Simultaneous downregulation of KLF5 and Fli1 is a key feature underlying systemic sclerosis

Recent Insights into Cellular and Molecular Mechanisms of Defective Angiogenesis in Systemic Sclerosis

In systemic sclerosis (SSc, or scleroderma), defective angiogenesis, clinically manifesting with abnormal capillary architecture and severe capillary reduction, represents a hallmark of early-stage disease, usually preceding the onset of tissue fibrosis, and is caused by several cellular and molecular mechanisms affecting microvascular endothelial cells with different outcomes. Indeed, once damaged, endothelial cells can be dysfunctionally activated, thus becoming unable to undergo angiogenesis and promoting perivascular inflammation. They can also undergo apoptosis, transdifferentiate into profibrotic myofibroblasts, or acquire a senescence-associated secretory phenotype characterized by the release of exosomes and several profibrotic and proinflammatory mediators. In this narrative review, we aimed to give a comprehensive overview of recent studies dealing with the cellular and molecular mechanisms underlying SSc defective angiogenesis and the related endothelial cell dysfunctions, mainly the endothelial-to-mesenchymal transition process. We also discussed potential novel vascular treatment strategies able to restore the angiogenic process and reduce the endothelial-to-mesenchymal transition in this complex disease.

Systemic Sclerosis-Associated Pulmonary Arterial Hypertension: From Bedside to Bench and Back Again

Systemic sclerosis (SSc) is a heterogeneous disease characterized by autoimmunity, vasculopathy, and fibrosis which affects the skin and internal organs. One key aspect of SSc vasculopathy is pulmonary arterial hypertension (SSc-PAH) which represents a leading cause of morbidity and mortality in patients with SSc. The pathogenesis of pulmonary hypertension is complex, with multiple vascular cell types, inflammation, and intracellular signaling pathways contributing to vascular pathology and remodeling. In this review, we focus on shared molecular features of pulmonary hypertension and those which make SSc-PAH a unique entity. We highlight advances in the understanding of the clinical and translational science pertinent to this disease. We first review clinical presentations and phenotypes, pathology, and novel biomarkers, and then highlight relevant animal models, key cellular and molecular pathways in pathogenesis, and explore emerging treatment strategies in SSc-PAH.

Morroniside improves AngII-induced cardiac fibroblast proliferation, migration, and extracellular matrix deposition by blocking p38/JNK signaling pathway through the downregulation of KLF5

Myocardial fibrosis (MF), which is an inevitable pathological manifestation of many cardiovascular diseases in the terminal stage, often contributes to severe cardiac dysfunction and sudden death. Morroniside (MOR) is the main active component of Cornus officinalis with a variety of biological activities. This study was designed to explore the efficacy of MOR in MF and to investigate its pharmacological mechanism. The viability of MOR-treated human cardiac fibroblast (HCF) cells with or without Angiotensin II (AngII) induction was assessed with Cell Counting Kit-8 (CCK-8). The migration of AngII-induced HCF cells was appraised with a transwell assay. Gelatin zymography analysis was adopted to evaluate the activities of MMP2 and MMP9, while immunofluorescence assay was applied for the estimation of Collagen I and Collagen III. By means of western blot, the expressions of migration-, fibrosis-, and p38/c-Jun N-terminal kinase (JNK) signal pathway-related proteins were resolved. The transfection efficacy of oe-Kruppel-like factor 5 (KLF5) was examined with reverse transcription-quantitative PCR (RT-qPCR) and western blot. In this study, it was found that MOR treatment inhibited AngII-induced hyperproliferation, migration, and fibrosis of HCF cells, accompanied with decreased activities of matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9), connective tissue growth factor (CTGF), Fibronectin, and α-SMA, which were all reversed by KLF5 overexpression. Collectively, MOR exerted protective effects on MF by blocking p38/JNK signal pathway through the downregulation of KLF5.

Tree shrews as a new animal model for systemic sclerosis research

Objective

Systemic sclerosis (SSc) is a chronic systemic disease characterized by immune dysregulation and fibrosis for which there is no effective treatment. Animal models are crucial for advancing SSc research. Tree shrews are genetically, anatomically, and immunologically closer to humans than rodents. Thus, the tree shrew model provides a unique opportunity for translational research in SSc.

Methods

In this study, a SSc tree shrew model was constructed by subcutaneous injection of different doses of bleomycin (BLM) for 21 days. We assessed the degree of inflammation and fibrosis in the skin and internal organs, and antibodies in serum. Furthermore, RNA sequencing and a series of bioinformatics analyses were performed to analyze the transcriptome changes, hub genes and immune infiltration in the skin tissues of BLM induced SSc tree shrew models. Multiple sequence alignment was utilized to analyze the conservation of selected target genes across multiple species.

Results

Subcutaneous injection of BLM successfully induced a SSc model in tree shrew. This model exhibited inflammation and fibrosis in skin and lung, and some developed esophageal fibrosis and secrum autoantibodies including antinuclear antibodies and anti-scleroderma-70 antibody. Using RNA sequencing, we compiled skin transcriptome profiles in SSc tree shrew models. 90 differentially expressed genes (DEGs) were identified, which were mainly enriched in the PPAR signaling pathway, tyrosine metabolic pathway, p53 signaling pathway, ECM receptor interaction and glutathione metabolism, all of which are closely associated with SSc. Immune infiltration analysis identified 20 different types of immune cells infiltrating the skin of the BLM-induced SSc tree shrew models and correlations between those immune cells. By constructing a protein-protein interaction (PPI) network, we identified 10 hub genes that were significantly highly expressed in the skin of the SSc models compared to controls. Furthermore, these genes were confirmed to be highly conserved in tree shrews, humans and mice.

Conclusion

This study for the first time comfirmed that tree shrew model of SSc can be used as a novel and promising experimental animal model to study the pathogenesis and translational research in SSc.

Epigenetic mechanisms driving the pathogenesis of systemic lupus erythematosus, systemic sclerosis and dermatomyositis

Autoimmune connective tissue disorders, including systemic lupus erythematosus, systemic sclerosis (SSc) and dermatomyositis (DM), often manifest with debilitating cutaneous lesions and can result in systemic organ damage that may be life-threatening. Despite recent therapeutic advancements, many patients still experience low rates of sustained remission and significant treatment toxicity. While genetic predisposition plays a role in these connective tissue disorders, the relatively low concordance rates among monozygotic twins (ranging from approximately 4% for SSc to about 11%-50% for SLE) have prompted increased scrutiny of the epigenetic factors contributing to these diseases. In this review, we explore some seminal studies and key findings to provide a comprehensive understanding of how dysregulated epigenetic mechanisms can contribute to the development of SLE, SSc and DM.

