Epigenetic modifications: novel therapeutic strategies for systemic sclerosis?

Circulating Connective Tissue Growth Factor Is Associated with Diastolic Dysfunction in Patients with Diastolic Heart Failure

Background: Connective tissue growth factor (CTGF) and transforming growth factor β1 (TGF-β1) are emerging biomarkers for tissue fibrosis. The aim of this study was to investigate the association between circulating CTGF, TGF-β1 levels and cardiac diastolic dysfunction in patients with diastolic heart failure (DHF). Methods: Admitted subjects were screened for heart failure and those with left ventricular (LV) ejection fraction <45% were excluded. Diastolic dysfunction was defined as functional abnormalities that exist during LV relaxation and filling by echocardiographic criteria. Totally 114 patients with DHF and 72 controls were enrolled. Plasma levels of CTGF, TGF-β1, and B-type natriuretic peptide (BNP) were determined. Results: The plasma CTGF and TGF-β1 levels increased significantly in patients with DHF. Circulating CTGF and TGF-β1 levels were correlated with echocardiographic parameter E/e’ and diastolic dysfunction grading in DHF patients. In multivariate logistic analysis, CTGF was significantly associated with diastolic dysfunction (odds ratio: 1.027, p < 0.001). Plasma CTGF (AUC: 0.770 ± 0.036, p < 0.001) and CTGF/BNP (AUC: 0.839 ± 0.036, p < 0.001) showed good predictive power to the diagnosis of DHF. Conclusions: This finding suggested CTGF could be involved in the pathophysiology of diastolic heart failure and CTGF/BNP might have auxiliary diagnostic value on diastolic heart failure.

Current and upcoming therapies to modulate skin scarring and fibrosis

Skin is the largest organ of the human body. Being the interface between the body and the outer environment, makes it susceptible to physical injury. To maintain life, nature has endowed skin with a fast healing response that invariably ends in the formation of scar at the wounded dermal area. In many cases, skin remodelling may be impaired, leading to local hypertrophic scars or keloids. One should also consider that the scarring process is part of the wound healing response, which always starts with inflammation. Thus, scarring can also be induced in the dermis, in the absence of an actual wound, during chronic inflammatory processes. Considering the significant portion of the population that is subject to abnormal scarring, this review critically discusses the state-of-the-art and upcoming therapies in skin scarring and fibrosis.

Poly(ADP-ribose) polymerase-1 regulates fibroblast activation in systemic sclerosis

OBJECTIVES

The enzyme poly(ADP-ribose) polymerase-1 (PARP-1) transfers negatively charged ADP-ribose units to target proteins. This modification can have pronounced regulatory effects on target proteins. Recent studies showed that PARP-1 can poly(ADP-ribosyl)ate (PARylate) Smad proteins. However, the role of PARP-1 in the pathogenesis of systemic sclerosis (SSc) has not been investigated.

METHODS

The expression of PARP-1 was determined by quantitative PCR and immunohistochemistry. DNA methylation was analysed by methylated DNA immunoprecipitation assays. Transforming growth factor-β (TGFβ) signalling was assessed using reporter assays, chromatin immunoprecipitation assays and target gene analysis. The effect of PARP-1 inactivation was investigated in bleomycin-induced and topoisomerase-induced fibrosis as well as in tight-skin-1 (Tsk-1) mice.

RESULTS

The expression of PARP-1 was decreased in patients with SSc, particularly in fibroblasts. The promoter of PARP-1 was hypermethylated in SSc fibroblasts and in TGFβ-stimulated normal fibroblasts. Inhibition of DNA methyltransferases (DNMTs) reduced the promoter methylation and reactivated the expression of PARP-1. Inactivation of PARP-1 promoted accumulation of phosphorylated Smad3, enhanced Smad-dependent transcription and upregulated the expression of TGFβ/Smad target genes. Inhibition of PARP-1 enhanced the effect of TGFβ on collagen release and myofibroblast differentiation in vitro and exacerbated experimental fibrosis in vivo. PARP-1 deficiency induced a more severe fibrotic response to bleomycin with increased dermal thickening, hydroxyproline content and myofibroblast counts. Inhibition of PARylation also exacerbated fibrosis in Tsk-1 mice and in mice with topoisomerase-induced fibrosis.

