Altered Skin and Gut Microbiome in Hidradenitis Suppurativa

IL-17 Control of Cutaneous Immune Homeostasis

IL-17 is widely recognized for its roles in host defense and inflammatory disorders. However, it has become clear that IL-17 is also an essential regulator of barrier tissue physiology. Steady-state microbe sensing at the skin surface induces low-level IL-17 expression that enhances epithelial integrity and resists pathogens without causing overt inflammation. Recent reports describe novel protective roles for IL-17 in wound healing and counteracting physiologic stress; however, chronic amplification of these beneficial responses contributes to skin pathologies as diverse as fibrosis, cancer, and autoinflammation. In this paper, we discuss the context-specific roles of IL-17 in skin health and disease and therapeutic opportunities.

Efficacy of laser hair removal in hidradenitis suppurativa: A systematic review and meta-analysis

OBJECTIVES

Hidradenitis suppurativa (HS) is a chronic inflammatory condition characterized by painful nodules, draining tunnels, and fibrotic scarring in intertriginous, hair-bearing areas. The pathogenesis involves follicular occlusion and subsequent rupture, leading to uncontrolled inflammation. Treatment options for HS are limited and lack universal effectiveness. Laser hair removal (LHR) has been explored as a potential treatment; however, the efficacy and appropriate laser modalities remain unclear. This systematic review examined the efficacy and adverse effects of LHR in HS.

METHODS

A comprehensive literature search was conducted from inception to September 2023 in Ovid MEDLINE, Ovid Embase, and The Cochrane Library (Wiley) with predefined inclusion and exclusion criteria, and a meta-analysis was conducted.

RESULTS

Ten studies were selected (n = 227 total patients) and included six randomized controlled trials, two nonrandomized experimental studies, and two case series. Various laser modalities, including long-pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) (n = 115), intense pulsed light (n = 18), Alexandrite (n = 54), intralesional 1064 nm diode (n = 20), and combined fractional CO2 and long-pulsed Nd:YAG laser (n = 20), consistently demonstrated significant improvement in HS disease severity, irrespective of the disease scoring method used. Minimal adverse effects (primarily mild pain and erythema) were reported. A meta-analysis of three studies utilizing long-pulsed Nd:YAG laser demonstrated a standardized mean difference in disease severity of -1.68 (95% confidence interval: -2.99; -0.37), favoring treatment with LHR for HS.

CONCLUSIONS

Hair follicles are key in HS pathogenesis and all included studies showed a significant improvement in HS disease severity after LHR regardless of the laser device used, likely related to hair follicle unit destruction. HS is a complex and heterogenous condition, and multiple disease scoring methods complicate outcome comparisons across studies. However, LHR, utilizing various techniques, is an effective treatment option for HS with minimal adverse effects.

Gram-negative anaerobes elicit a robust keratinocytes immune response with potential insights into HS pathogenesis

Hidradenitis Suppurativa (HS) is a chronic autoinflammatory skin disease with activated keratinocytes, tunnel formation and a complex immune infiltrate in tissue. The HS microbiome is polymicrobial with an abundance of commensal gram-positive facultative (GPs) Staphylococcus species and gram-negative anaerobic (GNA) bacteria like Prevotella, Fusobacterium and Porphyromonas with increasing predominance of GNAs with disease severity. We sought to define the keratinocyte response to bacteria commonly isolated from HS lesions to probe pathogenic relationships between HS and the microbiome. Type strains of Prevotella nigrescens, Prevotella melaninogenica, Prevotella intermedia, Prevotella asaccharolytica, Fusobacterium nucleatum, as well as Staphylococcus aureus and the normal skin commensal Staphylococcus epidermidis were heat-killed and co-incubated with normal human keratinocytes. RNA was collected and analysed using RNAseq and RT-qPCR. The supernatant was collected from cell culture for protein quantification. Transcriptomic profiles between HS clinical samples and stimulated keratinocytes were compared. Co-staining of patient HS frozen sections was used to localize bacteria in lesions. A mouse intradermal injection model was used to investigate early immune recruitment. TLR4 and JAK inhibitors were used to investigate mechanistic avenues of bacterial response inhibition. GNAs, especially F. nucleatum, stimulated vastly higher CXCL8, IL17C, CCL20, IL6, TNF and IL36γ transcription in normal skin keratinocytes than the GPs S. epidermidis and S. aureus. Using RNAseq, we found that F. nucleatum (and Prevotella) strongly induced the IL-17 pathway in keratinocytes and overlapped with transcriptome profiles of HS patient clinical samples. Bacteria were juxtaposed to activated keratinocytes in vivo, and F. nucleatum strongly recruited murine neutrophil and macrophage migration. Both the TLR4 and pan-JAK inhibitors reduced cytokine production. Detailed transcriptomic profiling of healthy skin keratinocytes exposed to GNAs prevalent in HS revealed a potent, extensive inflammatory response vastly stronger than GPs. GNAs stimulated HS-relevant genes, including many genes in the IL-17 response pathway, and were significantly associated with HS tissue transcriptomes. The close association of activated keratinocytes with bacteria in HS lesions and innate infiltration in murine skin cemented GNA pathogenic potential. These novel mechanistic insights could drive future targeted therapies.

