A cyclosporine-sensitive psoriasis-like disease produced in Tie2 transgenic mice

Abnormal dermal microvascular endothelial cells in psoriatic excessive angiogenesis

Psoriasis is characterized by excessive angiogenesis, with increased distortion and dilation of the dermal blood vessels. These vascular alterations are ascribed, at least in part, to the changes in dermal microvascular endothelial cell functions. However, despite the recognition of vascular normalization as an emerging strategy for the treatment of psoriasis, in-depth studies of human dermal microvascular endothelial cells (HDMECs) have been missing. The difficulty of isolation and culture of HDMECs has impeded the study of endothelial dysfunction in psoriasis. Researchers have done a great deal of work to study the abnormal characteristics of keratinocytes, fibroblasts, and leukocytes in psoriatic skin tissue. Recently, with successful isolation of HDMECs from psoriasis, great progress has been made in the elucidation of the pathogenic role of these cells in psoriasis. It is of great therapeutic significance to study the molecular mechanism of HDMECs in psoriasis. We review here the abnormalities of HDMECs in psoriasis.

Proteomic and Metabolomic Changes in Psoriasis Preclinical and Clinical Aspects

Skin diseases such as psoriasis (Ps) and psoriatic arthritis (PsA) are immune-mediated inflammatory diseases. Overlap of autoinflammatory and autoimmune conditions hinders diagnoses and identifying personalized patient treatments due to different psoriasis subtypes and the lack of verified biomarkers. Recently, proteomics and metabolomics have been intensively investigated in a broad range of skin diseases with the main purpose of identifying proteins and small molecules involved in the pathogenesis and development of the disease. This review discusses proteomics and metabolomics strategies and their utility in research and clinical practice in psoriasis and psoriasis arthritis. We summarize the studies, from in vivo models conducted on animals through academic research to clinical trials, and highlight their contribution to the discovery of biomarkers and targets for biological drugs.

Polymorphisms in TIE2 and ANGPT-1 genes are associated with protection against diabetic retinopathy in a Brazilian population

Objective

The objective of this study was to investigate the association between SNPs in the TIE2 and ANGPT-1 genes and diabetic retinopathy (DR).

Subjects and methods

This study comprised 603 patients with type 2 diabetes mellitus (T2DM) and DR (cases) and 388 patients with T2DM for more than 10 years and without DR (controls). The TIE2 rs639225 (A/G) and rs638203 (A/G) SNPs and the ANGPT-1 rs4324901 (G/T) and rs2507800 (T/A) SNPs were genotyped by real-time PCR using TaqMan MGB probes.

Results

The G/G genotype of the rs639225/TIE2, the G/G genotype of the rs638203/ TIE2 and the T allele of the rs4324901/ANGPT-1 SNPs were associated with protection against DR after adjustment for age, glycated hemoglobin, gender, and presence of hypertension (P = 0.042, P = 0.003, and P = 0.028, respectively). No association was found between the rs2507800/ANGPT-1 SNP and DR.

Conclusion

We demonstrated, for the first time, the association of TIE2 rs638203 and rsrs939225 SNPs and ANGPT-1 rs4324901 SNP with protection against DR in a Brazilian population.

The Experimental Animal Models in Psoriasis Research: A Comprehensive Review

Psoriasis is an autoimmune, chronic, inflammatory skin condition mediated by T cells. It differs from other inflammatory conditions by causing significant alterations in epidermal cell proliferation and differentiation that are both complicated and prominent. The lack of an appropriate animal model has significantly hindered studies into the pathogenic mechanisms of psoriasis since animals other than humans typically do not exhibit the complex phenotypic features of human psoriasis. A variety of methods, including spontaneous mutations, drug-induced mutations, genetically engineered animals, xenotransplantation models, and immunological reconstitution approaches, have all been employed to study specific characteristics in the pathogenesis of psoriasis. Although some of these approaches have been used for more than 50 years and far more models have been introduced recently, they have surprisingly not yet undergone detailed validation. Despite their limitations, these models have shown a connection between keratinocyte hyperplasia, vascular hyperplasia, and a cell-mediated immune response in the skin. The xenotransplantation of diseased or unaffected human skin onto immune-compromised recipients has also significantly aided psoriasis research. This technique has been used in a variety of ways to investigate the function of T lymphocytes and other cells, including preclinical therapeutic studies. The design of pertinent in vivo and in vitro psoriasis models is currently of utmost concern and a crucial step toward its cure. This article outlines the general approach in the development of psoriasis-related animal models, aspects of some specific models, along with their strengths and limitations.

Adaptor Protein ShcD/SHC4 Interacts with Tie2 Receptor to Synergistically Promote Glioma Cell Invasion

Gliomas are characterized by diffuse infiltration of tumor cells into surrounding brain tissue, and this highly invasive nature contributes to disease recurrence and poor patient outcomes. The molecular mechanisms underlying glioma cell invasion remain incompletely understood, limiting development of new targeted therapies. Here, we have identified phosphotyrosine adaptor protein ShcD as upregulated in malignant glioma and shown that it associates with receptor tyrosine kinase Tie2 to facilitate invasion. In human glioma cells, we find that expression of ShcD and Tie2 increases invasion, and this significant synergistic effect is disrupted with a ShcD mutant that cannot bind Tie2 or hyperphosphorylate the receptor. Expression of ShcD and/or Tie2 further increases invadopodia formation and matrix degradation in U87 glioma cells. In a coculture model, we show that U87-derived tumor spheroids expressing both ShcD and Tie2 display enhanced infiltration into cerebral organoids. Mechanistically, we identify changes in focal adhesion kinase phosphorylation in the presence of ShcD and/or Tie2 in U87 cells upon Tie2 activation. Finally, we identify a strong correlation between transcript levels of ShcD and Tie2 signaling components as well as N-cadherin in advanced gliomas and those with classical or mesenchymal subtypes, and we show that elevated expression of ShcD correlates with a significant reduction in patient survival in higher grade gliomas with mesenchymal signature. Altogether, our data highlight a novel Tie2-ShcD signaling axis in glioma cell invasion, which may be of clinical significance. IMPLICATIONS: ShcD cooperates with Tie2 to promote glioma cell invasion and its elevated expression correlates with poor patient outcome in advanced gliomas.

Tek (Tie2) is not required for cardiovascular development in zebrafish

Angiopoietin/TIE signalling plays a major role in blood and lymphatic vessel development. In mouse, Tek (previously known as Tie2) mutants die prenatally due to a severely underdeveloped cardiovascular system. In contrast, in zebrafish, previous studies have reported that although embryos injected with tek morpholinos (MOs) exhibit severe vascular defects, tek mutants display no obvious vascular malformations. To further investigate the function of zebrafish Tek, we generated a panel of loss-of-function tek mutants, including RNA-less alleles, an allele lacking the MO-binding site, an in-frame deletion allele and a premature termination codon-containing allele. Our data show that all these mutants survive to adulthood with no obvious cardiovascular defects. MO injections into tek mutants lacking the MO-binding site or the entire tek locus cause similar vascular defects to those observed in MO-injected +/+ siblings, indicating off-target effects of the MOs. Surprisingly, comprehensive phylogenetic profiling and synteny analyses reveal that Tek was lost in the largest teleost clade, suggesting a lineage-specific shift in the function of TEK during vertebrate evolution. Altogether, these data show that Tek is dispensable for zebrafish development, and probably dispensable in most teleost species.

