Monocyte chemoattractant protein 1 released from glycosaminoglycans mediates its profibrotic effects in systemic sclerosis via the release of interleukin-4 from T cells

OBJECTIVE: Monocyte chemoattractant protein 1 (MCP-1; CCL2) has been implicated in the pathogenesis of fibrotic diseases and is up-regulated in patients with systemic sclerosis (SSc). The aim of the present study was to examine the mechanisms by which MCP-1 mediates its profibrotic effects in the setting of SSc. METHODS: The expression of receptors for MCP-1 on dermal fibroblasts was analyzed by real-time polymerase chain reaction and fluorescence-activated cell sorting. The ability of extracellular matrix proteins to bind and release MCP-1 was quantified by enzyme-linked immunosorbent assay. Th0 cells were isolated using a magnetic-activated cell sorting system and were stimulated twice in the presence of MCP-1. The synthesis of collagen was measured using the Sircol collagen assay kit. RESULTS: The glycosaminoglycan chondroitin sulfate, but not fibronectin or collagens, bound and released MCP-1 in a time-dependent manner. MCP-1 that was released from chondroitin sulfate induced the differentiation of interleukin-4 (IL-4)-producing T cells in a dose-dependent manner. In turn, dermal fibroblasts from patients with SSc expressed IL-4 receptor, and stimulation with IL-4 significantly increased the production of collagen in dermal fibroblasts. In contrast, CCR2a and CCR2b, as well as D6 and US28 (other potential receptors of MCP-1), were not detectable in SSc and normal fibroblasts, and their expression was not induced by platelet-derived growth factor, IL-1beta, or IL-4. In addition, MCP-1 had no direct effects on collagen production by fibroblasts. CONCLUSION: MCP-1 has no direct effects on dermal fibroblasts but contributes to fibrosis in patients with SSc by inducing the differentiation of IL-4-producing T cells. Because MCP-1 has both proinflammatory and profibrotic effects, pharmacologic targeting of MCP-1 could be a promising therapeutic approach in SSc.     

Systemic sclerosis Th2 cells inhibit collagen production by dermal fibroblasts via membrane-associated tumor necrosis factor alpha

OBJECTIVE: In systemic sclerosis (SSc; scleroderma), T cells infiltrate organs undergoing fibrotic changes and may participate in dysregulated production of collagen by fibroblasts. The objective of this study was to functionally characterize T cells infiltrating skin lesions in early SSc and investigate their capacity to affect production of type I collagen and interstitial collagenase (matrix metalloproteinase 1 [MMP-1]) by dermal fibroblasts. METHODS: Four-color cytometric analysis was used to characterize subset distribution and production of interferon-gamma (IFN gamma) and interleukin-4 (IL-4) in T cell lines generated from the skin of patients with SSc. T cell clones were generated, and their capacity to modulate collagen and MMP-1 production by fibroblasts derived from patients with SSc and from normal individuals was assessed. Neutralizing reagents were used to identify T cell mediators involved in fibroblast modulation. RESULTS: The skin of individuals with early-stage SSc contained T cells preferentially producing high levels of IL-4. Cloned CD4+ Th2-like cells inhibited collagen production by normal fibroblasts. Th2 cell-dependent inhibition was, at least in part, contact-dependent, was essentially mediated by tumor necrosis factor alpha (TNF alpha), and was dominant over the enhancement induced by profibrotic IL-4 and transforming growth factor beta cytokines. The simultaneous induction of MMP-1 production confirmed the specificity of these observations. To be inhibitory, Th2 cells required activation by CD3 ligation. Th2 cells were less potent than were Th1 cells in inhibiting collagen production by normal fibroblasts via cell-to-cell interaction, and SSc fibroblasts were resistant to inhibition. CONCLUSION: These findings indicate that, despite their production of IL-4, Th2 cells reduce type I collagen synthesis by dermal fibroblasts because of the dominant effect of TNF alpha, and suggest that strategies based on TNF alpha blockade aimed at controlling fibrosis in SSc may be unwise.     

