Single-cell and spatial transcriptomics have transformed the ability to chart human tissue organization at high resolution, enabling the construction of reference atlases and robust gene marker identification. The skin,...Single-cell and spatial transcriptomics have transformed the ability to chart human tissue organization at high resolution, enabling the construction of reference atlases and robust gene marker identification. The skin, as the largest human organ, lacks a comprehensive integrated atlas, particularly for the pilosebaceous unit, a key epithelial structure involved in homeostasis and disease. We present a framework for a scalable healthy Human Skin Cell Atlas (HSCA), systematically integrating 34 publicly available single-cell RNA sequencing datasets comprising 819,068 cells, with harmonized metadata and standardized cell type nomenclature. In addition, we generated a new high-resolution Visium HD spatial transcriptomics dataset, demonstrating the benefits of integrating spatial information with single-cell data and enabling mapping of hair follicle compartments and identification of critical signaling hubs. The integrated atlas revealed cell types not detectable in individual datasets, including Merkel cells, and refined the classification of pilosebaceous unit subtypes. Importantly, the HSCA enables rapid annotation of new datasets and assessment of mapping uncertainties, facilitating the discovery of rare or disease-specific cell types. This resource provides a comprehensive and expandable reference of healthy human skin and illustrates the value of combining single-cell and spatial data for studies of tissue organization, disease mechanisms, and regenerative medicine.
Transcription-coupled nucleotide excision repair (TC-NER) safeguards transcription by repairing transcription-blocking lesions (TBLs), which are highly cytotoxic if unresolved. TC-NER is triggered when RNA Polymerase II...Transcription-coupled nucleotide excision repair (TC-NER) safeguards transcription by repairing transcription-blocking lesions (TBLs), which are highly cytotoxic if unresolved. TC-NER is triggered when RNA Polymerase II (Pol II) stalls at a TBL and is recognized by CSB, followed by recruitment of the TC-NER factors CSA and UVSSA. Loss of any of these factors causes complete TC-NER deficiency. Mutations in CSB or CSA typically result in Cockayne syndrome (CS), a disorder marked by neurodegeneration and severe premature aging, highlighting the importance of TC-NER. By contrast, mutations in UVSSA cause the much milder UV-sensitive syndrome (UVS), limited to cutaneous symptoms. Recently, this difference has been linked to the ability of UVSSA-deficient, but not CSB- or CSA-deficient, cells to clear stalled Pol II through proteasomal degradation, allowing alternative repair routes. Unexpectedly, patients with an early nonsense mutation in CSB (R77X), leading to undetectable protein levels, develop UVS rather than CS. We examined this paradox and found that R77X cells can still degrade lesion-stalled Pol II, which is caused by residual but functional CSB expression in these cells. Together, our findings refine the model that defective Pol II processing is central to CS pathogenesis and extend its relevance across TC-NER related mutations.
Candida auris (C. auris) is an emerging fungal pathogen with a remarkable ability to persist on human skin, but how structural skin cells respond to colonization is unclear. We used ex vivo human skin models, together wi...Candida auris (C. auris) is an emerging fungal pathogen with a remarkable ability to persist on human skin, but how structural skin cells respond to colonization is unclear. We used ex vivo human skin models, together with primary keratinocytes and fibroblasts, to characterize epithelial and stromal responses to C. auris compared with Candida albicans. C. auris formed biofilms and induced a wound-model-dependent pattern of cytokine secretion dominated by IL-1β and IL-6, yet caused minimal epithelial damage and modest reductions in leukocyte viability. RNA sequencing revealed complementary but cell-type-specific responses. Keratinocytes and fibroblasts both amplified a pro-inflammatory IL-6/CXCL8 response, while keratinocytes additionally upregulated antimicrobial genes such as RNASE7, TSLP, DEFB103A (encoding hBD-3), and the neutrophil-recruiting chemokines CXCL2 and CXCL3. Fibroblasts further induced CCL28, supporting T cell recruitment, alongside transcriptional programs associated with tissue remodeling. Recombinant RNase 7 and short form TSLP directly inhibited C. auris growth in vitro in a dose-dependent manner. Together, these findings identify keratinocytes as epithelial sentinels that integrate inflammatory and antimicrobial defenses against skin-tropic C. auris and suggest that fibroblast-driven cytokine amplification and especially antimicrobial peptides from within the skin barrier may provide therapeutic targets to limit C. auris skin colonization.
