Alopecia areata registry: an overview

Exploring the overlap between alopecia areata and major depressive disorder: Epidemiological and genetic perspectives

BACKGROUND

Research suggests that Alopecia areata (AA) and Major Depressive Disorder (MDD) show substantial comorbidity. To date, no study has investigated the hypothesis that this is attributable to shared genetic aetiology.

OBJECTIVES

To investigate AA-MDD comorbidity on the epidemiological and molecular genetic levels.

METHODS

First, epidemiological analyses were performed using data from a cohort of adult German health insurance beneficiaries (n = 1.855 million) to determine the population-based prevalence of AA-MDD comorbidity. Second, analyses were performed to determine the prevalence of MDD in a clinical AA case-control sample with data on psychiatric phenotypes, stratifying for demographic factors to identify possible contributing factors to AA-MDD comorbidity. Third, the genetic overlap between AA and MDD was investigated using a polygenic risk score (PRS) approach and linkage disequilibrium score (LDSC) regression. For PRS, summary statistics from a large MDD GWAS meta-analysis (PGC-MD2) were used as the training sample, while a Central European AA cohort, including the above-mentioned AA patients, and an independent replication US-AA cohort were used as target samples. LDSC was performed using summary statistics of PGC-MD2 and the largest AA meta-analysis to date.

RESULTS

High levels of AA-MDD comorbidity were reported in the population-based (MDD in 24% of AA patients), and clinical samples (MDD in 44% of AA patients). MDD-PRS explained a modest proportion of variance in AA case-control status (R²  = 1%). This signal was limited to the major histocompatibility complex (MHC) region on chromosome 6. LDSC regression (excluding MHC) revealed no significant genetic correlation between AA and MDD.

CONCLUSIONS

As in previous research, AA patients showed an increased prevalence of MDD. The present analyses suggest that genetic overlap may be confined to the MHC region, which is implicated in immune function. More detailed investigation is required to refine understanding of how the MHC is involved in the development of AA and MDD comorbidity.

Racial characteristics of alopecia areata in the United States

BACKGROUND

Epidemiologic studies on the association between race and alopecia areata (AA) are limited.

OBJECTIVE

To characterize racial differences of AA in the United States.

METHODS

Cross-sectional study of self-registered AA patients and noncases in the National Alopecia Areata Registry (NAAR). We evaluated odds of AA and its subtypes for 5 ethnic/racial groups using logistic regression. A sex-stratified analysis and a sensitivity analysis among dermatologist-confirmed cases were also performed.

RESULTS

We identified 9340 AA patients and 2064 noncases. Compared with whites, African Americans had greater odds of AA (odds ratio, 1.77; 95% confidence interval, 1.37-2.28) and Asians had lower odds (odds ratio, 0.40; 95% confidence interval, 0.32-0.50) of AA. The results were consistent in AA subtypes, dermatologist-confirmed cases, and by sex.

LIMITATIONS

Residual confounding due to limited number of covariates. Recall or recruitment bias not representative of the entire disease spectrum. Also, outcome misclassification was possible because not all AA cases in the registry were confirmed by dermatologists.

CONCLUSION

Our findings suggest higher odds of AA in African Americans and lower odds in Asians compared with whites. Future studies examining racial disparity in AA from clinical and genetic perspectives are warranted for a better understanding of the disease pathogenesis.

Molecular functional analyses revealed essential roles of HSP90 and lamin A/C in growth, migration, and self-aggregation of dermal papilla cells

