Lichen planopilaris is characterized by immune privilege collapse of the hair follicle's epithelial stem cell niche

Activation of the integrated stress response in human hair follicles

Unravelling how energy metabolism and stress responses are regulated in human scalp hair follicles could reveal novel insights into the controls of hair growth and provide new targets to manage hair loss disorders. The Mitochondrial Pyruvate Carrier (MPC) imports pyruvate, produced via glycolysis, into the mitochondria, fuelling the TCA cycle. Previous work has shown that MPC inhibition promotes lactate generation, which activates murine epithelial hair follicle stem cells (eHFSCs). However, by pharmacologically targeting the MPC in short-term human hair follicle ex vivo organ culture experiments using UK-5099, we induced metabolic stress-responsive proliferative arrest throughout the human hair follicle epithelium, including within Keratin 15+ eHFSCs. Through transcriptomics, MPC inhibition was shown to promote a gene expression signature indicative of disrupted FGF, IGF, TGFβ and WNT signalling, mitochondrial dysfunction, and activation of the integrated stress response (ISR), which can arrest cell cycle progression. The ISR, mediated by the transcription factor ATF4, is activated by stressors including amino acid deprivation and ER stress, consistent with MPC inhibition within our model. Using RNAScope, we confirmed the upregulation of both ATF4 and the highly upregulated ATF4-target gene ADM2 on human hair follicle tissue sections in situ. Moreover, treatment with the ISR inhibitor ISRIB attenuated both the upregulation of ADM2 and the proliferative block imposed via MPC inhibition. Together, this work reveals how the human hair follicle, as a complex and metabolically active human tissue system, can dynamically adapt to metabolic stress.

Upregulation of caveolae-associated structural proteins in the hair follicle bulge of lichen planopilaris and frontal fibrosing alopecia

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are primary cicatricial alopecia that cause a major impact on quality of life due to irreversible hair loss and symptoms as itching, burning and pain. They are characterized by permanent loss of hair follicle stem cells (HFSCs) by pathomechanisms still poorly understood, resulting in poor efficacy of currently available treatments. Caveolae are flask-shaped lipid rafts invaginated within the plasma membrane of multiple cell types. Although their role in the HF physiology and pathophysiology is relatively unknown, we have previously demonstrated that the primary structural component of caveolae (caveolin-1 or Cav1) is upregulated in FFA. Thus, we propose to investigate the expression and localization of caveolae-associated structural proteins (Cav1, Cav2, and Cavin-1) and HFSCs (identified by K15) in both LPP and FFA. We analyzed 4 patients with LPP biopsied in affected and non-affected (NA) scalp, 4 patients with FFA biopsied in affected scalp and 4 healthy controls. Affected scalp of LPP and FFA demonstrated increased levels of Cav1 and Cavin-1 compared with HC and LPP-NA. Moreover, Cav1, Cav2 and Cavin1 all exhibit high colocalization with K15 and their expression appears to be negatively correlated, supporting the hypothesis that these proteins are important players in LPP/FFA and may serve as therapeutic targets in future treatments.

A review of isotretinoin in the treatment of frontal fibrosing alopecia

INTRODUCTION

Frontal fibrosing alopecia (FFA) is characterized by scarring alopecia of the frontotemporal scalp and facial papules. Isotretinoin is a vitamin A-derived retinoid discovered in 1955 and approved for treating nodulocystic acne. This drug can also affect facial papules and frontotemporal hair loss in patients with FFA. In this article, we conducted a review of the available studies investigating the use of oral isotretinoin for FFA treatment. Our study provides insights into the efficacy and safety of isotretinoin as a potential treatment option for FFA and highlights areas for future research.

METHOD

In this study, we aimed to investigate the potential advantages and disadvantages of isotretinoin as a treatment for FFA. To identify all relevant articles, we developed a comprehensive search strategy and conducted a thorough search of three major databases: PubMed, Embase, and Science Direct. We retrieved a total of 82 articles from the search results. Two independent reviewers then screened each of the 82 articles based on our inclusion and exclusion criteria, resulting in the identification of 15 articles that were deemed relevant to our study.

RESULTS

Across the 15 articles, 232 patients who suffered from FFA were involved. Nearly 90% of patients experienced a significant reduction of symptoms after receiving oral isotretinoin at 10-40 mg daily. We conclude that isotretinoin can positively affect facial papules and help suppress hair loss.

A Case of Graham-Little-Piccardi-Lasseur Syndrome Successfully Treated with Minocycline

Abstract is missing (Short communication)

Proteomic Profiling of Central Centrifugal Cicatricial Alopecia Reveals Role of Humoral Immune Response Pathway and Metabolic Dysregulation

Proteomic profiling on other primary cicatricial alopecias, such as frontal fibrosing alopecia and lichen planopilaris, have suggested a T helper 1-mediated inflammatory pathway, but in central centrifugal cicatricial alopecia (CCCA), the protein expression patterns are unknown. In this study, we sought to characterize protein expression patterns in CCCA to identify biomarkers of disease activity that will identify potential therapeutic avenues for treatment. Scalp protein quantification was performed to understand protein expression patterns in affected versus unaffected scalps in CCCA. A total of 5444 proteins were identified, of which 148 proteins were found to be differentially expressed in CCCA-affected scalp, with upregulation of adaptive immune pathways (IGHG3, P = .034; IGHG4, P = .01; IGG1, P = .026) and markers of fibrosis (ITGA1, P = .016; SFRP2, P = .045; TPM2, P = .029; SLMAP, P = .016) and downregulation of metabolic proteins (ALOX15B, P = .003; FADS2, P = .006; ELOVL5, P = .007; FA2H, P = .017; FAR2, P = .011; SC5D, P < .001). Our analysis revealed, to our knowledge, previously unknown humoral immune canonical pathways, notably IgG, implicated in CCCA and additionally confirmed aberrant lipid metabolism pathways implicated in diabetes mellitus, suggesting unique mechanisms of disease in patients with CCCA.

