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

Enhancing hair growth through phytochemicals: mechanisms, supporting evidence, and future directions

AIMS

To explore the mechanisms, formulations, delivery strategies, and therapeutic potential of phytochemicals in promoting hair growth, emphasizing their effects on hair follicle physiology and growth cycles.

METHODS

Databases including PubMed, Springer, Wiley Online Library, Web of Science, CBM, CNKI, Elsevier, Google Scholar, and other databases were searched using key terms such as "phytochemicals," "hair growth," "hair follicles," "growth factors," and "natural treatments" were used to identify experimental and clinical studies on phytochemicals affecting hair growth.

KEY FINDINGS

Key phytochemicals stimulate hair follicles and promote keratinocyte proliferation. Malva verticillata influences the (Wingless/Integrated and β-catenin) Wnt/β-catenin pathway and AKT (protein kinase B) signaling. Elephantopus scaber L. extracts elevate insulin-like growth factor 1 (IGF-1) and vascular endothelial growth factor (VEGF), while Sophora flavescens boosts IGF-1 and keratinocyte growth factor (KGF) by increasing mRNA levels. Similarly, Epigallocatechin-3-gallate activates AKT signaling, caffeine reduces transforming growth factor-β2 (TGF-β2) and raises IGF-1, and Carthamus tinctorius enhances VEGF and KGF while suppressing TGF-β1. Although evidence highlights their potential, challenges remain in improving bioavailability and standardizing formulations.

CONCLUSIONS

Phytochemicals offer natural, safer alternatives for promoting hair growth with fewer side effects than conventional drugs. Further research is needed to optimize formulations and improve bioavailability.

Unveiling the immune and vitamin profiles of blood: the potential biomarkers for alopecia areata

Background

Alopecia areata is a hair follicle disorder characterized by the development of multiple circular bald patches on the scalp, often accompanied by elevated cytokine production and immune cell infiltration around hair follicles. Our aspiration is to explore whether blood analysis can reveal additional factors that contribute to the disparities between individuals with alopecia areata and those who are healthy. Such research could potentially establish a robust foundation for the advancement of future therapeutic strategies.

Methods

In Fujian, China, we have collected blood samples from a cohort of 28 alopecia areata patients and a control group of 28 healthy individuals for comparative analysis. A detailed assessment of cytokines, eosinophil counts, vitamin levels, and immunoglobulin profiles within these samples was conducted. Subsequently, statistical analysis was applied to elucidate the differences between the two groups.

Results

While the blood analysis revealed higher average levels of IL-4, IL-10, and TNF-α in alopecia areata patients compared to healthy individuals, these differences were not statistically significant. Similarly, vitamin levels showed no significant variation between the patient and healthy groups. However, the Wilcoxon rank sum test identified a significant increase in IFN-γ and a significant decrease in immunoglobulin IgG4 levels among alopecia areata patients, pointing to a possible role in the disease's pathogenesis. Receiver operating characteristic (ROC) curve analysis had demonstrated that the area under the ROC curve (AUC) for IFN-γ and IgG4 was 0.656 and 0.704, respectively, suggesting that IFN-γ and IgG4 had a certain discrimination effect on alopecia areata. Utilizing the Youden index to optimize specificity, we propose that IgG4 levels below 824.85 mg/L and IFN-γ levels above 0.565 pg/mL could serve as biomarkers for assessing the risk of alopecia areata.

Conclusions

These findings highlight the need for further exploration of the link among alopecia areata, IgG4- and IFN-γ-related mechanisms, potentially uncovering novel therapeutic targets for managing this condition.

Alopecia Areata: Pathogenesis, Diagnosis, and Therapies

Alopecia areata (AA) is a complex, chronic inflammatory skin disorder characterized by unpredictable, nonscarring hair loss, affecting millions worldwide. Its pathogenesis remains poorly understood, driven by intricate interactions among immune dysregulation, genetic predisposition, and environmental triggers. Despite significant advances in identifying these contributing factors, substantial gaps persist in our understanding of the full spectrum of AA's molecular mechanisms and in the development of effective therapeutic approaches. This review aims to comprehensively explore the immunological, genetic, epigenetic, and environmental factors underlying AA, with a focus on immune-mediated mechanisms. We also evaluate diagnostic approaches and recent advancements in assessing disease severity. Furthermore, the review discusses evolving therapeutic options, including traditional therapies, biologics, small-molecule agents, and emerging treatments. The academic value of this work lies in its synthesis of current knowledge on the multifaceted nature of AA, providing insights for future research and clinical practice. By elucidating the interconnected factors underlying AA, this review seeks to advance both understanding and management of this prevalent, clinically challenging disorder.

Hair follicle targeting via gelatin coated transferosomes loaded with tofacitinib citrate for enhanced treatment of alopecia areata: Clinical evaluation of alopecia areata patients

Alopecia areata (AA) is a complex autoimmune disease that has a negative impact on the psychological well-being of patients. AA is associated with T-cells activation and cytokines release leading to collapse of immune privilege of hair follicles (HF). Tofacitinib, a JAK 1&3 inhibitor, exhibited effectiveness in AA treatment. The aim of this study was to develop gelatin-coated transferosomes (GLTS) to deliver tofactinib specifically to the HF to enhance the treatment of AA. GLTS were evaluated for ex vivo skin permeation, localization in skin layers by the tape stripping technique and Confocal microscopy. Finally, GLTS gel was applied topically for the treatment of AA patients, where seven AA patients with recalcitrant lesions (5 males and 2 females) were included in this study, then they were evaluated clinically and dermoscopically to assess the efficacy of treatment. GLTS of size 223.23 ± 16.43 nm, exhibited the highest HF localization by tape stripping (7.8561 ± 0.77 μg), and the highest mean fluorescence intensity in HF (84.63 ± 7.98 rfu). Additionally, hair regrowth in all AA patients was observed after 12 weeks with up to 80 % improvement. The present work proposed effective formulations for HF targeting of tofacitinib and proved enhanced clinical efficacy in recalcitrant AA patients with positive feedback.

Crosstalk Between the Skin Environment and Microbial Community in Immune-Related Skin Diseases

The skin surface hosts diverse skin microbiota, including bacteria, fungi, and viruses. Intricate interactions between the skin microenvironment and microbial community are crucial for maintaining cutaneous homeostasis. This review explores the bidirectional relationship between the skin ecosystem and its microbiota. The skin microenvironment is shaped by a combination of intrinsic factors, dominated by sweat glands and pilosebaceous units, and external factors, such as UV radiation and personal care products, which create distinct niches that influence microbial colonization patterns across different skin regions. The skin microbiome, in turn, modulates the physical, chemical, immunological, and microbial barriers of the skin. We also discuss the alterations in this crosstalk in various immune-related skin conditions such as atopic dermatitis, psoriasis, rosacea, hidradenitis suppurativa, skin cancer, and aging. Understanding these interactions is vital for developing targeted microbiome-based therapies for various skin disorders. Further researches are needed to deepen insights into the microbial roles and their therapeutic potentials in skin health and disease.

Identifying effective immune biomarkers in alopecia areata diagnosis based on machine learning methods

BACKGROUND

Alopecia areata (AA) is a common non-scarring hair loss disorder associated with autoimmune conditions. However, the pathobiology of AA is not well understood, and there is no targeted therapy available for AA.  METHODS: In this study, differential gene expression analysis, immune status assessment, weighted correlation network analysis (WGCNA), and functional enrichment analysis were performed to identify shared genes associated with both immunological response and AA. Machine learning methods were then used to identify three hub genes as potential diagnostic markers for AA. External validation was performed, and the correlation of hub genes with immune infiltration, immune checkpoint genes, and key marker genes and pathways were evaluated.

RESULTS

Three hub genes were identified, which accurately predicted the progression of AA and the immune status. The hub genes were found to be diagnostic markers for AA with high predictive accuracy. External validation confirmed the efficacy of these markers in identifying AA patients.

CONCLUSION

Overall, the study provides a novel approach for the diagnosis, prevention, and treatment of AA. The findings could potentially lead to the development of targeted therapies for AA based on the identified hub genes. The study also highlights the potential of machine learning and bioinformatics analysis in identifying new biomarkers for autoimmune diseases.

