Endogenous retinoids in the pathogenesis of alopecia areata

Epidermal retinol dehydrogenases cyclically regulate stem cell markers and clock genes and influence hair composition

The hair follicle (HF) is a self-renewing adult miniorgan that undergoes drastic metabolic and morphological changes during precisely timed cyclic organogenesis. The HF cycle is known to be regulated by steroid hormones, growth factors and circadian clock genes. Recent data also suggest a role for a vitamin A derivative, all-trans-retinoic acid (ATRA), the activating ligand of transcription factors, retinoic acid receptors, in the regulation of the HF cycle. Here we demonstrate that ATRA signaling cycles during HF regeneration and this pattern is disrupted by genetic deletion of epidermal retinol dehydrogenases 2 (RDHE2, SDR16C5) and RDHE2-similar (RDHE2S, SDR16C6) that catalyze the rate-limiting step in ATRA biosynthesis. Deletion of RDHEs results in accelerated anagen to catagen and telogen to anagen transitions, altered HF composition, reduced levels of HF stem cell markers, and dysregulated circadian clock gene expression, suggesting a broad role of RDHEs in coordinating multiple signaling pathways.

Vitamin A resolves lineage plasticity to orchestrate stem cell lineage choices

Lineage plasticity-a state of dual fate expression-is required to release stem cells from their niche constraints and redirect them to tissue compartments where they are most needed. In this work, we found that without resolving lineage plasticity, skin stem cells cannot effectively generate each lineage in vitro nor regrow hair and repair wounded epidermis in vivo. A small-molecule screen unearthed retinoic acid as a critical regulator. Combining high-throughput approaches, cell culture, and in vivo mouse genetics, we dissected its roles in tissue regeneration. We found that retinoic acid is made locally in hair follicle stem cell niches, where its levels determine identity and usage. Our findings have therapeutic implications for hair growth as well as chronic wounds and cancers, where lineage plasticity is unresolved.

HOXB8 overexpression induces morphological changes in chicken mandibular skin: an RNA-seq analysis

The Huiyang beard chicken is a well-known Chinese local breed known for its elongated feathers gathered from both sides of the face (muffs) and below the beak (beard), as well as short wattles (SW). The muff and beard (Mb) mutation is caused by ectopic upregulation of the homeobox B8 (HOXB8) gene in the mandibular skin; and the chi-square test showed a significant correlation between SW and Mb genotypes. However, the underlying molecular mechanisms that regulate Mb and SW variations remain unclear. In this study, we investigated the transcriptomes of the mandibular skin and wattles of chickens with and without the Mb genotype to elucidate the molecular basis of these traits. Our results show that HOXB8 is expressed at significantly higher levels in both the mandibular skin and wattles of Mb chickens than in those of wild-type chickens, indicating that HOXB8 regulates both the Mb and SW phenotypes. Key genes for keratin synthesis were highly expressed in the mandibular skin of Mb chickens, suggesting that HOXB8 may play a role in feather development. In wattles, changes in the expression of extracellular matrix synthesis genes may contribute to SW traits. DNA-binding motif analyses revealed that differentially expressed genes were likely to be directly regulated by HOXB8 binding, indicating that HOXB8 may directly or indirectly regulate feather follicle development and wattle growth. Our study identified both known and novel targets, including several genes not previously implicated in feather development and mesenchymal formation. These findings provide insights into the molecular mechanisms of skin appendage variation in birds and offer potential applications in breeding poultry breeds with unique phenotypes.

Epidemiologic Study of Gene Distribution in Romanian and Brazilian Patients with Non-Cicatricial Alopecia

Background: Androgenetic alopecia (AGA) and alopecia areata (AA) are the most common types of non-cicatricial alopecia. Both diseases have limited effective therapeutic options and affect patient quality of life. Pharmacogenetic tests can help predict the most appropriate treatment option by evaluating the single nucleotide polymorphisms (SNPs) corresponding to genes related to alopecia. The objective of the study was to evaluate and compare selected SNPs and genes in AA and AGA patients from Romania and Brazil. Materials and Methods: We performed a retrospective study regarding the associations between AA and AGA and 45 tag SNPs of 15 genes in 287 Romanian and 882 Brazilian patients. The DNA samples were collected from oral mucosa using a swab. The SNPs were determined by the qPCR technique. Each genetic test displays the subject's genotype of the selected gene and the prediction of a successful treatment (e.g., genotype AA of the GR-alpha gene is related to a predisposition to normal sensibility to topical glucocorticoid, and, therefore, glucocorticoids should be effective). Results: The GR-alpha, GPR44-2, SULT1A1, and CRABP2 genes were statistically significantly different in Brazil compared to Romania. The SULT1A1 activity that predicts the response to minoxidil treatment showed in our analysis that minoxidil is recommended in half of the cases of AGA and AA. Patients with AGA and a high expression of SRD5A1 or PTGFR-2 may benefit from Dutasteride or Latanoprost treatment, respectively. Most of the studied genes showed no differences between the two populations. Conclusions: The DNA analysis of the patients with alopecia may contribute to a successful treatment.

Effects of age and sex on the comorbidities of alopecia areata: A cross-sectional hospital-based study

Background and Aims

Alopecia areata (AA) is a common autoimmune nonscarring hair disorder with strong genetic links. It seems to be associated with several comorbidities affecting the AA treatment plan. On the other hand, the prevalence of comorbidities in different populations can be different based on genetic differences. This study aimed to clarify the association between age and sex with various comorbidities in AA patients.