The promising prospect of human hair follicle regeneration in the shadow of new tissue engineering strategies

Hair loss disorder (alopecia) affects numerous people around the world. The low effectiveness and numerous side effects of common treatments have prompted researchers to investigate alternative and effective solutions. Hair follicle (HF) bioengineering is the knowledge of using hair-inductive (trichogenic) cells. Most bioengineering-based approaches focus on regenerating folliculogenesis through manipulation of regulators of physical/molecular properties in the HF niche. Despite the high potential of cell therapy, no cell product has been produced for effective treatment in the field of hair regeneration. This problem shows the challenges in the functionality of cultured human hair cells. To achieve this goal, research and development of new and practical approaches, technologies and biomaterials are needed. Based on recent advances in the field, this review evaluates emerging HF bioengineering strategies and the future prospects for the field of tissue engineering and successful HF regeneration.

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.

Regulatory T cells in skin mediate immune privilege of the hair follicle stem cell niche

Immune tolerance is maintained in lymphoid organs (LOs). Despite the presence of complex immune cell networks in non-LOs, it is unknown whether self-tolerance is maintained in these tissues. We developed a technique to restrict genetic recombination to regulatory T cells (Tregs) only in skin. Selective depletion of skin Tregs resulted in T cell-mediated inflammation of hair follicles (HFs). Suppression did not rely on CTLA-4, but instead on high-affinity interleukin-2 (IL-2) receptor expression by skin Tregs, functioning exclusively in a cell-extrinsic manner. In a novel model of HF stem cell (HFSC)-driven autoimmunity, we reveal that skin Tregs immunologically protect the HFSC niche. Finally, we used spatial transcriptomics to identify aberrant IL-2 signaling at stromal-HF interfaces in a rare form of human alopecia characterized by HFSC destruction and alopecia areata. Collectively, these results reveal the fundamental biology of Tregs in skin uncoupled from the systemic pool and elucidate a mechanism of self-tolerance.

Controlling Hair Loss by Regulating Apoptosis in Hair Follicles: A Comprehensive Overview

Apoptosis is a physiological process that occurs in all cell types of the human body, and it profoundly changes the fate of hair by affecting hair follicle cells. This review outlines the cellular changes, intrinsic biochemical characteristics, and mechanisms underlying apoptosis and summarizes the hair follicle life cycle, including development, cycle stages, and corresponding cellular changes. Finally, the relationship between apoptosis and the hair cycle is discussed and the significance of apoptosis in hair loss conditions and drug treatments is highlighted. Apoptosis induces cellular changes and exhibits distinctive properties through intricate signaling pathways. Hair follicles undergo cyclic periods of growth, regression, and dormancy. Apoptosis is closely correlated with the regression phase by triggering hair follicle cell death and shedding. Regulation of apoptosis in hair follicles plays an essential role in hair loss due to maladies and drug treatments. Mitigating apoptosis can enhance hair growth and minimize hair loss. A comprehensive understanding of the correlation between apoptosis and the hair cycle can facilitate the development of novel treatments to prevent hair loss and stimulate hair regeneration.

Genotyping of the rs1800440 Polymorphism in CYP1B1 Gene and the rs9258883 Polymorphism in HLA-B Gene in a Spanish Cohort of 223 Patients with Frontal Fibrosing Alopecia

The pathogenesis of frontal fibrosing alopecia has been linked to specific genetic variants. CYP1B1 codes for a component of the cytochrome p450 machinery that is involved in the metabolism of xenobiotic oestrogens. The study of the prevalence of polymorphisms in this gene may help to understand their role in the development of frontal fibrosing alopecia. The aim of this study is to describe the frequency of genetic variations in the alleles HLA-B*07:02 and CYP1B1 in patients with frontal fibrosing alopecia. A cross-sectional study was designed to evaluate blood samples from patients with frontal fibrosing alopecia who attended the Dermatology Department at University Hospital Ramón y Cajal (Madrid, Spain), in search of the polymorphisms rs9258883 and rs1800440 in the alleles HLA-B*07:02 and CYP1B1, respectively. A total of 223 patients were included in the study. Among the 83.8% of patients who carried the rs9258883 polymorphism in HLA-B*07:02, 58.7% were heterozygous for this variant and it was not present in 14.8% of the cases. The majority of patients with frontal fibrosing alopecia lacked the protective rs1800440 polymorphism in CYP1B1 (75.2%). This suggests a relevant role of this variant in development of frontal fibrosing alopecia. The genetic approach to this condition might influence patient prognosis and therapy options.

