Lung Fibrosis In Systemic Sclerosis Research Articles

Role of Extracellular Vesicles in the Propagation of Lung Fibrosis in Systemic Sclerosis.

Systemic sclerosis (SSc) has the highest mortality rate among the rheumatic diseases, with lung fibrosis leading as the cause of death. A characteristic of severe SSc-related lung fibrosis is its progressive nature. Although most research has focused on the pathology of the fibrosis, the mechanism mediating the fibrotic spread remains unclear. We hypothesized that extracellular vesicle (EV) communication drives the propagation of SSc lung fibrosis. EVs were isolated from normal (NL) or SSc-derived human lungs and primary lung fibroblasts (pLFs). EVs were also isolated from human fibrotic lungs and pLFs induced experimentally with transforming growth factor-β (TGFβ). Fibrotic potency of EVs was assessed using functional assays in vitro and in vivo. Transmission electron microscopy, nanoparticle tracking analysis, real-time quantitative polymerase chain reaction(RT-qPCR), immunoblotting, and immunofluorescence were used to analyze EVs, their cargo, extracellular matrix (ECM) fractions, and conditioned media. SSc lungs and pLFs released significantly more EVs than NL lungs, and their EVs showed increased fibrotic content and activity. TGFβ-stimulated NL lung cores and pLFs increased packaging of fibrotic proteins, including fibronectin, collagens, and TGFβ, into released EVs. The EVs induced a fibrotic phenotype in recipient pLFs and in vivo in mouse lungs. Furthermore, EVs interacted with and contributed to the ECM. Finally, suppressing EV release in vivo reduced severity of murine lung fibrosis. Our findings highlight EV communication as a novel mechanism for propagation of SSc lung fibrosis. Identifying therapies that reduce EV release, activity, and/or fibrotic cargo in SSc patient lungs may be a viable therapeutic strategy to improve fibrosis.

Long-term Outcomes After Rituximab Treatment for Patients With Systemic Sclerosis

Rituximab is emerging as a promising therapeutic option for systemic sclerosis (SSc), but its long-term outcomes and response markers are unknown. To evaluate the long-term outcomes after rituximab treatment for SSc and identify potential response markers. In this single-center cohort study, patients with SSc who continued to receive rituximab after the DESIRES trial were analyzed with a median follow-up of 96 weeks. Among the 43 patients who completed the DESIRES trial, 31 continued to receive rituximab, of which 29 with complete data were included in this study. Rituximab treatment. A post hoc analysis of the clinical and laboratory data. In 29 patients with SSc (27 female [93%]; median [IQR] age, 48 [35-45] years), significant improvement in modified Rodnan skin score (MRSS) and percentage of predicted forced vital capacity (FVC%) were observed after 1 (median [IQR] change in MRSS, -7 [-8.5 to -4]; P < .001) and 3 (median [IQR] change in FVC% predicted, 1.85 [0.13-5.68]; P < .001) courses of rituximab, respectively, both of which were sustained during follow-up. High responders (MRSS improvement of ≥9; n = 16) experienced a greater decrease in serum levels of IgG (median [IQR] change in IgG, -125 [-207 to -83] vs 7 [-120 to 43]; P = .008) and IgA (median [IQR] change in IgA, -45 [-96 to -32] vs -11 [-20 to 3]; P < .001) compared with low responders (MRSS improvement of ≤8; n = 13). In particular, decrease in serum IgA levels significantly correlated with the improvement in MRSS (r = 0.64; P < .001). At the last follow-up, low IgM, low IgA, and low IgG was observed in 7, 1, and 1 patient, respectively, of which low IgM was associated with greater improvement in FVC% predicted (median [IQR] change in FVC% predicted, 7.2 [3.8-8.9] vs 3.6 [1.4-6.2]; P = .003). In this cohort study, rituximab treatment was associated with significantly improved skin and lung fibrosis in SSc in a long-term follow-up. Decrease in serum immunoglobulins was associated with greater clinical response.

Reduced Cathepsin L expression and secretion into the extracellular milieu contribute to lung fibrosis in systemic sclerosis.

