Genetic linkage studies in alopecia areata

Genome-Wide Association Study of Alopecia Areata in Taiwan: The Conflict Between Individuals and Hair Follicles

Purpose

Alopecia areata (AA) is one of the most prevalent autoimmune diseases affecting humans. Given that hair follicles are immune-privileged, autoimmunity can result in disfiguring hair loss. However, the genetic basis for AA in the Taiwanese population remains unknown.

Materials and Methods

A genome-wide association study was conducted using a cohort of 408 AA cases and 8167 controls. To link variants to gene relationships, we used 882 SNPs (P<1E-05) within 74 genes that were associated with AA group to build the biological networks by IPA software. HLA diplotypes and haplotypes were analyzed using Attribute Bagging (HIBAG)-R package and chi-square analysis.

Results

Seven single nucleotide polymorphisms (SNPs) including LINC02006 (rs531166736, rs187306735), APC (rs112800832_C_CAT), SRP19 (rs139948960, rs144784670), EGFLAM (rs16903975) and LDLRAD3 (rs79874564) were closely associated with the AA phenotype (P<5E-08). Examination of biological networks revealed that these genomic areas are associated with antigen presentation signaling, B cell and T cell development, Th1 and Th2 activation pathways, Notch signaling, crosstalk signaling between dendritic cells and natural killer cells, and phagosome maturation. Based on human leukocyte antigen (HLA) genotype analysis, four HLA genotypes (HLA-B*15:01-*40:01, HLA-DQA1*01:02-*03:03, HLA-DQA1*01:02, and HLA-DQB1*02:01) were found to be associated with AA (adjusted p-value<0.05). HLA-DQA1*01:02 is the most significantly related gene in the Taiwanese population (adjusted p-value = 2.09E-05).

Conclusion

This study successfully identified susceptibility loci associated with AA in the Taiwanese population. These findings not only shed light on the origins of AA within the Taiwanese context but also contribute to a comprehensive understanding of the genetic factors influencing AA susceptibility.

The Relationship Between ABO and Rh Blood Groups with Alopecia Areata

INTRODUCTION

Alopecia areata (AA) is a common non-scaring hair loss disease. Genetic susceptibility and environmental factors can develop the disease.

OBJECTIVES

We investigated the association between AA and ABO and Rh blood groups.

METHODS

This cross-sectional study was done on 200 patients with AA and 200 healthy controls (HCs) between March 2021 and September 2021.

RESULTS

The prevalence of blood groups O, A, B, and AB in patients with AA was 30%, 30.5%, 10.5%, and 29%, respectively. A significant difference was detected between the two groups in the frequency of the ABO and ABO*Rh blood groups (p-value < 0.05). Compared to the HCs, the prevalence of the AB and AB+ blood group was higher in AA patients. No significant relationship was detected between sex, BMI, duration of disease, age at onset, severity of alopecia tool (SALT) score, hair loss pattern, and nail involvement with ABO and Rh blood groups (p-value > 0.05).

CONCLUSION

In conclusion, the highest difference was related to the AB+ blood group, so compared to HCs, the AB+ blood group frequency was higher in patients with AA. However, more studies with larger sample sizes on different ethnicities should be performed to verify the results of this study.

Health-related quality of life (HRQoL) among patients with alopecia areata (AA): A systematic review

Alopecia areata (AA) is a common skin disease that is frequently emotionally devastating. Several studies have examined the effect of AA on health-related quality of life (HRQoL). We performed a systematic review of all published studies of HRQoL in patients with AA. Eleven studies met inclusion criteria, incorporating data from 1986 patients. Patients with AA consistently demonstrate poor HRQoL scores, with greater extent of scalp involvement associated with lower HRQoL. HRQoL experienced by patients with AA is similar to that seen in patients with other chronic skin diseases including atopic dermatitis and psoriasis.

Association between PTPN22 C1858T polymorphism and alopecia areata risk

Alopecia areata (AA) is a skin condition in which hair is lost from certain or all areas of the body. This condition has been described as an immune-mediated complex genetic disease, characterized by the presence of lymphocytes that are directed to the hair follicles in the anagen phase. The gene encoding the protein tyrosine phosphatase, non-receptor type 22 (PTPN22), which is exclusively expressed in immune cells, has been considered as a risk factor associated with a number of autoimmune diseases. In AA, the single nucleotide polymorphism, rs2476601, has been identified as a risk factor in several populations. The aim of the present study was to investigate the effect of PTPN22 C1858T inherited genetic polymorphism on the predisposition to severe forms of AA, in a case-control study on individuals. The study included 64 unrelated patients diagnosed with several types of AA, as well as 225 healthy unrelated subjects. The DNA samples were genotyped for PTPN22 C1858T polymorphism using the polymerase chain reaction-restriction fragment length polymorphism technique. Causal associations were determined by χ² test and their respective odds ratio (OR) was assessed in a 2×2 contingency table. The results demonstrated a significant association of the T allele [P=0.040; OR=3.196; 95% confidence interval (CI), 0.094-10.279] and the CT genotype (P=0.038; OR=3.313; 95% CI, 1.008-10.892) with patchy AA. In conclusion, the results of the present study suggested the possible involvement of the T allele of the PTPN22 C1858T SNP as a genetic risk factor for this type of AA in the population studied.