Cytokine directed therapy in scleroderma: rationale,current status,and the future

The hallmark of scleroderma is cutaneous and visceral fibrosis characterized and by increased biosynthesis of multiple matrix proteins by interstitial fibroblasts. Studies over recent years have delineated pathways involved in promoting matrix synthesis and elucidated the molecular pathways of regulation. Central to the regulation of fibrosis are extracellular mediators, called cytokines, which are elaborated by a variety of cells, including those in the immune system, vascular cells, and fibroblasts themselves. The concept that inhibiting or promoting the action of these naturally occurring profibrotic or antifibrotic molecules, respectively, is a rational therapeutic approach to treating scleroderma and other fibrotic diseases finds support in animal studies and anticytokine therapy conducted in relation to rheumatoid arthritis and other disorders. This review looks at cytokines known or thought to play a role in scleroderma and/or other fibrotic states and at potential therapy directed at these mediators. Potential targets for therapy include transforming growth factor beta (TGF-beta), connective tissue growth factor (CTGF), IL-4, IL-13, MCP-1, and endothelin, among others.     

Association between enhanced type I collagen expression and epigenetic repression of the FLI1 gene in scleroderma fibroblasts

OBJECTIVE: Scleroderma (systemic sclerosis; SSc) is an autoimmune disease characterized by vasculopathy and widespread organ fibrosis. Altered fibroblast function, both in vivo and in vitro, is well documented and illustrated by augmented synthesis and deposition of extracellular matrix proteins. We undertook this study to investigate the possibility that epigenetic mechanisms mediate the emergence and persistence of the altered SSc fibroblast phenotype. METHODS: The effects of DNA methyltransferase and histone deacetylase inhibitors on collagen expression and the level of epigenetic mediators in fibroblasts were examined. The effects of transient transfection of SSc fibroblasts with FLI1 gene and normal cells with FLI1 antisense construct on collagen expression were determined. The methylation status of the FLI1 promoter was tested in cultured cells and in SSc and normal skin biopsy specimens. RESULTS: Increased levels of epigenetic mediators in SSc fibroblasts were noted. The addition of epigenetic inhibitors to cell cultures normalized collagen expression in SSc fibroblasts. The augmented collagen synthesis by SSc fibroblasts was linked to epigenetic repression of the collagen suppressor gene FLI1. Heavy methylation of the CpG islands in the FLI1 promoter region was demonstrated in SSc fibroblasts and skin biopsy specimens. CONCLUSION: The results of this study indicate that epigenetic mechanisms may mediate the fibrotic manifestations of SSc. The signal transduction leading to the SSc fibrotic phenotype appears to converge on DNA methylation and histone deacetylation at the FLI1 gene.     

Systemic sclerosis Th2 cells inhibit collagen production by dermal fibroblasts via membrane‐associated tumor necrosis factor α

Objective

In systemic sclerosis (SSc; scleroderma), T cells infiltrate organs undergoing fibrotic changes and may participate in dysregulated production of collagen by fibroblasts. The objective of this study was to functionally characterize T cells infiltrating skin lesions in early SSc and investigate their capacity to affect production of type I collagen and interstitial collagenase (matrix metalloproteinase 1 [MMP‐1]) by dermal fibroblasts.

Methods

Four‐color cytometric analysis was used to characterize subset distribution and production of interferon‐γ (IFNγ) and interleukin‐4 (IL‐4) in T cell lines generated from the skin of patients with SSc. T cell clones were generated, and their capacity to modulate collagen and MMP‐1 production by fibroblasts derived from patients with SSc and from normal individuals was assessed. Neutralizing reagents were used to identify T cell mediators involved in fibroblast modulation.

Results

The skin of individuals with early‐stage SSc contained T cells preferentially producing high levels of IL‐4. Cloned CD4+ Th2‐like cells inhibited collagen production by normal fibroblasts. Th2 cell‐dependent inhibition was, at least in part, contact‐dependent, was essentially mediated by tumor necrosis factor α (TNFα), and was dominant over the enhancement induced by profibrotic IL‐4 and transforming growth factor β cytokines. The simultaneous induction of MMP‐1 production confirmed the specificity of these observations. To be inhibitory, Th2 cells required activation by CD3 ligation. Th2 cells were less potent than were Th1 cells in inhibiting collagen production by normal fibroblasts via cell‐to‐cell interaction, and SSc fibroblasts were resistant to inhibition.

Conclusion

These findings indicate that, despite their production of IL‐4, Th2 cells reduce type I collagen synthesis by dermal fibroblasts because of the dominant effect of TNFα, and suggest that strategies based on TNFα blockade aimed at controlling fibrosis in SSc may be unwise.

