Collapse and restoration of MHC class-I-dependent immune privilege: exploiting the human hair follicle as a model

Immunology of alopecia areata

Alopecia areata is a condition that affects hair follicles and leads to hair loss ranging from small well-defined patches to complete loss of all body hair. Despite its high incidence, the pathobiology is not fully understood, and no single concept could be universally accepted.

Alopecia areata is mostly considered to be an autoimmune disease, in which the collapse of hair follicle immune privilege plays a key role. Higher incidence rate in the female population and increased overall risk of other autoimmune disorders militate in favor of autoimmune hypothesis. Antibodies against multiple components of hair follicles almost exclusively attack in anagen phase, where melanogenesis takes place. It suggests involvement of melanogenesis-associated autoantigens as a target epitope.

Some investigators believed that alopecia areata is not a truly autoimmune disease but is only ‘consistent with’ autoimmune mechanisms. High frequency of a positive family history up to 42% may reflects the contribution of heredity factors. In addition, no specific target autoantigen has been identified so far, and autoantibodies to hair follicle-associated antigens are detectable in normal individuals.

Mouse Models of Alopecia Areata: C3H/HeJ Mice Versus the Humanized AA Mouse Model

The C3H/HeJ model has long dominated basic alopecia areata (AA) in vivo research and has been used as proof-of-principle that Jak inhibitors are suitable agents for AA management in vivo. However, its histologic features are not typical of human AA, and it is questionable whether it is sufficiently clinically predictive for evaluating the therapeutic effects of candidate AA agents. Instead, the humanized mouse model of AA has been used to functionally demonstrate the role of key immune cells in AA pathogenesis and to discover human-specific pharmacologic targets in AA management. Therefore, we advocate the use of both models in future preclinical AA research.

Macrophage Migration Inhibitory Factor in Alopecia Areata and Vitiligo: A Case-Controlled Serological Study

BACKGROUND: Alopecia areata and vitiligo vulgaris are common autoimmune diseases whose pathophysiology are not completely elucidated. Genetic susceptibility, immunological background, and stress have significant roles in their pathogenesis. Although macrophage migration inhibitory factor (MIF) is crucial for the maintenance of immune privilege in certain sites, it can upregulate different inflammatory cytokines and contribute to the pathogenesis of different autoimmune diseases. There is controversy about its role in alopecia and no adequate data about its role in vitiligo. OBJECTIVES: We sought to assess the serum level of MIF in alopecia areata and vitiligo and its relationship with different variables of both diseases. METHOD: Serum level of MIF was measured in 20 patients with vitiligo, 22 patients with alopecia areata, and 20 controls by ELISA. RESULTS: MIF was significantly higher in alopecia areata (8.477±4.1761ng/mL) and vitiligo vulgaris (3.930±2.7071ng/mL) compared to controls (0.725±0.5108 ng/mL) (P<0.01). In addition, MIF levels were positively correlated with the severity of alopecia areata and vitiligo. CONCLUSION: The MIF has an active role in the pathogenesis of alopecia areata and vitiligo and could be a target for the treatment of both diseases.

Translational Neuroendocrinology of Human Skin: Concepts and Perspectives

Human skin responds to numerous neurohormones, neuropeptides, and neurotransmitters that reach it via the vasculature or skin nerves, and/or are generated intracutaneously, thus acting in a para- and autocrine manner. This review focuses on how neurohormones impact on human skin physiology and pathology. We highlight basic concepts, major open questions, and translational research perspectives in cutaneous neuroendocrinology and argue that greater emphasis on neuroendocrine human skin research will foster the development of novel dermatological therapies. Furthermore, human skin and its appendages can be used as highly accessible and clinically relevant model systems for probing nonclassical, ancestral neurohormone functions. This calls for close interdisciplinary collaboration between dermatologists, skin biologists, neuroendocrinologists, and neuropharmacologists.

Pro-inflammatory Vδ1+T-cells infiltrates are present in and around the hair bulbs of non-lesional and lesional alopecia areata hair follicles

BACKGROUND

It is widely accepted that NKG2D⁺cells are critically involved in alopecia areata (AA) pathogenesis. However, besides being expressed in CD8⁺T-cells and NK cells, NKG2D is also found in human γδT-cells. AA lesional hair follicles (HFs) overexpress NKG2D and γδTCR activating ligands, e.g. MICA and CD1d, and chemoattractants for γδT-cells, such as CXCL10.

OBJECTIVE

To investigate whether abnormal activities of γδT-cells may be involved in AA pathogenesis.

METHODS

We analyzed the number and activation status of γδT-cells in human healthy, lesional and non-lesional AA scalp biopsies by FACS and/or quantitative (immuno-)histomorphometry.

RESULTS

In healthy human scalp skin, the few skin-resident γδT-cells were found to be mostly Vδ1⁺, non-activated (CD69^-NKG2D^dim) and positive for CXCL10, and CXCL12 receptors. These Vδ1⁺T-cells predominantly localized in/around the HF infundibulum. In striking contrast, the number of Vδ1⁺T-cells was significantly higher around and even inside the proximal (suprabulbar and bulbar) epithelium of lesional AA HFs. These cells also showed a pro-inflammatory phenotype, i.e. higher NKG2D, and IFN-γ and lower CD200R expression. Importantly, more pro-inflammatory Vδ1⁺T-cells were seen also around non-lesional AA HFs. Lesional AA HFs also showed significantly higher expression of CXCL12.

