Alterations in innate immunity and epithelial cell differentiation are the molecular pillars of hidradenitis suppurativa

The Sebaceous Gland: A Key Player in the Balance Between Homeostasis and Inflammatory Skin Diseases

The sebaceous gland (SG) is an integral part of the pilosebaceous unit and is a very active and dynamic organ that contributes significantly to the maintenance of skin homeostasis. In addition to its primary role in sebum production, the SG is involved in the maintenance of skin barrier function, local endocrine/neuroendocrine function, the innate immune response, and the regulation of skin bacterial colonization. Structural and functional alterations of SGs leading to the dysregulation of sebum production/composition and immune response may contribute to the pathogenesis of inflammatory dermatoses. This review summarises the current knowledge on the contribution of SGs to the pathogenesis of common inflammatory skin diseases. These findings are crucial for the development of more effective therapeutic strategies for the treatment of inflammatory dermatoses.

Hidradenitis Suppurativa Tunnels: Unveiling a Unique Disease Entity

Hidradenitis suppurativa tunnel structures lined with epithelium within the dermis are unique features of advanced disease stages that significantly impair patients' QOL. The presence of hidradenitis suppurativa tunnels is associated with a decreased likelihood of achieving a clinical response, even when receiving biological therapy. The cellular and molecular mechanisms underlying tunnel formation and pathology are only partially understood, which hampers the development of more effective targeted therapies. Tunnels create a unique microenvironment that drives a vicious cycle of hidradenitis suppurativa inflammation, with tunnel keratinocytes exhibiting an activated phenotype characterized by distinct gene expression signatures. In this review, we summarize the current literature and discuss aspects of the pathophysiology of tunnels, including the role of hair follicle epidermal stem cells in tunnel formation, potential role of fibroblast-mediated epithelial-mesenchymal transition, role of dermal papilla fibroblasts, and aberrant proinflammatory repair response contributing to the observed fibrosis and scarring. Finally, tunnel structures are characterized by unique microbial dysbiosis and an overabundance of Gram-negative anaerobes that are not targeted by current therapeutics. In addition to outlining the possible mechanisms of tunnel formation, we provide perspectives on the translation of current knowledge into more effective treatment approaches for patients with hidradenitis suppurativa tunnels.

The roles of interleukin (IL)-17A and IL-17F in hidradenitis suppurativa pathogenesis: evidence from human in vitro preclinical experiments and clinical samples

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic relapsing inflammatory skin disease associated with significant comorbidities and poor quality of life. Despite uncertainty about pathways driving inflammation in HS lesions, the cytokines interleukin (IL)-17A and IL-17F have been shown to be upregulated in patients with HS. Previous studies have demonstrated that the monoclonal IgG1 antibody bimekizumab selectively inhibits IL-17F in addition to IL-17A.

OBJECTIVES

To further investigate the roles of IL-17A and IL-17F in HS pathogenesis.

METHODS

RNA sequencing (RNAseq) was conducted on skin biopsies taken at baseline and after treatment at week 12 of a phase II proof-of-concept study of bimekizumab in patients with moderate-to-severe HS. Differentially expressed genes were identified between baseline lesional and nonlesional samples and between lesional samples before and after bimekizumab treatment, to describe molecular disease mechanisms and treatment effect. Human hair follicular keratinocytes (HHFK) were cultured and treated with a supernatant of stimulated T helper (Th)17 cells in combination with anti-IL-17A, anti-IL-17F, anti-IL-17A and anti-IL-17F, or IgG control antibodies. Total mRNA was analysed by RNAseq. Cellular supernatants from the stimulated HHFKs were used as a source of Th17-induced chemoattractants in neutrophil chemotaxis assays.

RESULTS

RNAseq revealed that the most prominently upregulated genes in HS lesions included those associated with neutrophil biology. Bimekizumab treatment resulted in reduced expression of these genes. The extent of reduction in gene expression was dependent on achieving HiSCR50 (≥ 50% reduction from baseline in the total abscess and inflammatory nodule count, with no increase from baseline in abscess or draining tunnel count). In vitro dual inhibition of IL-17A and IL-17F had greater attenuation of Th17-induced HS-associated genes and neutrophil migration in HHFKs vs. IL-17A or IL-17F inhibition alone. In situ hybridization found that IL-17A- and IL-17F-producing cells in HS lesions can lack the IL-23 receptor and IL-1β could induce IL-23-independent IL-17F expression in vitro. Furthermore, mucosal-associated invariant cells in HS tunnels expressed IL-17F and IL-1 receptor type 1. IL-1β-, IL-17A- and IL-17F-expressing cells were found to be co-localized in HS lesions.

CONCLUSIONS

These data support the hypothesis that IL-17A and IL-17F play central roles in HS, a neutrophilic dermatosis. The presence of IL-1β may partly explain the high expression of IL-17F in lesional HS tissue.

Proteomics Reveals the Role of PLIN2 in Regulating the Secondary Hair Follicle Cycle in Cashmere Goats

Based on comprehensive proteomic analysis conducted across various stages of secondary hair follicles (SHFs), the growth and development regulatory mechanisms of SHFs in Jiangnan cashmere goats were studied. Proteomic analysis of skin tissue from the SHF anagen (An), catagen (Cn), and telogen (Tn) revealed 145 differentially expressed proteins (DEPs) between the An and Tn, 53 DEPs between the Cn and An, and 168 DEPs between the Cn and Tn. Gene Ontology (GO) annotations indicated that the DEPs were predominantly involved in keratin filament formation (KRTAP3-1, KRT1, KRT8), intermediate filament formation (KRT26, KRT35, KRT19, etc.), and lipid metabolism (FA2H, CERS6, ECH1, TECR, etc.). Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis identified significant enrichment of DEPs in pathways related to hair follicle growth and development. Notably, these included the PPAR signaling pathway (PLIN2, PLIN4, ACSL5, etc.), the IL-17 signaling pathway (S100A7A, LOC108633164), and the estrogen signaling pathway (KRT26, KRT35, LOC102176457.). Western blotting (WB) experiments were then performed on five DEPs (KRT28, FA2H, PLIN2, FABP7, and VNN1) to validate the consistency of the WB results with the proteomic data. Overexpression and siRNA interference of PLIN2 in dermal papilla cells (DPCs) were followed by CCK8 and flow cytometry assays, revealing that PLIN2 knockdown significantly decreased DPC proliferation while inducing apoptosis, compared to controls. These findings suggest that the PLIN2 gene plays a crucial role in modulating SHF growth cycles in cashmere goats by influencing DPC proliferation. These results provide novel insights that could inform the development of breeding strategies aimed at enhancing the cashmere yield in such goats.

Hepatocyte Growth Factor Has Unique Functions in Keratinocytes that Differ from those of IL-17A and TNF and May Contribute to Inflammatory Pathways in Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory disease that is difficult to control, and its mechanism remains unclear. Hepatocyte GF (HGF) has been reported to be significantly upregulated in the serum and skin of patients with HS, especially in the lesions with tunnels. In this study, we examined the transcriptome of HGF-treated keratinocytes and compared it with genetic profiling of HS lesions. HGF was highly expressed in HS skin, especially in the deep dermis, compared with that in healthy controls, and its source was mainly fibroblasts. HGF upregulated more genes in keratinocytes than IL-17A or TNF-a, and these genes included multiple epithelial-mesenchymal transition-related genes. Differentially expressed genes in HGF-stimulated keratinocytes were involved in activation of epithelial-mesenchymal transition-related pathways. These HGF-induced genes were significantly upregulated in HS lesions compared with those in healthy skin and nonlesions and were more strongly associated with HS tunnels. In summary, HGF was highly expressed in HS and induced epithelial-mesenchymal transition-related genes in keratinocytes; HGF-induced genes were highly associated with gene profiling of HS with tunnels, suggesting that HGF may be involved in HS tunnel formation through epithelial-mesenchymal transition.

Australasian hidradenitis suppurativa management guidelines

Hidradenitis Suppurativa is a burdensome inflammatory skin disease with significant quality of life impact. These management guidelines were developed to direct appropriate clinical management in the Australasian context. A systematic review was used for the basis of the consensus guidelines. Thirteen clinical experts were involved in a modified Delphi consensus process to develop the guidelines and treatment algorithms. Overall management strategies include appropriate severity assessment of disease and comorbidities, multimodal therapy with systemic and local treatments, and evidence-based progression along the therapeutic ladder in the event of inadequate response. Sequential monotherapy with antibiotics and/or single agent therapy is discouraged and aggressive treatment of moderate to severe disease to capture the window of opportunity is highly emphasised. Specific considerations in the setting of disease comorbidities, pregnancy and breastfeeding are also addressed. Overall, the complex nature of HS requires a complex and multimodal therapeutic response with medical, physical and surgical therapies to achieve best patient outcomes.

