A four-gene biomarker predicts skin disease in patients with diffuse cutaneous systemic sclerosis

Epstein-Barr virus infection induces aberrant TLR activation pathway and fibroblast-myofibroblast conversion in scleroderma

Scleroderma (SSc) is a complex and heterogeneous connective tissue disease mainly characterized by autoimmunity, vascular damage, and fibrosis that mostly involve the skin and lungs. Epstein–Barr virus (EBV) is a lymphotropic γ-herpesvirus that has co-evolved with human species, infecting >95% of the adult population worldwide, and has been a leading candidate in triggering several autoimmune diseases. Here we show that EBV establishes infection in the majority of fibroblasts and endothelial cells in the skin of SSc patients, characterized by the expression of the EBV noncoding small RNAs (EBERs) and the increased expression of immediate-early lytic and latency mRNAs and proteins. We report that EBV is able to persistently infect human SSc fibroblasts in vitro, inducing an aberrant innate immune response in infected cells. EBV–Toll-like receptor (TLR) aberrant activation induces the expression of selected IFN-regulatory factors (IRFs), IFN-stimulated genes (ISGs), transforming growth factor-β1 (TGFβ1), and several markers of fibroblast activation, such as smooth muscle actin and Endothelin-1, and all of these genes play a key role in determining the profibrotic phenotype in SSc fibroblasts. These findings imply that EBV infection occurring in mesenchymal, endothelial, and immune cells of SSc patients may underlie the main pathological features of SSc including autoimmunity, vasculopathy, and fibrosis, and provide a unified disease mechanism represented by EBV reactivation.

[Expression of endoglin in human non-small cell lung cancer and its clinical significance]

OBJECTIVE

To investigate the expression of endoglin (ENG) in human non small cell lung cancer (NSCLC) cell lines, cancer and adjacent non-cancer tissues, and its role in NSCLC development, progression, metastasis and recurrence.

METHODS

Five strains of NSCLC cells and one strain of normal human bronchial epithelial (HBE) cells were cultured in vitro. Human NSCLC tissues and their corresponding adjacent lung tissues were taken from 22 NSCLC cases to detect the mRNA and protein levels of ENG using real-time PCR and Western blotting, respectively. Chi-square test was performed to analyze the correlations between the ENG expression and clinical data.

RESULTS

The mRNA and protein levels of ENG were up-regulated in 3 NSCLC cell strains of high metastasis. However, the expression of ENG was missing in the other low-metastatic NSCLC cell strains and the HBE cell strain. Besides, the mRNA and protein levels of ENG were up-regulated in the 19 out of 22 lung cancer tissues (86.36%), which were significantly higher than those in the adjacent non-cancer tissues (P<0.01). The over-expression of ENG was significantly correlated positively with lymph node metastasis (P<0.01), but not with age, sex, tumor size, clinical stage, pathological grade or histopathological type.

CONCLUSION

The expression of ENG in NSCLC is significantly correlated positively with lymph node metastasis, and it might be a biomarker for the metastasis and prognosis of NSCLC.

Global chemokine expression in systemic sclerosis (SSc): CCL19 expression correlates with vascular inflammation in SSc skin

OBJECTIVE

To characterise global chemokine expression in systemic sclerosis (SSc) skin in order to better understand the relationship between chemokine expression and vascular inflammation in this disease.

METHODS

We investigated chemokine mRNA expression in the skin through quantitative PCR analysis comparing patients with diffuse cutaneous (dcSSc) or limited cutaneous (lcSSc) disease with healthy controls. We tested correlations between the most regulated chemokines and vascular inflammation and macrophage recruitment. CCL19 expression was examined in human primary immune cells treated with innate immune activators.

RESULTS

The chemokines, CCL18, CCL19 and CXCL13, were upregulated in dcSSc skin, and CCL18 in lcSSc skin. Expression of CCL19 in dcSSc skin correlated with markers of vascular inflammation and macrophage recruitment. Immunofluorescence data showed CCL19 colocalisation with CD163 macrophages in dcSSc skin. In vitro studies on human primary cells demonstrated that CCL19 expression was induced after toll-like receptor activation of peripheral blood mononuclear cells and separated populations of CD14 monocytes.