CONCLUSION

Our pilot study introduces skin-resident γδT-cells as a previously overlooked, but potentially important, mostly (auto-)antigen-independent, new innate immunity protagonist in AA pathobiology. The HF infiltration of these activated, IFN-γ-releasing cells already around non-lesional AA HFs suggest that Vδ1⁺T-cells are involved in the early stages of human AA pathobiology, and may thus deserve therapeutic targeting for optimal AA management.

Destruction of the stem cell Niche, Pathogenesis and Promising Treatment Targets for Primary Scarring Alopecias

The Primary Scarring Alopecias are characterised by the irreversible destruction and fibrosis of hair follicles, leading to permanent and often disfiguring loss of hair. The pathophysiology of these diseases is not well understood. However, follicular-fibrosis and loss of the stem-cell niche appears to be a common theme. This review explores the pathogenesis of primary scarring alopecias, asking what happens to the stem cells of the hair follicle and how they may contribute to the progression of these diseases. Bulge-resident cells are lost (leading to loss of capacity for hair growth) from the follicle either by inflammatory-mediate apoptosis or through epigenetic reprogramming to assume a mesenchymal-like identity. What proportion of bulge cells is lost to which process is unknown and probably differs depending on the individual PCA and its specific inflammatory cell infiltrate. The formation of fibroblast-like cells from follicular stem cells may also mean that the cells of the bulge have a direct role in the pathogenesis. The identification of specific cells involved in the pathogenesis of these diseases could provide unique diagnostic and therapeutic opportunities to prevent disease progression by preventing EMT and specific pro-fibrotic signals.

Collapse and Restoration of Hair Follicle Immune Privilege Ex Vivo: A Model for Alopecia Areata

Alopecia areata (AA) is a hair follicle (HF) autoimmune disease leading to hair loss. Interferon gamma (IFNγ) is regarded as the key cytokine involved in AA development, which has been shown to play a role in the collapse of HF immune privilege (IP), CD8⁺ T-cell-driven inflammation toward the HF bulb, and premature catagen development. We present here the procedure to induce IP collapse in human healthy HFs ex vivo. This assay can be suitable not only to investigate mechanisms involved in the HF IP collapse but also to test substances for either preventing and/or reversing the HF IP collapse for the management of AA or other autoimmune diseases sharing similar pathogenesis.

Hair(y) Matters in Melanoma Biology

Melanocyte stem cells (MeSCs), one candidate for the cellular origin of melanoma, reside in the bulge region of the hair follicle (HF), an immune-privileged tissue niche with impaired tumor immunosurveillance. Surprisingly, however, primary melanoma is only very rarely associated with HFs. Here, we explore the hypothesis that this profoundly immunoinhibitory signaling environment deprives both MeSCs and melanocytes of the anagen hair matrix of proinflammatory signals required for full oncogenic transformation. Understanding the cellular and molecular mechanisms for generating a putative antimelanoma tissue habitat, namely in the bulge, could help to recreate a similar melanoma-suppressive signaling environment in melanoma high-risk individuals. We further discuss how mimicking the bulge immune privilege may be an effective melanoma prevention strategy.

Toward Predicting the Spatio-Temporal Dynamics of Alopecia Areata Lesions Using Partial Differential Equation Analysis

Hair loss in the autoimmune disease, alopecia areata (AA), is characterized by the appearance of circularly spreading alopecic lesions in seemingly healthy skin. The distinct spatial patterns of AA lesions form because the immune system attacks hair follicle cells that are in the process of producing hair shaft, catapults the mini-organs that produce hair from a state of growth (anagen) into an apoptosis-driven regression state (catagen), and causes major hair follicle dystrophy along with rapid hair shaft shedding. In this paper, we develop a model of partial differential equations (PDEs) to describe the spatio-temporal dynamics of immune system components that clinical and experimental studies show are primarily involved in the disease development. Global linear stability analysis reveals there is a most unstable mode giving rise to a pattern. The most unstable mode indicates a spatial scale consistent with results of the humanized AA mouse model of Gilhar et al. (Autoimmun Rev 15(7):726-735, 2016) for experimentally induced AA lesions. Numerical simulations of the PDE system confirm our analytic findings and illustrate the formation of a pattern that is characteristic of the spatio-temporal AA dynamics. We apply marginal linear stability analysis to examine and predict the pattern propagation.

