Systemic sclerosis (SSc)-related interstitial lung disease (ILD) has phenotypic similarities to lung involvement in idiopathic interstitial pneumonia (IIP). We aimed to assess whether genetic susceptibility loci recently identified in the large IIP genome-wide association studies (GWASs) were also risk loci for SSc overall or severity of ILD in SSc.
A total of 2571 SSc patients and 4500 healthy controls were investigated from the US discovery GWAS and additional US replication cohorts. Thirteen IIP-related selected single nucleotide polymorphisms (SNPs) were genotyped and analyzed for their association with SSc.
We found an association of SSc with the SNP rs6793295 in the LRRC34 gene (OR = 1.14, CI 95 % 1.03 to 1.25, p value = 0.009) and rs11191865 in the OBFC1 gene (OR = 1.09, CI 95 % 1.00 to 1.19, p value = 0.043) in the discovery cohort. Additionally, rs7934606 in MUC2 (OR = 1.24, CI 95 % 1.01 to 1.52, p value = 0.037) was associated with SSc-ILD defined by imaging. However, these associations failed to replicate in the validation cohort. Furthermore, SNPs rs2076295 in DSP (β = -2.29, CI 95 % -3.85 to -0.74, p value = 0.004) rs17690703 in SPPL2C (β = 2.04, CI 95 % 0.21 to 3.88, p value = 0.029) and rs1981997 in MAPT (β = 2.26, CI 95 % 0.35 to 4.17, p value = 0.02) were associated with percent predicted forced vital capacity (FVC%) even after adjusting for the anti-topoisomerase (ATA)-positive subset. However, these associations also did not replicate in the validation cohort.
Our results add new evidence that SSc and SSc-related ILD are genetically distinct from IIP, although they share phenotypic similarities.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-016-0923-3) contains supplementary material, which is available to authorized users.
Idiopathic interstitial pneumonia (IIP); SSc-ILD; Genetic susceptibility
HLA-B*35 is associated with increased risk of developing pulmonary hypertension in SSc patients. We previously reported that HLA-B*35 induces endothelial cell dysfunction via activation of ER stress/UPR and upregulation of the inflammatory response. Because PBMCs from lcSSc-PAH patients are also characterized by activation of ER stress/UPR and inflammation, the goal of this study was to assess whether the presence of HLA-B*35 contributes to those characteristics.
PBMCs were purified from healthy controls (n = 49 HC) and lcSSc patients, (n = 44 with PAH, n = 53 without PAH). PBMCs from each group were stratified for the presence of HLA-B*35. Global changes in gene expression in response to HLA-B*35, HLA-B*8 or empty lentivirus were investigated by microarray analysis in HC PBMCs. Total RNA was extracted and qPCR was performed to measure gene expression.
ER stress markers, in particular the chaperones BiP and DNAJB1 were significantly elevated in PBMC samples carrying the HLA-B*35 allele. IL-6 expression was also significantly increased in HLA-B*35 lcSSc PBMCs and positively correlated with ER stress markers. Likewise, HMGB1 was increased in HLA-B*35-positive lcSSc PBMCs. Global gene expression analysis was used to further probe the role of HLA-B*35. Among genes downregulated by HLA-B*35 lentivirus were genes related to complement (C1QB, C1QC), cell cycle (CDNK1A) and apoptosis (Bax, Gadd45). Interestingly, complement genes (C1QC and C1QB) showed elevated expression in lcSSc without PAH, but were expressed at the low levels in lcSSc-PAH. The presence of HLA-B*35 correlated with the decreased expression of the complement genes. Furthermore, HLA-B*35 correlated with decreased expression of cyclin inhibitors (p21, p57) and pro-apoptotic genes (Bax, Gadd45) in lcSSc B35 subjects. FYN, a tyrosine kinase involved in proliferation of immune cells, was among the genes that were positively regulated by HLA-B*35. HLA-B*35 correlated with increased levels of FYN in lcSSc PBMCs.
Our study demonstrates that HLA-B*35 contributes to the dysregulated expression of selected ER stress, inflammation and proliferation related genes in lcSSc patient PBMCs, as well as healthy individuals, thus supporting a pathogenic role of HLA-B*35 in the development of PAH in SSc patients.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0881-1) contains supplementary material, which is available to authorized users.