Case Report: Baricitinib improved alopecia areata in a pediatric patient with atopic dermatitis

Alopecia areata (AA) is a common non-scarring hair loss condition whose specific pathogenesis is not yet fully understood. In children, AA often co-occurs with atopic dermatitis (AD), complicating treatment. Here, we report the case of a child with myasthenia gravis who had severe AA and moderate AD. The child had previously been treated with local injections of corticosteroids and developed total hair loss and AD after discontinuing corticosteroid use. After approximately one year of treatment with baricitinib, 4 mg once daily, combined with twice-daily application of a corticosteroid ointment, a significant improvement in the child's condition was observed, with the Severity of Alopecia Tool score dropping from 100 to 24.4 and Eczema Area Severity Index score to 0. New vellus hairs were clearly observable under trichoscopy, which contrasted significantly with the pre-treatment state. Throughout the treatment process, the patient's clinical symptoms, blood cell counts, liver and kidney function, and coagulation functions were essentially normal, with no significant adverse reactions observed except for folliculitis on the scalp. We discuss common targets in the pathogenesis of AA and AD as well as the safety and prospects of Janus kinase inhibitors for the treatment of pediatric patients with these conditions.

JAK-STAT1 as therapeutic target for EGFR deficiency-associated inflammation and scarring alopecia

The hair follicle stem cell niche is an immune-privileged microenvironment, characterized by reduced antigen presentation, thus shielding against permanent immune-mediated tissue damage. In this study, we demonstrated the protective role of hair follicle-specific epidermal growth factor receptor (EGFR) against scarring hair follicle destruction. Mechanistically, disruption of EGFR signaling generated a cell-intrinsic hypersensitivity within the JAK-STAT1 pathway, which, synergistically with interferon gamma expressing CD8 T-cell and NK-cell-mediated inflammation, compromised the stem cell niche. Hair follicle-specific genetic depletion of either JAK1/2 or STAT1 or therapeutic inhibition of JAK1/2 ameliorated the inflammation, restored skin barrier function and activated the residual stem cells to resume hair growth in mouse models of epidermal and hair follicle-specific EGFR deletion. Skin biopsies from EGFR inhibitor-treated and cicatricial alopecia patients revealed an active JAK-STAT1 signaling signature along with upregulation of antigen presentation and downregulation of key components of the EGFR pathway. Our findings offer molecular insights and highlight a mechanism-based therapeutic strategy for addressing chronic folliculitis associated with EGFR-inhibitor anti-cancer therapy and cicatricial alopecia.

Infectious events in patients with alopecia areata treated with JAK inhibitors: low burden and minimal impact on persistence in treatment

BACKGROUND

Alopecia areata (AA) is a non-scarring disorder characterized by hair loss that greatly affects patients' quality of life and has a chronic, recurring course. This disease is marked by an inflammatory process, mainly on an autoimmune basis primarily regulated by Janus kinase (JAK).

RESEARCH DESIGN AND METHODS

We conducted a retrospective study evaluating the safety of JAKi in a real-world setting in 91 AA patients, with a specific focus on the assessment of infectious events.

RESULTS

Overall, 34 infectious events were observed in 28 patients (30.8%), among them 17 patients (60.7%) suspended treatment with JAKi until the infection was clinically resolved. Only in one case the infectious event led to a permanent discontinuation of the treatment. The data we observed in the study are consistent with results reported in clinical trials.

CONCLUSION

It can be stated that, during treatment with JAKi in AA patients, infectious events may occur, but in most cases these events are easily manageable and do not result in permanent discontinuation of the drug.

Epidermal growth factor receptor/mitogen-activated kinase inhibitor treatment induces a distinct inflammatory hair follicle response that includes collapse of immune privilege

BACKGROUND

Inhibitors of epidermal growth factor receptor (EGFRi) or mitogen-activated kinase (MEKi) induce a folliculitis in 75-90% of patients, the pathobiology of which remains insufficiently understood.

OBJECTIVES

To characterize changes in the skin immune status and global transcriptional profile of patients treated with EGFRi; to investigate whether EGFRi affects the hair follicle's (HF) immune privilege (IP); and to identify early proinflammatory signals induced by EGFRi/MEKi in human scalp HFs ex vivo.

METHODS

Scalp biopsies were taken from patients exhibiting folliculitis treated long term with EGFRi ('chronic EGFRi' group, n = 9) vs. healthy scalp skin (n = 9) and patients prior to commencing EGFRi treatment and after 2 weeks of EGFRi therapy ('acute EGFRi' group, n = 5). Healthy organ-cultured scalp HFs were exposed to an EGFRi (erlotinib, n = 5) or a MEKi (cobimetinib, n = 5). Samples were assessed by quantitative immunohistomorphometry, RNA sequencing (RNAseq) and in situ hybridization.

RESULTS

The 'chronic EGFRi' group showed CD8+ T-cell infiltration of the bulge alongside a partial collapse of the HF's IP, evidenced by upregulated major histocompatibility complex (MHC) class I, β2-microglobulin (B2 M) and MHC class II, and decreased transforming growth factor-β1 protein expression. Healthy HFs treated with EGFRi/MEKi ex vivo also showed partial HF IP collapse and increased transcription of human leucocyte antigen (HLA)-A, HLA-DR and B2 M transcripts. RNAseq analysis showed increased transcription of chemokines (CXCL1, CXCL13, CCL18, CCL3, CCL7) and interleukin (IL)-26 in biopsies from the 'chronic EGFRi' cohort, as well as increased IL-33 and decreased IL-37 expression in HF biopsies from the 'acute EGFRi' group and in organ-cultured HFs.

CONCLUSIONS

The data show that EGFRi/MEKi compromise the physiological IP of human scalp HFs and suggest that future clinical management of EGFRi/MEKi-induced folliculitis requires HF IP protection and inhibition of IL-33.

Dandruff lesional scalp skin exhibits epidermal T cell infiltration and a weakened hair follicle immune privilege

OBJECTIVE

Dandruff is characterised by the presence of perivascular leukocytes and mild inflammation; however, the immune microenvironment of dandruff-affected scalp skin and the potential changes to the hair follicle's (HF) physiological immune privilege (HF IP) remain unknown. Here, we characterised the HF immune microenvironment and immune privilege status in dandruff-affected scalp skin.

METHODS

We assessed relevant key parameters in healthy versus dandruff-affected human scalp biopsies using quantitative immunohistomorphometry, laser capture microdissection, and RNA sequencing.

RESULTS

The number of epidermal CD4+ and CD8+ T cells was increased in lesional dandruff scalp skin, while the number of MHC class II+/CD1a+ Langerhans cells was decreased in the infundibulum. The number of intrafollicular and perifollicular CD4+ T cells and CD8+ T cells, perifollicular CD68+ macrophages, and tryptase+ mast cells remained unchanged. Interestingly, MHC class Ia and ß2-microglobulin protein expression were significantly increased specifically in the suprabulbar outer root sheath (ORS) compartment of dandruff-associated HFs. RNAseq analysis of laser capture micro-dissected suprabulbar ORS compartment revealed antigen presentation pathway as the top regulated canonical pathway, along with the upregulation of HF-IP genes such as HLA-C, HLA-DP, and TAP1, which are normally down-regulated in healthy HFs. Intrafollicular protein expression of known HF IP guardians (CD200 and α-MSH) and 'danger signals' (MICA and CXCL10) remained unaltered at the IP sites of dandruff lesional HFs compared to non-lesional and healthy HFs. Instead, the expression of macrophage migration inhibiting factor (MIF), another HF IP guardian, was reduced.

CONCLUSION

Together, this work shows that dandruff is associated with epidermal T-cell infiltration and a weakened HF IP in the suprabulbar ORS of HFs in dandruff lesional scalp.

Cyclosporine-induced alopecia:a case report, FDA adverse event reporting system analysis and literature assessment

Cyclosporine is a potent immunosuppressive drug for various immune-mediated diseases in children. Cyclosporine's expected therapeutic effect also carries a wide range of side effects. One of the most common and intriguing dermatological side effects is hypertrichosis. However, recent reports have recognized alopecia as a potential adverse effect of cyclosporine. Here, we report a case of a 29-month-old boy diagnosed with aplastic anemia. During cyclosporine therapy, the patient presented with hair loss on the scalp, which and subsequently spread to the eyebrows and eyelashes. The alopecic symptoms were not relieved following topical minoxidil liniment interventions. When the cyclosporine was discontinued, a remarkable improvement was observed in the scalp, with complete hair regrowth. Data concerning cyclosporine from the FDA Adverse Event Reporting System (FAERS) database were extracted from January 2004 to January 2023. Within FAERS, our post-marketing pharmacovigilance analysis detected the reporting association of cyclosporine and alopecia. In monotherapy, cyclosporine-induced alopecia was observed in 118 cases, and tacrolimus-induced alopecia signals were detected in 197 cases. Although the potential mechanism of medication-induced hair loss is unclear, we identified a potential correlation between alopecia and cyclosporine, and it is still necessary to adequately recognize and clinically monitor this paradoxical reaction.