A "hair-raising" history of alopecia areata

A 3500-year-old papyrus from ancient Egypt provides a list of treatments for many diseases including "bite hair loss," most likely alopecia areata (AA). The treatment of AA remained largely unchanged for over 1500 years. In 30 CE, Celsus described AA presenting as scalp alopecia in spots or the "windings of a snake" and suggested treatment with caustic compounds and scarification. The first "modern" description of AA came in 1813, though treatment still largely employed caustic agents. From the mid-19th century onwards, various hypotheses of AA development were put forward including infectious microbes (1843), nerve defects (1858), physical trauma and psychological stress (1881), focal inflammation (1891), diseased teeth (1902), toxins (1912) and endocrine disorders (1913). The 1950s brought new treatment developments with the first use of corticosteroid compounds (1952), and the first suggestion that AA was an autoimmune disease (1958). Research progressively shifted towards identifying hair follicle-specific autoantibodies (1995). The potential role of lymphocytes in AA was made implicit with immunohistological studies (1980s). However, studies confirming their functional role were not published until the development of rodent models (1990s). Genetic studies, particularly genome-wide association studies, have now come to the forefront and open up a new era of AA investigation (2000s). Today, AA research is actively focused on genetics, the microbiome, dietary modulators, the role of atopy, immune cell types in AA pathogenesis, primary antigenic targets, mechanisms by which immune cells influence hair growth, and of course the development of new treatments based on these discoveries.

Plasmacytoid dendritic cells as a possible key player to initiate alopecia areata in the C3H/HeJ mouse

BACKGROUND

Alopecia areata (AA) is a tissue-specific autoimmune disease, and interferon (IFN)-γ has been regarded as the key cytokine in the pathogenesis of AA. The clinical observation that AA can occur after viral infection or IFN-α administration implies that IFN-α-producing plasmacytoid dendritic cells (pDCs) may be involved in the AA pathogenesis.

METHODS

We generated AA in C3H/HeJ mice by intradermal injection of T cells derived from lymph nodes of AA-bearing syngeneic mice and stimulated IL-2, IL-7, and IL-15. Distribution of IFN-γ producing pDCs were immunohistochemically analyzed. Realtime PCR were also demonstrated to detect the expression of IFN-γ mRNA. Hair follicles were cultured with IFN-α in order to calculate the hair elongation. Imiquimod was employed to induce catagen stage. PDCs were injected into C3H/HeJ mice to initiate AA.

RESULTS

In this mouse, IFN-α-producing pDCs densely infiltrated around HFs in not only AA lesional but also vicinity of AA lesion. Importantly, intradermal injection of pDCs induced AA lesions. Finally, IFN-α inhibited hair elongation of murine vibrissae and upregulated MHC class I and CXCL10 levels in vitro.

CONCLUSIONS

These findings suggest that IFN-α-producing pDCs initiate AA by inducing apoptosis and increasing Th1/Tc1 chemokine production such as CXCL10, that accumulates Th1/Tc1 cells and result in autoimmune reactions against hair follicles.

Childhood Alopecia Areata: An Overview of Treatment and Recent Patents

BACKGROUND

Alopecia Areata (AA) is a systemic autoimmune condition that usually starts in childhood.

OBJECTIVE

This article aims to review genetics, therapy, prognosis, and recent patents for AA.

METHODS

We used clinical queries and keywords "alopecia areata" AND "childhood" as a search engine. Patents were searched using the key term "alopecia areata" in Patents.google.com and freepatentsonline. com.

RESULTS

Due to an immune-mediated damage to the hair follicles, hair is lost from the scalp and other areas of the body temporarily or even permanently. Children with AA are generally healthy. Evidence of genetic association and increased predisposition for AA was found by studying families with affected members. Pathophysiologically, T- lymphocytes attack hair follicles and cause inflammation and destruction of the hair follicles and hair loss. In mild cases, there would be well-demarcated round patchy scalp hair loss. The pathognomonic "exclamation mark hairs" may be seen at the lesion periphery. In more severe cases, the hair loss may affect the whole scalp and even the whole body. The clinical course is also variable, which may range from transient episodes of recurrent patchy hair loss to an indolent gradually deteriorating severe hair loss. The treatment of AA depends on factors including patients' age, the extent of the hair loss, duration of disease, psychological impact, availability and side effect profile of the treatments. For localized patchy alopecia, topical application of corticosteroids and/or intralesional corticosteroids are the treatment of choice. Other topical treatments include minoxidil, anthralin, coal tar and immunotherapy. In severe resistant cases, systemic immunosuppressants may be considered. Although herbal medicine, acupuncture, complementary and alternative medicine may be tried on children in some Asian communities, the evidence to support these practices is lacking. To date, only a few recent patents exist in topical treatments, including Il-31, laser and herbal medications. Clinical efficacy is pending for these treatment modalities.

CONCLUSION

None of the established therapeutic options are curative. However, newer treatment modalities, including excimer laser, interleukin-31 antibodies and biologics, are evolving so that there may be significant advances in treatment in the near future. AA can be psychosocially devastating. It is important to assess the quality of life, degree of anxiety, social phobia and mood of the patients and their families. Psychological support is imperative for those who are adversely affected psychosocially.

Methods to Study Human Hair Follicle Growth Ex Vivo: Human Microdissected Hair Follicle and Human Full Thickness Skin Organ Culture

The culture of microdissected hair follicles (HFs) and scalp skin enriched in terminal HFs are the best currently available preclinical assays for studying hair and skin biology/pathology in the human system. While microdissected HF organ culture only allows the testing of compounds added into the culture medium, mimicking a systemic application, the scalp skin organ culture also is suitable to test topical and intradermal applications. Here, we describe different methods for isolation of human scalp HFs, the procedures for culturing the scalp skin and microdissected HFs and we also outline different delivery techniques (e.g., topical, systemic) to test active and control substances.