Methods

This cross-sectional study was conducted on 402 patients suffering from AA referred to our hospitals between 2018 and 2021. The clinical records of the patients were reviewed, including demographic and clinical information.

Results

The most common diseases associated with AA were anxiety (36%), dermatitis (30%), hypothyroidism (9%), hyperlipidemia (5%), and vitamin D deficiency (4%). The most common comorbidities in AA patients over 18 years were allergic rhinitis, psychological problems, diabetes, hypertension, and hypothyroidism (p < 0.05). Hypothyroidism was more common in female patients than in male patients (p = 0.002). In contrast, hyperlipidemia was more common in male patients than in female patients (p = 0.024). There was a significant association between the severity of AA and hyperlipidemia and vitiligo (p = 0.003 and 0.045).

Conclusion

Sex and age could affect comorbidities. The prevalence of hypothyroidism was higher in our study; it was higher in women than in men. Thyroid function tests were recommended for AA patients.

Construction of regulatory network for alopecia areata progression and identification of immune monitoring genes based on multiple machine-learning algorithms

Objectives

Alopecia areata (AA) is an autoimmune-related non-cicatricial alopecia, with complete alopecia (AT) or generalized alopecia (AU) as severe forms of AA. However, there are limitations in early identification of AA, and intervention of AA patients who may progress to severe AA will help to improve the incidence rate and prognosis of severe AA.

Methods

We obtained two AA-related datasets from the gene expression omnibus database, identified the differentially expressed genes (DEGs), and identified the module genes most related to severe AA through weighted gene co-expression network analysis. Functional enrichment analysis, construction of a protein-protein interaction network and competing endogenous RNA network, and immune cell infiltration analysis were performed to clarify the underlying biological mechanisms of severe AA. Subsequently, pivotal immune monitoring genes (IMGs) were screened through multiple machine-learning algorithms, and the diagnostic effectiveness of the pivotal IMGs was validated by receiver operating characteristic.

Results

A total of 150 severe AA-related DEGs were identified; the upregulated DEGs were mainly enriched in immune response, while the downregulated DEGs were mainly enriched in pathways related to hair cycle and skin development. Four IMGs (LGR5, SHISA2, HOXC13, and S100A3) with good diagnostic efficiency were obtained. As an important gene of hair follicle stem cells stemness, we verified in vivo that LGR5 downregulation may be an important link leading to severe AA.

Conclusion

Our findings provide a comprehensive understanding of the pathogenesis and underlying biological processes in patients with AA, and identification of four potential IMGs, which is helpful for the early diagnosis of severe AA.

Differential impact of environmental factors on systemic and localized autoimmunity

The influence of environmental factors on the development of autoimmune disease is being broadly investigated to better understand the multifactorial nature of autoimmune pathogenesis and to identify potential areas of intervention. Areas of particular interest include the influence of lifestyle, nutrition, and vitamin deficiencies on autoimmunity and chronic inflammation. In this review, we discuss how particular lifestyles and dietary patterns may contribute to or modulate autoimmunity. We explored this concept through a spectrum of several autoimmune diseases including Multiple Sclerosis (MS), Systemic Lupus Erythematosus (SLE) and Alopecia Areata (AA) affecting the central nervous system, whole body, and the hair follicles, respectively. A clear commonality between the autoimmune conditions of interest here is low Vitamin D, a well-researched hormone in the context of autoimmunity with pleiotropic immunomodulatory and anti-inflammatory effects. While low levels are often correlated with disease activity and progression in MS and AA, the relationship is less clear in SLE. Despite strong associations with autoimmunity, we lack conclusive evidence which elucidates its role in contributing to pathogenesis or simply as a result of chronic inflammation. In a similar vein, other vitamins impacting the development and course of these diseases are explored in this review, and overall diet and lifestyle. Recent work exploring the effects of dietary interventions on MS showed that a balanced diet was linked to improvement in clinical parameters, comorbid conditions, and overall quality of life for patients. In patients with MS, SLE and AA, certain diets and supplements are linked to lower incidence and improved symptoms. Conversely, obesity during adolescence was linked with higher incidence of MS while in SLE it was associated with organ damage. Autoimmunity is thought to emerge from the complex interplay between environmental factors and genetic background. Although the scope of this review focuses on environmental factors, it is imperative to elaborate the interaction between genetic susceptibility and environment due to the multifactorial origin of these disease. Here, we offer a comprehensive review about the influence of recent environmental and lifestyle factors on these autoimmune diseases and potential translation into therapeutic interventions.

Granzyme B in Autoimmune Skin Disease

Autoimmune diseases often present with cutaneous symptoms that contribute to dysfunction, disfigurement, and in many cases, reduced quality-of-life. Unfortunately, treatment options for many autoimmune skin diseases are limited. Local and systemic corticosteroids remain the current standard-of-care but are associated with significant adverse effects. Hence, there is an unmet need for novel therapies that block molecular drivers of disease in a local and/or targeted manner. Granzyme B (GzmB) is a serine protease with known cytotoxic activity and emerging extracellular functions, including the cleavage of cell-cell junctions, basement membranes, cell receptors, and other structural proteins. While minimal to absent in healthy skin, GzmB is markedly elevated in alopecia areata, interface dermatitis, pemphigoid disease, psoriasis, systemic sclerosis, and vitiligo. This review will discuss the role of GzmB in immunity, blistering, apoptosis, and barrier dysfunction in the context of autoimmune skin disease. GzmB plays a causal role in the development of pemphigoid disease and carries diagnostic and prognostic significance in cutaneous lupus erythematosus, vitiligo, and alopecia areata. Taken together, these data support GzmB as a promising therapeutic target for autoimmune skin diseases impacted by impaired barrier function, inflammation, and/or blistering.

