Scientists are discovering how hair follicle stem cells eliminate dangerous cells and reduce the risk of melanoma
Gray hair is usually seen as a sign of aging, but a new Japanese study, as it writes ScienceAlert, suggests that they may actually be indication that our body is naturally protecting itself from cancer.
A study conducted on mice has shown that The human body has evolved a mechanism to eliminate cells that are at risk of forming tumors., even if it means losing hair color.
The role of stem cells
Our cells are exposed every day to various environmental factors that can damage DNA. Skin cells are particularly sensitive, because they act as the first line of defense for internal organs. DNA damage can contribute to both cell aging, as well as in cancer development.
Although experts still do not fully understand all the mechanisms that link DNA damage to physical signs of aging, this study brings interesting new data.
The researchers focused on melanoma, a form of cancer that usually appears on the skin and arises from melanocytes, the cells that produce melamine, the pigment responsible for skin and hair color. Melanocytes develop from melanocyte stem cells (McSCs) located in hair follicles, where they regularly regenerate skin and hair pigmentation, reports the Telegraph.
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Study on mice
By studying mice, scientists analyzed gene expression to follow the fate of McSC cells after various DNA damages. In the case of injuries called "double chain breaks", where both DNA strands are broken, McSC cells were irreversibly differentiated and then disappeared. As a result, The mice's hair turned gray..
This process is called “senescence-induced differentiation” or aging-differentiation and is based on activation of the p53–p21 signaling pathway, which regulates the cell cycle. In this way, the body eliminates cells that could become cancerous, even though this leads to the loss of hair color.
However, exposure to certain carcinogens caused a different reaction. The mice were exposed to UVB radiation and to 7,12-dimethylbenz(a)anthracene (DMBA), a potent carcinogen often used in research to induce tumors. The study showed that McSC cells they bypassed the differentiation process that occurs after double-strand breaks, even though they had suffered DNA damage.
Carcinogens can change the fate of cells
These findings suggest that, Sometimes, "knowing when to stop" can be the key to survival.For McSC cells, withdrawal and cessation of function in response to DNA damage may be protective even though they lose pigment, the body protects itself from skin cancer.
When McSC cells were exposed to UVB or DMBA, they retained the ability for self-regeneration and continued to be cloned. This process is supported by stem cell factor (SCF), one cytokine that guides melanocytes to their location in the skin. FMŚ also prevents aging, which means that damaged McSC cells can survive and divide further, taking increased risk of cancer.
"The same stem cell population can follow opposite fates – exhaustion or proliferation – depending on the type of stress and signals from the microenvironment," explains the lead author. Emi Nishimura, biologist at the University of Tokyo.
She adds that this discovery changes the way we understand gray hair and melanoma – not as separate events, but as different outcomes of stem cell responses to stress.
A new perspective on the complex role of stem cells
Even though this does not mean that gray hair directly protects against cancer, researchers emphasize that Gray hair is the result of a protective process, differentiation induced by aging that helps the body eliminate potentially dangerous cells. When this process is absent, the survival and proliferation of damaged McSC cells may increase the risk of melanoma.
Although more research is needed to understand all the mechanisms and to see if the same phenomenon occurs in humans, this study already constitutes an important step in understanding the link between tissue aging and cancer.
The study was published in the prestigious journal Nature Cell Biology and offers a new perspective on the complex role of stem cells in skin and hair health.
Stress increases the likelihood of going gray before the age of 30: a single hormone can cause inflammation of the scalp. /Telegraph/