     

Role of B cells in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is an orphan disease characterized by progressive fibrosis of the skin and internal organs. Aside from vasculopathy and fibrotic processes, its pathogenesis involves an aberrant activation of immune cells, among which B cells seem to play a significant role. Indeed, B cell homeostasis is disturbed during SSc: the memory subset is activated and displays an increased susceptibility to apoptosis, which is responsible for their decreased number. This chronic loss of B cells enhances bone marrow production of the naïve subset that accounts for their increased number in peripheral blood. This permanent activation state can be explained mainly by two mechanisms: a dysregulation of B cell receptor (BCR) signaling, and an overproduction of B cell survival signals, B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL). These disturbances of B cell homeostasis induce several functional anomalies that participate in the inflammatory and fibrotic events observed during SSc: autoantibody production (some being directly pathogenic); secretion of pro-inflammatory and pro-fibrotic cytokines (interleukin-6); direct cooperation with other SSc-involved cells [fibroblasts, through transforming growth factor-β (TGF-β) signaling, and T cells]. These data justify the evaluation of anti-B cell strategies as therapeutic options for SSc, such as B cell depletion or blockage of B cell survival signaling.     

Scleroderma,fibroblasts, signaling,and excessive extracellular matrix

Excessive extracellular matrix (ECM) deposition in the skin, lung, and other organs is a hallmark of systemic sclerosis (SSc). The pathogenesis of SSc is still poorly understood, but increasing evidence suggests that various cytokines such as transforming growth factor (TGF)-β and their signaling pathways are key mediators of tissue fibrosis as a consequence of ECM accumulation in the pathogenesis of fibrosis such as SSc. TGF-β regulates diverse biologic activities including cell growth, cell death or apoptosis, cell differentiation, and ECM synthesis. TGF-β is known to induce the expression of ECM proteins in mesenchymal cells, and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the ECM. This paper focuses on the possible role of ECM, various cytokines, especially TGF-β signal transduction pathways in the pathogenesis of fibrosis in SSc.     

T cells expressing allograft inflammatory factor 1 display increased chemotaxis and induce a profibrotic phenotype in normal fibroblasts in vitro

OBJECTIVE: Allograft inflammatory factor 1 (AIF-1) was first identified in rat cardiac allografts undergoing chronic rejection. The vasculopathy of chronic allograft rejection is strikingly similar to that seen in patients with systemic sclerosis (SSc). We previously demonstrated AIF-1 expression in inflammatory cells infiltrating skin and lungs from SSc patients, but its role in SSc pathogenesis is unknown. The present study was undertaken to investigate the effects of AIF-1 on T cell migration and production of cytokines capable of modulating normal dermal fibroblast functions. METHODS: Stably transfected Jurkat T cells expressing 2 AIF-1 splicing variants were prepared, and their migration toward fibroblast monolayers assayed in Transwell cultures. Cytokine production was assessed by real-time polymerase chain reaction (PCR) and multiplex enzyme-linked immunosorbent assay. Fibroblast gene expression was quantified by real-time PCR, and collagen production by Western blot analysis of culture media. RESULTS: AIF-1 significantly increased Jurkat T cell migration toward fibroblast monolayers. Expression of AIF-1 isoform 2 in Jurkat T cells up-regulated their production of interleukin-4 (IL-4) and IL-17. Conditioned media from AIF-1-expressing clones stimulated synthesis of types I and III collagen and expression of IL-6, transforming growth factor beta, endothelin receptor, and alpha-smooth muscle actin by normal dermal fibroblasts. CONCLUSION: These results suggest that AIF-1 may participate in the early pathogenesis of SSc by promoting tissue T cell infiltration and production of cytokines capable of inducing the expression of a fibrotic phenotype in normal fibroblasts.     

