Histological features of peripilar signs associated with androgenetic alopecia

Disturbance of Immune Microenvironment in Androgenetic Alopecia through Spatial Transcriptomics

Androgenetic alopecia (AGA) is characterized by microinflammation and abnormal immune responses, particularly in the upper segment of hair follicles (HFs). However, the precise patterns of immune dysregulation remain unclear, partly due to limitations in current analysis techniques to preserve tissue architecture. The infundibulum, a major part of the upper segment of HFs, is associated with significant clusters of immune cells. In this study, we investigated immune cells around the infundibulum, referred to as peri-infundibular immune infiltration (PII). We employed spatial transcriptome profiling, a high-throughput analysis technology, to investigate the immunological disruptions within the PII region. Our comprehensive analysis included an evaluation of overall immune infiltrates, gene set enrichment analysis (GSEA), cellular deconvolution, differential expression analysis, over-representation analysis, protein-protein interaction (PPI) networks, and upstream regulator analysis to identify cell types and molecular dysregulation in immune cells. Our results demonstrated significant differences in immune signatures between the PII of AGA patients (PII-A) and the PII of control donors (PII-C). Specifically, PII-A exhibited an enrichment of CD4+ helper T cells, distinct immune response patterns, and a bias toward a T helper (Th) 2 response. Immunohistochemistry revealed disruptions in T cell subpopulations, with more CD4+ T cells displaying an elevated Th2 response and a reduced Th1-cytotoxic response compared to PII-C. These findings reveal the unique immune landscapes of PII-A and PII-C, suggesting potential for the development of innovative treatment approaches.

Androgenetic Alopecia: A Review

This study reviewed the current knowledge on the epidemiology, pathophysiology, clinical presentations, diagnosis, treatment, quality-of-life assessment and recent trends in androgenetic alopecia (AGA). Relevant articles on AGA from PubMed, Google Scholar, Medline and Scopus from 1950 to 2024 were obtained and scrutinized.. Key search words included each term like 'androgenetic alopecia', 'androgenic alopecia', 'pattern baldness' and 'pattern hair loss' AND each term like 'epidemiology', 'pathophysiology', 'genetics', 'hormones', 'micronutrient', 'stress and inflammation', 'growth factors', 'clinical features', 'staging', 'cardiovascular associations', 'diagnosis' and 'management' were used in the search. AGA is a non-scarring hair loss that is exemplified by a progressive decline of hair follicles, or non-functional or dead hair follicles in the scalp in a defined pattern. It is the most common hair loss, more common in men but can also present in younger age as premature AGA. Hormones, genetics, micronutrient deficiency, microinflammation and stress have been implicated, while psychosocial distress and cutaneous correlate of cardiovascular diseases have become sources of relentless research. AGA is a patterned hair loss that is more prevalent in Men. It results from the interactions between hormonal, genetic and other factors which determine the extent of hair loss and associated disorders (psychosocial and cardiovascular). As results of more research become available, the extent of AGA, its comorbidities as well as the full spectrum of their manifestations will continue to be sources of health education and more holistic examination by dermatologists and patients.

Trichoscopy of Androgenetic Alopecia: A Systematic Review

Background: Androgenetic alopecia, the most common cause of non-scarring hair loss, is a consequence of the gradual miniaturization of the hair follicles. In the majority of male androgenetic alopecia cases, a patient's history and clinical evaluation may be sufficient to establish the diagnosis, while for women, they should be supplemented with trichoscopy. Methods: The PubMed and Scopus databases were used to collate published studies and to analyze the most typical trichoscopic findings in patients diagnosed with androgenetic alopecia. A total of 34 articles were retrieved after exclusion. Results: The most common features identified using trichoscopy included hair diameter variability (94.07% of patients), vellus hairs (66.45%) and the peripilar sign (43.27%). Others, such as the honeycomb pattern, yellow and white dots, were less relevant. Conclusions: We concluded that hair diameter variability, vellus hairs and the peripilar sign represented valuable indicators for the diagnosis of androgenetic alopecia.

Trichoscopy Features of Indonesian Males with Androgenetic Alopecia in Association with Disease Severity

Introduction

Androgenetic alopecia (AGA) is a progressive loss of terminal hairs in a specific pattern distribution related to androgen. The dermoscopy of hair and scalp, known as trichoscopy, is a noninvasive method for diagnosing alopecia and other hair and scalp disorders.

Objective

This study aims to report the correlation between the severity of males with AGA based on Hamilton-Norwood's scale with the clinical characteristics found in trichoscopy.

Materials and Methods

This study included 40 patients aged 25-58 years who visited the dermatology outpatient clinic in a tertiary health facility in Indonesia. Clinical diagnosis was determined through history taking, physical examination, and trichoscopy. Based on Hamilton-Norwood's criteria, patients were divided into two groups: early and late stage. Parameters examined in trichoscopy include yellow dots, white dots, peripilar sign, vellus hair, hair diameter diversity, single-hair follicles, and empty follicles. The Chi-square test and Fisher's exact test were used to analyze the statistical significance between the groups.

Results

All participants presented with hair diameter diversity, vellus hair, and empty follicles (100%). None of the study participants had yellow dots. White dots and single-hair follicles were seen in 32 (80%) and 30 cases (75%), respectively. In the late-stage group, these features were more prevalent. Peripilar sign was found in 25 participants (62.50%), and it was more common in the early-stage group. No significant association was found between disease severity and trichoscopy features.

Conclusion

The most common trichoscopy findings in particular order were hair diameter diversity, vellus hair, and empty follicles, followed by white dots, single-hair follicles, and peripilar signs. No significant association between alopecia severity and trichoscopy parameters was observed. Studies with a larger number of participants, including a control group, should be conducted to yield more significant results.

Bioinformatic analysis of gene expression data reveals Src family protein tyrosine kinases as key players in androgenetic alopecia

Introduction

Androgenetic alopecia (AGA) is a common progressive scalp hair loss disorder that leads to baldness. This study aimed to identify core genes and pathways involved in premature AGA through an in-silico approach.

Methods

Gene expression data (GSE90594) from vertex scalps of men with premature AGA and men without pattern hair loss was downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between the bald and haired samples were identified using the limma package in R. Gene ontology and Reactome pathway enrichment analyses were conducted separately for the up-regulated and down-regulated genes. The DEGs were annotated with the AGA risk loci, and motif analysis in the promoters of the DEGs was also carried out. STRING Protein-protein interaction (PPI) and Reactome Functional Interaction (FI) networks were constructed using the DEGs, and the networks were analyzed to identify hub genes that play could play crucial roles in AGA pathogenesis.

