Expression and function of surface antigens on scleroderma fibroblasts

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.

Centromere defects, chromosome instability, and cGAS-STING activation in systemic sclerosis

Centromere defects in Systemic Sclerosis (SSc) have remained unexplored despite the fact that many centromere proteins were discovered in patients with SSc. Here we report that lesion skin fibroblasts from SSc patients show marked alterations in centromeric DNA. SSc fibroblasts also show DNA damage, abnormal chromosome segregation, aneuploidy (only in diffuse cutaneous (dcSSc)) and micronuclei (in all types of SSc), some of which lose centromere identity while retaining centromere DNA sequences. Strikingly, we find cytoplasmic "leaking" of centromere proteins in limited cutaneous SSc (lcSSc) fibroblasts. Cytoplasmic centromere proteins co-localize with antigen presenting MHC Class II molecules, which correlate precisely with the presence of anti-centromere antibodies. CENPA expression and micronuclei formation correlate highly with activation of the cGAS-STING/IFN-β pathway as well as markers of reactive oxygen species (ROS) and fibrosis, ultimately suggesting a link between centromere alterations, chromosome instability, SSc autoimmunity, and fibrosis.

Pathophysiology of systemic sclerosis (scleroderma)

Systemic sclerosis (scleroderma) is an autoimmune-triggered chronic fibrosing disease that affects the skin and many other organs. Its pathophysiology is complex and involves an early endothelial damage, an inflammatory infiltrate and a resulting fibrotic reaction. Based on a predisposing genetic background, an altered balance of the acquired and the innate immune system leads to the release of many cytokines and chemokines as well as autoantibodies, which induce the activation of fibroblasts with the formation of myofibroblasts and the deposition of a stiff and rigid connective tissue. A curative treatment is still not available but remarkable progress has been made in the management of organ complications. In addition, several breakthroughs in the pathophysiology have led to new therapeutic concepts. Based on these, many new compounds have been developed during the last years, which target these different pathways and offer specific therapeutic approaches.

Selective deletion of connective tissue growth factor attenuates experimentally-induced pulmonary fibrosis and pulmonary arterial hypertension

Connective tissue growth factor (CTGF, CCN2) is a matricellular protein which plays key roles in normal mammalian development and in tissue homeostasis and repair. In pathological conditions, dysregulated CCN2 has been associated with cancer, cardiovascular disease, and tissue fibrosis. In this study, genetic manipulation of the CCN2 gene was employed to investigate the role of CCN2 expression in vitro and in experimentally-induced models of pulmonary fibrosis and pulmonary arterial hypertension (PAH). Knocking down CCN2 using siRNA reduced expression of pro-fibrotic markers (fibronectin p < 0.01, collagen type I p < 0.05, α-SMA p < 0.0001, TIMP-1 p < 0.05 and IL-6 p < 0.05) in TGF-β-treated lung fibroblasts derived from systemic sclerosis patients. In vivo studies were performed in mice using a conditional gene deletion strategy targeting CCN2 in a fibroblast-specific and time-dependent manner in two models of lung disease. CCN2 deletion significantly reduced pulmonary interstitial scarring and fibrosis following bleomycin-instillation, as assessed by fibrotic scores (wildtype bleomycin 3.733 ± 0.2667 vs CCN2 knockout (KO) bleomycin 4.917 ± 0.3436, p < 0.05) and micro-CT. In the well-established chronic hypoxia/Sugen model of pulmonary hypertension, CCN2 gene deletion resulted in a significant decrease in pulmonary vessel remodelling, less right ventricular hypertrophy and a reduction in the haemodynamic measurements characteristic of PAH (RVSP and RV/LV + S were significantly reduced (p < 0.05) in CCN2 KO compared to WT mice in hypoxic/SU5416 conditions). These results support a prominent role for CCN2 in pulmonary fibrosis and in vessel remodelling associated with PAH. Therefore, therapeutics aimed at blocking CCN2 function are likely to benefit several forms of severe lung disease.

Potential Biomarkers in Systemic Sclerosis: A Literature Review and Update

Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by dysregulation of the immune system, vascular damage, and fibrosis of the skin and internal organs. Patients with SSc show a heterogeneous phenotype and a range of clinical courses. Therefore, biomarkers that are helpful for precise diagnosis, prediction of clinical course, and evaluation of the therapeutic responsiveness of disease are required in clinical practice. SSc-specific autoantibodies are currently used for diagnosis and prediction of clinical features, as other biomarkers have not yet been fully vetted. Krebs von den Lungen-6 (KL-6), surfactant protein-D (SP-D), and CCL18 have been considered as serum biomarkers of SSc-related interstitial lung disease. Moreover, levels of circulating brain natriuretic peptide (BNP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) can provide diagnostic information and indicate the severity of pulmonary arterial hypertension. Assessment of several serum/plasma cytokines, chemokines, growth factors, adhesion molecules, and other molecules may also reflect the activity or progression of fibrosis and vascular involvement in affected organs. Recently, microRNAs have also been implicated as possible circulating indicators of SSc. In this review, we focus on several potential SSc biomarkers and discuss their clinical utility.

The immunopathogenesis of fibrosis in systemic sclerosis

Systemic sclerosis (SSc) is an idiopathic systemic autoimmune disease. It is characterized by a triad of hallmarks: immune dysfunction, fibrosis and vasculopathy. Immune dysfunction in SSc is characterized by the activation and recruitment of immune cells and the production of autoantibodies and cytokines. How immune abnormalities link the fibrosis and vasculopathy in SSc is poorly understood. A plethora of immune cell types are implicated in the immunopathogenesis of SSc, including T cells, B cells, dendritic cells, mast cells and macrophages. How these different cell types interact to contribute to SSc is complicated, and can involve cell-to-cell interactions and communication via cytokines, including transforming growth factor (TGF)-β, interleukin (IL)-6 and IL-4. We will attempt to review significant and recent research demonstrating the importance of immune cell regulation in the immunopathogenesis of SSc with a particular focus on fibrosis.

Biomarkers in systemic sclerosis: Their potential to predict clinical courses

The concept of a biomarker was defined as "a characteristic marker that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention" by the National Institutes of Health Biomarkers Definitions Working group in 2001. Clinical features, disease progress, therapeutic response and prognosis are heterogeneous among patients with systemic sclerosis (SSc). Therefore, biomarkers that can predict these matters are required for the progress of clinical practice. At present, SSc-specific autoantibodies are the most useful biomarkers for diagnosis and predicting clinical features. Otherwise, biomarkers specific only for SSc have not been identified yet. The glycoprotein krebs von den Lungen-6, surfactant protein-D and CCL18 are promising serum biomarkers of SSc-related interstitial lung diseases. Serum/plasma levels of brain natriuretic peptide and serum N-terminal pro-brain natriuretic peptide have been used as biomarkers for SSc-related pulmonary arterial hypertension. Other potential serum/plasma biomarkers for fibrosis and vascular involvement of SSc are connective tissue growth factor, interleukin-6, CCL2, CXCL4, intercellular adhesion molecule (ICAM)-1, P-selectin, vascular endothelial growth factor, von Willebrand factor, endostatin, endoglin and endothelin-1. In our multicenter prospective studies of Japanese early SSc, serum ICAM-1 levels were predictive for subsequent respiratory dysfunction and serum levels of CXCL8 and P-selectin were predictive for subsequent physical disability. Further large, multicenter, prospective, longitudinal studies will be needed to identify and validate critical biomarkers of SSc.

