Genomic Risk Score impact on susceptibility to systemic sclerosis.

OBJECTIVES: Genomic Risk Scores (GRS) successfully demonstrated the ability of genetics to identify those individuals at high risk for complex traits including immune-mediated inflammatory diseases (IMIDs). We aimed to test the performance of GRS in the prediction of risk for systemic sclerosis (SSc) for the first time. METHODS: Allelic effects were obtained from the largest SSc Genome-Wide Association Study (GWAS) to date (9 095 SSc and 17 584 healthy controls with European ancestry). The best-fitting GRS was identified under the additive model in an independent cohort that comprised 400 patients with SSc and 571 controls. Additionally, GRS for clinical subtypes (limited cutaneous SSc and diffuse cutaneous SSc) and serological subtypes (anti-topoisomerase positive (ATA+) and anti-centromere positive (ACA+)) were generated. We combined the estimated GRS with demographic and immunological parameters in a multivariate generalised linear model. RESULTS: The best-fitting SSc GRS included 33 single nucleotide polymorphisms (SNPs) and discriminated between patients with SSc and controls (area under the receiver operating characteristic (ROC) curve (AUC)=0.673). Moreover, the GRS differentiated between SSc and other IMIDs, such as rheumatoid arthritis and Sjögren's syndrome. Finally, the combination of GRS with age and immune cell counts significantly increased the performance of the model (AUC=0.787). While the SSc GRS was not able to discriminate between ATA+ and ACA+ patients (AUC<0.5), the serological subtype GRS, which was based on the allelic effects observed for the comparison between ACA+ and ATA+ patients, reached an AUC=0.693. CONCLUSIONS: GRS was successfully implemented in SSc. The model discriminated between patients with SSc and controls or other IMIDs, confirming the potential of GRS to support early and differential diagnosis for SSc.

Relationship of Wnt pathway activity and organ involvement in scleroderma types.

OBJECTIVE: Scleroderma (SSc) is a chronic inflammatory autoimmune disease characterized by fibrosis in the skin and internal organs. In SSc, the heart, lung, kidney, gastrointestinal (GIS) system, muscle, and peri-articular structures are damaged. There is no study of the relationship between SSc type, stage, pathogenesis, organ involvement, and Wnt signaling. In this study, we aimed to show the relationship of the Wnt gene family and antagonists in SSc subtypes and different organ involvement. METHODS: Eighty-five SSc patients and 77 controls were included in this study. The gene expressions and protein levels of the Wnt family and antagonists were analyzed from blood samples. The relationship between these parameters and disease stage, type, and organ involvement were evaluated. RESULTS: Wnt-1, Wnt-10b, Wnt-2, and Wnt-6 gene expressions are increased and Axin-2, DKK-1, and Kremen protein expressions are decreased in SSc. Wnt-3a and Wnt-10a gene expressions are increased in generalized SSc compared to limited SSc. Wnt-1, Wnt-2 gene expressions are increased significantly in pulmonary arterial hypertension (PAH)(+) SSc compared to PAH(-) SSc. There was a positive correlation between the modified Rodnan skin score and Wnt-2 in SSc. There was a significant positive correlation between GIS involvement score and Wnt-1, Wnt-2, Wnt-4, Wnt-8a, Wnt-9b in SSc. CONCLUSION: Wnt-1 and Wnt-2 were found higher in scleroderma and organ involvement. They may play a role in the pathogenesis of the disease.

The Roles of IL-1 Family Cytokines in the Pathogenesis of Systemic Sclerosis.

