Single-cell profiling of prurigo nodularis demonstrates immune-stromal crosstalk driving profibrotic responses and reversal with nemolizumab

Emerging Techniques in Spatial Multiomics: Fundamental Principles and Applications to Dermatology

Molecular pathology, such as high-throughput genomic and proteomic profiling, identifies precise disease targets from biopsies but require tissue dissociation, losing valuable histologic and spatial context. Emerging spatial multi-omic technologies now enable multiplexed visualization of genomic, proteomic, and epigenomic targets within a single tissue slice, eliminating the need for labeling multiple adjacent slices. Although early work focused on RNA (spatial transcriptomics), spatial technologies can now concurrently capture DNA, genome accessibility, histone modifications, and proteins with spatially-resolved single-cell resolution. This review outlines the principles, advantages, limitations, and potential for spatial technologies to advance dermatologic research. By jointly profiling multiple molecular channels, spatial multiomics enables novel studies of copy number variations, clonal heterogeneity, and enhancer dysregulation, replete with spatial context, illuminating the skin's complex heterogeneity.

Natural killer cells' functional impairment drives the immune escape of pre-malignant clones in early-stage myelodysplastic syndromes

Dissecting the preneoplastic disease states' biological mechanisms that precede tumorigenesis can lead to interventions that can slow down disease progression and/or mitigate disease-related comorbidities. Myelodysplastic syndromes (MDS) cannot be cured by currently available pharmacological therapies, which fail to eradicate aberrant hematopoietic stem cells (HSCs), most of which are mutated by the time of diagnosis. Here, we sought to elucidate how MDS HSCs evade immune surveillance and expand in patients with clonal cytopenias of undetermined significance (CCUS), the pre-malignant stage of MDS. We used multi-omic single-cell approaches and functional in vitro studies to show that immune escape at disease initiation is mainly mediated by mutant, dysfunctional natural killer (NK) cells with impaired cytotoxic capability against cancer cells. Preclinical in vivo studies demonstrated that injecting NK cells from healthy donors efficiently depleted CCUS mutant cells while allowing normal cells to regenerate hematopoiesis. Our findings suggest that early intervention with adoptive cell therapy can prevent or delay the development of MDS.

Prurigo nodularis and the microbiome

Prurigo nodularis (PN) is a chronic skin condition that profoundly impacts quality of life. Histopathological studies of itchy hyperkeratotic nodules show dense infiltrates of T lymphocytes, mast cells, and eosinophils. A robust inflammatory response is implicated, coupled with key changes in neuronal plasticity that affect nerve fiber architecture and function. The microbial community in PN lesions exhibits a distinct composition, marked by decreased α-diversity and a prominent increase in Staphylococcus aureus (S aureus). This alteration appears to contribute to the disease's pathophysiology, causing further disruption of the skin barrier, immune dysregulation, and neuronal plasticity. There is ample evidence that virulence factors of S aureus promote Th2, Th17, and Th22 cytokine production, which are key to PN. In addition, S aureus V8 protease (Endoproteinase Glu-C) has recently been identified to trigger robust itch by activating protease-activated receptor 1 (PAR1) on sensory neurons. This review underscores the complex interplay between the altered microbiome and the itch-scratch cycle of PN, providing insights into potential therapeutics targeting the skin microbiome. A multidisciplinary approach is crucial for providing relief to individuals suffering from this skin condition.

The big four in the pathogenesis and pathophysiology of prurigo nodularis: Interplay among type 2 inflammation, epidermal hyperplasia, dermal fibrosis, and itch from neuroimmune dysregulation

Prurigo nodularis (PN) is a distinct inflammatory dermatosis. It is characterized by intensely pruritic, firm nodules, typically 1 to 2 cm in diameter, which usually develop on the extensor surfaces of the extremities. Histopathologically, the following characteristics are observed in PN lesions: (1) dermal cellular infiltrates composed of type 2 inflammation-associated immune cells with lesional overexpression of type 2 cytokines (including interleukin [IL]-4, IL-13, and IL-31), (2) dermal fibrosis, and (3) epidermal hyperplasia with hyperkeratosis. Additionally, functional and structural alterations of cutaneous sensory nerve fibers profoundly contribute to itch in cooperation with type 2 inflammation. This abnormal interaction is referred to as neuroimmune dysregulation. The scratching behavior induced by itching from neuroimmune dysregulation initiates the development of prurigo nodules. This distinctive pathogenic feature of "itch-first" in PN is distinct from "inflammation-first" in atopic dermatitis, where the skin initially exhibits type 2 inflammation, which is subsequently followed by itching. The interplay between the four elements, namely type 2 inflammation, epidermal hyperplasia, dermal fibrosis, and itch resulting from neuroimmune dysregulation, appears to be pivotal in the pathogenesis and pathophysiology of PN.

