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

European S2k guidelines for hidradenitis suppurativa/acne inversa part 2: Treatment

INTRODUCTION

This second part of the S2k guidelines is an update of the 2015 S1 European guidelines.

OBJECTIVE

These guidelines aim to provide an accepted decision aid for the selection, implementation and assessment of appropriate and sufficient therapy for patients with hidradenitis suppurativa/acne inversa (HS).

METHODS

The chapters have been selected after a Delphi procedure among the experts/authors. Certain passages have been adopted without changes from the previous version. Potential treatment complications are not included, being beyond the scope of these guidelines.

RESULTS

Since the S1 guidelines publication, validation of new therapeutic approaches has almost completely overhauled the knowledge in the field of HS treatment. Inflammatory nodules/abscesses/draining tunnels are the primary lesions, which enable the classification of the disease severity by new validated tools. In relation to the degree of detectable inflammation, HS is classified into the inflammatory and the predominantly non-inflammatory forms. While the intensity of the inflammatory form can be subdivided by the IHS4 classification in mild, moderate and severe HS and is treated by medication accordingly, the decision on surgical treatment of the predominantly non-inflammatory form is based on the Hurley stage of the affected localization. The effectiveness of oral tetracyclines as an alternative to the oral combination of clindamycin/rifampicin should be noted. The duration of systemic antibiotic therapy can be shortened by a 5-day intravenous clindamycin treatment. Adalimumab, secukinumab and bimekizumab subcutaneous administration has been approved by the EMA for the treatment of moderate-to-severe HS. Various surgical procedures are available for the predominantly non-inflammatory form of the disease. The combination of a medical therapy to reduce inflammation with a surgical procedure to remove irreversible tissue damage is currently considered a holistic therapeutic approach.

CONCLUSIONS

Suitable therapeutic options while considering HS severity in the therapeutic algorithm according to standardized criteria are aimed at ensuring a proper therapy.

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.

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.

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.

Setting the Stage for Standardized Reporting of Clinical and Demographic Information in Laboratory-Based Studies of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a complex inflammatory skin condition affecting 0.1-4% of the population that leads to permanent scarring in the axilla, inframammary region, groin, and buttocks. Its complex pathogenesis involves genetics, innate and adaptive immunity, microbiota, and environmental stimuli. Specific populations have a higher incidence of HS, including females and Black individuals and those with associated comorbidities. HS registries and biobanks have set standards for the documentation of clinical data in the context of clinical trials and outcomes research, but collection, documentation, and reporting of these important clinical and demographic variables are uncommon in HS laboratory research studies. Standardization in the laboratory setting is needed because it helps to elucidate the factors that contribute mechanistically to HS symptoms and pathophysiology. The purpose of this article is to begin to set the stage for standardized reporting in the laboratory setting. We discuss how clinical guidelines can inform laboratory research studies, and we highlight what additional information is necessary for the use of samples in the wet laboratory and interpretation of associated mechanistic data. Through standardized data collection and reporting, data harmonization between research studies will transform our understanding of HS and lead to novel discoveries that will positively impact patient care.

Biologic drugs in hidradenitis suppurativa: what does the GP have to know? A narrative review

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease with a profound disease burden. In recent years, the advent of biologic therapies has improved the treatment landscape for patients with moderate to severe HS. In this new therapeutic era, the role of the general practitioner (GP) in HS treatment is becoming more important than ever. This review discusses how to recognize and diagnose HS by detailing common symptoms. HS can also present with multiple comorbidities. The GP's role in screening for and treating these important comorbidities is pivotal. This review highlights the HS treatment landscape, with a specific focus on what the GP can recommend. The three approved biologics for treating HS include adalimumab, secukinumab and bimekizumab; the benefits and concerns of biologics in everyday clinical practice are detailed. In summary, this review serves as a HS management guide for GPs, with a particular focus on the biologic treatment landscape.

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.