Placenta accreta spectrum: biomarker discovery using plasma proteomics

BACKGROUND

Many cases of placenta accreta spectrum are not diagnosed antenatally, despite identified risk factors and improved imaging methods. Identification of plasma protein biomarkers could further improve the antenatal diagnosis of placenta accreta spectrum .

OBJECTIVE

The purpose of this study was to determine if women with placenta accreta spectrum have a distinct plasma protein profile compared with control subjects.

STUDY DESIGN

We obtained plasma samples before delivery from 16 participants with placenta accreta spectrum and 10 control subjects with similar gestational ages (35.1 vs 35.5 weeks gestation, respectively). We analyzed plasma samples with an aptamer-based proteomics platform for alterations in 1305 unique proteins. Heat maps of the most differentially expressed proteins (T test, P<.01) were generated with matrix visualization and analysis software. Principal component analysis was performed with the use of all 1305 proteins and the top 21 dysregulated proteins. We then confirmed dysregulated proteins using enzyme-linked immunosorbent assay and report significant differences between placenta accreta spectrum and control cases (Wilcoxon-rank sum test, P<.05).

RESULTS

Many of the top 50 proteins that significantly dysregulated in participants with placenta accreta spectrum were inflammatory cytokines, factors that regulate vascular remodeling, and extracellular matrix proteins that regulate invasion. Placenta accreta spectrum, with the use of the top 21 proteins, distinctly separated the placenta accreta spectrum cases from control cases (P<.01). Using enzyme-linked immunosorbent assay, we confirmed 4 proteins that were dysregulated in placenta accreta spectrum compared with control cases: median antithrombin III concentrations (240.4 vs 150.3 mg/mL; P=.002), median plasminogen activator inhibitor 1 concentrations (4.1 vs 7.1 ng/mL; P<.001), soluble Tie2 (13.5 vs 10.4 ng/mL; P=.02), soluble vascular endothelial growth factor receptor 2 (9.0 vs 5.9 ng/mL; P=.003).

CONCLUSION

Participants with placenta accreta spectrum had a unique and distinct plasma protein signature.

Animal models of psoriasis-highlights and drawbacks

Research into the pathophysiology of psoriasis remains challenging, because this disease does not occur naturally in laboratory animals. However, specific aspects of its complex immune-pathology can be illuminated through transgenic, knockout, xenotransplantation, immunological reconstitution, drug-induced, or spontaneous mutation models in rodents. Although some of these approaches have already been pursued for more than 5 decades and even more models have been described in recent times, they have surprisingly not yet been systematically validated. As a consequence, researchers regularly examine specific aspects that only partially reflect the complex overall picture of the human disease. Nonetheless, animal models are of great utility to investigate inflammatory mediators, the communication between cells of the innate and the adaptive immune systems, the role of resident cells as well as new therapies. Of note, various manipulations in experimental animals resulted in rather similar phenotypes. These were called "psoriasiform", "psoriasis-like" or even "psoriasis" usually on the basis of some similarities with the human disorder. Xenotransplantation of human skin onto immunocompromised animals can overcome this limitation only in part. In this review, we elucidate approaches for the generation of animal models of psoriasis and assess their strengths and limitations with a certain focus on more recently developed models.

Nephroprotective Potential of Mesenchymal Stromal Cells and Their Extracellular Vesicles in a Murine Model of Chronic Cyclosporine Nephrotoxicity

Background

Cell therapies and derived products have a high potential in aiding tissue and organ repairing and have therefore been considered as potential therapies for treating renal diseases. However, few studies have evaluated the impact of these therapies according to the stage of chronic kidney disease. The aim of this study was to evaluate the renoprotective effect of murine bone marrow mesenchymal stromal cells (BM-MSCs), their extracellular vesicles (EVs) and EVs-depleted conditioned medium (dCM) in an aggressive mouse model of chronic cyclosporine (CsA) nephrotoxicity in a preventive and curative manner.

Methods

After 4 weeks of CsA-treatment (75 mg/kg daily) mice developed severe nephrotoxicity associated with a poor survival rate of 25%, and characterized by tubular vacuolization, casts, and cysts in renal histology. BM-MSC, EVs and dCM groups were administered as prophylaxis or as treatment of CsA nephrotoxicity. The effect of the cell therapies was analyzed by assessing renal function, histological damage, apoptotic cell death, and gene expression of fibrotic mediators.

Results

Combined administration of CsA and BM-MSCs ameliorated the mice survival rates (6-15%), but significantly renal function, and histological parameters, translating into a reduction of apoptosis and fibrotic markers. On the other hand, EVs and dCM administration were only associated with a partial recovery of renal function or histological damage. Better results were obtained when used as treatment rather than as prophylactic regimen i.e., cell therapy was more effective once the damage was established.

Conclusion

In this study, we showed that BM-MSCs induce an improvement in renal outcomes in an animal model of CsA nephrotoxicity, particularly if the inflammatory microenvironment is already established. EVs and dCM treatment induce a partial recovery, indicating that further experiments are required to adjust timing and dose for better long-term outcomes.

Promotion of macrophage activation by Tie2 in the context of the inflamed synovia of rheumatoid arthritis and psoriatic arthritis patients

OBJECTIVE

To examine the role of Tie2 signalling in macrophage activation within the context of the inflammatory synovial microenvironment present in patients with RA and PsA.

METHODS

Clinical responses and macrophage function were examined in wild-type and Tie2-overexpressing (Tie2-TG) mice in the K/BxN serum transfer model of arthritis. Macrophages derived from peripheral blood monocytes from healthy donors, RA and PsA patients, and RA and PsA synovial tissue explants were stimulated with TNF (10 ng/ml), angiopoietin (Ang)-1 or Ang-2 (200 ng/ml), or incubated with an anti-Ang2 neutralizing antibody. mRNA and protein expression of inflammatory mediators was analysed by quantitative PCR, ELISA and Luminex.

RESULTS

Tie2-TG mice displayed more clinically severe arthritis than wild-type mice, accompanied by enhanced joint expression of IL6, IL12B, NOS2, CCL2 and CXCL10, and activation of bone marrow-derived macrophages in response to Ang-2 stimulation. Ang-1 and Ang-2 significantly enhanced TNF-induced expression of pro-inflammatory cytokines and chemokines in macrophages from healthy donors differentiated with RA and PsA SF and peripheral blood-derived macrophages from RA and PsA patients. Both Ang-1 and Ang-2 induced the production of IL-6, IL-12p40, IL-8 and CCL-3 in synovial tissue explants of RA and PsA patients, and Ang-2 neutralization suppressed the production of IL-6 and IL-8 in the synovial tissue of RA patients.

