Dermal Compartment Research Articles

Impact of human mesenchymal cells of different body site origins on the maturation of dermo-epidermal skin substitutes.

The use of autologous bio-engineered dermo-epidermal skin substitutes (DESS) yields a pivotal opportunity to cover large skin defects in human patients. These skin grafts consist of both epidermal and dermal compartments necessary for robust and permanent functional wound closure. In this study, we investigated the impact of mesenchymal cells derived from different body site origins on the expression pattern of diverse markers within DESS. Human keratinocytes were obtained from interfollicular epidermis, and mesenchymal cells were isolated from foreskin, palmar skin, fat tissue, and tonsils. After expansion, epidermal cells were seeded on collagen I hydrogels containing stromal cells. These human DESS were transplanted on the back of immune-incompetent rats. After 3 weeks, transplants were excised and analyzed using immunohistology techniques. The macroscopic appearance of skin grafts containing tonsil, fat tissue, or palmar derived mesenchymal cells, was similar to substitutes with foreskin derived dermal fibroblasts. All skin grafts had a strong membrane-localized expression of Lingo-1 in the epidermis. Additionally, we observed an intense expression of transglutaminase 5 in upper epidermal cell layers of the skin grafts confirming a proper keratinocyte differentiation. Tropoelastin was localized throughout the dermal compartments and tightly in contact with the dermo-epidermal junction suggesting an advanced maturation of all skin grafts. Our data implicate that stromal cells derived from tonsil, fat tissue, and palmar skin can assume fibroblast functions supporting keratinocyte proliferation and differentiation. These findings indicate that distinct types of mesenchymal cells can be clinically used for skin engineering purposes.

3D Cell Printing of Perfusable Vascularized Human Skin Equivalent Composed of Epidermis, Dermis, and Hypodermis for Better Structural Recapitulation of Native Skin.

Although skin cell-printing has exhibited promises for fabrication of functional skin equivalents, existing skin models through 3D cell printing are still composed of dermal and epidermal layers. However, a key hope for printing skin is to improve structural complexity of human skin over conventional construction, enabling the precise localization of multiple cell types and biomaterials. Here, the complexity of skin anatomy is increased using 3D cell printing. A novel printing platform is suggested for engineering a matured perfusable vascularized 3D human skin equivalent composed of epidermis, dermis, and hypodermis. The skin model is evaluated using functional markers representing each region of epidermis, dermis, and hypodermis to confirm tissue maturation. It is hypothesized that the vascularized dermal and hypodermal compartments that provide a more realistic microenvironment can promote cross-talks with the epidermal compartment, producing better recapitulation of epidermal morphogenesis. Skin stemness in epithelial tissue is investigated. These findings reveal that the full-thickness skin has more similarities to the native human skin compared with the dermal and epidermal skin model, indicating that it better reflects the actual complexity of native human skin. It is envisioned that it offers better predictive and reliable in vitro platform for investigation of mechanisms of pathological research and skin disease modeling.

Comparative inhalation toxicity testing using in vitro organotypic rat and human airway epithelial models

Human cell-based approaches to assess defined key events in allergic contact dermatitis (ACD) are well-established, but lack cutaneous penetration and biotransformation as well as cellular cross-talk. Herein, we integrated in vitro-generated immature MUTZ-3-derived Langerhans-like cells (MUTZ-LCs) or monocyte-derived LC-like cells (MoLCs) into reconstructed human skin (RHS), consistent of a stratified epidermis formed by primary keratinocytes on a dermal compartment with collagen-embedded primary fibroblasts. LC-like cells were mainly localized in the epidermal compartment and distributed homogenously in accordance with native human skin. Topical application of the strong contact sensitizer 2,4-dinitrochlorobenzene (DNCB) induced IL-6 and IL-8 secretion in RHS with LC-like cells, whereas no change was observed in reference models. Increased gene expression of CD83, PD-L1, and CXCR4 in the dermal compartment indicated LC maturation. Importantly, exposure to DNCB enhanced mobility of the LC-like cells from epidermal to dermal compartments. In response to the moderate sensitizer isoeugenol and irritant sodium dodecyl sulphate, the obtained response was less pronounced. In summary, we integrated immature and functional MUTZ-LCs and MoLCs into RHS and provide a unique comparative experimental setting to monitor early events during skin sensitization.

