The impact of oxidative stress on hair

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.

Androgenetic alopecia is the most common hair loss disorder, affecting both men and women. Initial signs of androgenetic alopecia usually develop during teenage years leading to progressive hair loss with a pattern distribution. Moreover, its frequency increases with age and affects up to 80 % Caucasian men and 42 % of women. Patients diagnosed with androgenetic alopecia may undergo significant impairment of quality of life. Despite the high prevalence and the variety of therapeutic options available, there have been no national or international evidence-based guidelines for the treatment of androgenetic alopecia in men and women so far. Therefore, the European Dermatology Forum (EDF) initiated a project to develop an evidence-based S3 guideline for the treatment of andro-genetic alopecia. Based on a systematic literature research the efficacy of the currently available therapeutic options was assessed and therapeutic recommendations were passed in a consensus conference. The purpose of the guideline is to provide dermatologists as well as general practitioners with an evidence-based tool for choosing an efficacious and safe therapy for patients with androgenetic alopecia. © 2011 The Authors • JDDG © 2011 Blackwell Verlag GmbH, Berlin.

Androgens have profound effects on scalp and body hair in humans. Scalp hair grows constitutively in the absence of androgens, while body hair growth is dependent on the action of androgens. Androgenetic alopecia, referred to as male pattern hair loss (MPHL) in men and female pattern hair loss (FPHL) in women, is due to the progressive miniaturization of scalp hair. Observations in both eunuchs, who have low levels of testicular androgens, and males with genetic 5alpha-reductase (5alphaR) deficiency, who have low levels of dihydrotestosterone (DHT), implicate DHT as a key androgen in the pathogenesis of MPHL in men. The development of finasteride, a type 2-selective 5alphaR inhibitor, further advanced our understanding of the role of DHT in the pathophysiology of scalp alopecia. Controlled clinical trials with finasteride demonstrated improvements in scalp hair growth in treated men associated with reductions in scalp DHT content, and a trend towards reversal of scalp hair miniaturization was evident by histopathologic evaluation of scalp biopsies. In contrast to its beneficial effects in men, finasteride did not improve hair growth in postmenopausal women with FPHL. Histopathological evaluation of scalp biopsies confirmed that finasteride treatment produced no benefit on scalp hair in these women. These findings suggest that MPHL and FPHL are distinct clinical entities, with disparate pathophysiologies. Studies that elucidate the molecular mechanisms by which androgens regulate hair growth would provide greater understanding of these differences. Copyright 2002 Elsevier Science Ireland Ltd.