Role of the transcription factor Fli-1 on the CXCL10/CXCR3 Axis

The transcription factor Fli-1, a member of the ETS family of transcription factors, is implicated in the pathogenesis of lupus disease. Reduced Fli-1 expression in lupus mice leads to decreased renal Cxcl10 mRNA levels and renal infiltrating CXCR3+ T cells that parallels reduced renal inflammatory cell infiltration and renal damage. Inflammatory chemokine CXCL10 is critical for attracting inflammatory cells expressing the chemokine receptor CXCR3. The CXCL10/CXCR3 axis plays a role in the pathogenesis of various inflammatory diseases including lupus. Our data here demonstrate that renal CXCL10 protein levels are significantly lower in Fli-1 heterozygous MRL/lpr mice compared to wild-type MRL/lpr mice. Knockdown of Fli-1 significantly reduced CXCL10 secretion in mouse and human endothelial cells, and human mesangial cells, upon LPS or TNFα stimulation. The Fli-1 inhibitor, Camptothecin, significantly reduced CXCL10 production in human monocyte cells upon interferon stimulation. Four putative Ets binding sites in the Cxcl10 promoter showed significant enrichment for FLI-1; however, FLI-1 did not directly drive transcription from the human or mouse promoters, suggesting FLI-1 may regulate CXCL10 expression indirectly. Our results also suggest that the DNA binding domain of FLI-1 is necessary for regulation of human hCXCR3 promotor activity in human T cells and interactions with co-activators. Together, these results support a role for FLI-1 in modulating the CXCL10-CXCR3 axis by directly or indirectly regulating the expression of both genes to impact lupus disease development. Signaling pathways or drugs that reduce FLI-1 expression may offer novel approaches to lupus treatment.

Epigenetics as a versatile regulator of fibrosis

Fibrosis, a process caused by excessive deposition of extracellular matrix (ECM), is a common cause and outcome of organ failure and even death. Researchers have made many efforts to understand the mechanism of fibrogenesis and to develop therapeutic strategies; yet, the outcome remains unsatisfactory. In recent years, advances in epigenetics, including chromatin remodeling, histone modification, DNA methylation, and noncoding RNA (ncRNA), have provided more insights into the fibrotic process and have suggested the possibility of novel therapy for organ fibrosis. In this review, we summarize the current research on the epigenetic mechanisms involved in organ fibrosis and their possible clinical applications.

The Exciting Future for Scleroderma

Emerging evidence shows that a complex interplay between cells and mediators and extracellular matrix factors may underlie the development and persistence of fibrosis in systemic sclerosis. Similar processes may determine vasculopathy. This article reviews recent progress in understanding how fibrosis becomes profibrotic and how the immune system, vascular, and mesenchymal compartment affect disease development. Early phase trials are informing about pathogenic mechanisms in vivo and reverse translation for observational and randomized trials is allowing hypotheses to be developed and tested. In addition to repurposing already available drugs, these studies are paving the way for the next generation of targeted therapeutics.

Mindin (SPON2) Is Essential for Cutaneous Fibrogenesis in a Mouse Model of Systemic Sclerosis

Systemic sclerosis is a fibrotic disease that initiates in the skin and progresses to internal organs, leading to a poor prognosis. Unraveling the etiology of a chronic, multifactorial disease such as systemic sclerosis has been aided by various animal models that recapitulate certain aspects of the human pathology. We found that the transcription factor SNAI1 is overexpressed in the epidermis of patients with systemic sclerosis, and a transgenic mouse recapitulating this expression pattern is sufficient to induce many clinical features of the human disease. Using this mouse model as a discovery platform, we have uncovered a critical role for the matricellular protein Mindin (SPON2) in fibrogenesis. Mindin is produced by SNAI1 transgenic skin keratinocytes and aids fibrogenesis by inducing early inflammatory cytokine production and collagen secretion in resident dermal fibroblasts. Given the dispensability of Mindin in normal tissue physiology, targeting this protein holds promise as an effective therapy for fibrosis.

The Involvement of Smooth Muscle, Striated Muscle, and the Myocardium in Scleroderma: A Review

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by heterogeneous changes involving numerous organs and systems. The currently available data indicate that muscle injury (both smooth and striated muscles) is widespread and leads to significant morbidity, either directly or indirectly. From the consequences of smooth muscle involvement in the tunica media of blood vessels or at the level of the digestive tract, to skeletal myopathy (which may be interpreted strictly in the context of SSc, or as an overlap with idiopathic inflammatory myopathies), muscular injury in scleroderma translates to a number of notable clinical manifestations. Heart involvement in SSc is heterogenous depending on the definition used in the various studies. The majority of SSc patients experience a silent form of cardiac disease. The present review summarizes certain important features of myocardial, as well as smooth and skeletal muscle involvement in SSc. Further research is needed to fully describe and understand the pathogenic pathways and the implications of muscle involvement in scleroderma.

A broad look into the future of systemic sclerosis

Systemic sclerosis (SSc) is a systemic autoimmune disease with the key features of inflammation, vasculopathy and fibrosis. This article focussed on emerging fields based on the authors’ current work and expertise. The authors provide a hierarchical structure into the studies of the pathogenesis of SSc starting with the contribution of environmental factors. Regulatory autoantibodies (abs) are discussed, which are parts of the human physiology and are specifically dysregulated in SSc. Abs against the angiotensin II receptor subtype 1 (AT1R) and the endothelin receptor type A (ETAR) are discussed in more detail. Extracellular vesicles are another novel player to possess disease processes. Fibroblasts are a key effector cell in SSc. Therefore, the current review will provide an overview about their plasticity in the phenotype and function. Promising nuclear receptors as key regulators of transcriptional programmes will be introduced as well as epigenetic modifications, which are pivotal to maintain the profibrotic fibroblast phenotype independent of external stimuli. Fibroblasts from SSc patients exhibit a specific signalling and reactivate developmental pathways and stem cell maintenance such as by employing hedgehog and WNT, which promote fibroblast-to-myofibroblast transition and extracellular matrix generation. Pharmacological interventions, although for other indications, are already in clinical use to address pathologic signalling.

Metallopeptidades 2 and 9 genes epigenetically modulate equine endometrial fibrosis

Endometrium type I (COL1) and III (COL3) collagen accumulation, periglandular fibrosis and mare infertility characterize endometrosis. Metalloproteinase-2 (MMP-2), MMP-9 and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) are involved in collagen turnover. Since epigenetic changes may control fibroproliferative diseases, we hypothesized that epigenetic mechanisms could modulate equine endometrosis. Epigenetic changes can be reversed and therefore extremely promising for therapeutic use. Methylation pattern analysis of a particular gene zone is used to detect epigenetic changes. DNA methylation commonly mediates gene repression. Thus, this study aimed to evaluate if the transcription of some genes involved in equine endometrosis was altered with endometrial fibrosis, and if the observed changes were epigenetically modulated, through DNA methylation analysis. Endometrial biopsies collected from cyclic mares were histologically classified (Kenney and Doig category I, n = 6; category IIA, n = 6; category IIB, n = 6 and category III, n = 6). Transcription of COL1A1, COL1A2, COL3A1, MMP2, MMP9, TIMP1, and TIMP2 genes and DNA methylation pattern by pyrosequencing of COL1A1, MMP2, MMP9, TIMP1 genes were evaluated. Both MMP2 and MMP9 transcripts decreased with fibrosis, when compared with healthy endometrium (category I) (P < 0.05). TIMP1 transcripts were higher in category III, when compared to category I endometrium (P < 0.05). No differences were found for COL1A1, COL1A2, COL3A1 and TIMP2 transcripts between endometrial categories. There were higher methylation levels of (i) COL1A1 in category IIB (P < 0.05) and III (P < 0.01), when compared to category I; (ii) MMP2 in category III, when compared to category I (P < 0.001) and IIA (P < 0.05); and (iii) MMP9 in category III, when compared to category I and IIA (P < 0.05). No differences in TIMP1 methylation levels were observed between endometrial categories. The hypermethylation of MMP2 and MMP9, but not of COL1A1 genes, occurred simultaneously with a decrease in their mRNA levels, with endometrial fibrosis, suggesting that this hypermethylation is responsible for repressing their transcription. Our results show that endometrosis is epigenetically modulated by anti-fibrotic genes (MMP2 and MMP9) inhibition, rather than fibrotic genes activation and therefore, might be promising targets for therapeutic use.