An overview of the genetic aspects of hair loss and its connection with nutrition

Hair loss is a widespread concern in dermatology clinics, affecting both men's and women's quality of life. Hair loss can have many different causes, which are critical to identify in order to provide appropriate treatment. Hair loss can happen due to many variables, such as genetic factors or predisposition, vitamin and mineral deficiencies, skin problems, hair growth disorders, poor diet, hormonal problems, certain internal diseases, drug use, stress and depression, cosmetic factors, childbirth, and the chemotherapy process. Treatment for hair loss varies depending on the type of alopecia, deficiency, or excess of structures such as vitamins and minerals, and also on hair and skin structure. The Mediterranean diet is characterized by low amounts of saturated fat, animal protein, and high amounts of unsaturated fat, fiber, polyphenols, and antioxidants. The main nutrients found in the Mediterranean Diet are rich in antioxidant, anti-inflammatory components. It also has an important place in hair loss treatment, since recently treatment strategies have included polyphenols and unsaturated oils more and more frequently. The goal of this work was to review published articles examining alopecia and its types, the many micronutrients that affect alopecia, and the role of the Mediterranean diet in alopecia. The literature shows that little is known about hair loss, nutritional factors, and diet, and that the data collected are conflicting. Given these differences, research into the function of diet and nutrition in the treatment of baldness is a dynamic and growing topic.

Vitamin A in Skin and Hair: An Update

Vitamin A is a fat-soluble micronutrient necessary for the growth of healthy skin and hair. However, both too little and too much vitamin A has deleterious effects. Retinoic acid and retinal are the main active metabolites of vitamin A. Retinoic acid dose-dependently regulates hair follicle stem cells, influencing the functioning of the hair cycle, wound healing, and melanocyte stem cells. Retinoic acid also influences melanocyte differentiation and proliferation in a dose-dependent and temporal manner. Levels of retinoids decline when exposed to ultraviolet irradiation in the skin. Retinal is necessary for the phototransduction cascade that initiates melanogenesis but the source of that retinal is currently unknown. This review discusses new research on retinoids and their effects on the skin and hair.

Comprehensive Assessment of Skin Disorders in Patients with Common Variable Immunodeficiency (CVID)

BACKGROUND

Common variable immunodeficiency (CVID) is an inborn error of immunity (IEI) characterized by various clinical manifestations such as hypogammaglobulinemia, recurrent infections, and autoimmune diseases. Among different clinical manifestations, skin manifestations have been less reported in these patients.

METHODS

In this study, we investigated the prevalence of dermatologic features in 387 CVID patients. Demographic information, clinical manifestations, laboratory data, and genetic findings were collected from medical records. All data were analyzed based on the presence or absence of skin disorders in CVID patients.

RESULTS

We observed at least one skin manifestation in about 40% of these patients. Among these complications, skin infection (n = 64, 42.1%) was the most frequent presentation, followed by non-infectious skin lesions (n = 54, 35.6%). Among skin infections, abscesses (n = 34, 22.4%) were the most common complication. Skin infections such as cellulitis, impetigo, measles, and warts were also documented. Eczema (n = 34, 22.4%) was the most common complication in atopic lesions, and vitiligo (n = 13, 8.5%) was prevalent in autoimmune/pigmentation disorders. Among all the patients with genetic mutations, one-quarter had a deleterious mutation in the LRBA gene, relating to the autoimmune and atopic skin lesions.

CONCLUSION

This rate of skin disorders in our cohort demonstrating these manifestations could be significant in CVID patients, and they are not rare. Low data of skin complications in CVID patients could be attributed to insufficient attention of physicians and also might alert dermatologists to perform immunological investigations in children with certain skin manifestations.

Dietary Habits in Japanese Patients with Alopecia Areata

Purpose

Alopecia areata (AA) is characterized by non-scarring, patchy hair loss caused by autoimmune reactions to anagen hair follicles. The pathogenesis of AA may be affected by the diet. However, the dietary habits of patients with AA have not been precisely examined. Therefore, the aim of this study was to investigate the dietary habits of patients with AA in comparison to those of healthy controls.

Patients and Methods

We evaluated the dietary habits of 70 adult Japanese patients with AA using a brief-type self-administered diet history questionnaire and compared them to the habits of age- and sex-matched healthy controls.

Results

Japanese patients with AA had a higher body mass index (BMI) and higher intakes of vitamin C and fruit than the controls. Logistic regression analysis showed that AA was associated with BMI. Retinol intake was positively correlated with severity of alopecia tool (SALT) score, and linear regression analysis revealed that retinol intake was a predictor of SALT score. Retinol intake among patients with moderate to severe AA (ie, a SALT score >25) was higher than that in patients with mild AA (a SALT score ≤25). The mean age of AA patients with atopic dermatitis (AD) was lower than that of AA patients without AD; however, there were no differences in nutrient or food intake between these two groups. Logistic regression analysis showed that the comorbidity AD was negatively associated with age.

Conclusion

AA was associated with a high BMI, and high retinol intake was a predictor of SALT score. Further studies should be conducted to clarify whether dietary intervention to reduce BMI or limit retinol intake can alter the development or severity of AA.

