Graying hairs are signs of stress

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Graying hairs might be signs of stress, revealed by researchers in a new study. Stress that does damage to DNA decreases amount of melanocyte stem cells (MSCs) within hair follicles that are responsible for making those pigment-producing cells.

The new research is reported in the June 12 issue of Cell, a Cell Press publication.

“The DNA in cells is under constant attack by exogenously- and endogenously-arising DNA-damaging agents such as mutagenic chemicals, ultraviolet light and ionizing radiation,” said Emi Nishimura of Tokyo Medical and Dental University. “It is estimated that a single cell in mammals can encounter approximately 100,000 DNA damaging events per day.”

Consequently, she explained, cells have elaborate ways to repair damaged DNA and prevent the lesions from being passed on to their daughter cells.

“Once stem cells are damaged irreversibly, the damaged stem cells need to be eliminated to maintain the quality of the stem cell pools,” Nishimura continued. “We found that excessive genotoxic stress triggers differentiation of melanocyte stem cells.”

The findings lend support to the notion that genome instability is a significant factor underlying aging in general, the researchers said. They also support the “stem cell aging hypothesis,” which proposes that DNA damage to long-lived stem cells can be a major cause for the symptoms that come with age.

In addition to the aging-associated stem cell depletion typically seen in melanocyte stem cells, qualitative and quantitative changes to other body stem cells have been reported in blood stem cells, cardiac muscle, and skeletal muscle, the researchers said. Stresses on stem cell pools and genome maintenance failures have also been implicated in the decline of tissue renewal capacity and the accelerated appearance of aging-related characteristics.

Source: Cell Press, USA


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