CONCLUSION

Tie2 signalling enhances TNF-dependent activation of macrophages within the context of ongoing synovial inflammation in RA and PsA, and neutralization of Tie2 ligands might be a promising therapeutic target in the treatment of these diseases.

Characterization of a Porcine Model for Von Willebrand Disease Type 1 and 3 Regarding Expression of Angiogenic Mediators in the Nonpregnant Female Reproductive Tract

Von Willebrand disease (VWD), a blood coagulation disorder, is also known to cause angiodysplasia. Hitherto, no animal model has been found with angiodysplasia that can be studied in vivo. In addition, VWD patients tend to have a higher incidence of miscarriages for reasons unknown. Thus, we aimed to examine the influence of von Willebrand factor (VWF) on the female reproductive tract histology and the expression and distribution of angiogenic factors in a porcine model for VWD types 1 and 3. The disease-causing tandem duplication within the VWF gene occurred naturally in these pigs, making them a rare and valuable model. Reproductive organs of 6 animals (2 of each mutant genotype and 2 wildtype (WT) animals) were harvested. Genotype plus phenotype were confirmed. Several angiogenic factors were chosen for possible connections to VWF and analyzed alongside VWF by immunohistochemistry and quantitative gene expression studies. VWD type 3 animals showed angiodysplasia in the uterus and shifting of integrin α_Vβ₃ from the apical membrane of uterine epithelium to the cytoplasm accompanied by increased vascular endothelial growth factor (VEGF) expression. Varying staining patterns for angiopoietin (Ang)-2 were observed among the genotypes. As compared with WT, the ovaries of the VWD type 3 animals showed decreased gene expression of ANG2 and increased gene expression of TIE (tyrosine kinase with immunoglobulin and epidermal growth factor homology domains) 2, with some differences in the ANG/TIE-system among the mutant genotypes. In conclusion, severely reduced VWF seems to evoke angiodysplasia in the porcine uterus. Varying distribution and expression of angiogenic factors suggest that this large animal model is promising for investigation of influence of VWF on angiogenesis in larger groups.

Hypoxia-inducible factor-1α: a promising therapeutic target for autoimmune diseases

INTRODUCTION

Hypoxia-inducible factor-1α (HIF-1α) plays a crucial role in both innate and adaptive immunity. Emerging evidence indicates that HIF-1α is associated with the inflammation and pathologic activities of autoimmune diseases. Areas covered: Considering that the types of autoimmune diseases are complicated and various, this review aims to cover the typical kinds of autoimmune diseases, discuss the molecular mechanisms, biological functions and expression of HIF-1α in these diseases, and further explore its therapeutic potential. Expert opinion: Inflammation and hypoxia are interdependent. HIF-1α as a key regulator of hypoxia, exerts a crucial role in the balance between Th17 and Treg, and involves in the inflammation and pathologic activities of autoimmune diseases. Although there are many challenges remaining to be overcome, targeting HIF-1α could be a promising strategy for autoimmune diseases therapies.

Vasculotide, an Angiopoietin-1 mimetic, ameliorates several features of experimental atopic dermatitis-like disease

Background

Earlier studies by our group have demonstrated that a transgenic animal engineered to express Tie2 under the control of the Tie2 promoter produced animals with a scaly skin phenotype that recapitulated many of the hallmarks of atopic dermatitis (AT-Derm). To test the hypothesis that this model of AT-Derm is driven by dysregulated Tie2-signalling, we have bred AT-Derm transgenic (TG) animals with TG-animals engineered to overexpress Angiopoietin-1 or -2, the cognate Tie2 ligands. These two ligands act to antagonize one another in a context-dependent manner. To further evaluate the role of Ang1-driven-Tie2 signalling, we examined the ability of Vasculotide, an Ang1-mimetic, to modulate the AT-Derm phenotype.

Results

AT-Derm+Ang2 animals exhibited an accentuated phenotype, whereas AT-Derm+Ang1 presented with a markedly reduced skin disease, similarly VT-treated AT-Derm animals present with a clear decrease in the skin phenotype. Moreover, a decrease in several important inflammatory cytokines and a decrease in the number of eosinophils was noted in VT-treated animals. Bone marrow differentiation in the presence of VT produced fewer CFU-G colonies, further supporting a role for Tie2-signalling in eosinophil development. Importantly, we demonstrate activation of Tie2, the VT-target, in lung tissue from naïve animals treated with increasing amounts of VT.

Conclusions

The AT-Derm phenotype in these animals is driven through dysregulation of Tie2 receptor signalling and is augmented by supplemental Ang2-dependent stimulation. Overexpression of Ang1 or treatment with VT produced a similar amelioration of the phenotype supporting the contention that VT and Ang1 have a similar mechanism of action on the Tie2 receptor and can both counteract the signalling driven by Ang2. Our results also support a possible role for Tie2-signalling in the development of eosinophilic diseases and that activation of Tie2 may directly or indirectly modulate the differentiation of eosinophils, which express Tie2. In summary, these data support the hypothesis that this AT-Derm mouse model is driven by dysregulation of the Tie2 signalling pathway and increased Ang2 levels can aggravate it, whereas it can be reversed by either Ang1-overexpression or VT treatment. Moreover, our data supports the contention that VT acts as an Angiopoietin-1 mimetic and may provide a novel entry point for Tie2-agonist-based therapies for atopic diseases.

An Overview of the Pathogenesis of Immune-mediated Skin Injury

The skin has a relatively limited range of responses to injury regardless of the specific mechanism underlying the insult. When the skin's barrier function is disrupted, it mounts an inflammatory and proliferative response in an effort to restore this essential function. The epidermal keratinocyte is central to the initiation of the skin's response, triggering an immunologic cascade that leads to the stereotypic morphologic responses that we encounter as pathologists. Drug-induced immune-mediated cutaneous injuries or "drug eruptions" are relatively common, sometimes with overlapping mechanisms, and it is often possible to classify these based on the classical hypersensitivity-type reactions. A specific type of immune-mediated skin injury is psoriasis. The pathogenesis of psoriasis is multifactorial but involves the interaction of environmental factors with a genetic predisposition. The initial stimulus triggering the development of psoriatic lesions involves activation of epidermal keratinocytes, with subsequent amplification driven by cross talk between the adaptive and innate immune systems. Several cytokines produced by Th17 T helper cells have recently been shown to be important in the pathogenesis of psoriasis, namely, interleukin-23 (IL-23) and IL-17, due to demonstrated clinical efficacy of cytokine blockade; and IL-22, based on its effects in both in vitro and in vivo models.

Cross Talk between Proliferative, Angiogenic, and Cellular Mechanisms Orchestred by HIF-1α in Psoriasis

Psoriasis is a chronic inflammatory skin disease where the altered regulation in angiogenesis, inflammation, and proliferation of keratinocytes are the possible causes of the disease, and the transcription factor “hypoxia-inducible factor 1-alpha” (HIF-1α) is involved in the homeostasis of these three biological phenomena. In this review, the role of HIF-1α in the cross talk between the cytokines and cells of the immunological system involved in the pathogenesis of psoriasis is discussed.