Unveiling a Shared Precursor Condition for Acne Keloidalis Nuchae and Primary Cicatricial Alopecias

Purpose

Small observational studies suggest subclinical disease occurrence in the normal-appearing scalp zones of several primary cicatricial alopecias. To aid patient management, we began routinely evaluating the entire scalp of patients with acne keloidalis nuchae (AKN), including trichoscopy-guided biopsies.

Patients and Methods

This retrospective study evaluated 41 patients sequentially presenting with AKN at a single clinic between June and December 2022. Primary lesions and normal-appearing scalp in the superior parietal scalp at least 5 cm away from AKN-affected zones were clinically evaluated, and areas showing perifollicular erythema or scales/casts on trichoscopy were biopsied and histologically analyzed.

Results

Forty-one men with AKN, including 20 men of African descent, 17 Hispanic, and 4 European-descended Whites, were evaluated. All patients, including 22% with associated folliculitis decalvans, showed scalp-wide trichoscopy signs of perifollicular erythema or scaling in normal-appearing scalp areas. All patients showed histologic evidence of perifollicular infundibulo-isthmic lymphocytoplasmic infiltrates and fibrosis (PIILIF), with 96% showing Vellus or miniaturized hair absence. PIILIF was often clinically mistaken for seborrheic dermatitis (44-51%). All White patients had mild papular acne keloidalis nuchae lesions mistaken for seborrheic dermatitis.

Conclusion

PIILIF may be a precursor to a wide spectrum of primary cicatricial alopecias, including AKN and folliculitis decalvans. This finding carries implications for the early diagnosis and management of AKN and other primary cicatricial alopecias.

Nivolumab-Induced Lichen Planopilaris: Case Report and Literature Review of Hair Disorders Associated with Targeted Oncological Therapies

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapies. Their mechanism promotes a cytotoxic T-cell activation against the tumor cells, but as a consequence, immune-mediated toxicities are increasingly being identified. Cutaneous immune-mediated adverse events (AE) occur in 32% of patients, with possible higher grade AEs seen with anti-programmed cell death protein 1, such as nivolumab. A 67-year-old woman with metastatic melanoma, previously treated for 2 years on dual ICI (ipilimumab and nivolumab), had her treatment interrupted due to grade-3 hepatitis. She was subsequently recommenced on single-agent nivolumab with good response, before discontinuation due to remission. She reported worsening scalp pruritus with associated erythema, scaling, and global hair thinning. On examination, she had significant erythema throughout the scalp with perifollicular scaling and evidence of scarring. She reported severe distress from her symptoms. Her scalp biopsy demonstrated features of scarring alopecia with infundibular and isthmic inflammation and interface change in keeping with lichen planopilaris. Follicular toxicities are rarely reported, possibly due to imprecise AE phenotyping or underreporting. However, growing evidence suggests that patients can develop follicular pigmentary changes and nonscarring alopecia. To our knowledge, this is the first case of scarring alopecia reported with nivolumab. Current treatments for ICI-induced toxicities are limited.

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.

Actinic lichen planopilaris: a new variant of lichen planopilaris triggered by ultraviolet radiation

We present the case of a Sri Lankan woman with a novel clinical entity, actinic lichen planopilaris. Treatment with high-potency topical corticosteroids and adherence to strict photoprotection was successful in treating the disorder.

Study of the Thyroid Profile of Patients with Alopecia

Thyroid hormones are required for the physiological growth and maintenance of hair follicles. We aim to study the thyroid profile of patients with alopecia. This is a narrative review. PubMed literature was searched from 2013 to 2022. We followed different types of alopecia: alopecia areata (AA), androgenic alopecia in males and females, telogen effluvium (TE), frontal fibrosing alopecia (FFA), lichen planopilaris, and alopecia neoplastica (AN). AA shares a common autoimmune background with autoimmune thyroid diseases, either sporadic or belonging to autoimmune polyglandular syndromes. Some data suggested that AA is more severe if thyroid anomalies are confirmed, including subclinical dysfunction or positive antithyroid antibodies with normal hormone values. However, routine thyroid screening for patients with AA, if the patients are asymptomatic from a thyroid point of view and they have negative personal and family history of autoimmunity, remains controversial. TE, apart from the autoimmune type, associates thyroid anomalies of a hormonal assay (between 5.7% and 17%). FFA, mostly a postmenopausal entity (however, not exclusive), associates a higher prevalence of thyroid conditions (up to 50%) than the general population. However, these might have an age-dependent pattern, thus the association may be incidental since there are a limited number of studies. Overall, alopecia remains a very challenging condition for patients and physicians; a multidisciplinary team is required to improve the outcome and quality of life. The common autoimmune background is suggestive of some types of alopecia and thyroid disorders, yet, the underlying mechanisms are still a matter of debate. AA, TE, FFA, LPP, and, potentially, female pattern hair loss have been found to be connected with thyroid entities, thus a state of awareness from a dual perspective, of trichology and endocrinology, is helpful.

Beyond the Hot Comb: Updates in Epidemiology, Pathogenesis, and Treatment of Central Centrifugal Cicatricial Alopecia from 2011 to 2021

Central centrifugal cicatricial alopecia (CCCA) is a form of scarring alopecia that predominantly affects middle-aged women of African descent. Recent data suggest a multifactorial etiology of CCCA that is influenced by environmental and genetic factors. Emerging evidence regarding the genetic basis of the condition may elucidate new therapies. While topical and intralesional steroids and tetracycline antibiotics are the mainstay of treatment, refractory cases may be considered for hair transplantation. Emerging therapies using platelet-rich plasma, botanical formulas, and cosmetic procedures have shown promising results for the future management of CCA. As recent notable advances in CCCA have been achieved, this review provides an update on the epidemiology, pathophysiology, and management of CCCA.

