Gastrointestinal Involvement in Systemic Sclerosis: Overview, Neglected Aspects, Malnutrition, Body Composition and Management

Gastrointestinal tract (GIT) involvement is the most common internal organ manifestation and is present in up to 90% of patients with systemic sclerosis (SSc). Clinical manifestations can differ according to the part of the GIT affected, disease course and symptoms. A majority of the symptoms are caused by GIT dysmotility. Up to 8% of SSc patients develop several GIT symptoms, which increase the mortality. Although GIT involvement is rarely the direct cause of death, it can lead to several comorbidities including malnutrition and negative alterations of body composition. These factors have a negative impact on quality of life and increase the mortality. To date, the treatment is rather symptomatic. The pathogenesis of GIT involvement in SSc still remains to be clarified to improve the treatment approaches including intravenous immunoglobulins and microRNA interventions

Atherosclerosis and Cardiovascular Risk in Systemic Sclerosis

Atherosclerosis (ATS) has been considered to be a degenerative disease affecting large and medium-sized arteries, resulting in a passive build-up of cholesterol in the artery wall. In the last decade, immune system was proved to play the key role in the pathogenesis of ATS, suggesting ATS to be more progressive and accelerated in chronic inflammatory conditions. Studies in patients with autoimmune diseases, particularly in the most prevalent ones such as rheumatoid arthritis and systemic lupus erythematosus, confirmed the significantly more serious atherosclerotic disease and increased cardiovascular (CV) risk compared to the general population, suggesting these diseases as an independent risk factor for CV diseases. There are only few studies evaluating ATS and CV risk in systemic sclerosis (SSc). Moreover, these studies present contradictory results. Furthermore, it is complicated to differentiate primary vascular affection related to the pathogenesis of SSc from the secondary vascular infliction due to ATS. Nevertheless, most of the studies to date suggest ATS and its clinical manifestations to be more prevalent in SSc. Future studies evaluating larger cohorts of patients are required to determine the relevance of ATS and CV disease and management of these comorbidities in SSc

Animal Models of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare, chronic connective tissue disease affecting the skin, vessels, musculoskeletal system, and internal organs. Despite advances in pharmacotherapy of organ manifestations and new knowledge about the pathogenesis of SSc, there is still no effective universal treatment of this serious disease. The aim of this chapter is to introduce traditional, most commonly used experimental animal models of SSc, clarify their basic pathological mechanism, describe their advantages and limitations, and outline their use in preclinical tests of potential therapeutic agents with subsequent clinical trials in patients with SSc. The existing models have already contributed significantly to preclinical testing of several available biological agents and small molecules, some of which achieved promising results in early clinical studies, and could provide better prospects for patients with this incurable disease

Atherosclerosis in Rheumatology: Old and New Insights

Cardiovascular diseases are the leading cause of morbidity and mortality in general population worldwide. There is an increasing significance of cardiovascular risk in the field of rheumatology, and accordingly, the evidence on the relation between immune system disorders and atherosclerosis has been substantially growing especially in last decades. Since novel immune and metabolic factors are considered to participate in pathogenesis of atherosclerosis and increased cardiovascular risk in rheumatic patients, they are getting to the forefront of the research. Since novel therapeutic approaches have improved survival of rheumatic patients, and decreased morbidity caused by rheumatic disease activity and damage, the significance of other comorbidities leading to premature mortality has arisen. Nevertheless, appropriate recommendations for the management of cardiovascular risk are still lacking. Recently, European League Against Rheumatism (EULAR) recommendations for management of the cardiovascular risk and comorbidities in patients with inflammatory arthropathies have been published. However, the cardiovascular management of these patients is still suboptimal. In addition, the situation in other orphan diseases such as idiopathic inflammatory myopathies, systemic sclerosis and others is even more uncertain and strongly requires further research. This chapter provides an overview of epidemiology, pathogenesis, clinical manifestations, screening and management of atherosclerosis in patients with rheumatic diseases

Editorial: Osteoarticular-immunological interplay in response to disease and therapy

Editorial on the Research Topic Osteoarticular-immunological Interplay in Response to Disease and Therap

Sirt1 regulates canonical TGF-β signalling to control fibroblast activation and tissue fibrosis