Role of Antigenic Stimulation in Cutaneous T-Cell Lymphomas

Cutaneous T-cell lymphoma (CTCL) involves a clonal expansion of malignant cells accumulating in the skin, a primary barrier site. CTCL has long been hypothesized to be caused or perpetuated by chronic antigen stimulation due to unknown exposures. These antigenic triggers, defined as any element that may cause activation of malignant T cells through TCR signaling, have been hypothesized to range from chemicals to microbes. This review covers current evidence supporting chemical and microbial stimuli that may act as antigenic triggers of CTCL and summarizes novel areas of investigation, in which the potential antigenicity of the exposure is still unknown.

The gut microbiome in systemic lupus erythematosus: lessons from rheumatic fever

For more than a century, certain bacterial infections that can breach the skin and mucosal barriers have been implicated as common triggers of autoimmune syndromes, especially post-infection autoimmune diseases that include rheumatic fever and post-streptococcal glomerulonephritis. However, only in the past few years has the importance of imbalances within our own commensal microbiota communities, and within the gut, in the absence of infection, in promoting autoimmune pathogenesis become fully appreciated. A diversity of species and mechanisms have been implicated, including disruption of the gut barrier. Emerging data suggest that expansions (or blooms) of pathobiont species are involved in autoimmune pathogenesis and stimulate clonal expansion of T cells and B cells that recognize microbial antigens. This Review discusses the relationship between the gut microbiome and the immune system, and the potential consequence of disrupting the community balance in terms of autoimmune development, focusing on systemic lupus erythematosus. Notably, inter-relationships between expansions of certain members within gut microbiota communities and concurrent autoimmune responses bear features reminiscent of classical post-infection autoimmune disease. From such insights, new therapeutic opportunities are being considered to restore the balance within microbiota communities or re-establishing the gut-barrier integrity to reinforce immune homeostasis in the host.

Unveiling the therapeutic symphony of probiotics, prebiotics, and postbiotics in gut-immune harmony

The gut microbiota and immune system interaction play a crucial role in maintaining overall health. Probiotics, prebiotics, and postbiotics have emerged as promising therapeutic approaches to positively influence this complex axis and enhance health outcomes. Probiotics, as live bacteria, promote the growth of immune cells, shape immune responses, and maintain gut barrier integrity. They modify the gut microbiota by fostering beneficial bacteria while suppressing harmful ones. Additionally, probiotics interact with the immune system, increasing immune cell activity and anti-inflammatory cytokine production. Prebiotics, as indigestible fibers, selectively nourish beneficial microorganisms in the gut, enhancing gut microbial diversity and activity. This, in turn, improves gut health and boosts immune responses while controlling inflammation through its immunomodulatory properties. Postbiotics, produced during probiotic fermentation, such as short-chain fatty acids and antimicrobial peptides, positively impact gut health and modulate immune responses. Ensuring quality control and standardization will be essential for successful clinical implementation of these interventions. Overall, understanding and harnessing the gut microbiota-immune system interplay offer promising avenues for improving digestive and immunological health.

An Atlas of the Hidradenitis Suppurativa Transcriptome

INTRODUCTIONS

Hidradenitis suppurativa (HS) is a chronic inflammatory condition of the skin. Both genetic and environmental factors contribute to the risk of developing HS, but the pathogenesis of this disease is currently not fully understood. The aim of this study was to further current understanding of the molecular background of HS with the use of global transcriptome analyses.

METHODS

Transcriptome profiling of perilesional and lesional skin of five patients with HS and six healthy control patients was performed by next-generation sequencing. Groups of differentially expressed genes characteristic of the skin of patients with HS were shortlisted by bioinformatic analysis.

RESULTS

RNA sequencing followed by bioinformatic profiling revealed profound enrichment of inflammatory-related processes in both lesional and perilesional skin of patients with HS. There were, however, distinct differences in the gene expression profiles between the lesional and perilesional skin, with 1488 genes differentially expressed. Genes encoding typical proinflammatory cytokines were profoundly enriched within HS lesions. In contrast, those encoding mediators of extracellular matrix organization were highly expressed mostly in the perilesional area.

CONCLUSIONS

Our study provides novel insights into the mechanisms underlying the pathogenesis of HS, and the results also have potential clinical implications in both diagnosis and therapeutics.

Causal relationship between gut microbiota and hidradenitis suppurativa: a two-sample Mendelian randomization study

Background

Accumulating evidence suggests that alterations in gut microbiota composition are associated with the hidradenitis suppurativa (HS). However, the causal association between gut microbiota and HS remain undetermined.