Hidradenitis Suppurativa Preclinical Studies: Models and Results

Hidradenitis suppurativa is a solely human disease for which-unlike for other inflammatory dermatoses-applied animal models are not available. In order to study skin cell immunology under conditions which approximate the in vivo functions, maintenance of structural tissue integrity in experimental models is essential. Consequently, several ex vivo human models using lesional, perilesional hidradenitis suppurativa and control healthy skin, have been described, which claim to represent fast and relatively simple methods to investigate the pathophysiology of hidradenitis suppurativa and to preclinically detect the effectiveness of candidate therapeutic agents. At least some of these models seem to approximate the in vivo situation by maintaining patients' skin architecture for several days and expressing biomarkers also detected in hidradenitis suppurativa skin in vivo. Validation still remains to be performed for the majority of the models by evaluating the ex vivo efficacy of drugs, which are introduced in clinical studies and/or have been approved for HS treatment.

Unravelling the complex pathogenesis of hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a complex inflammatory disease, with rapid advances being made in our understanding of the complex immunological pathogenesis of the condition. New insights into the genomic landscape of HS have identified a number of genes that contribute to the development of HS in a polygenic manner, contributing to inflammatory dysregulation and alterations in epidermal stem cell fate in the follicular unit. These genomic variations can explain unique aspects of the disease such as the development and presence of epithelialized tunnels and abnormalities in wound healing. From genetic and translational studies, it is likely that these genetic alterations predispose to an innate immune dysregulation that can be triggered through sex hormone-responsive transcription factors with hormonal changes such as puberty, pregnancy and the menstrual cycle. The role of sex hormones in HS also has direct effects upon the development and maturation of inflammatory cells such as monocytes, which has the potential to explain differential patient response to treatments such as interleukin-23 antagonism. The role of adipose tissue as an active immunological organ also plays a role in the immune dysregulation seen in the disease. Fibrotic tissue and immunologically active fibroblasts play a significant role in the perpetuation of inflammation and development of adaptive immune dysfunction in the disease. The cutaneous and gut microbiomes play significant roles in the activation of innate immunity, although conflicting data exist as to their central or peripheral role in disease pathogenesis. Overall, our understanding of disease pathogenesis in HS is moving toward a more nuanced, complex paradigm in which patient heterogeneity in presentation and immunological characteristics are moving closer to the identification of therapeutic biomarkers to guide therapeutic modalities in the management of this burdensome condition.

Neutrophil extracellular traps activate Notch-γ-secretase signaling in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is an inflammatory chronic skin disorder of unknown etiology characterized by inflamed abscess-like nodules and boils resulting in sinus tract formation, tissue scarring, and massive infiltration of neutrophils. Multiple lines of evidence have highlighted the potential association between alterations in the Notch pathway and HS pathogenesis, but the mechanisms remain incompletely characterized.

OBJECTIVE

We aimed to elucidate the role of neutrophil extracellular traps in Notch-γ-secretase signaling.

METHODS

Twenty-six HS lesional tissues, primary HS macrophages, and skin fibroblasts were interrogated by quantitative PCR, Western blot, and ELISA analyses. γ-Secretase and TNF-α converting enzyme activities were measured in HS skin lesions, macrophages, and skin fibroblasts. Immunofluorescence and RNAscope analyses were performed in HS and control skin.

RESULTS

A prominent presence of Notch ligands, Delta-like ligand 4 (DLL4), and Jagged (JAG) 2 were detected at the protein and mRNA levels in HS skin lesion compared to control. Levels of DLL4, JAG1, citrullinated histone H3 DNA, and γ-secretase activity correlated with HS disease severity. Additionally, significantly elevated levels of Notch ligands and γ-secretase activity were found in dissected sinus tracts compared to the rest of HS tissue. Immunofluorescence microscopy of HS skin lesions revealed activation of Notch-1 signaling in macrophages and skin fibroblasts. Neutrophil extracellular traps (NETs) purified from HS patients displayed elevated levels of DLL4. HS NETs activated the Notch pathway in macrophages and dermal fibroblasts isolated from HS patients. HS skin fibroblasts displayed elevated levels of CD90 and DPP4 in association with increased migratory capacity and Notch activation. Inhibition of Notch decreased migratory capacity and profibrotic markers in HS fibroblasts.

CONCLUSION

These data support a pathogenic connection between NETs, Notch-γ-secretase activation, and the release of profibrotic molecules that promote dysregulation of macrophages and skin fibroblasts in HS. Unveiling the relevance of these molecular events not only expands our understanding of HS but also opens new venues for the development of targeted therapies to address the fibrotic complications of advanced stages of HS.

The epithelial barrier theory and its associated diseases

The prevalence of many chronic noncommunicable diseases has been steadily rising over the past six decades. During this time, over 350,000 new chemical substances have been introduced to the lives of humans. In recent years, the epithelial barrier theory came to light explaining the growing prevalence and exacerbations of these diseases worldwide. It attributes their onset to a functionally impaired epithelial barrier triggered by the toxicity of the exposed substances, associated with microbial dysbiosis, immune system activation, and inflammation. Diseases encompassed by the epithelial barrier theory share common features such as an increased prevalence after the 1960s or 2000s that cannot (solely) be accounted for by the emergence of improved diagnostic methods. Other common traits include epithelial barrier defects, microbial dysbiosis with loss of commensals and colonization of opportunistic pathogens, and circulating inflammatory cells and cytokines. In addition, practically unrelated diseases that fulfill these criteria have started to emerge as multimorbidities during the last decades. Here, we provide a comprehensive overview of diseases encompassed by the epithelial barrier theory and discuss evidence and similarities for their epidemiology, genetic susceptibility, epithelial barrier dysfunction, microbial dysbiosis, and tissue inflammation.

Transcriptomic Analyses Predict Enhanced Metabolic Activity and Therapeutic Potential of mTOR Inhibitors in Acne-Prone Skin

Current acne therapies center on preventing new lesions in patients with acne. These therapies were historically found to be beneficial yet were chosen without knowledge of the specific changes in the skin that favor lesion development. A major challenge in developing new treatments is the incomplete understanding of nonlesional (NL), acne-prone skin's molecular characteristics. To address this, we compared RNA-sequencing data from NL skin of 49 patients with acne (denoted as NL acne [NLA]) with those from 19 healthy controls with no acne history. We found 77 differentially expressed genes in NLA (log fold change > 1; P < .05), including genes associated with innate immunity and epidermal barrier function. Notably, K RT 6C, K RT 16, S100A8, S100A9, and lactotransferrin were upregulated, and LCE4A, LCE6A, and CTSE were downregulated. Gene set enrichment analysis revealed that metabolic pathways were enriched in NLA skin, whereas keratinization was negatively enriched. To identify compounds that could shift the gene expression signature of NLA skin toward healthy control skin, we performed connectivity mapping with the Library of Integrated Network-Based Signatures. We identified 187 compounds, particularly mTOR inhibitors, that could potentially normalize the gene expression profile of acne-prone skin to that of healthy skin. Our findings indicate that NLA skin has distinct differences in epidermal differentiation, cellular metabolism, and innate immunity that may promote lesion formation and suggest that mTOR inhibitors could restore NLA skin toward a healthier state, potentially reversing the predisposition to lesion development.

Exome Profiling Suggests Combined Effect of Myeloperoxidase, Toll-Like Receptors, and Metallopeptidase in Hidradenitis Suppurativa

BACKGROUND

Hidradenitis suppurativa, also called acne inversa, is a chronic skin inflammatory condition involving hair follicles, sebaceous glands, and apocrine glands. Symptoms can be variable in intensity, ranging from mild to severe. The exact causes of hidradenitis suppurativa are not fully understood, but the etiology is presumed to be multifactorial, encompassing genetics and environmental factors.

METHODS

Two families presented with hidradenitis suppurativa with an autosomal dominant pattern. We performed whole-exome sequencing in two unrelated patients from the two families.

RESULTS

We identified two and three variants in the two families, respectively. Variants involved the TLR2 and MPO genes in the first family and the MMP2, GJB2, and TLR4 genes, some of which have already been previously reported as possible candidates for hidradenitis suppurativa.

CONCLUSION

It is very likely that variants in a single gene only rarely cause the condition and that most cases, especially familial hidradenitis suppurativa cases, may more probably take the form of polygenic disorders.

Proof-of-concept study exploring the effect of spesolimab in patients with moderate-to-severe hidradenitis suppurativa: a randomized double-blind placebo-controlled clinical trial

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease with a considerable disease burden. Existing treatment options are limited and often suboptimal; a high unmet need exists for effective targeted therapies.

OBJECTIVES

To explore the effects of spesolimab treatment in patients with HS.

METHODS

This randomized double-blind placebo-controlled proof-of-clinical-concept (PoCC) study was conducted at 25 centres across 12 countries from 3 May 2021 to 21 April 2022. Patients had moderate-to-severe HS for ≥ 1 year before enrolment. Patients were randomized (2 : 1) to receive a loading dose of 3600-mg intravenous spesolimab (1200 mg at weeks 0, 1 and 2) or matching placebo, followed by maintenance with either 1200-mg subcutaneous spesolimab every 2 weeks from weeks 4 to 10 or matching placebo. The primary endpoint was the percentage change from baseline in total abscess and inflammatory nodule (AN) count at week 12. Secondary endpoints were the absolute change from baseline in the International Hidradenitis Suppurativa Severity Score System (IHS4), percentage change from baseline in draining tunnel (dT) count, the proportion of patients achieving a dT count of 0, absolute change from baseline in the revised Hidradenitis Suppurativa Area and Severity Index (HASI-R), the proportion of patients achieving Hidradenitis Suppurativa Clinical Response (HiSCR50), the proportion of patients with ≥ 1 flare (all at week 12) and patient-reported outcomes.

