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Introduction: The 6-minute walking distance (6MWD) is a well-established predictor for mortality in patients with interstitial lung disease (ILD). In this study, we aimed to investigate the 6MWD as a possible predictor for long-term survival after double lung transplantation (DLuTx) in patients with ILD. Methods: A single-center, retrospective data analysis in patients with ILD undergoing DLuTx was conducted (EC: 1251/2019). All ILD patients transplanted between 2013 and 2018 having a 6MWD measurement were included. Patients were divided into quintiles according to their 6MWD (QI: 0-10m; QII: ≥10-70m; QIII: 71-230m; QIV: 231-360m; QV: 361-600m) and compared to short- and long-term survival after DLuTx. Statistical calculations included Kaplan-Meier survival and Cox proportional hazard models. Results: A total of 115 patients were included and 61.7% (n=71) were diagnosed with IPF. The median age was 56 years and 67.8% (n=78) were males. The survival probability after 1 year was 78.1% and after 5 years 71.3%, with significant differences between the quintiles (log-rank test p=0.037). The 5-year survival probability for the five groups was: QI: 50.2% (95% CI 29%-71%); QII: 81.8% (95% CI 66%-98%); QIII: 64% (95% CI 44%-84%); QIV: 78.3% (95% CI 61%-95%); QV: 82.4% (95% CI 67%-98%). In contrast, lung function parameters and lung allocation score could not be identified as predictors for survival. Conclusion: The collected 6MWD of patients with ILD at the time of listing showed a significant association with the survival after DLuTx. These findings may impact the pre-transplant management of patients with ILD.

Background The use of organs from polytrauma donors for lung transplantation is controversial in the literature. For many centers, the radiologic manifestation of lung contusions is a clear reason to reject an organ offer. This results in the loss of potentially viable organs for the donor pool. Methods We analyzed 1152 donor lungs procured by our transplant center between January 2010 and June 2018. These included 118 lungs with a history of polytrauma involving the chest. Sixteen polytrauma donor lungs were rejected after procurement. A total of 102 lungs were transplanted, divided into 2 groups: the polytrauma contusion group (n = 44), comprising polytrauma donors with radiologic signs of lung contusion at the time of offer, and the polytrauma clear group (n = 58), comprising polytrauma donors without lung contusion. Nontrauma donor lungs transplanted during the study period were assigned to a polytrauma control group (n = 650). Short- and long-term outcomes of the 3 groups were compared. Results Basic demographic data and preoperative factors were similar in the 3 groups. Rates of primary graft dysfunction grade 3 at 72 hours did not differ among the 3 groups (0.0% vs 3.4% vs 3.9%; P = .409). The duration of ventilation was similar the 3 groups: 45 hours (interquartile range [IQR], 28-94 hours), 37 hours (IQR, 22-71 hours), and 42 hours (IQR, 22-96 hours), respectively (P = .674). Long-term graft survival was not impaired in the trauma groups compared with controls. One-year survival rates were 84.1% for the polytrauma contusion group, 93.1% for the polytrauma clear group, and 83.1% for the no polytrauma group. Five-year graft survival in the 3 groups was 74.7%, 87.2%, and 70.0%, respectively. Conclusions Lung transplantation using organs from polytrauma donors is associated with similar short- and long-term results as transplantation from nontrauma donors. The presence or absence of radiologic signs of lung contusion at the time of offer has no impact on primary graft function and long-term survival.

RationaleLung transplantation is the ultimate treatment option for patients with end-stage respiratory diseases but bears the highest mortality rate among all solid organ transplantations due to chronic lung allograft dysfunction (CLAD). The mechanisms leading to CLAD remain elusive due to an insufficient understanding of the complex post-transplant adaptation processes.ObjectivesTo better understand these lung adaptation processes after transplantation and to investigate their association with future changes in allograft function.MethodsWe performed an exploratory cohort study of bronchoalveolar lavage samples from 78 lung recipients and donors. We analysed the alveolar microbiome using 16S rRNA sequencing, the cellular composition using flow cytometry, as well as metabolome and lipidome profiling.Measurements and main resultsWe established distinct temporal dynamics for each of the analysed data sets. Comparing matched donor and recipient samples, we revealed that recipient-specific as well as environmental factors, rather than the donor microbiome, shape the long-term lung microbiome. We further discovered that the abundance of certain bacterial strains correlated with underlying lung diseases even after transplantation. A decline in forced expiratory volume during the first second (FEV1) is a major characteristic of lung allograft dysfunction in transplant recipients. By using a machine learning approach, we could accurately predict future changes in FEV1 from our multi-omics data, whereby microbial profiles showed a particularly high predictive power.ConclusionBronchoalveolar microbiome, cellular composition, metabolome and lipidome show specific temporal dynamics after lung transplantation. The lung microbiome can predict future changes in lung function with high precision.

