Desmogleins 1 and 3 in the Companion Layer Anchor Mouse Anagen Hair to the Follicle

Transcriptome Profiling of Human Follicle Dermal Papilla Cells in response to Porphyra-334 Treatment by RNA-Seq

Porphyra-334 is a kind of mycosporine-like amino acid absorbing ultraviolet-A. Here, we characterized porphyra-334 as a potential antiaging agent. An in vitro assay revealed that porphyra-334 dramatically promoted collagen synthesis in fibroblast cells. The effect of porphyra-334 on cell proliferation was dependent on the cell type, and the increase of cell viability by porphyra-334 was the highest in keratinocyte cells among the three tested cell types. An in vivo clinical test with 22 participants demonstrated the possible role of porphyra-334 in the improvement of periorbital wrinkles. RNA-sequencing using human follicle dermal papilla (HFDP) cells upon porphyra-334 treatment identified the upregulation of metallothionein- (MT-) associated genes, confirming the antioxidant role of porphyra-334 with MT. Moreover, the expression of genes involved in nuclear chromosome segregation and the encoding of components of kinetochores was upregulated by porphyra-334 treatment. Furthermore, we found that several genes associated with the hair follicle cycle, the hair follicle structure, the epidermal structure, and stem cells were upregulated by porphyra-334 treatment, suggesting the potential role of porphyra-334 in hair follicle growth and maintenance. In summary, we provided several new pieces of evidence of porphyra-334 as a potential antiaging cosmetic agent and elucidated the expression network in HFDP cells upon porphyra-334.

An Intrinsic Oscillation of Gene Networks Inside Hair Follicle Stem Cells: An Additional Layer That Can Modulate Hair Stem Cell Activities

This article explores and summarizes recent progress in and the characterization of main players in the regulation and cyclic regeneration of hair follicles. The review discusses current views and discoveries on the molecular mechanisms that allow hair follicle stem cells (hfSCs) to synergistically integrate homeostasis during quiescence and activation. Discussion elaborates on a model that shows how different populations of skin stem cells coalesce intrinsic and extrinsic mechanisms, resulting in the maintenance of stemness and hair regenerative potential during an organism’s lifespan. Primarily, we focus on the question of how the intrinsic oscillation of gene networks in hfSCs sense and respond to the surrounding niche environment. The review also investigates the existence of a cell-autonomous mechanism and the reciprocal interactions between molecular signaling axes in hfSCs and niche components, which demonstrates its critical driving force in either the activation of whole mini-organ regeneration or quiescent homeostasis maintenance. These exciting novel discoveries in skin stem cells and the surrounding niche components propose a model of the intrinsic stem cell oscillator which is potentially instructive for translational regenerative medicine. Further studies, deciphering of the distribution of molecular signals coupled with the nature of their oscillation within the stem cells and niche environments, may impact the speed and efficiency of various approaches that could stimulate the development of self-renewal and cell-based therapies for hair follicle stem cell regeneration.

Sequence Characterization of DSG3 Gene to Know Its Role in High-Altitude Hypoxia Adaptation in the Chinese Cashmere Goat

The Tibetan cashmere goat is one of the main goat breeds used by people living in the plateau. It exhibits the distinct phenotypic characteristics observed in lowland goats, allowing them to adapt to the challenging conditions at high altitudes. It provides an ideal model for understanding the genetic mechanisms underlying high-altitude adaptation and hypoxia-related diseases. Our previous exome sequencing of five Chinese cashmere breeds revealed a candidate gene, DSG3 (Desmoglein 3), responsible for the high-altitude adaptation of the Tibetan goat. However, the whole DSG3 gene (44 kbp) consisting of 16 exons in the goat genome was not entirely covered by the exome sequencing. In this study, we resequenced all the 16 exons of the DSG3 gene in ten Chinese native goat populations. Twenty-seven SNP variants were found between the lowland and highland goat populations. The genetic distance (F_ST) of significant SNPs between the lowland and highland populations ranged from 0.42 to 0.58. By using correlation coefficient analysis, linkage disequilibrium, and haplotype network construction, we found three non-synonymous SNPs (R597E, T595I, and G572S) in exon 5 and two synonymous SNPs in exons 8 and 16 in DSG3. These mutations significantly segregated high- and low-altitude goats in two clusters, indicating the contribution of DSG3 to the high-altitude hypoxia adaptation in the Tibetan goat.