RESULTS

In this completed trial, randomized patients (n = 52) received spesolimab (n = 35) or placebo (n = 17). The difference vs. placebo in least squares mean is reported. At week 12, the percentage change in total AN count was similar between treatment arms: -4.1% [95% confidence interval (CI) -31.7 to 23.4]. There was greater numerical improvement in the spesolimab arm, as measured by IHS4 (13.9, 95% CI -25.6 to -2.3); percentage change from baseline in dT count (-96.6%, 95% CI -154.5 to -38.8); and the proportion of patients achieving a dT count of 0 (18.3%, 95% CI -7.9 to 37.5). Spesolimab treatment also improved HASI-R and HiSCR50 vs. placebo. Spesolimab demonstrated a favourable safety profile, similar to that observed in trials in other diseases.

CONCLUSIONS

This exploratory PoCC study supports the development of spesolimab as a new therapeutic option in HS.

Comparative transcriptome analysis of acne vulgaris, rosacea, and hidradenitis suppurativa supports high-dose dietary zinc as a therapeutic agent

Acne vulgaris, rosacea, and hidradenitis suppurativa are enduring inflammatory skin conditions that frequently manifest with akin clinical attributes, posing a considerable challenge for their distinctive diagnosis. While these conditions do exhibit certain resemblances, they also demonstrate distinct underlying pathophysiological mechanisms and treatment modalities. Delving into both the molecular parallels and disparities among these three disorders can yield invaluable insights for refined diagnostics, effective management, and targeted therapeutic interventions. In this report, we present a comparative analysis of transcriptomic data across these three diseases, elucidating differentially expressed genes and enriched pathways specific to each ailment, as well as those shared among them. Specifically, we identified multiple zinc-binding proteins (SERPINA1, S100A7, S100A8, S100A9 and KRT16) as consistently highly upregulated genes across all three diseases. Our hypothesis suggests that these proteins could bind and sequester zinc, potentially leading to localized zinc deficiency and heightened inflammation. We identified high-dose dietary zinc as a promising therapeutic approach and confirmed its effectiveness through validation in an acne mouse model.

Efficacy and safety of bimekizumab in patients with moderate-to-severe hidradenitis suppurativa (BE HEARD I and BE HEARD II): two 48-week, randomised, double-blind, placebo-controlled, multicentre phase 3 trials

BACKGROUND

Patients with hidradenitis suppurativa have substantial unmet clinical needs and scarce therapeutic options. We aimed to assess the efficacy and safety of bimekizumab, a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)-17F and IL-17A, in patients with moderate-to-severe hidradenitis suppurativa.

METHODS

BE HEARD I and II were two identically designed, 48-week randomised, double-blind, placebo-controlled, multicentre phase 3 trials. Patients aged 18 years or older with moderate-to-severe hidradenitis suppurativa were randomly assigned 2:2:2:1 using interactive response technology (stratified by worst Hurley Stage at baseline and baseline systemic antibiotic use) to receive subcutaneous bimekizumab 320 mg every 2 weeks; bimekizumab 320 mg every 2 weeks to week 16, then every 4 weeks to week 48; bimekizumab 320 mg every 4 weeks to week 48; or placebo to week 16, then bimekizumab 320 mg every 2 weeks. The primary outcome was an hidradenitis suppurativa clinical response of at least 50%, defined as a reduction in total abscess and inflammatory nodule count of at least 50% from baseline with no increase from baseline in abscess or draining tunnel count (HiSCR50) at week 16. Efficacy analyses included all randomly assigned study patients (intention-to-treat population). Safety analyses included all patients who received at least one full or partial dose of study treatment in the safety set, and of bimekizumab in the active-medication set. These trials are registered at ClinicalTrials.gov, NCT04242446 and NCT04242498, and both are completed.

FINDINGS

Patients for BE HEARD I were recruited from Feb 19, 2020, to Oct 27, 2021, and 505 patients were enrolled and randomly assigned. Patients for BE HEARD II were recruited from March 2, 2020, to July 28, 2021, and 509 patients were enrolled and randomly assigned. The primary outcome at week 16 was met in the group who received bimekizumab every 2 weeks using modified non-responder imputation; higher responder rates were observed with bimekizumab versus placebo in both trials: 138 (48%) of 289 patients versus 21 (29%) of 72 patients in BE HEARD I (odds ratio [OR] 2·23 [97·5% CI 1·16-4·31]; p=0·0060) and 151 (52%) of 291 patients versus 24 (32%) of 74 patients in BE HEARD II (2·29 [1·22-4·29]; p=0·0032). In BE HEARD II, HiSCR50 was also met in the group who were administered bimekizumab every 4 weeks (77 [54%] of 144 vs 24 [32%] of 74 with placebo; 2·42 [1·22-4·80]; p=0·0038). Responses were maintained or increased to week 48. Serious treatment-emergent adverse events were reported in 40 (8%) patients in BE HEARD I and in 24 (5%) patients in BE HEARD II treated with bimekizumab over 48 weeks. The most frequently reported treatment-emergent adverse events to week 48 were hidradenitis in both trials, in addition to coronavirus infection and diarrhoea in BE HEARD I, and oral candidiasis and headache in BE HEARD II. One death was reported across the two trials, and was due to congestive heart failure in a patient with substantial cardiovascular history treated with bimekizumab every 2 weeks in BE HEARD I (considered unrelated to bimekizumab treatment by the investigator). No new safety signals were observed.

INTERPRETATION

Bimekizumab was well tolerated by patients with hidradenitis suppurativa and produced rapid and deep clinically meaningful responses that were maintained up to 48 weeks. Data from these two trials support the use of bimekizumab for the treatment of patients with moderate-to-severe hidradenitis suppurativa.

FUNDING

UCB Pharma.

S2k‐Leitlinie zur Therapie der Hidradenitis suppurativa/Acne inversa – Kurzfassung

Die S2k‐Leitlinie der Hidradenitis suppurativa/Acne inversa (HS/AI) soll eine akzeptierte Entscheidungshilfe für die Auswahl/Durchführung einer geeigneten/suffizienten Therapie liefern. Hidradenitis suppurativa/Acne inversa ist eine chronisch‐rezidivierende, entzündliche, potenziell mutilierende Hauterkrankung des terminalen Haartalgdrüsenapparats, mit schmerzhaften, entzündlichen Läsionen in den apokrinen drüsenreichen Körperregionen. Ihre Punktprävalenz in Deutschland ist 0,3%, sie wird mit einer Verspätung von 10,0 ± 9,6 Jahren diagnostiziert. Abnormale Differenzierung der Keratinozyten des Haartalgdrüsenapparats und eine begleitende Entzündung bilden die zentrale pathogenetische Grundlage. Primäre HS/AI‐Läsionen sind entzündliche Knoten, Abszesse und drainierende Tunnel. Rezidive in den letzten 6 Monaten mit mindestens zwei Läsionen an den Prädilektionsstellen verweisen auf eine HS/AI mit einer 97‐prozentigen Genauigkeit. HS/AI‐Patienten leiden an einer deutlichen Einschränkung der Lebensqualität. Zur korrekten Therapieentscheidung sollen Klassifikation und Aktivitätsbewertung mit einem validierten Instrument erfolgen, wie dem International Hidradenitis Suppurativa Severity Scoring System (IHS4). Hidradenitis suppurativa/Acne inversa wird nach der Ausprägung der nachweisbaren Entzündung in zwei Formen eingeteilt: aktive, entzündliche (milde, mittelschwere und schwere nach IHS4) und vorwiegend inaktive, nicht entzündliche (Hurley‐Grad‐I, ‐II und ‐III) HS/AI. Orale Tetrazykline oder eine 5‐tägige intravenöse Therapie mit Clindamycin sind mit der Effektivität von Clindamycin/Rifampicin vergleichbar. Subkutan applizierbares Adalimumab, Secukinumab und Bimekizumab sind für die Therapie der HS/AI zugelassen. Für die vorwiegend nicht entzündliche Erkrankungsform stehen verschiedene operative Verfahren zur Verfügung. Medikamentöse/chirurgische Kombinationen gelten als ganzheitliches Therapieverfahren.