Angiogenesis and lymphangiogenesis in inflammatory skin disorders

Angiogenesis, the growth of new blood vessels from pre-existing vessels, occurs physiologically in wound healing, during inflammatory diseases, and in tumor growth. Lymphangiogenesis can be activated in inflammation and tumor metastasis. The family of vascular endothelial growth factors (VEGFs) and angiopoietins are essential for angiogenesis and lymphangiogenesis. The angiogenic process is tightly regulated by VEGFs, angiopoietins, and endogenous inhibitors. VEGFs and angiopoietins exert their effects by activating specific receptors present on blood and lymphatic endothelial cells. There is now compelling evidence that cells of innate and adaptive immunity (macrophages, mast cells, neutrophils, eosinophils, lymphocytes) are a major source of angiogenic and lymphangiogenic factors. Chronic inflammatory skin diseases such as psoriasis and atopic dermatitis are characterized by altered angiogenesis, lymphangiogenesis, or both. Also such acute inflammatory skin disorders as urticaria, ultraviolet B-induced damage, and angioedema are associated with changes in angiogenic factors. In systemic sclerosis there is a switch from proangiogenic to antiangiogenic factors that play a role in the defective vascular process of this disorder. As yet, there are no clinical trials showing that canonical VEGF/VEGF receptor-targeted strategies can modulate inflammatory skin diseases. Novel strategies targeting other angiogenic/lymphangiogenic pathways should also be investigated.

The angiopoietin:Tie 2 interaction: a potential target for future therapies in human vascular disease

Angiopoietin-1 and -2 are endogenous ligands for the vascular endothelial receptor tyrosine kinase Tie2. Signalling by angiopoietin-1 promotes vascular endothelial cell survival and the sprouting and reorganisation of blood vessels, as well as inhibiting activation of the vascular endothelial barrier to reduce leakage and leucocyte migration into tissues. Angiopoietin-2 generally has an opposing action, and is released naturally at times of vascular growth and inflammation. There is a significant body of emerging evidence that promoting the actions of angiopoietin-1 through Tie2 is of benefit in pathologies of vascular activation, such as sepsis, stroke, diabetic retinopathy and asthma. Similarly, methods to inhibit the actions of angiopoietin-2 are emerging and have been demonstrated to be of preclinical and clinical benefit in reducing tumour angiogenesis. Here the author reviews the evidence for potential benefits of modulation of the interaction of angiopoietins with Tie2, and the potential applications. Additionally, methods for delivery of the complex protein angiopoietin-1 are discussed, as well as potentially deleterious consequences of administering angiopoietin-1.

Angiogenic and inflammatory properties of psoriatic arthritis

Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy associated with psoriasis and included in seronegative spondyloarthropathy. PsA has several unique characteristics different from rheumatoid arthritis (RA), such as enthesopathy, dactylitis, and abnormal bone remodeling. As compared with synovitis of RA (pannus), proliferation of PsA synovium is mild and characterized by hypervascularity and increased infiltration of polymorphonuclear leukocytes in the synovial tissues. Angiogenesis plays a crucial role in cutaneous psoriasis, and several angiogenic factors such as vascular endothelial growth factor, interleukin-8, angiopoietin, tumor necrosis factor- α and transforming growth factor-β, are suggested to play an important role also in the pathophysiology of PsA. Further, IL-17 has various functions such as upregulation of proinflammatory cytokines, attraction of neutrophils, stimulation of keratinocytes, endothelial cell migration, and osteoclast formation via RANKL from activated synovial fibroblasts. Thus, IL-17 may be important in angiogenesis, fibrogenesis, and osteoclastogenesis in PsA. In this paper, roles of angiogenesis in the psoriatic synovium are discussed, which may strengthen the understanding of the pathogenesis of PsA.

IL-1F5, -F6, -F8, and -F9: a novel IL-1 family signaling system that is active in psoriasis and promotes keratinocyte antimicrobial peptide expression

IL-1F6, IL-1F8, and IL-1F9 and the IL-1R6(RP2) receptor antagonist IL-1F5 constitute a novel IL-1 signaling system that is poorly characterized in skin. To further characterize these cytokines in healthy and inflamed skin, we studied their expression in healthy control, uninvolved psoriasis, and psoriasis plaque skin using quantitative RT-PCR and immunohistochemistry. Expression of IL-1F5, -1F6, -1F8, and -1F9 were increased 2 to 3 orders of magnitude in psoriasis plaque versus uninvolved psoriasis skin, which was supported immunohistologically. Moreover, treatment of psoriasis with etanercept led to significantly decreased IL-1F5, -1F6, -1F8, and -1F9 mRNAs, concomitant with clinical improvement. Similarly increased expression of IL-1F5, -1F6, -1F8, and -1F9 was seen in the involved skin of two mouse models of psoriasis. Suggestive of their importance in inflamed epithelia, IL-1α and TNF-α induced IL-1F5, -1F6, -1F8, and -1F9 transcript expression by normal human keratinocytes. Microarray analysis revealed that these cytokines induce the expression of antimicrobial peptides and matrix metalloproteinases by reconstituted human epidermis. In particular, IL-1F8 increased mRNA expression of human β-defensin (HBD)-2, HBD-3, and CAMP and protein secretion of HBD-2 and HBD-3. Collectively, our data suggest important roles for these novel cytokines in inflammatory skin diseases and identify these peptides as potential targets for antipsoriatic therapies.

Activated protein C enhances human keratinocyte barrier integrity via sequential activation of epidermal growth factor receptor and Tie2

Keratinocytes play a critical role in maintaining epidermal barrier function. Activated protein C (APC), a natural anticoagulant with anti-inflammatory and endothelial barrier protective properties, significantly increased the barrier impedance of keratinocyte monolayers, measured by electric cell substrate impedance sensing and FITC-dextran flux. In response to APC, Tie2, a tyrosine kinase receptor, was rapidly activated within 30 min, and relocated to cell-cell contacts. APC also increased junction proteins zona occludens, claudin-1 and VE-cadherin. Inhibition of Tie2 by its peptide inhibitor or small interfering RNA abolished the barrier protective effect of APC. Interestingly, APC did not activate Tie2 through its major ligand, angiopoietin-1, but instead acted by binding to endothelial protein C receptor, cleaving protease-activated receptor-1 and transactivating EGF receptor. Furthermore, when activation of Akt, but not ERK, was inhibited, the barrier protective effect of APC on keratinocytes was abolished. Thus, APC activates Tie2, via a mechanism requiring, in sequential order, the receptors, endothelial protein C receptor, protease-activated receptor-1, and EGF receptor, which selectively enhances the PI3K/Akt signaling to enhance junctional complexes and reduce keratinocyte permeability.