CONCLUSION

PARP-1 negatively regulates canonical TGFβ signalling in experimental skin fibrosis. The downregulation of PARP-1 in SSc fibroblasts may thus directly contribute to hyperactive TGFβ signalling and to persistent fibroblast activation in SSc.

Copy Number Variation of HLA-DQA1 and APOBEC3A/3B Contribute to the Susceptibility of Systemic Sclerosis in the Chinese Han Population

OBJECTIVE

Systemic sclerosis (SSc) is a systemic connective tissue disease caused by a genetic aberrant. The involvement of the copy number variations (CNV) in the pathogenesis of SSc is unclear. We tried to identify some CNV that are involved with the susceptibility to SSc.

METHODS

A genome-wide CNV screening was performed in 20 patients with SSc. Five SSc-associated common CNV that included HLA-DRB5, HLA-DQA1, IRGM, CDC42EP3, and APOBEC3A/3B were identified from the screening and were then validated in 365 patients with SSc and 369 matched healthy controls.

RESULTS

Three hundred forty-four CNV (140 gains and 204 losses) and 2 CNV hotspots (6q21.3 and 22q11.2) were found in the SSc genomes (covering 24.2 megabases), suggesting that CNV were ubiquitous in the SSc genome and played important roles in the pathogenesis of SSc. The high copy number of HLA-DQA1 was a significantly protective factor for SSc (OR 0.07, p = 2.99 × 10(-17)), while the high copy number of APOBEC3A/B was a significant risk factor (OR 3.45, p = 6.4 × 10(-18)), adjusted with sex and age. The risk prediction model based on genetic factors in logistic regression showed moderate prediction ability, with area under the curve = 0.80 (95% CI 0.77-0.83), which demonstrated that APOBEC3A/B and HLA-DQA1 were powerful biomarkers for SSc risk evaluation and contributed to the susceptibility to SSc.

CONCLUSION

CNV of HLA-DQA1 and APOBEC3A/B contribute to the susceptibility to SSc in a Chinese Han population.

MicroRNAs Regulating Signaling Pathways: Potential Biomarkers in Systemic Sclerosis

Systemic sclerosis (SSc) is a multisystem fibrotic and autoimmune disease. Both genetic and epigenetic elements mediate SSc pathophysiology. This review summarizes the role of one epigenetic element, known as microRNAs (miRNAs), involved in different signaling pathways of SSc pathogenesis. The expression of key components in transforming growth factor-β (TGF-β) signaling pathway has been found to be regulated by miRNAs both upstream and downstream of TGF-β. We are specifically interested in the pathway components upstream of TGF-β, while miRNAs in other signaling pathways have not been extensively studied. The emerging role of miRNAs in vasculopathy of SSc suggests a promising new direction for future investigation. Elucidation of the regulatory role of miRNAs in the expression of signaling factors may facilitate the discovery of novel biomarkers in SSc and improve the understanding and treatment of this disease.

Epigenetic modifications in fibrotic diseases: implications for pathogenesis and pharmacological targets

Organ fibrosis is a complex and chronic disorder that results from a variety of acute injuries and contributes to thirty percent of naturally occurring deaths worldwide. The main feature of organ fibrosis is the excessive accumulation and deposit of extracellular matrix, thereby leading to organ dysfunction, loss of elasticity, and development of a rigid organ. Accumulating evidence shows that epigenetic remodeling, including aberrant DNA methylation and noncoding RNA expression as well as histone post-translational modifications, play important roles in the pathogenesis of fibrosis through the regulation of fibroblast activation, differentiation, and apoptosis, as well as collagen synthesis and profibrotic gene transcription. In this review, we discuss the basic regulation of DNA methylation, noncoding RNA expression, and histone post-translational modification, and their participation in the pathogenesis and development of organ fibrosis. This review also provides the latest insights into the novel biomarkers and therapeutic targets for fibrosis through modulation of epigenetic remodeling.

Potential of epigenetic therapies in non-cancerous conditions

There has been an explosion of knowledge in the epigenetics field in the past 20 years. The first epigenetic therapies have arrived in the clinic for cancer treatments. In contrast, much of the promise of epigenetic therapies for non-cancerous conditions remains in the laboratories. The current review will focus on the recent progress that has been made in understanding the pathogenic role of epigenetics in immune and inflammatory conditions, and how the knowledge may provide much needed new therapeutic targets for many autoimmune diseases. Dietary factors are increasingly recognized as potential modifiers of epigenetic marks that can influence health and diseases across generations. The current epigenomics revolution will almost certainly complement the explosion of personal genetics medicine to help guide treatment decisions and disease risk stratification.