Multitranscriptome analysis reveals stromal cells in the papillary dermis to promote angiogenesis in psoriasis vulgaris

BACKGROUND

The pathogenesis of psoriasis is incompletely understood. Growing evidence suggests the involvement of stromal cells in the inflammatory process.

OBJECTIVES

To investigate the roles of stromal cells, including fibroblasts, vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs), in the psoriatic inflammatory microenvironment, and the possible underlying mechanisms involved.

METHODS

We used a combination of single-cell, spatial transcriptome and bulk RNA sequencing of lesional and nonlesional skin samples from patients with psoriasis vulgaris (PV) and healthy skin samples from unaffected individuals.

RESULTS

By analysing transcriptomes from 364 098 single cells, we uncovered WNT5A+ (Wnt-5a) fibroblasts, ITIH5+ (inter-α-trypsin inhibitor heavy chain 5) VECs and VCAN+ (versican) VSMCs, with significantly increased proportions of these cells in the papillary dermis of lesional psoriatic skin. We defined eight unique subclusters of fibroblasts in the skin and observed a shift of WIF1+ (Wnt inhibitory factor 1) fibroblasts toward WNT5A+ fibroblasts, with abnormal activation of the noncanonical Wnt signalling pathway and increased angiogenic and proinflammatory capabilities. VSMCs were able to undergo phenotypic transformation from a contractile to a synthetic phenotype during the development of psoriatic inflammation. ITIH5+ VECs and VCAN+ VSMCs were found to have an essential role in regulating angiogenesis and vascular remodelling in the pathological changes seen in PV. Ligand receptor analyses found that WNT5A+ fibroblasts are extensively implicated in interactions with various skin cell types, especially TIH5+ VECs and VCAN+ VSMCs in the papillary dermis.

CONCLUSIONS

Interactions of stromal cells in the papillary dermis were identified as possible pathogenic elements in PV. Improving the inflammatory microenvironment by targeting stromal cells might be a potential treatment strategy in PV.

SPP1hi macrophages, NKG7 T cells, CCL5hi fibroblasts, and IgM plasma cells are dominant features of necrobiosis

Necrobiosis is a histologic term used to describe abnormal deposits of "degenerating" collagen within the skin. It can be found as an incidental finding in various granulomatous conditions, but is a hallmark of necrobiosis lipoidica (NL) and necrobiotic xanthogranuloma (NXG). There is limited prior research on necrobiosis. Here, we employed single-cell analysis of lesional and nonlesional skin to study the pathophysiology of necrobiosis. Our findings demonstrate that necrobiotic lesional skin is characterized by SPP1hi macrophages expressing MARCO; NKG7-expressing effector CD8+ T cells coexpressing CCL5, IFNG, GZMs, and PRF1; CCL5hi fibroblasts coexpressing CXCL9, diverse collagens (e.g., COL4A4, COL11A1, COL8A1), and TIMP1; and IGHM-expressing plasma cells. Integrative analysis of signaling ligands and receptor expression identified strong cell-cell communication between NKG7+ T cells, CCL5hi fibroblasts, and SPP1-expressing macrophages. In contrast, these cell populations were not dominant features of systemic sclerosis, another collagen deposition disease. Furthermore, although SPP1-expressing macrophages were detectable in sarcoidosis, IFNG-expressing T cells were a more defining feature of sarcoidosis compared with NL and NXG. From these findings, we speculate that necrobiosis results from the deposition of diverse collagens and ECM proteins through a process driven by CCL5-expressing fibroblasts and SPP1-expressing macrophages.

IL-9 sensitizes human TH2 cells to proinflammatory IL-18 signals in atopic dermatitis

BACKGROUND

TH2 cells crucially contribute to the pathogenesis of atopic dermatitis (AD) by secreting high levels of IL-13 and IL-22. Yet the upstream regulators that activate TH2 cells in AD skin remain unclear. IL-18 is a putative upstream regulator of TH2 cells because it is implicated in AD pathogenesis and has the capacity to activate T cells.

