Genetics, Epigenetics, and Genomics of Systemic Sclerosis

Clinical features of pulmonary arterial hypertension associated with systemic sclerosis

Systemic sclerosis is an autoimmune disorder of the connective tissue characterized by disordered inflammation and fibrosis leading to skin thickening and visceral organ complications. Pulmonary involvement, in the form of pulmonary arterial hypertension and/or interstitial lung disease, is the leading cause of morbidity and mortality among individuals with scleroderma. There are no disease-specific therapies for pulmonary involvement of scleroderma, and pulmonary arterial hypertension in this cohort has typically been associated with worse outcomes and less clinical response to modern therapy compared to other forms of Group I pulmonary hypertension in the classification from the World Symposium on Pulmonary Hypertension. Ongoing research aims to delineate how pathologic microvascular remodeling and fibrosis contribute to this poor response and offer a window into future therapeutic targets.

Target organ expression and biomarker characterization of chemokine CCL21 in systemic sclerosis associated pulmonary arterial hypertension

Introduction

Systemic sclerosis (SSc) is a heterogenous disorder that appears to result from interplay between vascular pathologies, tissue fibrosis and immune processes, with evidence for deregulation of chemokines, which normally control immune trafficking. We recently identified altered levels of chemokine CCL21 in SSc associated pulmonary arterial hypertension (PAH). Here, we aimed to define target organ expression and biomarker characteristics of CCL21.

Materials and methods

To investigate target organ expression of CCL21, we performed immunohistochemistry (IHC) on explanted lung tissues from SSc-PAH patients. We assessed serum levels of CCL21 by ELISA and Luminex in two well-characterized SSc cohorts from Oslo (OUH, n=552) and Zurich (n=93) University hospitals and in 168 healthy controls. For detection of anti-CCl21 antibodies, we performed protein array analysis applying serum samples from SSc patients (n=300) and healthy controls. To characterize circulating CCL21 in SSc, we applied immunoprecipitation (IP) with antibodies detecting both full length and tailless and a custom-made antibody detecting only the C-terminal of CCL21. IP products were analyzed by SDS-PAGE/western blot and Mass spectrometry (MS).

Results

By IHC, we found that CCL21 was mainly expressed in the airway epithelial cells of SSc patients with PAH. In the analysis of serum levels of CCL21 we found weak correlation between Luminex and ELISA (r=0.515, p<0.001). Serum levels of anti-CCL21 antibodies were higher in SSc patients than in healthy controls (p<0.001), but only 5% of the SSc population were positive for anti-CCL21 antibodies in SSc, and we found no correlation between anti-CCl21 and serum levels of CCL21. By MS, we only identified peptides located within amino acid (aa) 23-102 of CCL21, indicating that CCL21 in SSc circulate as a truncated protein without the C-terminal tail.

Conclusion

This study demonstrates expression of CCL21 in epithelial lung tissue from SSc patients with PAH, and indicate that CCL21 in SSc circulates as a truncated protein. We extend previous observations indicating biomarker potential of CCL21, but find that Luminex is not suitable as platform for biomarker analyses. Finally, in vivo generated anti-CCL21 antibodies exist in SSc, but do not appear to modify serum CCL21 levels in patients with SSc-PAH.

Novel Concepts in Systemic Sclerosis Pathogenesis: Role for miRNAs

Systemic sclerosis (SSc) is a rare connective tissue disease with heterogeneous clinical phenotypes. It is characterized by the pathogenic triad: microangiopathy, immune dysfunction, and fibrosis. Epigenetic mechanisms modulate gene expression without interfering with the DNA sequence. Epigenetic marks may be reversible and their differential response to external stimuli could explain the protean clinical manifestations of SSc while offering the opportunity of targeted drug development. Small, non-coding RNA sequences (miRNAs) have demonstrated complex interactions between vasculature, immune activation, and extracellular matrices. Distinct miRNA profiles were identified in SSc skin specimens and blood samples containing a wide variety of dysregulated miRNAs. Their target genes are mainly involved in profibrotic pathways, but new lines of evidence also confirm their participation in impaired angiogenesis and aberrant immune responses. Research approaches focusing on earlier stages of the disease and on differential miRNA expression in various tissues could bring novel insights into SSc pathogenesis and validate the clinical utility of miRNAs as biomarkers and therapeutic targets.

