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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.
... Складовими частинами шкіри є придатки шкіри, до яких належать такі утворення: нігті, волосся, потові, сальні та молочні залози. Усі вони так чи інакше беруть участь у виконанні вищезазначених функцій [5,31]. ...
... Воно покриває голову, тулуб та кінцівки людини за невеликими винятками, як-от губи, долонна поверхня рук, підошовна поверхня стоп та деякі ділянки зовнішніх статевих органів. Волосся має як епідермальне, так і мезенхімальне походження та складається з волосяного стрижня і фолікула [5]. Процес формування волосся під час внутрішньоутробного розвитку має чітку послідовність: спочатку відбувається формування так званого волосяного плакода. ...
... Відповідно до особливостей будови волосся поділяють на кілька різновидів: пушкове волосся (дрібне і непігментоване), щетинкове волосся (довге і пігментоване) та довге волосся (також довге і пігментоване). Щетинкове волосся, як і пушкове, на відміну від довгого типу волосся, є андроген незалежним [5]. Так само як інші органи та тканини людини, волосся зазнає вікових змін, що полягають у зменшенні кількості меланоцитів у волосяних фолікулах (посивіння) та ушкодженні стрижня і кореня волосся [18]. ...
Annotation. Alopecia is a widespread disease that affects different strata of the population by age, gender, socio-economic status and causes pathological hair loss on the human body. First of all, attention is drawn to the loss of hair follicles on the head, which causes significant psychological discomfort in these patients. Complex pathogenesis, high costs of treatment and lack of etiotropic treatment require a comprehensive review of this pathology. One of such promising, but underestimated directions is anthropometric, which involves the study of height, weight, circumferences and other parameters of the human body. The purpose of the study is to conduct a review of literary sources for the period 2013-2023, which is related to human anthropometric indicators and alopecia, using the inclusion and exclusion criteria for the analysis of publications. Taking into account the criteria for inclusion in the review, an analysis of 33 literary sources was carried out. The result of summarizing the research data shows that for many diseases of the skin and its appendages, anthropometric indicators have been identified, which allow forming risk groups of the occurrence or severity of the course of the disease. The results related to the analysis of samples of patients with one or another form of alopecia show that this disease is characterized by pronounced manifestations of sexual dimorphism in relation to anthropometric indicators, and most often correlations relate to such indicators as weight, body mass index, and waist circumference. Thus, the analysis of literary sources proves that there is a need to conduct an anthropometric study of representatives of the Ukrainian nationality suffering from alopecia of various genesis in order to further identify indicators that can be used to predict the risk of occurrence and course of this disease. During the research, it is necessary to pay special attention to the formation of a homogeneous sample according to the most key indicators, such as age, sex, concomitant diseases, type of alopecia, etc. In the future, it is planned to carry out a clinical study on a sample of people, residents of the Podillia region of Ukraine, suffering from alopecia.
... Hair can be classified into three types [5,6]: lanugo, vellus, and terminal hair. Lanugo hair is a fine and soft hair that covers the fetus during development and typically disappears after birth. ...
... From a functional perspective [5], terminal hair can be further categorized into androgendependent areas (scalp, beard, chest, axillae, and pubic region) and androgen-independent areas (eyebrows and eyelashes). Vellus hair, on the other hand, is not influenced by androgens and is independent of its effects. 2 ...
... At the level of the 3 infundibulum, the hair follicle exhibits a degree of keratinization similar to that of the epidermis, characterized by a distinguishable granular layer and stratum corneum. (Figure 2) [5,8,9,11] The only part of the hair follicle involved in the hair growth cycle is the lower segment. On the scalp, approximately 85 to 100% of hairs are typically found in the anagen phase, which lasts between 2 to 7 years. ...
Accurately diagnosing specific variants of alopecia remains challenging for pathologists, potentially delaying appropriate therapeutic decisions by dermatologists. Issues such as limited knowledge on optimal biopsy types and processing methods add complexity. Understanding the normal histology of hair follicles and their changes throughout the follicular cycle further complicates microscopic evaluation. This paper aims to summarize these characteristics and highlight essential diagnostic clues for pathologists to confidently suggest a diagnosis, therefore playing a key role in alopecia diagnosis. Ongoing education, collaboration with dermatologists, and staying updated on advancements is crucial for accurate diagnosis and effective management of different types of alopecia.
... The IRS cuticle layer connects to the hair shaft's cuticle, securing the hair shaft to the follicle. IRS cells produce keratins and trichohyalin, which act as an intracellular cement, giving the IRS strength to support and shape the growing hair shaft while also guiding its upward movement [8] The hair bulb is the portion of the follicle which actively produces the hair. The hair bulb encloses the follicular dermal papilla which is thought to be one of the most important factors in instructing the hair follicle to grow and form a specific sized and pigmented hair shaft. ...
... The hair bulb encloses the follicular dermal papilla which is thought to be one of the most important factors in instructing the hair follicle to grow and form a specific sized and pigmented hair shaft. [8] The hair follicle can be divided into three distinct zones. The innermost zone, in and around the bulb, is where hair cells are biologically synthesized. ...
... [10] Some, but not all, hair follicles are surrounded at the level of the sebaceous gland by a collar of nerves known as the hair end organ, which is divided into an outer circular layer and an inner longitudinal layer. [8] ...
Dandruff is a common scalp disorder affecting almost 50% of the human population caused by M. globosa and M. furfur which are two naturally occurring skin fungus. This review discusses in detail the anatomy, pathophysiology, causes and symptoms, and treatment methods available for Dandruff. It also highlights the herbal ingredients with anti-dandruff activity that are used in novel shampoo formulations as a treatment strategy. This review discusses various bioactivities through which these compounds treat dandruff such as anti-inflammatory, antifungal, as well as their mechanism of action. Due to its amphibious status, dandruff is the most commercially exploited skin and scalp disorder/disease by personal care enterprises because there is less medical intervention for treatment.
... The hair is made up of dermal papilla cells and ends up going all the way to the top of the dermis [1]. Hair protects the body from the outside world, makes the body look elegant, and adds to the person's personality. ...
... The hair bulb is the part of the hair follicle at the bottom that is relatively enlarged and is called the inferior segment. The bulb is a living, growing cell that is an important part of hair growth [1,10,12]. ...
... In the germinal matrix, melanocyte cells are present. Melanocyte cells generate the pigment melanin, which imparts color to hair [1,10]. The arrector pili muscle is a smooth muscle situated beneath the hair follicle. ...
Polymer, lipid, and natural protein-based hair care nanocarriers are in preclinical testing. Nanomedicine has enhanced therapeutic efficacy and decreased side effects. This review examines herbal nanomedicine for hair care. We also reviewed the hair cycle, its morphology, and the mechanisms of herbal-based medicine that regulate the hair cycle to treat hair loss. Nano-formulations have better solubility, permeability, therapeutic efficacy, and prolonged distribution than standard herbal medicines. This review also discussed the nanotechnology barrier and nano formulations for hair loss and growth and includes a recent herbal nanomedicine study. Researchers interested in using herbs to treat hair problems and clinically translating hair care products may find the results presented significant.
