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

Experimentally Induced Epithelial-Mesenchymal Transition of Human Hair Follicle Stem Cells as a Model of Scarring Alopecia Ex Vivo

Primary cicatricial alopecia is characterized by a permanent "scarring" alopecia. This condition is characterized by the irreversible loss of hair follicles (HF) as a result of apoptosis and epithelial-mesenchymal transition (EMT) of epithelial stem cells localized in the HF bulge.We here report the procedure for experimentally induced EMT in healthy human epidermal stem cells (eSCs) using full-length HF organ culture ex vivo. The present model can be used to recapitulate the complex processes observed in scarring alopecia patient tissues, to further investigate the mechanisms involved in EMT transformation of HFeSCs, and to test substances that could prevent and/or rescue HFeSCs from EMT for the management of scarring alopecias.

PPAR-γ signalling as a key mediator of human hair follicle physiology and pathology

Peroxisome proliferator-activated receptors (PPARs) are abundantly expressed in human skin, with PPAR-γ being the most intensively investigated isoform. In various ex vivo and in vivo models, PPAR-γ-mediated signalling has recently surfaced as an essential element of hair follicle (HF) development, growth and stem cell biology. Moreover, the availability of novel, topically applicable PPAR-γ modulators with a favourable toxicological profile has extended the range of potential applications in clinical dermatology. In this review, we synthesize where this field currently stands and sketch promising future research avenues, focussing on the role of PPAR-γ-mediated signalling in the biology and pathology of human scalp HFs, with special emphasis on scarring alopecias such as lichen planopilaris and frontal fibrosing alopecia as model human epithelial stem cell diseases. In particular, we discuss whether and how pharmacological modulation of PPAR-γ signalling may be employed for the management of hair growth disorders, for example, in scarring alopecia (by reducing HF inflammation as well as by promoting the survival and suppressing pathological epithelial-mesenchymal transition of keratin 15 + epithelial stem cells in the bulge) and in hirsutism/hypertrichosis (by promoting catagen development). Moreover, we explore the potential role of PPAR-γ in androgenetic alopecia, HF energy metabolism and HF ageing, and consider clinical perspectives that emanate from the limited data available on this so far. As this field of translational human hair research is still in its infancy, many open questions exist, for which we briefly delineate selected experimental approaches that promise to generate instructive answers in the near future.

Transepidermal UV radiation of scalp skin ex vivo induces hair follicle damage that is alleviated by the topical treatment with caffeine

Objectives

Although the effect of ultraviolet radiation (UVR) on human skin has been extensively studied, very little is known on how UVR impacts on hair follicle (HF) homeostasis. Here, we investigated how solar spectrum UVR that hits the human skin surface impacts on HF biology, and whether any detrimental effects can be mitigated by a widely used cosmetic and nutraceutical ingredient, caffeine.

Methods

Human scalp skin with terminal HFs was irradiated transepidermally ex vivo using either 10 J/cm²UVA (340–440 nm) + 20 mJ/cm²UVB (290–320 nm) (low dose) or 50 J/cm²UVA + 50 mJ/cm²UVB (high dose) and organ‐cultured under serum‐free conditions for 1 or 3 days. 0.1% caffeine (5.15 mmol/L) was topically applied for 3 days prior to UV exposure with 40 J/cm²UVA + 40 mJ/cm²UVB and for 3 days after UVR. The effects on various toxicity and vitality read‐out parameters were measured in defined skin and HF compartments.

Results

Consistent with previous results, transepidermal UVR exerted skin cytotoxicity and epidermal damage. Treatment with high and/or low UVA+UVB doses also induced oxidative DNA damage and cytotoxicity in human HFs. In addition, it decreased proliferation and promoted apoptosis of HF outer root sheath (ORS) and hair matrix (HM) keratinocytes, stimulated catagen development, differentially regulated the expression of HF growth factors, and induced perifollicular mast cell degranulation. UVR‐mediated HF damage was more severe after irradiation with high UVR dose and reached also proximal HF compartments. The topical application of 0.1% caffeine did not induce skin or HF cytotoxicity and stimulated the expression of IGF‐1 in the proximal HF ORS. However, it promoted keratinocyte apoptosis in selected HF compartments. Moreover, caffeine provided protection towards UVR‐mediated HF cytotoxicity and dystrophy, keratinocyte apoptosis, and tendential up‐regulation of the catagen‐promoting growth factor.

Conclusion

Our study highlights the clinical relevance of our scalp UV irradiation ex vivo assay and provides the first evidence that transepidermal UV radiation negatively affects important human HF functions. This suggests that it is a sensible prophylactic strategy to integrate agents such as caffeine that can act as HF photoprotectants into sun‐protective cosmeceutical and nutraceutical formulations.