OBJECTIVE

We sought to decipher the role of IL-18 in TH2 responses in blood and skin of AD patients.

METHODS

Peripheral blood mononuclear cells and skin biopsy samples from AD patients and healthy donors were used. Functional assays were performed ex vivo using stimulation or blocking experiments. Analysis was performed by flow cytometry, bead-based multiplex assays, RT-qPCR, RNA-Seq, Western blot, and spatial sequencing.

RESULTS

IL-18Rα+ TH2 cells were enriched in blood and lesional skin of AD patients. Of all the cytokines for which TH2 cells express the receptor, only IL-9 was able to induce IL-18R via an IL-9R-JAK1/JAK3-STAT1 signaling pathway. Functionally, stimulation of circulating TH2 cells with IL-18 induced secretion of IL-13 and IL-22, an effect that was enhanced by costimulation with IL-9. Mechanistically, IL-18 induced TH2 cytokines via activation of IRAK4, NF-κB, and AP-1 signaling in TH2 cells, and neutralization of IL-18 inhibited these cytokines in cultured explants of AD skin lesions. Finally, IL-18 protein levels correlated positively with disease severity in lesional AD skin.

CONCLUSION

Our data identify a novel IL-9/IL-18 axis that contributes to TH2 responses in AD. Our findings suggest that both IL-9 and IL-18 could represent upstream targets for future treatment of AD.

Translating tissue expression of STAT 1, 3 and 6 in prurigo nodularis to clinical efficacy of oral tofacitinib - A prospective single-arm investigational study

Background Interleukin (IL)-4, IL-13, IL-17, IL-22 and IL-3 are overexpressed in prurigo nodularis (PN). They mediate their action via the Janus Kinase (JAK) Signal transducer and activator of transcription (STAT) pathway. Objectives Our aim was to study the expression of tissue STAT1, STAT3, and STAT6, as well as the efficacy of the JAK-STAT inhibitor, tofacitinib, in PN. Methods A prospective study was conducted in a tertiary care hospital. Patients with PN were recruited after excluding secondary causes. Pruritus was graded using Pruritus Grading System Score (PGSS). All cases underwent histological assessment using immunohistochemical markers for STAT1, STAT3, and STAT6 in both lesional and perilesional skin. Tofacitinib was initiated at a dose of 5 mg twice daily or 11 mg once daily and then tapered to a maintenance dose. The final PGSS at the time of data evaluation, as well as the occurrence of remissions and relapses, was assessed. Results The majority of the 17 patients included in the study had moderate to severe disease. Immunohistochemical analysis revealed marked tissue expression of STAT6 in 13 and STAT3 in 10 patients, while STAT1 expression was seen in only 4 patients [p < 0.05], suggesting a Th2/Th17 tissue response. The mean onset of action of tofacitinib was 11.2 ± 6.44 days and the mean duration of treatment was 5.6 ± 2.2 months. A significant reduction in PGSS was noted after treatment (66.1%, P value 0.0004). Fourteen of the patients maintained remission on low-dose therapy (5 mg OD or A/D) while one patient experienced a relapse. No serious adverse effects were noted. Limitation We could not study the tissue cytokines and the expression of STATs after achieving clinical response on oral tofacitinib. Conclusion The efficacy of tofacitinib in PN is based on its inhibitory effect on Th2 and Th17 cytokines, which is dependent on STAT6 and STAT3.

IL-27 as a novel biomarker for pruritus in nodular prurigo and bullous pemphigoid

Introduction

Bullous pemphigoid (BP) and prurigo nodularis (PN) are chronic pruritic skin diseases that severely impact patients' quality of life. Despite the widespread attention these two diseases have garnered within the dermatological field, the specific pathogenesis, particularly the molecular mechanisms underlying the pruritus, remains largely unclear. Limited clinical sequencing studies focusing on BP and PN have hindered the identification of pathological mechanisms and the exploration of effective treatment strategies.

Methods

To address this gap, we collected a total of 23 peripheral blood mononuclear cell samples from BP and PN patients, as well as healthy controls, and performed RNA sequencing analysis. By integrating bioinformatics and machine learning techniques, we aimed to uncover the shared immune regulatory networks and pruritus-related mechanisms between BP and PN.