The IL-1 family consists of 11 cytokines, 7 ligands with agonist activity (IL-1α, IL-1ß, IL-18, IL-33, IL-36α, IL-36ß, IL-36γ) and four members with antagonistic activities [IL-1 receptor antagonist (IL-1Ra), IL-36Ra, IL-37, IL-38]. Recent articles have described that most members of IL-1 family cytokines are involved in the process of innate and adaptive immunity as well as fibrosis in systemic sclerosis (SSc). IL-1 family gene polymorphisms, abnormal expression of IL-1 and its potential role in the fibrosis process have been explored in SSc. IL-33 and IL-18 have also been discussed in the recent years. IL-33 may contribute to the fibrosis of SSc, while IL-18 remains to be researched to confirm its role in fibrosis process. There is a lack of study on the pathophysiological roles of IL-36, IL-37, and IL-38 in SSc, which might provide us new study area. Here, we aim to give a brief overview of IL-1 family cytokines and discuss their pivotal roles in the pathogenesis of SSc.

IRF7 gene expression profile and methylation of its promoter region in patients with systemic sclerosis.

OBJECTIVE: The aim of the current study was to evaluate if methylation status of CpG sites of interferon regulatory factor 7 (IRF7) promoter in peripheral blood mononuclear cells (PBMCs) of systemic sclerosis (SSc) patients is involved in pathogenesis of the disease. METHODS: PBMCs were isolated from whole blood of 50 SSc patients and 30 controls. After the extraction of total RNA and DNA contents from PBMCs, complementary DNA (cDNA) was synthesized. Afterwards, quantitative analysis of IRF7 messenger RNA (mRNA) was conducted by real-time polymerase chain reaction (PCR). To evaluate the methylation status of the promoter region of IRF7 gene, PCR products of bisulfite-treated DNA from SSc patients and controls were sequenced. RESULTS: The mRNA expression of IRF7 in PBMCs from patients compared with controls was significantly upregulated. While limited cutaneous SSc patients expressed the mRNA of IRF7 higher than controls, the diffuse cutaneous SSc group did not demonstrate significantly increased expression in comparison to controls. Insignificant promoter hypomethylation of IRF7 was observed in SSc patients compared with the control group. However, CpG2 hypomethylation was significantly associated with increased SSc risk. Furthermore, overall promoter methylation and mRNA level of IRF7 were significantly correlated with each other. Nonetheless, none of them correlated with Rodnan score of SSc patients. There was significant difference in IRF7 mRNA expression between CpG8 methylated and unmethylated SSc patients. Moreover, the difference of methylation and expression was not significant between anti-nuclear antibody (ANA)-positive and ANA-negative SSc patients. CONCLUSIONS: It is suggested that hypomethylation of the IRF7 promoter might play a role in SSc pathogenesis, probably through promoting the IRF7 expression in PBMCs of patients with SSc.

Brief Report: Association of Elevated Adipsin Levels With Pulmonary Arterial Hypertension in Systemic Sclerosis.

OBJECTIVE: Adipose tissues secrete adipokines, peptides with potent effects modulating fibrosis, inflammation, and vascular homeostasis. Dysregulated adipose tissue biology and adipokine balance have recently been implicated in systemic sclerosis (SSc). This study was undertaken to determine whether altered circulating adipokine levels correlate with SSc disease subsets or clinical manifestations. METHODS: Multiplex assays were used to measure circulating adipokine levels in 198 patients with SSc and 33 healthy controls. Data were evaluated for correlations between serum adipokine levels and demographic and clinical features, including pulmonary arterial hypertension (PAH). To assess the relevance of adipsin, an adipokine involved in complement pathway activation, in SSc, we analyzed publicly available genetic and transcriptomic data. RESULTS: Levels of adiponectin and adipsin differed significantly between controls and patients. Adipsin was significantly elevated in patients with limited cutaneous SSc (odds ratio [OR] 28.3 [95% confidence interval (95% CI) 7.0-113.8]; P < 0.0001), and its levels were associated with serum autoantibody status, pulmonary function and cardiovascular parameters, and PAH (OR 3.3 [95% CI 1.3-8.7]; P = 0.02). Elevated adipsin was more strongly associated with PAH than B-type natriuretic peptide was. Moreover, in SSc patients, adipsin gene single-nucleotide polymorphisms were associated with PAH. Transcriptome data set analysis demonstrated elevated adipsin expression in patients with SSc-related PAH. CONCLUSION: We identify adipsin as a novel adipose tissue-derived marker of SSc-related PAH. Circulating adipsin levels might serve as predictive biomarkers in SSc. Mechanistically, adipsin might represent a pathogenic link between adipocyte dysfunction and complement pathway activation and play an important role in the pathogenesis of SSc-related PAH.

