Abnormalities of adhesion molecules and chemokines in scleroderma:

Anti-Th/To Antibodies in Scleroderma: Good Prognosis or Serious Concern?

Systemic sclerosis (SSc) represents a rare and intricate autoimmune connective tissue disease, the pathophysiology of which has not been fully understood. Its key features include progressive fibrosis of the skin and internal organs, vasculopathy and aberrant immune activation. While various anti-nuclear antibodies can serve as biomarkers for the classification and prognosis of SSc, their direct role in organ dysfunction remains unclear. Anti-Th/To antibodies are present in approximately 5% of SSc patients, and are particularly prevalent among those with the limited subtype of the disease. Although the presence of these autoantibodies is associated with a mild course of the disease, there is a strong connection between them and severe clinical manifestations of SSc, including interstitial lung disease, pulmonary arterial hypertension and gastrointestinal involvement. Also, the additional clinical correlations, particularly with malignancies, need further research. Moreover, the disease's course seems to be influenced by antibodies, specific serum cytokines and TLR signaling pathways. Understanding the relationships between presence of anti-Th/To, its molecular aspects and response to treatment options is crucial for the development of novel, personalized therapeutic techniques and should undergo profound analysis in future studies.

Angiostatic and Angiogenic Chemokines in Systemic Sclerosis: An Overview

In systemic sclerosis (SSc), the dysregulation of several molecular pathways seem to have a role in the disease pathogenesis. Either angiogenesis and vasculogenesis are disturbed and impaired, and an imbalance between angiogenic and angiostatic factors may be involved in the genesis and maintenance of vasculopathy. Aberrant immune system activation and function involves both B and T cells, as well as many different chemokines and cytokines. Particularly, chemokines are central to the initiation and maintenance of inflammatory responses as well as angiogenesis and fibrosis. Increased expression of several chemokines as CXCL4 (platelet factor 4), CXCL8 (IL8), CXCL5 (ENA-78), CCL5 (RANTS), CXCL9 (MIG), CCL24, CXCL10 IP-10), CXCL12, CXCL16 (SRPSDX), CCL2 (MCP-1), CCL19 (MIP-3β/ELC), CCL24 (Eotaxin 2), suggests a complex mechanism by which many immune cell types, including T cells, macrophages and neutrophils are recruited to the skin in SSc patients. Many of these chemokines have redundant roles, possibly to ensure recruitment of specific cell types. Several studies have shown a synergistic effect of combinations of these chemokines in cell recruitment, emphasizing the importance of understanding global chemokine expressions. urthermore, chemokines can be detected in peripheral blood compared with cytokines or growth factors. The utility of cytokines as biomarkers has been investigated but longitudinal studies are necessary to clarify their clinical utility for the evaluation of disease activity, therapeutic effects on skin sclerosis or interstitial lung disease and risk stratification of SSc patients. An effective therapeutic agent, able to interfere with complex chemokine networks, is warranted to attenuate perivascular inflammation, dysregulated angiogenesis and the evolution of skin and internal organ fibrosis, is the most ambitious goal for the scientific research of the future.

The Pathogenesis of Systemic Sclerosis

Systemic sclerosis is a multisystem disorder with a high associated mortality. The hallmark abnormalities of the disease are in the immune system, vasculature, and connective tissue. Systemic sclerosis occurs in susceptible individuals and is stimulated by initiating events that are poorly understood at present. In order for the disease phenotype to appear there is dysfunction in the homoeostatic mechanisms of immune tolerance, endothelial physiology, and extracellular matrix turnover. The progression of disease is not sequential but requires simultaneous dysfunction in these normal regulatory mechanisms. Better understanding of the interplay of these factors is likely to contribute to improved treatment options.

Increased circulating soluble vascular adhesion protein-1 levels in systemic sclerosis: association with lower frequency and severity of interstitial lung disease

AIM

To determine circulating soluble vascular adhesion protein-1 (sVAP-1) levels and their clinical associations in patients with systemic sclerosis (SSc).

METHOD

Serum VAP-1 levels were examined by enzyme-linked immunosorbent assay in 71 SSc patients, 13 systemic lupus erythematosus patients and 50 healthy individuals.

