Ever wonder what caused gray hair? (no, not kids)
Aging brings on many changes in the human body, among them the graying of hair. Nishimura et al. (p. 720; published online 23 December 2004) found in a mouse model of hair graying that a deficiency of the gene Bcl-2 caused progressive loss of pigment cells in the bulge of the hair follicle--the hair stem-cell niche. Thus, the physiology of hair graying involves defective self-maintenance of melanocyte stem cells with aging, and may serve as a paradigm for understanding aging mechanisms in other tissues.
Mechanisms of Hair Graying: Incomplete Melanocyte Stem Cell Maintenance in the Niche
Emi K. Nishimura,1* Scott R. Granter,2 David E. Fisher1*
Hair graying is the most obvious sign of aging in humans, yet its mechanism is largely unknown. Here, we used melanocyte-tagged transgenic mice and aging human hair follicles to demonstrate that hair graying is caused by defective self-maintenance of melanocyte stem cells. This process is accelerated dramatically with Bcl2 deficiency, which causes selective apoptosis of melanocyte stem cells, but not of differentiated melanocytes, within the niche at their entry into the dormant state. Furthermore, physiologic aging of melanocyte stem cells was associated with ectopic pigmentation or differentiation within the niche, a process accelerated by mutation of the melanocyte master transcriptional regulator Mitf.
Picture of genetically-altered grey-haired mousy!
Reference: Science, Vol 307, Issue 5710, 720-724, 4 February 2005