Control of IL-6 expression and response in fibroblasts from patients with systemic sclerosis

The Molecular Mechanisms of Systemic Sclerosis-Associated Lung Fibrosis

Systemic sclerosis (SSc), also known as scleroderma, is an autoimmune disorder that affects the connective tissues and has the highest mortality rate among the rheumatic diseases. One of the hallmarks of SSc is fibrosis, which may develop systemically, affecting the skin and virtually any visceral organ in the body. Fibrosis of the lungs leads to interstitial lung disease (ILD), which is currently the leading cause of death in SSc. The identification of effective treatments to stop or reverse lung fibrosis has been the main challenge in reducing SSc mortality and improving patient outcomes and quality of life. Thus, understanding the molecular mechanisms, altered pathways, and their potential interactions in SSc lung fibrosis is key to developing potential therapies. In this review, we discuss the diverse molecular mechanisms involved in SSc-related lung fibrosis to provide insights into the altered homeostasis state inherent to this fatal disease complication.

Neutrophil extracellular traps contribute to myofibroblast differentiation and scar hyperplasia through the Toll-like receptor 9/nuclear factor Kappa-B/interleukin-6 pathway

Background

Inflammation is an important factor in pathological scarring. The role of neutrophils, one of the most important inflammatory cells, in scar hyperplasia remains unclear. The purpose of this article is to study the correlation between neutrophil extracellular traps (NETs) and scar hyperplasia and identify a new target for inhibiting scar hyperplasia.

Methods

Neutrophils were isolated from human peripheral blood by magnetic-bead sorting. NETs in plasma and scars were detected by enzyme-linked immunosorbent assays (ELISAs), immunofluorescence and flow cytometry. Immunohistochemistry was used to assess neutrophil (CD66B) infiltration in hypertrophic scars. To observe the entry of NETs into fibroblasts we used immunofluorescence and flow cytometry.

Results

We found that peripheral blood neutrophils in patients with hypertrophic scars were more likely to form NETs (p < 0.05). Hypertrophic scars showed greater infiltration with neutrophils and NETs (p < 0.05). NETs activate fibroblasts in vitro to promote their differentiation and migration. Inhibition of NETs with cytochalasin in wounds reduced the hyperplasia of scars in mice. We induced neutrophils to generate NETs with different stimuli in vitro and detected the proteins carried by NETs. We did not find an increase in the expression of common scarring factors [interleukin (IL)-17 and transforming growth factor-β (TGF-β), p > 0.05]. However, inhibiting the production of NETs or degrading DNA reduced the differentiation of fibroblasts into myofibroblasts. In vitro, NETs were found to be mediated by Toll-like receptor 9 (TLR-9) in fibroblasts and further phosphorylated nuclear factor Kappa-B (NF-κB). We found that IL-6, which is downstream of NF-κB, was increased in fibroblasts. Additionally, IL-6 uses autocrine and paracrine signaling to promote differentiation and secretion.

Conclusions

Our experiments found that NETs activate fibroblasts through the TLR-9/NF-κB/IL-6 pathway, thereby providing a new target for regulating hypertrophic scars.

Phenotypic Characterization of Transgenic Mice Expressing Human IGFBP-5

Pulmonary fibrosis is one of the important causes of morbidity and mortality in fibroproliferative disorders such as systemic sclerosis (SSc) and idiopathic pulmonary fibrosis (IPF). Insulin-like growth factor binding protein-5 (IGFBP-5) is a conserved member of the IGFBP family of proteins that is overexpressed in SSc and IPF lung tissues. In this study, we investigated the functional role of IGFBP-5 in the development of fibrosis in vivo using a transgenic model. We generated transgenic mice ubiquitously expressing human IGFBP-5 using CRISPR/Cas9 knock-in. Our data show that the heterozygous and homozygous mice are viable and express human IGFBP-5 (hIGFBP-5). Transgenic mice had increased expression of extracellular matrix (ECM) genes, especially Col3a1, Fn, and Lox in lung and skin tissues of mice expressing higher transgene levels. Histologic analysis of the skin tissues showed increased dermal thickness, and the lung histology showed subtle changes in the heterozygous and homozygous mice as compared with the wild-type mice. These changes were more pronounced in animals expressing higher levels of hIGFBP-5. Bleomycin increased ECM gene expression in wild-type mice and accentuated an increase in ECM gene expression in transgenic mice, suggesting that transgene expression exacerbated bleomycin-induced pulmonary fibrosis. Primary lung fibroblasts cultured from lung tissues of homozygous transgenic mice showed significant increases in ECM gene expression and protein levels, further supporting the observation that IGFBP-5 resulted in a fibrotic phenotype in fibroblasts. In summary, transgenic mice expressing human IGFBP-5 could serve as a useful animal model for examining the function of IGFBP-5 in vivo.

Systemic sclerosis-associated interstitial lung disease

Systemic sclerosis is an autoimmune connective tissue disease, which is characterised by immune dysregulation and progressive fibrosis that typically affects the skin, with variable internal organ involvement. It is a rare condition that affects mostly young and middle-aged women, resulting in disproportionate morbidity and mortality. Currently, interstitial lung disease is the most common cause of death among patients with systemic sclerosis, with a prevalence of up to 30% and a 10-year mortality of up to 40%. Interstitial lung disease is more common among African Americans and in people with the diffuse cutaneous form of systemic sclerosis or anti-topoisomerase 1 antibodies. Systemic sclerosis-associated interstitial lung disease most commonly presents with dyspnoea, cough, and a non-specific interstitial pneumonia pattern on CT scan, with a minority of cases fulfilling the criteria for usual interstitial pneumonia. The standard therapy has traditionally been combinations of immunosuppressants, particularly mycophenolate mofetil or cyclophosphamide. These immunosuppressants can be supplemented by targeted biological and antifibrotic therapies, whereas autologous haematopoietic stem-cell transplantation and lung transplantation are reserved for refractory cases.

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.