Priming mobilization of hair follicle stem cells triggers permanent loss of regeneration after alkylating chemotherapy

The maintenance of genetic integrity is critical for stem cells to ensure homeostasis and regeneration. Little is known about how adult stem cells respond to irreversible DNA damage, resulting in loss of regeneration in humans. Here, we establish a permanent regeneration loss model using cycling human hair follicles treated with alkylating agents: busulfan followed by cyclophosphamide. We uncover the underlying mechanisms by which hair follicle stem cells (HFSCs) lose their pool. In contrast to immediate destructive changes in rapidly proliferating hair matrix cells, quiescent HFSCs show unexpected massive proliferation after busulfan and then undergo large-scale apoptosis following cyclophosphamide. HFSC proliferation is activated through PI3K/Akt pathway, and depletion is driven by p53/p38-induced cell death. RNA-seq analysis shows that HFSCs experience mitotic catastrophe with G2/M checkpoint activation. Our findings indicate that priming mobilization causes stem cells to lose their resistance to DNA damage, resulting in permanent loss of regeneration after alkylating chemotherapy.

Hair follicles (HFs) are sensitive to chemotherapy but recover from quiescent HF stem cells, although sometimes chemotherapy results in permanent loss. Here, Kim et al. establish a model of permanent chemotherapy-induced alopecia to uncover the underlying mechanisms depleting human HF stem cells.

Non-invasive Approaches for the Diagnosis of Autoimmune/Autoinflammatory Skin Diseases-A Focus on Psoriasis and Lupus erythematosus

The traditional diagnostic gold standard for inflammatory skin lesions of unclear etiology is dermato-histopathology. As this approach requires an invasive skin biopsy, biopsy processing and analysis by specialized histologists, it is a resource intensive approach requiring trained healthcare professionals. In many health care settings access to this diagnostic approach can be difficult and outside emergency cases will usually take several weeks. This scenario leads to delayed or inappropriate treatment given to patients. With dramatically increased sensitivity of a range of analysis systems including mass spectrometry, high sensitivity, multiplex ELISA based systems and PCR approaches we are now able to "measure" samples with unprecedented sensitivity and accuracy. Other important developments include the long-term monitoring of parameters using microneedle approaches and the improvement in imaging systems such as optical coherence tomography. In this review we will focus on recent achievements regarding measurements from non-invasive sampling, in particular from plucked hair and skin tape-strips which seem well suited for the diagnosis of lupus erythematosus and psoriatic inflammation, respectively. While these approaches will not replace clinical observation-they can contribute to improved subgroup diagnosis, stratified therapeutic approaches and have great potential for providing molecular and mechanistic insight in to inflammatory skin diseases.

Plucked hair follicles from patients with chronic discoid lupus erythematosus show a disease-specific molecular signature

OBJECTIVE

When faced with clinical symptoms of scarring alopecia-the standard diagnostic pathway involves a scalp biopsy which is an invasive and expensive procedure. This project aimed to assess if plucked hair follicles (HFs) containing living epithelial cells can offer a non-invasive approach to diagnosing inflammatory scalp lesions.

METHODS

Lesional and non-lesional HFs were extracted from the scalp of patients with chronic discoid lupus erythematosus (CDLE), psoriasis and healthy controls. RNA was isolated from plucked anagen HFs and microarray, as well as quantitative real-time PCR was performed.

RESULTS

Here, we report that gene expression analysis of only a small number of HF plucked from lesional areas of the scalp is sufficient to differentiate CDLE from psoriasis lesions or healthy HF. The expression profile from CDLE HFs coincides with published profiles of CDLE from skin biopsy. Genes that were highly expressed in lesional CDLE corresponded to well-known histopathological diagnostic features of CDLE and included those related to apoptotic cell death, the interferon signature, complement components and CD8+ T-cell immune responses.

CONCLUSIONS

We therefore propose that information obtained from this non-invasive approach are sufficient to diagnose scalp lupus erythematosus. Once validated in routine clinical settings and compared with other scarring alopecias, this rapid and non-invasive approach will have great potential for paving the way for future diagnosis of inflammatory scalp lesions.

Downregulation of integrin-αvβ6 on keratinocytes in the scar of lichen planopilaris and folliculitis decalvans: Relevance for the disappearance of epidermal Langerhans cells

Primary cicatricial alopecia (PCA) is a group of poorly understood mechanisms in which the destruction of hair follicles leads to permanent hair loss. Lichen planopilaris (LPP) is a type of lymphocytic PCA and it has been known for epidermal Langerhans cells (LC) to disappear in the scar of LPP. We also found that epidermal LC also disappeared in the scar of folliculitis decalvans (FD), a type of neutrophilic PCA. Of note was that epidermal LC did not disappear in the scar of discoid lupus erythematosus, another type of lymphocytic PCA, suggesting that LC disappearance in the scar was not always a common feature of PCA. We found that the expression of integrin (ITG)-αvβ6 in scar epidermis was significantly diminished in LPP and FD, but not in other PCA and disorders accompanied with scar formation. We also found that exogenous interleukin-1β and α-interferon downregulated ITG-αvβ6 expression in normal human epidermal keratinocytes. These data suggest that downregulation of ITG-αvβ6 may be one of the causes of LC disappearance in the scar of LPP and FD.