Results and discussion

The in-silico study revealed that genes involved in the structural makeup of the skin epidermis, hair follicle development, and hair cycle are down-regulated, while genes associated with the innate and adaptive immune systems, cytokine signaling, and interferon signaling pathways are up-regulated in the balding scalps of AGA. The PPI and FI network analyses identified 25 hub genes namely CTNNB1, EGF, GNAI3, NRAS, BTK, ESR1, HCK, ITGB7, LCK, LCP2, LYN, PDGFRB, PIK3CD, PTPN6, RAC2, SPI1, STAT3, STAT5A, VAV1, PSMB8, HLA-A, HLA-F, HLA-E, IRF4, and ITGAM that play crucial roles in AGA pathogenesis. The study also implicates that Src family tyrosine kinase genes such as LCK, and LYN in the up-regulation of the inflammatory process in the balding scalps of AGA highlighting their potential as therapeutic targets for future investigations.

Assessment, reliability, and validity of trichoscopy in the evaluation of alopecia in women

Background

Alopecia in women is generally difficult to diagnose clinically. Trichoscopy may help make the correct diagnosis in doubtful cases.

Objective

The aims of the study were to assess the trichoscopic features of different types of alopecia in women, the reliability of trichoscopy vis-à-vis clinical findings, and the validity of trichoscopy in cases with a doubtful clinical diagnosis.

Methods

A hospital-based observational, cross-sectional study was carried out on female patients with alopecia. A trichoscopic diagnosis was made and correlated with a clinical diagnosis. The validity of trichoscopy in doubtful cases was evaluated by reporting the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic value.

Results

On trichoscopy, increased hair diameter diversity > 20%, single-hair follicular unit, vellus hair, peripilar sign, and focal atrichia were commonly seen in female pattern hair loss. In telogen effluvium, there was a scarceness of specific findings. In cicatricial alopecias, loss of follicular ostia, erythema, white macules, blue-gray dots, white dots, tufted hair, and keratotic follicular plugging were observed. A good agreement between trichoscopy and clinical diagnosis was found (Cohen’s Kappa = 0.824; 95% confidence interval, 0.756–0.892). The validity of trichoscopy in doubtful cases was evaluated using the validity parameters, which were high in all alopecias.

Limitations

Histopathology testing was not done in all patients.

Conclusion

Trichoscopy helped reach a definitive diagnosis in patients in whom the clinical diagnosis was doubtful. Thus, trichoscopy is a sensitive and specific investigation that can be valuable in women with alopecia.

Understanding Causes of Hair Loss in Women

Hair loss affects millions of people worldwide and can have devastating effects on an individual's psychoemotional well-being. Today hair restoration technologies through hair transplantation have advanced with the use of robots and follicular unit extraction and grafting that it is possible to offer to patient's excellent clinical results. Adjuvant modalities such as platelet-rich plasma injections, lasers, and stem cells can further enhance the durability, health, and appearance of hair transplants.

Clinical Patterns of Hair Loss in Men: Is Dihydrotestosterone the Only Culprit?

A number of pathways and factors including oxidative stress, inflammation, prostaglandins, vasculogenesis, Wnt/β-catenin, and transforming growth factor-β have been shown to be important in male androgenetic alopecia. There is limited but increasing evidence of the potential usefulness of antioxidants, anti-inflammatory agents, prostaglandins, and growth factors for treating of androgenetic alopecia. Lifestyle factors and comorbidities including cardiovascular risk factors have been shown to be associated with male androgenetic alopecia. Further study of these pathways, factors, and comorbidities is needed to better understand the pathophysiology, find potentially useful therapeutic targets, and ensure a comprehensive approach to the management of androgenetic alopecia in men.

Low-Level Light Therapy Downregulates Scalp Inflammatory Biomarkers in Men With Androgenetic Alopecia and Boosts Minoxidil 2% to Bring a Sustainable Hair Regrowth Activity

BACKGROUND AND OBJECTIVES

Low-level light therapies using visible to infrared light are known to activate several cellular functions, such as adenosine triphosphate and nitric oxide synthesis. However, few clinical observations report its biological consequences for skin and scalp homeostasis. Since scalp inflammation was recognized as a potential physiological obstacle to the efficacy of the reference hair regrowth drug Minoxidil in vivo and since perifollicular inflammation is the hallmark of about 50%-70% follicular units in androgenetic alopecia, we decided to investigate whether the anti-inflammatory activity of LLLT/GentleWaves® device were assigned to L'Oréal by Light BioScience L.L.C., Virginia Beach, VA (US) could enhance hair regrowth activity of Minoxidil.

STUDY DESIGN/MATERIALS AND METHODS

We conducted a first experimental clinical study on 64 men with androgenetic alopecia using LLLT/GentleWaves®, 590-nm predominant wavelength 70 seconds, specifically pulsed once per day, for 3 days, and we performed a whole-genome analysis of treated scalp biopsies. In a second clinical study, including 135 alopecic volunteers, we evaluated the hair regrowth activity in response to the upgraded LLLT/GentleWaves® device and Minoxidil.

RESULTS

In the first clinical study, whole-genome analysis of treated scalp biopsies showed downregulation of scalp inflammatory biomarkers, such as AP1/FOSB messenger RNA (mRNA) and mir21, together with the disappearance of CD69 mRNA, specific to scalp-infiltrating T cells of about 50% of the studied volunteers prior to the LLLT/GentleWaves® treatment. In the second clinical study, we observed that LLLT/GentleWaves® was able to boost the hair regrowth activity of a Minoxidil 2% lotion to the extent of the highest concentration (5%) in terms of efficacy, number of responders, and perceived performance.

CONCLUSIONS

Altogether, these observations suggest the potential benefit of LLLT/GentleWaves® as a noninvasive adjunctive technology for skin and scalp conditions, where a mild perifollicular inflammation is involved. Lasers Surg. Med. 2021. Copyright © 2021 Wiley Periodicals LLC.

Conflicting Reports Regarding the Histopathological Features of Androgenic Alopecia: Are Biopsy Location, Hair Diameter Diversity, and Relative Hair Follicle Miniaturization Partly to Blame?

Despite decades of study, debate persists over the role of inflammation, fibrosis, and prostaglandins in the histopathology of androgenic alopecia (AGA). This brief review proposes that inconsistent findings across histological studies are a consequence of three inadequately controlled variables: 1) biopsy location, 2) hair diameter diversity (HDD), and 3) relative hair follicle miniaturization (HFM) within and across subjects. We suggest new methodological considerations to improve AGA histopathological research, as well as a novel classification system to quantify HFM by its stages. Finally, we hypothesize a dynamic relationship between inflammation, fibrosis, and prostaglandin activity dependent on relative HFM.