Results

Our study identified 161 differentially expressed genes shared between BP and PN, which were primarily enriched in immune activation and neural pathways, providing crucial molecular insights into the pruritus-related mechanisms of both diseases. Furthermore, using the machine learning algorithms of support vector machines and random forest, we pinpoint 7 crucial genes shared between the BP and PN databases. Among these, IL-27 emerged as a potential pivotal gene, as its mRNA expression levels strongly correlated with clinical parameters including pruritus scores, immunoglobulin E levels, and eosinophil counts. Validation experiments conducted on clinical samples from an additional 22 participants confirmed the upregulation of IL-27 expression in both BP and PN lesions.

Discussion

This study is the first to unveil the shared inflammatory and immune pathways common to BP and PN, highlighting the critical role of IL-27 in the pathogenesis of these conditions. Our findings not only enhance the understanding of the intricate relationship between BP and PN, but also provide a foundation for the development of novel therapeutic strategies targeting these two dermatological conditions.

Effect of COL11A1 on oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor of the oral cavity, which is mainly a series of atypical hyperplasia of oral epithelial cells, and the overall prognosis remains poor.

METHODS

GSE37991 and GSE38517 were downloaded from gene expression omnibus (GEO) to identify differentially expressed genes (DEGs). Functional enrichment analysis of DEGs was performed, weighted gene co-expression network analysis (WGCNA) was used. Protein-protein interaction (PPI) network was constructed. Core gene expression was visualized using a heatmap. Comparative toxicogenomics database (CTD) and miRNA analyses identified related diseases and regulatory miRNAs. Western blot (WB) was conducted to examine expression of COL11A1 and TGF-SMAD signaling components in OSCC samples.

RESULTS

5163 DEGs were identified. DEGs were enriched in metabolic processes and signaling pathways, including TGF-β/SMAD and PI3K-Akt. WGCNA identified 11 core modules. PPI network analysis revealed five core genes: COL11A1, AURKA, MELK, CCNA2, and BUB1. Heatmap analysis showed that COL11A1 is highly expressed in OSCC. CTD analysis indicated that COL11A1 is associated with OSCC. miRNA prediction identified potential regulatory factors. Western blot analysis demonstrated that COL11A1 is overexpressed in OSCC and is associated with TGF-SMAD signaling, inflammation, and cell cycle progression.

CONCLUSION

COL11A1 is highly expressed in OSCC and may serve as a target gene interacting with the TGF-SMAD signaling pathway.

Omics in allergy and asthma

This review explores the transformative impact of omics technologies on allergy and asthma research in recent years, focusing on advancements in high-throughput technologies related to genomics and transcriptomics. In particular, the rapid spread of single-cell RNA sequencing has markedly advanced our understanding of the molecular pathology of allergic diseases. Furthermore, high-throughput genome sequencing has accelerated the discovery of monogenic disorders that were previously overlooked as ordinary intractable allergic diseases. We also introduce microbiomics, proteomics, lipidomics, and metabolomics, which are quickly growing areas of research interest, although many of their current findings remain inconclusive as solid evidence. By integrating these omics data, we will gain deeper insights into disease mechanisms, leading to the development of precision medicine approaches that promise to enhance treatment outcomes.

Single-cell transcriptomics analysis of bullous pemphigoid unveils immune-stromal crosstalk in type 2 inflammatory disease

Bullous pemphigoid (BP) is a type 2 inflammation- and immunity-driven skin disease, yet a comprehensive understanding of the immune landscape, particularly immune-stromal crosstalk in BP, remains elusive. Herein, using single-cell RNA sequencing (scRNA-seq) and in vitro functional analyzes, we pinpoint Th2 cells, dendritic cells (DCs), and fibroblasts as crucial cell populations. The IL13-IL13RA1 ligand-receptor pair is identified as the most significant mediator of immune-stromal crosstalk in BP. Notably, fibroblasts and DCs expressing IL13RA1 respond to IL13-secreting Th2 cells, thereby amplifying Th2 cell-mediated cascade responses, which occurs through the specific upregulation of PLA2G2A in fibroblasts and CCL17 in myeloid cells, creating a positive feedback loop integral to immune-stromal crosstalk. Furthermore, PLA2G2A and CCL17 contribute to an increased titer of pathogenic anti-BP180-NC16A autoantibodies in BP patients. Our work provides a comprehensive insight into BP pathogenesis and shows a mechanism governing immune-stromal interactions, providing potential avenues for future therapeutic research.