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.

Effects of the immunosuppressant rapamycin on the expression of human α2(I) collagen and matrix metalloproteinase 1 genes in scleroderma dermal fibroblasts

BACKGROUND

Rapamycin has been shown to exert an anti-fibrotic effect on skin fibrosis in a certain subset of patients with systemic sclerosis (SSc) and in bleomycin-treated animal models.

OBJECTIVES

To investigate the mechanism responsible for the anti-fibrotic effect of rapamycin especially by focusing on human α2(I) collagen (COL1A2) and matrix metalloproteinase 1 (MMP1) genes in normal and systemic sclerosis (SSc) dermal fibroblasts.

METHODS

The expression levels of type I procollagen and MMP1 proteins were analyzed by immunoblotting and the mRNA levels of COL1A2 and MMP1 genes were evaluated by quantitative real-time RT-PCR. The activities of COL1A2 and MMP1 promoters were determined by reporter analysis.

RESULTS

Rapamycin significantly decreased the levels of type I procollagen protein and COL1A2 mRNA, while significantly increasing the levels of MMP1 protein and mRNA in normal dermal fibroblasts. Similar effects of rapamycin were also observed in SSc dermal fibroblasts. Importantly, the inhibitory and stimulatory effects of rapamycin on the mRNA levels of COL1A2 and MMP1 genes, respectively, were significantly greater in SSc dermal fibroblasts than in normal dermal fibroblasts. In SSc dermal fibroblasts, rapamycin affected the expression of COL1A2 gene at the post-transcriptional level. In contrast, rapamycin altered the expression of MMP1 gene at the transcriptional level through the JNK/c-Jun signaling pathway in those cells.

CONCLUSION

Rapamycin has a potential to directly regulate the deposition of type I collagen in extracellular matrix through inhibiting type I collagen synthesis and promoting its degradation by MMP1, suggesting that this drug is useful for the treatment of SSc.

Serum adhesion molecule levels as prognostic markers in patients with early systemic sclerosis: a multicentre, prospective, observational study

Objective

To assess the utility of circulating adhesion molecule levels as a prognostic indicator of disease progression in systemic sclerosis (SSc) patients with early onset disease.

Methods

Ninety-two Japanese patients with early onset SSc presenting with diffuse skin sclerosis and/or interstitial lung disease were registered in a multicentre, observational study. Concentrations of intercellular adhesion molecule (ICAM) −1, E-selectin, L-selectin, and P-selectin in serum samples from all patients were measured by enzyme-linked immunosorbent asssay (ELISA). In 39 patients, adhesion molecule levels were measured each year for four years. The ability of baseline adhesion molecule levels to predict subsequent progression and severity in clinical and laboratory features were evaluated statistically.

Results

At their first visit, serum levels of ICAM-1, E-selection, P-selectin were significantly elevated and serum L-selectin levels were significantly reduced in patients with SSc compared with healthy controls. Overall, serum ICAM-1 levels at each time point were significantly inversely associated with the %vital capacity (VC) of the same time and subsequent years by univariate analysis. The initial serum ICAM-1 levels were significantly inversely associated with the %VC at the fourth year by multiple regression analysis. The initial serum P-selectin levels were significantly associated with the health assessment questionnaire disability index (HAQ-DI) at the fourth year by multiple regression analysis. Initial adhesion molecule levels were not significantly associated with other clinical features including skin thickness score. Baseline adhesion molecule levels were not significantly associated with subsequent rate of change of clinical parameters.

Conclusion

In patients with SSc, serum levels of ICAM-1 and P-selectin may serve as prognostic indicators of respiratory dysfunction and physical disability, respectively. Further longitudinal studies of larger populations are needed to confirm these findings.

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.

T cells in systemic sclerosis: a reappraisal

SSc is an autoimmune disease characterized by inflammation and extracellular matrix deposition that ultimately leads to loss of organ function. T cells appear to play a prominent role in its pathogenesis. The evidence for this comes from their being at the site of fibrosis, their activated phenotype and alteration in their number and frequency in peripheral blood. This review examines the role of T cells in the pathogenesis of SSc and specifically examines the key soluble profibrotic mediators (IL-4, IL-6, IL-13) secreted by Th2 cells and their interactions with fibroblasts that deposit excess extracellular matrix leading to fibrosis. We finally examine possible therapeutic options in targeting T-cell mediators to disrupt the cellular interactions between T cells and fibroblasts that serve to drive the fibrotic response. One of the factors driving fibrosis is IL-6 and this can be neutralized in vivo not only to limit IL-6-driven tissue fibrosis but concomitantly to suppress switching of Tregs to Th17 T cells that will provide more IL-6, thus perpetuating the fibrosis. Taken together, these data implicate the role of T cells in SSc and suggest that Th2-polarized T cells and the fibrotic mediators subsequently released directly induce fibrosis. Targeting such cytokines may be therapeutic not only in SSc but more generally in diseases where fibrosis is directed by inflammatory signals.

Potential immunologic targets for treating fibrosis in systemic sclerosis: a review focused on leukocytes and cytokines

OBJECTIVES

Systemic sclerosis (SSc) is a connective tissue disease characterized by tissue fibrosis. Although the pathogenesis remains unclear, a variety of cells contribute to the fibrotic process via interactions with each other and production of various cytokines. Recent literature related to the immunologic pathogenesis and future strategies for treating the fibrosis of SSc are discussed and, especially, this literature-based review that includes the authors' perspective, focused on leukocytes and cytokines.

METHODS

A PubMed search for articles published between January 2005 and January 2012 was conducted using the following keywords: systemic sclerosis, leukocyte, cytokine, growth factor, and chemokine. The reference lists of identified articles were searched for further articles.

RESULTS

Targeting profibrogenic cytokines, including transforming growth factor-β, is still a very active area of research in SSc and most cellular studies have focused on the roles of fibroblasts in SSc. However, a growing number of recent studies indicate a role for B cells in the development of SSc and other autoimmune diseases such as systemic lupus erythematosus. Therefore, B-cell-targeted therapies, including currently available monoclonal antibodies against CD19, CD20, CD22, and B-cell-activating factor, belonging to the tumor necrosis factor family represent possible treatment options. Furthermore, the modulation of T-cell costimulatory molecules such as a recombinant fusion protein of cytotoxic T-lymphocyte antigen-4 may be as effective in SSc as it is in treating other autoimmune diseases. Approaches to antagonize interleukin (IL)-1, IL-6, or IL-17A signaling may also be attractive.

CONCLUSIONS

This review describes recent advances in the treatment of fibrosis in SSc patients focused on immunologic strategies, such as leukocyte- or cytokine-targeted therapies.

