Therapeutic interleukin-6 blockade reverses transforming growth factor-beta pathway activation in dermal fibroblasts: insights from the faSScinate clinical trial in systemic sclerosis

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.

News and failures from recent treatment trials in systemic sclerosis

There have been many recent trials in systemic sclerosis (SSc) that have explored treatment for skin or lung. Some have been encouraging, but there has also been disappointment reflecting potential limitations of treatment effect of study design. These trials are discussed and reviewed. Studies conducted in SSc are described and discussed with a focus on endpoint selection and trial design as well as potential mechanism of action and treatment effect. Studies have included very encouraging trials of interleukin 6 blockade, immunosuppression, and broad-spectrum tyrosine kinase inhibition. Other trials including recent studies of peroxisome proliferator-activated receptor agonists and specific intracellular signaling inhibitors such as imatinib or anti-transforming growth factor beta blocking strategies have been more disappointing. Trial design is improving, and overall, there are now almost positive trials using agents with great promise, and studies are also providing important biological insight into SSc. It is hoped that ongoing studies will further progress the field and move it toward better treatments for SSc that still represent a major unmet medical need.

Current and Potential New Targets in Systemic Sclerosis Therapy: a New Hope

PURPOSE OF REVIEW

Systemic sclerosis (SSc) is an autoimmune connective tissue disease in which there is an activation of fibroblast to a myofibroblast that secretes huge amounts of extracellular matrix. Currently, no treatment exists that modifies the fibrosis elements and new therapeutic targets are badly needed. This review examines the current state of treatments and emerging therapeutics.

RECENT FINDINGS

Nintedanib was found to significantly reduce the rate of decline in SSc associated FVC, although it has no benefit on skin fibrosis. New cannabinoid receptor2 agonist has shown superb effects in phase II and results in phase III are anticipated. Other targets are currently being tested in clinical trials and new targets that are yet to be tested are increasing in the SSc literature. Nintedanib is now licenced for SSc interstitial lung disease but this does not modify the skin fibrosis. Current ongoing trials will determine the role of various targets. New targets are emerging as we gain a deeper understanding of disease pathogenesis.

Is biological therapy in systemic sclerosis the answer?

Systemic sclerosis is a systemic fibrosing disorder associated with significant morbidity and mortality, with no universally accepted disease-modifying therapy. Significant advances in the understanding of systemic sclerosis in recent years have guided the exploration of biological drugs in systemic sclerosis. In this narrative review, we summarize the published literature on biologic therapies in systemic sclerosis. A double-blind randomized trial, and an open label trial of tocilizumab (which antagonizes the interleukin 6 receptor), identified potential benefits in skin and lung fibrosis in systemic sclerosis; however, these differences failed to attain statistical significance. Two open-label trials compared rituximab (which depletes B lymphocytes) to conventional treatment/ cyclophosphamide in systemic sclerosis-associated interstitial lung disease (ILD), and revealed significant improvements in lung functions and skin disease with rituximab. Significant observational data also support the use of rituximab in skin, lung, muscle and joint manifestations of systemic sclerosis. Abatacept (which blocks T lymphocyte activation) has demonstrated utility for skin and joint disease in systemic sclerosis; a recent clinical trial failed to demonstrate benefits in improving skin thickness compared to placebo. Agents targeting type I interferons, interleukin 17 pathway, CD19 and plasma cells hold promise in systemic sclerosis; however, high-quality evidence is lacking. The results of different ongoing clinical trials targeting B lymphocytes, T lymphocytes, various cytokines (interleukins 6, 17, 4, 13, IL-1α), platelet-derived growth factor receptor, proteasome, integrins or oncostatin M may help guide future therapeutic regimens with biological agents in systemic sclerosis.