CONCLUSIONS

CCL18, CCL19 and CXCL13-chemoattractants for macrophage and T cell recruitment-were three of six chemokines with the highest expression in dcSSc skin. Increased CCL19 expression in the skin suggests a role for CCL19 in the recruitment of immune cells to the peripheral tissue. Induction of CCL19 in macrophages but not structural cells indicates a role for skin-resident or recruited immune cells in perivascular inflammation. This study demonstrates that CCL19 is a sensitive marker for the perivascular inflammation and immune cell recruitment seen in dcSSc skin disease.

Targeted therapies for systemic sclerosis

Pathogenic processes that underlie the development and progression of systemic sclerosis (SSc) are being defined in preclinical, clinical and genetic studies. Important evidence of interplay between the vasculature, connective tissue and specialized epithelial structures is emerging, and abnormalities of both the innate and adaptive immune systems have been identified. In this context, information regarding pivotal mediators, pathways or cell types that could be targets for therapeutic intervention, and that might offer potential for true disease modification, is accruing. Precedent for the regression of some aspects of the pathology has been set in clinical studies showing that potential exists to improve tissue structure and function as well as to prevent disease progression. This article reviews the concept of targeted therapies and considers potential pathways and processes that might be attenuated by therapeutic intervention in SSc. As well as improving outcomes, such approaches will undoubtedly provide information about pathogenesis. The concept of translational medicine is especially relevant in SSc, and we anticipate that the elusive goal of an effective antifibrotic treatment will emerge from one of the several clinical trials currently underway or planned in this disease. Therapeutic advances in SSc would have implications and potential beyond autoimmune rheumatic diseases.

Correlation of interferon-inducible chemokine plasma levels with disease severity in systemic sclerosis

OBJECTIVE

To measure interferon (IFN)-inducible chemokines in the plasma of patients with systemic sclerosis (SSc) and investigate whether the chemokine levels are correlated with disease severity.

METHODS

Plasma levels of the IFN-inducible chemokines IFNγ-inducible protein 10 (IP-10/CXCL10), IFN-inducible T cell α chemoattractant (I-TAC/CXCL11), and monocyte chemoattractant protein 1 (CCL2) were measured in SSc patients and examined for correlation with the IFN gene expression signature. A composite IFN-inducible chemokine score was generated for chemokines showing a correlation with the IFN gene signature (IP-10 and I-TAC), and this score was compared between 266 patients with SSc enrolled in the Genetics versus Environment in Scleroderma Outcome Study (GENISOS) cohort and 97 matched control subjects. Subsequently, the correlation between the IFN-inducible chemokine score at baseline and markers of disease severity was assessed. In addition, the course of the IFN-inducible chemokine score over time was examined.

RESULTS

The plasma IFN-inducible chemokine score correlated with the IFN gene expression signature, and this score was higher in SSc patients compared to controls. The IFN-inducible chemokine score was also associated with the absence of anti-RNA polymerase III antibodies and presence of anti-U1 RNP antibodies, but not with disease duration, disease type, or other autoantibodies. The chemokine score correlated with concomitantly obtained scores on the Medsger Severity Index for muscle, skin, and lung involvement in SSc, as well as the forced vital capacity, diffusing capacity for carbon monoxide, and creatine kinase levels. The association of the chemokine score with disease severity was independent of the presence of anti-U1 RNP or other potential confounders (age, sex, ethnicity, disease duration, and treatment with immunosuppressive agents). Finally, there was not a significant change in the IFN-inducible chemokine score over time.

CONCLUSION

The IFN-inducible chemokine score is a stable serologic marker of a more severe form of SSc and may be useful for risk stratification of patients, regardless of disease type (limited or diffuse) or duration of disease.

Molecular signatures in skin associated with clinical improvement during mycophenolate treatment in systemic sclerosis

Heterogeneity in systemic sclerosis/SSc confounds clinical trials. We previously identified ‘intrinsic’ gene expression subsets by analysis of SSc skin. Here we test the hypotheses that skin gene expression signatures including intrinsic subset are associated with skin score/MRSS improvement during mycophenolate mofetil (MMF) treatment. Gene expression and intrinsic subset assignment were measured in 12 SSc patients’ biopsies and ten controls at baseline, and from serial biopsies of one cyclophosphamide-treated patient, and nine MMF-treated patients. Gene expression changes during treatment were determined using paired t-tests corrected for multiple hypothesis testing. MRSS improved in four of seven MMF-treated patients classified as the inflammatory intrinsic subset. Three patients without MRSS improvement were classified as normal-like or fibroproliferative intrinsic subsets. 321 genes (FDR <5%) were differentially expressed at baseline between patients with and without MRSS improvement during treatment. Expression of 571 genes (FDR <10%) changed between pre- and post-MMF treatment biopsies for patients demonstrating MRSS improvement. Gene expression changes in skin are only seen in patients with MRSS improvement. Baseline gene expression in skin, including intrinsic subset assignment, may identify SSc patients whose MRSS will improve during MMF treatment, suggesting that gene expression in skin may allow targeted treatment in SSc.