... Hair can be classified into three types [5,6]: lanugo, vellus, and terminal hair. Lanugo hair is a fine and soft hair that covers the fetus during development and typically disappears after birth. ...
... At the level of the infundibulum, the hair follicle exhibits a degree of keratinization similar to that of the epidermis, characterized by a distinguishable granular layer and stratum corneum. (Figure 2) [5,8,9,11] The only part of the hair follicle involved in the hair growth cycle is the lower segment. On the scalp, approximately 85 to 100% of hairs are typically found in the anagen phase, which lasts between 2 and 7 years. ...
Accurately diagnosing specific variants of alopecia remains challenging for pathologists, potentially delaying appropriate therapeutic decisions by dermatologists. Issues such as limited knowledge on optimal biopsy types and processing methods add complexity. Understanding the normal histology of hair follicles and their changes throughout the follicular cycle further complicates microscopic evaluation. This paper aims to summarize these characteristics and highlight essential diagnostic clues for pathologists to confidently suggest a diagnosis, therefore playing a key role in alopecia diagnosis. Ongoing education, collaboration with dermatologists, and staying up to date on advancements is crucial for the accurate diagnosis and effective management of different types of alopecia.
... 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 [49,7,46]. The glabrous skin is found in the palms of our hands and feet. ...
... Heterogeneous mechanics of skin 7 The sinusoidal interface reduces the average stress jump along the interface Considering the strip-x biaxial loading, the simplified model with the three strips loaded in parallel, illustrated in Fig. 1e, was solved. Figure 3a left shows the results for this analytical model. ...
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.
... As an important appendage of skin organs, hair is a unique feature of mammals [18,19]. The main functions of hair include protecting the skin from mechanical damage, heat preservation, and sensory functions, and it has an influence on social interaction, psychology, and quality of life [20,21]. ...
... For the hair cycle, the number and shape of hair follicle precursor cells, as well as their proliferation rate, affect the length and fineness of the hair; the longer the hair follicle 10 BioMed Research International growth period, the longer the hair [18]. The histopathological sections revealed that there were more hair follicles following baicalin treatment, the hair follicles were long and large, and the expression of melanin was obvious. ...
The aim of the present study was to explore the potential pharmacological mechanism of baicalin by combining network pharmacology prediction and the experimental verification of alopecia. Networks of baicalin-associated targets and alopecia-related genes were constructed using the STRING database. Potential targets and pathways associated with the therapeutic efficacy of baicalin were identified via enrichment analysis using Cytoscape and the database for annotation, visualization and integrated discovery (Metascape). The back hair of C57BL/6J mice was removed with depilatory cream to verify the therapeutic effect of baicalin. Human hair dermal papilla cells (HHDPCs) were used to explore the mechanism of action of baicalin. Network pharmacology analysis revealed that the potential targets of baicalin mainly include protein serine/threonine kinase, Src protein, epidermal growth factor receptor, and insulin-like growth factor 1 (IGF1), which were indicated to mediate neutrophil degranulation and regulation of cell-cell adhesion, vesicle lumen, cytoplasmic vesicle, membrane raft, and endopeptidase activity. Multiple pathways were identified, such as proteoglycans in cancer, PI3K/AKT, and forkhead box O signaling pathways. Following baicalin treatment for the experimental mice, the coverage, length, and weight of the hair increased in a baicalin dose-dependent manner. Moreover, the histological evaluation showed that the number of hair follicles increased after baicalin treatment and melanin formation were pronounced. In addition, baicalin induced an increase in the phosphorylated p-AKT, p-glycogen synthase kinase-3β, p-PI3K, TGF-β1, and vascular endothelial growth factor levels. Furthermore, the activation levels of key protein p-AKT were increased. Baicalin induced the proliferation of HHDPCs in vitro and significantly upregulated p-AKT, IGF1, and alkaline phosphatase. In conclusion, the present study revealed that the pharmacological mechanisms of baicalin in alopecia therapy were associated with the proliferation of DPCs, the activation of the AKT pathway, and the transmission of downstream signals, indicating that baicalin is a potential drug candidate for the clinical treatment of hair loss.
... 8,10 Furthermore, no prior studies have compared electrolysis and laser for removal of genital hair, 8,10 which has anatomy and physiology different from hair in other body regions. 11 Understanding relative outcomes of electrolysis and LHR is crucial for helping patients select the most optimal hair-removal techniques in preparation for surgery. Optimizing the process of hair removal has the potential to significantly improve patients' quality of life by minimizing delays in proceeding with surgery, maximizing efficiency and tolerability, and minimizing cost. ...
... 12 Both electrolysis and LHR are nearly always associated with some degree of hair regrowth. 11,23,33,44,[51][52][53][54][55][56] Many studies support the durability of LHR results. 23,33,44,[51][52][53][54][55][56] One study reported that both diode and alexandrite lasers resulted in over 70% hair clearance lasting 18 months (the study duration) after 6 treatments. ...
Introduction
Permanent genital hair removal is required before gender-affirming vaginoplasty to prevent hair-related complications. No previous studies have directly compared the relative efficacy, costs, and patient experiences with laser hair removal (LHR) vs electrolysis treatments. Food and Drug Administration (FDA) oversight of medical devices is poorly understood and commonly misrepresented, adversely affecting patient care.
Aim
This study compares treatment outcomes of electrolysis and LHR for genital hair removal and investigates FDA regulation of electrolysis and LHR devices.
Methods
Penile-inversion vaginoplasty and shallow-depth vaginoplasty patients completed surveys about their preoperative hair removal, including procedure type, number/frequency of sessions, cost, and discomfort. Publicly available FDA-review documents and databases were reviewed.
Main Outcomes Measure
Compared to electrolysis, LHR was associated with greater efficiency, decreased cost, decreased pain, and improved patient satisfaction.
Results
Of 52 total (44 full-depth and 8 shallow-depth) vaginoplasty patients, 22 of 52 underwent electrolysis only, 15 of 52 underwent laser only, and 15 of 52 used both techniques. Compared to patients that underwent LHR only, patients that underwent only electrolysis required a significantly greater number of treatment sessions (mean 24.3 electrolysis vs 8.1 LHR sessions, P < .01) and more frequent sessions (every 2.4 weeks for electrolysis vs 5.3 weeks for LHR, P < .01) to complete treatment (defined as absence of re-growth over 2 months). Electrolysis sessions were significantly longer than LHR sessions (152 minutes vs 26 minutes, P < .01). Total treatment costs for electrolysis ($5,161) were significantly greater than for laser ($981, P < .01). Electrolysis was associated with greater pain and significantly increased need for pretreatment analgesia, which further contributed to higher net costs for treatment with electrolysis vs laser. Many LHR and electrolysis devices have been FDA-cleared for safety, but the FDA does not assess or compare clinical efficacy or efficiency.
