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The human hair: From anatomy to physiology
Abstract
Hair is a unique character of mammals and has several functions, from protection of the skin to sexual and social communication. In literature, there are various studies about hair that take into consideration different aspects within many fields of science, including biology, dermatology, cosmetics, forensic sciences, and medicine.
We carried out a search of studies published in PubMed up to 2013.
In this review, we summarized the principal anatomical and physiological aspects of the different types of human hair, and we considered the clinical significance of the different structures and the distribution of the hair in the human body.
This review could be the basis for improvement and progression in the field of hair research.
... Derived from the epidermis, hair comprises two distinct parts: a visible shaft on the skin's surface and a follicle within it ( Figure 1). 20 Among the growth phase, the hair shaft (HS) has three primary concentric areas: the medulla, cortex and cuticle. 21 The hair follicle (HF) has an essential role in hair growth, 20 forming a pilosebaceous unit alongside the sebaceous gland (SG) and arrector pili muscle (APM). ...
... 20 Among the growth phase, the hair shaft (HS) has three primary concentric areas: the medulla, cortex and cuticle. 21 The hair follicle (HF) has an essential role in hair growth, 20 forming a pilosebaceous unit alongside the sebaceous gland (SG) and arrector pili muscle (APM). 22 The HF consists of three segments, which are lower, middle, and upper: the lower segment is the region from the base of the HF to the insertion of APM and could be divided into the bulb and suprabulb regions; the middle segment (isthmus) is short and extends from the insertion of APM to the meatus of the SG duct; the upper segment (infundibulum) spans from the meatus of the SG duct to the follicular orifice. ...
... 21 The suprabulb region lies between the isthmus and the hair bulb (HB), consisting of the HS, inner root sheath (IRS), outer root sheath (ORS), vitreous layer (VR) and fibrous root sheath (FRS). 21 IRS has three layers: Henle's layer, Huxley's layer, and cuticle, the latter layer being adjacent to the cuticle of HS and thus anchors HS to HF. 20 The IRS acts as a divider between the HS and ORS. 20 The ORS shields the IRS while it rises from the matrix cells at the bottom side of the HB to the meatus of the SG duct. ...
Alopecia is considered a widespread yet troubling health issue, with limited treatment options. As membranous structures derived from cells carrying proteins, nucleic acids and lipids, exosomes functionally medicate intercellular communication and alter the responses of recipient cells, resulting in disease restraint or promotion. Exosomes have broad prospects in diagnosis and treatment of diseases. Studies using animal models and at the cellular level have clearly shown that exosomes from several types of cells, including dermal papilla cells and mesenchymal stem cells, have a notable capacity to promote hair growth, suggesting that exosomes may provide a new option to treat alopecia. Here, we present a thorough review of the most recent progress in the application of exosomes to hair growth.
... 4 The content of different types of melanin in the hair is an individual feature. 4,5 Melanin is a natural protection against the negative effects of UV rays. The protective effect of melanin is based on the principle of absorbing UV rays and protecting against free radicals. ...
... These should be left-on products so that it stays on the surface of the hair and protect it from UV rays penetrating the cuticle. 5 Biological changes in hair pigment include its darkening or lightening observed occasionally at a very young age, or graying. 4,6 In the course of particular diseases, there might be also a change in hair color. ...
... The hair becomes less resistant to mechanical damage and becomes brittle. 5 Exposure to UV radiation leads to the oxidation of lipid and protein components of the hair. Although melanin provides some protection against the oxidation process, the hair becomes lighter and lighter, due to the oxidation of the hair dyes. ...
Background
Solar radiation is responsible for changes in the structure of human hair, the damages include proteins (65%–95%), lipids, and melanin. The aim was to examine the effectiveness of sunscreen in hair cosmetics and whether hair color affects it.
Materials and Methods
The study included nine women, divided according to hair color to three groups: light, dark, and gray hair. The 410‐Solar reflectometer was used in five time points. The hair was divided into three strands, one product applied to each.
Results
Dark hair showed the highest absorption of radiation in all wavelength ranges, the reflectance before products application was significantly higher than the hair reflectance immediately after application. The effect of sunscreens on light hair reflectance was found at wavelengths 400 and 720 nm and between 1000 and 2500 nm, the reflectance before application was significantly higher than the reflectance after. The use of products on gray hair did not have a significant effect on hair reflectance at wavelengths 400–1100 nm, the effect of sunscreens on the gray hair reflectance was observed in the UV and infrared range, the reflectance before application was significantly higher than immediately after.
Conclusions
The results showed that the 410‐Solar reflectometer is useful to assess the effectiveness of hair sunscreens. All three tested hair products do not show the expected protection properties. Dark hair showed the highest absorption of radiation in all wavelength ranges, suggesting that dark hair should be more protected against radiation than light and gray hair.
... Włosy są wytworem naskórka i wyrastają z mieszków włosowych -zagłębień w skórze o kształcie kanału, w których znajduje się cebulka włosa [14]. ...
... Na dnie mieszka włosowego znajduje się dobrze unaczyniona brodawka włosa, której funkcją jest zaopatrywanie cebulki w składniki odżywcze [15]. U zdrowych osób faza anagenu trwa zazwyczaj od 3 do 5 lat [14] i w każdej chwili znajduje się w niej ok. 90% włosów głowy [16]. ...
Prostaglandins are hormones found in almost all mammalian tissues. As signaling molecules, they play a key role in the regulation of many physiological processes, including hair growth cycle. The article describes the history of the discovery of prostaglandins, including the work of Professor Ryszard Gryglewski - the discoverer of prostacyclin. Particular attention was paid to the synthetic analogue of prostaglandin F2α - latanoprost. Indicated for the treatment of glaucoma, the drug is known for inducing eyelash growth as a side effect. A prodrug, latanoprost is converted to its active metabolite, latanoprost acid. Recent research demonstrated that latanoprost acid has a chance to become an effective alternative to minoxidil and finasteride - the only drugs currently registered for the treatment of androgenetic alopecia. The development of anti-alopecia drugs containing prostaglandin derivatives, including latanoprost acid, will be a much faster process compared to the traditional path of product development based on a new chemical compound.
... The entire scalp may become infected as the condition spreads. Close to the center of the circular patch, the skin of the infected area of the scalp may be normal; nevertheless, the edges are likely to show signs of irritation, redness, or inflammation [38]. Alopecia, redness, itching, and scale formation are all signs of tinea capitis. ...
The purpose of this research was to identify the role of keratin proteins in causing inherited as well as pathogenic alopecia, pinpoint deleterious SNPs, and predict structural changes affecting protein-protein interactions in hair disorders. To elucidate the role of keratin proteins and genetic mutations in alopecia by analyzing protein structures through bioinformatics and identifying a mutation in the LPAR6 gene. It sought to identify the microorganisms linked to alopecia and conducted a comprehensive bioinformatics analysis of proteins with unknown experimental structures and molecular simulation analysis. The study identified a genetic mutation (c.188 A > T, p.Asp63Val) in the LPAR6 gene associated with hereditary hair loss. Pathogenic alopecia was identified to be associated with S. aureus and two ic keratinophilic fungi namely M. canis, and T. violaceum. Additionally, among 14 proteins lacking prior structural information, four proteins namely Keratin, type II cuticular Hb3 (KR1), Keratin, type II cuticular Hb6 (KR2), Keratin, type II cytoskeletal 74 (KR3) and Keratin, type II cuticular Hb1 (KR4) exhibited common ‘K-head’ and ‘F’ domains. Docking analysis revealed five distinct binding sites (C1-C5) for each protein. The ‘K-head’ displayed the highest predicted binding affinities with Vina scores of -5.6 for KR2 and − 4.7 for KR4 whereas the ‘F’ domain showed Vina scores of -6.0 for KR3 and − 5.7 for KR2. This research underscores the crucial role of keratin proteins in both hereditary and pathogenic alopecia, emphasizing their significance for future investigations.
... Hair is one of the characteristic features of mammals and has various functions, such as protection against external factors; producing sebum, sweat, and pheromones; thermoregulation and being a resource for stem cells [35,36]. The most common phenomenon of aging in hair is greying. ...
... However, there are insufficient studies on the macroscopic appearance of cricetid hair spines and bat claws. Mammalian hairs are broadly variable in shape and structure, and this variation is related to each species, climates, adaptations, their functions in organs, body position, populations, and alleles (Kondo 2000;Meyer et al. 2002;Buffoli et al. 2014). Furthermore, the observed claw-size similarities and differences may be related to the roosting and fossorial habits of bats and rodents because the evolution, together with different lifestyles and habits, has influenced the form and function of claws in mammals (Maiolino et al. 2011). ...
Phyllostomus discolor is considered an omnivore, with a high consumption of nectar. The consumption of vertebrates has never been do-cumented in P. discolor. However, there is a documented attack on Eptesicus furinalis, and frog remains were found under a colony of this bat. We obtained a fecal sample from P. discolor, which contained a potential record of mammal predation. The main objective of this study was to compare this sample with the anatomy of some small mammals occurring in the Chocó, as well as report other findings from this sample. We contrasted a part of the sample with photographs of bats and rodents’ claws. We applied a PCA analysis to compare this part of the sample with bat and rodent claw sizes. We used field guides and literature to identify insects, seeds, and minerals. The sample contained insects, gravel, one seed, hair spines, and a claw. The spines found were morphologically more related to the spines identified in Neacomys marci in comparison to Heteromys australis. Although the claw shape-size was similar to N. marci, some bats had a similar appearance, and the differences were small. This note would represent the first potential record of P. discolor hunting a mammal in natural conditions, but we recommend further analyses and comparisons on its dietary composition.
... This phase is also distinguished by the development of the onion-like shape of the hair follicle [24]. The anagen phase is divided further into two phases; pro-anagen (anagen I -V) and metanagen (anagen VI) [25]. During pro-anagen, hair progenitor cells actively proliferate and initiate the process of differentiation. ...
Human hair is characterised by significant variability, determined by genetic and macromolecular factors. Whilst European hair type has been a focus of extensive research, Afro-textured hair care faces challenges created by insufficient knowledge of its unique properties. Applications of hair care products that are incompatible with Afro-textured hair frequently have detrimental effects on the scalp, including alopecia. This highlights the need for scientific and clinical partnerships to bridge the gap between research and hair care practices and address challenges related to Afro-textured hair. In this review, we performed data mining of the existing literature and in-silico network analysis of the biomarkers relevant to Afro-textured hair. The approaches to hair maintenance are highlighted in the context of hair anatomy and growth cycles, organisation of keratins, surface lipids and chemical bonds. We discuss a range of biomarkers affecting hair fibre's shape and mechanical strength, with the gene interactive network pointing to the hierarchical organisation of important traits, notably hair shaft diameter, keratinisation, hair follicle development and patterning. We propose a better understanding of the genetic traits, molecular structure and biomechanics of Afro-textured hair is required to initiate more effective hair care solutions that would benefit the wider population.
... All mammalian body surfaces are covered with hair except for small areas such as the palms, soles, buccal surface of the lips, and parts of the external genitalia. Body hair can be divided into androgendependent hair, such as the scalp, beard, chest, axilla, and pubic hair, and androgenindependent such as the eyebrows, eyelashes, and vulvar hair (Buffoli et al., 2014). Excess facial hair is found in about 41 million women in the United States (Hamzavi et al., 2007). ...