Estrogen regulates the expression of retinoic acid synthesis enzymes and binding proteins in mouse skin

Topical 17-beta-estradiol (E2) regulates the hair cycle, hair shaft differentiation, and sebum production. Vitamin A also regulates sebum production. Vitamin A metabolism proteins localized to the pilosebaceous unit (PSU; hair follicle and sebaceous gland); and were regulated by E2 in other tissues. This study tests the hypothesis that E2 also regulates vitamin A metabolism in the PSU. First, aromatase and estrogen receptors localized to similar sites as retinoid metabolism proteins during mid-anagen. Next, female and male wax stripped C57BL/6J mice were topically treated with E2, the estrogen receptor antagonist ICI 182,780 (ICI), letrozole, E2 plus letrozole, or vehicle control (acetone) during mid-anagen. E2 or one of its inhibitors regulated most of the vitamin A metabolism genes and proteins examined in a sex-dependent manner. Most components were higher in females and reduced with ICI in females. ICI reductions occurred in the premedulla, sebaceous gland, and epidermis. Reduced E2 also reduced RA receptors in the sebaceous gland and bulge in females. However, reduced E2 increased the number of retinal dehydrogenase 2 positive hair follicle associated dermal dendritic cells in males. These results suggest that estrogen regulates vitamin A metabolism in the skin. Interactions between E2 and vitamin A have implications in acne treatment, hair loss, and skin immunity.

Liver Damage and Exposure to Toxic Concentrations of Endogenous Retinoids in the Pathogenesis of COVID-19 Disease: Hypothesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has a marked tropism for the biliary tract; it damages the bile ducts and hepatocytes and can lead to liver decompensation, cirrhosis, and sepsis. The pathogenesis of liver damage and its association with damage to the lung, heart, and brain and to the other protean manifestations of COVID-19 disease are not fully understood. In particular, tissue damage from thinning and leaky blood vessels appears to result from an inflammatory response to the virus rather than the virus itself. This article outlines a new hypothesis of the nature of the inflammatory factor responsible for tissue damage in COVID-19. Review of the literature reveals that COVID-19 disease closely resembles an endogenous form of hypervitaminosis A. We propose that SARS-CoV-2 virus-induced liver damage causes retinoic acid and stored retinyl esters to be released into the circulation in toxic concentrations, unbound to protein, with resulting damage to organs including the lungs, heart, blood vessels, and skin. Several lines of evidence support this model of disease causation. Subject to testing, strategies for the effective treatment and prevention of COVID-19 could include targeting the action and accumulation of retinoids.

Dietary Vitamin A Impacts Refractory Telogen

Hair follicles cycle through periods of growth (anagen), regression (catagen), rest (telogen), and release (exogen). Telogen is further divided into refractory and competent telogen based on expression of bone morphogenetic protein 4 (BMP4) and wingless-related MMTV integration site 7A (WNT7A). During refractory telogen hair follicle stem cells (HFSC) are inhibited. Retinoic acid synthesis proteins localized to the hair follicle and this localization pattern changed throughout the hair cycle. In addition, excess retinyl esters arrested hair follicles in telogen. The purpose of this study was to further define these hair cycle changes. BMP4 and WNT7A expression was also used to distinguish refractory from competent telogen in C57BL/6J mice fed different levels of retinyl esters from two previous studies. These two studies produced opposite results; and differed in the amount of retinyl esters the dams consumed and the age of the mice when the different diet began. There were a greater percentage of hair follicles in refractory telogen both when mice were bred on an unpurified diet containing copious levels of retinyl esters (study 1) and consumed excess levels of retinyl esters starting at 12 weeks of age, as well as when mice were bred on a purified diet containing adequate levels of retinyl esters (study 2) and remained on this diet at 6 weeks of age. WNT7A expression was consistent with these results. Next, the localization of vitamin A metabolism proteins in the two stages of telogen was examined. Keratin 6 (KRT6) and cellular retinoic acid binding protein 2 (CRABP2) localized almost exclusively to refractory telogen hair follicles in study 1. However, KRT6 and CRABP2 localized to both competent and refractory telogen hair follicles in mice fed adequate and high levels of retinyl esters in study 2. In mice bred and fed an unpurified diet retinol dehydrogenase SDR16C5, retinal dehydrogenase 2 (ALDH1A2), and cytochrome p450 26B1 (CYP26B1), enzymes and proteins involved in RA metabolism, localized to BMP4 positive refractory telogen hair follicles. This suggests that vitamin A may contribute to the inhibition of HFSC during refractory telogen in a dose dependent manner.