HLA-B*35; ER stress; Inflammation; Proliferation; Scleroderma; PBMCs
To report population based percentile reference values for selected spinal mobility measures in a nationally representative sample of 5103 U.S. adults ages 20–69 years examined in the 2009–10 U.S. National Health and Nutrition Examination Survey (NHANES).
Occiput-to-Wall Distance (OWD), Thoracic Expansion (TE), and Anterior Lumbar Flexion (ALF – modified Schober test) were measured by trained examiners in a standardized fashion. TE was measured at the xyphosternal level while the lower reference point for ALF was a line marked at the level of the superior margin of the lateral iliac crests. We report reference values based on the 95th percentile of OWD and 5th percentile of TE and ALF measurements, as well as other summary statistics for these measures in the study population.
An OWD of more than zero was present in 3.8 % of participants while 8.8% of participants had out of range values for TE based the commonly used threshold of 2.5 cm. The 95th percentile of OWD measurement was zero while the 5th percentile measurements for TE and ALF were 1.9 and 2 cm, respectively. The spinal measures were significantly associated with gender, age, ethnicity, height, and body mass index. Exclusion of individuals with severe obesity (BMI > 35) changed the proposed reference values for TE and ALF to 2.2 and 1.9 cm, respectively.
We verified the reference value of zero for OWD. Using the reported population based percentile values, new reference values for TE and the ALF can be derived.
Signs and symptoms of arrhythmias or conduction defects are frequently reported in patients with SSc. These rhythm disorders may have several origins (i.e. related to primary heart involvement, pericardial disease, valvular regurgitation or pulmonary arterial hypertension) and may negatively affect the overall prognosis of these patients. It is therefore important to identify patients at high risk for cardiac arrhythmias with a complete cardiological evaluation and to identify the underlying heart disease, including SSc-related myocardial involvement. In addition, some therapeutic options in SSc patients may differ from those recommended in other populations.
systemic sclerosis; arrhythmias; conduction defects; cardiac involvement; mortality
Diffuse systemic sclerosis is associated with high mortality; however, the pathogenesis of cardiac death in these patients is not clear.
A 56-year-old Caucasian female patient presented with dyspnea and requested to donate her body to science in order to improve understanding of diffuse systemic sclerosis pathogenesis. She had extensive testing for dyspnea including pulmonary function tests, an echocardiogram, cardiac magnetic resonance imaging, and right heart catheterization to characterize her condition. Her case highlights the morbidity seen in this disease, including the presence of extensive skin thickening, digital ulcerations, and scleroderma renal crisis.
In this case report, we present the finding of cardiac tissue metabolomics, which may indicate a problem with vasodilation as a contributor to cardiac death in diffuse systemic sclerosis. The use of autopsy and tissue metabolomics in rare disease may help clarify disease pathogenesis.
Autopsy; Metabolomics; Scleroderma; Systemic sclerosis
Despite being a common problem in Systemic Sclerosis (SSc), the extant literature on pain has primarily focused on biomedical correlates, or bivariate relationships with a few psychological characteristics. There is a need to investigate the more heuristic biopsychosocial model, which incorporates the simultaneous contributions of medical, psychological, and social variables in understanding pain.
Patients with SSc (N = 333) received clinical exams and completed self-report surveys at enrollment to the Genetics versus ENvironment In Scleroderma Outcome Study (GENISOS). Latent profile analysis was used to derive biopsychosocial profiles of patients using skin thickening, percent predicted forced vital lung capacity, perceived physical health, health worry, mental health, and social support. The profiles were examined in relation to pain and pain medication usage.
A 3-profile solution provided the best fit to the data. Based on the biopsychosocial indicators, the profiles were characterized as Managing (n = 217), Resilient (n = 86), and Distressed (n = 30). Between-group differences for pain emerged, with the Distressed group, whose disease was less severe than the Resilient group, reporting the highest pain and the greatest utilization of pain medication.
Clinicians should consider biopsychosocial characteristics as contributing factors to the experience of pain in patients with SSc. Patients who are similar to those in the Distressed profile may be at an increased risk for pain and would likely benefit from a referral to a behavioral health or other ancillary service provider for pain management, rather than relying solely on pharmacological therapies.
To evaluate whether the systemic sclerosis (SSc)-associated IRAK1 non-synonymous single-nucleotide polymorphism rs1059702 is responsible for the Xq28 association with SSc or whether there are other independent signals in the nearby methyl-CpG-binding protein 2 gene (MECP2).