Th17 peripheral cells are increased in diffuse cutaneous systemic sclerosis compared with limited illness: a cross-sectional study

Systemic Sclerosis (SSc) is an autoimmune disease characterized by fibrosis and vasculopathy. A key feature is the presence of T cells in inflammatory lesions. To establish the differences in peripheral blood T helper (Th) subpopulations in diffuse cutaneous (dc) and limited cutaneous (lc) SSc patients, blood samples from 57 dcSSc and 78 lcSSc patients were obtained. Controls were collected from healthy volunteers (n = 16), active systemic lupus erythematosus (aSLE) patients (n = 13), and active rheumatoid arthritis (aRA) patients (n = 12). Mononuclear cells were analyzed by flow cytometry to determine Th1 (CD4+/IFN-γ+), Th2 (CD4+/IL-4+), Th17 (CD4+/IL-17+), and regulatory T cells (Tregs; CD4+/CD25+/Foxp3+) subsets. Th17 and Th1 subsets were increased in SSc groups versus healthy controls (P < 0.001) and aSLE patients (P < 0.001 for Th17 and P < 0.008 for Th1). Th2 cells were higher in dcSSc patients than in the healthy and aSLE groups (P = 0.03 and P = 0.009, respectively). Tregs were increased in the aRA group when compared with SSc patients and healthy controls (P ≤ 0.003). Patients with immunosuppressive treatment had lower numbers of Th17 and Th2 cells (P = 0.02). Our results shed further light into the preponderant role of Th17 and Th1 in patients with SSc. However, these findings certainly deserve to be studied in depth.

Junctional adhesion molecule-A is abnormally expressed in diffuse cutaneous systemic sclerosis skin and mediates myeloid cell adhesion

OBJECTIVE

To investigate the role of junctional adhesion molecule-A (JAM-A) in the pathogenesis of systemic sclerosis (SSc).

METHODS

Biopsy specimens from proximal and distal arm skin and serum were obtained from patients with SSc and normal volunteers. To determine the expression of JAM-A on SSc dermal fibroblasts and in SSc skin, cell surface ELISAs and immunohistology were performed. An ELISA was designed to determine the amount of soluble JAM-A (sJAM-A) in serum. Myeloid U937 cell-SSc dermal fibroblast and skin adhesion assays were performed to determine the role of JAM-A in myeloid cell adhesion.

RESULTS

The stratum granulosum and dermal endothelial cells (ECs) from distal arm SSc skin exhibited significantly decreased expression of JAM-A in comparison with normal volunteers. However, sJAM-A was increased in the serum of patients with SSc compared with normal volunteers. Conversely, JAM-A was increased on the surface of SSc compared with normal dermal fibroblasts. JAM-A accounted for a significant portion of U937 binding to SSc dermal fibroblasts. In addition, JAM-A contributed to U937 adhesion to both distal and proximal SSc skin.

CONCLUSIONS

JAM-A expression is dysregulated in SSc skin. Decreased expression of JAM-A on SSc ECs may result in a reduced response to proangiogenic basic fibroblast growth factor. Increased JAM-A expression on SSc fibroblasts may serve to retain myeloid cells, which in turn secrete angiogenic factors.

The proadhesive phenotype of systemic sclerosis skin promotes myeloid cell adhesion via ICAM-1 and VCAM-1

OBJECTIVE

SSc is characterized by microvascular abnormalities and leucocyte infiltration. Previous studies have suggested a proadhesive phenotype in SSc skin, but the functional consequences of this phenotype are not fully understood. Molecules known to mediate leucocyte adhesion include those present at intracellular junctions, such as junctional adhesion molecule-B (JAM-B), JAM-C and CD99, as well as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). The aim of this study was to examine adhesive interactions in SSc skin.

METHODS

The expression of JAM-B, JAM-C, CD99, ICAM-1 and VCAM-1 in SSc skin was determined by immunohistology and cell surface ELISA. Myeloid U937 cell-SSc dermal fibroblast adhesion assays or in situ adhesion assays to SSc skin were performed.

RESULTS

JAM-C and CD99 expression on endothelial cells (ECs) in SSc skin was decreased compared with expression on normal ECs. CD99 was overexpressed on mononuclear cells in SSc skin and on SSc dermal fibroblasts. Neutralizing ICAM-1 inhibited the binding of U937 cells to SSc dermal fibroblasts. In addition, blocking both ICAM-1 and VCAM-1 inhibited U937 cell adhesion to either proximal (less involved) or distal (more involved) SSc skin.

CONCLUSIONS

These studies show that JAM-C and CD99 are aberrantly expressed in SSc skin. However, these adhesion molecules do not mediate myeloid cell-SSc skin adhesion. In contrast, we demonstrate an important role for ICAM-1 and VCAM-1 in the retention of myeloid cells in SSc skin, suggesting that targeting these molecules may be useful SSc therapies.

Effect of nitric oxide and peroxynitrite on type I collagen synthesis in normal and scleroderma dermal fibroblasts

Nitric oxide ((.-)NO) is an important physiological signaling molecule and potent vasodilator. Recently, we have shown abnormal (.-)NO metabolism in the plasma of patients with systemic sclerosis (SSc), a disease that features excessive collagen overproduction as well as vascular dysfunction. The current study investigates the effects of (.-)NO and peroxynitrite (ONOO(-)) on secretion of type I collagen by SSc dermal fibroblasts, compared with those from normal dermal fibroblasts (CON) and a dermal fibroblast cell line (AG). Dermal fibroblasts were incubated with (.-)NO donors (SNP, DETA-NONOate) with or without the antioxidant ascorbic acid, or ONOO(-) for 24-72 h. In CON and AG fibroblasts, type I collagen was dose dependently decreased by SNP or DETA-NONOate. However, (.-)NO had no effect in SSc fibroblasts. Furthermore, the inhibition of collagen synthesis by (.-)NO was reversed by ascorbic acid and was not affected by 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one, an inhibitor of soluble guanyl cyclase, or 8-bromoguanosine cyclic 3',5'-monophosphate, a cGMP agonist. SNP also showed a significant up-regulation of matrix metalloproteinase-1 (MMP-1) protein and activity levels, an essential collagenase involved in collagen degradation, in the AG fibroblasts. Additionally, (.-)NO-treated fibroblasts had lower prolyl hydroxylase activity, an enzyme important in the post-translational processing of collagen, while there was no effect on total protein levels. There were no significant effects on type I collagen levels when dermal fibroblasts were treated with ONOO(-). Taken together, ()NO inhibits collagen secretion in normal dermal fibroblasts but regulation is lost in SSc fibroblasts, while ONOO(-) itself is ineffective. (.-)NO inhibition of collagen was by cGMP-independent regulatory mechanisms and in part may be due to up-regulation of MMP-1 and/or inhibition of prolyl hydroxylase. These differences may contribute to the observed pathology of SSc.

