The genetics of systemic sclerosis

Current perspectives on the immunopathogenesis of systemic sclerosis

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

Human adipose-derived stromal cells for cell-based therapies in the treatment of systemic sclerosis

The present study was designed to evaluate the clinical outcome of cell-based therapy with cultured adipose derived stromal cells (ASCs) for the treatment of cutaneous manifestations in patients affected by systemic sclerosis (SSc). ASCs have an extraordinary developmental plasticity, including the ability to undergo multilineage differentiation and self-renewal. Moreover, ASCs can be easily harvested from small volumes of liposuction aspirate, showing great in vitro viability and proliferation rate. Here we isolated, characterized, and expanded ASCs, assessing both their mesenchymal origin and their capability to differentiate towards the adipogenic, osteogenic, and chondrogenic lineage. We developed an effective method for ASCs transplantation into sclerodermic patients by means of a hyaluronic acid (HA) solution, which allowed us to achieve precise structural modifications. ASCs were isolated from subcutaneous adipose tissue of six sclerodermic patients and cultured in a chemical-defined medium before autologous transplantation to restore skin sequelae. The results indicated that transplantation of a combination of ASCs in HA solution determined a significant improvement in tightening of the skin without complications such as anechoic areas, fat necrosis, or infections, thus suggesting that ASCs are a potentially valuable source of cells for skin therapy in rare diseases such as SSc and generally in skin disorders.

Interleukin-13-producing CD8+ T cells mediate dermal fibrosis in patients with systemic sclerosis

OBJECTIVE

Fibrosis is a major contributor to morbidity and mortality in systemic sclerosis (SSc). T cells are the predominant inflammatory infiltrate in affected tissue and are thought to produce cytokines that drive the synthesis of extracellular matrix (ECM) proteins by fibroblasts, resulting in excessive fibrosis. We have previously shown that aberrant interleukin-13 (IL-13) production by peripheral blood effector CD8+ T cells from SSc patients correlates with the extent of skin fibrosis. The present study was undertaken to investigate the role of IL-13 production by CD8+ T cells in dermal fibrosis, an early and specific manifestation of SSc.

METHODS

ECM protein production by normal dermal fibroblasts cocultured with SSc CD8+ T cell supernatants was determined by quantitative polymerase chain reaction and Western blotting. Skin-homing receptor expression and IL-13 production by CD8+ T cells in the peripheral blood of SSc patients were measured by flow cytometry. IL-13+ and CD8+ cells in sclerotic skin were identified by immunohistochemistry.

RESULTS

IL-13-producing circulating CD8+ T cells from patients with SSc expressed skin-homing receptors and induced a profibrotic phenotype in normal dermal fibroblasts, which was inhibited by an anti-IL-13 antibody. High numbers of CD8+ T cells and IL-13+ cells were found in the skin lesions of SSc patients, particularly during the early inflammatory phase of the disease.

CONCLUSION

These findings show that IL-13-producing CD8+ T cells are directly involved in modulating dermal fibrosis in SSc. The demonstration that CD8+ T cells homing to the skin early in the course of SSc are associated with accumulation of IL-13 is an important mechanistic contribution to the understanding of the pathogenesis of dermal fibrosis in SSc and may represent a potential target for therapeutic intervention.

CD8+ T cells in systemic sclerosis

Systemic sclerosis (SSc) is a progressive and highly debilitating autoimmune disorder characterized by inflammation, fibrosis, and vascular damage of the connective tissue. T cell-derived cytokines have been implicated in the induction of fibrosis. We found that high levels of the profibrotic type-2 cytokine IL-13 are produced by peripheral blood effector CD8(+) T cells from SSc patients compared to normal controls. This abnormality correlates with increased expression of the transcription factor GATA-3 and the extent of skin fibrosis. Together, the data provide new insights into SSc pathogenesis and identify a specific T cell phenotype that can be used as a biomarker of immune dysfunction in patients with SSc and as a novel therapeutic target for this currently incurable disease.

Role of IL-13 in systemic sclerosis

Systemic sclerosis (SSc) has the highest fatality rate among connective tissue diseases and is characterized by vascular damage, inflammation and fibrosis. Currently, no therapy has proven effective in modifying the course of SSc, a reflection of its complex pathogenesis. T cell-derived cytokines have been implicated in the induction of fibrosis. The role of the pro-fibrotic type 2 cytokine IL-13 and its regulation appear to be important in the pathogenesis of SSc and other fibrotic disorders. Recent work has shown that dysregulated production of IL-13 by effector CD8+ T cells is critical for predisposing patients to more severe forms of cutaneous disease and that this dysregulation is associated with defects in the molecular control of IL-13 production, such as increased expression of the transcription factor GATA-3. Silencing of GATA-3 with siRNA significantly reduces IL-13 production by CD8+ T cells from patients. We review these new insights into SSc pathogenesis that will enable establishment of highly relevant biomarkers of immune dysfunction in patients predisposed to develop SSc and open new possibilities for development of more specific diagnosis and treatment.

Targeting TNF for Treatment of Cancer and Autoimmunity

Tumor necrosis factor-alpha (TNF-alpha) was first isolated two decades ago as a macrophageproduced protein that can effectively kill tumor cells. TNF-alpha is also an essential component of the immune system and is required for hematopoiesis, for protection from bacterial infection and for immune cell-mediated cytotoxicity. Extensive research, however, has revealed that TNF-alpha is one of the major players in tumor initiation, proliferation, invasion, angiogenesis and metastasis. The proinflammatory activities link TNF-alpha with a wide variety of autoimmune diseases, including psoriasis, inflammatory bowel disease, rheumatoid arthritis, systemic sclerosis, systemic lupus erythematosus, multiple sclerosis, diabetes and ankylosing spondylitis. Systemic inhibitors of TNF such as etanercept (Enbrel) (a soluble TNF receptor) and infliximab (Remicade) and adalimumab (Humira) (anti-TNF antibodies) have been approved for the treatment inflammatory bowel disease, psoriasis and rheumatoid arthritis. These drugs, however, exhibit severe side effects and are expensive. Hence orally active blockers of TNF-alpha that are safe, efficacious and inexpensive are urgently needed. Numerous products from fruits, vegetable and traditional medicinal plants have been described which can suppress TNF expression and TNF signaling but their clinical potential is yet uncertain.