We analysed a total of 3065 women with SSc and 2630 unaffected controls from five independent Caucasian cohorts. Four tag single-nucleotide polymorphisms of MECP2 (rs3027935, rs17435, rs5987201 and rs5945175) and the IRAK1 variant rs1059702 were genotyped using TaqMan predesigned assays. A meta-analysis including all cohorts was performed to test the overall effect of these Xq28 polymorphisms on SSc.
IRAK1 rs1059702 and MECP2 rs17435 were associated specifically with diffuse cutaneous SSc (PFDR=4.12×10−3, OR=1.27, 95% CI 1.09 to 1.47, and PFDR=5.26×10−4, OR=1.30, 95% CI 1.14 to 1.48, respectively), but conditional logistic regression analysis showed that the association of IRAK1 rs1059702 with this subtype was explained by that of MECP2 rs17435. On the other hand, IRAK1 rs1059702 was consistently associated with presence of pulmonary fibrosis (PF), because statistical significance was observed when comparing SSc patients PF+ versus controls (PFDR=0.039, OR=1.30, 95% CI 1.07 to 1.58) and SSc patients PF+ versus SSc patients PF− (p=0.025, OR=1.26, 95% CI 1.03 to 1.55).
Our data clearly suggest the existence of two independent signals within the Xq28 region, one located in IRAK1 related to PF and another in MECP2 related to diffuse cutaneous SSc, indicating that both genes may have an impact on the clinical outcome of the disease.
Purpose of review
The purpose of this study is to review recent hypothesis-driven studies that utilize global gene expression data for elucidating the molecular basis of systemic sclerosis (SSc) and its various clinical manifestations.
The longitudinal skin gene expression studies indicate that the previously identified molecular subsets are stable over time and might identify inherent subgroups of SSc patients. Skin transcript follow-up studies indicate that the Wnt/β-catenin pathway plays an important role in promotion of fibrogenesis in fibroblasts and preadipocytes. Furthermore, the transcript profile of sclerodermatous graft-versus-host disease (sclGVHD) mice resembles the skin transcriptomes of a subgroup of SSc patients with IL13/IL4-inducible skin signature wherein the profibrotic chemokine CCL2 plays a key role. The comparison of skin biopsies from SSc patients to skin lesions of patients with cutaneous lupus and dermatomyositis has provided valuable information about the interferon (IFN) signature in these autoimmune diseases. Furthermore, plasma IFN-inducible chemokines correlate with the IFN gene expression score in SSc patients, enabling researchers to examine this molecular signature in large SSc cohorts with serum or plasma collection.
Global gene expression profiling in skin and peripheral blood can contribute to a better understanding of SSc pathogenesis and identify novel biomarkers and therapeutic targets.
gene expression profiling; pathogenesis; systemic sclerosis
We undertook this hypothesis-generating study to identify skin transcripts correlating with severity of interstitial lung disease (ILD) in systemic sclerosis (SSc).
Skin biopsy samples from 59 patients enrolled in the Genetics versus Environment in Scleroderma Outcome Study (GENISOS) cohort or an open-label imatinib study (baseline visit) were examined by global gene expression analysis using Illumina HT-12 arrays. Skin transcripts correlating with concomitantly obtained forced vital capacity (FVC) values and the modified Rodnan skin thickness score (MRSS) were identified by quantitative trait analysis. Also, immunofluorescence staining for selected transcripts was performed in affected skin and lung tissue. Plasma levels of CCL2, soluble SELP, and soluble P-selectin glycoprotein ligand 1 (sPSGL-1) were examined in all patients enrolled in the GENISOS cohort (n = 266).
Eighty-two skin transcripts correlated significantly with FVC. This gene list distinguished patients with more severe ILD (FVC <70% predicted) in unsupervised hierarchical clustering analysis (P < 0.001). These genes included SELP, CCL2, and matrix metalloproteinase 3, which are involved in extravasation and adhesion of inflammatory cells. Among the FVC correlates, 8 genes (CCL2, HAPLN3, GPR4, ADCYAP1, WARS, CDC25B, PLP1, and STXBP6) also correlated with the MRSS. Immunofluorescence staining revealed that SELP and CCL2 were also overexpressed in affected skin and lung tissue from SSc patients compared to those from controls. Plasma levels of CCL2 and sPSGL-1 correlated with concomitantly obtained FVC values (r = −0.22, P = 0.001 and r = 0.17, P = 0.015, respectively). This relationship was independent of potential confounders (age, sex, ethnicity, smoking status, anti–topoisomerase I positivity, treatment with immunosuppressive agents, MRSS, disease type, and disease duration).
