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Anais Brasileiros de Dermatologia 2022Little is known about the ultrastructure of pili annulati.
BACKGROUND
Little is known about the ultrastructure of pili annulati.
OBJECTIVES
To examine with transmission electron microscopy affected hairs of a family, whose diagnosis had been confirmed in five individuals with scanning electron microscopy, which showed surface undulations with "curtain-like" folding of the hair cuticula and to compare the findings with normal control.
METHODS
Hairs of two affected patients and one control were embedded in resin and cut lengthwise to produce ultra-thin sections.
RESULTS
The normal hair showed a parallel arrangement of dark lines associated with less electron-dense wide bands. Small cavities could be observed, mostly in the dark lines, affected hairs had a large number of cavities, associated or not with the insertion of melanosomes and loss of parallelism of the dark lines. Higher magnification showed a significant loss of this parallelism, resembling "wood grooves". Widened dark lines were observed in some areas.
STUDY LIMITATIONS
Only a few hairs were examined.
CONCLUSIONS
The present results suggest that the microcanaliculi of the hair surface, easily found with scanning electron microscopy, may be secondary not only to the cavities seen in the sections but also to the disorder of proteins that form this region, demonstrated by the changes of the cortex dark lines.
Topics: Hair; Hair Diseases; Hair Follicle; Humans; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission
PubMed: 36100477
DOI: 10.1016/j.abd.2021.10.011 -
Dermatology Online Journal Oct 1998The hair follicle is one of a few human tissues containing stem cells. The stem cells are interspersed within the basal layer of the outer root sheath and in an area... (Review)
Review
The hair follicle is one of a few human tissues containing stem cells. The stem cells are interspersed within the basal layer of the outer root sheath and in an area called the bulge. From this reservoir stem cells migrate to hair matrix and start to divide and differentiate. Their behavior is controlled by numerous cytokines produced by cells of the dermal papilla. Dermal papilla cells and some cells of the inner and outer sheaths of the follicle from androgen-dependent hairs have androgen receptors in their cytoplasm and nucleus. Androgens indirectly control hair growth by influencing the synthesis and release of cytokines from the dermal papilla cells. Drugs affecting hair growth belong to one of the following groups: cytotoxic drugs, antiandrogens and drugs acting on potassium channels. Further development of drugs selective for certain steps in the process of hair growth will enable more successful therapy of hair growth disorders.
Topics: Hair; Hair Follicle; Hirsutism; Humans; Hypertrichosis; Hypotrichosis
PubMed: 10217742
DOI: No ID Found -
Scandinavian Journal of Immunology Oct 2020Cartilage-hair hypoplasia (CHH) is an autosomal recessive syndromic immunodeficiency with skeletal dysplasia, short stature, hypotrichosis, variable degree of immune... (Review)
Review
Cartilage-hair hypoplasia (CHH) is an autosomal recessive syndromic immunodeficiency with skeletal dysplasia, short stature, hypotrichosis, variable degree of immune dysfunction and increased incidence of anaemia, Hirschsprung disease and malignancy. CHH is caused by variants in the RMRP gene, encoding the untranslated RNA molecule of the mitochondrial RNA-processing endoribonuclease, which participates in for example cell cycle regulation and telomere maintenance. Recent studies have expanded our understanding of the complex pathogenesis of CHH. Immune dysfunction has a major impact on clinical course and prognosis. Clinical features of immune dysfunction are highly variable, progressive and include infections, lung disease, immune dysregulation and malignancy. Mortality is increased compared with the general population, due to infections, malignancy and pulmonary disease. Several risk factors for early mortality have been reported in the Finnish CHH cohort and can be used to guide management. Newborn screening for severe combined immunodeficiency can possibly be of prognostic value in CHH. Regular follow-up by a multidisciplinary team should be implemented to address immune dysfunction in all patients with CHH, also in asymptomatic cases. Haematopoietic stem cell transplantation can cure immune dysfunction, but its benefits in mildly symptomatic patients with CHH remain debatable. Further research is needed to understand the mechanisms behind the variability of clinical features, to search for potential molecular treatment targets, to examine and validate risk factors for early mortality outside the Finnish CHH cohort and to develop management guidelines. This review focuses on the pathogenesis, clinical course and management of CHH.