Hair Follicle Terminal Differentiation Is Orchestrated by Distinct Early and Late Matrix Progenitors

During development and regeneration, matrix progenitors undergo terminal differentiation to form the concentric layers of the hair follicle. These differentiation events are thought to require signals from the mesenchymal dermal papilla (DP); however, it remains unclear how DP-progenitor cell interactions govern specific cell fate decisions. Here, we show that the hair follicle differentiated layers are specified asynchronously, with early matrix progenitors initiating differentiation before surrounding the DP. Furthermore, these early matrix cells can undergo terminal differentiation in the absence of Shh, BMP signaling, and DP maturation. Whereas early matrix progenitors form the hair follicle companion layer, later matrix populations progressively form the inner root sheath and hair shaft. Altogether, our findings characterize some of the earliest terminal differentiation events in the hair follicle and reveal that the matrix progenitor pool can be divided into early and late phases based on distinct temporal, molecular, and functional characteristics.

Is Myc an Important Biomarker? Myc Expression in Immune Disorders and Cancer

The proto-oncogene Myc serves as a paradigm for understanding the dynamics of transcriptional regulation. Myc protein has been linked to immune dysfunction, cancer development and neoplastic transformation. We review recent research regarding functions of Myc as an important modulator in immune disorders, postallogeneic hematopoietic stem cell transplantation (HSCT) and several cancers. Myc overexpression has been repeatedly linked to immune disorders and specific cancers, such as myasthenia gravis, psoriasis, pemphigus vulgaris, atherosclerosis, long-term allogeneic survival among HSCT patients, (primary) inflammatory breast cancer, (primary) ovarian carcinoma and hematological malignancies: acute myeloid leukemia, chronic myelogenous leukemia, Hodgkin's lymphoma and diffuse large B-cell lymphoma. However, decreased expression of Myc has been observed in HSCT patients who did not survive. Understanding impaired or inappropriate expression of Myc may present a path for the discovery of new targets for therapeutic applications.

t-Flavanone Improves the Male Pattern of Hair Loss by Enhancing Hair-Anchoring Strength: A Randomized, Double-Blind, Placebo-Controlled Study

Introduction

trans-3,4′-Dimethyl-3-hydroxyflavanone (t-flavanone) is a derivative of astilbin that actively stimulates hair growth. The aim of the present study was to identify the mechanisms of action of t-flavanone on hair growth.

Methods

A double-blind usage test was performed with healthy volunteers who had androgenic alopecia (AGA). The subjects were divided into three groups with equal average baldness. The members in each group applied a vasodilator-containing hair lotion supplemented with either 0, 0.1, or 0.3% (wt) t-flavanone twice a day for 30 weeks. The efficacy of t-flavanone was evaluated based on the parietal global and microscopic images. At week 30, the anchoring strength of hair was measured by the average peak force required for plucking out a single hair in a non-bald area using a digital force gauge. Desmoglein expression in the cultured human hair follicle was analyzed by Western blotting.

Results

After 30 weeks, t-flavanone significantly improved AGA and enhanced the hair-anchoring strength in a hair diameter-independent manner. Culture of human hair follicles in vitro with t-flavanone resulted in the upregulation of desmoglein protein expression.

Conclusions

The results of our in vivo and in vitro studies demonstrated that t-flavanone enhanced the cell-cell adhesions in hair follicles; thus, reinforcement of hair rooting may be a mechanism by which t-flavanone promotes hair growth.

Funding

Kao Corp.