Mechanistic biomarkers for clinical decision making in rheumatic diseases

The use of biomarkers is becoming increasingly intrinsic to the practice of medicine and holds great promise for transforming the practice of rheumatology. Biomarkers have the potential to aid clinical diagnosis when symptoms are present or to provide a means of detecting early signs of disease when they are not. Some biomarkers can serve as early surrogates of eventual clinical outcomes or guide therapeutic decision making by enabling identification of individuals likely to respond to a specific therapy. Using biomarkers might reduce the costs of drug development by enabling individuals most likely to respond to be enrolled in clinical trials, thereby minimizing the number of participants required. In this Review, we discuss the current use and the potential of biomarkers in rheumatology and in select fields at the forefront of biomarker research. We emphasize the value of different types of biomarkers, addressing the concept of 'actionable' biomarkers, which can be used to guide clinical decision making, and 'mechanistic' biomarkers, a subtype of actionable biomarker that is embedded in disease pathogenesis and, therefore, represents a potentially superior biomarker. We provide examples of actionable and mechanistic biomarkers currently available, and discuss how development of such biomarkers could revolutionize clinical practice and drug development.

Pharmacogenomics and translational simulations to bridge indications for an anti-interferon-α receptor antibody

A type I interferon (IFN) gene signature shared by systemic lupus erythematous (SLE) and systemic sclerosis (SSc) was used to evaluate an anti-type I IFN-α receptor (IFN-αR) monoclonal antibody, MEDI-546, in a phase I trial in SSc. MEDI-546 suppressed IFN signature in blood and skin of SSc patients in a dose-dependent manner. To bridge clinical indications to SLE, we developed a model incorporating (i) pharmacokinetics (PK) and pharmacodynamics (PD) in SSc patients, (ii) internalization kinetics of MEDI-546/IFN-αR complex, and (iii) the different IFN signatures between SSc and SLE. Simulations predicted that i.v. administration of MEDI-546 at 300- or 1,000-mg monthly doses could suppress IFN signature in blood to levels of healthy subjects in 53 and 68% of SLE patients, respectively. An innovative approach utilizing a novel biomarker characterized the PD of MEDI-546 by modeling and simulation and allowed rapid progression of MEDI-546 from a phase I study in SSc to a randomized, multiple-dose phase II trial.

Ciprofloxacin has antifibrotic effects in scleroderma fibroblasts via downregulation of Dnmt1 and upregulation of Fli1

Systemic sclerosis (SSc) is characterized by fibrosis of the skin and internal organs. The present study was undertaken to examine the effects of ciprofloxacin, a fluoroquinolone antibiotic implicated in matrix remodeling, on dermal and lung fibroblasts obtained from SSc patients. Dermal and lung fibroblasts from SSc patients and healthy subjects were treated with ciprofloxacin. Western blotting was used to analyze protein levels and RT-PCR was used to measure mRNA expression. The pharmacologic inhibitor UO126 was used to block Erk1/2 signaling. SSc dermal fibroblasts demonstrated a significant decrease in collagen type I mRNA and protein levels after antibiotic treatment, while healthy dermal fibroblasts were less sensitive to ciprofloxacin, downregulating collagen only at the protein levels. Connective tissue growth factor (CCN2) gene expression was significantly reduced and matrix metalloproteinase 1 (MMP1) levels were enhanced after ciprofloxacin treatment to a similar extent in healthy and SSc fibroblasts. Ciprofloxacin induced Erk1/2 phosphorylation, and Erk1/2 blockade completely prevented MMP1 upregulation. However, Smad1 and Smad3 activation in response to TGFβ was not affected. The expression of friend leukemia integration factor 1 (Fli1), a transcriptional repressor of collagen, was increased after treatment with ciprofloxacin only in SSc fibroblasts, and this was accompanied by a decrease in the levels of DNA methyltransferase 1 (Dnmt1). Similar effects were observed in SSc-interstitial lung disease (ILD) lung fibroblasts. In summary, our study demonstrates that ciprofloxacin has antifibrotic actions in SSc dermal and lung fibroblasts via the downregulation of Dnmt1, the upregulation of Fli1 and induction of MMP1 gene expression via an Erk1/2-dependent mechanism. Thus, our data suggest that ciprofloxacin may be an attractive therapy for SSc skin and lung fibrosis.