Methods

We performed a bidirectional two-sample Mendelian randomization (MR) analysis using genome-wide association study summary data of gut microbiota and hidradenitis suppurativa from the MiBioGen consortium which concluded 18,340 individuals analyzed by the MiBioGen Consortium, comprising 211 gut microbiota. HS data were acquired from strictly defined HS data collected by FinnGenbiobank analysis, which included 211,548 European ancestors (409 HS patients, 211,139 controls). The inverse variance weighted method (IVW), weighted median (WME), simple model, weighted model, weighted median, and MR-Egger were used to determine the changes of HS pathogenic bacterial taxa, followed by sensitivity analysis including horizontal pleiotropy analysis. The MR Steiger test evaluated the strength of a causal association and the leave-one-out method assessed the reliability of the results. Additionally, a reverse MR analysis was carried out to seek for possible reverse causality.

Results

By combining the findings of all the MR steps, we identified four causal bacterial taxa, namely, Family XI, Porphyromonadaceae, Clostridium innocuum group and Lachnospira. The risk of HS might be positively associated with a high relative abundance of Clostridium innocuum group (Odds ratio, OR 2.17, p = 0.00038) and Lachnospira (OR 2.45, p = 0.017) but negatively associated with Family XI (OR 0.67, p = 0.049) and Porphyromonadaceae (OR 0.29, p = 0.014). There were no noticeable outliers, horizontal pleiotropy, or heterogeneity. Furthermore, there was no proof of reverse causation found in the reverse MR study.

Conclusion

This study indicates that Clostridium innocuum group and Lachnospira might have anti-protective effect on HS, whereas Family XI and Porphyromonadaceae might have a protective effect on HS. Our study reveals that there exists a beneficial or detrimental causal effect of gut microbiota composition on HS and offers potentially beneficial methods for therapy and avoidance of HS.

Neutrophil extracellular traps and neutrophilic dermatosis: an update review

Neutrophils have both antimicrobial ability and pathogenic effect in the immune system, neutrophil extracellular traps (NETs) formation is one of the representative behaviors of their dual role. NETs formation was triggered by pathogen-related components and pathogen non-related proteins as cytokines to exert its effector functions. Recent studies indicate that the pathogenicity of NETs contributed to several skin diseases such as psoriasis, Stevens-Johnson syndrome, toxic epidermal necrolysis, and neutrophilic dermatosis. Especially in neutrophilic dermatosis, a heterogeneous group of inflammatory skin disorders characterized with sterile neutrophilic infiltrate on dermis, NETs formation was reported as the way of participation of neutrophils in the pathogenesis of these diseases. In this review, we describe the different processes of NETs formation, then summarized the most recent updates about the pathogenesis of neutrophilic dermatosis and the participation of NETs, including pyoderma gangrenosum and PAPA syndrome, Behçet syndrome, hidradenitis suppurativa, Sweet Syndrome, pustular dermatosis and other neutrophilic dermatosis. Furthermore, we discuss the link between NETs formation and the development of neutrophilic dermatosis.

A Catastrophic Biodiversity Loss in the Environment Is Being Replicated on the Skin Microbiome: Is This a Major Contributor to the Chronic Disease Epidemic?

There has been a catastrophic loss of biodiversity in ecosystems across the world. A similar crisis has been observed in the human gut microbiome, which has been linked to "all human diseases affecting westernized countries". This is of great importance because chronic diseases are the leading cause of death worldwide and make up 90% of America's healthcare costs. Disease development is complex and multifactorial, but there is one part of the body's interlinked ecosystem that is often overlooked in discussions about whole-body health, and that is the skin microbiome. This is despite it being a crucial part of the immune, endocrine, and nervous systems and being continuously exposed to environmental stressors. Here we show that a parallel biodiversity loss of 30-84% has occurred on the skin of people in the developed world compared to our ancestors. Research has shown that dysbiosis of the skin microbiome has been linked to many common skin diseases and, more recently, that it could even play an active role in the development of a growing number of whole-body health problems, such as food allergies, asthma, cardiovascular diseases, and Parkinson's, traditionally thought unrelated to the skin. Damaged skin is now known to induce systemic inflammation, which is involved in many chronic diseases. We highlight that biodiversity loss is not only a common finding in dysbiotic ecosystems but also a type of dysbiosis. As a result, we make the case that biodiversity loss in the skin microbiome is a major contributor to the chronic disease epidemic. The link between biodiversity loss and dysbiosis forms the basis of this paper's focus on the subject. The key to understanding why biodiversity loss creates an unhealthy system could be highlighted by complex physics. We introduce entropy to help understand why biodiversity has been linked with ecosystem health and stability. Meanwhile, we also introduce ecosystems as being governed by "non-linear physics" principles-including chaos theory-which suggests that every individual part of any system is intrinsically linked and implies any disruption to a small part of the system (skin) could have a significant and unknown effect on overall system health (whole-body health). Recognizing the link between ecosystem health and human health allows us to understand how crucial it could be to maintain biodiversity across systems everywhere, from the macro-environment we inhabit right down to our body's microbiome. Further, in-depth research is needed so we can aid in the treatment of chronic diseases and potentially change how we think about our health. With millions of people currently suffering, research to help mitigate the crisis is of vital importance.