The effect of parathyroid hormones on hair follicle physiology: implications for treatment of chemotherapy-induced alopecia

Parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) influence hair follicles through paracrine and intracrine routes. There is significant evidence that PTH and PTHrP influence the proliferation and differentiation of hair follicle cells. The PTH/PTHrP receptor signalling plays an important role in the hair follicle cycle and may induce premature catagen-telogen transition. Transgenic mice with an overexpression or blockade (PTH/PTHrP receptor knockout mice) of PTHrP activity revealed impaired or increased hair growth, respectively. Some findings also suggest that PTHrP may additionally influence the hair cycle by inhibiting angiogenesis. Antagonists of the PTH/PTHrP receptor have been shown to stimulate proliferation of hair follicle cells and hair growth. A hair-stimulating effect of a PTH/PTHrP receptor antagonist applied topically to the skin has been observed in hairless mice, as well as in mice treated with cyclophosphamide. These data indicate that the PTH/PTHrP receptor may serve as a potential target for new (topical) hair growth-stimulating drugs, especially for chemotherapy-induced alopecia.

Preclinical studies identify non-apoptotic low-level caspase-3 as therapeutic target in pemphigus vulgaris

The majority of pemphigus vulgaris (PV) patients suffer from a live-threatening loss of intercellular adhesion between keratinocytes (acantholysis). The disease is caused by auto-antibodies that bind to desmosomal cadherins desmoglein (Dsg) 3 or Dsg3 and Dsg1 in mucous membranes and skin. A currently unresolved controversy in PV is whether apoptosis is involved in the pathogenic process. The objective of this study was to perform preclinical studies to investigate apoptotic pathway activation in PV pathogenesis with the goal to assess its potential for clinical therapy. For this purpose, we investigated mouse and human skin keratinocyte cultures treated with PV antibodies (the experimental Dsg3 monospecific antibody AK23 or PV patients IgG), PV mouse models (passive transfer of AK23 or PVIgG into adult and neonatal mice) as well as PV patients' biopsies (n=6). A combination of TUNEL assay, analyses of membrane integrity, early apoptotic markers such as cleaved poly-ADP-ribose polymerase (PARP) and the collapse of actin cytoskeleton failed to provide evidence for apoptosis in PV pathogenesis. However, the in vitro and in vivo PV models, allowing to monitor progression of lesion formation, revealed an early, transient and low-level caspase-3 activation. Pharmacological inhibition confirmed the functional implication of caspase-3 in major events in PV such as shedding of Dsg3, keratin retraction, proliferation including c-Myc induction, p38MAPK activation and acantholysis. Together, these data identify low-level caspase-3 activation downstream of disrupted Dsg3 trans- or cis-adhesion as a major event in PV pathogenesis that is non-synonymous with apoptosis and represents, unlike apoptotic components, a promising target for clinical therapy. At a broader level, these results posit that an impairment of adhesive functions in concert with low-level, non-lethal caspase-3 activation can evoke profound cellular changes which may be of relevance for other diseases including cancer.

A guide for building biological pathways along with two case studies: hair and breast development

Genomic information is being underlined in the format of biological pathways. Building these biological pathways is an ongoing demand and benefits from methods for extracting information from biomedical literature with the aid of text-mining tools. Here we hopefully guide you in the attempt of building a customized pathway or chart representation of a system. Our manual is based on a group of software designed to look at biointeractions in a set of abstracts retrieved from PubMed. However, they aim to support the work of someone with biological background, who does not need to be an expert on the subject and will play the role of manual curator while designing the representation of the system, the pathway. We therefore illustrate with two challenging case studies: hair and breast development. They were chosen for focusing on recent acquisitions of human evolution. We produced sub-pathways for each study, representing different phases of development. Differently from most charts present in current databases, we present detailed descriptions, which will additionally guide PESCADOR users along the process. The implementation as a web interface makes PESCADOR a unique tool for guiding the user along the biointeractions, which will constitute a novel pathway.