Comparison of 5% minoxidil lotion monotherapy versus its combination with autologous platelet rich plasma in androgenetic alopecia in hundred males

Background

Androgenetic alopecia (AGA) is the most common form of alopecia in men, affecting 70% by the age of 20 years. The present study was conducted with the objective of comparing the efficacy of monotherapy with topical 5% minoxidil and its combination with intradermal platelet rich plasma (PRP), in male AGA.

Methods

This observational study was conducted at the dermatology department of a tertiary care hospital over a duration of 2 years. 100 patients with AGA were selected and divided randomly into 2 treatment arms: Group A (MM): received topical 5% Minoxidil monotherapy for 12 months and; Group B (M + PRP): received combination therapy of PRP and topical 5% Minoxidil for 12 months. The following parameters were subsequently analyzed on follow up: Physician-assessed global photography by a 4-point improvement scale and trichoscopic improvement of mean hair diameter.

Results

The combination was statistically superior to the monotherapy group in promoting hair growth in men with AGA for both measures of hair growth - photographic assessment and trichoscopic mean diameter.

Conclusion

We hereby conclude that intradermal PRP injections should be offered to all patients with AGA along with the existing therapeutic modalities, for faster hair regrowth and improved compliance.

Trichoscopic Findings in Androgenetic Alopecia

Background:

Androgenetic alopecia (AGA) is an androgen-related condition that develops in genetically predisposed individuals. The condition is characterized by the progressive loss of terminal hairs on the scalp in a characteristic distribution. Trichoscopy represents the dermoscopy imaging of the scalp and hair. Structures which may be visualized by trichoscopy include hair shafts, hair follicle openings, perifollicular epidermis and cutaneous microvessels.

Objective:

The aim of this prospective study was to identify the trichoscopic features of androgenetic alopecia.

Methods:

Hundred-four patients with AGA and 80 healthy subjects were enrolled in this study. Data on age, gender, personal and family history, clinical type and duration of disease were collected and analyzed. Control group consisted of 80 generally healthy subjects. Trichoscopic examination was performed using either videodermatoscope or handheld dermatoskope. Trichoscopy results were obtained in frontal, occipital and both temporal areas of the scalp, including number of yellow dots and vellus hairs, number of hairs in one pilosebaceous unit and percentage of follicular ostia with perifollicular hyperpigmentation. The data were statistically evaluated.

Results:

The number of yellow dots, pilosebaceous units with only one hair and with perifollicular hyperpigmentation was significantly increased in androgenetic alopecia (p<0.05). The percentage of thin hairs (<0.03 mm) in AGA was significantly higher than in healthy controls (p<0.05).

Conclusion:

Our study has shown the significances of trichoscopy of patients with AGA. Regular clinical and trichoscopical follow-ups are very important to monitor disease activity and treatment tolerance.

Androgenetic alopecia in women and men: Italian guidelines adapted from European Dermatology Forum/European Academy of Dermatology and Venereology guidelines

Androgenetic alopecia (AGA) is the most common form of alopecia, affecting up to 80% of men and 50% of women in the course of their life. AGA is caused by a progressive reduction in the diameter, length and pigmentation of the hair, resulting from the effects of the testosterone metabolite dihydrotestosterone (DHT) on androgen-sensitive hair follicles. Clinical presentation is different in men and women. Trichoscopy is used routinely in patients with androgenetic alopecia, for diagnosis and differential diagnosis with other diseases, allowing staging of severity and monitoring the progress of the disease and the response to treatment. Medical treatment of AGA includes topical minoxidil, antiandrogen agents, 5-alpha reductase inhibitors and many other options. This guideline for the treatment of androgenetic alopecia has been developed by an Italian group of experts taking into account the Italian pharmacological governance. The article is adapted from the original of the European Dermatology Forum (EDF) in collaboration with the European Academy of Dermatology and Venereology (EADV). It summarizes evidence-based and expert-based recommendations (S3 level).

Accuracy of clinical diagnosis and videodermoscopy in female pattern hair loss

BACKGROUND

Female pattern hair loss (FPHL) is a non-scarring hair disease characterized by progressive hair diminishment and decrease of its density. Although typical cases of FPHL are usually straightforward to diagnose, its initial forms can be unrecognized and often need the use of other diagnostic methods.

OBJECTIVE

To describe the accuracy of a diagnosis of FPHL based on clinical grounds and videodermoscopy compared with scalp biopsy.

METHODS

An observational diagnostic test study was performed. Scalp biopsies were read by the same dermatopathologist and processed horizontally to allow follicle's number and size evaluation. Digital videodermoscopy was also performed.

RESULTS

A total of 202 patients were enrolled, but only 35 women were assessed with digital videodermoscopy. When clinical diagnosis was compared to scalp biopsy, a sensitivity, specificity, positive predictive value (PPV), and a negative predictive value (NPV), of 77% %, 72.4%, 82.2%; and 65.5%, were respectively obtained. Videodermoscopy showed a sensitivity, specificity, PPV and NPV of 88.9%, 100%, 100%, and 72.7%, respectively.

CONCLUSIONS

This study provided valuable information on the accuracy of clinical examination of FPHL, showed the usefulness of videodermoscopy as a method that in the future may replace scalp biopsy for its diagnosis, or also could aid patient´s follow-up.

Female Androgenetic Alopecia: An Update on Diagnosis and Management

Female androgenetic alopecia (FAGA) is a common cause of non-scarring alopecia in women. The onset may be at any age following puberty and the frequency increases with age. Clinically, it shows a diffuse hair thinning over the central scalp, while the frontal hairline is usually retained. FAGA can have a significant psychological impact, leading to anxiety and depression. For this reason, early diagnosis is very important to stop the progression of the disease. The sex hormonal milieu is the main pathogenetic mechanism studied in FAGA. The role of androgens is not clearly defined and only one-third of women with FAGA show abnormal androgen levels. Endocrinological diseases with hyperandrogenism associated with FAGA comprise polycystic ovarian syndrome (PCOS), hyperprolactinemia, adrenal hyperplasia and, rarely, ovarian and adrenal tumours. Usually the diagnosis of FAGA is made clinically. A complete clinical examination and a blood examination can reveal other signs of hyperandrogenism. Trichoscopy shows the typical hair miniaturization. A scalp biopsy can be useful when the clinical evaluation does not provide a definitive diagnosis or when cicatricial alopecias with hair loss in the distribution of FAGA or alopecia areata are suspected. FAGA is a slowly progressive disease. The goal of therapy is to stop the progression and to induce a cosmetically acceptable hair regrowth. The most important drugs are topical minoxidil and oral anti-androgens. The purpose of this review is to provide an update on FAGA and to create a guideline on diagnosis and management of this frequent hair disease, not always easily recognizable from cicatricial alopecias with a similar distribution.