Mesenchymal Stem Cell Therapy in Alopecia Areata: Visual and Molecular Evidence from a Mouse Model

Recent studies have highlighted the potential of Mesenchymal Stem Cells (MSCs) as an alternative treatment for Alopecia Areata (AA) due to their immunosuppressive properties. While MSCs have shown promise in cell experiments, their effectiveness in vivo remains uncertain. This study aims to validate local administration of MSC therapy's efficacy in AA treatment through animal experiments. AA was induced through Interferon-gamma (IFN-γ) administration in mice, and MSC treatment (MSCT)'s effects were assessed visually and through tissue analysis. The MSC-treated group showed more hair regrowth compared to the control (CTL) group. MSCT notably reduced local inflammatory cytokines (JAK1, JAK2, STAT1, STAT3, IFN-γR, IL-1β, IL-16, IL-17α, and IL-18) in AA-induced mice's skin, but systemic cytokine levels remained unchanged. Furthermore, MSC treatment normalized the expression of Wnt/β-catenin signaling pathway genes (LEF1 and β-catenin) and growth factors (FGF7 and FGF2), which are crucial for hair cycle regulation. This study lays the groundwork for further exploring MSCs as a potential treatment for AA, but more research is needed to fully understand their therapeutic potential.

Interleukin-33 links asthma to alopecia areata: Mendelian randomization and mediation analysis

OBJECTIVE

The objective of this study is to elucidate the causal association between asthma and alopecia areata (AA) through the application of Mendelian randomization (MR) analysis, leveraging summary data from genome-wide association studies (GWAS). Additionally, it explores potential mediating factors.

MATERIALS AND METHODS

Mendelian randomization (MR) analysis was employed to investigate the causal relationship between asthma and AA using genetic instrumental variables (IVs) for asthma, 91 circulating inflammatory proteins, and AA extracted from large-scale GWAS. The primary analytical approach utilized the inverse-variance weighted (IVW) method, supplemented by weighted median and MR-Egger methods to assess robustness. Tests for heterogeneity and pleiotropy were conducted to ensure result reliability. Furthermore, the study examined the mediating role of circulating inflammatory proteins in the asthma-AA relationship.

RESULTS

The findings revealed an increased risk of AA among asthma patients (odds ratio (OR) = 14.070; 95% confidence interval (CI) = 1.410-140.435; P = 0.024). Interleukin-33 (IL-33) emerged as a significant mediator in the asthma-AA relationship, explaining 13.1% of the mediation effect. Bidirectional Mendelian randomization analyses did not establish a causal effect of AA on asthma occurrence.

CONCLUSION

This study, utilizing Mendelian Randomization, elucidates the causal link between asthma and AA, highlighting the mediating role of IL-33. These findings underscore the importance of considering AA risk in asthma management and offer insights for potential therapeutic strategies targeting IL-33. Future research should explore additional biomarkers and mediating mechanisms between asthma and AA to enhance treatment approaches and patient quality of life.

Risk Factors and Hazards of Recipient-Area Perifollicular Erythema After Hair Transplantation: A Multicenter Retrospective Cohort Study

BACKGROUND

Recipient-area perifollicular erythema (RPE) may delay graft growth after hair transplantation. However, there is currently a lack of observational clinical studies of RPE.

OBJECTIVE

To study the clinical features and risk factors associated with RPE while analyzing its correlation with graft growth.

METHODS

We conducted a multicenter retrospective cohort study between June 2020 and January 2023.

RESULTS

A total of 1090 participants were included, 178 (16.33%) showed mild RPE, 56 (5.14%) showed moderate RPE, and 10 (0.92%) showed severe RPE. Patients with RPE had severe hair shaft shedding (P < 0.001) and a lower survival rate (P < 0.001) of grafts. Logistic regression analysis showed that folliculitis is a significant risk factor for mild RPE (OR 6.061, 95% CI 3.343-10.991, P < 0.001) and moderate RPE (OR 3.397, 95% CI 1.299-8.882, P = 0.013). Besides, untimely first postoperative hair washing was associated with the development of moderate RPE (OR 0.724, 95% CI 0.553-0.947, P = 0.018) and severe RPE (OR 1.553, 95% CI 1.156-2.086, P = 0.003).

CONCLUSION

RPE is a postoperative complication closely related to high hair shaft shedding proportion and low graft survival rate. Both postoperative folliculitis and untimely first postoperative hair washing may induce the occurrence of RPE.

LEVEL OF EVIDENCE III

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Deciphering the Complex Immunopathogenesis of Alopecia Areata

Alopecia areata (AA) is an autoimmune-mediated disorder in which the proximal hair follicle (HF) attack results in non-scarring partial to total scalp or body hair loss. Despite the growing knowledge about AA, its exact cause still needs to be understood. However, immunity and genetic factors are affirmed to be critical in AA development. While the genome-wide association studies proved the innate and acquired immunity involvement, AA mouse models implicated the IFN-γ- and cytotoxic CD8+ T-cell-mediated immune response as the main drivers of disease pathogenesis. The AA hair loss is caused by T-cell-mediated inflammation in the HF area, disturbing its function and disrupting the hair growth cycle without destroying the follicle. Thus, the loss of HF immune privilege, autoimmune HF destruction mediated by cytotoxic mechanisms, and the upregulation of inflammatory pathways play a crucial role. AA is associated with concurrent systemic and autoimmune disorders such as atopic dermatitis, vitiligo, psoriasis, and thyroiditis. Likewise, the patient's quality of life (QoL) is significantly impaired by morphologic disfigurement caused by the illness. The patients experience a negative impact on psychological well-being and self-esteem and may be more likely to suffer from psychiatric comorbidities. This manuscript aims to present the latest knowledge on the pathogenesis of AA, which involves genetic, epigenetic, immunological, and environmental factors, with a particular emphasis on immunopathogenesis.

CD80 on skin stem cells promotes local expansion of regulatory T cells upon injury to orchestrate repair within an inflammatory environment

Following tissue damage, epithelial stem cells (SCs) are mobilized to enter the wound, where they confront harsh inflammatory environments that can impede their ability to repair the injury. Here, we investigated the mechanisms that protect skin SCs within this inflammatory environment. Characterization of gene expression profiles of hair follicle SCs (HFSCs) that migrated into the wound site revealed activation of an immune-modulatory program, including expression of CD80, major histocompatibility complex class II (MHCII), and CXC motif chemokine ligand 5 (CXCL5). Deletion of CD80 in HFSCs impaired re-epithelialization, reduced accumulation of peripherally generated Treg (pTreg) cells, and increased infiltration of neutrophils in wounded skin. Importantly, similar wound healing defects were also observed in mice lacking pTreg cells. Our findings suggest that upon skin injury, HFSCs establish a temporary protective network by promoting local expansion of Treg cells, thereby enabling re-epithelialization while still kindling inflammation outside this niche until the barrier is restored.

Interleukin-15 is a hair follicle immune privilege guardian

The autoimmunity-promoting cytokine, Interleukin-15 (IL-15), is often claimed to be a key pathogenic cytokine in alopecia areata (AA). Yet, rhIL-15 promotes human hair follicle (HF) growth ex vivo. We have asked whether the expression of IL-15 and its receptor (IL-15R) isoforms is altered in human AA and how IL-15 impacts on human HF immune privilege (HF-IP) in the presence/absence of interferon-γ (IFNγ), the well-documented key AA-pathogenic cytokine, as well as on hair regrowth after experimental AA induction in vivo. Quantitative immunohistomorphometry showed the number of perifollicular IL-15+ T cells in AA skin biopsies to be significantly increased compared to healthy control skin, while IL-15, IL-15Rα, and IL-15Rγ protein expression within the hair bulb were significantly down-regulated in AA HFs. In organ-cultured human scalp HFs, rhIL-15 significantly reduced hair bulb expression of MICA, the key "danger" signal in AA pathogenesis, and increased production of the HF-IP guardian, α-MSH. Crucially, ex vivo, rhIL-15 prevented IFNγ-induced HF-IP collapse, restored a collapsed HF-IP by IL-15Rα-dependent signaling (as documented by IL-15Rα-silencing), and protected AA-preventive immunoinhibitory iNKT10 cells from IFNγ-induced apoptosis. rhIL-15 even promoted hair regrowth after experimental AA induction in human scalp skin xenotransplants on SCID/beige mice in vivo. Our data introduce IL-15 as a novel, functionally important HF-IP guardian whose signaling is constitutively defective in scalp HFs of AA patients. Our data suggest that selective stimulation of intrafollicular IL-15Rα signaling could become a novel therapeutic approach in AA management, while blocking it pharmacologically may hinder both HF-IP restoration and hair re-growth and may thus make HFs more vulnerable to AA relapse.

