Looking for an extra nerdy costume this year? Look no further than zombie (cells) and how they endanger us all year round, not just at Halloween!
Some cells in the body simply refuse to die. Biologists call these cells senescent cells or “zombie cells”, a nod to the undead.
A new study led by Selim Chaib and James Kirkland at the Cedars-Sinai Medical Center in Los Angeles, USA, was published in Cell Metabolism. It suggests that one reason these cells linger is that they wear a sort of invisibility cloak. Removing this disguise could help our bodies clear them.
In our bodies, when a cell is damaged by stress, it can enter a state of arrest that stops it from multiplying and possibly becoming cancerous. This protective response is called senescence.
Over time however, these cells tend to build up in the body, releasing inflammatory molecules called the senescence-associated secretory phenotype (SASP).
These molecules cause inflammation and can damage nearby tissue. The build-up of these cells has been linked to age-related conditions like insulin resistance or physical decline.
In young bodies, immune cells regularly find and remove senescent cells. With age, the monitoring system by immune cells lessens and senescent cells evade by displaying “don’t attack me” signals that switch off the immune cells that would otherwise destroy them.
PD-L2 is one of those proteins and the focus of this study.
Researchers found that the PD-L2 protein acts as an invisibility cloak worn by human zombie cells, protecting them from cell death.
So how did researchers find this out?
They forced human cells into senescence by causing damage to them through radiation and chemotherapy drugs.
When cells were damaged, they produced more PD-L2. They tested this in the organs of old mice, as well as in fat tissue from older humans and the same pattern was recurring.
The most valuable result came from the mice. Mice that were bred without PD-L2 had fewer senescent cells (or zombie cells) and less inflammation overall. Old male mice had better insulin sensitivity and old females had greater grip strength.
With further research, scientists can aim to block the PD-L2 protein in order to decrease age-related conditions. They also tackle zombie cells in an atypical way, targeting the disguise, the PD-L2 protein, rather than directly targeting senescent cells or other more major proteins which may cause further autoimmune consequences.
It’s important to note that this is all early research and so far it has only shown results in mice. However it does point to a new way to fight these zombie cells in the human body.
Instead of killing them with drugs, take off their invisibility cloak and let the immune system do its job.
So when you see all the zombie costumes this Halloween, fear not. Inside the human body, zombies may not be so invincible after all.
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