Topics: Animals; Hair; Hirschsprung Disease; Humans; Osteochondrodysplasias; Primary Immunodeficiency Diseases
PubMed: 32506568
DOI: 10.1111/sji.12913 -
BioMed Research International 2013Endocrine changes supervening after parturition and menopause participate in the control of sebum production and hair growth modulation. The ensuing conditions include... (Review)
Review
Endocrine changes supervening after parturition and menopause participate in the control of sebum production and hair growth modulation. The ensuing conditions include some peculiar aspects of hair loss (effluvium), alopecia, and facial hirsutism. The hair cycling is of major clinical relevance because most hair growth disorders result from disturbances in this chronobiological feature. Of note, any correlation between a biologic abnormality and hair cycling disturbance does not prove a relationship of causality. The proportion of postmenopausal women is rising in the overall population. Therefore, the prevalence of these hair follicle disturbances is globally on the rise. Current therapies aim at correcting the underlying hormonal imbalances, and at improving the overall cosmetic appearance. However, in absence of pathogenic diagnosis and causality criteria, chances are low that a treatment given by the whims of fate will adequately control hair effluvium. The risk and frequency of therapeutic inertia are further increased. When the hair loss is not controlled and/or compensated by growth of new hairs, several clinical aspects of alopecia inexorably develop. Currently, there is little evidence supporting any specific treatment for these endocrine hair disorders in post-partum and postmenopausal women. Current hair treatment strategies are symptomatic and nonspecific so current researchers aim at developing new, targeted methods.
Topics: Alopecia; Female; Hair; Hair Diseases; Hair Follicle; Humans; Menopause; Sebum
PubMed: 24455742
DOI: 10.1155/2013/957432 -
ELife Mar 2024The etiology of hair loss remains enigmatic, and current remedies remain inadequate. Transcriptome analysis of aging hair follicles uncovered changes in immune pathways,...
The etiology of hair loss remains enigmatic, and current remedies remain inadequate. Transcriptome analysis of aging hair follicles uncovered changes in immune pathways, including Toll-like receptors (TLRs). Our findings demonstrate that the maintenance of hair follicle homeostasis and the regeneration capacity after damage depend on TLR2 in hair follicle stem cells (HFSCs). In healthy hair follicles, TLR2 is expressed in a cycle-dependent manner and governs HFSCs activation by countering inhibitory BMP signaling. Hair follicles in aging and obesity exhibit a decrease in both TLR2 and its endogenous ligand carboxyethylpyrrole (CEP), a metabolite of polyunsaturated fatty acids. Administration of CEP stimulates hair regeneration through a TLR2-dependent mechanism. These results establish a novel connection between TLR2-mediated innate immunity and HFSC activation, which is pivotal to hair follicle health and the prevention of hair loss and provide new avenues for therapeutic intervention.
Topics: Humans; Hair Follicle; Toll-Like Receptor 2; Hair; Alopecia
PubMed: 38483447
DOI: 10.7554/eLife.89335 -
The Journal of Investigative... Dec 2007The diagnosis and management of hair and scalp disorders in the clinic or office presents a unique challenge for the physician. In addition to identifying and treating... (Review)
Review
The diagnosis and management of hair and scalp disorders in the clinic or office presents a unique challenge for the physician. In addition to identifying and treating the underlying cause of the disorder, the physician also needs to take into account the impact of these disorders on the patient's self-esteem and quality of life. The first stage in determining the correct treatment strategy is to evaluate the underlying cause of the condition; and to that end, there are a number of invasive and non-invasive methods available to the office physician. These methods range from traditional biopsy and microscopic techniques to new optical methods such as videodermoscopy. Once the type and cause of the condition have been identified, the next stage is to determine the most appropriate holistic treatment strategy. In addition to any prescribed medical treatment, the use of cosmetic hair care products can often play an important role in improving the patient's quality of life. These products (particularly conditioners and styling aids) have been shown to provide the patient with improvements in hair feel, appearance, behavior, and protection against damage. Many of these cosmetic benefits can be measured directly on the hair fiber, using a variety of techniques.