Contribution of Interleukin-6 to the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology, manifesting in patients as tissue fibrosis, endothelial dysfunction, and inflammation. The disease is characterized by autoantibodies, a hallmark of autoimmunity. Various cytokines and growth factors are elevated in the systemic circulation and fibrotic lesions of patients with SSc. In particular, several studies over the past 2 decades have shown that interleukin-6 (IL-6) appears to be involved in the pathogenesis of SSc. Based on the association between aberrant IL-6 production and tissue fibrosis in patients with SSc, the anti-IL-6 receptor antibody, tocilizumab, is being investigated in clinical trials. This article reviews the biological features of IL-6 and the IL-6 receptor; the role of IL-6 in the pathogenesis of SSc; and the potential for IL-6 inhibition to be used in the treatment of patients with SSc.

Managing Systemic Sclerosis-Related Interstitial Lung Disease in the Modern Treatment Era

Interstitial lung disease (ILD) affects the majority of patients with systemic sclerosis (SSc) and is the leading cause of death in SSc. Traditionally, treatments for SSc-ILD have targeted broad suppression of the immune system with agents such as cyclophosphamide and mycophenolate. The recently published Scleroderma Lung Study (SLS) II demonstrated that treatment with either oral cyclophosphamide or mycophenolate led to similar improvement in lung function, dyspnea and radiographic extent of fibrosis. However, with the emergence of anti-fibrotic therapy for the treatment of idiopathic pulmonary fibrosis, the repurposing of biologic agents used to treat other connective tissue diseases, and the introduction of hematopoetic stem-cell transplantation for patients with early diffuse SSc, options for managing SSc-ILD have increased. For the first time ever, patients and physicians have choices for how to treat SSc-ILD. At the same time, the study and administration of these novel therapeutic agents have raised important clinical research questions that warrant further investigation. This review describes the current and experimental therapies available for SSc-ILD. This review also explores unanswered questions directly relevant to patient care and future research efforts in this area, including questions on indications for initiation of SSc-ILD therapy, the use of maintenance SSc-ILD therapy and the duration of SSc-ILD therapy. Conducting studies designed to answer these important questions is central to advancing SSc-ILD research and improving outcomes for patients with this devastating disease.

Spotlight on tocilizumab and its potential in the treatment of systemic sclerosis

Systemic sclerosis (SSc) is a multisystem disease characterized by extensive collagen deposition in skin and internal organs, fibrointimal microvasculopathy, and activation of the immune system. T cells and B cells can promote fibrosis in SSc. Interleukin (IL)-6 is implicated in the pathogenesis of SSc. IL-6 is increased in the peripheral blood and lesional skin from patients with SSc, and induces fibroblast collagen production directly and indirectly by inducing profibrotic M2 macrophages. IL-6 also induces Th17 differentiation and promotes B cell differentiation toward Ig-producing plasma cells. IL-6 is also implicated in the pathogenesis of SSc in animal models as it is increased in mice with bleomycin-induced fibrosis, whereas neutralization of IL-6 in these mice prevents skin fibrosis. IL-6 acts on cells by binding to IL-6 receptor (IL-6R) which is transmembrane or soluble, and then recruits the signal-transducing glycoprotein 130 which is ubiquitously expressed. Tocilizumab is an anti-IL-6R humanized monoclonal antibody that blocks IL-6-mediated signaling. Tocilizumab has been approved for the treatment of moderate-to-severe rheumatoid arthritis, for polyarticular and systemic juvenile idiopathic arthritis, and for Castleman’s disease, and is well tolerated. Case reports and a Phase II, randomized trial in SSc have shown some improvement of skin tightness and delayed deterioration of lung function. A Phase III randomized trial in SSc is anticipated.

A Co-Culture Model of Fibroblasts and Adipose Tissue-Derived Stem Cells Reveals New Insights into Impaired Wound Healing After Radiotherapy

External radiation seems to be associated with increased amounts of cytokines and other cellular modulators. Impaired microcirculation and fibrosis are examples of typical long term damage caused by radiotherapy. Adipose tissue-derived stem cells (ASC) are discussed to enhance wound healing, but their role in wounds due to radiotherapy is poorly understood. Normal human fibroblasts (NHF) and ASCs were co-cultured and external radiation with doses from 2-12 Gray (Gy) was delivered. Cell proliferation and mRNA levels of matrix metalloproteinases (MMP1, MMP2 and MMP13) were determined 48 h after irradiation of the co-cultures by qPCR. Additionally, tissue inhibitors of matrix metalloproteinases (TIMP1, TIMP2) were determined by enzyme-linked immunosorbent assay (ELISA). There was a reduction of cell proliferation after external radiation in mono-cultures of NHFs and ASCs compared to controls without irradiation. The co-culture of ASCs and NHFs showed reduced impairment of cell proliferation after external radiation. Gene expression of MMP1 and MMP13 was reduced after external irradiation in NHF. MMP2 expression of irradiated NHFs was increased. In the co-culture setting, MMP1 and MMP2 gene expression levels were upregulated. TIMP1 and TIMP2 protein expression was increased after irradiation in NHFs and their co-cultures with ASCs. ASCs seem to stimulate cell proliferation of NHFs and modulate relevant soluble mediators as well as proteinases after external radiation.