Drug discovery for alopecia: gone today, hair tomorrow

INTRODUCTION

Hair loss or alopecia affects the majority of the population at some time in their life, and increasingly, sufferers are demanding treatment. Three main types of alopecia (androgenic [AGA], areata [AA] and chemotherapy-induced [CIA]) are very different, and have their own laboratory models and separate drug-discovery efforts.

AREAS COVERED

In this article, the authors review the biology of hair, hair follicle (HF) cycling, stem cells and signaling pathways. AGA, due to dihydrotesterone, is treated by 5-α reductase inhibitors, androgen receptor blockers and ATP-sensitive potassium channel-openers. AA, which involves attack by CD8(+)NK group 2D-positive (NKG2D(+)) T cells, is treated with immunosuppressives, biologics and JAK inhibitors. Meanwhile, CIA is treated by apoptosis inhibitors, cytokines and topical immunotherapy.

EXPERT OPINION

The desire to treat alopecia with an easy topical preparation is expected to grow with time, particularly with an increasing aging population. The discovery of epidermal stem cells in the HF has given new life to the search for a cure for baldness. Drug discovery efforts are being increasingly centered on these stem cells, boosting the hair cycle and reversing miniaturization of HF. Better understanding of the molecular mechanisms underlying the immune attack in AA will yield new drugs. New discoveries in HF neogenesis and low-level light therapy will undoubtedly have a role to play.

The association of lacrimal gland inflammation with alopecia areata

PURPOSE

To describe the association of lacrimal gland inflammation with alopecia areata.

METHODS

We reviewed the medical records of 4 patients diagnosed with lacrimal gland inflammation who had an antecedent or subsequent episode of alopecia. Data was collected on the presentation age, gender, medical history, disease onset, symptoms and signs, imaging, histopathology, systemic evaluation, management and outcome. Pathology and imaging results were correlated with clinical findings.

RESULTS

Three patients were Asian and one Caucasian. Two developed alopecia after presentation for lacrimal inflammation. The remaining two had a history of alopecia totalis (2 years and 10 years). Three of the 4 patients presented or developed other systemic disorders, including seizures, thrombocytopenia, optic neuritis, ulcerative colitis, allergic rhinitis, lymphadenopathy, vasculitic rash and positive p-ANCA values. All received oral corticosteroids, with the addition of methotrexate therapy in one for relapsing inflammation.

CONCLUSIONS

Lacrimal gland inflammation and alopecia areata are autoimmune processes that can be seen in association with each other.

Effect of thioredoxin reductase 1 on glucocorticoid receptor activity in human outer root sheath cells

Alopecia areata (AA) is a common disease of patchy hair loss on the scalp that can progress to cover the entire scalp and eventually the entire body. Intralesional injection of corticosteroids is the first-line therapy for adult patients, however some patients do not respond to glucocorticoid treatment effectively. To delineate the molecular mechanism underlying glucocorticoid insensitivity, we examined the expression of glucocorticoid receptor (GR) and thioredoxin reductase 1 (TrxR1). In some case of glucocorticoid-resistant AA patients, the expression of TrxR1 was decreased in outer root sheath (ORS). We then investigated the effect of TrxR1 on GR activity using recombinant adenoviruses. Overexpression of TrxR1 markedly increased GR activity in ORS cells cultured in vitro. In addition, TrxR1 protected GR activity against H(2)O(2). Finally, TrxR1-enhanced GR activity was significantly inhibited by the overexpression of dominant negative form of Trx (Trx(C32S/C35S)). These results suggest that decreased TrxR1 may be one putative cause for glucocorticoid resistance in AA, through the impact on intracellular redox system.

Genomewide scan for linkage reveals evidence of several susceptibility loci for alopecia areata

Alopecia areata (AA) is a genetically determined, immune-mediated disorder of the hair follicle that affects 1%-2% of the U.S. population. It is defined by a spectrum of severity that ranges from patchy localized hair loss on the scalp to the complete absence of hair everywhere on the body. In an effort to define the genetic basis of AA, we performed a genomewide search for linkage in 20 families with AA consisting of 102 affected and 118 unaffected individuals from the United States and Israel. Our analysis revealed evidence of at least four susceptibility loci on chromosomes 6, 10, 16 and 18, by use of several different statistical approaches. Fine-mapping analysis with additional families yielded a maximum multipoint LOD score of 3.93 on chromosome 18, a two-point affected sib pair (ASP) LOD score of 3.11 on chromosome 16, several ASP LOD scores >2.00 on chromosome 6q, and a haplotype-based relative risk LOD of 2.00 on chromosome 6p (in the major histocompatibility complex locus). Our findings confirm previous studies of association of the human leukocyte antigen locus with human AA, as well as the C3H-HeJ mouse model for AA. Interestingly, the major loci on chromosomes 16 and 18 coincide with loci for psoriasis reported elsewhere. These results suggest that these regions may harbor gene(s) involved in a number of different skin and hair disorders.