Lung fibrosis is the leading cause of death in SSc, with no cure currently available. Antifibrotic Endostatin (ES) production does not reach therapeutic levels in SSc patients, suggesting a deficit in its release from Collagen XVIII by the main cleavage enzyme, Cathepsin L (CTSL). Thus, elucidating a potential deficit in CTSL expression and activity unravels an underlying molecular cause for SSc-driven lung fibrosis. Fibrosis was induced experimentally using TGF-β in vitro, in primary human lung fibroblasts (pLFs), and ex vivo, in human lung tissues. ES and CTSL expression was quantified using ELISA, RT-qPCR, immunoblotting or immunofluorescence. Recombinant NC1-FLAG peptide was used to assess CTSL cleavage activity. CTSL expression was also compared between SSc vs normal (NL)-derived pLFs and lung tissues. ES levels were significantly reduced in media conditioned by TGF-β-induced pLFs. TGF-β-stimulated pLFs significantly reduced expression and secretion of CTSL into the extracellular matrix (ECM). CTSL was also sequestered in its inactive form into extracellular vesicles, further reducing its availability in the ECM. Media conditioned by TGF-β-induced pLFs showed reduced cleavage of NC1-Flag and reduced release of the antifibrotic ES fragment. SSc-derived pLFs and lung tissues expressed significantly lower levels of CTSL compared with NL. Our findings identify CTSL as a protein protective against lung fibrosis via its activation of antifibrotic ES, and whose expression in SSc pLFs and lung tissues is suppressed. Identifying strategies to boost CTSL endogenous levels in SSc patients could serve as a viable therapeutic strategy.

Myofibroblast transcriptome indicates SFRP2hi fibroblast progenitors in systemic sclerosis skin

Skin and lung fibrosis in systemic sclerosis (SSc) is driven by myofibroblasts, alpha-smooth muscle actin expressing cells. The number of myofibroblasts in SSc skin correlates with the modified Rodnan skin score, the most widely used clinical measure of skin disease severity. Murine fibrosis models indicate that myofibroblasts can arise from a variety of different cell types, but their origin in SSc skin has remained uncertain. Utilizing single cell RNA-sequencing, we define different dermal fibroblast populations and transcriptome changes, comparing SSc to healthy dermal fibroblasts. Here, we show that SSc dermal myofibroblasts arise in two steps from an SFRP2hi/DPP4-expressing progenitor fibroblast population. In the first step, SSc fibroblasts show globally upregulated expression of transcriptome markers, such as PRSS23 and THBS1. A subset of these cells shows markers indicating that they are proliferating. Only a fraction of SFRP2hi SSc fibroblasts differentiate into myofibroblasts, as shown by expression of additional markers, SFRP4 and FNDC1. Bioinformatics analysis of the SSc fibroblast transcriptomes implicated upstream transcription factors, including FOSL2, RUNX1, STAT1, FOXP1, IRF7 and CREB3L1, as well as SMAD3, driving SSc myofibroblast differentiation.

Rational repurposing of tocilizumab for treatment of lung fibrosis in systemic sclerosis.

Rational repurposing of tocilizumab for treatment of lung fibrosis in systemic sclerosis.

P153 Tocilizumab in systemic sclerosis: real world experience from a single centre cohort supports potential benefit on lung function for anti-topoisomerase (Scl-70) positive subgroup