Exploring the Gut Microbiome and Metabolome in Individuals with Alopecia Areata Disease

In recent years, heightened attention has been devoted to unravelling the intricate interplay between genetic and environmental factors shaping the gut microbiota and its significance for human health. This study delves into exploring the plausible connection between Alopecia Areata (AA), an autoimmune disease, and the dynamics of the gut microbiome. Examining a cohort of healthy adults and individuals with AA, both the gut microbiota composition and volatile organic compound (VOC) metabolites from faeces and urine were analysed. While overall microbiota composition showed no significant differences, intra-individual variability revealed distinctions related to age, gender, and pathology status, with AA individuals exhibiting reduced species richness and evenness. Differential abundance analysis identified microbial biomarkers for AA, notably Firmicutes, Lachnospirales, and Blautia, while Coprococcus stood out for healthy individuals. The Data Integration Analysis for Biomarker discovery using Latent Components (DIABLO) method further supported these findings including metabolite biomarkers, such as esters of branched chain fatty acids and branched chain amino acids as predictors for AA, suggesting potential links to oxidative stress. Despite certain limitations, the study highlights the complexity of the gut microbiome and its metabolites in the context of AA, while the biomarkers identified could be useful starting points for upcoming studies.

Deciphering the molecular mechanisms of stem cell dynamics in hair follicle regeneration

Hair follicles, which are connected to sebaceous glands in the skin, undergo cyclic periods of regeneration, degeneration, and rest throughout adult life in mammals. The crucial function of hair follicle stem cells is to maintain these hair growth cycles. Another vital aspect is the activity of melanocyte stem cells, which differentiate into melanin-producing melanocytes, contributing to skin and hair pigmentation. Sebaceous gland stem cells also have a pivotal role in maintaining the skin barrier by regenerating mature sebocytes. These stem cells are maintained in a specialized microenvironment or niche and are regulated by internal and external signals, determining their dynamic behaviors in homeostasis and hair follicle regeneration. The activity of these stem cells is tightly controlled by various factors secreted by the niche components around the hair follicles, as well as immune-mediated damage signals, aging, metabolic status, and stress. In this study, we review these diverse stem cell regulatory and related molecular mechanisms of hair regeneration and disease conditions. Molecular insights would provide new perspectives on the disease mechanisms as well as hair and skin disorder treatment.

Assessing the Efficacy of Monthly 308 nm Excimer Lamp Double-Stacked Pulse Adjusted Therapy for Alopecia Areata

Introduction

Alopecia areata (AA) is an autoimmune disease characterized by T cell-mediated attack on the hair follicle. Although there are a wide range of therapies, the majority of them are not satisfactory due to side effects, pain due to intralesional injections or limited efficacy. In this study, we sought to evaluate the efficacy, influence factors, and safety of 308 nm excimer lamp used in a monthly basis in a double-stacked pulse manner for the treatment of AA.

Methods

This was a prospective study, using 308 nm excimer lamp in a double-stacked pulse therapy for AA. The primary endpoint was the improvement in SALT score.

Results

A total of 40 patients with AA were enrolled in this study. Forty (100%) patients achieved clinical response. Hyperpigmentation and erythema occurred on the treated alopecic areas of all patients but they were considered tolerable. Patients of younger age or with a smaller area of affection had a better overall treatment response.

Conclusion

308 nm excimer lamp therapy is an excellent option for single or multiple AA because it achieves a good clinical response with less adverse effects than other therapies. This therapy may be useful for low-income countries where new JAK inhibitors are not available, however, for patients with extensive hair loss, it is not as effective and thus, it may be unfit for patients with alopecia totalis and alopecia universals.

Topical sodium valproate-loaded nanospanlastics versus conventional topical steroid therapy in alopecia areata: a randomized controlled study

BACKGROUND

A myriad of therapeutic modalities for alopecia areata are available; however, none is of high level of evidence, creating an immense need for the evaluation of other treatment modalities, of which topical sodium valproate is of potential role via proposed decrease in beta-catenin breakdown, despite its well-known side effect of hair fall as an oral therapy.

OBJECTIVE

Evaluating the efficacy and the safety of sodium valproate (SV)-loaded nanospanlastics, in comparison to topical corticosteroids, this is the currently available gold standard topical treatment for patchy AA.

METHODOLOGY

A total of 66 patients with patchy AA were randomly assigned to receive either topical mometasone furoate lotion or topical SV applied twice daily to all patches except a control patch, which was left untreated. Clinical, trichoscopic and biochemical assessments of beta-catenin tissue levels and Axin-2 gene expression were carried out at baseline and after 3 months.

RESULTS

Both therapeutic modalities were comparable. Potential efficacy was highlighted by significant improvement in the representative patch, the largest treated patch, to the control patch, the smallest untreated patch in both steroid and valproate groups (p = 0.027, 0.003 respectively). Both beta-catenin levels and Axin-2 gene expression were reduced after treatment, pointing to the inhibitory effect of dominating uncontrolled inflammatory milieu. Baseline beta-catenin was found to significantly negatively correlate with improvement in the representative patch in patients with baseline level above 0.42 ng/ml (p = - 0.042).

CONCLUSION

Both topical SV and steroids are of comparable modest efficacy. Thus, further evaluation of SV is due in combination with intralesional steroids and other anti-inflammatory treatment modalities, together with developing individualized approaches based on baseline beta-catenin level.

CLINICALTRIALS

GOV IDENTIFIER

NCT05017454, https://clinicaltrials.gov/ct2/show/NCT05017454 .

When to expect scalp hair regrowth during treatment of severe alopecia areata with baricitinib: insights from trajectories analyses of patients enrolled in two phase III trials

BACKGROUND

Baricitinib is approved for the treatment of adults with severe alopecia areata (AA). In the absence of robust data on the patterns of regrowth during treatment of severe AA, there is a gap in the knowledge regarding treatment expectations.

OBJECTIVES

To examine whether different clinical response subgroups could be identified in baricitinib-treated patients with severe AA and factors that contribute to these subgroups.

METHODS

The BRAVE-AA1 and BRAVE-AA2 phase III trials enrolled patients with severe AA [Severity of Alopecia Tool (SALT) score ≥ 50 (≥ 50% scalp hair loss)]. Patients randomized to baricitinib 4 mg or 2 mg retained their treatment allocation for 52 weeks. Based on patterns identified through growth mixture modelling (GMM), patients were categorized into responder subgroups according to when they first achieved ≥ 30% improvement from baseline in SALT score (SALT30). For each responder subgroup, trajectories of response (i.e. achievement of a SALT score ≤ 20, SALT score ≤ 10 and ≥ 50% change from baseline in SALT score) and baseline disease characteristics are reported.

RESULTS

Respectively, 515 and 340 patients were randomized to once-daily baricitinib 4 mg and 2 mg at baseline; 69% and 51%, respectively, achieved SALT30 at least once by week 52. Based on GMM findings, we identified three responder subgroups: early (SALT30 by week 12), gradual (SALT30 after week 12-week 36) and late (SALT30 after week 36-week 52). The proportions of early, gradual and late responders and nonresponders were, respectively, 33%, 28%, 8% and 31% among patients treated with baricitinib 4 mg, and 20%, 23%, 9% and 49%, respectively, among those treated with baricitinib 2 mg. Early responders had a shorter trajectory to maximal clinical outcomes (e.g. > 78% achieved a SALT score ≤ 20 by week 36) vs. gradual or late responders. Early responders were more frequent among patients with baseline severe AA (SALT score 50 to < 95) vs. very severe AA (SALT score 95-100). Overall, responders (early to late) were more frequent in patients with short (< 4 years) episodes of hair loss.

CONCLUSIONS

These analyses identified early, gradual and late responder subgroups for scalp hair regrowth in baricitinib-treated patients with severe AA, and that these subgroups are influenced by baseline characteristics. Findings from these analyses will help to inform treatment expectations for scalp hair regrowth.