Genetically engineered cell factories produce glycoengineered vaccines that target antigen-presenting cells and reduce antigen-specific T-cell reactivity

Genetically engineered cell factories produce glycoengineered vaccines that target antigen-presenting cells and reduce antigen-specific T-cell reactivity

Foxn1 in Skin Development, Homeostasis and Wound Healing.

Intensive research effort has focused on cellular and molecular mechanisms that regulate skin biology, including the phenomenon of scar-free skin healing during foetal life. Transcription factors are the key molecules that tune gene expression and either promote or suppress gene transcription. The epidermis is the source of transcription factors that regulate many functions of epidermal cells such as proliferation, differentiation, apoptosis, and migration. Furthermore, the activation of epidermal transcription factors also causes changes in the dermal compartment of the skin. This review focuses on the transcription factor Foxn1 and its role in skin biology. The regulatory function of Foxn1 in the skin relates to physiological (development and homeostasis) and pathological (skin wound healing) conditions. In particular, the pivotal role of Foxn1 in skin development and the acquisition of the adult skin phenotype, which coincides with losing the ability of scar-free healing, is discussed. Thus, genetic manipulations with Foxn1 expression, specifically those introducing conditional Foxn1 silencing in a Foxn1+/+ organism or its knock-in in a Foxn1−/− model, may provide future perspectives for regenerative medicine.

Actin cytoskeleton assembly regulates collagen production via TGF-β type II receptor in human skin fibroblasts.

The dermal compartment of skin is primarily composed of collagen‐rich extracellular matrix (ECM), which is produced by dermal fibroblasts. In Young skin, fibroblasts attach to the ECM through integrins. During ageing, fragmentation of the dermal ECM limits fibroblast attachment. This reduced attachment is associated with decreased collagen production, a major cause of skin thinning and fragility, in the elderly. Fibroblast attachment promotes assembly of the cellular actin cytoskeleton, which generates mechanical forces needed for structural support. The mechanism(s) linking reduced assembly of the actin cytoskeleton to decreased collagen production remains unclear. Here, we report that disassembly of the actin cytoskeleton results in impairment of TGF‐β pathway, which controls collagen production, in dermal fibroblasts. Cytoskeleton disassembly rapidly down‐regulates TGF‐β type II receptor (TβRII) levels. This down‐regulation leads to reduced activation of downstream effectors Smad2/Smad3 and CCN2, resulting in decreased collagen production. These responses are fully reversible; restoration of actin cytoskeleton assembly up‐regulates TβRII, Smad2/Smad3, CCN2 and collagen expression. Finally, actin cytoskeleton‐dependent reduction of TβRII is mediated by induction of microRNA 21, a potent inhibitor of TβRII protein expression. Our findings reveal a novel mechanism that links actin cytoskeleton assembly and collagen expression in dermal fibroblasts. This mechanism likely contributes to loss of TβRII and collagen production, which are observed in aged human skin.

Past, present and future of in vitro 3D reconstructed inflammatory skin models to study psoriasis.

Psoriasis is a common chronic inflammatory skin disease with a significant socio-economic impact that can greatly affect the patients' quality of life. The prevailing dogma in the aetiology and pathophysiology of this complex disease is that skin cells, immune cells and environmental factors contribute to psoriatic skin inflammation. For a better understanding of the disease pathogenesis, models are required that mimic the disease and which can be used to develop therapeutics. Over the last decades, in vitro human reconstructed skin models have been widely used in dermatological research and have also been developed to mimic psoriatic skin. This viewpoint summarizes the most commonly used in vitro models and the latest accomplishments for the combination of the dermal and epidermal compartments with other cell types and factors that are important players in the psoriatic skin environment. We aim to critically list the most complete and best-validated models that include major psoriasis hallmarks with regard to gene and protein expression profile and epidermal morphology, but also discuss the shortcoming of the current models. This viewpoint intends to guide the development of in vitro 3D skin models that faithfully mimic all features of psoriatic skin. Such model will enable fundamental biological studies for a better understanding of the aetiology and pathophysiology of psoriasis and aid in novel therapeutic target identification and drug development studies.

