PU.1 controls fibroblast polarization and tissue fibrosis

Fibroblasts are polymorphic cells with pleiotropic roles in organ morphogenesis, tissue homeostasis and immune responses. In fibrotic diseases, fibroblasts synthesize abundant amounts of extracellular matrix, which induces scarring and organ failure. By contrast, a hallmark feature of fibroblasts in arthritis is degradation of the extracellular matrix because of the release of metalloproteinases and degrading enzymes, and subsequent tissue destruction. The mechanisms that drive these functionally opposing pro-fibrotic and pro-inflammatory phenotypes of fibroblasts remain unknown. Here we identify the transcription factor PU.1 as an essential regulator of the pro-fibrotic gene expression program. The interplay between transcriptional and post-transcriptional mechanisms that normally control the expression of PU.1 expression is perturbed in various fibrotic diseases, resulting in the upregulation of PU.1, induction of fibrosis-associated gene sets and a phenotypic switch in extracellular matrix-producing pro-fibrotic fibroblasts. By contrast, pharmacological and genetic inactivation of PU.1 disrupts the fibrotic network and enables reprogramming of fibrotic fibroblasts into resting fibroblasts, leading to regression of fibrosis in several organs

Engrailed 1 coordinates cytoskeletal reorganization to induce myofibroblast differentiation

Transforming growth factor-β (TGFβ) is a key mediator of fibroblast activation in fibrotic diseases, including systemic sclerosis. Here we show that Engrailed 1 (EN1) is reexpressed in multiple fibroblast subpopulations in the skin of SSc patients. We characterize EN1 as a molecular amplifier of TGFβ signaling in myofibroblast differentiation: TGFβ induces EN1 expression in a SMAD3-dependent manner, and in turn, EN1 mediates the profibrotic effects of TGFβ. RNA sequencing demonstrates that EN1 induces a profibrotic gene expression profile functionally related to cytoskeleton organization and ROCK activation. EN1 regulates gene expression by modulating the activity of SP1 and other SP transcription factors, as confirmed by ChIP-seq experiments for EN1 and SP1. Functional experiments confirm the coordinating role of EN1 on ROCK activity and the reorganization of cytoskeleton during myofibroblast differentiation, in both standard fibroblast culture systems and in vitro skin models. Consistently, mice with fibroblast-specific knockout of En1 demonstrate impaired fibroblast-to-myofibroblast transition and are partially protected from experimental skin fibrosis

Dersimelagon, a novel oral melanocortin 1 receptor agonist, demonstrates disease-modifying effects in preclinical models of systemic sclerosis

BACKGROUND Activation of melanocortin 1 receptor (MC1R) is known to exert broad anti-inflammatory and anti-fibrotic effects. The purpose of this study is to investigate the potential of dersimelagon, a novel oral MC1R agonist, as a therapeutic agent for systemic sclerosis (SSc). METHODS The effects of dersimelagon phosphoric acid (MT-7117) on skin fibrosis and lung inflammation were evaluated in bleomycin (BLM)-induced SSc murine models that were optimized for prophylactic and therapeutic evaluation. Microarray-based gene expression analysis and serum protein profiling were performed in the BLM-induced SSc models. The effect of MT-7117 on transforming growth factor-β (TGF-β)-induced activation of human dermal fibroblasts was evaluated in vitro. Immunohistochemical analyses of MC1R expression in the skin of SSc patients were performed. RESULTS Prophylactic treatment with MT-7117 (≥ 0.3 mg/kg/day p.o.) significantly inhibited skin fibrosis and lung inflammation, and therapeutic treatment with MT-7117 (≥ 3 mg/kg/day p.o.) significantly suppressed the development of skin fibrosis in the BLM-induced SSc models. Gene array analysis demonstrated that MT-7117 exerts an anti-inflammatory effect via suppression of the activation of inflammatory cells and inflammation-related signals; additionally, vascular dysfunction was extracted as the pathology targeted by MT-7117. Serum protein profiling revealed that multiple SSc-related biomarkers including P-selectin, osteoprotegerin, cystatin C, growth and differentiation factor-15, and S100A9 were suppressed by MT-7117. MT-7117 inhibited the activation of human dermal fibroblasts by suppressing TGF-β-induced ACTA2 (encoding α-smooth muscle actin) mRNA elevation. MC1R was expressed by monocytes/macrophages, neutrophils, blood vessels (endothelial cells), fibroblasts, and epidermis (keratinocytes) in the skin of SSc patients, suggesting that these MC1R-positive cells could be targets for MT-7117. CONCLUSIONS MT-7117 demonstrates disease-modifying effects in preclinical models of SSc. Investigations of its mechanism of action and target expression analyses indicate that MT-7117 exerts its positive effect by affecting inflammation, vascular dysfunction, and fibrosis, which are all key pathologies of SSc. The results of the present study suggest that MT-7117 is a potential therapeutic agent for SSc. A phase 2 clinical trial investigating the efficacy and tolerability of MT-7117 in patients with early, progressive diffuse cutaneous SSc is currently in progress

