Grey hair maybe linked to body's cancer defense mechanism, new study suggests

Greying hair may indicate ageing, but it's not a bad thing health-wise, a new study suggests. Having grey hair could be a reflection of the body’s natural defense against cancer.

The research explored how hair pigment stem cells, which had DNA damage, made decisions that led to either greying or melanoma (a tumour of melanin forming cells).

The study led by Dr Emi K Nishimura at the Tokyo Medical and Dental University found that, based on the environment, the hair pigment stem cells could respond in the two ways depending on their environment, the university's press release said.

The researchers studied Melanocyte stem cells, the cells that give hair and skin their colour, using mouse models and tissue samples. These cells reside at the base of hair follies and generate mature melanocytes and go through cyclical regeneration which continues to give hair its pigment.

They observed how the cells reacted when they were exposed to forms of stress that damaged DNA, like chemicals that mimic UV exposure.

Some of the cells responded to the damage (DNA double-strand breaks) by stopping their renewal process and then maturing and dying, which leads to grey hair.

The process is due to the activation of the p53–p21 pathway," a tumour-suppressor mechanism.

However, when the researchers altered the surroundings, the cells refused to die. When the cells were exposed to (carcinogens) cancer-causing agents or to ultraviolet B light, they could bypass the response even when they were damaged.

Instead of dying, the damaged cells will continue to regenerate and then multiply by cloning, which would then lead to a tumour-prone state.

In the press release, Nishimura said, “These findings reveal that the same stem cell population can follow antagonistic fates—exhaustion or expansion—depending on the type of stress and microenvironmental signals.” She adds, “It reframes hair greying and melanoma not as unrelated events, but as divergent outcomes of stem cell stress responses.”

The study is not saying that greying hair prevents cancer, but it showed that damaged cells chose a protective pathway, removing themselves based on cues from the environment, instead of becoming cells that turn into cancer.

The researchers say that the discovery helps understand the process of hair greying and how it relates to cancer development.

The study was published in the journal Nature Cell Biology.

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