RESULTS

Serum sVAP-1 levels were significantly elevated in SSc patients (617.2 ± 338.7 ng/mL) compared with healthy individuals (320.2 ± 144.2 ng/mL; P < 0.001) and patients with systemic lupus erythematosus (329.0 ± 176.1 ng/mL; P < 0.001). Among SSc patients, there were no differences in serum sVAP-1 levels between those with limited cutaneous SSc and those with diffuse cutaneous SSc. SSc patients with raised sVAP-1 levels had interstitial lung disease and decreased percent vital capacity less often than those with normal sVAP-1 levels. sVAP-1 levels were positively correlated with percent vital capacity in patients with SSc.

CONCLUSION

Serum sVAP-1 levels were increased in patients with SSc, and associated with a lower frequency and severity of interstitial lung disease in SSc, suggesting that sVAP-1 plays a role in the pathogenesis of interstitial lung disease in SSc.

Differential expression of junctional adhesion molecules in different stages of systemic sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is characterized by early perivascular inflammation, microvascular endothelial cell (MVEC) activation/damage, and defective angiogenesis. Junctional adhesion molecules (JAMs) regulate leukocyte recruitment to sites of inflammation and ischemia-reperfusion injury, vascular permeability, and angiogenesis. This study was undertaken to investigate the possible role of JAMs in SSc pathogenesis.

METHODS

JAM-A and JAM-C expression levels in skin biopsy samples from 25 SSc patients and 15 healthy subjects were investigated by immunohistochemistry and Western blotting. Subcellular localization of JAMs in cultured healthy dermal MVECs and SSc MVECs was assessed by confocal microscopy. Serum levels of soluble JAM-A (sJAM-A) and sJAM-C in 64 SSc patients and 32 healthy subjects were examined by enzyme-linked immunosorbent assay.

RESULTS

In control skin, constitutive JAM-A expression was observed in MVECs and fibroblasts. In early-stage SSc skin, JAM-A expression was strongly increased in MVECs, fibroblasts, and perivascular inflammatory cells. In late-stage SSc, JAM-A expression was decreased compared with controls. JAM-C was weakly expressed in control and late-stage SSc skin, while it was strongly expressed in MVECs, fibroblasts, and inflammatory cells in early-stage SSc. Surface expression of JAM-A was higher in early-stage SSc MVECs and increased in healthy MVECs stimulated with early-stage SSc sera. JAM-C was cytoplasmic in resting healthy MVECs, while it was recruited to the cell surface upon challenge with early-stage SSc sera. Early-stage SSc MVECs exhibited constitutive surface JAM-C expression. In SSc, increased levels of sJAM-A and sJAM-C correlated with early disease and measures of vascular damage.

CONCLUSION

Our findings indicate that JAMs may participate in MVEC activation, inflammatory processes, and impaired angiogenesis in different stages of SSc.

Serum IL-33 levels are raised in patients with systemic sclerosis: association with extent of skin sclerosis and severity of pulmonary fibrosis

To determine serum interleukin-33 (IL-33) levels and their associations with clinical parameters in patients with systemic sclerosis (SSc). Serum IL-33 levels were examined by enzyme-linked immunosorbent assay in 69 patients with SSc and 30 healthy individuals. In a retrospective longitudinal study, sera from 14 patients with SSc were analyzed (follow-up, 1-7 years). Serum IL-33 levels were elevated in SSc patients (261.7 ± 141.9 pg/ml) compared with healthy individuals (174.9 ± 72.4 pg/ml; P < 0.001). Patients with diffuse cutaneous SSc had higher levels of IL-33 (287.5 ± 146.6 pg/ml) than those with limited cutaneous SSc (221.5 ± 126.5 pg/ml; P < 0.05). Pulmonary fibrosis and decreased forced vital capacity were more commonly found in patients with elevated IL-33 levels than in those with normal IL-33 levels. IL-33 levels correlated positively with the extent of skin sclerosis, and inversely with percent predicted forced vital capacity. IL-33 levels were increased in SSc patients and correlated with the extent of skin sclerosis and the severity of pulmonary fibrosis. Therefore, IL-33 possibly plays a role in cutaneous and pulmonary fibrosis in SSc patients.

Endothelial/lymphocyte activation leads to prominent CD4+ T cell infiltration in the gastric mucosa of patients with systemic sclerosis

OBJECTIVE

Although gastrointestinal tract dysfunction is a common feature in patients with systemic sclerosis (SSc; scleroderma), few studies have addressed the pathogenetic mechanisms of gastrointestinal tract involvement in SSc. We previously showed that severe fibrosis and increased expression of profibrotic cytokines are important hallmarks in the gastric wall of patients with SSc. The aim of the present study was to investigate whether immune and/or microvascular abnormalities may account for tissue damage in gastric wall specimens obtained from patients with SSc.

