Early stage alopecia areata is associated with inflammation in the upper dermis and damage to the hair follicle infundibulum

Current Protocols: Alopecia Areata Mouse Models for Drug Efficacy and Mechanism Studies

Alopecia areata is the second most common form of hair loss in humans after androgenetic alopecia. Although a variety of animal models for alopecia areata have been described, currently the C3H/HeJ mouse model is the most commonly used and accepted. Spontaneous hair loss occurs in 15%-25% of older mice in which the lesions wax and wane, similar to the human disease, with alopecia being more common and severe in female mice. Full-thickness skin grafts from mice with spontaneous alopecia areata to young, normal-haired, histocompatible mice provide a highly reproducible model with progressive lesions that makes it useful for drug efficacy and mechanism-based studies. As alopecia areata is a cell-mediated autoimmune disease, transfer of cultured lymph node cells from affected mice to unaffected, histocompatible recipients also promotes disease development and provides an alternative, nonsurgical protocol. Protocols are presented to produce these models such that they can be used to study alopecia areata and to develop novel drug therapies. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Full-thickness skin grafts to reproducibly induce alopecia areata in C3H/HeJ mice Basic Protocol 2: Adoptive transfer of cultured lymphoid cells provides a nonsurgical method to induce alopecia areata in C3H/HeJ mice.

Dupilumab induces hair regrowth in pediatric alopecia areata: a real-world, single-center observational study

Alopecia areata (AA) is nonscarring hair loss characterized by Th1 and concomitant Th2 skewing, particularly in atopic patients. Despite novel developments for adult AA, safe and effective treatments for pediatric patients remain limited. Dupilumab, with a well-studied safety profile, may have therapeutic potential for atopic pediatric AA. To evaluate the ability of dupilumab to regrow hair in pediatric AA patients. We conducted a single-center, retrospective, observational study to evaluate hair regrowth [using Severity of Alopecia Tool (SALT)] with dupilumab in 20 children with both AD and AA (age range 5-16 years, mean 10.8 years; baseline SALT range 3-100, mean 54.4). Patient demographics, atopic history, IgE and SALT scores were collected at 12wk follow-up visits, up to > 72wks, to evaluate hair regrowth. Spearman correlations with clinical data were performed. Patients showed clinical improvement over the follow-up period (range 24 to > 72wks, mean 67.6wks) with significant mean(± SD) reduction in SALT at 48wks versus baseline [20.4(± 35.1) vs 54.4(± 37.6), respectively; p < 0.01] and continued improvement up to > 72wks [2.2(± 4.9), p < 0.01]. Baseline SALT positively correlated with disease duration (r = 0.54, p < 0.01), and negatively correlated with improvement in SALT at weeks 24, 36, and 48 (|r|≥ 0.65, p < 0.01 for all comparisons). Baseline IgE positively correlated with improvement in SALT at week 36 (r > 0.60, p < 0.05). Dupilumab was well-tolerated, with no new safety concerns. These real-world data support the utility of dupilumab to safely treat pediatric AA patients, corroborating the role of Th2 skewing in children with AA and associated atopy, warranting larger clinical trials.

Modeling of solar UV-induced photodamage on the hair follicles in human skin organoids

Solar ultraviolet (sUV) exposure is known to cause skin damage. However, the pathological mechanisms of sUV on hair follicles have not been extensively explored. Here, we established a model of sUV-exposed skin and its appendages using human induced pluripotent stem cell-derived skin organoids with planar morphology containing hair follicles. Our model closely recapitulated several symptoms of photodamage, including skin barrier disruption, extracellular matrix degradation, and inflammatory response. Specifically, sUV induced structural damage and catagenic transition in hair follicles. As a potential therapeutic agent for hair follicles, we applied exosomes isolated from human umbilical cord blood-derived mesenchymal stem cells to sUV-exposed organoids. As a result, exosomes effectively alleviated inflammatory responses by inhibiting NF-κB activation, thereby suppressing structural damage and promoting hair follicle regeneration. Ultimately, our model provided a valuable platform to mimic skin diseases, particularly those involving hair follicles, and to evaluate the efficacy and underlying mechanisms of potential therapeutics.