Objective
Body hair removal plays an important role in beauty standards, particularly for women. Finding a method that is easy to use, cheap, and can be done without supervision can significantly affect long-term hair reduction and reduce the side effects of hair removal. The present study investigated the impact of a containing 20% broad bean (Vicia faba) extract cream on axillary hair removal.
Materials and Methods
Twenty-five female volunteers were randomly divided into A (right axillary intervention - left axillary placebo) and B (right axillary placebo - left axillary intervention). Depending on the group, each person used a cream containing 20% broad bean extract )"The extract made from the seeds and pods of broad beans.") on one side and a placebo on the other twice a day for three months. Volunteers shaved their axillary hairs three days before each visit and took pictures of both sides on the day of the visit with a trichoscope (to check the diameter and thickness of the hairs).
Results
We found a decrease in thickness on the intervention group (the axilla where a cream containing broad bean extract was applied); however, this difference was not significant between the intervention side and the placebo. In terms of the number of hairs, the difference between the two groups was significant only in the second month despite the decrease on the intervention side. Evaluation based on the personal judgment of the volunteers showed that there was a substantial difference in terms of the number of hairs (p=0.012) and thinning of hair (p=0.02).
Conclusion
Our findings showed that 20% broad bean extract cream could potentially reduce axillary hair growth.
... This type of hair usually extends more than 3 mm into the hypodermis. The rest of the body is covered with vellus hairs (short, thin, devoid of pigment, and located more shallowly in the skin compared with terminal hairs) [8]. ...
Diagnosis of persistent erythematous, scaly patches, or plaques can be complex since psoriasis (Ps), eczematous dermatitis (ED), and mycosis fungoides (MF) can be considered. Dermoscopy, which is a noninvasive diagnostic tool, is commonly used to examine blood vessels, scales, and background color; however, research on hair shaft evaluation in inflammatory dermatoses remains scarce. The aim of the study was dermoscopic evaluation of hair shafts in skin lesions localized on the non-scalp skin areas in patients diagnosed with MF, Ps, and ED.
This was a retrospective evaluation of 55 patients diagnosed with MF, Ps, and ED. Photographic and dermoscopic documentation of these patients and detailed medical history were evaluated.
A total of 21 patients with MF, 21 patients with Ps, and 13 patients with ED were evaluated. The examination revealed the presence of various abnormalities of hair shafts (e.g., numerous pili torti, single pili torti, 8-shaped hairs, pigtail hairs, broken hairs, hair shafts rapidly tapered over long sections, hair shafts irregular in thickness, angulated hairs, branched hairs, the presence of trichorrhexis nodosa, and monilethrix-like hairs), yellow dots, and black dots. The presence of pili torti was found in 80% of patients with MF, compared with 16% of patients with Ps and 8% of patients with ED (p < 0.005), with multiple pili torti found only in MF patients (67%) (p < 0.005). Statistically significant differences also applied to hair shafts rapidly tapering over long sections and 8-shaped hairs, which occurred only in MF patients (p < 0.005 and p = 0.035, respectively).
The presence of hair shaft abnormalities such as numerous pili torti, 8-shaped hairs, and hair shafts rapidly tapering over long sections is an important criterion that should be considered in the dermoscopic differentiation of the patchy/plaque mycosis fungoides and inflammatory dermatoses, such as psoriasis and eczematous dermatitis localized on the non-scalp skin areas.
... DHT triggers the shrinking of hair follicles, resulting in the finer vellus hair being transformed from thick terminal hair. 5α-reductase (Buffoli et al., 2013;Kučerová R et al., 2006;Thomas J, 2005) (Cole &Hfrzunger, 1984) 4 Syphilitic alopecia The disease syphilis was caused by Treponema pallidum. Individuals suffering from sudden and partial hair loss were diagnosed with syphilitic alopecia. ...
Androgenetic alopecia (AGA) is a common problem where people experience gradual hair loss, especially on the scalp. Men and women both experience it, but the most severe hair loss happens in the middle of the scalp. It often starts during puberty and can really affect how someone feels about themselves and their life. However, there are not many approved treatments available for it. Some products claim to help with hair loss, but not all of them have been proven to work. Right now, minoxidil and finasteride are approved by the Food and Drug Administration (FDA) for treating androgenetic alopecia. Additionally, the HairMax LaserComb, which has FDA clearance, is recognized by the FDA as a treatment option for this condition.
... An individual with a healthy scalp is thought to have between 50,000 and 65,000 hairs on average. [34] The three stages of the hair development cycle are anagen, catagen, and telogen. It is a complicated process. ...
Hair is an important physiological component of the human body that serves several purposes. Hair follicles on the scalp are root structures that promote hair growth. Keratin is a protein that is produced in the follicles and makes up the structure of hair. Hair serves multiple roles, including regulating body temperature and protecting against environmental elements. Hair loss or poor hair health is frequently associated with all body health and can be caused by a variety of circumstances, therefore hair health can be viewed as a mirror of overall health. Adenomatous polyposis coli down-regulated 1 (APCDD1) has been implicated in the regulation of hair follicle development and cycling. The research's newfound insights give a fresh viewpoint on the genetic causes of hair loss as well as possible areas for therapeutic intervention. Gaining insight into the molecular processes that cause hair loss could result in the creation of innovative treatment plans that enhance the lives of those who are impacted by the condition by maintaining or regaining hair follicle function. This review highlights the significance of APCDD1 and related pathways in hair follicle biology and is a major step forward in our understanding of the genetic drivers of hair loss. The information provided here paves the way for more research into the intricacies of hair loss and the creation of individualized strategies for both prevention and therapy. This review also contributes to a better understanding of the causes of hair loss and the implementation of new treatment options in this sector, since it provides a new perspective on the genetic mapping of hair loss via the APCDD1 gene pathway.
... On the outside, hair is thin, flexible tubes of fully keratinized epithelial cells. In terms of macrostructure, hair differs between ethnic groups and between individual people in terms of length, diameter, colour, and cross-sectional shape (Buffoli et al., 2014). ...
Debilitating and long-lasting, rheumatoid arthritis is an inflammatory disease that affects the bone and cartilage around joints. The whole body, including the internal organs like the heart, lungs, and eyes, may be affected by this systemic illness. Unfortunately, the efficacy of the therapeutic intervention can be compromised by the negative effects of the various synthetic drugs that are now the gold standard for rheumatoid arthritis. Unfortunately, no effective drug exists at this time to treat rheumatoid arthritis, and what little medical expertise there is mostly deals with the symptoms of the condition, such as inflammation and joint discomfort. Herbs and plants, in various forms, help alleviate joint inflammation and discomfort. The anti-rheumatoid arthritis properties of several medicinal plants have been well documented. Plants and plant extracts have significant advantages for treating rheumatoid arthritis. This review mainly focuses on medicinal herbs that have an activity on rheumatoid arthritis.
... The human hair follicle (HF) is an appendage of the skin known for its wide range of functions, from external protection and thermoregulation to social interactions [1]. The diversity of its roles is also well presented on the cellular level, where a single follicle is composed of several cell types [2] with very distinct cell-to-cell interactions [3] and multifaceted signaling [4]. ...
In vitro hair follicle models are currently limited to ex vivo hair follicle organ cultures (HFOC) or 2D models that are of low availability and do not reproduce the architecture or behavior of the hair, leading to poor screening systems. To resolve this issue, we developed a technology for the construction of a human in vitro hair construct based on the assemblage of different types of cells present in the hair organ. First, we demonstrated that epithelial cells, when isolated in vitro, have similar genetic signatures regardless of their dissection site, and their trichogenic potential is dependent on the culture conditions. Then, using cell aggregation techniques, 3D spheres of dermal papilla were constructed, and subsequently, epithelial cells were added, enabling the production and organization of keratins in hair, similar to what is seen in vivo. These reconstructed tissues resulted in the following hair compartments: K71 (inner root-sheath), K85 (matrix region), K75 (companion layer), and vimentin (dermal papilla). Furthermore, the new hair model was able to elongate similarly to ex vivo HFOC, resulting in a shaft-like shape several hundred micrometers in length. As expected, when the model was exposed to s hair growth enhancers, such as ginseng extract, or inhibitors, such as TGF-B-1, significant effects similar to those in vivo were observed. Moreover, when transplanted into skin biopsies, the new constructs showed signs of integration and hair bud generation. Owing to its simplicity and scalability, this model fully enables high throughput screening of molecules, which allows understanding of the mechanism by which new actives treat hair loss, finding optimal concentrations, and determining the synergy and antagonism among different raw materials. Therefore, this model could be a starting point for applying regenerative medicine approaches to treat hair loss.
... The growth of human hair occurs everywhere on the body except for the soles of the feet, the inside of the mouth, the lips, the backs of the ears, the palms of the hands, some external genital areas, the navel, scar tissue, and apart from eyelashes, the eyelids. 1 Appearance of hair makes an important impact on total body feature. Color, length and appearance of hair make a significant difference from person to person. 2 Indian herbs are the prosperous source to be used in cosmetic industries. ...
For maintaining healthy, attractive appearance hair has the vital role. Hair problems are common and can diminish self-esteem and selfconfidence of a person. Many forms of hair problems, baldness, alopecia, hair fall, gray hair, dryness, and most common dandruff require clinical care by a health care professional. Hair is sensitive to changes in the environment, diet, and overall health. Identifying these changes and resorting to the wisdom of Ayurveda for their coping mechanisms can help maintain good hair health. Ayurveda formulations always have attracted considerable attention because of their good activity and comparatively lesser side effects with synthetic drugs. This review gives knowledge regarding the beneficial effects and recent progress of medicinal plants for the treatment of hair disorders.
... In humans, it is a unique and priceless characteristic, especially in females, but its primary purposes to enable homeothermy and protect the skin from mechanical harm; For instance, scalp hair protects the head and neck from the sun, cold, and physical harm, while eyebrows and eyelashes prevent items from entering the eyes. 1 Having healthy hair is a sign of health, youth, and vigor for both men and women. Hair has evolved to fulfill defensive and evolutionary purposes in mammals. ...
... As the name indicates, hairy skin contains hair follicles, while glabrous skin lacks hair. Hairy skin varies further in the geometry of its hair follicles and their density, e.g., the scalp versus the rest of the body (Whitting et al. 2008;Buffoli et al. 2014;Vogt et al. 2007). The glabrous skin is found in the palms of our hands and feet. ...
The skin is the largest organ in the human body and serves various functions, including mechanical protection and mechanosensation. Yet, even though skin’s biomechanics are attributed to two main layers—epidermis and dermis—computational models have often treated this tissue as a thin homogeneous material or, when considering multiple layers, have ignored the most prominent heterogeneities of skin seen at the mesoscale. Here, we create finite element models of representative volume elements (RVEs) of skin, including the three-dimensional variation of the interface between the epidermis and dermis as well as considering the presence of hair follicles. The sinusoidal interface, which approximates the anatomical features known as Rete ridges, does not affect the homogenized mechanical response of the RVE but contributes to stress concentration, particularly at the valleys of the Rete ridges. The stress profile is three-dimensional due to the skin’s anisotropy, leading to high-stress bands connecting the valleys of the Rete ridges through one type of saddle point. The peaks of the Rete ridges and the other class of saddle points of the sinusoidal surface form a second set of low-stress bands under equi-biaxial loading. Another prominent feature of the heterogeneous stress pattern is a switch in the stress jump across the interface, which becomes lower with respect to the flat interface at increasing deformations. These features are seen in both tension and shear loading. The RVE with the hair follicle showed strains concentrating at the epidermis adjacent to the hair follicle, the epithelial tissue surrounding the hair right below the epidermis, and the bulb or base region of the hair follicle. The regions of strain concentration near the hair follicle in equi-biaxial and shear loading align with the presence of distinct mechanoreceptors in the skin, except for the bulb or base region. This study highlights the importance of skin heterogeneities, particularly its potential mechanophysiological role in the sense of touch and the prevention of skin delamination.