Exosomal Micro RNAs Derived from Dermal Papilla Cells Mediate Hair Follicle Stem Cell Proliferation and Differentiation

Recent studies have demonstrated that dermal papilla cell-derived exosomes (DPC-Exos) promote the anagen stage of hair follicle (HF) growth and delay the catagen stage. However, the roles of DPC-Exos in regulating hair follicle stem cell (HFSC) quiescence and activation remain unknown. Here, we found that HFSC differentiation was induced by co-culture with DPCs, and that DPC-Exos attached to the surface of HFSCs. Using micro RNA (miRNA) high-throughput sequencing, we identified 111 miRNAs that were significantly differentially expressed between DPC-Exos and DPCs, and the predicted target genes of the top 34 differentially expressed miRNAs indicated that DPC-Exos regulate HFSCs proliferation and differentiation via genes involved in cellular signal transduction, fatty acid expression regulation, and cellular communication. The overexpression of miR-22-5p indicated that it negatively regulates HFSC proliferation and LEF1 was revealed as the direct target gene of miR-22-5p. We therefore propose the miR-22-5p-LEF1 axis as a novel pathway regulating HFSC proliferation.

UVB-induced depletion of donor-derived dendritic cells prevents allograft rejection of immune-privileged hair follicles in humanized mice

Dendritic cells (DCs) are key targets for immunity and tolerance induction; they present donor antigens to recipient T cells by donor- and recipient-derived pathways. Donor-derived DCs, which are critical during the acute posttransplant period, can be depleted in graft tissue by forced migration via ultraviolet B light (UVB) irradiation. Here, we investigated the tolerogenic potential of donor-derived DC depletion through in vivo and ex vivo UVB preirradiation (UV) combined with the injection of anti-CD154 antibody (Ab) into recipients in an MHC-mismatched hair follicle (HF) allograft model in humanized mice. Surprisingly, human HF allografts achieved long-term survival with newly growing pigmented hair shafts in both Ab-treated groups (Ab-only and UV plus Ab) and in the UV-only group, whereas the control mice rejected all HF allografts with no hair regrowth. Perifollicular human CD3⁺ T cell and MHC class II⁺ cell infiltration was significantly diminished in the presence of UV and/or Ab treatment. HF allografts in the UV-only group showed stable maintenance of the immune privilege in the HF epithelium without evidence of antigen-specific T cell tolerance, which is likely promoted by normal HFs in vivo. This immunomodulatory strategy targeting the donor tissue exhibited novel biological relevance for clinical allogeneic transplantation without generalized immunosuppression.

Genome-wide association study in frontal fibrosing alopecia identifies four susceptibility loci including HLA-B*07:02

Frontal fibrosing alopecia (FFA) is a recently described inflammatory and scarring type of hair loss affecting almost exclusively women. Despite a dramatic recent increase in incidence the aetiopathogenesis of FFA remains unknown. We undertake genome-wide association studies in females from a UK cohort, comprising 844 cases and 3,760 controls, a Spanish cohort of 172 cases and 385 controls, and perform statistical meta-analysis. We observe genome-wide significant association with FFA at four genomic loci: 2p22.2, 6p21.1, 8q24.22 and 15q2.1. Within the 6p21.1 locus, fine-mapping indicates that the association is driven by the HLA-B*07:02 allele. At 2p22.1, we implicate a putative causal missense variant in CYP1B1, encoding the homonymous xenobiotic- and hormone-processing enzyme. Transcriptomic analysis of affected scalp tissue highlights overrepresentation of transcripts encoding components of innate and adaptive immune response pathways. These findings provide insight into disease pathogenesis and characterise FFA as a genetically predisposed immuno-inflammatory disorder driven by HLA-B*07:02.

Frontal fibrosing alopecia (FFA) features lichenoid cutaneous inflammation and scarring hair loss. Here, Tziotzios et al. identify four genetic loci associated with FFA by GWAS followed by Bayesian fine-mapping, co-localisation and HLA imputation which highlights HLA-B*07:02 as a risk factor.

Evidence for neurogenic inflammation in lichen planopilaris and frontal fibrosing alopecia pathogenic mechanism

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are lymphocytic scarring alopecias affecting primarily the scalp. Although both diseases may share some clinical and histopathological features, in the last decade, FFA has become an "epidemic" particularly in Europe, North and South America with unique clinical manifestations compared to LPP, thus, raising the idea that this disease may have a different pathogenesis. Symptoms such as scalp burning, pruritus or pain are usually present in both diseases, suggesting a possible role for nerves and neuropeptides in the pathogenesis of both diseases. Based on some previous studies, neuropeptides, such as substance P (SP) and calcitonin gene-related peptide (CGRP), have been associated with lipid metabolism and many chronic inflammatory disorders. In this study, we asked if these neuropeptides are associated with LPP and FFA scalp lesions. Alteration in the expression of SP and CGRP in affected and unaffected scalp skin from patients with both diseases was found with examination of sections using immunohistochemical techniques and confocal microscopy. We then quantitatively assessed and compared SP and CGRP expression from control, LPP and FFA scalp biopsies. Although LPP and FFA share similar histopathologic findings, opposite results were found in affected and unaffected scalp in the ELISA tests, suggesting that these diseases may have different pathogenic mechanisms. We also found presence of histopathological inflammation irrespective of evident clinical lesions, which raises the possibility that both diseases may be more generalized processes affecting the scalp.