Effects of the Complex of Panicum miliaceum Extract and Triticum aestivum Extract on Hair Condition

Proso millet (Panicum miliaceum L.) and common wheat (Triticum aestivum L.) have been used as major crops in multiple regions since ancient times, and they contain various nutrients that can affect human hair health. This study investigated the various biological effects of a complex of millet extract and wheat extract (MWC) on hair health. Human immortalized dermal papilla cells (iDPCs) for an in vitro study and an anagen-synchronized mouse model for an in vivo study were employed. These findings revealed that the application of the MWC in vitro led to an increase in the mRNA levels of antioxidant enzymes (catalase and SOD1), growth factors (IGF-1, VEGF, and FGF7), and factors related to hair growth (wnt10b, β-catenin) while decreasing inflammatory cytokine mRNA levels (IL-6 and TNFα). The mRNA levels of hair follicles (HFs) in the dorsal skin of the mouse model in the early and late telogen phases were also measured. The mRNA levels in the in vivo study showed a similar alteration tendency as in the in vitro study in the early and late telogen phases. In this model, MWC treatment elongated the anagen phase of the hair cycle. These findings indicate that the MWC can suppress oxidative stress and inflammation and may elongate the anagen phase by enhancing the growth factors involved in the wnt10b/β-catenin signaling pathway. This study suggests that the MWC might have significant potential as a functional food for maintaining hair health.

Integrative and Mechanistic Approach to the Hair Growth Cycle and Hair Loss

The hair cycle is composed of four primary phases: anagen, catagen, telogen, and exogen. Anagen is a highly mitotic phase characterized by the production of a hair shaft from the hair follicle, whereas catagen and telogen describe regression and the resting phase of the follicle, respectively, ultimately resulting in hair shedding. While 9% of hair follicles reside in telogen at any time, a variety of factors promote anagen to telogen transition, including inflammation, hormones, stress, nutritional deficiency, poor sleep quality, and cellular division inhibiting medication. Conversely, increased blood flow, direct stimulation of the hair follicle, and growth factors promote telogen to anagen transition and subsequent hair growth. This review seeks to comprehensively describe the hair cycle, anagen and telogen balance, factors that promote anagen to telogen transition and vice versa, and the clinical utility of a variety of lab testing and evaluations. Ultimately, a variety of factors impact the hair cycle, necessitating a holistic approach to hair loss.

Infiltration of Mast Cells in Scalp Biopsies of Patients with Alopcia Areata or Androgenic Alopecia Versus Healthy Individuals: A Case Control Study

BACKGROUND

Alopecia areata (AA) and androgenic alopecia (AGA) are of the most common types of alopecias. Recently, the role of mastcells in inflammatory diseases has become the focus of many studies. However, few studies have been conducted on their role in AA and AGA. Therefore, our study aimed to quantitatively evaluate the presence of mastcells in the AA and AGA specimens.

MATERIALS AND METHODS

Three groups of AA, AGA, and healthy control were studied (each group with 20 subjects). Patients were randomly selected from those referred to the dermatology clinics of Shahid Beheshti University. Specimens were obtained from the scalp, and perifollicular and perivascular areas were investigated.

RESULTS

Significantly higher perifollicular and perivascular mastcell counts were seen in both AGA and AA groups as compared to healthy control (P<0.001 for both). Moreover, AA patients had more frequent perivascular mastcells than the AGA group (P=0.042). Among patients aged <40 years, perifollicular and perivascular mastcell counts were not significantly different among three groups; however, subjects over 40 years of age in both groups had significantly more perifollicular and perivascular mastcells than healthy participants. There was a significant positive correlation between disease severity and mast cell counts in both perifollicular and perivascular areas in AA patients (P=0.001 for both).

CONCLUSION

There is a significantly increased infiltration of mastcells in AA and AGA patients, and this increase is age and severity dependent. Moreover, the increase in mastcell proliferation is more dominant in AA patients.

Assessment of Prolonged Dengue Virus Infection in Dermal Fibroblasts and Hair-Follicle Dermal Papilla Cells

Dengue virus (DENV)-mediated hair loss is one of the post-dengue fatigue syndromes and its pathophysiology remains unknown. Whether long-term or persistent infection with DENV in the scalp results in hair loss is unclear. In this study, we cultured human dermal fibroblasts (WS1 cells) and primary human hair-follicle dermal papilla cells (HFDPCs) in the long term with DENV-2 infection. The production of virion, the expression of inflammatory and anti-virus genes, and their signaling transduction activity in the infected cells were analyzed. DENV-2 NS3 protein and DENV-2 5′ UTR RNA were detected in fibroblasts and HFDPCs that were subjected to long-term infection with DENV-2 for 33 days. A significant amount of DENV-2 virion was produced by both WS1 cells and HFDPCs in the first two days of acute infection. The virion was also detected in WS1 cells that were infected in the long term, but HFDPCs failed to produce DENV-2 after long-term culture. Type I and type III interferons, and inflammatory cytokines were highly expressed in the acute phase of DENV infection in HFPDC and WS1 cells. However, in the long-term cultured cells, modest levels of anti-viral protein genes were expressed and we observed reduced signaling activity, which was correlated with the level of virus production changes. Long-term infection of DENV-2 downregulated the expression of hair growth regulatory factors, such as Rip1, Wnt1, and Wnt4. This in vitro study shows that the long-term infection with DENV-2 in dermal fibroblasts and dermal papilla cells may be involved with the prolonged-DENV-infection-mediated hair loss of post-dengue fatigue syndrome. However, direct evidence for viral replication in the human hair of a dengue victim or animal infection model is required.