Clinical Implications
For patients with dark-pigmented hair, providers should consider LHR as the first-line treatment option for preoperative hair removal before gender-affirming vaginoplasty.
Strength and Limitations
This is the first study to compare electrolysis and LHR for genital hair removal. The discussion addresses FDA review/oversight of devices, which is commonly misrepresented. Limitations include the survey format for data collection.
Conclusion
When compared with electrolysis, LHR showed greater treatment efficiency (shorter and fewer treatment sessions to complete treatment), less pain, greater tolerability, and lower total cost. Our data suggests that, for patients with dark genital hair, providers should consider recommending laser as the first-line treatment for permanent genital hair removal before vaginoplasty.
Yuan N, Feldman A, Chin P, et al. Comparison of Permanent Hair Removal Procedures before Gender-Affirming Vaginoplasty: Why We Should Consider Laser Hair Removal as a First-Line Treatment for Patients Who Meet Criteria. Sex Med 2022;10:100545.
... It varies according to the ethnic group and among individuals. With the exception of some areas such as foot soles, hand palms, buccal surface of the lips and parts of the external genitalia, mammalian skin generates hair almost all over the body surface [70]. Hair is comprised of two parts: the follicle which is in the skin and the shaft which can be seen on the surface of the body. ...
... Hair begins from the epidermis surface and extends to various depths in the skin according to the type of hair. Thick, long and pigmented hair (terminal hair) is produced from hair follicles that extend into the deep epidermis, while thin, short and light-coloured hair (vellus hair) is produced from follicles which extend into the upper epidermis [70,71]. ...
The poor aqueous solubility of many approved drugs and most new chemical entities poses a challenge to drug delivery scientists working in academic and industrial labs. Despite the high pharmacological activity these drugs may have, their limited water solubility leads to poor absorption and consequently to sub-therapeutic drug concentrations in target tissues. The formulation of drug nanocrystals (NCs) has emerged as one the most promising approaches for increasing the biopharmaceutical performance of hydrophobic drugs. Initially aimed at increasing the absorption of drugs administered orally, NCs have been increasingly utilised to allow drug delivery via multiple routes, namely, parenteral injections, transdermal, ocular, intranasal, and pulmonary. This review aims to describe the recent progress in the field and demonstrate how the NCs technology enabled the delivery of hydrophobic drugs through multiple administration routes.
... A mouse has three waves of HF morphogenesis that result in the presence of four types of HF types: guard, awl, auchene, and zigzag hair, and also the special type-vibrissa follicles [118]. A Human has two generations of HFs: the embryo-type lanugo hairs and the adult, which are divided into terminal hairs in the scalp and beard, pubic/axillary hairs, and vellus hairs throughout the body [119]. The HF is composed of the epithelial part which includes the hair shaft, inner, and outer root sheaths. ...
Most of the knowledge about human skin homeostasis, development, wound healing, and diseases has been accumulated from human skin biopsy analysis by transferring from animal models and using different culture systems. Human-to-mouse xenografting is one of the fundamental approaches that allows the skin to be studied in vivo and evaluate the ongoing physiological processes in real time. Humanized animals permit the actual techniques for tracing cell fate, clonal analysis, genetic modifications, and drug discovery that could never be employed in humans. This review recapitulates the novel facts about mouse skin self-renewing, regeneration, and pathology, raises issues regarding the gaps in our understanding of the same options in human skin, and postulates the challenges for human skin xenografting.
... The CTS is a thin-membrane tissue surrounded by muscle fibers that are entangled to provide a supportive structure for other tissues. Within the HFs, a CTS surrounds the ORS [13]. ...
Alopecia areata (AA) is an autoimmune dermatological disease with multifactorial etiology and is characterized by reversible hair loss in patches. AA may be closely related to emotional stress and influenced by psychological factors as part of its pathophysiology; however, its etiology remains predominantly unknown. This review aimed to elucidate the association between AA occurrence and the neuropeptide substance P (SP) and corticotropin-releasing hormone (CRH), which are secreted during emotional stress, and have been understood to initiate and advance the etiopathogenesis of AA. Therefore, this review aimed to explain how SP and CRH initiate and contribute to the etiopathogenesis of AA. To assess the etiopathogenesis of AA, we conducted a literature search on PubMed and ClinicalTrials.gov. Overall, several authors described interactions between the hair follicles (HFs) and the stress-associated signaling substances, including SP and CRH, in the etiology of AA; this was attributed to the understanding in that AA can occur without the loss of HFs, similar to that observed in hereditary hair loss with age. Most studies demonstrated that the collapse of “immune privilege” plays a crucial role in the development and exacerbation of the AA; nonetheless, a few studies indicated that substances unrelated to autoimmunity may also cause apoptosis in keratocytes, leading to the development of AA. We investigated both the autoimmune and apoptotic pathways within the etiology of AA and assessed the potential interactions between the key substances of both pathways to evaluate potential therapeutic targets for the treatment of AA. Clinical trials of marketed/unreviewed intervention drugs for AA were also reviewed to determine their corresponding target pathways.
... Hair follicles are primarily composed of epithelial and dermal components. Hair follicles are hair shaft-producing mini-organs and exhibit regular cycles of regeneration, known as the hair cycle [2] . The hair follicle, undergoes successive cyclic periods of growth, involving an active growing phase (anagen) during which the previous hair is shed, a small transitionary regressive phase (catagen) and a dormant resting phase (telogen) [3] , which allows the follicle to produce different types of hair in response to hormonal changes. ...
... Análise e discussãoEstrutura da fibra capilar O cabelo é uma estrutura queratinizada que se forma a partir da invaginação da epiderme na derme, e se divide em folículo piloso e haste capilar, que se subdivide em cutícula, córtex e medula (MIRANDA-VILELA; BOTELHO; MUEHLMANN, 2013). A medula, quando presente no fio, se apresenta como sendo a estrutura mais central do fio(BUFFOLI et al., 2013). O córtex é constituído de células corticais fusiformes compactadas ricas em filamentos de queratina, que recobrem a medula, e essa camada cortical determina muitas das propriedades mecânicas do cabelo(SINCLAIR, 2007).A cutícula localiza-se na parte mais externa das fibras capilares, recobrindo todo o fio de modo a proteger o córtex de agressões físicas e químicas (BUFFOLI, 2013). ...