Purpose The diagnosis and treatment of antibody-mediated rejection (AMR) after LTx has gained increasing recognition within the transplant community. Extracorporeal photopheresis (ECP) modulates various pathways of the immune system and is currently used to treat CLAD. In AMR, adding ECP to established AMR treatments could potentially prevent rebound of DSA. This study aimed to analyze the role of ECP as adjunct treatment of AMR. Methods Patients who developed antibody-mediated rejection between 2009 and 2019 were included in this single-center retrospective analysis. The following parameters were evaluated: DSAs, C4d deposition and lung histology. Results A total of 39 patients developed clinical AMR during follow-up. Nineteen (48%) patients had positive DSA against HLA Class I and eighteen (46%) HLA Class II. Median time to diagnosis of AMR was 180 days (IQR: 2-2477). First line treatment was immunoadsorption (IA) in 34 (87%) patients, intravenous immunoglobulins with concomitant immunoadsorption in 3 (8%) patients and in 2 cases ATG. Twenty (51%) patients primarily treated with IA and the two patients treated with ATG received ECP. Among the patients treated with ECP, 12 had DSA against HLA Class I and 13 against HLA Class II. ECP treatment was initially performed twice a week. After stabilization of lung function and improvement of clinical situation, ECP was then performed once a month for a minimum of 6 months. Median length of treatment was 12 months. Patients who received ECP after first line treatment had 1-year survival rate of 62% compared to 27% of other AMR patients. In all patients treated with IA followed by ECP, DSA disappeared or MFI reduced below our institutional threshold of 5000. Conclusion Extracorporeal photopheresis is associated with a reduction of de novo DSA after antibody-mediated rejection. Prospective studies are necessary to confirm the beneficial effect of ECP as an add-on therapy after AMR.

Background Lung transplantation has evolved to a routinely performed surgical procedure in patients with end-stage pulmonary disease. Bronchial healing problems are rare but represent a potential life-threatening complication. Herein, we aimed to define the incidence, classification, and treatment of bronchial complications after lung transplantation. Material and Methods All patients receiving lung transplantation between January 1999 and December 2017 were included in this retrospective study. All bronchial anastomoses were performed in a standardized technique using a single, polydioxanone running suture. The rate of anastomotic complications requiring an intervention, type of complication according the 2018 International Society for Heart and Lung Transplantation classification, and the clinical management were retrospectively analyzed. Results A total of 2941 anastomoses were performed in 1555 patients. The overall incidence of relevant anastomotic complications was 1.56%, 0.68% for left anastomoses, and 2.44% for right anastomoses. In 6 patients, a surgical revision or retransplantation was performed, whereas endoscopic treatment alone was sufficient in 39 patients. One patient underwent right-sided retransplantation 6 months after the first lung transplantation after failed endoscopic treatment attempts. International Society for Heart and Lung Transplantation grade “S Lc Ec” was the most common type of anastomotic complication. The overall incidence decreased within the study period from 2.4% in the era 1999 to 2003 to 0.8% in the era 2014 to 2017. We found no significant difference in overall survival of patients with and without anastomotic complications (P = .995; hazard ratio, 0.99; 95% confidence interval, 0.63-1.58). Conclusions The single running suture technique is associated with a very low rate of true anastomotic complications. Close follow-up and early endoscopic treatment of patients with anastomotic complications result in excellent long-term outcomes.