Effector CD8+ T cells in systemic sclerosis patients produce abnormally high levels of interleukin-13 associated with increased skin fibrosis

OBJECTIVE

T lymphocytes play an important role in systemic sclerosis (SSc), a connective tissue disease characterized by inflammation, fibrosis, and vascular damage. While their precise role and antigen specificity are unclear, T cell-derived cytokines likely contribute to the induction of fibrosis. The aim of this study was to establish the role of cytokine dysregulation by T cells in the pathogenesis of SSc.

METHODS

To identify relationships between a specific cytokine, T cell subset, and the disease course, we studied a large cohort of patients with diffuse cutaneous SSc (dcSSc) or limited cutaneous SSc (lcSSc). Using Luminex analysis and intracellular cytokine staining, we analyzed the intrinsic ability of CD4+ and CD8+ T cell subsets to produce cytokines following in vitro activation.

RESULTS

High levels of the profibrotic type 2 cytokine interleukin-13 (IL-13) were produced following activation of peripheral blood effector CD8+ T cells from SSc patients as compared with normal controls or with patients with rheumatoid arthritis. In contrast, CD4+ T cells showed a lower and more variable level of IL-13 production. This abnormality correlated with the extent of fibrosis and was more pronounced in dcSSc patients than in lcSSc patients.

CONCLUSION

Dysregulated IL-13 production by effector CD8+ T cells is important in the pathogenesis of SSc and is critical in the predisposition to more severe forms of cutaneous disease. Our study is the first to identify a specific T cell phenotype that correlates with disease severity in SSc and can be used as a marker of immune dysfunction in SSc and as a novel therapeutic target.

Genetic susceptibility to systemic sclerosis from clinical aspect to genetic factor analyses

BACKGROUND

Systemic sclerosis is a rare autoimmune disease mainly characterized by vascular alteration and fibrosis involving skin but also visceral organs such as lungs, digestive tract, and heart. This disease leads to high morbidity and mortality. Its pathogenesis remains unclear, but recent attention has focus on genetic factors.

OBJECTIVE

We first recall the main manifestations associated with systemic sclerosis and leading to its diagnosis and prognosis. Then we propose an overview on human genetics studies, as a number of genetic loci have been identified that appear to be associated with the disease.

METHODS

Articles concerning association studies with candidate genes encoding for extracellular matrix proteins, cytokines, growth factors, chemokines, and proteins involved in vascular tone and immune regulations are presented and discussed.

RESULTS/CONCLUSION

Systemic sclerosis is a multigenic complex disorder. Genetic associations are observed in distinct phenotypes such as the diffuse cutaneous form or the limited form, or in association with specific autoantibody pattern. Promising candidate genes are those involved in pathways that lead to the vascular damage and fibrosis. A better knowledge of crucial mediators involved in systemic sclerosis could in the future provide new therapeutic strategies to control the disease.

[Pathogenesis of systemic sclerosis]

Systemic sclerosis is a complex multi-systemic disease with a mostly unresolved pathogenesis. Following an inflammatory reaction, overproduction of collagen and other extra-cellular matrix components leads to a characteristic fibrosis. It remains unclear why this overproduction by fibroblasts and myofibroblasts occurs. Micro-vascular disturbances and endothelial cells, as well as immunomodulation and inflammation are central factors. Besides intrinsic influences, such as genetic polymorphisms, multiple mediators with fibrotic effects such as Platelet Derived Growth Factor, Transforming Growth Factor-beta and Connective Tissue Growth Factor have been characterized. These have become targets for innovative therapeutic strategies that might lead to specific treatments for systemic sclerosis.

Statins as Immunomodulators in Systemic Sclerosis

Systemic sclerosis (SSc) has the highest case-specific mortality among the rheumatic diseases. Vascular dysfunction and structural wall abnormalities are among the earliest and fundamental alterations in SSc. Statins have a number of immunomodulating effects on vascular wall cells, which may modify the progression of vascular injury. The aim of this study was to evaluate the potential efficacy of statin therapy in ameliorating endothelial dysfunction (ED) in SSc by investigating the effect of statins on some markers that reflect endothelial activation in SSc. Forty patients with SSc were randomized into two groups to receive 6 months' treatment with atorvastatin (n = 20; dose, 40 mg/day) or placebo (n = 20) as an adjuvant to existing therapy. Markers of ED including ET-1, plasma nitrate levels, and thrombomodulin (TM) were evaluated by the enzyme-linked immunosorbent assay (ELISA) technique. Fibrinogen, high-sensitivity C-reactive protein (hsCRP), ESR, lipid peroxide (LP), and malonylaldehyde (MDA) levels were also assessed. Brachial flow-mediated vasodilatation was assessed by ultrasonography. Patients were studied at base line and after 6 months of statin therapy. After 6 months of therapy, ET-1, ICAM-1, sE-selectin, vWF, fibrinogen, ESR, hsCRP as well as LP and MDA levels declined and NO increased significantly in the statin-treated SSc group when compared to the placebo-treated group. Endothelium-dependent vasodilatation (EDV) improved significantly in the atorvastatin-treated group. The findings of this study demonstrated statin-mediated improvements in the endothelial function of SSc patients as well as immunomodulating effects. Statins may thus prove to be an invaluable addition to the therapy of the vasculopathy of SSc.

Incidence and prevalence of systemic sclerosis: a systematic literature review

OBJECTIVES

To determine the incidence and prevalence of systemic sclerosis (SSc) in adults, its epidemiological tendencies over time, and its possible key determinants.

METHODS

We performed a systematic literature review using the keywords "systemic sclerosis," "incidence," "prevalence," and "epidemiology."

RESULTS

We found 32 articles published from 1969 to 2006 in which the prevalence of SSc ranged from 7/million to 489/million and its incidence from 0.6/million/y to 122/million/y. There were many geographical variations: SSc prevalence was higher in the USA (276/million in 1990) and Australia (233/million in 1999) than in Japan and Europe, where a north-south gradient was also observed (France: 158/million in 2001 and England: 88/million in 2000). In some regions (Ontario, Rome, near London's airports) there was an unusually high number of SSc cases (3, 5, or 1000 times greater than expected), suggesting spatiotemporal clustering, although no key determinants could be identified. Furthermore, there seemed to be a trend toward an increase in the incidence of SSc over time, but this tendency is uncertain due to lack of uniformity in study methods and designs. We also found that susceptibility to the disease differed according to sex, age, and race.