O composto ácido 18-metileicosanoico é um tipo de ácido graxo que ocorre naturalmente nos cabelos e funciona como um componente chave da superfície cuticular. Especificamente, ele cria uma barreira hidrofóbica que ajuda a lubrificar os cabelos e manter sua aparência. O objetivo deste estudo foi examinar o papel do 18-MEA no cuidado dos cabelos e seu potencial impacto no comportamento e aparência de cada fio. Para guiar nossa investigação, formulamos a seguinte pergunta: "O ácido 18-metileicosanoico (18-MEA) é um fator significativo na influência das propriedades das fibras capilares e no aprimoramento da aparência dos cabelos?" Foi realizada uma revisão integrativa da literatura usando fontes como o Google Scholar e a Biblioteca Nacional de Medicina (PUBMED) com os descritores DeCS / MeSH: "ácido 18-metileicosanoico", "hair", "análise capilar". Foram incluídos artigos em português e inglês publicados entre 2002 e 2022, com critérios de exclusão baseados em relevância e acessibilidade, resultando na seleção de 14 artigos. A análise desses artigos revelou que a ausência de 18-MEA na superfície cuticular do cabelo pode levar a uma diminuição no ângulo de contato e um aumento na força de fricção. Além disso, estudos mostraram que a incorporação de 18-MEA por meio de formulações cosméticas pode resultar em hidrofobicidade persistente nos cabelos, destacando ainda mais sua importância na influência das propriedades capilares, como adesão e redução de fricção, promovendo uma aparência mais saudável para os cabelos.
... Also, in a previous study from our laboratory we have shown that lenalidomide inhibited the vitiligo progression in a vitiligo mouse model [11]. For the repigmentation of vitiliginous skin, melanocyte reservoir in the hair follicles must be activated, differentiated and migrated toward depigmented epidermis of vitiliginous skin [17,18]. ...
Introduction:
Melanocyte progenitors are embryonically derived from the neural crest and subsequently get localized in hair follicles and epidermis to provide hair and skin pigmentation. These progenitor cells in hair follicles repeatedly proliferate and differentiate to maintain pigmentation. Vitiligo, a pigmentary disorder, is associated with loss of melanocytes. Repigmentation of vitiligo lesions mainly depends upon the proliferation, migration and differentiation of melanocyte stem cells (MelSCs) into functional melanocytes. The current study is designed to check the efficacy of lenalidomide, an imide drug in the differentiation of MelSCs into functional melanocytes.
Objectives:
The aim of the study is to check the effect of lenalidomide in the proliferation, migration of cultured hair follicle derived melanocyte stem cells and their differentiation into functional melanocytes.
Methods:
Primary culture of MelSCs was established from whisker hair of C57BL/6 mice. Proliferation and migration of cultured cells were done by MTT assay and Boyden's chamber migration assay, respectively. Effect of lenalidomide on the MelSCs differentiation was checked at gene level by qPCR and protein expression was checked by immunocytochemistry.
Results:
A significant increase in the migration of MelSCs in comparison to control was also observed. Lenalidomide treatment significantly increased the expression of melanocyte specific genes in cultured MelSCs as compared to control.
Conclusions:
From the results we concluded that lenalidomide induce the proliferation and migration of MelSCs and accelerate the differentiation of MelSCs into functional melanocytes.
... The supply of the pilosebaceous unit is provided by a vascular network located in the lower portion of the hair follicle close to the outer root sheath. 70 In our previous experiments, we have shown the sustained urinary excretion of Gf after the topical administration of Gf-loaded vaterite particles, which indicates drug permeation into the circulatory system through the perifollicular vessels. 30 Since we cannot exclude the probability of the interaction for our carriers with immune and blood cells, we have further investigated the cytotoxic effect of the obtained Gf-loaded vaterite particles and free Gf drug on immune cells (particularly, on macrophages), as well as their impact on the integrity of RBCs. ...
The search for novel therapeutic strategies to treat fungal diseases is of special importance nowadays given the emerging threat of drug resistance. Various particulate delivery systems are extensively being developing to enhance bioavailability, site-specific penetration, and therapeutic efficacy of antimycotics. Recently, we have designed a novel topical formulation for griseofulvin (Gf) drug, which is currently commercially available in oral dosage forms due to its limited skin permeation. The proposed formulation is based on vaterite carriers that enabled effective incorporation and ultrasonically assisted delivery of Gf to hair follicles improving its dermal bioavailability. Here, we evaluated the effect of ultrasound on the viability of murine fibroblasts co-incubated with either Gf-loaded carriers or a free form of Gf and investigated the influence of both forms on different subpopulations of murine blood cells. The study revealed no sufficient cyto- and hemotoxicity of the carriers, even at the highest investigated concentrations. We also conducted a series of in vivo experiments to assess their multi-dose dermal toxicity and antifungal efficiency. Visual and histological examinations of the skin in healthy rabbits showed no obvious adverse effects after US-assisted application of the Gf-loaded carriers. At the same time, investigation of therapeutic efficiency for the designed formulation in comparison with free Gf and isoconazole drugs in a guinea pig model of trichophytosis revealed that the vaterite-based form of Gf provided the most rapid and effective cure of infected animals together with the reduction in therapeutic procedure number. These findings pave the way to improving antifungal therapy of superficial mycoses and justifying further preclinical studies.
... It is reported that the proportion of heteroplasmy in hair was about 34.7% when 95 hair samples were analysed [149]. Numerous scientific studies have shown that genetic drift and bottleneck effects are responsible for the high incidence of mitochondrial heteroplasmy in hair, because hair bulb cells have an exceptionally high mitotic rate and therefore have a higher potential for mutations [101,[168][169][170]. Studies have shown that the root and shaft of the same hair can have different frequencies of heteroplasmy, especially when the hair follicle tissue is attached to the hair root [142]. ...
Hair is one of the most common pieces of biological evidence found at a crime scene and plays an essential role in forensic investigation. Hairs, especially non-follicular hairs, are usually found at various crime scenes, either by natural shedding or by forcible shedding. However, the genetic material in hairs is usually highly degraded, which makes forensic analysis difficult. As a result, the value of hair has not been fully exploited in forensic investigations and trials. In recent years, with advances in molecular biology, forensic analysis of hair has achieved remarkable strides and provided crucial clues in numerous cases. This article reviews recent developments in DNA and protein analysis of hair and attempts to provide a comprehensive solution to improve forensic hair analysis.
... The main pathophysiological characteristics of Androgenic Alopecia are altered hair cycle development and Follicular miniaturization [7] . Hair growth occurs in three cyclical phases: anagen (growth), catagen (transition), and telogen (rest) [8] . In this condition, the telogen phase, which either remains the same length or lengthens with each cycle, but the anagen phase shortens. ...
... information. It is also possible to retrieve temporal data from hair as the growth rate of human head hair is well known at approximately 1 cm per month 11 and where the segment of hair closest to the scalp contains the most recent information compared to the distal ends. Fingernails grow faster than toenails at approximately 3.5 mm per month compared to toenails at an average rate of 1.6 mm per month 12 . ...
The utility of stable hydrogen and oxygen isotope analysis of human tissues for geolocation is an important area of study within forensic science. This study aimed to first validate the latitudinal relationship between stable hydrogen and oxygen isotopes in drinking water and human keratinous tissues through the analysis of human samples with known geographical origin. And secondly, to explore the use of classification and regression tree (CART) models to geographically classify individuals based on the stable isotope values of tissues themselves. Human hair and toenails were collected from four distinct study sites across Canada. The comparison of stable isotope values in drinking water and human tissues produced low R² values indicating that linear models may not fully explain the variation observed for both hydrogen and oxygen values. Additionally, large intrapopulation variations were observed for Canadian cities and highlights the importance of understanding the regional isotopic spread of human values. Further, this study demonstrated that a closed group of unknown individuals known to have originated from a limited number of geographically distinct regions may be classified into their respective groups through the use of CART models. The potential for the CART model approach for human geolocation presents a promising new tool.