... Ki-67 is a widely used cell proliferation marker for the quantification of cellular expression levels during the anagen phase [26,30]. To evaluate cell proliferation, we performed Ki-67 IF staining (Fig. 2D). ...
Introduction
Hair loss is a common phenomenon associated with various environmental and genetic factors. Mitochondrial dysfunction-induced oxidative stress has been recognized as a crucial determinant of hair follicle (HF) biology. Aldehyde dehydrogenase 2 (ALDH2) mitigates oxidative stress by detoxifying acetaldehyde. This study investigated the potential role of ALDH2 modulation in HF function and hair growth promotion.
Objectives
To evaluate the effects of ALDH2 activation on oxidative stress in HFs and hair growth promotion.
Methods
The modulatory role of ALDH2 on HFs was investigated using an ALDH2 activator. ALDH2 expression in human HFs was evaluated through in vitro immunofluorescence staining. Ex vivo HF organ culture was employed to assess hair shaft elongation, while the fluorescence probe 2′,7′- dichlorodihydrofluorescein diacetate was utilized to detect reactive oxygen species (ROS). An in vivo mouse model was used to determine whether ALDH2 activation induces anagen.
Results
During the anagen phase, ALDH2 showed significantly higher intensity than that in the telogen phase, and its expression was primarily localized along the outer layer of HFs. ALDH2 activation promoted anagen phase induction by reducing ROS levels and enhancing reactive aldehyde clearance, which indicated that ALDH2 functions as a ROS scavenger within HFs. Moreover, ALDH2 activation upregulated Akt/GSK 3β/β-catenin signaling in HFs.
Conclusions
Our findings highlight the hair growth promotion effects of ALDH2 activation in HFs and its potential as a promising therapeutic approach for promoting anagen induction.
... Hair cortisol assessment is an excellent biomarker of chronic stress, correlating with salivary cortisol levels, which has been corroborated by several studies on stress in different populations [35]. The cortisol available in the hair represents the percentage of this biomarker that diffuses from the blood into the growing hair follicles and is incorporated into the hair without undergoing degradation [36,37]. ...
Background: Anxiety and stress are common mental health conditions reported by university workers. Practices of mindfulness represent one promising approach as an effective and feasible means to reduce stress, improve mental health and promote well-being; however, there are no clinical trials that have combined long-term stress biomarkers (hair cortisol) and psychometric assessments in a sample of university workers. Objective: This study investigated the effectiveness of a mindfulness-based program on long-term stress, by measuring hair cortisol concentration and perceived stress and anxiety among workers who were undergoing high levels of stress. Method: We conducted a randomized clinical trial at work among the employees of a public university. We compared a group that received the eight-week mindfulness intervention with the wait list group who received no intervention. Results: A total of 30 participants were included in the study, with n = 15 subjects in the intervention group and n = 15 in the control group. Hair cortisol, perceived stress and anxiety significantly reduced after the intervention compared to the control group, which had no appreciable decline in the measured variables. Conclusion: This clinical trial showed the effectiveness of a mindfulness program on mental health psychometric measures (perceived stress and anxiety) and on a long-term stress biomarker (hair cortisol). It can be concluded that an eight-week mindfulness program could be implemented as an effective strategy to reduce stress biomarkers (hair cortisol) as well as perceived stress and anxiety, improving the mental health of university workers.
The human skin is composed of three layers: the epidermis, the dermis, and subcutaneous tissue or hypodermis. The epidermis is the most superficial layer and consists of packed epithelial cells. The middle layer, the dermis, is made of connective tissue, blood and lymphatic vessels, hair follicles, and sweat glands. Beneath the dermis lies subcutaneous tissue, which is composed of adipose tissue.
In addition to protecting against pathogens (mainly microorganisms), chemicals, physical agents, and ultraviolet radiation, the skin also contains a range of immune cells that contribute to innate and adaptive immune responses.
Drug delivery via hair follicles has attracted much research attention due to its potential to serve for both local and systemic therapeutic purposes. Recent studies on topical application of various particulate formulations have demonstrated a great role of this delivery route for targeting numerous cell populations located in skin and transporting the encapsulated drug molecules to the bloodstream. Despite a great promise of follicle-targeting carriers, their clinical implementation is very rare, mostly because of their poorer characterization compared to conventional topical dosage forms, such as ointments and creams, which have a history spanning over a century. Gathering as complete information as possible on the intrafollicular penetration depth, storage, degradation/metabolization profiles of such carriers and the release kinetics of drugs they contain, as well as their impact on skin health would significantly contribute to understanding the pros and cons of each carrier type and facilitate the selection of the most suitable candidates for clinical trials. Optical imaging and spectroscopic techniques are extensively applied to study dermal penetration of drugs. Current paper provides the state-of-the-art overview of techniques, which are used in optical monitoring of follicular drug delivery, with a special focus on non-invasive in vivo methods. It discusses key features, advantages and limitations of their use, as well as provide expert perspectives on future directions in this field.
Background
Eyebrows significantly influence facial aesthetics and are often linked to attractiveness and personality. Eyebrow loss and alopecia impact physical and psychological well‐being. Several treatments, including mesotherapy (MT), aim to enhance eyebrow density and quality. Despite the availability of MT for hair growth, its application in eyebrow revitalization is less explored.
Aims
This study evaluates clients' perceptions and satisfaction with eyebrow MT (EB MT) using AQ skin solutions' growth factor‐based MT cocktail serum.
Patients/Methods
Thirty‐two healthy women (ages 21–55) with thin or weakened eyebrows underwent three EB MT sessions spaced 2–4 weeks apart. Exclusion criteria included chronic diseases, allergies, and conditions like pregnancy. Each session lasted about 40 min, and “point by point” and “nappage” techniques were employed. Satisfaction and pain levels were assessed through a Numeric Rating Scale for Satisfaction (NRSS) and Pain scale, while photographic analysis and the Global Aesthetic Improvement Scale (GAIS) evaluated effectiveness.
Results
The average GAIS score was 8.28, while the NRSS satisfaction score was 8.06. Pain levels were moderately low, averaging 4.0. A high majority (90.6%) were satisfied and willing to continue treatment, with 100% recommending EB MT to others. Notable improvements in overall appearance were reported by participants.
Conclusions
EB MT demonstrated high satisfaction and low pain levels, with significant improvements in eyebrow density and appearance. This treatment is a practical option for eyebrow enhancement with a strong safety profile, motivating further clinical application.
This chapter provides a comprehensive exploration of the anatomy and physiology of hair, offering insights into the classification of hair and types of hair follicles. A thorough analysis of the structure of the hair follicle and the hair shaft throws light on the complex makeup of these vital parts. Moving beyond anatomy, this chapter delves into the physiology of hair, with a particular focus on the growth cycle. The hair growth cycle is elucidated through its three distinct stages—Anagen, Catagen, and Telogen. The initiation of the Anagen phase is correlated with the developmental process of the hair follicle, emphasizing the dynamic nature of this cycle. The Catagen phase is explored as a carefully controlled involution process marked by a notable episode of apoptosis, contributing to the regulated progression of the hair growth cycle. Additionally, the maturation of the hair shaft during the Telogen stage is detailed, highlighting the formation of club hairs and their subsequent shedding. Furthermore, this chapter extends its exploration to the secretory glands associated with hair follicles, namely, the sebaceous gland, sweat gland, and apocrine gland. Each gland’s role in contributing to the health and characteristics of hair is discussed, with a focus on sebum’s impact on hair appearance, the composition of sweat, and the unique features of apocrine gland secretions.
Human hair is characterised by variability, determined by genetic and macromolecular factors. Whilst the European hair type has been a focus of extensive research, Afro-textured hair care faces challenges created by insufficient knowledge of its properties. Applications of hair care products that are incompatible with Afro-textured hair frequently have detrimental effects on the scalp. This highlights the need for partnerships to bridge the gap between research and hair care practices and address challenges related to Afro-textured hair. In this review, we performed data mining of the existing literature and in silico network analysis of the biomarkers relevant to Afro-textured hair. The approaches to hair maintenance are highlighted in the context of hair anatomy and growth cycles, organisation of keratins, surface lipids, and chemical bonds. We discuss a range of biomarkers affecting hair fibre’s shape and mechanical strength, with the gene interactive network pointing to the hierarchical organisation of important traits, notably hair shaft diameter, keratinization, and hair follicle patterning, which likely contribute to the increased sensitivity of hair to extrinsic factors. We propose that a better understanding of the genetic traits, molecular structure, and biomechanics of Afro-textured hair is required to initiate more effective hair care solutions that would benefit the wider population.
Objective
To investigate the role of miR‐30a‐5p on the proliferation and apoptosis of hair follicle stem cells (HFSCs) and whether the Wnt/β‐catenin signaling pathway is involved.
Methods
HFSCs derived from the vibrissa of mammary rats were obtained by enzymatic digestion, and subsequently the obtained HFSCs were treated with Lipofectamine 2000 cell transfection and divided into normal cell culture group (control), miR‐30a‐5p overexpression group (miR‐30a‐5p mimic), miR‐30a‐5p empty vector group (miR‐NC), miR‐30a‐5p inhibitor group (in‐miR‐30a‐5p), and in‐miR‐30a‐5p empty vector group (in‐miR‐NC). After transfection, the cell proliferation and apoptosis rates were examined separately. In addition, the mRNA expression of β‐catenin, proliferating cell nuclear antigen (PCNA) and apoptosis‐related genes (Bax and Bcl‐2) were examined.
Results
The results of cell proliferation ability showed that in‐miR‐30a‐5p group promoted cell proliferation of HFSCs relative to other groups, along with significant upregulation of gene levels of PCNA. Apoptosis analysis indicated that apoptosis rate was reduced in the in‐miR‐30a‐5p group, and the expression of Bax was suppressed, while that of Bcl‐2 was promoted. Wnt/β‐catenin signaling pathway investigation revealed a significant increase in the levels of β‐catenin in HFSCs in the in‐miR‐30a‐5p group.
Conclusion
Downregulation of miR‐30a‐5p levels inhibited HFSCs apoptosis and simultaneously promoted proliferation, furthermore, the increased expression of β‐catenin indirectly confirmed the activation of the Wnt/β‐catenin signaling pathway.
Androgenetic alopecia (AGA) is the most common form of hair loss characterized by miniaturization of hair follicles. Low-level light therapy (LLLT) and microneedling have shown potential in promoting hair regrowth. This study aims to evaluate the efficacy of an innovative light-emitting diode (LED) helmet cooperated with a novel light-guiding microneedle patch (LMNP) for stimulating hair growth in AGA. In this randomized clinical trial, 16 AGA patients received treatments using light-guiding microneedle patches (LMNPs) illuminated by a LED helmet equipped with green (522 nm) and red (633 nm) LEDs, delivering 50 mW/cm2 power and 40 J/cm2 energy. Treatments were applied weekly for 24 weeks, targeting the frontal recession area. The right side of the scalp was treated with green light and the left with red light, each combined with a LMNP featuring 900 µm height needles at a density of 105 per square centimeter. Hair density and diameter, along with patient and physician satisfaction scores, were assessed monthly. Both red and green LED treatments with LMNP, significantly enhanced hair density and diameter. Satisfaction scores, as reported by both physicians and participants, increased over time. Comparative analyses revealed no statistically significant differences in average satisfaction scores or in changes in hair density and diameter between the groups by the end of the study. Additionally, no serious adverse effects were reported, highlighting the safety of the treatments. The combined Light sources which is portable LED helmet and LMNPs shows promise as a non-invasive, effective treatment for AGA, with similar efficacy between red and green wavelengths.
