Androgen Receptor Accelerates Premature Senescence of Human Dermal Papilla Cells in Association with DNA Damage

et al. (2013) Androgen Receptor Accelerates Premature Senescence of Human Dermal Papilla Cells in Association with DNA Damage. PLoS ONE 8(11): e79434. doi:10.1371/journal.pone.0079434 Androgen Receptor Accelerates Premature Senescence of Human Dermal Papilla Cells in Association with DNA Damage Yo Kang 0 Yi-Chien Yang 0 Hung-Chun Fu 0 Ching-Yuan Wu 0 Kuo-Ting Wei 0 Ko-En Huang 0 Hong- 0 Arianna L. Kim, Columbia University Medical Center, United States of America 0 1 Department of Dermatology, Kaohsiung Chang Gung Memorial Hospital , Kaohsiung, Taiwan , 2 Department of Obstetrics and Gynecology, Kaohsiung Chang Gung Memorial Hospital , Kaohsiung, Taiwan , 3 Department of Chinese Medicine, Chang Gung Memorial Hospital , Chiayi, Taiwan , 4 Graduate Institute of Clinical Medical Sciences, Chang Gung University, College of Medicine, Kaohsiung, Taiwan, 5 Center for Menopause and Reproductive Research, Kaohsiung Chang Gung Memorial Hospital , Kaohsiung , Taiwan The dermal papilla, located in the hair follicle, expresses androgen receptor and plays an important role in hair growth. Androgen/Androgen receptor actions have been implicated in the pathogenesis of androgenetic alopecia, but the exact mechanism is not well known. Recent studies suggest that balding dermal papilla cells exhibit premature senescence, upregulation of p16INK4a, and nuclear expression of DNA damage markers. To investigate whether androgen/AR signaling influences the premature senescence of dermal papilla cells, we first compared frontal scalp dermal papilla cells of androgenetic alopecia patients with matched normal controls and observed that premature senescence is more prominent in the dermal papilla cells of androgenetic alopecia patients. Exposure of androgen induced premature senescence in dermal papilla cells from non-balding frontal and transitional zone of balding scalp follicles but not in beard follicles. Overexpression of the AR promoted androgen-induced premature senescence in association with p16INK4a upregulation, whereas knockdown of the androgen receptor diminished the effects of androgen. An analysis of c-H2AX expression in response to androgen/androgen receptor signaling suggested that DNA damage contributes to androgen/androgen receptor-accelerated premature senescence. These results define androgen/androgen receptor signaling as an accelerator of premature senescence in dermal papilla cells and suggest that the androgen/androgen receptor-mediated DNA damagep16INK4a axis is a potential therapeutic target in the treatment of androgenetic alopecia. - Funding: This study was supported by grants GMRPG89091 (12), CMRPG86026(13), CMRPG8A106(12), and CMRPD891182 from Kaohsiung Chang Gung Memorial Hospital. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Androgenetic alopecia (AGA) is an androgen-mediated disorder that causes hair thinning in a defined pattern [1,2]. The prevalence of AGA increases with aging, from 31% at age 40 55 years to 53% at age 6569 years [3]. However, the pathogenetic mechanisms underlying AGA are not fully understood. The skin and the pilosebaceous unit are androgen target tissues. In dermal papilla cells (DPCs), the major circulating androgen, testosterone (T), can be locally metabolized to dihydrotestosterone (DHT) by steroid 5a-reductase. Based on its affinity for binding to the androgen receptor (AR), DHT is ten-fold more potent than testosterone [4]. According to the observation that male subjects with genetic deficiency of type 2 5a-reductase do not develop scalp hair loss [5], DHT has been suggested to be a major determinant in the pathophysiology of AGA in men. In AGA, DPCs from androgen-sensitive frontal scalp contain more AR and steroid 5a-reductase than those from androgen-insensitive occipital scalp [6]. AGA is characterized by miniaturization of hair follicles in the androgen-sensitive frontal scalp. The volume of dermal papilla (DP) depends on its number of DPCs and the amount of extracellular matrix, and correlates with the size of the hair fiber produced [7]. Whereas previous studies have shown that androgens do not alter the proliferation of DPCs [8,9]. In clinical observations, blocking the conversion of T to DHT with finasteride, a 5a reductase inhibitor, does not reverse miniaturized follicles to thick hair fibers in advanced AGA [10], suggesting that androgens/AR might irreversibly cause the damage of hair follicles. Premature senescence is thought to accelerate the appearance of senescent phenotypes in cells upon exposure to sublethal stressors [11]. Several studies have shown that senescent cells are morphologically altered (enlarged and flattened) [12], and express more extracellular matrix-degrading proteases, collagenase, and matrix metalloproteinases [13,14]. In addition to its ability to deplete the renewal capacity of tissues by causing proliferative arrest, senescence may contribute to aging by influencing neighboring cells be means of secretory molecules thus disrupting the integrity and homeostasis of tissues [1517]. A recent study indicated that balding DPCs undergo premature senescence in vitro in association with expression of senescence-associated bgalactosidase (SA b-gal) and p16INK4a protein, and markers of oxidative and DNA damage [18]. It has been known that the DNA-damage response is a central mediator in triggering cellular senescence [19] and androgens act as DNA-damaging agents that generate DNA double-strained breaks (DSBs) and thus facilitate chromosomal translocation in androgen-sensitive prostate cancer cell lines [20]. However, how androgen/AR signaling leads to DNA damage in DPCs has not been elucidated. To examine whether androgens may contribute to premature senescence by promoting DNA damage in DPCs of AGA patients, we cultured DPCs obtained from the frontal scalp of AGA and non-AGA individuals and determined their senescence phenotypes and investigated the effects of androgen/AR signaling on the development of premature senescence. We also studied the p16INK4a protein and the relationship between androgen/AR signaling and DNA damage markers to elucidate the possible mechanisms of androgen/AR-accelerated premature senescence in DPCs. Materials and Methods Ethics Statements The Chang Gung Medical Foundation institutional review board approved all described studies (protocol number 99-1933B). The study was conducted according to the Declaration of Helsinki Principles. Informed written consent was obtained from all patients. Isolation and Culture of Human DPCs Specimens were taken from beard, transitional zone of balding, balding or non-balding frontal scalps of ten males undergoing surgical excision of benign cutaneous tumors. The donors of beard specimen were aged 28 and 34 years, and the donor of transitional zone of balding scalp was aged 38 an (...truncated)