Experience with oral tofacitinib in two adolescents and seven adults with alopecia areata

Alopecia areata (AA) is a common disease that results in nonscarring hair loss. Recently, tofacitinib (TOFA) has been a novel promising therapy for AA. The aim of this study is to determine the efficacy of oral TOFA treatment for alopecia areata (AA), and alopecia universalis (AU). Data of nine patients treated with oral TOFA with either AA or AU were retrospectively evaluated. Treatment outcome, disease severity, and therapeutic response were evaluated by Severity of Alopecia Tool (SALT) scores along with regular photographic surveillance done at third and sixth months. Treatment response was established on four categories: complete response (90% change in latest SALT score), intermediate response (51-90% change), moderate response (6-50% change), and nonresponse (<5% change). Nine patients aged 13-33 years were reviewed. Four patients (44.4%) did not respond to oral TOFA therapy, three patients (33.3%) were moderate responders, 1 (11.1%) was intermediate responder, and 1 (11.1%) was complete responder at the end of 6 months. The clinical response rate (those who achieved ≥5-100% change in SALT score) was 41.4% for all patients. Most of the patients who responded to TOFA had AA instead of AU. Adverse effects were mild. The clinical response rate of TOFA seems reasonable and TOFA was well-tolerated in this cohort. However, to truly evaluate efficacy, future studies are needed to assess the efficacy, adverse effects, and durability of treatment with TOFA in randomized controlled trials.

Frontiers in alopecia areata pathobiology research

This current review explores selected and as yet insufficiently investigated frontiers in current alopecia areata (AA) pathobiology research, with an emphasis on potential "new" players in AA pathobiology that deserve more systematic exploration and therapeutic targeting. Indeed, new evidence suggests that CD8⁺ T cells, which have long been thought to be the central players in AA pathobiology, are not the only drivers of disease. Instead, subsets of natural killer (NK) and so-called "unconventional" T cells (invariant NK T cells, γδ T cells, classic NK cells, and type 1 innate lymphoid cells), all of which can produce large amounts of IFN-γ, might also drive AA pathobiology independent of classical, autoantigen-dependent CD8⁺ T-cell functions. Another important new frontier is the role of regulatory lymphocyte subsets, such as regulatory T cells, γδ regulatory T cells, NKT10 cells, and perifollicular mast cells, in maintaining physiologic hair follicle immune privilege (IP); the extent to which these functions are defective in patients with AA; and how this IP-protective role could be restored therapeutically in patients with established AA. Broadening our AA research horizon along the lines suggested above promises not only to open the door to innovative and even more effective immunotherapy strategies for AA but will also likely be relevant for other autoimmune disorders in which pathobiology, ectopic MHC class I expression, and IP collapse play an important role.

Targeting the Janus Kinase Family in Autoimmune Skin Diseases

Autoimmune skin diseases are characterized by significant local and systemic inflammation that is largely mediated by the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway. Advanced understanding of this pathway has led to the development of targeted inhibitors of Janus kinases (JAKinibs). As a class, JAK inhibitors effectively treat a multitude of hematologic and inflammatory diseases. Growing evidence suggests that JAK inhibitors are efficacious in atopic dermatitis, alopecia areata, psoriasis, and vitiligo. Additional evidence suggests that JAK inhibition might be broadly useful in dermatology, with early reports of efficacy in several other conditions. JAK inhibitors can be administered orally or used topically and represent a promising new class of medications. Here we review the evolving data on the role of the JAK-STAT pathway in inflammatory dermatoses and the potential therapeutic benefit of JAK-STAT antagonism.

Plucked hair follicles from patients with chronic discoid lupus erythematosus show a disease-specific molecular signature

OBJECTIVE

When faced with clinical symptoms of scarring alopecia-the standard diagnostic pathway involves a scalp biopsy which is an invasive and expensive procedure. This project aimed to assess if plucked hair follicles (HFs) containing living epithelial cells can offer a non-invasive approach to diagnosing inflammatory scalp lesions.

METHODS

Lesional and non-lesional HFs were extracted from the scalp of patients with chronic discoid lupus erythematosus (CDLE), psoriasis and healthy controls. RNA was isolated from plucked anagen HFs and microarray, as well as quantitative real-time PCR was performed.

RESULTS

Here, we report that gene expression analysis of only a small number of HF plucked from lesional areas of the scalp is sufficient to differentiate CDLE from psoriasis lesions or healthy HF. The expression profile from CDLE HFs coincides with published profiles of CDLE from skin biopsy. Genes that were highly expressed in lesional CDLE corresponded to well-known histopathological diagnostic features of CDLE and included those related to apoptotic cell death, the interferon signature, complement components and CD8+ T-cell immune responses.

CONCLUSIONS

We therefore propose that information obtained from this non-invasive approach are sufficient to diagnose scalp lupus erythematosus. Once validated in routine clinical settings and compared with other scarring alopecias, this rapid and non-invasive approach will have great potential for paving the way for future diagnosis of inflammatory scalp lesions.