S2k guideline for the treatment of hidradenitis suppurativa / acne inversa - Short version

The S2k guideline on hidradenitis suppurativa/acne inversa (HS/AI) aims to provide an accepted decision aid for the selection/implementation of appropriate/sufficient therapy. HS/AI is a chronic recurrent, inflammatory, potentially mutilating skin disease of the terminal hair follicle-glandular apparatus, with painful, inflammatory lesions in the apocrine gland-rich regions of the body. Its point prevalence in Germany is 0.3%, it is diagnosed with a delay of 10.0 ± 9.6 years. Abnormal differentiation of the keratinocytes of the hair follicle-gland apparatus and accompanying inflammation form the central pathogenetic basis. Primary HS/AI lesions are inflammatory nodules, abscesses and draining tunnels. Recurrences in the last 6 months with at least 2 lesions at the predilection sites point to HS/AI with a 97% accuracy. HS/AI patients suffer from a significant reduction in quality of life. For correct treatment decisions, classification and activity assessment should be done with a validated tool, such as the International Hidradenitis Suppurativa Severity Scoring System (IHS4). HS/AI is classified into two forms according to the degree of detectable inflammation: active, inflammatory (mild, moderate, and severe according to IHS4) and predominantly inactive, non-inflammatory (Hurley grade I, II and III) HS/AI. Oral tetracyclines or 5-day intravenous therapy with clindamycin are equal to the effectiveness of clindamycin/rifampicin. Subcutaneously administered adalimumab, secukinumab and bimekizumab are approved for the therapy of HS/AI. Various surgical procedures are available for the predominantly non-inflammatory disease form. Drug/surgical combinations are considered a holistic therapy method.

Alterations to the Hidradenitis Suppurativa Serum Proteome with Spleen Tyrosine Kinase Antagonism: Proteomic Results from a Phase 2 Clinical Trial

Hidradenitis suppurativa is a disease in great need of novel therapies. Given the heterogeneous nature of the disease and the variable response to therapies, biomarkers are essential to predict response to therapies and increase our understanding of disease pathogenesis. Our recent phase 2 clinical trial of spleen tyrosine kinase antagonism using fostamatinib in hidradenitis suppurativa demonstrated a 75% clinical response, with the greatest benefit in individuals with elevated serum inflammation and IgG. In this study, we present results of an in-depth serum proteomic analysis in this patient cohort identifying downregulation of IL-12B as well as B-cell-associated proteins CCL19 and CCL20 and IFN-γ-mediated proteins CXCL10 and CX3CL1. Clinical responders demonstrated greater reduction in serum IL-17A, IL-6, IL-8, and CX3CL1 compared with clinical nonresponders. Baseline levels of CCL28 were associated with clinical response to fostamatinib therapy at week 12. Overall, this suggests that fostamatinib, by targeting B-cell receptor and Fc receptor activity in B cells, monocytes, and macrophages, has a significant molecular impact on the inflammatory serum proteome of hidradenitis suppurativa. In addition, potential therapeutic biomarkers may aid in patient selection for targeted therapy.

A systematic review of Janus kinase inhibitors and spleen tyrosine kinase inhibitors for Hidradenitis suppurativa treatment

BACKGROUNDS AND AIMS

Hidradenitis suppurativa (HS) is a challenging skin disease with an underlying inflammatory process. Substantial progress has been made in our understanding of HS over the last few years, with the advancement of novel treatment approaches. The current systematic review aims to evaluate the safety and efficacy of Janus kinase (JAK) inhibitors and spleen tyrosine kinase (Syk) inhibitors in treating HS.

METHOD

A thorough systematic search was performed on PubMed/Medline, Web of Science, and Ovid Embase databases up to September 23th, 2023. Clinical studies published in English were included.

RESULTS

Our search yielded ten articles with a total of 165 patients treated with four types of JAK inhibitors (upadacitinib, povorcitinib, tofacitinib, and baricitinib) and one Syk inhibitor (fostamatinib). Upadacitinib, povorcitinib, and tofacitinib improved clinical outcomes, with a significant reduction in hidradenitis suppurativa clinical response (HiSCR) and abscess and inflammatory nodule count (AN count) during the treatment period. Also, these drugs are well tolerated in most HS patients with minimal adverse events (AEs). Moreover, baricitinib depicted an amelioration in signs and symptoms of HS in one case report. Also, fostamatinib exhibited favorable tolerability throughout a 12-week in moderate-to-severe HS patients. The remarkable clinical improvement, as assessed through HiSCR and hidradenitis suppurativa severity (IHS4), corresponded closely with serological indicators of inflammation following fostamatinib administration was achieved.

CONCLUSION

JAK and Syk inhibitors are potentially efficacious in managing moderate-to-severe HS since the proinflammatory cytokines are mediated by JAK and Syk signaling pathways. However, further research with a more rigorous examination is mandatory to evaluate such medication's long-term safety and efficacy.

Intrapatient comparison of atopic dermatitis skin transcriptome shows differences between tape-strips and biopsies

BACKGROUND

Our knowledge of etiopathogenesis of atopic dermatitis (AD) is largely derived from skin biopsies, which are associated with pain, scarring and infection. In contrast, tape-stripping is a minimally invasive, nonscarring technique to collect skin samples.

METHODS

To construct a global AD skin transcriptomic profile comparing tape-strips to whole-skin biopsies, we performed RNA-seq on tape-strips and biopsies taken from the lesional skin of 20 moderate-to-severe AD patients and the skin of 20 controls. Differentially expressed genes (DEGs) were defined by fold-change (FCH) ≥2.0 and false discovery rate <0.05.

RESULTS

We detected 4104 (2513 Up; 1591 Down) and 1273 (546 Up; 727 Down) DEGs in AD versus controls, in tape-strips and biopsies, respectively. Although both techniques captured dysregulation of key immune genes, tape-strips showed higher FCHs for innate immunity (IL-1B, IL-8), dendritic cell (ITGAX/CD11C, FCER1A), Th2 (IL-13, CCL17, TNFRSF4/OX40), and Th17 (CCL20, CXCL1) products, while biopsies showed higher upregulation of Th22 associated genes (IL-22, S100As) and dermal cytokines (IFN-γ, CCL26). Itch-related genes (IL-31, TRPV3) were preferentially captured by tape-strips. Epidermal barrier abnormalities were detected in both techniques, with terminal differentiation defects (FLG2, PSORS1C2) better represented by tape-strips and epidermal hyperplasia changes (KRT16, MKI67) better detected by biopsies.

CONCLUSIONS

Tape-strips and biopsies capture overlapping but distinct features of the AD molecular signature, suggesting their respective utility for monitoring specific AD-related immune, itch, and barrier abnormalities in clinical trials and longitudinal studies.

The Features of Shared Genes among Transcriptomes Probed in Atopic Dermatitis, Psoriasis, and Inflammatory Acne: S100A9 Selection as the Target Gene

BACKGROUND

Atopic dermatitis (AD), psoriasis (PS), and inflammatory acne (IA) are well-known as inflammatory skin diseases. Studies of the transcriptome with altered expression levels have reported a large number of dysregulated genes and gene clusters, particularly those involved in inflammatory skin diseases.

OBJECTIVE

To identify genes commonly shared in AD, PS, and IA that are potential therapeutic targets, we have identified consistently dysregulated genes and disease modules that overlap with AD, PS, and IA.

METHODS

Microarray data from AD, PS, and IA patients were downloaded from Gene Expression Omnibus (GEO), and identification of differentially expressed genes from microarrays of AD, PS, and IA was conducted. Subsequently, gene ontology and gene set enrichment analysis, detection of disease modules with known disease-associated genes, construction of the protein-protein interaction (PPI) network, and PPI sub-mapping analysis of shared genes were performed. Finally, the computational docking simulations between the selected target gene and inhibitors were conducted.

RESULTS

We identified 50 shared genes (36 up-regulated and 14 down-regulated) and disease modules for each disease. Among the shared genes, 20 common genes in PPI network were detected such as LCK, DLGAP5, SELL, CEP55, CDC20, RRM2, S100A7, S100A9, MCM10, AURKA, CCNB1, CHEK1, BTC, IL1F7, AGTR1, HABP4, SERPINB13, RPS6KA4, GZMB, and TRIP13. Finally, S100A9 was selected as the target gene for therapeutics. Docking simulations between S100A9 and known inhibitors indicated several key binding residues, and based on this result, we suggested several cannabinoids such as WIN-55212-2, JZL184, GP1a, Nabilone, Ajulemic acid, and JWH-122 could be potential candidates for a clinical study for AD, PS, and IA via inhibition of S100A9-related pathway.

CONCLUSION

Overall, our approach may become an effective strategy for discovering new disease candidate genes for inflammatory skin diseases with a reevaluation of clinical data.

Comparative Transcriptome Analysis of Acne vulgaris, Rosacea, and Hidradenitis Suppurativa Supports High Dose Dietary Zinc as a Therapeutic Agent

Acne vulgaris, rosacea, and hidradenitis suppurativa are enduring inflammatory skin conditions that frequently manifest with akin clinical attributes, posing a considerable challenge for their distinctive diagnosis. While these conditions do exhibit certain resemblances, they also demonstrate distinct underlying pathophysiological mechanisms and treatment modalities. Delving into both the molecular parallels and disparities among these three disorders can yield invaluable insights for refined diagnostics, effective management, and targeted therapeutic interventions. In this report, we present a comparative analysis of transcriptomic data across these three diseases, elucidating differentially expressed genes and enriched pathways specific to each ailment, as well as those shared among them. We also identified high dose dietary zinc as a potential therapeutic agent and validated its efficacy in an acne mouse model.

Aberrant expression of interleukin-17A in mast cells contributes to the pathogenesis of hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) significantly diminishes the quality of life for patients. Delayed diagnosis represents a significant challenge in effectively managing HS.