Deciphering the pro-fibrotic phenotype of fibroblasts in systemic sclerosis

LeRoy's seminal work on the phenotypic features of scleroderma fibroblasts has been directing fibrosis research in the field of systemic sclerosis (SSc, scleroderma) for the past 30 years. His principal experiment, to culture skin fibroblasts from patients with SSc and study their pro-fibrotic phenotype in comparison with skin fibroblasts from healthy individuals, has been used by most basic and translational fibrosis studies in SSc. LeRoy's findings have revolutionized our understanding of the disease pathogenesis and guided the development of novel antifibrotic therapies towards fibroblast-specific approaches.

The Wnt antagonists DKK1 and SFRP1 are downregulated by promoter hypermethylation in systemic sclerosis

OBJECTIVES

Activated Wnt signalling with decreased expression of endogenous inhibitors has recently been characterised as a central pathomechanism in systemic sclerosis (SSc). Aberrant epigenetic modifications also contribute to the persistent activation of SSc fibroblasts. We investigated whether increased Wnt signalling and epigenetic changes in SSc are causally linked via promoter hypermethylation-induced silencing of Wnt antagonists.

METHODS

The methylation status of endogenous Wnt antagonists in leucocytes and fibroblasts was evaluated by methylation-specific PCR. 5-aza-2'-deoxycytidine was used to inhibit DNA methyltransferases (Dnmts) in cultured fibroblasts and in the mouse model of bleomycin-induced skin fibrosis. Activation of Wnt signalling was assessed by analysing Axin2 mRNA levels and by staining for β-catenin.

RESULTS

The promoters of DKK1 and SFRP1 were hypermethylated in fibroblasts and peripheral blood mononuclear cells of patients with SSc. Promoter hypermethylation resulted in impaired transcription and decreased expression of DKK1 and SFRP1 in SSc. Treatment of SSc fibroblasts or bleomycin-challenged mice with 5-aza prevented promoter methylation-induced silencing and increased the expression of both genes to normal levels. Reactivation of DKK1 and SFRP1 transcription by 5-aza inhibited canonical Wnt signalling in vitro and in vivo and effectively ameliorated experimental fibrosis.

CONCLUSIONS

We demonstrate that hypermethylation of the promoters of DKK1 and SFRP1 contributes to aberrant Wnt signalling in SSc and that Dnmt inhibition effectively reduces Wnt signalling. These data provide a novel link between epigenetic alterations and increased Wnt signalling in SSc and also have translational implications because Dnmt inhibitors are already approved for clinical use.

Novel investigational agents for the treatment of scleroderma

INTRODUCTION

The purpose of this article is to highlight novel therapies that are being used in scleroderma (SSc). Therapeutic interventions in SSc generally target at least one of three ongoing biological processes characteristic of the disease: vasculopathy, autoimmunity and tissue fibrosis. Treatment decisions in SSc are determined by the level of disease activity and the degree of specific organ involvement. Traditional therapy has primarily focused on organ-specific management without clear evidence of overall disease modification.

AREAS COVERED

The authors provide a review of a variety of agents, which are already used for other autoimmune diseases, that are now being used to treat active SSc skin or lung disease, including rituximab, tocilizumab and IVIG. Several agents studied in vitro and in animal models of fibrosis have shown promise, including bortezomib, LPA-1 antagonists, anti-CCN2 therapy, anti-IL-13 and thrombin antagonists. The authors also provide details on targeting intracellular molecular pathways and matricellular proteins, which is another novel area of investigation.

EXPERT OPINION

Combination therapy may be necessary to control the complex biological network active in SSc. Most of the current evidence that suggest benefit of these agents is based on small population studies. Ultimately well-designed clinical trials are required to define the role of these agents in treating SSc.

Connective tissue growth factor (CTGF/CCN2): diagnostic and prognostic value in acute heart failure

BACKGROUND

As a mediator of ECM homeostasis, connective tissue growth factor (CTGF) appears to be involved in adverse structural remodeling processes in the heart. However, the diagnostic and prognostic value of CTGF levels in acute heart failure (AHF) in addition to natriuretic peptide testing has not yet been evaluated.