Frontal fibrosing alopecia: An update on the hypothesis of pathogenesis and treatment

Frontal fibrosing alopecia (FFA) is a relatively new scarring alopecia that is considered a variant of lichen planopilaris (LPP) with no recognized promising treatments. In this study, we tried to clarify the underlying signaling pathways and their roles in the pathogenesis and progression of FFA. Because of several differences in clinical manifestations, response to treatments, and pathological findings, these two conditions could be differentiated from each other. Taking into account the already discussed signaling pathways and involved players such as T cells, mast cells, and sebaceous glands, different possible therapeutic options could be suggested. In addition to treatments supported by clinical evidence, such as 5 alpha-reductase inhibitors, topical calcineurin inhibitors, hydroxychloroquine, peroxisome proliferator-activated receptor gamma agonists, and oral retinoid agents, various other treatment strategies and drugs, such as phototherapy, Janus kinase inhibitors, dehydroepiandrosterone, sirolimus, cetirizine, and rituximab, could be suggested to mitigate disease progression. Of course, such lines of treatment need further evaluation in clinical trials.

Study of Human Leukocyte Antigen (HLA) in 13 cases of familial frontal fibrosing alopecia: CYP21A2 gene p.V281L mutation from congenital adrenal hyperplasia linked to HLA class I haplotype HLA-A*33:01; B*14:02; C*08:02 as a genetic marker

BACKGROUND/OBJECTIVES

The aetiology of frontal fibrosing alopecia is unknown, and its genetic aspect remains uncharacterised. The aim of this report is to elucidate if major histocompatibility complex is associated with familial frontal fibrosing alopecia.

METHODS

A case-control study was performed of 13 patients with frontal fibrosing alopecia belonging to six families. Their human leukocyte antigen profiles were compared to the data of 636 healthy controls without frontal fibrosing alopecia. Patients underwent high-resolution genomic typing for human leukocyte antigen class I and II loci by PCR-SSO for Luminex. In addition, CYP21A2 gene (major histocompatibility complex class III) mutations were detected by PCR-SSO on strips.

RESULTS

61.5% of patients shared CYP21A2 gene p.V281L linked to the F16A human leukocyte antigen class I haplotype (HLA-A*33:01; B*14:02; C*08:02; Pc < 0.000001). The patients F16A-negative shared other human leukocyte antigen class I haplotypes: Y16A (3/13) and S26 (2/13).

CONCLUSION

CYP21A2 gene p.V281L mutation can be used as a genetic marker for susceptibility to familial frontal fibrosing alopecia. Both the linkage of the mutation to F16A and the fact that F16A-negative patients share other human leukocyte antigen class I haplotype, point to an antigen-driven mechanism in susceptible patients with these haplotypes.

Immune Privilege Collapse and Alopecia Development: Is Stress a Factor

Hair is a defining mammalian feature that serves as a hallmark of human communication. Given the critical significance of hair in social, religious, and political contexts, it is important to understand factors that play a role in hair loss disorders. The hair follicle is an immune privileged site, and mounting evidence suggests that the collapse of immune privilege contributes to the pathogenesis of autoimmune hair loss disorders, including alopecia areata and lichen planopilaris. This review comprehensively appraises the current literature to shed light on mechanisms for immune privilege collapse, and examines the role of neurogenic stress in triggering this process.

The eyelash follicle features and anomalies: A review

The primary role of eyelashes is to protect and maintain the health of the lid margin. However, the mechanisms to fulfill this role are not fully understood. Unraveling these mechanisms will stand to greatly improve the efficiency of eye care professionals' interventions in anomalies of the eyelashes. The aim of this article is to provide a review on eyelashes including highlights and new avenues for research; the biology of both the lash and its follicle; the pathophysiology and management of lash anomalies by eye care professionals; and the effect of iatrogenic factors on lashes. Using the database of Ovid MEDLINE, we reviewed studies specifically directed on human/mammalian eyelashes and key articles on current trends in scalp hair methodologies that can be applicable to lash research. The eyelash morphology, pigmentation and growth rate have been documented using techniques ranging from lash imaging to follicle immunohistochemistry. Furthermore, studies have demonstrated that the lash follicle is sensitive to many factors of the external environment, a variety of systemic/topical medications and cosmetics. Recently, aerodynamic studies using a mammalian eye model confirmed that an optimal lash length was needed so that eyelashes serve a protective role in reducing the number of particles that can reach the eye. Despite recent advances in lash research, studies are still scarce, due to the limited availability of the human lid for sampling. This review brings awareness that further research is needed with respect to eyelashes and will hopefully reduce the gap with scalp hair research.