Purpose Spirometric lung function is one of the central clinical parameters to assess allograft function after lung transplantation (LTX). Reduction in FEV1 can be the result of infections, rejections episodes and most importantly development of CLAD. Currently, there is no means to predict short-term changes in lung function after LTX. Methods Bronchoalveolar samples of patients after standard double LTX were taken during follow-up bronchoscopy at multiple different time points. Lipidomic, metabolomic, flow cytometric and bacterial 16S rRNA gene sequencing (microbiome) data were analyzed. We then used a machine learning approach to predict future changes in FEV1 from these sample data to characterize patient lung function trajectories. We trained support vector machine (SVM) regressors on the collected lipidomic, metabolomic, microbiome and flow cytometry datasets. Changes in FEV1 within 30, 60 or 90 days after lavage sample collection were used as response variables. To train hyper-parameters and evaluate model accuracy, a nested leave-one-out cross validation scheme was used. Model accuracy was benchmarked against a model trained on clinical metadata. Results At a prediction timeframe of 30 days, lipidomic data were available from 34 samples of 20 patients. Lipidomics showed the highest predictive power for short-term changes 30 and 60 days after sample collection. Prediction accuracy (R2) of intra-alveolar lipid composition for a 30-day projection was 0.24, meaning that BAL lipid profiles could explain more than 20 percent of total variation in relative change in FEV1 for this time span. R² for clinical metadata alone was only 0.1, and metabolomics, microbiome and FACS analysis of BAL showed no predictive accuracy at this time point. Conclusion Our results suggest that the intra-alveolar lipid composition is a powerful predictor of short-term changes in lung allograft function. This could potentially facilitate pre-emptive therapeutic interventions.

Purpose The pulmonary microbiome after lung transplantation has recently come into the focus of research. Especially, host-microbiome interactions are thought to be an important factor in graft-related immunological processes. In lung transplantation, temporal changes of the pulmonary microbiome have not yet been elucidated. Methods In a total cohort of 80 patients receiving standard double lung transplantation, 50 bronchioalveolar lavage (BAL) samples from donors were collected prior to cold ischemia. After transplantation, 128 BAL samples were collected at various time points of routine follow-up bronchoscopies between 0 and 400 days post-transplant. Bacterial 16S rRNA gene sequencing was conducted to analyze the composition of the pulmonary microbiome in these samples. Results The lung microbiome showed significant temporal dynamics after lung transplantation. Recipient-donor similarity between matched samples decreased after the first week post transplantation. Underlying transplant indications were significantly associated with microbial profiles even after transplantation. Shannon diversity and Chao1 richness at the species level showed an increasing diversity of the microbiome over time. Conclusion Our data provides new insights into the dynamics of microbial profiles after transplantation. We observed that recipient-associated factors, rather than the donor microbiome, shape the lung microbiome after transplantation.

Purpose New biomarkers reflecting the degree of immunosuppression in transplant recipients are needed to provide an optimal balance between risk for rejection and risk of severe infections. Methods We prospectively measured plasma TTV-DNA dynamics in 365 lung transplant recipients (LuTR) transplanted between 1/2013 and 12/2020. Severe infections, acute cellular and humoral rejection, incidence of CLAD and malignancies were recorded and correlated with dynamic changes in TTV levels. Results Patient demographics are summarized in Table 1. 95% of patients had detectable TTV levels pre-transplant with a mean log value of 4.0±1.6. Post-transplant, all LuTR became TTV positive with a peak value of log9.6±0.6 (range 5.9-10.9). TTV peaked at a mean of 143±109 days after transplantation. Mean TTV PCR values after 3, 4 and 5 years were log6.9±1,4, log6,4±1,4 and log6.0±1.2, respectively. TTV loads were significantly lower in LuTR who had episodes of acute cellular rejection (TTV PCR Conclusion TTV PCR measurement is a potent tool to predict acute cellular rejection episodes, infectious complications and CLAD. It represents a promising tool to monitor individualized immunosuppressive therapy in near future.

Torque teno viruses (TTV) are small DNA-viruses, of the genus Alphatorquevirus, whose replication is linked to immune status. TTV load may be an indicator for efficacy of IS in lung transplant recipients (LTRs). In a prospective single-center-study 143 LTRs were followed up and tested by quantitative TTV-DNA PCR. Using multivariate Cox-regression contribution of TTV-load to the occurrence of severe infections, chronic lung allograft dysfunction (CLAD), acute cellular rejection (ACR), and death was assessed. During follow-up 28 (20%) patients developed infections with a rate of 7.7 per 100 patient-years (PY). The hazard-ratio (HR) associated with a one-log10 increase of TTV-load before the event was 5.05. CLAD occurred with a rate of 6.0%-PY. HR for a 1 log10 increase of the lowest TTV level before the event was 0.71 (CI: 0.54-0.93). TTV-load predicts clinical events and may be useful to optimize IS during the first years of follow-up of LTRs.