METHODS AND RESULTS

A total of 212 patients presenting with acute dyspnea and/or peripheral edema to the Emergency Department were evaluated. CTGF and NT-proBNP plasma levels were measured at the initial presentation. All patients were followed up to 1 and 5 years. The first endpoint tested was the diagnostic non-inferiority of combined CTGF plus NT-proBNP compared to NT-proBNP alone for AHF diagnosis. Afterwards, the additional diagnostic value of CTGF plus NT-proBNP was tested. CTGF levels were higher in NYHA class III/IV and AHA/ACC class C/D patients compared to lower class patients (p = 0.04). Patients with HFREF revealed highest CTGF levels (median 93.3 pg/ml, IQR 18.2-972 pg/ml, n = 48) compared to patients with a normal heart function (i.e., without HFREF and HFPEF) (median 25.9, IQR <1-82.2 pg/ml, n = 37) (p < 0.05), followed by patients with HFPEF (median 82.2 pg/ml, IQR 11.5-447 pg/ml, n = 32) as assessed by echocardiography. Finally, CTGF levels were higher in patients with AHF (median 77.3 pg/ml, IQR 22.5-1012 pg/ml, n = 66) compared to those without (p = 0.002). CTGF plus NT-proBNP was non-inferior to NT-proBNP testing alone for AHF diagnosis (AUC difference 0.01, p > 0.05). CTGF plus NT-proBNP improved the diagnostic capacity for AHF (accuracy 82 %, specificity 83 %, positive predictive value 66 %, net reclassification improvement +0.11) compared to NT-proBNP alone (p = 0.0001). CTGF levels were not able to differentiate prognostic outcomes after 1 and 5 years.

CONCLUSIONS

Additional CTGF measurements might lead to a better discrimination of higher functional and structural heart failure stages and might identify patients of an increased risk for an acute cardiac decompensation.

Epigenetic control of cytokine gene expression: regulation of the TNF/LT locus and T helper cell differentiation

Epigenetics encompasses transient and heritable modifications to DNA and nucleosomes in the native chromatin context. For example, enzymatic addition of chemical moieties to the N-terminal "tails" of histones, particularly acetylation and methylation of lysine residues in the histone tails of H3 and H4, plays a key role in regulation of gene transcription. The modified histones, which are physically associated with gene regulatory regions that typically occur within conserved noncoding sequences, play a functional role in active, poised, or repressed gene transcription. The "histone code" defined by these modifications, along with the chromatin-binding acetylases, deacetylases, methylases, demethylases, and other enzymes that direct modifications resulting in specific patterns of histone modification, shows considerable evolutionary conservation from yeast to humans. Direct modifications at the DNA level, such as cytosine methylation at CpG motifs that represses promoter activity, are another highly conserved epigenetic mechanism of gene regulation. Furthermore, epigenetic modifications at the nucleosome or DNA level can also be coupled with higher-order intra- or interchromosomal interactions that influence the location of regulatory elements and that can place them in an environment of specific nucleoprotein complexes associated with transcription. In the mammalian immune system, epigenetic gene regulation is a crucial mechanism for a range of physiological processes, including the innate host immune response to pathogens and T cell differentiation driven by specific patterns of cytokine gene expression. Here, we will review current findings regarding epigenetic regulation of cytokine genes important in innate and/or adaptive immune responses, with a special focus upon the tumor necrosis factor/lymphotoxin locus and cytokine-driven CD4+ T cell differentiation into the Th1, Th2, and Th17 lineages.

Cubilin expression is monoallelic and epigenetically augmented via PPARs

Background

Cubilin is an endocytic receptor that is necessary for renal and intestinal absorption of a range of ligands. Endocytosis mediated by cubilin and its co-receptor megalin is the principal mechanism for proximal tubule reabsorption of proteins from the glomerular filtrate. Cubilin is also required for intestinal endocytosis of intrinsic factor-vitamin B₁₂ complex. Despite its importance, little is known about the regulation of cubilin expression.