Cutaneous lupus erythematosus (CLE) is a lymphocytic interface dermatitis condition that affects the skin and mucosa. Many patients experience photosensitivity and itch. Recent work has demonstrated that Merkel cells in...Cutaneous lupus erythematosus (CLE) is a lymphocytic interface dermatitis condition that affects the skin and mucosa. Many patients experience photosensitivity and itch. Recent work has demonstrated that Merkel cells in the skin are important for itch responses in allokinesis and sunburn-induced itch. We asked whether Merkel cells were important for skin inflammation in the context of CLE given the overlap of symptoms. To address this, we bred Merkel cell deficient mice to our adoptive T cell transfer CLE mouse model. Mice lacking half of their Merkel cells had increased skin disease scores compared to littermates and CLE parental strain controls following adoptive transfer of model autoantigen-specific T cells. Examination of gene expression in the skin revealed increases in CXCL1, IL6 and IL1R2 among other DEGs. Flow cytometry analysis of skin from Merkel-deficient mice revealed an influx of CD11b+ cells, which was mainly comprised of Ly6G+Ly6C+ neutrophils, as compared to genetic controls. We conclude that Merkel cells play a key immunoregulatory role in innate immune system activation in T cell driven interface dermatitis.
Exposure to excess ultraviolet radiation is associated with approximately three-quarters of the global burden of melanoma. Yet, much of what is known about the effects of UV on melanocytes comes from studies of cell line...Exposure to excess ultraviolet radiation is associated with approximately three-quarters of the global burden of melanoma. Yet, much of what is known about the effects of UV on melanocytes comes from studies of cell lines, animal models, and ex vivo-cultured human skin. In this in vivo study of human melanocytic nevi, we describe a protocol that facilitates the characterization of the effects of simulated solar radiation (SSR) on a wide array of cell types using RNA sequencing of single nuclei (snRNAseq) isolated from OCT-embedded frozen tissue. With no enrichment for rare cell types, our snRNAseq data reveal the transcriptional diversity of melanocytes, keratinocytes of the epidermis and adnexa, lymphatic and vascular endothelium, fibroblasts, and immune cells of the skin. Differences in gene expression between interfollicular basilar and nevomelanocytes, including those involved in senescence, are delineated. Co-expression analysis identified changes elicited by SSR in gene modules containing SERPINE2, and components of the IGF-1 signaling axis, in nevus cells and fibroblasts and endothelial cells. These findings were corroborated by RNAscope analysis of FFPE samples, thereby providing valuable pharmacologic targets and biomarkers for clinical trials of melanoma prevention agents.
Armstrong AW, Roberts AM, Kostandy G
… +10 more, Choudhury F, Yee D, Luu M, Jones ME, Alizadeh ER, Cotliar J, Chren MM, Gelfand JM, Cockburn M, Doctor JN
BACKGROUND: Atopic dermatitis (AD) is a chronic skin disease that can significantly affect quality of life and require regular access to dermatologic care. However, traditional in-person visits often impose logistical ch...BACKGROUND: Atopic dermatitis (AD) is a chronic skin disease that can significantly affect quality of life and require regular access to dermatologic care. However, traditional in-person visits often impose logistical challenges. OBJECTIVES: To evaluate whether an online, team-based connected health (TCH) teledermatology model provides equivalent improvements in quality of life compared to in-person management of AD and examine access to care. METHODS: We conducted a 12-month, pragmatic, randomized, controlled, equivalence trial (NCT03981926) involving 300 participants aged ≥1 year with physician-diagnosed AD. Participants were randomized 1:1 to the online or in-person arm. Quality of life was assessed using the Dermatology Life Quality Index (DLQI) and EQ-5D-5L. Access was measured via average time needed for evaluation. RESULTS: For all quality-of-life measures, the difference in mean change between arms fell within the prespecified equivalence margins: 0.12 (95% CI: -0.18 to 0.42) for DLQI, 0.00 (95% CI: -0.01, 0.01) for utility index, and -0.11 (95% CI: -0.70, 0.48) for VAS. TCH significantly reduced time needed for evaluation at baseline (P = 0.03). CONCLUSION: For patients with atopic dermatitis, the online TCH model resulted in equivalent improvements in quality of life and reduced time needed for evaluation at baseline.
Maho-Vaillant M, Lefebvre A, Golinski ML
… +10 more, Calbo S, Lebourgeois L, Carrette M, Jouen F, Challamel C, Fazilleau N, Paul C, Joly P, Tedbirt B, Hébert V
Rituximab combined with short-term corticosteroids is the standard first-line treatment for pemphigus, but a subset of patients remains refractory, with limited effective alternatives. Daratumumab, an anti-CD38 monoclona...Rituximab combined with short-term corticosteroids is the standard first-line treatment for pemphigus, but a subset of patients remains refractory, with limited effective alternatives. Daratumumab, an anti-CD38 monoclonal antibody targeting plasma cells, has emerged as a potential option in severe autoimmune diseases. We report two cases of life-threatening pemphigus refractory to rituximab and alternative therapies, successfully treated with daratumumab, with longitudinal clinical and immunological monitoring of anti-desmoglein responses. Rituximab failure was associated with incomplete B-cell depletion, with persistence of memory B cells and plasmablasts. Daratumumab induced rapid clinical improvement, depletion of CD38 plasma cells, and reduction of anti-desmoglein antibodies. In one patient, relapse occurred after daratumumab discontinuation, with subsequent rituximab inefficacy due to anti-rituximab antibodies; combined daratumumab and belimumab led to sustained complete remission, likely through complementary targeting of plasma cells and prevention of autoreactive B-cell reconstitution. In the second patient, remission induced by daratumumab was consolidated with additional rituximab. No treatment-related adverse events were observed. These findings suggest that daratumumab, alone or in combination with B-cell-targeting agents, may represent a promising therapeutic strategy for rituximab-refractory pemphigus.
