The contribution of endothelial cells to tissue fibrosis.

PURPOSE OF REVIEW: Tissue fibrosis is an increasingly prevalent condition associated with various diseases and heavily impacting on global morbidity and mortality rates. Growing evidence indicates that common cellular and molecular mechanisms may drive fibrosis of diverse cause and affecting different organs. The scope of this review is to highlight recent findings in support for an important role of vascular endothelial cells in the pathogenesis of fibrosis, with a special focus on systemic sclerosis as a prototypic multisystem fibrotic disorder. RECENT FINDINGS: Although transition of fibroblasts to chronically activated myofibroblasts is widely considered the central profibrotic switch, the endothelial cell involvement in development and progression of fibrosis has been increasingly recognized over the last few years. Endothelial cells can contribute to the fibrotic process either directly by acting as source of myofibroblasts through endothelial-to-myofibroblast transition (EndMT) and concomitant microvascular rarefaction, or indirectly by becoming senescent and/or secreting a variety of profibrotic and proinflammatory mediators with consequent fibroblast activation and recruitment of inflammatory/immune cells that further promote fibrosis. SUMMARY: An in-depth understanding of the mechanisms underlying EndMT or the acquisition of a profibrotic secretory phenotype by endothelial cells will provide the rationale for novel endothelial cell reprogramming-based therapeutic approaches to prevent and/or treat fibrosis.

Endothelial Dysfunction in Systemic Sclerosis.

Systemic sclerosis, commonly known as scleroderma, is an autoimmune disorder characterized by vascular abnormalities, autoimmunity, and multiorgan fibrosis. The exact etiology is not known but believed to be triggered by environmental agents in a genetically susceptible host. Vascular symptoms such as the Raynaud phenomenon often precede other fibrotic manifestations such as skin thickening indicating that vascular dysfunction is the primary event. Endothelial damage and activation occur early, possibly triggered by various infectious agents and autoantibodies. Endothelial dysfunction, along with defects in endothelial progenitor cells, leads to defective angiogenesis and vasculogenesis. Endothelial to mesenchymal cell transformation is another seminal event during pathogenesis that progresses to tissue fibrosis. The goal of the review is to discuss the molecular aspect of the endothelial dysfunction that leads to the development of systemic sclerosis.

Effects of faecal microbiota transplantation on the small intestinal mucosa in systemic sclerosis.

OBJECTIVES: In SSc, gastrointestinal tract (GIT) involvement is a major concern, with no disease-modifying and limited symptomatic therapies available. Faecal microbiota transplantation (FMT) represents a new therapeutic option for GIT-affliction in SSc, showing clinical promise in a recent controlled pilot trial. Here, we aim to investigate effects of FMT on duodenal biopsies collected from SSc patients by immunohistochemistry and transcriptome profiling. METHODS: We analysed duodenal biopsies obtained pre-intervention (week 0) and post-intervention (weeks 2 and 16) from nine SSc patients receiving an intestinal infusion of FMT (n = 5) or placebo (n = 4). The analysis included immunohistochemistry (IHC) with a selected immune function and fibrosis markers, and whole biopsy transcriptome profiling. RESULTS: In patients receiving FMT, the number of podoplanin- and CD64-expressing cells in the mucosa were lower at week 2 compared with baseline. This decline in podoplanin- (r = 0.94) and CD64-positive (r = 0.89) cells correlated with improved patient-reported lower GIT symptoms. Whole biopsy transcriptome profiling from week 2 showed significant enrichment of pathways critical for cellular and endoplasmic reticulum stress responses, microvillus and secretory vesicles, vascular and sodium-dependent transport, and circadian rhythm. At week 16, we found enrichment of pathways mandatory for binding activity of immunoglobulin receptors, T cell receptor complexes, and chemokine receptors, as well as response to zinc-ions. We found that 25 genes, including Matrix metalloproteinase-1 were upregulated at both week 2 and week 16. CONCLUSION: Combining selective IHC and unbiased gene expression analyses, this exploratory study highlights the potential for disease-relevant organ effects of FMT in SSc patients with GIT involvement. TRIAL REGISTRATION: ClinicalTrials.gov, http://clinicaltrials.gov, NCT03444220.

