An eosinophil immune response characterizes the inflammatory skin disease observed in Tie-2 transgenic mice

Although mouse models of inflammatory skin diseases such as psoriasis and atopic dermatitis fail to completely phenocopy disease in humans, they provide invaluable tools to examine the molecular and cellular mechanisms responsible for the epidermal hyperplasia, inflammation, and excess angiogenesis observed in human disease. We have previously characterized a tyrosine kinase with immunoglobin-like and epidermal growth factor-like domain-2 (Tie-2) transgenic mouse model of an inflammatory skin disease exhibiting these features. More specifically, we demonstrated that the inflammatory component consisted of increased infiltration of CD3-positive T lymphocytes and mast cells in the skin. Here, we further characterize the inflammatory component in the blood and skin of Tie-2 transgenic mice at cellular and molecular levels. We observed increased numbers of CD3-positive T lymphocytes in the blood and increased infiltration of eosinophils in the skin. Furthermore, we characterized cytokine protein and gene expression in the blood and skin, respectively, and observed the deregulated expression of cytokines associated with Th1 and eosinophil immune responses. Interestingly, treatment of Tie-2 transgenic mice with anti-CD4 antibody appeared to resolve aspects of inflammation but did not resolve epidermal hyperplasia, suggesting an important role for eosinophils in mediating the inflammatory skin disease observed in Tie-2 transgenic mice.     

TLRs to cytokines: Mechanistic insights from the imiquimod mouse model of psoriasis

Psoriasis is an inflammatory disease of the skin affecting 2–3% of the population, characterized by a thickening of the epidermis and immune infiltrates throughout the dermis and epidermis, causing skin lesions that can seriously affect quality of life. The study of psoriasis has historically been hampered by the lack of good animal models. Various genetically induced models exist, which have provided some information about possible mechanisms of disease, but these models rely mostly on intrinsic imbalances of homeostasis. However, a mouse model of psoriasiform dermatitis caused by the repeated topical application of Aldara? containing 5% imiquimod was described in 2009. The mechanisms of action of Aldara? are complex. Imiquimod is an effective ligand for TLR7 (and TLR8 in humans) and also interferes with adenosine receptor signaling. In addition, isostearic acid present in the Aldara? vehicle has been shown to be biologically active and of importance for activating the inflammasome. Interestingly, the repetitive application of Aldara? reveals a complex aetiology involving multiple cell types, cytokines, and inflammatory pathways. In this review, we will dissect the findings of the imiquimod model to date and ask how this model can inform us about the immunological aspects of human disease.     

The Malassezia sympodialis Allergen Mala s 11 with Sequence Similarity to Manganese Superoxide Dismutase Induces Maturation and Production of Inflammatory Cytokines in Human Dendritic Cells

The chronic inflammatory skin disease atopic eczema (AE) affects almost 15% of the population in many countries today. The pathogenesis of AE is not fully understood. A combination of genetic predisposition and environmental factors like microorganisms seems to contribute to the symptoms. The yeast Malassezia sympodialis is part of our normal skin micro flora but can act as an allergen and elicit specific IgE and T-cell reactivity in patients with AE. Recently, we identified a novel major M. sympodialis allergen, designated Mala s 11 (22.4 kDa), with sequence similarity to the mitochondrial enzyme manganese superoxide dismutase (MnSOD). Interestingly, Mala s 11 has a high degree of homology to human MnSOD. The aim of this study was to examine the effects of recombinant Mala s 11 on antigen-presenting dendritic cells. Monocyte-derived dendritic cells (MDDCs) from healthy blood donors were cultured with or without Mala s 11 for different time periods. It was found that the maturation marker CD83 and the costimulatory molecules CD80 and CD86 were upregulated on the MDDCs exposed to Mala s 11 for 24 h, as demonstrated by flow cytometry. Furthermore, coculture of MDDCs with Mala s 11 for 9 h induced an increased production of the inflammatory cytokines IL-6 (200-fold), TNF-α (100-fold) and IL-8 (sixfold), as detected by the cytometric bead array (CBA) analysis. Our results suggest that Mala s 11 affects the immune response through DC maturation and production of inflammatory cytokines. The potential cross-reactivity with human MnSOD needs to be explored and the exact role of Mala s 11 in the pathogenesis of AE assessed in clinical studies involving skin prick and atopy patch tests.     