Female-patterned alopecia in teenage brothers with unusual histologic features

BACKGROUND

Patterned hair loss, follicular miniaturization, and increased telogen hair counts characterize androgenic alopecia (AGA). Follicular inflammation in AGA has been associated with treatment resistance and progressive hair loss.

CASE REPORT

Brothers, 15 and 18 years old, presented with frontal and mid-scalp hair loss with an intact frontal hairline noted over a 1-year period. The elder reported past use of androgenic steroids. Laboratory assessment for metabolic and hormonal abnormalities was unrevealing, and hair pull test was negative. Scalp biopsies revealed decreased terminal hairs, marked diameter variation of anagen hairs, decreased terminal to vellus hair ratios (3.7:1/3.4:1, older/younger), and increased telogen counts (23%/21%). Infrabulbar and peri-isthmic (follicular bulge region) lymphocytic infiltrates were present. Hair loss has progressed, unabated by daily topical 0.5% clobetasol (for 6 months), daily 5% minoxidil (1 year), and latter, daily oral finasteride (2 years - older brother only).

DISCUSSION

Based on patterned hair loss and miniaturized hairs, these brothers have AGA. The female pattern of hair loss (diffuse hair loss affecting the central scalp with preservation of frontal hair line) coupled with follicular isthmic lymphocytic inflammation represents an unusual presentation, possibly a treatment resistant, inflammatory variant of AGA. The differential diagnosis includes exogenous androgen-mediated hair loss, cicatricial pattern hair loss, or the superimposition of alopecia areata.

Association of HLA haplotype with alopecia areata in Chinese Hans

BACKGROUND

Some studies have shown discrepancies in human leucocyte antigen (HLA) associated with alopecia areata (AA) between different ethnic populations.

OBJECTIVE

To investigate whether HLA-I, -DQA1 and -DQB1 alleles and the HLA haplotype are associated with AA, and the correlation between the HLA haplotype profile, age of onset and severity of AA in Chinese Hans.

METHODS

The polymerase chain reaction-sequence specific primer (PCR-SSP) method was used to analyse the frequencies of HLA class I, -DQA1 and -DQB1 alleles in 192 patients with AA and 252 controls in Chinese Hans. The linkage disequilibrium was calculated using the 2 x 2 table.

RESULTS

The 24 two-locus haplotypes [including A*02-B*18, A*02-B*27, A*02-B*52, A*02-Cw*0704, A*02-DQA1*0104, A*02-DQB1*0604, A*02-DQB1*0606, B*18-Cw*0704, B*18-DQA1*0104, B*18-DQA1*0302, B*18-DQB1*0606, B*27-Cw*0704, B*27-DQA1*0104, B*27-DQA1*0302, B*52-Cw*0704, B*52-DQA1*0104, B*52-DQA1*0302, B52-DQB1*0606, Cw*0704-DQA1*0104, Cw*0704-DQA1*0302, Cw*0704-DQB1*0606, DQA1*0104-DQB1*0604, DQA1*0104-DQB1*0606, DQA1*0302-DQB1*0606 (P<0.05)] were associated with AA, while eight extended haplotypes (A*02-B*18-DQA1*0104, A*02-B*27-DQA1*0104, A*02-B*52-DQA1*0104, A*02-B*52-DQA1*0302, A*02-B*52-DQB1*0606, B*52-Cw*0704-DQA1*0104, B*52-Cw*0704-DQA1*0302, A*02-B*52-DQA1*0302-DQB1*0606) were found to be related to AA in Chinese Hans. Through stratified analysis, we found that the extended haplotype B*52-Cw*0704-DQA1*0302 was related to early onset of AA, and no haplotype was only associated with severe AA.

CONCLUSION

This is the first detailed report to elucidate HLA haplotypes associated with AA and that demonstrates the significant HLA haplotypes in Chinese Hans AA. The haplotype B*52-Cw*0704-DQA1*0302 was identified to be related to early onset of AA. Our results provide some information for future research on predisposing genes in HLA regions in Chinese Hans.

Adult-onset Alopecia areata is a complex polygenic trait in the C3H/HeJ mouse model

Alopecia areata (AA) is an autoimmune disease that targets actively growing (anagen) hair follicles in humans and other mammals. C3H/HeJ, but not C57BL/6J, mice spontaneously develop an adult-onset form of AA. A segregating population of C3HB6F2 female mice (n=1096), generated from crossing these two strains, was used for genome-wide linkage analysis to identify AA genetic susceptibility. Previous analysis identified susceptibility intervals on chromosomes 17 (Alaa1) and 9 (Alaa2). Using additional markers in these intervals and saturation mapping purported intervals on chromosomes 8 and 15, two additional regions were identified (Alaa3 and Alaa4, respectively). Human gene association studies identified specific human leukocyte antigen intervals comparable with those (major histocompatibility complex) found in Alaa1 in the mouse. Other human studies identified genes not found in this linkage study, but these human transcription factors are directly regulated by genes within Alaa1. These results indicate the necessity of integrating both gene association and genome-wide linkage studies in both mice and humans to understand the complex nature of these and other polygenic diseases.