title: Towards a "free radical theory of graying": melanocyte apoptosis in the aging human hair follicle is an indicator of oxidative stress induced tissue damage.
abstract: Oxidative stress is generated by a multitude of environmental and endogenous challenges such as radiation, inflammation, or psychoemotional stress. It also speeds the aging process. Graying is a prominent but little understood feature of aging. Intriguingly, the continuous melanin synthesis in the growing (anagen) hair follicle generates high oxidative stress. We therefore hypothesize that hair bulb melanocytes are especially susceptible to free radical-induced aging. To test this hypothesis, we subjected human scalp skin anagen hair follicles from graying individuals to macroscopic and immunohistomorphometric analysis and organ culture. We found evidence of melanocyte apoptosis and increased oxidative stress in the pigmentary unit of graying hair follicles. The "common" deletion, a marker mitochondrial DNA-deletion for accumulating oxidative stress damage, occurred most prominently in graying hair follicles. Cultured unpigmented hair follicles grew better than pigmented follicles of the same donors. Finally, cultured pigmented hair follicles exposed to exogenous oxidative stress (hydroquinone) showed increased melanocyte apoptosis in the hair bulb. We conclude that oxidative stress is high in hair follicle melanocytes and leads to their selective premature aging and apoptosis. The graying hair follicle, therefore, offers a unique model system to study oxidative stress and aging and to test antiaging therapeutics in their ability to slow down or even stop this process.
authors.affiliation: Cutaneous Neuroimmunology, Biomedical Research Center, Rm. Nr. 2.0549, University Medicine Charité, Virchow Campus, Humboldt University of Berlin, Augustenburger Platz 1, Berlin 13353, Germany. eva.peters@charite.de
authors.forename: Petra Clara
authors.initials: PC
authors.lastname: Arck
authors.forename: Rupert
authors.initials: R
authors.lastname: Overall
authors.forename: Katharina
authors.initials: K
authors.lastname: Spatz
authors.forename: Christiane
authors.initials: C
authors.lastname: Liezman
authors.forename: Bori
authors.initials: B
authors.lastname: Handjiski
authors.forename: Burghard F
authors.initials: BF
authors.lastname: Klapp
authors.forename: Mark A
authors.initials: MA
authors.lastname: Birch-Machin
authors.forename: Eva Milena Johanne
authors.initials: EM
authors.lastname: Peters
mesh_terms: D000375:Aging / Q000502:physiology*; D005609:Free Radicals; D006200:Hair Color / Q000502:physiology*; D018859:Hair Follicle / Q000254:growth & development* / Q000473:pathology / Q000502:physiology*; D006801:Humans; D008544:Melanocytes / Q000166:cytology / Q000502:physiology; D008954:Models, Biological; D018384:Oxidative Stress / Q000502:physiology*
chemical_list: D005609:Free Radicals