CONCLUSION

Uniform clinico-epidemiological studies with standard diagnostic and classification criteria are needed to refine the epidemiological features of SSc. Homogeneous study methods with exhaustive case ascertainment as seen in a "capture-recapture" analysis will also be necessary to obtain reliable data.

Association of -318 C/T and +49 A/G cytotoxic T lymphocyte antigen-4 (CTLA-4) gene polymorphisms with a clinical subset of Italian patients with systemic sclerosis

Systemic sclerosis (SSc) is a complex and heterogeneous autoimmune disorder with a multi-factorial pathogenesis. Like other autoimmune disorders, the possible role of specific cytotoxic T lymphocyte antigen-4 (CTLA-4) gene polymorphisms in predisposing to SSc has been hypothesized, but it remains controversial. CTLA-4 promoter (-318C/T) and exon 1 (+49 A/G) polymorphisms have been analysed in 43 Italian females with SSc and in 93 unrelated matched healthy controls by a newly designed tetra-primer amplification refractory mutation system-polymerase chain reaction (T-ARMS-PCR) method. No significant association has been found with either polymorphisms.Nevertheless, SSc patients without concomitant Hashimoto's thyroiditis (HT) were carrying both the -318T allele (P = 0.031) and the +49 G allele (P = 0.076) more frequently than SSc patients with HT [defined by positivity for anti-thyroperoxidase (TPO) and anti-thyroglobulin (TGA) autoantibodies] than controls. Haplotype analysis confirms this association (P = 0.028), and suggests the predominant role of the -318T, whereas that of the +49 G, if any, seems weak. Thus, in Italian SSc patients the CTLA-4 -318C/T promoter polymorphism appears to be associated with the susceptibility to develop SSc without thyroid involvement. Larger studies are needed to confirm these findings and to clarify whether the -318C/T polymorphism is the functional responsible or whether it reflects the presence of another linked genetic element in the same chromosomal region.

Systemic sclerosis in childhood: clinical and immunologic features of 153 patients in an international database

OBJECTIVE

To determine the clinical and immunologic features of systemic sclerosis (SSc) in a large group of children and describe the clinical evolution of the disease and compare it with the adult form.

METHODS

Data on 153 patients with juvenile SSc collected from 55 pediatric rheumatology centers in Europe, Asia, and South and North America were analyzed. Demographic, clinical, and immunologic characteristics of children with juvenile SSc at the onset, at diagnosis, and during the disease course were evaluated.

RESULTS

Raynaud's phenomenon was the most frequent symptom, followed by skin induration in approximately 75% of patients. Musculoskeletal symptoms were present in one-third of patients, and the most frequently involved internal organs were respiratory and gastrointestinal, while involvement of renal, cerebral, and cardiovascular systems was extremely rare. Antinuclear antibodies were present in the sera of 81% of patients. Anti-topoisomerase I (Scl-70) and anticentromere antibodies were found to be positive in 34% and 7.1% of patients, respectively. Involvement of the respiratory, gastrointestinal, and cardiovascular systems was more frequent and occurred earlier in patients who died than in those who survived. Compared with the adult form, juvenile SSc appears to be less severe, with the involvement of fewer internal organs, particularly at the time of diagnosis, and has a less characterized immunologic profile.

CONCLUSION

This study provides information on the largest collection of patients with juvenile SSc ever reported. Juvenile SSc appears to be less severe than in adults because children have less internal organ involvement, a less specific autoantibody profile, and a better long-term outcome.

Analysis of TIMP-1 gene polymorphisms in Italian sclerodermic patients

Systemic sclerosis (SSc) is an autoimmune disease characterized by skin and internal organs fibrosis due to an extracellular matrix (ECM) accumulation of type I collagen. The turnover of the ECM is dependent on the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs). The disruption of this balance is involved in SSc because higher serum TIMP-1 levels have been demonstrated in SSc patients than in controls. On this basis, we analyzed three polymorphisms: -19A>G, +261C>T, and +372T>C of the TIMP-1 gene in SSc patients (67 females, eight males) and controls (29 females, nine males). The C allele of the +372T>C single nucleotide polymorphism (SNP) was observed at a higher frequency in male patients than in healthy individuals (P=0.02), while no differences were observed in the female subjects. Our findings suggest that the +372T>C polymorphism of the TIMP-1 gene is associated with SSc in male individuals. No association with the clinical characteristics of SSc Italian patients and TIMP-1 gene polymorphisms was observed. Thus, the role of TIMP-1 gene in predisposition to SSc remains controversial.

Trichostatin A prevents the accumulation of extracellular matrix in a mouse model of bleomycin-induced skin fibrosis

OBJECTIVE

Tissue fibrosis is a hallmark compromising feature of many disorders. In this study, we investigated the antifibrogenic effects of the histone deacetylase inhibitor trichostatin A (TSA) on cytokine-driven fibrotic responses in vitro and in vivo.

METHODS

Skin fibroblasts from patients with systemic sclerosis (SSc) and normal healthy control subjects were stimulated with profibrotic cytokines in combination with TSA. Human Colalpha1(I) and fibronectin were measured using real-time polymerase chain reaction, and levels of soluble collagen were estimated using the SirCol collagen assay. Electromobility shift assay and confocal fluorescence microscopy were used to investigate the intracellular distribution of Smad transcription factors. For in vivo analysis, skin fibrosis was quantified by histologic assessment of mouse skin tissue in a model of bleomycin-induced fibrosis.

RESULTS

Reductions in the cytokine-induced transcription of Colalpha1(I) and fibronectin were observed in both normal and SSc skin fibroblasts following the addition of TSA. Similarly, the expression of total collagen protein in TSA-stimulated SSc skin fibroblasts was reduced to basal levels. The mechanism of action of TSA included inhibition of the nuclear translocation and DNA binding of profibrotic Smad transcription factors. Western blot analysis revealed an up-regulation of the cell cycle inhibitor p21 by TSA, leading to reduced proliferation of fibroblasts. In addition, in bleomycin-induced fibrosis in mice, TSA prevented dermal accumulation of extracellular matrix in vivo.