Post-natal all-trans-retinoic acid biosynthesis

Generation of the autacoid all-trans-retinoic acid (ATRA) from retinol (vitamin A) relies on a complex metabolon that includes retinol binding-proteins and enzymes from the short-chain dehydrogenase/reductase and aldehyde dehydrogenase gene families. Serum retinol binding-protein delivers all-trans-retinol (vitamin A) from blood to cells through two membrane receptors, Stra6 and Rbpr2. Stra6 and Rbpr2 convey retinol to cellular retinol binding-protein type 1 (Crbp1). Holo-Crbp1 delivers retinol to lecithin: retinol acyl transferase (Lrat) for esterification and storage. Lrat channels retinol directly into its active site from holo-Crbp1 by protein-protein interaction. The ratio apo-Crbp1/holo-Crbp1 directs flux of retinol into and out of retinyl esters, through regulating esterification vs ester hydrolysis. Multiple retinol dehydrogenases (Rdh1, Rdh10, Dhrs9, Rdhe2, Rdhe2s) channel retinol from holo-Crbp1 to generate retinal for ATRA biosynthesis. β-Carotene oxidase type 1 generates retinal from carotenoids, delivered by the scavenger receptor-B1. Retinal reductases (Dhrs3, Dhrs4, Rdh11) reduce retinal into retinol, thereby restraining ATRA biosynthesis. Retinal dehydrogenases (Raldh1, 2, 3) dehydrogenate retinal irreversibly into ATRA. ATRA regulates its own concentrations by inducing Lrat and ATRA degradative enzymes. ATRA exhibits hormesis. Its effects relate to its concentration as an inverted J-shaped curve, transitioning from beneficial in the "goldilocks" zone to toxicity, as concentrations increase. Hormesis has distorted understanding physiological effects of ATRA post-nataly using chow-diet fed, ATRA-dosed animal models. Cancer, immune deficiency and metabolic abnormalities result from mutations and/or insufficiency in Crbp1 and retinoid metabolizing enzymes.

Alopecia areata and isotretinoin; coincidence or causal relation

Isotretinoin is a safe and useful medication for acne management. Adverse effects are mostly related to cutaneous and mucous membranes. We present a case of a 24-year-old female patient who was on treatment with isotretinoin for acne vulgaris Grade 4. After 6 months of treatment, the patient presented with localized patch of hair loss. Beginning of alopecia areata in patients with acne vulgaris could be regarded as a side effect of retinoids due to anti-acne therapy. The exact mechanism by which retinoids cause hair loss is not known.

Cellular retinol-binding protein-1 expression increases with increasing clinical severity of alopecia areata

BACKGROUND

Alopecia areata (AA) is multifactorial disease mostly autoimmune affecting anagen hair follicles. Many researchers hypothesize that adequate retinoic acid (RA) levels are important for proper hair follicle behavior. Previous animal studies revealed increase in RA synthesis proteins and decrease in RA degradation proteins in AA patients when compared with controls.

OBJECTIVE

To evaluate cellular retinol-binding protein-1 expression in lesional skin of alopecia areata in comparison with controls, in an attempt to know its role in the pathogenesis of alopecia areata .

METHODS

Immunohistochemical expression of cellular retinol-binding protein-1 CRBP1 was evaluated in skin biopsies taken from lesions of alopecia areata in 30 patients and 10 normal biopsy specimens taken from skin of healthy controls (HC) who were within the same age and sex.

RESULTS

CRBP1 expression was significantly increased in lesional alopecia areata skin in comparison with normal skin of controls (P < 0.001*). Significant positive correlation was found between expression of CRBP-1 and percentage of hair loss in the scalp (SALT score; r = 0.840, P = <0.001).

CONCLUSION

These results may enhance the idea of the possible role of CRBP1 in the pathogenesis of AA, and ensuring the importance of its level in AA treatment.

Alopecia Areata: Review of Epidemiology, Clinical Features, Pathogenesis, and New Treatment Options

Alopecia areata (AA) is a complex autoimmune condition that causes nonscarring hair loss. It typically presents with sharply demarcated round patches of hair loss and may present at any age. In this article, we review the epidemiology, clinical features, pathogenesis, and new treatment options of AA, with a focus on the immunologic mechanism underlying the treatment. While traditional treatment options such as corticosteroids are moderately effective, a better understanding of the disease pathogenesis may lead to the development of new treatments that are more directed and effective against AA. Sources were gathered from PubMed, Embase, and the Cochrane database using the keywords: alopecia, alopecia areata, hair loss, trichoscopy, treatments, pathogenesis, and epidemiology.

The Role of Micronutrients in Alopecia Areata: A Review

Alopecia areata (AA) is a common, non-scarring form of hair loss caused by immune-mediated attack of the hair follicle. As with other immune-mediated diseases, a complex interplay between environment and genetics is thought to lead to the development of AA. Deficiency of micronutrients such as vitamins and minerals may represent a modifiable risk factor associated with development of AA. Given the role of these micronutrients in normal hair follicle development and in immune cell function, a growing number of investigations have sought to determine whether serum levels of these nutrients might differ in AA patients, and whether supplementation of these nutrients might represent a therapeutic option for AA. While current treatment often relies on invasive steroid injections or immunomodulating agents with potentially harmful side effects, therapy by micronutrient supplementation, whether as a primary modality or as adjunctive treatment, could offer a promising low-risk alternative. However, our review highlights a need for further research in this area, given that the current body of literature largely consists of small case-control studies and case reports, which preclude any definite conclusions for a role of micronutrients in AA. In this comprehensive review of the current literature, we found that serum vitamin D, zinc, and folate levels tend to be lower in patients with AA as compared to controls. Evidence is conflicting or insufficient to suggest differences in levels of iron, vitamin B12, copper, magnesium, or selenium. A small number of studies suggest that vitamin A levels may modify the disease. Though understanding of the role for micronutrients in AA is growing, definitive clinical recommendations such as routine serum level testing or therapeutic supplementation call for additional studies in larger populations and with a prospective design.

Alopecia areata: What's new in epidemiology, pathogenesis, diagnosis, and therapeutic options?

Alopecia areata (AA) is a common and stressful disorder that results in hair loss, and resistant to treatment in some cases. Experimental and clinical evidence suggests that AA is caused by autoimmune attack against the hair follicles. The precise pathomechanism, however, remains unknown. Here, we focus on the recent progress in multidisciplinary approaches to the epidemiology, pathogenesis, and new treatments of AA in 996 publications from January 2010 to July 2016, and provide an overview of the current understanding in clinical management and research directions.