Graft versus host disease in the bone marrow, liver and thymus humanized mouse model

Mice bearing a “humanized” immune system are valuable tools to experimentally manipulate human cells in vivo and facilitate disease models not normally possible in laboratory animals. Here we describe a form of GVHD that develops in NOD/SCID mice reconstituted with human fetal bone marrow, liver and thymus (NS BLT mice). The skin, lungs, gastrointestinal tract and parotid glands are affected with progressive inflammation and sclerosis. Although all mice showed involvement of at least one organ site, the incidence of overt clinical disease was approximately 35% by 22 weeks after reconstitution. The use of hosts lacking the IL2 common gamma chain (NOD/SCID/γc^−/−) delayed the onset of disease, but ultimately did not affect incidence. Genetic analysis revealed that particular donor HLA class I alleles influenced the risk for the development of GVHD. At a cellular level, GVHD is associated with the infiltration of human CD4+ T cells into the skin and a shift towards Th1 cytokine production. GVHD also induced a mixed M1/M2 polarization phenotype in a dermal murine CD11b+, MHC class II+ macrophage population. The presence of xenogenic GVHD in BLT mice both presents a major obstacle in the use of humanized mice and an opportunity to conduct preclinical studies on GVHD in a humanized model.

Tyrosine kinase signaling in fibrotic disorders: Translation of basic research to human disease

Tyrosine kinases regulate a broad variety of physiological cell processes, including metabolism, growth, differentiation and apoptosis. Abnormal tyrosine kinase activity disturbs the physiological cell homeostasis and can lead to cancer, vascular disease, and fibrosis. In regard to fibrosis, different tyrosine kinases have been identified as determinants of disease progression and potential targets for anti-fibrotic therapies. This includes both receptor tyrosine kinases (e.g., PDGF receptor, VEGF receptor, EGF receptor, and JAK kinases) as well as non-receptor tyrosine kinases (e.g., c-Abl, c-Kit, and Src kinases). Given their central role in the pathogenesis of fibrosis, researchers of our field study the anti-fibrotic effects of monoclonal antibodies or small-molecule inhibitors to block the aberrant tyrosine kinase activity and treat fibrosis in preclinical models of various fibrotic diseases (e.g., idiopathic pulmonary fibrosis, renal fibrosis, liver fibrosis, and dermal fibrosis). The results of these studies were promising and prompted clinical trials with different compounds in fibrotic diseases. So far, results from studies with intedanib in idiopathic pulmonary fibrosis and imatinib in idiopathic pulmonary fibrosis and systemic sclerosis have been reported. Although none of these studies reported a positive primary outcome, promising trends in anti-fibrotic efficacy awaken our hopes for a new class of effective anti-fibrotic targeted therapies. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

The Role of TGF-β Receptors in Fibrosis

Recent advances in defining TGF-β signaling pathways have provided a new level of understanding of the role of this pleiotropic growth factor in the development of fibrosis. Here, we review selected topics related to the profibrotic role of TGF-β . We will discuss new insights into the mechanisms of ligand activation and the contribution of Erk1/2 MAPK, PI3K/FAK, and Endoglin/Smad1 signaling pathways to the process of fibrosis. There is growing evidence of the disease-specific alterations of the downstream components of the TGF-β signaling pathway that may be explored for the future therapeutic interventions.