A limited number of skin transcripts including genes involved in extravasation and adhesion of inflammatory cells correlate with severity of ILD.
Systemic sclerosis (SSc) and systemic lupus erythematosus (SLE) are two archetypal systemic autoimmune diseases which have been shown to share multiple genetic susceptibility loci. In order to gain insight into the genetic basis of these diseases, we performed a pan-meta-analysis of two genome-wide association studies (GWASs) together with a replication stage including additional SSc and SLE cohorts. This increased the sample size to a total of 21 109 (6835 cases and 14 274 controls). We selected for replication 19 SNPs from the GWAS data. We were able to validate KIAA0319L (P = 3.31 × 10−11, OR = 1.49) as novel susceptibility loci for SSc and SLE. Furthermore, we also determined that the previously described SLE susceptibility loci PXK (P = 3.27 × 10−11, OR = 1.20) and JAZF1 (P = 1.11 × 10−8, OR = 1.13) are shared with SSc. Supporting these new discoveries, we observed that KIAA0319L was overexpressed in peripheral blood cells of SSc and SLE patients compared with healthy controls. With these, we add three (KIAA0319L, PXK and JAZF1) and one (KIAA0319L) new susceptibility loci for SSc and SLE, respectively, increasing significantly the knowledge of the genetic basis of autoimmunity.
Systemic sclerosis (SSc) is a chronic autoimmune disease clinically manifesting as progressive fibrosis of the skin and internal organs. Recent microarray studies demonstrated that cadherin 11 (Cad-11) expression is increased in the affected skin of patients with SSc. The purpose of this study was to examine our hypothesis that Cad-11 is a mediator of dermal fibrosis.
Biopsy samples of skin from SSc patients and healthy control subjects were used for real-time quantitative polymerase chain reaction analysis to assess Cad-11 expression and for immunohistochemistry to determine the expression pattern of Cad-11. To determine whether Cad-11 is a mediator of dermal fibrosis, Cad-11–deficient mice and anti–Cad-11 monoclonal antibodies (mAb) were used in the bleomycin-induced dermal fibrosis model. In vitro studies with dermal fibroblasts and bone marrow–derived macrophages were used to determine the mechanisms by which Cad-11 contributes to the development of tissue fibrosis.
Levels of messenger RNA for Cad-11 were increased in skin biopsy samples from patients with SSc and correlated with the modified Rodnan skin thickness scores. Cad-11 expression was localized to dermal fibroblasts and macrophages in SSc skin. Cad-11–knockout mice injected with bleomycin had markedly attenuated dermal fibrosis, as quantified by measurements of skin thickness, collagen levels, myofibroblast accumulation, and profibrotic gene expression, in lesional skin as compared to the skin of wild-type mice. In addition, anti–Cad-11 mAb decreased fibrosis at various time points in the bleomycin-induced dermal fibrosis model. In vitro studies demonstrated that Cad-11 regulated the production of transforming growth factor β (TGFβ) by macrophages and the migration of fibroblasts.
These data demonstrate that Cad-11 is a mediator of dermal fibrosis and TGFβ production and suggest that Cad-11 may be a therapeutic target in SSc.
Multiple alleles of the Human leukocyte antigen (HLA) DRB1 have been strongly associated with systemic sclerosis (SSc) and its clinical or serological subsets. However, the associations vary in different ethnic populations. To define SSc-risk and/or -protective alleles of HLA-DRB1 in Chinese population, we studied a Han Chinese cohort containing 585 patients with SSc and 458 gender-matched, unrelated controls. The HLA-DRB1 genotyping was performed with sequence-based typing method. Exact p-values were obtained (Fisher’s test) from 2×2 tables of allele frequency and disease status. The major SSc-risk allele subtypes of HLA-DRB1 are the DRB1*15∶02 and *16∶02 in this Chinese cohort. Particularly, DRB1*15∶02 was most significantly associated with anti-centromere autoantibodies (ACA) positive, and DRB1*16∶02 with anti-topoisomerase I autoantibodies (ATA) positive patients. On the other hand, DRB1*01∶01 and *04∶06 were strong SSc-protective alleles in Chinese, especially in patients who were ACA positive and had diffuse cutaneous SSc (dcSSc), respectively. In addition, DRB1*11 and *07∶01 also showed significant association with SSc as a risk for and protection from SSc, respectively, and which is consistent with the studies of Spanish, US Caucasian and Hispanic populations. DRB1*15 was associated with ATA positive Chinese SSc that is consistent with Black South African and Korean SSc. These findings of HLA-DRB1 alleles in association with Chinese SSc provide the growing knowledge of genetics of SSc, and indicate that the genetic heterogeneity among ethnicities may significantly impact the complex trait of SSc.