Histology and ultrastructure of transitional changes in skin morphology in the juvenile and adult four-striped mouse (Rhabdomys pumilio)

The four-striped mouse has a grey to brown coloured coat with four characteristic dark stripes interspersed with three lighter stripes running along its back. The histological differences in the skin of the juvenile and adult mouse were investigated by Haematoxylin and Eosin and Masson Trichrome staining, while melanocytes in the skin were studied through melanin-specific Ferro-ferricyanide staining. The ultrastructure of the juvenile skin, hair follicles, and melanocytes was also explored. In both the juvenile and adult four-striped mouse, pigment-containing cells were observed in the dermis and were homogeneously dispersed throughout this layer. Apart from these cells, the histology of the skin of the adult four-striped mouse was similar to normal mammalian skin. In the juvenile four-striped mouse, abundant hair follicles of varying sizes were observed in the dermis and hypodermis, while hair follicles of similar size were only present in the dermis of adult four-striped mouse. Ultrastructural analysis of juvenile hair follicles revealed that the arrangement and differentiation of cellular layers were typical of a mammal. This study therefore provides unique transition pattern in the four-striped mouse skin morphology different from the textbook description of the normal mammalian skin.

Protease activity, localization and inhibition in the human hair follicle

Objective

In humans, the process of hair shedding, referred to as exogen, is believed to occur independently of the other hair cycle phases. Although the actual mechanisms involved in hair shedding are not fully known, it has been hypothesized that the processes leading to the final step of hair shedding may be driven by proteases and/or protease inhibitor activity. In this study, we investigated the presence of proteases and protease activity in naturally shed human hairs and assessed enzyme inhibition activity of test materials.

Methods

We measured enzyme activity using a fluorescence-based assay and protein localization by indirect immunohistochemistry (IHC). We also developed an ex vivo skin model for measuring the force required to pull hair fibres from skin.

Results

Our data demonstrate the presence of protease activity in the tissue material surrounding club roots. We also demonstrated the localization of specific serine protease protein expression in human hair follicle by IHC. These data provide evidence demonstrating the presence of proteases around the hair club roots, which may play a role during exogen. We further tested the hypothesis that a novel protease inhibitor system (combination of Trichogen® and climbazole) could inhibit protease activity in hair fibre club root extracts collected from a range of ethnic groups (UK, Brazil, China, first-generation Mexicans in the USA, Thailand and Turkey) in both males and females. Furthermore, we demonstrated that this combination is capable of increasing the force required to remove hair in an ex vivo skin model system.

Conclusion

These studies indicate the presence of proteolytic activity in the tissue surrounding the human hair club root and show that it is possible to inhibit this activity with a combination of Trichogen® and climbazole. This technology may have potential to reduce excessive hair shedding.

Résumé

Ultrastructural localization of desmoglein and plakophilin in the human hair suggests that the cell membrane complex is a long desmosomal remnant

Unlike the superficial part of the corneous layer of the epidermis (Stratum corneum) where desmosomes are degraded and corneocytes flake away, the trichocytes in the hair remain attached to each other after cornification. The permanence and fine localization of cell junctions, in particular of desmosomal proteins in the cornifying and mature human hair, is not known. The present electron microscope immunolocalization study indicates that two protein markers for desmosomes such as desmoglein 4 and plakophilins 1 and 3 are still present in mature cortical and cuticle cells. These proteins remain mainly localized in the cornified cytoplasmic side of desmosomal remnants of cortical cells, but also in the delta layer of the extracellular region of the membrane complex. This suggests that the delta layer represents an extensive desmosomal remnant formed between mature cortical cells and in cuticle cells. The endocuticle appears to be the site of accumulation of desmosomal proteins and degraded nuclear material. The cornification of desmosomal junctions in both cortical and cuticle cells likely contributes to stabilize the integrity of the hair shaft.

Desmogleins: hair perspective

Desmogleins (Dsgs) are calcium-dependent, transmembrane glycoproteins belonging to the desmosomal cadherin superfamily, which play significant roles in selective calcium ions (Ca²⁺) dependent adhesion interactions between cell surfaces. Four subtypes of Dsg have been identified. Recent observations show the distribution of Dsgs can correlate with specific types of keratinization, anchorage of the hair, and hypotrichosis.

