New research in mice has revealed a surprising link between grey hair and the body’s defence mechanisms against cancer. Scientists have found that the loss of pigment in hair may be a byproduct of a protective process that eliminates cells at risk of becoming malignant.
Melanocyte stem cells, which reside in hair follicles and produce pigment, normally replenish melanocytes through cyclical regeneration. However, when these stem cells sustain DNA damage, particularly double-strand breaks, they undergo a process called seno-differentiation. This triggers them to irreversibly mature into pigment cells and then disappear from the stem cell pool, leading to greying hair.
This self-removal prevents the accumulation of genetic mutations that could promote cancer. Each grey hair, in effect, represents a cell that has chosen to bow out rather than risk turning malignant. However, the study also found that not all damage triggers this protective response.
When melanocyte stem cells were exposed to potent cancer-causing chemicals or UV radiation, they bypassed seno-differentiation. Instead, signals from surrounding tissues encouraged the damaged cells to self-renew and continue dividing, creating a cellular environment ripe for melanoma.
The researchers describe this as “antagonistic fates,” where the same stem cell population can take two different paths depending on the type of damage and molecular cues. This suggests that greying and melanoma are not unrelated outcomes but twin results of the body’s struggle to balance tissue renewal and avoid cancer.
It is important to note that the study was conducted in mice, and further research is needed to confirm these mechanisms in humans. The findings may help explain why cancer risk increases with age, as control mechanisms may falter over time.