Hair loss is a common problem in adults including both male and female. Correct diagnosis of hair disorders is complex and requires evaluation of clinical presentation, history, physical examination, and laboratory tests. Hair loss may be categorized as hair shaft abnormalities, permanent alopecia, or nonpermanent alopecia. Physicians should always be careful not to underestimate the emotional impact of hair loss for some patients. Patients may present with focal patches of hair loss or more diffuse hair loss, which may include predominant hair thinning or increased hair shedding. Focal hair loss can be further broken down into scarring and nonscarring. Scarring alopecia is best evaluated by a dermatologist. The cause of focal hair loss may be diagnosed by the appearance of the patch and examination for fungal agents. A scalp biopsy may be necessary if the cause of hair loss is unclear. Male and female pattern hair losses have recognizable patterns and can be treated with topical minoxidil, and also with finasteride in men. Management of alopecia requires a holistic approach including psychosocial support because treatments are only available for some hair loss conditions, and even the available treatments are not always effective. Diagnostic tools for hair loss in children include a detailed history, physical examination with a focused evaluation of the child's hair and scalp, fungal screens, hair pull and tug test, and if possible, light microscopy and/or trichoscopy. In this review, we highlighted the clinical presentations, advancements in diagnosis and treatment modalities for hair loss (alopecia) and discussed management of these various hair loss disorders.
People nowadays are very much concerned about their appearance and personality traits. Among these, hair colour plays an imperative role in overall look and adds to aesthetic value in this modern era of cosmetology mutiny. Hair graying whether timely or premature has a direct pessimistic impact on one’s social well-being. However, in latter the management of hair graying is believed to have significant and direct impact on the quality of life in adolescents. The hair cycle responsible for pigmentation of hairs is dependent on multiple factors viz. enzymes, pH, excessive stress, hormones, hereditary causes, sedentary lifestyle and nutritional deficiencies. Of these, if considered carefully, macronutrients and micronutrients obtained from diet in human body are playing an immense role directly or indirectly in normal hair cycle. A caloric deprivation or deficiency of these dietary components can lead to structural abnormalities in hair as well as pigmentation changes. In this review, an effort is being made to understand the role of various vitamins, minerals, proteins and antioxidants in canities. A broad literature search of PubMed and Google Scholar was performed to compile the information available in research as well as review articles. As per the available data, it can be suggested that there is direct relationship between the low levels of copper, iron and vitamin B12 and PHG. However, reaching a defined conclusion seemed unlikely because of limitations in studies related to the above-mentioned scenario.
Introduction
Nowadays, most people are suffering from dandruff which when not treated becomes flaky and causes major damage to the scalp of a person. Dandruff is a common scalp illness caused by the yeast Pittosporum. It is not possible to completely eradicate dandruff; it can only be appropriately handled.
Methods
When used as indicated, a shampoo's surfactant, often referred to as a surface-active agent, in its proper form—liquid, solid, or powder—will safely remove skin fragments, dirt, and surface oil from the scalp and hair shaft. Numerous hair care solutions use a variety of anti-fungal substances to treat dandruff. Many adverse reactions to these products have been reported, includ-ing hair loss, heightened headache, nausea, scaling, itching, and irritation.
Results
Thus, an attempt was undertaken to develop a herbal anti-dandruff shampoo form safe and more successful in treating the dandruff problem by using a marketed herbal tincture. The anti-dandruff formulation was prepared by combining natural polyherbal tincture, and these tincture shows the different medicinal effects on hair.
Conclusion
A number of parameters, including visual observation, pH, consistency, particle per-centage, filth dispersion, surface phenomena, and foaming content were used to assess the shampoo formulations. Also, the estimation of an anti-microbial activity by using the inoculation method. The greatest zone of inhibition demonstrated a strong antimicrobial effect for the formulation.
Therapeutic needs for hair loss are intended to find small interfering ribonucleic acid (siRNA) therapeutics for breakthrough. Since naked siRNA is restricted to meet a druggable target in clinic,, delivery systems are indispensable to overcome intrinsic and pathophysiological barriers, enhancing targetability and persistency to ensure safety, efficacy, and effectiveness. Diverse carriers repurposed from small molecules to siRNA can be systematically or locally employed in hair loss therapy, followed by the adoption of new compositions associated with structural and environmental modification. The siRNA delivery systems have been extensively studied via conjugation or nanoparticle formulation to improve their fate in vitro and in vivo. In this review, we introduce clinically tunable siRNA delivery systems for hair loss based on design principles, after analyzing clinical trials in hair loss and currently approved siRNA therapeutics. We further discuss a strategic research framework for optimized siRNA delivery in hair loss from the scientific perspective of clinical translation.
The male and female skin differ in many ways. The skin is thicker in males than in females in all age groups, while subcutaneous tissue is thicker in females than in males. Sex hormones influence hair thickness, hair growth, sebaceous gland development and activity, and eccrine and apocrine gland development. The female skin exhibits faster skin barrier recovery, better wound healing, and stronger immune responses to infections than the male skin. Anatomical and physiological differences between the male and female skin lead to differences in prevalence and severity in skin diseases.
This narrative review aims to examine the therapeutic potential and mechanism of action of plant extracts in preventing and treating alopecia (baldness). We searched and selected research papers on plant extracts related to hair loss, hair growth, or hair regrowth, and comprehensively compared the therapeutic efficacies, phytochemical components, and modulatory targets of plant extracts. These studies showed that various plant extracts increased the survival and proliferation of dermal papilla cells in vitro, enhanced cell proliferation and hair growth in hair follicles ex vivo, and promoted hair growth or regrowth in animal models in vivo. The hair growth-promoting efficacy of several plant extracts was verified in clinical trials. Some phenolic compounds, terpenes and terpenoids, sulfur-containing compounds, and fatty acids were identified as active compounds contained in plant extracts. The pharmacological effects of plant extracts and their active compounds were associated with the promotion of cell survival, cell proliferation, or cell cycle progression, and the upregulation of several growth factors, such as IGF-1, VEGF, HGF, and KGF (FGF-7), leading to the induction and extension of the anagen phase in the hair cycle. Those effects were also associated with the alleviation of oxidative stress, inflammatory response, cellular senescence, or apoptosis, and the downregulation of male hormones and their receptors, preventing the entry into the telogen phase in the hair cycle. Several active plant extracts and phytochemicals stimulated the signaling pathways mediated by protein kinase B (PKB, also called AKT), extracellular signal-regulated kinases (ERK), Wingless and Int-1 (WNT), or sonic hedgehog (SHH), while suppressing other cell signaling pathways mediated by transforming growth factor (TGF)-β or bone morphogenetic protein (BMP). Thus, well-selected plant extracts and their active compounds can have beneficial effects on hair health. It is proposed that the discovery of phytochemicals targeting the aforementioned cellular events and cell signaling pathways will facilitate the development of new targeted therapies for alopecia.
The advent of biosensors has tremendously increased our potential of identifying and solving important problems in various domains, ranging from food safety and environmental analysis, to healthcare and medicine. However, one of the most prominent drawbacks of these technologies, especially in the biomedical field, is to employ conventional samples, such as blood, urine, tissue extracts and other body fluids for analysis, which suffer from the drawbacks of invasiveness, discomfort , and high costs encountered in transportation and storage, thereby hindering these products to be applied for point-of-care testing that has garnered substantial attention in recent years. Therefore, through this review, we emphasize for the first time, the applications of switching over to noninvasive sampling techniques involving hair and nails that not only circumvent most of the aforementioned limitations, but also serve as interesting alternatives in understanding the human physiology involving minimal costs, equipment and human interference when combined with rapidly advancing technologies, such as microfluidics and organ-on-a-chip to achieve miniaturization on an unprecedented scale. The coalescence between these two fields has not only led to the fabrication of novel microdevices involving hair and nails, but also function as robust biosensors for the detection of biomarkers, chemicals, metabolites and nucleic acids through noninvasive sampling. Finally, we have also elucidated a plethora of futuristic innovations that could be incorporated in such devices, such as expanding their applications in nail and hair-based drug delivery, their potential in serving as next-generation wearable sensors and integrating these devices with machine-learning for enhanced automation and decentralization.
Hair analysis is a reliable and widely used tool to evaluate drug exposure in many fields, including workplace testing, drug abuse history and withdrawal control, post-mortem toxicology, doping control, therapeutic drug monitoring of pharmaceuticals and even environmental exposure to toxic agents. Compounds incorporated into the hair structure resist hair growth and regular washing for several months, leading to a potential chronological trace of exposure, with farther periods corresponding to the hair segments more distant from the hair root. The relentless improvement of analytical procedures and instrumental technologies, together with the continuous introduction of new psychoactive substances, have led to an increasing number of studies and practical applications of hair analysis.
This book is a comprehensive guide to hair analysis from general concepts, ideal for students and those new to the field, to interpretation and advanced methods for experts working in the area. With contributions from world-leading scientists in each field, this book describes state-of-the-art, emerging issues and recent analytical approaches to hair analysis that will serve as an essential tool to clinical and forensic toxicology laboratories across the globe.
Hair analysis is a reliable and widely used tool to evaluate drug exposure in many fields, including workplace testing, drug abuse history and withdrawal control, post-mortem toxicology, doping control, therapeutic drug monitoring of pharmaceuticals and even environmental exposure to toxic agents. Compounds incorporated into the hair structure resist hair growth and regular washing for several months, leading to a potential chronological trace of exposure, with farther periods corresponding to the hair segments more distant from the hair root. The relentless improvement of analytical procedures and instrumental technologies, together with the continuous introduction of new psychoactive substances, have led to an increasing number of studies and practical applications of hair analysis.
This book is a comprehensive guide to hair analysis from general concepts, ideal for students and those new to the field, to interpretation and advanced methods for experts working in the area. With contributions from world-leading scientists in each field, this book describes state-of-the-art, emerging issues and recent analytical approaches to hair analysis that will serve as an essential tool to clinical and forensic toxicology laboratories across the globe.
This study evaluated the effects of laser application of diverse wavelengths applied simultaneously and on different skins. The sample included two participants, a woman with light skin with abdominal hair and a woman with dark skin and hair on the inner part of the lower limbs, who received a laser therapy session. After 45 days from laser application, abdominoplasty and thigh dermolipectomy surgery were performed. In the control sample, the hair follicles were in the anagen phase, showing the presence of Bcl-2 expression. In the treated areas, follicles were observed in an advanced phase (telogen), with the presence of CK-18 and negativity of Bcl-2, highlighting the phase of hair loss at that moment and the complete apoptosis of the investigated follicle. Significant difference was observed in the comparison of the anagen phase (p = .00) and it similarly occurred in the comparison of the telogen phase (p = .00). The presence of a greater amount of follicles in the anagen phase in the control area and follicles in the telogen phase in the treated area demonstrates the efficiency of the laser at different wavelengths when reaching different skin phototypes and hair thickness, being reinforced by apoptosis and cell proliferation markers. Therefore, the hair-removal process has been optimized with various laser wavelengths.