Previous expression study using quantitative proteomics has shown that immune-mediated pathway may not be the main mechanism inducing alopecia areata (AA). Nevertheless, functional impact of such expression data set remained unknown and unexplored. This study thus aimed to define potentially novel mechanisms of the AA pathogenesis by functional investigations of the differentially expressed proteins previously identified from lesional biopsies. From 122 altered proteins, protein–protein interactions network analysis revealed that downregulated heat shock protein 90 (HSP90) and lamin A/C served as the central nodes of protein–protein interactions involving in several crucial biological functions, including cytoskeleton organization, extracellular matrix organization, and tissue development. Interaction between HSP90 and lamin A/C in dermal papilla cells (DPCs) was confirmed by reciprocal immunoprecipitation and immunofluorescence co-staining. Small-interfering RNA (siRNA) targeting to HSP90 (siHSP90) and lamin A/C (siLamin A/C) effectively reduced levels of HSP90 and lamin A/C, respectively and vice versa, comparing to non-transfected and siControl-transfected cells, strengthening their interactive roles in DPCs. Functional investigations revealed that DPCs transfected with siHSP90 and siLamin A/C had defective cell proliferation and growth, prolonged doubling time, cell cycle arrest at G0/G1 phase, and defective self-aggregation formation. Moreover, siHSP90-transfected cells had less spindle index, reduced levels of vimentin (mesenchymal marker) and fibronectin (extracellular matrix), and defective migratory activity. Our data have demonstrated for the first time that HSP90 and lamin A/C physically interact with each other. Moreover, both of them are essential for growth, migration, and self-aggregation of DPCs and can be linked to the disease mechanisms of AA.

Differential proteomics of lesional vs. non-lesional biopsies revealed non-immune mechanisms of alopecia areata

Alopecia areata (AA) is one of the common hair disorders for which treatment is frequently ineffective and associated with relapsing episodes. Better understanding of disease mechanisms and novel therapeutic targets are thus required. From 10 AA patients, quantitative proteomics using LTQ-Orbitrap-XL mass spectrometer revealed 104 down-regulated, 4 absent, 3 up-regulated and 11 newly present proteins in lesional vs. non-lesional biopsies. Among these, the decreased levels of α-tubulin, vimentin, heat shock protein 70 (HSP70), HSP90, annexin A2 and α-enolase were successfully confirmed by Western blotting. Protein-protein interactions network analysis using STRING tool revealed that the most frequent biological processes/networks of the down-regulated proteins included tissue development, cell differentiation, response to wounding and catabolic process, whereas those for the up-regulated proteins included biological process, metabolic process, cellular transport, cellular component organization and response to stimulus. Interestingly, only 5 increased/newly present proteins were associated with the regulation of immune system, which may not be the predominant pathway in AA pathogenic mechanisms as previously assumed. In summary, we report herein the first proteome dataset of AA demonstrating a number of novel pathways, which can be linked to the disease mechanisms and may lead to discovery of new therapeutic targets for AA.

The Utility and Validity of the Alopecia Areata Symptom Impact Scale in Measuring Disease-Related Symptoms and their Effect on Functioning

Alopecia areata (AA) is an autoimmune disease that causes hair loss. Although persons with the disease can be physically described as having varying degrees of hair loss, the condition has significant ramifications on an individual's well-being. We previously reported the preliminary psychometric properties of the Alopecia Areata Symptom Impact Scale (AASIS), a disease-specific measure that asks participants about their AA symptoms and how these symptoms interfere with their daily functioning. The goals of this article are to provide a detailed description of the development of the AASIS items and to offer a psychometric update for the measure. Preliminary items for the AASIS were developed on the basis of responses from 1,649 participants to 125 health-related quality-of-life questions/items from the National Alopecia Areata Registry. Clinicians affiliated with the registry were asked to rate the relevance of these items for content validity. Cluster analysis and clinician ratings were used to reduce the number of items. The resulting 13-item AASIS was administered to 452 participants, who were also cognitively debriefed. Results showed that the AASIS is a valid and reliable measure of AA symptoms and their impact on functioning.