Fibrotic remodeling of tissue-engineered skin with deep dermal fibroblasts is reduced by keratinocytes

Two-thirds of burn patients with deep dermal injuries are affected by hypertrophic scars, and currently, there are no clinically effective therapies. Tissue-engineered skin is a very promising model for the elucidation of the role of matrix microenvironment and biomechanical characteristics and could help in the identification of new therapeutic targets for hypertrophic scars. Conventionally, tissue-engineered skin is made of heterogeneous dermal fibroblasts and keratinocytes; however, recent work has shown that superficial and deep dermal fibroblasts are antifibrotic and profibrotic, respectively. Furthermore, keratinocytes are believed to regulate the development and remodeling of fibrosis in skin. This study aimed to assess the influence of keratinocytes and layered fibroblasts on the characteristics of tissue-engineered skin. Layered fibroblasts and keratinocytes isolated from superficial and deep dermis and epidermis, respectively, of the lower abdominal tissue were independently co-cultured on collagen-glycosaminoglycan scaffolds, and the resulting tissue-engineered skin was assessed for differences in tissue remodeling based on the underlying specific dermal fibroblast subpopulation. Collagen production by deep fibroblasts but not by superficial fibroblasts was significantly reduced upon co-culture with keratinocytes. Also, keratinocytes in the tissue-engineered skin resulted in significantly reduced expression of profibrotic connective tissue growth factor and fibronectin, and increased expression of the antifibrotic matrix metalloproteinase-1 by deep fibroblasts but not by superficial fibroblasts. Tissue-engineered skin made of deep fibroblasts and keratinocytes had lower levels of small proteoglycans, decorin, and fibromodulin, and higher levels of large proteoglycan, versican, compared to tissue-engineered skin made of superficial fibroblasts and keratinocytes. Tissue-engineered skin made of deep fibroblasts and keratinocytes had lower expression of transforming growth factor (TGF)-α, interleukin (IL)-1, and keratinocyte growth factor but higher expression of platelet-derived growth factor and IL-6, compared to tissue-engineered skin made of superficial fibroblasts and keratinocytes. Furthermore, co-culture with keratinocytes reduced TGF-β1 production of deep but not superficial fibroblasts. Additionally, keratinocytes reduced the differentiation of deep fibroblasts to myofibroblasts in tissue-engineered skin constructs, but not that of superficial fibroblasts. Taken together, keratinocytes reduce fibrotic remodeling of the scaffolds by deep dermal fibroblasts. Our results therefore demonstrate that tissue-engineered skin made specifically with a homogeneous population of superficial fibroblasts and keratinocytes is less fibrotic than that with a heterogeneous population of fibroblasts and keratinocytes.

The IL-6 trans-signaling-STAT3 pathway mediates ECM and cellular proliferation in fibroblasts from hypertrophic scar

The molecular mechanisms behind the pathogenesis of post-burn hypertrophic scar (HS) remain unclear. Here, we investigate the role of interleukin-6 (IL-6) trans-signaling-STAT3 pathway in HS fibroblasts (HSF) derived from burned-induced HS skin. HSF showed increased Tyr 705 STAT3 phosphorylation over normal fibroblast (NF) after IL-6•IL-6Rα stimulation by immunoassays. The endogenous STAT3 target gene, SOCS3, was upregulated in HSF and showed increased STAT3 binding on its promoter relative to NF in Chromatin Immunoprecipitation assay. We observed that the cell surface signaling transducer glycoprotein 130 is upregulated in HSF using Q-RT-PCR and flow cytometry. The production of excessive extracellular matrix (ECM), including the expression of alpha2 (1) procollagen (Col1A2) and fibronectin 1 (FN) were seen in HSFs. A STAT3 peptide inhibitor abrogated FN and Col1A2 gene expression in HSF indicating involvement of STAT3 in ECM production. The cellular proliferation markers Cyclin D1, Bcl-Xl and c-Myc were also upregulated in HSF and knockdown of STAT3 by siRNA attenuated c-Myc expression indicating the essential role of STAT3 in fibroblast proliferation. Taken together, our results suggest that the IL-6-trans-signaling-STAT3 pathway may play an integral role in HS pathogenesis and disruption of this pathway could be a potential therapeutic strategy for the treatment of burn-induced HS.

Antifibrotic effects of roscovitine in normal and scleroderma fibroblasts

Heightened production of collagen and other matrix proteins underlies the fibrotic phenotype of systemic sclerosis (SSc). Roscovitine is an inhibitor of cyclin-dependent kinases that promote cell cycling (CDK1, 2), neuronal development (CDK5) and control transcription (CDK7,9). In an in vivo glomerulonephritis model, roscovitine treatment decreased mesangial cell proliferation and matrix proteins [1]. We investigated whether roscovitine could regulate fibrotic protein production directly rather than through cell cycling. Our investigations revealed that roscovitine coordinately inhibited the expression of collagen, fibronectin, and connective tissue growth factor (CTGF) in normal and SSc fibroblasts. This effect occurred on a transcriptional basis and did not result from roscovitine-mediated cell cycle inhibition. Roscovitine-mediated suppression of matrix proteins could not be reversed by the exogenous profibrotic cytokines TGF-β or IL-6. To our knowledge, we are the first to report that roscovitine modulates matrix protein transcription. Roscovitine may thus be a viable treatment option for SSc and other fibrosing diseases.

Th17 and regulatory T lymphocytes in primary biliary cirrhosis and systemic sclerosis as models of autoimmune fibrotic diseases

Fibrotic autoimmune diseases are characterized by an inflammatory process in which fibrogenic cytokines, such as TGFβ and IL6, have a major role. Interestingly, these cytokines are also involved in the generation and function of both an effector T lymphocyte subpopulation, the Th17 cells, and the regulatory T lymphocytes (Treg). These evidences raised the hypothesis that an unbalanced equilibrium induced by the overproduction of the fibrogenic cytokines may have pathogenic relevance in fibrotic autoimmune diseases. On this basis, this review analyzes the available data concerning Th17 and Treg generation and function in two representative fibrotic autoimmune diseases, primary biliary cirrhosis (PBC) and systemic sclerosis (SSc), as models for organ-specific and systemic diseases, respectively. With regard to the Th17 cells, their expansion was found to be a common feature associated with a relative contraction of Th1 immune responses. Concerning to the regulatory T cell compartment, quantitative and qualitative alterations were observed in both diseases. However, while PBC patients showed defects only in the CD8+ Treg subset, SSc patients demonstrated abnormalities regarding to both the CD4+CD25+ and the CD8+ Treg subpopulations. Hence, the CD8+ Treg subset seems to be the most involved in the pathogenic cascade leading to fibrotic disease onset and maintenance. Collectively, the reviewed data support the concept that altered homeostasis between effector and regulatory T cell circuits is present in fibrotic autoimmune diseases and that the major factors responsible for such disequilibrium are Th17 cells in the effector arm and CD8+ Treg in the regulatory arm.