Immunolocalization of junctional proteins in human hairs indicates that the membrane complex stabilizes the inner root sheath while desmosomes contact the companion layer through specific keratins

The inner root sheath (IRS) sustains and addresses the hair shaft outside the follicle. Ultrastructural analysis of immunolabeling for beta-catenin, plakophilin-1, desmoglein-4 and keratin-17 in human hairs has indicated that adherens junctions and desmosomes initially connect cells in mature IRS and the companion layer. Beta-catenin immunolabeling for adherens junctions is only seen in sparse regions of differentiating Huxley cells, Flugelzellen cells and Henle cells, but disappears in cornified cells of the IRS. Desmoglein-4 and plakophilin-1 immunolabeling are observed in differentiating and cornified desmosomes of the Huxley and Henle layers and in the membrane complex joining these cells. Desmoglein-4 and plakophilin-1 are more frequently immunolocalized in the intracellular side of the junctions, but some labeling is also present in the delta-layer of the membrane complex. The labeling indicates a prevalent intracellular redistribution of desmoglein-4 and plakophilin-1 when the final cornification of the IRS occurs. Intense keratin-17 immunolabeling is observed in tonofilaments of the companion layer joining the plakophilin-1 rich desmosomes of the Henle layer. This suggests that this elastic type of keratin is present at desmosome junctions during the movements of the companion layer along the slippage plane of the hair shaft.

Redefining the structure of the hair follicle by 3D clonal analysis

The hair follicle (HF) is a multi-tissue mini-organ that self-renews periodically. However, the cellular organisation of this much-studied model is not fully understood. The structures of the outer layer and of the bulb, which ensures HF growth, have not been completely established. To clarify these points, we have conducted in vivo clonal analyses with 3D imaging in mice. The upper two-thirds of the HF outer layer consists of two clonally unrelated groups of cells that exhibit different modes of growth. They correspond to the basal outer root sheath (ORS) and the companion layer (Cp). The basal ORS has an unusual anisotropic mode of growth from a suprabulbar zone, which we named the privileged proliferation zone. The Cp has a stem/transient-amplifying mode of growth and is shown to be an HF internal structure. Furthermore, we describe an additional element, the bulb outer layer, which is contiguous and shares markers (e.g. Lgr5) with the basal ORS but is formed by a separate lineage that belongs neither to the ORS nor Cp lineage. It represents a novel element with proximal cells that are contiguous with the germinative layer in the bulb. In reference to its shape and position we named it the lower proximal cup (LPC). These clonal hierarchies reveal a novel model of HF organisation and growth based on two major entities: the basal ORS and the LPC plus the seven internal layers.

The basic science of hair biology: what are the causal mechanisms for the disordered hair follicle?

A hair disorder can be difficult to define, but patients are typically motivated to seek treatment when their hair growth patterns are significantly different from their cultural group or when growth patterns change significantly. The causes of hair disorders are many and varied, but fundamentally the disorder is a consequence of aberrant alterations of normal hair biology. The potential trigger factors for hair disorders can be attributed to inflammation, genetics, the environment, or hormones, of which the relative contributions vary for different diagnoses, between individuals, and over time. This article discusses the causal mechanisms for the disordered hair follicle.

Alopecia as a rare but distinct manifestation of pemphigus vulgaris

BACKGROUND

Pemphigus vulgaris (PV) patients may develop scalp erosions, however, the development of alopecia has been reported to be extremely rare.

OBJECTIVE

To delineate the clinicopathological features of alopecia in PV and provide insight into the pathogenesis of this rarely observed manifestation.

METHODS

A retrospective case note review was performed on five PV patients presenting with progressive hair loss and alopecic patches. Data were collected on demographics and clinical findings. Results for hair pull tests, direct immunofluorescence study of plucked hairs, established laboratory tests to detect anti-desmoglein 1 and 3 autoantibodies and scalp swab culture were recorded. A combination of vertical and horizontal sectioning technique enabled detailed histopathological analysis of alopecic patches. Clinical course was monitored.

RESULTS

Anagen hair follicles with the outer root sheath structure were easily pulled from perilesional scalp, with intercellular IgG deposition on the outer root sheath keratinocytes. Acantholysis between outer root sheath keratinocytes extending from the infundibulum to suprabalbar level was evident in anagen hair follicles of affected lesions. Perifollicular cell infiltration was observed in the lesions where scalp swabs detected micro-organisms. The bulge stem cell area was mostly intact. Alopecia was non-scarring and following 4 weeks of therapy hair re-growth was seen in all patients.

