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Why hair turns gray

(Adapted from a posting by Edyta Zielinska on GernTalk, dated 11th June 2009:)

“Researchers have identified the mechanism for why hair goes gray with age and stress in the June 12, 2009 issue of Cell.

It’s generally thought that accumulated DNA damage is a likely culprit in aging phenotypes such as graying hair, but researchers have been unable to show a direct link, said David Fisher chairman of the department of dermatology at the Massachusetts General Hospital, who was not involved in the study. “Hair follicles are very deep,” said Fisher, so it’s unlikely that DNA damage would be caused by UV radiation from sunlight, for example.”

In order to understand the process involved in graying hair, scientists used radiation and other chemical inducers of DNA damage on pigment stem cells called melanocyte stem cells in mice. DNA damage resulted in premature graying in mice.

Dr. Park’s comment: As in every organ, the  main reason for DNA damage is telomere shortening, allowing the genetic code to be corrupted when the chromosomal ends are unprotected.

DNA damage normally causes two outcomes — cell death or shut down.  Scientist showed that induced DNA damage can also elicit a third pathway – forcing stem cells into terminal differentiation. As a result, stem cells lost their ability to replenish pigmented cells.

Dr. Park again: The source article goes on to evoke a teleological hand-waving that is sadly typical in science. They suggest that the “third pathway” of differentiation represents the body’s effort to “protect” itself from cancer.  In my opinion, evolution would never have allowed people to take advantage of such an “intelligent design” because humans never evolved in conditions where they could even survive long enough to exhibit cancer.

Loss of differentiation is, ex post facto, a good thing but is merely the unintended result of knocking out the established programming that was allowing appropriate, “asymmetric division,” or the production of a perfect master copy and a more differentiated cell.  That asymmetric division, along with immortalization, are the two hallmarks of  “stemness.”

The bottom line: cellualar dysfunction is caused by genetic aging caused by insufficient telomerase activation and its saltatory protection of your genetic code.
What is frightening is that even one end, of one chromosome, in one immortal stem cell, can spell disaster because of the unlimited reproduction of that defective stem cell’s faults.

To learn more about stem cells and their role in aging, visit our website at

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