Increased messenger RNA levels of the mesenchymal cadherin-11 in the peripheral blood of systemic sclerosis patients correlate with diffuse skin involvement.

OBJECTIVES: Cadherin-11 is a cell-cell adhesion molecule also involved in cellular migration and invasion. Experimental studies implicated this molecule in inflammatory arthritis and fibrosing conditions. Moreover, cadherin-11 protein is hyper-expressed on fibroblasts and macrophages in the skin of systemic sclerosis (SSc) patients, whereas the respective mRNA levels correlate with skin thickness. Herein, we searched for possible cadherin-11 expression also in cells that circulate in SSc peripheral blood. METHODS: Cadherin-11 mRNA was quantified by real-time reverse transcription-polymerase chain reaction in 3 ml blood samples obtained from 71 SSc patients (aged 53±2 years, 65 women) and 35 control non-SSc patients with Raynaud's phenomenon. RESULTS: Cadherin-11 mRNA transcripts were detected in blood samples from 39% of patients with diffuse SSc, versus 16% of those with limited SSc, versus 6% and 16% of patients with idiopathic or associated with other connective tissue diseases Raynaud's phenomenon, respectively (p=0.049). Cadherin-11 mRNA levels in SSc patients were increased by 3.74-fold comparing to controls (p=0.036). By multivariate logistic regression analysis we found that diffuse skin involvement correlated, independently of age, gender, disease duration, lung involvement, digital ulcers, inflammatory indices or anti-Scl-70 autoantibody presence, with cadherin-11 mRNA positivity (p=0.028), but also with increased cadherin-11 mRNA levels (≥3-fold of non-SSc levels, p=0.011). CONCLUSIONS: Cadherin-11 may be hyper-expressed in the peripheral blood of diffuse SSc patients. Studies on the origin and possible pathogenic function of these circulating cells may shed light into the complex disease pathogenesis and further support the notion that cadherin-11 is a potential therapeutic target in SSc.

Serum levels, tissue expression and cellular secretion of macrophage migration inhibitory factor in limited and diffuse systemic sclerosis.

OBJECTIVES: To investigate serum levels, tissue/cellular expression of macrophage migration inhibitory factor (MIF) in patients with limited (lSSc) and diffuse (dSSc) systemic sclerosis. METHODS: 10 lSSc-patients, 10 dSSc-patients and 10 controls were enrolled. MIF serum levels were assayed by ELISA. MIF and its receptors CD74/CD44 were evaluated by immunohistochemistry on skin biopsies from patients with dSSc, lSSc (affected and not-affected skin) and controls. MIF levels were assessed (ELISA) in supernatants of healthy dermal microvascular endothelial cells (MVECs) and in control (CTR), non-affected SSc (NA) and affected (SSc) fibroblasts treated for 48 h with 10% control serum and 10% SSc-serum. MIF supernatant (ELISA) and mRNA (quantitative real-time PCR) levels were determined in SSc dermal fibroblasts and in control dermal fibroblasts untreated or stimulated at 6 h-24 h-48 h with bleomycin (50 mU/ml). RESULTS: Serum MIF was significantly higher in dSSc (18.7±4.1 ng/ml, p<0.001) and in lSSc (10.4±4.4 ng/ml, p<0.001) patients respect to controls (2.6±1.4 ng/ml). Enhanced MIF immunoreactivity was found in keratinocytes, fibroblasts, endothelium, sebaceous/sweat glands from lSSc/dSSc affected skin. Faint MIF immunoreactivity was found in control skin and not-affected skin of lSSc patients. No differences were found in CD74/CD44 receptors' analysis among control and dSSc/lSSc affected and non-affected skin. MVECs and fibroblasts (CTR, NA and SSc) produced significantly more MIF, when stimulated with SSc serum respect to control-serum (p<0.001). Finally, MIF mRNA levels significantly increased at 6h (p<0.001) and decreased at 48 h (p<0.001) in control fibroblasts treated with bleomycin compared to control untreated. Simultaneously, MIF supernatant protein levels increased after 48 h (p<0.01) in bleomycin-treated fibroblasts respect to untreated ones. CONCLUSIONS: These results suggest that MIF could be implicated in the pathogenesis of SSc, probably acting as protective factor against the SSc stressful conditions.