UVB-induced depletion of donor-derived dendritic cells prevents allograft rejection of immune-privileged hair follicles in humanized mice

Dendritic cells (DCs) are key targets for immunity and tolerance induction; they present donor antigens to recipient T cells by donor- and recipient-derived pathways. Donor-derived DCs, which are critical during the acute posttransplant period, can be depleted in graft tissue by forced migration via ultraviolet B light (UVB) irradiation. Here, we investigated the tolerogenic potential of donor-derived DC depletion through in vivo and ex vivo UVB preirradiation (UV) combined with the injection of anti-CD154 antibody (Ab) into recipients in an MHC-mismatched hair follicle (HF) allograft model in humanized mice. Surprisingly, human HF allografts achieved long-term survival with newly growing pigmented hair shafts in both Ab-treated groups (Ab-only and UV plus Ab) and in the UV-only group, whereas the control mice rejected all HF allografts with no hair regrowth. Perifollicular human CD3⁺ T cell and MHC class II⁺ cell infiltration was significantly diminished in the presence of UV and/or Ab treatment. HF allografts in the UV-only group showed stable maintenance of the immune privilege in the HF epithelium without evidence of antigen-specific T cell tolerance, which is likely promoted by normal HFs in vivo. This immunomodulatory strategy targeting the donor tissue exhibited novel biological relevance for clinical allogeneic transplantation without generalized immunosuppression.

Alopecia Universalis in a Case of Rheumatoid Arthritis after Treatment with Etanercept

Alopecia universalis (AU) is a condition which causes generalized hair loss of the body. It is postulated that autoimmunity plays an important role in its pathogenesis. It is characterized by the involvement of multiple inflammatory cytokines such as tumor necrosis factor-alpha and multiple interferons. Hence, biologics like tumor necrosis factor alpha (TNF-α) antagonist may be used to block this inflammatory process. It is not very commonly appreciated that the use of biologics can lead to alopecia areata. Here, we report a case of severe alopecia areata which progressed to AU after etanercept administration. We here describe a 23-year-old unmarried female who was a known case of rheumatoid arthritis who developed AU after 6 months of continuous treatment with etanercept. TNF-α antagonist may not play a sufficient role in the treatment of alopecia areata. There exists a strong and significant connection between TNF-α blockers and development of alopecia and specifically AU and their role in the pathophysiology of the disease should be called into question if our findings are observed again.

Alopecia areata: A multifactorial autoimmune condition

Alopecia areata is an autoimmune disease that results in non-scarring hair loss, and it is clinically characterised by small patches of baldness on the scalp and/or around the body. It can later progress to total loss of scalp hair (Alopecia totalis) and/or total loss of all body hair (Alopecia universalis). The rapid rate of hair loss and disfiguration caused by the condition causes anxiety on patients and increases the risks of developing psychological and psychiatric complications. Hair loss in alopecia areata is caused by lymphocytic infiltrations around the hair follicles and IFN-γ. IgG antibodies against the hair follicle cells are also found in alopecia areata sufferers. In addition, the disease coexists with other autoimmune disorders and can come secondary to infections or inflammation. However, despite the growing knowledge about alopecia areata, the aetiology and pathophysiology of disease are not well defined. In this review we discuss various genetic and environmental factors that cause autoimmunity and describe the immune mechanisms that lead to hair loss in alopecia areata patients.

Epigallocatechin-3 Gallate Inhibits STAT-1/JAK2/IRF-1/HLA-DR/HLA-B and Reduces CD8 MKG2D Lymphocytes of Alopecia Areata Patients

BACKGROUND

Alopecia areata (AA) is associated with Interferon- γ (IFN-γ) mediated T-lymphocyte dysfunction and increased circulating Interleukine-17 (IL-17) levels. Epigallocatechin-3-gallate (EGCG) specifically inhibits IFN-γ pathways and unlike Janus Kinase 1 and 2 (JAK1/JAK2) inhibitors (tofacitinib, ruxolitinib), EGCG is safer, more cost-effective, and is a topically active agent. Our objective is to test the mode of action of EGCG in vitro and ex vivo using HaCat, Jurkat cell lines, and peripheral blood mononuclear cells (PBMCs) of AA patients and healthy controls (HCs), respectively.

METHODS

distribution of T helper cells (Th1, Th17), and cytotoxic cells (CD8) in PBMCs isolated from 30 AA patients and 30 HCs was investigated by flowcytomterty. In vitro treatment of HaCat and Jurkat cells with 40 μm EGCG for 48 h was performed to measure the level of phosphorylation of signal transducer and activator of transcription protein STAT1, and replicated in ex vivo model using PBMCs of AA patients.

RESULTS

Interestingly, 40 μm EGCG is capable of completely inhibiting phosphorylation of STAT1 after 48 h in HaCat and Jurkat cells and ex vivo in PBMCs of AA patients. Based on QPCR data, the action of EGCG on p-STAT1 seems to be mediated via downregulation of the expression of JAK2 but not JAK1 leading to the inhibition of human leukocyte antigens (HLA-DR and HLA-B) expression probably via IRF-1. On the other hand, AA patients have significantly increased levels of Th1, Th17, and CD8 cells and the production of IFN-γ and IL-17 by PBMCs in AA patients was significantly higher compared to HC; p = 0.008 and p = 0.006, respectively. Total numbers of CD8+ cells were not significantly different between treated and untreated samples. However, CD8+ cells with positive Natural killer group 2 member D (NKG2D) transmembrane receptor (CD8+ NKG2D+ subset) was significantly reduced when PBMCs were treated with 20 μm EGCG for 48 h.