A new era of atopic eczema research: Advances and highlights

Atopic eczema (AE) is an inflammatory skin disease with involvement of genetic, immunological and environmental factors. One hallmark of AE is a skin barrier disruption on multiple, highly interconnected levels: filaggrin mutations, increased skin pH and a microbiome dysbiosis towards Staphylococcus aureus overgrowth are observed in addition to an abnormal type 2 immune response. Extrinsic factors seem to play a major role in the development of AE. As AE is a first step in the atopic march, its prevention and appropriate treatment are essential. Although standard therapy remains topical treatment, powerful systemic treatment options emerged in the last years. However, thorough endotyping of the individual patients is still required for ideal precision medicine approaches in future. Therefore, novel microbial and immunological biomarkers were described recently for the prediction of disease development and treatment response. This review summarizes the current state of the art in AE research.     

The pathogenic role of tissue-resident immune cells in psoriasis

Psoriasis is a common chronic inflammatory skin disease, the study of which might also be of considerable value to the understanding of other inflammatory and autoimmune-type diseases, such as rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis and diabetes mellitus. There is clear evidence that T cells and dendritic cells have a central role in psoriasis. Based on recent data from humans and animal models, we propose that a psoriasis lesion can be triggered and sustained by the local network of skin-resident immune cells. This concept focuses attention on local, rather than systemic, components of the immune system for rationalized therapeutic approaches of psoriasis and possibly also other chronic inflammatory diseases.     

Mouse models of intestinal inflammation as tools to understand the pathogenesis of inflammatory bowel disease

Mouse models of intestinal inflammation resemble aspects of inflammatory bowel disease in humans. These models have provided important insights into mechanisms that control intestinal homeostasis and regulation of intestinal inflammation. This viewpoint discusses themes that have emerged from mouse models of intestinal inflammation including bacterial recognition, autophagy, the IL‐23/Th‐17 axis of inflammation as well as the role of negative regulators. Many of the pathways highlighted by model systems have been identified in recent genome‐wide association studies in human validating the relevance of mouse models to human inflammatory bowel disease. Understanding of the complex biological mechanisms that lead to intestinal inflammation in mouse models may help to define targets for treatment of human diseases.     

A genetic basis for shared autoimmunity in mouse models

Development of autoimmune disease is the result of activation of the immune system that subsequently leads to tissue destruction. Although the clinical outcome significantly differs between autoimmune diseases, some pathogenic pathways could be shared. During the recent years, intense efforts to find the genetic factors behind development of the complex and polygenic autoimmune diseases have been undertaken. The difficulties in addressing what genetic factors predispose for autoimmunity in humans underline the importance of animal models in the understanding of the general mechanisms behind the initiation of disease. Interestingly, it has been observed in studies of experimental models of autoimmune diseases, that many of the genetic linkages to disease development are located in the same genetic regions and potentially could be controlled by the same gene. Furthermore, comparison of the mouse/rat genetic regions with regions of association to human inflammatory diseases, also demonstrates some homologous loci between species. Some mouse strains can develop disease in more than one model for autoimmunity. This not only argues for some general mechanisms, but it also supports mechanisms related to the specific tissues attacked in the various autoimmune diseases. Here, we will discuss some aspects of shared autoimmunity in mouse models from a genetic point of view.     

A genetic basis for shared autoimmunity in mouse models

Development of autoimmune disease is the result of activation of the immune system that subsequently leads to tissue destruction. Although the clinical outcome significantly differs between autoimmune diseases, some pathogenic pathways could be shared. During the recent years, intense efforts to find the genetic factors behind development of the complex and polygenic autoimmune diseases have been undertaken. The difficulties in addressing what genetic factors predispose for autoimmunity in humans underline the importance of animal models in the understanding of the general mechanisms behind the initiation of disease. Interestingly, it has been observed in studies of experimental models of autoimmune diseases, that many of the genetic linkages to disease development are located in the same genetic regions and potentially could be controlled by the same gene. Furthermore, comparison of the mouse/rat genetic regions with regions of association to human inflammatory diseases, also demonstrates some homologous loci between species. Some mouse strains can develop disease in more than one model for autoimmunity. This not only argues for some general mechanisms, but it also supports mechanisms related to the specific tissues attacked in the various autoimmune diseases. Here, we will discuss some aspects of shared autoimmunity in mouse models from a genetic point of view.     

