Graying and hair loss have long been considered natural signs of aging, but a recent scientific study has revealed a deeper dimension to this phenomenon, indicating its connection to defense mechanisms the body employs to protect against the risk of developing cancer. The study, conducted by researchers from the University of Tokyo and published in the journal Nature Cell Biology, highlighted the role of stem cells in hair follicles in combating DNA damage.
Hair color is determined by the pigment melanin, which is produced by specialized cells known as melanocytes. These cells originate from pigment stem cells found within hair follicles. Under normal conditions, these stem cells divide regularly with each hair growth cycle, allowing hair to maintain its color for extended periods.
However, continuous exposure to harmful environmental factors, such as radiation, chemicals, and pollutants, can lead to DNA damage within these cells. As this damage accumulates over time, the stem cells enter a state of suspended division, directly impacting pigment production and causing hair to turn gray or white.
In this context, biologist Don Bennett, as reported by Live Science, explained that when stem cells reach a certain level of DNA damage, they stop dividing as a protective mechanism, leading to a halt in melanin production and the appearance of gray hair.
The study concluded that pigment stem cells employ two distinct pathways when exposed to DNA damage.
The first pathway is a protective and safe one, where the cells enter a process known as "senescence-associated differentiation," a natural mechanism by which the body eliminates cells that could later become cancerous.
In this regard, Professor Emi Nishimura, head of the research team, emphasized that this process represents one of the body's primary defense mechanisms, preventing damaged cells from continuing to divide and transforming into malignant tumors.
The second pathway is described as dangerous, as this protective mechanism can be overcome when pigment stem cells are exposed to potent carcinogens, such as UVB radiation or certain cancer-causing chemicals. In this case, cells continue to divide despite DNA damage, which may not initially lead to gray hair, but it increases the risk of developing skin cancer, particularly melanoma, later in life.
The study cautions against the assumption that the absence of gray hair or hair loss is always an indicator of better health. Nishimura points out that hair retaining its natural color may, in some cases, mean that damaged cells have managed to evade the body's biological defense mechanisms.
Despite this correlation, the researchers emphasize that gray hair or hair loss is not a direct way to prevent cancer, but rather a reflection of a protective cellular process that halts the development of potentially dangerous cells.
The research team concludes that gray hair does not prevent cancer in itself, but it is evidence that the body has activated one of its cellular defense mechanisms to stop the growth of cells with damaged DNA before they can become cancerous.