Intercellular Adhesion Molecule-1 Deficiency Attenuates the Development of Skin Fibrosis in Tight-Skin Mice

The tight-skin (TSK/+) mouse, a genetic model for systemic sclerosis, develops cutaneous fibrosis. Although a fibrillin 1 gene mutation and immunological abnormalities have been demonstrated, the roles of adhesion molecules have not been investigated. To directly assess roles of adhesion molecules in skin fibrosis, TSK/+ mice lacking L-selectin and/or ICAM-1 were generated. The deficiency of ICAM-1, but not L-selectin, significantly suppressed ( approximately 48%) the development of skin sclerosis in TSK/+ mice. Similarly, ICAM-1 antisense oligonucleotides inhibited skin fibrosis in TSK/+ mice. Although T cell infiltration was modest into the skin of TSK/+ mice, ICAM-1 deficiency down-regulated this migration, which is consistent with the established roles of endothelial ICAM-1 in leukocyte infiltration. In addition, altered phenotype or function of skin fibroblasts was remarkable and dependent on ICAM-1 expression in TSK/+ mice. ICAM-1 expression was augmented on TSK/+ dermal fibroblasts stimulated with IL-4. Although growth or collagen synthesis of TSK/+ fibroblasts cultured with IL-4 was up-regulated, it was suppressed by the loss or blocking of ICAM-1. Collagen expression was dependent on the strain of fibroblasts, but not on the strain of cocultured T cells. Thus, our findings indicate that ICAM-1 expression contributes to the development of skin fibrosis in TSK/+ mice, especially via ICAM-1 expressed on skin fibroblasts.

Vasoactive Intestinal Peptide Inhibits Adhesion Molecule Expression in Activated Human Colon Serosal Fibroblasts by Preventing NF-κB Activation

BACKGROUND

Stricture formation in Crohn's disease (CD) occurs as a result of persistent intestinal inflammatory activation, which leads to enhanced adhesion molecule expression in serosal fibroblasts (SFs). Vasoactive intestinal peptide (VIP) has anti-inflammatory and immunoregulatory properties. Treatment with VIP prevents experimental CD in animal models at the clinical and pathologic levels. The present study reports the effect of VIP on the expression of intracellular adhesion molecule-1 (ICAM-1) in IL-1beta-stimulated human colon SFs.

MATERIALS AND METHODS

Primary human colon SFs were incubated with or without IL-1beta (10 ng/mL) in the presence or absence of VIP at various concentrations (0.1 to 100 nM) for designated time. Cell surface and cytosolic ICAM-1 expression were evaluated by flow cytometry and Western blot analysis, respectively. The DNA binding capacity of NF-kappaB was analyzed by electrophoretic mobility shift assay. The phosphorylation of IkappaB-alpha was examined by Western blot analysis.

RESULTS

VIP inhibited IL-1beta-induced expression of ICAM-1 in a dose-dependent manner. The IL-1beta-induced ICAM-1 was also inhibited by a potent inhibitor of NF-kappaB, MG132. VIP also decreased IL-1beta-induced NF-kappaB DNA binding capacity and phosphorylation of IkappaB-alpha.

CONCLUSION

VIP has an inhibitory effect on IL-1beta-induced ICAM-1 expression in SFs, which may be associated with NF-kappaB activity. This may make VIP potentially a novel therapeutic agent for preventing stricture formation in Crohn's disease.

Peripheral T lymphocytes from patients with early systemic sclerosis co-cultured with autologous fibroblasts undergo an oligoclonal expansion similar to that occurring in the skin

In recent years several reports have suggested that T cells may have a role in systemic sclerosis (SSc). The aim of our study was to investigate the dynamics of T cell repertoire in early SSc disease analysing a target organ, the skin, and the peripheral blood. To date, indeed, it is not clear if T cell expansions found in SSc reflect a general activation or result from specific antigen stimulation in the target organs. This is an important point to assess in order to characterize the role of T cells in the development of SSc. To address these questions we studied T cell repertoire by CDR3 length analysis in skin biopsies and peripheral blood obtained from patients affected by SSc and we found that a skewed T cell repertoire was present only in the biopsies. In order to characterize more effectively the meaning of these data, we performed co-cultures using fibroblasts and peripheral blood mononuclear cells (PBMCs) obtained from SSc patients. These experiments showed that same T cell expansions were detectable in the skin of SSc patients and in the cultures of PBMCs and autologous fibroblasts of the patients but not in their peripheral blood. Taken together, these data suggest that fibroblasts trigger specific T cell expansions in the early phase of SSc.

Constitutively phosphorylated Smad3 interacts with Sp1 and p300 in scleroderma fibroblasts

OBJECTIVE

To elucidate the role of transforming growth factor-beta (TGF-beta)/Smad signalling in the increased expression of the collagen gene in systemic sclerosis (SSc) fibroblasts.

METHODS

Dermal fibroblasts from seven patients with diffuse SSc of recent onset and from seven healthy individuals were studied. The expression levels of Smad2, Smad3 and Smad4 proteins were determined by immunoblotting. Smad3 phosphorylation and the interaction of Smad3 with Sp1 or p300 were analysed using immunoprecipitation. The effects of overexpression of Smad proteins or Sp1 on the human alpha2(I) collagen gene transcription were investigated with chloramphenicol acetyltransferase (CAT) assays using the -772 COL1A2/CAT construct.

RESULTS

Constitutive increased Smad3 phosphorylation was detected in SSc fibroblasts compared with normal fibroblasts. Increased interaction of Smad3 with Sp1 as well as p300 was also detected in SSc fibroblasts. The overexpression of Smad3 caused an increase of up to 5-fold in COL1A2 promoter activity in normal fibroblasts, while Smad3 caused a small increase in COL1A2 promoter activity in SSc fibroblasts. However, neither Smad2 nor Smad4 caused significant effects in COL1A2 promoter activity in normal fibroblasts or SSc fibroblasts. The overexpression of Sp1 caused further increase in COL1A2 promoter activity stimulated by TGF-beta in normal fibroblasts, but did not change COL1A2 promoter activity in the presence of TGF-beta in SSc fibroblasts. The combined overexpression of Smad3 and Sp1 significantly enhanced TGF-beta response in normal fibroblasts, but less markedly in SSc fibroblasts.

CONCLUSIONS

These results suggested that SSc fibroblasts are less sensitive to exogenous TGF-beta stimulation because they are already activated by the autocrine TGF-beta loop.

Changes in Soluble Adhesion Molecules in Gingival Crevicular Fluid Following Periodontal Surgery

BACKGROUND

Inflammation of periodontal tissues during postoperative wound healing is mediated by cell surface adhesion molecules. Soluble forms of these antigens have also been identified and shown to be important in immunoregulatory processes, but have previously not been investigated during periodontal repair and regeneration. The present study has examined the presence and possible changes in soluble intercellular adhesion molecule-1 (sICAM-1; CD54) and lymphocyte function-associated antigen-3 (sLFA-3; CD58) in gingival crevical fluid (GCF) following periodontal surgery.

METHODS

GCF samples were collected from four groups: 1) a guided tissue regeneration (GTR) test; 2) a GTR control, at least one complete tooth unit away from the periodontal defect; 3) a conventional flap (CF) surgery; and 4) a crown lengthening (CL). Sandwich enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of sICAM-1 and sLFA-3 in the GCF samples.

RESULTS

A marked increase in GCF volumes was found in all sites after surgery, although a persistent increase was associated only with the period of membrane retention at the GTR test sites. In addition, sICAM-1 and sLFA-3 were found in the GCF of healthy as well as diseased sites prior to treatment and the total amounts of both increased transiently following surgical intervention, especially sLFA-3. However, the concentrations of these GCF components, particularly sICAM-1, tended to decrease.

CONCLUSIONS

The temporal decrease in the concentration of sICAM-1 and sLFA-3 in GCF may serve to enhance inflammatory reactions at surgically-treated periodontal sites, thereby limiting repair and regeneration in the periodontium. These soluble adhesion molecules may thereby be of potential therapeutic value and might also be useful markers for monitoring periodontal wound healing.