Research progress in the cell origin of basal cell carcinoma

Identification of the cell origin of human neoplasms remains a challenging but important task in cancer research. The outcomes in this area of study may allow us to design novel strategies for early cancer detection and targeted cancer therapeutics. Skin is a great organ to study cancer stem cells because stem cells in skin have been well investigated and approaches of genetic manipulation in specific cell compartments are available to mimic clinical skin cancer in a mouse model. Recently, by using different genetic engineered mouse models, several groups have tried to discover which cell type in skin was responsible for the initiation of basal cell carcinoma, the most common type of skin cancer. These studies raised more questions but also showed more ways for future investigation.     

Increased expression of RANTES, CCR3 and CCR5 in the lesional skin of patients with atopic eczema

BACKGROUND: Atopic eczema (AE) is a relapsing inflammatory disease based on IgE sensitization and characterized by peripheral blood eosinophilia and eosinophil infiltration into the lesional skin. In the patch test reaction of AE by allergens, an increased infiltration of activated eosinophils has been demonstrated peaking at 24-48 h. Regulated on activation normal T cell expressed and secreted (RANTES/CCL5) is a chemokine that induces eosinophil migration, and CCR3 and CCR5 are the receptors of RANTES. OBJECTIVE: In order to further clarify the pathomechanisms of eosinophil infiltration in ongoing chronic inflammation in the skin of patients with AE and its relation to disease severity, we examined the expression of RANTES and its receptors CCR3 and CCR5 in challenged and unchallenged lesional skin of AE. METHODS: We examined the number of RANTES+ cells, CCR3+ cells, CCR5+cells, activated (EG2+) eosinophils and CD3+ T cells in normal skin of healthy volunteers, and in challenged lesional skin (24 h after mite patch test) as well as unchallenged lesional skin of AE patients by immunohistochemistry. The cellular source of RANTES, CCR3 and CCR5 was analyzed by double immunohistochemistry using specific antibodies to RANTES, CCR3 or CCR5, and antibodies to ECP (EG2) or CD3. RESULTS: The numbers of RANTES+ cells, CCR3+ cells, CCR5+ cells, EG2+ cells and CD3+ cells were all significantly increased in challenged (mite patch-tested) lesional skin of AE patients as compared to those in unchallenged lesional skin and normal skin. The numbers of these cells in unchallenged lesional skin were greater than those in normal skin. The number of EG2+ cells in the unchallenged lesional skin correlated with both the peripheral blood eosinophil count and the SCORAD index. The number of EG2+ cells in challenged lesional skin correlated with the number of CCR5+ cells. Activated eosinophils and T cells expressed RANTES and various proportions of these cells were CCR3+ and CCR5+ in both challenged and unchallenged lesional skin. CONCLUSION: Taken together, these results suggest that RANTES as well as its receptors CCR3 and CCR5 may play important roles in the orchestration of eosinophil infiltration in ongoing chronic inflammation in AE, and also reflect the severity of disease.     

Recent advances in mouse models for systemic sclerosis

SSc is a complex rheumatoid disease characterized by autoimmunity, fibrosis and vasculopathy. Mouse models provide powerful research tools for exploring the pathogenesis of the human diseases. Each mouse model can represent a specific way leading to the development of disease. Moreover, mouse models can be used to investigate the role of candidate molecule in the pathogenesis of disease. So far, more than twenty mouse models for SSc have been established and provide new insights in the understanding of the pathogenesis of SSc. In this review, we provide an overview on recent advances in the field of experimental SSc. We introduce novel mouse models generated in the recent years and discuss their relevance to the SSc pathogenesis. Moreover, we summarize and discuss recent findings in the pathogenesis of classical SSc mouse models.     

Relevance of differential immunogenicity of human and mouse recombinant desmoglein-3 for the induction of acantholytic autoantibodies in mice