The transcriptional co-activators YAP and TAZ are key regulators of cell proliferation, apoptosis, and differentiation, thereby maintaining tissue homeostasis and controlling organ size. While their roles in epithelial c...The transcriptional co-activators YAP and TAZ are key regulators of cell proliferation, apoptosis, and differentiation, thereby maintaining tissue homeostasis and controlling organ size. While their roles in epithelial cancers and fibrosis are well established, their involvement in the physiological regulation of the dermal extracellular matrix (ECM) by fibroblasts is less understood. Here, we investigated the role of Yap/Taz during postnatal development of the dermal ECM. During postnatal growth, mouse skin steadily undergoes significant surface expansion. Postnatal deletion of Yap/Taz in dermal fibroblasts, the primary cells responsible for dermal ECM homeostasis, significantly impaired dermal ECM maturation, as evidenced by marked deficiencies in collagen expression, deposition, and organization. Isolated fibroblasts from Yap/Taz knockout mice showed reduced expression of Yap/Taz target genes (Ccn1, Ccn2, Col1a1), which were rescued by reintroduction of active Yap/Taz. RNA-seq, spatial transcriptomics, and proteomics of Yap/Taz knockout skin revealed substantial downregulation of ECM-related genes, including type I (Col1a1, Col1a2) and type III (Col1a3) collagens, which together constitute more than 90% of the skin's collagen content. Mechanistically, deletion of Yap/Taz impaired mouse dermal maturation, at least in part through suppression of TGF-β/Smad signaling, the primary pathway governing fibroblast collagen synthesis. These findings demonstrate that YAP/TAZ are essential for postnatal dermal ECM homeostasis.
Keloid radiotherapy is clinically effective but has an incomplete underlying molecular mechanism and limited accessibility; we used X-ray exposure to identify effector pathways replicating its antifibrotic benefits witho...Keloid radiotherapy is clinically effective but has an incomplete underlying molecular mechanism and limited accessibility; we used X-ray exposure to identify effector pathways replicating its antifibrotic benefits without further radiation. After collecting patient keloid samples, primary human keloid fibroblasts and normal skin fibroblasts, non-targeted metabolomics and RNA-seq were performed, identifying phytosphingosine (PHS) and KIF20A as key mediators of fibrosis and cell death in keloid radiotherapy. X-ray irradiation increased PHS release in keloid fibroblasts; exogenous PHS and X-ray irradiation independently induced cell death and reduced fibrosis, their combination exerted radiosensitization by boosting G2/M arrest and apoptosis while lowering fibrosis progression, and both PHS and irradiation reduced KIF20A whose loss induced cell cycle arrest and apoptosis. Our findings reveal that X-ray irradiation enhances keloid fibroblast PHS secretion that downregulates KIF20A to exert keloid therapeutic effects, and topical PHS or KIF20A-targeting agents are immediately translatable alternatives for radiotherapy-ineligible patients.
Interleukin-31 (IL-31) drives chronic pruritus in patients with dermatological and even certain systemic diseases. However, fast-onset anti-pruritic effects of blocking IL-31 receptors, for instance with nemolizumab in a...Interleukin-31 (IL-31) drives chronic pruritus in patients with dermatological and even certain systemic diseases. However, fast-onset anti-pruritic effects of blocking IL-31 receptors, for instance with nemolizumab in atopic dermatitis patients, are incompletely understood, in part due to ethical restrictions in humans and species differences to mice. Therefore, we used sensory neuron cultures from pig to investigate direct neuronal IL-31 effects. We first mapped functional characteristics of afferents encoding histamine itch in humans onto a recently established transcriptome-based DRG neuron taxonomy to identify pig pruriceptors. IL-31 acutely sensitized responses to repeated pruritogen and electrical stimulation only in these histamine- and capsaicin-responsive pruriceptors and also activated these afferents with silent nociceptor phenotype in vivo as validated by dermal axon-reflex erythema measurements. Thus, our data functionally and transcriptionally identifies the likely sensory neuron class underlying IL-31-driven chronic pruritus and opens a perspective for translational research on distinct neuronal classes differentially driving skin inflammation and clinical chronic pruritus via specific neuro-immune signaling patterns.