Prurigo Nodularis: Pathogenesis and the Horizon of Potential Therapeutics

Chronic pruritus that lasts for over 6 weeks can present in various forms, like papules, nodules, and plaque types, with prurigo nodularis (PN) being the most prevalent. The pathogenesis of PN involves the dysregulation of immune cell-neural circuits and is associated with peripheral neuropathies, possibly due to chronic scratching. PN is a persistent and challenging condition, involving complex interactions among the skin, immune system, and nervous system. Lesional skin in PN exhibits the infiltration of diverse immune cells like T cells, eosinophils, macrophages, and mast cells, leading to the release of inflammatory cytokines and itch-inducing substances. Activated sensory nerve fibers aggravate pruritus by releasing neurotransmitters, perpetuating a vicious cycle of itching and scratching. Traditional treatments often fail, but recent advancements in understanding the inflammatory and itch transmission mechanisms of PN have paved the way for innovative therapeutic approaches, which are explored in this review.

Molecular mechanisms of pruritus in prurigo nodularis

Pruritus is the most common symptom of dermatological disorders, and prurigo nodularis (PN) is notorious for intractable and severe itching. Conventional treatments often yield disappointing outcomes, significantly affecting patients' quality of life and psychological well-being. The pathogenesis of PN is associated with a self-sustained "itch-scratch" vicious cycle. Recent investigations of PN-related itch have partially revealed the intricate interactions within the cutaneous neuroimmune network; however, the underlying mechanism remains undetermined. Itch mediators play a key role in pruritus amplification in PN and understanding their action mechanism will undoubtedly lead to the development of novel targeted antipruritic agents. In this review, we describe a series of pruritogens and receptors involved in mediating itching in PN, including cytokines, neuropeptides, extracellular matrix proteins, vasculogenic substances, ion channels, and intracellular signaling pathways. Moreover, we provide a prospective outlook on potential therapies based on existing findings.

Keratin 17- and PKCα-dependent transient amplification of neutrophil influx after repeated stress to the skin

Neutrophils contribute to the pathogenesis of chronic inflammatory skin diseases. Little is known about the source and identity of the signals mediating their recruitment in inflamed skin. We used the phorbol ester TPA and UVB, alone or in combination, to induce sterile inflammation in mouse skin and assess whether keratinocyte-derived signals impact neutrophil recruitment. A single TPA treatment results in a neutrophil influx in the dermis that peaks at 12h and resolves within 24h. A second TPA treatment or a UVB challenge, when applied at 24h but not 48h later, accelerates, amplifies, and prolongs neutrophil infiltration. This transient amplification response (TAR) is mediated by local signals in inflamed skin, can be recapitulated in ex vivo culture, and involves the K17-dependent sustainment of protein kinase Cα (PKCα) activity and release of neutrophil chemoattractants by stressed keratinocytes. We show that K17 binds RACK1, a scaffold essential for PKCα activity. Finally, analyses of RNAseq data reveal the presence of a transcriptomic signature consistent with TAR and PKCα activation in chronic inflammatory skin diseases. These findings uncover a novel, transient, and keratin-dependent mechanism that amplifies neutrophil recruitment to the skin under stress, with direct implications for inflammatory skin disorders.

New insight into the role of fibroblasts in the epithelial immune microenvironment in the single-cell era

The skin is exposed to environmental challenges and contains heterogeneous cell populations such as epithelial cells, stromal cells, and skin-resident immune cells. As the most abundant type of stromal cells, fibroblasts have been historically considered silent observers in the immune responses of the cutaneous epithelial immune microenvironment (EIME), with little research conducted on their heterogeneity and immune-related functions. Single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) have overcome the limitations of bulk RNA sequencing and help recognize the functional and spatial heterogeneity of fibroblasts, as well as their crosstalk with other types of cells in the cutaneous EIME. Recently, emerging single-cell sequencing data have demonstrated that fibroblasts notably participate in the immune responses of the EIME and impact the initiation and progression of inflammatory skin diseases. Here, we summarize the latest advances in the role of fibroblasts in the cutaneous EIME of inflammatory skin diseases and discuss the distinct functions and molecular mechanisms of activated fibroblasts in fibrotic skin diseases and non-fibrotic inflammatory skin diseases. This review help unveil the multiple roles of fibroblasts in the cutaneous EIME and offer new promising therapeutic strategies for the management of inflammatory skin diseases by targeting fibroblasts or the fibroblast-centered EIME.