IL-17 Expression in the Perifollicular Fibrosis in Biopsies From Lichen Planopilaris

BACKGROUND

Lichen planopilaris (LPP) is a primary lymphocytic cicatricial alopecia for which therapy is often ineffective and there is no cure.

OBJECTIVES

Looking for a new targetable molecule in the treatment of LPP, we sought to verify whether IL-17 expression is increased in scalp biopsies from patients with active scalp lesions of LPP.

METHODS

Horizontal sections of hematoxylin and eosin-stained slides from 40 scalp biopsies of active LPP were retrospectively collected and stained with the monoclonal antibody against IL-17 (Abcam, Cambridge, MA; ab79056, dilution 1:100). Twenty biopsies from patients with chronic telogen effluvium served as controls because of their morphological resemblance to the normal scalp. Statistical analysis was performed using IBM SPSS Statistics for Windows (IBM Corporation, Armonk, NY).

RESULTS

The main finding was the positive cytoplasmic expression of IL-17 in the perifollicular fibrosis of the affected follicles in LPP which was statistically significant compared with the controls ( P < 0.0001). The labeled cells were identified as fibroblasts based on their spindle shape and fascicular concentric arrangement in tight perifollicular distribution. Although most of the LPP specimens (n = 35; 87.5%) also revealed cytoplasmic IL-17 expression in the lichenoid inflammatory infiltrate, the results were not statistically significant ( P = 0.1351).

CONCLUSION

Our immunohistochemistry results show that blocking the IL-17 inflammatory pathway may interfere with the progression of the perifollicular fibrosis and inflammation in LPP.

Frontal fibrosing alopecia: A review of disease pathogenesis

Frontal fibrosing alopecia (FFA) is a primary patterned cicatricial alopecia that mostly affects postmenopausal women and causes frontotemporal hairline regression and eyebrow loss. Although the incidence of FFA has increased worldwide over the last decade, its etiology and pathology are still unclear. We cover the latest findings on its pathophysiology, including immunomodulation, neurogenic inflammation, and genetic regulation, to provide more alternatives for current clinical treatment. A persistent inflammatory response and immune privilege (IP) collapse develop and lead to epithelial hair follicle stem cells (eHFSCs) destruction and epithelial-mesenchymal transition (EMT) in the bulge area, which is the key process in FFA pathogenesis. Eventually, fibrous tissue replaces normal epithelial tissue and fills the entire hair follicle (HF). In addition, some familial reports and genome-wide association studies suggest a genetic susceptibility or epigenetic mechanism for the onset of FFA. The incidence of FFA increases sharply in postmenopausal women, and many FFA patients also suffer from female pattern hair loss in clinical observation, which suggests a potential association between FFA and steroid hormones. Sun exposure and topical allergens may also be triggers of FFA, but this conjecture has not been proven. More evidence and cohort studies are needed to help us understand the pathogenesis of this disease.

Frontal Fibrosing Alopecia: A Histopathological Comparison of the Frontal Hairline with Normal-Appearing Scalp

Frontal fibrosing alopecia is characterized by the presence of a lymphocytic inflammatory infiltrate around the upper follicle and by perifollicular fibrosis, which results in the destruction of the hair follicle. Recent reports have also found the presence of those findings in clinically unaffected areas. The aim of this report is to perform a deeper analysis of the histopathological features of this apparently unaffected scalp. A cross-sectional study including 52 women with frontal fibrosing alopecia was performed. Two areas were biopsied: the frontal hairline and a normal-appearing scalp area. Sebaceous glands were reduced/absent in 80.8% of the frontal hairline samples compared to 42.3% of the "healthy scalp" samples (p = 0.001). Inflammatory infiltrate was observed in 92.3% of patients in the frontal hairline and in 86.5% of them in the "healthy scalp" area (p = 0.508), although the severity was higher in the former (p = 0.013). Follicular epithelium changes were seen in 70.6% of the frontal hairline biopsies compared to 48.1% of the "healthy scalp" biopsies (p = 0.012). Fibrous tissular changes were noted in 80.8% and 53.8% of the frontal hairline and "healthy scalp" biopsies, respectively (p = 0.003). In conclusion, the histopathological features of frontal fibrosing alopecia are shared by both affected and clinically unaffected areas.