Results

Here we show that cubilin expression is under epigenetic regulation by at least two processes. The first process involves inactivation of expression of one of the cubilin alleles. This monoallelic expression state could not be transformed to biallelic by inhibiting DNA methylation or histone deacetylation. The second process involves transcriptional regulation of cubilin by peroxisome proliferator-activated receptor (PPAR) transcription factors that are themselves regulated by DNA methylation and histone deacetylation. This is supported by findings that inhibitors of DNA methylation and histone deacetylation, 5Aza and TSA, increase cubilin mRNA and protein in renal and intestinal cell lines. Not only was the expression of PPARα and γ inducible by 5Aza and TSA, but the positive effects of TSA and 5Aza on cubilin expression were also dependent on both increased PPAR transcription and activation. Additionally, 5Aza and TSA had similar effects on the expression of the cubilin co-receptor, megalin.

Conclusions

Together, these findings reveal that cubilin and megalin mRNA expression is under epigenetic control and thus point to new avenues for overcoming pathological suppression of these genes through targeting of epigenetic regulatory processes.

Inhibition of H3K27 histone trimethylation activates fibroblasts and induces fibrosis

OBJECTIVES

Epigenetic modifications such as DNA methylation and histone acetylation have been implicated in the pathogenesis of systemic sclerosis. However, histone methylation has not been investigated so far. We therefore aimed to evaluate the role of the trimethylation of histone H3 on lysine 27 (H3K27me3) on fibroblast activation and fibrosis.

METHODS

H3K27me3 was inhibited by 3-deazaneplanocin A (DZNep) in cultured fibroblasts and in two murine models of dermal fibrosis. Fibrosis was analysed by assessment of the dermal thickening, determination of the hydroxyproline content and by quantification of the numbers of myofibroblasts. The expression of fos-related antigen 2 (fra-2) was assessed by real-time PCR, western blot and immunohistochemistry and modulated by siRNA.

RESULTS

Inhibition of H3K27me3 stimulated the release of collagen in cultured fibroblasts in a time and dose-dependent manner. Treatment with DZNep exacerbated fibrosis induced by bleomycin or by overexpression of a constitutively active transforming growth factor β receptor type I. Moreover, treatment with DZNep alone was sufficient to induce fibrosis. Inhibition of H3K27me3 induced the expression of the profibrotic transcription factor fra-2 in vitro and in vivo. Knockdown of fra-2 completely prevented the profibrotic effects of DZNep.

CONCLUSIONS

These data demonstrate a novel role of H3 Lys27 histone methylation in fibrosis. In contrast to other epigenetic modifications such as DNA methylation and histone acetylation, H3 Lys27 histone methylation acts as a negative regulator of fibroblast activation in vitro and in vivo by repressing the expression of fra-2.

Systemic sclerosis: genetics and epigenetics

Systemic sclerosis (SSc) is an autoimmune disease characterized by immune abnormalities, vascular obliteration, excessive extracellular matrix deposition, and fibrosis of the skin and/or internal organs. To date, the exact etiology of this complicated disease remains unknown. Over the past few years, however, the role of genetic susceptibility and epigenetic modifications caused by environmental factors have been intensively studied in relation to the pathogenesis of this disease, and important advances have been made. This review focuses on the recent progress in the field of SSc research, including HLA and non-HLA susceptibility genes identified in genome-wide association studies (GWAS), and aberrant epigenetic modifications of gene loci associated with SSc. HLA genes most closely linked with SSc susceptibility include HLA-A, -B, -C, -DR, -DP and -DQ. A large number of non-HLA genes were also reported. It has also been noted that different genetic variants can be linked to specific clinical patterns. Finally, DNA demethylation of regulatory genes (eNOS, CD40L and CD70), therapeutic effects associated with Trichostatin A (TSA) treatment, and abnormal expression of a large spectrum of microRNAs (miR-21, -31, -146, -503, -145, -29b, etc.) are all observed in SSc. Overall, the findings presented in this review illustrate how both genetic and epigenetic aberrations play important roles in the development of SSc; however, several unanswered questions continue to impede our understanding of this complex disease. Future research should focus on the identification of new biomarkers for early diagnosis and prognosis, which will help improve the clinical outcome of patients with SSc.

Inhibition of sumoylation prevents experimental fibrosis

OBJECTIVES

Fibrosis is a predominant cause of death in systemic sclerosis (SSc). First epigenetic modifications have recently been shown to contribute to activation of SSc fibroblasts. Here, we investigated inhibition of sumoylation as a novel antifibrotic approach.