CONCLUSION

In PV, the combination of anti-desmoglein autoantibody-mediated acantholysis in conjunction with secondary factors, such as inflammatory changes due to infection, may cause weakening of hair follicle anchorage resulting in hair loss and alopecic patches. This unusual clinical phenotype should alert physicians to PV as a potential diagnosis.

An adult passive transfer mouse model to study desmoglein 3 signaling in pemphigus vulgaris

Evidence has accumulated that changes in intracellular signaling downstream of desmoglein 3 (Dsg3) may play a significant role in epithelial blistering in the autoimmune disease pemphigus vulgaris (PV). Currently, most studies on PV involve passive transfer of pathogenic antibodies into neonatal mice which have not finalized epidermal morphogenesis, and do not permit analysis of mature hair follicles (HFs) and stem cell niches. To investigate Dsg3 antibody-induced signaling in the adult epidermis at defined stages of the HF cycle, we here developed a model with passive transfer of the monospecific pathogenic Dsg3 antibody AK23 into adult 8-week-old C57Bl/6J mice. Validated using histopathological and molecular methods, we found that this model faithfully recapitulates major features described in PV patients and PV models. Two hours after AK23 transfer we observed widening of intercellular spaces between desmosomes and EGFR activation, followed by increased Myc expression and epidermal hyperproliferation, desmosomal Dsg3 depletion and predominant blistering in HFs and oral mucosa. These data confirm that the adult passive transfer mouse model is ideally suited for detailed studies of Dsg3 antibody-mediated signaling in adult skin, providing the basis for investigations on novel keratinocyte-specific therapeutic strategies.

Desmosomes: adhesive strength and signalling in health and disease

Desmosomes are intercellular junctions whose primary function is strong intercellular adhesion, known as hyperadhesion. In the present review, we discuss how their structure appears to support this function as well as how they are assembled and down-regulated. Desmosomal components also have signalling functions that are important in tissue development and remodelling. Their adhesive and signalling functions are both compromised in genetic and autoimmune diseases that affect the heart, skin and mucous membranes. We conclude that much work is required on structure–function relationships within desmosomes in vivo and on how they participate in signalling processes to enhance our knowledge of tissue homoeostasis and human disease.

Keratinization of outer root sheath cells is prevented by contact with inner root sheath of rat hair follicles

The purpose of the present study was to elucidate why keratinocytes of the outer root sheath (ORS) do not keratinize in situ. Two possibilities were considered--inhibition of keratinization is caused by contact of ORS with inner root sheath (IRS) or insufficient supply of keratinization promoting factors from the surrounding tissues to the ORS. In order to distinguish between these possibilities mid-segments of hair follicles were liberated from the dermis by dissection followed by collagenase digestion. ORS cells were then either allowed to migrate from the mid-segments or were kept on the agarose layer which prevented cell spreading and preserved three dimensional structure of hair root. Cultures were stimulated with calcium or EGF, and studied morphologically at the light and transmission electron microscope level. The level of mRNA for differentiation cell markers was also studied by RealTime PCR. ORS cells growing in a medium with low Ca2+ content formed monolayers, which after elevation of Ca2+ produced multilayers with cells containing keratohyalin-like granules. Ca2+ or EGF treatment upregulated expression of involucrin, filaggrin and keratinocyte differentiation associated protein (Kdap). Culture of mid-segments of hair follicles in low calcium culture medium kept on agarose increased expression of filaggrin and Kdap, but downregulated expression of involucrin. Stimulation by Ca2+ further increased expression of filaggrin and Kdap, but had no effect on the level of involucrin expression. EGF stimulated expression of filaggrin only. It is concluded that IRS exerted an inhibitory effect on the expression of involucrin, an essential component of the cornified envelope, thus preventing keratinization of ORS cells in situ. On the other hand, improved access of nutrients or promoting factors of keratinization to the mid-segment of hair follicles augmented expression of filaggrin and Kdap, proteins engaged in the differentiation of keratinocytes but not involved in its terminal phase.