Tofacitinib for the treatment of lichen planopilaris: A case series

Lichen planopilaris (LPP) is an inflammatory cicatricial alopecia for which many different therapies are attempted with varying success. The Janus kinase (JAK) inhibitor, tofacitinib, has been shown to be effective in treating the noncicatricial alopecia, alopecia areata. As in alopecia areata, upregulation of interferon and JAK signaling may play a role in LPP. We retrospectively reviewed the cases of 10 patients with recalcitrant LPP who were treated with oral tofacitinib. Patients received oral tofacitinib 5 mg twice or three times daily for 2-19 months as either monotherapy or adjunctive therapy to other ongoing treatments including intralesional triamcinolone, hydroxychloroquine, and tacrolimus ointment. Eight patients had clinical improvement in LPP with tofacitinib as either monotherapy (4/10) or adjunctive therapy (4/10). LPP Activity Index (LPPAI) before and after treatment was measured in seven patients and was significantly different (6.22 before treatment, 3.08 after treatment; p value = .0014). Reduction in LPPAI ranged from 30 to 94%. One patient complained of 10 pound (4.5 kg) weight gain after 12 months on tofacitinib. No other adverse effects were reported. Treatment with oral tofacitinib either as monotherapy or adjunctive therapy can lead to measurable improvement in recalcitrant LPP.

A proposed mechanism for central centrifugal cicatricial alopecia

Central centrifugal cicatricial alopecia (CCCA) has an unknown mechanism. Analyzing other scarring diseases (lichen planopilaris, fibrotic kidney disease and scleroderma) may help to clarify the mechanism of scarring in CCCA. These diseases were chosen for comparison due to either their location of disease (skin or scalp specifically), or prominence in patients of African descent. Genetics, possible triggers, an autoimmune lymphocytic response, and epithelial to mesenchymal transition are potentially involved. Possible common pathways in scarring diseases and a better understanding of the CCCA mechanism will lead to further research into the pathogenesis and potential treatments of CCCA.

Needle-free cutaneous delivery of living human cells by Er:YAG fractional laser ablation

BACKGROUND

Dermatological diseases, including most skin cancers and rare genetic conditions frequently originate in the epidermis. Targeted, topical cell-based therapy is a promising therapeutic strategy. Here, we present the first report demonstrating that fractional laser ablation enables local 'needle-free' intraepidermal delivery of living human cells.

METHODS

The cells penetrated porcine ear skin via microchannels created by Er:YAG fractional laser ablation; cell delivery was quantified using a haemocytometer. Cutaneous distribution was confirmed visually by laser scanning confocal microscopy and histological analysis.

RESULTS

Total cell delivery (sum of amounts permeated and deposited) after 24 h increased from 5.7 ± 0.1 x10⁵ to 9.6 ± 1.6 x10⁵ cells/cm² when increasing pore density from 300 to 600 pores/cm², - corresponding to 19- and 32-fold increases over the control. At 600 pores/cm², cell deposition was 136-fold greater than cell permeation - the latter most likely due to transport from micropores into appendageal pathways. Production of GFP post-delivery confirmed cell remained viability.

CONCLUSION

The results demonstrate the feasibility of using controlled laser microporation to achieve local 'needle-free' cutaneous delivery of living human cells to the epidermis and dermis. This raises the possibility of using this technique for targeted new approaches for dermatological therapy in these regions.

Ruxolitinib protects skin stem cells and maintains skin homeostasis in murine graft-versus-host disease

Skin GVHD targets Lgr5+ HFSCs in association with impaired hair regeneration and wound healing. Topical ruxolitinib, unlike corticosteroids, protects Lgr5+ skin stem cells and maintains skin homeostasis in skin GVHD.

Autophagy is essential for maintaining the growth of a human (mini-)organ: Evidence from scalp hair follicle organ culture

Autophagy plays a crucial role in health and disease, regulating central cellular processes such as adaptive stress responses, differentiation, tissue development, and homeostasis. However, the role of autophagy in human physiology is poorly understood, highlighting a need for a model human organ system to assess the efficacy and safety of strategies to therapeutically modulate autophagy. As a complete, cyclically remodelled (mini-)organ, the organ culture of human scalp hair follicles (HFs), which, after massive growth (anagen), spontaneously enter into an apoptosis-driven organ involution (catagen) process, may provide such a model. Here, we reveal that in anagen, hair matrix keratinocytes (MKs) of organ-cultured HFs exhibit an active autophagic flux, as documented by evaluation of endogenous lipidated Light Chain 3B (LC3B) and sequestosome 1 (SQSTM1/p62) proteins and the ultrastructural visualization of autophagosomes at all stages of the autophagy process. This autophagic flux is altered during catagen, and genetic inhibition of autophagy promotes catagen development. Conversely, an anti-hair loss product markedly enhances intrafollicular autophagy, leading to anagen prolongation. Collectively, our data reveal a novel role of autophagy in human hair growth. Moreover, we show that organ-cultured scalp HFs are an excellent preclinical research model for exploring the role of autophagy in human tissue physiology and for evaluating the efficacy and tissue toxicity of candidate autophagy-modulatory agents in a living human (mini-)organ.