Primary cicatricial alopecias are characterized by dysregulation of shared gene expression pathways

The primary forms of cicatricial (scarring) alopecia (PCA) are a group of inflammatory, irreversible hair loss disorders characterized by immune cell infiltrates targeting hair follicles (HFs). Lichen planopilaris (LPP), frontal fibrosing alopecia (FFA), and centrifugal cicatricial alopecia (CCCA) are among the main subtypes of PCAs. The pathogenesis of the different types of PCAs are poorly understood, and current treatment regimens yield inconsistent and unsatisfactory results. We performed high-throughput RNA-sequencing on scalp biopsies of a large cohort PCA patients to develop gene expression-based signatures, trained into machine-learning-based predictive models and pathways associated with dysregulated gene expression. We performed morphological and cytokine analysis to define the immune cell populations found in PCA subtypes. We identified a common PCA gene signature that was shared between LPP, FFA, and CCCA, which revealed a significant over-representation of mast cell (MC) genes, as well as downregulation of cholesterogenic pathways and upregulation of fibrosis and immune signaling genes. Immunohistological analyses revealed an increased presence of MCs in PCAs lesions. Our gene expression analyses revealed common pathways associated with PCAs, with a strong association with MCs. The indistinguishable differences in gene expression profiles and immune cell signatures between LPP, FFA, and CCCA suggest that similar treatment regimens may be effective in treating these irreversible forms of hair loss.

Lichen Planopilaris Responsive to a Novel Phytoactive Botanical Treatment: A Case Series

INTRODUCTION

Lichen planopilaris (LPP) is characterized by chronic scarring alopecia that is progressive and typically refractory to therapy. Current drug treatments are suboptimal and not applicable for long-term use because of the high potential for adverse effects, warranting safer and more effective treatment alternatives.

METHODS

Based on our previous success in treating a patient with central centrifugal cicatricial alopecia using a topical botanical formulation (Gashee), we reviewed records of four patients with biopsy-proven LPP treated with the topical formulation alone or in combination with its oral preparation. Three patients had failed previous treatment with intralesional steroid injections, topical minoxidil, tacrolimus, and clobetasol. Physical examination and photographic documentation were also used as outcome measures. Treatment duration with the botanical formulations ranged from 6 weeks to 9.5 months.

RESULTS

All patients showed overall improvement in surrogate indicators of LPP activity as evidenced by the disappearance of symptoms (pruritus, tenderness, scalp irritation, and hair shedding), improvement in hair growth, and reduction in redness. All reported a high satisfaction level and no adverse effects.

CONCLUSIONS

Patients with treatment-refractory LPP responded to a novel botanical treatment. To the best of our knowledge, this is the first published report of LPP responding to a plant-based natural treatment. Further evaluation of this treatment in a controlled trial with a larger number of patients is warranted.

Folliculitis Decalvans and Lichen Planopilaris Phenotypic Spectrum: A Case Report

The folliculitis decalvans (FD) and lichen planopilaris (LPP) phenotypic spectrum combines biphasic features of FD and LPP. It is characterized by successive or concomitant occurrence of pustules, crusts, follicular tufts, perifollicular erythema, perifollicular scales, and cicatricial alopecia and includes mixed histologic features of both FD and LPP. Here, we report the case of a 33-year-old female patient with a 30-year history of FD-LPP phenotypic spectrum lesions.

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.

Drugs targeting epithelial-to-mesenchymal transition molecules for treatment of lichen planopilaris

Primary Cicatricial or scarring alopecia (PCA) is a diverse group of hair disorders that cause permanent destruction of the pilosebaceous unit, resulting in disappearance of the follicular ostia. Lichen Planopilaris (LPP) is a subtype of primary lymphocytic cicatricial alopecia and there urgent need to identify novel molecules that successfully target specific pathogenic pathways in LPP to inhibit and reverse disease progression. Recent studies into LPP pathogenesis have discovered that follicular stem cells undergo epithelial-to-mesenchymal transition (EMT). We sought to identify drugs that target molecules involved in EMT to repurpose these drugs for treatment of LPP. We identified 8 molecules and 15 drugs that target these EMT molecules. Only 4 of these drugs, pioglitazone, tofacitinib, barcitinib, and apremilast, have been reported in individual cases or case series of patients with LPP, and controlled studies are missing. We describe each drug and mechanism of action target EMT in detail in this review article. Although studies have demonstrated the efficacy of EMT inhibitors in anti-cancer therapy, there are no studies using EMT-attenuating drugs for the treatment of LPP. The treatment molecules discussed provide a new platform for clinical studies and controlled trials in LPP.

Frontiers in Lichen Planopilaris and Frontal Fibrosing Alopecia Research: Pathobiology Progress and Translational Horizons

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are primary, lymphocytic cicatricial hair loss disorders. These model epithelial stem cell (SC) diseases are thought to result from a CD8⁺ T-cell‒dominated immune attack on the hair follicle (HF) SC niche (bulge) after the latter has lost its immune privilege (IP) for as yet unknown reasons. This induces both apoptosis and pathological epithelial‒mesenchymal transition in epithelial SCs, thus depletes the bulge, causes fibrosis, and ultimately abrogates the HFs' capacity to regenerate. In this paper, we synthesize recent progress in LPP and FFA pathobiology research, integrate our limited current understanding of the roles that genetic, hormonal, environmental, and other factors may play, and define major open questions. We propose that LPP and FFA share a common initial pathobiology, which then bifurcates into two distinct clinical phenotypes, with macrophages possibly playing a key role in phenotype determination. As particularly promising translational research avenues toward direly needed progress in the management of these disfiguring, deeply distressful cicatricial alopecia variants, we advocate to focus on the development of bulge IP and epithelial SC protectants such as, for example, topically effective, HF‒penetrating and immunoinhibitory preparations that contain tacrolimus, peroxisome proliferator-activated receptor-γ, and/or CB1 agonists.