Application of biomarkers to clinical trials in systemic sclerosis

Important clinical advances in the treatment of systemic sclerosis have been made, yet fibrotic disease remains largely untreatable. Optimal design of clinical trials to test new therapeutics for fibrotic disease features has suffered from dual difficulties in patient selection and patient evaluation. Patient selection for entry into trials for treatment of interstitial lung disease and/or skin fibrosis is challenged by the natural history of the disease, which stabilizes in some patients while relentlessly progressing in others, and our lack of good clinical markers to distinguish between these trajectories. Patient evaluation is made difficult, particularly in skin disease, by the inherent difficulty in quantifying the extent of disease. Biomarkers hold the potential to solve many of these problems as surrogate outcome measures and as markers for disease progression. Identified biomarkers may have the potential to graduate to surrogate outcome singly or, more likely, in combination. Predictive biomarkers are still largely unknown.

Myocardial alternative RNA splicing and gene expression profiling in early stage hypoplastic left heart syndrome

Hypoplastic Left Heart Syndrome (HLHS) is a congenital defect characterized by underdevelopment of the left ventricle and pathological compensation of the right ventricle. If untreated, HLHS is invariably lethal due to the extensive increase in right ventricular workload and eventual failure. Despite the clinical significance, little is known about the molecular pathobiological state of HLHS. Splicing of mRNA transcripts is an important regulatory mechanism of gene expression. Tissue specific alterations of this process have been associated with several cardiac diseases, however, transcriptional signature profiles related to HLHS are unknown. In this study, we performed genome-wide exon array analysis to determine differentially expressed genes and alternatively spliced transcripts in the right ventricle (RV) of six neonates with HLHS, compared to the RV and left ventricle (LV) from non-diseased control subjects. In HLHS, over 180 genes were differentially expressed and 1800 were differentially spliced, leading to changes in a variety of biological processes involving cell metabolism, cytoskeleton, and cell adherence. Additional hierarchical clustering analysis revealed that differential gene expression and mRNA splicing patterns identified in HLHS are unique compared to non-diseased tissue. Our findings suggest that gene expression and mRNA splicing are broadly dysregulated in the RV myocardium of HLHS neonates. In addition, our analysis identified transcriptome profiles representative of molecular biomarkers of HLHS that could be used in the future for diagnostic and prognostic stratification to improve patient outcome.

An update on an immune system that goes awry in systemic sclerosis

PURPOSE OF REVIEW

This review aims to provide an overview of the recent data that emerged, further substantiating the critical role of innate immunity in systemic sclerosis (SSc).

RECENT FINDINGS

Driven by the evidence that newly identified SSc susceptibility genes are predominantly involved in immune regulation, we discuss the aberrant antigen presenting cell (APC) activation observed in the course of disease. In particular, we report the alternate activation of 'M1' and 'M2' macrophages reflecting different clinical phenotypes and the aberrant Toll-like receptor (TLR) response, whose effect on cytokine production is mostly evident in the early phases of disease; we especially highlight the increasing importance attributed to TLR3-mediated fibrosis. We next discuss the potential role for interferon (IFN) - producing plasmacytoid dendritic cells (pDCs) in triggering or perpetuating the inflammatory loop caused by TLR hyperactivation, possibly resulting in inflammasome-derived IL-1β-mediated fibrosis and IL-17 producing T helper cells (Th17) skewing.

SUMMARY

We propose to approach SSc as a multistep immune-mediated disease that is in need of a therapeutic strategy designed to interfere with one or more of these aberrant molecular pathways. Targeting of DCs could be such a target by which dampening the immune system could modify the course of SSc.

Interspecies comparison of human and murine scleroderma reveals IL-13 and CCL2 as disease subset-specific targets

Development of personalized treatment regimens is hampered by lack of insight into how individual animal models reflect subsets of human disease, and autoimmune and inflammatory conditions have proven resistant to such efforts. Scleroderma is a lethal autoimmune disease characterized by fibrosis, with no effective therapy. Comparative gene expression profiling showed that murine sclerodermatous graft-versus-host disease (sclGVHD) approximates an inflammatory subset of scleroderma estimated at 17% to 36% of patients analyzed with diffuse, 28% with limited, and 100% with localized scleroderma. Both sclGVHD and the inflammatory subset demonstrated IL-13 cytokine pathway activation. Host dermal myeloid cells and graft T cells were identified as sources of IL-13 in the model, and genetic deficiency of either IL-13 or IL-4Rα, an IL-13 signal transducer, protected the host from disease. To identify therapeutic targets, we explored the intersection of genes coordinately up-regulated in sclGVHD, the human inflammatory subset, and IL-13-treated fibroblasts; we identified chemokine CCL2 as a potential target. Treatment with anti-CCL2 antibodies prevented sclGVHD. Last, we showed that IL-13 pathway activation in scleroderma patients correlated with clinical skin scores, a marker of disease severity. Thus, an inflammatory subset of scleroderma is driven by IL-13 and may benefit from IL-13 or CCL2 blockade. This approach serves as a model for personalized translational medicine, in which well-characterized animal models are matched to molecularly stratified patient subsets.