Interleukin 6 in Systemic Sclerosis and Potential Implications for Targeted Therapy

Objective.

The purpose of this study was to review the potential importance of interleukin 6 (IL-6) in systemic sclerosis (SSc).

Methods.

PubMed and Scopus databases and American College of Rheumatology (from 2009–10) and European League Against Rheumatism abstracts (2009–11) were searched using keywords “scleroderma; SSc; cytokines; interleukins; interleukin 6” and publications were excluded if not pertaining to IL-6 in SSc. Data were extracted from selected articles to construct a cell interaction model of the effects of IL-6 in SSc.

Results.

A total of 416 reports were found (PubMed, n = 82; Scopus, n = 331; 3 abstracts); 372 were excluded (irrelevant) leaving 41 publications and 3 abstracts (39 from PubMed, 18 from Scopus; but 16 were repeated from PubMed search), where 40 suggested IL-6 was important in SSc and 4 did not. Effects of IL-6 in SSc were summarized schematically.

Conclusion.

Of the 44 publications, 40 suggested that IL-6 may be important in SSc, allowing for a conceptual framework within SSc including effects on macrophages, fibroblasts, plasma cells, monocytes, and extracellular matrix.

Systemic Sclerosis Fibroblasts Show Specific Alterations of Interferon-γ and Tumor Necrosis Factor-α-induced Modulation of Interleukin 6 and Chemokine Ligand 2

Objective.

We evaluated the effect of interferon-γ (IFN-γ) and/or tumor necrosis factor-α (TNF-α) on the secretion of prototype proinflammatory cytokine interleukin 6 (IL-6), compared to T-helper 1 [Th1; chemokine (C-X-C motif) ligand 10 (CXCL10)] or Th2 [chemokine (C-C motif) ligand 2 (CCL2)] chemokines, in primary cultured fibroblasts from patients with systemic sclerosis (SSc) at an early stage of the disease.

Methods.

Fibroblast cultures from 5 SSc patients (disease duration < 2 yrs) and 5 healthy controls were evaluated for the production of IL-6, CXCL10, and CCL2 at the basal level and after stimulation with IFN-γ and/or TNF-α.

Results.

SSc fibroblasts basally produced higher levels of IL-6 than controls, while no difference was observed about CCL2 and CXCL10. TNF-α was able to dose-dependently induce IL-6 and CCL2 secretion in SSc, but not in control fibroblasts. By stimulation with increasing doses of IFN-γ, SSc fibroblasts were induced to secrete CCL2 and CXCL10, while no effect was observed on IL-6. The combination of IFN-γ and TNF-α induced a strong secretion of IL-6 and CCL2 in SSc fibroblasts but not in controls. In contrast, the synergistic effect of IFN-γ and TNF-α on CXCL10 secretion was similar in SSc fibroblasts and in controls.

Conclusion.

SSc fibroblasts participate in the self-perpetuation of inflammation by releasing IL-6, CXCL10, and CCL2 under the influence of IFN-γ and/or TNF-α. SSc fibroblasts are more active than controls in the secretion of IL-6 at baseline, and in the production of IL-6 and CCL2 under the combined IFN-γ/TNF-α stimulation.

Th17 peripheral cells are increased in diffuse cutaneous systemic sclerosis compared with limited illness: a cross-sectional study

Systemic Sclerosis (SSc) is an autoimmune disease characterized by fibrosis and vasculopathy. A key feature is the presence of T cells in inflammatory lesions. To establish the differences in peripheral blood T helper (Th) subpopulations in diffuse cutaneous (dc) and limited cutaneous (lc) SSc patients, blood samples from 57 dcSSc and 78 lcSSc patients were obtained. Controls were collected from healthy volunteers (n = 16), active systemic lupus erythematosus (aSLE) patients (n = 13), and active rheumatoid arthritis (aRA) patients (n = 12). Mononuclear cells were analyzed by flow cytometry to determine Th1 (CD4+/IFN-γ+), Th2 (CD4+/IL-4+), Th17 (CD4+/IL-17+), and regulatory T cells (Tregs; CD4+/CD25+/Foxp3+) subsets. Th17 and Th1 subsets were increased in SSc groups versus healthy controls (P < 0.001) and aSLE patients (P < 0.001 for Th17 and P < 0.008 for Th1). Th2 cells were higher in dcSSc patients than in the healthy and aSLE groups (P = 0.03 and P = 0.009, respectively). Tregs were increased in the aRA group when compared with SSc patients and healthy controls (P ≤ 0.003). Patients with immunosuppressive treatment had lower numbers of Th17 and Th2 cells (P = 0.02). Our results shed further light into the preponderant role of Th17 and Th1 in patients with SSc. However, these findings certainly deserve to be studied in depth.

IFN-γ and TNF-α induce a different modulation of interleukin-6 in systemic sclerosis fibroblasts compared to healthy controls

BACKGROUND

To our knowledge, no previous study has evaluated the effect of interferon (IFN)-γ, tumour necrosis factor (TNF)-α, or their combination on the prototype proinflammatory cytokine interleukin (IL)-6 in primary cultured fibroblasts from patients with systemic sclerosis (SSc) at an early stage of the disease.

METHODS

Fibroblast cultures from five SSc patients (disease duration < 2 years) and five healthy controls were evaluated for the basal production of IL-6, and after stimulation with TNF-α or IFN-γ, alone or combined.