Differential effects of the immunosuppressant FK-506 on human ?2(I) collagen gene expression and transforming growth factor ? signaling in normal and scleroderma fibroblasts

OBJECTIVE

To investigate the effects of FK-506 on the expression of the human alpha2(I) collagen gene and transforming growth factor beta (TGFbeta) signaling in normal and scleroderma fibroblasts.

METHODS

The expression levels of type I procollagen protein and alpha2(I) collagen messenger RNA (mRNA) were analyzed by immunoblotting and Northern blotting, respectively. The promoter activities of alpha2(I) collagen gene and 3TP-Lux were determined by transient transfection assay. Interaction between TGFbeta receptor type I and FK-506 binding protein 12 (FKBP12) was evaluated by immunoprecipitation.

RESULTS

FK-506 did not affect the basal expression of type I procollagen protein or alpha2(I) collagen mRNA, but it significantly reduced the TGFbeta1-induced expression of type I procollagen protein and alpha2(I) collagen mRNA in normal fibroblasts. The effect of FK-506 was regulated posttranscriptionally, but not transcriptionally. In scleroderma fibroblasts, FK-506 significantly reduced the expression of type I procollagen protein and alpha2(I) collagen mRNA through posttranscriptional regulation, but not transcriptional regulation. FK-506 increased the basal activity of the 3TP-Lux promoter, but it did not affect the TGFbeta1-induced promoter activity in normal fibroblasts. In contrast, FK-506 did not affect the basal or the TGFbeta1-induced 3TP-Lux promoter activity in scleroderma fibroblasts. Furthermore, FKBP12, which protects TGFbeta receptor type I from ligand-independent activation by TGFbeta receptor type II, constitutively dissociated from TGFbeta receptor type I in scleroderma fibroblasts.

CONCLUSION

FK-506 inhibits alpha2(I) collagen gene expression by reducing the stability of mRNA without exhibiting its activation effect on TGFbeta signaling in scleroderma fibroblasts.

Melanocytes are potential immunocompetent cells: evidence from recognition of immunological characteristics of cultured human melanocytes

The dendritic nature, the strategic location, and other accumulated evidence about the immunologic characteristics of melanocytes suggest that they are not only professional melanin producing cells but are also immunocompetent cells. In this study, we demonstrated that cultured melanocytes express low levels of some immunologically important surface markers such as intercellular adhesion molecule-1 and CD 40. Moreover, we report for the first time CD 40 expression by melanocytes can be up-regulated by interferon-gamma (IFN-gamma) stimulation. Optimal enhancement of CD 40 expression was observed at an IFN-gamma concentration of 300 U/ml after a co-culture period of 72 h. Maximal melanocyte-driven T lymphocyte proliferation and interleukin-12 secretion were also observed following the same treatment and proved to be CD 40-dependent. Our data further suggest that upon CD 40 ligation, melanocytes up-regulate their co-stimulating and adhesion molecules. In addition to previous descriptions about the melanocyte's antigen processing and presenting capacity, we therefore hypothesize a dynamic model in which melanocytes alternatively work as heterogeneous antigen presenting cells. As a result of CD 40 expression on the cell surface, melanocytes might contact and subsequently stimulate CD8+ cytotoxic T lymphocytes directly via CD 40-CD 40 L interaction in some cases.

Long-term therapy with plasma exchange in systemic sclerosis: effects on laboratory markers reflecting disease activity

Plasma exchange (PEX) is a technique that has been applied to the treatment of many immunological disorders, including connective tissue diseases. The crucial role of some humoral factors in the pathogenesis of systemic sclerosis (SSc) could explain the good clinical results obtained in terms of slowing down the disease progression, but the efficacy of PEX in the treatment of SSc is not yet well defined, owing to the lack of controlled studies and validated parameters of disease activity. To demonstrate the long-term efficacy of PEX in the treatment of SSc we treated a group of 28 SSc patients affected with recent onset and/or rapidly progressive disease. Most of these had a diffuse form of SSc, with anti-Sc170 antibody as a disease marker. Before and after long-term PEX treatment we evaluated disease activity parameters including the serum levels of interleukin 2 soluble receptor (sIL-2R) and aminoterminal type III procollagen peptide (PIIINP), plus the percentage of DR+ T cells in the peripheral blood. We also assessed clinical parameters of total skin score and total visceral score. The same parameters were evaluated in 25 SSc patients who did not satisfy the admission criteria for PEX, treated long-term with drugs only. At baseline, serum PIIINP and sIL-2R levels and the percentage of DR+ T cells were significantly increased in PEX patients as compared to others. Following long-term PEX treatment, all the laboratory parameters significantly decreased and the clinical scores showed a slight but not significant improvement. Conversely, in the other group of SSc patients treated for the same period with drugs only, no significant change of laboratory parameters was detected and the clinical scores slightly worsened. Our data suggest that long-term PEX therapy seems to be effective in slowing down the clinical course of patients with severe and rapidly progressive SSc.

Flow cytometry analysis of guided tissue regeneration-associated human periodontal cells

BACKGROUND

Expanded polytetrafluoroethylene (ePTFE) barrier membranes have been widely used for guided tissue regeneration (GTR) of the human periodontal ligament (PL). However, the precise cellular and molecular events involved in the re-growth of the new tissue are still unclear.

METHODS

Retrieved membranes and the newly-regenerated soft tissue (RT) underlying the membranes were used to examine the cells associated with GTR compared with normal human PL and gingival cells. Flow cytometry (FCM) was used, for the first time, to analyze the spindle-shaped fibroblast-like cells which were adherent to these membranes and the cells which grew out of the RT.

RESULTS

The results showed that the membrane-associated (M) cells had the lowest rate of proliferation and appeared to be larger and more granular than the other types of cell. Moreover, both the M- and RT-derived cells were found to express higher levels of the extracellular matrix (ECM) proteins collagen type 1, fibronectin, tenascin, and decorin. In addition, evidence based on FCM profiles identified distinct sub-populations of GTR cells in which fibronectin expression was markedly up-regulated compared with normal PL cells and which also differed in size and granularity.

CONCLUSIONS

The results of this study show that cells associated with GTR barrier membranes and with the underlying tissue appear to have distinct phenotypic and functional activities consistent with the production of new periodontal connective tissue and periodontal regeneration.