Trichogenic effect of topical ketoconazole versus minoxidil 2% in female pattern hair loss: a clinical and trichoscopic evaluation

Background

Female pattern hair loss (FPHL) is a common non-scaring alopecia. Topical minoxidil is the only approved treatment for FPHL; however, it has frequent side effects. Ketoconazole is an antifungal with anti-androgenic properties.

Methods

The aim of this work was to evaluate the safety and possible trichogenic effects of ketoconazole in FPHL. Patients were randomly assigned into Group A with 20 patients who received 2% topical minoxidil solution and Group B involving 20 patients who were treated by 2% topical ketoconazole preparation. All patients were treated for 6 months and evaluated clinically plus via trichoscopy. Side effects were recorded, and patients’ satisfaction was measured.

Results

Regarding hair growth, a significant difference was detected between baseline and at 4th and 6th months in Group A. While in Group B, the improvement was delayed until the 6th month. Only 10% of Group B reported side effects. Patients’ satisfaction did not differ between the two groups.

Conclusions

Topical ketoconazole mediates a trichogenic effect in FPHL with few side effects. However, ketoconazole showed a delayed improvement versus minoxidil at similar concentrations. Further studies should evaluate the efficacy of higher concentrations of ketoconazole solutions for FPHL which is a promising therapy.

Trial registration

IRB approval status: reviewed and approved by IRB of Faculty of Medicine, Zagazig University; approval no. #3642

Precision Medicine and the Practice of Trichiatry: Adapting the Concept

Evidence-based medicine (EBM) aims for the ideal that healthcare professionals make conscientious, explicit, and judicious use of the best available evidence gained from the scientific method to clinical decision-making. It seeks to assess the strength of the evidence for benefits of diagnostic tests and treatments, using techniques from science, engineering, and statistics, such as the systematic review of medical literature, meta-analysis, risk-benefit analysis, and randomized controlled trials. The limited success rate of EBM therapies suggests that the complex nature of hair loss may be inadequately served by the present levels of evidence, and that physicians treating hair loss may have fallen short of adequately researching a robust evidence to underpin their practices. Against this backdrop, the concept of precision medicine (PM) is evolving. PM refers to the customization of medical care to the patient's individual characteristics based on the patient's genetic background and other molecular or cellular analysis, while classifying patients into subpopulations that differ in their susceptibility to a particular medical condition, in the biology or prognosis of those medical conditions, or in their response to a specific treatment. With the advances in hair research, the powerful tools of molecular biology and genetics, and innovative technologies, we have the robust scientific data and tools to adapt the concept of PM to the practice of trichiatry. Finally, databases pertaining to the development and efficacy of PM must be analyzed and be used to form the basis of evidence-based personalized trichiatry.

Female Pattern Hair Loss and Androgen Excess: A Report From the Multidisciplinary Androgen Excess and PCOS Committee

OBJECTIVE

To determine the current state of knowledge and provide evidence-based recommendations that could be valid for all specialists taking care of female pattern hair loss (FPHL), a common form of hair loss in women that is characterized by the reduction of hair density in the central area of the scalp, whereas the frontal hairline is generally well conserved.

PARTICIPANTS

An expert task force appointed by the Androgen Excess and PCOS Society, which included specialists from dermatology, endocrinology, and reproductive endocrinology.

DESIGN

Levels of evidence were assessed and graded from A to D. Peer-reviewed studies evaluating FPHL published through December 2017 were reviewed. Criteria for inclusion/exclusion of the published papers were agreed on by at least two reviewers in each area and arbitrated by a third when necessary.

CONCLUSIONS

(i) The term "female pattern hair loss" should be used, avoiding the previous terms of alopecia or androgenetic alopecia. (ii) The two typical patterns of hair loss in FPHL are centrifugal expansion in the mid scalp, and a frontal accentuation or Christmas tree pattern. (iii) Isolated FPHL should not be considered a sign of hyperandrogenism when androgen levels are normal. (iv) The assessment of patients with FPHL is primarily clinical. (v) In all patients with FPHL, assessment of a possible androgen excess is mandatory. Measurement of vitamin D, iron, zinc, thyroid hormones, and prolactin are optional but recommended. (vi) Treatment of FPHL should start with minoxidil (5%), adding 5α-reductase inhibitors or antiandrogens when there is severe hair loss or hyperandrogenism.

Correlation of Trichoscopic Findings in Androgenetic Alopecia and the Disease Severity

Background:

Androgenetic alopecia (AGA) refers to the appearance of the common nonscarring progressive patterned loss of terminal hair on the frontal scalp and/or vertex of the scalp in both men and women, seen with increasing age in genetically predisposed individuals. Until recently, a scalp biopsy was the only objective tool to diagnose and monitor the disease severity. Trichoscopy of scalp is a new noninvasive technique applied to facilitate the diagnosis of hair and scalp disorders using a manual or video dermatoscope. We found a significant difference in some of the variables such as brown peripilar sign (BPPS), white peripilar sign (WPPS), focal atrichia which may aid in the diagnosis of early and late stages of both male and female AGA along with its clinical correlation. No significant difference in the occipital area was found in all AGA patients.

Aims:

This study aims to study the trichoscopic findings of AGA and to correlate their relationship with disease severity in our tertiary care hospital.

Settings and Design:

This was a prospective, observational study.

Subjects and Methods:

A total of 91 patients (66 males and 25 females) of the age group between 18 and 70 years, were included in the study at the outpatient department of dermatology in 1 year. Each patient underwent a detailed general physical, systemic, and dermatological examination. The diagnosis of AGA was based on clinical grounds. The type of hair loss in each patient was recorded. Trichoscopic evaluation and capture of trichoscopic images was performed using an eScope Oitez Digital Microscope.

Ethics:

In accordance with the Helsinki Declaration of 1975 (revised in 2000), the study was approved by Ethical and Scientific Research committees of Care Institute of Medical Sciences, Hyderabad.

Statistical Analysis Used:

Statistical analysis was carried out with R-studio. Statistical significance in the difference in the outcome variables between the stages was assessed by Fisher's exact test. The statistical test was considered statistically significant at P < 0.05.