RESULTS

The fibroblasts from SSc patients produced higher levels of IL-6 in basal condition than controls [617 ± 173 vs. 213 ± 123 pg/mL; analysis of variance (ANOVA), p < 0.001]. TNF-α was able to dose-dependently induce IL-6 in SSc (609 ± 184, 723 ± 243, 1079 ± 297, 1436 ± 326 pg/mL, with TNF-α 0, 1, 5, 10 ng/mL, respectively) but not in control fibroblasts, whereas IFN-γ was unable to induce IL-6. Furthermore, the combination of IFN-γ and TNF-α induced a stronger secretion of IL-6 in SSc fibroblasts (ANOVA, p < 0.0001), without effect in controls.

CONCLUSIONS

SSc fibroblasts participate in the self-perpetuation of inflammation by releasing IL-6, under the influence of TNF-α and/or IFN-γ.

Toll-like receptor 3 upregulation by type I interferon in healthy and scleroderma dermal fibroblasts

Introduction

Increased levels of genes in the type I interferon (IFN) pathway have been observed in patients with systemic sclerosis (SSc), or scleroderma. How type I IFN regulates the dermal fibroblast and its participation in the development of dermal fibrosis is not known. We hypothesized that one mechanism by which type I IFN may contribute to dermal fibrosis is through upregulation of specific Toll-like receptors (TLRs) on dermal fibroblasts. Therefore, we investigated the regulation of TLR expression on dermal fibroblasts by IFN.

Methods

The expression of TLRs was assessed in cultured dermal fibroblasts from control and SSc patients stimulated with IFNα2. The ability of IFNα2 to regulate TLR-induced interleukin (IL)-6 and CC chemokine ligand 2 production was also assessed. Immunohistochemical analyses were performed to determine whether TLR3 was expressed in skin biopsies in the bleomycin-induced skin fibrosis model and in patients with SSc.

Results

IFNα2 increased TLR3 expression on human dermal fibroblasts, which resulted in enhanced TLR3-induced IL-6 production. SSc fibroblasts have an augmented TLR3 response to IFNα2 relative to control fibroblasts. Pretreatment of fibroblasts with transforming growth factor (TGF)-β increased TLR3 induction by IFNα2, but coincubation of TGF-β did not alter TLR3 induction by IFN. Furthermore, IFNα2 inhibits but does not completely block the induction of connective tissue growth factor and collagen expression by TGF-βin fibroblasts. TLR3 expression was observed in dermal fibroblasts and inflammatory cells from skin biopsies from patients with SSc as well as in the bleomycin-induced skin fibrosis model.

Conclusions

Type I IFNs can increase the inflammatory potential of dermal fibroblasts through the upregulation of TLR3.

Tumor-like stem cells derived from human keloid are governed by the inflammatory niche driven by IL-17/IL-6 axis

BACKGROUND

Alterations in the stem cell niche are likely to contribute to tumorigenesis; however, the concept of niche promoted benign tumor growth remains to be explored. Here we use keloid, an exuberant fibroproliferative dermal growth unique to human skin, as a model to characterize benign tumor-like stem cells and delineate the role of their "pathological" niche in the development of the benign tumor.

METHODS AND FINDINGS

Subclonal assay, flow cytometric and multipotent differentiation analyses demonstrate that keloid contains a new population of stem cells, named keloid derived precursor cells (KPCs), which exhibit clonogenicity, self-renewal, distinct embryonic and mesenchymal stem cell surface markers, and multipotent differentiation. KPCs display elevated telomerase activity and an inherently upregulated proliferation capability as compared to their peripheral normal skin counterparts. A robust elevation of IL-6 and IL-17 expression in keloid is confirmed by cytokine array, western blot and ELISA analyses. The altered biological functions are tightly regulated by the inflammatory niche mediated by an autocrine/paracrine cytokine IL-17/IL-6 axis. Utilizing KPCs transplanted subcutaneously in immunocompromised mice we generate for the first time a human keloid-like tumor model that is driven by the in vivo inflammatory niche and allows testing of the anti-tumor therapeutic effect of antibodies targeting distinct niche components, specifically IL-6 and IL-17.

CONCLUSIONS/SIGNIFICANCE

These findings support our hypothesis that the altered niche in keloids, predominantly inflammatory, contributes to the acquirement of a benign tumor-like stem cell phenotype of KPCs characterized by the uncontrolled self-renewal and increased proliferation, supporting the rationale for in vivo modification of the "pathological" stem cell niche as a novel therapy for keloid and other mesenchymal benign tumors.

The fibrotic phenotype induced by IGFBP-5 is regulated by MAPK activation and egr-1-dependent and -independent mechanisms

We have previously shown that insulin-like growth factor (IGF) binding protein- 5 (IGFBP-5) is overexpressed in lung fibrosis and induces the production of extracellular matrix components, such as collagen and fibronectin, both in vitro and in vivo. The exact mechanism by which IGFBP-5 exerts these novel fibrotic effects is unknown. We thus examined the signaling cascades that mediate IGFBP-5-induced fibrosis. We demonstrate for the first time that IGFBP-5 induction of extracellular matrix occurs independently of IGF-I, and results from IGFBP-5 activation of MAPK signaling, which facilitates the translocation of IGFBP-5 to the nucleus. We examined the effects of IGFBP-5 on early growth response (Egr)-1, a transcription factor that is central to growth factor-mediated fibrosis. Egr-1 was up-regulated by IGFBP-5 in a MAPK-dependent manner and bound to nuclear IGFBP-5. In fibroblasts from Egr-1 knockout mice, induction of fibronectin by IGFBP-5 was abolished. Expression of Egr-1 in these cells rescued the extracellular matrix-promoting effects of IGFBP-5. Moreover, IGFBP-5 induced cell migration in an Egr-1-dependent manner. Notably, Egr-1 levels, similar to IGFBP-5, were increased in vivo in lung tissues and in vitro in primary fibroblasts of patients with pulmonary idiopathic fibrosis. Taken together, our findings suggest that IGFBP-5 induces a fibrotic phenotype via the activation of MAPK signaling and the induction of nuclear Egr-1 that interacts with IGFBP-5 and promotes fibrotic gene transcription.