Perturbed desmosomal cadherin expression in grainy head-like 1-null mice

In Drosophila, the grainy head (grh) gene plays a range of key developmental roles through the regulation of members of the cadherin gene family. We now report that mice lacking the grh homologue grainy head-like 1 (Grhl1) exhibit hair and skin phenotypes consistent with a reduction in expression of the genes encoding the desmosomal cadherin, desmoglein 1 (Dsg1). Grhl1-null mice show an initial delay in coat growth, and older mice exhibit hair loss as a result of poor anchoring of the hair shaft in the follicle. The mice also develop palmoplantar keratoderma, analogous to humans with DSG1 mutations. Sequence analysis, DNA binding, and chromatin immunoprecipitation experiments demonstrate that the human and mouse Dsg1 promoters are direct targets of GRHL1. Ultrastructural analysis reveals reduced numbers of abnormal desmosomes in the interfollicular epidermis. These findings establish GRHL1 as an important regulator of the Dsg1 genes in the context of hair anchorage and epidermal differentiation, and suggest that cadherin family genes are key targets of the grainy head-like genes across 700 million years of evolution.

Exogen hair characterization in human scalp

BACKGROUND/AIM

Classically, the hair cycle is described as a sequence of three successive phases: a hair-growth phase named anagen, a regression phase or catagen and a resting phase or telogen. In rodents, it appears that the resting hair follicle population contains also a new phase that has been identified recently as the exogen phase of the hair cycle. This phase leads to the release of the telogen club and results in hair shedding. The aim of this paper is to propose a method that is applicable to humans and that is able to discriminate the two components of the resting hair population i.e. the telogen and the exogen hair follicles.

METHODS

We used non-invasive approaches to entrap exogen scalp hair into silicon-based polymers. We also extracted growing and non-growing hair with a calibrated dynamometer. We characterized differences between anagen, catagen, telogen and exogen root ends with histochemical stains and with the scanning electron microscope. Furthermore, we documented all known hair-cycle stages with the contrast-enhanced phototrichogram (CE-PTG) technique.

RESULTS

We demonstrated that anagen and telogen hair are firmly anchored to the hair follicle and that cohesion forces are correlated with hair thickness. On the contrary, exogen hair are passively retained within the hair follicle. Among the resting hair population, telogen clubs retain cellular elements of the outer root sheaths that are not found on exogen hair. The specificity of the new exogen collection method was documented with the simultaneous use of the CE-PTG method: indeed anagen, catagen and telogen follicles remain unaffected by the exogen extraction procedure.

CONCLUSION

Exogen hair can be sampled specifically from the human scalp with a new non-invasive method. Our data suggest that the casual levels of exogen hair, in normal individuals and under the present experimental conditions, are usually less than seven hair per cm(2).

Structure and function of desmosomes

Desmosomes are prominent adhesion sites that are tightly associated with the cytoplasmic intermediate filament cytoskeleton providing mechanical stability in epithelia and also in several nonepithelial tissues such as cardiac muscle and meninges. They are unique in terms of ultrastructural appearance and molecular composition with cell type-specific variations. The dynamic assembly properties of desmosomes are important prerequisites for the acquisition and maintenance of tissue homeostasis. Disturbance of this equilibrium therefore not only compromises mechanical resilience but also affects many other tissue functions as becomes evident in various experimental scenarios and multiple diseases.

Transforming growth factor-? receptor II is preferentially expressed in the companion layer of the human anagen hair follicle

BACKGROUND

Transforming growth factor (TGF)-beta is a multifunctional growth factor with multiple roles in skin including hair follicle development and cycling, where it regulates cell proliferation, differentiation and apoptosis, as well as in wound healing. While TGF-beta receptor I (TGF-beta RI) and receptor II (TGF-beta RII) expression helps define early human hair follicle morphogenesis, expression in the adult human hair follicle remains to be established.

OBJECTIVES

To assess TGF-beta receptor expression in human scalp anagen hair follicles.

METHODS

Immunohistochemical and double immunofluorescence analysis of TGF-beta RI and RII was conducted on frozen sections of haired human scalp obtained from 10 healthy individuals.

RESULTS

TGF-beta RI expression was detected in the outer root sheath of anagen hair follicles while TGF-beta RII was expressed almost exclusively in the companion layer of inner root sheath and less so in premedulla keratinocytes. Both receptors were colocalized in the companion layer of the proximal and mid follicle.