Monocyte chemoattractant proteins in the pathogenesis of systemic sclerosis

Activation of the immune system and increased synthesis of extracellular matrix proteins by fibroblasts are hallmarks in the pathogenesis of SSc. The molecular mechanisms underlying the infiltration of inflammatory cells into the skin and the subsequent activation of fibroblasts are still largely unknown. Chemokines are a family of small molecules that are classified according to the position of the NH(2)-terminal cysteine motif. Recent data indicate that chemokines and in particular two members of the subfamily of monocyte chemoattractant proteins, MCP-1 (CCL-2) and MCP-3 (CCL-7), might be involved in the pathogenesis of SSc. MCP-1 and -3 are overexpressed by SSc fibroblasts and in skin lesions from SSc patients compared to healthy controls. MCP-1 and -3 are chemotactic for inflammatory cells and stimulate their migration into the skin. In addition to their pro-inflammatory effects, MCP-1 and -3 contribute to tissue fibrosis by activating the synthesis of extracellular matrix proteins in SSc fibroblasts. Therapeutic strategies targeting MCP-1 have revealed promising results in several animal models of SSc. Antagonists against the receptor CCR2 are currently tested in clinical trials of a variety of diseases and also represent interesting candidates for target-directed therapy in SSc.     

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.

     

Monocyte chemoattractant protein 1 released from glycosaminoglycans mediates its profibrotic effects in systemic sclerosis via the release of interleukin‐4 from T cells

Objective

Monocyte chemoattractant protein 1 (MCP‐1; CCL2) has been implicated in the pathogenesis of fibrotic diseases and is up‐regulated in patients with systemic sclerosis (SSc). The aim of the present study was to examine the mechanisms by which MCP‐1 mediates its profibrotic effects in the setting of SSc.

Methods

The expression of receptors for MCP‐1 on dermal fibroblasts was analyzed by real‐time polymerase chain reaction and fluorescence‐activated cell sorting. The ability of extracellular matrix proteins to bind and release MCP‐1 was quantified by enzyme‐linked immunosorbent assay. Th0 cells were isolated using a magnetic‐activated cell sorting system and were stimulated twice in the presence of MCP‐1. The synthesis of collagen was measured using the Sircol collagen assay kit.

Results

The glycosaminoglycan chondroitin sulfate, but not fibronectin or collagens, bound and released MCP‐1 in a time‐dependent manner. MCP‐1 that was released from chondroitin sulfate induced the differentiation of interleukin‐4 (IL‐4)–producing T cells in a dose‐dependent manner. In turn, dermal fibroblasts from patients with SSc expressed IL‐4 receptor, and stimulation with IL‐4 significantly increased the production of collagen in dermal fibroblasts. In contrast, CCR2a and CCR2b, as well as D6 and US28 (other potential receptors of MCP‐1), were not detectable in SSc and normal fibroblasts, and their expression was not induced by platelet‐derived growth factor, IL‐1β, or IL‐4. In addition, MCP‐1 had no direct effects on collagen production by fibroblasts.

Conclusion

MCP‐1 has no direct effects on dermal fibroblasts but contributes to fibrosis in patients with SSc by inducing the differentiation of IL‐4–producing T cells. Because MCP‐1 has both proinflammatory and profibrotic effects, pharmacologic targeting of MCP‐1 could be a promising therapeutic approach in SSc.

     

Distinct expression of adhesion molecules on skin fibroblasts from patients with diffuse and limited systemic sclerosis. A pilot study

OBJECTIVE:. Systemic sclerosis (SSc) is characterized by excessive production of collagen and other components of the extracellular matrix (ECM) by fibroblasts. The ECM receptors, integrins and CD44 (hyaluronan receptor), play a key role in the homeostasis of connective tissue and may also have a role in the pathogenesis of fibrosis. We investigated the expression of integrins and CD44 on skin fibroblasts from patients with limited and diffuse SSc. METHODS: We studied 13 patients with SSc, 8 with limited SSc, and 5 with diffuse SSc, and 8 control subjects. Fibroblasts were isolated and cultured from biopsies taken from the lesional skin of the second finger of the left hand. Cell-surface expression of beta1, beta3, alpha1-alpha6, alphav integrins, and CD44 was evaluated by immunofluorescence and flow cytometry analysis. RESULTS: Fibroblasts from limited SSc showed significantly decreased expression of alpha2, alpha3, alpha4 integrins, while diffuse SSc fibroblasts had significantly reduced expression of alpha5, alphav integrins, and CD44. Diffuse SSc also had significantly increased expression of alpha6 integrin on fibroblasts. In controls, the expression of alpha4 and alpha5 correlated positively, while in limited and diffuse SSc it did not. CONCLUSION: This is the first study evaluating separately the expression of adhesion molecules on skin fibroblasts from limited and diffuse subsets of SSc. We detected a distinct pattern of expression with decrease of collagen and fibronectin receptors in limited SSc, and downregulation of fibronectin and hyaluronan receptors in diffuse SSc. These results suggest that changes of fibroblasts/ECM interactions and mechanisms underlying the pathogenesis of fibrosis in SSc may differ in the single subset of the disease.     