... In the hair follicle matrix, there are melanocytes, which produce the hair pigment. In the suprabulbar area the hair follicle epithelium is located, composed of concentric layers forming the outermost outer root sheath, the inner root sheath, and the most internal hair shaft (it will be the visible part of the emerging hair) [29]. ...
Alopecia areata is a multifactorial autoimmune-based disease with a complex pathogenesis. As in all autoimmune diseases, genetic predisposition is key. The collapse of the immune privilege of the hair follicle leading to scalp loss is a major pathogenic event in alopecia areata. The microbiota considered a bacterial ecosystem located in a specific area of the human body could somehow influence the pathogenesis of alopecia areata, as it occurs in other autoimmune diseases. Moreover, the Next Generation Sequencing of the 16S rRNA bacterial gene and the metagenomic methodology have provided an excellent characterization of the microbiota. The aim of this narrative review is to examine the published literature on the cutaneous and intestinal microbiota in alopecia areata to be able to establish a pathogenic link. In this review, we summarize the influence of the microbiota on the development of alopecia areata. We first introduce the general pathogenic mechanisms that cause alopecia areata to understand the influence that the microbiota may exert and then we summarize the studies that have been carried out on what type of gut and skin microbiota is found in patients with this disease.
... This is also true for other purposes such as personal, social, and sexual engagement. [2,3]. As a result, hair condition is regarded as a key indicator of health [4]. ...
Hair quality is viewed as an important factor of health. It is a fundamental structure made up of simple uncomplicated filaments that provides protection from heat from either direct sunlight or any processes involved in hair care treatments. Moreover, it mirrors a person's social status and relationships, including features like youthful appearance, age, and lifestyle trends. Cosmetic products intended for hair care are used for several purposes to enhance overall hair, shaft, and scalp health. This is where nanotechnology-based delivery for hair care enters. The advancement of research and development demonstrated by nanotechnology boosts hair care product efficacy by delivering creative solutions. This review paper aims to discuss and provide an overview regarding nanotechnology and its incorporation into hair care cosmetics in order to enhance quality as well as hair care delivery. Specifically it presents a summary of all the gathered publications with relevance to nanotechnology and its application to hair care products in terms of delivery, benefits, and the risks involved with its inclusion. With this, the major findings of several studies presented that nanoparticles can increase the advantages of active substances when incorporated into hair care products and that the improved understanding regarding pathways of the hair care delivery has helped in the personalization of products which in turn improves hair cosmesis.
... sebum, apocrine sweat and pheromones and thermoregulation. The hair also plays important roles for the individual's social and sexual interaction (1) . ...
... The current study is aimed at evaluating the effects of a meditation intervention on hair cortisol concentrations as a chronic stress biomarker in an undergraduate student population of a medical faculty. Hair cortisol levels represent free cortisol percentage which diffuses from capillary blood to growing pilose follicles, incorporating into the hair, where it remains without degradation [29,32]. The measurement of cortisol in hair is considered an excellent biomarker of chronic stress; its levels correlate positively with salivary cortisol, corroborated by many studies in the research about stressors affecting the population [33]. ...
Methods:
Undergraduate students from the University of Chile's health careers were divided at random into control (n = 7) and treated groups (n = 15). The treated group participated in an active meditation program once a week for three months. This treatment included different techniques such as Chakra Sounds, Nataraj, Mandala, Kundalini, Devavani, Gourishankar, and Nadabrahma. Hair samples were taken before and after the treatment period to measure cortisol.
Results:
The control group increased cortisol level 168.9 ± 76.8 pg/mg compared with initial levels. The treated group shows a decrease of initial cortisol values in 28.5 ± 12.8 pg/mg after meditation protocol application.
Conclusions:
Blending active meditation in students' daily routine through occupational therapy intervention might prevent undergraduate students' stress in healthcare careers.
... Almost all mammals have fur or other hair-related structures that help them adapt to their habitats. Hair usually provides thermal regulation and camouflage (Dawson et al., 2014) also it has also been related to some communication and mating processes (Buffoli et al., 2014). Beyond their functional role for animals, hair constitutes a habitat for multiple microorganisms on which they coexist and associate in complex ways with their host (Chen et al., 2018). ...
Sloths have a dense coat on which insects, algae, and fungi coexist in a symbiotic relationship. This complex ecosystem requires different levels of control, however, most of these mechanisms remain unknown. We investigated the bacterial communities inhabiting the hair of two‐ (Choloepus Hoffmani) and three‐toed (Bradypus variegatus) sloths and evaluated their potential for producing antibiotic molecules capable of exerting control over the hair microbiota. The analysis of 16S rRNA amplicon sequence variants (ASVs) revealed that the communities in both host species are dominated by Actinobacteriota and Firmicutes. The most abundant genera were Brevibacterium, Kocuria/Rothia, Staphylococcus, Rubrobacter, Nesterenkonia, and Janibacter. Furthermore, we isolated nine strains of Brevibacterium and Rothia capable of producing substances that inhibited the growth of common mammalian pathogens. The analysis of the biosynthetic gene clusters (BCGs) of these nine isolates suggests that the pathogen‐inhibitory activity could be mediated by the presence of siderophores, terpenes, beta‐lactones, Type III polyketide synthases (T3PKS), ribosomally synthesized, and post‐translationally modified peptides (RiPPs), non‐alpha poly‐amino acids (NAPAA) like e‐Polylysin, ectoine or nonribosomal peptides (NRPs). Our data suggest that Micrococcales that inhabit sloth hair could have a role in controlling microbial populations in that habitat, improving our understanding of this highly complex ecosystem. This article is protected by copyright. All rights reserved.
... Relying on these effects, HHF is a kind of natural nanocomposite absorption substrate with good economic performance. Moreover, HHF, as a natural polymer, will not have a negative effect on water when it is used as an absorbent and oil/water separation material 24 . Herein HHF, a cheap solid waste, was rationally selected as a substrate to fabricate the advanced oil/water separation material by attaching hydrophobic coating onto the HHF surface. ...
Frequent oil spill accidents and industrial wastewater discharge has always been one of the most severe worldwide environmental problems. To cope with this problem, many fluorine-containing and high-cost materials with superwettability have been extensively applied for oil–water separation, which hinders its large-scale application. In this work, a novel human hair fiber (HHF)-polymerized octadecylsiloxane (PODS) fiber was fabricated with a facile one-pot dip-coating synthesis approach, inspired by the self-assembly performance and hydrophobicity of OTS modification. The benefits of prominent hydrophobic/lipophilic behavior lie in the low surface energy, and a rough PODS coating was rationally adhered on the surface of HHF. Driven solely by gravity and capillary force, the HHF-PODS showed excellent oil/water separation efficiency (> 99.0%) for a wide range of heavy and light oil/water mixtures. In addition, HHF-PODS demonstrated durability toward different harsh environments like alkaline, acid, and salty solutions.