Current Concepts on the Pathogenesis of Systemic Sclerosis.

From the clinical standpoint, systemic sclerosis (SSc) is characterized by skin and internal organ fibrosis, diffuse fibroproliferative vascular modifications, and autoimmunity. Clinical presentation and course are highly heterogenous and life expectancy variably affected mostly dependent on lung and heart involvement. SSc touches more women than men with differences in disease severity and environmental exposure. Pathogenetic events originate from altered homeostasis favored by genetic predisposition, environmental cues and a variety of endogenous and exogenous triggers. Epigenetic modifications modulate SSc pathogenesis which strikingly associate profound immune-inflammatory dysregulation, abnormal endothelial cell behavior, and cell trans-differentiation into myofibroblasts. SSc myofibroblasts show enhanced survival and enhanced extracellular matrix deposition presenting altered structure and altered physicochemical properties. Additional cell types of likely pathogenic importance are pericytes, platelets, and keratinocytes in conjunction with their relationship with vessel wall cells and fibroblasts. In SSc, the profibrotic milieu is favored by cell signaling initiated in the one hand by transforming growth factor-beta and related cytokines and in the other hand by innate and adaptive type 2 immune responses. Radical oxygen species and invariant receptors sensing danger participate to altered cell behavior. Conventional and SSc-specific T cell subsets modulate both fibroblasts as well as endothelial cell dysfunction. Beside autoantibodies directed against ubiquitous antigens important for enhanced clinical classification, antigen-specific agonistic autoantibodies may have a pathogenic role. Recent studies based on single-cell RNAseq and multi-omics approaches are revealing unforeseen heterogeneity in SSc cell differentiation and functional states. Advances in system biology applied to the wealth of data generated by unbiased screening are allowing to subgroup patients based on distinct pathogenic mechanisms. Deciphering heterogeneity in pathogenic mechanisms will pave the way to highly needed personalized therapeutic approaches.

The Microbiome in Systemic Sclerosis: Pathophysiology and Therapeutic Potential.

Systemic sclerosis (SSc), also known as scleroderma, is an autoimmune disease with unknown etiology characterized by multi-organ fibrosis. Despite substantial investigation on SSc-related cellular and molecular mechanisms, effective therapies are still lacking. The skin, lungs, and gut are the most affected organs in SSc, which act as physical barriers and constantly communicate with colonized microbiota. Recent reports have documented a unique microbiome signature, which may be the pathogenic trigger or driver of SSc. Since gut microbiota influences the efficacy and toxicity of oral drugs, evaluating drug-microbiota interactions has become an area of interest in disease treatment. The existing evidence highlights the potential of the microbial challenge as a novel therapeutic option in SSc. In this review, we have summarized the current knowledge about molecular mechanisms of SSc and highlighted the underlying role of the microbiome in SSc pathogenesis. We have also discussed the latest therapeutic interventions using microbiomes in SSc, including drug-microbiota interactions and animal disease models. This review aims to elucidate the pathophysiological connection and therapeutic potential of the microbiome in SSc. Insights into the microbiome will significantly improve our understanding of etiopathogenesis and developing therapeutics for SSc.

Environmental Risks for Systemic Sclerosis.

There is an increasing body of literature suggesting a relationship between environmental factors and the development of systemic sclerosis (SSc). These include occupational exposures, chemical materials, medications, alterations in the microbiome, and dysbiosis. Environmental exposures may impact epigenetic regulation thereby triggering an aberrant immune response resulting in the clinical and serologic phenotype that we diagnose as SSc. Screening and studying putative triggers will not only improve our understanding of the pathogenesis of SSc but also inform the institution for protective measures.

Involvement of B cells in the development of systemic sclerosis.