cRel expression regulates distinct transcriptional and functional profiles driving fibroblast matrix production in systemic sclerosis

Objectives: NF-κB regulates genes that control inflammation, cell proliferation, differentiation and survival. Dysregulated NF-κB signalling alters normal skin physiology and deletion of cRel limits bleomycin-induced skin fibrosis. This study investigates the role of cRel in modulating fibroblast phenotype in the context of SSc. Methods: Fibrosis was assessed histologically in mice challenged with bleomycin to induce lung or skin fibrosis. RNA sequencing and pathway analysis was performed on wild type and Rel-/- murine lung and dermal fibroblasts. Functional assays examined fibroblast proliferation, migration and matrix production. cRel overexpression was investigated in human dermal fibroblasts. cRel immunostaining was performed on lung and skin tissue sections from SSc patients and non-fibrotic controls. Results: cRel expression was elevated in murine lung and skin fibrosis models. Rel-/- mice were protected from developing pulmonary fibrosis. Soluble collagen production was significantly decreased in fibroblasts lacking cRel while proliferation and migration of these cells was significantly increased. cRel regulates genes involved in extracellular structure and matrix organization. Positive cRel staining was observed in fibroblasts in human SSc skin and lung tissue. Overexpression of constitutively active cRel in human dermal fibroblasts increased expression of matrix genes. An NF-κB gene signature was identified in diffuse SSc skin and nuclear cRel expression was elevated in SSc skin fibroblasts. Conclusion: cRel regulates a pro-fibrogenic transcriptional programme in fibroblasts that may contribute to disease pathology. Targeting cRel signalling in fibroblasts of SSc patients could provide a novel therapeutic avenue to limit scar formation in this disease

The systemic lupus erythematosus IRF5 risk haplotype is associated with systemic sclerosis

Systemic sclerosis (SSc) is a fibrotic autoimmune disease in which the genetic component plays an important role. One of the strongest SSc association signals outside the human leukocyte antigen (HLA) region corresponds to interferon (IFN) regulatory factor 5 (IRF5), a major regulator of the type I IFN pathway. In this study we aimed to evaluate whether three different haplotypic blocks within this locus, which have been shown to alter the protein function influencing systemic lupus erythematosus (SLE) susceptibility, are involved in SSc susceptibility and clinical phenotypes. For that purpose, we genotyped one representative single-nucleotide polymorphism (SNP) of each block (rs10488631, rs2004640, and rs4728142) in a total of 3,361 SSc patients and 4,012 unaffected controls of Caucasian origin from Spain, Germany, The Netherlands, Italy and United Kingdom. A meta-analysis of the allele frequencies was performed to analyse the overall effect of these IRF5 genetic variants on SSc. Allelic combination and dependency tests were also carried out. The three SNPs showed strong associations with the global disease (rs4728142: P = 1.34×10<sup>−8</sup>, OR = 1.22, CI 95% = 1.14–1.30; rs2004640: P = 4.60×10<sup>−7</sup>, OR = 0.84, CI 95% = 0.78–0.90; rs10488631: P = 7.53×10<sup>−20</sup>, OR = 1.63, CI 95% = 1.47–1.81). However, the association of rs2004640 with SSc was not independent of rs4728142 (conditioned P = 0.598). The haplotype containing the risk alleles (rs4728142*A-rs2004640*T-rs10488631*C: P = 9.04×10<sup>−22</sup>, OR = 1.75, CI 95% = 1.56–1.97) better explained the observed association (likelihood P-value = 1.48×10<sup>−4</sup>), suggesting an additive effect of the three haplotypic blocks. No statistical significance was observed in the comparisons amongst SSc patients with and without the main clinical characteristics. Our data clearly indicate that the SLE risk haplotype also influences SSc predisposition, and that this association is not sub-phenotype-specific

Analysis of the association between CD40 and CD40 ligand polymorphisms and systemic sclerosis.