Abstract Background The FaSScinate and FocuSSced trials of tocilizumab versus placebo in early diffuse systemic sclerosis (SSc) highlighted the potential impact of tocilizumab on lung function with preservation of lung function in those treated with tocilizumab versus placebo, despite only a trend of benefit for skin fibrosis. Our centre have been using tocilizumab to treat SSc patients and overlap inflammatory arthritis, in line with NICE guidance treatment for inflammatory arthritis. We report here our experience of tocilizumab in SSc and the impact on lung function. Methods A retrospective medical chart review of patients attending our centre with SSc and having ever been on tocilizumab were identified, mostly with overlap inflammatory arthritis. Patients included in the FaSScinate trial were excluded, however patients receiving compassionate use of tocilizumab following the phase 3 FocuSSced trial were included. Mann-Whitney-U test was used for statistical analysis. Results In total 32 patients were identified. 68.8% (n = 22) of patients had a diagnosis of dcSSc. 75% (n = 24) patients were female. The most common autoantibodies were ATA (anti-topoisomerase antibody) (34.3%) and ARA (anti-RNA polymerase-III antibody) (18.8%). 46.9% (n = 17) patients had known interstitial lung disease. 6 patients received tocilizumab on a compassionate basis following completion of the open label phase of the focuSSced clinical trial, the remainder had overlap inflammatory arthritis. Mean age of disease onset was 38.6 years, and the median disease duration to tocilizumab initiation was 7.9 years. 11 patients discontinued tocilizumab: 6 due to cessation of the compassionate use access, 2 due to side effects, 3 due to lack of benefit. 75% (n = 24) patients had serial lung function data to compare FVC and DLCO before and after initiation of treatment. Baseline FVC prior to tocilizumab was 3.09L (sd = 0.98). To standardise results, the yearly change rate in FVC and DLCO was calculated. Median change in % predicted FVC was -1.5% (IQR=0.107) and median change in % predicted DLCO was -0.5% (IQR=0.061). Subgroup analysis revealed a significant difference between autoantibody groups and change in FVC while on tocilizumab. It was notable that there was an increase in median change in FVC in patients with ATA antibody (3.27%, IQR=0.1355) whereas there was a decrease in median change in FVC in all other autoantibody groups (-4.7%, IQR=0.111, p = 0.0019). There was a near significant difference in change in DLCO between these antibodies at 12 months (p = 0.056) in favour of improvement in ATA subgroup. Conclusion We report our experience of the impact of tocilizumab on lung function in SSc. Consistent with trial results, there is a signal of potential benefit for lung function among those with ATA autoantibody irrespective of disease subset. As this autoantibody confers high risk of extensive lung fibrosis in SSc it may help in future case selection. Disclosures K.E.N. Clark None. Y. Suleman None. S.I. Nihtyanova None. V.H. Ong None. C.P. Denton Grants/research support; Actelion, GlaxoSmithKline, Bayer, Sanofi, lnventiva, Boehringer Ingelheim, Roche, Bristol Myers Squibb, CSL Behring, UCB, Leadiant Biosciences.

Is biological therapy in systemic sclerosis the answer?

Systemic sclerosis is a systemic fibrosing disorder associated with significant morbidity and mortality, with no universally accepted disease-modifying therapy. Significant advances in the understanding of systemic sclerosis in recent years have guided the exploration of biological drugs in systemic sclerosis. In this narrative review, we summarize the published literature on biologic therapies in systemic sclerosis. A double-blind randomized trial, and an open label trial of tocilizumab (which antagonizes the interleukin 6 receptor), identified potential benefits in skin and lung fibrosis in systemic sclerosis; however, these differences failed to attain statistical significance. Two open-label trials compared rituximab (which depletes B lymphocytes) to conventional treatment/ cyclophosphamide in systemic sclerosis-associated interstitial lung disease (ILD), and revealed significant improvements in lung functions and skin disease with rituximab. Significant observational data also support the use of rituximab in skin, lung, muscle and joint manifestations of systemic sclerosis. Abatacept (which blocks T lymphocyte activation) has demonstrated utility for skin and joint disease in systemic sclerosis; a recent clinical trial failed to demonstrate benefits in improving skin thickness compared to placebo. Agents targeting type I interferons, interleukin 17 pathway, CD19 and plasma cells hold promise in systemic sclerosis; however, high-quality evidence is lacking. The results of different ongoing clinical trials targeting B lymphocytes, T lymphocytes, various cytokines (interleukins 6, 17, 4, 13, IL-1α), platelet-derived growth factor receptor, proteasome, integrins or oncostatin M may help guide future therapeutic regimens with biological agents in systemic sclerosis.

Pulmonary emphysema not combined with lung fibrosis in systemic sclerosis.

Interstitial Lung Disease (ILD) is a common finding of Systemic Sclerosis (SSc) mainly presenting in the form of Nonspecific Interstitial Pneumonia (NSIP) and deeply affecting patients' prognosis. Beside NSIP, other types of ILD have been reported. The most recently described pattern is the so-called Combined-pulmonary emphysema and lung fibrosis, characterized by the coexistence of both upper lobes centrilobular and paraseptal emphysema and lower lobes ILD. We presented three cases of patients with SSc, in which High Resolution Computed Tomography examinations showed emphysema with atypical distribution and radiological presentation, without or with mild signs of fibrosing lung disease, that stabilized after immunosuppressive treatment.

226 Disease-specific autoantibodies associate with remarkably different risk of development of significant lung fibrosis in systemic sclerosis

226 Disease-specific autoantibodies associate with remarkably different risk of development of significant lung fibrosis in systemic sclerosis

The impact of slice-reduced computed tomography on histogram-based densitometry assessment of lung fibrosis in patients with systemic sclerosis.

