Pathophysiology Of Systemic Sclerosis Research Articles

Evaluating microangiopathy in systemic sclerosis: what have we learnt and what is left to discover?

Keywords:: digital ulcersendothelial cellsgiant capillariesmicroangiopathymicrocirculationnailfold capillaroscopyRaynaud’s phenomenonscleroderma patternsystemic sclerosis

Identification of new autoantibody specificities directed at proteins involved in the transforming growth factor β pathway in patients with systemic sclerosis

IntroductionAntinuclear antibodies (ANAs), usually detected by indirect immunofluorescence on HEp-2 cells, are identified in 90% of patients with systemic sclerosis (SSc). Thus, approximately 10% of SSc patients have no routinely detectable autoantibodies, and for 20% to 40% of those with detectable ANAs, the ANAs do not have identified specificity (unidentified ANAs). In this work, we aimed to identify new target autoantigens in SSc patients.MethodsUsing a proteomic approach combining two-dimensional electrophoresis and immunoblotting with HEp-2 cell total and enriched nuclear protein extracts as sources of autoantigens, we systematically analysed autoantibodies in SSc patients. Sera from 45 SSc patients were tested in 15 pools from groups of three patients with the same phenotype. A sera pool from 12 healthy individuals was used as a control. Proteins of interest were identified by mass spectrometry and analysed using Pathway Studio software.ResultsWe identified 974 and 832 protein spots in HEp-2 cell total and enriched nuclear protein extracts, respectively. Interestingly, α-enolase was recognised by immunoglobulin G (IgG) from all pools of patients in both extracts. Fourteen and four proteins were recognised by IgG from at least 75% of the 15 pools in total and enriched nuclear protein extracts, respectively, whereas 15 protein spots were specifically recognised by IgG from at least four of the ten pools from patients with unidentified ANAs. The IgG intensity for a number of antigens was higher in sera from patients than in sera from healthy controls. These antigens included triosephosphate isomerase, superoxide dismutase mitochondrial precursor, heterogeneous nuclear ribonucleoprotein L and lamin A/C. In addition, peroxiredoxin 2, cofilin 1 and calreticulin were specifically recognised by sera from phenotypic subsets of patients with unidentified ANAs. Interestingly, several identified target antigens were involved in the transforming growth factor β pathway.ConclusionsWe identified several new target antigens shared among patients with SSc or specific to a given phenotype. The specification of new autoantibodies could help in understanding the pathophysiology of SSc. Moreover, these autoantibodies could represent new diagnostic and/or prognostic markers for SSc.

The Pathogenesis of Systemic Sclerosis Revisited

Although infectiological stimuli, environmental factors and genotypic features are known to contribute to the initiation and perpetuation of systemic sclerosis (SSc), its etiology still remains to be enigmatic, and less elusive insights are to be achieved by ongoing and future investigations. Being characterized, however, as chronic autoimmune disease with excessive collagen accumulation in skin, synovia and visceral organs such as lung, heart, and digestive tract along with obliterating angiopathy, the pathophysiology of SSc can be summarized as being based on imbalances of the cellular and humoral immune system, vascular dysfunction and activation of resident connective tissue cells. A complex interplay between these major components manages to establish and maintain the inability of the vasculature to adequately react to the need for dilatation, constriction and growth of new vessels, to cause the increased deposition of extracellular matrix constituents as well as to facilitate immunological disarrangement. Despite parallels to the chicken and egg causality dilemma, all of these account for what later clinicians observe in patients suffering from Raynaud's phenomenon, digital ulcers, sclerodactyly, rigidity of the face, microstomia, sicca syndrome, dyspnea, dry cough, pulmonary hypertension, palpitations, syncopes, renal insufficiency, dysphagia, gastroesophageal reflux, dyspepsia, generalized arthralgias, but also dyspareunia, or erectile dysfunction.

Taurine: A Potential Novel Addition to the Anti-Systemic Sclerosis Weaponry

Vascular damage and immunological events leading to generation of fibrogenic fibroblasts are the main components of systemic sclerosis (SSc) pathogenesis. Superoxide anions play a role in endothelial damage by oxidizing circulating low-density lipoproteins. IL-1 plays a key role in the pathophysiology of SSc by inducing upregulation of adhesion molecules, inflammatory damage of the endothelium and tissue fibrosis. Elevated levels of proTh2 cytokines such as IL-6 in the early stages of SSc lead to enhanced fibroblast collagen production. Taurine, a semi-essential amino acid, is an antioxidant, inhibits the production of proinflammatory cytokines such as IL-1 and IL-6 and also inhibits production of TGF-beta, a major fibrogenic cytokine. Therefore, we conclude that taurine may be a novel addition to the treatment armamentarium of this disabling disorder.

