Transforming growth factor β--at the centre of systemic sclerosis

The role of long non-coding RNAs in rheumatic diseases

Long non-coding RNAs (lncRNAs) have emerged as key epigenetic regulators that govern gene expression and influence multiple biological processes. Accumulating evidence demonstrates that lncRNAs have critical roles in immune cell development and function. In this Review, the molecular mechanisms of gene expression regulation by lncRNAs are described and current knowledge of the role of lncRNAs in immune regulation and inflammation are presented, highlighting strategies for defining the roles of lncRNAs in the pathogenesis of multiple rheumatic diseases. Finally, research progress in understanding the role of lncRNAs in rheumatic diseases is discussed.

Therapeutic Targeting of TAZ and YAP by Dimethyl Fumarate in Systemic Sclerosis Fibrosis

Systemic sclerosis (scleroderma, SSc) is a devastating fibrotic disease with few treatment options. Fumaric acid esters, including dimethyl fumarate (DMF, Tecfidera; Biogen, Cambridge, MA), have shown therapeutic effects in several disease models, prompting us to determine whether DMF is effective as a treatment for SSc dermal fibrosis. We found that DMF blocks the profibrotic effects of transforming growth factor-β (TGFβ) in SSc skin fibroblasts. Mechanistically, we found that DMF treatment reduced nuclear localization of transcriptional coactivator with PDZ binding motif (TAZ) and Yes-associated protein (YAP) proteins via inhibition of the phosphatidylinositol 3 kinase/protein kinase B (Akt) pathway. In addition, DMF abrogated TGFβ/Akt1 mediated inhibitory phosphorylation of glycogen kinase 3β (GSK3β) and a subsequent β-transducin repeat-containing proteins (βTRCP) mediated proteasomal degradation of TAZ, as well as a corresponding decrease of TAZ/YAP transcriptional targets. Depletion of TAZ/YAP recapitulated the antifibrotic effects of DMF. We also confirmed the increase of TAZ/YAP in skin biopsies from patients with diffuse SSc. We further showed that DMF significantly diminished nuclear TAZ/YAP localization in fibroblasts cultured on a stiff surface. Importantly, DMF prevented bleomycin-induced skin fibrosis in mice. Together, our work demonstrates a mechanism of the antifibrotic effect of DMF via inhibition of Akt1/GSK3β/TAZ/YAP signaling and confirms a critical role of TAZ/YAP in mediating the profibrotic responses in dermal fibroblasts. This study supports the use of DMF as a treatment for SSc dermal fibrosis.

Morphea and Eosinophilic Fasciitis: An Update

Morphea, also known as localized scleroderma, encompasses a group of idiopathic sclerotic skin diseases. The spectrum ranges from relatively mild phenotypes, which generally cause few problems besides local discomfort and visible disfigurement, to subtypes with severe complications such as joint contractures and limb length discrepancies. Eosinophilic fasciitis (EF, Shulman syndrome) is often regarded as belonging to the severe end of the morphea spectrum. The exact driving mechanisms behind morphea and EF pathogenesis remain to be elucidated. However, extensive extracellular matrix formation and autoimmune dysfunction are thought to be key pathogenic processes. Likewise, these processes are considered essential in systemic sclerosis (SSc) pathogenesis. In addition, similarities in clinical presentation between morphea and SSc have led to many theories about their relatedness. Importantly, morphea may be differentiated from SSc based on absence of sclerodactyly, Raynaud’s phenomenon, and nailfold capillary changes. The diagnosis of morphea is often based on characteristic clinical findings. Histopathological evaluation of skin biopsies and laboratory tests are not necessary in the majority of morphea cases. However, full-thickness skin biopsies, containing fascia and muscle tissue, are required for the diagnosis of EF. Monitoring of disease activity and damage, especially of subcutaneous involvement, is one of the most challenging aspects of morphea care. Therefore, data harmonization is crucial for optimizing standard care and for comparability of study results. Recently, the localized scleroderma cutaneous assessment tool (LoSCAT) has been developed and validated for morphea. The LoSCAT is currently the most widely reported outcome measure for morphea. Care providers should take disease subtype, degree of activity, depth of involvement, and quality-of-life impairments into account when initiating treatment. In most patients with circumscribed superficial subtypes, treatment with topical therapies suffices. In more widespread disease, UVA1 phototherapy or systemic treatment with methotrexate (MTX), with or without a systemic corticosteroid combination, should be initiated. Disappointingly, few alternatives for MTX have been described and additional research is still needed to optimize treatment for these debilitating conditions. In this review, we present a state-of-the-art flow chart that guides care providers in the treatment of morphea and EF.

Endothelial cell-specific activation of transforming growth factor-β signaling in mice induces cutaneous, visceral, and microvascular fibrosis

In this study, we tested the hypothesis that constitutive endothelial cell-specific activation of TGF-β signaling induces tissue fibrosis and vasculopathy resembling the characteristic fibrotic and vascular alterations of systemic sclerosis. Transgenic mice with inducible expression of a constitutively active TGF-β receptor I specifically in endothelial cells were generated by intercrossing mice harboring a constitutively active TGF-β receptor I with a mouse strain containing the endothelial cell-specific Cdh5 gene promoter directing the tamoxifen-inducible expression of the Cre-ER^T2 cassette. Administration of tamoxifen to these mice would result in constitutive TGF-β activation and signaling confined to endothelial lineage cells. The effects of constitutive TGF-β endothelial cell activation were assessed by histopathological examination of skin and various internal organs, tissue hydroxyproline analysis, and assessment of expression of myofibroblast differentiation and TGF-β signaling genes employing real-time PCR and immunohistochemical staining of lung vessels for endothelial- and myofibroblast-specific proteins. Constitutive TGFβ-1 signaling in endothelial cells resulted in cutaneous and visceral fibrosis with prominent fibrotic involvement of the lungs and severe perivascular and subendothelial fibrosis of small arterioles. A marked increase in the expression of fibrosis-associated genes and of genes indicative of myofibroblast activation was also found. Confocal microscopy of lung vessels showed evidence consistent with the induction of endothelial-to-mesenchymal transition (EndoMT). Taken together, our data indicate that transgenic mice with constitutive endothelial cell-specific activation of TGF-β signaling display severe cutaneous, pulmonary, and microvascular fibrosis resembling the fibrotic and microvascular alterations characteristic of systemic sclerosis.

Scleroderma Induced by Pembrolizumab: A Case Series

Immune checkpoint inhibitors are approved for select cancer treatment and have shown survival benefit in patients with advanced melanoma. Adverse events, including immune-related adverse events, are common and potentially life-threatening. We describe cases of 2 patients with scleroderma (patient 1 had diffuse scleroderma, and patient 2 had limited scleroderma) that developed while they were receiving pembrolizumab therapy for metastatic melanoma. Prompt recognition and treatment of immune-related adverse events may improve tolerance to immune checkpoint inhibitors and contribute to an understanding of the manifesting autoimmune disease.

Transforming growth factor-β signaling in systemic sclerosis

Systemic sclerosis (SSc) is a complex, multiorgan autoimmune disease of unknown etiology. Manifestation of the disease results from an interaction of three key pathologic features including irregularities of the antigen-specific immune system and the non-specific immune system, resulting in autoantibody production, vascular endothelial activation of small blood vessels, and tissue fibrosis as a result of fibroblast dysfunction. Given the heterogeneity of clinical presentation of the disease, a lack of universal models has impeded adequate testing of potential therapies for SSc. Regardless, recent research has elucidated the roles of various ubiquitous molecular mechanisms that contribute to the clinical manifestation of the disease. Transforming growth factor β (TGF-β) has been identified as a regulator of pathological fibrogenesis in SSc. Various processes, including cell growth, apoptosis, cell differentiation, and extracellular matrix synthesis are regulated by TGF-β, a type of cytokine secreted by macrophages and many other cell types. Understanding the essential role TGF-β pathways play in the pathology of systemic sclerosis could provide a potential outlet for treatment and a better understanding of this severe disease.