The role of hepatocyte growth factor and its receptor c-met in interactions between lymphocytes and stromal cells in secondary human lymphoid organs

Secondary lymphoid tissue consists of two major populations of cells: lymphoid cells and stromal cells. It is generally accepted that these two cell populations influence each other however, factors mediating these processes are poorly understood. In this paper we characterize one of the possible means of communication between stroma and lymphocytes namely through hepatocyte growth factor/c-met receptor interactions. Hepatocyte growth factor (HGF) is a pleiotropic factor that is mainly produced by mesenchymal cells and acts on cells of epithelial origin which express the HGF receptor c-met. Here we demonstrate that biologically active HGF is constitutively produced by fibroblast-like stromal cells from human lymphoid tissues. HGF secretion from stromal cells was increased by direct contact with activated T cells. This increase was abrogated when activated T cells were separated physically from stromal cells. Using neutralizing antibody or cytokine inhibitors we provide evidence that enhancement of HGF production was due to additive effects of T-cell membrane-associated interleukin-1 (IL-1) and CD40 ligand. Finally, we also show that B lymphocytes activated with CD40L/anti-mu or phorbol 12-myristate 13-acetate (PMA) express c-met receptor. Co-culture of activated B cells with stromal cells from spleen leads to enhanced production of immunoglobulins. This can be partially inhibited by introduction of anti-HGF neutralizing antibodies to the culture system. Substitution of stromal cells with recombinant HGF did not produce enhancement of immunoglobulin secretion. On the other hand stimulation of c-met receptor with HGF leads to enhanced integrin-mediated adhesion of activated B cells to vascular cell adhesion molecule (VCAM-1) and fibronectin. On the basis of the above experiments we conclude that HGF production by fibroblast-like stromal cells can be modulated by activated T cells, thus providing signals for the regulation of adhesion of c-met expressing B cells to extracellular matrix proteins. In this way HGF may indirectly influence immunoglobulin secretion by B cells.

Blockade of endogenous transforming growth factor beta signaling prevents up-regulated collagen synthesis in scleroderma fibroblasts: association with increased expression of transforming growth factor beta receptors

OBJECTIVE

To elucidate the role of transforming growth factor beta (TGFbeta) in the increased expression of the collagen gene in scleroderma fibroblasts.

METHODS

Dermal fibroblasts from 10 patients with diffuse systemic sclerosis (SSc) of recent onset and from 10 healthy individuals were studied. The production of active and total (active + latent) TGFbeta1 levels from cultured dermal fibroblasts was measured using a TGFbeta1 enzyme-linked immunosorbent assay system. Expression of the TGFbeta type I and type II receptor proteins in dermal fibroblasts was determined by immunoblotting, and the level of expression of human alpha2(I) collagen messenger RNA (mRNA) was evaluated by Northern blot analysis. The transcriptional activity of the human alpha2(I) collagen gene was examined with chloramphenicol acetyltransferase (CAT) assays using the -772 COL1A2/CAT construct.

RESULTS

SSc fibroblasts expressed increased levels of TGFbeta type I and type II receptors but secreted amounts of TGFbeta similar to those secreted by normal fibroblasts. The blockade of TGFbeta signaling with anti-TGFbeta antibodies or a TGFbeta1 antisense oligonucleotide abolished the increased mRNA expression, as well as the up-regulated transcriptional activity of the human alpha2(I) collagen gene in SSc fibroblasts.

CONCLUSION

These results suggest that TGFbeta plays a crucial role in the pathogenesis of SSc and raise the possibility of a therapeutic approach with anti-TGFbeta antibodies or a TGF11 antisense oligonucleotide.

Increased phosphorylation of transcription factor Sp1 in scleroderma fibroblasts: association with increased expression of the type I collagen gene

OBJECTIVE

To determine the potential roles of transcription factors Sp1 and Sp3 in the increased expression of the human alpha2(I) collagen gene in scleroderma fibroblasts.

METHODS

Dermal fibroblasts from 7 patients with diffuse systemic sclerosis (SSc; scleroderma) of recent onset and from 7 healthy individuals were studied. The levels of expression of alpha2(I) procollagen, Sp1, and Sp3 messenger RNA (mRNA), with or without stimulation by transforming growth factor beta (TGFbeta) or oncostatin M (OSM), were evaluated by Northern blot analysis, and the respective protein levels were determined by immunoblotting. The DNA binding activity of nuclear proteins recognizing the cis-acting elements in the human alpha2(I) collagen promoter was examined by gel mobility shift assays. The levels of Sp1 phosphorylation were investigated by immunoprecipitation using an antiphosphoserine-specific antibody.

RESULTS

SSc fibroblasts showed basal alpha2(I) collagen mRNA levels that were approximately 3 times higher than those in normal fibroblasts. TGFbeta or OSM increased human alpha2(I) collagen mRNA expression in normal dermal fibroblasts, but these cytokines failed to increase alpha2(I) collagen mRNA levels in SSc fibroblasts. There were no significant differences in the levels of expression of Sp1 or Sp3 between SSc and normal fibroblasts. However, increased Sp1 phosphorylation was detected in SSc fibroblasts compared with normal fibroblasts. Mithramycin, a specific inhibitor of Sp1 binding, abolished the increased expression of the alpha2(I) collagen gene in SSc fibroblasts, in a dose-dependent manner.

CONCLUSION

These results demonstrate the involvement of Sp1 in the up-regulation of expression of the alpha2(I) collagen gene in SSc fibroblasts.

Scleroderma and related disorders: therapeutic aspects

Improvements in management of systemic sclerosis have occurred through a growing understanding of pathogenic events accompanied by advances in diagnosis and assessment, as well as developments in organ-based therapeutics. Unfortunately, disease-modifying therapies of proven efficacy remain elusive and several agents in current use have been shown in well-controlled clinical trials to be of questionable benefit. More positively, there have been advances in the treatment of major visceral complications such as renal crisis, pulmonary fibrosis, pulmonary hypertension, gastrointestinal involvement and in the management of scleroderma-associated Raynaud's phenomenon. Current approaches are reviewed, evidence supporting or refuting the use of putative disease-modifying agents is discussed, and new strategies are described that are currently being considered for this fascinating but complex multisystem connective tissue disease.

Flow cytometry analysis of effects of glass on response of osteosarcoma cells to plasma-sprayed hydroxyapatite/CaO-P(2)O(5) coatings

Multilayered coatings composed of mixtures of hydroxyapatite (HA) and P(2)O(5)-based bioactive glasses offer potential clinical benefits in orthopedic and dental surgery. In this study double-layer plasma-sprayed coatings were prepared and the biological response evaluated in tissue culture using two human osteosarcoma cell lines, MG63 and HOS TE85 (HOS). The cells were cultured on the materials and the effects on cell growth were determined using a spectrophometric assay of a mitochondrial enzyme that is active in viable cells. While none of the materials influenced the growth of the MG63 cells, the HOS cells appeared to undergo less proliferation on all the HA materials. Flow cytometry analysis was carried out using rabbit antibodies against osteonectin, osteopontin, bone sialoprotein, fibronectin, and collagen type I to measure the effects of the materials on key cellular functions. The results showed that the materials downregulated the expression of these extracellular matrix antigens by MG63 cells whereas they had less effect on the HOS cells compared to the same cells incubated on a plastic surface. Notably, with both cell lines the composite with the higher percentage of glass restored the production of connective tissue proteins to levels that were more similar to those present in the control cells.

The immunopathology of siliconosis. History, clinical presentation, and relation to silicosis and the chemistry of silicon and silicone

Recent evidence confirms the fundamental involvement of the human immune system in the reaction to implantation of silicone-based medical devices. An as yet-to-be particularized epitope of many complex substances sharing siloxane structures is presented through the MHC-II apparatus with development and retention of T cell memory. This memory can be tested for in practical terms using one or more forms of silica, which links the immuno-histopathology and autoimmune attributes of "silicosis" with those of "siliconosis." The lesions of siliconosis are typical of those for persistent antigens and delayed, cell mediated hypersensitivity. The basic descriptive pathology of the reaction to silicone has been known since soon after introduction of silicones in medical procedures, with the exception of some details related to the more recent discoveries on the role of cytokines in the immunopathic process. The clinical consequences of siliconosis are common and can be severe in some individuals implanted with silicone devices.