Halting angiogenesis by non-viral somatic gene therapy alleviates psoriasis and murine psoriasiform skin lesions

Dysregulated angiogenesis is a hallmark of chronic inflammatory diseases, including psoriasis, a common skin disorder that affects approximately 2% of the population. Studying both human psoriasis in 2 complementary xenotransplantation models and psoriasis-like skin lesions in transgenic mice with epidermal expression of human TGF-β1, we have demonstrated that antiangiogenic non-viral somatic gene therapy reduces the cutaneous microvasculature and alleviates chronic inflammatory skin disorders. Transient muscular expression of the recombinant disintegrin domain (RDD) of metargidin (also known as ADAM-15) by in vivo electroporation reduced cutaneous angiogenesis and vascularization in all 3 models. As demonstrated using red fluorescent protein-coupled RDD, the treatment resulted in muscular expression of the gene product and its deposition within the cutaneous hyperangiogenic connective tissue. High-resolution ultrasound revealed reduced cutaneous blood flow in vivo after electroporation with RDD but not with control plasmids. In addition, angiogenesis- and inflammation-related molecular markers, keratinocyte proliferation, epidermal thickness, and clinical disease scores were downregulated in all models. Thus, non-viral antiangiogenic gene therapy can alleviate psoriasis and may do so in other angiogenesis-related inflammatory skin disorders.

Psoriasis: what we have learned from mouse models

Psoriasis is a common inflammatory skin disease of unknown etiology, for which there is no cure. This heterogeneous, cutaneous, inflammatory disorder is clinically characterized by prominent epidermal hyperplasia and a distinct inflammatory infiltrate. Crosstalk between immunocytes and keratinocytes, which results in the production of cytokines, chemokines and growth factors, is thought to mediate the disease. Given that psoriasis is only observed in humans, numerous genetic approaches to model the disease in mice have been undertaken. In this Review, we describe and critically assess the mouse models and transplantation experiments that have contributed to the discovery of novel disease-relevant pathways in psoriasis. Research performed using improved mouse models, combined with studies employing human cells, xenografts and patient material, will be key to our understanding of why such distinctive patterns of inflammation develop in patients with psoriasis. Indeed, a combination of genetic and immunological investigations will be necessary to develop both improved drugs for the treatment of psoriasis and novel curative strategies.

Vascular endothelial growth factor (VEGF) in the pathogenesis of psoriasis--a possible target for novel therapies?

Angiogenesis is defined as the formation of new capillaries from pre-existing blood vessels. The process of angiogenesis is tightly regulated by a balance between pro- and anti-angiogenic factors. Vascular endothelial growth factor (VEGF) is a pro-angiogenic factor and several anti-VEGF therapies are used in the treatment of diseases that are characterized by abnormal formation of blood vessels such as certain cancers and age-related macular degeneration. In addition, dysregulated angiogenesis has been observed in inflammatory diseases and might underly chronic cutaneous inflammation in psoriasis. Several experimental studies and clinical reports suggest that VEGF is involved in psoriasis pathogenesis. Among those, transgenic over-expression of VEGF in keratinocytes in mice resulted in skin inflammation and a phenotype resembling human psoriasis. In different psoriasis models, anti-VEGF antibody treatment of mice, already displaying disease symptoms, resulted in an overall improvement of the cutaneous lesions. On the molecular level human keratinocytes produce VEGF after stimulation with cytokines involved in psoriasis pathogenesis. Finally, patients with psoriasis receiving anti-VEGF treatment for cancer showed complete remission of their cutaneous symptoms. Therefore, VEGF might be an underappreciated pro-inflammatory factor in the pathogenesis of psoriasis. In this review, current knowledge on the significance of VEGF in psoriasis pathogenesis is summarized. Furthermore, current reports on treatments directed against VEGF or its receptors and their potential as future therapy for psoriasis are discussed.

Evidence for altered Wnt signaling in psoriatic skin

The Wnt gene family encodes a set of highly conserved secreted signaling proteins that have major roles in embryogenesis and tissue homeostasis. Yet the expression of this family of important mediators in psoriasis, a disease characterized by marked changes in keratinocyte growth and differentiation, is incompletely understood. We subjected 58 paired biopsies from lesional and uninvolved psoriatic skin and 64 biopsies from normal skin to global gene expression profiling. WNT5A transcripts were upregulated fivefold in lesional skin, accompanied by increased Wnt-5a protein levels. Notably, WNT5A mRNA was markedly induced by IL-1alpha, tumor necrosis factor-alpha, IFN-gamma, and transforming growth factor-alpha in cultured keratinocytes. Frizzled 2 (FZD2) and FZD5, which encode receptors for Wnt5A, were also increased in lesional psoriatic skin. In contrast, expression of WIF1 mRNA, encoding a secreted antagonist of the Wnt proteins, was downregulated >10-fold in lesional skin, along with decreased WNT inhibitory factor (WIF)-1 immunostaining. Interestingly, pathway analysis along with reduced AXIN2 expression and lack of nuclear translocation of beta-catenin indicated a suppression of canonical Wnt signaling in lesional skin. The results of our study suggest a shift away from canonical Wnt signaling toward noncanonical pathways driven by interactions between Wnt-5a and its cognate receptors in psoriasis, accompanied by impaired homeostatic inhibition of Wnt signaling by WIF-1 and dickkopf.

Angiopoietin-1 reduces H(2)O(2)-induced increases in reactive oxygen species and oxidative damage to skin cells

UV light-based damage to skin cells can cause photoaging and skin cancer. A major cause of UV light-induced damage to skin is increased free radicals, such as superoxides. Increased superoxides can cause oxidative and nitrative damage to cell components. Thus, agents that counteract these damages may have therapeutic value. Herein, we show that angiopoietin-1 (ang1) prevented and blocked H(2)O(2)-induced increases in superoxides in human spontaneously immortalized keratinocyte line, HaCaT, and primary melanocytes (HeMn). Ang1 prevented H(2)O(2)-induced increases in damage to DNA (8-hydroxy-2'-deoxyguanosine) and proteins (nitrotyrosinylation). Ang1 promoted skin cell metabolism/viability, adhesion, and akt and MAPK(p42/44) activations. Using multi-gene transcriptional profiling, we found that skin cells express integrin subunits {(beta(1), beta(4-6), beta(8), alpha(v), alpha(2), alpha(3), alpha(6) (HaCaT)), (beta(1), beta(3), beta(5), beta(8), alpha(v), alpha(3) (HeMn))} and lack tie2 receptor mRNA. Integrin antibodies (alpha(v), beta(1)) disrupted skin cell adhesion to ang1 and ang1-induced decreases in superoxides. Our findings show that ang1 blocks free radical damage to skin cells and may be clinically useful to prevent and/or reduce photoaging and skin cancer.