Prevention and management of hypertrophic scars and keloids after burns in children

Hypertrophic scars and keloids are challenging to manage, particularly as sequelae of burns in children in whom the psychologic burden and skin characteristics differ substantially from adults. Prevention of hypertrophic scars and keloids after burns is currently the best strategy in their management to avoid permanent functional and aesthetical alterations. Several actions can be taken to prevent their occurrence, including parental and children education regarding handling sources of fire and flammable materials, among others. Combination of therapies is the mainstay of current burn scar management, including surgical reconstruction, pressure therapy, silicon gels and sheets, and temporary garments. Other adjuvant therapies such as topical imiquimod, tacrolimus, and retinoids, as well as intralesional corticosteroids, 5-fluorouracil, interferons, and bleomycin, have been used with relative success. Cryosurgery and lasers have also been reported as alternatives. Newer treatments aimed at molecular targets such as cytokines, growth factors, and gene therapy, currently in developing stages, are considered the future of the treatment of postburn hypertrophic scars and keloids in children.

Functional implications of the IL-6 signaling pathway in keloid pathogenesis

The molecular mechanism(s) behind keloid pathogenesis remains unclear. Previously by global gene expression analysis of keloid fibroblasts (KFs), we implicated the IL-6 signaling pathway in keloid pathogenesis. Here, we determine a functional role of IL-6 signaling in keloid scars. Primary cultures of KFs and surrounding nonlesional fibroblasts (NFs) were subjected to induction or inhibition of IL-6 or its specific receptor IL-6 receptor alpha (IL-6R alpha) and detection of their effects on extracellular matrix gene expression. The levels of gp130 and several downstream targets in IL-6 signaling were also examined. IL-6 secretion was significantly higher in KFs than NFs. Addition of IL-6 peptide to NFs culture or inhibition of IL-6 or its receptor IL-6R alpha by their corresponding antibodies in KFs culture revealed a dose-dependent increase or decrease in collagen type I alpha 2 and fibronectin 1 mRNAs, respectively. Induction of IL-6 by IL-1beta peptide and stimulation by IL-6 peptide in NFs, or inhibition of IL-6 or IL-6R alpha in KFs cultures demonstrated a dose-dependent increase or decrease in procollagen I synthesis, respectively. The mRNA and protein expressions of gp130 and several downstream targets in IL-6 signaling (JAK1, STAT3, RAF1, and ELK1) were upregulated in KFs versus NFs. Our results indicate that IL-6 signaling may play an integral role in keloid pathogenesis and provide clues for development of IL-6 receptor blocking strategies for therapy or prophylaxis of keloid scars.

Tubal occlusion causing infertility due to an excessive inflammatory response in patients with predisposition for keloid formation

Infertility is a condition that affects approximately 15-25% of couples with the desire to procreate. The integrity of the feminine reproductive tract is essential for this purpose, but the occlusion of the Fallopian tubes occurs in 12-33% of infertile women. The infection by Chlamydia trachomatis is one of the principle causes of tubal injury, which could finally lead to tubal occlusion. The tract infection has also been related to the use of intrauterine device, basically due to the fact that the insertion of the device could carry bacteria to the endometrial cavity. Keloid scars result from alterations in the normal process of wound healing, and it affects principally the population in reproductive age, maybe due to specific hormonal influence. These fibroproliferative alterations may produce significant deformations and alter organ function. The genetic factors have been studied in order to have a better understanding of the pathophysiology of keloid scarring. With these assessments, many other factors have been known to have a relationship with this abnormal healing process. This keloid scarring involves an excess in extracellular matrix production and inhibition of apoptosis, for which a several growth factors and interleukins are needed. One of the most important growth factors is IGF-1, which increases the expression of type I and III procollagen (found in the uterus); the IGF-1 receptor is overexpressed in the fibroblasts of keloids. Based on those previous observations a hypothesis that the chronic and repeated infection, and the use of IUD, generate an exaggerated inflammatory response in patients with a predisposition for keloid formation (which frequently form in childbearing age), in comparison to the patients that do not form this type of scarring, has been proposed. This makes a major frequency of adherences and finally tubal occlusion and infertility. The tendency of excessive scarring could not be exclusive of skin and generate abnormal scarring responses in feminine reproductive tract, leading to a major frequency of infertility. Thus, it could be suggested the use of other contraceptive methods and a more aggressive treatment against infections of the reproductive tract, taking in consideration the pathophysiology of keloid scar formation and its relationship with tubal occlusion.

Global Gene Expression Analysis of Keloid Fibroblasts in Response to Electron Beam Irradiation Reveals the Involvement of Interleukin-6 Pathway

Keloid is a dermal fibroproliferative lesion of unknown etiology that commonly recurs after surgical excision. Post-operative adjuvant electron beam (EB) irradiation has been successfully used to reduce keloid recurrences. To provide new insights into the molecular mechanism behind the effect of EB irradiation, we used a cDNA microarray screening of more than 5000 genes to assess early changes in gene expression between EB-irradiated and non-irradiated keloid and non-lesional dermal fibroblasts. Primary fibroblast cultures from keloid and associated non-lesional dermis obtained from five patients were exposed to 15 Gy EB irradiation and analyzed after 15 min incubation. Early response to EB irradiation showed that 96 (1.8%) genes were modulated 2-fold or more in keloid fibroblasts. Upregulated genes accounted for 29.2% (28 genes), whereas downregulated genes comprised 70.8% (68 genes), indicating a silencing of many genes in keloid fibroblasts after EB irradiation. Many of the downregulated genes play roles in the enhancement of cell proliferation and extracellular matrix production, whereas several of the upregulated genes involves in the promotion of apoptosis and extracellular matrix (ECM) degradation. Using emerging bioinformatic tools and further corroboration, the interleukin 6 (IL-6) signaling pathway was found to be mainly involved in EB irradiation response. We also showed co-expression of IL-6 and its specific receptor (IL-6Ralpha) in keloid fibroblasts that points to the existence of an IL-6 autocrine loop in these cells. These results suggested that at the molecular level, EB irradiation might hinder keloid formation by regularizing disturbances in the homeostatic equilibrium between inducer and inhibitor activities in the matrix system most likely through the IL-6 pathway. Our study provides clues for the molecular mechanism(s) behind the beneficial effect of EB irradiation in reducing keloid recurrences and may help develop alternative strategies for the therapy and prophylaxis of this lesion.