Primary cicatricial alopecia: Recent advances in evaluation and diagnosis based on trichoscopic and histopathological observation, including overlapping and specific features

Primary cicatricial alopecia (PCA) is a form of alopecia in which inflammatory cells target follicles, including the bulge region containing follicular stem cells, leading to permanent alopecia. New classifications of PCA subtypes have recently been proposed, including those that account for novel trichoscopic and histopathological features of PCA, enabling greater precision in the evaluation and diagnosis of this condition. Nonetheless, diagnosis remains challenging clinically and histopathologically because the etiology of PCA is multifactorial. Inconsistent use of terminology, overlapping disease concepts, and changes in the clinical or histopathological severity of inflammation in the disease course in the same patient also make diagnosis quite challenging. The present study comprehensively reviews recent progress in diagnostic techniques, including the use of clinical, trichoscopic, and histopathological features, in evaluating each PCA subtype, containing overlapping and specific features. Elucidating the features of PCA, including those that are common to multiple subtypes as well as specific to each in both early and advanced-stage lesions, is important for accurate diagnosis. Improving the evaluation and treatment of this disease depends on having a broader clinical understanding that takes into account not only the features of the disease at a given point in time, but also the changes that occur during the entire disease course.

Frontal Fibrosing Alopecia survey of severity assessment methods in routine clinical practice and validation of the IFFACG measurement guidance

BACKGROUND

Lack of validated and responsive outcome measures in the management of Frontal Fibrosing Alopecia (FFA) significantly limits our ability to assess disease progression and treatment response over time.

OBJECTIVES

The aim of this study was to understand how FFA extent and progression is currently assessed in UK specialist centres, validate components of the International FFA Cooperative Group (IFFACG) statement on FFA assessment, and identify pragmatic advice to improve FFA management in clinic.

METHODS

Consultant Dermatologists with a specialist interest in hair loss (n=17) were invited to take part. Preferred FFA assessment methods were explored using questionnaires and clinical scenarios. Participants were asked to identify and mark the current hairline in 10 frontal and 10 temporal hairline images, with assessment repeated 3 months later (to assess intra-individual variability) and 12 months later (to test whether inter-individual accuracy could be improved with simple instruction).

RESULTS

All 17 clinicians (100%) completed the questionnaire at each time interval. We identified a wide variation in assessment techniques between our experts. Measurements were perceived as the most accurate method of assessing frontal recession whereas photography was preferred for temporal recession. Inter-rater reliability between clinicians measuring the frontal hairline scenarios indicated a moderate strength of agreement (ICC 0.613; 95% CI: 0.398 to 0.848), yet intra-rater reliability was found to be poor with wide limits of agreement (-8.71mm to 9.92mm) on follow-up. Importantly, when clear guidance was provided on how the hairline should be identified (questionnaire 3), inter-rater reliability improved significantly, with an ICC 0.702 suggesting moderate agreement (95% CI: 0.508 to 0.890; p<0.001). A similar pattern was seen with temporal hairline measurements, which again improved in accuracy with instruction.

CONCLUSION

We show that accuracy of measurements in FFA can be improved with simple instruction and validate components of the IFFACG measurement recommendations.

Scarring Alopecias: Pathology and an Update on Digital Developments

Primary cicatricial alopecias (PCA) represent a challenging group of disorders that result in irreversible hair loss from the destruction and fibrosis of hair follicles. Scalp skin biopsies are considered essential in investigating these conditions. Unfortunately, the recognised complexity of histopathologic interpretation is compounded by inadequate sampling and inappropriate laboratory processing. By sharing our successes in developing the communication pathway between the clinician, laboratory and histopathologist, we hope to mitigate some of the difficulties that can arise in managing these conditions. We provide insight from clinical and pathology practice into how diagnoses are derived and the key histological features observed across the most common PCAs seen in practice. Additionally, we highlight the opportunities that have emerged with advances in digital pathology and how these technologies may be used to develop clinicopathological relationships, improve working practices, enhance remote learning, reduce inefficiencies, optimise diagnostic yield, and harness the potential of artificial intelligence (AI).

Essential Role of STAT3 Signaling in Hair Follicle Homeostasis

Dominant-negative mutations associated with signal transducer and activator of transcription 3 (STAT3) signaling, which controls epithelial proliferation in various tissues, lead to atopic dermatitis in hyper IgE syndrome. This dermatitis is thought to be attributed to defects in STAT3 signaling in type 17 helper T cell　specification. However, the role of STAT3 signaling in skin epithelial cells remains unclear. We found that STAT3 signaling in keratinocytes is required to maintain skin homeostasis by negatively controlling the expression of hair follicle-specific keratin genes. These expression patterns correlated with the onset of dermatitis, which was observed in specific pathogen-free conditions but not in germ-free conditions, suggesting the involvement of Toll-like receptor-mediated inflammatory responses. Thus, our study suggests that STAT3-dependent gene expression in keratinocytes plays a critical role in maintaining the homeostasis of skin, which is constantly exposed to microorganisms.

Clinicopathological characteristics and treatment outcomes of fibrosing alopecia in a pattern distribution: A retrospective cohort study

BACKGROUND

Fibrosing alopecia in a pattern distribution (FAPD) is a primary cicatricial alopecia considered a subtype of lichen planopilaris (LPP).

OBJECTIVE

The clinical and histopathological features, and treatment response of 24 female patients with FAPD were evaluated.