Results:

A positive correlation between clinical and trichoscopic findings with respect to disease severity was seen in some of the variables in our study. Both male and female AGA patients have hair shaft thickness heterogeneity as the most common feature. BPPS is seen in early grades of AGA (P < 0.01); WPPS and focal atrichia are seen in later grades of AGA (P < 0.01). Scalp honeycomb pigmentation was most commonly seen in all stages and is not correlated to the disease severity of AGA.

Conclusion:

As trichoscopy can reveal early variations in hair follicle diameter long before hair loss becomes clinically visible and has the advantage of examining larger areas in a relatively short duration makes it a practical choice for clinic set up. It adds new easily recognizable images for visual teledermatology. Besides, the easy documentation allows the doctor and patient to view the video graphics images simultaneously and helps in evaluating a therapeutic response by comparing it with pre-treatment images.

The new paradigm for androgenetic alopecia and plant-based folk remedies: 5α-reductase inhibition, reversal of secondary microinflammation and improving insulin resistance

ETHNOPHARMACOLOGICAL RELEVANCE

Research in the past half a century has gradually sketched the biological mechanism leading to androgenetic alopecia (AGA). Until recently the aetiological paradigm has been too limited to enable intelligent commentary on the use of folk remedies to treat or reduce the expression of this condition. However, our understanding is now at a point where we can describe how some folk remedies work, predict how effective they will be or why they fail.

RESULTS

The new paradigm of AGA is that inheritance and androgens (dihydrotestosterone) are the primary contributors and a secondary pathology, microinflammation, reinforces the process at more advanced stages of follicular miniaturisation. The main protagonist to microinflammation is believed to be microbial or Demodex over-colonisation of the infundibulum of the pilosebaceous unit, which can be ameliorated by antimicrobial/acaricidal or anti-inflammatory therapies that are used as adjuvants to androgen dependent treatments (either synthetic or natural). Furthermore, studies reveal that suboptimal androgen metabolism occurs in both AGA and insulin resistance (low SHBG or high DHT), suggesting comorbidity. Both can be ameliorated by dietary phytochemicals, such as specific classes of phenols (isoflavones, phenolic methoxy abietanes, hydroxylated anthraquinones) or polycyclic triterpenes (sterols, lupanes), by dual inhibition of key enzymes in AGA (5α-reductase) and insulin resistance (ie., DPP-4 or PTP1B) or agonism of nuclear receptors (PPARγ). Evidence strongly indicates that some plant-based folk remedies can ameliorate both primary and secondary aetiological factors in AGA and improve insulin resistance, or act merely as successful adjuvants to mainstream androgen dependent therapies.

CONCLUSION

Thus, if AGA is viewed as an outcome of primary and secondary factors, then it is better that a 'multimodal' or 'umbrella' approach, to achieve cessation and/or reversal, is put into practice, using complementation of chemical species (isoflavones, anthraquinones, procyanidins, triterpenes, saponins and hydrogen sulphide prodrugs), thereby targeting multiple 'factors'.

A New Classification of Early Female Pattern Hair Loss

Background:

Global photographs (GPs) have been widely used to grade the severity in female pattern hair loss (FPHL). However, existing classifications for FPHL are not useful in the evaluation of early FPHL. Although there are some variations in early FPHL, even to a mild degree, all types of early FPHL are included in just one category. Therefore, the authors have devised a grading system for early FPHL with five levels focusing on the changes revealed by the surface reflected light of flash generated on GPs.

Aims:

This study aims to examine the possibility of evaluating the treatment course of early FPHL using the grading system based on changes in hair surface reflection patterns.

Subjects and Methods:

Retrospective chart review of 114 early FPHL patients was performed. GPs of these patients were classified into five grades. Photographs of the lowest and the highest grades of each patient were selected and paired. First, the relevance between the value of FPHL-severity index (FPHL-SI) and grades of all the selected photos was analyzed. Next three volunteers graded the paired photographs and chose the milder degree, and then, the concordance rate among author's and volunteers' evaluations were analyzed.

Results:

The value of FPHL-SI and incidence rate of hair diameter diversity tended to rise along with increasing of GP grade. Concordance rate of grading among author and more than two volunteers was 57%. The concordance rate of course evaluation between author and two volunteers was 97%.

Conclusion:

The new classification can finely classify the grade of early FPHL and can be used for treatment course evaluation.

Female Pattern Hair Loss: a clinical and pathophysiological review

Female Pattern Hair Loss or female androgenetic alopecia is the main cause of hair loss in adult women and has a major impact on patients' quality of life. It evolves from the progressive miniaturization of follicles that lead to a subsequent decrease of the hair density, leading to a non-scarring diffuse alopecia, with characteristic clinical, dermoscopic and histological patterns. In spite of the high frequency of the disease and the relevance of its psychological impact, its pathogenesis is not yet fully understood, being influenced by genetic, hormonal and environmental factors. In addition, response to treatment is variable. In this article, authors discuss the main clinical, epidemiological and pathophysiological aspects of female pattern hair loss.

Trichoscopic Findings of Hair Loss in Koreans

Background

Trichoscopic findings of hair loss have been well described for the differential diagnosis of alopecia; however, critical findings were not thoroughly investigated or compared among all ethnic groups, including Asians.

Objective

We aimed to find any characteristic trichoscopic findings in Korean alopecia patients and to verify whether those findings are closely related to previously reported observations.

Methods

Three hundred and twenty-seven patients with hair loss of various causes and 160 normal scalps were analyzed. Trichoscopic examination was performed with a polarized-light handheld dermoscope.

Results

A total of 35 patterns of trichoscopic features were represented, and certain features were significantly common or observed exclusively in a particular type of alopecia as follows: yellow dots, exclamation mark hairs, and proximal tapering hairs (alopecia areata), trichoptilosis and pointed hairs (trichotillomania), corkscrew hairs, septate hyphae hairs, and comma hairs (tinea capitis), diffuse white area, fibrotic white dots, and tufting hairs (primary cicatricial alopecia), hair diameter diversity and peripilar sign (androgenetic alopecia), and short nonvellus hairs (telogen effluvium).

Conclusion

The characteristic trichoscopic features for the differential diagnosis of alopecia in Koreans, shown as follicular, perifollicular, and hair shaft patterns, are similar to those of Caucasians; however, the frequencies of the pigment patterns are different between Koreans and Caucasians because of the contrast effect of the skin and hair color. Therefore, racial difference should be considered in the trichoscopic evaluation for differential diagnosis.