Overview of alopecia areata

Alopecia areata is a complex genetic, immune-mediated disease that targets anagen hair follicles. The disease affects children and adults and is characterized by round or oval patches of hair loss, loss of all scalp hair (alopecia totalis), body hair (alopecia universalis), or ophiasis pattern hair loss. Patients may also present with patchy loss in multiple hair-bearing areas. Commonly associated diseases include asthma, allergic rhinitis, atopic dermatitis, thyroid disease, and automimmune diseases, such as thyroiditis and vitiligo. Nail abnormalities may precede, follow, or occur concurrently with hair loss activity. Alopecia areata has no known age, race, or ethnic preponderance and in contrast to other autoimmune diseases such as thyroiditis or lupus, the hair follicle does not usually sustain permanent injury and maintains its potential to regrow hair. It is estimated that alopecia areata affects between six and seven million individuals in the United States. Genes, the immune and nervous systems have all been implicated in the pathogenesis of alopecia areata. Although many treatments are available, there is still no cure. Bolstered by new scientific and translational opportunities from recently published genome-wide association studies, an ambitious treatment development program has recently been initiated by the National Alopecia Areata Foundation.

What causes alopecia areata?

The pathobiology of alopecia areata (AA), one of the most frequent autoimmune diseases and a major unsolved clinical problem, has intrigued dermatologists, hair biologists and immunologists for decades. Simultaneously, both affected patients and the physicians who take care of them are increasingly frustrated that there is still no fully satisfactory treatment. Much of this frustration results from the fact that the pathobiology of AA remains unclear, and no single AA pathogenesis concept can claim to be universally accepted. In fact, some investigators still harbour doubts whether this even is an autoimmune disease, and the relative importance of CD8(+) T cells, CD4(+) T cells and NKGD2(+) NK or NKT cells and the exact role of genetic factors in AA pathogenesis remain bones of contention. Also, is AA one disease, a spectrum of distinct disease entities or only a response pattern of normal hair follicles to immunologically mediated damage? During the past decade, substantial progress has been made in basic AA-related research, in the development of new models for translationally relevant AA research and in the identification of new therapeutic agents and targets for future AA management. This calls for a re-evaluation and public debate of currently prevalent AA pathobiology concepts. The present Controversies feature takes on this challenge, hoping to attract more skin biologists, immunologists and professional autoimmunity experts to this biologically fascinating and clinically important model disease.

Genome-wide association study in alopecia areata implicates both innate and adaptive immunity

Alopecia areata (AA) is among the most highly prevalent human autoimmune diseases, leading to disfiguring hair loss due to the collapse of immune privilege of the hair follicle and subsequent autoimmune attack. The genetic basis of AA is largely unknown. We undertook a genome-wide association study (GWAS) in a sample of 1,054 cases and 3,278 controls and identified 139 single nucleotide polymorphisms that are significantly associated with AA (P <or= 5 x 10(-7)). Here we show an association with genomic regions containing several genes controlling the activation and proliferation of regulatory T cells (T(reg) cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros family zinc finger 4; IKZF4), as well as the human leukocyte antigen (HLA) region. We also find association evidence for regions containing genes expressed in the hair follicle itself (PRDX5 and STX17). A region of strong association resides within the ULBP (cytomegalovirus UL16-binding protein) gene cluster on chromosome 6q25.1, encoding activating ligands of the natural killer cell receptor NKG2D that have not previously been implicated in an autoimmune disease. By probing the role of ULBP3 in disease pathogenesis, we also show that its expression in lesional scalp from patients with AA is markedly upregulated in the hair follicle dermal sheath during active disease. This study provides evidence for the involvement of both innate and acquired immunity in the pathogenesis of AA. We have defined the genetic underpinnings of AA, placing it within the context of shared pathways among autoimmune diseases, and implicating a novel disease mechanism, the upregulation of ULBP ligands, in triggering autoimmunity.