Non-Coding RNA in Systemic Sclerosis: A Valuable Tool for Translational and Personalized Medicine

Epigenetic factors are heritable and ultimately play a role in modulating gene expression and, thus, in regulating cell functions. Non-coding RNAs have growing recognition as novel biomarkers and crucial regulators of pathological conditions in humans. Their characteristic feature is being transcribed in a tissue-specific pattern. Now, there is emerging evidence that lncRNAs have been identified to be involved in the differentiation of human skin, wound healing, fibrosis, inflammation, and immunological response. Systemic sclerosis (SSc) is a heterogeneous autoimmune disease characterized by fibrosis, vascular abnormalities, and immune system activation. The pathogenesis remains elusive, but clinical manifestations reveal autoimmunity with the presence of specific autoantibodies, activation of innate and adaptive immunity, vascular changes, and active deposition of extracellular matrix components leading to fibrosis. The use of multi-omics studies, including NGS, RNA-seq, or GWAS, has proposed that the non-coding genome may be a significant player in its pathogenesis. Moreover, it may unravel new therapeutic targets in the future. The aim of this review is to show the pathogenic role of long non-coding RNAs in systemic sclerosis. Investigation of these transcripts' functions has the potential to elucidate the molecular pathology of SSc and provide new opportunities for drug-targeted therapy for this disorder.

Idiopathic pulmonary fibrosis and systemic sclerosis: pathogenic mechanisms and therapeutic interventions

Fibrotic diseases take a very heavy toll in terms of morbidity and mortality equal to or even greater than that caused by metastatic cancer. In this review, we examine the pathogenesis of fibrotic diseases, mainly addressing triggers for induction, processes that lead to progression, therapies and therapeutic trials. For the most part, we have focused on two fibrotic diseases with lung involvement, idiopathic pulmonary fibrosis, in which the contribution of inflammatory mechanisms may be secondary to non-immune triggers, and systemic sclerosis in which the contribution of adaptive immunity may be predominant.

Association of Lymphangiogenic Factors With Pulmonary Arterial Hypertension in Systemic Sclerosis

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a major complication in systemic sclerosis (SSc), a disease marked by vascular and lymphatic vessel abnormalities. This study was undertaken to assess the role of the lymphangiogenic factors vascular endothelial growth factor C (VEGF-C) and angiopoietin 2 (Ang-2) and the soluble forms of their respective cognate receptors, soluble VEGF receptor 3 (sVEGFR-3) and soluble TIE-2, in patients with SSc, and to evaluate their predictive ability as markers for PAH development in SSc.

METHODS

In this cohort study, we used multiplex bead assays to assess serum levels of lymphangiogenic factors in 2 well-characterized SSc cohorts: an unselected identification cohort of SSc patients from Oslo University Hospital (n = 371), and a PAH-enriched validation cohort of SSc patients from Zurich University Hospital and Oslo University Hospital (n = 149). As controls for the identification and validation cohorts, we obtained serum samples from 100 healthy individuals and 68 healthy individuals, respectively. Patients in whom SSc-related PAH was identified by right-sided heart catheterization (RHC) in both cohorts were studied in prediction analyses. PAH was defined according to the European Society of Cardiology/European Respiratory Society 2015 guidelines for the diagnosis and treatment of PAH. Associations of serum levels of lymphangiogenic factors with the risk of PAH development were assessed in logistic regression and Cox regression analyses. Associations in Cox regression analyses were expressed as the hazard ratio (HR) with 95% confidence interval (95% CI).