Trichoscopic findings of androgenetic alopecia and their association with disease severity

Trichoscopy is a novel tool for the diagnosis of hair loss disorders such as androgenetic alopecia (AGA), but there are still few reports on the association between trichoscopic findings and disease severity, especially in the Chinese population. A case-control observational study was conducted to observe the trichoscopic findings of AGA and to evaluate their relationship with disease severity. Trichoscopic examination was performed with a handheld dermoscope on 750 Chinese male AGA (MAGA) and 200 female AGA (FAGA) patients, along with 100 male and 50 female normal controls. Trichoscopically, AGA was featured by hair shaft thickness heterogeneity (HSTH), brown peripilar sign (BPPS), white peripilar sign (WPPS), yellow dots, pinpoint white dots, focal atrichia and scalp pigmentation. No significant difference in the occipital area was found between AGA and controls (P > 0.05). HSTH of more than 20% was demonstrated in all MAGA patients, and HSTH of more than 10% was seen in all FAGA patients. WPPS, yellow dots, pinpoint white dots, focal atrichia and scalp pigmentation were positively related to severity of disease (P < 0.05), while BPPS was the contrary (P < 0.05). HSTH is an essential criterion for diagnosing AGA. BPPS was more common in early AGA. However, WPPS, yellow dots, pinpoint white dots, focal atrichia and scalp pigmentation are positively correlated with advanced AGA.

Evaluation and diagnosis of the hair loss patient: part II. Trichoscopic and laboratory evaluations

The use of trichoscopy for evaluating a number of hair and scalp disorders is gaining popularity. It is a simple and noninvasive in vivo tool for visualizing hair shafts and the scalp. Recently, alopecias have been classified according to their trichoscopic findings. The second part of this 2-part continuing medical education article reviews recent advances in this field and describes a systematic approach for using the differential diagnostic findings of trichoscopy in alopecia.

Effect of a nutritional supplement on hair loss in women

BACKGROUND

Female pattern hair loss is a frequent and distressing condition.

AIM

To evaluate vs. control, the effects on hair loss of a 6-month supplementation with specific omega 3&6 and antioxidants.

METHODS

One hundred and twenty healthy female subjects participated in this 6-month, randomized, comparative study. The primary endpoint was the change in hair density evaluated on standardized photographs. Secondary endpoints included changes in telogen hair percentage and diameter distribution of anagen hair (>40 µm vs. ≤40 µm) measured by trichogram. Overall changes in hair density and diameter were also measured by trichometer and by subjects' self-assessment.

RESULTS

After 6 months of treatment, photograph assessment demonstrated a superior improvement in the supplemented group (P < 0.001). The telogen hair percentage was significantly (P < 0.001) reduced in the supplemented group. The proportion of nonvellus anagen hair (>40 µm) increased compared to the control group. The trichometer index increased in the supplemented group, while it decreased in the control group. A large majority of supplemented subjects reported a reduction in hair loss (89.9% of subjects at 6 months), as well as an improvement in hair diameter (86.1%) and hair density (87.3%).

CONCLUSION

A 6-month supplementation with omega 3&6 and antioxidants acts efficiently against hair loss in improving hair density and reducing the telogen percentage and the proportion of miniaturized anagen hair. Objectively measured improvements were confirmed by the subjects' perception of efficacy.

Scalp dermatoscopic findings in androgenetic alopecia and their relations with disease severity

Background

Clinicians are searching for new methods to diagnose and predict the course of androgenetic alopecia noninvasively.

Objective

Our aim is to evaluate trichoscopic findings and their relations with disease severity in androgenetic alopecia.

Methods

The videodermatoscopic findings of 143 female and 63 male patients with androgenetic alopecia were compared with each other, with those of healthy subjects (n=100), and with those of patients with other nonscarring alopecias (n=208). Mann-Whitney U-test, χ² analyses, and logistic regression analysis were used for statistical analysis.

Results

No statistically significant relation was found between trichoscopic findings and severity in male androgenetic alopecia (MAGA) on the basis of the modified Hamilton Norwood scale (among 7 degrees); however, multihair follicular unit and perifollicular pigmentation were related to low severity whereas white dots, honeycomb pattern pigmentation, and brown dots were related to high severity. On the other hand, according to the Ludwig classification, arborizing red lines were related to low severity and brown dots were related to high severity, whereas there was no difference in stages between the Ebling and Olsen classifications in female androgenetic alopecia (FAGA). In the characteristic trichoscopic findings in this study, perifollicular pigmentation was found as a normal feature of the scalp, whereas multihair follicular unit and honeycomb pigment pattern, which were previously considered as normal features, were observed to be related to androgenetic alopecia.

Conclusion

No relation was found between MAGA severity and trichoscopic findings, as well as between FAGA severity according to different disease severity classifications and trichoscopic findings.

Vellus hairs in the frontal scalp in early female pattern hair loss

Background:

Dermoscopy of the scalp (trichoscopy) is a technique to evaluate the skin of the scalp and the hair disorders. It clinically helps to establish early female pattern hair loss (FPHL) without the need for more invasive techniques.

Objectives:

This work intends to demonstrate new adjunct criteria for the clinical diagnosis of FPHL by determining the number of short vellus hairs encountered in the frontal area of the scalp of female patients with FPHL.

Materials and Methods:

We retrospectively reviewed the trichoscopy images from 45 women affected by FPHL in initial stages, at 20 fold magnification dermoscopy at 2 cm from the hairline into the frontal area of the scalp.

Results:

A total of 45 patients images included had more than 20% variability at dermoscopy, criteria utilized to diagnose and included them in the study. All patients were graded as Ludwig I severity, 14 patients had frontal accentuation. The average number of vellus hairs in the frontal area at 20-fold magnification of all patients was of 12.02 vellus hair in the frontal area. When comparing the Ludwid I pattern group versus the Ludwig I with frontal accentuation pattern group there was no statistical difference between the two clinical groups.

Conclusions:

All 45 patients analyzed in this study were clinically diagnosed with FPHL. The number of vellus hairs in the frontal area was greater than the average found in normal subjects. Most patients (80%) with FPHL had more than or equal to seven vellus hairs per 20-fold magnification field in the frontal area, therefore we suggest that the presence of more than 6 vellus hairs in the frontal scalp at 20-fold magnification can be used as an additional criterion of FPHL.

Trichoscopy: how it may help the clinician

Trichoscopy (or dermoscopy of hair and scalp) is an easy in-office technique that may be performed with a handheld dermoscope or a digital videodermoscopy system. This method is gaining increasing popularity, because it may be applied in differential diagnosis of multiple hair and scalp diseases. The focus of this article is application of trichoscopy in differential diagnosis of the most frequent hair and scalp diseases in dermatologic practice. Trichoscopy of genetic hair shaft abnormalities are briefly addressed. A new classification of perifollicular and interfollicular skin surface abnormalities is proposed.