Interferon-alpha does not improve outcome at one year in patients with diffuse cutaneous scleroderma: results of a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To determine whether interferon-alpha (IFNalpha) reduces the severity of skin involvement in early (<3 years) diffuse scleroderma.

METHODS

In a randomized, placebo-controlled, double-blind trial, 35 patients with early scleroderma received subcutaneous injections of either IFNalpha (13.5 x 10(6) units per week in divided doses) or indistinguishable placebo. Outcomes assessed were the modified Rodnan skin score, as determined by a single observer at baseline, 6 months, and 12 months, as well as data on renal, cardiac, and lung function. Pre- and posttreatment skin biopsy samples were analyzed and blood was obtained for assessment of procollagen peptide levels.

RESULTS

There were 11 withdrawals from the IFNalpha group and 3 from the placebo group due to either toxicity, lack of efficacy, or death. In the intent-to-treat analysis, there was a greater improvement in the skin score in the placebo group between 0 and 12 months (mean change IFNalpha -4.7 versus placebo -7.5; P = 0.36). There was also a greater deterioration in lung function in patients receiving active therapy, as assessed by either the forced vital capacity (mean change IFNalpha -8.2 versus placebo +1.3; P = 0.01) or the diffusing capacity for carbon monoxide (mean change IFNalpha -9.3 versus placebo +4.7; P = 0.002). Skin biopsy showed no significant decrease in collagen synthesis in the IFNalpha group, and no significant differences in the levels of procollagen peptides were seen between the 2 groups.

CONCLUSION

This study suggests that IFNalpha is of no value in the treatment of scleroderma, and that it may in fact be deleterious.

Serum levels of soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and interleukin-2 receptor in patients with vernal keratoconjunctivitis and allergic conjunctivitis

BACKGROUND

Vernal keratoconjunctivitis (VKC) is characterized by severe ocular allergic inflammation that may have a poor visual prognosis. Due to the high frequency of the presence of atopic dermatitis (AD) in VKC, most systemic parameters are dependent on the clinical severity of AD.

METHODS

Serum levels of sICAM-1, sVCAM-1, and sIL-2R were measured by enzyme-linked immunoassay using samples from 30 VKC patients, 30 allergic conjunctivitis (AC) patients, and 20 normal subjects, to determine whether the concentrations of these molecules are elevated.

RESULTS

Circulating sICAM-1 and sIL-2R levels were increased in patients with VKC with AD compared with those in VKC without AD, AC, and normal controls. Serum levels of sVCAM-1 in VKC patients with and without AD were significantly higher than those in controls. No significant difference was found in the levels of sVCAM-1 between patients with VKC with and without AD. In VKC patients with AD, the sIL-2R level correlated significantly with severity of AD, whereas no such correlation was found for sICAM-1 and sVCAM-1.

CONCLUSIONS

These results suggest that serum sVCAM-1 can be used as a marker to differentiate VKC from nonproliferative ocular allergic diseases, and specific immunologic features of VKC may underlie the upregulation of serum sVCAM-1.

Scleroderma fibroblasts promote migration of mononuclear leucocytes across endothelial cell monolayers

Perivascular infiltrates of inflammatory cells are a hallmark of lesional skin in scleroderma. We have explored the potential for scleroderma fibroblasts to modulate mononuclear leucocyte migration across endothelial cell monolayers in tissue culture, and to regulate expression of endothelial cell adhesion molecules. Fibroblasts were grown from skin biopsies of eight patients with active diffuse cutaneous scleroderma and from four healthy controls. Co-culture and conditioned medium transfer experiments examined the effect of soluble fibroblast products on mononuclear leucocyte (U937) cell migration across endothelial cell (1E-7) monolayers grown on tissue culture inserts. Co-culture of scleroderma, but not control fibroblasts, promoted transendothelial migration of U937 cells. Scleroderma fibroblast-conditioned medium had qualitatively similar effects and equivalent results were obtained using Jurkat-6 (T lymphocyte) cells, and with peripheral blood mononuclear cells from a patient with diffuse cutaneous scleroderma. Promotion of leucocyte migration does not appear to result from increased endothelial adhesion molecule expression, since fibroblast-conditioned medium did not up-regulate endothelial cell expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) or E-selectin. Moreover, leucocyte migration across cytokine-activated endothelial cell layers in co-culture with fibroblasts was less than across resting cells, although the selective effect of scleroderma fibroblast co-culture persisted. Recombinant monocyte chemoattractant protein-1 (MCP-1) or IL-8 increased passage of mononuclear leucocytes across endothelial cell monolayers, whilst anti-MCP-1, but not anti-IL-8 antibodies, significantly reduced the effect of fibroblast conditioned medium. These data suggest that systemic sclerosis (SSc) fibroblasts promote leucocyte migration across endothelial cell monolayers in tissue culture via an MCP-1-dependent mechanism. These findings may be relevant to the perivascular mononuclear leucocyte infiltrates characteristic of early SSc lesions.

Flow cytometry for assessing biocompatibility

Flow cytometry (FCM) was examined as a possible procedure for measuring in vitro the biocompatibility of implant materials for orthopedic and dental surgery. The human osteoblast-like cell line MG63 was grown on hydroxyapatite (HA) and P2O5 glass-reinforced HA composite discs and compared with the same cells grown on polystyrene culture dishes. While morphological observation at the light and electron microscopic levels showed no major deleterious effects, FCM indicated that cell size was somewhat reduced, particularly by growth on the HA composite. Morever, this material also appeared to delay the progression of the cells from the G0/G1 into the S phase of the cell cycle. In addition to this low level of inhibition of cell growth relative to control cultures, FCM analysis also demonstrated that the glass-reinforced HA caused some down-regulation of the expression of osteocalcin and fibronectin, two antigens which play a vital part in the integrity and function of bone and soft connective tissue, respectively. These results thus show, first, that although HA and the HA composite used in these experiments were generally biocompatible, they nevertheless had certain suboptimal effects on the cells; and second, that FCM could be a highly useful procedure for effectively screening and evaluating important biological responses to implant materials.

Direct contact between T lymphocytes and human dermal fibroblasts or synoviocytes down-regulates types I and III collagen production via cell-associated cytokines

In many inflammatory diseases where tissue remodeling occurs, T cells are in close contact with mesenchymal cells. We investigated the effect of direct cell-cell contact between peripheral blood T lymphocytes or HUT-78 lymphoma cells and dermal fibroblasts or synoviocytes on the deposition of the major extracellular matrix components: types I and III collagen. Incubation of dermal fibroblasts and synoviocytes with plasma membrane preparations from resting T cells slightly increased the production of collagen I but did not significantly affect that of collagen III. Conversely, direct contact with either plasma membranes or fixed phytohemagglutinin/phorbol myristate acetate-activated T cells markedly inhibited the synthesis of types I and III collagen by 60-70% in untreated dermal fibroblasts and synoviocytes and by 85% in transforming growth factor beta-stimulated fibroblasts. This decrease of collagen synthesis was abrogated when fixed T cells were separated physically from fibroblasts, demonstrating that direct contact between the two cell types was necessary. This inhibition was associated with a marked decrease in steady-state levels of pro-alpha1(I) and pro-alpha1(III) collagen mRNAs. T cell contact decreased the transcription rate but did not significantly alter the stability of the alpha1(I) and alpha1(III) transcripts. Finally, using neutralizing antibodies or cytokine inhibitors we provide evidence that this inhibition of extracellular matrix production mediated by T cell contact was partially due to additive effects of T cell membrane-associated interferon gamma, tumor necrosis factor alpha, and interleukin-1alpha.