OBJECTIVES

To identify and characterize the key mediator in HS.

METHODS

Bioinformatic transcriptomic analysis was applied to identify potential candidates contributing to the disease process of HS. Skin samples from 40 patients with HS, four with psoriasis and 29 with normal skin were included. The expression of interleukin (IL)-17A was evaluated and compared among samples of normal skin, psoriatic skin and skin from different stages of HS by immunohistochemistry or dual-colour immunofluorescence. In vitro experiments and RNA sequencing analysis were also conducted to validate the expression of IL-17A and its pathogenic effect in HS.

RESULTS

Transcriptomic database analyses identified IL-17 signalling as a potential contributor to HS. In HS, the predominant IL-17A+ cell population was identified as mast cells. IL-17A+ mast-cell density was significantly elevated in HS, especially in samples with advanced Hurley stages, compared with normal skin and psoriasis samples. The close contact between IL-17A+ mast cells and IL-17 receptor A (IL-17RA)-expressing keratinocytes was demonstrated, along with the significant effects of IL-17A on keratinocyte cell proliferation and HS pathogenic gene expression. Treatment with biologics (brodalumab or adalimumab) reduced the severity of the disease and the number of IL-17A+ mast cells in affected tissues.

CONCLUSIONS

The presence of high-density IL-17A+ mast cells may serve as a valuable pathological marker for diagnosing HS. Moreover, developing therapeutic drugs targeting IL-17A+ mast cells may provide a new approach to treating HS.

Human dermal fibroblast subpopulations and epithelial mesenchymal transition signals in hidradenitis suppurativa tunnels are normalized by spleen tyrosine kinase antagonism in vivo

Hidradenitis Suppurativa is a chronic inflammatory disease of which the pathogenesis is incompletely understood. Dermal fibroblasts have been previously identified as a major source of inflammatory cytokines, however information pertaining to the characteristics of subpopulations of fibroblasts in HS remains unexplored. Using in silico-deconvolution of whole-tissue RNAseq, Nanostring gene expression panels and confirmatory immunohistochemistry we identified fibroblast subpopulations in HS tissue and their relationship to disease severity and lesion morphology. Gene signatures of SFRP2+ fibroblast subsets were increased in lesional tissue, with gene signatures of SFRP1+ fibroblast subsets decreased. SFRP2+ and CXCL12+ fibroblast numbers, measured by IHC, were increased in HS tissue, with greater numbers associated with epithelialized tunnels and Hurley Stage 3 disease. Pro-inflammatory CXCL12+ fibroblasts were also increased, with reductions in SFRP1+ fibroblasts compared to healthy controls. Evidence of Epithelial Mesenchymal Transition was seen via altered gene expression of SNAI2 and altered protein expression of ZEB1, TWIST1, Snail/Slug, E-Cadherin and N-Cadherin in HS lesional tissue. The greatest dysregulation of EMT associated proteins was seen in biopsies containing epithelialized tunnels. The use of the oral Spleen tyrosine Kinase inhibitor Fostamatinib significantly reduced expression of genes associated with chronic inflammation, fibroblast proliferation and migration suggesting a potential role for targeting fibroblast activity in HS.

The genetic aspects of hidradenitis suppurativa

Genetic aspects have a substantial role in hidradenitis suppurativa (HS) pathogenesis. A positive family history of HS occurs in about one-third of HS cases and is significantly higher in patients with early onset of the disease. Recent twin studies have shown a high heritability in HS, fortifying the importance of genetic factors in disease pathogenesis. Based on existing knowledge on the genomics of HS, the disease can be categorized as familial HS, sporadic, syndromic HS, and "HS plus" associated with other syndromes. In familial HS, autosomal dominant transmission is proposed, and monogenic inheritance is rare. This monogenic trait is related to mutations of γ-secretase component genes and Notch signaling or defects in inflammasome function. With newly discovered gene mutations, such as those related to innate and adaptive immunity, skin microbiome, inflammasome, epidermal homeostasis, and keratinization pathway, we can define HS as a polygenic, multifactorial, autoinflammatory disease. To fully elucidate the genetic aspects of HS, we need extensive, long-term global collaborations.

Intrinsic Immunogenic Tumor Cell Death Subtypes Delineate Prognosis and Responsiveness to Immunotherapy in Lung Adenocarcinoma

Recent studies have highlighted the combination of activation of host immunogenic cell death (ICD) and tumor-directed cytotoxic strategies. However, overall multiomic analysis of the intrinsic ICD property in lung adenocarcinoma (LUAD) has not been performed. Therefore, the aim of this study was to develop an ICD-based risk scoring system to predict overall survival (OS) and immunotherapeutic efficacy in patients. In our study, both weighted gene co-expression network analysis (WGCNA) and LASSO-Cox analysis were utilized to identify ICDrisk subtypes (ICDrisk). Moreover, we identify genomic alterations and differences in biological processes, analyze the immune microenvironment, and predict the response to immunotherapy in patients with pan-cancer. Importantly, immunogenicity subgroup typing was performed based on the immune score (IS) and microenvironmental tumor neoantigens (meTNAs). Our results demonstrate that ICDrisk subtypes were identified based on 16 genes. Furthermore, high ICDrisk was proved to be a poor prognostic factor in LUAD patients and indicated poor efficacy of immune checkpoint inhibitor (ICI) treatment in patients with pan-cancer. The two ICDrisk subtypes displayed distinct clinicopathologic features, tumor-infiltrating immune cell patterns, and biological processes. The IS^lowmeTNA^high subtype showed low intratumoral heterogeneity (ITH) and immune-activated phenotypes and correlated with better survival than the other subtypes within the high ICDrisk group. This study suggests effective biomarkers for the prediction of OS in LUAD patients and immunotherapeutic response across Pan-cancer and contributes to enhancing our understanding of intrinsic immunogenic tumor cell death.

HS 3D-SeboSkin Model Enables the Preclinical Exploration of Therapeutic Candidates for Hidradenitis Suppurativa/Acne Inversa

Despite the rapid development in hidradenitis suppurativa (HS) research, the immediate introduction of potent therapeutic compounds in clinical trials and the lack of definitive outcome measures have led to the discontinuation of potential therapeutic compound studies. HS is a solely human disease, and therefore, the search for preclinical human models has been given priority. The 3D-SeboSkin model, a co-culture of human skin explants with human SZ95 sebocytes as a feeder layer, has been shown to prevent the rapid degeneration of human skin in culture and has been validated for HS preclinical studies. In this work, the HS 3D-SeboSkin model has been employed to characterize cellular and molecular effects of the EMA- and FDA-approved biologic adalimumab. Adalimumab, a tumor necrosis factor-α inhibitor, was shown to target inflammatory cells present in HS lesions, inducing a prominent anti-inflammatory response and contributing to tissue regeneration through a wound healing mechanism. Adalimumab inhibited the lesional tissue expression of TNF-α, IL-3, IL-15, and MCP-3 and downregulated the secretion of IL-1α, IL-5, RANTES, MCP-2, TNF-α, TNF-β, TGF-β, and IFN-γ. In contrast, IL-6 was stimulated. The compound failed to modify abnormal epithelial cell differentiation present in the HS lesions. Patients with Hurley stage II lesions exhibited stronger expression of autophagy proteins in perilesional than in lesional skin. Adalimumab modified the levels of the pro-apoptotic proteins LC3A, LC3B, and p62 in an individual, patient-dependent manner. Finally, adalimumab did not modify the NFκB signal proteins in SZ95 sebocytes and NHK-19 keratinocytes, used to study this specific pathway. The administration of the validated HS 3D-SeboSkin model in ex vivo studies prior to clinical trials could elucidate the individual pathogenetic targets of therapeutic candidates and, therefore, increase the success rates of clinical studies, minimizing HS drug development costs.

Protective Barriers Provided by the Epidermis

The skin is the largest organ of the body and consists of an epidermis, dermis and subcutaneous adipose tissue. The skin surface area is often stated to be about 1.8 to 2 m² and represents our interface with the environment; however, when one considers that microorganisms live in the hair follicles and can enter sweat ducts, the area that interacts with this aspect of the environment becomes about 25-30 m². Although all layers of the skin, including the adipose tissue, participate in antimicrobial defense, this review will focus mainly on the role of the antimicrobial factors in the epidermis and at the skin surface. The outermost layer of the epidermis, the stratum corneum, is physically tough and chemically inert which protects against numerous environmental stresses. It provides a permeability barrier which is attributable to lipids in the intercellular spaces between the corneocytes. In addition to the permeability barrier, there is an innate antimicrobial barrier at the skin surface which involves antimicrobial lipids, peptides and proteins. The skin surface has a low surface pH and is poor in certain nutrients, which limits the range of microorganisms that can survive there. Melanin and trans-urocanic acid provide protection from UV radiation, and Langerhans cells in the epidermis are poised to monitor the local environment and to trigger an immune response as needed. Each of these protective barriers will be discussed.