The Role of IL-6 in Skin Fibrosis and Cutaneous Wound Healing

The timely resolution of wound healing is critical for restoring the skin as a protective barrier. The switch from a proinflammatory to a reparative microenvironment must be tightly regulated. Interleukin (IL)-6 is a key modulator of the inflammatory and reparative process: it is involved in the differentiation, activation, and proliferation of leukocytes, endothelial cells, keratinocytes, and fibroblasts. This review examines the role of IL-6 in the healing of cutaneous wounds, and how dysregulation of IL-6 signaling can lead to either fibrosis or a failure to heal. The role of an IL-6/TGF-β feedback loop is discussed in the context of fibrogenesis, while IL-6 expression and responses in advanced age, diabetes, and obesity is outlined regarding the development of chronic wounds. Current research on therapies that modulate IL-6 is explored. Here, we consider IL-6′s diverse impact on cutaneous wound healing.

Nanomaterials for Nanotheranostics: Tuning Their Properties According to Disease Needs

Nanotheranostics is one of the biggest scientific breakthroughs in nanomedicine. Most of the currently available diagnosis and therapies are invasive, time-consuming, and associated with severe toxic side effects. Nanotheranostics, on the other hand, has the potential to bridge this gap by harnessing the capabilities of nanotechnology and nanomaterials for combined therapeutics and diagnostics with markedly enhanced efficacy. However, nanomaterial applications in nanotheranostics are still in its infancy. This is due to the fact that each disease has a particular microenvironment with well-defined characteristics, which promotes deeper selection criteria of nanomaterials to meet the disease needs. In this review, we have outlined how nanomaterials are designed and tailored for nanotheranostics of cancer and other diseases such as neurodegenerative, autoimmune (particularly on rheumatoid arthritis), and cardiovascular diseases. The penetrability and retention of a nanomaterial in the biological system, the therapeutic strategy used, and the imaging mode selected are some of the aspects discussed for each disease. The specific properties of the nanomaterials in terms of feasibility, physicochemical challenges, progress in clinical trials, its toxicity, and their future application on translational medicine are addressed. Our review meticulously and critically examines the applications of nanotheranostics with various nanomaterials, including graphene, across several diseases, offering a broader perspective of this emerging field.

Pathogenesis of systemic sclerosis associated interstitial lung disease

Systemic sclerosis is an autoimmune disease leading to vasculopathy and fibrosis of skin and internal organs. Despite likely shared pathogenic mechanisms, the patterns of skin and lung fibrosis differ. Pathogenesis of interstitial lung disease, a major cause of death in systemic sclerosis, reflects the intrinsic disease pathobiology and is associated with distinct clinical phenotypes and laboratory characteristics. The commonest histological pattern of systemic sclerosis–interstitial lung disease is non-specific interstitial pneumonia. Systemic sclerosis–interstitial lung disease pathogenesis involves multiple components, including susceptibility and triggering factors, which could be genetic or environmental. The process is amplified likely through ongoing inflammation and the link between inflammatory activity and fibrosis with IL6 emerging as a key mediator. The disease is driven by epithelial injury, reflected by markers in the serum, such as surfactant proteins and KL-6. In addition, mediators that are produced by epithelial cells and that regulate inflammatory cell trafficking may be important, especially CCL2. Other factors, such as CXCL4 and CCL18, point towards immune-mediated damage or injury response. Monocytes and alternatively activated macrophages appear to be important. Transforming growth factor beta appears central to pathogenesis and regulates epithelial repair and fibroblast activation. Understanding pathogenesis may help to unravel the stages of systemic sclerosis–interstitial lung disease, risks of progression and determinants of outcome. With this article, we set out to review the multiple factors, including genetic, environmental, cellular and molecular, that may be involved in the pathogenesis of systemic sclerosis–interstitial lung disease and the mechanisms leading to sustained fibrosis. We propose a model for the pathogenesis of systemic sclerosis–interstitial lung disease, based on the available literature.