CONCLUSION

These results suggest that EGCG has a synergistic action that inhibits expression of HLA-DR and HLA-B molecules via the IFN-γ pathway to maintain immune privilege in HF; also it reduces CD8+ NKG2D+ subset.

Alopecia areata: a review of disease pathogenesis

BACKGROUND

Alopecia areata is a disorder that results in nonscarring hair loss. The psychological impact can be significant, leading to feelings of depression and social isolation. Objectives In this article, we seek to review the pathophysiological mechanisms proposed in recent years in a narrative fashion.

METHODS

We searched MEDLINE and Scopus for articles related to alopecia areata, with a particular emphasis on its pathogenesis.

RESULTS

The main theory of alopecia areata pathogenesis is that it is an autoimmune phenomenon resulting from a disruption in hair follicle immune privilege. What causes this breakdown is an issue of debate. Some believe that a stressed hair follicle environment triggers antigen presentation, while others blame a dysregulation in the central immune system entangling the follicles. Evidence for the latter theory is provided by animal studies, as well investigations around the AIRE gene. Different immune-cell lines including plasmacytoid dendritic cells, natural killer cells and T cells, along with key molecules such as interferon-γ, interleukin-15, MICA and NKG2D, have been identified as contributing to the autoimmune process.

CONCLUSIONS

Alopecia areata remains incurable, although it has been studied for years. Available treatment options at best are beneficial for milder cases, and the rate of relapse is high. Understanding the exact mechanisms of hair loss in alopecia areata is therefore of utmost importance to help identify potential therapeutic targets.

Enhancing Skin Health: By Oral Administration of Natural Compounds and Minerals with Implications to the Dermal Microbiome

The history of cosmetics goes back to early Egyptian times for hygiene and health benefits while the history of topical applications that provide a medicinal treatment to combat dermal aging is relatively new. For example, the term cosmeceutical was first coined by Albert Kligman in 1984 to describe topical products that afford both cosmetic and therapeutic benefits. However, beauty comes from the inside. Therefore, for some time scientists have considered how nutrition reflects healthy skin and the aging process. The more recent link between nutrition and skin aging began in earnest around the year 2000 with the demonstrated increase in peer-reviewed scientific journal reports on this topic that included biochemical and molecular mechanisms of action. Thus, the application of: (a) topical administration from outside into the skin and (b) inside by oral consumption of nutritionals to the outer skin layers is now common place and many journal reports exhibit significant improvement for both on a variety of dermal parameters. Therefore, this review covers, where applicable, the history, chemical structure, and sources such as biological and biomedical properties in the skin along with animal and clinical data on the oral applications of: (a) collagen, (b) ceramide, (c) β-carotene, (d) astaxanthin, (e) coenzyme Q10, (f) colostrum, (g) zinc, and (h) selenium in their mode of action or function in improving dermal health by various quantified endpoints. Lastly, the importance of the human skin microbiome is briefly discussed in reference to the genomics, measurement, and factors influencing its expression and how it may alter the immune system, various dermal disorders, and potentially be involved in chemoprevention.

High-throughput T cell receptor sequencing identifies clonally expanded CD8+ T cell populations in alopecia areata

Alopecia areata (AA) is an autoimmune disease in which cytotoxic T cells specifically target growing hair follicles. We used high-throughput TCR sequencing in the C3H/HeJ mouse model of AA and in human AA patients to gain insight into pathogenic T cell populations and their dynamics, which revealed clonal CD8+ T cell expansions in lesional skin. In the C3H/HeJ model, we observed interindividual sharing of TCRβ chain protein sequences, which strongly supports a model of antigenic drive in AA. The overlap between the lesional TCR repertoire and a population of CD8+NKG2D+ T cells in skin-draining lymph nodes identified this subset as pathogenic effectors. In AA patients, treatment with the oral JAK inhibitor tofacitinib resulted in a decrease in clonally expanded CD8+ T cells in the scalp but also revealed that many expanded lesional T cell clones do not completely disappear from either skin or blood during treatment with tofacitinib, which may explain in part the relapse of disease after stopping treatment.

Immune Privilege Collapse and Alopecia Development: Is Stress a Factor

Hair is a defining mammalian feature that serves as a hallmark of human communication. Given the critical significance of hair in social, religious, and political contexts, it is important to understand factors that play a role in hair loss disorders. The hair follicle is an immune privileged site, and mounting evidence suggests that the collapse of immune privilege contributes to the pathogenesis of autoimmune hair loss disorders, including alopecia areata and lichen planopilaris. This review comprehensively appraises the current literature to shed light on mechanisms for immune privilege collapse, and examines the role of neurogenic stress in triggering this process.