METHODS

Gastric biopsy samples from 27 patients with SSc and 15 healthy control subjects were analyzed by immunohistochemistry for CD45/leukocyte common antigen, CD3/T cells, CD4/T helper cells, CD8/cytotoxic T cells, CD20/B cells, CD14/monocytes, CD68/macrophages, cell adhesion molecules CD11a/lymphocyte function-associated antigen 1 (LFA-1), CD49d/very late activation antigen 4 (VLA-4), CD54/intercellular adhesion molecule 1 (ICAM-1), CD106/vascular cell adhesion molecule 1 (VCAM-1), CD31/platelet endothelial cell adhesion molecule 1, and vascular endothelial growth factor (VEGF).

RESULTS

T cell infiltration was a prominent finding in gastric specimens from patients with SSc. The CD4+/CD8+ T cell ratio was significantly increased in SSc specimens compared with controls. T cells were found in both lymphocyte aggregates and diffuse infiltrates and strongly expressed the activation markers VLA-4, LFA-1, and ICAM-1. Endothelial cells showed corresponding surface activation with strong expression of VCAM-1 and ICAM-1. Mature B cells were frequently observed arranged in aggregates and rarely were seen in a diffuse pattern. Most lymphocyte aggregates lacked monocyte/macrophages. No difference in microvascular density was observed between SSc specimens and controls. Both SSc and control specimens showed weak or no expression of VEGF.

CONCLUSION

Our findings provide the first evidence that endothelial/lymphocyte activation leading to prominent CD4+ T cell infiltration may play a key pathogenetic role within the gastric wall of patients with SSc and may represent an important therapeutic target.

Mechanisms in the loss of capillaries in systemic sclerosis: angiogenesis versus vasculogenesis

Systemic sclerosis (SSc, scleroderma) is a chronic, multisystem connective tissue disorder affecting the skin and various internal organs. Although the disease is characterized by a triad of widespread microangiopathy, fibrosis and autoimmunity, increasing evidence indicates that vascular damage is a primary event in the pathogenesis of SSc. The progressive vascular injury includes persistent endothelial cell activation/damage and apoptosis, intimal thickening, delamination, vessel narrowing and obliteration. These profound vascular changes lead to vascular tone dysfunction and reduced capillary blood flow, with consequent tissue ischemia and severe clinical manifestations, such as digital ulceration or amputation, pulmonary arterial hypertension and scleroderma renal crisis. The resulting tissue hypoxia induces complex cellular and molecular mechanisms in the attempt to recover endothelial cell function and tissue perfusion. Nevertheless, in SSc patients there is no evidence of significant angiogenesis and the disease evolves towards chronic tissue ischemia, with progressive and irreversible structural changes in multiple vascular beds culminating in the loss of capillaries. A severe imbalance between pro-angiogenic and angiostatic factors may also lead to impaired angiogenic response during SSc. Besides insufficient angiogenesis, defective vasculogenesis with altered numbers and functional defects of bone marrow-derived endothelial progenitor cells may contribute to the vascular pathogenesis of SSc. The purpose of this article is to review the contribution of recent studies to the understanding of the complex mechanisms of impaired vascular repair in SSc. Indeed, understanding the pathophysiology of SSc-associated vascular disease may be the key in dissecting the disease pathogenesis and developing novel therapies. Either angiogenic or vasculogenic mechanisms may potentially become in the future the target of therapeutic strategies to promote capillary regeneration in SSc.

Up-regulated macrophage migration inhibitory factor protects apoptosis of dermal fibroblasts in patients with systemic sclerosis