TGF-β pathway activation by idiopathic pulmonary fibrosis (IPF) fibroblast derived soluble factors is mediated by IL-6 trans-signaling

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic and ultimately fatal disease characterized by a progressive decline in lung function. Fibrotic diseases, such as IPF, are characterized by uncontrolled activation of fibroblasts. Since the microenvironment is known to affect cell behavior, activated fibroblasts can in turn activate healthy neighboring cells. Thus, we investigated IPF paracrine signaling in human lung fibroblasts (HLFs) derived from patients with IPF.

Methods

Primary human fibroblast cultures from IPF (IPF-HLF) and control donor (N-HLF) lung tissues were established and their supernatants were collected. These supernatants were then added to N-HLFs for further culture. Protein and RNA were extracted from IPF/ N-HLFs at baseline. Interleukin-6 (IL-6) and TGF-β-related signaling factors (e.g. STAT3, Smad3) were evaluated by western blot and qPCR. IL-6 levels were measured by ELISA. IL-6 signaling was blocked by Tocilizumab (TCZ) (10 ng/ml).

Results

IPF-HLFs were found to significantly overexpress IL-6 receptor (IL-6R), suppressor of cytokine signaling 3 (SOCS3), phospho-STAT3-Y705 and phospho-Smad3 in comparison to N-HLFs (p < 0.05). In addition, they were found to proliferate faster, secrete more IL-6 and express higher levels of the soluble IL-6R. IPF-HLF increased proliferation was inhibited by TCZ. Moreover, IPF-HLF derived supernatants induced both direct and indirect STAT3 activation that resulted in Smad3 phosphorylation and elevated Gremlin levels in N-HLFs. These effects were also successfully blocked by TCZ.

Conclusions

IPF-HLF paracrine signaling leads to IL-6R overexpression, which in turn, affects N-HLF survival. The IL-6/STAT3/Smad3 axis facilitates cellular responses that could potentially promote fibrotic disease. This interplay was successfully blocked by TCZ.

Emerging targets of disease-modifying therapy for systemic sclerosis

Systemic sclerosis (SSc) has the highest cause-specific mortality of all the connective tissue diseases, and the aetiology of this complex and heterogeneous condition remains an enigma. Current disease-modifying therapies for SSc predominantly target inflammatory and vascular pathways but have variable and unpredictable clinical efficacy, and none is curative. Moreover, many of these therapies possess undesirable safety profiles and have no appreciable effect on long-term mortality. This Review describes the most promising of the existing therapeutic targets for SSc and places them in the context of our evolving understanding of the pathophysiology of this disease. As well as taking an in-depth look at the immune, inflammatory, vascular and fibrotic pathways implicated in the pathogenesis of SSc, this Review discusses emerging treatment targets and therapeutic strategies. The article concludes with an overview of important unanswered questions in SSc research that might inform the design of future studies of treatments aimed at modifying the course of this disease.

Targeted therapies in systemic sclerosis, myositis, antiphospholipid syndrome, and Sjögren's syndrome

Targeted therapies using biological disease-modifying antirheumatic drugs (bDMARDs) and small molecule synthetic drugs have revolutionized rheumatological practice. Initially developed for the treatment of immune arthritis (rheumatoid arthritis, psoriatic arthritis, and spondylarthritis), both bDMARDs and small molecule synthetic drugs are now increasingly entering the space of connective tissue disease (CTD) treatment. Recent clinical trial data in systemic sclerosis (SSc) have been particularly encouraging with positive effects on outcomes having been observed with nintedanib preventing the decline of lung function in patients with SSc-related interstitial lung disease. Randomized trials targeting B-cells by rituximab in primary Sjogren's syndrome have led to mixed results. Novel strategies to target B-cells in primary Sjögren's syndrome including ianalumab and belimumab are underway and will hopefully result in clear treatment effects. Inflammatory idiopathic myositis (polymyositis (PM) and dermatomyositis (DM)) and antiphospholid syndrome are proving to be more difficult to tackle but are nonetheless the subject of ongoing studies. To what extent new compounds can replace more traditional immunosuppressive drugs remains to be determined, but if the experience in immune arthritis has taught us anything it is that combination therapy may be the way to go.