Pemphigus vulgaris (PV) is an antibody-mediated autoimmune disease of the skin and mucous membranes. Desmoglein-3 (dsg-3) expressed in the suprabasal layer of the skin serves as an autoantigen in PV. Passive transfer of sera, either from patients with PV or from experimental animals immunized with a recombinant human dsg3 (hdsg3) into neonatal BALB/c mice results in blister formation, suggesting strongly that there is significant cross-reactivity between the mouse dsg3 (mdsg3) and the hdsg3. However, efforts to induce disease in adult mice through active immunization using hdsg-3 have not been successful, suggesting that the epitopes required for the induction of pathogenic antibodies in adult mice might not be present in hdsg3. Therefore, in this study, we expressed a full-length mdsg3 in insect cells and compared its serological reactivity with that of the hdsg3 using species specific polyclonal sera and a panel of seven monoclonal antibodies (MoAbs) with unique binding specificities to hdsg3. Studies using sera demonstrated a considerable cross-reactivity, while studies using MoAbs exhibited specific epitope differences between the two proteins. Because of these differences, we reasoned that immunization with mdsg3 might induce disease in adult mice. Immunization of four strains of mice (i.e. BALB/c, DBA/1, HRS/J and SJL/J) with mdsg3 resulted in considerable antibody response, but failed to induce lesions. However, sera from immunized BALB/c mice induced acantholysis of neonatal mouse skin in vitro. These studies indicated that our inability to induce lesions in adult mice through active immunization is not due to differences in the ability of mouse and human dsg3 to induce acantholytic antibodies, but due probably to structural differences between adult and neonatal mouse skin. Alternatively, immunization with a combination of dsg3 protein along with other proteins might be necessary to induce pemphigus disease in adult mice. Nevertheless, our current studies show that molecular mechanisms leading to the production of acantholytic antibodies in mice can now be studied using homologous mdsg3.     

Experimental models of inflammatory bowel disease

The etiology and pathogenesis of inflammatory bowel disease (IBD) remains unsolved, but improved experimental models of enterocolitis have led to progress. Intestinal inflammation and experimental IBD can be induced by chemical or dietary factors or by microbial products. Many animal models of IBD can be used to evaluate new anti-inflammatory drugs. These models, however, usually demonstrate acute, self-limiting colitis. The spontaneous colitis models developed in the cotton-top tamarin monkey and the C3H/HeJBir mouse mimic more features of human IBD. Inflammation is chronic and is under genetic control. The differential genetic susceptibility of inbred rat strains to chronic inflammation have been exploited. Lewis rats injected with bacterial products, peptidoglycan polysaccharide or indomethicin develop chronic relapsing enterocolitis, whereas closely related Buffalo or Fisher rat strains develop only transient inflammation. These models are also useful to test the specific inhibition of inflammatory mediators and target molecules. Over-expression (transgenic) or deletion (knockout) of specific genes have led to the development of rodent models of spontaneous colitis. Inflammation arises from a number of mutations of immunomodulatory molecules, supporting the concept of genetic heterogeneity for IBD. The results obtained from experimental models have generated new hypotheses, expanded human studies, and suggested novel forms of therapy for IBD patients.     

Novel insights into mechanisms of food allergy and allergic airway inflammation using experimental mouse models

Over the last decades, considerable efforts have been undertaken in the development of animal models mimicking the pathogenesis of allergic diseases occurring in humans. The mouse has rapidly emerged as the animal model of choice, due to considerations of handling and costs and, importantly, due to the availability of a large and increasing arsenal of genetically modified mouse strains and molecular tools facilitating the analysis of complex disease models. Here, we review latest developments in allergy research that have arisen from in vivo experimentation in the mouse, with a focus on models of food allergy and allergic asthma, which constitute major health problems with increasing incidence in industrialized countries. We highlight recent novel findings and controversies in the field, most of which were obtained through the use of gene‐deficient or germ‐free mice, and discuss new potential therapeutic approaches that have emerged from animal studies and that aim at attenuating allergic reactions in human patients.     

Transgenic analysis of scleroderma: understanding key pathogenic events in vivo

Modern molecular genetic methods have allowed better understanding of established mouse models of scleroderma and also facilitated the development of new and better defined mouse strains for investigating the pathogenesis of the disease. The best characterized scleroderma animal model is the type 1 tight skin mouse (Tsk1). Backcrossing these animals with other mutant strains has been informative. These experiments implicate the IL-4 ligand-receptor axis in the development of skin fibrosis. Parallel expression analysis of genes using microarrays has provided insight into novel mediators of fibrosis including the C-C chemokine MCP-3. Other experiments suggest that embryonically defined fibroblast-specific regulatory elements may be targets for activation in this model. The same lineage-specific elements have been used to selectively activate TGF beta signaling pathways in fibrosis to generate a novel model for scleroderma and also have been used to develop systems for ligand-dependent fibroblast-specific genetic recombination that will allow further analysis key candidate genes implicated in scleroderma pathogenesis. Better mouse models will improve understanding of this intractable rheumatic disease and can be expected to ultimately lead to improved treatments and outcome.     