Female pattern hair loss: clinico-laboratory findings and trichoscopy depending on disease severity

BACKGROUND

Female pattern hair loss (FPHL) is a progressive hair loss disorder with unclear triggering and supporting factors. Trichoscopic features of each stage of FPHL have not been specifically elaborated previously.

AIMS

To analyze characteristics and investigate associations of clinico-laboratory and trichoscopic features of female patients in regard to the severity of hair loss in FPHL and to facilitate its diagnosis using noninvasive scalp dermoscopy (trichoscopy) in Fitzpatrick skin type III patients.

MATERIALS AND METHODS

Clinico-laboratory and trichoscopic data from 60 patients with FPHL were analyzed using Spearman's correlation test.

RESULTS

Patients had mean age of 34.4±10.6 years and mean duration of hair loss of 4.49±3.76 years. Of all, 45% (27/60) had a family history of pattern hair loss (PHL) and had an earlier onset of hair loss. Stage of hair loss positively correlated with duration and age at presentation. No association was found between the severity of FPHL and laboratory values including anemic and gonadal hormone profiles. Characteristic trichoscopic features (at 10-fold magnification) of FPHL were peripilar signs (PPS) (brown, BPPS and white, WPPS), white dots, scalp pigmentation, and focal atrichia. WPPS, scalp pigmentation, and focal atrichia positively correlated with the stage and duration of hair loss.

CONCLUSIONS

Family history of PHL causes an earlier onset of hair loss but does not influence its course or severity. The latter is also not affected by abnormal anemic profile or hormonal levels. PPS, scalp pigmentation, focal atrichia, and white dots are characteristic of PHL. WPPS, scalp pigmentation, and focal atrichia reflect advanced PHL.

Value of trichoscopy versus trichogram for diagnosis of female androgenetic alopecia

Background:

Female androgenetic alopecia (FAGA) is a frequent cause of hair loss in women. Standard diagnostic methods are clinical inspection, pull test, and trichogram. It has been suggested that scalp dermoscopy (trichoscopy) revealing diversity of hair shaft diameter >20% is diagnostic of FAGA.

Objective:

To evaluate the value of trichoscopy as compared to the trichogram for the diagnosis of FAGA.

Patients and Methods:

Retrospective case study of 162 women with the complaint of hair loss who underwent trichoscopic examination and trichograms.

Results:

Of all women diagnosed FAGA (55%), 62% were diagnosed by trichogram, 72% by trichoscopy with a cut-off point of 20%, and 100% irrespective of the degree of diversity of hair shaft diameter.

Conclusions:

Trichoscopy is a valuable and superior method to the trichogram for diagnosis of FAGA, especially in early cases, with the highest yield irrespective of the suggested cut-off of 20% diversity of hair shaft.

Trichoscopy (hair and scalp videodermoscopy) in the healthy female. Method standardization and norms for measurable parameters

BACKGROUND

Trichoscopy is a newly developed method of hair image analysis, based on videodermoscopy of hair and scalp.

OBJECTIVE

The aim of the study was to establish normal values and set the standard for trichoscopy in female population.

PATIENTS AND METHODS

A total of 60 healthy females with no symptoms of hair or scalp diseases in anamnesis, upon clinical examination and in classic hair diagnostic techniques were included into the study. Mean age of these females was 36.5 (19-64) years. Trichoscopy was performed with the use of Fotofinder II. In all patients trichoscopy was performed in four locations (frontal area, occipital area, left and right temporal area). Hair and perifollicular area were evaluated. Measurements were performed with the application of the MoleAnalyzer software.

RESULTS

Mean hair thickness was 0.061mm±0.008mm in frontal area vs. 0.057mm±0.007mm in occiput (p<0,001) and vs. 0.058mm±0.008mm in left temporal area and 0.059mm±0.008mm in right temporal area (p>0.005). The percentage of thin hairs (below 0.03mm) was 5%±4.3 in frontal area vs. 5.5%±4.8 in occiput vs. 6.4%±5.7 in right temporal area. The highest proportion of single-hair pilosebaceous units was observed in the temporal areas (29.1±16.2 vs. 23.2±13.5 in frontal and 18.4±12.1 in occipital areas; p<0.005). Based on study results, the norms for parameters measured in trichoscopy were assessed: mean hair thickness bigger than 0,053mm in frontal area and bigger than 0,050mm in others; percentage of thin hairs should be less than 10% in frontal and occipital area and less than 13% in temporal areas. The percentage of pilosebaceous units with single hair should be less than 35% in frontal area, 30% in occiput and 40% in temporal areas. Yellow dots were seen sporadically and they shouldn't be in a higher number than 3 in 4 fields of vision with 70-fold magnification in frontal area and only 1 in others. Perifollicular discoloration should be lower than 25% for frontal area, lower than 15% in occiput and 20% for temporal areas.

CONCLUSION

A standard procedure to perform trichoscopy (hair and scalp videodermoscopy) for diagnostic purposes was developed. Norms of measurable parameters were established for the population of adult white females.

Dermoscopy in female androgenic alopecia: method standardization and diagnostic criteria

Objective:

Establishing the trichoscopy criteria of female androgenic alopecia (FAGA).

Design:

Trichoscopy images were retrospectively evaluated.

Setting:

Dermatologic hospital-based clinic and private practice offices.

Patients and methods:

One hundred and thirty-one females (59 with androgenic alopecia, 33 with chronic telogen effluvium (CTE), 39 healthy controls). The diagnosis was based on clinical examination and confirmed by histopatology.

Main Outcome Measure:

Trichoscopy results obtained in frontal, occipital and both temporal areas of the scalp under a 20-fold and 70-fold magnification, including average hair thickness, number of 'yellow dots' and vellus hairs, number of hairs in one pilosebaceous unit and percentage of follicular ostia with perifollicullar hyperpigmentation.

Results:

Average hair thickness in frontal area versus occiput was, respectively, 0.061 ± 0.008 mm versus 0.058 ± 0.007 mm in healthy controls, 0.047 ± 0.007 mm versus 0.052 ± 0.008 mm in androgenic alopecia and 0.056 ± 0.007 mm versus 0.053 ± 0.009 mm in CTE. Mean percentage of thin hairs (< 0.03 mm) in androgenic alopecia was 20.9 ± 12% and was significantly higher than in healthy controls (6.15 ± 4.6%, P < 0.001) or in CTE (10.4 ± 3.9%, P < 0.001). The number of yellow dots, pilosebaceous units with only one hair and with perifollicular hyperpigmentation was significantly increased in androgenic alopecia. Classification and Regression Tree Analysis was performed to establish diagnostic criteria for FAGA.