To examine the predictive significance of 2 pneumoproteins, surfactant protein D (SP-D) and CC-chemokine ligand 18 (CCL18), for the course of systemic sclerosis (SSc)-related interstitial lung disease.
The pneumoproteins were determined in the baseline plasma samples of 266 patients with early SSc enrolled in the GENISOS observational cohort. They also were measured in 83 followup patient samples. Pulmonary function tests were obtained annually. The primary outcome was decline in forced vital capacity (FVC percentage predicted) over time. The predictive significance for longterm change in FVC was investigated by a joint analysis of longitudinal measurements (sequentially obtained FVC percentage predicted) and survival data.
SP-D and CCL18 levels were both higher in patients with SSc than in matched controls (p < 0.001 and p = 0.015, respectively). Baseline SP-D levels correlated with lower concomitantly obtained FVC (r = −0.27, p < 0.001), but did not predict the short-term decline in FVC at 1 year followup visit or its longterm decline rate. CCL18 showed a significant correlation with steeper short-term decline in FVC (p = 0.049), but was not a predictor of its longterm decline rate. Similarly, a composite score of SP-D and CCL18 was a significant predictor of short-term decline in FVC but did not predict its longterm decline rate. Further, the longitudinal change in these 2 pneumoproteins did not correlate with the concomitant percentage change in FVC.
SP-D correlated with concomitantly obtained FVC, while CCL18 was a predictor of short-term decline in FVC. However, neither SP-D nor CCL18 was a longterm predictor of FVC course in patients with early SSc.
SYSTEMIC SCLEROSIS; SURFACTANT D
There are no identified clinical markers that reliably predict long-term progression of interstitial lung disease (ILD) in systemic sclerosis (SSc; scleroderma). Elevated C-reactive protein (CRP) levels have been reported in SSc patients. We examined the predictive significance of CRP level for long-term ILD progression in a large early SSc cohort.
First, the CRP levels were compared between baseline samples of 266 SSc patients enrolled in the Genetics Versus Environment in Scleroderma Outcome Study cohort and 97 unaffected matched controls. Subsequently, the correlation between CRP levels and concomitantly obtained markers of disease severity was assessed. Serially obtained % predicted forced vital capacity (FVC) was used to examine the long-term ILD progression. The predictive significance of CRP level was investigated by a joint analysis of longitudinal measurements (serial FVCs up to 13 years) and survival data. This approach allowed inclusion of all 1,016 FVC measurements and accounted for survival dependency.
We confirmed that baseline CRP levels were higher in SSc patients than controls. CRP levels were associated with absence of anticentromere antibodies and correlated with the concomitant severity of lung, skin, and joint involvement. More importantly, higher baseline CRP levels were associated with shorter survival (P < 0.001) and predicted the long-term decline in FVC independent of potential confounders (age at baseline, sex, ethnicity, disease type, current smoking, body mass index, topoisomerase status, and treatment with immunosuppressive agents) in the multivariable model (P = 0.006).
Baseline CRP levels are predictive of long-term ILD progression. CRP level might aid clinicians in identifying patients that require more intensive monitoring and treatment.
Illness behaviors (cognitive, affective, and behavioral reactions) among individuals with systemic sclerosis (SSc) are of clinical concern due to relationships between these behaviors and physical and mental-health quality of life such as pain and symptoms of depression. Self-report measures with good psychometric properties can aid in the accurate assessment of illness behavior. The Illness Behavior Questionnaire (IBQ) was designed to measure abnormal illness behaviors; however, despite its long-standing use, there is disagreement regarding its subscales. The goal of the present study was to evaluate the validity of the IBQ in a cohort of patients with SSc.