Acceleration of diabetic wound healing by an angiopoietin peptide mimetic

Angiopathies are one of the leading underlying causes of morbidity in diabetic patients. Poorly managed blood glucose levels contribute to vascular defects that manifest themselves in numerous different clinical conditions, including diabetic retinopathy, nephropathy, peripheral artery disease, and compromised wound healing. The angiopoietin family (Angs 1-4) has been shown to play a critical role in the growth and maintenance of vasculature. Here we evaluate the efficacy of a new Ang-based peptidomimetic compound, Vasculotide, on diabetic-related wound healing. Stimulation of endothelial cells (ECs) with Vasculotide results in activation of the Ang receptor, Tie 2, and its associated signaling pathways. This activation promoted biological responses such as EC survival, migration, and matrix metalloproteinase 2 (MMP2) production. We show that Vasculotide alone and in combination with vascular endothelial growth factor (VEGF) results in the production of well-arborized vessels supported by myogenic cells. Using an excisional skin-wound model produced on the back of diabetic B6.Cg-m(+/+)Lepr(db)/J (db/db) mice, we found that Vasculotide-treated wounds presented with decreased wound closure times (p < 0.05) and dramatic increases in granulation tissue (p < 0.01). Although the potential of this novel proangiogenic compound in treating microvascular dysfunction is not strictly limited to topical administration, we provide mechanistic evidence as a proof of principle in support of its efficacious use in diabetic wound healing.

Angiogenesis drives psoriasis pathogenesis

Psoriasis pathogenesis is closely associated with disease-inducing Th1 and Th17 cells. Yet, several studies suggest that aberrant keratinocyte or endothelial cell signalling significantly contributes to disease manifestation. Histological hallmarks of psoriatic skin include the infiltration of multiple immune cells, keratinocyte proliferation and increased dermal vascularity. Formation of new blood vessels starts with early psoriatic changes and disappears with disease clearance. Several angiogenic mediators like vascular endothelial growth factor, hypoxia-inducible factors, angiopoietins and pro-angiogenic cytokines, such as tumour necrosis factor (TNF), interleukin (IL)-8 and IL-17, are up-regulated in psoriasis development. Contact- and mediator-dependent factors derived from keratinocytes, mast cells and immune cells may contribute to the strong blood vessel formation of psoriasis. New technologies and experimental models provide new insights into the role of angiogenesis in psoriasis pathogenesis. Interestingly, many therapies target not only immune cells, but also protein structures of endothelial cells. Here we summarize the role of pro-angiogenic factors in psoriasis development and discuss angiogenesis as a potential target of novel therapies.

Keratinocyte but not endothelial cell-specific overexpression of Tie2 leads to the development of psoriasis

Psoriasis is initiated and maintained through a multifaceted interplay between keratinocytes, blood vessels, gene expression, and the immune system. One previous psoriasis model demonstrated that overexpression of the angiopoietin receptor Tie2 in endothelial cells and keratinocytes led to the development of a psoriasiform phenotype; however, the etiological significance of overexpression in each cell type alone was unclear. We have now engineered two new mouse models whereby Tie2 expression is confined to either endothelial cells or keratinocytes. Both lines of mice have significant increases in dermal vasculature but only the KC-Tie2-overexpressing mice developed a cutaneous psoriasiform phenotype. These mice spontaneously developed characteristic hallmarks of human psoriasis, including extensive acanthosis, increases in dermal CD4(+) T cells, infiltrating epidermal CD8(+) T cells, dermal dendritic cells and macrophages, and increased expression of cytokines and chemokines associated with psoriasis, including interferon-gamma, tumor necrosis factor-alpha, and interleukins 1alpha, 6, 12, 22, 23, and 17. Host-defense molecules, cathelicidin, beta-defensin, and S100A8/A9, were also up-regulated in the hyperproliferative skin. All of the phenotypic traits were completely reversed without any scarring following repression of the transgene and were significantly improved following treatment with the anti-psoriasis systemic therapeutic, cyclosporin A. Therefore, confining Tie2 overexpression solely to keratinocytes results in a mouse model that meets the clinical, histological, immunophenotypic, biochemical, and pharmacological criteria required for an animal model of human psoriasis.

Serum levels of angiogenic molecules in autoimmune thyroid diseases and their correlation with laboratory and clinical features

CONTEXT

Because angiogenesis has a role in the pathogenesis of inflammatory conditions, we studied angiogenesis soluble markers in autoimmune thyroid diseases.

OBJECTIVE

The aim of the study was to measure concentrations of angiopoietins, Tie-2, and vascular endothelial growth factor in sera from autoimmune thyroid disease patients.

DESIGN

Soluble Tie-2 (sTie-2), angiopoietin-1, angiopoietin-2, and vascular endothelial growth factor were quantified by ELISA in sera from 44 untreated Graves' disease (GD) patients, 25 untreated Hashimoto's thyroiditis (HT) patients, 13 non-GD hyperthyroid patients, and 22 age-matched controls. Subgroups of patients with active and non-active Graves' ophthalmopathy (GO) were analyzed. Correlations among these markers and clinical parameters were assessed by bivariate and multivariate analyses.

RESULTS

STIE-2 levels were higher in GD or HT patients compared to controls (P < 0.01). In addition, serum Ang-2 concentrations were higher in untreated GD patients compared to controls, HT patients, or non-GD hyperthyroid patients (P < 0.01), and no difference was observed between HT patients and controls. Significant correlations were found between free T(4)/sTie-2 and free T(4)/Ang-2 levels (r = 0.464, P < 0.01; and r = 0.463, P < 0.01, respectively) as well as between sTie-2/anti-TSH receptor antibody (r = 0.527; P < 0.01) and sTie-2/Ang-2 (r = 0.563; P = 0.001). Furthermore, sTie-2 levels were significantly higher in patients with active GO when compared to those with inactive GO (P < 0.05). Interestingly, Ang-2 levels decreased significantly after treatment with antithyroid drugs (P < 0.01).

CONCLUSIONS

Ang-2 and sTie-2 could participate in the pathogenesis of GD and potentially be used as markers of GO activity. Antithyroid drugs affect the angiogenic pattern in GD.

Role of Ceacam1 in VEGF induced vasculogenesis of murine embryonic stem cell-derived embryoid bodies in 3D culture

CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1), a type I transmembrane glycoprotein involved in cell-cell adhesion has been shown to act as an angiogenic factor for mouse and human endothelial cells. Based on the ability of CEACAM1 to initiate lumen formation in human mammary epithelial cells grown in 3D culture (Matrigel), we hypothesized that murine CEACAM1 may play a similar role in vasculogenesis. In order to test this hypothesis, murine embryonic stem (ES) cells stimulated with VEGF were differentiated into embryoid bodies (EB) for 8 days (-8-0 d) and transferred to Matrigel in the presence or absence of anti-CEACAM1 antibody for an additional 12 days (0-12 d). In the absence of anti-CEACAM1 antibody or in the presence of an isotype control antibody, the EB in Matrigel underwent extensive sprouting, generating lengthy vascular structures with well-defined lumina as demonstrated by confocal microscopy, electron microscopy, and immunohistochemical analysis. Both the length and architecture of the vascular tubes were inhibited by anti-CEACAM1 mAb CC1, a mAb that blocks the cell-cell adhesion functions of CEACAM1, thus demonstrating a critical role for this cell-cell adhesion molecule in generating and maintaining vasculogenesis. QRT-PCR analysis of the VEGF treated ES cells grown under conditions that convert them to EB revealed expression of Ceacam1 as early as -5 to -3 d reaching a maximum at day 0 at which time EBs were transferred to Matrigel, thereafter levels at first declined and then increased over time. Other markers of vasculogenesis including Pecam1, VE-Cad, and Tie-1 were not detected until day 0 when EBs were transferred to Matrigel followed by a steady increase in levels, indicating later roles in vasculogenesis. In contrast, Tie-2 and Flk-1 (VEGFR2) were detected on day five of EB formation reaching a maximum at day 0 on transfer to Matrigel, similar to Ceacam1, but after which Tie-2 declined over time, while Flk-1 increased over time. QRT-PCR analysis of the anti-CEACAM1 treated ES cells revealed a significant decrease in the expression of Ceacam1, Pecam1, Tie-1, and Flk-1, while VE-Cad and Tie-2 expression were unaffected. These results suggest that the expression and signaling of CEACAM1 may affect the expression of other factors known to play critical roles in vasculogenesis. Furthermore this 3D model of vasculogenesis in an environment of extracellular matrix may be a useful model for comparison to existing models of angiogenesis.