Systemic Sclerosis at the Cellular Level: Molecular Pathways of Pathogenesis and its Implication on Future Drug Design

Endothelial cell abnormalities and the effects on the surrounding microvasculature is a focal point in the pathogenesis of Systemic Sclerosis disease and may even be the sentinel event for the initiation of this disorder. A better understanding of these processes may improve our understanding of the pathophysiology of Systemic Sclerosis and more specifically the vasculopathy observed. Such knowledge will help us to further current treatments options and design novel therapies for Systemic Sclerosis and other fibrotic disorders.

Association of hypoxia‐inducible factor 1A (HIF1A) gene polymorphisms with systemic sclerosis in a French European Caucasian population

Objective: Systemic sclerosis (SSc) is a connective tissue disease characterized by generalized microangiopathy leading to chronic hypoxia. The aim of this study was to determine whether polymorphisms of the hypoxia‐inducible factor 1A gene (HIF1A) affects susceptibility to SSc in a large French European Caucasian population.Methods: A case–control study was performed in 659 SSc patients and 511 healthy matched controls. Three tag single nucleotide polymorphisms (SNPs) of the HIF1A gene (rs12434438 A/G, rs1957757 C/T, and rs11549465 C/T) were genotyped allowing whole gene coverage according to HapMap data.Results: The frequency of genotypes carrying at least one G allele (A/G and/or GG) of the rs12434438 SNP was significantly higher in SSc patients than in controls [pcorr = 0.018, odds ratio (OR) 1.44, 95% confidence interval (CI) 1.08–1.91]. Regarding SSc subgroup analyses, the heterozygous genotype A/G was associated with SSc (pcorr = 0.012, OR 1.47, 95% CI 1.13–1.9), with the limited cutaneous form of SSc (pcorr = 0.04, OR 1.43, 95% CI 1.08–1.91), and with positive anti‐centromere antibodies (ACA; pcorr = 0.016, OR 1.61, 95% CI 1.16–2.23). No association was detected for the remaining two HIF1A SNPs tested. Haplotype analyses did not detect any association with SSc.Conclusions: We observed an association between the HIF1A gene and SSc in a European Caucasian population, supporting a role for HIF1 in the pathophysiology of SSc.

Autoantibody profile in the experimental model of scleroderma induced by type V human collagen

The aim of this study is to evaluate the humoral autoimmune response in the experimental model of systemic sclerosis (SSc) induced by human type V collagen (huCol V). New Zealand rabbits were immunized with huCol V in Freund's complete adjuvant (FCA) and boosted twice with 15 days intervals with huCol V in Freund's incomplete adjuvant. Control groups included animals injected only with FCA or bovine serum albumin. Bleeding was done at days 0, 30, 75 and 120. Tissue specimens were obtained for histopathological investigation. Serological analysis included detection of antibodies against huCol V and anti-topoisomerase I (Anti-Scl70) by enzyme-linked immunosorbent assay, antinuclear antibodies (ANA) by indirect immunofluorescence, and rheumatoid factor (RF) by a latex agglutination test. Target antigens were characterized by immunoblot. Histological analysis revealed extracellular matrix remodeling with fibrosis and vasculitis. Anti-Scl70 and ANA were detected as early as 30 days in all huCol V animals. The universal ANA staining pattern was Golgi-like. This serum reactivity was not abolished by previous absorption with huCol V. Characterization of the target antigen by immunoblot revealed two major protein fractions of 175,000 and 220,000 MW. Similarly to ANA, there was a gradual increase of reactivity throughout the immunization and also it was not abolished by preincubation of serum samples with huCol V. RF testing was negative in hyperimmune sera. The production of autoantibodies, including anti-Scl70, a serological marker for SSc associated with histopathological alterations, validates huCol V induced-experimental model and brings out its potential for understanding the pathophysiology of SSc.

Systemic sclerosis and related connective tissue diseases: present and future

In April 2006, 30 international experts gathered in Athens, Greece, to discuss systemic sclerosis (SSc) and related connective tissue diseases (CTDs). SSc is a clinically heterogeneous and complex disease that is characterized by vascular dysfunction, vascular and extravascular fibrosis, and characteristic immune derangements, and for which few treatment options are available. The aims of the CTD International Scientific Advisory Board were threefold: to define the role of local mediators in CTDs, in particular to identify the nature of the initial insult in CTDs and to consider the role of genetic perturbations in CTDs; to translate what has been learned from clinical trials into clinical practice and to evaluate current treatment options for CTDs and their complications; and to address future directions for the management of CTDs and associated rare diseases, based on the biologic mechanisms elucidated. This supplement provides a comprehensive review of the 2-day meeting in order to share important insights, opinions, and clinical approaches to management of CTDs. The first paper in this supplement, that by Abraham and Distler [1], reviews the potential role of endothelin (ET)-1 and the crosstalk and interplay between the various inflammatory mediators that lead to the vascular changes characteristic of the pathophysiology of SSc and other CTDs. The authors present the available evidence suggesting that ET-1 may play a key role at the early stages of CTDs by activating fibroblasts and pericytes. As yet, the event triggering endothelial cell injury is unknown.