New Data on the Features of Skin Barrier in Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a Th1/17-driven inflammatory skin disease of the apocrine gland-rich (AGR) skin regions, where keratinocytes seem to be the crucial drivers of the initial pathogenic steps. However, the possible role of permeability barrier alteration in activating keratinocytes during HS development has not been clarified. We compared the major permeability barrier elements of non-lesional HS (HS-NL; n = 10) and lesional HS (HS-L; n = 10) skin with healthy AGR regions (n = 10) via RT-qPCR and immunohistochemistry. Stratum corneum components related to cornified envelope formation, corneocyte desquamation and (corneo)desmosome organization were analyzed along with tight junction molecules and barrier alarmins. The permeability barrier function was also investigated with transepidermal water loss (TEWL) measurements (n = 16). Junction structures were also visualized using confocal microscopy. At the gene level, none of the investigated molecules were significantly altered in HS-NL skin, while 11 molecules changed significantly in HS-L skin versus control. At the protein level, the investigated molecules were similarly expressed in HS-NL and AGR skin. In HS-L skin, only slight changes were detected; however, differences did not show a unidirectional alteration, as KRT1 and KLK5 were detected in decreased levels, and KLK7, KRT6 and DSG1 in increased levels. No significant differences in TEWL or the expression of junction structures were assessed. Our findings suggest that the permeability barrier is not significantly damaged in HS skin and permeability barrier alterations are not the driver factors of keratinocyte activation in this disease.

Sebaceous immunobiology - skin homeostasis, pathophysiology, coordination of innate immunity and inflammatory response and disease associations

This review presents several aspects of the innovative concept of sebaceous immunobiology, which summarizes the numerous activities of the sebaceous gland including its classical physiological and pathophysiological tasks, namely sebum production and the development of seborrhea and acne. Sebaceous lipids, which represent 90% of the skin surface lipids in adolescents and adults, are markedly involved in the skin barrier function and perifollicular and dermal innate immune processes, leading to inflammatory skin diseases. Innovative experimental techniques using stem cell and sebocyte models have clarified the roles of distinct stem cells in sebaceous gland physiology and sebocyte function control mechanisms. The sebaceous gland represents an integral part of the pilosebaceous unit and its status is connected to hair follicle morphogenesis. Interestingly, professional inflammatory cells contribute to sebocyte differentiation and homeostasis, whereas the regulation of sebaceous gland function by immune cells is antigen-independent. Inflammation is involved in the very earliest differentiation changes of the pilosebaceous unit in acne. Sebocytes behave as potent immune regulators, integrating into the innate immune responses of the skin. Expressing inflammatory mediators, sebocytes also contribute to the polarization of cutaneous T cells towards the Th17 phenotype. In addition, the immune response of the perifollicular infiltrate depends on factors produced by the sebaceous glands, mostly sebaceous lipids. Human sebocytes in vitro express functional pattern recognition receptors, which are likely to interact with bacteria in acne pathogenesis. Sex steroids, peroxisome proliferator-activated receptor ligands, neuropeptides, endocannabinoids and a selective apoptotic process contribute to a complex regulation of sebocyte-induced immunological reaction in numerous acquired and congenital skin diseases, including hair diseases and atopic dermatitis.

S100 Proteins as Novel Therapeutic Targets in Psoriasis and Other Autoimmune Diseases

Psoriasis is one of the most common inflammatory skin diseases affecting about 1-3% of the population. One of the characteristic abnormalities in psoriasis is the excessive production of antimicrobial peptides and proteins, which play an essential role in the pathogenesis of the disease. Antimicrobial peptides and proteins can be expressed differently in normal and diseased skin, reflecting their usefulness as diagnostic biomarkers. Moreover, due to their very important functions in innate immunity, members of host defense peptides and proteins are currently considered to be promising new therapeutic targets for many inflammatory diseases. Koebnerisin (S100A15) belongs to an S100 family of antimicrobial proteins, which constitute the multigenetic group of calcium-binding proteins involved in ion-dependent cellular functions and regulation of immune mechanisms. S100A15 was first discovered to be overexpressed in 'koebnerized' psoriatic skin, indicating its involvement in the disease phenotype and the same promising potential as a new therapeutic target. This review describes the involvement of antimicrobial peptides and proteins in inflammatory diseases' development and therapy. The discussion focuses on S100 proteins, especially koebnerisin, which may be involved in the underlying mechanism of the Köebner phenomenon in psoriasis, as well as other immune-mediated inflammatory diseases described in the last decade.

Transcriptome Meta-Analysis Confirms the Hidradenitis Suppurativa Pathogenic Triad: Upregulated Inflammation, Altered Epithelial Organization, and Dysregulated Metabolic Signaling

Hidradenitis suppurativa (HS) is an inflammatory skin condition clinically characterized by recurrent painful deep-seated nodules, abscesses, and sinus tracks in areas bearing apocrine glands, such as axillae, breasts, groins, and buttocks. Despite many recent advances, the pathophysiological landscape of HS still demands further clarification. To elucidate HS pathogenesis, we performed a meta-analysis, set analysis, and a variant calling on selected RNA-Sequencing (RNA-Seq) studies on HS skin. Our findings corroborate the HS triad composed of upregulated inflammation, altered epithelial differentiation, and dysregulated metabolism signaling. Upregulation of specific genes, such as KRT6, KRT16, serpin-family genes, and SPRR3 confirms the early involvement of hair follicles and the impairment of barrier function in HS lesioned skin. In addition, our results suggest that adipokines could be regarded as biomarkers of HS and metabolic-related disorders. Finally, the RNA-Seq variant calling identified several mutations in HS patients, suggesting potential new HS-related genes associated with the sporadic form of this disease. Overall, this study provides insights into the molecular pathways involved in HS and identifies potential HS-related biomarkers.

Interpreting the spectrum of gamma-secretase complex missense variation in the context of hidradenitis suppurativa—An in-silico study

Hidradenitis suppurativa (HS) is a disease of the pilosebaceous unit characterized by recurrent nodules, abscesses and draining tunnels with a predilection to intertriginous skin. The pathophysiology of HS is complex. However, it is known that inflammation and hyperkeratinization at the hair follicle play crucial roles in disease manifestation. Genetic and environmental factors are considered the main drivers of these two pathophysiological processes. Despite a considerable proportion of patients having a positive family history of disease, only a minority of patients suffering from HS have been found to harbor monogenic variants which segregate to affected kindreds. Most of these variants are in the ɣ secretase complex (GSC) protein-coding genes. In this manuscript, we set out to characterize the burden of missense pathogenic variants in healthy reference population using large scale genomic dataset thereby providing a standard for comparing genomic variation in GSC protein-coding genes in the HS patient cohort.

Advances in molecular pathogenesis of hidradenitis suppurativa: Dysregulated keratins and ECM signaling

Hidradenitis suppurativa (HS) is characterized by deep-seated, highly inflamed, and painful lumps/abscesses, fistulae, and sinus tracts that grow extensively deep in the dermis and are highly immunogenic in nature. In about one-third of the HS patients there is strong evidence for the role of γ-secretase mutations along with dysregulated Notch signaling. However, the contribution of dysregulated Notch signaling in HS pathogenesis in relation to hair follicle alterations and hyper-activation of the immune system remains undefined. A genome-wide association study (GWAS), proteomic data and functional investigations of identified sequence variants in HS pathology are not fully revealing. The disease initiation or progression may involve bacterial infection besides intrinsic functional defects in keratinocytes, which may be key to further exacerbate immune cell infiltration and cytokine production in and around the lesional tissue. The absence of a suitable animal model that could fully recapitulate the pathogenesis of HS is a major impediment for proper understanding the underlying mechanisms and development of effective treatments. The presence of extracellular matrix (ECM) degradation products along with dysregulation in keratinocytes and, dermal fibroblasts ultimately affect immune regulation and are various components of HS pathogenesis. Bacterial infection further exacerbates the complexity of the disease progression. While anti-TNFα therapy shows partial efficacy, treatment to cure HS is absent. Multiple clinical trials targeting various cytokines, complement C5a and ECM products are in progress. This review provides state-of-the-art information on these aspects with a focus on dysregulated keratinocyte and immune cells; and role of ECM, and Keratin functions in this regard.

Stress signaling and STAT1 activation characterize the keratinocytic gene expression pattern in Hidradenitis suppurativa

BACKGROUND

The pathogenetic factors generating the innate immune signal necessary for T cell activation, initiation and chronification of Hidradenitis suppurativa (HS, also known as Acne inversa) are still poorly understood. Emerging evidence suggests that a defective keratinocyte function critically contributes to HS disease development and progression.

OBJECTIVES

To elucidate the role of keratinocytes in HS lesion formation, we compared the transcriptomes of lesional and perilesional epidermis isolated from HS patients by RNA sequencing (RNA Seq).

METHODS

Pairwise-matched lesional and perilesional HS skin samples of five different donors were obtained and epidermal keratinocytes freshly isolated and processed for RNA extraction and RNA seq. Lesionally regulated genes were analyzed by large scale promotor analysis and functional annotation clustering to identify epidermally overrepresented transcription factor binding sites and functionally related gene groups. Results were experimentally validated with independent epidermal isolates of patient-matched lesional and perilesional HS skin employing qRT-PCR, cell culture, immunoblot, and immunostaining.