Anti-connective tissue growth factor (CTGF/CCN2) monoclonal antibody attenuates skin fibrosis in mice models of systemic sclerosis

Background

Systemic sclerosis (SSc) is characterized by fibrosis of the skin and internal organs. Although the involvement of connective tissue growth factor (CTGF/CCN2) has been well-documented in SSc fibrosis, the therapeutic potential of targeting CTGF in SSc has not been fully investigated. Our aim was to examine the therapeutic potential of CTGF blockade in a preclinical model of SSc using two approaches: smooth muscle cell fibroblast-specific deletion of CTGF (CTGF knockout (KO)) or a human anti-CTGF monoclonal antibody, FG-3019.

Methods

Angiotensin II (Ang II) was administered for 14 days by subcutaneous osmotic pump to CTGF KO or C57BL/6 J mice. FG-3019 was administered intraperitoneally three times per week for 2 weeks. Skin fibrosis was evaluated by histology and hydroxyproline assay. Immunohistochemistry staining was used for alpha smooth muscle actin (αSMA), platelet-derived growth factor receptor β (PDGFRβ), pSmad2, CD45, von Willebrand factor (vWF), and immunofluorescence staining was utilized for procollagen and Fsp1.

Results

Ang II-induced skin fibrosis was mitigated in both CTGF KO and FG-3019-treated mice. The blockade of CTGF reduced the number of cells expressing PDGFRβ, procollagen, αSMA, pSmad2, CD45, and Fsp1 in the dermis. In addition, inhibition of CTGF attenuated vascular injury as measured by the presence of vWF-positive cells.

Conclusions

Our data indicate that inhibition of CTGF signaling presents an attractive therapeutic approach in SSc.

Use of Patterned Collagen Coated Slides to Study Normal and Scleroderma Lung Fibroblast Migration

Systemic sclerosis (SSc) is a spreading fibrotic disease affecting the skin and internal organs. We aimed to model pathogenic fibroblast migration in SSc in order to identify enhancing factors, measure the effect of migrating cells on underlying extracellular matrix (ECM) and test possible therapeutic inhibitors. Novel patterned collagen substrates were used to investigate alignment and migration of skin and lung fibroblasts from SSc patients and healthy controls. Normal lung but not skin fibroblasts consistently elongated and aligned with underlying collagen and migrated dependent on PDGF or serum. SSc lung fibroblasts remained growth factor dependent, did not migrate more rapidly and were less restricted to alignment of the collagen. Multiple collagen proline and lysine-modifying enzymes were identified in SSc but not control fibroblast extracellular matrix preparations, indicating differential levels of ECM modification by the diseased cells. Profiling of migrating cells revealed a possible SCF/c-Kit paracrine mechanism contributing to migration via a subpopulation of cells. Heparin, which binds ligands including PDGF and SCF, and imatininib which blocks downstream tyrosine kinase receptors, both inhibited lung fibroblast migration individually but showed synergy in SSc cells. Pathologic lung fibroblasts from SSc patients modify ECM during migration but remain growth factor dependent and sensitive to inhibitors.

Recent advances in understanding contextual TGFβ signaling

The appearance of the first animal species on earth coincides with the emergence of transforming growth factor β (TGFβ) pathways. The evolution of these animals into more complex organisms coincides with a progressively increased TGFβ repertoire through gene duplications and divergence, making secreted TGFβ molecules the largest family of morphogenetic proteins in humans. It is therefore not surprising that TGFβ pathways govern numerous aspects of human biology from early embryonic development to regeneration, hematopoiesis, neurogenesis, and immunity. Such heavy reliance on these pathways is reflected in the susceptibility to minor perturbations in pathway components that can lead to dysregulated signaling and a diverse range of human pathologies such as cancer, fibrosis, and developmental disorders. Attempts to comprehensively resolve these signaling cascades are complicated by the long-recognized paradoxical role the pathway plays in cell biology. Recently, several groups have probed examples of the disparate aspects of TGFβ biology in a variety of animal models and uncovered novel context-dependent regulatory mechanisms. Here, we briefly review recent advancements and discuss their overall impact in directing future TGFβ research.

Interleukin-9 and T helper type 9 cells in rheumatic diseases

Interleukin (IL)-9 is a 28-30 kDa monomeric glycosylated polypeptide belonging to the IL-7/IL-9 family of proteins that bind to a composite receptor consisting of the private receptor IL-9R and the IL-2 receptor, gamma (IL-2RG), a common gamma subunit shared by the receptors of many different cytokines. The IL-9R is expressed widely and IL-9 impacts a number of effector cells, such as effector T cells, B cells, innate lymphoid cells, mast cells, polymorphonuclear cells, epithelial cells and smooth muscle cells, playing an important role in regulating inflammatory immunity. The critical role of IL-9 in promoting cellular and humoral immune responses makes it an important focus of potential therapeutic interventions. Recently, a defined subset of T helper type cells, Th9 cells, has been identified by the potent production of IL-9. The involvement of the Th9 cell subset has been described in many types of inflammatory diseases, namely atopic diseases, helminth infections, experimental autoimmune encephalomyelitis and ulcerative colitis. In this review, we summarize the IL-9 biological activities, highlighting roles for IL-9 and Th9 cells in rheumatoid and psoriatic arthritis, systemic vasculitis, systemic lupus erythematosus and systemic sclerosis.

Apolipoprotein A1 Inhibits the TGF-β1-Induced Endothelial-to-Mesenchymal Transition of Human Coronary Artery Endothelial Cells

OBJECTIVE

Transforming growth factor β1 (TGF-β1) is the major cytokine for stimulating endothelial cells (ECs) to transdifferentiate to mesenchymal cells (MCs) in the process known as endothelial-to-mesenchymal transition (EndMT). Recently, TGF-β1-induced EndMT has been implicated in the pathogenesis of atherosclerosis (AS). It has been identified that apolipoprotein A1 (ApoA-I) obstructs TGF-β1-induced endothelial dysfunction, providing a protective effect for ECs and also anti-AS activity. However, the exact role of ApoA-I in TGF-β1-induced EndMT is not clear. In this study, we aimed to investigate whether ApoA-I can modulate TGF-β1-induced EndMT in human coronary artery ECs (HCAECs).

METHODS AND RESULTS

The HCAECs were treated with TGF-β1 with or without ApoA-I. Morphological changes in HCAECs and the expression of EndMT-related markers were evaluated. HCAECs treated with TGF-β1 were found to transform to MC morphology, with inconspicuous expression of EC markers such as vascular endothelial cadherin and CD31, and conspicuous expression of fibroblast-specific protein 1 (FSP-1) and α-smooth muscle actin. The treatment of HCAECs with ApoA-I inhibited the TGF-β1-induced EndMT, and elevated expression of EC markers was observed but reduced expression of MC markers. Moreover, ApoA-I impeded the expression level of Slug and Snail, crucial transcriptional factors of EndMT, and it inhibited the TGF-β1-induced phosphorylation of Smad2 and Smad3 which affected the EC morphology. In addition, the knockdown of ABCA1 by RNA interference eliminated the inhibition effect of ApoA-I on TGF-β1-induced EndMT.

CONCLUSIONS

Our findings revealed a novel mechanism for the ApoA-I protective effect on endothelium function via the inhibition of TGF-β1-induced EndMT. This might provide new insights for developing strategies for modulating AS and vascular remodeling.

