SciCombinator

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Concept: Facial hair

509

We report a genome-wide association scan in over 6,000 Latin Americans for features of scalp hair (shape, colour, greying, balding) and facial hair (beard thickness, monobrow, eyebrow thickness). We found 18 signals of association reaching genome-wide significance (P values 5 × 10(-8) to 3 × 10(-119)), including 10 novel associations. These include novel loci for scalp hair shape and balding, and the first reported loci for hair greying, monobrow, eyebrow and beard thickness. A newly identified locus influencing hair shape includes a Q30R substitution in the Protease Serine S1 family member 53 (PRSS53). We demonstrate that this enzyme is highly expressed in the hair follicle, especially the inner root sheath, and that the Q30R substitution affects enzyme processing and secretion. The genome regions associated with hair features are enriched for signals of selection, consistent with proposals regarding the evolution of human hair.

Concepts: Protein, United States, Spanish language, Facial features, Hair, Hair follicle, Facial hair, Moustache

172

Body hair shafts from the beard, trunk, and extremities can be used to treat baldness when patients have inadequate amounts of scalp donor hair, but reports in the literature concerning use of body hair to treat baldness are confined to case reports.

Concepts: Human body, Hair, Hair transplantation, Scalp, Facial hair, Follicular unit transplantation, Follicular Unit Extraction, Beard

168

Studies on bimatoprost were performed with two objectives: (i) to determine whether bimatoprost possesses hair growth-stimulating properties beyond eyelash hypertrichosis and (ii) to investigate the biodisposition of bimatoprost in skin for the first time. Bimatoprost, at the dose used clinically for eyelash growth (0.03%) and given once daily for 14 days, increased pelage hair growth in C57/black 6 mice. This occurred as a much earlier onset of new hair growth in shaved mice and the time taken to achieve complete hair regrowth, according to photographic documentation and visual assessment. Bimatoprost biodisposition in the skin was determined at three concentrations: 0.01%, 0.03% and 0.06%. Dose-dependent C(max) values were obtained (3.41, 6.74, 12.3 μg/g tissue), and cutaneous bimatoprost was well maintained for 24 h following a single dose. Bimatoprost was recovered from the skin only as the intact molecule, with no detectable levels of metabolites. Thus, bimatoprost produces hypertrichosis as the intact molecule.

Concepts: Skin, Tissue, According to Jim, Mouse, Hair follicle, Keratin, Facial hair, Hair removal

167

Ginger (Zingiber officinale) has been traditionally used to check hair loss and stimulate hair growth in East Asia. Several companies produce shampoo containing an extract of ginger claimed to have anti-hair loss and hair growth promotion properties. However, there is no scientific evidence to back up these claims. This study was undertaken to measure 6-gingerol, the main active component of ginger, on hair shaft elongation in vitro and hair growth in vivo, and to investigate its effect on human dermal papilla cells (DPCs) in vivo and in vitro. 6-Gingerol suppressed hair growth in hair follicles in culture and the proliferation of cultured DPCs. The growth inhibition of DPCs by 6-gingerol in vitro may reflect a decrease in the Bcl-2/Bax ratio. Similar results were obtained in vivo. The results of this study showed that 6-gingerol does not have the ability to promote hair growth, on the contrary, can suppress human hair growth via its inhibitory and pro-apoptotic effects on DPCs in vitro, and can cause prolongation of telogen phase in vivo. Thus, 6-gingerol rather than being a hair growth stimulating drug, it is a potential hair growth suppressive drug; i.e. for hair removal.

Concepts: In vivo, In vitro, Hair, Hair care, Hair follicle, Ginger, Facial hair, Long hair

162

Case study A boy aged 6 years was referred to our clinic for evaluation of the presence of fair, thin hair on both of his elbows. This condition had first been observed when he was 2 years of age and the hair had subsequently increased in length and thickness (Figure 1). He had a history of asthma and was being treated by a paediatrician. His family medical record was otherwise unremarkable. This unusual hairiness was symmetrically distributed on the extensor surfaces of both proximal forearms and distal arms. The underlying skin showed no abnormalities. No hypertrichosis was found elsewhere and examination of teeth, skeleton and fingernails was also normal. No other morphological changes were noted. In addition, his height was appropriate for his age. No developmental, mental or physical impairment was observed. The blood cell count and general biochemistry, as well as thyroid and sexual hormonal profiles were all normal. Radiological examination, which was performed on the parents' request, was normal. The boy was diagnosed with hypertrichosis cubiti (HC), and shaving of the areas was recommended.

Concepts: Scientific method, Protein, Height, Hair, Hair follicle, Keratin, Facial hair, Long hair

31

Propolis is a natural honeybee hive product with the potential for use in the treatment of dermatological conditions, such as cutaneous abrasions, burns, and acne. In this study, we investigated whether propolis stimulates hair growth in mice. Ethanol-extracted propolis, which contains various physiologically active substances such as caffeic acid and kaempferol, stimulated anagen induction in the shaved back skin. Anagen induction occurred without any detectable abnormalities in the shape of the hair follicles (HFs), hair stem cells in the bulge, proliferating hair matrix keratinocytes in the hair bulb, or in the localization of versican in the dermal papilla. Propolis treatment also stimulated migration of hair matrix keratinocytes into the hair shaft in HFs during late anagen in the depilated back skin. Organotypic culture of skin containing anagen stage HFs revealed significant stimulation of hair matrix keratinocyte proliferation by propolis. Furthermore, propolis facilitated the proliferation of epidermal keratinocytes. These results indicate that propolis stimulates hair growth by inducing hair keratinocyte proliferation.