Basal Activation of Type I Interferons (Alpha2 and Beta) and 2'5'OAS Genes: Insights into Differential Expression Profiles of Interferon System Components in Systemic Sclerosis

Objective. Systemic sclerosis (SSc) is a complex autoimmune disease in which interferons (IFNs) may play an essential role. We hypothesized that type I and III IFNs may be found in increased levels in patients and be responsible for SSc autoimmune status. Methods. Type I and III IFN and ISG basal expression profiles were measured by qPCR using RNA from PBMCs of patients and controls . Results. Type I IFNs are increased in SSc patients, while no induction of type III IFNs was detected. This induction cannot be related to IRF7, since no upregulation of this gene was seen on patients. Of the ISGs tested, 2′5′OAS levels were increased in patients, while 6–16 and MxA levels were not. Conclusions. While there is no indication of type III IFN induction, increased levels of type I IFNs may lead to abnormal regulation of ISGs that can be responsible for immune system alterations described for SSc.

Identification and characterization of cartilage oligomeric matrix protein as a novel pathogenic factor in keloids

To elucidate pathogenic molecules in keloids, microarray analysis was performed using RNAs extracted from keloid-derived fibroblasts and normal skin-derived fibroblasts from the same patient with a typical keloid. Among 11 up-regulated extracellular matrix genes, cartilage oligomeric matrix protein (COMP) was most prominently increased. Up-regulation of COMP mRNA and protein was confirmed in the keloid tissue by quantitative RT-PCR and Western blot. Using immunohistochemistry, we compared 15 keloids and 6 control normal tissues using a COMP-specific antibody and found that COMP stained positively in 10 keloids (66.7%), whereas no staining was observed in normal tissues, demonstrating the ectopic expression of COMP in keloids. Comparing keloids smaller or larger than 10 cm(2), the larger keloids were significantly more intensely stained with the COMP-specific antibody. Because COMP reportedly accelerates collagen type I fibril assembly, we examined whether extracellular type I collagen deposition is altered by silencing COMP mRNA by small interfering RNA (siRNA). Immunocytochemistry showed at 96 hours after transfection with COMP siRNA that the extracellular deposition of type I collagen was decreased compared to that observed with control siRNA. Further, COMP knockdown decreased amount collagens type I to V in the medium and on the cell surfaces. Our data suggest that COMP facilitates keloid formation by accelerating collagen deposition, thus providing a new therapeutic target.

Interferon and alternative activation of monocyte/macrophages in systemic sclerosis-associated pulmonary arterial hypertension

OBJECTIVE

To explore the relationship between biomarkers of pulmonary arterial hypertension (PAH), interferon (IFN)-regulated gene expression, and the alternative activation pathway in systemic sclerosis (SSc).

METHODS

Peripheral blood mononuclear cells (PBMCs) were purified from healthy controls, patients with idiopathic PAH, and SSc patients (classified as having diffuse cutaneous SSc, limited cutaneous SSc [lcSSc] without PAH, and lcSSc with PAH). IFN-regulated and "PAH biomarker" genes were compared after supervised hierarchical clustering. Messenger RNA levels of selected IFN-regulated genes (Siglec1 and MX1), biomarker genes (IL13RA1, CCR1, and JAK2), and the alternative activation marker gene (MRC1) were analyzed on PBMCs and on CD14- and CD14+ cell populations. Interleukin-13 (IL-13) and IL-4 concentrations were measured in plasma by immunoassay. CD14, MRC1, and IL13RA1 surface expression was analyzed by flow cytometry.