Purpose Within the last years increasing attention has been given to antibody-mediated rejection (AMR) due to its poor long-term outcomes. The impact of alemtuzumab on donor-specific antibodies (DSAs) and AMR in lung transplantation is currently unclear and most evidence comes from kidney transplantation. This study aimed to analyze the impact of alemtuzumab induction on the incidence of DSAs and AMR. Methods All patients transplanted between 2007 and 2017, who received alemtuzumab as induction therapy, were included in this retrospective single-center analysis. The following parameters were evaluated: donor-specific antibodies, C4d deposition, lung histology and occurrence of antibody-mediated rejection. Results Within the study period 525 patients received alemtuzumab as induction therapy. Pre-transplant DSAs were present in 64 (12.2%) recipients (53 anti-HLA class I and 40 anti-HLA class II). De novo (dn) DSAs developed in 93 (17.7%) recipients after transplantation (78 anti-HLA class I and 113 anti-HLA class II). Median time to development of dnDSA was 104 days (42-165) and incidence rates at 1 and 5-years after transplantation were 12.1% and 21.4%, respectively. In 20 (3.8%) recipients clinical AMR was diagnosed. Among them, 7 (35%) patients had a definite diagnosis, 9 (45%) a probable one and 4 (20%) a possible one as defined by the latest ISHLT AMR grading system. Deposition of C4d was only positive in 4 (20%) clinical AMR patients. Capillaritis was observed in 4 (20%) cases and neutrophilic septal margination in 3 cases (15%). Anti-HLA class I and class II were positive in 11 (55%) and 13 (65%) recipients, respectively. Long-term survival of recipients, who developed AMR, was significantly worse than other recipients, with a 5-years rate of 45% vs 75% (p Conclusion Alemtuzumab induction therapy is associated with a low incidence of dnDSAs and AMR. Long-term outcome of these patients remains poor.

Long acting β₂-agonists (LABA) have been reported to modify the extracellular matrix (ECM) composition in the airway wall. Based on our earlier studies we here investigated the mechanism underlying the control of ECM modification by LABA in primary human airway smooth muscle cells. Cells were treated with formoterol or salmeterol (30 min) before TGF-β₁ stimulation (2-3 days) Using RT-PCT, immuno-blotting and ELISA the de novo synthesis and deposition of collagen type-I, -III, -IV and fibronectin were determined. Matrix metalloproteinases (MMP)-2 and -9 were analyzed by zymography. Both LABA activated cAMP and its corresponding transcription factor CREB within 60 min and thus partly reduced TGF-β₁-induced gene transcription of collagen type-I, -III, fibronectin and connective tissue growth factor (CTGF). The inhibitory effect of both LABA on collagen type-I and -III deposition involved a cAMP dependent mechanism, while the inhibitory effect of the two drugs on TGF-β1-induced fibronectin deposition and on CTGF secretion was independent of cAMP. Interestingly, none of the two LABA reduced CTGF-induced synthesis of collagen type-I or type-III deposition. In addition, none of the two LABA modified collagen type-IV deposition or the expression and activity of MMP-2 or MMP-9. Our results show that LABA can prevent de novo deposition of specific ECM components through cAMP dependent and independent signaling. However, they do not reduce all ECM components by the same mechanism and they do not reduce existing collagen deposits. This might explain some of the controversial reports on the anti-remodeling effect of LABA in chronic inflammatory lung diseases.

Background Incidentally discovered lung cancers in lung transplant (LuTX) recipients are rare but may affect outcome. We aim to report our single center experience with incidence, management, and survival of patients with previously unverified primary lung cancer discovered at the time of LuTX. Methods A total of 1262 patients undergoing LuTX between 1989 and 2012 were retrospectively analyzed in our prospective database. Results Patients identified were six men and five women with a mean age of 54.4±9.9 years. The indication for LuTX was COPD (n=9), pulmonary fibrosis (n=1), and cystic fibrosis (n=1). Histological diagnosis of the explanted lung revealed adenocarcinoma in six, squamous cell carcinoma in three, and lepidic predominant adenocarcinoma in two cases, respectively. Staging revealed stage IA (pT1a/b pN0) in eight and IB (pT2a pN0) in two cases and one patient in stage IIA (pT1b pN1). Subsequent cancer staging after LuTX revealed no metastasis. Immunosuppression was adjusted and no adjuvant chemo- or radiotherapy was administered. The 5-year survival rate was 90.5% with no detection of recurrence. Conclusion In patients with incidentally detected early stage lung cancer at the time of LuTX, rates of recurrence and survival based on this sample appear to be acceptable.

