Skin biopsy analysis of concurrent keloidal morphoea and systemic sclerosis confirms overlapping pathogenic pathways.

OBJECTIVES: Although localised forms of scleroderma (morphoea) have very different clinical features and outcomes from systemic sclerosis the two conditions can occur together in some patients. In this study we have explored skin gene expression in a series of patients with keloidal morphoea, a distinct clinical variant, concurrently with systemic sclerosis. METHODS: We compared skin gene expression from the keloidal lesions with that from skin elsewhere. We also examined a series of patients with diffuse or limited cutaneous SSc without morphoea and some healthy control skin biopsies. RESULTS: Keloidal morphoea has a distinct gene expression signature that is mainly driven by differential expression of fibroblast-related genes compared with other cell types. Indeed, the signature reflects a profibrotic pattern seen in diffuse cutaneous SSc but is much more extreme. We propose that keloidal morphoea skin provides unique insight into the profibrotic population of cells driving dcSSc. CONCLUSIONS: Understanding the biology of keloidal morphoea may give valuable insight into the molecular and cellular pathology of systemic sclerosis. The discrete nature of keloidal lesions raises the possibility of haematogenous spread and we suggest that the driving cells could represent blood derived cells derived from circulating progenitors.

Scleroderma fibroblasts suppress angiogenesis via TGF-ß/caveolin-1 dependent secretion of pigment epithelium-derived factor.

OBJECTIVES: Systemic sclerosis (SSc) is characterised by tissue fibrosis and vasculopathy with defective angiogenesis. Transforming growth factor beta (TGF-ß) plays a major role in tissue fibrosis, including downregulation of caveolin-1 (Cav-1); however, its role in defective angiogenesis is less clear. Pigment epithelium-derived factor (PEDF), a major antiangiogenic factor, is abundantly secreted by SSc fibroblasts. Here, we investigated the effect of TGF-ß and Cav-1 on PEDF expression and the role of PEDF in the ability of SSc fibroblasts to modulate angiogenesis. METHODS: PEDF and Cav-1 expression in fibroblasts and endothelial cells were evaluated by means of immunohistochemistry on human and mouse skin biopsies. PEDF and Cav-1 were silenced in cultured SSc and control fibroblasts using lentiviral short-hairpin RNAs. Organotypic fibroblast-endothelial cell co-cultures and matrigel assays were employed to assess angiogenesis. RESULTS: PEDF is highly expressed in myofibroblasts and reticular fibroblasts with low Cav-1 expression in SSc skin biopsies, and it is induced by TGF-ß in vitro. SSc fibroblasts suppress angiogenesis in an organotypic model. This model is reproduced by silencing Cav-1 in normal dermal fibroblasts. Conversely, silencing PEDF in SSc fibroblasts rescues their antiangiogenic phenotype. Consistently, transgenic mice with TGF-ß receptor hyperactivation show lower Cav-1 and higher PEDF expression levels in skin biopsies accompanied by reduced blood vessel density. CONCLUSIONS: Our data reveal a new pathway by which TGF-ß suppresses angiogenesis in SSc, through decreased fibroblast Cav-1 expression and subsequent PEDF secretion. This pathway may present a promising target for new therapeutic interventions in SSc.

Endothelial injury in a transforming growth factor ß-dependent mouse model of scleroderma induces pulmonary arterial hypertension.

OBJECTIVE: To delineate the constitutive pulmonary vascular phenotype of the TßRIIΔk-fib mouse model of scleroderma, and to selectively induce pulmonary endothelial cell injury using vascular endothelial growth factor (VEGF) inhibition to develop a model with features characteristic of pulmonary arterial hypertension (PAH). METHODS: The TßRIIΔk-fib mouse strain expresses a kinase-deficient transforming growth factor ß (TGFß) receptor type II driven by a fibroblast-specific promoter, leading to ligand-dependent up-regulation of TGFß signaling, and replicates key fibrotic features of scleroderma. Structural, biochemical, and functional assessments of pulmonary vessels, including in vivo hemodynamic studies, were performed before and following VEGF inhibition, which induced pulmonary endothelial cell apoptosis. These assessments included biochemical analysis of the TGFß and VEGF signaling axes in tissue sections and explanted smooth muscle cells. RESULTS: In the TßRIIΔk-fib mouse strain, a constitutive pulmonary vasculopathy with medial thickening, a perivascular proliferating chronic inflammatory cell infiltrate, and mildly elevated pulmonary artery pressure resembled the well-described chronic hypoxia model of pulmonary hypertension. Following administration of SU5416, the pulmonary vascular phenotype was more florid, with pulmonary arteriolar luminal obliteration by apoptosis-resistant proliferating endothelial cells. These changes resulted in right ventricular hypertrophy, confirming hemodynamically significant PAH. Altered expression of TGFß and VEGF ligand and receptor was consistent with a scleroderma phenotype. CONCLUSION: In this study, we replicated key features of systemic sclerosis-related PAH in a mouse model. Our results suggest that pulmonary endothelial cell injury in a genetically susceptible mouse strain triggers this complication and support the underlying role of functional interplay between TGFß and VEGF, which provides insight into the pathogenesis of this disease.