Conclusion:

FAGA may be differentiated from CTE based on trichoscopy criteria. Major criteria are ratio of (1) more than four yellow dots in four images (70-fold magnification) in the frontal area, (2) lower average hair thickness in the frontal area compared to the occiput and (3) more than 10% of thin hairs (below 0.03 mm) in the frontal area. Minor criteria encompass increased frontal to occipital ratio of (1) single-hair pilosebaceous units, (2) vellus hairs and (3) perifollicular discoloration. Fulfillment of two major criteria or one major and two minor criteria allows to diagnose FAGA based on trichoscopy with a 98% specificity.

Androgenetic alopecia in the paediatric population: a retrospective review of 57 patients

BACKGROUND

Hair loss is an unwelcome event at any age, but it can be particularly distressing for adolescents and their families. While androgenetic alopecia (AGA) is the most common form of hair loss in adults, little is known about its prevalence, clinical features and response to treatments in the paediatric population.

OBJECTIVES

To better characterize the causes of alopecia in a paediatric population.

METHODS

We performed a retrospective chart review to identify all patients with hair loss seen in an academic paediatric dermatology practice at New York University over a 12-year period to better characterize the causes of alopecia in this population. We review the clinical and histological features, natural progression and associated laboratory abnormalities of AGA in 57 paediatric patients.

RESULTS

AGA was identified as the most frequent cause of hair loss in adolescents and the second most common diagnosis overall. The male to female ratio was 2 : 1 and the average age at initial presentation with AGA was 14.8 years. Adolescent girls had diffuse thinning or thinning at the crown, and boys frequently presented with female pattern hair loss. When biopsies were performed, perifollicular inflammation was a common finding. A family history of AGA was reported in 83% of patients. Laboratory evaluation for androgens revealed polycystic ovarian syndrome in three girls and late-onset congenital adrenal hyperplasia in one boy.

CONCLUSIONS

AGA is the most common form of hair loss in adolescents, and can be the presenting sign of an underlying endocrine disorder. An accurate and timely diagnosis is essential for appropriate medical and psychosocial intervention when warranted.

Prostaglandin metabolism in human hair follicle

Prostaglandins regulate a wide number of physiological functions. Recently PGF(2alpha) analogue such as latanoprost was shown to have a real impact on hair regrowth. The aim of this study was to investigate and describe the expression profile in human hair follicle of prostaglandin metabolism key enzymes, i.e. carbonyl reductase-1 (CBR1), microsomal prostaglandin E synthase-1 (mPGES-1) and microsomal prostaglandin E synthase-2 (mPGES-2), cytosolic prostaglandin E synthase (cPGES), the aldoketoreductase AKR1C1 and the prostaglandin F synthase AKR1C3. Quantitative RT-PCR on plucked hair follicles revealed some sex-related differences, mPGES-2 and AKR1C3 expression levels being higher in women. Cell and hair follicle compartment specificity was investigated using Western blot, PGE(2) and PGF(2alpha) ELISA assays and immunohistochemistry. Most of the hair cell types were endowed with prostaglandin metabolism machinery and were thus able to produce PGE(2) and/or PGF(2alpha). The epithelial part of the hair bulb was identified by immunohistology and EIA assays as the main source of prostaglandin synthesis and interconversion. All these observations support the concept that prostaglandins might be involved in hair growth and differentiation control.

Videodermoscopy in the evaluation of hair and scalp disorders

BACKGROUND

The standard methods used to diagnose scalp and hair disorders (eg, simple clinical inspection, pull test, biopsy) vary in sensitivity, reproducibility, and invasiveness. Studies on a few entities suggest that use of dermoscopy can improve clinical accuracy, but further investigation is needed.

OBJECTIVES

We sought to: (1) characterize features of several nontumoral scalp and hair conditions using videodermoscopy; and (2) assess the potential usefulness of videodermoscopy in the clinical evaluation of these conditions.

METHODS

Images (x20-70 magnification) obtained with videodermoscopy from 220 patients with various scalp and hair disorders and 15 unaffected control subjects were reviewed for distinguishing features.

RESULTS

Conditions evaluated included psoriasis (23), seborrheic dermatitis (26), alopecia areata (58), androgenetic alopecia (64), chronic telogen effluvium (7), trichotillomania (12), and primary cicatricial alopecia (30). Clinical features evident to the naked eye were seen in great detail when videodermoscopy was used. Novel features (eg, yellow dots in alopecia areata) were also identified.

LIMITATIONS

Findings require confirmation by blinded, prospective investigation.

CONCLUSIONS

Use of videodermoscopy in the clinical evaluation of scalp and hair disorders improves diagnostic capability beyond simple clinical inspection and reveals novel features of disease, which may extend clinical and pathogenetic understanding.

[The life of human hair follicle revealed]

The human hair follicle is a unique appendage which results from epithelio-mesenchymal interactions initiated around the 3rd month of development. This appendage has a very complex structure, with a dermal compartment and an epithelial compartment. The dermal compartment comprises the connective tissue sheath and the dermal papilla, both of which are irrigated by microvessels. The epithelial compartment is made of highly replicating matrix cells giving rise to three concentrical domains, namely the outer root sheath, the inner root sheath and the hair shaft. The pigmentation unit, responsible for hair color, is made of fully active melanocytes located on top of the dermal papilla. Altogether a hair follicle contains more than 20 different cell types, engaged in different differentiation pathways and/or interacting with each other. This complex appendage has a unique behavior in mammals since, after a hair production phase, it involutes in place before entering a resting phase after which it renews itself under a cyclical but stochastic way, out of a double reservoir of pluripotent stem cells able to also regenerate epidermis. For yet unknown reasons, this well ordered process can be disturbed, provoking alopecia. The pigmentation unit also renews itself under a cyclical way, out of a melanocyte progenitor reservoir which progressively declines with time, provoking the hair whitening process. Finally, the shape of the hair shaft is programmed from the bulb. What makes this appendage unique and fascinating is its high degree of autonomy, its incredibly complex though stable structure, the number of different cell types interacting under an equilibrated way and its potential of regeneration. It represents a true paradigm of tissue homeostasis, exemplifying in a small living cylinder all the fundamental laws of cell-cell and tissue interactions. This life is revealed in this short synthesis.