Extracellular Matrix as a Regulator of Epidermal Stem Cell Fate

Epidermal stem cells reside within the specific anatomic location, called niche, which is a microenvironment that interacts with stem cells to regulate their fate. Regulation of many important processes, including maintenance of stem cell quiescence, self-renewal, and homeostasis, as well as the regulation of division and differentiation, are common functions of the stem cell niche. As it was shown in multiple studies, extracellular matrix (ECM) contributes a lot to stem cell niches in various tissues, including that of skin. In epidermis, ECM is represented, primarily, by a highly specialized ECM structure, basement membrane (BM), which separates the epidermal and dermal compartments. Epidermal stem cells contact with BM, but when they lose the contact and migrate to the overlying layers, they undergo terminal differentiation. When considering all of these factors, ECM is of fundamental importance in regulating epidermal stem cells maintenance, proper mobilization, and differentiation. Here, we summarize the remarkable progress that has recently been made in the research of ECM role in regulating epidermal stem cell fate, paying special attention to the hair follicle stem cell niche. We show that the destruction of ECM components impairs epidermal stem cell morphogenesis and homeostasis. A deep understanding of ECM molecular structure as well as the development of in vitro system for stem cell maintaining by ECM proteins may bring us to developing new approaches for regenerative medicine.

Effects of Synchrotron X-Ray Micro-beam Irradiation on Normal Mouse Ear Pinnae

Toanalyze the effects of micro-beam irradiation (MBI) on the normal tissues of the mouse ear. Normal mouse ears are a unique model, which in addition to skin contain striated muscles, cartilage, blood and lymphatic vessels, and few hair follicles. This renders the mouse ear an excellent model for complex tissue studies. The ears of C57BL6 mice were exposed to MBI (50-μm-wide micro-beams, spaced 200μm between centers) with peak entrance doses of 200, 400, or 800Gy (atultra-high dose rates). Tissue samples were examined histopathologically, with conventional light and electron microscopy, at 2, 7, 15, 30, and 240days after irradiation (dpi). Sham-irradiated animals acted as controls. Only an entrance dose of 800Gy caused a significant increase in the thickness of both epidermal and dermal ear compartments seen from 15 to 30 dpi; the number of sebaceous glands was significantly reduced by 30 dpi. The numbers of apoptotic bodies and infiltrating leukocytes peaked between 15 and 30 dpi. Lymphatic vessels were prominently enlarged at 15 up to 240 dpi. Sarcomere lesions in striated muscle were observed after all doses, starting from 2 dpi; scar tissue within individual beam paths remained visible up to 240 dpi. Cartilage and blood vessel changes remained histologically inconspicuous. Normal tissues such as skin, cartilage, and blood and lymphatic vessels are highly tolerant to MBI after entrance doses up to 400Gy. The striated muscles appeared to be the most sensitive to MBI. Those findings should be taken into consideration in future micro-beam radiation therapy treatment schedules.

Skin corrosion test: a comparison between reconstructed human epidermis and full thickness skin models

Currently, there is a strong global trend towards the development of in vitro models to replace the use of animals in safety evaluation tests. Reconstructed Human Epidermis (RHE) models have been employed as an alternative method to animal testing of skin corrosion and irritation potential of chemical compounds. However, the consequences of an absence of the dermal compartment in these models should be considered since the cross-talk between fibroblasts and keratinocytes is fundamental for promoting proper epidermal stratification, homeostasis, inflammatory response and wound healing. In this study, we compare in-house developed models of Reconstructed Human Epidermis (i.e. USP-RHE) and full thickness skin (i.e. USP-FTS) regarding their response when submitted to skin corrosion assays, based on Guideline 431 (OECD). The results show that both models correctly classified the four substances tested (2-phenylethyl bromide, benzylacetone, lactic acid, octanoic acid) as corrosive or non-corrosive. Furthermore, we have demonstrated higher cell viability of the USP-FTS model compared to the USP-RHE model, a sign of its improved barrier function, following the exposure to the substances test on the corrosion assay. This emphasizes the importance of employing in vitro models that are more physiologically relevant and that better mimic the in vivo situation for the toxicological screening of substances.

Morphological and molecular characterization of actinic lentigos reveals alterations of the dermal extracellular matrix.