Revisiting ANCA-associated vasculitis in systemic sclerosis: clinical, serological and immunogenetic factors.

OBJECTIVES: To define the clinical, serological, histological and immunogenetic features of patients with scleroderma and ANCA-associated vasculitis (AAV). METHODS: We examined a clinical database of 2,200 patients with either limited or diffuse cutaneous systemic sclerosis (SSc). Patients with a confirmed diagnosis of vasculitis who were ANCA positive with either MPO or PR3 reactivity had their clinical features, serology, histology and HLA haplotypes examined in detail. RESULTS: From this SSc cohort, 35 patients (1.6%) had evidence of vasculitis, and the SSc autoantibody profiles in this group were comparable to those previously published from the whole cohort. Of these 35 patients, 8 (0.4% of whole SSc cohort) had either anti-MPO or anti-PR3 antibodies and two further patients were ANCA positive without defined specificities. Of the eight ANCA-positive patients, seven had limited cutaneous SSc and anti-MPO antibodies and only one had anti-PR3 antibodies, associated with diffuse cutaneous SSc. Two ANCA-positive patients had anti-U3RNP antibodies, usually associated with overlap disease. None of the patients had granulomatous disease. The majority had glomerulonephritis, renal arteritis and pulmonary fibrosis. There were several shared HLA haplotypes from the DP and DQ loci in these overlap patients. CONCLUSION: SSc in overlap with ANCA-associated vasculitis is rare, and clinical features are more mixed than when either of these two conditions occurs separately. From our database, U3RNP antibodies may be more associated with overlap AAV than the other scleroderma-specific antibodies.

Gut fibrosis with altered colonic contractility in a mouse model of scleroderma.

OBJECTIVE: Gastrointestinal involvement occurs in up to 90% of patients with SSc. Animal models of SSc mimic some of the pathophysiological disease processes of SSc. The transgenic (TG) mouse strain TßRIIΔk-fib is characterized by ligand-dependent up-regulation of TGF-ß signalling and has been shown to develop skin fibrosis, lung fibrosis and diminished aortic ring contractility and adventitial fibrosis. We investigated if similar changes are observed in the gut tissue in this mouse model. METHODS: Colonic tissue was examined using histology and immunohistochemistry analyses. Tissue architecture was examined by haematoxylin and eosin (H&E), picrosirius red and immunohistochemical markers for α-smooth muscle actin (α-SMA), phospho-Smad 2/3 (pSmad2/3), Ki-67, protein gene product 9.5 and S-100. Fibrosis was quantified using the NIS Elements BR 2.30 system and by Sircol assay. Colonic strip contractile responses to potassium chloride (KCl) and carbachol were assessed in isolated organ baths. Confirmatory gut fibroblast and intestinal tissue biochemical assays, including cellular signalling mechanisms, were performed. RESULTS: H&E staining and staining for α-SMA, Ki-67, pSmad2/3 or neural tissue staining showed no differences between TG and wild-type (WT) mice gut tissue. There was increased collagen deposition in the gut of TG mice. Quantitative PCR results of TG gut fibroblasts showed evidence of up-regulated collagen and CTGF transcription, and non-canonical TGF-ß signalling pathways were also up-regulated. The organ bath studies showed diminished colonic strip contractility in TG mice compared with WT control mice to KCl and carbachol. CONCLUSION: We have shown that this TG mouse model, previously shown to develop skin and lung, develops colonic fibrosis with associated effects on colonic tissue contractility. This may offer further insight in pathological processes leading to the development of gut fibrosis.

An essential role for resident fibroblasts in experimental lung fibrosis is defined by lineage-specific deletion of high-affinity type II transforming growth factor ß receptor.