Comparative diet-gut microbiome analysis in Crohn's disease and Hidradenitis suppurativa

Introduction

The chronic inflammatory skin disease Hidradenitis suppurativa (HS) is strongly associated with Crohn's Disease (CD). HS and CD share clinical similarities and similar inflammatory pathways are upregulated in both conditions. Increased prevalence of inflammatory disease in industrialised nations has been linked to the Western diet. However, gut microbiota composition and diet interaction have not been compared in HS and CD.

Methods

Here we compared the fecal microbiota (16S rRNA gene amplicon sequencing) and habitual diet of previously reported subjects with HS (n = 55), patients with CD (n = 102) and controls (n = 95).

Results and discussion

Patients with HS consumed a Western diet similar to patients with CD. Meanwhile, habitual diet in HS and CD was significantly different to controls. Previously, we detected differences in microbiota composition among patients with HS from that of controls. We now show that 40% of patients with HS had a microbiota configuration similar to that of CD, characterised by the enrichment of pathogenic genera (Enterococcus, Veillonella and Escherichia_Shigella) and the depletion of putatively beneficial genera (Faecalibacterium). The remaining 60% of patients with HS harboured a normal microbiota similar to that of controls. Antibiotics, which are commonly used to treat HS, were identified as a co-varying with differences in microbiota composition. We examined the levels of several inflammatory markers highlighting that growth-arrest specific 6 (Gas6), which has anti-inflammatory potential, were significantly lower in the 40% of patients with HS who had a CD microbiota configuration. Levels of the pro-inflammatory cytokine IL-12, which is a modulator of intestinal inflammation in CD, were negatively correlated with the abundance of health-associated genera in patients with HS. In conclusion, the fecal microbiota may help identify patients with HS who are at greater risk for development of CD.

Targeting dysbiosis in psoriasis, atopic dermatitis, and hidradenitis suppurativa: the gut-skin axis and microbiome-directed therapy

Emerging evidence highlights the gut-skin microbiota as a potential therapeutic target for the management of inflammatory-driven cutaneous diseases as well as the interconnection of the gut-skin microbiota in disease pathogenesis and progression. Although not fully understood, recent research has indicated that commensal microbiota and the interaction of the gut-skin axis play an important role in maintaining skin homeostasis. Dysbiosis and disruption of the skin-gut microbiome may lead to impaired skin barrier function, thus triggering downstream inflammatory responses involved in the development of inflammatory skin disorders, especially in atopic dermatitis, psoriasis, and hidradenitis suppurativa. The skin microbiome may also serve as adjunctive therapeutic modalities for treatment. Herein, we review the latest reports on the interrelationship between microbial dysbiosis and inflammatory cutaneous diseases as well as emerging microbiome-directed therapeutics in atopic dermatitis, psoriasis, and hidradenitis suppurativa.

Skin and Gut Microbiome in Hidradenitis Suppurativa: A Systematic Review

Hidradenitis suppurativa (HS) is a chronic skin disease that significantly impairs the quality of life of affected individuals. The disease is characterized by persistent purulent lesions in specific anatomical areas, and its pathophysiology involves multiple factors, including inflammation, genetics, the microbiome, and environmental components. Recent research suggests a potential role for pathogenic bacteria in HS, highlighting the importance of the communication between the human host and the microbiome in maintaining homeostasis and immune system reactivity. However, the exact mechanisms underlying the gut-skin microbial interactions in HS remain unclear. This systematic review aims to examine the existing literature on the differences in skin and gut microbiome composition between HS patients and healthy controls. The review identifies methodological inconsistencies and calls for further research to elucidate the microbiome's role in HS pathogenesis and to explore new therapeutic interventions. The review highlights the need for advancements in microbiome research methodologies, such as metataxonomics and metagenomics, to improve our understanding of the microbiota's impact on health and disease.