Sclérodermie systémique: épidémiologie et facteurs environnementaux

The pathophysiology of systemic sclerosis (SSc), probably multifactorial, is not yet well elucidated. Among the many endogenous and exogenous factors probably involved, environmental and occupational elements may play an essential role. SSc is a rare disease. Prevalence is estimated between 3 and 24 per 100,000 population. Reports of sporadic clusters of higher prevalence suggest environmental factors, which have not yet been defined. Silica, first suggested in 1917, plays a role in SSc development, as officially recognized in France for purposes of workers' compensation. Solvents have been associated with SSc by several rigorous case-control studies that suggest a causal role. Current data about other toxic agents (epoxy resins, vibrations, welding fumes) do not justify conclusions about their role in SSc. The severity of SSc (determined by the extent of diffuse cutaneous lesions, pulmonary involvement, and immunological profile) is probably associated with occupational exposure.

Bosentan for the treatment of systemic sclerosis-associated pulmonary arterial hypertension, pulmonary fibrosis and digital ulcers

Systemic sclerosis (SSc) is a devastating multisytemic autoimmune disease associated with widespread vascular damage. Pulmonary arterial hypertension (PAH) occurs in a significant proportion of patients and contributes to the morbidity and mortality that occurs in this disease. The recent development of specific therapies for the treatment of PAH mandates the early recognition, appropriate evaluation and judicious management of PAH in patients with SSc. Because endothelin (ET)-1 plays an important role in the development of PAH in SSc, and may also contribute to the vascular damage and fibrosis that occur in multiple organs in patients with the disease, inhibiting the production and activity of ET-1 is an appealing strategy for the treatment of SSc. This article reviews the pathophysiology of SSc and its vascular complications, and critically evaluates the current knowledge regarding the potential role of the ET-1 receptor blocker bosentan in the management of patients with SSc.

Novel Fibrogenic Pathways Are Activated in Response to Endothelial Apoptosis: Implications in the Pathophysiology of Systemic Sclerosis

Apoptosis of endothelial cells (EC) is appreciated as a primary pathogenic event in systemic sclerosis. Yet, how apoptosis of EC leads to fibrosis remains to be determined. We report that apoptosis of EC triggers the release of novel fibrogenic mediators. Medium conditioned by apoptotic EC (SSC) was found to inhibit apoptosis of fibroblasts, whereas medium conditioned by EC in which apoptosis was blocked (with either pan-caspase inhibition or Bcl-x(L) overexpression) did not. PI3K was activated in fibroblasts exposed to SSC. This was associated with downstream repression of Bim-EL and long-term up-regulation of Bcl-x(L) protein levels. RNA interference for Bim-EL in fibroblasts blocked apoptosis. SSC also induced PI3K-dependent myofibroblast differentiation with expression of alpha-smooth muscle actin, formation of stress fibers, and production of collagen I. A C-terminal fragment of the domain V of perlecan was identified as one of the fibrogenic mediators present in SSC. A synthetic peptide containing an EGF motif present on the perlecan fragment and chondroitin 4-sulfate, a glycosaminoglycan anchored on the domain V of perlecan, induced PI3K-dependent resistance to apoptosis in fibroblasts and myofibroblast differentiation. Human fibroblasts derived from sclerodermic skin lesions were more sensitive to the antiapoptotic activities of the synthetic peptide and chondroitin 4-sulfate than fibroblasts derived from normal controls. Hence, we propose that a chronic increase in endothelial apoptosis and/or increased sensitivity of fibroblasts to mediators produced by apoptotic EC could form the basis of a fibrotic response characterized by sustained induction of an antiapoptotic phenotype in fibroblasts and persistent myofibroblast differentiation.