Actinic lentigos (AL) are benign hyperpigmented skin lesions associated with photoageing. Despite their high prevalence, biological mechanisms driving their formation remain unclear. To provide new insights about the physiopathology of AL through a comprehensive description of their histological and molecular features. Quantitative analysis of dermoscopic images was used to select AL containing elongated patterns, predicted to display a highly deformed dermal-epidermal junction (DEJ), on the back of the hands of 15 Caucasian women. Biopsies from lesional and adjacent nonlesional (NL) areas were processed for histological analysis or gene expression profiling. Histological staining confirmed a drastic deformation of the DEJ in AL, with deep epidermal invaginations into the dermis. Although the melanin content was significantly higher in AL compared with NL epidermis, the distribution of melanocytes along the DEJ was unchanged. Transcriptomic analysis revealed a signature of 529 genes differently expressed in AL vs. NL skin. Alteration of epidermal homeostasis was confirmed by the dysregulation of keratinocyte proliferation and differentiation markers. Surprisingly, canonical genes involved in melanogenesis were not significantly modulated in AL. A striking finding was the overexpression of a large group of genes involved in dermal extracellular matrix organization and remodelling. Dermal alterations were confirmed by immunolabellings on AL and NL sections. Drastic disorganization of the cutaneous structure in AL is accompanied by a specific molecular signature revealing alterations in both epidermal and dermal compartments. In particular, our results suggest that local modifications of the dermal extracellular matrix might contribute to hyperpigmentation in AL.

Vitiligo Skin: Exploring the Dermal Compartment

There is an increasing interest in the apparently normal skin in vitiligo. Altered expression of the adhesion molecule E-cadherin and persistent deregulated intracellular redox status that promotes the acquisition of a stress-induced senescent phenotype in melanocytes of normally pigmented skin from patients with vitiligo have been described. Growing evidence has shown that such cellular and functional alterations are not necessarily restricted to melanocytes but may be extended to other cutaneous cell populations in both lesional and nonlesional areas. However, whether dermal fibroblasts exhibit related alterations that may contribute to the defects associated with melanocytes in vitiligo is not known. Here we reveal within the dermal compartment cells a myofibroblast phenotype and a predisposition to premature senescence, indicating the existence of altered cross-talk between dermal and epidermal components that may affect melanocyte functionality even in the apparently normal skin of patients with vitiligo.

Characterization of reconstructed human skin containing Langerhans cells to monitor molecular events in skin sensitization

Human cell-based approaches to assess defined key events in allergic contact dermatitis (ACD) are well-established, but lack cutaneous penetration and biotransformation as well as cellular cross-talk. Herein, we integrated in vitro-generated immature MUTZ-3-derived Langerhans-like cells (MUTZ-LCs) or monocyte-derived LC-like cells (MoLCs) into reconstructed human skin (RHS), consistent of a stratified epidermis formed by primary keratinocytes on a dermal compartment with collagen-embedded primary fibroblasts. LC-like cells were mainly localized in the epidermal compartment and distributed homogenously in accordance with native human skin. Topical application of the strong contact sensitizer 2,4-dinitrochlorobenzene (DNCB) induced IL-6 and IL-8 secretion in RHS with LC-like cells, whereas no change was observed in reference models. Increased gene expression of CD83, PD-L1, and CXCR4 in the dermal compartment indicated LC maturation. Importantly, exposure to DNCB enhanced mobility of the LC-like cells from epidermal to dermal compartments. In response to the moderate sensitizer isoeugenol and irritant sodium dodecyl sulphate, the obtained response was less pronounced. In summary, we integrated immature and functional MUTZ-LCs and MoLCs into RHS and provide a unique comparative experimental setting to monitor early events during skin sensitization.

Horse hair follicles: A novel dermal stem cell source for equine regenerative medicine.

The easily accessible niche represented by skin and its appendages may serve as a promising source to complement modern regenerative medicine for horses. In humans and in animal models for human medicine, the hair follicle and its stem cell niches are well characterized. Since literature in this field of equine research is scarce, we sought to analyze cells of the dermal stem cell niche of the equine hair follicle morphologically and for a subset of markers useful for cell characterization via immunolabeling. We cultured equine forelock skin explants to obtain cultures with cells migrating from the hair follicles. Isolation of cells revealed typical fibroblast morphology with a strong tendency to aggregate and form spheroids. For immunofluorescent characterization of primary isolations, we tested an antibody panel consisting of lineage makers for the dermal compartment of the hair follicle, markers associated with an undifferentiated cell status and markers for epithelial cell types as negative controls. All antibodies used were also tested on equine skin sections. The isolated cells displayed clear profiles of dermal and undifferentiated cells. To substantiate our findings, we tested our primary isolations for established equine multipotent mesenchymal stromal cell antigen expression markers in flow cytometry experiments yielding strong convergence. The data presented here provide insights to a stem cell source in horses almost unnoticed to date. The basic investigations of the equine dermal hair follicle stem cell niche confirm the expression of standard markers used in other species and lay the foundation for future studies on this easily available adult stem cell source. © 2017 International Society for Advancement of Cytometry.