Blockade of PDGF Receptors by Crenolanib Has Therapeutic Effect in Patient Fibroblasts and in Preclinical Models of Systemic Sclerosis

Systemic sclerosis (SSc) is a multi-organ fibrotic disease with few treatment options. Activated fibroblasts are the key effector cells in SSc responsible for the excessive production of collagen and the development of fibrosis. Platelet-derived growth factor (PDGF), a potent mitogen for cells of mesenchymal origin, has been implicated in the activation of SSc fibroblasts. Our aim was to examine the therapeutic potential of crenolanib, an inhibitor of PDGF receptor signaling, in cultured fibroblasts and in angiotensin II-induced skin and heart fibrosis. Crenolanib effectively inhibited proliferation and migration of SSc and healthy control fibroblasts and attenuated basal and transforming growth factor-β-induced expression of CCN2/CTGF and periostin. In contrast to healthy control fibroblasts, SSc fibroblasts proliferated in response to PDGFAA, whereas a combination of PDGFAA and CCN2 was required to elicit a similar response in healthy control fibroblasts. PDGF receptor α mRNA correlated with CCN2 and other fibrotic markers in the skin of SSc patients. In mice challenged with angiotensin II, PDGF receptor α-positive cells were increased in the skin and heart. These PDGF receptor α-positive cells co-localized with PDGF receptor β, procollagen, and periostin. Treatment with crenolanib attenuated the skin and heart fibrosis. Our data indicate that inhibition of PDGF signaling presents an attractive therapeutic approach for SSc.

Stretching Reduces Skin Thickness and Improves Subcutaneous Tissue Mobility in a Murine Model of Systemic Sclerosis

Objective

Although physical therapy can help preserve mobility in patients with systemic sclerosis (SSc), stretching has not been used systematically as a treatment to prevent or reverse the disease process. We previously showed in rodent models that stretching promotes the resolution of connective tissue inflammation and reduces new collagen formation after injury. Here, we tested the hypothesis that stretching would impact scleroderma development using a mouse sclerodermatous graft-versus-host disease (sclGvHD) model.

Methods

The model consists in the adoptive transfer (allogeneic) of splenocytes from B10.D2 mice (graft) into Rag2^−/− BALB/c hosts (sclGvHD), resulting in skin inflammation followed by fibrosis over 4 weeks. SclGvHD mice and controls were randomized to stretching in vivo for 10 min daily versus no stretching.

Results

Weekly ultrasound measurements of skin thickness and subcutaneous tissue mobility in the back (relative tissue displacement during passive trunk motion) successfully captured the different phases of the sclGvHD model. Stretching reduced skin thickness and increased subcutaneous tissue mobility compared to no stretching at week 3. Stretching also reduced the expression of CCL2 and ADAM8 in the skin at week 4, which are two genes known to be upregulated in both murine sclGvHD and the inflammatory subset of human SSc. However, there was no evidence that stretching attenuated inflammation at week 2.

Conclusion

Daily stretching for 10 min can improve skin thickness and mobility in the absence of any other treatment in the sclGvHD murine model. These pre-clinical results suggest that a systematic investigation of stretching as a therapeutic modality is warranted in patients with SSc.

Recent advances in managing systemic sclerosis

How the main components in systemic sclerosis—namely autoimmunity, vasculopathy, and fibrosis—fit together is still not sufficiently clear. However, vascular treatment options are well established, the body of evidence for the efficacy of immunomodulatory approaches is increasing, and now at least one hopeful substance that may directly interfere with fibrosis is being tested. Although we still wait for important breakthroughs, there is grounds for hope that better therapeutic options will be available in the near future.

Biomarkers in systemic sclerosis: Their potential to predict clinical courses

The concept of a biomarker was defined as "a characteristic marker that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention" by the National Institutes of Health Biomarkers Definitions Working group in 2001. Clinical features, disease progress, therapeutic response and prognosis are heterogeneous among patients with systemic sclerosis (SSc). Therefore, biomarkers that can predict these matters are required for the progress of clinical practice. At present, SSc-specific autoantibodies are the most useful biomarkers for diagnosis and predicting clinical features. Otherwise, biomarkers specific only for SSc have not been identified yet. The glycoprotein krebs von den Lungen-6, surfactant protein-D and CCL18 are promising serum biomarkers of SSc-related interstitial lung diseases. Serum/plasma levels of brain natriuretic peptide and serum N-terminal pro-brain natriuretic peptide have been used as biomarkers for SSc-related pulmonary arterial hypertension. Other potential serum/plasma biomarkers for fibrosis and vascular involvement of SSc are connective tissue growth factor, interleukin-6, CCL2, CXCL4, intercellular adhesion molecule (ICAM)-1, P-selectin, vascular endothelial growth factor, von Willebrand factor, endostatin, endoglin and endothelin-1. In our multicenter prospective studies of Japanese early SSc, serum ICAM-1 levels were predictive for subsequent respiratory dysfunction and serum levels of CXCL8 and P-selectin were predictive for subsequent physical disability. Further large, multicenter, prospective, longitudinal studies will be needed to identify and validate critical biomarkers of SSc.

Human Fibrotic Diseases: Current Challenges in Fibrosis Research

Human fibrotic diseases constitute a major health problem worldwide owing to the large number of affected individuals, the incomplete knowledge of the fibrotic process pathogenesis, the marked heterogeneity in their etiology and clinical manifestations, the absence of appropriate and fully validated biomarkers, and, most importantly, the current void of effective disease-modifying therapeutic agents. The fibrotic disorders encompass a wide spectrum of clinical entities including systemic fibrotic diseases such as systemic sclerosis (SSc), sclerodermatous graft vs. host disease, and nephrogenic systemic fibrosis, as well as numerous organ-specific disorders including radiation-induced fibrosis and cardiac, pulmonary, liver, and kidney fibrosis. Although their causative mechanisms are quite diverse and in several instances have remained elusive, these diseases share the common feature of an uncontrolled and progressive accumulation of fibrotic tissue in affected organs causing their dysfunction and ultimate failure. Despite the remarkable heterogeneity in the etiologic mechanisms responsible for the development of fibrotic diseases and in their clinical manifestations, numerous studies have identified activated myofibroblasts as the common cellular element ultimately responsible for the replacement of normal tissues with nonfunctional fibrotic tissue. Critical signaling cascades, initiated primarily by transforming growth factor-β (TGF-β), but also involving numerous cytokines and signaling molecules which stimulate profibrotic reactions in myofibroblasts, offer potential therapeutic targets. Here, we briefly review the current knowledge of the molecular mechanisms involved in the development of tissue fibrosis and point out some of the most important challenges to research in the fibrotic diseases and to the development of effective therapeutic approaches for this often fatal group of disorders. Efforts to further clarify the complex pathogenetic mechanisms of the fibrotic process should be encouraged to attain the elusive goal of developing effective therapies for these serious, untreatable, and often fatal disorders.

Egr2 and Egr3 in regulatory T cells cooperatively control systemic autoimmunity through Ltbp3-mediated TGF-β3 production

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease characterized by multiorgan inflammation induced by autoantibodies. Early growth response gene 2 (Egr2), a transcription factor essential for T-cell anergy induction, controls systemic autoimmunity in mice and humans. We have previously identified a subpopulation of CD4⁺ regulatory T cells, CD4⁺CD25^-LAG3⁺ cells, that characteristically express both Egr2 and LAG3 and control mice model of lupus via TGF-β3 production. However, due to the mild phenotype of lymphocyte-specific Egr2-deficient mice, the presence of an additional regulator has been speculated. Here, we show that Egr2 and Egr3 expressed in T cells cooperatively prevent humoral immune responses by supporting TGF-β3 secretion. T cell-specific Egr2/Egr3 double-deficient (Egr2/3DKO) mice spontaneously developed an early onset lupus-like disease that was more severe than in T cell-specific Egr2-deficient mice. In accordance with the observation that CD4⁺CD25^-LAG3⁺ cells from Egr2/3DKO mice completely lost the capacity to produce TGF-β3, the excessive germinal center reaction in Egr2/3DKO mice was suppressed by the adoptive transfer of WT CD4⁺CD25^-LAG3⁺ cells or treatment with a TGF-β3-expressing vector. Intriguingly, latent TGF-β binding protein (Ltbp)3 expression maintained by Egr2 and Egr3 was required for TGF-β3 production from CD4⁺CD25^-LAG3⁺ cells. Because Egr2 and Egr3 did not demonstrate cell intrinsic suppression of the development of follicular helper T cells, Egr2- and Egr3-dependent TGF-β3 production by CD4⁺CD25^-LAG3⁺ cells is critical for controlling excessive B-cell responses. The unique attributes of Egr2/Egr3 in T cells may provide an opportunity for developing novel therapeutics for autoantibody-mediated diseases including SLE.