Immune Privileges as a Result of Mutual Regulation of Immune and Stem Systems

Immune privileges of cancer stem cells is a well-known and widely studied problem, as presence of such cells in tumors is associated with refractoriness, recurrence, and metastasis. Accumulating evidence also suggests presence of immune privileges in non-pathological stem cells in addition to their other defense mechanisms against damaging factors. This similarity between pathological and normal stem cells raises the question of why stem cells have such a potentially dangerous property. Regulation of vital processes of autoimmunity control and regeneration realized through interactions between immune cells, stem cells, and their microenvironment are reviewed in this work as causes of formation of the stem cell immune privilege. Deep mutual integration between regulations of stem and immune cells is noted. Considering diversity and complexity of mutual regulation of stem cells, their microenvironment, and immune system, I suggest the term "stem system".

Alopecia Areata: Current Treatments and New Directions

Alopecia areata is an autoimmune hair loss disease that is non-scarring and is characterized by chronic inflammation at the hair follicle level. Clinically, patients' presentation varies from patchy, circumscribed scalp involvement to total body and scalp hair loss. Current management is guided by the degree of scalp and body involvement, with topical and intralesional steroid injections as primarily first-line for mild cases and broad immunosuppressants as the mainstay for more severe cases. Until recently, the limited number of blinded, randomized, placebo-controlled clinical trials for this disease had made establishing an evidence-based treatment paradigm challenging. However, growing insights into the pathogenesis of alopecia areata through blood and tissue analysis of human lesions have identified several promising targets for therapy. T-helper (Th) 1/interferon skewing has traditionally been described as the driver of disease; however, recent investigations suggest activation of additional immune mediators, including the Th2 pathway, interleukin (IL)-9, IL-23, and IL-32, as contributors to alopecia areata pathogenesis. The landscape of alopecia areata treatment has the potential to be transformed, as several novel targeted drugs are currently undergoing clinical trials. Given the recent US FDA approval of baricitinib and ritlecitinib, Janus kinase (JAK) inhibitors are a promising drug class for treating severe alopecia areata cases. This article will review the efficacy, safety, and tolerability of current treatments for alopecia areata, and will provide an overview of the emerging therapies that are leading the revolution in the management of this challenging disease.

Comorbid Conditions Associated with Alopecia Areata: A Systematic Review and Meta-analysis

BACKGROUND

Alopecia areata (AA) is a complex autoimmune condition resulting in nonscarring hair loss. In recent years, many studies have provided new evidence on comorbid diseases present in patients with AA. However, some studies have conflicting results, and analyses conducting a comprehensive approach are lacking.

OBJECTIVE

The aim of our study was to provide an updated systematic review and meta-analysis of medical comorbidities associated with AA.

METHODS

We searched PubMed, Embase, and Web of Science for case-control, cross-sectional, and cohort studies investigating medical comorbidities in AA published from inception through 1 February 2023.

RESULTS

We screened 3428 abstracts and titles and reviewed 345 full text articles for eligibility. Ultimately, 102 studies were analyzed, comprising 680,823 patients with AA and 72,011,041 healthy controls. Almost all included studies (100 of 102 studies) were of satisfactory to high quality (Newcastle-Ottawa scale score ≥ 4). Among patients with AA, comorbidities with the highest odds ratios (OR) compared with healthy controls and data available from more than one study included vitamin D deficiency (OR 10.13, 95% CI 4.24-24.20), systemic lupus erythematous (OR 5.53, 95% CI 3.31-9.23), vitiligo (OR 5.30, 95% CI 1.86-15.10), metabolic syndrome (OR 5.03, 95% CI 4.18-6.06), and Hashimoto's thyroiditis (OR 4.31, 95% CI 2.51-7.40). AA may be a protective factor for certain disorders, for which the AA group had lower odds compared with healthy controls, such as irritable bowel syndrome (OR 0.38, 95% CI 0.14-0.99) and colorectal cancer (OR 0.61, 95% CI 0.42-0.89).

CONCLUSION

These findings corroborate and contextualize the risks across comorbidities for patients with AA. Further work should be done to identify the underlying pathophysiology and understand appropriate screening criteria.

Treatments for alopecia areata: a network meta-analysis

BACKGROUND

Alopecia areata is an autoimmune disease leading to nonscarring hair loss on the scalp or body. There are different treatments including immunosuppressants, hair growth stimulants, and contact immunotherapy.

OBJECTIVES

To assess the benefits and harms of the treatments for alopecia areata (AA), alopecia totalis (AT), and alopecia universalis (AU) in children and adults.

SEARCH METHODS

The Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase, ClinicalTrials.gov and WHO ICTRP were searched up to July 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that evaluated classical immunosuppressants, biologics, small molecule inhibitors, contact immunotherapy, hair growth stimulants, and other therapies in paediatric and adult populations with AA.

DATA COLLECTION AND ANALYSIS

We used the standard procedures expected by Cochrane including assessment of risks of bias using RoB2 and the certainty of the evidence using GRADE. The primary outcomes were short-term hair regrowth ≥ 75% (between 12 and 26 weeks of follow-up), and incidence of serious adverse events. The secondary outcomes were long-term hair regrowth ≥ 75% (greater than 26 weeks of follow-up) and health-related quality of life. We could not perform a network meta-analysis as very few trials compared the same treatments. We presented direct comparisons and made a narrative description of the findings.

MAIN RESULTS

We included 63 studies that tested 47 different treatments in 4817 randomised participants. All trials used a parallel-group design except one that used a cross-over design. The mean sample size was 78 participants. All trials recruited outpatients from dermatology clinics. Participants were between 2 and 74 years old. The trials included patients with AA (n = 25), AT (n = 1), AU (n = 1), mixed cases (n = 31), and unclear types of alopecia (n = 4). Thirty-three out of 63 studies (52.3%) reported the proportion of participants achieving short-term hair regrowth ≥ 75% (between 12 and 26 weeks). Forty-seven studies (74.6%) reported serious adverse events and only one study (1.5%) reported health-related quality of life. Five studies (7.9%) reported the proportion of participants with long-term hair regrowth ≥ 75% (greater than 26 weeks). Amongst the variety of interventions found, we prioritised some groups of interventions for their relevance to clinical practice: systemic therapies (classical immunosuppressants, biologics, and small molecule inhibitors), and local therapies (intralesional corticosteroids, topical small molecule inhibitors, contact immunotherapy, hair growth stimulants and cryotherapy). Considering only the prioritised interventions, 14 studies from 12 comparisons reported short-term hair regrowth ≥ 75% and 22 studies from 10 comparisons reported serious adverse events (18 reported zero events and 4 reported at least one). One study (1 comparison) reported quality of life, and two studies (1 comparison) reported long-term hair regrowth ≥ 75%. For the main outcome of short-term hair regrowth ≥ 75%, the evidence is very uncertain about the effect of oral prednisolone or cyclosporine versus placebo (RR 4.68, 95% CI 0.57 to 38.27; 79 participants; 2 studies; very low-certainty evidence), intralesional betamethasone or triamcinolone versus placebo (RR 13.84, 95% CI 0.87 to 219.76; 231 participants; 1 study; very low-certainty evidence), oral ruxolitinib versus oral tofacitinib (RR 1.08, 95% CI 0.77 to 1.52; 80 participants; 1 study; very low-certainty evidence), diphencyprone or squaric acid dibutil ester versus placebo (RR 1.16, 95% CI 0.79 to 1.71; 99 participants; 1 study; very-low-certainty evidence), diphencyprone or squaric acid dibutyl ester versus topical minoxidil (RR 1.16, 95% CI 0.79 to 1.71; 99 participants; 1 study; very low-certainty evidence), diphencyprone plus topical minoxidil versus diphencyprone (RR 0.67, 95% CI 0.13 to 3.44; 30 participants; 1 study; very low-certainty evidence), topical minoxidil 1% and 2% versus placebo (RR 2.31, 95% CI 1.34 to 3.96; 202 participants; 2 studies; very low-certainty evidence) and cryotherapy versus fractional CO2 laser (RR 0.31, 95% CI 0.11 to 0.86; 80 participants; 1 study; very low-certainty evidence). The evidence suggests oral betamethasone may increase short-term hair regrowth ≥ 75% compared to prednisolone or azathioprine (RR 1.67, 95% CI 0.96 to 2.88; 80 participants; 2 studies; low-certainty evidence). There may be little to no difference between subcutaneous dupilumab and placebo in short-term hair regrowth ≥ 75% (RR 3.59, 95% CI 0.19 to 66.22; 60 participants; 1 study; low-certainty evidence) as well as between topical ruxolitinib and placebo (RR 5.00, 95% CI 0.25 to 100.89; 78 participants; 1 study; low-certainty evidence). However, baricitinib results in an increase in short-term hair regrowth ≥ 75% when compared to placebo (RR 7.54, 95% CI 3.90 to 14.58; 1200 participants; 2 studies; high-certainty evidence). For the incidence of serious adverse events, the evidence is very uncertain about the effect of topical ruxolitinib versus placebo (RR 0.33, 95% CI 0.01 to 7.94; 78 participants; 1 study; very low-certainty evidence). Baricitinib and apremilast may result in little to no difference in the incidence of serious adverse events versus placebo (RR 1.47, 95% CI 0.60 to 3.60; 1224 participants; 3 studies; low-certainty evidence). The same result is observed for subcutaneous dupilumab compared to placebo (RR 1.54, 95% CI 0.07 to 36.11; 60 participants; 1 study; low-certainty evidence). For health-related quality of life, the evidence is very uncertain about the effect of oral cyclosporine compared to placebo (MD 0.01, 95% CI -0.04 to 0.07; very low-certainty evidence). Baricitinib results in an increase in long-term hair regrowth ≥ 75% compared to placebo (RR 8.49, 95% CI 4.70 to 15.34; 1200 participants; 2 studies; high-certainty evidence). Regarding the risk of bias, the most relevant issues were the lack of details about randomisation and allocation concealment, the limited efforts to keep patients and assessors unaware of the assigned intervention, and losses to follow-up.