Potential roles of CCL2/monocyte chemoattractant protein-1 in the pathogenesis of cutaneous sclerosis

Scleroderma is a connective tissue disease of unknown etiology characterized by the excessive deposition of extracellular matrix in the skin. Cellular infiltrates of certain immune cells and pro-inflammatory mediators are suggested to play a crucial role in cutaneous fibrosis, forming complicated networks between fibroblasts and immune cells and/or cell-cell communications. Tissue-selective trafficking of leukocytes is mediated by combinations of adhesion molecules and chemokines. Although chemokines and their receptors are considered to be mediators of inflammation and fibrosis in scleroderma, their pathophysiological role remains incompletely understood. Recent studies suggest that CCL2/monocyte chemoattractant protein-1 plays an important role in the fibrotic process, including liver fibrosis, pulmonary fibrosis, and scleroderma. This review summarizes recent findings of the potential roles of CCL2 in cutaneous sclerosis in experimental animal models of scleroderma as well as human scleroderma.     

Hypoxia-induced increase in the production of extracellular matrix proteins in systemic sclerosis

OBJECTIVE: Insufficient angiogenesis with tissue ischemia and accumulation of extracellular matrix are hallmarks of systemic sclerosis (SSc). Based on the severely decreased oxygen levels in the skin of patients with SSc, we aimed to investigate the role of hypoxia in the pathogenesis of SSc. METHODS: Subtractive hybridization was used to compare gene expression in dermal fibroblasts under hypoxic and normoxic conditions. Dermal fibroblasts were further characterized by exposure to different concentrations of oxygen and for different time periods as well as by interference with hypoxia-inducible factor 1alpha (HIF-1alpha). The systemic normobaric hypoxia model in mice was used for in vivo analyses. RESULTS: Several extracellular matrix proteins and genes involved in extracellular matrix turnover, such as thrombospondin 1, proalpha2(I) collagen, fibronectin 1, insulin-like growth factor binding protein 3, and transforming growth factor beta-induced protein, were induced by hypoxia in SSc and healthy dermal fibroblasts. The induction of these genes was time- and dose-dependent. Experiments with HIF-1alpha-knockout mouse embryonic fibroblasts, deferoxamine/cobalt ions as chemical stabilizers of HIF-1alpha, and HIF-1alpha small interfering RNA consistently showed that extracellular matrix genes are induced in dermal fibroblasts by HIF-1alpha-dependent, as well as HIF-1alpha-independent, mechanisms. Using the systemic normobaric hypoxia mouse model, we demonstrated that dermal hypoxia leads to the induction of the identified extracellular matrix genes in vivo after both short exposure and prolonged exposure to hypoxia. CONCLUSION: These data show that hypoxia contributes directly to the progression of fibrosis in patients with SSc by increasing the release of major extracellular matrix proteins. Targeting of hypoxia pathways might therefore be of therapeutic value in patients with SSc.     

Cytokines as therapeutic targets for the gastrointestinal manifestations of scleroderma.

Systemic sclerosis (SSc), or scleroderma, is a connective tissue disorder characterized by progressive fibrosis of the skin and internal organs. It has significance for gastroenterologists because the gastrointestinal tract is involved in 90% of SSc patients, who often present with esophageal dysfunction. Though the exact pathogenesis of SSc is unknown, there is increasing evidence supporting an immune mechanism. Cytokines are the soluble mediators of immune activation, altered fibroblast proliferation and extracellular matrix accumulation in SSc and thereby provide important therapeutic targets. In the present review, the involvement of cytokines in SSc is discussed with particular emphasis on cytokines and growth factors that have been implicated in the disease process and likely play an important role in the gastrointestinal manifestations of scleroderma. The role of cytokines as therapeutic targets in scleroderma forms the basis of this timely review.     