The JAK/STAT pathway is activated in systemic sclerosis and is effectively targeted by tofacitinib

Rationale

Fibrosis leads to failure of the skin, lungs, and other organs in systemic sclerosis; accounts for substantial morbidity and mortality; and lacks effective therapy. Myofibroblast activation underlies organ fibrosis, but the key extracellular cues driving persistence of the process remain incompletely characterized.

Objectives

The objectives were to evaluate activation of the IL6/JAK/STAT axis associated with fibrosis in skin and lung biopsies from systemic sclerosis patients and effects of the Food and Drug Administration-approved JAK/STAT inhibitor, tofacitinib, on skin and lung fibrosis in animal models.

Methods

Bioinformatic analysis showed that IL6/JAK/STAT3 and tofacitinib gene signatures were aberrant in biopsies from systemic sclerosis patients in four independent cohorts. The results were confirmed by JAK and STAT3 phosphorylation in both skin and lung biopsies from patients with systemic sclerosis. Furthermore, treatment of mice with the selective JAK inhibitor tofacitinib not only prevented bleomycin-induced skin and lung fibrosis but also reduced skin fibrosis in TSK1/+ mice.

Conclusion

These findings implicate the JAK/STAT pathway in systemic sclerosis skin and lung fibrosis and identify tofacitinib as a potential antifibrotic agent for the treatment of systemic sclerosis and other fibrotic diseases.

Transgenic interleukin 11 expression causes cross-tissue fibro-inflammation and an inflammatory bowel phenotype in mice

Interleukin 11 (IL11) is a profibrotic cytokine, secreted by myofibroblasts and damaged epithelial cells. Smooth muscle cells (SMCs) also secrete IL11 under pathological conditions and express the IL11 receptor. Here we examined the effects of SMC-specific, conditional expression of murine IL11 in a transgenic mouse (Il11SMC). Within days of transgene activation, Il11SMC mice developed loose stools and progressive bleeding and rectal prolapse, which was associated with a 65% mortality by two weeks. The bowel of Il11SMC mice was inflamed, fibrotic and had a thickened wall, which was accompanied by activation of ERK and STAT3. In other organs, including the heart, lung, liver, kidney and skin there was a phenotypic spectrum of fibro-inflammation, together with consistent ERK activation. To investigate further the importance of stromal-derived IL11 in the inflammatory bowel phenotype we used a second model with fibroblast-specific expression of IL11, the Il11Fib mouse. This additional model largely phenocopied the Il11SMC bowel phenotype. These data show that IL11 secretion from the stromal niche is sufficient to drive inflammatory bowel disease in mice. Given that IL11 expression in colonic stromal cells predicts anti-TNF therapy failure in patients with ulcerative colitis or Crohn's disease, we suggest IL11 as a therapeutic target for inflammatory bowel disease.

Non-canonical (non-SMAD2/3) TGF-β signaling in fibrosis: Mechanisms and targets

Transforming growth factor (TGF)-β uses several intracellular signaling pathways besides canonical ALK5-Smad2/3 signaling to regulate a diverse array of cellular functions. Several of these so-called non-canonical (non-Smad2/3) pathways have been implicated in the pathogenesis of fibrosis and may therefore represent targets for therapeutic intervention. This review summarizes our current knowledge on the mechanisms of non-canonical TGF-β signaling in fibrosis, the potential molecular targets and the use of agonists/antagonists for therapeutic intervention.

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.

Inflammatory stays inflammatory: a subgroup of systemic sclerosis characterized by high morbidity and inflammatory resistance to cyclophosphamide

Background/purpose

Elevated levels of C-reactive protein (CRP) in systemic sclerosis (SSc) have been linked to early inflammatory stages of the disease. This study has been designed to investigate CRP levels longitudinally in a cohort of SSc patients and to correlate these findings with comorbidities and disease characteristics.