CONCLUSION

These findings provide novel insights into the epigenetic regulation of fibrosis. TSA and similar inhibitory compounds appear to represent early therapeutic strategies for achieving reversal of the cytokine-driven induction of matrix synthesis that leads to fibrosis.

Update on pathophysiology of scleroderma with special reference to immunoinflammatory events

Scleroderma or systemic sclerosis (SSc) is a complex disease in which the vasculopathy and the activation of the immune system with production of inflammatory mediators lead to dysregulated fibroblast activation. The resulting excessive deposition of collagens and other extracellular matrix proteins ends in fibrosis and organ dysfunction. The cause is unknown, but environmental factors are thought to play a role by triggering abnormal responses in genetically susceptible hosts. The recent past has witnessed important advances in the definition of mechanisms that underlie the persistent activation in fibroblasts of genes involved in uncontrolled fibrosis, a hallmark of SSc. These include the preferential production of type 2 T cell cytokines in target organs, the presence of autoantibodies with fibroblast-activating capacities, the production of vasoconstrictive mediators that impact on fibroblast biosynthetic properties, the transforming growth factor-beta-related metabolic signature, and the presence of altered signaling pathways in fibroblasts. Furthermore, while no animal models recapitulate all the features of SSc, they have been instrumental for assessing the relevance of specific processes to the development of fibrosis. More importantly, some of the research findings are leading to therapies that target altered processes with the potential of changing the prognosis of some dismal aspects of the disease.

Evaluation of interleukin 13 polymorphisms in systemic sclerosis

Systemic sclerosis (SSc) is a multisystem disease of unknown etiology. It is characterized by excessive cutaneous and visceral fibrosis, damage to small blood vessels, and production of autoantibodies. Interleukin-13 (IL-13) has been shown to be involved in abnormal fibrosis in other diseases. Therefore, we have evaluated its possible involvement in SSc. We analyzed four IL13 gene polymorphisms, rs1800925 (IL13-1055), rs20541 (Arg130Gln), rs847, and rs2243204 in 107 unrelated SSc patients (40 patients having diffuse cutaneous form and 67 patients having limited cutaneous form) and in 170 controls. All subjects were Caucasians. In the total patient population and in the diffuse cutaneous subset, we observed an association between two IL13 polymorphisms, IL13 rs1800925 (IL13-1055), and IL13 rs2243204, and disease (p=0.03-0.04). The IL13 rs2243204T allele was more common in SSc patients (p=0.01, OR=2.3 CI 1.21-4.38) and in the diffuse cutaneous form (p=0.01, OR=2.95, CI 1.35-6.49) than in control subjects. Our result supports the suggestion that polymorphisms in IL13 are associated to SSc and skin fibrosis process. However, further studies on larger and independent population and functional analyses are needed to confirm these findings.

Sklerodermie-assoziierte Autoantikörper – klinische und diagnostische Relevanz

In systemic sclerosis (SSc) and its variants, autoantibodies are the best known immunological aberration. In more than 95% of the patients, antinuclear antibodies or other autoantibodies can be detected. In about 90% of SSc patients with antinuclear antibodies, scleroderma associated autoantibodies highly specific for systemic sclerosis are found. These autoantibodies usually exclude each other in individual patients, and they are detectable early, persisting during the course of the disease. SSc patients characterized by scleroderma associated autoantibodies belong to disease subsets which are relatively homogeneous in clinical, genetic and prognostic terms. Besides these diagnostically relevant autoantibodies, numerous additional ones have also been described. These are neither SSc specific nor mutually exclusive, and their antigens have only been partially characterized. Some, however, are thought to be relevant to the as yet unanswered question of whether autoantibodies are directly involved in SSc pathogenesis.

Scleroderma: from cell and molecular mechanisms to disease models

Scleroderma [also known as systemic sclerosis (SSc)] is a complex autoimmune disease characterised by pathological remodelling of connective tissues. Although the earliest and most frequent manifestations include blood vessel and immunological abnormalities, the systemic and progressive pathology suggests that fundamental interactions between microvascular damage and inflammation are mechanistically linked to obliterative tissue fibrosis. This review will focus on how model systems have provided clues to these relationships and will discuss new data from the study of novel animal disease models. These reveal how vascular damage and leukocyte accumulation generate the molecular cues that control the profiles of soluble mediators, which regulate the aberrant behaviour of mesenchymal cells within connective tissues, and how the dysregulated expression of these components and their differentiation contribute to the persistent fibrogenic response.

Autoantibodies in systemic sclerosis

OBJECTIVES

To describe the clinical, laboratory, and prognostic features associated with the scleroderma-specific autoantibodies.

METHODS

Using the Pittsburgh Scleroderma Databank, all consecutive patients seen between 1980 and 1995 who had autoantibody studies performed were studied. Anticentromere antibodies (ACA), antitopoisomerase (TOPO), anti-U1-RNP (U1-RNP), anti-RNA Polymerase III (Pol 3), anti-U3-RNP (U3-RNP), anti-Th/To (Th/To), and anti-Pm/Scl (Pm/Scl) were determined according to previously described methods. The frequency of clinical features, organ system outcomes, and survival within the patients with a specific antibody were cumulative over the course of the disease. The frequency of a specific feature was compared across groups to identify significant manifestations and outcomes in patients with a specific antibody.

RESULTS

Some demographic, clinical, and organ system findings were associated with the specific antibody, and other features with the scleroderma subtype (limited cutaneous or diffuse cutaneous scleroderma). U3-RNP, U1-RNP, and TOPO were seen more commonly in African-American patients, and ACA was seen in older, female Caucasians. Muscle inflammation was seen in patients with U1-RNP and U3-RNP. Digital tip ulcers and digital tuft resorption were seen more frequently in those with ACA and TOPO. A vasculopathy causing pulmonary hypertension typically occurs with ACA and pulmonary fibrosis with TOPO; however, both types of lung disease were seen in patients with nucleolar antibodies, Th/To and U3-RNP. Importantly, severe interstitial fibrosis was rarely seen in cases with Pol 3. Renal crisis was strongly associated with Pol 3. Survival within limited scleroderma was decreased in the Th/To patients compared with ACA patients. Within the diffuse scleroderma group, patients with Pol 3 had the best survival.