Effects of glucocorticoids on stratum corneum lipids and function in human skin—A detailed lipidomic analysis

BackgroundTopical glucocorticoids (GCs) are known to induce atrophy of human skin including thinning of epidermal and dermal compartments by influencing keratinocyte proliferation and synthesis of extracellular matrix proteins. GCs are also known to reduce skin barrier integrity but little is known about the changes in lipid composition in human skin following topical administration of GCs. ObjectiveThis study investigated the effects of GCs on stratum corneum (SC) function and lipid profile of human skin in vivo. MethodOver a period of 4 weeks, 16 healthy volunteers were treated on the forearms once daily with topical clobetasol proprionate (CP), betamethasone diproprionate (BDP) or vehicle. One day after last application (Day 29) SC lipids were collected by tape stripping and analysed by a high sensitivity liquid chromatography–mass spectrometry method. Gene expression was analysed in skin biopsies. The full skin, epidermal and SC thickness were assessed by ultrasound, optical coherence tomography and confocal microscopy, respectively, and barrier integrity was assessed by measuring transepidermal water loss (TEWL). ResultsCompared to vehicle controls, GCs induced significant alterations in SC lipid profiles. CP caused a reduction in 98 lipids of 226 analysed while BDP treatment only resulted in a significant change of 29 lipids. Most pronounced changes occurred among long chain, ester-linked, ceramide classes while other ceramide classes were much less affected. Almost the complete profile of triacylglycerols (TGs) was significantly decreased by CP while more modest changes were observed in free fatty acids. Topical GCs reduced the thickness of skin layers and increased TEWL. GC treatment also induced changes in expression of genes coding for extracellular markers and enzymes involved in lipid synthesis. ConclusionsThis study shows a reduction in specific SC lipid classes following topical GC treatment of human skin and contributes to the characterisation of the barrier disruption in human skin induced by topical steroids.

Human Adipose Mesenchymal Cells Inhibit Melanocyte Differentiation and the Pigmentation of Human Skin via Increased Expression of TGF-β1

There is accumulating evidence that interactions between epidermal melanocytes and stromal cells play an important role in the regulation of skin pigmentation. In this study we established a pigmented dermo-epidermal skin model, melDESS, of human origin to investigate the effects of distinct stromal cells on melanogenesis. melDESS is a complex, clinically relevant skin equivalent composed of an epidermis containing both melanocytes and keratinocytes. Its dermal compartment consists either of adipose tissue-derived stromal cells, dermal fibroblasts (Fbs), or a mixture of both cell types. These skin substitutes were transplanted for 5 weeks on the backs of immuno-incompetent rats and analyzed. Gene expression and Western blot analyses showed a significantly higher expression of transforming growth factor-β1 by adipose tissue-derived stromal cells compared with dermal Fbs. In addition, we showed that melanocytes responded to the increased levels of transforming growth factor-β1 by down-regulating the expression of key melanogenic enzymes such as tyrosinase. This caused decreased melanin synthesis and, consequently, greatly reduced pigmentation of melDESS. The conclusions are of utmost clinical relevance, namely that adipose tissue-derived stromal cells derived from the hypodermis fail to appropriately interact with epidermal melanocytes, thus preventing the sustainable restoration of the patient's native skin color in bioengineered skin grafts.

Cyclophosphamide preconditioning facilitates autoimmune vitiligo and enhanced antitumor efficacy following vaccination with activated dendritic cells.

Abstract Cyclophosphamide (CTX) has been used as a lymphoablative conditioning agent to deplete regulatory T cells (Tregs) and enhance the efficacy of adoptive immune therapies. We initially investigated whether CTX conditioning could enhance the immunogenicity of melanoma Ag-pulsed dendritic cells (DC) in a murine model. CTX enhanced Ag-specific CD8+ T cell responses and control of SC-growing OVA+ melanoma following immunization with activated OVA257–265-pulsed DC; immunogenicity and tumor control were abrogated by reconstitution of Treg compartments. Unexpectedly, CTX-conditioned, DC-immunized animals developed significant vitiligo, despite the absence of exogenous melanocyte-specific Ag in the vaccine. CTX treatment or DC immunization alone failed to induce vitiligo. Injection of CTX-conditioned mice with MHC class II−/− DC, but not β2 microglobulin−/− DC, induced vitiligo regardless of exogenous Ag, suggesting that the induction of vitiligo may result from cross-presentation of endogenous melanocyte Ag in an environment of relaxed tolerance. Ab-mediated depletion of CD8 cells abrogated the vitiligo. These data suggest that CTX conditioning liberates class I-restricted melanocyte Ag for cross-presentation by activated DC to cognate CD8 cells, which in turn, achieve full activation and effector function in the absence of a normal regulatory environment. CTX conditioning may also open dermal compartments for increased effector T cell infiltration. Thus, CTX mediates multiple immunomodulatory mechanisms that may impact the future design of immunotherapy for melanoma.