Allergy promotes alopecia areata in a subset of patients

In this commentary, we focus on allergy as a facilitating factor in the pathogenesis of alopecia areata (AA). From previous studies on AA, it is well known that subsets of patients can have one or more of; seasonal relapse, comorbid atopic rhinitis, asthma and dermatitis, lesion infiltrating eosinophils and plasma cells, high levels of total IgE, specific IgE for house dust mites (HDMs), and/or disrupted skin barrier function by the evaluation of filaggrin. Allergy and AA share a similar genetic background; both contributing to an immune reaction imbalance. Furthermore, adjunctive treatment with antihistamines, or desensitization for HDM, can reduce the severity of alopecia in atopic AA patients. Therefore, allergies may contribute to the onset and relapse of AA. Identification of an allergic or atopic immune component in AA patient subsets may indicate adjunctive treatment intervention measures against allergies should be taken which may improve the success of conventional AA treatment.

Sequential cyclic changes of hair roots revealed by dermoscopy demonstrate a progressive mechanism of diffuse alopecia areata over time

BACKGROUND

Diffuse alopecia areata (DAA) often leads to a complete hair shedding within a few months.

OBJECTIVE

To explore features and mechanisms underlying DAA.

MATERIALS AND METHODS

Scalp and hair root dermoscopy were conducted on 23 DAA patients throughout the disease process, 20 patchy Alopecia areata patients, 23 acute telogen effluvium (ATE) patients and 10 normal controls. Histopathology was also evaluated.

RESULTS

We found almost all hair roots were anagen in early stage DAA in 18 patients (18/23, 78.3%) within the first 4-8 weeks after hair loss onset. Anagen effluvium (~4 weeks) was followed by catagen (~4 weeks) and then telogen/exogen (~8 weeks) effluvium with overlap. Hair root and proximal hair shaft depigmentation was more prominent in later DAA disease stages. Black dots, exclamation mark hairs and inconsistent thickness of hair shafts were found more often in early than later DAA (Ps < 0.01). Early DAA histopathology revealed more prominent inflammation and hair follicle regression than that observed in the later stages. Patchy alopecia areata patients showed mixed anagen, catagen and telogen hair roots while ATE patients showed increased exogen and mildly decreased hair root pigmentation.

CONCLUSION

Sequential cyclic staging of shed hairs in DAA indicates the insult may be hair-cycle specific. We suggest that DAA is initially an anagen effluvium disease involving an intense inflammatory insult, later progressing to a brief catagen effluvium, and then to telogen effluvium with premature exogen, in later stages of DAA.

iNOS inhibits hair regeneration in obese diabetic (ob/ob) mice

Previous studies have shown that androgenic alopecia is associated with metabolic syndrome and diabetes. However, the detailed mechanism whereby diabetes causes alopecia still remains unclear. We focused on the inflammatory response that is caused by diabetes or obesity, given that inflammation is a risk factor for hair loss. Inducible nitric oxide synthase (iNOS) is known to be upregulated under conditions of acute or chronic inflammation. To clarify the potential role of iNOS in diabetes-related alopecia, we generated obese diabetic iNOS-deficient (ob/ob; iNOS-KO mice). We observed that ob/ob; iNOS-KO mice were potentiated for the transition from telogen (rest phase) to anagen (growth phase) in the hair cycle compared with iNOS-proficient ob/ob mice. To determine the effect of nitric oxide (NO) on the hair cycle, we administered an iNOS inhibitor intraperitoneally (compound 1400 W, 10 mg/kg) or topically (10% aminoguanidine) in ob/ob mice. We observed that iNOS inhibitors promoted anagen transition in ob/ob mice. Next, we administered an NO donor (S-nitrosoglutathione, GSNO), to test whether NO has the telogen elongation effects. The NO donor was sufficient to induce telogen elongation in wild-type mice. Together, our data indicate that iNOS-derived NO plays a role in telogen elongation under the inflammatory conditions associated with diabetes in mice.