Background: Sirt1 is a member of the sirtuin family of proteins. Sirt1 is a class III histone deacetylase with important regulatory roles in transcription, cellular differentiation, proliferation and metabolism. As aberrant epigenetic modifications have been linked to the pathogenesis of systemic sclerosis (SSc), we aimed to investigate the role of Sirt1 in fibroblast activation. Methods: Sirt1 expression was analysed by real-time PCR, western blot and immunohistochemistry. Sirt1 signalling was modulated with the Sirt1 agonist resveratrol and by fibroblast-specific knockout. The role of Sirt1 was evaluated in bleomycin-induced skin fibrosis and in mice overexpressing a constitutively active transforming growth fac­tor-β (TGF-β) receptor I (TBRIact). Results: The expression of Sirt1 was decreased in patients with SSc and in experimental fibrosis in a TGF-β-dependent manner. Activation of Sirt1 potentiated the profibrotic effects of TGF-β with increased Smad reporter activity, elevated transcription of TGF-β target genes and enhanced release of collagen. In contrast, knockdown of Sirt1 inhibited TGF-β/SMAD signalling and reduced release of collagen in fibroblasts. Consistently, mice with fibroblast-specific knockdown of Sirt1 were less susceptible to bleomycin- or TBRIact-induced fibrosis. Conclusions: We identified Sirt1 as a crucial regulator of TGF-β/Smad signalling in SSc. Although Sirt1 is downregulated, this decrease is not sufficient to counterbalance the excessive activation of TGF-β signalling in SSc. However, augmentation of this endogenous regulatory mechanism, for example, by knockdown of Sirt1, can effectively inhibit TGF-β signalling and exerts potent antifibrotic effects. Sirt1 may thus be a key regulator of fibroblast activation in SSc

Heat shock protein 90 (Hsp90) inhibition targets canonical TGF-β signalling to prevent fibrosis

Objectives: Targeted therapies for systemic sclerosis (SSc) and other fibrotic diseases are not yet available. We evaluated the efficacy of heat shock protein 90 (Hsp90) inhibition as a novel approach to inhibition of aberrant transforming growth factor (TGF)-β signalling and for the treatment of fibrosis in preclinical models of SSc. Methods: Expression of Hsp90 was quantified by quantitative PCR, western blot and immunohistochemistry. The effects of Hsp90 inhibition were analysed in cultured fibroblasts, in bleomycin-induced dermal fibrosis, in tight-skin (Tsk-1) mice and in mice overexpressing a constitutively active TGF-β receptor I (TβRI). Results: Expression of Hsp90β was increased in SSc skin and in murine models of SSc in a TGF-β-dependent manner. Inhibition of Hsp90 by 17-dimethylaminoethylamino-17-demethoxy-geldanamycin (17-DMAG) inhibited canonical TGF-β signalling and completely prevented the stimulatory effects of TGF-β on collagen synthesis and myofibroblast differentiation. Treatment with 17-DMAG decreased the activation of canonical TGF-β signalling in murine models of SSc and exerted potent antifibrotic effects in bleomycin-induced dermal fibrosis, in Tsk-1 mice and in mice overexpressing a constitutively active TβRI. Dermal thickness, number of myofibroblasts and hydroxyproline content were all significantly reduced on treatment with 17-DMAG. No toxic effects were observed with 17-DMAG at antifibrotic doses. Conclusions: Hsp90 is upregulated in SSc and is critical for TGF-β signalling. Pharmacological inhibition of Hsp90 effectively blocks the profibrotic effects of TGF-β in cultured fibroblasts and in different preclinical models of SSc. These results have translational implications, as several Hsp90 inhibitors are in clinical trials for other indications

A synthetic PPAR-γ agonist triterpenoid ameliorates experimental fibrosis: PPAR-γ-independent suppression of fibrotic responses