Animal Models of Systemic Sclerosis: Using Nailfold Capillaroscopy as a Potential Tool to Evaluate Microcirculation and Microangiopathy: A Narrative Review

Systemic sclerosis (SSc) is an autoimmune disease with three pathogenic hallmarks, i.e., inflammation, vasculopathy, and fibrosis. A wide plethora of animal models have been developed to address the complex pathophysiology and for the development of possible anti-fibrotic treatments. However, no current model comprises all three pathological mechanisms of the disease. To highlight the lack of a complete model, a review of some of the most widely used animal models for SSc was performed. In addition, to date, no model has accomplished the recreation of primary or secondary Raynaud’s phenomenon, a key feature in SSc. In humans, nailfold capillaroscopy (NFC) has been used to evaluate secondary Raynaud’s phenomenon and microvasculature changes in SSc. Being a non-invasive technique, it is widely used both in clinical studies and as a tool for clinical evaluation. Because of this, its potential use in animal models has been neglected. We evaluated NFC in guinea pigs to investigate the possibility of applying this technique to study microcirculation in the nailfold of animal models and in the future, development of an animal model for Raynaud’s phenomenon. The applications are not only to elucidate the pathophysiological mechanisms of vasculopathy but can also be used in the development of novel treatment options.

A New Hypothetical Concept in Metabolic Understanding of Cardiac Fibrosis: Glycolysis Combined with TGF-β and KLF5 Signaling

The accumulation of fibrosis in cardiac tissues is one of the leading causes of heart failure. The principal cellular effectors in cardiac fibrosis are activated fibroblasts and myofibroblasts, which serve as the primary source of matrix proteins. TGF-β signaling pathways play a prominent role in cardiac fibrosis. The control of TGF-β by KLF5 in cardiac fibrosis has been demonstrated for modulating cardiovascular remodeling. Since the expression of KLF5 is reduced, the accumulation of fibrosis diminishes. Because the molecular mechanism of fibrosis is still being explored, there are currently few options for effectively reducing or reversing it. Studying metabolic alterations is considered an essential process that supports the explanation of fibrosis in a variety of organs and especially the glycolysis alteration in the heart. However, the interplay among the main factors involved in fibrosis pathogenesis, namely TGF-β, KLF5, and the metabolic process in glycolysis, is still indistinct. In this review, we explain what we know about cardiac fibroblasts and how they could help with heart repair. Moreover, we hypothesize and summarize the knowledge trend on the molecular mechanism of TGF-β, KLF5, the role of the glycolysis pathway in fibrosis, and present the future therapy of cardiac fibrosis. These studies may target therapies that could become important strategies for fibrosis reduction in the future.

Epigenetic Modifications in the Pathogenesis of Systemic Sclerosis

Systemic sclerosis is a rare chronic autoimmune disease, which mainly manifests as immune disorders, vascular damage, and progressive fibrosis. The etiology of SSc is complex and involves multiple factors. Both genetic and environmental factors are involved in its pathogenesis. As one of the molecular mechanisms of environmental factors, epigenetic regulation plays an important role in the occurrence and development of systemic sclerosis, which involves DNA methylation, histone modification and non-coding RNA regulation. This review summarizes research advances in epigenetics, including exosomes, lncRNA, and mentions possible biomarkers and therapeutic targets among them.

The m6A RNA Modification Modulates Gene Expression and Fibrosis-Related Pathways in Hypertrophic Scar

Purpose: To systematically analyze the overall m⁶A modification pattern in hyperplastic scars (HS). Methods: The m⁶A modification patterns in HS and normal skin (NS) tissues were described by m⁶A sequencing and RNA sequencing, and subsequently bioinformatics analysis was performed. The m⁶A-related RNA was immunoprecipitated and verified by real-time quantitative PCR. Results: The appearance of 14,791 new m⁶A peaks in the HS sample was accompanied by the disappearance of 7,835 peaks. The unique m⁶A-related genes in HS were thus associated with fibrosis-related pathways. We identified the differentially expressed mRNA transcripts in HS samples with hyper-methylated or hypo-methylated m⁶A peaks. Conclusion: This study is the first to map the m⁶A transcriptome of human HS, which may help clarify the possible mechanism of m⁶A-mediated gene expression regulation.

Bushen Yijing Decoction (BSYJ) exerts an anti-systemic sclerosis effect via regulating MicroRNA-26a /FLI1 axis

Systemic sclerosis (SSc) refers to a group of autoimmune rheumatic diseases. Bushen Yijing decoction (BSYJ) is used for treating SSc. However, its underlying mechanism remains unknown. The present study aims to investigate potential roles of Friend leukemia integration factor 1 (FLI1) and microRNA in the beneficial effects of BSYJ on SSc. Primary skin fibroblasts were isolated from healthy individuals and SSc patients through tissue-explant technique and validated by immunocytochemistry. mRNA and microRNA levels were determined by quantitative RT-PCR. Protein expression was measured by western blotting. MiR-26a mimics or inhibitor were transfected to induce miR-26a overexpression or knockdown in vitro and in vivo, respectively. Histological changes of skin tissues from SSc mouse were evaluated by H&E and Masson trichrome staining. Results showed that FLI1 expression significantly decreased in primary skin fibroblasts of SSc patients. MiR-26a was predicted to target FLI1 untranslated region. Transfection of miR-26 mimics in SSc skin fibroblasts (SFB) leads to decrease in FLI1 expression and increase in collagen I gene expression and fibronectin accumulation. On the other hand, miR-26a knockdown increased FLI1 expression and decreased collagen I and fibronectin expression in SFB. In addition, BSYJ-containing rat serum suppressed miR-26a expression, while it elevated FLI1 expression and inhibited fibronectin and collagen I accumulation in SFB. In the mouse SSc model, BSYJ-containing serum inhibited dermal fibrosis by suppressing miR-26a expression and restoring FLI1 protein levels. Overall, our study demonstrates that BSYJ decoction exerts anti-dermal fibrosis in SSc patients via suppressing miR-26a level and thus to increase FLI1 expression in fibroblasts.

Pathophysiology of systemic sclerosis

Systemic sclerosis (SSc) is a rare connective tissue disease characterized by vascular remodeling, fibroblast activation and extra-cellular matrix production in excess and autoimmunity. Environmental factors including mainly silica and solvents have been assumed to contribute to the development of SSc, together with genetic factors including gene variants implicated in innate immunity such as IRF5 and STAT4, and epigenetic factors including histone post-translational modifications, DNA hypomethylation, and microRNAs or long- non coding RNAs system were reported to participate in immune activation and fibrosis processes in patients with SSc. A number of animal models of SSc have been set up over the years, including genetic and induced SSc models. These models, together with data obtained from human SSc patients, contributed to better understand the mechanisms contributing to vasculopathy and fibrosis. Alongside the pathophysiological process of SSc, several cellular and molecular actors are involved, such as dysregulations in the innate and adaptive immune cells, of the fibroblast, the implication of pro-inflammatory and pro-fibrosing signaling pathways such as the Wnt, TGF-β pathways or other cytokines, with a strong imprint of oxidative stress. The whole lead to the overactivity of the fibroblast with genetic dysregulation, apoptosis defect, hyperproduction of elements of extracellular matrix, and finally the phenomena of vasculopathy and fibrosis. These advances contribute to open new therapeutic areas through the design of biologics and small molecules.