The field of forensic biology is an ever-evolving and constantly developing field. It utilizes knowledge of biological concepts and practical approaches that assists in a legal investigation. Forensic biology serves as a significant discipline dealing with multifarious sub-disciplines such as forensic genetics, forensic serology, forensic anthropology, forensic botany, forensic entomology, forensic microbiology, etc. For examination of different biological evidences, bodily fluids, and cellular components related to humans, animals plant or micro-organisms that are encountered at the crime scene or are relatable to the concerned crime. From the development of amthropometrical science in the 1870s by Alphonse Bertillon for personal identification to the currently emerging and developing field of DNA fingerprinting and microbial patterns, forensic biology has provided novel approaches and improved methodology for collection, preservation and analysis of compromised evidences encountered at the crime scene. This chapter deals with the basic introduction of various sub-branches of forensic biology and their utilization in the field of forensic science. The chapter also describes various bodily substances such as hairs, nails, seminal fluid, teeth and botanical evidences such as wood, leaves, pollens, etc., that are generally encountered at the crime scene along with the techniques of their identification and segregation and application in the forensic context. A detailed approach of wildlife forensics, forensic entomology, forensic limnology and forensic mycology towards assistance in the criminal investigation has been elucidated in this chapter.
Human hair is a natural fiber with keratin and keratin-related proteins as a main component. Externally, hair is a thin, pliable tube of dead, fully keratinized epithelial cells, while inside the skin, it is part of a single living hair follicle. In addition to a large amount of protein, hair also contains low levels of lipids and pigments. The hair also has its own ecological balance system. Although the lipid content in hair is much lower than the protein content, it plays an important role in hair and influences hair texture to some extent. For example, prevent hair breakage and thinning; To act as a barrier to moisture loss; and improve the gloss, elasticity and tensile strength of the hair stem. Environment, hair dressing and daily care can all cause hair damage to varying degrees. Factors such as ultraviolet light and chemicals can make hair dry, rough, dull, stiff and brittle by destroying the proteins, pigment sand lipid sin the hair. In this paper, the composition, classification and influencing factors of hair were reviewed. The composition and function of lipids in hair were investigated emphatically. It aims to improve people's understanding of the physical and chemical properties and structure of hair. It provides reference value for the research and development of hair cosmetics for different hair states and washing purposes. The function of hair lipids on hair is not accurate. In addition, there is still some controversy on the existing role of hair lipids, which needs further research.
Background:
Hair diseases may present with hair loss, hirsutism, hair melanin abnormalities and other manifestations. Hair follicles are known as mini-organs that undergo periodic remodeling, and their constant regeneration in vivo reflects interesting anti-aging functions. Telomerase prevents cellular senescence by maintaining telomere length, but its excessive proliferation in cancer cells may also induce cancer. However, the effects of telomerase in hair growth have rarely been reported.
Methods:
In this study, we reviewed the role of telomerase in hair growth and the effects of hair disorders through literature search and analysis.
Results:
There is growing evidence that telomerase plays an important role in maintaining hair follicle function and proliferation. Changes in telomerase levels in hair follicles have also been found in a variety of hair disorders.
Conclusion:
Telomerase plays a positive role in hair growth and is expected to become a new target for the treatment of alopecia or other hair diseases in the future.
Background:
Human scalp hair is a validated bio-substrate for monitoring various exposures in childhood including contextual stressors, environmental toxins, prescription or non-prescription drugs. Linear hair growth rates (HGR) are required to accurately interpret hair biomarker concentrations.
Methods:
We measured HGR in a prospective cohort of preschool children (N = 266) aged 9-72 months and assessed demographic factors, anthropometrics, and hair protein content (HPC). We examined HGR differences by age, sex, race, height, hair pigment, and season, and used univariable and multivariable linear regression models to identify HGR-related factors.
Results:
Infants below 1 year (288 ± 61 μm/day) had slower HGR than children aged 2-5 years (p = 0.0073). Dark-haired children (352 ± 52 μm/day) had higher HGR than light-haired children (325 ± 50 μm/day; p = 0.0019). Asian subjects had the highest HGR overall (p = 0.016). Younger children had higher HPC (p = 0.0014) and their HPC-adjusted HGRs were slower than older children (p = 0.0073). Age, height, hair pigmentation, and HPC were related to HGR in multivariable regression models.
Conclusions:
We identified age, height, hair pigment, and hair protein concentration as significant determinants of linear HGRs. These findings help explain the known hair biomarker differences between children and adults and aid accurate interpretation of hair biomarker results in preschool children.
Impact:
Discovery of hair biomarkers in the past few decades has transformed scientific disciplines like toxicology, pharmacology, epidemiology, forensics, healthcare, and developmental psychology. Identifying determinants of hair growth in children is essential for accurate interpretation of hair biomarker results in pediatric clinical studies. Childhood hair growth rates define the time-periods of biomarker incorporation into growing hair, essential for interpreting the biomarkers associated with environmental exposures and the mind-brain-body connectome. Our study describes age-, sex-, and height-based distributions of linear hair growth rates and provides determinants of linear hair growth rates in a large population of children. Age, height, hair pigmentation, and hair protein content are determinants of hair growth rates and should be accounted for in child hair biomarkers studies. Our findings on hair protein content and linear hair growth rates may provide physiological explanations for differences in hair growth rates and biomarkers in preschool children as compared to adults.
The skin is the largest organ of the body, composed of the epidermis, dermis, and subcutaneous tissue, each with unique functions. The development of ex-vivo human skin models for chemical testing is a current challenge in skin research. While 3D printing technology has been used to develop bioprinted skin, few studies have included 3D printed sebaceous glands, making it challenging to create a fully functional skin model. The ideal biomaterial for skin bioprinting should have mechanical properties similar to those of native skin, support high cell viability, have adequate biodegradation rate, provide a suitable microenvironment for skin cell functionality, and be highly biocompatible. Natural biomaterials are commonly used in skin bioprinting, but they lack stable mechanical properties and have low gelation levels. Synthetic materials have controllable mechanical and chemical properties, but low biocompatibility and biodegradability. Composite natural and synthetic biomaterials can help balance the biological and mechanical features and provide more stable bioink. The development of bioprinted skin models will help to advance skin research and provide a customizable approach to the development of skin tissue. In summary, both skin bioprinting and organoid technology have revolutionized the field of tissue engineering and modeling. Skin bioprinting has shown promising results in the fabrication of skin substitutes for wound healing and has the potential to transform the cosmetic industry. Organoids have broad applications in disease modeling, drug testing, and the development of treatment strategies for various genetic and infectious diseases. While animal models remain the gold standard, organoids provide a closer recapitulating system of human organs and have the advantage of being easily cultured, genetically modified, and cryopreserved while maintaining their phenotype. Overall, these technologies offer new possibilities for research, dermatopathology, wound healing, and drug and vaccine development.KeywordsSkin bioprintingOrganoid technologyTissue engineeringWound healing and drug testing
BACKGROUND: Ultraviolet (UVB) radiation induces hair photoaging by triggering oxidative stress, causing alterations in hair diameter and length, which contribute to the development of senile alopecia. Development of alternative anti-photoaging agents to prevent hair loss from various materials, including natural products, is currently being explored. Rosmarinus officinalis essential oil (ROEO) has been known to have antioxidant and vasodilation properties. However, the effect and mechanism of ROEO on UVB-exposed hair are still unclear. Therefore, this study was conducted to evaluate the effects of ROEO on the hair length and follicle diameter in UVB-exposed mice as well as the skin vascular endothelial growth factor (VEGF) level.METHODS: Thirty male Swiss mice were treated topically with/without paraffin oil, 2% minoxidil, or various concentrations of ROEO, every day for 21 days. Meanwhile, UVB exposure was performed 3×/week. On day 21, the hair length was measured, the skin tissue was collected for hair follicle diameter and VEGF measurements.RESULTS: ROEO contained phenolic, including flavonoids and tannins, as well as non-phenolic antioxidants, including 1.8-cineole, α-pinene, and camphor. The IC50 value of ROEO was 15.977 ppm. Significant higher hair length, follicle diameter, and VEGF level of 10% ROEO+UVB-treated mice were observed, compared with the ones of mice exposed with UVB merely (LSD test, p<0.05).CONCLUSION: Since 10% ROEO could significantly increase hair length, follicle diameter and VEGF level, and contained antioxidant compounds, it can be suggested that ROEO might increase hair length, follicle diameter, and VEGF level through its antioxidant component.KEYWORDS: Rosmarinus officinalis, hair follicle diameter, hair length, VEGF, ultraviolet B, antioxidant
Abstract is missing (Letter).
It has long been known that the testis is an immunologically privileged site in the body, and that human seminal plasma possesses a generalized immunosuppressive activity. Multiple factors participate in the establishment of immunotolerance in the testis: the blood–tubular barrier; the local production of immunosuppressive molecules by Sertoli cells; and the Fas system as regulator of immunological homeostasis in both physiological and pathological conditions. Cytokine-induced up-regulation of Fas as well as of integrin ligands, which are known to be specific binding molecules for lymphocytes on the Sertoli cell surface, indicates that the ‘nursing’ cells of seminiferous epithelium might be important in the impairment of immune privilege, causing autoimmune orchitis. In addition, the soluble form of Fas-ligand protein present in the seminal plasma of infertile patients might suggest a role for this immunomodulatory protein in male infertility. Finally, an understanding of the mechanisms underlying immune privilege in the testis and in semen might help to clarify how cells expressing ‘non-self’ antigens (such as male gametes) can escape the immune system in both the male and female genital tracts.
ABSTRACT: Correction to Wu DD, Irwin DM, Zhang YP: Molecular evolution of the keratin associated protein gene family in mammals, role in the evolution of mammalian hair. BMC Evol Biol 2008, 8:241.
Five hundred adults aged between 18-35 years were used for the study. The aim of this study was to provide a reference document for Nigerians on the distribution of phalangeal hair using a sample population of Yorubas resident in Ilorin and to assess the effect of job type, age and sex hair distribution. With the help of a hand lens, the pattern and frequency of hair distribution on the proximal, intermediate and distal were randomly chosen from the population. Proximal phalangeal hair was absent in 10 (2%) individuals who were all males. The highest frequency distribution (51%) was found on the 2-3-4-5, digits of proximal phalanges (26% in males and 25% females) while the least (1%) was the 3-5; 1-2-3-5 digital pattern. It was observed that the frequency of middle phalangeal hair was low (1%). Females had less phalangeal hair. Hair was absent on the distal phalanges. Distribution is similar to other populations reported. Age was not a factor in the distribution but individual's job type and sex had effect on hair distribution. Hence people engaged in wet work should wear gloves.
Hair is unique to mammals. Keratin associated proteins (KRTAPs), which contain two major groups: high/ultrahigh cysteine and high glycine-tyrosine, are one of the major components of hair and play essential roles in the formation of rigid and resistant hair shafts.
The KRTAP family was identified as being unique to mammals, and near-complete KRTAP gene repertoires for eight mammalian genomes were characterized in this study. An expanded KRTAP gene repertoire was found in rodents. Surprisingly, humans have a similar number of genes as other primates despite the relative hairlessness of humans. We identified several new subfamilies not previously reported in the high/ultrahigh cysteine KRTAP genes. Genes in many subfamilies of the high/ultrahigh cysteine KRTAP genes have evolved by concerted evolution with frequent gene conversion events, yielding a higher GC base content for these gene sequences. In contrast, the high glycine-tyrosine KRTAP genes have evolved more dynamically, with fewer gene conversion events and thus have a lower GC base content, possibly due to positive selection.