Identification of Autoantigen Epitopes in Alopecia Areata

Alopecia areata (AA) is believed to be a cell-mediated autoimmune hair loss disease. Both CD4 and cytotoxic CD8 T cells (CTLs) are important for the onset and progression of AA. Hair follicle (HF) keratinocyte and/or melanocyte antigen epitopes are suspected potential targets of autoreactive CTLs, but the specific epitopes have not yet been identified. We investigated the potential for a panel of known epitopes, expressed by HF keratinocytes and melanocytes, to induce activation of CTL populations in peripheral blood mononuclear cells. Specific synthetic epitopes derived from HF antigens trichohyalin and tyrosinase-related protein-2 induced significantly higher frequencies of response in AA CTLs compared with healthy controls (IFN-gamma secretion). Apoptosis assays revealed conditioned media from AA peripheral blood mononuclear cells stimulated with trichohyalin peptides elevated the expression of apoptosis markers in primary HF keratinocytes. A cytokine array revealed higher expression of IL-13 and chemokine ligand 5 (CCL5, RANTES) from AA peripheral blood mononuclear cells stimulated with trichohyalin peptides compared with controls. The data indicate that AA affected subjects present with an increased frequency of CTLs responsive to epitopes originating from keratinocytes and melanocytes; the activated CTLs secreted soluble factors that induced apoptosis in HF keratinocytes. Potentially, CTL response to self-antigen epitopes, particularly trichohyalin epitopes, could be a prognostic marker for human AA.

The role of lymphocytes in the development and treatment of alopecia areata

Alopecia areata (AA) development is associated with both innate and adaptive immune cell activation, migration to peri- and intra-follicular regions, and hair follicle disruption. Both CD4(+) and CD8(+) lymphocytes are abundant in AA lesions; however, CD8(+) cytotoxic T lymphocytes are more likely to enter inside hair follicles, circumstantially suggesting that they have a significant role to play in AA development. Several rodent models recapitulate important features of the human autoimmune disease and demonstrate that CD8(+) cytotoxic T lymphocytes are fundamentally required for AA induction and perpetuation. However, the initiating events, the self-antigens involved, and the molecular signaling pathways, all need further exploration. Studying CD8(+) cytotoxic T lymphocytes and their fate decisions in AA development may reveal new and improved treatment approaches.

Alopecia areata profiling shows TH1, TH2, and IL-23 cytokine activation without parallel TH17/TH22 skewing

BACKGROUND

Alopecia areata (AA) is a common T cell-mediated disorder with limited therapeutics. A molecular profile of cytokine pathways in AA tissues is lacking. Although studies have focused on TH1/IFN-γ responses, several observations support a shared genetic background between AA and atopy.

OBJECTIVE

We sought to define the AA scalp transcriptome and associated biomarkers with comparisons with atopic dermatitis (AD) and psoriasis.

METHODS

We performed microarray and RT-PCR profiling of 27 lesional and 17 nonlesional scalp samples from patients with AA for comparison with normal scalp samples (n = 6). AA gene expression was also compared with samples from patients with lesional or nonlesional AD and those with psoriasis. A fold change of greater than 1.5 and a false discovery rate of less than 0.05 were used for differentially expressed genes (DEGs).

RESULTS

We established the AA transcriptomes (lesional vs nonlesional: 734 DEGs [297 upregulated and 437 downregulated]; lesional vs normal: 4230 DEGs [1980 upregulated and 2250 downregulated]), including many upregulated immune and downregulated hair keratin genes. Equally impressive as upregulation in TH1/interferon markers (IFNG and CXCL10/CXCL9) were those noted in TH2 (IL13, CCL18, CCL26, thymic stromal lymphopoietin, and periostin), TH9/IL-9, IL-23 (p40 and p19), and IL-16 mediators (all P < .05). There were no increases in TH17/TH22 markers. Hair keratin (KRT) expressions (ie, KRT86 and KRT85) were significantly suppressed in lesional skin. Greater scalp involvement (>25%) was associated with greater immune and keratin dysregulation and larger abnormalities in nonlesional scalp samples (ie, CXCL10 and KRT85).

CONCLUSIONS

Our data associate the AA signature with TH2, TH1, IL-23, and IL-9/TH9 cytokine activation, suggesting consideration of anti-TH2, anti-TH1, and anti-IL-23 targeting strategies. Similar to psoriasis and AD, clinical trials with selective antagonists are required to dissect key pathogenic pathways.

Clinical observations in alopecia areata: Implications and hypotheses

Alopecia areata (AA) is a T-cell-mediated hair loss disorder but the exact cause is unknown. In this report we describe patterns of onset, regrowth and relapse in AA and propose potential underlying mechanisms. We believe that these aspects of AA require integration into modern theories of AA pathogenesis.