Lichen planopilaris and frontal fibrosing alopecia cannot be differentiated by histopathology

BACKGROUND

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) represent 2 entities that cause primary cicatricial alopecia. These entities are clinically different; nevertheless, the literature suggests that FFA represents a form of LPP. The main argument in support of this hypothesis is that previous studies comparing the histologic findings have not found obvious differences between these diseases.

METHODS

Our objective was to more critically compare and contrast 20 histologic findings of these diseases in a large number of patients in order to determine any significant histologic differences between LPP and FFA.

RESULTS

We found 3 parameters that were statistically different, namely the presence of terminal catagen-telogen hairs (50% FFA vs 23.5% LPP; P = .020); a severe perifollicular inflammatory infiltrate (29.4% LPP vs 4.6% FFA; P = .010) and a zone of concentric lamellar fibroplasia (85.3% LPP vs 63.6% FFA; P = .041).

CONCLUSIONS

Although a few histologic features differ between FFA and LPP, we believe that these differences are too subtle or non-specific to distinguish between them with confidence. Therefore, clinical correlation is essential to establish the diagnosis.

Classic Ulcerative Pyoderma Gangrenosum Is a T Cell-Mediated Disease Targeting Follicular Adnexal Structures: A Hypothesis Based on Molecular and Clinicopathologic Studies

Background

Pyoderma gangrenosum (PG) is a debilitating ulcerative skin disease that is one of the most common associated diseases seen in patients with inflammatory bowel disease and rheumatoid arthritis. Although PG is classified as a neutrophilic dermatosis, its pathophysiology is poorly understood.

Objective

Use data obtained from patient-reported histories, immunohistochemistry, and gene expression analysis to formulate a hypothesis on PG pathophysiology.

Methods

Ten PG patients participated and answered questions about new ulcer formation. Skin biopsies of healed prior ulcers and adjacent normal skin were obtained from four patients for immunohistochemistry. Scars from healthy patients and patients with discoid lupus were used as additional controls. New onset PG papules were analyzed using immunohistochemistry and gene expression analysis via quantitative real-time PCR.

Results

All PG patients reported that healed sites of previous ulceration are refractory to re-ulceration. Simultaneous biopsies of healed and uninvolved skin triggered ulceration only in the latter. On immunohistochemistry, healed PG scars showed complete loss of pilosebaceous units, which were present in normal skin, and to a lesser extent in control scars, and discoid scars. Early PG papules showed perivascular and peripilosebaceous T cell infiltrates, rather than neutrophils. These early inflammatory events were dominated by increased gene expression of CXCL9, CXCL10, CXCL11, IL-8, IL-17, IFNG, and IL-36G and transcription factors consistent with Th1 phenotype.

Limitations

Small sample size was the main limitation.

Conclusion

We put forth the hypothesis that PG is a T cell response resulting in the destruction of pilosebaceous units.

Lichen planopilaris: A retrospective study of 32 cases in an Australian tertiary referral hair clinic

BACKGROUND/OBJECTIVES

Lichen planopilaris is a primary lymphocytic cicatricial alopecia. Management of patients with lichen planopilaris is difficult due to a paucity of high-quality data on its epidemiology and pathogenesis and the efficacy of therapies. The purpose of this study was to report the characteristics and treatment outcomes of patients with lichen planopilaris in a tertiary referral centre.

METHODS

A retrospective review of medical records in patients with lichen planopilaris seen in the Hair Clinic at the Skin & Cancer Foundation Inc., Melbourne, from 2012 to 2016.

RESULTS

Altogether 32 patients with lichen planopilaris (29 women) were included. The onset age ranged from 17 to 77 years with a mean age of 55.2 ± 13.5 years. Scalp pruritus (84%) and perifollicular erythema (72%) were the most common presenting symptoms and signs, respectively. Lichen planopilaris involved the frontal scalp in 66% of patients, the parietal in 56%, and vertex scalp in 50%. There were wide variations in treatment response.

CONCLUSION

Lichen planopilaris is characterised by a marked female predominance and clinically with pruritus, perifollicular erythema and perifollicular scale. The current range of treatments used produced mixed and often unsatisfactory results. Multicentre, prospective, randomised controlled trials are warranted to provide clearer data on efficacious treatment options.