Most of the subfamilies emerged early in the evolution of mammals, thus we propose that the mammalian ancestor should have a diverse KRTAP gene repertoire. We propose that hair content characteristics have evolved and diverged rapidly among mammals because of rapid divergent evolution of KRTAPs between species. In contrast, subfamilies of KRTAP genes have been homogenized within each species due to concerted evolution.
Nearly 50 years ago, Chase published a review of hair cycling in which he detailed hair growth in the mouse and integrated hair biology with the biology of his day. In this review we have used Chase as our model and tried to put the adult hair follicle growth cycle in perspective. We have tried to sketch the adult hair follicle cycle, as we know it today and what needs to be known. Above all, we hope that this work will serve as an introduction to basic biologists who are looking for a defined biological system that illustrates many of the challenges of modern biology: cell differentiation, epithelial-mesenchymal interactions, stem cell biology, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-beta, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. For the immediate future, our challenge is to define the molecular basis for hair follicle growth control, to regenerate a mature hair follicle in vitro from defined populations, and to offer real solutions to our patients' problems.
It has long been known that the testis is an immunologically privileged site in the body, and that human seminal plasma possesses a generalized immunosuppressive activity. Multiple factors participate in the establishment of immunotolerance in the testis: the blood-tubular barrier; the local production of immunosuppressive molecules by Sertoli cells; and the Fas system as regulator of immunological homeostasis in both physiological and pathological conditions. Cytokine-induced up-regulation of Fas as well as of integrin ligands, which are known to be specific binding molecules for lymphocytes on the Sertoli cell surface, indicates that the 'nursing' cells of seminiferous epithelium might be important in the impairment of immune privilege, causing autoimmune orchitis. In addition, the soluble form of Fas-ligand protein present in the seminal plasma of infertile patients might suggest a role for this immunomodulatory protein in male infertility. Finally, an understanding of the mechanisms underlying immune privilege in the testis and in semen might help to clarify how cells expressing 'non-self' antigens (such as male gametes) can escape the immune system in both the male and female genital tracts.
Recent genetic and molecular studies of hair follicle (HF) biology have provided substantial insight; however, the molecular data, including expression patterns, cannot be properly appreciated without an understanding of the basic cellular rearrangements and interactions that underpin HF cyclic transformations. We present a novel interpretation of the major cellular processes that take place during HF cycling--the hypothesis of hair follicle predetermination. This hypothesis is an extension of previous models of HF cellular kinetics but has two critical modifications: the dual origin of the cycling portion of the HF, and the timing of the recruitment of stem cells. A compilation of evidence suggests that the ascending portion of the HF (hair shaft and inner root sheath) arises not from bulge-located HF stem cells that contribute to the formation of only the outer root sheath (ORS), but instead from the germinative cells localized in the secondary hair germ. In middle anagen, upon completion of the downward growth of the HF, cells derived from the bulge region migrate downward along the ORS to reside at the periphery of the HF bulb as a distinct, inactive cell population that has specific patterns of gene expression - 'the lateral disc'. These cells survive catagen-associated apoptosis and, under the direct influence of the follicular papilla (FP), transform into the hair germ and acquire the ability to respond to FP signaling and produce a new hair. Thus, we propose that the specific sensitivity of germ cells to FP signaling and their commitment to produce the ascending HF layers are predetermined by the previous hair cycle during the process of transformation of bulge-derived lateral disc cells into the secondary hair germ.
The structure, chemistry, and physical properties of the human hair cuticle are reviewed, and the role of the covalently linked fatty acids, notably 18-methyl eicosanoic acid (18-MEA), contained therein, is discussed. Differential friction in hair is considered, and it is argued that this property normally facilitates the parallel alignment of hairs on the scalp and aids the rejection of macroscopic scalp surface detritus, to the owner's benefit. The hair seems to possess a natural process of surface repair that, by the gradual mechanical attrition of cuticle, aids in the retention of the hair's differential frictional behavior and in the retention of the associated benefits.
This chapter reviews the functions of hair, its structure and the processes occurring during the hair growth cycle, the changes which can occur with the seasons, and the importance of the main regulator of human hair growth, the androgens. Its main focus lies on human hair growth. Mammalian skin produces hair everywhere except for the glabrous skin of the lips, palms, and soles. Although obvious in most mammals, human hair growth is so reduced with tiny, virtually colorless vellus hairs in many areas, that we are termed the “naked ape.” Externally hairs are thin, flexible tubes of dead, fully keratinised epithelial cells; they vary in color, length, diameter, and cross-sectional shape. Inside the skin hairs are part of individual living hair follicles, cylindrical epithelial downgrowths into the dermis, and subcutaneous fat, which enlarge at the base into the hair bulb surrounding the mesenchyme-derived dermal papilla. Human hair's main functions are protection and communication; it has virtually lost insulation and camouflage roles, although seasonal variation and hair erection when cold indicate the evolutionary history. Children's hairs are mainly protective; eyebrows and eyelashes stop things entering the eyes, while scalp hair probably prevents sunlight, cold, and physical damage to the head and neck.
Background and Design:
The few articles published on the interactions between psychological factors and alopecia seem to yield contrasting results. To assess the relationships between alopecia, gender, Diagnostic Statistical Manual of Mental Disorders, Revised Third Edition personality disorders, and psychopathologic symptoms reactive to alopecia, we administered the Personality Disorders Questionnaire-Revised and the Symptoms Checklist-90 to a randomly selected sample of 116 outpatients with androgenetic alopecia.
Results:
The prevalence of personality disorders in subjects with androgenetic alopecia proved to be significantly higher than the prevalence of such diagnoses in the general population. Women did not show a higher prevalence of personality disorders or more psychopathologic symptoms than men. The factor analysis demonstrated the existence of three personality profiles (F1, F2, and F3) significantly and specifically associated with the subject's gender and with the psychopathologic reactive symptoms, measured using the Symptoms Checklist-90.
Conclusions:
The most important factor in developing a psychopathologic reaction to alopecia seems to be the presence of a Diagnostic Statistical Manual of Mental Disorders, Revised Third Edition personality disorder and not the subject's gender.(Arch Dermatol. 1994;130:868-872)
All living organisms are constantly challenged by a diversity of exogenous (environmental, psychological, social) and endogenous stimuli or stressors, which induce general or local biological responses to protect or adapt the organism to the stressor(s). 1 The systemic biological response of the organism to exogenous stressors (or classical stress response) includes activation of the hypothalamic-pituitary-adrenal axis and release of hypothalamic corticotropin-releasing hormone (CRH) that activates pituitary CRH receptors (CRH-R) followed by the production and release of proopiomelanocortin-derived peptides and adrenal hormones. 2,3 Systemic stress response also includes the modulation of the autonomic nervous and immune systems: neuroendocrine hormones and neurotransmitters influence the function of the immune system that reciprocally regulate CNS functions through cytokine release. 4
Human and murine skin are prominent extrapituitary sources and targets for POMC products. The expression of, for example, ACTH, α-MSH, β-endorphin, and MC-1-receptors fluctuates during synchronized hair follicle cycling in C57BL/6 mice. Since hair growth can be induced by ACTH injections in mice and mink, and since high doses of MSH peptides modulate epidermal and/or follicle keratinocyte proliferation in murine skin organ culture, some POMC products may operate as locally generated growth modulators, in addition to their roles in cutaneous pigment and immunobiology. Intrafollicularly generated ACTH and α-MSH as well as their cognate receptors may assist in the maintenance of the peculiar immune privilege of the anagen hair bulb. Possibly, they are also involved in the development of the follicle pigmentary unit, with whose generation their expression coincides. Given that murine skin also expresses (in a hair-cycle-dependent way) CRH and CRH-R, which control pituitary POMC expression and in view of the fact that CRH arrests follicles in telogen, this suggests the existence of a local skin POMC system (SPS). This may be an integral component of cutaneous stress response-systems, and may most instructively be studied using the murine hair cycle as a model.
Penetration of topically applied compounds may occur via the stratum corneum, skin appendages and hair follicles. The follicular infundibulum increases the surface area, disrupts the epidermal barrier towards the lower parts of the follicle, and serves as a reservoir. Topical delivery of active compounds to specific targets within the skin, especially to distinct hair follicle compartments or cell populations, may help to treat local inflammatory reactions selectively, with reduced systemic side-effects. Various in vitro and in vivo methods exist for studying the hair follicle structure and follicular penetration pathways. These include cyanoacrylate skin surface stripping, confocal microscopy and cyanoacrylate scalp follicle biopsy. The complex anatomical structure as well as the cyclical activity of the hair follicle must be taken into consideration when designing delivery systems. In addition, delivery into and retention inside the infundibular reservoir are controlled by, for example, molecule or particle size, their polarity and the type of preparation. Preferred penetration depth and storage time must also be considered. Particles with release mechanisms should be preferred; however, the release of drugs from nanoparticles still requires further investigations.
Hair examinations and comparisons conducted by forensic scientists often provide investigative and associative information. Apart from its length and its natural color, hair displays a morphologic diversity both macroscopically and microscopically. Pseudogenization of <phihHaA type I hair keratin gene inactivation highlights dramatic differences and is thought to be one of the strongest reasons for localization of hair in human. Therefore, humans have several different types of hair that can be classified depending on their body position and form. Size, angle of penetrance through the skin, embryological time of first appearance, and structural variations in the hair follicles are all taken into account when classifying hair types. However, the classification of differential types of hair quantitative traits in human is yet to be undertaken. An attempt has been made in the present study to understand the variation by using the histomorphological and quantitative variables of 540 hair strands (180 each scalp, axillary and pubic hair) of 18 adult Bengalee Hindu caste females. Apart from variation in histomorphological variables, quantitative variables regarding shaft and medulla diameter demonstrated variation in terms of being significantly higher (p < 0.05) in pubic hair compared to that of axillary and scalp hair. Therefore, the present study envisaged that variability in histomorphological and quantitative traits in different areas of human could be one of the important criteria for personal identification in forensic research.
Cosmetic surgical procedures, including hair transplantation and face-lift surgery, are becoming increasingly popular. However, there is very little information regarding the associated development of dermatological conditions following these procedures. Lichen planopilaris (LPP) is an uncommon inflammatory hair disorder of unknown aetiology that results in permanent alopecia and replacement of hair follicles with scar-like fibrous tissue. Frontal fibrosing alopecia (FFA), a variant of LPP, involves the frontal hairline and shares similar histological findings with those of LPP. We report 10 patients who developed LPP/FFA following cosmetic scalp surgery. Seven patients developed LPP following hair transplantation, and three patients developed FFA following face-lift surgery. In all cases there was no previous history of LPP or FFA. There is currently a lack of evidence to link the procedures of hair transplantation and cosmetic face-lift surgery to LPP and FFA, respectively. This is the first case series to describe this connection and to postulate the possible pathological processes underlying the clinical observation. Explanations include Koebner phenomenon induced by surgical trauma, an autoimmune process targeting an (as yet, unknown) hair follicle antigen liberated during surgery or perhaps a postsurgery proinflammatory milieu inducing hair follicle immune privilege collapse and follicular damage in susceptible individuals.