Nutrition and skin: Kids are not just little people

There has been a surge of new data regarding the pathophysiology of skin diseases. We are appreciating the sophisticated interplay among the skin, the immune system, and the environment. More elegant and highly specific medicines have been designed to target certain immune mediators of the adaptive immune system. In parallel fashion, we are learning more about the elegance of the innate immune system and how nutrition as early as the prenatal period can affect the priming of other immune cells. Concerns about the long-term impact of new immune-modulating medicines-especially in the pediatric population-have patients asking their dermatologists for nutritional alternatives to medical therapies. Nutrients and nutritional therapies appear to play a role at different ages for different dermatoses. Probiotics are showing promise as a therapeutic option for patients older than 1 year for atopic dermatitis. Systemic contact allergens appear to be a bigger burden on the adult population with atopic dermatitis. Obesity is a growing concern for both children and adults with psoriasis. Milk and high glycemic foods have a strong impact on the teenage acne population. Vitamins A and D are addressed as piece of the alopecia areata puzzle. Zinc and homeopathy are presented finally as possible treatments to the everlasting wart.

The Aldo-Keto Reductase AKR1B10 Is Up-Regulated in Keloid Epidermis, Implicating Retinoic Acid Pathway Dysregulation in the Pathogenesis of Keloid Disease

Keloid disease is a recurrent fibroproliferative cutaneous tumor of unknown pathogenesis for which clinical management remains unsatisfactory. To obtain new insights into hitherto underappreciated aspects of keloid pathobiology, we took a laser capture microdissection-based, whole-genome microarray analysis approach to identify distinct keloid disease-associated gene expression patterns within defined keloid regions. Identification of the aldo-keto reductase enzyme AKR1B10 as highly up-regulated in keloid epidermis suggested that an imbalance of retinoic acid metabolism is likely associated with keloid disease. Here, we show that AKR1B10 transfection into normal human keratinocytes reproduced the abnormal retinoic acid pathway expression pattern we had identified in keloid epidermis. Cotransfection of AKR1B10 with a luciferase reporter plasmid showed reduced retinoic acid response element activity, supporting the hypothesis of retinoic acid synthesis deficiency in keloid epidermis. Paracrine signals released by AKR1B10-overexpressing keratinocytes into conditioned medium resulted in up-regulation of transforming growth factor-β1, transforming growth factor-β2, and collagens I and III in both keloid and normal skin fibroblasts, mimicking the typical profibrotic keloid profile. Our study results suggest that insufficient retinoic acid synthesis by keloid epidermal keratinocytes may contribute to the pathogenesis of keloid disease. We refocus attention on the role of injured epithelium in keloid disease and identify AKR1B10 as a potential new target in future management of keloid disease.

Alopecia areata: Animal models illuminate autoimmune pathogenesis and novel immunotherapeutic strategies

One of the most common human autoimmune diseases, alopecia areata (AA), is characterized by sudden, often persisting and psychologically devastating hair loss. Animal models have helped greatly to elucidate critical cellular and molecular immune pathways in AA. The two most prominent ones are inbred C3H/HeJ mice which develop an AA-like hair phenotype spontaneously or after experimental induction, and healthy human scalp skin xenotransplanted onto SCID mice, in which a phenocopy of human AA is induced by injecting IL-2-stimulated PBMCs enriched for CD56+/NKG2D+ cells intradermally. The current review critically examines the pros and cons of the available AA animal models and how they have shaped our understanding of AA pathobiology, and the development of new therapeutic strategies. AA is thought to arise when the hair follicle's (HF) natural immune privilege (IP) collapses, inducing ectopic MHC class I expression in the HF epithelium and autoantigen presentation to autoreactive CD8+ T cells. In common with other autoimmune diseases, upregulation of IFN-γ and IL-15 is critically implicated in AA pathogenesis, as are NKG2D and its ligands, MICA, and ULBP3. The C3H/HeJ mouse model was used to identify key immune cell and molecular principles in murine AA, and proof-of-principle that Janus kinase (JAK) inhibitors are suitable agents for AA management in vivo, since both IFN-γ and IL-15 signal via the JAK pathway. Instead, the humanized mouse model of AA has been used to demonstrate the previously hypothesized key role of CD8+ T cells and NKG2D+ cells in AA pathogenesis and to discover human-specific pharmacologic targets like the potassium channel Kv1.3, and to show that the PDE4 inhibitor, apremilast, inhibits AA development in human skin. As such, AA provides a model disease, in which to contemplate general challenges, opportunities, and limitations one faces when selecting appropriate animal models in preclinical research for human autoimmune diseases.

Dermal lymphatic dilation in a mouse model of alopecia areata

Mouse models of various types of inflammatory skin disease are often accompanied by increased dermal angiogenesis. The C3H/HeJ inbred strain spontaneously develops alopecia areata (AA), a cell mediated autoimmune disorder that can be controllably expanded using full thickness skin grafts to young unaffected mice. This provides a reproducible and progressive model for AA in which the vascularization of the skin can be examined. Mice receiving skin grafts from AA or normal mice were evaluated at 5, 10, 15, and 20 weeks after engraftment. Lymphatics are often overlooked as they are small slit-like structures above the hair follicle that resemble artifact-like separation of collagen bundles with some fixatives. Lymphatics are easily detected using lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1) by immunohistochemistry to label their endothelial cells. Using LYVE1, there were no changes in distribution or numbers of lymphatics although they were more prominent (dilated) in the mice with AA. Lyve1 transcripts were not significantly upregulated except at 10 weeks after skin grafting when clinical signs of AA first become apparent. Other genes involved with vascular growth and dilation or movement of immune cells were dysregulated, mostly upregulated. These findings emphasize aspects of AA not commonly considered and provide potential targets for therapeutic intervention.