Peripheral blood gene expression in alopecia areata reveals molecular pathways distinguishing heritability, disease and severity

Alopecia areata (AA) is an autoimmune hair loss disorder in which systemic disturbances have been described, but are poorly understood. To evaluate disease mechanisms, we examined gene expression in the blood of defined clinical subgroups (patchy AA persistent type, AAP, n=5; alopecia universalis, AU, n=4) and healthy controls (unaffected relatives, UaR, n=5; unaffected non-relatives, UaNR, n=4) using microarrays. Unsupervised hierarchical clustering separates all four patient and control groups, producing three distinct expression patterns reflective of 'inheritance', 'disease' and 'severity' signatures. Functional classification of differentially expressed genes (DEGs) comparing disease (AAP, AU) vs normal (UaR) groups reveals upregulation in immune response, cytokine signaling, signal transduction, cell cycle, proteolysis and cell adhesion-related genes. Pathway analysis further reveals the activation of several genes related to natural killer-cell cytotoxicity, apoptosis, mitogen activated protein kinase, Wnt signaling and B- and T-cell receptor signaling in AA patients. Finally, 35 genes differentially expressed in AA blood overlap with DEGs previously identified in AA skin lesions. Our results implicate innate and adaptive immune processes while also revealing novel pathways, such as Wnt signaling and apoptosis, relevant to AA pathogenesis. Our data suggest that peripheral blood expression profiles of AA patients likely carry new biomarkers associated with disease susceptibility and expression.

Alopecia areata update: part I. Clinical picture, histopathology, and pathogenesis

Alopecia areata (AA) is an autoimmune disease that presents as nonscarring hair loss, although the exact pathogenesis of the disease remains to be clarified. Disease prevalence rates from 0.1% to 0.2% have been estimated for the United States. AA can affect any hair-bearing area. It often presents as well demarcated patches of nonscarring alopecia on skin of overtly normal appearance. Recently, newer clinical variants have been described. The presence of AA is associated with a higher frequency of other autoimmune diseases. Controversially, there may also be increased psychiatric morbidity in patients with AA. Although some AA features are known poor prognostic signs, the course of the disease is unpredictable and the response to treatment can be variable. Part one of this two-part series on AA describes the clinical presentation and the associated histopathologic picture. It also proposes a hypothesis for AA development based on the most recent knowledge of disease pathogenesis.

LEARNING OBJECTIVES

After completing this learning activity, participants should be familiar with the most recent advances in AA pathogenesis, recognize the rare and recently described variants of AA, and be able to distinguish between different histopathologic stages of AA.

History of atopy or autoimmunity increases risk of alopecia areata

BACKGROUND

The association between a history of atopy or autoimmune diseases and risk of alopecia areata (AA) is not well established.

OBJECTIVE

The purpose of this study was to use the National AA Registry database to further investigate the association between history of atopy or autoimmune diseases and risk of AA.

METHODS

A total of 2613 self-registered sporadic cases (n = 2055) and controls (n = 558) were included in this analysis.

RESULTS

Possessing a history of any atopic (odds ratio = 2.00; 95% confidence interval 1.50-2.54) or autoimmune (odds ratio = 1.73; 95% confidence interval 1.10-2.72) disease was associated with an increased risk of AA. There was no trend for possessing a history of more than one atopic or autoimmune disease and increasing risk of AA.

LIMITATIONS

Recall, reporting, and recruiting bias are potential sources of limitations in this analysis.

CONCLUSION

This analysis revealed that a history of atopy and autoimmune disease was associated with an increased risk of AA and that the results were consistent for both the severe subtype of AA (ie, alopecia totalis and alopecia universalis) and the localized subtype (ie, AA persistent).

Lymphocytes, neuropeptides, and genes involved in alopecia areata

Many lessons in autoimmunity - particularly relating to the role of immune privilege and the interplay between genetics and neuroimmunology - can be learned from the study of alopecia areata, the most common cause of inflammation-induced hair loss. Alopecia areata is now understood to represent an organ-restricted, T cell-mediated autoimmune disease of hair follicles. Disease induction is associated with collapse of hair follicle immune privilege in both humans and in animal models. Here, the role of HLA associations, other immunogenetic factors, and neuroendocrine parameters in alopecia areata pathogenesis are reviewed. This instructive and clinically significant model disease deserves more widespread interest in the immunology community.