RESULTS

In the identification cohort, SSc patients had lower mean serum levels of VEGF-C and higher mean serum levels of Ang-2 compared to healthy controls (for VEGF-C, mean ± SD 2.1 ± 0.5 ng/ml in patients versus 2.5 ± 0.4 ng/ml in controls; for Ang-2, mean ± SD 6.1 ± 7.6 ng/ml in patients versus 2.8 ± 1.8 ng/ml in controls; each P < 0.001); these same trends were observed in SSc patients with PAH compared to those without PAH. The association of serum VEGF-C levels with SSc-PAH was confirmed in the PAH-enriched RHC validation cohort. For prediction analyses, we assembled all 251 cases of SSc-PAH identified by RHC from the identification and validation cohorts. In multivariable Cox regression analyses adjusted for age and sex, the mean serum levels of VEGF-C and sVEGFR-3 were predictive of PAH development in patients with SSc (for VEGF-C, HR 0.53 [95% CI 0.29-0.97], P = 0.04; for sVEGFR-3, HR 1.21 [95% CI 1.01-1.45], P = 0.042).

CONCLUSION

These findings support the notion that lymphangiogenesis is deregulated during PAH development in SSc, and indicate that VEGF-C could be a promising marker for early PAH detection in patients with SSc.

Associated factors of early-onset pulmonary hypertension and clinical difference between early- and late-onset pulmonary hypertension in Thai systemic sclerosis

OBJECTIVES

Pulmonary hypertension (PH) is a major cause of death in systemic sclerosis (SSc). Detection of early-onset PH and its associated factors would be helpful for improving patient care. Our aims were to determine the factors associated with early-onset PH and to define the differences between early- and late-onset PH among SSc patients.

METHODS

A cohort study was conducted of 409 adult SSc patients who had followed-up between January 2014 and December 2016. Early-PH is defined when the onset of PH is diagnosed within 5 years of the disease. Logistic regression analysis was applied to determine the factors associated with early-PH.

RESULTS

In 3409 person-years, we diagnosed 50 cases with PH confirmation by right heart catheterization, of whom 26 were early-PH (incidence 0.7 per 100 person-years; 95%CI:0.5-1.1). Among SSc with early-PH, 69.2% had the diffuse cutaneous SSc subset and the most common PH classification was PH due to interstitial lung disease (18 cases;69.2%). According to a logistic regression analysis, early-PH was associated with a WHO functional class (WHO-FC) II and higher, cardiomegaly according to chest radiography, and tricuspid regurgitation jet maximum velocity (TRVmax)>2.8 m/s with the respective OR of 20.12 (95%CI:1.59-255.35), 7.42 (95%CI:1.35-40.88), and 8.20 (95%CI:1.17-57.64). To contrast, early-PH had a negative association with gastrointestinal involvement (OR 0.08; 95%CI:0.01-0.56).

CONCLUSIONS

Early-PH is prevalent among SSc patients and the most common cause is interstitial lung disease. A poor WHO-FC, cardiomegaly, and a high TRVmax are associated with early-PH. Gastrointestinal involvement is a protective factor for early-PH in SSc.

Genetics of systemic sclerosis

Systemic sclerosis is an autoimmune disease characterized by generalized fibrosis in connective tissues and internal organs as consequences of microvascular dysfunction and immune dysfunctions, which leads to premature death in affected individuals. The etiology of systemic sclerosis is complex and poorly understood, but as with most autoimmune diseases, it is widely accepted that both environmental and genetic factors contribute to disease risk. During the last decade, the number of genetic markers convincingly associated with systemic sclerosis has exponentially increased. In this article, we briefly mention the genetic components of systemic sclerosis. Then, we review the classical and novel genetic associations with systemic sclerosis, analyzing the firmest and replicated signals within non-human leukocyte antigen genes, identified by both candidate gene approach and genome-wide association studies. We also provide an insight into the future perspectives that will shed more light into the complex genetic background of the disease. Despite the remarkable advance of systemic sclerosis genetics during the last decade, the use of the new genetic technologies such as next-generation sequencing, as well as the deep phenotyping of the study cohorts, to fully characterize the genetic component of this disease is imperative to identify causal variants, which leads to more targeted and effective treatment of systemic sclerosis.