RESULTS

Increased PBMC expression of both IFN-regulated and biomarker genes distinguished SSc patients from healthy controls. Expression of genes in the biomarker cluster, but not in the IFN-regulated cluster, distinguished lcSSc with PAH from lcSSc without PAH. The genes CCR1 (P<0.001) and JAK2 (P<0.001) were expressed more highly in lcSSc patients with PAH compared with controls and mainly by CD14+ cells. MRC1 expression was increased exclusively in lcSSc patients with PAH (P<0.001) and correlated strongly with pulmonary artery pressure (r=0.52, P=0.03) and higher mortality (P=0.02). MRC1 expression was higher in CD14+ cells and was greatly increased by stimulation with IL-13. IL-13 concentrations in plasma were most highly increased in lcSSc patients with PAH (P<0.001).

CONCLUSION

IFN-regulated and biomarker genes represent distinct, although related, clusters in lcSSc patients with PAH. MRC1, a marker for the effect of IL-13 on alternative monocyte/macrophage activation, is associated with this severe complication and is related to mortality.

Thrombospondin 1 in hypoxia-conditioned media blocks the growth of human microvascular endothelial cells and is increased in systemic sclerosis tissues

Background

Systemic sclerosis (SSc) is a chronic inflammatory autoimmune disease characterised by vascular dysfunction and damage, excess collagen deposition and subsequent organ manifestations. Vasculopathy is an early feature of the disease which leads to a chronic hypoxic environment in the tissues. Paradoxically, there is a lack of angiogenesis. We hypothesised that this may in part be due to a nonphysiological, overriding upregulation in antiangiogenic factors produced by the hypoxic tissues. We considered thrombospondin 1 (TSP-1) as a candidate antiangiogenic factor.

Results

Conditioned media from human microvascular endothelial cells cultured in both normoxic and hypoxic environments were able to block endothelial cell proliferation, with the latter environment having a more profound effect. Filtration to remove > 100-kDa proteins or heparin-binding proteins from the conditioned media eliminated their antiproliferative effect. TSP-1 was expressed in high concentrations in the hypoxic media, as was vascular endothelial growth factor (VEGF). Depletion of TSP-1 from the media by immunoprecipitation reduced the antiproliferative effect. We then show that, in a dose-dependent fashion, recombinant TSP-1 blocks the proliferation of endothelial cells. Immunohistochemistry of skin biopsy material revealed that TSP-1 expression was significantly higher throughout the skin of patients with SSc compared with healthy controls.

Conclusions

Despite the environment of chronic tissue hypoxia in SSc, there is a paradoxical absence of angiogenesis. This is thought to be due in part to aberrant expression of antiangiogenic factors, including TSP-1. We have demonstrated that TSP-1 is released in high concentrations by hypoxic endothelial cells. The conditioned media from these cells is able to block proliferation and induce apoptosis in microvascular endothelial cells, an effect that is reduced when TSP-1 is immunoprecipitated out. Further, we have shown that recombinant TSP-1 is able to block proliferation and induce apoptosis at concentrations consistent with those found in the plasma of patients with SSc and that its effect occurs in the presence of elevated VEGF levels. Taken together, these data are consistent with a model wherein injured microvascular cells in SSc fail to repair because of dysregulated induction of TSP-1 in the hypoxic tissues.

The pathogenesis of systemic sclerosis

Systemic sclerosis (SSc), also known as scleroderma, is a rare connective tissue disease characterized by vascular and immune dysfunction, leading to fibrosis that can damage multiple organs. Its pathogenesis is complex and poorly understood. Two major clinical subtypes are the limited and diffuse forms. Research into SSc has been hampered by its rarity, its clinical heterogeneity, and the lack of mouse models that accurately recapitulate the disease. Clinical and basic studies have yielded some mechanistic clues regarding pathogenesis. Recent insights gained through the use of microarrays have revealed distinctive subsets of SSc within and beyond the limited and diffuse subsets. In this review, we discuss potential mechanisms underlying the vascular, autoimmune, and fibrotic points of dysregulation. Proper categorization of SSc patients for research studies by use of microarrays or other biomarkers is critical, as disease heterogeneity may explain some of the inconsistencies of prior studies.

dsRNA activation of endothelin-1 and markers of vascular activation in endothelial cells and fibroblasts

BACKGROUND

In patients with systemic sclerosis (SSc), the relationship between innate immune activation, represented by increased expression of interferon (IFN)-regulated genes, and vascular injury/activation, manifest by increased endothelin-1 (ET-1), endothelin converting enzyme-1 (ECE1) and intercellular adhesion molecule-1, is uncertain.

OBJECTIVE

To investigate the potential roles of innate immune ligands in both these pathogenic pathways.