... Because HFSCs can differentiate into a variety of skin cells, we believe that T2DM inhibits the skin renewal capacity by inhibiting the Lgr5 HFSCs activation. Hair follicles are distributed in most areas of the body, but there are differences in distribution and morphology [43]. In humans, most of the hair on the body surface is small and colorless, while the hair on the head is longer and denser. ...
Background:
Hair follicles are important accessory organs of the skin, and it is important for skin renewal and performs variety of important functions. Diabetes can cause several dermatoses; however, its effect on hair follicles is unclear. The purpose of this study was to investigate the effect of type II diabetes (T2DM) on the hair follicles of mice.
Methods:
Seven-week-old male C57BL/6 littermate mice were divided into two groups. The treatment group was injected with streptozotocin (STZ) to induce T2DM, and the control group was parallelly injected with the same dose of buffer. Seven days after injection, the back is depilated to observe the hair follicle regeneration. Hair follicle regeneration was observed by naked eyes and HE staining. The proliferation of the skin cells was observed by PCNA and K14 staining. The altered genes were screened by RNA sequencing and verified by qRT-PCR. In addition, Lgr5 + GFP/mTmG transgenic mice were used to observe the effect of T2DM on Lgr5 hair follicle stem cells (HFSC). And the expression of WNT4 and WNT8A were measured by Western Blot.
Results:
T2DM inhibited hair follicle regeneration. Compared to control mice, T2DM mice had smaller hair follicles, reduced skin thickness, and less expression of PCNA and K14. RNA sequencing showed that the two groups had significant differences in cell cycle and proliferation-related pathways. Compared with the control mice, the mRNA expression of Lgr4, Lgr5, Wnt4, and Wnt8a was decreased in the T2DM group. Moreover, T2DM inhibited the activation of Lgr5 HFSC and the expression of WNT4 and WNT8A.
Conclusions:
T2DM inhibited hair follicle regeneration and skin cells proliferation by inhibiting WNT-dependent Lgr5 HFSC activation. This may be an important reason for the reduction of skin renewal ability and the formation of chronic wounds caused by diabetes. It is important for the treatment of chronic diabetic wounds and the development of tissue engineering.
... Hair is a unique character in mammals, and has important biological functions, such as mate attraction, skin protection, and social communication [1,31]. Alopecia is a common phenomenon in mammal, including humans, and can seriously affect health. ...
Background
The giant panda ( Ailuropoda melanoleuca ) is a threatened species endemic to China. Alopecia, characterized by thinning and broken hair, mostly occurs in breeding males. Alopecia significantly affects the health and public image of the giant panda and the cause of alopecia is unclear.
Results
Here, we researched gene expression profiles of four alopecia giant pandas and seven healthy giant pandas. All pandas were approximately ten years old and their blood samples collected during the breeding season. A total of 458 up-regulated DEGs and 211 down-regulated DEGs were identified. KEGG pathway enrichment identified that upregulated genes were enriched in the Notch signaling pathway and downregulated genes were enriched in ribosome, oxidative phosphorylation, and thermogenesis pathways. We obtained 28 hair growth-related DEGs, and identified three hub genes NOTCH1 , SMAD3 , and TGFB1 in PPI analysis. Five hair growth-related signaling pathways were identified with abnormal expression, these were Notch, Wnt, TGF-β, Mapk, and PI3K-Akt. The overexpression of NOTCH1 delays inner root sheath differentiation and results in hair shaft abnormalities. The delayed hair regression was associated with a significant decrease in the expression levels of TGFB1.
Conclusions
Our data confirmed the abnormal expression of several hair-related genes and pathways and identified alopecia candidate genes in the giant panda. Results of this study provide theoretical basis for the establishment of prevention and treatment strategies for giant pandas with alopecia.
... Nevertheless, the hair loss can be consequence of metabolic and hormonal dysfunctions or stress. 19 Figure 3 shows the main functions of the hair by Buffoliet al. 20 It has also a sensory function, increasing the perception of the skin surface for tactile stimuli, and sub-serves important roles in sexual and social communication. In addition, authors have reported that hair can be used as a specimen to quantify the concentration of cortisol in the body (Figure 1b). ...
Introduction The physical inactivity has been identified as the fourth leading risk factor for mortality in the world. Physical activity may exert beneficial influence on the cardiovascular system, besides to bring benefits to the lipid metabolism, the increase of the lean mass, and the increase of the basal metabolism. As a response of the physical activity, the concentration of several hormones is altered, as the cortisol. Different specimens are used to determination of concentration of the cortisol, like saliva, urine, blood samples and hair. The aim of this narrative review is to present scientific information about the use of the hair to evaluate the concentration of cortisol in individuals that have performed physical activity. Materials and Methods Publications were accessed in the database PubMed September 12th, 2018 using the keywords hair and “physical activity” and cortisol. Results In general, it was found that the hair can be used to determine the concentration of cortisol in different populations. Conclusions In conclusion, all the considerations of this review, it is possible to conclude that the hair can be used successfully, as a specimen, to determine the concentration of the cortisol in the body. This would have an importance to verify the response of the hypothalamus-pituitary-adrenocortical axis to the physical activity.
... Trichotillomania and traction alopecia are the two types of self-inflicted hair loss that involve pulling the hair and heat, worsening hair condition using hair straighteners, respectively. out to fall out on its own (7,8,9). (13). ...
There are many diseases in which one of the main symptoms is hair loss. Hair loss in medical terms is called "Alopecia". Many reasons can cause alopecia. Hair loss can be due to nutritional factors, genetic problems, metals toxicity, and body inflammation. Hormonal changes in the body can also lead to a loss of hair. Physiology and stages of reproduction of hair in humans are also discussed. There are three stages in the process of the hair reproduction cycle. Many factors can be responsible for the disruption of hair, and stress is one of them. A hair pulling test should be done to check the quality of hair. Doctors prescribe the medication and treatment according to the cause of the hair loss. If the hair loss is due to nutritional changes, proper diet and supplements should be taken to reduce the hair loss. A clinical evaluation of a patient with hair loss is important to conclude. Doctors should keep themselves refreshed with the new advances in treatment. Age factor is one of the primary reasons for hair color changes and hair loss. Trichotillomania and traction alopecia are the two types of self-inflicted hair loss that involve pulling the hair and heat, worsening hair condition using hair straighteners, respectively.
... These stem cells provide the necessary number and type of specialized cells that take part in the hair cycle, with precise regulation by various factors, including those from the perineural niche. HFs are innervated at the bulb and bulge including somatic sensory afferents and autonomic sympathetic nerves [31]. Sensory nerves not only feel the movement of hair [32], but support the Gli1expressing upper bulge (Gli1 + ) HFSCs as a peri-neural niche, participate in hair follicle growth when another anagen phase is initiated [33]. ...