RESULTS

We show that HS is characterized by a strong epidermal stress state evident by a significant overrepresentation of an AP-1-driven gene signature and a substantial activation of the stress-activated cJun N-terminal kinase (JNK) pathway in lesional epidermis. Additionally, our data reveal a strong induction of STAT1 activation in lesional HS epidermis that likely results from IFNγ production and triggered expression of key inflammatory genes coordinating innate immune activation and the adaptive T cell response in HS.

CONCLUSIONS

Our data implicate a key role of stress signaling and JAK/STAT1 activation in disease progression of HS and suggest interference with JAK/STAT1 signaling as a potentially promising therapeutic approach for HS.

Register, multicenter and genome-wide association studies in hidradenitis suppurativa

The European Hidradenitis Suppurativa Foundation (EHSF) e.V. has taken several initiatives to collaborative studies. They result from the data of the European Registry of Hidradenitis Suppurativa (ERHS) based on the knowledge obtained from the regional Northern countries (HISREG) and Italian (IRHIS) registries and the real-world data generated from claims data from insurance databases. Multicenter studies, such as the Hidradenitis Suppurativa collaborative study of subtypes (HORUS) and the Global Hidradenitis Suppurativa Atlas (GHISA) are planned to provide an ideal complement to the register studies. Most recently, the role of EHSF as a coordinator or key player is being explored in multiple genetic studies, such as a genome-wide association study (GWAS) and the exome sequencing and cellular/molecular profiling project, which will speed up gene and drug discovery in HS.

Integrated analysis of lncRNAs and mRNAs by RNA-Seq in secondary hair follicle development and cycling (anagen, catagen and telogen) of Jiangnan cashmere goat (Capra hircus)

BACKGROUND

Among the world's finest natural fiber composites is derived from the secondary hair follicles (SHFs) of cashmere goats yield one of the world's best natural fibres. Their development and cycling are characterized by photoperiodism with diverse, well-orchestrated stimulatory and inhibitory signals. Long non-coding RNA (lncRNAs) and mRNAs play important roles in hair follicle (HF) development. However, not many studies have explored their specific functions in cashmere development and cycling. This study detected mRNAs and lncRNAs with their candidate genes and related pathways in SHF development and cycling of cashmere goat. We utilized RNA sequencing (RNA-Seq) and bioinformatics analysis on lncRNA and mRNA expressions in goat hair follicles to discover candidate genes and metabolic pathways that could affect development and cycling (anagen, catagen, and telogen).

RESULTS

We identified 228 differentially expressed (DE) mRNAs and 256 DE lncRNA. For mRNAs, catagen and anagen had 16 upregulated and 35 downregulated DEGs, catagen and telogen had 18 upregulated and 9 downregulated DEGs and telogen and anagen had 52 upregulated and 98 downregulated DEGs. LncRNA witnessed 22 upregulated and 39 downregulated DEGs for catagen and anagen, 36 upregulated and 29 downregulated DEGs for catagen and telogen as well as 66 upregulated and 97 downregulated DEGs for telogen and anagen. Several key genes, including MSTRG.5451.2, MSTRG.45465.3, MSTRG.11609.2, CHST1, SH3BP4, CDKN1A, GAREM1, GSK-3β, DEFB103A KRTAP9-2, YAP1, S100A7A, FA2H, LOC102190037, LOC102179090, LOC102173866, KRT2, KRT39, FAM167A, FAT4 and EGFL6 were shown to be potentially important in hair follicle development and cycling. They were related to, WNT/β-catenin, mTORC1, ERK/MAPK, Hedgehog, TGFβ, NFkB/p38MAPK, caspase-1, and interleukin (IL)-1a signaling pathways.

CONCLUSION

This work adds to existing understanding of the regulation of HF development and cycling in cashmere goats via lncRNAs and mRNAs. It also serves as theoretical foundation for future SHF research in cashmere goats.

Large-scale serum analysis identifies unique systemic biomarkers in psoriasis and hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is now recognized as a systemic inflammatory disease, sharing molecular similarities with psoriasis. Direct comparison of the systemic inflammation in HS with psoriasis is lacking.

OBJECTIVES

To evaluate the serum proteome of HS and psoriasis, and to identify biomarkers associated with disease severity.

METHODS

In this cross-sectional study, 1536 serum proteins were assessed using the Olink Explore (Proximity Extension Assay) high-throughput panel in patients with moderate-to-severe HS (n = 11), patients with psoriasis (n = 10) and age- and body mass index-matched healthy controls (n = 10).

RESULTS

HS displayed an overall greater dysregulation of circulating proteins, with 434 differentially expressed proteins (absolute fold change ≥ 1·2; P ≤ 0·05) in patients with HS vs. controls, 138 in patients with psoriasis vs. controls and 503 between patients with HS and patients with psoriasis. Interleukin (IL)-17A levels and T helper (Th)1/Th17 pathway enrichment were comparable between diseases, while HS presented greater tumour necrosis factor- and IL-1β-related signalling. The Th17-associated markers peptidase inhibitor 3 (PI3) and lipocalin 2 (LCN2) were able to differentiate psoriasis from HS accurately. Both diseases presented increases of atherosclerosis-related proteins. Robust correlations between clinical severity scores and immune and atherosclerosis-related proteins were observed across both diseases.

CONCLUSIONS

HS and psoriasis share significant Th1/Th17 enrichment and upregulation of atherosclerosis-related proteins. Despite the greater body surface area involved in psoriasis, HS presents a greater serum inflammatory burden.

Identification and Verification of Five Potential Biomarkers Related to Skin and Thermal Injury Using Weighted Gene Co-Expression Network Analysis

Background: Burn injury is a life-threatening disease that does not have ideal biomarkers. Therefore, this study first applied weighted gene co-expression network analysis (WGCNA) and differentially expressed gene (DEG) screening methods to identify pivotal genes and diagnostic biomarkers associated with the skin burn process.

Methods: After obtaining transcriptomic datasets of burn patient skin and normal skin from Gene Expression Omnibus (GEO) and performing differential analysis and functional enrichment, WGCNA was used to identify hub gene modules associated with burn skin processes in the burn patient peripheral blood sample dataset and determine the correlation between modules and clinical features. Enrichment analysis was performed to identify the functions and pathways of key module genes. Differential analysis, WGCNA, protein-protein interaction analysis, and enrichment analysis were utilized to screen for hub genes. Hub genes were validated in two other GEO datasets, tested by immunohistochemistry for hub gene expression in burn patients, and receiver operating characteristic curve analysis was performed. Finally, we constructed the specific drug activity, transcription factors, and microRNA regulatory network of the five hub genes.

Results: A total of 1,373 DEGs in GSE8056 were obtained, and the top 5 upregulated genes were S100A12, CXCL8, CXCL5, MMP3, and MMP1, whereas the top 5 downregulated genes were SCGB1D2, SCGB2A2, DCD, TSPAN8, and KRT25. DEGs were significantly enriched in the immunity, epidermal development, and skin development processes. In WGCNA, the yellow module was identified as the most closely associated module with tissue damage during the burn process, and the five hub genes (ANXA3, MCEMP1, MMP9, S100A12, and TCN1) were identified as the key genes for burn injury status, which consistently showed high expression in burn patient blood samples in the GSE37069 and GSE13902 datasets. Furthermore, we verified using immunohistochemistry that these five novel hub genes were also significantly elevated in burn patient skin. In addition, MCEMP1, MMP9, and S100A12 showed perfect diagnostic performance in the receiver operating characteristic analysis.

Conclusion: In conclusion, we analyzed the changes in genetic processes in the skin during burns and used them to identify five potential novel diagnostic markers in blood samples from burn patients, which are important for burn patient diagnosis. In particular, MCEMP1, MMP9, and S100A12 are three key blood biomarkers that can be used to identify skin damage in burn patients.

High inflammation in hidradenitis suppurativa extends to perilesional skin and can be subdivided by lipocalin-2 expression

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease presenting with diverse manifestations ranging from nodules and abscesses to draining tunnels. Whether the underlying inflammation from lesions extends to relatively healthy-appearing adjacent perilesional and distant nonlesional skin has not been systematically evaluated.

OBJECTIVE

We sought to characterize lesional, perilesional, and nonlesional skin in patients with HS.

METHODS

Skin biopsy samples were collected under ultrasound guidance from patients with active, untreated moderate-to-severe HS. Site-matched control biopsy samples from healthy volunteers were used for comparison.

RESULTS

RNA sequencing demonstrated that HS skin clustered separately from healthy control skin, with perilesional and lesion skin clustering together and away from nonlesional skin. Immunohistochemistry analysis identified psoriasiform hyperplasia with keratin 16 positivity in both perilesional and lesional skin, with comparable levels of CD3+, CD11c+, and neutrophil elastase-positive cellular infiltration. There was a marked upregulation of IL-17 signaling in perilesional and lesional skin. HS samples clustered on the basis of expression of lipocalin-2 (LCN2), with samples characterized by high LCN2 expression in the skin exhibiting a differing transcriptomic profile with significantly higher overall inflammation than that of skin characterized by low LCN2 levels.