CONCLUSIONS

Scleroderma autoantibodies are associated with very specific demographic, clinical, organ system, and survival features.

RELEVANCE

The determination of scleroderma autoantibodies may be helpful in assessing the prognosis, monitoring, and treatment of scleroderma patients.

Alpha4beta1 and alpha4beta7 CD4 T cell numbers increase and CLA CD4 T cell numbers decrease in systemic sclerosis

We studied the expression of adhesion molecules affecting recirculation and homing on peripheral blood CD4(+) T cells of patients with systemic sclerosis (SSc), in order to evaluate whether the distribution of tissue targeted subsets could reflect the participation of internal organs or the extent of cutaneous involvement [i.e. limited cutaneous (lc) and diffuse cutaneous (dc)]. Peripheral blood mononuclear cells (PBMC) from 51 patients with SSc and 19 sex- and age-matched controls were investigated by cytofluorimetric analysis for lymphocyte subpopulations carrying the following surface molecules: CD3, CD4, CLA, alpha4beta7 and alpha4beta1. Standard routine biochemistry and clinical examinations were also performed in all patients. We found that both alpha4beta1(+) and alpha4beta7(+) cells within the CD4(+) T cell population were significantly increased, while CLA(+) CD4(+) T cells were significantly reduced in SSc, compared to healthy donors. Significantly lower absolute numbers of alpha4beta7(+) cells were found in lc- compared to dc-SSc. Patients with oesophageal involvement had high numbers of alpha4beta7(+) cells, while those with nephritis also showed low levels of CLA(+) cells. Lung involvement was related directly to alpha4beta1(+) cell numbers and inversely to alpha4beta7(+) CD4 cell numbers. Taken together, our findings demonstrate that distinct CD4(+) T cell populations with selective homing properties show changes from normal distribution in SSc, and such changes are related to clinical expression and organ involvement in the course of the disease.

Facteurs de prédisposition génétiques à la fibrose au cours de la sclérodermie systémique

PURPOSE

Physiopathology of systemic sclerosis includes autoimmunity factors, endothelial lesions and abnormal fibrotic process which characterizes this disease in the field of systemic autoimmune disorders. Genetic factors of susceptibility are showed by possibility of familial forms of the disease, Choctaw American Indians homogenous population with high disease prevalence of systemic sclerosis and experimental animal models.

KEY POINTS

We propose a review of the articles published to date in the literature concerning genetical analysis of genes coding for factors potentially involved in the fibrotic process of systemic sclerosis. This includes cytokines (TNF-alpha, interleukin-1, chemokines), growth factors (TGF-beta), extracellular matrix proteins (collagen, fibrillin, fibronectine) and agents acting on vascular tone (angiotensin-converting enzyme and NO synthase).

PERSPECTIVES

Identification of genetic factors involved in the susceptibility to fibrosis of systemic sclerosis would lead to a better understanding of physiopathological mechanisms of this disease and to therapeutic targets using immunomodulation with drugs, such as already performed in rheumatoid arthritis.

Genetics and proteomics in scleroderma

The pathogenesis of systemic sclerosis (SSc; scleroderma) is still enigmatic. Genetic, familial, and twin studies suggest that SSc occurs in genetically susceptible individuals. Recent high-throughput technologies, including gene expression profiling and proteomics, have accelerated the rate of information acquired on possible mechanisms involved in SSc pathogenesis. The potential of the data obtained lies in their use for identifying new disease markers, monitoring disease activity, and developing tailored therapies. The result is an era of unprecedented advance that will benefit SSc and many other diseases.

Cytokine and chemokine levels in systemic sclerosis: relationship with cutaneous and internal organ involvement

Systemic sclerosis (SSc) is a connective tissue disorder characterized by excessive collagen deposition in the skin and internal organs. Several cytokines and chemokines have been implicated in the induction of fibrosis, but a definitive relationship between specific cytokines and organ involvement has not been established yet. Serum samples, PBMC and T cell lines (TCL) obtained from 54 patients affected by SSc and 20 healthy donors (HD) were examined by ELISA for Interferon-gamma (IFN-gamma ), interleukin (IL)-4, IL-6, IL-10, IL-18, Transforming growth factor (TGF)-beta1, Tumour necrosis factor (TNF)-alpha, sCD30, Macrophage derived chemokine (MDC), Monocyte chemoattractant protein (MCP)-1, Macrophage inflammatory protein (MIP)-1alpha and Regulated on activation normal T-cell expressed and secreted (RANTES). In all the SSc serum samples, we found significantly increased levels of IL6, TNFalpha and MCP-1 but reduced amounts of gamma-IFN and MDC. IL6, IL10, IL18, MIP-1alpha and TNFalpha measured in supernatants from PHA-stimulated PBMC and IL6, MCP-1 and RANTES in supernatants from stimulated TCL were also increased in patients. MDC was decreased in all the biological SSc sources studied. TGF-beta1, IL10, and sCD30 were produced at a significantly lower level by SSc TCL. Serum IL6 and sCD30 levels were significantly increased in dc-SSc patients compared to lc-SSc as were levels of MCP-1 produced by PBMC and IL10 from TCL. We observed a strict relationship between pulmonary fibrosis and IL10, MCP-1 (both from TCL) and serum IL6. Kidney involvement was related to serum MCP-1 levels and IL18 production from PBMC. Oesophageal involvement correlated with MDC production from PBMC and IL10 synthesis by TCL. We showed that IL-6, IL-10, MDC and MCP-1 are variably associated with internal organ involvement and allow the discrimination between limited and diffuse forms of the disease.

Monozygotic twins clinically discordant for scleroderma show concordance for fibroblast gene expression profiles

OBJECTIVE

Fewer than 5% of monozygotic (MZ) and dizygotic (DZ) twin pairs are clinically concordant for systemic sclerosis (SSc), yet the majority of MZ twins are concordant for antinuclear antibodies. To discover genetic versus nongenetic molecular pathways important to the pathogenesis of SSc, we compared global gene expression patterns in twins discordant for SSc.

