Hair greying and melanoma have emerged as two divergent fates of stressed stem cells—protection or peril, according to new research from Japan.
Scientists from The Institute of Medical Science (based at The University of Tokyo) have discovered that hair greying and melanoma share a surprising cellular origin. When DNA damage strikes melanocyte stem cells, they may undergo a protective process called seno-differentiation, leading to hair greying.
However, carcinogens can override this safeguard, allowing the damaged cells to persist and turn cancerous. This balance between cell loss and survival reveals a hidden connection between ageing and cancer.
Melanocyte stem cells (McSCs) are specialised cells that give rise to melanocytes, the pigment-producing cells responsible for the colour of our hair and skin. In mammals, these stem cells are found in a region of the hair follicle known as the bulge-sub-bulge area. Here, they exist as immature melanoblasts, ensuring that hair and skin maintain their colour through repeated cycles of regeneration.
Discovering How DNA Damage Drives Hair Greying
The researchers explored how McSCs react to different types of DNA damage. Using long-term lineage tracing and gene expression profiling in mice, the researchers discovered that when McSCs experience DNA double-strand breaks, they undergo a senescence-coupled differentiation (seno-differentiation).
In this state, the stem cells permanently mature and are eventually lost, which leads to hair turning gray. The process is controlled by the activation of the p53-p21 signaling pathway.
When McSCs are exposed to certain carcinogens, including 7,12-dimethylbenz(a)anthracene or ultraviolet B radiation, they do not follow the same protective path. Even with DNA damage present, these cells avoid seno-differentiation and continue to renew themselves.
The cells expand clonally instead, aided by KIT ligand signals released from surrounding tissue and the epidermis. These niche-derived signals block the protective differentiation response, pushing the stem cells toward a cancer-prone state.
Opposing Cellular Fates: Greying or Cancer
The findings reveal that the same stem cell population can follow antagonistic fates — exhaustion or expansion — depending on the type of stress and microenvironmental signals. Hence, the study reframes hair greying and melanoma not as unrelated events, but as divergent outcomes of stem cell stress responses.
The researchers emphasize that their findings do not imply that developing grey hair prevents cancer. Instead, seno-differentiation appears to serve as a stress-triggered defence mechanism that removes damaged stem cells before they can become harmful. When this safeguard fails or is bypassed, those damaged cells can survive and potentially lead to melanoma.
Cellular Self-Destruction
By uncovering the molecular pathways that determine whether stem cells undergo protective exhaustion or dangerous expansion, the study connects the biology of tissue ageing with cancer formation.
The research also highlights the value of naturally removing compromised stem cells through “senolysis,” a biological process that helps prevent cancer by sacrificing cells that could otherwise become malignant.
The research appears in the journal Nature Cell Biology, titled “Antagonistic stem cell fates under stress govern decisions between hair greying and melanoma.”