Deregulated Long Non-Coding RNAs (lncRNA) as Promising Biomarkers in Hidradenitis Suppurativa

Background/Objectives: In recent times, epigenetics alterations in Hidradenitis suppurativa (HS) have been explored and exploited translationally to guide investigation of new therapeutic approaches. On the other hand, long noncoding RNAs (LncRNAs), main regulators of the epigenetic status of the human genome, have been scarcely investigated, notwithstanding their potential relevance in broad pathogenesis comprehension. Here, we aim to explore the methylation pattern of lncRNAs in HS. Methods: In this case-control study, 24 HS patients and age-, sex- and BMI-matched controls were analyzed to characterize the methylome of lncRNA genes in peripheral blood cells. Gene ontology analysis (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, protein-protein interaction (PPI) network, and MCODE analysis were performed. Results: A set of fifteen lncRNA genes exhibited significantly differential methylation patterns, with ten of them showing hypomethylation and five displaying hypermethylation at specific CpG sites. The hypomethylated lncRNA genes were DLEU2, MESTIT1, CASC2, TUG1, KCNQ1DN, PSORS1C3, PCA3, DSCR8, RFPL1S, and PVT1, while the hypermethylated ones were HAR1A, FAM66B, SNHG9, HCG9, and HCP5. These lncRNA genes have been linked to various important biological processes, including cell proliferation, apoptosis, inflammation, chronic inflammatory skin diseases, and wound healing. Their altered methylation status suggests potential roles in regulating these processes, and may contribute to HS pathogenesis and healing mechanisms. Conclusions: This study revealed an interesting dysregulation pattern of definite lncRNAs in the methylome which is linked to both the development of HS and its comorbidities. Epigenetically altered lncRNAs genes could represent useful biomarkers, and could help in guiding innovative treatment strategies.

Biologics for Hidradenitis suppurativa: evolution of the treatment paradigm

INTRODUCTION

Hidradenitis suppurativa (HS) is an autoinflammatory skin disease with a high unmet need for effective medical management. Clinically, it is characterized by inflammatory nodules that may progress into abscesses, draining tunnels and extensive scarring, mainly affecting apocrine gland-bearing areas.

AREAS COVERED

Treatment options include topical and systemic medications and a variety of surgical procedures. The anti-TNF-α antibody adalimumab and the anti-IL-17 secukinumab are the only two approved biologics for HS, showing moderate efficacy. HS research is a rapidly growing field, with a wide range of agents leveraging distinct mechanisms of action currently under development. Drugs targeting the IL-17 and Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathways are the most advanced in both ongoing and completed Phase 3 studies, promising deeper levels of response. Use of other, off-label biologics is also discussed.

EXPERT OPINION

A therapeutic algorithm is proposed based on comorbidities and existing evidence. Patient-tailored combinations between biologics and other biologics or small molecules will hopefully allow clinicians to target most events in HS pathophysiology in a complementary way while obtaining a meaningful effect on their devastating manifestations.

Is Exploration of Alternate Immune Pathways Needed in Hidradenitis Suppurativa? A Case of Atopic Dermatitis and Concurrent Hidradenitis Suppurativa Responding to Dupilumab

Hidradenitis suppurativa (HS) is an inflammatory dermatosis associated with overactive T helper 1/T helper 17 (Th1/Th17) cells. HS has been effectively treated with biologic medications; however, many such biologics lack large randomized controlled trials. Only one such biologic, adalimumab, has been approved by the US Food and Drug Administration (FDA) for the treatment of HS. Other such biologics currently being studied for HS downregulate Th1/Th17 inflammatory pathways. We describe a patient with atopic dermatitis (AD) and comorbid HS, both of which improved several months into treatment with dupilumab. Interestingly enough, dupilumab targets Th2-mediated inflammatory skin conditions through the inhibition of IL-4/IL-13 cytokines. While dupilumab is known for its success in treating Th2-mediated inflammation, this presents a paradox as HS is a Th1/Th17 inflammatory condition. This case highlights how the inflammatory process of HS is not fully understood and how biologic pharmacologic interventions need to be further studied to determine their efficacy in treating HS.

Discovery and Potential Functional Characterization of Long Noncoding RNAs Associated with Familial Acne Inversa with NCSTN Mutation

BACKGROUND

Long noncoding RNAs (lncRNAs) are associated with many dermatologic diseases. However, little is known about the regulatory function of lncRNAs in familial acne inversa (AI) patients with nicastrin (NCSTN) mutation.

OBJECTIVES

The aim of this study was to explore the regulatory function of lncRNAs in familial AI patients with NCSTN mutation.

METHODS

The expression profiles of lncRNAs and mRNAs in skin tissues from familial AI patients with NCSTN mutation and healthy individuals were analysed in this study via RNA sequencing (RNA-seq).