Graft versus Host Disease Presenting as Fibrosing Alopecia in a Pattern Distribution: A Model for Pathophysiological Understanding of Cicatricial Pattern Hair Loss

A case of cutaneous graft versus host disease (GvHD) presenting as fibrosing alopecia in a pattern distribution (FAPD) is discussed, possibly providing a mechanistic model for a better understanding of the pathogenic events underlying cicatricial pattern hair loss. The implication of a follicular inflammation and fibrosis associated with patterned hair loss has emerged from several independent studies. Eventually, Zinkernagel and Trüeb reported a peculiar type of cicatricial pattern hair loss with histopathological features consistent with lichen planopilaris (LPP) associated with androgenetic alopecia (AGA). With regard to its pathogenesis, LPP is regarded to constitute a T-cell-mediated autoimmune reaction. An as yet unknown antigenic stimulus from the malfunctioning hair follicle may initiate a lichenoid tissue reaction that triggers apoptosis of the follicular epithelial cells in the susceptible individual. GvHD is a complication following allogeneic tissue transplantation and is induced and maintained by immunocompetent cells from the donor tissue that particularly attack epithelia of fast-proliferating tissues in the recipient. Due to its analogies with lichen planus, GvHD constitutes a valid immunologic model for lichen planus, LPP and ultimately FAPD. Specifically, the presentation of GvHD of the scalp combines features of AGA and of LPP, as originally proposed in earlier observations on permanent alopecia after bone marrow transplantation.

Lichen Planopilaris Caused by Wig Attachment: A Case of Koebner Phenomenon in Frontal Fibrosing Alopecia

Frontal fibrosing alopecia (FFA) represents a distinctive condition with a marginal scarring alopecia along the frontal and temporal hairline. Since its original description, the condition has been recognized to represent a more generalized than localized process, with extension beyond the frontotemporal hairline to include the parieto-occipital hairline and involve peculiar facial papules as evidence of facial vellus hair involvement and loss of peripheral body hair. Finally, the association of FFA with oral lichen planus, nail involvement, and concomitant lichen planopilaris (LPP) points to a close relationship to lichen planus. The Koebner phenomenon or isomorphic reaction has been described in lichen planus, LPP, and ultimately FFA, with face-lift procedures and hair restoration surgery having been implicated as the culprits in the latter. We report the first case of FFA in whom LPP developed at the sites of wig attachments, providing the evidence for Koebner phenomenon. Therefore, wigs are to be included to the list of procedures for hair restoration at risk of eliciting an isomorphic reaction in patients with FFA. Ultimately, the association of Koebner phenomenon with LPP-type lesions in FFA may provide further insight into the underlying pathology and nosology of the condition.

Autologous Hair Transplantation in Frontal Fibrosing Alopecia

We report a patient with frontal fibrosing alopecia (FFA), in whom autologous hair transplantation was successfully performed despite evidence of active disease. Since the underlying pathology of FFA is usually lichen planopilaris, reservations, and caveats have been expressed with respect to the risk of köbnerization phenomena following hair transplantation surgery. An important question that arises is how the lichenoid tissue reaction pattern is generated around the hair follicles in FFA. Follicles with some form of damage or malfunction might express cytokine profiles that attract inflammatory cells to assist in damage repair or in the initiation of apoptosis-mediated organ deletion. Alternatively, an as yet unknown antigenic stimulus from the damaged or malfunctioning hair follicle might initiate a lichenoid tissue reaction in the immunogenetically susceptible individual. Therefore, it might be expected that the transplantation of whole healthy hair follicles might less give rise to an inflammatory reaction than the disease itself, as revealed in our case report of successful hair transplantation in FFA.

PPAR-γ Agonists and Their Role in Primary Cicatricial Alopecia

Peroxisome proliferator-activated receptor γ (PPAR-γ) is a ligand-activated nuclear receptor that regulates the transcription of various genes. PPAR-γ plays roles in lipid homeostasis, sebocyte maturation, and peroxisome biogenesis and has shown anti-inflammatory effects. PPAR-γ is highly expressed in human sebaceous glands. Disruption of PPAR-γ is believed to be one of the mechanisms of primary cicatricial alopecia (PCA) pathogenesis, causing pilosebaceous dysfunction leading to follicular inflammation. In this review article, we discuss the pathogenesis of PCA with a focus on PPAR-γ involvement in pathogenesis of lichen planopilaris (LPP), the most common lymphocytic form of PCA. We also discuss clinical trials utilizing PPAR-agonists in PCA treatment.