Methods

In this retrospective study, patients with SSc treated at the outpatient clinic of the Department of Rheumatology and Clinical Immunology, University Medical Center Freiburg, were analyzed. Only patients with at least three consecutive visits and at least 1 year follow-up were included in this study. CRP serum levels were measured at every visit and categorized as positive if CRP concentrations were ≥ 5 mg/l. Subjects with elevated CRP levels at more than 80% of visits were defined as inflammatory SSc. The longitudinal CRP profiles were correlated with disease characteristics and comorbidities.

Results

A total of 1815 consecutive visits of 131 SSc patients were analyzed. Over the observed time span (7.6 (1.0–19.5) years), 18.3% (n = 24) of patients had continuously elevated CRP levels (inflammatory SSc), whereas in 29% (n = 38), CRP levels were always in the normal range. There was no association between disease duration and CRP levels at first visit. Inflammatory SSc was associated with male gender (p = 0.022), anti-Scl-70 antibodies (p = 0.009), diffuse cutaneous SSc (p = 0.036), pulmonary fibrosis (p < 0.001), rheumatoid arthritis (p = 0.007), and cardiac arrhythmia (p = 0.048). Moreover, patients with inflammatory SSc revealed higher modified Rodnan skin scores (p < 0.001); lower forced vital capacity (FVC) (p < 0.001), total lung capacity (p = 0.001), and diffusing capacity (p = 0.008); and faster decline of FVC per year (p = 0.007). Even treatment with cyclophosphamide (CYC) did not decrease CRP levels (p = 0.754).

Conclusion

Inflammatory SSc is characterized by a more severe phenotype, high morbidity, and a large proportion of male patients. Even treatment with CYC does not alter CRP levels in this subpopulation with a high unmet medical need.

Insights into myofibroblasts and their activation in scleroderma: opportunities for therapy?

PURPOSE OF REVIEW

The persistence of myofibroblasts is a key feature of fibrosis and in fibrotic diseases including scleroderma. This review evaluates the emerging concepts of the origins and cell populations that contribute to myofibroblasts and the molecular mechanisms that govern phenotypic conversion and that highlight opportunities for new interventional treatments in scleroderma.

RECENT FINDINGS

Studies have defined heterogeneity in fibroblast-like cells that can develop into myofibroblast in normal wound healing, scarring and fibrosis. Characterizing these distinct cell populations and their behaviour has been a key focus. In addition, the overarching impact of epigenetic regulation of genes associated with inflammatory responses, cell signalling and cell communication and the extracellular matrix (ECM) has provided important insights into the formation of myofibroblast and their function. Important new studies include investigations into the relationship between inflammation and myofibroblast production and further evidence has been gathered that reveal the importance of ECM microenvironment, biomechanical sensing and mechanotransduction.

SUMMARY

This review highlights our current understanding and outlines the increasing complexity of the biological processes that leads to the appearance of the myofibroblast in normal functions and in diseased tissues. We also focus on areas of special interest in particular, studies that have therapeutic potential in fibrosis and scleroderma.

Inhibition of the Progression of Skin Inflammation, Fibrosis, and Vascular Injury by Blockade of the CX3 CL1/CX3 CR1 Pathway in Experimental Mouse Models of Systemic Sclerosis

OBJECTIVE

To assess the preclinical efficacy and mechanism of action of an anti-CX₃ CL1 monoclonal antibody (mAb) in systemic sclerosis (SSc).

METHODS

Cultured human dermal fibroblasts were used to evaluate the direct effect of anti-CX₃ CL1 mAb on fibroblasts. In addition, bleomycin-induced and growth factor-induced models of SSc were used to investigate the effect of anti-CX₃ CL1 mAb on leukocyte infiltration, collagen deposition, and vascular damage in the skin.

