Article

The Biology of Hair Follicles

Department of Dermatology, University Hospital Eppendorf, University of Hamburg, Germany.
New England Journal of Medicine (Impact Factor: 55.87). 09/1999; 341(7):491-7. DOI: 10.1056/NEJM199908123410706
Source: PubMed
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    • "Hair growth is controlled by a unique repetitive cycle comprising a hair fiber production phase (anagen), a brief regression phase (catagen) and a resting period (telogen) (Stenn et al., 1996;Paus and Cotsarelis, 1999). The regulatory mechanism of the hair cycle has not yet been fully understood as several factors were implicated to exert their specific roles in hair growth control. "

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    • "D. brevis, on the other hand, primarily inhabits the sebaceous glands associated with vellus hairs [11], typically at densities of just one to a few mites per gland. With approximately 5 million hair follicles spread across the body [12] and more than 7 billion humans on Earth, the total habitat area available to these mites is immense. Methods used to collect Demodex mites from humans include biopsy, the cellophane tape method (placing tape on the face to stick to the mites), scraping areas where mites are likely to reside, and plucking eyelash and eyebrow hairs. "
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    ABSTRACT: Demodex mites are a group of hair follicle and sebaceous gland-dwelling species. The species of these mites found on humans are arguably the animals with which we have the most intimate interactions. Yet, their prevalence and diversity have been poorly explored. Here we use a new molecular method to assess the occurrence of Demodex mites on humans. In addition, we use the 18S rRNA gene (18S rDNA) to assess the genetic diversity and evolutionary history of Demodex lineages. Within our samples, 100% of people over 18 years of age appear to host at least one Demodex species, suggesting that Demodex mites may be universal associates of adult humans. A phylogenetic analysis of 18S rDNA reveals intraspecific structure within one of the two named human-associated Demodex species, D. brevis. The D. brevis clade is geographically structured, suggesting that new lineages are likely to be discovered as humans from additional geographic regions are sampled.
    Full-text · Article · Aug 2014 · PLoS ONE
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    • "The DP is a discrete population of specialized dermal fibroblasts found at the base of the hair follicle (Paus and Cotsarelis, 1999), and plays a central role in hair follicle morphogenesis (Jahoda and Reynolds, 2000; Reynolds et al., 1999) and mesenchymal-epithelial interactions (Richardson et al., 2005). DP cells have been the focus of much interest because the DP not only regulates hair follicle development and growth, but is also thought to be a reservoir of multipotent stem cells (Driskell et al., 2011). "
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    ABSTRACT: Crude Panax ginseng has been documented to possess hair growth activity and is widely used to treat alopecia, but the effects of ginsenoside Rg3 on hair growth have not to our knowledge been determined. The aim of the current study was to identify the molecules through which Rg3 stimulates hair growth. The thymidine incorporation for measuring cell proliferation was determined. We used DNA microarray analysis to measure gene expression levels in dermal papilla (DP) cells upon treatment with Rg3. The mRNA and protein expression levels of vascular endothelial growth factor (VEGF) in human DP cells were measured by real-time polymerase chain reaction and immunohistochemistry, respectively. We also used immunohistochemistry assays to detect in vivo changes in VEGF and 3-stemness marker expressions in mouse hair follicles. Reverse transcription polymerase chain reaction showed dose-dependent increases in VEGF mRNA levels on treatment with Rg3. Immunohistochemical analysis showed that expression of VEGF was significantly up-regulated by Rg3 in a dose-dependent manner in human DP cells and in mouse hair follicles. In addition, the CD8 and CD34 were also up-regulated by Rg3 in the mouse hair follicles. It may be concluded that Rg3 might increase hair growth through stimulation of hair follicle stem cells and it has the potential to be used in hair growth products. Copyright © 2013 John Wiley & Sons, Ltd.
    Full-text · Article · Jul 2014 · Phytotherapy Research
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