Control of vascular morphogenesis and homeostasis through the angiopoietin-Tie system

Angiogenesis, the growth of blood vessels, is a fundamental biological process that controls embryonic development and is also involved in numerous life-threatening human diseases. Much work in the field of angiogenesis research has centred on the vascular endothelial growth factor (VEGF)-VEGF receptor system. The Tie receptors and their angiopoietin (Ang) ligands have been identified as the second vascular tissue-specific receptor Tyr kinase system. Ang-Tie signalling is essential during embryonic vessel assembly and maturation, and functions as a key regulator of adult vascular homeostasis. The structural characteristics and the spatio-temporal regulation of the expression of receptors and ligands provide unique insights into the functions of this vascular signalling system.

Preeclampsia and small-for-gestational age are associated with decreased concentrations of a factor involved in angiogenesis: soluble Tie-2

OBJECTIVE

An anti-angiogenic state has been described in patients with preeclampsia, small-for-gestational age (SGA) fetuses and fetal death, and changes in the concentration of circulating angiogenic and anti-angiogenic factors can precede the clinical recognition of preeclampsia and SGA by several weeks. Gene deletion studies demonstrate that a selective group of endothelial growth factors are required for vascular development, including members of the vascular endothelial growth factor (VEGF) family, as well as angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2), both ligands for the tyrosine kinase endothelial cell receptor Tie-2. These angiogenic factors have been proposed to promote angiogenesis in a coordinated and complementary fashion. Soluble Tie-2 (sTie-2) is the soluble form of the Tie-2 receptor, which is detectable in biological fluids. The purpose of this study was to determine whether patients with preeclampsia and mothers who deliver a SGA neonate have changes in the plasma concentrations of sTie-2.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) non-pregnant women (n = 40), (2) women with normal pregnancies (n = 135), (3) patients with preeclampsia (n = 112), and (4) patients who delivered an SGA neonate (n = 53). Maternal plasma concentrations of sTie-2 were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) The median maternal plasma concentration of sTie-2 was lower in normal pregnant women than in non-pregnant women [median 16.0 ng/mL (range 5.0-71.6) vs. median 20.7 ng/mL (range 10.8-52.4), respectively; p = 0.01)). (2) Plasma sTie-2 concentrations in normal pregnancy changed significantly as a function of gestational age. (3) Patients with preeclampsia and those who delivered SGA neonates had a lower median maternal plasma concentration of sTie-2 than those with a normal pregnancy [preeclampsia: median 14.9 ng/mL (range 4.9-67.3); SGA: median 10.9 ng/mL (range 5.1-29.1); normal pregnancy: median 16.0 ng/mL (range 5.0-71.6); p = 0.048 and p < 0.001, respectively]. (4) Patients with SGA neonates had a lower median plasma concentration of sTie-2 than that of those with preeclampsia [median 10.9 ng/mL (range 5.1-29.1) vs. median 14.9 ng/mL (range 4.9-67.3), respectively; p < 0.001]. (5) Patients with early-onset preeclampsia (<or=34 weeks) had lower concentrations of sTie-2 than women with late-onset preeclampsia (>34 weeks) median of delta values: -0.13 ng/mL (range -0.47-0.58) vs. median of delta values: -0.09 ng/mL (range: -0.60-0.58), respectively; p = 0.043]. In contrast, there were no significant differences in the maternal plasma sTie-2 concentration between women with severe and mild preeclampsia (p = 0.6).

CONCLUSION

Patients with preeclampsia and those with SGA fetuses have lower median plasma concentrations of soluble Tie-2 than women with normal pregnancies.

Review Paper: Preclinical Models of Psoriasis

Psoriasis is the most common autoimmune disease in man and is characterized by focal to coalescing raised cutaneous plaques with consistent scaling and variable erythema. The specific pathogenesis of psoriasis is not completely understood, but the underlying mechanisms involve a complex interplay between epidermal keratinocytes, T lymphocytes as well as other leukocytes (including dendritic cells and other antigen presenting cells [APCs]), and vascular endothelium. Mirroring the complexity of mechanisms that underlie psoriasis, there are a relatively large number of models of psoriasis. Each model is based on a slightly different pathogenic mechanism, and each has its similarities to psoriasis as well as its limitations. In general, psoriasis models can be very broadly divided on the basis of the pathogenic mechanisms that interplay to cause psoriasis, with the addition of several relatively poorly defined spontaneous murine mutant models. Other than the spontaneous mutant models, murine models of psoriasis can be divided into those that are genetically engineered (transgenic and knockout—with manipulation of either the epidermis, leukocytes, or the endothelium), and those that are induced (either by immune transfer or by xenotransplantation of skin from psoriatic patients). In addition to the murine models, in vitro human epidermal models have recently become more widely utilized. While no one single model of psoriasis is ideal, many have proven to be extremely valuable in investigating and better understanding the molecular mechanisms that underlie the complex interplay between epidermal keratinocytes, the innate and adaptive immune system, and the vascular endothelium in psoriasis.

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.

Immunopathogenesis of psoriasis

Investigations into the cause and treatment of psoriasis remain at the forefront of basic and applied clinical research efforts around the world. The purpose for this review is to provide an up-to-date synopsis of recent progress in ten sections exploring the immunological and inflammatory basis for psoriasis. Given the breadth of this topic in investigative skin biology and frequent paradigm shifts, it should not be surprising that the bibliography contains more than 150 references; many of which have been published in the last 5 years. Whereas considerable progress has been made into the immunopathogenesis of psoriasis, many fundamentally important questions remain regarding the role of cells located in both epidermal and dermal compartments. Attempts to characterize various animal models of psoriasis, delineation of the mechanism of action for biological agents, and consideration of molecular links between skin inflammation and various extracutaneous comorbidities are likely to continue challenging investigators and clinicians for many years to come.