Systemic sclerosis (SSc) is a rare intractable systemic disease that causes fibrosis and vasculopathy against a background of autoimmune abnormalities. Although the etiology is not yet fully understood, the type of autoantibodies detected in SSc is closely associated with disease severity and prognosis, supporting that those autoimmune abnormalities play an important role in the pathogenesis of SSc. Although the direct pathogenicity of autoantibodies found in SSc is unknown, many previous studies have shown that B cells are involved in the development of SSc through a variety of functions. Furthermore, a number of clinical studies have been conducted in which B-cell depletion therapy has been tried for SSc, and many of these studies have found B-cell depletion therapy to be effective for SSc. However, the involvement of B cells in pathogenesis is complex, as they not only promote inflammation but also play an inhibitory role. This article outlines the role of B cells in the development of SSc, including the latest research.

T cell abnormalities in systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune disease with a poor prognosis. To date, the pathogenesis of SSc is still unclear; moreover, its pathological conditions include microvascular damage, inflammation, and immune abnormalities. Different types of T cells may cause vasculitis and fibrosis in SSc by means of up- and down-regulation of cell surface molecules, abnormal release of pro-fibrotic or pro-inflammatory cytokines and direct contact with fibroblasts. These T cells, which are mainly CD4 + T cells, include the subtypes, T follicular helper (Tfh) cells, regulatory T Cells (Treg), interleukin-17 (IL-17)-producing Th17 cells, CD4+ cytotoxic T lymphocytes (CTLs), and angiogenic T (Tang) cells. In addition to the Th1/Th2 imbalance, which has long been established, there is also a Th17/Treg imbalance in SSc. This imbalance may be closely related to the abnormal immune status of SSc. There is mounting evidence that suggest T cell abnormalities may be crucial to the pathogenesis of SSc. In terms of treatment, existing therapies that target T cells, such as immunosuppressive therapy (tacrolimus), Janus kinase(JAK) inhibitors, and biologics(abatacept), have had some success. Other non-drug therapies, including Mesenchymal stem cells (MSCs), have extensive and complex mechanisms of action actually including T cell regulation. Based on the current evidence, we believe that the study of T cells will further our understanding of the pathogenesis of SSc, and may lead to more targeted treatment optionsfor patients with SSc.

Precursors to Systemic Sclerosis and Systemic Lupus Erythematosus: From Undifferentiated Connective Tissue Disease to the Development of Identifiable Connective Tissue Diseases.

The pathogenesis of connective tissue diseases (CTDs), such as systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), is characterized by derangements of the innate and adaptive immune system, and inflammatory pathways leading to autoimmunity, chronic cytokine production, and chronic inflammation. The diagnosis of these diseases is based on meeting established criteria with symptoms, signs and autoantibodies. However, there are pre-clinical states where criteria are not fulfilled but biochemical and autoimmune derangements are present. Understanding the underlying processes responsible for disease pathogenesis in pre-clinical states, which place patients at increased risk for the development of established connective tissue diseases, represents an opportunity for early identification and potentially enables timely treatment with the goal of limiting disease progression and improved prognosis. This scoping review describes the role of the innate and adaptive immune responses in the pre-clinical states of undifferentiated CTD at risk for SSc and prescleroderma, the evolution of antibodies from nonspecific to specific antinuclear antibodies prior to SLE development, and the signaling pathways and inflammatory markers of fibroblast, endothelial, and T cell activation underlying immune dysregulation in these pre-clinical states.

PDGF/PDGFR: A Possible Molecular Target in Scleroderma Fibrosis.

Systemic sclerosis (SSc) is a clinically heterogeneous disorder of the connective tissue characterized by vascular alterations, immune/inflammatory manifestations, and organ fibrosis. SSc pathogenesis is complex and still poorly understood. Therefore, effective therapies are lacking and remain nonspecific and limited to disease symptoms. In the last few years, many molecular and cellular mediators of SSc fibrosis have been described, providing new potential options for targeted therapies. In this review: (i) we focused on the PDGF/PDGFR pathway as key signaling molecules in the development of tissue fibrosis; (ii) we highlighted the possible role of stimulatory anti-PDGFRα autoantibodies in the pathogenesis of SSc; (iii) we reported the most promising PDGF/PDGFR targeting therapies.