Reassessing the Role of the Active TGF-β1 as a Biomarker in Systemic Sclerosis: Association of Serum Levels with Clinical Manifestations

Objective. To determine active TGF-β1 (aTGF-β1) levels in serum, skin, and peripheral blood mononuclear cell (PBMC) culture supernatants and to understand their associations with clinical parameters in systemic sclerosis (SSc) patients. Methods. We evaluated serum samples from 56 SSc patients and 24 healthy controls (HC). In 20 SSc patients, we quantified spontaneous or anti-CD3/CD28 stimulated production of aTGF-β1 by PBMC. The aTGF-β1 levels were measured by ELISA. Skin biopsies were obtained from 13 SSc patients and six HC, and TGFB1 expression was analyzed by RT-PCR. Results. TGF-β1 serum levels were significantly higher in SSc patients than in HC (p < 0.0001). Patients with increased TGF-β1 serum levels were more likely to have diffuse subset (p = 0.02), digital ulcers (p = 0.02), lung fibrosis (p < 0.0001), positive antitopoisomerase I (p = 0.03), and higher modified Rodnan score (p = 0.046). Most of our culture supernatant samples had undetectable levels of TGF-β1. No significant difference in TGFB1 expression was observed in the SSc skin compared with HC skin. Conclusion. Raised active TGF-β1 serum levels and their association with clinical manifestations in scleroderma patients suggest that this cytokine could be a marker of fibrotic and vascular involvement in SSc.

Glycyrrhizin Ameliorates Fibrosis, Vasculopathy, and Inflammation in Animal Models of Systemic Sclerosis

Systemic sclerosis (SSc) is a multisystem inflammatory and vascular disease resulting in extensive tissue fibrosis. Glycyrrhizin, clinically used for chronic hepatic diseases and itching dermatitis, modulates the pathological processes of inflammation, vasculopathy, and fibrosis in human diseases and their animal models. Therefore, we investigated a potential impact of glycyrrhizin on the key pathological manifestations of SSc, including inflammation, vasculopathy, and tissue fibrosis, with bleomycin-treated mice mimicking the fibrotic and inflammatory components of SSc and endothelial cell-specific Fli1-knockout mice recapitulating SSc vasculopathy. Glycyrrhizin significantly ameliorated dermal fibrosis in bleomycin-treated mice, which was partly attributable to blockade of transforming growth factor-β signaling in dermal fibroblasts through the down-regulation of thrombospondin 1, a latent transforming growth factor-β receptor, and transcription factors Smad3 and Ets1. Furthermore, bleomycin-dependent induction of T helper type 2-skewed immune polarization, M2 macrophage infiltration, and endothelial-to-mesenchymal transition were greatly suppressed in mice administered glycyrrhizin. Glycyrrhizin also improved vascular permeability of endothelial cell-specific Fli1-knockout mice by increasing the expression of molecules regulating vascular integrity. These results indicate that glycyrrhizin ameliorates bleomycin-induced dermal fibrosis through the inhibition of fibroblast activation, T helper type 2-skewed immune polarization, M2 macrophage infiltration, and endothelial-to-mesenchymal transition and improves endothelial Fli1 deficiency-dependent vascular disintegrity, implying its potential as a disease-modifying drug for SSc.

Bosentan and macitentan prevent the endothelial-to-mesenchymal transition (EndoMT) in systemic sclerosis: in vitro study

BACKGROUND

Systemic sclerosis (SSc) is characterized by early vascular abnormalities and subsequent fibroblast activation to myofibroblasts, leading to fibrosis. Recently, endothelial-to-mesenchymal transition (EndoMT), a complex biological process in which endothelial cells lose their specific markers and acquire a mesenchymal or myofibroblastic phenotype, has been reported in SSc. In the present study, we evaluated the ability of endothelin-1 (ET-1) dual receptor antagonists bosentan (BOS) and macitentan (MAC) to antagonize EndoMT in vitro.

METHODS

Ten women with limited SSc were enrolled. They underwent double skin biopsy (affected and nonaffected skin). Fibroblasts and microvascular endothelial cells (MVECs) were isolated from biopsies. We performed mono- or coculture of MVECs (isolated from nonaffected skin) with fibroblasts (isolated from affected skin and stimulated with ET-1 and transforming growth factor beta [TGF-β]). In cocultures, the MVEC layer was left undisturbed or was preincubated with BOS or MAC. After 48 h of coculture, MVECs were analyzed for their tube formation ability and for messenger RNA and protein expression of different vascular (CD31, vascular endothelial growth factor-A [VEGF-A], VEGF-A165b) and profibrotic (alpha-smooth muscle actin [α-SMA], collagen type I [Col I], TGF-β) molecules.

RESULTS

After 48 h, MVECs showed a reduced tube formation ability when cocultured with SSc fibroblasts. CD31 and VEGF-A resulted in downregulation, while VEGF-A165b, the antiangiogenic isoform, resulted in upregulation. At the same time, mesenchymal markers α-SMA, Col I, and TGF-β resulted in overexpression in MVECs. Tube formation ability was restored when MVECs were preincubated with BOS or MAC, also reducing the expression of mesenchymal markers and restoring CD31 expression and the imbalance between VEGF-A and VEGF-A165b.

CONCLUSIONS

With this innovative EndoMT in vitro model realized by coculturing nonaffected MVECs with affected SSc fibroblasts, we show that the presence of a myofibroblast phenotype in the fibroblast layer, coupled with an ET-1-TGF-β synergic effect, is responsible for EndoMT. BOS and MAC seem able to antagonize this phenomenon in vitro, confirming previous evidence of endothelium-derived fibrosis in SSc and possible pharmacological interference.

Anti-fibrotic effects of soluble guanylate cyclase stimulators and activators: A review of the preclinical evidence

It is now well established that the NO-sGC-cGMP signal transduction system mediates many different physiological functions in almost every conceivable organ system; this has been best characterized in the cardiovascular system where NO-driven cGMP production exerts a plethora of cytoprotective and anti-atherogenic effects, including dilatation, inhibition of vascular smooth muscle proliferation, blockade of leukocyte recruitment, and anti-platelet activity. Accordingly, dysfunctional NO-sGC-cGMP mediated signaling is perceived as the underlying pathophysiological cause of many cardiovascular and non-cardiovascular diseases. Due to the fundamental role of sGC in the signaling pathways triggered by NO, novel sGC 'modulators' have been identified that directly stimulate both heme-containing as well as heme-free sGC, the so-called 'sGC activators' and 'sGC stimulators', respectively. The beneficial effects of this new family of sGC 'modulators' extend beyond vasodilation, and their potential in other cardiovascular diseases aside from pulmonary arterial hypertension is promising. In animal models of hypertension and heart failure, reno-protective effects, attenuated cardiac fibrosis, and attenuated hypertrophy independent of hemodynamic effects have been shown. During recent years it has become obvious that cGMP increase by sGC modulators exerts direct antifibrotic efficacy in various organs as well as the skin. This review will provide an overview of the preclinical in vitro and in vivo studies for different fibrotic disorders including chronic renal, cardiac, liver, and lung fibrosis, as well as sclerosis and wound healing. Moreover, this review provides evidence for a new mode of action of sGC 'modulators' and its implication for clinical investigations in the treatment of fibrotic disorders such as pulmonary fibrosis and skin fibrosis.