Topography of Protein Kinase C βII in Benign and Malignant Melanocytic Lesions

Protein kinase C βII promotes melanogenesis and affects proliferation of melanocytic cells but is frequently absent or decreased in melanoma cells in vitro. To investigate PKC-βII expression and spatial distribution within a lesion in various benign and malignant melanocytic proliferations. Expression of PKC-βII was semiquantitatively assessed in the various existing compartments (intraepidermal [not nested], junctional [nested], and dermal) of benign (n = 43) and malignant (n = 28) melanocytic lesions by immunohistochemistry. Melanocytes in the basal layer of normal skin or in lentigo simplex stained strongly for PKC-βII. Common nevi lacked completely PKC-βII. All other lesions expressed variably PKC-βII, with cutaneous melanoma metastases displaying the lowest rate of positivity (14%). In the topographical analysis within a lesion, PKC-βII expression was largely retained in the intraepidermal and junctional part of all other lesions (dysplastic nevus, lentigo maligna, and melanoma). Reduced expression of PKC-βII was found in the dermal component of benign and malignant lesions ( P = .041 vs intraepidermal). PKC-βII expression in the various compartments did not differ significantly between benign and malignant lesions. The current study revealed a significant correlation between PKC-βII expression and spatial localization of melanocytes, with the lowest expression found in the dermal compartment and the highest in the epidermal compartment.

Multifaceted role of hair follicle dermal cells in bioengineered skins.

The method of generating bioengineered skin constructs was pioneered several decades ago; nowadays these constructs are used regularly for the treatment of severe burns and nonhealing wounds. Commonly, these constructs are comprised of skin fibroblasts within a collagen scaffold, forming the skin dermis, and stratified keratinocytes overlying this, forming the skin epidermis. In the past decade there has been a surge of interest in bioengineered skins, with researchers seeking alternative cell sources, or scaffolds, from which constructs can be established, and for more biomimetic equivalents with skin appendages. To evaluate whether human hair follicle dermal cells can act as an alternative cell source for engineering the dermal component of engineered skin constructs. We established in vitro skin constructs by incorporating into the collagenous dermal compartment: (i) primary interfollicular dermal fibroblasts, (ii) hair follicle dermal papilla cells or (iii) hair follicle dermal sheath cells. In vivo skins were established by mixing dermal cells and keratinocytes in chambers on top of immunologically compromised mice. All fibroblast subtypes were capable of supporting growth of overlying epithelial cells, both in vitro and in vivo. However, we found hair follicle dermal sheath cells to be superior to fibroblasts in their capacity to influence the establishment of a basal lamina. Human hair follicle dermal cells can be readily interchanged with interfollicular fibroblasts and used as an alternative cell source for establishing the dermal component of engineered skin both in vitro and in vivo.

IL‐36γ has proinflammatory effects on human endothelial cells

Interleukin-36 cytokines are predominantly expressed by epithelial cells. Significant upregulation of epidermal IL-36 is now a recognised characteristic of psoriatic skin inflammation. IL-36 is known to induce inflammatory responses in dendritic cells, fibroblasts and epithelial cells. Although vascular alterations are a hallmark of psoriatic lesions and dermal endothelial cells are well known to play a critical role in skin inflammation, the effects of IL-36 on endothelial cells are unexplored. We here show that endothelial cells including dermal microvascular cells express a functionally active IL-36 receptor. Adhesion molecules VCAM-1 and ICAM-1 are upregulated by IL-36γ stimulation, and this is reversed by the presence of the endogenous IL-36 receptor antagonist. IL-36γ-stimulated endothelial cells secrete the proinflammatory chemokines IL-8, CCL2 and CCL20. Chemotaxis assays showed increased migration of T-cells following IL-36γ stimulation of endothelial cells. These results suggest a role for IL-36γ in the dermal vascular compartment, and it is likely to enhance psoriatic skin inflammation by activating endothelial cells and promoting leucocyte recruitment.