METHODS

Total RNA from dermal fibroblasts of 15 discordant twin pairs (10 MZ and 5 DZ) and 5 normal controls were used in microarray analysis. Aberrantly expressed genes were confirmed using quantitative real-time reverse transcriptase-polymerase chain reaction.

RESULTS

Lesional and nonlesional fibroblasts from SSc patients showed no significant differences in gene expression, while SSc patients had gene profiles that were significantly different from those of unaffected DZ twins and normal controls. Unaffected MZ twins, however, were not significantly different from SSc patients. Unsupervised hierarchical clustering segregated the fibroblast samples as originating from 2 major groups. Group A contained 5 discordant MZ twin pairs, 3 affected MZ twins, and 3 affected DZ twins. Group B contained all 5 normal population controls, all 5 healthy DZ twins, 2 discordant MZ twins, and 2 discordant DZ twin pairs. Normal fibroblasts incubated with serum from an SSc-affected patient or with serum from her unaffected MZ twin sister developed the increased expression of COL1A2, SPARC, and CTGF typically seen in SSc fibroblasts.

CONCLUSION

These results demonstrate that dermal fibroblasts from SSc patients and from 40-50% of their genetically identical but clinically unaffected MZ twins exhibit a similar gene expression pattern which can be induced in normal fibroblasts by sera from both. Thus, a stronger genetic predisposition to SSc (than can be detected clinically) is apparent at the molecular level in skin fibroblasts.

−238 and +489 TNF-α along with TNF-RII gene polymorphisms associate with the diffuse phenotype in patients with Systemic Sclerosis

OBJECTIVE

To investigate possible associations of TNF-alpha and TNF-RII gene polymorphisms with diffuse or limited skin involvement phenotype in a cohort of Systemic Sclerosis (SSc) patients.

METHODS

One-hundred and fourteen consecutive SSc patients attending the referral centres of three academic hospitals in Italy (University of Naples, Pavia and Udine), 56 with the diffuse (dcSSc) and 58 with limited (lcSSc) skin involvement subsets, and 170 healthy blood donors (HBDs) were included in the study. The extracted DNA was genotyped for the following polymorphisms: TNF-alpha (-238, +489) and TNF-RII (+196), using the polymerase chain reaction (PCR) and the restriction enzymes BamHI, HpyCH4 IV and NlaIII, respectively.

RESULTS

The AG/AA (presence of allele A) genotypes in position -238 and the AG genotype in position +489 of the TNF-alpha gene were found significantly increased in SSc, as a whole, when compared with healthy blood donors (chi(nu=2)(2)=4.48, p=0.03 for -238 and chi(nu=2)(2)=7.82, p=0.02 for +489, respectively). The rare GG genotype in exon 6 (codon 196) of the TNF-RII gene was also found increased in SSc compared to HBDs, even though the difference did not show statistical significance (chi(nu=2)(2)=3.56, p=0.17). The strength of the association was mainly due to the dcSSc phenotype (Fisher test, p=0.04 for -238, chi(nu=2)(2)=10.07, p<0.01 for +489 and chi(nu=2)(2)=6.25, p=0.04 for the +196 TNF-RII, respectively).

CONCLUSIONS

TNF-alpha and TNF-RII gene polymorphisms seem to contribute to the development of SSc and in particular to the diffuse phenotype.

Lack of association between arylamine N-acetyltransferase 2 (NAT2) polymorphism and systemic sclerosis

OBJECTIVES

It has been shown that exposure to some environmental toxins may induce scleroderma-like illness in predisposed individuals, but the etiopathogenesis of the idiopathic form of systemic sclerosis (SSc) remains obscure. The genetic background of this illness has been confirmed in multiple studies. We investigated whether patients with SSc differ from healthy subjects with regard to the enzymatic activity of polymorphic N-acetyltransferase 2 (NAT2).

METHODS

The study was carried out in 39 patients with SSc; 15 fulfilled the criteria of diffuse SSc (dSSc) and 24 of limited SSc (lSSc); an ethnically matched control group consisted of 100 healthy volunteers. Acetylation phenotype was estimated using the isoniazid as a model drug. The most common mutations in the Caucasian population at positions 481T, 803G, 590A and 857A on the NAT2 gene were determined using the polymerase chain reaction-restriction fragment length polymorphism method with deoxyribonucleic acid (DNA) extracted from peripheral blood.

RESULTS

In the group of patients with SSc, the frequency of fast acetylator genotypes was 38.5% (95% CI 23.4-55.4), while that for the genotypes coding slow acetylator status was 51.3% (95% CI 34.8-67.6). There was a strong correlation between NAT2 phenotype and NAT2 genotype with a concordance of 97%. We did not observe a preponderance of slow acetylators among patients with SSc and in two subsets of SSc. With the sample size analyzed in the present study, there is a 90% probability of detecting significant differences in distribution of slow, fast, and intermediate phenotypes between patients with SSc and controls, there is a difference of at least 30.3, 28.7 and 21.9% in the distribution of these phenotypes in the general population, respectively.

CONCLUSION

Acetylator status does not seem to be the significant factor in the development of SSc in patients with both subsets of this autoimmune disease, but further studies are required to confirm this conclusion.

A modified model of graft-versus-host-induced systemic sclerosis (scleroderma) exhibits all major aspects of the human disease

OBJECTIVE

Diffuse systemic sclerosis (SSc; scleroderma) is a debilitating disease characterized by excessive dermal fibrosis with later progression to internal organs. In addition to the fibrotic component, major aspects of the disease include vascular or circulatory involvement and immune dysregulation evidenced by inflammatory cells in affected tissues and production of autoantibodies. Many animal models resembling this disease have been studied, including genetic models in mice and chickens, challenge with chemicals such as bleomycin or vinyl chloride to induce fibrosis, and models of graft-versus-host (GVH)-induced disease using certain strains of mice with differences in minor histocompatibility loci. The present studies were undertaken to determine if alteration of the induction of GVH-induced scleroderma could result in a model that more fully represented the human condition.

METHODS

Disease was induced by injection of spleen cells from B10.D2 mice into BALB/c mice deficient in mature T and B cells (recombination-activating gene 2 targeted). Dermal thickening, collagen deposition, vasoconstriction, and parameters of immunity were analyzed.