The contribution of epigenetics to the pathogenesis and gender dimorphism of systemic sclerosis: a comprehensive overview

Systemic sclerosis (SSc) is a life-threatening connective tissue disorder of unknown etiology characterized by widespread vascular injury and dysfunction, impaired angiogenesis, immune dysregulation and progressive fibrosis of the skin and internal organs. Over the past few years, a new trend of investigations is increasingly reporting aberrant epigenetic modifications in genes related to the pathogenesis of SSc, suggesting that, besides genetics, epigenetics may play a pivotal role in disease development and clinical manifestations. Like many other autoimmune diseases, SSc presents a striking female predominance, and even if the reason for this gender imbalance has yet to be completely understood, it appears that the X chromosome, which contains many gender and immune-related genes, could play a role in such gender-biased prevalence. Besides a short summary of the genetic background of SSc, in this review we provide a comprehensive overview of the most recent insights into the epigenetic modifications which underlie the pathophysiology of SSc. A particular focus is given to genetic variations in genes located on the X chromosome as well as to the main X-linked epigenetic modifications that can influence SSc susceptibility and clinical phenotype. On the basis of the most recent advances, there is realistic hope that integrating epigenetic data with genomic, transcriptomic, proteomic and metabolomic analyses may provide in the future a better picture of their functional implications in SSc, paving the right way for a better understanding of disease pathogenesis and the development of innovative therapeutic approaches.

Epigenetic Control of Scleroderma: Current Knowledge and Future Perspectives

PURPOSE OF REVIEW

Epigenetics has been implicated in the pathogenesis of systemic sclerosis (SSc). In this review, the involvement of the three epigenetic mechanisms in SSc development and progression-DNA methylation, histone modifications, and non-coding RNAs-will be discussed.

RECENT FINDINGS

Alteration in epigenetics was observed in immune cells, dermal fibroblasts, and endothelial cells derived from SSc patients. Genes that are affected include those involved in immune cell function and differentiation, TGFβ and Wnt pathways, extracellular matrix accumulation, transcription factors, and angiogenesis. All the studies remain in the pre-clinical stage. Extensive research provides evidence that epigenetic alterations are critical for SSc pathogenesis. Future epigenomic studies will undoubtedly continue to broaden our understanding of disease pathogenesis and clinical heterogeneity. They will also provide the scientific basis for repurposing epigenetic-modifying agents for SSc patients.

Screening and identification of biomarkers for systemic sclerosis via microarray technology

Systemic sclerosis (SSc) is a complex autoimmune disease. The pathogenesis of SSc is currently unclear, although like other rheumatic diseases its pathogenesis is complicated. However, the ongoing development of bioinformatics technology has enabled new approaches to research this disease using microarray technology to screen and identify differentially expressed genes (DEGs) in the skin of patients with SSc compared with individuals with healthy skin. Publicly available data were downloaded from the Gene Expression Omnibus (GEO) database and intra-group data repeatability tests were conducted using Pearson's correlation test and principal component analysis. DEGs were identified using an online tool, GEO2R. Functional annotation of DEGs was performed using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Finally, the construction and analysis of the protein-protein interaction (PPI) network and identification and analysis of hub genes was carried out. A total of 106 DEGs were detected by the screening of SSc and healthy skin samples. A total of 10 genes [interleukin-6, bone morphogenetic protein 4, calumenin (CALU), clusterin, cysteine rich angiogenic inducer 61, serine protease 23, secretogranin II, suppressor of cytokine signaling 3, Toll-like receptor 4 (TLR4), tenascin C] were identified as hub genes with degrees ≥10, and which could sensitively and specifically predict SSc based on receiver operator characteristic curve analysis. GO and KEGG analysis showed that variations in hub genes were mainly enriched in positive regulation of nitric oxide biosynthetic processes, negative regulation of apoptotic processes, extracellular regions, extracellular spaces, cytokine activity, chemo-attractant activity, and the phosphoinositide 3 kinase-protein kinase B signaling pathway. In summary, bioinformatics techniques proved useful for the screening and identification of biomarkers of disease. A total of 106 DEGs and 10 hub genes were linked to SSc, in particular the TLR4 and CALU genes.