AUTHORS' CONCLUSIONS

We found that treatment with baricitinib results in an increase in short- and long-term hair regrowth compared to placebo. Although we found inconclusive results for the risk of serious adverse effects with baricitinib, the reported small incidence of serious adverse events in the baricitinib arm should be balanced with the expected benefits. We also found that the impact of other treatments on hair regrowth is very uncertain. Evidence for health-related quality of life is still scant.

AIRE Deficiency Leads to the Development of Alopecia Areata‒Like Lesions in Mice

Alopecia areata (AA) is an autoimmune hair loss disorder with no cure. Patients with sequence variation in AIRE are 15 times more likely to develop AA than the general population, yet the roles of AIRE in AA pathogenesis are unknown. In this study, we report that 62% of C57BL/6J female Aire^‒/‒ mice spontaneously developed persistent AA-like lesions that displayed several hallmarks of human AA. Lesional Aire^‒/‒ skin exhibited hair follicle (HF) dystrophy as determined by a reduced number of anagen HFs, decreased anagen HF proliferation, hair pigmentary changes, and decreased hair width and length. Inflammatory infiltrate comprising CD8⁺ T cells, CD4⁺ T cells, CD68⁺ macrophages, and mast cells was prominent in lesional Aire^‒/‒ HFs. From gene expression analyses, we found lesional Aire^‒/‒ skin to have significantly increased expression of human AA signature genes, including H2-Ab1, Ifnγ, IFN-γ‒induced chemokines (Ccl5, Cxcl9‒11), γ_c family cytokine receptor Il2RA, and JAK‒signal transducer and activator of transcription (STAT) signaling components (Stat1, Stat2, Stat4). By immunostaining, lesional Aire^‒/‒ HFs also show upregulated major histocompatibility complex class I and downregulated α-melanocyte-stimulating hormone, signifying immune privilege collapse, and increased STAT1 activation in HF keratinocytes. Our study highlights a role for AIRE in HF biology and shows that Aire^‒/‒ mice may serve as a valuable model system to study AA pathogenesis.

Recent advances in the genetics of alopecia areata

Alopecia areata (AA) is a common autoimmune-mediated hair loss disorder in humans with an estimated lifetime risk of approximately 2 %. Episodes of hair loss usually begin with isolated hairless patches that may progress to complete hair loss over the entire body. A familial occurrence of AA is well established, with recurrence risks of about 6-8 % in first-degree relatives. AA is a multifactorial disorder involving both environmental and genetic risk factors. Previous research has identified 14 susceptibility loci, most of which implicate genes involved in the immune response. The following review presents a summary of the latest findings from genome-wide association, sequencing and gene expression studies of AA, as well as their contribution to the recent therapeutic developments.

Alopecia areata and risk of atopic and autoimmune conditions: population-based cohort study

BACKGROUND

Alopecia areata (AA) has features of both autoimmune and atopic pathogenesis, but information on the risk of people with AA developing autoimmune and atopic conditions is limited.

OBJECTIVE

To assess the prevalence and incidence of atopic and autoimmune conditions in people with AA.

METHODS

This was a population-based cohort study of 8051 adults with newly diagnosed AA (AA group) and 32 204 adults in the matched control group, using the UK Oxford-Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) network primary care database, 2009-2018 (trial registration number: NCT04239521). Baseline prevalence of common atopic and autoimmune conditions, and risk of new-onset atopic and autoimmune disease, were estimated.

RESULTS

Atopic and autoimmune conditions were more prevalent in the AA group than the control group (atopic 37.2% vs. 26.7%, autoimmune 11.5% vs. 7.9%). The AA group were 43% more likely to develop any new-onset atopic condition [adjusted hazard ratio (aHR) 1.43. 95% confidence interval (CI) 1.28-1.61] and 45% more likely to develop any autoimmune condition (aHR 1.45, 95% CI 1.28-1.66) compared with the control group. When examining individual conditions, the AA group were at increased risk of atopic dermatitis (aHR 1.91, 95% CI 1.67-2.19), allergic rhinitis (aHR 1.32, 95% CI 1.14-1.54), autoimmune hypothyroidism (aHR 1.65, 95% CI 1.35-2.02), systemic lupus erythematosus (aHR 4.51, 95% CI 1.88-10.82) and vitiligo (aHR 2.39, 95% CI 1.49-3.82). There was no evidence for a higher incidence of other conditions examined.

CONCLUSION

People with AA have an increased burden of atopic and autoimmune comorbidity. This supports previous work suggesting that both T helper cell (Th)1 and Th2 immune responses may be implicated in the pathogenesis of AA.

Involvement of ILC1-like innate lymphocytes in human autoimmunity, lessons from alopecia areata

Here, we have explored the involvement of innate lymphoid cells-type 1 (ILC1) in the pathogenesis of alopecia areata (AA), because we found them to be significantly increased around lesional and non-lesional HFs of AA patients. To further explore these unexpected findings, we first co-cultured autologous circulating ILC1-like cells (ILC1lc) with healthy, but stressed, organ-cultured human scalp hair follicles (HFs). ILClc induced all hallmarks of AA ex vivo: they significantly promoted premature, apoptosis-driven HF regression (catagen), HF cytotoxicity/dystrophy, and most important for AA pathogenesis, the collapse of the HFs physiological immune privilege. NKG2D-blocking or IFNγ-neutralizing antibodies antagonized this. In vivo, intradermal injection of autologous activated, NKG2D+/IFNγ-secreting ILC1lc into healthy human scalp skin xenotransplanted onto SCID/beige mice sufficed to rapidly induce characteristic AA lesions. This provides the first evidence that ILC1lc, which are positive for the ILC1 phenotype and negative for the classical NK markers, suffice to induce AA in previously healthy human HFs ex vivo and in vivo, and further questions the conventional wisdom that AA is always an autoantigen-dependent, CD8 +T cell-driven autoimmune disease.

Platelet-rich plasma in alopecia areata and primary cicatricial alopecias: A systematic review

Background

Immune-mediated alopecias (IMAs), a group of hair disorders associated with immunological reactions, remain a therapeutic challenge since available treatments are generally unfavorable with potential side effects. Platelet-rich plasma (PRP) has been recently proposed as a treatment option based on several limited-quality studies; however, there is no systematic evaluation of PRP efficacy on IMAs in the literature.

Objective

To assess PRP's effects in treating IMAs using a systematic review.

Methods

Electronic searches were conducted using PubMed, Embase, Scopus, and Cochrane Library databases. A search strategy was designed to retrieve all studies exploring PRP in treating IMAs, including alopecia areata (AA) and primary cicatricial alopecias (PCAs). In addition, all randomized and non-randomized studies reporting subjective and/or objective outcomes of alopecia treatment with PRP were included.

Results

Thirty-two studies were included, comprising 621 patients with AA and 19 patients with PCAs. PRP had superior efficacy as monotherapy in five studies, comparable to intralesional corticosteroids in six studies in AA treatment. In addition, in the analysis of PCAs, including lymphocytic and neutrophilic subtypes, PRP was efficacious in alleviating disease progression in nine studies.