Autologous Haematopoietic Stem Cell Transplantation and Systemic Sclerosis: Focus on Interstitial Lung Disease.

Autologous hematopoietic stem cells transplantation (AHSCT) has been employed as treatment for severe systemic sclerosis (SSc) with high risk of organ failure. In the last 25 years overall survival and treatment-related mortality have improved, in accordance with a better patient selection and mobilization and conditioning protocols. This review analyzes the evidence from the last 5 years for AHSCT-treated SSc patients, considering in particular the outcomes related to interstitial lung disease. There are increasing data supporting the use of AHSCT in selected patients with rapidly progressive SSc. However, some unmet needs remain, such as an accurate patient selection, pre-transplantation analysis to identify subclinical conditions precluding the transplantation, and the alternatives for post-transplant ILD recurrence.

Systemic sclerosis in adults. Part I: Clinical features and pathogenesis.

Systemic sclerosis (SSc), also referred to as systemic scleroderma or scleroderma, is a rare, complex immune-mediated connective tissue disease characterized by progressive skin fibrosis and other clinically heterogenous features. The etiopathogenesis of SSc involves vasculopathy and immune system dysregulation occurring on a permissive genetic and epigenetic background, ultimately leading to fibrosis. Recent developments in our understanding of disease-specific autoantibodies and bioinformatic analyses has led to a reconsideration of the purely clinical classification of diffuse and limited cutaneous SSc subgroups. Autoantibody profiles are predictive of skin and internal organ involvement and disease course. Early diagnosis of SSc, with commencement of disease-modifying treatment, has the potential to improve patient outcomes. In SSc, many of the clinical manifestations that present early signs of disease progression and activity are cutaneous, meaning dermatologists can and should play a key role in the diagnosis and management of this significant condition. The first article in this continuing medical education series discusses the epidemiology, clinical characteristics, and pathogenesis of SSc in adults, with an emphasis on skin manifestations, the important role of dermatologists in recognizing these, and their correlation with systemic features and disease course.

Systemic sclerosis complicated with renal thrombotic microangiopathy: a case report and literature review.

BACKGROUND: Systemic sclerosis (SSc) may overlap with other connective tissue diseases, which is named overlap syndrome. Scleroderma renal crisis (SRC) is a rare but severe complication of SSc. SSc related thrombotic microangiopathy (SSc-TMA) is an infrequent pathology type of SRC, while SSc-TMA accompanied by overlap syndrome is very rare. CASE PRESENTATION: This study reported a case of acute kidney injury (AKI) accompanied with overlap syndrome of SSc, systemic lupus erythematosus (SLE) and polymyositis (PM). The renal pathology supported the diagnosis of SSc-TMA but not SLE or PM-related renal injury, characterized by renal arteriolar thrombosis, endothelial cells edema, little cast in tubules and mild immune complex deposition. The primary TMA related factors (ADAMTS13 and complement H factor) were normal. Thus, this case was diagnosed as secondary TMA associated with SSc. The patient was treated with renin angiotensin system inhibitors, sildenafil, supportive plasma exchange/dialysis, and rituximab combined with glucocorticoids. After 2 months of peritoneal dialysis treatment, her renal function recovered and dialysis was stopped. CONCLUSION: This study presented a case of SSc-TMA with overlap syndrome. Rituximab can be used as a treatment option in patients with high SRC risk or already manifesting SRC.

Anti-programmed death ligand 1 immunotherapies in cancer patients with pre-existing systemic sclerosis: A postmarketed phase IV safety assessment study.