Divergent proliferation patterns of distinct human hair follicle epithelial progenitor niches in situ and their differential responsiveness to prostaglandin D2

Human scalp hair follicles (hHF) harbour several epithelial stem (eHFSC) and progenitor cell sub-populations organised into spatially distinct niches. However, the constitutive cell cycle activity of these niches remains to be characterized in situ. Therefore, the current study has studied these characteristics of keratin 15+ (K15), CD200+ or CD34+ cells within anagen VI hHFs by immunohistomorphometry, using Ki-67 and 5-ethynyl-2'-deoxyuridine (EdU). We quantitatively demonstrate in situ the relative cell cycle inactivity of the CD200+/K15+ bulge compared to other non-bulge CD34+ and K15+ progenitor compartments and found that in each recognized eHFSC/progenitor niche, proliferation associates negatively with eHFSC-marker expression. Furthermore, we also show how prostaglandin D2 (PGD2), which is upregulated in balding scalp, differentially impacts on the proliferation of distinct eHFSC populations. Namely, 24 h organ-cultured hHFs treated with PGD2 displayed reduced Ki-67 expression and EdU incorporation in bulge resident K15+ cells, but not in supra/proximal bulb outer root sheath K15+ progenitors. This study emphasises clear differences between the cell cycle behaviour of spatially distinct stem/progenitor cell niches in the hHF, and demonstrates a possible link between PGD2 and perturbed proliferation dynamics in epithelial stem cells.

Epithelial-to-Mesenchymal Stem Cell Transition in a Human Organ: Lessons from Lichen Planopilaris

Epithelial-to-mesenchymal transition (EMT) is critical for embryonic development and wound healing, and occurs in fibrotic disease and carcinoma. Here, we show that EMT also occurs within the bulge, the epithelial stem cell (eSC) niche of human scalp hair follicles, during the inflammatory permanent alopecia, lichen planopilaris. We show that a molecular EMT signature can be experimentally induced in healthy human eSCs in situ by antagonizing E-cadherin, combined with transforming growth factor-β1, epidermal growth factor, and IFN-γ administration, which to our knowledge has not been reported previously. Moreover, induction of EMT within primary human eSCs can be prevented and even partially reversed ex vivo by peroxisome proliferator-activated receptor-γ agonists, likely through suppression of the transforming growth factor-β signaling pathway. Furthermore, we show that peroxisome proliferator-activated receptor-γ agonists also attenuates the EMT signature even in lesional lichen planopilaris hair follicles ex vivo. We introduce lichen planopilaris as a model disease for pathological EMT in human adult eSCs, report a preclinical assay for therapeutically manipulating eSC EMT within a healthy human (mini-)organ, and show that peroxisome proliferator-activated receptor-γ agonists are promising agents for suppressing and partially reversing EMT in human hair follicles eSCs ex vivo, including in lichen planopilaris.

Delayed Hair Follicle Morphogenesis and Hair Follicle Dystrophy in a Lipoatrophy Mouse Model of Pparg Total Deletion

PPARγ regulates multiple aspects of skin physiology, including sebocyte differentiation, keratinocyte proliferation, epithelial stem cell survival, adipocyte biology, and inflammatory skin responses. However, the effects of its global deletion, namely of nonredundant key functions of PPARγ signaling in mammalian skin, are yet unknown because of embryonic lethality. Here, we describe the skin and hair phenotype of a whole-body PPARγ-null mouse (Pparg^Δ/Δ), obtained by preserving PPARγ expression in the placenta. Pparg^Δ/Δ mice exhibited total lipoatrophy and complete absence of sebaceous glands. Right after birth, hair follicle (HF) morphogenesis was transiently delayed, along with reduced expression of HF differentiation markers and of transcriptional regulators necessary for HF development. Later, adult Pparg^Δ/Δ mice developed scarring alopecia and severe perifollicular inflammation. Skin analyses in other models of lipodystrophy, AZIP^tg/+ and Adipoq-Cre^tg/+Pparg^fl/fl mice, coupled with skin graft experiments, showed that the early defects observed in hair morphogenesis were caused by the absence of adipose tissue. In contrast, the late alteration of HF cycle and appearance of inflammation were observed only in Pparg^Δ/Δ mice and likely were due to the lack sebaceous glands. Our findings underscore the increasing appreciation for the importance of adipose tissue-mediated signals in HF development and function.

Lichen Planopilaris with Pustules: A Diagnostic Challenge

Introduction

Lichen planopilaris (LPP) is a lymphocytic primary cicatricial alopecia presenting with scarring hair loss and variable degrees of perifollicular erythema and scaling. Pustules are infrequent and may mimic folliculitis decalvans (FD) and other forms of neutrophilic alopecia. We present a series of LPP cases with pustules and discuss the importance of differentiating them from primary neutrophilic folliculitis.

Materials and Methods

Demographic, clinical, histopathological, and follow-up data of 13 cases of LPP with pustules followed at the Department of Dermatology of the University of São Paulo Medical School were described.

Results

Seven females and 6 males were included. Onset of signs and symptoms ranged from 23 to 61 years of age. Previous diagnoses were FD in 3 patients, pityriasis amiantacea in 2 cases, and folliculitis keloidalis nuchae in 1 case. Other 7 cases presented typical clinical features of LPP.

Discussion

There is limited data concerning LPP with pustules. Our analysis shows that LPP should be considered a differential diagnosis in patients with refractory folliculitis. Cautious examination of the entire scalp with dermoscopy and/or reevaluation after a course of antibiotics can avoid misdiagnosis. Further studies are required to establish the etiology of pustules in the setting of LPP.