METHODS

Demographic, clinical, histopathological and treatment data of patients with FAPD were retrospectively collected.

RESULTS

Twenty-four women were included (mean age 60.7 years). The mean Lichen Planopilaris Activity Index score was 1.50, and the median Sinclair grade was 3. Twelve patients had diffuse alopecia in the centroparietal region, four had frontal accentuation and eight had vertex accentuation of hair loss. Eight had associated loss of facial hair. Predominant trichoscopic features included hair shaft diameter variability (100%), perifollicular erythema and/or scaling (95%) and loss of follicular ostia (95%). Histopathological examination revealed features of scarring alopecia with interface changes in follicular epithelia mainly targeting terminal and intermediate hairs, and less frequently, vellus hairs. Treatment with hair growth-promoting, anti-inflammatory and anti-androgen agents arrested disease progression in 14 patients and resulted in hair regrowth in two patients. Six patients had progression of their hair loss in spite of treatment.

LIMITATIONS

Referral bias to a specialist hair clinic, retrospective design and small sample size.

CONCLUSIONS

We present clinicopathological features of FAPD which can aid in the diagnosis of this insidious scarring alopecia. Our findings suggest a more favourable outcome if treatment is initiated in early stages of the disease.

An Approach to Patients with Alopecia

Alopecia is a dermatologic condition in which sudden or gradual loss of hair occurs on 1 or more areas of the body, most commonly the scalp. Hair loss can be acute or chronic in nature as a result of underlying inflammation, autoimmune processes, stressors, chemotherapy, or hairstyling practices. Alopecia can have substantial psychological consequences, having a negative impact on the quality of life in affected patients. The ability to both recognize and distinguish these condition holds great significance not only in providing adequate and timely treatment to improve outcomes but also meeting patient needs.

Hair follicle stem cells as a skin-organizing signaling center during adult homeostasis

Stem cells are the essential source of building blocks for tissue homeostasis and regeneration. Their behavior is dictated by both cell-intrinsic cues and extrinsic cues from the microenvironment, known as the stem cell niche. Interestingly, recent work began to demonstrate that hair follicle stem cells (HFSCs) are not only passive recipients of signals from the surroundings, but also actively send out signals to modulate the organization and function of their own niches. Here, we discuss recent findings, and briefly refer to the old, on the interaction of HFSCs and their niches with the emphasis on the outwards signals from HFSCs toward their niches. We also highlight recent technology advancements that further promote our understanding of HFSC niches. Taken together, the HFSCs emerge as a skin-organizing center rich in signaling output for niche remodeling during various stages of adult skin homeostasis. The intricate crosstalk between HFSCs and their niches adds important insight to skin biology that will inform clinical and bioengineering fields aiming to build complete and functional 3D organotypic cultures for skin replacement therapies.

Scalp and serum profiling of frontal fibrosing alopecia reveals scalp immune and fibrosis dysregulation with no systemic involvement

BACKGROUND

Frontal fibrosing alopecia (FFA) is a progressive, scarring alopecia of the frontotemporal scalp that poses a substantial burden on quality of life. Large-scale global profiling of FFA is lacking, preventing the development of effective therapeutics.

OBJECTIVE

To characterize FFA compared to normal and alopecia areata using broad molecular profiling and to identify biomarkers linked to disease severity.

METHODS

This cross-sectional study assessed 33,118 genes in scalp using RNA sequencing and 350 proteins in serum using OLINK high-throughput proteomics. Disease biomarkers were also correlated with clinical severity and a fibrosis gene set.

RESULTS

Genes differentially expressed in lesional FFA included markers related to Th1 (IFNγ/CXCL9/CXCL10), T-cell activation (CD2/CD3/CCL19/ICOS), fibrosis (CXCR3/FGF14/FGF22/VIM/FN1), T-regulatory (FOXP3/TGFB1/TGFB3), and Janus kinase/JAK (JAK3/STAT1/STAT4) (Fold changes [FCH]>1.5, FDR<.05 for all). Only one protein, ADM, was differentially expressed in FFA serum compared to normal (FCH>1.3, FDR<.05). Significant correlations were found between scalp biomarkers (IL-36RN/IL-25) and FFA severity, as well as between JAK/STAT and fibrosis gene-sets (r>.6; P <.05).

LIMITATIONS

This study was limited by a small sample size and predominantly female FFA patients.

CONCLUSION

Our data characterize FFA as an inflammatory condition limited to scalp, involving Th1/JAK skewing, with associated fibrosis and elevated T-regulatory markers, suggesting the potential for disease reversibility with JAK/STAT inhibition.

A Cell Membrane-Level Approach to Cicatricial Alopecia Management: Is Caveolin-1 a Viable Therapeutic Target in Frontal Fibrosing Alopecia?