Topics: Hair; Hair Diseases; Hair Follicle; Hair Preparations; Holistic Health; Hot Temperature; Humans; Scalp Dermatoses; Stress, Mechanical
PubMed: 18004293
DOI: 10.1038/sj.jidsymp.5650051 -
Experimental Dermatology Apr 2015Present-day hairs and feathers are marvels of biological engineering perfected over 200 million years of convergent evolution. Prominently, both follicle types coevolved...
Present-day hairs and feathers are marvels of biological engineering perfected over 200 million years of convergent evolution. Prominently, both follicle types coevolved regenerative cycling, wherein active filament making (anagen) is intermitted by a phase of relative quiescence (telogen). Such regenerative cycling enables follicles to “reload” their morphogenetic program and make qualitatively different filaments in the consecutive cycles. Indeed, many species of mammals and birds undergo regenerative metamorphosis, prominently changing their integument between juvenile and adult forms. This phenomenon is inconspicuous in mice, which led to the conventional perception that hair type is hardwired during follicle morphogenesis and cannot switch. A series of recent works by Chi and Morgan change this perception, and show that many mouse follicles naturally switch hair morphologies, for instance from “wavy” zigzag to straight awl, in the second growth cycle. A series of observations and genetic experiments show that back and forth hair type switching depends on the number of cells in the follicle's dermal papilla, with the critical threshold being around 40-50 cells. Pigmentation is another parameter that hair and feather follicles can reload between cycles, and even midway through anagen. Recent works show that hair and feather pigmentation “printing” programs coevolved to rely on pulsed expression of Agouti, a melanocortin receptor-1 antagonist, in the follicular mesenchyme. Here, we discuss broader implications of hair and feather regenerative plasticity.
Topics: Animals; Biological Evolution; Feathers; Hair; Hair Follicle; Metamorphosis, Biological; Regeneration
PubMed: 25557541
DOI: 10.1111/exd.12627 -
The Journal of Investigative Dermatology Apr 2004
Review
Topics: Animals; Hair; Humans; Models, Biological; Twins, Monozygotic
PubMed: 15102103
DOI: 10.1111/j.0022-202X.2004.22436.x -
Experimental Cell Research Jul 2014The vertebrate ectoderm gives rise to organs that produce mineralized or keratinized substances, including teeth, hair, and claws. Most of these ectodermal derivatives... (Review)
Review
The vertebrate ectoderm gives rise to organs that produce mineralized or keratinized substances, including teeth, hair, and claws. Most of these ectodermal derivatives grow continuously throughout the animal׳s life and have active pools of adult stem cells that generate all the necessary cell types. These organs provide powerful systems for understanding the mechanisms that enable stem cells to regenerate or renew ectodermally derived tissues, and remarkable progress in our understanding of these systems has been made in recent years using mouse models. We briefly compare what is known about stem cells and their niches in incisors, hair follicles, and claws, and we examine expression of Gli1 as a potential example of a shared stem cell marker. We summarize some of the features, structures, and functions of the stem cell niches in these ectodermal derivatives; definition of the basic elements of the stem cell niches in these organs will provide guiding principles for identification and characterization of the niche in similar systems.
Topics: Animals; Ectoderm; Epithelial Cells; Hair; Hoof and Claw; Humans; Stem Cell Niche; Tooth
PubMed: 24530577
DOI: 10.1016/j.yexcr.2014.02.003 -
Scientific Reports Jun 2021Quantifying the continuous variation in human scalp hair morphology is of interest to anthropologists, geneticists, dermatologists and forensic scientists, but existing...
Quantifying the continuous variation in human scalp hair morphology is of interest to anthropologists, geneticists, dermatologists and forensic scientists, but existing methods for studying hair form are time-consuming and not widely used. Here, we present a high-throughput sample preparation protocol for the imaging of both longitudinal (curvature) and cross-sectional scalp hair morphology. Additionally, we describe and validate a new Python package designed to process longitudinal and cross-sectional hair images, segment them, and provide measurements of interest. Lastly, we apply our methods to an admixed African-European sample (n = 140), demonstrating the benefit of quantifying hair morphology over classification, and providing evidence that the relationship between cross-sectional morphology and curvature may be an artefact of population stratification rather than a causal link.
Topics: Cross-Sectional Studies; Hair; Humans; Image Processing, Computer-Assisted; Scalp
PubMed: 34075066
DOI: 10.1038/s41598-021-90409-x