Proinflammatory cytokines differentially modulate their own expression in human intestinal mucosal mesenchymal cells

BACKGROUND & AIMS

Intestinal homeostasis is coordinated through the response of different cell types, including the interaction of immune with nonimmune cells. This study investigated the effect of immune cell-derived proinflammatory cytokines on mesenchymal cell proliferation and gene product expression.

METHODS

Primary cultures of human mucosal mesenchymal cells were activated with interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha). Proliferation was measured by thymidine incorporation, messenger RNA (mRNA) expression was assessed by Northern blot analysis, and IL-1 receptor type was identified by reverse-transcription polymerase chain reaction.

RESULTS

Mesenchymal cells dose-dependently proliferated in response to IL-1 beta, IL-6, and TNF-alpha. Each cytokine differentially induced mRNA expression in a dose-dependent and selective fashion: IL-1 beta was the most potent inducer, TNF-alpha was weaker, and IL-6 induced little or no mRNA; in contrast, IL-6 mRNA was the most abundantly induced, followed by IL-1 beta mRNA, whereas TNF-alpha mRNA was weakly and infrequently expressed. The IL-1 receptor antagonist inhibited cytokine mRNA expression, and mesenchymal cells expressed the type II, but not the type I, IL-1 receptor.

CONCLUSIONS

The ability of intestinal mesenchymal cells to express proinflammatory gene products implicates them as regulators of local immune cells through immune-nonimmune interactions. Thus, mesenchymal cells should be considered as active regulators of intestinal immunity under normal and inflammatory conditions.

Flow cytometry analysis of gingival and periodontal ligament cells

Gingival and periodontal ligament (PDL) fibroblasts are the major cellular components of periodontal soft connective tissues, but the precise differences between these cells are not yet known. In the present study, we have therefore examined the phenotypic and functional features of the cells obtained from gingival and PDL biopsy samples. Spindle-shaped cells characteristic of fibroblasts were the main cell type observed in vitro, although epithelial cells were also present in primary gingival cell cultures. Flow cytometry was used to measure the size and granularity of the cultured cells, and showed that the gingival fibroblasts were smaller and less granular compared with the PDL cells. The expression of certain key extracellular matrix (ECM) proteins, fibronectin, collagen type I, and tenascin was measured by flow cytometry. Analysis of the fluorescence profiles of these cultures showed that the majority of cells expressed fibronectin and that the average fluorescence intensity of this antigen in the PDL cells was higher than that in the gingival fibroblasts. Moreover, the fibronectin-positive PDL cells apparently comprised two subpopulations which expressed fibronectin at different levels, suggesting that the cells in the PDL cultures were functionally heterogeneous. The level of collagen type I was also found to be up-regulated in the PDL compared with the gingival cells and, as with fibronectin, was expressed at two different levels by subsets of the PDL cells. In contrast, tenascin was expressed at very similar levels by both the gingival fibroblasts and PDL cells. In addition, measurement of alkaline phosphatase, a marker enzyme for mineralized tissue-forming cells, showed that the PDL cells had higher activity than the gingival fibroblasts and that the alkaline phosphatase activity in the PDL cells was far more markedly up-regulated by dexamethasone. Our findings demonstrate that, despite their similar spindle-shaped appearance, fibroblasts derived from gingival and PDL tissues appear to display distinct functional activities which are likely to play a vital part in the maintenance of tissue integrity and regenerative processes.

Increased expression of TGF-beta receptors by scleroderma fibroblasts: evidence for contribution of autocrine TGF-beta signaling to scleroderma phenotype

Scleroderma fibroblasts exhibit numerous phenotypic differences when compared with healthy skin fibroblasts. Some of these differences, in particular overexpression of collagen type I and other extracellular matrix proteins, parallel the effect of transforming growth factor-beta (TGF-beta) on dermal fibroblasts, suggesting that the scleroderma fibroblast phenotype may result from activation of autocrine TGF-beta signaling. To test this hypothesis we examined the role of TGF-beta Type I and Type II receptors in regulating collagen type I transcription. We have shown that overexpression of either Type I or Type II receptors significantly (3-4-fold) increases alpha2 (I) collagen promoter activity in transient transfection assays in dermal fibroblasts. Addition of anti-TGF-beta antibody abolished, whereas addition of plasmin enhanced, the stimulatory effect of receptor overexpression on collagen promoter activity, suggesting that this effect depends on autocrine TGF-beta. Moreover, these cotransfection experiments indicated that expression levels of TGF-beta receptors is a limiting factor in the autocrine regulation of collagen type I transcription by TGF-beta. Comparison of the TGF-beta receptor Type I and Type II mRA expression levels in scleroderma and normal fibroblasts have indicated elevated expression (2-fold) of both receptor types in scleroderma cells, which correlated with increased binding of TGF-beta. Significantly, elevated TGF-beta receptor levels correlated with elevated alpha2 (I) collagen mRNA levels. These results suggest that the elevated production of collagen type I by scleroderma fibroblasts results from overexpression of TGF-beta receptors.

Scleroderma fibroblasts show increased responsiveness to endothelial cell-derived IL-1 and bFGF

Fibroblasts cultured from lesional skin in scleroderma (systemic sclerosis) demonstrate an activated phenotype that may be important in pathogenesis. Endothelial cell-derived cytokines can modulate fibroblast properties, and endothelial cell changes occur early in scleroderma. Thus, endothelial cell and fibroblast dysfunction may be linked through the paracrine activity of soluble endothelial cell products. We have explored endothelial cell-fibroblast interactions in vitro by investigating the modulation of scleroderma and control fibroblast properties by endothelial cell-conditioned medium (EC-CM). EC-CM caused a concentration-dependent stimulation of fibroblast DNA and protein synthesis and upregulation of cell surface ICAM-1 expression. Scleroderma fibroblasts showed consistently greater responses than control cells. Medium conditioned by mechanically wounded endothelial cells had a greater effect than that from resting endothelial cells. Pre-incubation of EC-CM with anti-bFGF significantly reduced the promotion of fibroblast thymidine incorporation but did not affect endothelial cell-induced leucine incorporation. Conversely, anti-IL-1 antibodies abrogated EC-CM-induced leucine incorporation and ICAM-1 expression but did not diminish thymidine incorporation. Recombinant bFGF or IL-1 modulated fibroblast properties similarly. These data demonstrate that endothelial cell-derived IL-1 and bFGF modulate fibroblast properties independently and that lesional scleroderma strains are more responsive than control fibroblasts to endothelial cell-induced modulation, which supports the hypothesis that altered endothelial cell-fibroblast communication may be involved in the pathogenesis of scleroderma.