The Biology of Hair Growth

Randall, Valerie A.; Botchkareva, Natalia V.

doi:10.1016/b978-0-8155-1572-2.50006-3

Cited by 22 publications

(30 citation statements)

References 171 publications

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“…This region is also commonly described as the bulge, and contains a population of epithelial HF stem cells, the identity of which has recently been reviewed . The progeny of these stem cells produce the hair bulb matrix keratinocytes, as well as contributing to the formation of the epidermis, particularly during wound healing, and it is damage to these cells that severely impairs long‐term hair shaft production . The suprabulbar region contains multiple layers of the outer root sheath (ORS) and inner root sheath (IRS), which form concentric cylinders wrapping the hair shaft itself (Fig.…”

Section: The Hair Folliclementioning

confidence: 99%

“…The hair bulb contains the matrix keratinocytes, a population of rapidly‐dividing progenitor cells that differentiate (specialize) to form the IRS and hair shaft. Matrix cells in the lower part of the hair bulb have a higher mitotic (proliferation) rate than those of the upper part and migrate upwards while differentiating . The bulb also contains the HF pigmentary unit, within which are found the melanocytes responsible for hair color.…”

Section: The Hair Folliclementioning

confidence: 99%

“…The old hair shaft forms the club hair, which comes to reside entirely in the dermis. Overall, catagen lasts for 7–14 days, with ∼2% of scalp HFs estimated to be in catagen at any one time .…”

Section: The Hair Folliclementioning

confidence: 99%

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A Clinical and Biological Guide for Understanding Chemotherapy-Induced Alopecia and Its Prevention

et al. 2017

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Chemotherapy-induced alopecia (CIA) represents perhaps the most distressing side effect of chemotherapeutic agents and is of huge concern to the majority of patients. Scalp cooling is currently the only safe option to combat CIA. Clinical and biological evidence suggests improvements can be made, including efficacy in delivering adequately low temperature to the scalp and patient-specific cap design. The increased use of scalp cooling, an understanding of how to deliver it most effectively, and biological evidence-based approaches to improve its efficacy have enormous potential to ease the psychological burden of CIA, as this could lead to improvements in treatment and patient quality-of-life.

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Section: The Hair Folliclementioning

confidence: 99%

Section: The Hair Folliclementioning

confidence: 99%

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A Clinical and Biological Guide for Understanding Chemotherapy-Induced Alopecia and Its Prevention

et al. 2017

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“…Such thermodynamic heating further leads to: chemical denaturation of cellular proteins and phospholipid membranes causing irreversible damage to the HF cells. modification of activity of the signalling pathways that control hair growth and cycling of the HF . …”

Section: Introductionmentioning

confidence: 99%

Light‐based home‐use devices for hair removal: Why do they work and how effective they are?

et al. 2019

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Objectives This review has the following objectives: Firstly, it provides an explanation of the evolution of laser/intense pulsed light (IPL) hair reduction modalities from high fluence professional devices to low fluence home‐use appliances. Secondly, it summarises published literature reviews on home‐use devices (HUDs) as evidence of their growing credibility. Thirdly, it proposes mechanistic differences in light delivery regimes and the resulting divergences in mode of action. Materials and Methods An extensive literature search was performed to review the progress of laser/IPL‐induced hair reduction and determine what evidence is available to explain the mode of action of professional and HUDs for hair removal. Establishing the likely biological mode of action of professional high‐fluence systems versus home‐use low‐fluence appliances was performed by combining data obtained using ex vivo hair follicle (HF) organ culture and the clinical results involving human participants. Results Significant basic science and clinical evidence has been published to confirm the clinical efficacy and technical safety of many laser and IPL home‐use devices for hair removal. Clearly, HUDs are different compared to professional systems both in terms of fluence per pulse and in terms of biological mechanisms underlying hair removal. Here we presented data showing that a single low fluence pulse of both 810 nm laser (6.6 J/cm2, 16 ms) and IPL (9 J/cm2, 15 ms and 6.8 J/cm2, 1.9 ms) leads to induction of catagen transition. Catagen transition was characterized by morphological changes similar to what occurs in vivo with occasional detection of apoptosis in the dermal papilla and outer root sheath cells. This suggests that high hair reduction can be expected in vivo and longer‐term treatment might result in HF miniaturization due to a cumulative effect on the dermal papilla and outer root sheath cells. In line with this hypothesis, in this review we demonstrate that long‐term application of a commercially‐available home‐use IPL appliance resulted in persistent hair reduction (80%) one year after last treatment. These data are in line with what was previously reported in the literature, where clinical studies with home‐use IPL appliances demonstrated high efficacy of hair reduction on female legs, armpits and bikini zones, with full hair regrowth after four treatments following cessation of IPL administration. Limitations of HUDs include lack of hair clearance for very dark skin types and low speed of treatment compared with professional devices. Numerous uncontrolled and controlled clinical efficacy studies and technical safety investigations on consumer‐use appliances support many of the leading manufacturers' claims. Analysis & Conclusions Manufacturers make consumer appliances safe and easy to use by considering “human factors,” needs and capabilities of a variety of users. Safety is of primary concern to manufacturers, regulators and standards bodies as these appliances may be accessible to children or their use attempted on uns...

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“…Despite that hair disorders are not life threatening, hair still play a significant role in human from aesthetics and social perspectives (Randall & Botchkareva, 2008). The treatments for alopecia patients include drug therapy or hair transplantation.…”

Section: Introductionmentioning

confidence: 99%

Induced pluripotent stem cells from human hair follicle keratinocytes as a potential source for in vitro hair follicle cloning

Lim

Mok

et al. 2016

PeerJ

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BackgroundHuman hair follicles are important for the renewal of new hairs and their development. The generation of induced pluripotent stem cells (iPSCs) from hair follicles is easy due to its accessibility and availability. The pluripotent cells derived from hair follicles not only have a higher tendency to re-differentiate into hair follicles, but are also more suited for growth in hair scalp tissue microenvironment.MethodsIn this study, human hair follicular keratinocytes were used to generate iPSCs, which were then further differentiated in vitro into keratinocytes. The derived iPSCs were characterised by using immunofluorescence staining, flow cytometry, and reverse-transcription PCR to check for its pluripotency markers expression.ResultsThe iPSC clones expressed pluripotency markers such as TRA-1-60, TRA-1-81, SSEA4, OCT4, SOX2, NANOG, LEFTY, and GABRB. The well-formed three germ layers were observed during differentiation using iPSCs derived from hair follicles. The successful formation of keratioctyes from iPSCs was confirmed by the expression of cytokeratin 14 marker.DiscussionHair follicles represent a valuable keratinocytes source for in vitro hair cloning for use in treating hair balding or grafting in burn patients. Our significant findings in this report proved that hair follicles could be used to produce pluripotent stem cells and suggested that the genetic and micro-environmental elements of hair follicles might trigger higher and more efficient hair follicles re-differentiation.

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The Biology of Hair Growth

Cited by 22 publications

References 171 publications

A Clinical and Biological Guide for Understanding Chemotherapy-Induced Alopecia and Its Prevention

A Clinical and Biological Guide for Understanding Chemotherapy-Induced Alopecia and Its Prevention

Light‐based home‐use devices for hair removal: Why do they work and how effective they are?

Induced pluripotent stem cells from human hair follicle keratinocytes as a potential source for in vitro hair follicle cloning

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