Matrix metalloproteinase expression in cytokine stimulated human dermal fibroblasts

In this study, we investigated the effect of inflammatory cytokines on matrix metalloproteinase (MMP-1) and TIMP-1 production in human dermal fibroblasts, which play a pivotal role in wound healing, ranging from the synthesis and remodeling of extracellular matrix (ECM) to the synthesis of growth factors. The balance of MMPs and TIMPs is crucial in directing successful wound repair. Human adult dermal fibroblasts were seeded in six well plates (7.5 x 10(4) cells/ml) in complete media. Eighty to ninety percent confluent cells were treated with interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) (10 ng/ml) for 6h in serum free media with suitable controls run in triplicate. Supernatants were assayed for pro-MMP-1 & TIMP-1. Extracted total RNA was used for reverse transcription polymerase chain reaction (RT-PCR) with sequence specific primers for MMP-1, TIMP-1 and beta-actin. Signal intensity was normalized to the internal control (beta-actin). Statistical analysis used ANOVA. MMP-1 and TIMP-1 mRNA expression were markedly increased with IL-6 and TNF-alpha treatment and remains unchanged with IL-1beta. Pro-MMP-1 protein levels are unchanged with TNF-alpha and significantly increased with IL-1beta and IL-6 treatment. However, TNF-alpha significantly increases TIMP-1 protein levels. Data suggests differential regulation of MMP-1 and TIMP-1 protein levels by the cytokines found in stimulated dermal fibroblasts. Further characterization of this response will provide an understanding of the mechanisms of pathogenesis of extracellular matrix (ECM) and the potential role of metalloproteinases in tissue remodeling after injury.

Establishment and characterization of a human B cell line from the lung tissue of a patient with scleroderma; extraordinary high level of IL-6 secretion by stimulated fibroblasts

Progressive systemic sclerosis is a connective tissue disease of unknown aetiology. This is the first study to demonstrate induction by a human B cell line of IL-6 secretion from fibroblasts. The cell line was established from lesional lung tissue of a patient with progressive systemic sclerosis. These cells, referred to as kon-1 cells, showed characteristics of pro-B cell by flow cytometry. Although kon-1 cells alone secreted a small amount of IL-6, a co-culture of kon-1 cells with normal lung fibroblasts significantly increased IL-6 levels. Whereas IL-6 mRNA was weakly expressed in kon-1 cells alone, it was clearly expressed in cells from the co-culture. Immunocytochemical identification of IL-6 showed localization in the cytoplasm of fibroblasts. IL-6 is a pleiotropic cytokine, essential for B cell differentiation, which has been shown to stimulate the production of collagen and glycosaminoglycan. Thus, abnormally augmented B cell proliferation and the inflammatory response stimulated by these cells may cause the fibrotic changes in patients with progressive systemic sclerosis.

Elevated interleukin-6 expression in keloid fibroblasts

Keloids are characterized by a net accumulation of collagen. To date, the role of growth factors and various cytokines in the pathogenesis of these lesions has not been fully characterized. Interleukin-6 (IL-6) is an important immunoregulatory cytokine that has been implicated in a number of fibrotic autoimmune diseases such as scleroderma, interstitial nephritis, and pulmonary interstitial fibrosis. However, the role of IL-6 in the development of keloids has yet to be defined. This study demonstrates increased expression of the IL-6 gene in fibroblasts isolated from patients with keloids when compared with control fibroblasts using the ribonuclease protection assay. Subsequent detection of increased levels of IL-6 secretion by keloid fibroblasts is also demonstrated under unstimulated and stimulated conditions using serum and interferon gamma (IFN-gamma) (unstimulated: 0.3694 + 0.2499 pg/cell vs 0.0662 + 0.0786 pg/cell, P = 0.0137; serum: 1.066 + 0.513 pg/cell vs 0.233 + 0.231 pg/cell, P = 0.0027; serum and IFN-gamma: 1.286 + 0.395 pg/cell vs 0.244 + 0.199 pg/cell, P < 0.0001). These results suggest that IL-6 may play a significant role in the pathogenesis of keloids.

The FeLV-945 LTR confers a replicative advantage dependent on the presence of a tandem triplication

Feline leukemia virus (FeLV), like other naturally occurring retroviruses, is characterized by a high degree of genetic diversity. FeLV-945 is a natural isolate derived from non-B-cell non-T-cell lymphomas classified anatomically as multicentric. FeLV-945 exhibits a unique structural motif in the LTR composed of a 21-bp tandem triplication downstream of a single copy of enhancer. The unique FeLV-945 LTR is precisely conserved among eight independent multicentric lymphomas collected in a geographic cluster. Previous studies using reporter gene constructs predict that the FeLV-945 LTR would confer a replicative advantage on the virus that contains it, particularly in primitive hematopoietic cells. Such an advantage may account for the precise conservation of the unique LTR sequence. To test that prediction, a set of recombinant, infectious FeLVs was developed that are isogenic other than the presence of the FeLV-945 LTR or mutations of it. Replication assays show that the FeLV-945 LTR confers a distinct growth advantage in K-562, FEA, and 3201 cells and implicate the 21-bp triplication in that function. Replacement of two copies of the triplicated element with random sequence greatly diminished the replicative capacity, thus implicating the triplicated sequence itself in LTR function. The 21-bp triplication was shown to contain specific nuclear protein binding sites, which may account for the selective pressure to conserve the sequence.

