Having gray hair can actually be a good sign. According to a new investigation conducted by scientists at the University of Tokyo, and published in the journal Nature Cell Biology, the appearance of gray hair may indicate that the body is protecting itself from potential cancer.
The new study focuses specifically on melanoma, an aggressive type of cancer found predominantly on the skin, where it originates in melanocytes – specialized skin cells that generate melanin, the pigment responsible for skin and hair color.
The body’s cells are constantly exposed to factors that damage DNA, known as “genotoxic attacks”. In the case of skin, this exposure is even greater due to direct contact with the environment. This type of damage can contribute to both cellular aging and the development of cancer.
The researchers then focused on melanocytes (cells that produce melanin, responsible for skin and hair color) and their mother cells, located in hair follicles. When these cells suffer a serious break in their DNA, the body activates a safety mechanism: the damaged cells stop regenerating and end up disappearing. The visible result is the hair turning white, scientists found in experiments carried out on mice.
This process, known as “sine-differentiation”depends on the activation of a set of cellular defense genes, the so-called p53-p21 pathway, which helps prevent cells with damaged DNA from continuing to multiply.
When the defense fails
However, not all types of damage provoke this reaction. When researchers exposed mice skin to ultraviolet B (UVB) radiation and a potent carcinogen called DMBA, the cells’ behavior was the opposite.: instead of “reforming” and disappearing, they continued to divide, even though they were damaged.
This process is powered by a molecule called SCF (stem cell factor), which helps guide melanocytes but also prevents sine-differentiation. In practice, this causes potentially dangerous cells to remain alive and increases the risk of developing melanomaan aggressive type of skin cancer.
Two possible answers
“These findings show that the same population of stem cells can follow completely opposite paths – exhaustion or expansion – depending on the type of stress and the cellular environment,” he explained. Emi Nishimurabiologist and lead author of the study.
According to the researcher, this changes the way we understand gray hair and melanoma: they are not separate phenomena, but rather two different results of how cells react to genetic stress.