Serum level of interleukin-17A in patients with alopecia areata and its relationship to age

BACKGROUND

There is strong evidence for an autoimmune etiology of alopecia areata (AA). Interleukin-17A (IL-17A) is a Th17 proinflammatory cytokine that has been linked to the pathogeneses of diverse autoimmune and inflammatory diseases.

OBJECTIVES

This study aimed to measure serum IL-17A in AA patients and to study associations between IL-17A levels and AA severity, duration, and age of onset, and patient gender and age.

METHODS

The study enrolled 39 AA patients and 37 healthy control subjects. Scalp involvement was assessed using the Severity of Alopecia Tool (SALT), and clinical disease severity was determined. Serum IL-17A was measured using ELISAs.

RESULTS

Serum IL-17A was significantly higher in AA patients than in control subjects (P < 0.001). Correlations between serum IL-17A and gender, disease duration, SALT score, and disease severity were non-significant. Serum IL-17A was significantly higher in patients aged ≤30 years than in patients aged >30 years (P = 0.045). Age and serum IL-17A were significantly negatively correlated in patients with AA (rs = -0.363, P = 0.023) but not in control subjects (rs = -0.294, P = 0.077). Patients with juvenile-onset AA had significantly higher IL-17A levels than those with maturity-onset disease (P = 0.034). There was a significant negative correlation between age at disease onset and serum IL-17A (rs = -0.349, P = 0.029).

CONCLUSIONS

It is possible that IL-17A plays a role in the pathogenesis of AA. Serum IL-17A may be influenced by patient age and age of onset of AA but does not seem to influence disease severity.

Alcohol exposure in utero perturbs retinoid homeostasis in adult rats

BACKGROUND

Maternal alcohol exposure and adult alcohol intake have been shown to perturb the metabolism of various micro- and macro-nutrients, including vitamin A and its derivatives (retinoids). Therefore, it has been hypothesized that the well-known detrimental consequences of alcohol consumption may be due to deregulations of the metabolism of such nutrients rather than to a direct effect of alcohol. Alcohol exposure in utero also has long-term harmful consequences on the health of the offspring with mechanisms that have not been fully clarified. Disruption of tissue retinoid homeostasis has been linked not only to abnormal embryonic development, but also to various adult pathological conditions, including cancer, metabolic disorders and abnormal lung function. We hypothesized that prenatal alcohol exposure may permanently perturb tissue retinoid metabolism, predisposing the offspring to adult chronic diseases.

METHODS

Serum and tissues (liver, lung and prostate from males; liver and lung from females) were collected from 60-75 day-old sprague dawley rats born from dams that were: (I) fed a liquid diet containing 6.7% alcohol between gestational day 7 and 21; or (II) pair-fed with isocaloric liquid diet during the same gestational window; or (III) fed ad libitum with regular rat chow diet throughout pregnancy. Serum and tissue retinoid levels were analyzed by reverse-phase high-performance liquid chromatography (HPLC). Serum retinol-binding protein (RBP) levels were measured by western blot analysis, and liver, lung and prostate mRNA levels of lecithin-retinol acyltransferase (LRAT) were measured by qPCR.

RESULTS

Retinyl ester levels were significantly reduced in the lung of both males and females, as well as in the liver and ventral prostate of males born from alcohol-fed dams. Tissue LRAT mRNA levels remained unchanged upon maternal alcohol treatment.

CONCLUSIONS

Prenatal alcohol exposure in rats affects retinoid metabolism in adult life, in a tissue- and sex-dependent manner. We propose that the alcohol-induced perturbations of vitamin A metabolism may predispose to detrimental consequnces on adult health.

Drug discovery for alopecia: gone today, hair tomorrow

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Crisp1 and alopecia areata in C3H/HeJ mice

Alopecia areata (AA), a cell mediated autoimmune disease, is the second most common form of hair loss in humans. While the autoimmune disease is responsible for the underlying pathogenesis, the alopecia phenotype is ultimately due to hair shaft fragility and breakage associated with structural deficits. Quantitative trait genetic analyses using the C3H/HeJ mouse AA model identified cysteine-rich secretory protein 1 (Crisp1), a hair shaft structural protein, as a candidate gene within the major AA locus. Crisp1 transcripts in the skin at various times during disease development were barely detectable. In situ hybridization identified Crisp1 expression within the medulla of hair shafts from clinically normal strains of mice but not C3H/HeJ mice with AA. Follow-up work with 5-day-old C3H/HeJ mice with normal hair also had essentially no expression of Crisp1. Other non-inflammatory based follicular dystrophy mouse models with similar hair shaft abnormalities also have little or no Crisp1 expression. Shotgun proteomics, used to determine strain difference in hair proteins, confirmed that there was very little CRISP1 within normal C3H/HeJ mouse hair in comparison to 11 other strains. However, mutant mice with hair medulla defects also had undetectable levels of CRISP1 in their hair. Crisp1 null mice had normal skin, hair follicles, and hair shafts indicating that the lack of the CRISP1 protein does not translate directly into defects in the hair shaft or hair follicle. These results suggest that CRISP1 may be an important structural component of mouse hair and that its strain-specific dysregulation may indicate a predisposition to hair shaft disease such as AA.