Hidradenitis Suppurativa: A Literature Review Comparing Current Therapeutic Modalities

Hidradenitis suppurativa (HS) is a disease with a poor prognosis, often misinterpreted as an infection, with the highest impact on the patient's quality of life among all the assessed dermatological diseases. The main aim of this study was to compare various therapeutic interventions that are currently available for the treatment of HS. The pathogenesis of HS is not well understood, but it is mostly multifactorial involving a number of factors like genetic factors, androgens, local immunity, microflora, smoking, and obesity. Despite limited evidence on their effectiveness, topical antibiotics and antiseptics are commonly employed. Due to the colonization of bacteria and the presence of biofilms in the sinus tracts formed by HS lesions, systemic antibiotics are commonly employed as the primary form of therapy. In females with HS who experience menstrual flares or display symptoms of polycystic ovary syndrome, hormonal agents are often considered to be a viable and effective therapeutic option. At present, the sole treatment approved by both the Food and Drug Administration and the European Medicines Agency for addressing moderate to severe HS is adalimumab, an antibody that targets tumor necrosis factor alpha. Many surgical procedures in the management of HS aim to address inflammation by eliminating the affected folliculo-pilosebaceous unit, sinus tracts, and associated debris to impede further progression and scarring. HS continues to pose a considerable treatment challenge, necessitating a comprehensive approach for patients. However, the available evidence for most of these treatments is limited, indicating the need for more extensive research to identify the most effective interventions for managing HS.

Emerging Treatments and the Clinical Trial Landscape for Hidradenitis Suppurativa-Part II: Procedural and Wound Care Therapies

Procedural treatments are a cornerstone of hidradenitis suppurativa (HS) management. New interventional therapies are being studied as part of the upsurge in HS research and clinical trials. Additionally, draining wounds can impart a significant negative impact on patients' quality of life, requiring daily dressing changes. However, standardized guidelines on how to best manage HS wounds both day-to-day and post-procedure are lacking. In part II of this emerging therapies review, procedural treatments and wound care dressings and devices that are being investigated for HS management are discussed.

The Current Clinical Trial Landscape for Hidradenitis Suppurativa: A Narrative Review

Hidradenitis suppurativa (HS) is a skin disease resulting from chronic, recurrent inflammation around hair follicles, characterized by proinflammatory cytokines such as IL-1, IL-17, IL-23, and TNF-α. While adalimumab, a TNF-α targeting human IgG monoclonal antibody, is the only approved treatment for HS, there are many other therapies being investigated now targeting other key players in inflammatory pathways such as the cytokines listed above, C5a in the complement pathway, and Janus kinase (JAK). This review discusses current clinical trials for biologics and small molecules, procedures, and wound dressings undergoing study in hidradenitis suppurativa.

Role of gut microbiota in infectious and inflammatory diseases

Thousands of microorganisms compose the human gut microbiota, fighting pathogens in infectious diseases and inhibiting or inducing inflammation in different immunological contexts. The gut microbiome is a dynamic and complex ecosystem that helps in the proliferation, growth, and differentiation of epithelial and immune cells to maintain intestinal homeostasis. Disorders that cause alteration of this microbiota lead to an imbalance in the host’s immune regulation. Growing evidence supports that the gut microbial community is associated with the development and progression of different infectious and inflammatory diseases. Therefore, understanding the interaction between intestinal microbiota and the modulation of the host’s immune system is fundamental to understanding the mechanisms involved in different pathologies, as well as for the search of new treatments. Here we review the main gut bacteria capable of impacting the immune response in different pathologies and we discuss the mechanisms by which this interaction between the immune system and the microbiota can alter disease outcomes.

Consistency of Bacterial Triggers in the Pathogenesis of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is an inflammatory skin disease whose pathogenesis remains poorly defined. Over the past decades, the bacterial role in HS patients has been a focus of research. According to the literature, the HS skin (and probably gut) bacterial composition is different to that of healthy controls. To date, a key question is whether compositional changes in the microbial populations are responsible for the development of HS (primum movens), or only secondarily reflect the ongoing inflammatory process. The great diversity of methodologies that have been used to study microbial role in HS have led to an accumulation of conflicting results. Thus, in view of these considerations, the aim of this article is to provide the reader with an overview about different hypotheses proposed to explain the bacterial role in HS pathogenesis.

Adalimumab therapy is associated with increased faecal short chain fatty acids in hidradenitis suppurativa

Altered gut microbiota composition has been observed in individuals with hidradenitis suppurutiva (HS) and many other inflammatory diseases, including obesity, type 1 and type 2 diabetes. Here, we addressed whether adalimumab, a systemic anti-inflammatory therapy, may impact the microbiota biochemical profile, particularly on beneficial metabolites such as short-chain fatty acids (SCFAs). We conducted an observational single-arm pilot trial to assess gut microbiota composition by 16S rRNA gene sequence analysis and to detect metabolite signatures by gas chromatography in stool samples from participants with HS prior to and 12 weeks after commencing adalimumab therapy. HS individuals that better responded to adalimumab treatment showed a shift in the composition and function of the gut microbiota with significantly increased SCFA acetate and propionate compared to age, gender and BMI-matched healthy controls. A positive correlation was observed between propionate with Prevotella sp and Faecalibacterium prausnitsii. Increased SCFAs, changes in gut microbiota composition, function and metabolic profile following 12 weeks of adalimumab suggest that targeting SCFAs may be considered a potential biomarker to be evaluated as a complementary protective factor or as a diagnostically relevant signal in HS.