Insight into the role of dermal white adipose tissue loss in dermal fibrosis

The loss of dermal white adipose tissue (dWAT) is vital to the formation of dermal fibrosis (DF), but the specific mechanism is not well understood. A few studies are reviewed to explore the role of dWAT in the formation of DF. Recent findings indicated that the adipocytes-to-myofibroblasts transition in dWAT reflects the direct contribution to the DF formation. While adipose-derived stem cells (ADSCs) contained in dWAT express antifibrotic cytokines, the loss of ADSCs leads to skin protection decreased, which indirectly exacerbates DF and tissue damage. Therefore, blocking or reversing the adipocytes-to-myofibroblasts transition or improving the survival of ADSCs in dWAT and the expression of antifibrotic cytokines may be an effective strategy for the treatment of DF.

Contribution to the peripheral vasculopathy and endothelial cell dysfunction by CXCL4 in Systemic Sclerosis

BACKGROUND

CXCL4, a chemokine with anti-angiogenic property, is involved in systemic sclerosis (SSc) related pulmonary arterial hypertension (PAH).

OBJECTIVE

To investigated the contribution of CXCL4 to SSc development by focusing on the correlation of circulatory CXCL4 levels with their peripheral vasculopathy, and the effect of CXCL4 on endothelial cell dysfunction and the potential signaling.

METHODS

We measured the plasma CXCL4 levels in 58 patients with SSc, 10 patients with the very early diagnosis of SSc (VEDOSS), and 80 healthy controls (HCs). Then, CXCL4 concentrations were correlated with clinical features, especially the peripheral vasculopathy. These observations were further validated in an additional cohort. Moreover, we studied the anti-angiogenic effects of CXCL4 and the underlying downstream signaling in human umbilical vein endothelial cells (HUVECs) in vitro.

RESULTS

Circulating CXCL4 levels were 103.62 % higher in patients with SSc and 201.51 % higher in patients with VEDOSS than matched HCs, which were confirmed in two independent cohorts. CXCL4 levels were associated with digital ulcers (DU) and nailfold videocapillaroscopy (NVC) abnormalities in SSc. The proliferation, migration, and tube formation of HUVECs were inhibited by CXCL4 or SSc derived plasma, which reversed by CXCL4 neutralizing antibody, but failed by CXCR3 inhibitor. CXCL4 downregulated the transcription factor Friend leukaemia integration factor-1 (Fli-1) via c-Abl signaling. Furthermore, CXCL4 blocked the transforming growth factor (TGF) -β or platelet-derived growth factor (PDGF) induced cell proliferation of HUVECs.

CONCLUSIONS

CXCL4 may contribute to peripheral vasculopathy in SSc by downregulating Fli-1 via c-Abl signaling in endothelial cells and interfering angiogenesis.

Advances in epigenetics in systemic sclerosis: molecular mechanisms and therapeutic potential

Systemic sclerosis (SSc) is a prototypical inflammatory fibrotic disease involving inflammation, vascular abnormalities and fibrosis that primarily affect the skin and lungs. The aetiology of SSc is unknown and its pathogenesis is only partially understood. Of all the rheumatic diseases, SSc carries the highest all-cause mortality rate and represents an unmet medical need. A growing body of evidence implicates epigenetic aberrations in this intractable disease, including specific modifications affecting the three main cell types involved in SSc pathogenesis: immune cells, endothelial cells and fibroblasts. In this Review, we discuss the latest insights into the role of DNA methylation, histone modifications and non-coding RNAs in SSc and how these epigenetic alterations affect disease features. In particular, histone modifications have a role in the regulation of gene expression pertinent to activation of fibroblasts to myofibroblasts, governing their fate. DNA methyltransferases are crucial in disease pathogenesis by mediating methylation of DNA in specific promoters, regulating expression of specific pathways. We discuss targeting of these enzymes for therapeutic gain. Innovative epigenetic therapy could be targeted to treat the disease in a precision epigenetics approach.

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.

TGFβ promotes fibrosis by MYST1-dependent epigenetic regulation of autophagy

Activation of fibroblasts is essential for physiological tissue repair. Uncontrolled activation of fibroblasts, however, may lead to tissue fibrosis with organ dysfunction. Although several pathways capable of promoting fibroblast activation and tissue repair have been identified, their interplay in the context of chronic fibrotic diseases remains incompletely understood. Here, we provide evidence that transforming growth factor-β (TGFβ) activates autophagy by an epigenetic mechanism to amplify its profibrotic effects. TGFβ induces autophagy in fibrotic diseases by SMAD3-dependent downregulation of the H4K16 histone acetyltransferase MYST1, which regulates the expression of core components of the autophagy machinery such as ATG7 and BECLIN1. Activation of autophagy in fibroblasts promotes collagen release and is both, sufficient and required, to induce tissue fibrosis. Forced expression of MYST1 abrogates the stimulatory effects of TGFβ on autophagy and re-establishes the epigenetic control of autophagy in fibrotic conditions. Interference with the aberrant activation of autophagy inhibits TGFβ-induced fibroblast activation and ameliorates experimental dermal and pulmonary fibrosis. These findings link uncontrolled TGFβ signaling to aberrant autophagy and deregulated epigenetics in fibrotic diseases and may contribute to the development of therapeutic interventions in fibrotic diseases.

Engineering Advanced In Vitro Models of Systemic Sclerosis for Drug Discovery and Development

Systemic sclerosis (SSc) is a complex multisystem disease with the highest case-specific mortality among all autoimmune rheumatic diseases, yet without any available curative therapy. Therefore, the development of novel therapeutic antifibrotic strategies that effectively decrease skin and organ fibrosis is needed. Existing animal models are cost-intensive, laborious and do not recapitulate the full spectrum of the disease and thus commonly fail to predict human efficacy. Advanced in vitro models, which closely mimic critical aspects of the pathology, have emerged as valuable platforms to investigate novel pharmaceutical therapies for the treatment of SSc. This review focuses on recent advancements in the development of SSc in vitro models, sheds light onto biological (e.g., growth factors, cytokines, coculture systems), biochemical (e.g., hypoxia, reactive oxygen species) and biophysical (e.g., stiffness, topography, dimensionality) cues that have been utilized for the in vitro recapitulation of the SSc microenvironment, and highlights future perspectives for effective drug discovery and validation.

The Role of Pro-fibrotic Myofibroblasts in Systemic Sclerosis: from Origin to Therapeutic Targeting

Systemic sclerosis (SSc, scleroderma) is a complex connective tissue disorder characterized by multisystem clinical manifestations resulting from immune dysregulation/autoimmunity, vasculopathy and, most notably, progressive fibrosis of the skin and internal organs. In recent years, it has emerged that the main drivers of SSc-related tissue fibrosis are myofibroblasts, a type of mesenchymal cells with both the extracellular matrix-synthesizing features of fibroblasts and the cytoskeletal characteristics of contractile smooth muscle cells. The accumulation and persistent activation of pro-fibrotic myofibroblasts during SSc development and progression result into elevated mechanical stress and reduced matrix plasticity within the affected tissues and may be ascribed to a reduced susceptibility of these cells to pro-apoptotic stimuli, as well as their increased formation from tissue-resident fibroblasts or transition from different cell types. Given the crucial role of myofibroblasts in SSc pathogenesis, finding the way to inhibit myofibroblast differentiation and accumulation by targeting their formation, function and survival may represent an effective approach to hamper the fibrotic process or even halt or reverse established fibrosis. In this review, we discuss the role of myofibroblasts in SSc-related fibrosis, with a special focus on their cellular origin and the signaling pathways implicated in their formation and persistent activation. Furthermore, we provide an overview of potential therapeutic strategies targeting myofibroblasts that may be able to counteract fibrosis in this pathological condition.