METHODS

The effect of known Toll-like receptor (TLR) ligands was tested in vitro on dermal microvascular and pulmonary arterial endothelial cells, and on dermal fibroblasts cultured from healthy controls and patients with SSc. To test the effect of double-stranded RNA (dsRNA) on vascular activation/injury in vivo, polyinosinic/polycytidylic acid (poly(I:C)) was administered continuously over 7 days by subcutaneous osmotic pump.

RESULTS

dsRNA/poly(I:C), but not other TLR ligands, highly stimulated ET-1 protein and mRNA (EDN1), as well as intercellular adhesion molecule-1 (ICAM-1) and IFN-regulated MX2, by endothelial cells and dermal fibroblasts. Poly(I:C) induced EDN1, ECE1, and ICAM-1 mRNA expression in poly(I:C) treated skin. Poly(I:C)-induced EDN1, ECE1 and MX2 was not blocked in mice with the type I IFN receptor deleted. However, poly(I:C)-induced EDN1 and ECE1, but not poly(I:C)-induced ICAM-1 expression was blocked in mice with the TLR3 signalling protein TRIF/TICAM-1 deleted.

CONCLUSION

Together these data show that the dsRNA can regulate genes associated with vascular activation, as seen in SSc, that type I IFNs do not mediate these effects, and that EDN1 and ECE1 but not ICAM-1 activation is mediated by TLR3.

Proteomic analysis identification of a pattern of shared alterations in the secretome of dermal fibroblasts from systemic sclerosis and nephrogenic systemic fibrosis

A proteomic analysis of the secretome of cultured dermal fibroblasts from patients with systemic sclerosis (SSc) and nephrogenic systemic fibrosis (NSF) was performed to identify proteins that reflect the fibrotic process. Confluent culture supernatants from three cell strains each of normal, SSc, and NSF dermal fibroblasts were pooled separately, and each pool was labeled with a specific fluorochrome. The three pools were electrophoresed together on two-dimension SDS gels, and protein differential expression was evaluated by quantitative fluorescence analysis. The secretome analysis identified 1694 spots per sample, among which 890 spots (52%) were differentially increased or decreased (more than twofold) in SSc fibroblasts, and 985 spots (58%) were differentially increased or decreased in NSF fibroblasts compared with normal fibroblasts. Mass spectrometry analysis was then used to identify the proteins that had increased by the greatest extent in both NSF and SSc secretomes. Three reticulocalbin family members were among the 10 most up-regulated proteins. Confocal microscopy results validated the differential increase of reticulocalbin-1 in affected SSc and NSF skin, and Western blot findings demonstrated its presence in SSc sera. The secretomes of both SSc and NSF fibroblasts display a pattern of shared changes compared with the normal fibroblast secretome. The differentially increased proteins reflect an activated fibroblast phenotype and may represent a specific "fibrosis signature" that can be used as a biomarker for fibrotic diseases.

Poly(I:C) drives type I IFN- and TGFβ-mediated inflammation and dermal fibrosis simulating altered gene expression in systemic sclerosis

Immune activation of fibrosis likely has a crucial role in the pathogenesis of systemic sclerosis (SSc). The aim of this study was to better understand the innate immune regulation and associated IFN- and transforming growth factor-β (TGFβ)-responsive gene expression in SSc skin and dermal fibroblasts, in particular the effect of different Toll-like receptor (TLR) ligands. To better understand the relationship between inflammation and fibrosis in vivo, we developed a murine model for chronic innate immune stimulation. We found that expression of both IFN- and TGFβ-responsive genes is increased in SSc skin and SSc fibroblasts when stimulated by TLR ligands. In contrast, cutaneous lupus skin showed much more highly upregulated IFN-responsive and much less highly upregulated TGFβ-responsive gene expression. Of the TLRs ligands tested, the TLR3 ligand, polyinosinic/polycytidylic acid (Poly(I:C)), most highly increased fibroblast expression of both IFN- and TGFβ-responsive genes as well as TLR3. Chronic subcutaneous immune stimulation by Poly(I:C) stimulated inflammation, and IFN- and TGFβ-responsive gene expression. However, in this model, type I IFNs had no apparent role in regulating TGFβ activity in the skin. These results suggest that TLR agonists may be important stimuli of dermal fibrosis, which is potentially mediated by TLR3 or other innate immune receptors.