Alteration of circulating miRNAs in SSc: miR-30b regulates the expression of PDGF receptor ß.

OBJECTIVE: Although several miRNAs have been shown to regulate autoimmune pathogenesis by affecting lymphocyte function, the roles of miRNAs in the pathogenesis of SSc remain unclear. Therefore the purpose of this study was to identify miRNAs that play a role in the pathogenesis of SSc by quantitative PCR screening of serum miRNAs. METHODS: Ninety-five miRNAs that were predicted to target SSc-related genes [IL-4, TGF-ß, CTGF, PDGF-B, PDGF receptor (PDGFR) α/ß and COL1A2) by in silico analyses were selected. The expression of these miRNAs in sera of SSc patients and healthy controls was measured by quantitative PCR. Involvement of miR-30b, which was most strongly down-regulated in SSc patients, in the regulation of PDGFR-ß expression was examined by transfection experiments and 3'-untranslated region (3'-UTR) target luciferase assays. The expression of miR-30b in skin was evaluated in a bleomycin-induced dermal fibrosis model in mice and in SSc patients. RESULTS: Nineteen of 95 miRNAs were significantly decreased in the sera of SSc patients. Among them, miR-30b was most strongly down-regulated in SSc patients (P = 0.00006) and the levels of miR-30b were inversely correlated with modified Rodnan skin scores. Transfection of a miR-30b mimic repressed PDGFR-ß expression in dermal fibroblasts and the activity of a luciferase reporter containing 3'-UTR of PDGFR-ß. Moreover, the expression of miR-30b was down-regulated in bleomycin-treated sclerotic skin and in affected skin in SSc patients. CONCLUSION: Down-regulation of miR-30b might be involved in the pathogenesis of SSc.

Increased expression of endoplasmic reticulum stress and unfolded protein response genes in peripheral blood mononuclear cells from patients with limited cutaneous systemic sclerosis and pulmonary arterial hypertension.

OBJECTIVE: Pulmonary arterial hypertension (PAH), a common complication of limited cutaneous systemic sclerosis (lcSSc), is associated with alterations of markers of inflammation and vascular damage in peripheral blood mononuclear cells (PBMCs). Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) have been implicated in autoimmune and inflammatory diseases. The goal of this study was to assess whether markers of ER stress and the UPR are present in PBMCs from lcSSc patients with PAH. METHODS: PBMCs were purified from 36 healthy controls, 32 lcSSc patients with PAH, and 34 lcSSc patients without PAH. Gene expression in healthy control PBMCs stimulated with thapsigargin was analyzed by DNA microarray. Genes were validated by quantitative real-time reverse transcription-polymerase chain reaction in PBMCs from healthy controls and lcSSc patients. RESULTS: Several ER stress/UPR genes, including BiP, activating transcription factor 4 (ATF-4), ATF-6, and a spliced form of X-box binding protein 1, were up-regulated in PBMCs from lcSSc patients, with the highest levels in patients with PAH. Thapsigargin up-regulated heat-shock proteins (HSPs) and interferon (IFN)-regulated genes in PBMCs from healthy controls. Selected HSP genes (particularly DnaJB1) and IFN-related genes were also found at significantly elevated levels in PBMCs from lcSSc patients, while IFN regulatory factor 4 expression was significantly decreased. There was a positive correlation between DnaJB1 and severity of PAH (measured by pulmonary artery pressure) (r = 0.56, P < 0.05) and between ER stress markers and interleukin-6 levels (r = 0.53, P < 0.0001) in PBMCs from lcSSc patients. CONCLUSION: This study demonstrates an association between select ER stress/UPR markers and lcSSc with PAH, suggesting that ER stress and the UPR may contribute to the altered function of circulating immune cells in lcSSc.