RESULTS

In total, 359 lncRNAs and 1,863 mRNAs were differentially expressed between the two groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that the dysregulated mRNAs targeted by lncRNAs were mainly associated with the immune regulation, Staphylococcus aureus infection and B cell receptor signalling pathways. The lncRNA-miRNA-mRNA coexpression network contained 265 network pairs comprising 55 dysregulated lncRNAs, 11 miRNAs, and 74 mRNAs. Conservation analysis of the differentially expressed lncRNAs between familial AI patients with NCSTN mutation and Ncstn keratinocyte-specific knockout (NcstnΔKC) mice identified 6 lncRNAs with sequence conservation; these lncRNAs may participate in apoptosis, proliferation, and skin barrier function.

CONCLUSIONS

These findings provide a direction for exploring the regulatory mechanisms underlying the progression of familial AI patients with NCSTN mutation.

Hidradenitis Suppurativa: Molecular Etiology, Pathophysiology, and Management-A Systematic Review

Hidradenitis suppurativa is a chronic inflammatory skin condition that affects the hair follicles in areas of the body with apocrine glands. The condition is characterized by recurrent, painful nodules, abscesses, and draining sinuses that can lead to scarring and disfigurement. In this present study, we provide a focused evaluation of recent developments in hidradenitis suppurativa research, including novel therapeutics and promising biomarkers that may facilitate clinical diagnosis and treatment. We conducted a systematic review of controlled trials, randomized controlled trials, meta-analyses, case reports, and Cochrane Review articles in accordance with the PRISMA guidelines. The Cochrane Library, PubMed, EMBASE, and Epistemonikos databases were queried via Title/Abstract screen. Eligibility criteria included the following: (1) has a primary focus on hidradenitis suppurativa, (2) includes measurable outcomes data with robust comparators, (3) details the sample population, (4) English language, and (5) archived as full-text journal articles. A total of 42 eligible articles were selected for review. Qualitative evaluation identified numerous developments in our understanding of the disease's multiple potential etiologies, pathophysiology, and treatment options. It is important for individuals with hidradenitis suppurativa to work closely with a healthcare provider to develop a comprehensive treatment plan that addresses their individual needs and goals. To meet this objective, providers must keep current with developments in the genetic, immunological, microbiological, and environmental factors contributing to the disease's development and progression.

Employing Adalimumab in Treatment of Moderate-to-Severe Hidradenitis Suppurativa: Real-Life Multicenter Data from the Czech Republic

Adalimumab is the only approved biologic treatment for moderate-to-severe hidradenitis suppurativa, nonetheless, long-term data from real-life setting are still limited. The objective of this observational multicenter study was to evaluate the effectiveness, safety, and drug survival of adalimumab in patients with hidradenitis suppurativa included in the BIOREP registry. A total of 299 patients who initiated adalimumab therapy for hidradenitis suppurativa from 2011 to November 2021 were included. The Dermatology-Life-Quality-Index (DLQI), pain scale, the number of abscesses, inflammatory nodules and draining tunnels, and International Hidradenitis Suppurativa Severity Score System (IHS4) were recorded in the 0th, 3rd, and 6th months; then every 6 months during the ongoing adalimumab treatment. Studied patients underwent treatment for up to 48 months, with the average duration of treatment lasting 2.3 years. The mean age of the patients was 44.9 years, 79% were smokers or ex-smokers, 54.8% were obese, and 26.4% were overweight, the mean BMI was 30.8. The mean time from diagnosis to initiation adalimumab therapy was 9.1 years. The number of patients with severe IHS4 dropped from the initial 249 (83.3%) to 65 (30.1%) after 12 months and this trend was maintained up to the 48th month. A decreasing number of inflammatory lesions were rapid and sustained and correlated to the improvement of patients’ quality of life, the mean DLQI score dropped from 17.6 to 8.5 after 3 months and to 5, 7 after 48 months. No unexpected risk signals were observed. Our long-term study demonstrates the effectiveness and safety of adalimumab in a real-life setting.

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.

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.

Discovering KYNU as a feature gene in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic auto-inflammatory skin condition characterized by nodules, abscesses, and fistulae in skin folds. The underlying pathogenesis of HS remains unclear, and effective therapeutic drugs are limited.

METHODS

We acquired mRNA expression profiles from the Gene Expression Omnibus (GEO) database and conducted differential expression analysis between control and HS samples using R software. Four machine learning algorithms (SVM, RF, ANN, and lasso) and WCGNA were utilized to identify feature genes. GO, KEGG, Metascape, and GSVA were utilized for the enrichment analysis. CIBERSORT and ssGSEA were employed to analyze immune infiltration.