Degradation of selenoprotein S and selenoprotein K through PPARγ-mediated ubiquitination is required for adipocyte differentiation

Adipocyte differentiation is known to be related with endoplasmic reticulum (ER) stress. We have reported that selenoprotein S (SelS) and selenoprotein K (SelK) have a function in the regulation of ER stress and ER-associated degradation. However, the association between adipocyte differentiation and the ER-resident selenoproteins, SelS and SelK, is unclear. In this study, we found that the levels of SelS and SelK were decreased during adipocyte differentiation and were inversely related to the levels of peroxisome proliferator-activated receptor γ (PPARγ), a central regulator of adipogenesis. It has been recently reported that PPARγ has E3 ubiquitin ligase activity. Here, we report that PPARγ directly interacts with both SelS and SelK via its ligand-binding domain to induce ubiquitination and degradation of the selenoproteins. Lysine residues at the 150th position of SelS and the 47th and 48th positions of SelK were the target sites for ubiquitination by PPARγ. We also found that adipocyte differentiation was inhibited when either SelS or SelK was not degraded by PPARγ. Thus, these data indicate that PPARγ-mediated ubiquitination and degradation of SelS and SelK is required for adipocyte differentiation.

Alopecia areata and the gut-the link opens up for novel therapeutic interventions

INTRODUCTION

This review aims to raise the potential of the modern society's impact on gut integrity often leading to increased intestinal permeability, as a cause or driver of Alopecia Areata (AA) in genetically susceptible people. With the increasing rate of T cell-driven autoimmunity, we hypothesize that there is a common root cause of these diseases that originates from chronic inflammation, and that the gut is the most commonly exposed area with our modern lifestyle. Areas covered: We will discuss the complexity in the induction of AA and its potential link to increased intestinal permeability. Our main focus will be on the gut microbiome and mechanisms involved in the interplay with the immune system that may lead to local and/or peripheral inflammation and finally, tissue destruction. Expert opinion: We have seen a link between AA and a dysfunctional gastrointestinal system which raised the hypothesis that an underlying intestinal inflammation drives the priming and dysregulation of immune cells that lead to hair follicle destruction. While it is still important to resolve local inflammation and restore the IP around the hair follicles, we believe that the root cause needs to be eradicated by long-term interventions to extinguish the fire driving the disease.

Human αβ and γδ T Cells in Skin Immunity and Disease

γδ T lymphocytes maintain skin homeostasis by balancing keratinocyte differentiation and proliferation with the destruction of infected or malignant cells. An imbalance in skin-resident T cell function can aggravate skin-related autoimmune diseases, impede tumor eradication, or disrupt proper wound healing. Much of the published work on human skin T cells attributes T cell function in the skin to αβ T cells, while γδ T cells are an often overlooked participant. This review details the roles played by both αβ and γδ T cells in healthy human skin and then focuses on their roles in skin diseases, such as psoriasis and alopecia areata. Understanding the contribution of skin-resident and skin-infiltrating T cell populations and cross-talk with other immune cells is leading to the development of novel therapeutics for patients. However, there is still much to be learned in order to effectively modulate T cell function and maintain healthy skin homeostasis.

Fibroblast cell-based therapy prevents induction of alopecia areata in an experimental model

Alopecia areata (AA) is an autoimmune hair loss disease with infiltration of proinflammatory cells into hair follicles. Current therapeutic regimens are unsatisfactory mainly because of the potential for side effects and/or limited efficacy. Here we report that cultured, transduced fibroblasts, which express the immunomodulatory molecule indoleamine 2,3-dioxygenase (IDO), can be applied to prevent hair loss in an experimental AA model. A single intraperitoneal (IP) injection of IDO-expressing primary dermal fibroblasts was given to C3H/HeJ mice at the time of AA induction. While 60–70% of mice that received either control fibroblasts or vehicle injections developed extensive AA, none of the IDO-expressing fibroblast-treated mice showed new hair loss up to 20 weeks post injection. IDO cell therapy significantly reduced infiltration of CD4⁺ and CD8⁺ T cells into hair follicles and resulted in decreased expression of TNF-α, IFN-γ and IL-17 in the skin. Skin draining lymph nodes of IDO fibroblast-treated mice were significantly smaller, with more CD4⁺ CD25⁺ FoxP3⁺ regulatory T cells and fewer Th17 cells than those of control fibroblast and vehicle-injected mice. These findings indicate that IP injected IDO-expressing dermal fibroblasts can control inflammation and thereby prevent AA hair loss.

iNKT cells ameliorate human autoimmunity: Lessons from alopecia areata

Alopecia areata (AA) is understood to be a CD8+/NKG2D+ T cell-dependent autoimmune disease. Here, we demonstrate that human AA pathogenesis of is also affected by iNKT10 cells, an unconventional T cell subtype whose number is significantly increased in AA compared to healthy human skin. AA lesions can be rapidly induced in healthy human scalp skin xenotransplants on Beige-SCID mice by intradermal injections of autologous healthy-donor PBMCs pre-activated with IL-2. We show that in this in vivo model, the development of AA lesions is prevented by recognized the iNKT cell activator, α-galactosylceramide (α-GalCer), which stimulates iNKT cells to expand and produce IL-10. Moreover, in pre-established humanized mouse AA lesions, hair regrowth is promoted by α-GalCer treatment through a process requiring both effector-memory iNKT cells, which can interact directly with CD8+/NKG2D+ T cells, and IL-10. This provides the first in vivo evidence in a humanized model of autoimmune disease that iNKT10 cells are key disease-protective lymphocytes. Since these regulatory NKT cells can both prevent the development of AA lesions and promote hair re-growth in established AA lesions, targeting iNKT10 cells may have preventive and therapeutic potential also in other autoimmune disorders related to AA.