Narrowband ultraviolet B response in cutaneous T-cell lymphoma is characterized by increased bacterial diversity and reduced Staphylococcus aureus and Staphylococcus lugdunensis

Skin microbiota have been linked to disease activity in cutaneous T-cell lymphoma (CTCL). As the skin microbiome has been shown to change after exposure to narrowband ultraviolet B (nbUVB) phototherapy, a common treatment modality used for CTCL, we performed a longitudinal analysis of the skin microbiome in CTCL patients treated with nbUVB. 16S V4 rRNA gene amplicon sequencing for genus-level taxonomic resolution, tuf2 amplicon next generation sequencing for staphylococcal speciation, and bioinformatics were performed on DNA extracted from skin swabs taken from lesional and non-lesional skin of 25 CTCL patients receiving nbUVB and 15 CTCL patients not receiving nbUVB from the same geographical region. Disease responsiveness to nbUVB was determined using the modified Severity Weighted Assessment Tool: 14 (56%) patients responded to nbUVB while 11 (44%) patients had progressive disease. Microbial α-diversity increased in nbUVB-responders after phototherapy. The relative abundance of Staphylococcus, Corynebacterium, Acinetobacter, Streptococcus, and Anaerococcus differentiated nbUVB responders and non-responders after treatment (q<0.05). Microbial signatures of nbUVB-treated patients demonstrated significant post-exposure depletion of S. aureus (q=0.024) and S. lugdunensis (q=0.004) relative abundances. Before nbUVB, responder lesional skin harboured higher levels of S. capitis (q=0.028) and S. warneri (q=0.026) than non-responder lesional skin. S. capitis relative abundance increased in the lesional skin of responders (q=0.05) after phototherapy; a similar upward trend was observed in non-responders (q=0.09). Post-treatment skin of responders exhibited significantly reduced S. aureus (q=0.008) and significantly increased S. hominis (q=0.006), S. pettenkoferi (q=0.021), and S. warneri (q=0.029) relative abundances compared to that of no-nbUVB patients. Staphylococcus species abundance was more similar between non-responders and no-nbUVB patients than between responders and no-nbUVB patients. In sum, the skin microbiome of CTCL patients who respond to nbUVB is different from that of non-responders and untreated patients, and is characterized by shifts in S. aureus and S. lugdunensis. Non-responsiveness to phototherapy may reflect more aggressive disease at baseline.

Alterations of the Human Gut Microbiome in Patients With Hidradenitis Suppurativa: A Case-control Study and Review of the Literature

INTRODUCTION

Hidradenitis suppurativa (HS) is a chronic and systemic inflammatory disease that extends beyond the skin. The role of gut microbiome (GM) alterations in the pathogenesis of inflammatory and autoimmune disorders is remarkable.

OBJECTIVES

Based on the hypothesis that dysbiosis in the GM may trigger systemic inflammation in the pathogenesis of HS, this study aimed to investigate whether the GM is altered in HS patients compared with healthy subjects.

METHODS

In the present case-control study, fecal samples from 15 patients with HS and 15 age- and sex-matched healthy individuals were collected and analyzed using 16S rRNA-based metagenomic analysis, New Generation Sequencing (NGS). The V3 and V4-hypervariable regions of the bacterial 16S rDNA gene were amplified from all samples and sequenced by the Illumina MiSeq platform. Bioinformatics analyses were performed in QIIME2.

RESULTS

Shannon alpha diversity index showed significantly reduced diversity in HS patients (P = 0.048). Bray-Curtis Dissimilarity and Jaccard Distance revealed that the gut microbial composition of HS patients was significantly distinctive from that of controls (P = 0.01 and P = 0.007, respectively). The relative abundance of unclassified Clostridiales, unclassified Firmicutes, and Fusicatenibacter in HS was significantly lower than that in controls (P = 0.005, P = 0.029, and P = 0.046, respectively).

CONCLUSIONS

This study indicated that significant alterations in the GM of HS patients could play a critical role in the pathogenesis of HS and might be a trigger for systemic inflammation. Increased understanding of the pathogenesis of HS will shed light on the new potential therapeutic targets and novel treatment options.

Microbiome in Hidradenitis Suppurativa—What We Know and Where We Are Heading

Recently, interest in the microbiome of cutaneous diseases has increased tremendously. Of particular interest is the gut-brain-skin axis proposed by Stokes and Pillsbury in 1930. The microbiome has been suggested in the pathogenesis of hidradenitis suppurativa, however the link between the commensals and the host is yet to be established. Across all studies, the increased abundance of Porphyromonas, Peptoniphilus, and Prevotella spp., and a loss of skin commensal species, such as Cutibacterium in HS lesions, is a consistent finding. The role of gut and blood microbiome in hidradenitis suppurativa has not been fully elucidated. According to studies, the main link with the intestine is based on the increased risk of developing Crohn’s disease and ulcerative colitis, however, further research is highly needed in this area. Lifestyle, dietary approaches, and probiotics all seem to influence the microbiome, hence being a promising modality as adjuvant therapy. The aim of this review was to present the latest reports in the field of research on skin, blood, and gut microbiome in terms of hidradenitis suppurativa.

