In humans, gray hair is listed among life's certainties, alongside growing old. However, thus far researchers have had no idea as to what is causing it. The only known thing about the growth process was that two types of cells are required for the hair to develop and get colored, and that sometimes these cells fail to do their job. According to a new scientific study, conducted by researchers at the Tokyo Medical and Dental University, in Japan, it may be true that stress is causing people to turn gray early, but not the type they believe.

 

In other words, it's not stress caused by the work place that causes your hair to turn gray. But rather genotoxic stress, the kind that can really damage your DNA. Over time, as the acid gets more and more damaged, it has a direct effect on the color of the hair, causing it to whiten, and appear gray on the outside. Emi Nishimura, the lead researcher on the new paper, also discovered back in 2004 that the hair follicles had in them melanocyte stem cells. These cells could either turn into regular melanocyte cells, which give the hair its natural pigment, or remain as stem cells, storing the pigment for use on future generations of hair. Usually, a strand grows for several years, then stalls, and ultimately dies and falls off.

 

In theory, this stem cell system should last a lifetime, but researchers have revealed that, over time, the amount of melanocyte stem cells decreases, which means that, from a certain point on, only the hair will be created, but without its pigment reserves. So the entire head, or portions of it, will appear to be covered in white/gray hair. What caused the stem cells to stop functioning in producing pigment has thus far remained a mystery.

 

Ultraviolet radiation, household chemicals, and environmental pollutants are all stressors that can place unnecessary strain on the DNA. As they do, they force changes inside the double-helix strands, which eventually become incapable of performing some of their tasks. “The mature cells lose their regeneration capabilities. The mice then can’t produce enough pigment-making cells,” Nishimura said. “Genotoxic stress happens to everyone over time, and its accumulation is the main cause of aging,” added Medical Research Council geneticist Ian Jackson, from Edinburgh.

 

In the experiments, Nishimura subjected young, unsuspecting mice to x-rays or chemotherapy drugs, both of which are believed to have negative effects on their genetic material. The animals spectacularly turned gray, and, moreover, samples of their genetic material showed no signs of difference from those harvested from older mice that had not been subjected to the treatment. This means that genotoxic stress may also be the root cause of gray hair caused by old age. The find could help researchers create new treatments for the condition, especially suited for the elderly, ScienceNow informs.