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that has been demonstrated to regulate the apoptosis of several cell types. Dysregulated apoptosis of fibroblasts has been implicated in a variety of fibrotic diseases, including systemic sclerosis (SSc). In this study, we investigated the role of MIF in the apoptosis of dermal fibroblasts. The concentrations of MIF were measured in sera and in culture supernatants of peripheral blood mononuclear cells (PBMCs) and dermal fibroblasts by enzyme-linked immunosorbent assay. The degree of apoptosis was determined by colorimetric assay, and signalling pathways were examined by Western blot. The results showed that serum levels of MIF were significantly higher in patients with SSc (n = 47) than in healthy controls (n = 56). Stimulation of PBMCs by anti-CD3 and anti-CD28 increased the production of MIF by fourfold over the constitutive levels. SSc dermal fibroblasts produced higher amounts of MIF than normal dermal fibroblasts. When treated with sodium nitroprusside (SNP), SSc dermal fibroblasts showed a lower degree of apoptosis compared with normal dermal fibroblasts. Exogenous MIF (1-100 ng/ml) inhibited SNP-induced apoptosis of dermal fibroblasts dose-dependently. Both extracellular regulated kinase (ERK) inhibitor (PD98059) and protein kinase B (Akt) inhibitor (LY294002) almost completely blocked the inhibitory effect of MIF on apoptosis. Furthermore, MIF increased the expression of Bcl-2, phospho-ERK and phospho-Akt activity in dermal fibroblasts. Taken together, our data suggest that MIF released by activated T cells and dermal fibroblasts decreases the apoptosis of dermal fibroblasts through activation of ERK, Akt and Bcl-2 signalling pathways, which might be associated with excessive fibrosis in SSc.

Association of CTLA-4 gene promoter polymorphisms with systemic sclerosis in Iranian population

In a recent study, we were unable to show any association between CTLA-4 exon-1 polymorphism and systemic sclerosis (SSc) in Iranian population. In order to further explore the role of this immune inhibitory gene in SSc development, in the present study, the polymorphisms in the CTLA-4 promoter region (-1,722 T/C, -1,661 A/G and -318 C/T) were investigated in 83 SSc patients and 166 healthy controls. All genotypes and allele frequencies in patients were significantly different from the control group (P=0.022 for -1,722 T/C, P=0.03 for -1,661 A/G and P=0.014 for -318 C/T genotypes). The -1,722C, -1,661G and -318T alleles contributed to SSc with P=0.012, odds ratio (OR) 2.16, P=0.031, OR 1.82 and P=0.023, OR 2.45, respectively. A significant difference was observed in the frequency homozygous 'genotype combination' -1,722TT/-1,661AA/-318CC of these three polymorphisms (P(c)=0.003). The frequency of this genotype combination was significantly higher in the control group than in patients. Results of this investigation indicate that -1,722C, -1,661G and -318T alleles of CTLA-4 gene promoter appear to be associated with SSc, and individuals carrying these alleles may be more susceptible to this disease.

Antibodies against human cytomegalovirus in the pathogenesis of systemic sclerosis: a gene array approach

BACKGROUND

Systemic sclerosis is an autoimmune disease characterized by immunological abnormalities, vascular damage, and fibroblast proliferation. We have previously shown that a molecular mimicry mechanism links antibodies against the human-cytomegalovirus-derived protein UL94 to the pathogenesis of systemic sclerosis. The UL94 epitope shows homology with NAG-2, a surface molecule highly expressed on endothelial cells. Anti-UL94 peptide antibodies purified from patients' sera induce apoptosis of endothelial cells upon engagement of the NAG-2-integrin complex.

METHODS AND FINDINGS

We show here that NAG-2 is expressed on dermal fibroblasts and that anti-UL94 antibodies bind to fibroblasts. We have used the gene array strategy (Affimetrix oligonucleotide microarrays) to analyze the transcriptional profile in response to a 4-h and an 8-h treatment with antibodies against the UL94 peptide in endothelial cells and dermal fibroblasts. Exposure of endothelial cells to anti-UL94 antibodies had a profound impact on gene expression, resulting in the upregulation of 1,645 transcripts. Several gene clusters were upregulated including genes encoding adhesion molecules, chemokines, colony-stimulating factors (CSFs), growth factors, and molecules involved in apoptosis. Following antibody stimulation, dermal fibroblasts showed an upregulation of 989 transcripts and acquired a "scleroderma-like" phenotype. Indeed, genes involved in extracellular matrix deposition, growth factors, chemokines, and cytokines were upregulated. We confirmed the microarray results by real-time quantitative polymerase chain reaction and by measuring some of the corresponding proteins with ELISA and Western blotting.

CONCLUSION

Our results show that anti-human-cytomegalovirus antibodies may be linked to the pathogenesis of systemic sclerosis not only by inducing endothelial cell activation and apoptosis but also by causing activation of fibroblasts, one of the hallmarks of the disease.