CONCLUSIONS

The well-described role of TGF-beta in keratinocyte apoptosis during catagen is likely to involve anagen-specific hair follicle components including the companion layer, as this layer provides the slippage plane supporting the inner root sheath and hair shaft as they ascend to the skin surface. Results of this study suggest that the colocalization of TGF-beta RI/RII complexes at the companion layer would facilitate TGF-beta signalling at this site to regulate apoptosis of the companion layer keratinocytes, facilitating shrinkage/contraction of this cell layer during hair follicle regression/catagen.

Delineation of diversified desmoglein distribution in stratified squamous epithelia: implications in diseases

Desmogleins play critical roles in cell adhesion and skin blistering diseases, as they are the target antigens of autoimmune antibodies and bacterial toxins. We recently cloned several novel members of the desmoglein gene family, bringing the number of desmogleins to four in the rat and human genomes and six in the mouse. Here, we have produced a monoclonal antibody to a cytoplasmic epitope of Dsg4, assessed its specificity and compared it to several existing Dsg1-3 antibodies. We also demonstrated cross-reactivity of commercially available and often used Dsg1 antibodies. Using these tools, we delineated the unique expression patterns of each desmoglein isoform in various human and mouse stratified squamous epithelia, including skin, hair, palm, and oral mucosa. Interestingly, in the epidermis, the expression of each desmoglein correlates with their gene arrangement in the cadherin locus. In human, Dsg4 was detected primarily in the granular and cornified cell layers of the epidermis, while present throughout all differentiated layers of the oral mucosa and palm, and in the matrix cells of anagen hair bulb. Similar pattern of expression for Dsg4 was observed in mouse, with the exception that it was expressed at significantly lower levels in the mouse epidermis. These results demonstrate the complexity of desmoglein gene expression and provide additional insights into the correlation between tissue expression patterns and disease phenotypes.

The calcium-binding protein calretinin is a marker of the companion cell layer of the human hair follicle

BACKGROUND

Ultrastructural studies of the hair follicle show that the outer root sheath (ORS) does not consist of a homogeneous cell population. The innermost cell layer of the ORS, also called the companion layer, is a single cell layer closely associated with the Henle layer of the inner root sheath.

OBJECTIVES

To describe the immunohistochemical expression of calretinin, a calcium-binding protein, in the human hair follicle.

METHODS

Immunohistochemical studies using two different antisera to calretinin were performed in paraffin-embedded and in frozen scalp specimens using standard techniques.

RESULTS

Calretinin immunostaining was consistently and specifically found in the companion cell layer of hair follicles.

CONCLUSIONS

These findings provide further evidence to support the notion that the companion layer is not only morphologically, but also immunohistochemically, different from the other cells of the ORS.

In search of the "hair cycle clock": a guided tour

The hair follicle, a unique characteristic of mammals, represents a stem cell-rich, prototypic neuroectodermal-mesodermal interaction system. This factory for pigmented epithelial fibers is unique in that it is the only organ in the mammalian body which, for its entire lifetime, undergoes cyclic transformations from stages of rapid growth (anagen) to apoptosis-driven regression (catagen) and back to anagen, via an interspersed period of relative quiescence (telogen). While it is undisputed that the biological "clock" that drives hair follicle cycling resides in the hair follicle itself, the molecular nature of the underlying oscillator system remains to be clarified. To meet this challenge is of profound general interest, since numerous key problems of modern biology can be studied exemplarily in this versatile model system. It is also clinically important, since the vast majority of patients with hair growth disorders suffers from an undesired alteration of hair follicle cycling. Here, we sketch basic background information and key concepts that one needs to keep in mind when exploring the enigmatic "hair cycle clock"(HCC), and summarize competing models of the HCC. We invite the reader on a very subjective guided tour, which focuses on our own trials, errors, and findings toward the distant goal of unravelling one of the most fascinating mysteries of biology: Why does the hair follicle cycle at all? How does it do it? What are the key players in the underlying molecular controls? Attempting to offer at least some meaningful answers, we share our prejudices and perspectives, and define crucial open questions.