Nasal Dysbiosis in Cutaneous T-Cell Lymphoma Is Characterized by Shifts in Relative Abundances of Non-Staphylococcus Bacteria

The nasal microbiome of patients with cutaneous T-cell lymphoma (CTCL) remains unexplored despite growing evidence connecting nasal bacteria to skin health and disease. Nasal swabs from 45 patients with CTCL (40 with mycosis fungoides, 5 with Sézary syndrome) and 20 healthy controls from the same geographical region (Chicago Metropolitan Area, Chicago, IL) were analyzed using sequencing of 16S ribosomal RNA and tuf2 gene amplicons. Nasal α-diversity did not differ between mycosis fungoides/Sézary syndrome and healthy controls (Shannon index, genus level, P = 0.201), but distinct microbial communities were identified at the class (R2 = 0.104, P = 0.023) and order (R2 = 0.0904, P = 0.038) levels. Increased relative abundance of the genera Catenococcus, Vibrio, Roseomonas, Acinetobacter, and unclassified Clostridiales was associated with increased skin disease burden (P < 0.005, q < 0.05). Performed to accurately resolve nasal Staphylococcus at the species level, tuf2 gene amplicon sequencing revealed no significant differences between mycosis fungoides/Sézary syndrome and healthy controls. Although S. aureus has been shown to worsen CTCL through its toxins, no increase in the relative abundance of this taxon was observed in nasal samples. Despite the lack of differences in Staphylococcus, the CTCL nasal microbiome was characterized by shifts in numerous other bacterial taxa. These data add to our understanding of the greater CTCL microbiome and provide context for comprehending nasal-skin and host‒tumor‒microbial relationships.

Innate immunity and microbial dysbiosis in hidradenitis suppurativa – vicious cycle of chronic inflammation

Hidradenitis Suppurativa (HS) is a chronic multifactorial inflammatory skin disease with incompletely understood mechanisms of disease pathology. HS is characterized by aberrant activation of the innate immune system, resulting in activation of pathways that aim to protect against pathogenic microorganisms, and also contribute to failure to resolve inflammation. Imbalance in innate immunity is evident in deregulation of host antimicrobial peptides (AMPs) and the complement system associated with the microbiome dysbiosis. The pathology is further complicated by ability of pathogens associated with HS to overcome host immune response. Potential roles of major AMPs, cathelicidin, defensins, dermcidin, S100 proteins, RNAse 7 and complement proteins are discussed. Dysregulated expression pattern of innate immunity components in conjunction with bacterial component of the disease warrants consideration of novel treatment approaches targeting both host immunity and pathogenic microbiome in HS.

Gut Microbiota Shifting in Irritable Bowel Syndrome: The Mysterious Role of Blastocystis sp

Irritable bowel syndrome (IBS) is a chronic disorder, which its causative agent is not completely clear; however, the interaction between microorganisms and gastrointestinal (GI) epithelial cells plays a critical role in the development of IBS and presenting symptoms. During recent decades, many studies have highlighted the high prevalence of Blastocystis sp. in patients with IBS and suggested a probable role for this protist in this disease. Recent studies have documented changes in the gut microbiota composition in patients with IBS regarding the presence of Blastocystis sp., but it is not clear that either disturbance of the gut during GI disorders is a favorable condition for Blastocystis sp. colonization or the presence of this protist may lead to alteration in the gut microbiota in IBS patients. In this review, we comprehensively gather and discuss scientific findings covering the role of Blastocystis sp. in IBS via gut microbiota shifting.

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.

Gut dysbiosis in cutaneous T-cell lymphoma is characterized by shifts in relative abundances of specific bacterial taxa and decreased diversity in more advanced disease

BACKGROUND

Cutaneous T-cell lymphoma (CTCL) patients often suffer from recurrent skin infections and profound immune dysregulation in advanced disease. The gut microbiome has been recognized to influence cancers and cutaneous conditions; however, it has not yet been studied in CTCL.

OBJECTIVES

To investigate the gut microbiome in patients with CTCL and in healthy controls.

METHODS

Case-control study conducted between January 2019 and November 2020 at Northwestern's busy multidisciplinary CTCL clinic (Chicago, Illinois, USA) utilizing 16S ribosomal RNA gene amplicon sequencing and bioinformatics analyses to characterize the microbiota present in fecal samples of CTCL patients (n=38) and age-matched healthy controls (n=13) from the same geographical region.