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.

Autoantibodies to a collagen-specific molecular chaperone, heat-shock protein 47, in systemic sclerosis

Heat-shock proteins are highly conserved and immunogenic proteins, which may be involved in the initiation and perpetuation of autoimmune diseases. Heat-shock protein 47 (HSP47) is expressed by collagen-secreting cells such as fibroblasts and serves as a collagen-specific molecular chaperone that plays a crucial role in collagen metabolism. Abnormal collagen accumulation and autoimmunity are characteristics of systemic sclerosis (SSc). We determined the presence and prevalence of autoantibodies to HSP47 in patients with SSc and also in tight-skin (TSK/+) mice, an animal model for SSc. Anti-HSP47 autoantibodies were present in SSc patients with a frequency of 26%, while patients with systemic lupus erythematosus, those with dermatomyositis, those with keloid and healthy subjects did not have anti-HSP47 antibodies. IgG1 and IgG2 were the major Ig isotypes of the autoantibodies. Patients positive for anti-HSP47 had a significantly shorter duration of disease than those who were negative. Anti-HSP47 autoantibodies were also positive in 79% of TSK/+ mice. Thus, autoantibodies to HSP47 were present in the sera from SSc patients as well as those from TSK mice, and may be associated with the pathogenesis of SSc.

T cell repertoire in patients with stable scleroderma

At onset of systemic sclerosis (SSc), T cells have been found to oligoclonally expand in the skin, presumably in response to auto-antigens, but the T cell repertoire has not been evaluated at a later stage. To determine whether a perpetuating immune response contributes to the pathogenesis of stable SSc, the T cell repertoire was analysed in patients with diffuse (d) or limited (l) SSc, and compared to patients with primary Raynaud's phenomenon (RP) or healthy volunteers (Ctrl). The T cell repertoire (total, CD4 or CD8 sorted blood T cells) was analysed by qualitative and quantitative immunoscope (14 BV families analysed) in 11 untreated dSSc and 11 untreated lSSc, 10 RP and 11 Ctrl. To better detect in vivo activated cells, repertoire analysis was also performed on sorted CD4 T cells after in vitro culture with IL-2. In parallel, 6 skin biopsies from SSc patients were analysed. After 7-8 years of disease evolution, SSc patients did not show detectable clonal T cell expansions in the skin, even after tentative expansion from the biopsy with IL-2. Total T cell, sorted CD4 and CD8 T cell repertoires from the blood of patients with SSc did not show significant perturbation as compared to patients with RP and Ctrl. After IL-2 culture for 7 days, blood CD4 T cells from the patients did not preferentially expand as compared to RP and Ctrl. These findings suggest that antigen-driven immune responses may play a lesser role in established SSc than at disease onset.

Augmented production of transforming growth factor-beta by cultured peripheral blood mononuclear cells from patients with systemic sclerosis

We sought to determine whether the spontaneous production of transforming growth factor-beta (TGF-beta) by peripheral blood mononuclear cells (PBMC) is increased in patients with systemic sclerosis (SSc). Culture supernatants of PBMC from SSc patients (n = 88) and healthy controls (n = 44) were analyzed by enzyme-linked immunosorbent assay. The production of active TGF-beta1 and total (active and latent) TGF-beta1 by PBMC from patients with limited cutaneous SSc (lSSc) and by PBMC from patients with diffuse cutaneous SSc (dSSc) was significantly elevated compared to the production by PBMC from normal controls. Production of active TGF-beta1 by dSSc PBMC was higher than that by lSSc PBMC, although not significantly. Patients with PBMC with increased active or total TGF-beta1 production showed significantly shorter disease duration than patients with PBMC with normal production levels. PBMC from patients without anticentromere antibody showed enhanced active TGF-beta1 production more frequently than those from patients with anticentromere antibody. PBMC from SSc patients more frequently showed enhanced total TGF-beta2 production than PBMC from normal controls. Among each leukocyte subset, spontaneous production of total TGF-beta1 was significantly higher in cultured peripheral monocytes/macrophages, but not in T cells, B cells, or NK cells, from patients than from normal controls. Thus, the enhanced production of TGF-beta by PBMC may contribute to the disease process in SSc

Function blocking autoantibodies against matrix metalloproteinase-1 in patients with systemic sclerosis