CONCLUSIONS

Perilesional HS skin has a transcriptomic and molecular profile comparable to that of lesional skin. HS can be grouped into 2 distinct subtypes based on molecular levels of LCN2 in the skin, with the LCN2-high subtype exhibiting an overall higher inflammatory burden and an upregulation of targetable cytokines. To our knowledge, this is the first study to characterize a unique HS subtype (and a potential endotype) that may guide future therapeutic targets.

Hidradenitis Suppurativa and Comorbid Disorder Biomarkers, Druggable Genes, New Drugs and Drug Repurposing-A Molecular Meta-Analysis

Chronic inflammation and dysregulated epithelial differentiation, especially of hair follicle keratinocytes, have been suggested as the major pathogenetic pathways of hidradenitis suppurativa/acne inversa (HS). On the other hand, obesity and metabolic syndrome have additionally been considered as an important risk factor. With adalimumab, a drug has already been approved and numerous other compounds are in advanced-stage clinical studies. A systematic review was conducted to detect and corroborate HS pathogenetic mechanisms at the molecular level and identify HS molecular markers. The obtained data were used to confirm studied and off-label administered drugs and to identify additional compounds for drug repurposing. A robust, strongly associated group of HS biomarkers was detected. The triad of HS pathogenesis, namely upregulated inflammation, altered epithelial differentiation and dysregulated metabolism/hormone signaling was confirmed, the molecular association of HS with certain comorbid disorders, such as inflammatory bowel disease, arthritis, type I diabetes mellitus and lipids/atherosclerosis/adipogenesis was verified and common biomarkers were identified. The molecular suitability of compounds in clinical studies was confirmed and 31 potential HS repurposing drugs, among them 10 drugs already launched for other disorders, were detected. This systematic review provides evidence for the importance of molecular studies to advance the knowledge regarding pathogenesis, future treatment and biomarker-supported clinical course follow-up in HS.

Primary alterations during the development of hidradenitis suppurativa

Background

Hidradenitis suppurativa (HS) is a chronic, inflammatory disease of the apocrine gland‐rich (AGR) skin region. The initial steps of disease development are not fully understood, despite intense investigations into immune alterations in lesional HS skin.

Objectives

We aimed to systematically investigate the inflammatory molecules involved in three stages of HS pathogenesis, including healthy AGR, non‐lesional HS and lesional HS skin, with the parallel application of multiple mRNA and protein‐based methods.

Methods

Immune cell counts (T cells, dendritic cells, macrophages), Th1/Th17‐related molecules (IL‐12B, TBX21, IFNG, TNFA, IL‐17, IL10, IL‐23A, TGFB1, RORC, CCL20), keratinocyte‐related sensors (TLR2,4), mediators (S100A7, S100A8, S100A9, DEFB4B, LCN2, CAMP, CCL2) and pro‐inflammatory molecules (IL1B, IL6, TNFA, IL‐23A) were investigated in the three groups by RNASeq, RT‐qPCR, immunohistochemistry and immunofluorescence.

Results

Epidermal changes were already detectable in non‐lesional HS skin; the epidermal occurrence of antimicrobial peptides (AMPs), IL‐1β, TNF‐α and IL‐23 was highly upregulated compared with healthy AGR skin. In lesional HS epidermis, TNF‐α and IL‐1β expression remained at high levels while AMPs and IL‐23 increased even more compared with non‐lesional skin. In the dermis of non‐lesional HS skin, signs of inflammation were barely detectable (vs. AGR), while in the lesional dermis, the number of inflammatory cells and Th1/Th17‐related mediators were significantly elevated.

Conclusions

Our findings that non‐lesional HS epidermal keratinocytes produce not only AMPs and IL‐1β but also high levels of TNF‐α and IL‐23 confirm the driver role of keratinocytes in HS pathogenesis and highlight the possible role of keratinocytes in the transformation of non‐inflammatory Th17 cells (of healthy AGR skin) into inflammatory cells (of HS) via the production of these mediators. The fact that epidermal TNF‐α and IL‐23 appear also in non‐lesional HS seems to prove these cytokines as excellent therapeutic targets.

Hidradenitis suppurativa: Disease pathophysiology and sex hormones

Hidradenitis suppurativa is a cutaneous chronic inflammatory disease that is estimated to affect about 1% of the population and caused pain, malodorous discharge, disfigurement, and poor quality of life with psychosocial problems. The typical features are recurrent painful nodules, abscesses, and sinus tracts on the axillae, groins, gluteal areas, and anogenital regions since postpuberty. Smoking and obesity are two major triggering factors of hidradenitis suppurativa. Women are prone to have hidradenitis suppurativa than men in Western countries, but the male-to-female ratio is reversed in oriental countries. The disease severity can be affected by menstruation, pregnancy, and menopause. Furthermore, the phenotypes are different among men and women with hidradenitis suppurativa. Men are prone to have buttock involvement while women are prone to have axillary, groins, and submammary lesions. This review introduces the skin appendages and pathophysiology of hidradenitis suppurativa and then focuses on the sex difference and the effects of sex hormones on hidradenitis suppurativa and current hormone-associated treatments.

Insights into the Pathogenesis of HS and Therapeutical Approaches

Hidradenitis suppurativa (HS) is a debilitating, chronic, (auto)inflammatory disease primarily affecting apocrine gland-rich areas of the body. Although pathogenic mechanisms responsible for HS have not yet been fully elucidated, it is a multifactorial process whose main target is the terminal follicle. The role of the inflammatory process (and consequently of cytokine milieu) and of several other factors (genetics, lifestyle, hormonal status, microbiome, innate and adaptive immune systems) involved in HS pathogenesis has been investigated (and often defined) over the years with a view to transferring research results from bench to bedside and describing a unique and universally accepted pathogenetic model. This review will update readers on recent advances in our understanding of HS pathogenesis and novel (potential) medical therapies for patients with moderate-to-severe HS.

Hidradenitis suppurativa: A folliculotropic disease of innate immune barrier dysfunction?

The innate immune system of human skin consists of a multi-layered barrier consisting of cells and soluble effector molecules charged with maintaining homeostasis and responding to insults and infections. It has become increasingly clear that these barrier layers become compromised in skin diseases, especially in disorders of an (auto)inflammatory nature. In the case of hidradenitis suppurativa, great strides have been made in recent years in characterizing the underlying breakdown in homeostatic innate immunity, including an increasing understanding of the central role of the hair follicle in this process. This breakdown appears to occur at multiple levels: the pilosebaceous unit, associated epithelium, the cutaneous microbiome, alteration of immune cell function and local molecular events such as complement activation. This review seeks to summarize, contextualize and analyse critically our current understanding of how these innate immune barriers become dysregulated in the early stage(s) of hidradenitis suppurativa, and to speculate on where potential hidradenitis suppurativa research could be most fruitful.

Metabolic Disorders/Obesity Is a Primary Risk Factor in Hidradenitis Suppurativa: An Immunohistochemical Real-World Approach

BACKGROUND

Hidradenitis suppurativa (HS) is an inflammatory, potentially scarring disease of the hair follicle, affecting the apocrine gland-bearing skin areas. The major comorbid disorders associated with the occurrence or the aggravation of the disease are obesity and smoking. Numerous efforts to dissociate these factors led to controversial results.

OBJECTIVES

To assess the importance of metabolic disorders/obesity, smoking/environmental toxins, and inflammation in HS by utilizing the differential expression of major relevant protein markers in lesional skin of obese/smoking versus non-obese/non-smoking HS patients.

METHODS

Lesional skin specimens deriving from two groups of HS patients (BMI >30 and smokers, n = 12 vs. BMI <30 and non-smokers, n = 10) were stained with antibodies raised against irisin, PPARγ, and IGF-1R, which correlate with metabolic disorders/obesity, EGFR and AhR, associated with smoking, and IL-17, IL-17R, and S100A8, as markers of inflammation.

RESULTS

Metabolic disorders/obesity-related markers exhibited marked differential expression between the two groups, while smoking-associated markers a limited one. IL-17R expression was stronger in obese/smokers, and S100A8 staining exhibited intense strong immunoreactivity in both groups without significant difference.

CONCLUSIONS

The notion that obesity plays a role in HS development appears to be supported by the prominent regulation of the associated lesional biomarkers. Tobacco smoking might contribute less to HS than previously suspected.

[Pathogenesis of hidradenitis suppurativa/acne inversa]

Hidradenitis suppurativa/acne inversa (HS) has a multifactorial pathogenesis. In addition to a sporadic form, a familial form is reported in around 40% of patients, for whom an autosomal dominant (AD) inheritance with reduced gene penetrance is assumed. The phenotype of the disease with inflammatory nodules, abscesses and secreting sinus tracts suggests an infectious origin, but the exact role of the bacteria detected in HS pathogenesis remains unclear. Smoking and metabolic syndrome are regarded as important trigger factors in HS, with obesity and hormonal changes playing a pathogenic role in the latter. Ultimately, Toll-like receptors, antimicrobial peptides, immune cells and key cytokines are involved in the excessive inflammatory reaction of HS and are also the targets of future therapies.