RESULTS

Gut microbial α-diversity trended lower in patients with CTCL and was significantly lower in patients with advanced CTCL relative to controls (p=0.015). No differences in β-diversity were identified. Specific taxa were significantly reduced in patient samples; significance was determined using adjusted p-values (q-values) that accounted for a false discovery rate threshold of 0.05. Significantly reduced taxa in patient samples included the phylum Actinobacteria (q=0.0002), classes Coriobacteriia (q=0.002) and Actinobacteria (q=0.03), order Coriobacteriales (q=0.003), and genus Anaerotruncus (q=0.01). The families of Eggerthellaceae (q=0.0007) and Lactobacillaceae (q=0.02) were significantly reduced in patients with high skin disease burden.

CONCLUSIONS

Gut dysbiosis can be seen in patients with CTCL compared to healthy controls and is pronounced in more advanced CTCL. The taxonomic shifts associated with CTCL are similar to those previously reported in atopic dermatitis and opposite those of psoriasis, suggesting microbial parallels to the immune profile and skin barrier differences between these conditions. These findings may suggest new microbial disease biomarkers and reveal a new angle for intervention.

Impact of gut microbiome on skin health: gut-skin axis observed through the lenses of therapeutics and skin diseases

The human intestine hosts diverse microbial communities that play a significant role in maintaining gut-skin homeostasis. When the relationship between gut microbiome and the immune system is impaired, subsequent effects can be triggered on the skin, potentially promoting the development of skin diseases. The mechanisms through which the gut microbiome affects skin health are still unclear. Enhancing our understanding on the connection between skin and gut microbiome is needed to find novel ways to treat human skin disorders. In this review, we systematically evaluate current data regarding microbial ecology of healthy skin and gut, diet, pre- and probiotics, and antibiotics, on gut microbiome and their effects on skin health. We discuss potential mechanisms of the gut-skin axis and the link between the gut and skin-associated diseases, such as psoriasis, atopic dermatitis, acne vulgaris, rosacea, alopecia areata, and hidradenitis suppurativa. This review will increase our understanding of the impacts of gut microbiome on skin conditions to aid in finding new medications for skin-associated diseases.

Human skin microbiota in health and disease: The cutaneous communities' interplay in equilibrium and dysbiosis: The cutaneous communities' interplay in equilibrium and dysbiosis

Cutaneous microbial composition is driven by the microenvironment of the skin, as well as by internal and external factors. Local changes in the microenvironment can affect the configuration of the community, which may lead toward an imbalance of microbiota. Alterations in the microbial profile are common in both inflammatory skin diseases and chronic infections. A shift in balance within the microbiota, toward limited variation and a greater abundance of specific pathogens, may further worsen the pathogenicity of the diseases. These alterations may be prevented by topical treatment of probiotic solutions stimulating a balanced multispecies community. Compositional variations may further constitute potential biomarkers to predict flares or monitor efficacy during therapy. New approaches such as machine learning may contribute to this prediction of microbial alterations prior to the development of chronic infections and flares. This review provides insight into the composition and distribution of a healthy community of microorganisms in the skin and draws parallels with the community in chronic infections and chronic inflammatory skin diseases such acne vulgaris and Hidradenitis Suppurativa. We discuss the potential role of specific species in the pathogenesis and the possible prevention of disease exacerbation.

Hyperhidrosis treatments in hidradenitis suppurativa: A systematic review

Hyperhidrosis impairs quality of life (QOL) in hidradenitis suppurativa (HS) patients and may exacerbate HS. However, there is limited literature on whether hyperhidrosis treatments improve HS disease. To systematically review literature on efficacy and tolerability of hyperhidrosis treatments in HS patients. In May 2021, MEDLINE and EMBASE databases were systematically searched by two reviewers per PRISMA guidelines for articles on hyperhidrosis and HS. Sixteen articles met inclusion criteria (2 randomized controlled trials [RCTs], one case-control study, three cross-sectional studies, 10 case-studies/series), encompassing 252 HS patients across studies. They examined botulinum toxin A (BTX-A) (n = 6) and B (BTX-B) (n = 1), suction-curettage (n = 1), diode laser (n = 1), and microwave-based energy device (MED) (n = 3). Overall, BTX treatments improve HS severity, QOL, hyperhidrosis, and were well-tolerated. Suction-curettage did not improve disease. One HS patient tolerated diode laser well, with improvement in sweating and HS. One RCT studying MED was discontinued due to adverse events. Two studies reported MED-induced HS. BTX was overall helpful in HS patients, including in patients without concomitant hyperhidrosis. However, more prospective studies are needed to examine its utility in HS. There is potential harm of MEDs in HS. Most studies examining hyperhidrosis treatments in HS patients are low level of evidence. Larger RCTs should examine the efficacy and tolerability of hyperhidrosis treatments in HS.