Background Pulmonary alveolar microlithiasis (PAM) is a rare lung disease caused by calcifications within the alveolar space. The only known effective treatment for an end-stage PAM is lung transplantation (LuTX). Methods We performed a retrospective chart review of all individuals that underwent lung transplantation at our center between 1989 and 2013. Five consecutive patients with PAM were identified. Results Four females and one male with a mean age of 46.3 yr were identified. Extracorporeal membrane oxygenation (ECMO) support was required intraoperatively in four cases and post-operatively in one case. Mean post-operative intubation time was 3.3 (range, 2-5) d and mean intensive care unit (ICU) stay was 8.3 (range, 4-12) d. No intraoperative complications were observed. One early patient (operated in 1995) underwent acute re-transplantation on the second post-operative day (POD) and died from sepsis on the 11 POD. In one patient reperfusion edema was observed requiring a prolonged weaning process. No other severe perioperative complications were observed. Four of five patients are currently still alive with normal follow-up parameters. No recurrence of PAM was observed. Conclusions Lung transplantation is a feasible therapy option in patients with end-stage PAM showing good post-operative results comparable to other indications for LuTX.

Gram-negative sepsis resulting in endotoxin triggered septic shock is one of the leading causes of death in critically ill patients. Because treatment options are limited, recent approaches focus on immunomodulatory effects of antimicrobials. Thus, we characterized the immunomodulatory effects of linezolid at mRNA and on cytokine levels in supernatants of an ex vivo model of endotoxemia. Whole blood from 10 healthy volunteers was incubated with 50 pg/ml LPS with or without 13 microg/ml linezolid (concentrations were chosen to reflect in vivo conditions) for 2 and 4 hours (h). Quantitative real-time PCR was performed from messenger RNA (mRNA) of IL-1beta;, IL-6, IL-8 or TNF-alpha;. Cytokine levels in the supernatant were measured by ELISA for IL-6, IL-8 and TNF-alpha;. Incubation of human whole blood with LPS increased mRNA levels of cytokines several thousand fold compared with baseline. The addition of linezolid significantly reduced mRNA levels of IL-1beta, IL-6, IL-8 and TNF-alpha; (p < 0.05) after 2 and 4 h. LPS stimulation also increased levels of IL-6, IL-8 and TNF-alpha between 100 and 1000-fold. However, in contrast to mRNA - except for IL-6 - no significant reduction at protein level was observed. These results indicate that immunosuppressive effects of linezolid on mRNA transcription are only partially reflected by cytokine release.

Vasoactive intestinal peptide (VIP) is one of the most abundant molecules found in the respiratory tract. Due to its anti-inflammatory and bronchodilatatory properties, it has been proposed as a novel treatment for chronic obstructive pulmonary disease (COPD). The actions of VIP are mediated via three different G-protein-coupled receptors (VPAC1, VPAC2 and PAC1) which are expressed in the respiratory tract and on immunocompetent cells including macrophages. Alveolar macrophages (AM) are key players in the pathogenesis of COPD and contribute to the severity and progression of the disease. While VPAC1 has been reported to be elevated in subepithelial cells in smokers with chronic bronchitis, little is known about VPAC expression of AM in COPD patients. AM from COPD patients show a strong VPAC1 expression which exceeds VPAC2. A similar receptor expression pattern was also observed in lipopolysaccharide (LPS)-activated monocyte-derived macrophages (MDM) from healthy volunteers and COPD patients. VIP has been shown to down-regulate interleukin 8 (IL-8) secretion significantly in MDM after LPS stimulation. The response to VIP was similar in MDM from COPD patients and healthy volunteers. Our results indicate that VPAC1 up-regulation in macrophages is a common mechanism in response to acute and chronic pro-inflammatory stimuli. Although VPAC1 up-regulation is dominant, both receptor subtypes are necessary for optimal anti-inflammatory signaling. The high VPAC1 expression in AM may reflect the chronic pro-inflammatory environment found in the lung of COPD patients. Treatment with VIP may help to decrease the chronic inflammation in the lung of COPD patients.