RESULTS

Anti-CX₃ CL1 mAb treatment significantly inhibited Smad3 phosphorylation (P < 0.05) and expression of type I collagen and fibronectin 1 (P < 0.01) in dermal fibroblasts stimulated with transforming growth factor β1 (TGFβ1). In the bleomycin model, daily subcutaneous bleomycin injection increased serum CX₃ CL1 levels (P < 0.05) and augmented lesional CX₃ CL1 expression. Simultaneous administration of anti-CX₃ CL1 mAb or CX₃ CR1 deficiency significantly suppressed the dermal thickness, collagen content, and capillary loss caused by bleomycin (P < 0.05). Injection of bleomycin induced expression of pSmad3 and TGFβ1 in the skin, which was inhibited by anti-CX₃ CL1 mAb. Further, the dermal infiltration of CX₃ CR1+ cells, macrophages (inflammatory and alternatively activated [M2-like] subsets), and CD3+ cells significantly decreased following anti-CX₃ CL1 mAb therapy (P < 0.05), as did the enhanced skin expression of fibrogenic molecules, such as thymic stromal lymphopoietin and secreted phosphoprotein 1 (P < 0.05). However, the treatment did not significantly reduce established skin fibrosis. In the second model, simultaneous anti-mCX₃ CL1 mAb therapy significantly diminished the skin fibrosis induced by serial subcutaneous injection of TGFβ and connective tissue growth factor (P < 0.01).

CONCLUSION

Anti-CX₃ CL1 mAb therapy may be a novel approach for treating early skin fibrosis in inflammation-driven fibrotic skin disorders such as SSc.

CCN1 expression by fibroblasts is required for bleomycin-induced skin fibrosis

The microenvironment contributes to the excessive connective tissue deposition that characterizes fibrosis. Members of the CCN family of matricellular proteins are secreted by fibroblasts into the fibrotic microenvironment; however, the role of endogenous CCN1 in skin fibrosis is unknown. Mice harboring a fibroblast-specific deletion for CCN1 were used to assess if CCN1 contributes to dermal homeostasis, wound healing, and skin fibrosis. Mice with a fibroblast-specific CCN1 deletion showed progressive skin thinning and reduced accumulation of type I collagen; however, the overall mechanical property of skin (Young's modulus) was not significantly reduced. Real time-polymerase chain reaction analysis revealed that CCN1-deficient skin displayed reduced expression of mRNAs encoding enzymes that promote collagen stability (including prolyl-4-hydroxylase and PLOD2), although expression of COL1A1 mRNA was unaltered. CCN1-deficent skin showed reduced hydroxyproline levels. Electron microscopy revealed that collagen fibers were disorganized in CCN1-deficient skin. CCN1-deficient mice were resistant to bleomycin-induced skin fibrosis, as visualized by reduced collagen accumulation and skin thickness suggesting that deposition/accumulation of collagen is impaired in the absence of CCN1. Conversely, CCN1-deficient mice showed unaltered wound closure kinetics, suggesting de novo collagen production in response to injury did not require CCN1. In response to either wounding or bleomycin, induction of α-smooth muscle actin-positive myofibroblasts was unaffected by loss of CCN1. CCN1 protein was overexpressed by dermal fibroblasts isolated from lesional (i.e., fibrotic) areas of patients with early onset diffuse scleroderma. Thus, CCN1 expression by fibroblasts, being essential for skin fibrosis, is a viable anti-fibrotic target.

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The role of endogenous CCN1 in skin biology is largely unknown

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Fibroblast-specific deletion CCN1 causes thinner skin and misaligned collagen

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CCN1-deficient mice were resistant to bleomycin-induced skin fibrosis

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Wound healing closure kinetics was unaffected by loss of CCN1

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CCN1 may be as a target for anti-fibrotic therapy

Evolving insights into the cellular and molecular pathogenesis of fibrosis in systemic sclerosis