RESULTS

A total of 29 DEGs were identified, with the majority showing up-regulation in HS. Enrichment analysis revealed their involvement in immune responses and cytokine activities. KEGG analysis highlighted pathways such as IL-17 signaling, rheumatoid arthritis, and TNF signaling in HS. Immune infiltration analysis revealed the predominant presence of neutrophils, monocytes, and CD8 T cells. Machine learning algorithms and WCGNA identified KYNU as a feature gene associated with HS. We have also identified 59 potential drugs for HS based on the DEGs. Additionally, ceRNA network analysis identified the MUC19_hsa-miR-382-5p_KYNU pathway as a potential regulatory pathway.

CONCLUSIONS

KYNU emerged as a feature gene associated with HS, and the ceRNA network analysis identified the MUC19_hsa-miR-382-5p_KYNU pathway as a potential regulator.

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.

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.

Pharmacological interventions for hidradenitis suppurativa: a protocol for systematic review and network meta-analysis of randomised trials and non-randomised studies

INTRODUCTION

Therapeutic recommendations for hidradenitis suppurativa (HS) have recently shifted towards non-invasive pharmacological options. Recent evidence has shown promising efficacy for specific treatments. However, data regarding the comparative efficacy of these treatments in patients with HS are still limited. Therefore, we plan to conduct a systematic review and network meta-analysis (NMA) to summarise the benefits and harms of different pharmacological interventions for treating people living with HS.

METHODS AND ANALYSIS

We will search electronic databases, including Medline, Embase, PubMed, Web of Science, Scopus, CINAHL and Cochrane Library beginning from their inception dates with no language restrictions. A grey literature search will be performed to supplement the electronic databases. Both randomised trials and non-randomised studies using validated measurement tools that investigated the benefits and harms of pharmacological interventions among people living with HS will be included. The predefined primary outcomes will include treatment responses that reflect the patient's perspective and all-cause discontinuation. Screening, selection, extraction, assessment of the risk of bias and analysis of the strength of the evidence will be performed independently by a pair of reviewers. A two-step approach of traditional pairwise and NMA will be performed. Based on a random-effects model, standardised weighted mean differences and ORs with corresponding 95% CIs will be pooled as effect estimates for the continuous and categorical endpoints, respectively. Statistical and methodological heterogeneities will be assessed. Preplanned subgroup analyses and univariate meta-regression will be conducted to quantify the potential sources of heterogeneity. Evidence-based synthesis will be based on the magnitudes of effect size, evidence certainty and the surface under the cumulative ranking curve values.

ETHICS AND DISSEMINATION

Ethical approval is not required because this study is based on existing published data. These findings will be disseminated through scientific meetings and publications in peer-reviewed journals.

PROSPERO REGISTRATION NUMBER

CRD42022302795.

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.

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.

Molecular analysis of inflammatory diseases

If we try to describe the search for molecular actors involved in inflammatory diseases, the picture best representing this task is a mission to unexplored worlds. However, researchers nowadays have powerful tools to support this journey to the complexity of the unknown: Next generation Sequencing technologies have provided a plethora of data describing the different OMICs possibly involved in the different inflammatory diseases. Here we focused on autoinflammatory skin diseases showing the progress of OMICs-related findings in the understanding of Syndromic HS pathogenesis. We described the studies reporting possible genotype/phenotype correlation in PASH and PAPASH patients (both unrelated or familial cases), highlighting those just genetic variations associated with the diseases have been observed, but the information on common pathways shared by PASH and PAPASH patients were lacking, thus rendering difficult to decipher the common molecular basis of these autoinflammatory conditions. Aimed at filling this gap of knowledge, we proposed an integrated OMICs approach able to identify common pathways shared by subjects suffering from PASH and PAPASH: pathway-based whole sequencing analysis allowed the identification of 4 pathways, keratinization, formation of the cornified envelope steroid metabolism and ​​Vitamin D metabolism, disrupted in PASH and PAPASH patients. Finally, we mentioned the novel bioinformatic platform, named PlatOMICs, capable of integrating OMICs experimental findings also with the ones already reported in public repositories supporting the efforts of the researchers and clinicians to discover molecular pathways shared by individuals suffering of a disease, confronting, and integrating the bench findings with the in-silico ones.