Altered Dermal Fibroblasts in Systemic Sclerosis Display Podoplanin and CD90

Tissue injury triggers the activation and differentiation of multiple cell types to minimize damage and initiate repair processes. In systemic sclerosis, these repair processes appear to run unchecked, leading to aberrant remodeling and fibrosis of the skin and multiple internal organs, yet the fundamental pathological defect remains unknown. We describe herein a transition wherein the abundant CD34(+) dermal fibroblasts present in healthy human skin disappear in the skin of systemic sclerosis patients, and CD34(-), podoplanin(+), and CD90(+) fibroblasts appear. This transition is limited to the upper dermis in several inflammatory skin diseases, yet in systemic sclerosis, it can occur in all regions of the dermis. In vitro, primary dermal fibroblasts readily express podoplanin in response to the inflammatory stimuli tumor necrosis factor and IL-1β. Furthermore, we show that on acute skin injury in both human and murine settings, this transition occurs quickly, consistent with a response to inflammatory signaling. Transitioned fibroblasts partially resemble the cells that form the reticular networks in organized lymphoid tissues, potentially linking two areas of fibroblast research. These results allow for the visualization and quantification of a basic stage of fibroblast differentiation in inflammatory and fibrotic diseases in the skin.

Toll-like Receptor 9 Signaling Is Augmented in Systemic Sclerosis and Elicits Transforming Growth Factor β-Dependent Fibroblast Activation

OBJECTIVE

Although transforming growth factor β (TGFβ) is recognized as being a key trigger of fibroblast activation in systemic sclerosis (SSc), prominent innate immunity suggests that additional pathways contribute to disease persistence. Toll-like receptor 9 (TLR9) is implicated in autoimmunity and fibrosis; however, the expression, mechanism of action, and pathogenic role of TLR9 signaling in SSc remain uncharacterized. The aim of this study was to explore the expression, activity, and potential pathogenic role of TLR9 in the context of skin fibrosis in SSc and in mouse models of experimental fibrosis.

METHODS

Expression and localization of TLR9 were evaluated in SSc skin biopsy specimens and explanted skin fibroblasts. Fibrotic responses elicited by type A CpG oligonucleotide and mitochondrial DNA (mtDNA) were examined in human skin fibroblasts by a combination of real-time quantitative polymerase chain reaction, Western blot analysis, transient transfection, immunofluorescence microscopy, and functional assays. Expression of TLR9 was examined in 2 distinct mouse models of experimental fibrosis.

RESULTS

Skin biopsy specimens obtained from 2 independent cohorts of SSc patients showed up-regulation of TLR9, and myofibroblasts were the major cellular source. Moreover, SSc skin biopsy specimens showed evidence of TLR9 pathway activation. CpG induced robust TLR9-dependent fibrotic responses in explanted normal fibroblasts that could be blocked by bortezomib and were mediated through the action of endogenous TGFβ. Mice with experimental fibrosis showed a time-dependent increase in TLR9 localized primarily to myofibroblasts in the dermis.

CONCLUSION

In isolated fibroblasts, TLR9 elicits fibrotic responses mediated via endogenous TGFβ. In patients with SSc, mtDNA and other damage-associated TLR9 ligands in the skin might trigger localized activation of TLR9 signaling, TGFβ production, and consequent fibroblast activation. Disrupting this fibrotic process with inhibitors targeting TLR9 or its downstream signaling pathways might therefore represent a novel approach to SSc therapy.

The spectrum of orofacial manifestations in systemic sclerosis: a challenging management

Systemic sclerosis (SSc) is a rare multisystem connective tissue disorder characterized by the triad fibrosis, vasculopathy and immune dysregulation. This chronic disease has a significant impact on the orofacial region that is involved in more than two-thirds of the cases. SSc patients can show a wide array of oral manifestations, which are usually associated with a severe impairment of the quality of life. They often present a decreased the salivary flow and a reduced mouth opening that contribute substantially to the worsening of the oral health status. Therefore, SSc patients require specific and multidisciplinary interventions that should be initiated as early as possible. The identification of specific radiological and clinical signs at the early stage will improve the management of such patients. This study reviews the wide spectrum of orofacial manifestations associated with SSc and suggests clues for the oral management that remains challenging.

E3 ubiquitin ligase: A potential regulator in fibrosis and systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis in the skin and internal organs. The pathogenesis of SSc is not completely understood until now. Recently, many studies have focused on the role of E3 ubiquitin ligases in organ fibrosis. However, the possible regulatory mechanisms of E3 ubiquitin ligases in fibrosis and SSc are not well documented. In this review, we summarized that E3 ubiquitin ligases regulated fibrosis through ubiquitin-mediated degradation of TGF-β/Smad signaling pathway. Moreover, E3 ubiquitin ligases participated in regulating fibrosis by other methods, such as inducing epithelial transition to mesenchymal cell, enhancing the production of TGF-β and protecting activated hepatic stellate cells from apoptosis. However, the specific regulatory mechanisms of E3 ubiquitin ligases in scleroderma is still not fully understood. There are more works to be done to specify the mechanism of E3 ubiquitin ligases in regulation of fibrosis in SSc.

Updates on animal models of systemic sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology that is characterized by fibrosis of the skin and several internal organs, vasculopathy, inflammation and autoimmunity. Animal models have improved our understanding of the pathogenesis of SSc. Many inducible and genetic animal models of SSc have been developed and characterized in the last years. All of these models have different strengths and limitations and mimic different aspects of the pathogenesis of SSc. The purpose of this review is to summarize the characteristics of the various animal models of SSc and to provide an outline of how to use these models to study certain aspects in the pathogenesis of SSc and to test the effects of potential therapeutic approaches.

Perivascular Cells in Diffuse Cutaneous Systemic Sclerosis Overexpress Activated ADAM12 and Are Involved in Myofibroblast Transdifferentiation and Development of Fibrosis

Objective.

Microvascular damage is pivotal in the pathogenesis of systemic sclerosis (SSc), preceding fibrosis, and whose trigger is not still fully understood. Perivascular progenitor cells, with profibrotic activity and function, are identified by the expression of the isoform 12 of ADAM (ADAM12) and this molecule may be upregulated by transforming growth factor-β (TGF-β). The goal of this work was to evaluate whether pericytes in the skin of patients with diffuse cutaneous SSc (dcSSc) expressed ADAM12, suggesting their potential contribution to the fibrotic process, and whether TGF-β might modulate this molecule.

Methods.

After ethical approval, mesenchymal stem cells (MSC) and fibroblasts (FB) were isolated from bone marrow and skin samples collected from 20 patients with dcSSc. ADAM12 expression was investigated in the skin and in isolated MSC and FB treated with TGF-β by immunofluorescence, quantitative real-time PCR, and western blot. Further, we silenced ADAM12 expression in both dcSSc-MSC and -FB to confirm the TGF-β modulation.

Results.

Pericytes and FB of dcSSc skin showed an increased expression of ADAM12 when compared with healthy control skin. TGF-β in vitro treatment induced a significant increase of ADAM12 in both SSc-MSC and -FB, with the higher levels observed in dcSSc cells. After ADAM12 silencing, the TGF-β ability to upregulate α-smooth muscle actin in both SSc-MSC and SSc-FB was inhibited.

Conclusion.

Our results suggest that in SSc, pericytes that transdifferentiate toward activated FB are present in the vascular tree, and TGF-β, while increasing ADAM12 expression, may modulate this transdifferentiation.

Current perspectives on the immunopathogenesis of systemic sclerosis

Systemic sclerosis (SSc or scleroderma) is a progressive and highly debilitating autoimmune disorder characterized by inflammation, vasculopathy, and extensive fibrosis. SSc is highly heterogeneous in its clinical presentation, extent and severity of skin and internal organ involvement, and clinical course and has the highest fatality rate among connective tissue diseases. While clinical outcomes have improved in recent years, no current therapy is able to reverse or slow the natural progression of SSc, a reflection of its complex pathogenesis. Although activation of the immune system has long been recognized, the mechanisms responsible for the initiation of autoimmunity and the role of immune effector pathways in the pathogenesis of SSc remain incompletely understood. This review summarizes recent progress in disease pathogenesis with particular focus on the immunopathogenetic mechanisms of SSc.