Novel therapeutic strategies in scleroderma

Optimal management for scleroderma (systemic sclerosis) is likely to require treatment of the underlying disease process, which remains incompletely understood, and also of the organ-based complications of this heterogeneous condition. Clinical trials evaluating several potential agents have been completed recently, including D-penicillamine and interferon alpha. Unfortunately none of these studies has suggested significant efficacy. This article focuses on new treatment approaches using existing therapeutic agents, such as prostacyclin, and considers the potential usefulness of new agents (eg, relaxin, halofuginone) or strategies such as intensive immunosuppression with peripheral stem cell rescue. Ultimately, a better understanding of disease pathogenesis may facilitate the development of targeted therapy against key events or mediators, but for the present better evaluation of existing agents and a focus on optimizing protocols for organ-based complications, such as pulmonary vascular disease or hypertensive renal crisis, are important goals.

Endogenous IL-1alpha from systemic sclerosis fibroblasts induces IL-6 and PDGF-A

It is reported that fibroblasts derived from clinically affected skin areas of patients with systemic sclerosis (SSc) have the ability to overproduce several cytokines and growth factors (i.e., IL-6, PDGF), an ability that might be involved in the pathogenesis of SSc. We have previously shown that the expression of IL-1alpha was constitutively observed in SSc fibroblasts, whereas this was not detected in normal fibroblasts. Although it was suggested that the aberrant IL-1alpha production could be associated with the fibrogenic phenotype of SSc fibroblasts, little is known about the roles of IL-1alpha in SSc fibroblasts. IL-1alpha induced IL-6 and PDGF-A, which are potent stimulators of collagen production and proliferation in normal fibroblasts. This article examines the proposal that IL-6 and PDGF-A are elevated through the action of endogenous IL-1alpha in SSc fibroblasts. An antisense oligodeoxynucleotide complementary to IL-1alpha mRNA was used to suppress endogenous IL-1alpha. Inhibition of endogenous IL-1alpha led to decreased levels of IL-6 and PDGF-A expression in SSc fibroblasts. Moreover, the blocking of the IL-6 response using anti-IL-6 antibody resulted in a significant reduction of procollagen type I in cultured SSc fibroblasts. These results suggest that endogenous IL-1alpha expressed by SSc fibroblasts may play a key role in the abnormal function of SSc fibroblasts through the expression of IL-6 and PDGF-A.

Interleukin 6 and its receptor: ten years later

Ten years have passed since the molecular cloning of interleukin 6 (IL-6) in 1986. IL-6 is a typical cytokine, exhibiting functional pleiotropy and redundancy. IL-6 is involved in the immune response, inflammation, and hematopoiesis. The IL-6 receptor consists of an IL-6 binding alpha chain and a signal transducer, gp130, which is shared among the receptors for the IL-6 related cytokine subfamily. The sharing of a receptor subunit is a general feature of cytokine receptors and provides the molecular basis for the functional redundancy of cytokines. JAK tyrosine kinase is a key molecule that can initiate multiple signal-transduction pathways by inducing the tyrosine-phosphorylation of the cytokine receptor, gp130 in the case of IL-6, on which several signaling molecules are recruited, including STAT, a signal transducer and activator of transcription, and SHP-2, which links to the Ras-MAP kinase pathway. JAK can also directly activate signaling molecules such as STAT and Tec. These multiple signal-transduction pathways intimately regulate the expression of several genes including c-myc, c-myb, junB, IRF1, egr-1, and bcl-2, leading to the induction of cell growth, differentiation, and survival. The deregulated expression of IL-6 and its receptor is involved in a variety of diseases.

Increased expression of TGF-beta receptors by scleroderma fibroblasts: evidence for contribution of autocrine TGF-beta signaling to scleroderma phenotype

Scleroderma fibroblasts exhibit numerous phenotypic differences when compared with healthy skin fibroblasts. Some of these differences, in particular overexpression of collagen type I and other extracellular matrix proteins, parallel the effect of transforming growth factor-beta (TGF-beta) on dermal fibroblasts, suggesting that the scleroderma fibroblast phenotype may result from activation of autocrine TGF-beta signaling. To test this hypothesis we examined the role of TGF-beta Type I and Type II receptors in regulating collagen type I transcription. We have shown that overexpression of either Type I or Type II receptors significantly (3-4-fold) increases alpha2 (I) collagen promoter activity in transient transfection assays in dermal fibroblasts. Addition of anti-TGF-beta antibody abolished, whereas addition of plasmin enhanced, the stimulatory effect of receptor overexpression on collagen promoter activity, suggesting that this effect depends on autocrine TGF-beta. Moreover, these cotransfection experiments indicated that expression levels of TGF-beta receptors is a limiting factor in the autocrine regulation of collagen type I transcription by TGF-beta. Comparison of the TGF-beta receptor Type I and Type II mRA expression levels in scleroderma and normal fibroblasts have indicated elevated expression (2-fold) of both receptor types in scleroderma cells, which correlated with increased binding of TGF-beta. Significantly, elevated TGF-beta receptor levels correlated with elevated alpha2 (I) collagen mRNA levels. These results suggest that the elevated production of collagen type I by scleroderma fibroblasts results from overexpression of TGF-beta receptors.

Mast cells, eosinophils and fibrosis

We have presented results that increase our understanding of the roles MC and EOS play in modulating fibrotic processes. In vitro studies have provided clear-cut evidence for the direct involvement of these two inflammatory cells in enhancing proliferation, and either enhancing or decreasing collagen synthesis in human fibroblasts isolated from different anatomical locations. In addition, we have shown that MC and EOS interactions can also take part in modulating fibrosis. In vivo studies in murine and human cGVHD showed that MC activation is detrimental, and that MC stabilization therapy may be helpful in treating the fibrotic outcome of this disease. Much is still obscure. It is, for example, important to define the MC and EOS mediators involved in the modulation of fibroblast properties, and their pattern of influence, keeping in mind the ultimate goal of defining new therapeutic targets for the treatment of fibrotic diseases.