Association of serum CCL20 levels with pulmonary vascular involvement and primary biliary cholangitis in patients with systemic sclerosis

AIM

Systemic sclerosis (SSc) is a chronic autoimmune disease resulting in vasculopathy and fibrosis of the skin and major internal organs. Especially, interstitial lung disease and pulmonary arterial hypertension are the leading causes of mortality. C-C motif ligand 20 (CCL20) is known as a homeostatic and inflammatory chemokine, which is associated with fibrosis and angiogenesis and constantly expressed in organs involved in SSc. Therefore, we investigated the potential contribution of CCL20 to the development of SSc.

METHOD

We conducted cross-sectional analyses of 67 SSc patients and 20 healthy controls recruited in a single center for 9 years. Serum CCL20 levels were measured by enzyme-linked immunosorbent assay. Statistical analyses were performed with the Mann-Whitney U test, the Kruskal-Wallis test followed by Dunn's multiple comparison test, Fisher's exact probability test and the Spearman's rank correlation coefficient.

RESULTS

SSc patients had significantly higher serum CCL20 levels than healthy controls. In SSc patients, serum CCL20 levels correlated inversely with the percentage of predicated diffusion lung capacity for carbon monoxide and positively with mean pulmonary artery pressure (mPAP). In addition, SSc patients with increased serum CCL20 levels had anti-mitochondrial antibody M2 titer significantly elevated relative to those with normal levels, and SSc patients with asymptomatic primary biliary cholangitis (PBC) possessed higher serum CCL20 levels than those without. Importantly, serum CCL20 levels were associated positively with mPAP values and PBC presence by multivariate regression analysis.

CONCLUSION

Serum CCL20 levels may be involved in the development of pulmonary vascular involvement leading to pulmonary arterial hypertension and asymptomatic PBC in SSc patients.

Roles of Krüppel-like factor 5 in kidney disease

Transcription factor Krüppel-like factor 5 (KLF5) is a member of the Krüppel-like factors' (KLFs) family. KLF5 regulates a number of cellular functions, such as apoptosis, proliferation and differentiation. Therefore, KLF5 can play a role in many diseases, including, cancer, cardiovascular disease and gastrointestinal disorders. An important role for KLF5 in the kidney was recently reported, such that KLF5 regulated podocyte apoptosis, renal cell proliferation, tubulointerstitial inflammation and renal fibrosis. In this review, we have summarized the available information in the literature with a brief description on how transcriptional, post-transcriptional and post-translational modifications of KLF5 modulate its function in a variety of organs including the kidney with a focus of its importance on the pathogenesis of various kidney diseases. Furthermore, we also have outlined the current and possible mechanisms of KLF5 activation in kidney diseases. These studies suggest a need for more systemic investigations, particularly for generation of animal models with renal cell-specific deletion or overexpression of KLF5 gene to examine direct contributions of KLF5 to various kidney diseases. This will promote further experimentation in the development of therapies to prevent or treat various kidney diseases.

Association of functional (GA)n microsatellite polymorphism in the FLI1 gene with susceptibility to human systemic sclerosis

OBJECTIVE

Susceptibility genes that can account for characteristic features of SSc such as fibrosis, vasculopathy and autoimmunity remain to be determined. In mice, deficiency of Friend leukaemia integration 1 transcription factor (Fli1) causes SSc-like disease with these features. The human FLI1 gene contains (GA)n microsatellite, which has been shown to be associated with expression level. Because microsatellite polymorphisms are difficult to capture by genome-wide association studies, we directly genotyped FLI1 (GA)n microsatellite and examined its association with SSc.

METHODS

Genomic DNA from 639 Japanese SSc patients and 851 healthy controls was genotyped for (GA)n microsatellite using the fragment assay. The cut-off repeat number for susceptibility to SSc was determined by receiver operating characteristics (ROC) analysis. Association with susceptibility and clinical characteristics was examined using logistic regression analysis. FLI1 mRNA levels were determined using quantitative RT-PCR.

RESULTS

Based on the ROC analysis, (GA)n alleles with ≥22 repeats were collectively defined as L alleles and alleles with ≤21 repeats as S alleles. (GA)n L alleles were significantly associated with susceptibility to SSc (P = 5.0e-04, odds ratio 1.34, additive model). Significant association was observed both in diffuse cutaneous and limited cutaneous SSc. Among the SSc, (GA)n L alleles were significantly enriched in the patients with a modified Rodnan total skin thickness score ≥10 compared with those with a score <10. FLI1 mRNA levels were significantly decreased in healthy controls carrying (GA)n L alleles as compared with non-carriers.

CONCLUSION

Extended repeat alleles of FLI1 (GA)n microsatellite may be associated with lower FLI1 mRNA levels and susceptibility to human SSc.

TGF-β-induced epigenetic deregulation of SOCS3 facilitates STAT3 signaling to promote fibrosis

Fibroblasts are key effector cells in tissue remodeling. They remain persistently activated in fibrotic diseases, resulting in progressive deposition of extracellular matrix. Although fibroblast activation may be initiated by external factors, prolonged activation can induce an "autonomous," self-maintaining profibrotic phenotype in fibroblasts. Accumulating evidence suggests that epigenetic alterations play a central role in establishing this persistently activated pathologic phenotype of fibroblasts. We demonstrated that in fibrotic skin of patients with systemic sclerosis (SSc), a prototypical idiopathic fibrotic disease, TGF-β induced the expression of DNA methyltransferase 3A (DNMT3A) and DNMT1 in fibroblasts in a SMAD-dependent manner to silence the expression of suppressor of cytokine signaling 3 (SOCS3) by promoter hypermethylation. Downregulation of SOCS3 facilitated activation of STAT3 to promote fibroblast-to-myofibroblast transition, collagen release, and fibrosis in vitro and in vivo. Reestablishment of the epigenetic control of STAT3 signaling by genetic or pharmacological inactivation of DNMT3A reversed the activated phenotype of SSc fibroblasts in tissue culture, inhibited TGF-β-dependent fibroblast activation, and ameliorated experimental fibrosis in murine models. These findings identify a pathway of epigenetic imprinting of fibroblasts in fibrotic disease with translational implications for the development of targeted therapies in fibrotic diseases.

Intravital Imaging of Pulmonary Immune Response in Inflammation and Infection

Intravital microscopy (IVM) is a unique imaging method providing insights in cellular functions and interactions in real-time, without the need for tissue extraction from the body. IVM of the lungs has specific challenges such as restricted organ accessibility, respiratory movements, and limited penetration depth. Various surgical approaches and microscopic setups have been adapted in order to overcome these challenges. Among others, these include the development of suction stabilized lung windows and the use of more advanced optical techniques. Consequently, lung IVM has uncovered mechanisms of leukocyte recruitment and function in several models of pulmonary inflammation and infection. This review focuses on bacterial pneumonia, aspiration pneumonia, sepsis-induced acute lung Injury, and cystic fibrosis, as examples of lung inflammation and infection. In addition, critical details of intravital imaging techniques of the lungs are discussed.