Most epithelium tissues continuously undergo self-renewal through proliferation and differentiation of epithelial stem cells (known as homeostasis), within a specialized stem cell niche. In highly innervated epithelium, peripheral nerves compose perineural niche and support stem cell homeostasis by releasing a variety of neurotransmitters, hormones, and growth factors and supplying trophic factors to the stem cells. Emerging evidence has shown that both sensory and motor nerves can regulate the fate of epithelial stem cells, thus influencing epithelium homeostasis. Understanding the mechanism of crosstalk between epithelial stem cells and neurons will reveal the important role of the perineural niche in physiological and pathological conditions. Herein, we review recent discoveries of the perineural niche in epithelium mainly in tissue homeostasis, with a limited touch in wound repair and pathogenesis.
... The top and bottom diameter of hair cone were approximately 36 µm and 54 µm. The variation of diameter of the hair is generally between 16-80 µm [39], [40]. The hair protruded from the skin at an angle of 30 • [41]. ...
The purpose of this work is to evaluate local power and electric field distributions inside high-resolution 3D anatomical CAD models of cutaneous appendages at 60 GHz upcoming for 5G/6G. The microscale resolution models of cutaneous nerves, lymphatics, pilosebaceous unit, microvasculature, eccrine sweat glands, Meissner corpuscle and Pacinian corpuscle were designed based on morphometric data and microscopic images. The Maxwell’s and Hanai’s mixture equations were employed to retrieve the complex permittivity of cutaneous appendages based on their free water content. The cutaneous appendages were exposed to a uniform plane wave. The finite element method was used to compute the power loss density (
${\bm {PLD}}$
) and internal electric field (
${\bm {E}}$
). The results indicate that the maximal
${\bm {PLD}}$
in cutaneous appendages occurred for
${\bm {E}}$
polarized along their longest dimension. Higher peak
${\bm {PLD}}$
was observed in high water content cutaneous appendages such as acrosyringium (45%), epidermal axon (37.9%), Pacinian corpuscle (32.5%), blood capillary (30.6%), lymph capillary (20%) and arrector pili muscle (13.5%) compared to the surrounding skin. Higher
${\bm {E}}$
was detected in low water content hair with the peak
${\bm {E}}$
45.1% greater than in surrounding skin. The interfaces of the cutaneous appendages also manifested a boost (23.8%-60.9%) in
${\bm {PLD}}$
compared to the surrounding skin. Detailed physical interpretation of observed phenomena is provided in the article. These results provide an insight into microscale power deposition in skin at frequencies upcoming for wireless communications.
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:
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
Wound healing following trauma, illness, or surgery is a complex process and is comprised of a particularly fragile sequence of biochemical events that are susceptible to interruption or failure, which can lead to non-healing chronic wounds, scarring and other issues. Non-healing wounds are also commonly associated with diabetes, arterial disease, infection, and the metabolic deficiencies of aging. Treatment of dermal wounds can therefore be challenging, and as such the ability to localise the effect of drugs and treatments to promote healing through protective materials is an attractive area of research.
This book introduces the essential areas of skin anatomy and the wound healing process, and how this can be disrupted by various pathologies, and proceeds to outline how biomaterials and devices for dermal drug delivery (including controlled delivery via stimuli-responsive devices) can be utilised in effective wound management. This book is an ideal companion for postgraduates and researchers in a variety of disciplines including biomedical engineering, biomaterials, drug development and delivery, formulation science and tissue engineering.
Although pubic hair has been a subject of public interest, little is known about its structure or characteristics beyond its curly and coarse appearance. In this study, we investigated the surface and internal features of pubic hair from Korean males and compared them to those of scalp hair from the same donors. Our findings indicate that the cuticle layer of pubic hair has a greater number of scales than that of scalp hair, resulting in a thicker cuticle layer overall. Fourier-transform infrared (FT-IR) spectroscopy analysis showed that the protein in the cortex layer of pubic hair was less affected by exposure to urine or ammonia than the protein in the cortex layer of scalp hair. This suggests that the cuticle layer of pubic hair, which is thicker and composed of more scales, acts as a physical barrier that protects the hair's internal structure. Furthermore, we observed that the secondary and tertiary structures of keratin in the pubic hair cuticle layer are essentially different from those in scalp hair. Based on these findings, we hypothesize that the thickened cuticle layer in pubic hair may have evolved as a defence mechanism against chemical damage from urine, urea and ammonia.
Human skin consists of three compartments, each endowed with a particular structure and the presence of several immune and nonimmune cells that together comprise a protective shield and orchestrate multiple processes in the skin. Appropriate processing of human skin samples acquired from healthy volunteers or patients is essential for successful analysis in basic, translational, and clinical research to obtain accurate and reliable results, despite differences between individuals. From the wide range of available assays and methods, it is necessary to select the suitable method for separation of skin compartments, which will provide preservation or high viability of skin cells or whole structures that will be analyzed or further processed. In this paper, we review and discuss skin separation methods and compare their features such as processing time, cell viability, location of the basement membrane after detachment of the epidermis from the dermis, and their application. Furthermore, we visualize different cell populations and structures in epidermal and dermal sheets using confocal microscopy. It is aimed to provide an overview of the optimal processing of human skin samples and their possible application.
Human hairs are commonly collected from crime scenes and sent to a forensic laboratory for analysis. However, most of them are at the relatively quiescent telogen growth phase with little to no soft tissue remaining at the root end for nuclear DNA analysis. Since neither microscopical hair shaft comparisons nor mitochondrial DNA sequencing constitute a basis for personal identification, other complementary methods will be beneficial. This book chapter explores promising protein sequencing alternative methods for questioned and known hair shaft comparison.
Human body is one of the most complex creatures which has been mentioned in many divine and modern sources. The skin, or integumentary system is the set of organs forming the outermost layer of human’s body. The scientific research has been progresses tremendously in this area however, there is insufficiency review and description from Islamic perspective. Thus, this paper aims to synthesise available literature on integumentary sciences and relate with Islamic perspective. The roles of integumentary system in fingerprints identification, variation of skin colour, regeneration and replacement of skin in hell fire are explained from the Islamic perspective based on relevant Qur’anic verses and/or the hadith. It is hoped that by viewing and relating Islamic perspective and scientific knowledge it will become a single source of hidayah, the source of truth for this world and the hereafter.KeywordsIntegumentarySkinPhysiologyIslamic perspective
The term “alopecia” is used for abnormal hair loss and it is a chronic dermatological condition observed in both genders and all races. Androgenetic alopecia (AGA) or male pattern baldness is the most common type of alopecia; however, it may be observed in females. Alopecia areata (AA) is the second most common non-scarring alopecia or hair loss around the world. Beyond the fact that alopecia is a disease itself, sometimes it might be one of the major side effects of many drugs including chemotherapeutics. Since healthy hair has been a symbol of well-being, youth, and vitality for centuries, the treatment of alopecia has essential importance to increasing life quality of the individuals that have faced hair loss. Regarding the progressively generated high-throughput data at various omics levels, systems biology has gained importance to better understand biologic processes by utilizing high-throughput data from multiple sources to develop models of biologic processes In this review, we overviewed AGA and AA via systems biology with the aid of omics technologies point of view to highlight not only the molecular mechanisms of the hair loss phenomenon but also potential preventive and therapeutic avenues. We discussed the findings in light of the multi-omics data integration that converges the future of uncovering personalized therapeutic options targeting hair loss.