Loose anagen syndrome (LAS) is a benign, self-limiting condition where anagen hairs are easily and painlessly extracted. It is mainly reported in childhood; however, it may variably present in adulthood as well. The presence of anagen hair devoid of its sheath and with 'floppy sock appearance' is a characteristic feature of loose anagen hair (LAH) on trichogram. LAH can be seen in normal population and in alopecia areata. The percentage of LAH in LAS is more than 50%. The histopathological findings show clefting between the layers of hair and are very useful in differentiating LAS from alopecia areata. Here, a review on the diagnostic criteria and practical guidelines are discussed so as to enable the trichologist in managing this benign, self-limiting condition and differentiating it from the other causes of non-scarring alopecias.
The human keratin family comprises 54 members, 28 type I and 26 type II. Out of the 28 type I keratins, 17 are epithelial and 11 are hair keratins. Similarly, the 26 type II members comprise 20 epithelial and 6 hair keratins. As, however, 9 out of the 37 epithelial keratins are specifically expressed in the hair follicle, the total number of hair follicle-specific keratins (26) almost equals that of those expressed in the various forms of epithelia (28). Up to now, more than half of the latter have been found to be involved in inherited diseases, with mutated type I and type II members being roughly equally causal. In contrast, out of the 26 hair follicle-specific keratins only 5 have, at present, been associated with inherited hair disorders, while one keratin merely acts as a risk factor. In addition, all hair follicle-specific keratins involved in pathologies are type II keratins. Here we provide a detailed description of the respective hair diseases which are either due to mutations in hair keratins (monilethrix, ectodermal dysplasia of hair and nail type) or hair follicle-specific epithelial keratins (two mouse models, RCO3 and Ca(Rin) as well as pseudofolliculitis barbae).
Immune privilege (IP) is important in maintaining ocular health. Understanding the mechanism underlying this dynamic state would assist in treating inflammatory eye diseases. Despite substantial progress in defining eye IP mechanisms, because of the scarcity of human ocular tissue for research purposes, most of what we know about ocular IP is based on rodent models (of unclear relevance to human eye immunology) and on cultured human eye-derived cells that cannot faithfully mirror the complex cell-tissue interactions that underlie normal human ocular IP in situ. Therefore, accessible, instructive, and clinically relevant human in vitro models are needed for exploring the general principles of why and how IP collapses under clinically relevant experimental conditions and how it can be protected or even restored therapeutically. Among the few human IP sites, the easily accessible and abundantly available hair follicle (HF) may offer one such surrogate model. There are excellent human HF organ culture systems for the study of HF IP in situ that instructively complement in vivo autoimmunity research in the human system. In this article, we delineate that the human eye and HF, despite their obvious differences, share key molecular and cellular mechanisms for maintaining IP. We argue that, therefore, human scalp HFs can provide an unconventional, but highly instructive, accessible, easily manipulated, and clinically relevant preclinical model for selected aspects of ocular IP. This essay is an attempt to encourage professional eye researchers to turn their attention, with appropriate caveats, to this candidate surrogate model for ocular IP in the human system.
Most mammals are coated with pigmented hair. Melanocytes in each hair follicle produce melanin pigments for the hair during each hair cycle. The key to understanding the mechanism of cyclic melanin production is the melanocyte stem cell (MelSC) population, previously known as 'amelanotic melanocytes'. The MelSCs directly adhere to hair follicle stem cells, the niche cells for MelSCs and reside in the hair follicle bulge-subbulge area, the lower permanent portion of the hair follicle, to serve as a melanocyte reservoir for skin and hair pigmentation. MelSCs form a stem cell system within individual hair follicles and provide a 'hair pigmentary unit' for each cycle of hair pigmentation. This review focuses on the identification of MelSCs and their characteristics and explains the importance of the MelSC population in the mechanisms of hair pigmentation, hair greying, and skin repigmentation.
Middle phalangeal hair has been a focus of study in different populations for the absence or presence of this trait. Clinically, this is often perceived as a solely cosmetic feature. However, because of a series of patients questioning the presence of hair on this location, we have performed a more in-depth literature-based evaluation of the trait. The goal of this manuscript was to examine the clinical significance of this anthropological phenomenon. A literature review was performed that focused on the differences of this trait in terms of pattern of presentation, age, race, sex, and usage as an identifiable marker for medical significance in certain medications and criteria for tailored treatment. Anatomically, middle phalangeal hair is mostly on the fourth finger and more ulnar rather than central or symmetric in pattern of deviation. Its presence has been most associated with high prenatal androgen exposure, predisposing patients to suffer from adverse side effects from oral contraceptives. Phalangeal hair may be helpful in tailoring treatment to certain patients from different ethnic backgrounds, and particularly in individuals with unknown ancestry.
The role of neurohormones and neuropeptides in human hair follicle (HF) pigmentation extends far beyond the control of melanin synthesis by α-MSH and ACTH and includes melanoblast differentiation, reactive oxygen species scavenging, maintenance of HF immune privilege, and remodeling of the HF pigmentary unit (HFPU). It is now clear that human HFs are not only a target of multiple neuromediators, but also are a major non-classical production site for neurohormones such as CRH, proopiomelanocortin, ACTH, α-MSH, ß-endorphin, TRH, and melatonin. Moreover, human HFs have established a functional peripheral equivalent of the hypothalamic-pituitary-adrenal axis. By charting the author's own meanderings through the jungle of hair pigmentation research, the current perspectives essay utilizes four clinical observations - hair repigmentation, canities, poliosis, and 'overnight greying'- as points of entry into the enigmas and challenges of .pigmentary HF neuroendocrinology. After synthesizing key principles and defining major open questions in the field, selected research avenues are delineated that appear clinically most promising. In this context, novel neuroendocrinological strategies to retard or reverse greying and to reduce damage to the HFPU are discussed.
A thorough characterization of the morphological structure and physical properties is essential for an understanding of human hair. A number of techniques such as scanning electron microscopy, transmission electron microscopy and confocal microscopy have been used to study hair surfaces. Recently, atomic force microscopy (AFM) has emerged as an ideal method for the non-invasive examination of hair surfaces.
To investigate the effects of aging on normal Korean hair diameter and surface features using AFM.
We enrolled 60 Korean volunteers of various ages who had no hair diseases. We analyzed hair diameter, AFM images of the hair surface, cuticular descriptors and micro-scale mechanical properties for their associations with aging. Results: Hair diameter was found to increase for the first 20-30 years of life, after which it began to decrease. AFM images of most of the younger subjects showed typical step-like topographic properties with clear scale edges. The AFM images of most of the older subjects revealed dilapidated structures, poorly demarcated scale edges and undulated surfaces. Among the cuticular descriptors, surface roughness increased significantly with age. Force to distance analysis demonstrated a dependence on age.
These results suggest that aging causes changes in hair diameter and surface structure.
Cicatricial (scarring) alopecia results from irreversible damage to epithelial stem cells located in the bulge region of the hair follicle, generally as a result of inflammatory mechanisms (eg, in the context of autoimmune disease). In primary cicactricial alopecia (PCA), the hair follicle itself is the key target of autoaggressive immunity. This group of permanent hair loss disorders can be classified into distinct subgroups, characterized by the predominant peri-follicular inflammatory cell type. In none of these PCA forms do we know exactly why hair follicles begin to attract such an infiltrate. Thus, it is not surprising that halting or even reversing this inflammation in PCA is often extremely difficult. However, increasing evidence suggests that healthy hair follicle epithelial stem cells enjoy relative protection from inflammatory assault by being located in an immunologically "privileged" niche. Because this protection may collapse in PCA, one key challenge in PCA research is to identify the specific signaling pathways that endanger, or restore, the relative immunoprotection of these stem cells. After a summary of pathobiological principles that underlie the development and clinical phenotype of PCA, we close by defining key open questions that need to be answered if more effective treatment modalities for this therapeutically very frustrating, but biologically fascinating, group of diseases are to be developed.
Hair pigmentation is one of the most conspicuous phenotypes in humans. Melanocytes produce two distinct types of melanin pigment: brown to black, indolic eumelanin and yellow to reddish brown, sulfur-containing pheomelanin. Biochemically, the precursor tyrosine and the key enzyme tyrosinase and the tyrosinase-related proteins are involved in eumelanogenesis, while only the additional presence of cysteine is necessary for pheomelanogenesis. Other important proteins involved in melanogenesis include P protein, MATP protein, α-MSH, agouti signaling protein (ASIP), MC1R (the receptor for MSH and ASIP), and SLC7A11, a cystine transporter. Many studies have examined the effects of loss-of-function mutations of those proteins on mouse coat color pigmentation. In contrast, much less is known regarding the effects of mutations of the corresponding proteins on human hair pigmentation except for MC1R polymorphisms that lead to pheomelanogenesis. This perspective will discuss what we have/have not learned from mouse coat color pigmentation, with special emphasis on the significant roles of pH and the level of cysteine in melanosomes in controlling melanogenesis. Based on these data, a hypothesis is proposed to explain the diversity of human hair pigmentation.
The pilosebaceous unit is a complex structure that undergoes a specific growth cycle and comprises a few important drug targeting sites. For example, drugs can be targeted to the bulge region with stem cells or to the sebaceous glands. Interest in pilosebaceous units is directed towards their utilization as reservoirs for localized therapy and also as a transport pathway for systemic drug delivery. Improved investigative methods, such as differential stripping, are being developed in order to determine follicular penetration. This article reviews relevant aspects of effective follicle-targeting formulations and delivery systems as well as the activity status of hair follicles, and variations in follicle size and distribution throughout various body regions. Each of these factors strongly affects follicular permeation. We provide examples of improved penetration of particle-based formulations and of a size-dependent manner of follicular penetration. Contradictions are also discussed, indicating the need for detailed future investigations.
The hair-follicle bulge has recently been added to a growing list of human tissue compartments that exhibit a complex combination of immunosuppressive mechanisms, termed immune privilege (IP), which seem to restrict immune-mediated injury in specific locations. As epithelial hair-follicle stem cells (eHFSC) reside in the hair-follicle bulge region, it is conceivable that these IP mechanisms protect this vital compartment from immune-mediated damage, thereby ensuring the ongoing growth and cyclic regeneration of the hair follicle. Primary cicatricial alopecias (PCA) are a group of inflammatory hair disorders that result in hair-follicle destruction and permanent alopecia. Growing evidence suggests that eHFSC destruction is a key factor in the permanent follicle loss seen in these conditions.
To explore the possible role of bulge IP collapse in PCA pathogenesis.
We report three clinically distinct cases of PCA. Immunohistochemical analyses of paired biopsies from lesional and uninvolved scalp skin were compared using recognized markers of IP.
Immunohistochemical investigation found increased expression of major histocompatibility complex (MHC) classes I and II and of beta2-microglobulin in the bulge region of lesional follicles compared with uninvolved follicles in each case. Further, expression of the bulge marker keratin 15 was reduced in lesional skin in two of the cases.
This small series represents our first preliminary attempts to ascertain whether bulge IP collapse may play a role in PCA pathogenesis. We present standard parameters relating to hair-follicle IP in the bulge region of three patients with distinct PCA variants, and show the presence of features consistent with bulge IP collapse in each case.
Please cite this paper as: Methods in hair research: how to objectively distinguish between anagen and catagen in human hair follicle organ culture. Experimental Dermatology 2010; 19: 305–312.