Cellular and molecular mechanisms in fibrosis

The activation of fibroblasts is required for physiological tissue remodelling such as wound healing. However, when the regulatory mechanisms are disrupted and fibroblasts remain persistently activated, the progressive deposition of extracellular matrix proteins leads to tissue fibrosis, which results in dysfunction or even loss of function of the affected organ. Although fibrosis has been recognized as a major cause of morbidity and mortality in modern societies, there are only few treatment options available that directly disrupt the release of extracellular matrix from fibroblasts. Intensive research in recent years, however, identified several pathways as core fibrotic mechanisms that are shared across different fibrotic diseases and organs. We discuss herein selection of those core pathways, especially downstream of the profibrotic TGF-β pathway, which are druggable and which may be transferable from bench to bedside.

Expression of GM-CSF Is Regulated by Fli-1 Transcription Factor, a Potential Drug Target

Friend leukemia virus integration 1 (Fli-1) is an ETS transcription factor and a critical regulator of inflammatory mediators, including MCP-1, CCL5, IL-6, G-CSF, CXCL2, and caspase-1. GM-CSF is a regulator of granulocyte and macrophage lineage differentiation and a key player in the pathogenesis of inflammatory/autoimmune diseases. In this study, we demonstrated that Fli-1 regulates the expression of GM-CSF in both T cells and endothelial cells. The expression of GM-CSF was significantly reduced in T cells and endothelial cells when Fli-1 was reduced. We found that Fli-1 binds directly to the GM-CSF promoter using chromatin immunoprecipitation assay. Transient transfection assays indicated that Fli-1 drives transcription from the GM-CSF promoter in a dose-dependent manner, and mutation of the Fli-1 DNA binding domain resulted in a significant loss of transcriptional activation. Mutation of a known phosphorylation site within the Fli-1 protein led to a significant increase in GM-CSF promoter activation. Thus, direct binding to the promoter and phosphorylation are two important mechanisms behind Fli-1-driven activation of the GM-CSF promoter. In addition, Fli-1 regulates GM-CSF expression in an additive manner with another transcription factor Sp1. Finally, we demonstrated that a low dose of a chemotherapeutic drug, camptothecin, inhibited expression of Fli-1 and reduced GM-CSF production in human T cells. These results demonstrate novel mechanisms for regulating the expression of GM-CSF and suggest that Fli-1 is a critical druggable regulator of inflammation and immunity.

Etiological factors of systemic sclerosis in the southeast region of Romania

Systemic sclerosis (SSc) is a relatively rare autoimmune disease with skin and visceral involvement, having a yet unknown etiopathogenesis. Research has shown that professional exposure to various polluting chemicals such as dyes, aliphatic and aromatic organic solvents, inhalable silica dust or certain heavy metals, can be triggering factors for this disease when they overlap a predisposing genetic profile. Smoking is still a debated factor involved in the etiology of SSc, as authors have divergent opinions on this matter. The present study was designed to analyze the etiological factors identified in the group of 37 patients with diffuse and limited SSc from the southeast region of Romania and the results were compared to the literature data. In the group of patients included in this study, occupational exposure and smoking history were not present in all patients, and a hereditary factor was identified only in an isolated case. The majority of patients suffered from a major negative psychological event or from long-term stressful situations and these factors were associated with smoking history or occupational exposure; this suggests that SSc is initiated in a set of cumulative triggering factors.

Emerging role of Fli1 in autoimmune diseases

The Ets transcription factor family exerts crucial role in cell proliferation, apoptosis, differentiation and migration. Friend leukemia integration 1 (Fli1), a member of the Ets family, is expressed in fibroblasts, endothelial cells and immune cells. Fli1 gene is participated in the development, proliferation, activation, migration and other processes of immune cells. Fli1 can also affect the function of immune cells by regulating cytokines and chemokines. Emerging evidence has shown that Fli1 is implicated in the etiology of several autoimmune diseases, including systemic sclerosis (SSc) and systemic lupus erythematosus (SLE). In this review, we mainly discuss the current evidence for the role of Fli1 in these diseases.

Altered Properties of Endothelial Cells and Mesenchymal Stem Cells Underlying the Development of Scleroderma-like Vasculopathy in KLF5+/- ;Fli-1+/- Mice

OBJECTIVE

In prevous studies, we established a new animal model, KLF5^+/- ;Fli-1^+/- mice, in which fundamental pathologic features of systemic sclerosis (SSc) are broadly recapitulated. SSc vasculopathy is believed to occur as a result of impaired vascular remodeling, but its detailed mechanism of action remains unknown. To address this, the present study investigated the properties of dermal microvascular endothelial cells (DMECs), bone marrow-derived endothelial progenitor cells (BM-EPCs), and bone marrow-derived mesenchymal stem cells (BM-MSCs), a precursor of pericytes, in KLF5^+/- ;Fli-1^+/- mice.

METHODS

Neovascularization and angiogenesis were assessed in KLF5^+/- ;Fli-1^+/- mice by in vivo Matrigel plug assay and in vitro tube formation assay, respectively. The properties of mouse BM-EPCs and BM-MSCs were assessed with in vitro studies. Dermal vasculature was visualized in vivo by injecting the mice with fluorescein isothiocyanate-conjugated dextran.

RESULTS

Neovascularization was diminished in skin-embedded Matrigel plugs from KLF5^+/- ;Fli-1^+/- mice. DMECs from KLF5^+/- ;Fli-1^+/- mice showed defective tubulogenic activity, decreased expression of VE-cadherin and CD31, and an imbalance in the expression of Notch1/Dll4, suggesting that angiogenesis and anastomosis are disturbed. KLF5^+/- ;Fli-1^+/- mouse BM-MSCs exhibited enhanced proliferation and migration and increased collagen production following stimulation with transforming growth factor β1, indicating that these cells differentiate preferentially into myofibroblasts rather than pericytes. KLF5^+/- ;Fli-1^+/- mouse BM-EPCs displayed a transition toward mesenchymal cells, suggesting that vasculogenesis is impaired. Wound healing was delayed in KLF5^+/- ;Fli-1^+/- mice (mean ± SD healing time 15.67 ± 0.82 days versus 13.50 ± 0.84 days; P = 0.0017), and the vascular network was poorly developed in wound scar tissue.

CONCLUSION

The characteristics observed in the KLF5^+/- ;Fli-1^+/- mouse model - specifically, impaired neovascularization and vascular maturation - are similar to those observed in human SSc, and could be at least partially attributable to the induction of SSc-like properties in DMECs, BM-EPCs, and BM-MSCs. These findings indicate the critical contribution of Klf5 and Fli1 deficiency in vascular cells and related cell precursors to the development of SSc vasculopathy.