Irreversible destruction of the hair follicle (HF) in primary cicatricial alopecia and its most common variant, frontal fibrosing alopecia (FFA), results from apoptosis and pathological epithelial-mesenchymal transition (EMT) of epithelial HF stem cells (eHFSCs), in conjunction with the collapse of bulge immune privilege (IP) and interferon-gamma-mediated chronic inflammation. The scaffolding protein caveolin-1 (Cav1) is a key component of specialized cell membrane microdomains (caveolae) that regulates multiple signaling events, and even though Cav1 is most prominently expressed in the bulge area of human scalp HFs, it has not been investigated in any cicatricial alopecia context. Interestingly, in mice, Cav1 is involved in the regulation of (1) key HF IP guardians (TGF-β and α-MSH signaling), (2) IP collapse inducers/markers (IFNγ, substance P and MICA), and (3) EMT. Therefore, we hypothesize that Cav1 may be an unrecognized, important player in the pathobiology of cicatricial alopecias, and particularly, in FFA, which is currently considered as the most common type of primary lymphocytic scarring alopecia in the world. We envision that localized therapeutic inhibition of Cav1 in management of FFA (by cholesterol depleting agents, i.e., cyclodextrins/statins), could inhibit and potentially reverse bulge IP collapse and pathological EMT. Moreover, manipulation of HF Cav1 expression/localization would not only be relevant for management of cicatricial alopecia, but FFA could also serve as a model disease for elucidating the role of Cav1 in other stem cell- and/or IP collapse-related pathologies.

Resident Memory T Cells in Autoimmune Skin Diseases

Tissue resident memory T cells (TRM) are a critical component of the immune system, providing the body with an immediate and highly specific response against pathogens re-infecting peripheral tissues. More recently, however, it has been demonstrated that TRM cells also form during autoimmunity. TRM mediated autoimmune diseases are particularly destructive, because unlike foreign antigens, the self-antigens are never cleared, continuously activating self-reactive TRM T cells. In this article, we will focus on how TRMs mediate disease in autoimmune skin conditions, specifically vitiligo, psoriasis, cutaneous lupus erythematosus, alopecia areata and frontal fibrosing alopecia.

Frontal Fibrosing Alopecia: A Review

Frontal fibrosing alopecia is a scarring alopecia, the prevalence of which is increasing worldwide since its first description in 1994. The reason for this emerging epidemic may be a higher exposure to an unknown trigger, although its aethiology and pathogenesis still remain enigmatic. Clinical, trichoscopic, sonographic, and histopathologic findings are allowing clinicians to understand more aspects about this type of cicatricial alopecia. Several treatments have been used in frontal fibrosing alopecia, although the 5-alpha reductase inhibitors seem to be the most promising. The aim of this report is to provide a compilation about the published data regarding frontal fibrosing alopecia in a narrative review.

Compartmentalised metabolic programmes in human anagen hair follicles: New targets to modulate epithelial stem cell behaviour, keratinocyte proliferation and hair follicle immune status?

Human scalp hair follicles (HF) preferentially engage in glycolysis followed by lactate production in the presence of oxygen (i.e. the Warburg effect). Through the spatiotemporally controlled expression of key metabolic proteins, we hypothesise that the Warburg effect and other HF metabolic programmes are compartmentalised by region in order to regulate regional cell fate and phenotypes, such as epithelial stem cell quiescence in the bulge or keratinocyte proliferation in the hair matrix. We further propose that metabolic conditions in the HF are organised in accordance with the lactate shuttle, hypothesised to occur in other tissue systems and tumours, but never before described in the HF. Specifically, we argue that lactate is produced and exported by glycolytic GLUT1+ lower outer root sheath (ORS) keratinocytes. We further propose that lactate is then utilised by neighbouring highly proliferative matrix keratinocytes to fuel oxidative metabolism via MCT1-mediated uptake. Furthermore, as lactate has been described to be immunomodulatory, its production and accumulation could enhance immune tolerance in the HF bulb. Here we delineate how to experimentally probe this hypothesis, define major open questions and present preliminary immunohistological evidence in support of metabolic compartmentalisation and lactate shuttling. Overall, we argue that basic and translational hair research needs to rediscover the importance of lactate in human HF biology, well beyond its recognised role in murine HF epithelial stem cells, and should explore how HF metabolism can be therapeutically targeted to modulate hair growth and the immunological HF microenvironment as a novel strategy for managing hair loss disorders.

Human epithelial stem cell survival within their niche requires "tonic" cannabinoid receptor 1-signalling-Lessons from the hair follicle

The endocannabinoid system (ECS) regulates multiple aspects of human epithelial physiology, including inhibition/stimulation of keratinocyte proliferation/apoptosis, respectively. Yet, how the ECS impacts on human adult epithelial stem cell (eSC) functions remains unknown. Scalp hair follicles (HFs) offer a clinically relevant, prototypic model system for studying this directly within the native human stem cell niche. Here, we show in organ-cultured human HFs that, unexpectedly, selective activation of cannabinoid receptor-1 (CB1)-mediated signalling via the MAPK (MEK/Erk 1/2) and Akt pathways significantly increases the number and proliferation of cytokeratin CK15+ or CK19+ human HF bulge eSCs in situ, and enhances CK15 promoter activity in situ. In striking contrast, CB1-stimulation promotes apoptosis in the differentiated progeny of these eSCs (CK6+ HF keratinocytes). Instead, intrafollicular CB1 gene knockdown or CB1 antagonist treatment significantly reduces human HF eSCs numbers and stimulates their apoptosis, while CB1 knockout mice exhibit a reduced bulge eSCs pool in vivo. This identifies "tonic" CB1 signalling as a required survival stimulus for adult human HF eSCs within their niche. This novel concept must be taken into account whenever the human ECS is targeted therapeutically.