University of Tokyo Research Team Publishes in International Journal
"Gray Hair, Not Just Aging but a Biological Defense Response"
New research suggests that gray hair may not simply be a sign of aging, but could actually be a defensive response to help prevent cancer.
According to the Mainichi Shimbun and other Japanese media on October 27, a research team led by Professor Emi Nishimura at the Institute of Medical Science, University of Tokyo, published findings on the link between gray hair and malignant melanoma-a type of skin cancer-in the international journal Nature Cell Biology on October 6.
The team observed, through experiments on mice, how melanocyte stem cells (McSC)-which determine hair color-respond when they are damaged. These stem cells reside in hair follicles and are responsible for periodically generating cells that supply pigment to the hair.
The researchers induced DNA damage in the cells using ultraviolet B (UVB) radiation or similar chemicals. As a result, some of the stem cells recognized themselves as damaged and stopped their normal self-renewal process. These cells then differentiated into pigment cells, lost their function, and disappeared. During this process, the hair lost its color, resulting in gray hair.
In contrast, under the same conditions, some cells survived instead of being eliminated. Over time, these cells accumulated further damage, began to divide abnormally, and transformed into forms resembling cancer cells. In other words, if damaged stem cells are not properly removed, the likelihood of developing melanoma increases.
Based on these findings, the research team explained that gray hair could be a natural protective mechanism that reduces the potential risk of cancer by eliminating damaged cells. The team clarified, "This does not mean that gray hair directly prevents cancer," but added, "If the mechanism that causes the loss of pigment production as a natural defense does not function, the risk of cancer may increase."
Professor Nishimura stated, "Gray hair and melanoma, a type of skin cancer, are not unrelated. The different outcomes depend on the stress response of stem cells," emphasizing the importance of proper aging and removal of cells. She also cautioned, "Procedures or topical treatments whose safety and scientific basis have not been established may be dangerous, so please exercise caution."
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