RATIONALE: Fibrotic response to lung injury depends on development of a fibrogenic population of myofibroblasts. The importance of resident interstitial fibroblasts and role of transforming growth factor ß (TGFß) in this process is unclear. OBJECTIVES: To define the importance of TGFß signaling in resident lung fibroblasts in the development of experimental pulmonary fibrosis. METHODS: A compound genetic strategy in which mice homozygous for a floxed high-affinity type II TGFß receptor (TßRII) allele were crossed with a transgenic strain harboring a fibroblast-specific transgene encoding ligand-dependent Cre-recombinase was used. TßRII was deleted by postnatal administration of tamoxifen over 5 days to compound mutant mice with appropriate littermate controls. Illumina microarray gene profiling and quantitative reverse transcriptase-polymerase chain reaction were used to confirm anergy to TGFß in explanted lung fibroblasts. Bleomycin lung injury was used to induce lung fibrosis, which was analyzed by histology and biochemical methods. Immunofluorescence was used to define cell populations after lung injury. MEASUREMENTS AND MAIN RESULTS: There was significant attenuation of fibrosis in mice after deletion of TßRII in resident fibroblasts. At 7 days after injury the number of fibrocytes and myofibroblasts was substantially reduced. Potential regulators of fibrosis were suggested by gene expression profiles that identified key candidate profibrotic genes, including connective tissue growth factor and endothelin-1 expressed by wild-type but not mutant lung fibroblasts. CONCLUSIONS: Intact TGFß signaling in resident pulmonary fibroblasts is essential for pulmonary fibrosis to develop. Our data support a key regulatory role of these cells in determining fibrocyte recruitment and myofibroblast differentiation.

Using Autoantibodies and Cutaneous Subset to Develop Outcome-Based Disease Classification in Systemic Sclerosis.

OBJECTIVE: To describe the associations between autoantibodies, clinical presentation, and outcomes among patients with systemic sclerosis (SSc) in order to develop a novel SSc classification scheme that would incorporate both antibodies and the cutaneous disease subset as criteria. METHODS: Demographic and clinical characteristics, including cutaneous subset, time of disease and organ complication onset, and autoantibody specificities, were determined in a cohort of SSc subjects. Survival analysis was used to assess the effect of the autoantibodies on organ disease and death. RESULTS: The study included 1,325 subjects. Among the antibody/skin disease subsets, anticentromere antibody-positive patients with limited cutaneous SSc (lcSSc) (n = 374) had the highest 20-year survival (65.3%), lowest incidence of clinically significant pulmonary fibrosis (PF) (8.5%) and scleroderma renal crisis (SRC) (0.3%), and lowest incidence of cardiac SSc (4.9%), whereas the frequency of pulmonary hypertension (PH) was similar to the mean value in the SSc cohort overall. The anti-Scl-70+ groups of patients with lcSSc (n = 138) and patients with diffuse cutaneous SSc (dcSSc) (n = 149) had the highest incidence of clinically significant PF (86.1% and 84%, respectively, at 15 years). Anti-Scl-70+ patients with dcSSc had the lowest survival (32.4%) and the second highest incidence of cardiac SSc (12.9%) at 20 years. In contrast, in anti-Scl-70+ patients with lcSSc, other complications were rare, and these patients demonstrated the lowest incidence of PH (6.9%) and second highest survival (61.8%) at 20 years. Anti-RNA polymerase antibody-positive SSc patients (n = 147) had the highest incidence of SRC (28.1%) at 20 years. The anti-U3 RNP+ SSc group (n = 56) had the highest incidence of PH (33.8%) and cardiac SSc (13.2%) at 20 years. Among lcSSc patients with other autoantibodies (n = 295), the risk of SRC and cardiac SSc was low at 20 years (2.7% and 2.4%, respectively), while the frequencies of other outcomes were similar to the mean values in the full SSc cohort. Patients with dcSSc who were positive for other autoantibodies (n = 166) had a poor prognosis, demonstrating the second lowest survival (33.6%) and frequent organ complications. CONCLUSION: These findings highlight the importance of autoantibodies, cutaneous subset, and disease duration when assessing morbidity and mortality in patients with SSc. Our novel classification scheme may improve disease monitoring and benefit future clinical trial designs in SSc.

Animal models of scleroderma: lessons from transgenic and knockout mice.

PURPOSE OF REVIEW: The underlying pathogenesis of systemic sclerosis (SSc; scleroderma) involves a complex interplay of inflammation, fibrosis and vasculopathy that is incompletely understood. In this article, we highlight the important contributions that recent preclinical research has made to the knowledge base of pathogenesis and therapeutics in SSc, describe some of the newly developed models available for further investigation and discuss future research opportunities in this fascinating area. RECENT FINDINGS: Several well characterized SSc models are available for the study of fibrosis. However, recent study on transgenic and knockout models has advanced knowledge both in fibrosis research and in vascular disease in SSc. In the present review, we focus on models in which altered signalling, particularly transforming growth factor-beta (TGF-beta), is limited to fibroblasts. We discuss contemporary models of SSc vascular disease, transgenesis in fibrocyte research, the contribution to neurological signalling research and provide examples of how preclinical models have contributed to novel therapeutics development in SSc. We also look at how research from related disciplines impacts on the SSc knowledge base. SUMMARY: These new models represent exciting advances. However, none completely recapitulates the vasculopathic and inflammatory components of this disease. These advances help to delineate the relative contributions of specific ligands, receptors, their signalling pathways and feedback mechanisms, in fibrotic and inflammatory processes and this will provide new targets for potential therapies in SSc.