Mast Cells and Immunological Skin Diseases

Mast cells play an important role in both adaptive and innate immunity, and a large body of literature demonstrates their functions in skin immunity. This article reviews the literature on the role of this cell type in the pathogenesis of a number of immunological skin diseases, including contact dermatitis, atopic dermatitis, immunobullous disease, scleroderma, and chronic graft-vs.-host disease. In all these diseases, mast cells are noted to increase in number and undergo degranulation in the affected skin, and in some cases, their specific mediators are detected. Elucidation of the contribution of mast cells to the pathogenesis of these diseases has been aided significantly by the use of animal models, especially mouse models. The studies of mast cell-deficient mice in conjunction with normal congenic mice have been particularly fruitful, although in some cases, such as contact dermatitis, a definitive conclusion has not been achieved despite extensive efforts. The role of mast cells in atopic dermatitis has also been suggested by studies of gene polymorphism, which have linked some of the mast cell-related genes to the disease. In the case of scleroderma and chronic graft-vs.-host disease, the function of mast cells in fibrosis is further supported by the ability of these cells and their mediators to induce activation and proliferation of fibroblasts. Therapies targeting mast cells may prove beneficial for treatment of these inflammatory and autoimmune diseases.     

Immune regulation in psoriasis and psoriatic arthritis--recent developments

Psoriasis and psoriatic arthritis (PsA) are common diseases associated with considerable morbidity and disability. Their pathophysiology comprises a dysfunctional stromal-immune cell and cytokine network leading to inflammation of skin, entheses and joints. Recent advances in understanding of disease pathogenesis have led to the introduction of novel therapeutics providing the ultimate proof of concept in defining the role of these targets in the pathogenetic response. The pro-inflammatory cytokines TNF, IL-12/IL-23 and a variety of co-stimulator molecules have all been identified as critical factors in disease progression. In this short review we summarise key recent developments in understanding of the role of cytokines, T cells, B cells in psoriatic disease pathogenesis. We also describe the pathways that are believed to link such inflammatory pathways to articular matrix dysregulation.     

Immunopharmacological role of the Leukotriene Receptor Antagonists and inhibitors of leukotrienes generating enzymes in Multiple Sclerosis

Background and aim: Multiple sclerosis (MS) is a chronic inflammatory disease that involves central nervous system, and is generally associated with demyelination and axonal lesion. The effective factors for initiation of the inflammatory responses have not been known precisely so far. Leukotrienes (LTs) are inflammatory mediators with increased levels in the cerebrospinal fluid of MS patients and in experimental models of multiple sclerosis. Inhibition of LT receptors with specific antagonists can decrease inflammatory responses. In this review article we try to clarify the role of LT receptor antagonists and also inhibitors of enzymes which are involved in LTs generating pathway for treating multiple sclerosis as new targets for MS therapy. Moreover, we suggest that blockage of LT receptors by potent specific antagonists and/or agonists can be as a novel useful method in treatment of MS.     

Development of a bioengineered skin-humanized mouse model for psoriasis: dissecting epidermal-lymphocyte interacting pathways

Over the past few years, whole skin xenotransplantation models that mimic different aspects of psoriasis have become available. However, these models are strongly constrained by the lack of skin donor availability and homogeneity. We present in this study a bioengineering-based skin-humanized mouse model for psoriasis, either in an autologous version using samples derived from psoriatic patients or, more importantly, in an allogeneic context, starting from skin biopsies and blood samples from unrelated healthy donors. After engraftment, the regenerated human skin presents the typical architecture of normal human skin but, in both cases, immunological reconstitution through intradermal injection in the regenerated skin using in vitro-differentiated T1 subpopulations as well as recombinant IL-17 and IL-22 Th17 cytokines, together with removal of the stratum corneum barrier by a mild abrasive treatment, leads to the rapid conversion of the skin into a bona fide psoriatic phenotype. Major hallmarks of psoriasis were confirmed by the evaluation of specific epidermal differentiation and proliferation markers as well as the mesenchymal milieu, including angiogenesis and infiltrate. Our bioengineered skin-based system represents a robust platform to reliably assess the molecular and cellular mechanisms underlying the complex interdependence between epidermal cells and the immune system. The system may also prove suitable to assess preclinical studies that test the efficacy of novel therapeutic treatments and to predict individual patient response to therapy.