Human leukocyte antigen (HLA)-DRB1 allele polymorphisms and systemic sclerosis

Objectives: Human leukocyteantigen (HLA) is the most important gene for immune system regulation. Although studies have evaluated the association between HLA-DRB1 allele polymorphisms and systemic sclerosis (SSc), their results are still controversial. We performed a meta-analysis to assess the association of HLA-DRB1 alleles with risk of SSc.Methods: Electronic database were systematically searched for articles, a total of 11 case-control studies including 3268 cases and 5548 controls were analyzed. Odds ratio (ORs) and 95% confidence intervals were used to assess the association of HLA-DRB1 alleles with SSc. The relationship between SSc-related autoantibodies and DRB1 alleles was also analyzed.Results: In the overall analysis, four alleles (DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04) increased the risk of SSc; however, five alleles (DRB1*07, DRB1*11:01, DRB1*13, DRB1*13:01, and DRB1*14) had the opposite effect. Analysis of subgroups by ethnicity indicate that DRB1*11:01 and DRB1*13:01 confer a protective effect in Caucasians, while DRB1*11:04 was associated with a higher risk of SSc. For Asian, DRB1*13:02 was found to be a protective factor. In addition, the frequency of DRB1*11:04 alleles was significantly increased in ATA⁺ SSc patients compared with ATA^- SSc patients.Conclusion: DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04 were associated with the risk of SSc. Additionally, DRB1*11 and DRB1*11:04 were association with ATAs.

Paraneoplastic systemic sclerosis associated with colorectal carcinoma

A number of rheumatic disorders may appear as paraneoplastic syndromes, the most common being dermatomyositis or polymyositis. Systemic sclerosis is associated with a slightly increased risk of cancer, although its direct association with malignancies is controversial. We describe a case of a 57-year-old male with rectal adenocarcinoma and systemic sclerosis. Close temporal relationship between the initial presentation and parallel course of both conditions, as well as atypically rapid progression of systemic sclerosis symptoms, were observed in the reported case. The strict relation between these two conditions suggested that systemic sclerosis was a paraneoplastic syndrome rather than a concomitant morbidity in the presented patient. Current literature on systemic sclerosis coexisting with colorectal tumours is very limited, especially in the paraneoplastic setting.

Systemic sclerosis

Systemic sclerosis, also called scleroderma, is an immune-mediated rheumatic disease that is characterised by fibrosis of the skin and internal organs and vasculopathy. Although systemic sclerosis is uncommon, it has a high morbidity and mortality. Improved understanding of systemic sclerosis has allowed better management of the disease, including improved classification and more systematic assessment and follow-up. Additionally, treatments for specific complications have emerged and a growing evidence base supports the use of immune suppression for the treatment of skin and lung fibrosis. Some manifestations of the disease, such as scleroderma renal crisis, pulmonary arterial hypertension, digital ulceration, and gastro-oesophageal reflux, are now treatable. However, the burden of non-lethal complications associated with systemic sclerosis is substantial and is likely to become more of a challenge. Here, we review the clinical features of systemic sclerosis and describe the best practice approaches for its management. Furthermore, we identify future areas for development.

Expressions of p53 and PUMA in fibroblasts of systemic sclerosis patients are normal at transcription level

BACKGROUND

Systemic sclerosis (SSc) fibroblasts show resistance apoptosis mechanisms, which enhances the fibrosis stage of the disease. Impaired function of p53 upregulated modulator of apoptosis (PUMA) has been related to deficits in p53-dependant apoptosis pathway. This study aimed to evaluate the transcriptional levels of p53 and PUMA mRNAs in fibroblasts from SSc patients and compare it with healthy individuals.