Endothelial to Mesenchymal Transition (EndoMT) in the Pathogenesis of Human Fibrotic Diseases

Fibrotic diseases encompass a wide spectrum of clinical entities including systemic fibrotic diseases such as systemic sclerosis, sclerodermatous graft versus host disease, nephrogenic systemic fibrosis, and IgG₄-associated sclerosing disease, as well as numerous organ-specific disorders including radiation-induced fibrosis, and cardiac, pulmonary, liver, and kidney fibrosis. Although their causative mechanisms are quite diverse, these diseases share the common feature of an uncontrolled and progressive accumulation of fibrous tissue macromolecules in affected organs leading to their dysfunction and ultimate failure. The pathogenesis of fibrotic diseases is complex and despite extensive investigation has remained elusive. Numerous studies have identified myofibroblasts as the cells responsible for the establishment and progression of the fibrotic process. Tissue myofibroblasts in fibrotic diseases originate from several sources including quiescent tissue fibroblasts, circulating CD34+ fibrocytes, and the phenotypic conversion of various cell types including epithelial and endothelial cells into activated myofibroblasts. However, the role of the phenotypic transition of endothelial cells into mesenchymal cells (Endothelial to Mesenchymal Transition or EndoMT) in the pathogenesis of fibrotic disorders has not been fully elucidated. Here, we review the evidence supporting EndoMT's contribution to human fibrotic disease pathogenesis.

MiRNA-199a-5p influences pulmonary artery hypertension via downregulating Smad3

MicroRNAs (miRNAs) play important roles in pulmonary artery hypertension (PAH). Recently, it has been reported that miR-199a-5p participates in the progression of chronic obstructive pulmonary disease, ventricular hypertrophy and heart failure. However, the roles of miR-199a-5p in PAH are still unclear. In the present study, miR-199a-5p was investigated in PAH rat models and in human pulmonary artery smooth muscle cells (HPASMCs) and endothelial cells (HPAECs). The expression of miR-199a-5p was significantly increased following PAH induction, and anti-miR-199a-5p could increase the nitric oxide (NO) level and decrease the PAH-induced upregulation of pulmonary artery pressure and right ventricular hypertrophy. Moreover, in HPASMCs and HPAECs, miR-199a-5p overexpression could inhibit the level of NO and promote the concentration of Ca(2+), but anti-miR-199a-5p showed opposite results. Further analysis demonstrated that miR-199a-5p attenuated the expression of Smad3. Importantly, Smad3 was confirmed to be the target gene of miR-199a-5p using dual-luciferase reporter assay. Mechanism analyses revealed that the downregulation of NO and the upregulation of Ca(2+) caused by miR-199a-5p were all reversed by Smad3 overexpression in HPASMCs and HPAECs. Moreover, in PAH model, Smad3, p-Smad3 and Smad4 were all downregulated in lung tissues, and SIS3 (Smad3 inhibitor) could reverse the effects of anti-miR-199a-5p in PAH rats. Our date suggest that miR-199a-5p may function as a regulator of PAH by targeting Smad3, indicating a novel therapeutic strategy for patients with PAH.

Vascular Remodelling and Mesenchymal Transition in Systemic Sclerosis

Fibrosis of the skin and of internal organs, autoimmunity, and vascular inflammation are hallmarks of Systemic Sclerosis (SSc). The injury and activation of endothelial cells, with hyperplasia of the intima and eventual obliteration of the vascular lumen, are early features of SSc. Reduced capillary blood flow coupled with deficient angiogenesis leads to chronic hypoxia and tissue ischemia, enforcing a positive feed-forward loop sustaining vascular remodelling, further exacerbated by extracellular matrix accumulation due to fibrosis. Despite numerous developments and a growing number of controlled clinical trials no treatment has been shown so far to alter SSc natural history, outlining the need of further investigation in the molecular pathways involved in the pathogenesis of the disease. We review some processes potentially involved in SSc vasculopathy, with attention to the possible effect of sustained vascular inflammation on the plasticity of vascular cells. Specifically we focus on mesenchymal transition, a key phenomenon in the cardiac and vascular development as well as in the remodelling of injured vessels. Recent work supports the role of transforming growth factor-beta, Wnt, and Notch signaling in these processes. Importantly, endothelial-mesenchymal transition may be reversible, possibly offering novel cues for treatment.

Pan PPAR agonist IVA337 is effective in prevention and treatment of experimental skin fibrosis

Background

The pathogenesis of systemic sclerosis (SSc) involves a distinctive triad of autoimmune, vascular and inflammatory alterations resulting in fibrosis. Evidence suggests that peroxisome proliferator-activated receptors (PPARs) play an important role in SSc-related fibrosis and their agonists may become effective therapeutic targets.

Objective

To determine the expression of PPARs in human fibrotic skin and investigate the effects of IVA337, a pan PPAR agonist, in in vitro and in vivo models of fibrosis.

Methods

The antifibrotic effects of IVA337 were studied using a bleomycin-induced mouse model of dermal fibrosis. The in vivo effect of IVA337 on wound closure and inflammation were studied using an excisional model of wound healing.

Results

Low levels of PPARα and PPARγ were detected in the skin of patients with SSc compared with controls. In mice, IVA337 was associated with decreased extracellular matrix (ECM) deposition and reduced expression of phosphorylated SMAD2/3—intracellular effector of transforming growth factor (TGF)-β1. Although the antifibrotic effect of pan PPAR was similar to that of PPARγ agonist alone, a significant downregulation of several markers of inflammation was associated with IVA337. Despite its anti-inflammatory and antifibrotic properties, IVA337 did not interfere with wound closure. In vitro effects of IVA337 included attenuation of transcription of ECM genes and alteration of canonical and non-canonical TGF-β signalling pathways.

Conclusions

These findings indicate that simultaneous activation of all three PPAR isoforms exerts a dampening effect on inflammation and fibrosis, making IVA337 a potentially effective therapeutic candidate in the treatment of fibrotic diseases including SSc.

Transforming growth factor beta (TGF-β) isoforms in wound healing and fibrosis

Scar formation, with persistent alteration of the normal tissue structure, is an undesirable and significant result of both wound healing and fibrosing disorders. There are few strategies to prevent or to treat scarring. The transforming growth factor beta (TGF-β) superfamily is an important mediator of tissue repair. Each TGF-β isoform may exert a different effect on wound healing, which may be context-dependent. In particular, TGF-β1 may mediate fibrosis in adults' wounds, while TGF-β3 may promote scarless healing in the fetus and reduced scarring in adults. Thus, TGF-β3 may offer a scar-reducing therapy for acute and chronic wounds and fibrosing disorders.

Wenyang Huazhuo Tongluo formula, a Chinese herbal decoction, improves skin fibrosis by promoting apoptosis and inhibiting proliferation through down-regulation of survivin and cyclin D1 in systemic sclerosis

Background

Fibrosis is a major contributor to systemic sclerosis (SSc)-related morbidity, and rapid, progressive skin involvement predicts later mortality. Western medicine therapies for SSc cannot produce satisfactory effects currently, while Traditional Chinese Medicine (TCM), such as the Wenyang Huazhuo Tongluo (WYHZTL) formula, a Chinese herbal decoction, has shown amazing anti-fibrosis efficacy on SSc in clinical applications. This study is aiming to investigate the anti-fibrotic mechanism of WYHZTL formula for the treatment of SSc.

Methods

Fibroblasts from primary culture of skin lesions of SSc patients were exposed to rat medicated sera containing WYHZTL or XAV939, a small-molecule inhibitor of both tankyrase 1/2 and Wnt/β-catenin pathway. Cell counting kit-8 assay and Annexin V FITC/PI apoptosis kit were used to analyze cell proliferation and apoptosis in fibroblasts, respectively. Reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were used to detect the mRNA and protein levels of cyclin D1 and survivin.