Hair Follicle Immune Privilege Revisited: The Key to Alopecia Areata Management

The collapse of the immune privilege (IP) of the anagen hair bulb is now accepted as a key element in AA pathogenesis, and hair bulb IP restoration lies at the core of AA therapy. Here, we briefly review the essentials of hair bulb IP and recent progress in understanding its complexity. We discuss open questions and why the systematic dissection of hair bulb IP and its pharmacological manipulation (including the clinical testing of FK506 and α-melanocyte-stimulating hormone analogs) promise to extend the range of future therapeutic options in AA and other IP collapse-related autoimmune diseases.

Wnt/β-catenin and ERK pathway activation: A possible mechanism of photobiomodulation therapy with light-emitting diodes that regulate the proliferation of human outer root sheath cells

BACKGROUND

Outer root sheath cells (ORSCs) play important roles in maintaining hair follicle structure and provide support for the bulge area. The hair growth promoting effects of photobiomodulation therapy (PBMT) have been reported, but the mechanisms for this in human ORCs (hORSCs) have rarely been studied.

OBJECTIVE

The aim of this study was to investigate the effect of various wavelengths of light-emitting diode (LED) irradiation on human ORSCs (hORSCs).

METHODS

LED irradiation effects on hORSC proliferation and migration were examined with MTT assay, BrdU incorporation assay and migration assays. hORSCs were irradiated using four LED wavelengths (415, 525, 660, and 830 nm) with different low energy levels. LED irradiation effects on the expression of molecules associated with the Wnt/β-catenin signaling and ERK pathway, hair stem cell markers, and various growth factors and cytokines in hORSCs were examined with real-time PCR and Western blot assay. The effect of the LED-irradiated hORSCs on cell proliferation of human dermal papilla cells (hDPCs) was examined with co-culture and MTT assay.

RESULTS

PBMT with LED light variably promoted hORSC proliferation and suppressed cell apoptosis depending on energy level. LED irradiation induced Wnt5a, Axin2, and Lef1 mRNA expression and β-catenin protein expression in hORSCs. Phosphorylation of ERK, c-Jun, and p38 in hORSCs was observed after LED light irradiation, and ERK inhibitor treatment before irradiation reduced ERK and c-Jun phosphorylation. Red light-treated hORSCs showed substantial increase in IL-6, IL-8, TNF-a, IGF-1, TGF-β1, and VEGF mRNA. Light irradiation at 660 and 830 nm projected onto hORSCs accelerated in vitro migration. LED-irradiated hORSCs increased hDPCs proliferation when they were co-cultured. The conditioned medium from LED-irradiated hORSCs was sufficient to stimulate hDPCs proliferation.

CONCLUSION

These results demonstrate that LED light irradiation induced hORSC proliferation and migration and inhibited apoptosis in vitro. The growth-promoting effects of LEDs on hORSCs appear to be associated with direct stimulation of the Wnt5a/β-catenin and ERK signaling pathway. Lasers Surg. Med. 49:940-947, 2017. © 2017 Wiley Periodicals, Inc.

Sorafenib stimulates human skin type mast cell degranulation and maturation

BACKGROUND

Sorafenib is a multi-kinase inhibitor for treating advanced hepatocellular and renal cell carcinomas by targeting various types of receptors and signaling molecules, including vascular endothelial growth factor receptors, platelet-derived growth factor receptor, and Raf-1. Sorafenib may cause diverse cutaneous adverse reactions, including hand-foot reaction, facial and scalp eruptions, alopecia and pruritus. However, the mechanism of these adverse effects has not been well-investigated.

OBJECTIVE

Mast cells (MCs) are reported to be associated with various types of skin diseases. To investigate the mechanism of sorafenib-induced cutaneous adverse effects, we focused on MCs in situ.

METHODS

We evaluated skin samples of organ cultured normal human skin treated with sorafenib using c-Kit, tryptase, and stem cell factor (SCF), Ki-67, and TUNEL immunohistochemistry as well as quantitative real-time polymerase chain reaction to evaluate MC number, degranulation, proliferation, and apoptosis in situ.

RESULTS

Sorafenib significantly increased the number and degranulation of skin-type MCs compared with the vehicle-treated control group in situ. However, sorafenib did not affect MC proliferation and apoptosis, suggesting that it stimulated MC maturation from resident precursors. Furthermore, sorafenib increased SCF expression in situ. The increase in MC number by sorafenib was abrogated by co-administration of SCF neutralizing antibody or the phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin, but not the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor, PD98059. This suggests that SCF is involved in sorafenib-induced MC maturation. In addition, the compensatory upregulation of PI3K-signaling from inhibition of MAPK signaling by sorafenib might stimulate MC maturation in situ. We also evaluated MCs within the skin samples from patients with drug eruptions by sorafenib administration. The total and degranuated MCs number as well as SCF expression was significantly increased compared to healthy individuals.

CONCLUSION

Our results contribute to a better understanding of the mechanism by which sorafenib induces adverse cutaneous reactions via activation of skin-type MC degranulation and maturation. This activation appears to be related to PI3K signaling and SCF production, which could be a new targets for treating sorafenib-induced adverse reactions.