Introduction: The aim of the present study was to investigate the possible role of CD40 and CD40 ligand (CD40LG) genes in the susceptibility and phenotype expression of systemic sclerosis (SSc). Methods: In total, 2,670 SSc patients and 3,245 healthy individuals from four European populations (Spain, Germany, The Netherlands, and Italy) were included in the study. Five single-nucleotide polymorphisms (SNPs) of CD40 (rs1883832, rs4810485, rs1535045) and CD40LG (rs3092952, rs3092920) were genotyped by using a predesigned TaqMan allele-discrimination assay technology. Meta-analysis was assessed to determine whether an association exists between the genetic variants and SSc or its main clinical subtypes. Results: No evidence of association between CD40 and CD40LG genes variants and susceptibility to SSc was observed. Similarly, no significant statistical differences were observed when SSc patients were stratified by the clinical subtypes, the serologic features, and pulmonary fibrosis. Conclusions: Our results do not suggest an important role of CD40 and CD40LG gene polymorphisms in the susceptibility to or clinical expression of SSc

A genome-wide association study follow-up suggests a possible role for PPARG in systemic sclerosis susceptibility

Introduction: A recent genome-wide association study (GWAS) comprising a French cohort of systemic sclerosis (SSc) reported several non-HLA single-nucleotide polymorphisms (SNPs) showing a nominal association in the discovery phase. We aimed to identify previously overlooked susceptibility variants by using a follow-up strategy.<p></p> Methods: Sixty-six non-HLA SNPs showing a P value <10-4 in the discovery phase of the French SSc GWAS were analyzed in the first step of this study, performing a meta-analysis that combined data from the two published SSc GWASs. A total of 2,921 SSc patients and 6,963 healthy controls were included in this first phase. Two SNPs, PPARG rs310746 and CHRNA9 rs6832151, were selected for genotyping in the replication cohort (1,068 SSc patients and 6,762 healthy controls) based on the results of the first step. Genotyping was performed by using TaqMan SNP genotyping assays. Results: We observed nominal associations for both PPARG rs310746 (PMH = 1.90 × 10-6, OR, 1.28) and CHRNA9 rs6832151 (PMH = 4.30 × 10-6, OR, 1.17) genetic variants with SSc in the first step of our study. In the replication phase, we observed a trend of association for PPARG rs310746 (P value = 0.066; OR, 1.17). The combined overall Mantel-Haenszel meta-analysis of all the cohorts included in the present study revealed that PPARG rs310746 remained associated with SSc with a nominal non-genome-wide significant P value (PMH = 5.00 × 10-7; OR, 1.25). No evidence of association was observed for CHRNA9 rs6832151 either in the replication phase or in the overall pooled analysis.<p></p> Conclusion: Our results suggest a role of PPARG gene in the development of SSc

Disability, fatigue, pain and their associates in early diffuse cutaneous systemic sclerosis: the European Scleroderma Observational Study