Results

After 28, 48 and 72 h of incubation, the proliferative ability of the fibroblasts cells was obviously reduced by the sera containing WYHZTL compared with that in the control group; the percentage of apoptotic cell population in the sera containing WYHZTL treated fibroblasts cells was significantly higher than that in those treated with the control sera, and was about similar to that in those treated with XAV939. The sera containing WYHZTL could down-regulate both mRNA and protein levels of cyclin D1 and survivin, compared with the control group.

Conclusions

The present study demonstrates the antiproliferative and pro-apoptotic actions of WYHZTL formula against fibroblasts and the effect may be related to the down-regulation of mRNA and protein levels of cyclin D1 and survivin in SSc.

Increased expression of NAPDH oxidase 4 in systemic sclerosis dermal fibroblasts: regulation by transforming growth factor β

OBJECTIVE

Systemic sclerosis (SSc) is characterized by severe and often progressive fibrosis of the skin and multiple internal organs. The mechanisms responsible for these alterations remain obscure, although excessive reactive oxygen species (ROS)-mediated oxidative stress has been implicated. NOX-4 is 1 of 7 isoforms of NADPH oxidase responsible for the generation of ROS. The purpose of this study was to examine NOX-4 expression in skin and cultured dermal fibroblasts from SSc patients and to examine its regulation by transforming growth factor β1 (TGFβ1).

METHODS

NOX-4 was assessed in normal and SSc skin by immunohistologic analysis and in normal and SSc cultured dermal fibroblasts by quantitative polymerase chain reaction analysis, fluorescence microscopy, and Western blotting. ROS levels were assessed by fluorescence measurement of H2 O2 production. Specific kinase inhibitors were used to study the TGFβ1 signaling involved in NOX-4 stimulation. NOX-4 inhibition/down-regulation was induced with a selective NOX-4 small-molecule inhibitor and NOX-4 small interfering RNA (siRNA).

RESULTS

In contrast with normal skin fibroblasts, those from SSc skin showed intense NOX-4 staining. Cultured SSc fibroblasts displayed increased NOX-4 expression. TGFβ1 caused potent NOX-4 protein and messenger RNA stimulation in normal and SSc fibroblasts, which was mediated by the protein kinase Cδ (PKCδ) and Smad2/3 pathways. NOX-4 knockdown in SSc fibroblasts reduced the production of ROS and lowered the expression of type I collagen.

CONCLUSION

NOX-4 expression and production were found to be constitutively elevated in SSc skin and cultured SSc dermal fibroblasts. TGFβ1 stimulated NOX-4 expression in normal and SSc fibroblasts through PKCδ and Smad2/3 signaling pathways. A small-molecule NOX-4 inhibitor decreased collagen and fibronectin production by normal and SSc fibroblasts, and NOX-4 siRNA knockdown reduced ROS and collagen production by SSc fibroblasts. These results demonstrate the involvement of NOX-4 in SSc-associated fibrosis and indicate NOX-4 inhibitors as novel therapeutic approaches for SSc.

Pathobiological mechanisms of peritoneal adhesions: The mesenchymal transition of rat peritoneal mesothelial cells induced by TGF-β1 and IL-6 requires activation of Erk1/2 and Smad2 linker region phosphorylation

Peritoneal adhesions, primarily caused by surgical procedures, are the leading cause of pelvic pain, bowel obstruction, and infertility. TGF-β1 and IL-6 have been found to be elevated in the peritoneal fluid of patients during/after abdominal surgery. However, it remains to be determined whether these cytokines interact and facilitate adhesion formation by promoting mesothelial to mesenchymal transition (MMT). In the present study, isolated rat peritoneal mesothelial cells were treated with TGF-β1 and/or IL-6 which elicited MMT as determined by morphologic and biochemical techniques. During this transition, cellular morphology changed from that of cobblestone polygonal cells to elongated/spindle-shaped fibroblast-like cells. There was decreased expression of genes characteristic of mesothelial cells, such as E-cadherin, and increased expression of genes characteristic of the myofibroblast phenotype, including α-smooth muscle actin and the EDA form of fibronectin, both of which appear to mediate the transfer of force to the extracellular matrix. Partial characterization of relevant signaling pathways identified Erk1/2 activation, which was enhanced by combined TGF-β1/IL-6 administration, as a crucial necessary factor in the transition. Erk1/2 activation as well as the phosphorylation of the linker region of Smad2 and MMT could be blocked by the MEK inhibitor, U0126, suggesting that such activation may be a potential pharmaceutical target to prevent MMT. In addition, the phenotypic transition could be prevented by hydrocortisone.

Endothelial to mesenchymal transition (EndoMT) in the pathogenesis of Systemic Sclerosis-associated pulmonary fibrosis and pulmonary arterial hypertension. Myth or reality?

Systemic Sclerosis (SSc) is a systemic autoimmune disease characterized by progressive fibrosis of skin and multiple internal organs and severe functional and structural microvascular alterations. SSc is considered to be the prototypic systemic fibrotic disorder. Despite currently available therapeutic approaches SSc has a high mortality rate owing to the development of SSc-associated interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH), complications that have emerged as the most frequent causes of disability and mortality in SSc. The pathogenesis of the fibrotic process in SSc is complex and despite extensive investigation the exact mechanisms have remained elusive. Myofibroblasts are the cells ultimately responsible for tissue fibrosis and fibroproliferative vasculopathy in SSc. Tissue myofibroblasts in SSc originate from several sources including expansion of quiescent tissue fibroblasts and tissue accumulation of CD34+ fibrocytes. Besides these sources, myofibroblasts in SSc may result from the phenotypic conversion of endothelial cells into activated myofibroblasts, a process known as endothelial to mesenchymal transition (EndoMT). Recently, it has been postulated that EndoMT may play a role in the development of SSc-associated ILD and PAH. However, although several studies have described the occurrence of EndoMT in experimentally induced cardiac, renal, and pulmonary fibrosis and in several human disorders, the contribution of EndoMT to SSc-associated ILD and PAH has not been generally accepted. Here, the experimental evidence supporting the concept that EndoMT plays a role in the pathogenesis of SSc-associated ILD and PAH will be reviewed.

Inflammation as a Keystone of Bone Marrow Stroma Alterations in Primary Myelofibrosis

Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm where severity as well as treatment complexity is mainly attributed to a long lasting disease and presence of bone marrow stroma alterations as evidenced by myelofibrosis, neoangiogenesis, and osteosclerosis. While recent understanding of mutations role in hematopoietic cells provides an explanation for pathological myeloproliferation, functional involvement of stromal cells in the disease pathogenesis remains poorly understood. The current dogma is that stromal changes are secondary to the cytokine “storm” produced by the hematopoietic clone cells. However, despite therapies targeting the myeloproliferation-sustaining clones, PMF is still regarded as an incurable disease except for patients, who are successful recipients of allogeneic stem cell transplantation. Although the clinical benefits of these inhibitors have been correlated with a marked reduction in serum proinflammatory cytokines produced by the hematopoietic clones, further demonstrating the importance of inflammation in the pathological process, these treatments do not address the role of the altered bone marrow stroma in the pathological process. In this review, we propose hypotheses suggesting that the stroma is inflammatory-imprinted by clonal hematopoietic cells up to a point where it becomes “independent” of hematopoietic cell stimulation, resulting in an inflammatory vicious circle requiring combined stroma targeted therapies.

Chronic fatigue syndrome and circulating cytokines: A systematic review

There has been much interest in the role of the immune system in the pathophysiology of chronic fatigue syndrome (CFS), as CFS may develop following an infection and cytokines are known to induce acute sickness behaviour, with similar symptoms to CFS. Using the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-analyses) guidelines, a search was conducted on PubMed, Web of Science, Embase and PsycINFO, for CFS related-terms in combination with cytokine-related terms. Cases had to meet established criteria for CFS and be compared with healthy controls. Papers retrieved were assessed for both inclusionary criteria and quality. 38 papers met the inclusionary criteria. The quality of the studies varied. 77 serum or plasma cytokines were measured without immune stimulation. Cases of CFS had significantly elevated concentrations of transforming growth factor-beta (TGF-β) in five out of eight (63%) studies. No other cytokines were present in abnormal concentrations in the majority of studies, although insufficient data were available for some cytokines. Following physical exercise there were no differences in circulating cytokine levels between cases and controls and exercise made no difference to already elevated TGF-β concentrations. The finding of elevated TGF-β concentration, at biologically relevant levels, needs further exploration, but circulating cytokines do not seem to explain the core characteristic of post-exertional fatigue.