To evaluate usability of slice-reduced sequential computed tomography (CT) compared to standard high-resolution CT (HRCT) in patients with systemic sclerosis (SSc) for qualitative and quantitative assessment of interstitial lung disease (ILD) with respect to (I) detection of lung parenchymal abnormalities, (II) qualitative and semiquantitative visual assessment, (III) quantification of ILD by histograms and (IV) accuracy for the 20%-cut off discrimination. From standard chest HRCT of 60 SSc patients sequential 9-slice-computed tomography (reduced HRCT) was retrospectively reconstructed. ILD was assessed by visual scoring and quantitative histogram parameters. Results from standard and reduced HRCT were compared using non-parametric tests and analysed by univariate linear regression analyses. With respect to the detection of parenchymal abnormalities, only the detection of intrapulmonary bronchiectasis was significantly lower in reduced HRCT compared to standard HRCT (P=0.039). No differences were found comparing visual scores for fibrosis severity and extension from standard and reduced HRCT (P=0.051-0.073). All scores correlated significantly (P<0.001) to histogram parameters derived from both, standard and reduced HRCT. Significant higher values of kurtosis and skewness for reduced HRCT were found (both P<0.001). In contrast to standard HRCT histogram parameters from reduced HRCT showed significant discrimination at cut-off 20% fibrosis (sensitivity 88% kurtosis and skewness; specificity 81% kurtosis and 86% skewness; cut-off kurtosis ≤26, cut-off skewness ≤4; both P<0.001). Reduced HRCT is a robust method to assess lung fibrosis in SSc with minimal radiation dose with no difference in scoring assessment of lung fibrosis severity and extension in comparison to standard HRCT. In contrast to standard HRCT histogram parameters derived from the approach of reduced HRCT could discriminate at a threshold of 20% lung fibrosis with high sensitivity and specificity. Hence it might be used to detect early disease progression of lung fibrosis in context of monitoring and treatment of SSc patients.

MiR-155 in the progression of lung fibrosis in systemic sclerosis.

BackgroundMicroRNA (miRNA) control key elements of mRNA stability and likely contribute to the dysregulated lung gene expression observed in systemic sclerosis associated interstitial lung disease (SSc-ILD). We analyzed the miRNA gene expression of tissue and cells from patients with SSc-ILD. A chronic lung fibrotic murine model was used.MethodsRNA was isolated from lung tissue of 12 patients with SSc-ILD and 5 controls. High-resolution computed tomography (HRCT) was performed at baseline and 2–3 years after treatment. Lung fibroblasts and peripheral blood mononuclear cells (PBMC) were isolated from healthy controls and patients with SSc-ILD. miRNA and mRNA were analyzed by microarray, quantitative polymerase chain reaction, and/or Nanostring; pathway analysis was performed by DNA Intelligent Analysis (DIANA)-miRPath v2.0 software. Wild-type and miR-155 deficient (miR-155ko) mice were exposed to bleomycin.ResultsLung miRNA microarray data distinguished patients with SSc-ILD from healthy controls with 185 miRNA differentially expressed (q < 0.25). DIANA-miRPath revealed 57 Kyoto Encyclopedia of Genes and Genomes pathways related to the most dysregulated miRNA. miR-155 and miR-143 were strongly correlated with progression of the HRCT score. Lung fibroblasts only mildly expressed miR-155/miR-21 after several stimuli. miR-155 PBMC expression strongly correlated with lung function tests in SSc-ILD. miR-155ko mice developed milder lung fibrosis, survived longer, and weaker lung induction of several genes after bleomycin exposure compared to wild-type mice.ConclusionsmiRNA are dysregulated in the lungs and PBMC of patients with SSc-ILD. Based on mRNA-miRNA interaction analysis and pathway tools, miRNA may play a role in the progression of the disease. Our findings suggest that targeting miR-155 might provide a novel therapeutic strategy for SSc-ILD.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1054-6) contains supplementary material, which is available to authorized users.

Взаимосвязь гастроэзофагеальной рефлюксной болезни и интерстициального поражения легких при системной склеродермии

Взаимосвязь гастроэзофагеальной рефлюксной болезни и интерстициального поражения легких при системной склеродермии

Treating skin and lung fibrosis in systemic sclerosis: a future filled with promise?