METHODS

In this case-control study, skin biopsy samples were obtained from 19 patients with diffuse cutaneous SSc (DcSSc) and 16 healthy controls. Afterward, dermal fibroblasts were isolated and cultured. After extraction of total RNA from cultured fibroblasts, complementary DNA (cDNA) was synthesized. mRNA quantification was carried out using real-time PCR, SYBR Green PCR master mix, and specific primers for p53 and PUMA.

RESULTS

No significant alteration was observed in mRNA expression levels of p53 and PUMA (P = .99 and .23, respectively) in fibroblasts from SSc patients compared with controls.

CONCLUSIONS

Apoptosis pathways are impaired in fibroblasts from patients with SSc, leading to chronic fibrosis. Nonetheless, PUMA/p53 pathway may not be involved in dysfunction of apoptosis mechanisms in fibroblasts of patients with SSc.

Fresh Insights into Disease Etiology and the Role of Microbial Pathogens

Pathogens have been implicated in the initiation and/or promotion of systemic sclerosis (scleroderma, SSc); however, no evidence was found to substantiate the direct contribution to this disease in past years. Recently, significant advances have been made in understanding the role of the innate immune system in SSc pathogenesis, supporting the idea that pathogens might interact with host innate immune-regulatory responses in SSc. In light of these findings, we review the studies that identified the presence of pathogens in SSc, along with studies on pathogens implicated in driving the innate immune dysregulation in SSc. The goal of this review is to illustrate how these pathogens, specifically viruses, may play important role both as triggers of the innate immune system, and critical players in the development of SSc disease.

Current perspectives on the immunopathogenesis of systemic sclerosis

Systemic sclerosis (SSc or scleroderma) is a progressive and highly debilitating autoimmune disorder characterized by inflammation, vasculopathy, and extensive fibrosis. SSc is highly heterogeneous in its clinical presentation, extent and severity of skin and internal organ involvement, and clinical course and has the highest fatality rate among connective tissue diseases. While clinical outcomes have improved in recent years, no current therapy is able to reverse or slow the natural progression of SSc, a reflection of its complex pathogenesis. Although activation of the immune system has long been recognized, the mechanisms responsible for the initiation of autoimmunity and the role of immune effector pathways in the pathogenesis of SSc remain incompletely understood. This review summarizes recent progress in disease pathogenesis with particular focus on the immunopathogenetic mechanisms of SSc.

Treatment of Rapidly Progressive Systemic Sclerosis: Current and Futures Perspectives

INTRODUCTION

Systemic Sclerosis (SSc) is a systemic autoimmune disease characterized by severe and often progressive cutaneous, pulmonary, cardiac and gastrointestinal tract fibrosis, cellular and humoral immunologic alterations, and pronounced fibroproliferative vasculopathy. There is no effective SSc disease modifying therapy. Patients with rapidly progressive SSc have poor prognosis with frequent disability and very high mortality.

AREAS COVERED

This paper reviews currently available therapeutic approaches for rapidly progressive SSc and discuss novel drugs under study for SSc disease modification.

EXPERT OPINION

The extent, severity, and rate of progression of SSc skin and internal organ involvement determines the optimal therapeutic interventions for SSc. Cyclophosphamide for progressive SSc-associated interstitial lung disease and mycophenolate for rapidly progressive cutaneous involvement have shown effectiveness. Methotrexate has been used for less severe skin progression and for patients unable to tolerate mycophenolate. Rituximab was shown to induce improvement in SSc-cutaneous and lung involvement. Autologous bone marrow transplantation is reserved for selected cases in whom poor survival risk outweighs the high mortality rate of the procedure. Novel agents capable of modulating fibrotic and inflammatory pathways involved in SSc pathogenesis, including tocilizumab, pirfenidone, tyrosine kinase inhibitors, lipid lysophosphatidic acid 1, and NOX4 inhibitors are currently under development for the treatment of rapidly progressive SSc.