Patients with SSc (N = 278) completed the IBQ at enrollment to the Genetics versus ENvironment In Scleroderma Outcome Study (GENISOS). Structural validity of previously derived factor solutions was investigated using confirmatory factor analysis. Exploratory factor analysis was utilized to derive SSc-specific subscales.
None of the previously derived structural models were supported for SSc patients. Exploratory factor analysis supported a SSc-specific factor structure with 5 subscales. Validity analyses suggested that the subscales were generally independent of disease severity, but were correlated with other health outcomes (i.e., fatigue, pain, disability, social support, mental health).
The proposed subscales are recommended for use in SSc, and can be utilized to capture illness behavior that may be of clinical concern.
A recent genome-wide association study in European systemic sclerosis (SSc) patients identified three loci (PSORS1C1, TNIP1 and RHOB) as novel genetic risk factors for the disease. The aim of this study was to replicate the previously mentioned findings in a large multicentre independent SSc cohort of Caucasian ancestry.
4389 SSc patients and 7611 healthy controls from different European countries and the USA were included in the study. Six single nucleotide polymorphisms (SNP): rs342070, rs13021401 (RHOB), rs2233287, rs4958881, rs3792783 (TNIP1) and rs3130573 (PSORS1C1) were analysed. Overall significance was calculated by pooled analysis of all the cohorts. Haplotype analyses and conditional logistic regression analyses were carried out to explore further the genetic structure of the tested loci.
Pooled analyses of all the analysed SNPs in TNIP1 revealed significant association with the whole disease (rs2233287 pMH=1.94×10−4, OR 1.19; rs4958881 pMH=3.26×10−5, OR 1.19; rs3792783 pMH=2.16×10−4, OR 1.19). These associations were maintained in all the subgroups considered. PSORS1C1 comparison showed association with the complete set of patients and all the subsets except for the anti-centromere-positive patients. However, the association was dependent on different HLA class II alleles. The variants in the RHOB gene were not associated with SSc or any of its subsets.
These data confirmed the influence of TNIP1 on an increased susceptibility to SSc and reinforced this locus as a common autoimmunity risk factor.
Systemic sclerosis (SSc), or scleroderma, is a chronic multisystem autoimmune disorder characterised by thickening and fibrosis of the skin and by the involvement of internal organs such as the lungs, kidneys, gastrointestinal tract, and heart. Because there is no cure, feasibly-implemented and easily accessible evidence-based interventions to improve health-related quality of life (HRQoL) are needed. Due to a lack of evidence, however, specific recommendations have not been made regarding non-pharmacological interventions (e.g. behavioural/psychological, educational, physical/occupational therapy) to improve HRQoL in SSc. The Scleroderma Patient-centred Intervention Network (SPIN) was recently organised to address this gap. SPIN is comprised of patient representatives, clinicians, and researchers from Canada, the USA, and Europe. The goal of SPIN, as described in this article, is to develop, test, and disseminate a set of accessible interventions designed to complement standard care in order to improve HRQoL outcomes in SSc.
scleroderma; psychosocial; health-related quality of life; patient-centred care
A recent genome-wide association study (GWAS) comprising a French cohort of systemic sclerosis (SSc) reported several non-HLA single-nucleotide polymorphisms (SNPs) showing a nominal association in the discovery phase. We aimed to identify previously overlooked susceptibility variants by using a follow-up strategy.
Sixty-six non-HLA SNPs showing a P value <10-4 in the discovery phase of the French SSc GWAS were analyzed in the first step of this study, performing a meta-analysis that combined data from the two published SSc GWASs. A total of 2,921 SSc patients and 6,963 healthy controls were included in this first phase. Two SNPs, PPARG rs310746 and CHRNA9 rs6832151, were selected for genotyping in the replication cohort (1,068 SSc patients and 6,762 healthy controls) based on the results of the first step. Genotyping was performed by using TaqMan SNP genotyping assays.
We observed nominal associations for both PPARG rs310746 (PMH = 1.90 × 10-6, OR, 1.28) and CHRNA9 rs6832151 (PMH = 4.30 × 10-6, OR, 1.17) genetic variants with SSc in the first step of our study. In the replication phase, we observed a trend of association for PPARG rs310746 (P value = 0.066; OR, 1.17). The combined overall Mantel-Haenszel meta-analysis of all the cohorts included in the present study revealed that PPARG rs310746 remained associated with SSc with a nominal non-genome-wide significant P value (PMH = 5.00 × 10-7; OR, 1.25). No evidence of association was observed for CHRNA9 rs6832151 either in the replication phase or in the overall pooled analysis.