OBJECTIVES: Cancer patients with pre-existing autoimmune disease, such as systemic sclerosis (SSc), are excluded from clinical trials, so the data on tolerability and efficacy of immune checkpoint inhibitors in these patients are limited. This study investigated the tolerability and efficacy of anti-programmed death ligand 1 (PD (L)1) immunotherapies in patients with pre-existing SSc. METHODS: Scleronco-01 was a multicentre, nationwide, open-label, phase IV observational study, from 2019 to 2021. RESULTS: Seventeen SSc patients receiving treatment for lung carcinoma (n = 13, 77%), head and neck cancer (n = 2, 12%), melanoma (n = 1, 6%), and colorectal carcinoma (n = 1, 6%) were included. The median (interquartile range) patient age was 60 (34-82) years. Fifteen (88%) patients received anti-PD1 (nivolumab and pembrolizumab) and two (12%) anti-PD-L1 (durvalumab). The median follow-up duration was 12 (range, 2-38) months. Four patients (24%) experienced flare-up of SSc symptoms. Ten patients (59%) developed an immune-related adverse event (grade I-II in 11 patients [65%], grade III-IV in one [6%]) without grade V. The overall response rate was 41% (7/17 patients). The median overall survival was 15.8 (95% confidence interval: 7.3 to not reached) months. CONCLUSION: Anti-PD1 or PD-L1 immunotherapies are suitable options for cancer patients with pre-existing SSc. Longer follow-up periods are required for long-term safety analyses.

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 been observed 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 in 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.

The role of the cholinergic anti-inflammatory pathway in autoimmune rheumatic diseases.

The cholinergic anti-inflammatory pathway (CAP) is a classic neuroimmune pathway, consisting of the vagus nerve, acetylcholine (ACh)-the pivotal neurotransmitter of the vagus nerve-and its receptors. This pathway can activate and regulate the activities of immune cells, inhibit cell proliferation and differentiation, as well as suppress cytokine release, thereby playing an anti-inflammatory role, and widely involved in the occurrence and development of various diseases; recent studies have demonstrated that the CAP may be a new target for the treatment of autoimmune rheumatic diseases. In this review, we will summarize the latest progress with the view of figuring out the role of the cholinergic pathway and how it interacts with inflammatory reactions in several autoimmune rheumatic diseases, and many advances are results from a wide range of experiments performed in vitro and in vivo.

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-ß 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.

Insights into the knowledge of complex diseases: Environmental infectious/toxic agents as potential etiopathogenetic factors of systemic sclerosis.

Systemic sclerosis (SSc) is a connective tissue disease secondary to three cardinal pathological features: immune-system alterations, diffuse microangiopathy, and fibrosis involving the skin and internal organs. The etiology of SSc remains quite obscure; it may encompass multiple host genetic and environmental -infectious/chemical-factors. The present review focused on the potential role of environmental agents in the etiopathogenesis of SSc based on epidemiological, clinical, and laboratory investigations previously published in the world literature. Among infectious agents, some viruses that may persist and reactivate in infected individuals, namely human cytomegalovirus (HCMV), human herpesvirus-6 (HHV-6), and parvovirus B19 (B19V), and retroviruses have been proposed as potential causative agents of SSc. These viruses share a number of biological activities and consequent pathological alterations, such as endothelial dysfunction and/or fibroblast activation. Moreover, the acute worsening of pre-existing interstitial lung involvement observed in SSc patients with symptomatic SARS-CoV-2 infection might suggest a potential role of this virus in the overall disease outcome. A variety of chemical/occupational agents might be regarded as putative etiological factors of SSc. In this setting, the SSc complicating silica dust exposure represents one of the most promising models of study. Considering the complexity of SSc pathogenesis, none of suggested causative factors may explain the appearance of the whole SSc; it is likely that the disease is the result of a multifactorial and multistep pathogenetic process. A variable combination of potential etiological factors may modulate the appearance of different clinical phenotypes detectable in individual scleroderma patients. The in-deep investigations on the SSc etiopathogenesis may provide useful insights in the broad field of human diseases characterized by diffuse microangiopathy or altered fibrogenesis.