Systemic sclerosis (SSc, scleroderma) is a complex multisystem disease characterized by autoimmunity, vasculopathy, and most notably, fibrosis. Multiple lines of evidence demonstrate a variety of emerging cellular and molecular pathways which are relevant to fibrosis in SSc. The myofibroblast remains the key effector cell in SSc. Understanding the development, differentiation, and function of the myofibroblast is therefore crucial to understanding the fibrotic phenotype of SSc. Studies now show that (1) multiple cell types give rise to myofibroblasts, (2) fibroblasts and myofibroblasts are heterogeneous, and (3) that a large number of (primarily immune) cells have important influences on the transition of fibroblasts to an activated myofibroblasts. In SSc, this differentiation process involves multiple pathways, including well known signaling cascades such as TGF-β and Wnt/β-Catenin signaling, as well as epigenetic reprogramming and a number of more recently defined cellular pathways. After reviewing the major and emerging cellular and molecular mechanisms underlying SSc, this article looks to identify clinical applications where this new molecular knowledge may allow for targeted treatment and personalized medicine approaches.

Coordination of Immune-Stroma Crosstalk by IL-6 Family Cytokines

Stromal cells are a subject of rapidly growing immunological interest based on their ability to influence virtually all aspects of innate and adaptive immunity. Present in every bodily tissue, stromal cells complement the functions of classical immune cells by sensing pathogens and tissue damage, coordinating leukocyte recruitment and function, and promoting immune response resolution and tissue repair. These diverse roles come with a price: like classical immune cells, inappropriate stromal cell behavior can lead to various forms of pathology, including inflammatory disease, tissue fibrosis, and cancer. An important immunological function of stromal cells is to act as information relays, responding to leukocyte-derived signals and instructing leukocyte behavior in kind. In this regard, several members of the interleukin-6 (IL-6) cytokine family, including IL-6, IL-11, oncostatin M (OSM), and leukemia inhibitory factor (LIF), have gained recognition as factors that mediate crosstalk between stromal and immune cells, with diverse roles in numerous inflammatory and homeostatic processes. This review summarizes our current understanding of how IL-6 family cytokines control stromal-immune crosstalk in health and disease, and how these interactions can be leveraged for clinical benefit.

Treatment of systemic sclerosis associated fibrotic manifestations: Current options and future directions

Systemic sclerosis (SSc) is a complicated multisystem disease which is characterized by the highest standardized mortality ratio among all systemic rheumatic diseases with no approved therapies so far. From a pathogenetic point of view it is generally considered that autoimmunity, vasculopathy and fibrosis are the main pathophysiologic processes. In this opinion article/minireview we will discuss current and future options for SSc-related fibrotic manifestations (skin thickening and lung fibrosis). Based on the results of SLS II the best treatment option for skin involvement in SSc is mycophenolate mofetil (MMF). Methotrexate (MTX) is another option which is safe and of low cost but evidence supporting its use is weak. The standard of care for SSc-ILD nowadays is MMF. Patients not responding to MMF could be treated with rituximab (RTX) or cyclophosphamide (CYC) (tocilizumab [TCZ] could be an option as well but only for patients with increased inflammatory markers). Hematopoietic stem cell transplantation (HSCT) could be considered in patients with severe/life-threatening disease who have failed conventional treatment. The most promising therapeutic approach currently been evaluated in phase 3 trials is probably the combination of MMF plus pirfenidone.

Unraveling SSc Pathophysiology; The Myofibroblast

Systemic sclerosis (SSc) is a severe auto-immune disease, characterized by vasculopathy and fibrosis of connective tissues. SSc has a high morbidity and mortality and unfortunately no disease modifying therapy is currently available. A key cell in the pathophysiology of SSc is the myofibroblast. Myofibroblasts are fibroblasts with contractile properties that produce a large amount of pro-fibrotic extracellular matrix molecules such as collagen type I. In this narrative review we will discuss the presence, formation, and role of myofibroblasts in SSc, and how these processes are stimulated and mediated by cells of the (innate) immune system such as mast cells and T helper 2 lymphocytes. Furthermore, current novel therapeutic approaches to target myofibroblasts will be highlighted for future perspective.