Our results suggest a role of PPARG gene in the development of SSc.
To measure interferon (IFN) inducible chemokines in plasma of patients with systemic sclerosis (SSc) and investigate their correlation with disease severity.
We examined the correlation of IFN-inducible chemokines, IFNγ-inducible protein-10 (IP-10/CXCL10), IFN-inducible T cell alpha chemoattractant (I-TAC/CXCL11), and monocyte chemoattractant protein-1 (MCP-1/CCL2) with the IFN gene expression signature. We generated an IFN-inducible chemokine score with the correlated chemokines, IP-10 and I-TAC and compared it in 266 SSc patients enrolled in the GENISOS cohort to that of 97 matched controls. Subsequently, the correlation between the baseline IFN-inducible chemokine score and markers of disease severity was assessed. Finally, the course of IFN-inducible chemokine score over time was examined.
The plasma IFN-inducible chemokine score correlated with the IFN gene expression signature and this score was higher in SSc patients. It also was associated with the absence of anti–RNA polymerase III antibodies, presence of anti–U1 ribonucleoprotein antibodies (RNP), but not with disease duration, type, or other autoantibodies. The chemokine scores correlated with concomitantly obtained muscle, skin and lung components of the Medsger Severity Index, as well as, FVC, DLco, creatine kinase. Its association with disease severity was independent of anti-RNP or other potential confounders (age, gender, ethnicity, disease duration, and treatment with immunosuppressive agents). Finally, there was not a significant change in the IFN-inducible chemokine score over time.
The IFN-inducible chemokine score is a stable serological marker of more severe subtype of SSc and may be useful for risk stratification regardless of disease type or duration.
Systemic sclerosis (SSc) is a complex disease involving multiple genetic factors. A recent genome-wide association study (GWAS) indicated that CD247 was strongly associated with SSc, which was subsequently confirmed in a SSc cohort of European population. However, genetic heterogeneity in different ethnic populations may significantly impact the complex trait of SSc. The studies herein aimed to examine whether the SSc-associated SNP rs2056626 of CD247 identified in Caucasian is also associated with Han Chinese SSc. A Han Chinese cohort consisting of 387 SSc patients and 523 healthy controls were examined in the studies. TaqMan assays were performed to examine the SNP. Exact p-values were obtained (Fisher’s test) from 2x2 tables of allele counts and disease status. The results showed that there was no association between rs2056626 of CD247 and SSc or any SSc subtypes of Han Chinese. The negative results are important in understanding genetics of SSc in different ethnic populations, which further suggest complex nature of genetics of SSc.
CD247; Chinese population; genetics; polymorphism/SNP; scleroderma systemic sclerosis/SSc.
To evaluate the prognostic significance of baseline electrocardiogram (ECG) abnormalities in a multiethnic cohort of patients with early systemic sclerosis (SSc) and to determine the serological, clinical, and echocardiogram correlates of ECG findings.
SSc patients with disease duration of≤5 years were enrolled in the GENISOS (Genetics versus Environment in Scleroderma Outcome Study) cohort. At the first visit, a standard 12 lead ECG was obtained along with demographic information, clinical data, and autoantibodies. The results of echocardiograms were also recorded. All ECGs were interpreted by a cardiologist unaware of the patients' clinical data.
Of 265 SSc patients with average disease duration at enrollment of 2.5 years, 140 (52.8%) had abnormal ECG findings. These findings were not associated with SSc disease type or autoantibody profile but were associated with more severe heart and lung involvement. A total of 75 patients (28.3%) died over a follow up time of 9.9 years. Complete right bundle branch block (± left anterior hemiblock) on ECG, present in 7 (2.6%) patients, predicted a higher risk of mortality (HR: 5.3; 95% CI: 2.1 to 13.4; p<0.001). The predictive significance of right bundle branch block was independent of age at enrollment, gender, ethnicity and risk factors for coronary artery disease.
ECG abnormalities are common in patients with early SSc and are associated with the severity of lung and heart involvement. Right bundle branch block is an independent predictor of mortality, and should be considered a marker of disease severity in SSc.