METHODS

Sumoylation was inhibited by siRNA-mediated knockdown of the Small Ubiquitin-like MOdifiers (SUMO) E2-conjugating enzyme Ubc9, which is essential for sumoylation. The effects of knockdown of Ubc9 were analysed in bleomycin-induced dermal fibrosis, and in the model of fibrosis induced by overexpression of a constitutively active TGF-beta receptor type I (TBR). SUMO-1 and phosphorylated Smad3 were detected by immunohistochemistry.

RESULTS

Increased staining for SUMO-1 was detected in patients with SSc and in experimental fibrosis. Inhibition of sumoylation exerted potent antifibrotic effects and prevented dermal thickening, myofibroblast differentiation and accumulation of collagen induced by bleomycin, or by overexpression of constitutively active TBR. Moreover, knockdown of Ubc9 reduced the accumulation of phosphorylated Smad3 in experimental fibrosis indicating that inhibition of sumoylation may normalise canonical TGF-β signalling in vivo.

CONCLUSIONS

We demonstrate that inhibition of sumoylation reduces canonical TGF-β signalling and prevents experimental fibrosis in different preclinical models. These data provide first evidence that targeting of aberrant sumoylation may be a novel therapeutic approach for fibrotic diseases.

Animal models of intestinal fibrosis: new tools for the understanding of pathogenesis and therapy of human disease

Fibrosis is a serious condition complicating chronic inflammatory processes affecting the intestinal tract. Advances in this field that rely on human studies have been slow and seriously restricted by practical and logistic reasons. As a consequence, well-characterized animal models of intestinal fibrosis have emerged as logical and essential systems to better define and understand the pathophysiology of fibrosis. In point of fact, animal models allow the execution of mechanistic studies as well as the implementation of clinical trials with novel, pathophysiology-based therapeutic approaches. This review provides an overview of the currently available animal models of intestinal fibrosis, taking into consideration the methods of induction, key characteristics of each model, and underlying mechanisms. Currently available models will be classified into seven categories: spontaneous, gene-targeted, chemical-, immune-, bacteria-, and radiation-induced as well as postoperative fibrosis. Each model will be discussed in regard to its potential to create research opportunities to gain insights into the mechanisms of intestinal fibrosis and stricture formation and assist in the development of effective and specific antifibrotic therapies.

Screening of selective histone deacetylase inhibitors by proteochemometric modeling

BACKGROUND

Histone deacetylase (HDAC) is a novel target for the treatment of cancer and it can be classified into three classes, i.e., classes I, II, and IV. The inhibitors selectively targeting individual HDAC have been proved to be the better candidate antitumor drugs. To screen selective HDAC inhibitors, several proteochemometric (PCM) models based on different combinations of three kinds of protein descriptors, two kinds of ligand descriptors and multiplication cross-terms were constructed in our study.

RESULTS

The results show that structure similarity descriptors are better than sequence similarity descriptors and geometry descriptors in the leftacterization of HDACs. Furthermore, the predictive ability was not improved by introducing the cross-terms in our models. Finally, a best PCM model based on protein structure similarity descriptors and 32-dimensional general descriptors was derived (R2 = 0.9897, Qtest2 = 0.7542), which shows a powerful ability to screen selective HDAC inhibitors.

CONCLUSIONS

Our best model not only predict the activities of inhibitors for each HDAC isoform, but also screen and distinguish class-selective inhibitors and even more isoform-selective inhibitors, thus it provides a potential way to discover or design novel candidate antitumor drugs with reduced side effect.

[Scleroderma]

Scleroderma (synonyms: systemic sclerosis, systemic scleroderma) is a systemic disease which affects the skin as well as internal organs such as the lungs, gastrointestinal tract, kidneys, and the heart. Pathogenetically a distinction should be made between uncontrolled formation of extracellular matrix proteins (fibrosis) and vasculopathy. In addition to organ fibrosis, this leads to a clinical picture of vascular manifestations. These include fingertip ulcers, pulmonary arterial hypertension, and acute renal crisis. Localized forms of scleroderma, such as morphea, which do not involve organ complications, should be differentiated from systemic sclerosis. Due to its clinical heterogeneity and high rate of morbidity and mortality, systemic sclerosis poses an enormous diagnostic and therapeutic challenge in everyday clinical practice. This review article summarizes the current status of classification and epidemiology, pathogenesis, and the most important clinical manifestations such as interstitial fibrosis, pulmonary arterial hypertension, acute renal crisis, and peripheral vasculopathy and provides an overview of current and future treatment options.