Skin aging is one of the most evident signs of human aging. Modification of the skin during the life span is characterized by fine lines and wrinkling, loss of elasticity and volume, laxity, rough-textured appearance, and pallor. In contrast, photoaged skin is associated with uneven pigmentation (age spot) and is markedly wrinkled. At the cellular and molecular level, it consists of multiple interconnected processes based on biochemical reactions, genetic programs, and occurrence of external stimulation. The principal cellular perturbation in the skin driving senescence is the alteration of oxidative balance. In chronological aging, reactive oxygen species (ROS) are produced mainly through cellular oxidative metabolism during adenosine triphosphate (ATP) generation from glucose and mitochondrial dysfunction, whereas in extrinsic aging, loss of redox equilibrium is caused by environmental factors, such as ultraviolet radiation, pollution, cigarette smoking, and inadequate nutrition. During the aging process, oxidative stress is attributed to both augmented ROS production and reduced levels of enzymatic and non-enzymatic protectors. Apart from the evident appearance of structural change, throughout aging, the skin gradually loses its natural functional characteristics and regenerative potential. With aging, the skin immune system also undergoes functional senescence manifested as a reduced ability to counteract infections and augmented frequency of autoimmune and neoplastic diseases. This review proposes an update on the role of oxidative stress in the appearance of the clinical manifestation of skin aging, as well as of the molecular mechanisms that underline this natural phenomenon sometimes accelerated by external factors.
Human hair is a potential biomaterial for biomedical applications. Improper disposal of human hair may pose various adverse effects on the environment and human health. Therefore, proper management of human hair waste is pivotal. Human hair fibre and its derivatives offer various advantages as biomaterials such as biocompatibility, biodegradability, low toxicity, radical scavenging, electroconductivity, and intrinsic biological activity. Therefore, the favourable characteristics of human hair have rendered its usage in tissue engineering (TE) applications including skin, cardiac, nerve, bone, ocular, and periodontal. Moreover, the strategies by utilising human hair as a biomaterial for TE applications may reduce the accumulation of human hair. Thus, it also improves human hair waste management while promoting natural, environmentally friendly and non-toxic materials. Further, promoting sustainable materials production will benefit human health and well-being. Hence, this paper reviews and discusses human hair characteristics as sustainable biomaterials and their recent application in TE applications.
Hair lipid composition varies by ethnic hair type and by hair layer. Lipids in the cuticle, cortex, and medulla of the hair shaft provide a protective barrier to environmental and chemical damage, prevent hair breakage and desorption, and affect the elastic and tensile properties of hair. The aim of this systematic review is to provide an overview of the lipid composition and ethnic differences of human hair, effects of external damage on lipid content and properties, and changes in hair lipid composition associated with disease states. PubMed/MEDLINE was searched up to March 2021 according to PRISMA guidelines for articles discussing the lipid content of human hair and effects of physical, chemical, or environmental damage, and disease. Fifty‐nine articles investigating the lipid content of hair were included for review. Lipids affect fluid permeability, hydration, strength, and texture of ethnic hair fibers. Lipid loss is accelerated by hair‐damaging treatments such as bleach, dye, perm, straightening, and surfactant use, and sun and aging processes, leading to dehydrated, breakable, disordered, and dull hair. Diseases including acne, alopecia, and breast, gastric, prostate, lung, and rectal cancers display elevated hair lipid levels. Lipids are vital in protection against damage and maintenance of healthy hair. Further studies are needed to investigate the effects of lipids on the structural properties of ethnic hair, and changes in hair lipid composition with various dermatologic and systemic diseases.
The argan tree (Argania spinosa (L.) Skeels) is one of the most important floristic resources in Morocco. This Moroccan endemic tree is known for its numerous therapeutic and medicinal uses. In addition to some medicinal and cosmetic uses, argan fruit pulp and press cake are traditionally used by the Berber population for heating and feeding livestock. Molecular docking is an in silico approach that predicts the interaction between a ligand and a protein. This approach is mainly used in chemistry and pharmacology of natural products as a prediction tool with the purpose of selecting plant extracts or fractions for in vitro tests. The aim of this research is to study the evaluation of potential tyrosinase, collagenase, and elastase inhibitory activities of argan fruit press-cake and pulp extracts. Extracts were evaluated for their total phenolic content (TPC), and the major polyphenols of both press-cake and pulp extracts were submitted to molecular docking in order to determine the mechanisms of action of these compounds. Obtained results revealed that fruit pulp had the strongest dermocosmetic activities, as well as the highest TPC, with values above 55 mg gallic-acid equivalent per gram of dry matter (mgeq AG/gDM). Moreover, those results were positively correlated with the docking findings, suggesting that the pulp lead compounds have higher affinity with tyrosinase, collagenase, and elastase action sites. The results here presented are very promising and open new perspectives for the exploitation of argan-tree by-products as cosmetic agents towards the development of new anti-aging products.
The application of photobiomodulation (PBM) in regenerative medicine has expanded to the treatment of alopecia caused by various reasons. However, the mechanisms responsible for its effects are poorly understood. Here, we aimed to investigate the effects of PBM on hair regeneration in injured skin and to explore the underlying mechanisms. The scratched epidermis or dermis models were established in C57 mice aged 7–8 weeks. We found that the scratched epidermis had no influence on hair regeneration, but the scratched dermis led to obvious hair follicle atrophy and significantly influenced hair regeneration. The wounds in scratched dermis models were treated with PBM (655 nm, 3 J/cm² [10 min]) and the hair regeneration and cell proliferation in hair follicle were evaluated. Compared with control, the hair coverage level was significantly enhanced after PBM treatment. Sox9⁺ and PCNA⁺ cells in hair follicle were obviously observed in PBM-treated group, but not in control. In vitro, the effects of PBM on the function of dermal papilla cells (DPCs) were investigated. The results showed that the migration of DPCs was increased significantly by PBM (655 nm, 3 J/cm² [10 min]), whereas no effect was found on proliferation. Furthermore, we found that PBM promoted exosome secretion of DPCs, accompanied by the activation of Akt/GSK-3β/β-catenin pathway. AKT inhibitor MK-2206 effectively blocked PBM-induced migration and exosome secretion of DPCs. These findings suggest that the enhanced migration and exosome secretion of DPCs mediated by the Akt/GSK-3β/β-catenin pathway were responsible for the promotion of hair regeneration in injured skin by PBM.
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.
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.