Abstract: The organ culture of human scalp hair follicles (HFs) is the best currently available assay for hair research in the human system. In order to determine the hair growth-modulatory effects of agents in this assay, one critical read-out parameter is the assessment of whether the test agent has prolonged anagen duration or induced catagen in vitro. However, objective criteria to distinguish between anagen VI HFs and early catagen in human HF organ culture, two hair cycle stages with a deceptively similar morphology, remain to be established. Here, we develop, document and test an objective classification system that allows to distinguish between anagen VI and early catagen in organ-cultured human HFs, using both qualitative and quantitative parameters that can be generated by light microscopy or immunofluorescence. Seven qualitative classification criteria are defined that are based on assessing the morphology of the hair matrix, the dermal papilla and the distribution of pigmentary markers (melanin, gp100). These are complemented by ten quantitative parameters. We have tested this classification system by employing the clinically used topical hair growth inhibitor, eflornithine, and show that eflornithine indeed produces the expected premature catagen induction, as identified by the novel classification criteria reported here. Therefore, this classification system offers a standardized, objective and reproducible new experimental method to reliably distinguish between human anagen VI and early catagen HFs in organ culture.
Primary cicatricial alopecias (PCA) represent uncommon inflammatory disorders that result in permanent loss of scalp hair. Cutaneous autoimmunity, most prominently chronic cutaneous lupus erythematosus (CCLE), can result in this kind of scarring hair loss. The cosmetic disfigurement caused by PCA and the very unsatisfactory therapeutic options available to date all demand a better understanding of the obscure pathobiology of PCA so as to define new therapeutic targets and strategies. Hair follicle (HF) cycling and regeneration are abolished in PCA due to irreversible, epithelial hair follicle stem cell (eHFSC) damage, triggered by major, yet unclear pro-inflammatory events (e.g. type I interferon-associated cytotoxic inflammation, loss of HF immune privilege, loss of immunosuppressive "no danger" signals). Therefore, immuno-protection of eHFSC and restitution of their immune privilege are attractive future therapeutic strategies in PCA. Chronic cutaneous lupus erythematosus-associated PCA may serve as a model system for other diseases where epithelial stem cells undergo immuno-destruction.
This recently described entity begins in childhood and is characterized by actively growing hairs that can be easily and painlessly removed from the scalp, leading to alopecia.
Immunostaining techniques were used to investigate the relationship between immune cells, proteoglycan, and class I MHC distribution in skin during the hair cycle in rats. The growth stage, anagen, was characterized by absence of class I MHC staining on most cells of the lower follicle and presence of chondroitin proteoglycan in the follicle sheath and dermal papilla. Immune cells were few in number and not associated with follicles. Dramatic changes were observed during regression in catagen; class I MHC was expressed on all follicle epithelium, large numbers of activated macrophages aggregated around the follicles, and the chondroitin proteoglycans disappeared from the follicle sheath and dermal papilla. During the resting stage, telogen, class I MHC remained on cells of the secondary germ, but macrophages and chondroitin proteoglycans were absent. These observations lead us to propose a hypothesis of immune privilege in hair growth.
There is currently a debate in the literature on chemical drug analysis concerning the contribution of biophysical attributes associated with specimens and specimen donors to assay outcome. In recent years this debate has focused on hair analysis, but has in the past also been raised in urinalysis interpretation. In this article we examine several aspects of that controversy. First, we present data regarding the effects of hair color on the distribution of positive hair testing results for three drug classes. We compare these results to negative hair samples from comparable donors. This data is derived from head hair from preemployment donors that was classified according to seven visual color categories. We determined the distribution of colors for hair samples devoid of any of three assayed drugs (amphetamines, cocaine, and cannabinoids). Subsequently, this distribution was compared with the distributions for hairs that had tested positive for amphetamines, cocaine or cannabinoids. We examined a total of 2000 randomly selected samples; 500 negative hair samples and 500 positive samples for each of three drugs: cannabinoids, cocaine, and amphetamine. We also evaluated ethnic/racial factors in relation to positive urinalyses for various ethnic/racial groups. We examined approximately 4000 urine specimens from two different groups, each constituting around 2000 specimens. In addition to ethnicity/race and urinalysis outcome, we also examined the relationship between the hair color distributions of urine donors and the corresponding urinalysis results for the three drug classes. We also compared them to drug-negative samples. Our summary impression is that the observed outcome patterns were largely consistent with differences in drug preferences among the various societal groups. There was little evidence of a pattern attributable to hair color bias alone or selective binding of drugs to hair of a particular color. Likewise, there was no discernible pattern associated with race or ethnicity that would lend support to a “race effect” in drug analysis.
The Journal of Investigative Dermatology publishes basic and clinical research in cutaneous biology and skin disease.
The Journal of Investigative Dermatology publishes basic and clinical research in cutaneous biology and skin disease.
The few articles published on the interactions between psychological factors and alopecia seem to yield contrasting results. To assess the relationships between alopecia, gender, Diagnostic Statistical Manual of Mental Disorders, Revised Third Edition personality disorders, and psychopathologic symptoms reactive to alopecia, we administered the Personality Disorders Questionnaire-Revised and the Symptoms Checklist-90 to a randomly selected sample of 116 outpatients with androgenetic alopecia.
The prevalence of personality disorders in subjects with androgenetic alopecia proved to be significantly higher than the prevalence of such diagnoses in the general population. Women did not show a higher prevalence of personality disorders or more psychopathologic symptoms than men. The factor analysis demonstrated the existence of three personality profiles (F1, F2, and F3) significantly and specifically associated with the subject's gender and with the psychopathologic reactive symptoms, measured using the Symptoms Checklist-90.
The most important factor in developing a psychopathologic reaction to alopecia seems to be the presence of a Diagnostic Statistical Manual of Mental Disorders, Revised Third Edition personality disorder and not the subject's gender.
Growth factors are polypeptides that regulate growth and differentiation of many cell types. Different growth factor families including the epidermal growth factor (EGF)-related ligands, fibroblast growth factors (FGF), transforming growth factor-beta (TGF-beta), insulin-like growth factor (IGF), hepatocyte growth factor/scatter factor (HGF/SF), and platelet-derived growth factor (PDGF) have been shown to be crucial for the regulation of the hair cycle and hair growth. Growth factors and their receptors have been localized to the skin and hair follicles. Their biological activities on cells comprising the hair follicle have been tested in vitro and increasingly in transgenic mice. Herein we review selected important aspects of growth factors with regard to the hair organ, its development, and the hair growth cycle.
The hair follicle (HF) undergoes life-long cyclic transformations between "resting" (telogen), growth (anagen), and apoptosis-driven regression (catagen). Contrary to conventional wisdom, cyclic remodelling affects even the distal HF epithelium; telogen is not a mere resting period, since it shows substantial metabolic and proliferative activity and may encompass a phase of controlled hair shaft-extrusion ("exogen"). Even under physiological circumstances, very few (malfunctioning?) HF may leave this cycle over time to be removed by inflammatory cells ("programmed organ deletion"). Although numerous systemic, metabolic, immunological, and nerve-derived factors (e.g. hormones, cytokines, neuropeptides, neurotransmitters, mast cells) can profoundly alter hair growth in vivo, neither vascular nor neural stimuli nor extrafollicular cells are essential for HF development or cycling. Rather, an intrafollicular "hair cycle clock" of as yet unknown nature drives the HF cycle. This elusive chronobiological timing device likely exploits secondary changes in the intra- and perifollicular signalling milieu for guiding the HF through its transformations. However, the supreme generator of cycling activity ("oscillator") that dictates any of these signalling switches is still as unknown as is its exact location. Since, clinically, the control of catagen is of paramount importance (too early anagen termination: alopecia, effluvium; catagen too late: hirsutism, hypertrichosis), the controls of catagen-associated keratinocyte apoptosis and of dermal papilla secretory activities are discussed as crucial targets for future therapeutic manipulations.
The psychophysical responses to noxious cold stimulation of the skin in normal human subjects are not well understood. Continuous pain ratings with the visual analogue scale is an important method to assess these responses. In this study, we addressed several important issues about the parameters with which stimuli are delivered: the type of skin stimulated, the rate with which the stimulus temperature decreases, and the dimension of the pain rated by subjects. Cold stimuli were delivered to the thenar eminence (glabrous skin) and the dorso‐lateral hand (hairy skin) via a 4 cm2 Peltier‐type stimulator. Cold and pain thresholds were determined by the method of limits (MOL). A computerized visual analogue scale (VAS) was used to obtain continuous ratings of pain intensity and affect. The McGill Pain Questionnaire (MPQ) was used to assess the quality of cold‐evoked pain. Supra‐threshold stimuli (34°C base) were delivered at 0.5, 1 or 2°C/s to 2°C, held for 20s and returned to baseline at 9°C/s. These studies revealed: (1) Cold thresholds, measured with MOL, were lower (i.e. occurred at higher absolute temperatures) for the hairy skin of the dorso‐lateral hand compared to the glabrous skin of the thenar eminence. (2) A similar pattern was evident for cold induced pain thresholds with MOL at 1.5°C/s and with intensity and affect VAS scales at 0.5 and 1°C/s. (3) Exponents for supra‐threshold ratings fit to power functions were larger for the glabrous skin site than the hairy skin site regardless of cooling rate or dimension of pain measured. (4) All pain indices were higher for slower cooling rates. (5) No significant differences were found in the pain indices for pain ratings of intensity and affect. (6) A substantial proportion of subjects chose words representing paradoxical heat with the MPQ. (7) Painful paradoxical heat sensations occurred most often during cooling, while innocuous warm sensations mainly occurred during the rewarming phase.
There is currently a debate in the literature on chemical drug analysis concerning the contribution of biophysical attributes associated with specimens and specimen donors to assay outcome. In recent years this debate has focused on hair analysis, but has in the past also been raised in urinalysis interpretation. In this article we examine several aspects of that controversy. First, we present data regarding the effects of hair color on the distribution of positive hair testing results for three drug classes. We compare these results to negative hair samples from comparable donors. This data is derived from head hair from preemployment donors that was classified according to seven visual color categories. We determined the distribution of colors for hair samples devoid of any of three assayed drugs (amphetamines, cocaine, and cannabinoids). Subsequently, this distribution was compared with the distributions for hairs that had tested positive for amphetamines, cocaine or cannabinoids. We examined a total of 2000 randomly selected samples; 500 negative hair samples and 500 positive samples for each of three drugs: cannabinoids, cocaine, and amphetamine. We also evaluated ethnic/racial factors in relation to positive urinalyses for various ethnic/racial groups. We examined approximately 4000 urine specimens from two different groups, each constituting around 2000 specimens. In addition to ethnicity/race and urinalysis outcome, we also examined the relationship between the hair color distributions of urine donors and the corresponding urinalysis results for the three drug classes. We also compared them to drug-negative samples. Our summary impression is that the observed outcome patterns were largely consistent with differences in drug preferences among the various societal groups. There was little evidence of a pattern attributable to hair color bias alone or selective binding of drugs to hair of a particular color. Likewise, there was no discernible pattern associated with race or ethnicity that would lend support to a "race effect" in drug analysis.
The upper region of the outer root sheath of vibrissal follicles of adult mice contains multipotent stem cells that respond to morphogenetic signals to generate multiple hair follicles, sebaceous glands, and epidermis, i.e., all the lineages of the hairy skin. At the time when hair production ceases and when the lower region of the follicle undergoes major structural changes, the lower region contains a significant number of clonogenic keratinocytes, and can then respond to morphogenetic signals. This demonstrates that multipotent stem cells migrate to the root of the follicle to produce whisker growth. Moreover, our results indicate that the clonogenic keratinocytes are closely related, if not identical, to the multipotent stem cells, and that the regulation of whisker growth necessitates a precise control of stem cell trafficking.