Limited cutaneous systemic sclerosis skin demonstrates distinct molecular subsets separated by a cardiovascular development gene expression signature.

BACKGROUND: Systemic sclerosis (SSc; scleroderma) is an uncommon autoimmune rheumatic disease characterised by autoimmunity, vasculopathy and fibrosis. Gene expression profiling distinguishes scleroderma from normal skin, and can detect different subsets of disease, with potential to identify prognostic biomarkers of organ involvement or response to therapy. We have performed gene expression profiling in skin samples from patients with limited cutaneous SSc (lcSSc). METHODS: Total RNA was extracted from clinically uninvolved skin biopsies of 15 patients with lcSSc and 8 healthy controls (HC). Gene expression profiling was performed on a DNA oligonucleotide microarray chip. Differentially expressed genes (DEG) were identified using significance analysis of microarrays (SAM). Functional enrichment analysis of gene signatures was done via g:Profiler. RESULTS: There were 218 DEG between lcSSc and HC samples (false discovery rate <10%): 181/218 DEG were upregulated in lcSSc samples. Hierarchical clustering of DEG suggested the presence of two separate groups of lcSSc samples: "limited 1" and "limited 2". The limited-1 group (13 samples, 10 unique patients) showed upregulation of genes involved in cell adhesion, cardiovascular system (CVS) development, extracellular matrix and immune and inflammatory response. The CVS development signature was of particular interest as its genes showed very strong enrichment in response to wounding, response to transforming growth factor (TGF)-ß and kinase cascade. Neither limited-2 samples (six samples, five unique patients) nor HC samples showed functional enrichment. There were no significant differences in demographic or clinical parameters between these two groups. These results were confirmed using a second independent cohort. CONCLUSIONS: Our study suggests the presence of molecular subsets in lcSSc based on gene expression profiling of biopsies from uninvolved skin. This may reflect important differences in pathogenesis within these patient groups. We identify differential expression of a subset of genes that relate to CVS and are enriched in fibrotic signalling. This may shed light on mechanisms of vascular disease in SSc. The enrichment in profibrotic profile suggests that dysregulated gene expression may contribute to vasculopathy and fibrosis in different disease subsets.

Systemic vasculopathy with altered vasoreactivity in a transgenic mouse model of scleroderma.

INTRODUCTION: Vasculopathy, including altered vasoreactivity and abnormal large vessel biomechanics, is a hallmark of systemic sclerosis (SSc). However, the pathogenic link with other aspects of the disease is less clear. To assess the potential role of transforming growth factor beta (TGF-beta) overactivity in driving these cardiovascular abnormalities, we studied a novel transgenic mouse model characterized by ligand-dependent activation of TGF-beta signaling in fibroblasts. METHODS: The transgenic mouse strain Tbeta RIIDeltak-fib is characterized by balanced ligand-dependent upregulation of TGF-beta signaling. Aortic and cardiac tissues were examined with histologic, biochemical, and isolated organ bath studies. Vascular and perivascular architecture was examined by hematoxylin and eosin (H&E) and special stains including immunostaining for TGF-beta1 and phospho-Smad2/3 (pSmad2/3). Confirmatory aortic smooth muscle cell proliferation, phenotype, and functional assays, including signaling responses to exogenous TGF-beta and endothelin-1, were performed. Aortic ring contractile responses to direct and receptor-mediated stimulation were assessed. RESULTS: Aortic ring contractility and relaxation were diminished compared with wild-type controls, and this was associated with aortic adventitial fibrosis confirmed histologically and with Sircol assay. TGF-beta1 and pSmad 2/3 expression was increased in the adventitia and smooth muscle layer of the aorta. Aortic smooth muscle cells from transgenic animals showed significant upregulation of TGF-beta- responsive genes important for cytoskeletal function, such as transgelin and smoothelin, which were then resistant to further stimulation with exogenous TGF-beta1. These cells promoted significantly more contraction of free floating type I collagen lattices when compared with the wild-type, but were again resistant to exogenous TGF-beta1 stimulation. Aortic ring responses to receptor-mediated contraction were reduced in the transgenic animals. Specifically, bosentan reduced endothelin-mediated contraction in wild-type animals, but had no effect in transgenic animals, and endothelin axis gene expression was altered in transgenic animals. Transgenic mice developed cardiac fibrosis. CONCLUSIONS: The histologic, biochemical, and functional phenotype of this transgenic mouse model of scleroderma offers insight into the altered biomechanical properties previously reported for large elastic arteries in human SSc and suggests a role for perturbed TGF-beta and endothelin activity in this process.