Serum S100A12 levels: Possible association with skin sclerosis and interstitial lung disease in systemic sclerosis

Damage-associated molecular patterns (DAMPs) have drawn much attention as a member of disease-associated molecules in systemic sclerosis (SSc). In this study, we investigated the potential contribution of S100A12, a member of DAMPs, to the development of SSc by evaluating S100A12 expression in the lesional skin and the clinical correlation of serum S100A12 levels. S100A12 expression was markedly elevated in the epidermis of SSc-involved skin at protein levels and in the bulk skin at mRNA levels. The deficiency of transcription factor Fli1, a predisposing factor of SSc, enhanced S100A12 expression and Fli1 occupied the S100A12 promoter in normal human keratinocytes. Serum S100A12 levels were higher in SSc patients, especially in those with diffuse cutaneous involvement, than in healthy controls and positively correlated with skin score. Furthermore, the presence of interstitial lung disease significantly augmented serum levels of S100A12. Importantly, serum S100A12 levels correlated inversely with both per cent forced vital capacity and per cent diffusing capacity for carbon monoxide and positively with serum levels of KL-6 and surfactant protein-D. Collectively, these results indicate a possible contribution of S100A12 to skin sclerosis and interstitial lung disease associated with SSc, further supporting the critical roles of DAMPs in the pathogenesis of this disease.

Epigenetics and systemic sclerosis: An answer to disease onset and evolution?

There is growing evidence that implicates epigenetic modification in the pathogenesis of systemic sclerosis (SSc). The complexity of epigenetic regulation and its dynamic nature complicate the investigation of its role in the disease. We will review the current literature for factors that link epigenetics to SSc by discussing DNA methylation, histone acetylation and methylation, and non-coding RNAs (ncRNAs), particularly microRNA changes in endothelial cells, fibroblasts (FBs), and lymphocytes. These three cell types are significantly involved in the early stages and throughout the course of the disease and are particularly vulnerable to epigenetic regulation. The pathogenesis of SSc is likely related to modifications of the epigenome by environmental signals in individuals with a specific genetic makeup. The epigenome is an attractive therapeutic target; however, successful epigenetics-based treatments require a better understanding of the molecular mechanisms controlling the epigenome and its alteration in the disease.

Bi-directional communication: Conversations between fibroblasts and immune cells in systemic sclerosis

Systemic Sclerosis (SSc) is an autoimmune idiopathic connective tissue disease, characterized by aberrant fibro-proliferative and inflammatory responses, causing fibrosis of multiple organs. In recent years the interactions between innate and adaptive immune cells with resident fibroblasts have been uncovered. Cross-talk between immune and stromal cells mediates activation of stromal cells to myofibroblasts; key cells in the pathophysiology of fibrosis. These cells and their cytokines appear to mediate their effects in both a paracrine and autocrine fashion. This review examines the role of innate and adaptive immune cells in SSc, focusing on recent advances that have illuminated our understanding of ongoing bi-directional communication between immune and stromal cells. Finally, we appraise current and future therapies and how these may be useful in a disease that currently has no specific disease modifying treatment.

The Epigenetic Regulation of Scleroderma and Its Clinical Application

Scleroderma (systemic sclerosis; SSc) is a complex and highly heterogeneous multisystem rheumatic disease characterized by vascular abnormality, immunologic derangement, and excessive deposition of extracellular matrix (ECM) proteins. To date, the etiology of this life-threatening disorder remains not fully clear. More and more studies show epigenetic modifications play a vital role. The aberrant epigenetic status of certain molecules such as Fli-1, BMPRII, NRP1, CD70, CD40L, CD11A, FOXP3, KLF5, DKK1, SFRP1, and so on contributes to the pathogenesis of progressive vasculopathy, autoimmune dysfunction, and tissue fibrosis in SSc. Meanwhile, numerous miRNAs including miR-21, miR-29a, miR-196a, miR-202-3p, miR-150, miR-let-7a, and others are involved in the process. In addition, the abnormal epigenetic biomarker levels of CD11a, Foxp3, HDAC2, miR-30b, miR-142-3p, miR-150, miR-5196 in SSc are closely correlated with disease severity. In this chapter, we not only review new advancements on the epigenetic mechanisms involved in the pathogenesis of SSc and potential epigenetic biomarkers, but also discuss the therapeutic potential of epigenetic targeting therapeutics such as DNA methylation inhibitors, histone acetylase inhibitors, and miRNA replacement.

TJ-M2010-5, a novel MyD88 inhibitor, corrects R848-induced lupus-like immune disorders of B cells in vitro

B cell hyperactivities are involved in the development of systemic lupus erythematosus (SLE). Toll-like receptor 7 (TLR7) in the B cells plays a pivotal role in the pathogenesis of SLE. Previous studies have focused on the intrinsic role of B cells in TLR7/MyD88 signaling and consequently on immune activation, autoantibody production, and systemic inflammation. However, a feasible treatment for this immune disorder remains to be discovered. The in vitro cellular response that have been studied likely plays a central role in the production of some important autoantibodies in SLE. We successfully used R848 to build a lupus-like B cell model in vitro; these B cells were overactivated, differentiated into plasma cells, escaped apoptosis, massively proliferated, and produced large amounts of autoantibodies and cytokines. In the present study, we found that TJ-M2010-5, a novel MyD88 inhibitor previously synthesized in our lab, seemed to inhibit the lupus-like condition of B cells, including overactivation, massive proliferation, differentiation into plasma cells, and overproduction of autoantibodies and cytokines. TJ-M2010-5 also induce B cells apoptosis. Furthermore, TJ-M2010-5 was found to remarkably inhibit NF-κB and MAPK signaling. In summary, TJ-M2010-5 might correct R848-induced lupus-like immune disorders of B cells by blocking the TLR7/MyD88/NF-κB and TLR7/MyD88/MAPK signaling pathways.

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.

Therapeutic molecular targets of SSc-ILD

Systemic sclerosis is a fibrosing chronic connective tissue disease of unknown etiology. A major hallmark of systemic sclerosis is the uncontrolled and persistent activation of fibroblasts, which release excessive amounts of extracellular matrix, lead to organ dysfunction, and cause high mobility and motility of patients. Systemic sclerosis–associated interstitial lung disease is one of the most common fibrotic organ manifestations in systemic sclerosis and a major cause of death. Treatment options for systemic sclerosis–associated interstitial lung disease and other fibrotic manifestations, however, remain very limited. Thus, there is a huge medical need for effective therapies that target tissue fibrosis, vascular alterations, inflammation, and autoimmune disease in systemic sclerosis–associated interstitial lung disease. In this review, we discuss data suggesting therapeutic ways to target different genes in distinct tissues/organs that contribute to the development of SSc.

Regulation of skin fibrosis by RALDH1-producing dermal dendritic cells via retinoic acid-mediated regulatory T cell induction: A role in scleroderma

BACKGROUND

Skin fibrosis of systemic sclerosis (SSc) is believed to be driven by complex processes including immune abnormalities, but the underlying immune response remains enigmatic. In particular, the role of dermal dendritic cells (DCs) is totally unknown.

OBJECTIVE

We investigated the impact of CD103 loss on bleomycin-induced skin fibrosis because CD103 is a critical molecule determining DC phenotypes.

METHODS

Bleomycin-induced skin fibrosis was generated with Cd103^-/- mice. The alterations of tissue fibrosis and related inflammation were investigated by histologic examination, hydroxyproline assay, quantitative reverse transcription PCR and flow cytometry. SSc skin samples were evaluated by immunofluorescence.