In previous studies, tetracyclines have been shown to decrease the release of cytokines in experimental settings of endotoxaemia. Tigecycline is the first member of the closely related glycylglycines and, due to its broad antimicrobial spectrum, it is considered useful in the treatment of sepsis. We therefore tested its ability to influence the concentrations of the proinflammatory cytokines interleukin (IL)-1beta, tumour necrosis factor-alpha (TNFalpha) and IL-6 in an established ex vivo model of human endotoxaemia. Whole blood from ten healthy volunteers was incubated with either saline (negative control), tigecycline (1 microg/mL [therapeutic concentration] or 100 microg/mL [supratherapeutic concentration]), lipopolysaccharide (LPS; 50 pg/mL, control) or a combination of tigecycline plus LPS (test group). Concentrations of IL-1beta, TNFalpha and IL-6 in the supernatant were measured using commercially available enzyme-linked immunosorbent assay (ELISA) kits. As expected, incubation with LPS significantly increased the cytokine concentrations in whole blood compared with baseline (P

Background: Mediators of preferably mesenchymal repair such as transforming growth factor β1 (TGF-β1) and mediators of polarized cellular immunity such as interleukin (IL)-13 are thought to be of key importance for progression of lung fibrosis. Nonetheless, a correlation between these mediators and the clinical development of fibrosis has not been performed thus far. Objectives: We correlated the transcription of TGF-β1, connective tissue growth factor (CTGF), IL-4, IL-13 and interferon-γ (IFN-γ) with lung function development in progressive fibrosis in idiopathic interstitial pneumonia. Methods: One hundred seventy nine sets of RT-PCR measurements were analyzed in 49 patients with usual interstitial pneumonia, nonspecific interstitial pneumonia or both. Specimens were taken by surgical and transbronchial lung biopsy. Lung function was measured at the time of biopsy and 1 year later. All patients received conventional treatment. Thirteen individuals were used as controls. Results: Transcription of TGF-β1, CTGF and IL-13 was significantly higher in pulmonary fibrosis compared to control, whereas transcription of IFN-γ and IL-4 was virtually absent in both normal and fibrotic lungs. When comparing gene transcription with development of lung function, a significant correlation was observed between the decrease in both vital capacity and total lung capacity and increased transcription levels of TGF-β1 and IL-13. A reduced pulmonary diffusion capacity correlated with increased levels of TGF-β1 and CTGF. Transcription pattern in transbronchial and surgical samples was similar. Conclusions: We found a significant correlation between gene transcription and decrease in lung function that was more pronounced for TGF-β1 than for CTGF or IL-13. Our results suggest that transcription analysis may be used in clinical assessment of pulmonary fibrosis.

BACKGROUND: Pulmonary arterial hypertension is characterized by increased thickness of pulmonary vessel walls due to both increased proliferation of pulmonary arterial smooth muscle cell (PASMC) and deposition of extracellular matrix. In patients suffering from pulmonary arterial hypertension, endothelin-1 (ET-1) synthesis is up-regulated and may increase PASMC activity and vessel wall remodeling through transforming growth factor beta-1 (TGF-beta1) and connective tissue growth factor. OBJECTIVE: To assess the signaling pathway leading to ET-1 induced proliferation and extracellular matrix deposition by human PASMC. METHODS: PASMC were serum starved for 24 hours before stimulation with either ET-1 and/or TGF-beta1. ET-1 was inhibited by Bosentan, ERK1/2 mitogen activated protein kinase (MAPK) was inhibited by U0126 and p38 MAPK was inhibited by SB203580. RESULTS: ET-1 increased PASMC proliferation when combined with serum. This effect involved the mitogen activated protein kinases (MAPK) ERK1/2 MAPK and was abrogated by Bosentan which caused a G1- arrest through activation of p27((Kip)). Regarding the contribution of extracellular matrix deposition in vessel wall remodeling, TGF-beta1 increased the deposition of collagen type-I and fibronectin, which was further increased when ET-1 was added mainly through ERK1/2 MAPK. In contrast, collagen type-IV was not affected by ET-1. Bosentan dose-dependently reduced the stimulatory effect of ET-1 on collagen type-I and fibronectin, but had no effect on TGF-beta1. CONCLUSION AND CLINICAL RELEVANCE: ET-1 alone does not induce PASMC proliferation and extracellular matrix deposition. However, ET-1 significantly up-regulates serum induced proliferation and TGF-beta1 induced extracellular matrix deposition, specifically of collagen type-I and fibronectin. The synergistic effects of ET-1 on serum and TGF-beta1 involve ERK1/2 MAPK and may thus present a novel mode of action in the pathogenesis of pulmonary arterial hypertensi