Implication of IL-2/IL-21 region in systemic sclerosis genetic susceptibility.

OBJECTIVE: The interleukin 2 (IL-2) and interleukin 21 (IL-21) locus at chromosome 4q27 has been associated with several autoimmune diseases, and both genes are related to immune system functions. The aim of this study was to evaluate the role of the IL-2/IL-21 locus in systemic sclerosis (SSc). PATIENTS AND METHODS: The case control study included 4493 SSc Caucasian patients and 5856 healthy controls from eight Caucasian populations (Spain, Germany, The Netherlands, USA, Italy, Sweden, UK and Norway). Four single nucleotide polymorphisms (rs2069762, rs6822844, rs6835457 and rs907715) were genotyped using TaqMan allelic discrimination assays. RESULTS: We observed evidence of association of the rs6822844 and rs907715 variants with global SSc (pc=6.6E-4 and pc=7.2E-3, respectively). Similar statistically significant associations were observed for the limited cutaneous form of the disease. The conditional regression analysis suggested that the most likely genetic variation responsible for the association was the rs6822844 polymorphism. Consistently, the rs2069762A-rs6822844T-rs6835457G-rs907715T allelic combination showed evidence of association with SSc and limited cutaneous SSc subtype (pc=1.7E-03 and pc=8E-4, respectively). CONCLUSIONS: These results suggested that the IL-2/IL-21 locus influences the genetic susceptibility to SSc. Moreover, this study provided further support for the IL-2/IL-21 locus as a common genetic factor in autoimmune diseases.

Evaluation of a shared autoimmune disease-associated polymorphism of TRAF6 in systemic sclerosis and giant cell arteritis.

OBJECTIVE: We evaluated whether a single-nucleotide polymorphism (SNP) of the TRAF6 gene previously associated with systemic lupus erythematosus and rheumatoid arthritis may be a common risk factor for systemic sclerosis (SSc) and giant cell arteritis (GCA). METHODS: A total of 1185 patients with SSc, 479 patients with biopsy-proven GCA, and 1442 unrelated healthy controls of white Spanish origin were genotyped for the rs540386 variant using a specifically designed TaqMan(©) allele discrimination assay. RESULTS: No significant associations of this SNP with global SSc or GCA were found. This was also the case when the potential associations of the TRAF6 polymorphism with the main clinical phenotypes of the 2 diseases (e.g., limited cutaneous and diffuse cutaneous SSc, or presence of polymyalgia rheumatica and visual ischemic manifestations in GCA) were assessed. CONCLUSION: Our data do not support a role of the rs540386 TRAF6 variant as a key component of the genetic network underlying SSc and GCA.

Evidence that deletion at FCGR3B is a risk factor for systemic sclerosis.

There is increasing evidence that gene copy number (CN) variation influences clinical phenotype. The low-affinity Fc receptor 3B (FCGR3B) located in the FCGR gene cluster is a CN polymorphic gene involved in the recruitment of polymorphonuclear neutrophils to sites of inflammation and their activation. Given the genetic overlap between systemic lupus erythematosus and systemic sclerosis (SSc) and the strong evidence for FCGR3B CN in the pathology of SLE, we hypothesised that FCGR3B gene dosage influences susceptibility to SSc. We obtained FCGR3B deletion status in 777 European Caucasian cases and 1000 controls. There was an inverse relationship between FCGR3B CN and disease susceptibility. CN of ≤ 1 was a significant risk factor for SSc (OR=1.55 (1.13-2.14), P=0.007) relative to CN ≥ 2. Although requiring replication, these results suggest that impaired immune complex clearance arising from FCGR3B deficiency contributes to the pathology of SSc, and FCGR3B CN variation is a common risk factor for systemic autoimmunity.