Objectives; Our aim was to describe the burden of early dcSSc in terms of disability, fatigue and pain in the European Scleroderma Observational Study cohort, and to explore associated clinical features. Methods; Patients completed questionnaires at study entry, 12 and 24 months, including the HAQ disability index (HAQ-DI), the Cochin Hand Function Scale (CHFS), the Functional Assessment of Chronic Illness Therapy-fatigue and the Short Form 36 (SF36). Associates examined included the modified Rodnan skin score (mRSS), current digital ulcers and internal organ involvement. Correlations between 12-month changes were also examined. Results; The 326 patients recruited (median disease duration 11.9 months) displayed high levels of disability [mean (S.D.) HAQ-DI 1.1 (0.83)], with ‘grip’ and ‘activity’ being most affected. Of the 18 activities assessed in the CHFS, those involving fine finger movements were most affected. High HAQ-DI and CHFS scores were both associated with high mRSS (ρ = 0.34, P < 0.0001 and ρ = 0.35, P < 0.0001, respectively). HAQ-DI was higher in patients with digital ulcers (P = 0.004), pulmonary fibrosis (P = 0.005), cardiac (P = 0.005) and muscle involvement (P = 0.002). As anticipated, HAQ-DI, CHFS, the Functional Assessment of Chronic Illness Therapy and SF36 scores were all highly correlated, in particular the HAQ-DI with the CHFS (ρ = 0.84, P < 0.0001). Worsening HAQ-DI over 12 months was strongly associated with increasing mRSS (ρ = 0.40, P < 0.0001), decreasing hand function (ρ = 0.57, P < 0.0001) and increasing fatigue (ρ = −0.53, P < 0.0001). Conclusion; The European Scleroderma Observational Study highlights the burden of disability in early dcSSc, with high levels of disability and fatigue, associating with the degree of skin thickening (mRSS). Impaired hand function is a major contributor to overall disability

Treatment outcome in early diffuse cutaneous systemic sclerosis: the European Scleroderma Observational Study (ESOS).

OBJECTIVES: The rarity of early diffuse cutaneous systemic sclerosis (dcSSc) makes randomised controlled trials very difficult. We aimed to use an observational approach to compare effectiveness of currently used treatment approaches. METHODS: This was a prospective, observational cohort study of early dcSSc (within three years of onset of skin thickening). Clinicians selected one of four protocols for each patient: methotrexate, mycophenolate mofetil (MMF), cyclophosphamide or 'no immunosuppressant'. Patients were assessed three-monthly for up to 24 months. The primary outcome was the change in modified Rodnan skin score (mRSS). Confounding by indication at baseline was accounted for using inverse probability of treatment (IPT) weights. As a secondary outcome, an IPT-weighted Cox model was used to test for differences in survival. RESULTS: Of 326 patients recruited from 50 centres, 65 were prescribed methotrexate, 118 MMF, 87 cyclophosphamide and 56 no immunosuppressant. 276 (84.7%) patients completed 12 and 234 (71.7%) 24 months follow-up (or reached last visit date). There were statistically significant reductions in mRSS at 12 months in all groups: -4.0 (-5.2 to -2.7) units for methotrexate, -4.1 (-5.3 to -2.9) for MMF, -3.3 (-4.9 to -1.7) for cyclophosphamide and -2.2 (-4.0 to -0.3) for no immunosuppressant (p value for between-group differences=0.346). There were no statistically significant differences in survival between protocols before (p=0.389) or after weighting (p=0.440), but survival was poorest in the no immunosuppressant group (84.0%) at 24 months. CONCLUSIONS: These findings may support using immunosuppressants for early dcSSc but suggest that overall benefit is modest over 12 months and that better treatments are needed. TRIAL REGISTRATION NUMBER: NCT02339441

Analysis of the association between CD40 and CD40 ligand polymorphisms and systemic sclerosis

Journal Article; Research Support, Non-U.S. Gov't;INTRODUCTION The aim of the present study was to investigate the possible role of CD40 and CD40 ligand (CD40LG) genes in the susceptibility and phenotype expression of systemic sclerosis (SSc). METHODS In total, 2,670 SSc patients and 3,245 healthy individuals from four European populations (Spain, Germany, The Netherlands, and Italy) were included in the study. Five single-nucleotide polymorphisms (SNPs) of CD40 (rs1883832, rs4810485, rs1535045) and CD40LG (rs3092952, rs3092920) were genotyped by using a predesigned TaqMan allele-discrimination assay technology. Meta-analysis was assessed to determine whether an association exists between the genetic variants and SSc or its main clinical subtypes. RESULTS No evidence of association between CD40 and CD40LG genes variants and susceptibility to SSc was observed. Similarly, no significant statistical differences were observed when SSc patients were stratified by the clinical subtypes, the serologic features, and pulmonary fibrosis. CONCLUSIONS Our results do not suggest an important role of CD40 and CD40LG gene polymorphisms in the susceptibility to or clinical expression of SSc.Ye