Periostin in Skin Tissue Skin-Related Diseases

Extracellular matrix (ECM) is not only involved in the maintenance of normal physiological tissue but also in interactions with other ECM components, tissue remodeling, and modulating immune responses. The skin provides a distinctive environment characterized by rich fibroblasts producing various ECM proteins, epithelial-mesenchymal interactions, and immune responses induced by external stimuli.Recently, periostin—a matricellular protein—has been highlighted for its pivotal functions in the skin. Analysis of periostin null mice has revealed that periostin contributes to collagen fibrillogenesis, collagen cross-linking, and the formation of ECM meshwork via interactions with other ECM components. Periostin expression is enhanced by mechanical stress or skin injury; this is indicative of the physiologically protective functions of periostin, which promotes wound repair by acting on keratinocytes and fibroblasts. Along with its physiological functions, periostin plays pathogenic roles in skin fibrosis and chronic allergic inflammation. In systemic sclerosis (SSc) patients, periostin levels reflect the severity of skin fibrosis. Periostin null mice have shown reduced skin fibrosis in a bleomycin-induced SSc mouse model, indicating a key role of periostin in fibrosis. Moreover, in atopic dermatitis (AD), attenuated AD phenotype has been observed in periostin null mice in a house dust mite extract-induced AD mouse model. Th2 cytokine-induced periostin acts on keratinocytes to produce inflammatory cytokines that further enhance the Th2 response, thereby sustaining and amplifying chronic allergic inflammation. Thus, periostin is deeply involved in the pathogenesis of AD and other inflammation-related disorders affecting the skin. Understanding the dynamic actions of periostin would be key to dissecting pathogenesis of skin-related diseases and to developing novel therapeutic strategies.     

Decreased expression of caveolin 1 in patients with systemic sclerosis: crucial role in the pathogenesis of tissue fibrosis

OBJECTIVE: Recent studies have implicated caveolin 1 in the regulation of transforming growth factor beta (TGFbeta) downstream signaling. Given the crucial role of TGFbeta in the pathogenesis of systemic sclerosis (SSc), we sought to determine whether caveolin 1 is also involved in the pathogenesis of tissue fibrosis in SSc. We analyzed the expression of CAV1 in affected SSc tissues, studied the effects of lack of expression of CAV1 in vitro and in vivo, and analyzed the effects of restoration of caveolin 1 function on the fibrotic phenotype of SSc fibroblasts in vitro. METHODS: CAV1 expression in tissues was analyzed by immunofluorescence and confocal microscopy. The extent of tissue fibrosis in Cav1-knockout mice was assessed by histologic/histochemical analyses and quantified by hydroxyproline assays. Cav1-null and SSc fibroblast phenotypes and protein production were analyzed by real-time polymerase chain reaction, immunofluorescence, Western blot, and multiplexed enzyme-linked immunosorbent assay techniques. The effects of restoration of caveolin 1 function in SSc fibroblasts in vitro were also examined using a cell-permeable recombinant CAV1 peptide. RESULTS: CAV1 was markedly decreased in the affected lungs and skin of SSc patients. Cav1-knockout mice developed pulmonary and skin fibrosis. Down-regulation of caveolin 1 was maintained in cultured SSc fibroblasts, and restoration of caveolin 1 function in vitro normalized their phenotype and abrogated TGFbeta stimulation through inhibition of Smad3 activation. CONCLUSION: Caveolin 1 appears to participate in the pathogenesis of tissue fibrosis in SSc. Restoration of caveolin 1 function by treatment with a cell-permeable peptide corresponding to the CAV1 scaffolding domain may be a novel therapeutic approach in SSc.     

T cells and B cells in the pathogenesis of systemic sclerosis: Recent insights and therapeutic opportunities

Among the earliest pathologic events in systemic sclerosis (SSc) is the infiltration of mononuclear cells into the skin lesion. This inflammatory cell in filtration precedes the development of fibrosis, suggesting an integral role for the presence of these cells in the fibrotic events observed in the lesion. However, immunosuppressive therapies that are effective in other autoimmune disease have not been successful in the treatment of SSc, making the clinical management of this disease very difficult. The aim of this paper is to review the latest findings regarding the activation and the functional polarization of T cells and their role in the pathogenesis of SSc. Furthermore, the potential role of B cells, a hitherto scantily investigated inflammatory cell in SSc, is discussed. Understanding the interplay between T and B cells, and the processes that promote the fibrotic cytokine pattern seen in these patients is of utmost importance for the development of effective therapies to treat the clinical complications.