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Stress turns hair gray

india Updated: Jun 12, 2009 20:43 IST

ANI
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You must have heard many times from people that stress causes gray hairs. Now, new research suggests it's true.



According to a new report in the June 12 issue of Cell, a Cell Press publication, those pesky graying hairs are signs of stress.



Researchers have discovered that the kind of "genotoxic stress" that does damage to DNA depletes the melanocyte stem cells (MSCs) within hair follicles that are responsible for making those pigment-producing cells. Rather than dying off, when the going gets tough, those precious stem cells differentiate, forming fully mature melanocytes themselves. Anything that can limit the stress might stop the graying from happening, the researchers said.



"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," the expert added.



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," she said.



The expert added that differentiation might be a more sophisticated way to get rid of those cells than stimulating their death.



Nishimura's group earlier traced the loss of hair color to the gradual dying off of the stem cells that maintain a continuous supply of new melanocytes, giving hair its youthful color. Those specialized stem cells are not only lost, they also turn into fully committed pigment cells and in the wrong place.



Now, they show in mice that irreparable DNA damage, as caused by ionizing radiation, is responsible. They further found that the "caretaker gene" known as ATM (for ataxia telangiectasia mutated) serves as a so-called stemness checkpoint, protecting against MSCs differentiation. That's why people with Ataxia-telangiectasia, an aging syndrome caused by a mutation in the ATM gene, go gray prematurely.