Systemic sclerosis (SSc) is a rare autoimmune disorder characterized by immune activation, vascular damage and an excessive accumulation of extracellular matrix proteins in the skin and internal organs. Despite its high morbidity and increased mortality, currently available treatment options for fibrotic manifestations of SSc remain limited and their clinical antifibrotic effects are borderline. In this review, novel insights from recently published clinical trials in SSc on treatment concepts such as mycophenolate mofetil, oral type I collagen, recombinant human relaxin and autologous hematopoietic stem cell transplantation are discussed. In the past decade the most significant progress in this field has been made by the identification of a large number of cellular and molecular key players in the pathogenesis of fibrotic disease manifestations. This has led to the identification of novel candidates as molecular targets for treatment of fibrotic diseases. On the basis of their level of evidence from preclinical studies and based on the availability of first clinical results, the most promising targets are presented including inhibitors of B-cells, tyrosine kinases, 5-hydroxytryptamin receptors, interleukin-6 and Wnt signalling.

A10.27 Systemic Sclerosis – Role of Agonistic Autoantibodies Directed Against the Angiotensin Receptor Type 1 and the Endothelin Receptor Type A on Immune Cells in Disease Pathogenesis

Background and ObjectivesAgonistic autoantibodies against the angiotensin receptor type 1 (AT1R) and the endothelin receptor type A (ETAR) have been identified in the majority of systemic sclerosis (SSc) patients. We...

Mucin 5B promoter polymorphism is associated with idiopathic pulmonary fibrosis but not with development of lung fibrosis in systemic sclerosis or sarcoidosis

BackgroundA polymorphism (rs35705950) 3 kb upstream of MUC5B, the gene encoding Mucin 5 subtype B, has been shown to be associated with familial and sporadic idiopathic pulmonary fibrosis (IPF). We...

Lung fibrosis quantified by HRCT in scleroderma patients with different disease forms and ANA specificities

OBJECTIVE: To define the prevalence of interstitial lung fibrosis in systemic sclerosis (SSc) and its relationship with the different clinical forms of disease and ANA specificities. METHODS: Fifty patients with SSc were submitted to pulmonary high resolution computed tomography (HRCT). Lung abnormalities were evaluated according to Warrick's score that considers both the severity and the extent of fibrotic lesions. RESULTS: Pulmonary HRCT abnormalities were observed in 84% of SSc patients. Ground glass aspects (60%), irregular pleural margins (56%) and septal/subpleural lines (68%) were the most common lesions. The distribution of these abnormalities favoured the posterior basilar segments of both lungs. HRCT findings were significantly more frequent in males and in patients with the cutaneous diffuse form of SSc and with the specific antibody anti-Scl70. CONCLUSIONS: HRCT is a very useful method for the diagnosis of interstitial lung fibrosis in SSc. Warrick's score permits to quantify the HRCT findings and to evaluate their relationship with the disease clinical forms and ANA specificities.

A long-term prospective randomized controlled study of non-specific interstitial pneumonia (NSIP) treatment in scleroderma

The association of cyclophosphamide (CYC) and prednisone (PRED) for the treatment of lung fibrosis in systemic sclerosis (SSc) was only evaluated in uncontrolled studies, although in idiopathic interstitial lung disease (ILD) this association seems to be beneficial in patients with non-specific interstitial pneumonia (NSIP). To treat SSc-ILD in a prospective open-label controlled study based on lung pattern during 12months of treatment. A 3-year analysis was also performed. Twenty-four consecutive patients with SSc and ILD were submitted to an open lung biopsy. Eighteen patients (NSIP) were randomized in two groups: CYC versus CYC + PRED during 12months. Lung function tests (diffusion lung capacity of monoxide carbone corrected for hemoglobin concentration (DLCO-Hb), forced vital capacity (FVC), total lung capacity) and Modified Rodnan Skin Score (MRSS) were performed before, after one of treatment and after 3years from the end of the treatment. Pulmonary function tests were similar in both groups on baseline. After 1year of treatment, FVC% was comparable between CYC groups (p = 0.72) and in CYC + PRED (p = 0.40). Three years after the end of treatment, FVC% values (p = 0.39 in group CYC and p = 0.61 in CYC + PRED and p = 0.22 in CYC + PRED) and DLCO-Hb (p = 0.54 in CYC and p = 0.28 in CYC + PRED) were similar compared to 1year of treatment. We observed a reduction of the MRSS in the CYC + PRED group after 1year of treatment (p = 0.02); although after 3years, MRSS values remained stable in both groups. CYC was effective to stabilize lung function parameters in NSIP lung pattern of SSc disease for 3years after the end of a 1-year therapy.