Animal models of psoriasis

Research into the pathogenesis of psoriasis has been severely hampered by the lack of a naturally occurring disorder in laboratory animals that mimics the complex phenotype and pathogenesis of the human disease. A large variety of spontaneous mutations, genetically engineered rodents, immunological reconstitution approaches, and xenotransplantation models have been used to study specific aspects of the pathophysiology of psoriasis, however. Several manipulations of resident cutaneous cell types or immigrating immunocytes appear to result in remarkably similar hyperproliferative inflammatory phenotypes in mice, thus suggesting that interfering with cutaneous homeostasis in general may ultimately result in a rather uniform reaction pattern that mirrors some features of psoriasis. Fully animal models of psoriasis have nonetheless not only shed light on the biological functions of given inflammatory mediators or other molecules but also tremendously contributed to the discussion on central pathogenic questions, such as the roles of innate and adaptive immune mechanisms, keratinocytes, and endothelial cells in psoriasis. Psoriasis research has also been greatly nourished by xenotransplantation of diseased or unaffected human skin onto immunocompromised recipients, an approach that has in many variations been used to study the role of T lymphocytes and other cells and that has been used for preclinical therapeutic studies. General approaches to generate animal models of psoriasis, features of some specific models, their value for psoriasis research, and their use for drug development are discussed in this article.

Intra and extravascular transmembrane signalling of angiopoietin-1-Tie2 receptor in health and disease

Angiopoietin-1 (Ang-1) is the primary agonist for Tie2 tyrosine kinase receptor (Tie2), and the effect of Ang-1-Tie2 signalling is context-dependent. Deficiency in either Ang-1 or Tie2 protein leads to severe microvascular defects and subsequent embryonic lethality in murine model. Tie2 receptors are expressed in several cell types, including endothelial cells, smooth muscle cells, fibroblasts, epithelial cells, monocytes, neutrophils, eosinophils and glial cells. Ang-1-Tie2 signalling induces a chemotactic effect in smooth muscle cells, neutrophils and eosinophils, and induces differentiation of mesenchymal cells to smooth muscle cells. Additionally, this signalling pathway induces the secretion of serotonin, matrix metalloproteinases (MMPs) and plasmin. Ang-1 inhibits the secretion of tissue inhibitor of matrix metalloproteinase (TIMPs). Aberrant expression and activity of Tie2 in vascular and non-vascular cells may result in the development of rheumatoid arthritis, cancer, hypertension and psoriasis. Ang-1 has an anti-inflammatory effect, when co-localized with vascular endothelial growth factor (VEGF) in the vasculature. Thus, Ang-1 could be potentially important in the therapy of various pathological conditions such as pulmonary hypertension, arteriosclerosis and diabetic retinopathy. In this article, we have summarized and critically reviewed the pathophysiological role of Ang-1-Tie2 signalling pathway.

Regulation of endothelial cell cytoskeletal reorganization by a secreted frizzled-related protein-1 and frizzled 4- and frizzled 7-dependent pathway: role in neovessel formation

Consistent with findings of Wnt pathway members involved in vascular cells, a role for Wnt/Frizzled signaling has recently emerged in vascular cell development. Among the few Wnt family members implicated in vessel formation in adult, Wnt7b and Frizzled 4 have been shown as involved in vessel formation in the lung and in the retina, respectively. Our previous work has shown a role for secreted Frizzled-related protein-1 (sFRP-1), a proposed Wnt signaling inhibitor, in neovascularization after an ischemic event and demonstrated its role as a potent angiogenic factor. However the mechanisms involved have not been investigated. Here, we show that sFRP-1 treatment increases endothelial cell spreading on extracellular matrix as revealed by actin stress fiber reorganization in an integrin-dependent manner. We demonstrate that sFRP-1 can interact with Wnt receptors Frizzled 4 and 7 on endothelial cells to transduce downstream to cellular machineries requiring Rac-1 activity in cooperation with GSK-3beta. sFRP-1 overexpression in endothelium specifically reversed the inactivation of GSK-3 beta and increased neovascularization in ischemia-induced angiogenesis in mouse hindlimb. This study illustrates a regulated pathway by sFRP-1 involving GSK-3beta and Rac-1 in endothelial cell cytoskeletal reorganization and in neovessel formation.

Mouse models of psoriasis

Psoriasis is a T-cell-mediated chronic inflammatory skin disease believed to be of autoimmune nature that can be triggered or worsened by streptococcal throat infections. In addition to conventional chronic inflammatory changes, psoriasis is characterized by complex and striking alterations in epidermal growth and differentiation. Psoriasis is generally not observed in animals other than man, and this lack of a suitable animal model has greatly hindered research into the pathogenesis of psoriasis. Multiple transgenic, knockout, and reconstituted models of psoriasis have been developed over the past two decades. Despite their limitations, these models have demonstrated that keratinocyte hyperplasia, vascular hyperplasia, and cell-mediated immunity in the skin are closely interrelated. Xenograft models, in which involved and uninvolved psoriatic skin are transplanted onto immunodeficient mice, are the only models that come close to incorporating the complete genetic, immunologic, and phenotypic changes of the disease. They have shown conclusively that psoriasis is a T-cell-mediated disease, and have been used to elucidate novel pathogenic pathways. In this review, we describe various animal models, detail the immunologic and intracellular pathways that mediate these phenotypes and assess the utility of these models to better understand this disease.

Animal models in cardiovascular diseases: new insights from conditional models

Conditional systems have proven to be efficient and powerful to delineate several aspects of cardiac pathophysiology and diseases. The possibility of addressing a particular time point in animal life is certainly an important breakthrough allowed by conditional strategies with temporal control of either transgene expression or gene modifications. The purpose of this review is to present various mouse models for cardiovascular diseases based on conditional approaches.

Inhibition of angiogenic pathways in rheumatoid arthritis: potential for therapeutic targeting

Angiogenesis is a significant and possibly primary event in the pathogenesis of inflammatory diseases including arthritis. Abnormalities of vascular morphology and angiogenesis have been described at the macroscopic, histological and molecular levels in the synovial membrane in rheumatoid, seronegative and degenerative arthritis. The vascular endothelium is an active organ that participates in the initiation and maintenance of the inflammatory response. Endothelial cells (EC) are activated by a variety of stimuli to express surface adhesion molecules to bind and facilitate, via an active process, the movement of white blood cells such as neutrophils, macrophages and lymphocytes into the target tissue. The main stimuli known to activate EC and initiate angiogenesis include hypoxia, inflammatory mediators and mechanical stress. Irrespective of the trigger a series of messages, such as cytokine release, production of growth factors and subsequent downstream molecular messages, result in changes to vessel permeability, EC proliferation and migration, disruption of the basement membrane and formation of new vascular tubes. Several key growth factors are known to upregulate EC activation and proliferation leading to the sprouting of new vessels that then stabilise and mature, recruiting smooth muscle pericytes to consolidate vessel wall structure. In this review the process of angiogenesis in the arthritic joint, including the stimuli and molecular pathways will be discussed and potential therapeutic targeting of critical steps will be highlighted.