Concepts: Skin, Epidermis, Caffeic acid, Hair, Hair follicle, Facial hair, Sebaceous gland, Propolis

30

Negative frequency-dependent sexual selection maintains striking polymorphisms in secondary sexual traits in several animal species. Here, we test whether frequency of beardedness modulates perceived attractiveness of men’s facial hair, a secondary sexual trait subject to considerable cultural variation. We first showed participants a suite of faces, within which we manipulated the frequency of beard thicknesses and then measured preferences for four standard levels of beardedness. Women and men judged heavy stubble and full beards more attractive when presented in treatments where beards were rare than when they were common, with intermediate preferences when intermediate frequencies of beardedness were presented. Likewise, clean-shaven faces were least attractive when clean-shaven faces were most common and more attractive when rare. This pattern in preferences is consistent with negative frequency-dependent selection.

Concepts: Selection, Facial hair, Secondary sex characteristic, Shaving, Beard

28

In many species, male secondary sexual traits have evolved via female choice as they confer indirect (i.e. genetic) benefits or direct benefits such as enhanced fertility or survival. In humans, the role of men’s characteristically masculine androgen-dependent facial traits in determining men’s attractiveness has presented an enduring paradox in studies of human mate preferences. Male-typical facial features such as a pronounced brow ridge, a more robust jawline may signal underlying health while beards may signal men’s age and masculine social dominance. However, masculine faces are judged as more attractive for short-term relationships over less masculine faces, while beards are judged as more attractive than clean-shaven faces for long-term relationships. Why such divergent effects occur between preferences for two sexually dimorphic traits remains unresolved. In the present study, we used computer graphic manipulation to morph male faces varying in facial hair from clean-shaven, light stubble, heavy stubble and full beards to appear more (+25% and +50%) or less (-25% and -50%) masculine. Women (N=8520) were assigned to treatments wherein they rated these stimuli for physical attractiveness in general, for a short-term liaison or a long-term relationship. Results showed a significant interaction between beardedness and masculinity on attractiveness ratings. Masculinized and, to an even greater extent, feminized faces were less attractive than unmanipulated faces when all were clean-shaven, and stubble and beards dampened the polarising effects of extreme masculinity and femininity. Relationship context also had effects on ratings, with facial hair enhancing long-term, and not short-term, attractiveness. Effects of facial masculinisation appears to have been due to small differences in the relative attractiveness of each masculinity level under the three treatment conditions and not to any change in the order of their attractiveness. Our findings suggest that beardedness may be attractive when judging long-term relationships as a signal of intra-sexual formidability and the potential to provide direct benefits to females. More generally, our results hint at a divergence of signalling function, which may result in a subtle trade-off in women’s preferences, for two highly sexually dimorphic androgen-dependent facial traits. This article is protected by copyright. All rights reserved.

Concepts: Male, Sexual selection, Gender, Interpersonal relationship, Man, Physical attractiveness, Facial hair, Beard

28

Background:  Although there are clinical reports of hair loss associated with levodopa and dopamine agonists, it is unclear whether dopamine exerts any direct effects on the human hair follicle (HF). Objectives:  Given the widespread use of dopamine agonists and antagonists in clinical medicine, we sought to determine whether dopamine exerts direct effects on human HF growth and pigmentation in vitro, and whether human HFs express dopamine receptors (DRs). Methods:  Microdissected human scalp HFs from women were treated in serum-free organ culture for 7 days with dopamine (10-1000 nmol L(-1) ), and the effects on hair shaft production, HF cycling (i.e. anagen-catagen transition), hair matrix keratinocyte proliferation and apoptosis, and HF pigmentation were measured by quantitative (immuno)histomorphometry. Results:  Dopamine had no consistent effect on hair shaft production, but did promote HF regression (catagen). It was also associated with significantly reduced proliferation of HF matrix keratinocytes (P < 0.01) and reduced intrafollicular melanin production. Dopamine receptor transcripts were identified in HFs and skin. Conclusions:  These data provide evidence that dopamine is an inhibitor of human hair growth, via the promotion of catagen induction, at least in vitro. This may offer a rational explanation for the induction of telogen effluvium in some women treated with dopamine agonists such as bromocriptine. Moreover, dopaminergic agonists deserve further exploration as novel inhibitors of unwanted human hair growth (hirsutism, hypertrichosis).

Concepts: Skin, Dopamine receptor, Dopamine, Hair, Hair follicle, Facial hair, Dopamine agonists, Dopamine agonist

10

We previously demonstrated that whole hair follicles could be cryopreserved to maintain their stem-cells differentation potential. In the present study, we demonstrated that cryopreserved mouse whisker hair follicles maintain their hair growth potential. DMSO better cryopreserved mouse whisker follicles compared to glycerol. Cryopreserved hair follicles also maintained the hair follicle-associated-pluripotent (HAP) stem cells, evidenced by P75NTR expression. Subcutaneous transplantation of DMSO-cryopreserved hair follicles in nude mice resulted in extensive hair fiber growth over 8 weeks, indicating the functional recovery of hair shaft growth of cryopreserved hair follicles.

Concepts: Present, Gene, Mouse, Hair, Hair follicle, Cryobiology, Facial hair, Cryoprotectant