MicroRNA expression abnormalities in limited cutaneous scleroderma and diffuse cutaneous scleroderma.

Scleroderma (systemic sclerosis, SSc) is a complex autoimmune disease caused by progressive fibrotic replacement of normal tissue architecture, a progressive and ultimately fatal process that currently has no cure. Although dysregulation of microRNAs (miRNAs) is known to be involved in a variety of pathophysiologic processes, the role of miRNAs in SSc is unclear. In comparison with the normal skin tissues, miRNAs were aberrantly expressed in limited cutaneous scleroderma and diffuse cutaneous scleroderma skin tissues. We also identified miRNAs whose expressions were correlated with SSc fibrosis: miR-21, miR-31, miR-146, miR-503, miR-145, and miR-29b were predicted to be involved. This study further confirmed that miR-21 was increased whereas miR-145 and miR-29b were decreased both in the skin tissues and fibroblasts. As predicted target genes, SMAD7, SAMD3, and COL1A1 were regulated by these miRNAs. After stimulation with transforming growth factor ß, the expression of miR-21 was increased and that of SMAD7 mRNA was decreased. MiR-145 was upregulated whereas the mRNA level of SMAD3 was downregulated. The downregulation of miR-29b was correlated with the upregulation of COL1A1 mRNA. MiRNAs might play an important role in the pathogenesis of SSc and suggest a potential therapy.

Adiponectin expression is decreased in the involved skin and sera of diffuse cutaneous scleroderma patients.

In this study, we determined the adiponectin expression in the serum and lesional skin of patients with scleroderma (SSc). Serum adiponectin concentrations were measured in 32 patients with SSc, 10 patients with SLE, 12 patients with dermatomyositis patients and 13 healthy subjects with specific enzyme-linked immunosorbent assays. Adiponectin mRNA was determined in skin tissues of five patients with diffuse cutaneous SSc (dcSSc), seven patients with limited cutaneous SSc (lcSSc) and seven healthy subjects with real-time polymerase chain reaction. There was a significant reduction in serum adiponectin levels in patients with dcSSc. SSc patients with decreased serum adiponectin levels had higher total skin thickness score and higher incidence of pulmonary fibrosis. Adiponectin mRNA levels in skin tissues from patients with dcSSc were also reduced. Serum adiponectin levels may be a useful biomarker for fibrotic condition in patients with SSc. Clarifying the role of adiponectin in collagen diseases may lead to further understanding of the pathogenesis and new therapeutic approach.

Functional variants of Fc gamma receptor (FCGR2A) and FCGR3A are not associated with susceptibility to systemic sclerosis in a large European Study (EUSTAR).

OBJECTIVE: To investigate the possible role of FCGR2A 519A>G and FCGR3A 559A>C functional polymorphisms in the genetic predisposition to susceptibility to systemic sclerosis (SSc) or clinical phenotype. METHODS: A total of 1566 patients with SSc and 2271 geographically matched controls were included in our study. We analyzed the genotype and allele frequencies of the FCGR2A 519A>G and FCGR3A 559A>C functional variants in 6 independent European cohorts of white patients with SSc, and white controls. The cohorts comprised 165 Dutch patients with SSc and 1326 controls, 236 Spanish patients with SSc and 257 controls, 267 German patients with SSc and 270 controls, 202 Swedish patients with SSc and 261 controls, 416 Italian patients with SSc and 157 controls, and additionally 280 English patients with SSc. Genotyping was performed using Taqman 5' allelic discrimination assay. The study reached a 99% power to detect the effect of a polymorphism at an OR of 1.3. RESULTS: Neither FCGR2A 519A>G nor FCGR3A 559A>C was significantly associated with susceptibility to SSc. We did not find an association with specific disease phenotypes, limited or diffuse cutaneous involvement, autoantibody profiles, or pulmonary involvement. CONCLUSION: Our study strongly suggests the lack of a role for the FCGR2A 519A>G and FCGR3A 559A>C polymorphisms in SSc susceptibility or clinical phenotype in 6 independent European cohorts.