The Endothelial-mesenchymal Transition in Systemic Sclerosis Is Induced by Endothelin-1 and Transforming Growth Factor-β and May Be Blocked by Macitentan, a Dual Endothelin-1 Receptor Antagonist

OBJECTIVE

High endothelin-1 (ET-1) and transforming growth factor-β (TGF-β) levels may induce in healthy endothelial cells (EC) an endothelial-to-mesenchymal transition (EndMT). The same cytokines are associated with fibrosis development in systemic sclerosis (SSc). Although EndMT has not been definitively shown in SSc, this process, potentially induced by a stimulatory loop involving these 2 cytokines, overexpressed in this disease might contribute to fibroblast accumulation in affected tissues. Macitentan (MAC), an ET-1 receptor antagonist interfering with this loop, might prevent EndMT and fibroblast accumulation.

METHODS

EC, isolated from healthy controls (HC) and patients with SSc, were treated with ET-1 and TGF-β and successively analyzed for gene and protein expressions of endothelial and mesenchymal markers, and for Sma- and Mad-related (SMAD) phosphorylation. Further, in the supernatants, we evaluated ET-1 and TGF-β production by ELISA assay. In each assay we evaluated the ability of MAC to inhibit both the TGF-β and ET-1 effects.

RESULTS

We showed that both TGF-β and ET-1 treatments induced an activation of the EndMT process in SSc-EC as reported in HC cells. The ELISA assays showed a mutual TGF-β and ET-1 induction in both SSc-EC and HC-EC. A statistically significant increase of SMAD phosphorylation after treatment was observed in SSc-EC. In each assay, MAC inhibited both TGF-β and ET-1 effects.

CONCLUSION

Our work is the first demonstration in literature that SSc-EC, under the synergistic effect of TGF-β and ET-1, may transdifferentiate toward myofibroblasts, thus contributing to fibroblast accumulation. MAC, interfering with this process in vitro, may offer a new potential therapeutic strategy against fibrosis.

From pathogenesis to therapy--Perspective on treatment strategies in fibrotic diseases

Although fibrosis is becoming increasingly recognized as a major cause of morbidity and mortality in modern societies, there are very few treatment strategies available that specifically target the pathogenesis of fibrosis. Early in disease, inflammation and vascular changes and an increase in reactive oxygen species play pivotal roles. After inflammation has subsided, fibrosis and scarring are predominant in later phases. Fibrosis is driven by a complex, not-yet fully understood interplay between inflammatory cells on one hand and endothelium and fibroblasts on the other hand. The latter are regarded as the key players due to their extensive synthesis of extracellular matrix components which results in skin and organ fibrosis. Various cytokines orchestrate altered functions of the mentioned cell types. There are promising targets with therapeutic potential that have been extensively characterized in recent years connected with the hope to translate these preclinical results into clinical practice.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

Macro- and microvascular disease in systemic sclerosis

Vasculopathy is common in patients with connective tissue disease and can be directly implicated in the pathogenesis of the disease. Systemic sclerosis is an auto-immune multiorgan connective tissue disorder characterized by fibrosis of the skin and visceral organs and vascular disease. Micro- and macro-vessels are a direct target of the disease. In this review, we present the various clinical manifestations of the vasculopathy that can be present in SSc patients, and then discuss the various aspects of the pathophysiology of the vascular disorders.

Combined effect of genetic background and gender in a mouse model of bleomycin-induced skin fibrosis

INTRODUCTION

Systemic sclerosis (SSc) is a connective tissue disorder characterised by the development of skin fibrosis. Our current understanding of the disease pathogenesis is incomplete and the study of SSc is hindered, at least partially, by a lack of animal models that fully replicate the complex state of human disease. Murine model of bleomycin-induced dermal fibrosis encapsulates important events that take place early in the disease course.

METHODS

To characterise the optimum in vivo parameters required for the successful induction of dermal fibrosis we subjected three commonly used mouse strains to repeated subcutaneous bleomycin injections. We aimed to identify the effects of genetic background and gender on the severity of skin fibrosis. We used male and female Balb/C, C57BL/6, and DBA/2 strains and assessed their susceptibility to bleomycin-induced fibrosis by measuring dermal thickness, hydroxyproline/collagen content and number of resident myofibroblasts, all of which are important indicators of the severity of skin fibrosis. All data are expressed as mean values ± SEM. The Mann-Whitney U test was used for statistical analysis with GraphPad Prism 6.04 software.

RESULTS

Dermal fibrosis was most severe in Balb/C mice compared to C57BL/6 and DBA/2 suggesting that Balb/C mice are more susceptible to bleomycin-induced fibrosis. Analysis of the effect of gender on the severity of fibrosis showed that male Balb/C, C57BL/6, DBA/2 mice had a tendency to develop more pronounced fibrosis phenotype than female mice. Of potential importance, male Balb/C mice developed the most severe fibrosis phenotype compared to male C57BL/6 and male DBA/2 as indicated by significantly increased number of dermal myofibroblasts.

CONCLUSION

Our study highlights the importance of genetic background and gender in the induction of murine dermal fibrosis. Robust and reproducible animal models of fibrosis are important research tools used in pharmacological studies which may lead to better understanding of the pathogenesis of fibrotic diseases and assist in identification of new drugs.

A Role of Myocardin Related Transcription Factor-A (MRTF-A) in Scleroderma Related Fibrosis

In scleroderma (systemic sclerosis, SSc), persistent activation of myofibroblast leads to severe skin and organ fibrosis resistant to therapy. Increased mechanical stiffness in the involved fibrotic tissues is a hallmark clinical feature and a cause of disabling symptoms. Myocardin Related Transcription Factor-A (MRTF-A) is a transcriptional co-activator that is sequestered in the cytoplasm and translocates to the nucleus under mechanical stress or growth factor stimulation. Our objective was to determine if MRTF-A is activated in the disease microenvironment to produce more extracellular matrix in progressive SSc. Immunohistochemistry studies demonstrate that nuclear translocation of MRTF-A in scleroderma tissues occurs in keratinocytes, endothelial cells, infiltrating inflammatory cells, and dermal fibroblasts, consistent with enhanced signaling in multiple cell lineages exposed to the stiff extracellular matrix. Inhibition of MRTF-A nuclear translocation or knockdown of MRTF-A synthesis abolishes the SSc myofibroblast enhanced basal contractility and synthesis of type I collagen and inhibits the matricellular profibrotic protein, connective tissue growth factor (CCN2/CTGF). In MRTF-A null mice, basal skin and lung stiffness was abnormally reduced and associated with altered fibrillar collagen. MRTF-A has a role in SSc fibrosis acting as a central regulator linking mechanical cues to adverse remodeling of the extracellular matrix.

Promising pharmacological directions in the world of lysophosphatidic Acid signaling

Lysophosphatidic acid (LPA) is a signaling lipid that binds to six known lysophosphatidic acid receptors (LPARs), named LPA₁-LPA₆. These receptors initiate signaling cascades relevant to development, maintenance, and healing processes throughout the body. The diversity and specificity of LPA signaling, especially in relation to cancer and autoimmune disorders, makes LPA receptor modulation an attractive target for drug development. Several LPAR-specific analogues and small molecules have been synthesized and are efficacious in attenuating pathology in disease models. To date, at least three compounds have passed phase I and phase II clinical trials for idiopathic pulmonary fibrosis and systemic sclerosis. This review focuses on the promising therapeutic directions emerging in LPA signaling toward ameliorating several diseases, including cancer, fibrosis, arthritis, hydrocephalus, and traumatic injury.