering the level of memory loss. These Zombie cells were removed, before signs of cognitive impairment were present, but, in humans, there is no way to predict which people will develop AD (compared to mice studies, where the mice were all bred to have symptoms of AD). “Clearly, this same approach cannot be applied clinically, so we are starting to treat animals after disease establishment and working on new models to examine the specific molecular alterations that occur in the affected cells,” said Dr. Baker.
Conclusion
The research, which is ongoing, is very exciting news for the hope of a future Alzheimer’s cure, but, the jury is still out as far as whether Zombie cells can safety be identified and removed, once the symptom of AD have occurred.
Learn more about current Alzheimer’s research by CLICKING HERE to view Cogntive Vitality, a website aimed at educating the public on new medication, supplements and treatment for Alzheimer’s disease.
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Resources:
1. Science Daily: https://www.sciencedaily.com/releases/2018/08/180822092706.htm
2. Science Daily: https://www.sciencedaily.com/releases/2018/09/180919133024.htm
3. USC News: https://news.usc.edu/84786/heres-what-science-is-learning-about-zombie-cells/