RESULTS

CD103 loss decreased bleomycin-induced dermal thickness and collagen contents, along with TGF-β1 and CTGF suppression. Treg proportion was increased, while Th1/Th2/Th17 cell proportions were decreased in the skin of bleomycin-treated Cd103^-/- mice. Bleomycin injection enhanced CD11b^-CD103^- DC proportion in wild-type mice, which was further augmented in Cd103^-/- mice. Importantly, RALDH1/ALDH1A1 enzyme oxidizing retinaldehyde to retinoic acid, an inducer of Tregs, was preferentially expressed by CD11b^-CD103^- DCs and its expression levels were elevated in bleomycin-injected skin lesions, to a greater extent in Cd103^-/- mice than in wild-type mice. Importantly, the number of RALDH1-positive DCs was decreased in the lesional skin of SSc patients and tended to inversely correlate with skin fibrosis severity.

CONCLUSION

This study identified a critical role of dermal DCs as a regulator of Treg development through RALDH1 in bleomycin-treated mice and possibly in human SSc. This finding sheds new light on dermal DCs as a new therapeutic target of SSc.

DZ2002 ameliorates fibrosis, inflammation, and vasculopathy in experimental systemic sclerosis models

BACKGROUND

Systemic sclerosis is a multisystem inflammatory and vascular lesion leading to extensive tissue fibrosis. A reversible S-adenosyl-l-homocysteine hydrolase (SAHH) inhibitor, DZ2002, modulates the pathologic processes of various inflammatory diseases and autoimmune diseases. This study is designed to investigate the therapeutic potentiality of DZ2002 for experimental systemic sclerosis models.

METHODS

The anti-inflammatory and anti-fibrotic features of DZ2002 and its mechanisms were investigated in a bleomycin (BLM)-induced dermal fibrosis mice model. The effects of DZ2002 on expression of extracellular matrix components and TGF-β signaling in human dermal fibroblasts were analyzed. Simultaneously, the effects of DZ2002 on macrophage activation and endothelial cell adhesion molecule expression were also evaluated.

RESULTS

DZ2002 significantly attenuated dermal fibrosis in BLM-induced mice. Consistently, DZ2002 inhibited the expression of various molecules associated with dermal fibrosis, including transforming growth factor β1, connective tissue growth factor, tumor necrosis factor-α, interferon-γ, IL-1β, IL-4, IL-6, IL-10, IL-12p40, IL-17A, and monocyte chemotactic protein 1 in the lesional skin of BLM-induced mice. Furthermore, DZ2002 decreased the proportion of macrophages, neutrophils, and T cells (especially T helper cells) in the skin tissue of BLM-induced mice. In addition, DZ2002 attenuated both M1 macrophage and M2 macrophage differentiation in vivo and in vitro. Importantly, DZ2002 directly reversed the profibrotic phenotype of transforming growth factor-β1-treated dermal fibroblasts and suppressed ICAM-1, VCAM-1, VEGF, bFGF, and ET-1 expression in endothelial cells. Finally, our investigations showed that DZ2002 relieved systemic sclerosis by regulating fibrosis TGF-β/Smad signaling pathway.

CONCLUSIONS

DZ2002 prevents the development of experimental dermal fibrosis by reversing the profibrotic phenotype of various cell types and would be a potential drug for the treatment of systemic sclerosis.

Rationally-based therapeutic disease modification in systemic sclerosis: Novel strategies

Systemic sclerosis (SSc) is a highly challenging chronic condition that is dominated by the pathogenetic triad of vascular damage, immune dysregulation/autoimmunity and fibrosis in multiple organs. A hallmark of SSc is the remarkable degree of molecular and phenotypic disease heterogeneity, which surpasses that of other complex rheumatic diseases. Disease trajectories in SSc are unpredictable and variable from patient to patient. Disease-modifying therapies for SSc are lacking, long-term morbidity is considerable and mortality remains unacceptably high. Currently-used empirical approaches to disease modification have modest and variable clinical efficacy and impact on survival, are expensive and frequently associated with unfavorable side effects, and none can be considered curative. However, research during the past several years is yielding significant advances with therapeutic potential. In particular, the application of unbiased omics-based discovery technologies to large and well-characterized SSc patient cohorts, coupled with hypothesis-testing experimental research using a variety of model systems is revealing new insights into SSc that allow formulation of a more nuanced appreciation of disease heterogeneity, and a deepening understanding of pathogenesis. Indeed, we are now presented with numerous novel and rationally-based strategies for targeted SSc therapy, several of which are currently, or expected to be shortly, undergoing clinical evaluation. In this review, we discuss promising novel therapeutic targets and rationally-based approaches to disease modification that have the potential to improve long-term outcomes in SSc.

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.

A novel miRNA-4484 is up-regulated on microarray and associated with increased MMP-21 expression in serum of systemic sclerosis patients

Systemic sclerosis (SSc) is a complex, heterogeneous connective tissue disease, characterized by fibrosis and ECM deposition in skin and internal organs, autoimmunity, and changes in the microvasculature. Profiling of circulating miRNAs in serum has been found to be changed in pathological states, creating new possibilities for molecular diagnostics as blood-based biomarkers. This study was designed to identify miRNAs that are differentially expressed in SSc and might be potentially contributing to the disease etiopathogenesis or be used for diagnostic purposes. Thus, we compared the expression pattern of multiple miRNAs in serum of 10 SSc patients to 6 healthy controls using microarray analysis, and RT-qPCR to confirm the obtained results. In addition, bioinformatics analysis was performed to explore miRNAs target genes and the signaling pathways that may be potentially involved in SSc pathogenesis. Our study shows a different expression of 15 miRNAs in SSc patients. We identified that miR-4484, located on chromosome 10q26.2, was an 18-fold up-regulated in SSc patients compared to a control group. Bioinformatics analysis of the miR-4484 target genes and the signaling pathways showed that it might be potentially involved in the TGF-β signaling pathway, ECM-receptor interaction, and metalloproteinases expression. Based on the chromosomal location, the most interesting target gene of miR-4484 may be MMP-21. We found that the expression of MMP-21 significantly increased in SSc patients compared to healthy subjects (P < 0.05). Our results suggest that miR-4484, and MMP-21 might be novel serum biomarkers that may correspond to pathological fibrosis in SSc, but it needs to be validated in further studies.

Epigenetics of scleroderma: Integrating genetic, ethnic, age, and environmental effects

Scleroderma or systemic sclerosis is thought to result from the interplay between environmental or non-genetic factors in a genetically susceptible individual. Epigenetic modifications are influenced by genetic variation and environmental exposures, and change with chronological age and between populations. Despite progress in identifying genetic, epigenetic, and environmental risk factors, the underlying mechanism of systemic sclerosis remains unclear. Since epigenetics provides the regulatory mechanism linking genetic and non-genetic factors to gene expression, understanding the role of epigenetic regulation in systemic sclerosis will elucidate how these factors interact to cause systemic sclerosis. Among the cell types under tight epigenetic control and susceptible to epigenetic dysregulation, immune cells are critically involved in early pathogenic events in the progression of fibrosis and systemic sclerosis. This review starts by summarizing the changes in DNA methylation, histone modification, and non-coding RNAs associated with systemic sclerosis. It then discusses the role of genetic, ethnic, age, and environmental effects on epigenetic regulation, with a focus on immune system dysregulation. Given the potential of epigenome editing technologies for cell reprogramming and as a therapeutic approach for durable gene regulation, this review concludes with a prospect on epigenetic editing. Although epigenomics in systemic sclerosis is in its infancy, future studies will help elucidate the regulatory mechanisms underpinning systemic sclerosis and inform the design of targeted epigenetic therapies to control its dysregulation.