RESULTS

Similar to the human disease, this modified GVH model of SSc demonstrated evidence of dermal thickening, particularly in the extremities, progressive fibrosis of internal organs, vasoconstriction and altered expression of vascularity markers in skin and internal organs, early immune activation, inflammation in skin and internal organs, and autoantibody generation.

CONCLUSION

This modified model of GVH-induced SSc exhibits all major components of human disease and is likely to contribute to better understanding of the disease mechanisms and, ultimately, improved treatments for patients.

The use of streptolysin o for the treatment of scars, adhesions and fibrosis: initial investigations using murine models of scleroderma

Diseases and conditions involving the deposition of excessive amounts of collagen include scleroderma, fibrosis, and scar and surgical adhesion formation. Diseases such as scleroderma may result from acute and chronic inflammation, disturbances in the normal parenchymal area, and activation of fibroblasts. ML-05, a modified form of the hemolytic and cytotoxic bacterial toxin, streptolysin O, is being developed for the treatment of such collagen-related disorders. At sublytic concentrations in vitro, ML-05 was shown to activate CD44 expression. This may modulate production of collagen, hyaluronate, and their associated enzymes to allow a restoration of normal extracellular matrices within tissues. More importantly, ML-05 appeared to decrease skin collagen levels in two in vivo models of collagen disorders, the tight skin mouse (Tsk) model of scleroderma, and the bleomycin-induced mouse skin fibrosis model. In the Tsk model, levels of hydroxyproline (a measure of total collagen) decreased by 25% in the Tsk+ML-05 treatment group relative to the Tsk+saline control group over a 3-month period. In the bleomycin-induced skin fibrosis study, hydroxyproline levels decreased from 15-22% over a 6-week period in a bleomycin-induced ML-05 treatment group (relative to levels in a bleomycin-induced, untreated control group). Hydroxyproline levels in samples from this treatment group were only slightly greater than levels in an uninduced control group at 8 weeks. Thus, ML-05 treatment appeared to reduce collagen levels in two separate mouse skin fibrosis models, one genetically based and the other chemically induced.

Inhibition of fibrocyte differentiation by serum amyloid P

Wound healing and the dysregulated events leading to fibrosis both involve the proliferation and differentiation of fibroblasts and the deposition of extracellular matrix. Whether these fibroblasts are locally derived or from a circulating precursor population is unclear. Fibrocytes are a distinct population of fibroblast-like cells derived from peripheral blood monocytes that enter sites of tissue injury to promote angiogenesis and wound healing. We have found that CD14(+) peripheral blood monocytes cultured in the absence of serum or plasma differentiate into fibrocytes within 72 h. We purified the factor in serum and plasma that prevents the rapid appearance of fibrocytes, and identified it as serum amyloid P (SAP). Purified SAP inhibits fibrocyte differentiation at levels similar to those found in plasma, while depleting SAP reduces the ability of plasma to inhibit fibrocyte differentiation. Compared with sera from healthy individuals and patients with rheumatoid arthritis, sera from patients with scleroderma and mixed connective tissue disease, two systemic fibrotic diseases, were less able to inhibit fibrocyte differentiation in vitro and had correspondingly lower serum levels of SAP. These results suggest that low levels of SAP may thus augment pathological processes leading to fibrosis. These data also suggest mechanisms to inhibit fibrosis in chronic inflammatory conditions, or conversely to promote wound healing.

Association of transforming growth factor ?1 and tumor necrosis factor ? polymorphisms with anti-SSB/La antibody secretion in patients with primary Sj�gren's syndrome

OBJECTIVE

To determine whether cytokine gene polymorphisms of interferon-gamma (IFNgamma), interleukin-6 (IL-6), IL-10, tumor necrosis factor alpha (TNFalpha), and transforming growth factor beta1 (TGFbeta1) predispose subjects to the development of primary Sjögren's syndrome (SS).

METHODS

Single-base-exchange cytokine gene polymorphisms were analyzed in 129 French patients with primary SS who fulfilled the American-European Consensus Group criteria, as well as in 96 unrelated healthy subjects.

RESULTS

The frequency of the TNF-308A (TNF2) allele was significantly higher in the SS patients (26% versus 11%). This TNF2 association was restricted to patients with anti-SSB (37% versus 11% in controls). Stratification did not reveal an independent effect of TNF2 and HLA-DRB1*03 on disease or on anti-SSB antibody secretion. The frequency of allele C at codon 10 of TGFbeta1 was strongly increased in the subgroup of patients with anti-SSB; this allele acted synergistically with DRB1*03 to predispose patients to the secretion of anti-SSB. The IL-10 GCC haplotype carrier rate was significantly higher in SS patients than in controls (67% versus 48%), but the IL-10 allele and genotype frequencies were not significantly different. No association was found between IL-6 or IFNgamma polymorphisms and primary SS.

CONCLUSION

TNF2 was associated with anti-SSB antibody secretion, although this association was not independent of the association with DRB1*03. Allele C at codon 10 of TGFbeta1 was found to act synergistically with DRB1*03 in predisposing patients to the secretion of anti-SSB. These results therefore suggest that most of the known genetic predisposition to primary SS might concern the pattern of autoantibody diversification.

Genome-wide association study for regions of systemic sclerosis susceptibility in a Choctaw Indian population with high disease prevalence

OBJECTIVE

Systemic sclerosis (SSc) is a complex, multisystem connective tissue disease in which genetic factors contribute to disease susceptibility. The aim of this study was to localize chromosome regions associated with susceptibility to SSc in a relatively isolated and homogeneous population of Choctaw Indians with a high prevalence of SSc.

METHODS

A genome-wide microsatellite screen at 10 cM resolution (400 markers) was performed in 20 Choctaw patients with SSc and 76 ethically matched controls. Based on the results of the initial screen, fine-scale microsatellite mapping at < or =1 cM resolution was performed in 10 selected chromosome regions. Allele and marker haplotype frequencies were compared between SSc patients and controls.