Pathophysiology of systemic sclerosis

Pathophysiology of systemic sclerosis

Increased gelatinase activity in systemic sclerosis dermal fibroblast cultures with unaltered gelatinase A mRNA expression

Gelatinase A is one of the matrix metalloproteinases, the principle enzymes degrading extracellular matrix (ECM) and basement membrane components. The aim of this study was to study gelatinase expression in systemic sclerosis (SSc). Fibroblasts were grown from uninvolved and involved skin of SSc patients and from healthy controls. Gelatinase activity was assayed by degradation of tritium-labeled gelatin. Gelatinase A mRNA was quantitated by competitive reverse transcriptase-polymerase chain reaction (RT-PCR). Gelatinase activity was significantly increased in both uninvolved and involved SSc cultures. However, gelatinase A mRNA was unaltered in both cases. Neither SSc nor control skin fibroblasts expressed gelatinase B, indicating that the increased gelatinase activity is not due to gelatinase B induction. Gelatinase A is a specific basement membrane degrading enzyme, so increased gelatinase activity may be related to the pathophysiology of SSc by initiating microvascular damage and leakage of substances capable of producing further endothelial cell damage or fibroblast activation. Increased gelatinase activity in SSc fibroblasts seems to be regulated at translational and/or post-translational level.

Corrélations entre expression endothéliale salivaire de la E-sélectine et paramètres cliniques et biologiques au cours de la sclérodermie systémique

A body of evidence suggests the pivotal role of endothelial cells in the pathophysiology of systemic sclerosis. E-selectin is an adhesion molecule specifically expressed by activated endothelial cells. In previous studies we noticed that E-selectin was frequently expressed in the salivary gland tissue of patients with systemic sclerosis. Moreover, E-selectin expression was detectable very early in the course of the disease. To better define the role of E-selectin in the pathogenesis of systemic sclerosis, we conducted a study aimed at determining whether E-selectin expression was correlated to clinical and biological features in patients with systemic sclerosis. Thirty-one patients presenting with systemic sclerosis were included in the study. The following parameters were systematically assessed: duration and cutaneous extent of the disease, presence of secondary Sjögren's syndrome, antinuclear antibodies, and pulmonary and esophagus involvement. E-selectin expression was assessed by immunocytochemistry on minor labial salivary glands. E-selectin expression was detected in 21 out of 31 patients (67%). The disease duration was significantly shorter in patients with E-selectin expression (mean 9.1 +/- 8.5 years versus 4.2 +/- 3.3 years, P < 0.05). No significant difference was found for other features. This study shows that endothelial E-selectin expression is mainly detectable early in the course of systemic sclerosis, when active and non-cicatrical sclerosis may be evidenced. No correlation was found between E-selectin expression and immunological disorders (antinuclear antibodies, secondary Sjögren's syndrome).

Anti-interleukin-6 autoantibodies in rheumatic diseases. Increased frequency in the sera of patients with systemic sclerosis.

To investigate the presence and the roles of anti-interleukin-6 (anti-IL-6) autoantibodies in rheumatic diseases, and to further elucidate clinical and pathophysiologic significance of anticytokine autoantibodies. Anti-IL-6 IgG autoantibodies were measured by the 125I-IL-6 binding activity of IgG, which was isolated from serum by protein A-Sepharose. Nine of 52 sera (17.3%) from patients with systemic sclerosis (SSc) contained anti-IL-6 antibodies, whereas only 1.9% of sera from normal subjects and 0-5% of sera from patients with other rheumatic diseases were positive for the antibodies. Moreover, anti-IL-6 autoantibodies were found predominantly among patients with the limited form of SSc (42.9%), compared with those with the diffuse form (7.9%). Anti-IL-6 IgG autoantibodies were detected in patients with SSc, particularly those with the limited form of the disease, at a significantly increased frequency compared with normal subjects and patients with other rheumatic diseases. These results suggest that the development of anti-IL-6 autoantibodies and IL-6 may have a role in the pathophysiology of SSc.

Steady-State mRNA Levels of Collagens I, III, Fibronectin, and Collagenase in Skin Biopsies of Systemic Sclerosis Patients

Total RNA was extracted from skin biopsies of nine patients suffering from systemic sclerosis (SSc). Steady-state mRNA levels of collagen alpha 1(I) and alpha 1(III), collagenase, fibronectin, and beta-actin were studied using specific cDNA probes and compared to those of 12 sex- and age-matched healthy individuals. There was a more than three-fold elevation of collagen I mRNA levels in SSc skin compared to controls. No difference was found, however, for collagen III, collagenase, and fibronectin mRNA levels in SSc and control biopsies. The selective increase of collagen alpha 1(I) mRNA levels indicates a specific alteration of fibroblast metabolism in scleroderma. Analysis of mRNA levels in skin biopsies might not only offer a direct approach to the understanding of the pathophysiology of SSc, but also facilitate the monitoring of fibrotic activity in SSc patients during therapeutic trials.