Background: Persistent fibroblast activation initiated by transforming growth factor β (TGF-β) is a fundamental event in the pathogenesis of systemic sclerosis, and its pharmacological inhibition represents a potential therapeutic strategy. The nuclear receptor, peroxisome proliferator-activated receptor γ (PPAR-γ), exerts potent fibrotic activity. The synthetic oleanane triterpenoid, 2-cyano-3,12-dioxo-olean-1,9-dien-28-oic acid (CDDO), is a PPAR-γ agonist with potential effects on TGF-β signalling and dermal fibrosis. Objective: To examine the modulation of fibrogenesis by CDDO in explanted fibroblasts, skin organ cultures and murine models of scleroderma. Material and methods: The effects of CDDO on experimental fibrosis induced by bleomycin injection or by overexpression of constitutively active type I TGF-β receptor (TgfbR1ca) were evaluated. Modulation of fibrotic gene expression was examined in human skin organ cultures. To delineate the mechanisms underlying the antifibrotic effects of CDDO, explanted skin fibroblasts cultured in two-dimensional monolayers or in three-dimensional full-thickness human skin equivalents were studied. Results: CDDO significantly ameliorated dermal fibrosis in two complementary mouse models of scleroderma, as well as in human skin organ cultures and in three-dimensional human skin equivalents. In two-dimensional monolayer cultures of explanted normal fibroblasts, CDDO abrogated fibrogenic responses induced by TGF-β. These CDDO effects occurred via disruption of Smad-dependent transcription and were associated with inhibition of Akt activation. In scleroderma fibroblasts, CDDO attenuated the elevated synthesis of collagen. Remarkably, the in vitro antifibrotic effects of CDDO were independent of PPAR-γ. Conclusions: The PPAR-γ agonist triterpenoid CDDO attenuates fibrogenesis by antagonistically targeting canonical TGF-β/Smad and Akt signalling in a PPAR-γ-independent manner. These findings identify this synthetic triterpenoid as a potential new therapy for the control of fibrosis

Notch signalling regulates fibroblast activation and collagen release in systemic sclerosis

Background: Dermal fibroblasts from patients with systemic sclerosis (SSc) release excessive amounts of collagen resulting in tissue fibrosis. The molecular mechanisms underlying this pathological activation are incompletely understood. Objective: To investigate whether Notch signalling contributes to the uncontrolled activation of fibroblasts in SSc. Methods: Activation of the Notch pathway was assessed by immunohistochemistry or Western blot for the Notch intracellular domain and the Notch ligand Jagged-1 (Jag-1) and real-time PCR for the target gene hes-1. Differentiation of resting dermal fibroblasts into myofibroblasts was assessed by staining for α-smooth muscle actin. The synthesis of collagen was quantified by real-time PCR and Sircol assays. Results: Notch signalling was activated in lesional skin of patients with SSc. The activation persisted in cultured dermal SSc fibroblasts. Stimulation of healthy dermal fibroblasts with recombinant human Jag-1-Fc chimera resulted in an SSc-like phenotype with increased release of collagen and differentiation of resting fibroblasts into myofibroblasts. Consistent with the selective activation of the Notch pathway in dermal SSc fibroblasts, DAPT or siRNA against Notch strongly reduced the basal collagen expression in SSc fibroblasts, but not in fibroblasts from healthy volunteers. Conclusion: It was shown that Notch signalling is activated in SSc and plays an important role in fibroblast activation and collagen release. Inhibition of Notch signalling might be an effective strategy to selectively prevent the aberrant activation of SSc fibroblasts

The transcription factor JunD mediates transforming growth factor β-induced fibroblast activation and fibrosis in systemic sclerosis

Objectives: Transforming growth factor β (TGFβ) has been identified as a key player in fibrotic diseases. However, the molecular mechanisms by which TGFβ activates fibroblasts are incompletely understood. Here, the role of JunD, a member of the activator protein 1 (AP-1) family of transcription factors, as a downstream mediator of TGFβ signalling in systemic sclerosis (SSc), was investigated. Methods: The expression of JunD was analysed by real-time PCR, immunofluorescence, western blotting and immunohistochemistry. The canonical Smad pathway was specifically targeted by small interfering (si)RNA. The expression of extracellular matrix proteins in JunD deficient (JunD−/−) fibroblasts was analysed by real-time PCR and hydroxyproline assays. The mouse model of bleomycin-induced dermal fibrosis was used to assess the role of JunD in experimental fibrosis. Results: JunD was overexpressed in SSc skin and in cultured fibroblasts in a TGFβ dependent manner. The expression of JunD colocalised with pSmad 3 in fibrotic skin and silencing of Smad 3 or Smad 4 by siRNA prevented the induction of JunD by TGFβ. JunD−/− fibroblasts were less responsive to TGFβ and released less collagen upon stimulation with TGFβ. Moreover, JunD−/− mice were protected from bleomycin-induced fibrosis with reduced dermal thickening, decreased myofibroblast counts and lower collagen content of lesional skin. Conclusions: These data demonstrate that JunD is overexpressed in SSc and that JunD is a mediator of the profibrotic effects of TGFβ. Considering that inhibitors of AP-1 signalling have recently been developed and are available for clinical trials in SSc, these findings may have translational implications