RESULTS

From the genome-wide screen, 12 markers showed evidence of highly significant associations with SSc in this population (P < 0.01), while 5 other markers showed significant associations (0.01 < P < 0.05). Among these markers, loci D5S410, D6S422, D15S978, and D20S107 are near the SPARC, MHC, FBN1, and TOPOI genes, respectively, confirming the results of our previous studies, which used different markers. D1S2800 and D14S63 have been reported to show linkage to systemic lupus erythematosus (SLE) in family-based studies, and D1S206, D6S422, and D6S264 are loci on 1p21.2, 6p22.3, and 6q23-27, respectively, which are in regions reported as showing linkage to SLE and other autoimmune diseases. Other markers showing unique associations with SSc were D7S510 (7p12-11), D7S661 (7q35), D8S514 (8q24.12), D19S221 (19p13.2), D19S220 (19q13.2), D22S423 (22q13.1), DXS1068 (Xp11.4), and DXS8055 (Xq21-23). Further analysis with fine-scale microsatellite mapping revealed at least 14 potential haplotypes associated with SSc.

CONCLUSION

Our findings indicate that a number of genetic loci may contribute to the high prevalence of SSc in the Choctaw and are consistent with the paradigm that some autoimmune rheumatic diseases are likely to share genetic determinants.

Systemic sclerosis: current views of its pathogenesis

Systemic sclerosis (SSc) is an autoimmune disorder of unknown etiology characterized by severe and often progressive cutaneous and visceral fibrosis, pronounced alterations in the microvasculature, and numerous cellular and humoral immune abnormalities. Clinically, SSc is very heterogeneous, encompassing a spectrum ranging from mild limited forms of skin sclerosis with minimal internal organ involvement to severe skin and multiple internal organ fibrosis. Mortality and morbidity in SSc are very high and are directly related to the extent of the fibrotic and microvascular alterations. A better understanding of the pathogenesis of this incurable disorder will help to better target and design effective therapy in the future.

Scleroderma epidemiology

Evidence from multiple sources indicates that SSc does not occur randomly in the population; there are particular groups who are at greater risk. The overall incidence rate of SSc in the adult population of the United States is approximately 20 per million per year; this rate has increased from 1944 to 1973, but has been relatively stable since that time. The prevalence of SSc in the United States also seems to be stable over the past two decades with a prevalence estimate for adults of 240 per million. Recent population studies suggest that SSc occurs more frequently in the United States than in continental Europe, the United Kingdom, and in some areas in Asia. Overall survival has improved over the past few decades; mean survival is approximately 12 years from diagnosis. Renal disease accounts for some of the early mortality, but pulmonary disease has emerged as a major cause of death. Cardiac disease is also correlated with a poorer prognosis. Gastrointestinal involvement contributes to morbidity and, indirectly, to mortality, but the magnitude of this contribution is difficult to assess. Women are affected more frequently than men but the factors that are responsible for this are not apparent. Studies of reproductive history have provided conflicting data; some studies suggested that the number of pregnancies may influence later disease expression, whereas other studies found no correlation. Racial factors seem to play a role in disease susceptibility, as well as disease expression. Age-specific incidence rates are higher in black women than in white women; the greatest difference occurs in the young to middle adult age group (less than 54 years of age). Diffuse disease also seems to occur more commonly in the black population than in the white. Age at onset of diffuse disease is younger, on average, than the age at onset of limited disease; age-adjusted survival is worse in black women than in white women because of their predilection for diffuse disease. Reports of geographic clustering are intriguing; the reported clusters in London and Italy have not resulted in the identification of potential causal factors. The Choctaw Native American cluster suggests that genetic factors that have not been identified may play an important role. Familial clustering of SSc has been demonstrated in the United States and in Australia, which provides additional evidence of a genetic component. It is likely that there is a strong interplay among genetic factors, hormonal or reproductive-related events, and an external trigger that must interact to result in clinical disease.

The vasculopathy of Raynaud's phenomenon and scleroderma

The scleroderma (SSc) disease process involves dramatic dysfunction in acute and chronic vascular regulatory mechanisms; it presents initially with heightened vasoconstrictor or vasospastic activity and progresses to structural derangement or vasculopathy of the microcirculation. This article discusses the regulatory mechanisms that contribute to this dysfunction and the vascular changes in the context of the other aspects of the SSc disease process in a novel attempt to integrate the individual pathologies of the disease process.

Association of novel polymorphisms with the expression of SPARC in normal fibroblasts and with susceptibility to scleroderma

OBJECTIVE

Fibroblasts from patients with systemic sclerosis (SSc) have an activated phenotype characterized by increased synthesis of extracellular matrix (ECM) components. SPARC (secreted protein, acidic and rich in cysteine) regulates the deposition or assembly of ECM components. The aim of this study was to investigate the role of SPARC in SSc susceptibility by functional and genetic association studies.

METHODS

Complementary DNA (cDNA) microarrays were used to obtain gene expression data on cultured dermal fibroblasts from SSc patients. SPARC protein levels were assessed by Western blotting. Five polymorphic microsatellite markers within 5 cM of the SPARC gene (chromosome 5q31-32) were genotyped in Choctaw Indians, a population previously shown to have a high prevalence of SSc. Discovery of single-nucleotide polymorphisms (SNPs) was accomplished by sequencing the SPARC cDNA. These SNPs were then genotyped in a multi-ethnic cohort of SSc patients to determine potential associations with disease susceptibility in a broader population of SSc patients, as well as with various clinical and immunologic features of SSc. The functional relevance of these SNPs with regard to transcript stability of SPARC was also assessed.

RESULTS

Microarrays demonstrated increased expression of SPARC, along with other ECM genes, in SSc patients compared with normal controls. SSc fibroblasts also had increased SPARC protein levels. Three of 5 microsatellite markers near SPARC showed significant associations with SSc in the Choctaw SSc patients. Sequencing of SPARC cDNA revealed 3 novel SNPs in the 3'-untranslated region at +998 (C-->G), +1551 (C-->G), and +1922 (T-->G). Homozygosity for the C allele at SNP +998 was significantly increased in SSc patients across ethnic lines. SPARC SNPs +1551 and +1922 demonstrated correlations with Raynaud's phenomenon and pulmonary fibrosis, respectively. Functional studies of SPARC SNP +998 in normal fibroblast cultures suggested a correlation between the SNP +998 C allele polymorphism and an increased messenger RNA half-life.

CONCLUSION

This study is the first to show that polymorphisms of the SPARC gene are associated with susceptibility to, and clinical manifestations of, SSc and that they may also be functionally important in influencing SPARC expression in skin fibroblasts.