The lung megakaryocytes and pulmonary fibrosis in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune connective tissue disease characterized by fibrotic changes in several organs including the lungs, skin, kidneys, muscles and the joints. The leading cause of death in SSc is pulmonary involvement consisting of pulmonary fibrosis with pulmonary hypertension. The pathogenesis of lung involvement in SSc is not yet clear though several mechanisms involving genetic, environmental, vascular, and immunological factors have been postulated. At the same time, the presence of megakaryocytes in the lungs is a less recognized concept and may also be contributing to lung fibrosis in SSc. These cells normally thought to be present only in the bone marrow have been demonstrated to be an important factor in the development of fibrosis of the bone marrow in the condition, idiopathic myelofibrosis. The article describes available evidence for the presence of lung megakaryocytes and hypothesizes that these cells are responsible for the development of pulmonary fibrosis in SSc based on the myelofibrosis model.

Lung fibrosis: new classifications and therapy.

The recent American Thoracic Society/European Respiratory Society consensus classification of idiopathic interstitial pneumonia is equally applicable to pulmonary fibrosis associated with connective tissue disease. The most frequent histopathologic entities are usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP), which is more prevalent than UIP in systemic sclerosis. The prognostic significance of NSIP is unknown in connective tissue disease, although NSIP has a better prognosis than UIP in idiopathic interstitial pneumonia. The use of computed tomography to distinguish between UIP and NSIP requires further refinement. Recent therapeutic studies have reinforced disenchantment amongst clinicians with corticosteroid and immunosuppressive regimens in UIP. UIP is increasingly regarded an "epithelial-fibrotic" disease rather than a primarily inflammatory disorder, accounting for recent widespread interest in antifibrotic agents. This conclusion should not be extrapolated to NSIP, especially in connective tissue disease. Strong circumstantial evidence of a therapeutic benefit justifies the continued use of cyclophosphamide in progressive lung fibrosis in systemic sclerosis.

Depletion of protein kinase Cepsilon in normal and scleroderma lung fibroblasts has opposite effects on tenascin expression.

To determine whether the extracellular matrix protein tenascin-C (TN-C) is overexpressed in lung fibroblasts from systemic sclerosis (SSc) patients, the molecular mechanisms regulating TN-C secretion in SSc and normal lung fibroblasts, and how these processes might contribute to lung fibrosis in SSc patients. TN-C secretion by SSc and normal fibroblasts was compared in vivo (in bronchoalveolar lavage [BAL] fluid) and in vitro (in culture medium). The ability of thrombin to induce TN-C was confirmed at both the protein and the messenger RNA (mRNA) level. The role of protein kinase Cepsilon (PKCepsilon) in the expression of TN-C was evaluated by determining the effects of thrombin on PKCepsilon levels and by directly manipulating PKCepsilon levels via the use of antisense oligonucleotides. BAL fluid from SSc patients contained high levels of TN-C, whereas that from normal subjects contained little or no TN-C. In vitro, SSc lung fibroblasts expressed much higher amounts of TN-C than did normal lung fibroblasts. Consistent with the idea that thrombin is a physiologic inducer of TN-C, thrombin stimulated TN-C mRNA and protein expression in both SSc and normal lung fibroblasts by a mechanism that required proteolytic cleavage of the thrombin receptor. Surprisingly, thrombin treatment and antisense oligonucleotide-mediated depletion of PKCepsilon indicated that TN-C expression is regulated via opposite signaling mechanisms in SSc and normal cells. In SSc lung fibroblasts, thrombin decreased PKCepsilon levels, and the decreased PKCepsilon induced TN-C secretion; in normal fibroblasts, thrombin increased PKCepsilon levels, and the increased PKCepsilon induced TN-C secretion. Normal and SSc lung fibroblasts also differed in the subcellular localization of PKCepsilon, both before and after thrombin treatment. These studies are the first to demonstrate that thrombin is a potent simulator of TN-C in lung fibroblasts and that PKCepsilon is a critical regulator of TN-C protein levels in these cells. Furthermore, our results indicate that both the regulation of PKCepsilon levels by thrombin and the regulation of TN-C levels by PKCepsilon are defective in SSc lung fibroblasts.