Systemic sclerosis is characterized by fibrosis and systemic autoimmunity; however, roles of autoantibodies in the development of fibrosis remain unknown in systemic sclerosis. The net accumulation of extracellular matrix is dependent on the balance between the synthesis and degradation of extracellular matrix components, the latter process regulated by matrix metalloproteinases. Matrix metalloproteinase-1 (interstitial collagenase-1) can initiate degradation of collagen types I-III that are major extracellular matrix constituents in affected skin of systemic sclerosis. In this study, we tested the hypothesis that systemic autoimmunity in systemic sclerosis induced anti-matrix metalloproteinase-1 autoantibodies that inhibited matrix metallo-proteinase-1 activity, resulting in collagen accumulation. Enzyme-linked immunosorbent assay using human recombinant matrix metalloproteinase-1 revealed that IgG anti-matrix metalloproteinase-1 autoantibody levels were significantly elevated in sera from patients with systemic sclerosis, but not patients with active systemic lupus erythematosus or dermatomyositis, relative to normal controls. IgG anti-matrix metalloproteinase-1 autoantibody levels were significantly higher in patients with diffuse cutaneous systemic sclerosis than those found in patients with limited cutaneous systemic sclerosis. Furthermore, IgG anti-matrix metalloproteinase-1 antibody levels significantly correlated with the extent of fibrosis in the skin, lung, and renal blood vessels. The presence of IgG anti-matrix metalloproteinase-1 autoantibody in sera from systemic sclerosis patients was confirmed by immunoblotting analysis. Remarkably, IgG anti-matrix metalloproteinase-1 autoantibody in sera from systemic sclerosis patients inhibited matrix metalloproteinase-1 collagenase activity. Collectively, the results of this study suggest that anti-matrix metalloproteinase-1 autoantibody contributes to the development of fibrosis by inhibiting matrix metalloproteinase-1 collagenase activity and reducing the extracellular matrix turnover and suggest that the presence of anti-matrix metalloproteinase-1 autoantibody in systemic sclerosis is the link between systemic autoimmunity and fibrosis.

Targeting mediators of vascular injury in scleroderma

Increasing evidence suggests that the vasculopathy of scleroderma is mediated by a number of soluble factors and involves a complex interaction between endothelial cells, smooth muscle cells, extracellular matrix, intravascular coagulation factors, and circulating cells. Novel therapeutic approaches beyond vasodilator therapy are being developed by recognizing important molecular pathways involved in scleroderma vascular disease. The success of this strategy is most evident in pulmonary hypertension, an often fatal complication of scleroderma. In this article, the authors explore therapies for scleroderma that target endothelial cells, smooth muscle cells, reactive oxygen species, and circulating blood cells. The authors highlight clinical trials that have investigated the role of prostacyclin (and its analogues) and bosentan in managing scleroderma-related pulmonary hypertension. Finally, the authors look at the potential role of biomarkers as surrogate indicators of active vascular disease in scleroderma.

Antifibroblast antibodies from systemic sclerosis patients are internalized by fibroblasts via a caveolin-linked pathway

OBJECTIVE

Fibroblast activation is a crucial event in the development of systemic sclerosis (SSc). Antifibroblast autoantibodies (AFAs), detectable in the sera of SSc patients, are able to induce a proinflammatory phenotype on cultured fibroblasts. This study was undertaken to investigate the mechanisms of the interaction between AFAs and living fibroblasts.

METHODS

We coupled to fluorescein 1) IgG purified from AFA-positive and AFA-negative SSc sera (as assessed by cellular enzyme-linked immunosorbent assay) and 2) single healthy donor and pooled normal IgG. The interaction of IgG with living cultured fibroblasts from healthy individuals and from a patient with SSc was visualized by real-time confocal microscopy. Intracellular colocalization of caveolin and internalized AFA-positive IgG was assessed by immunofluorescence.

RESULTS

AFA-positive IgG bound to living fibroblasts and was internalized with a cytoplasmic fibrillar pattern, in contrast to AFA-negative IgG. In the IgG tested, no correlation with antinuclear antibody activity was found. Preincubation of fibroblasts with normal IgG did not affect internalization. Internalized AFA-positive IgG colocalized with caveolin, and internalization was entirely inhibited by disassembling fibroblast caveolae with filipin.