Dietary vitamin A regulates wingless-related MMTV integration site signaling to alter the hair cycle

Alopecia areata (AA) is an autoimmune hair loss disease caused by a cell-mediated immune attack of the lower portion of the cycling hair follicle. Feeding mice 3-7 times the recommended level of dietary vitamin A accelerated the progression of AA in the graft-induced C3H/HeJ mouse model of AA. In this study, we also found that dietary vitamin A, in a dose dependent manner, activated the hair follicle stem cells (SCs) to induce the development and growth phase of the hair cycle (anagen), which may have made the hair follicle more susceptible to autoimmune attack. Our purpose here is to determine the mechanism by which dietary vitamin A regulates the hair cycle. We found that vitamin A in a dose-dependent manner increased nuclear localized beta-catenin (CTNNB1; a marker of canonical wingless-type Mouse Mammary Tumor Virus integration site family (WNT) signaling) and levels of WNT7A within the hair follicle bulge in these C3H/HeJ mice. These findings suggest that feeding mice high levels of dietary vitamin A increases WNT signaling to activate hair follicle SCs.

Emerging treatments in alopecia

INTRODUCTION

Alopecia is a common concern encountered in the medical practice. Treatment approach varies according to the type and severity of alopecia. However, available treatment options have limited efficacy and several adverse effects. Presently, there are different treatment options being studied to overcome these limitations. Additionally, cellular pathways involved in the pathophysiology of alopecia are further being clarified to potentially target pathogenic molecules.

AREAS COVERED

We searched the literature for recently published articles discussing new treatment options as well as mechanisms involved in alopecia. We discuss the use of stem cells, growth factors, cellular pathways and robotic hair transplant, among other emerging therapies used for alopecia.

EXPERT OPINION

Future looks very promising and new effective treatments such as janus kinase inhibitors could possibly be available for alopecia areata. The stem-cell technology is advancing and companies involved in hair follicle neogenesis are starting clinical trials on patients with androgenetic alopecia.

Alopecia areata: updates from the mouse perspective

Alopecia areata (AA) is a cell-mediated autoimmune disease that targets actively growing hair follicles in mammals, including humans and mice. Development of the C3H/HeJ spontaneous mouse model AA nearly 20 years ago provided a much needed tool to test the hypotheses and ultimately serve as a preclinical model for drug testing. Discoveries in both human AA patients and the mouse model supported each other and lead to discoveries on the incredibly complex genetic basis of this disease. The discovery that A/J, MRL/MpJ, SJL/J, and SWR/J strains also develop AA now allows genome-wide association mapping studies to expand the list of genes underlying this disease. Potential new targets for unraveling the pathogenesis of AA include the role of retinoic acid metabolism in the severity of disease and hair shaft proteins that may be either the inciting antigen or ultimate target of the immune reaction leading to breakage of the shaft causing clinical alopecia. Comparing these model systems with human and mouse clinical disease, for both discovery and validation of the discoveries, continues to resolve the complex questions surrounding AA.

The enzyme Cyp26b1 mediates inhibition of mast cell activation by fibroblasts to maintain skin-barrier homeostasis

Mast cells (MCs) mature locally, thus possessing tissue-dependent phenotypes for their critical roles in both protective immunity against pathogens and the development of allergy or inflammation. We previously reported that MCs highly express P2X7, a receptor for extracellular ATP, in the colon but not in the skin. The ATP-P2X7 pathway induces MC activation and consequently exacerbates the inflammation. Here, we identified the mechanisms by which P2X7 expression on MCs is reduced by fibroblasts in the skin, but not in the other tissues. The retinoic-acid-degrading enzyme Cyp26b1 is highly expressed in skin fibroblasts, and its inhibition resulted in the upregulation of P2X7 on MCs. We also noted the increased expression of P2X7 on skin MCs and consequent P2X7- and MC-dependent dermatitis (so-called retinoid dermatitis) in the presence of excessive amounts of retinoic acid. These results demonstrate a unique skin-barrier homeostatic network operating through Cyp26b1-mediated inhibition of ATP-dependent MC activation by fibroblasts.

What causes alopecia areata?

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

Retinoid metabolism is altered in human and mouse cicatricial alopecia

C57BL/6 mice develop dermatitis and scarring alopecia resembling human cicatricial alopecias (CA), particularly the central centrifugal cicatricial alopecia (CCCA) type. To evaluate the role of retinoids in CA, expression of retinoid metabolism components were examined in these mice with mild, moderate, or severe CA compared to hair cycle matched mice with no disease. Two feeding studies were performed with dams fed either NIH 31 diet (study 1) or AIN93G diet (study 2). Adult mice were fed AIN93M diet with 4 (recommended), 28, or 56 IU vitamin A/g diet. Feeding the AIN93M diet to adults increased CA frequency over NIH 31 fed mice. Increased follicular dystrophy was seen in study 1 and increased dermal scars in study 2 in mice fed the 28 IU diet. These results indicate that retinoid metabolism is altered in CA in C57BL/6J mice that require precise levels of dietary vitamin A. Human patients with CCCA, pseudopelade (end stage scarring), and controls with no alopecia were also studied. Many retinoid metabolism proteins were increased in mild CCCA, but were undetectable in pseudopelade. Studies to determine if these dietary alterations in retinoid metabolism seen in C57BL/6J mice are also involved in different types of human CA are needed.