Conclusion

PRP is considered a promising treatment for AA and PCAs in patients who experienced unfavorable outcomes from conventional treatment. However, its clinical application remains to be standardized, and its recommendation as a treatment for IMAs could not be ascertained due to a lack of high-quality evidence.

Systematic review registration

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=353859], identifier [CRD42022353859].

Effects of Natural Polyphenols on Skin and Hair Health: A Review

The skin is the largest organ of the body and plays multiple essential roles, ranging from regulating temperature, preventing infections, to ultimately affecting human health. A hair follicle is a complex cutaneous appendage. Skin diseases and hair loss have a significant effect on the quality of life and psychosocial adjustment of individuals. However, the available traditional drugs for treating skin and hair diseases may have some insufficiencies; therefore, a growing number of researchers are interested in natural materials that could achieve satisfactory results and minimize adverse effects. Natural polyphenols, named for the multiple phenolic hydroxyl groups in their structures, are promising candidates and continue to be of scientific interest due to their multifunctional biological properties and safety. Polyphenols have a wide range of pharmacological effects. In addition to the most common effect, antioxidation, polyphenols have anti-inflammatory, bacteriostatic, antitumor, and other biological effects associated with reduced risk of a number of chronic diseases. Various polyphenols have also shown efficacy against different types of skin and hair diseases, both in vitro and in vivo, via different mechanisms. Thus, this paper reviews the research progress in natural polyphenols for the protection of skin and hair health, especially focusing on their potential therapeutic mechanisms against skin and hair disorders. A deep understanding of natural polyphenols provides a new perspective for the safe treatment of skin diseases and hair loss.

How Our Microbiome Influences the Pathogenesis of Alopecia Areata

Alopecia areata is a multifactorial autoimmune-based disease with a complex pathogenesis. As in all autoimmune diseases, genetic predisposition is key. The collapse of the immune privilege of the hair follicle leading to scalp loss is a major pathogenic event in alopecia areata. The microbiota considered a bacterial ecosystem located in a specific area of the human body could somehow influence the pathogenesis of alopecia areata, as it occurs in other autoimmune diseases. Moreover, the Next Generation Sequencing of the 16S rRNA bacterial gene and the metagenomic methodology have provided an excellent characterization of the microbiota. The aim of this narrative review is to examine the published literature on the cutaneous and intestinal microbiota in alopecia areata to be able to establish a pathogenic link. In this review, we summarize the influence of the microbiota on the development of alopecia areata. We first introduce the general pathogenic mechanisms that cause alopecia areata to understand the influence that the microbiota may exert and then we summarize the studies that have been carried out on what type of gut and skin microbiota is found in patients with this disease.

The First Evidence of Bacterial Foci in the Hair Part and Dermal Papilla of Scalp Hair Follicles: A Pilot Comparative Study in Alopecia Areata

The role of the microbiome in hair follicle (HF) growth represents a growing field of research. Here, we studied the bacterial population in the scalp hair follicles of subjects with alopecia areata (AA). Two Healthy and two AA subjects, respectively (20−60 years old), were enrolled and studied regarding the microbial community in the subepidermal scalp compartments by means of a 4-mm biopsy punch. Samples were examined by 16S sequencing, histochemical staining (Gram’s method), and transmission electron microscopy (TEM). Bacterial foci were observed in the AA subjects’ follicles with both the two adopted complementary approaches (electron microscopy and Gram staining). Significant (p < 0.05) differences were also found in the three-layer biopsy samples (p < 0.05) regarding the bacterial population. In particular, in the deep epidermis and dermis levels, a significant (p < 0.05) lower abundance of Firmicutes and a higher abundance of Proteobacteria were found in AA samples compared to the healthy control. Firmicutes also showed a significant (p < 0.05) lower abundance in hypodermis in AA subjects. In addition, Enterobacteriaceae and the genera Streptococcus, Gemella, Porphyromonas, and Granulicatella were relatively more abundant in AA groups at the deep epidermis level. The Staphylococcus and Flavobacterium genera were significantly less abundant in AA samples than in controls in all three-layer biopsy samples (p < 0.05). In contrast, Veillonella and Neisseriaceae were relatively more abundant in the healthy control group compared to the AA sample. Therefore, higher alpha diversity was observed in all three-layer biopsy samples of AA patients compared to the control. In conclusion, our data suggest that tAA could be defined as a “hair disease associated with dysregulated microbiome-immunity axis of hair follicles”.

Lichen Planopilaris: The first biopsy layer microbiota inspection

Lichen Planopilaris (LPP) is a lymphatic disease affecting the scalp that is characterized by a chronic and destructive inflammation process, named as ‘cicatricial alopecia’ in which the hair follicles are targeted and may involve predominantly lymphocytes or neutrophils. Scalp and biopsy layers have never been used to investigate microbial community composition and its relative taxa abundances in LPP. We sought to examine the significant taxa of this chronic relapsing inflammatory skin disease, together with inspect the existing connections with metabolic pathways featuring this microbial community. We used a multilevel analysis based on 16S rRNA marker sequencing in order to detect OTU abundances in pathologic/healthy samples, real time PCR for measuring the levels of IL-23 interleukin expression and urinary metabolomics to find out volatile organic metabolites (VOMs). By using a linear regression model, we described peculiar taxa that significantly differentiated LPP and healthy samples. We inspected taxa abundances and interleukin mRNA levels and the Microbacteriaceae family resulted negatively correlated with the IL-23 expression. Moreover, starting from 16S taxa abundances, we predicted the metabolic pathways featuring this microbial community. By inspecting microbial composition, sample richness, metabolomics profiles and the relative metabolic pathways in a cohort of LPP and healthy samples we deepened the contribution of significant taxa that are connected to inflammation maintenance and microbiota plasticity in LPP pathology.

Regulation and dysregulation of hair regeneration: aiming for clinical application

Hair growth and regeneration represents a remarkable example of stem cell function. Recent progress emphasizes the micro- and macro- environment that controls the regeneration process. There is a shift from a stem cell-centered view toward the various layers of regulatory mechanisms that control hair regeneration, which include local growth factors, immune and neuroendocrine signals, and dietary and environmental factors. This is better suited for clinical application in multiple forms of hair disorders: in male pattern hair loss, the stem cells are largely preserved, but androgen signaling diminishes hair growth; in alopecia areata, an immune attack is targeted toward the growing hair follicle without abrogating its regeneration capability. Genome-wide association studies further revealed the genetic bases of these disorders, although the precise pathological mechanisms of the identified loci remain largely unknown. By analyzing the dysregulation of hair regeneration under pathological conditions, we can better address the complex interactions among stem cells, the differentiated progeny, and mesenchymal components, and highlight the critical role of macroenvironment adjustment that is essential for hair growth and regeneration. The poly-genetic origin of these disorders makes the study of hair regeneration an interesting and challenging field.

The delicate relation between melanocytes and skin immunity: A game of hide and seek

Melanocytes exhibit a complex and intriguing relationship with the skin immune response, leading to several clinical conditions. In some disorders, inappropriate melanocyte destruction (e.g., vitiligo, halo naevi) is problematic, while in others, immune tolerance should be broken (melanoma). Important parts of the dysregulated pathways have been unraveled in pigment disorders, ranging from upregulated interferon (IFN)-γ signaling to memory T cells, regulatory T cells, and immune checkpoints. Although a network of many factors is involved, targeting key players such as IFN-γ or checkpoint inhibitors (e.g., programmed death-ligand 1 (PD-L1)] can shift the balance and lead to impressive outcomes. In this review, we focus on the immunological mechanisms of the most common inflammatory disorders where the interaction of the immune system with melanocytes plays a crucial role. This can provide new insights into the current state of melanocyte research.

Translational impact of omics studies in alopecia areata: recent advances and future perspectives

INTRODUCTION

Alopecia areata (AA) is a non-scarring, hair loss disorder and a common autoimmune-mediated disease with an estimated lifetime risk of about 2%. To date, the treatment of AA is mainly based on suppression or stimulation of the immune response. Genomics and transcriptomics studies generated important insights into the underlying pathophysiology, enabled discovery of molecular disease signatures, which were used in some of the recent clinical trials to monitor drug response and substantiated the consideration of new therapeutic modalities for the treatment of AA such as abatacept, dupilumab, ustekinumab and Janus Kinase (JAK) inhibitors.