CONCLUSION

The finding that both normal and pathologic fibroblasts specifically internalized AFA-positive, but not AFA-negative, IgG demonstrates that AFAs in SSc patient sera interact with constitutively expressed membrane molecules on fibroblasts, via an Fc-independent mechanism. The results of colocalization and inhibition experiments suggest that microdomains containing caveolin are involved in the interaction between AFAs and fibroblasts. These data, together with the reported ability of AFAs to activate fibroblasts, provide evidence for a role of AFAs in the pathogenesis of SSc.

Serum levels of interleukin-6 and interleukin-10 correlate with total skin thickness score in patients with systemic sclerosis

Various growth factors and cytokines have been suggested to play a central role in initiating and developing fibrosis in systemic sclerosis (SSc). To determine which serum levels of soluble mediators are the most relevant to the degree of skin sclerosis in SSc, serum levels of various soluble mediators were examined by ELISA and correlated with skin thickening that was measured using modified Rodnan total skin thickness scoring (TSS) system. Serum levels of IL-4, IL-12, IL-13, tumor necrosis factor-alpha, connective tissue growth factor (CTGF), vascular endothelial growth factor, monocyte chemotactic protein-1, macrophage inflammatory protein-1beta, soluble IL-6 receptor, and soluble L-selectin were higher in SSc patients than normal controls. Levels of IL-6, IL-10, and CTGF in patients with diffuse cutaneous SSc were higher than patients with limited cutaneous SSc and controls. Serum levels of IL-6 and IL-10 positively correlated with TSS in patients with SSc (r=0.625, P<0.0001 and r=0.663, P<0.0001, respectively). In addition, IL-10 levels significantly correlated with pulmonary fibrosis. Thus, serum levels of IL-6 and IL-10 most strongly reflect the extent of skin thickening in SSc, suggesting that levels of IL-6 and IL-10 are useful serological indicators for skin fibrosis in SSc.

Elevated serum L-selectin levels and decreased L-selectin expression on CD8(+) lymphocytes in systemic sclerosis

L-selectin is expressed on most circulating leucocytes and mediates leucocyte rolling on endothelium at sites of inflammation. Following rolling or activation of leucocytes, cell surface L-selectin is released as soluble L-selectin (sL-selectin). In the present study, we assessed serum levels of sL-selectin by ELISA and blood leucocyte L-selectin expression by flow cytometry in patients with systemic sclerosis (SSc). Serum levels of sL-selectin in patients with SSc (n = 51) were significantly higher than in normal controls (n = 30) while sL-selectin levels were similar for systemic lupus erythematosus patients (n = 20) and normal controls. Furthermore, SSc patients with elevated sL-selectin levels had inflammatory joint involvement, pitting scar/ulcers, and diffuse pigmentation more frequently than those with normal sL-selectin levels. The frequency of L-selectin(+) population among CD8(+) T cells was significantly decreased in SSc patients (n = 30) compared with normal controls (n = 20), while that among CD4(+) T cells, B cells, monocytes, and neutrophils was similar for SSc patients and normal controls. These suggest that elevated sL-selectin levels and decreased frequency of L-selectin+ CD8(+) T cells in SSc patients may be involved in inflammation associated with SSc.

Localized and systemic scleroderma

Scleroderma is a broad term encompassing both localized and systemic sclerosis. Localized scleroderma is a cutaneous limited fibrosis that manifests as plaque morphea, generalized morphea, linear scleroderma, and deep morphea. Systemic scleroderma (sclerosis) can manifest as either limited or diffuse disease. Limited systemic sclerosis is typically preceded by Raynaud's phenomenon, involves cutaneous sclerosis distal to the elbows, with gastrointestinal and pulmonary fibrosis, and anticentromere antibody positivity. Diffuse systemic scleroderma is characterized by simultaneous Raynaud's phenomenon, cutaneous skin involvement proximal to the elbow with gastrointestinal, pulmonary, renal and cardiac fibrosis, and positive serology for antitopoisomerase and anti-RNAP III antibodies. This article discusses the classification, epidemiology, pathogenesis, clinical manifestations, treatment, and prognosis of the scleroderma.

Assessment of damage and activity in systemic sclerosis

The determination of damage and activity in the course of a disease are important matters. Monitoring damage activity is critical in the evaluation of individual patients and in evaluating treatment efficacy in clinical trials. A disease damage (severity) scale has been published for systemic sclerosis. A number of potential cytokine and other soluble protein markers of disease activity for this disease have been proposed in recent publications, reviewed here.