Graying Hair and Fading Stem Cells

Hair loses its color with age due to a decline in activity of melanocyte pigment-producing cells, likely another symptom of the general fading of stem cell populations throughout the body. A recent paper adds evidence for that view: Hair graying is one of the prototypical signs of human aging, but its mechanism is largely unknown. To elucidate the mechanism of hair graying, we investigated gene expression related to melanogenesis in human hair. The key molecules in melanogenesis, microphthalmia-associated transcription factor-M (MITF-M), Sox10, Pax3, tyrosine related protein-1 (TRP-1), and tyrosinase, were absent or greatly reduced in the bulbs of white hair compared to black hair. Melanocyte stem cells (MSCs) or melanocytes express markers for neural crest cells, Sox10, Pax3, and MITF-M. Taken together, our data suggest that hair graying is caused by defective migration of MSCs into the bulb area of hair. Setting any given group of aging stem cells back to work by introducing appropriate biochemical signals - or cloning many more stem cells to reintroduce into the body - are very plausible projects for the decade ahead. Either could greatly improve the immediate situation, and the second strategy has already been demonstrated in heart therapies. I can envisage cloning...