AREAS COVERED

In this review, genomics and transcriptomics studies in AA are discussed in detail with particular emphasis on their past and prospective translational impacts. Microbiome studies are also briefly introduced.

EXPERT OPINION

The generation of large datasets using the new high-throughput technologies has revolutionized medical research and AA has also benefited from the wave of omics studies. However, the limitations associated with JAK inhibitors and clinical heterogeneity in AA patients underscore the necessity for continuing omics research in AA for discovery of novel therapeutic modalities and development of clinical tools for precision medicine.

CCL27 is a crucial regulator of immune homeostasis of the skin and mucosal tissues

Abundant immune cells reside in barrier tissues. Understanding the regulation of these cells can yield insights on their roles in tissue homeostasis and inflammation. Here, we report that the chemokine CCL27 is critical for establishment of resident lymphocytes and immune homeostasis in barrier tissues. CCL27 expression is associated with normal skin and hair follicle development independent of commensal bacterial stimulation, indicative of a homeostatic role for the chemokine. Accordingly, in the skin of CCL27-knockout mice, there is a reduced presence and dysregulated localization of T cells that express CCR10, the cognate receptor to CCL27. Besides, CCL27-knockout mice have overreactive skin inflammatory responses in an imiquimod-induced model of psoriasis. Beyond the skin, CCL27-knockout mice have increased infiltration of CCR10⁺ T cells into lungs and reproductive tracts, the latter of which also exhibit spontaneous inflammation. Our findings demonstrate that CCL27 is critical for immune homeostasis across barrier tissues.

Autoantigen Discovery in the Hair Loss Disorder, Alopecia Areata: Implication of Post-Translational Modifications

Alopecia areata (AA) is a chronic, multifactorial, polygenic, and heterogeneous disorder affecting growing hair follicles in susceptible individuals, which results in a non-scarring and reversible hair loss with a highly unpredictable course. Despite very considerable research effort, the nature of the precipitating factor(s) responsible for initiating AA in any given hair follicle remains unclear, due largely to significant gaps in our knowledge of the precise sequence of the etiopathogenic events in this dermatosis. However, disease-related changes in the immune-competence of the lower growing hair follicle, together with an active immune response (humoral and cellular) to hair follicle-associated antigens, are key associated phenomena. Confirmation of the hair follicle antigen(s) implicated in AA disease onset has remained stubbornly elusive. While it may be considered somewhat philosophical by some, it is also unclear whether immune-mediated hair loss in AA results from a) an ectopic (i.e., in an abnormal location) immune response to native (unmodified) self-antigens expressed by the healthy hair follicle, b) a normal immune response against modified self-antigens (or neoantigens), or c) a normal immune response against self-antigens (modified/non-modified) that were not previously visible to the immune system (because they were conformationally-hidden or sequestered) but become exposed and presentable in an MHC-I/-II molecule-restricted manner. While some candidate hair follicle antigen target(s) in AA are beginning to emerge, with a potential role for trichohyalin, it is not yet clear whether this represents the initial and immunodominant antigenic focus in AA or is simply one of an expanding repertoire of exposed hair follicle tissue damage-associated antigens that are secondary to the disease. Confirmation of autoantigen identity is essential for our understanding of AA etiopathogenesis, and consequently for developing a more informed therapeutic strategy. Major strides have been made in autoantigen discovery in other autoimmune conditions. In particular, some of these conditions may provide insights into how post-translational modifications (e.g., citrullination, deamidation, etc.) of hair follicle-restricted proteins may increase their antigenicity and so help drive the anti-hair follicle immune attack in AA.

Immune-mediated alopecias and their mechanobiological aspects

Alopecia is a non-specific term for hair loss clinically diagnosed by the hair loss pattern and histological analysis of patient scalp biopsies. The immune-mediated alopecia subtypes, including alopecia areata, lichen planopilaris, frontal fibrosing alopecia, and central centrifugal cicatricial alopecia, are common, significant forms of alopecia subtypes. For example, alopecia areata is the most common autoimmune disease with a lifetime incidence of approximately 2% of the world's population. In this perspective, we discuss major results from studies of immune-mediated alopecia subtypes. These studies suggest the key event in disease onset as the collapse in immune privilege, which alters the hair follicle microenvironment, e.g., upregulation of major histocompatibility complex molecules and increase of cytokine production, and results in immune cell infiltration, inflammatory responses, and damage of hair follicles. We note that previous studies have established that the hair follicle has a complex mechanical microenvironment, which may regulate the function of not only tissue cells but also immune cell infiltrates. This suggests a potential for mechanobiology to contribute to alopecia research by adding new methods, new approaches, and new ways of thinking, which is missing in the existing literature. To fill this a gap in the alopecia research space, we develop a mechanobiological hypothesis that alterations in the hair follicle microenvironment, specifically in the mechanically responsive tissues and cells, partially due to loss of immune privilege, may be contributors to disease pathology. We further focus our discussion on the potential for applying mechanoimmunology to the study of T cell infiltrates in the hair follicle, as they are considered primary contributors to alopecia pathology. To establish the connection between the mechanoimmunological hypothesis and immune-mediated alopecia subtypes, we discuss what is known about the role of T cells in immune-mediated alopecia subtypes, using the most extensively studied AA as our model.

Topical immunotherapy treatment of alopecia areata with diphenylcyclopropenone: regulatory T cells as biomarkers for treatment response

Treatment of alopecia areata is often challenging, especially for patients with extended disease. Contact immunotherapy with diphenylcyclopropenone (DPCP) has been reported as an effective topical treatment but the exact immunologic mechanism of diverting the immune response is still unknown. We investigated the efficacy of topical immunotherapy with DPCD in acute, intermediate, and chronic lesions of AA and the response rate was associated with perifollicular infiltrate of T regulatory cells. Approximately two-thirds of our patients (67.5%) had a response rate > 50% after 6 months of DPCP therapy. Patients with acute and intermediate onset of the disease were more likely to respond to the therapy. Although responders demonstrated FOXP3+ positive lymphocytes in immunohistochemistry, this association could not be confirmed by statistical significance (p = 0.052). In patients with multiple lesions, that had different chronological onset, the lesions with more recent onset responded faster than lesions of longer duration. This article is protected by copyright. All rights reserved.

CD4, CD8 and natural killer cells are depressed in patients with alopecia areata: their association with disease activity

BACKGROUND

Alopecia areata (AA) is a common inflammatory disorder targeting the hair follicles leading to non-scaring hair loss. The pathogenesis of AA is still unclear, despite the accumulating evidence of the immune-mediated nature of this disease. So, in this study, we aimed to assess the level of CD4 T cells, CD8 T cells and natural killer (NK) cells in the peripheral blood of patients with active AA and control subjects, and to evaluate the association between the level of those cells and the duration of disease in different subtypes of AA.

RESULTS

Fifty female patients and 50 age- and sex-matched healthy controls were enrolled in this case control study. CBC analysis and the level of CD4, CD8 T cells and NK cells were evaluated during the active stage of the disease. We found that CD4, CD8 T cells and NK cells proportion was significantly lower (P < 0.05) in patients with active stage AA compared with healthy subjects, however, the ratio of CD4:CD8 T cells was significantly higher in patients than control subjects. The level of CD4, CD8 T cells CD56 bright CD16^- % NK cells were positively correlated with the disease duration.

CONCLUSION

Active stage of AA disease is associated with a reduction of the circulating CD4, CD8 T cells and NK cells and an increase in CD4/CD8 T cells ratio, however, the level of those cells were higher with prolonged disease duration. Our findings confirm that immune mechanisms are involved in the pathogenesis of AA.

Alopecia areata - Current understanding and management

Alopecia areata (AA) is a chronic, immune-mediated disease characterized by acute or chronic non-scarring hair loss, with a heterogeneity in clinical manifestations ranging from patchy hair loss to complete scalp and body hair loss. An overview of the up-to-date pathophysiology and the underlying signaling pathways involved in AA together with diagnostic and therapeutic recommendations will be provided. Current treatments, including topical, systemic and injectable interventions show varying response and frequent relapses reflecting the unmet clinical need. Thus, the new emerging concepts and therapeutic approaches, including Janus kinase inhibitors are eagerly awaited. Traditional and emerging therapies of AA will be discussed, in order to provide physicians with guidance for AA management. Since the latter is so challenging and often tends to take a chronic course, it can have an enormous psychosocial burden on patients, compromising their quality of life and often causing depression and anxiety. Therefore, the psychosocial aspects of the disease need to be evaluated and addressed, in order to implement appropriate psychological support when needed.