Walter Klepetko

Imaging in Pulmonary Hypertension

Pulmonary hypertension is defined as an increase in mean pulmonary arterial pressure ≥25 mm Hg at rest and occurs in a majority of patients with heart failure. Diagnostic imaging targets the right ventricle and the pulmonary vasculature. Although echocardiography is cost-effective for screening and follow-up, right heart catheterization is still mandatory to differentiate pre- from post-capillary disease and to directly measure pressure and flow. An important goal is to rule out chronic thromboembolic pulmonary hypertension. This diagnostic step can be achieved by perfusion scintigraphy, whereas computed tomography and cardiac magnetic resonance have become indispensable ancillary methods for the diagnostic allocation to other World Health Organization subtypes of pulmonary hypertension.

Apelin Expression in Human Non-small Cell Lung Cancer: Role in Angiogenesis and Prognosis

Introduction: The recently discovered bioactive peptide, apelin, has been demonstrated to stimulate angiogenesis in various experimental systems. However, its clinical significance and role in tumor vascularization have not yet been investigated in a human malignancy. Therefore, our aim was to study whether apelin expression is associated with angiogenesis and/or tumor growth/behavior in human non-small cell lung cancer (NSCLC). Methods: A total of 94 patients with stage I–IIIA NSCLC and complete follow-up information were included. Apelin expression in human NSCLC samples and cell lines was measured by quantitative reverse-transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. Effects of exogenous apelin and apelin transfection were studied on NSCLC cell lines in vitro. In vivo growth of tumors expressing apelin or control vectors were also assessed. Morphometric variables of human and mouse tumor capillaries were determined by anti-CD31 labeling. Results: Apelin was expressed in all of the six investigated NSCLC cell lines both at the mRNA and protein levels. Although apelin overexpression or apelin treatments did not increase NSCLC cell proliferation in vitro, increasing apelin levels by gene transfer to NSCLC cells significantly stimulated tumor growth and microvessel densities and perimeters in vivo. Apelin mRNA levels were significantly increased in human NSCLC samples compared with normal lung tissue, and high apelin protein levels were associated with elevated microvessel densities and poor overall survival. Conclusions: This study reveals apelin as a novel angiogenic factor in human NSCLC. Moreover, it also provides the first evidence for a direct association of apelin expression with clinical outcome in a human cancer.

Dysregulation of the IL-13 receptor system: a novel pathomechanism in pulmonary arterial hypertension.

RATIONALEnIdiopathic pulmonary arterial hypertension (IPAH) is characterized by medial hypertrophy due to pulmonary artery smooth muscle cell (paSMC) hyperplasia. Inflammation is proposed to play a role in vessel remodeling associated with IPAH. IL-13 is emerging as a regulator of tissue remodeling; however, the contribution of the IL-13 system to IPAH has not been assessed.nnnOBJECTIVESnThe objective of this study was to assess the possible contribution of the IL-13 system to IPAH.nnnMETHODSnExpression and localization of IL-13, and IL-13 receptors IL-4R, IL-13Rα1, and IL-13Rα2 were assessed by real-time reverse transcription-polymerase chain reaction, immunohistochemistry, and flow cytometry in lung tissue, paSMC, and microdissected vascular lesions from patients with IPAH, and in lung tissue from rodents with hypoxia- or monocrotaline-induced pulmonary hypertension. A whole-genome microarray analysis was used to study IL-13-regulated genes in paSMC.nnnMEASUREMENTS AND MAIN RESULTSnPulmonary expression of the IL-13 decoy receptor IL-13Rα2 was up-regulated relative to that of the IL-13 signaling receptors IL-4R and IL-13Rα1 in patients with IPAH and in two animal models of IPAH. IL-13, signaling via STAT3 and STAT6, suppressed proliferation of paSMC by promoting G(0)/G(1) arrest. Whole-genome microarrays revealed that IL-13 suppressed endothelin-1 production by paSMC, suggesting that IL-13 controlled paSMC growth by regulating endothelin production. Ectopic expression of the il13ra2 gene resulted in partial loss of paSMC growth control by IL-13 and blunted IL-13 suppression of endothelin-1 production by paSMC, whereas small-interfering RNA knockdown of il13ra2 gene expression had the opposite effects.nnnCONCLUSIONSnThe IL-13 system is a novel regulator of paSMC growth. Dysregulation of IL-13 receptor expression in IPAH may partially underlie smooth muscle hypertrophy associated with pathological vascular remodeling in IPAH.

Efficacy and safety of TachoSil® versus standard treatment of air leakage after pulmonary lobectomy,

OBJECTIVESnAlveolar air leakage remains a serious problem in lung surgery, being associated with increased postoperative morbidity, prolonged hospital stay and greater health-care costs. The aim of this study was to evaluate the sealing efficacy and safety of the surgical patch, TachoSil®, in lung surgery.nnnMETHODSnPatients undergoing elective pulmonary lobectomy who had grade 1 or 2 air leakage (evaluated by the water submersion test) after primary stapling and limited suturing were randomised at 12 European centres to open-label treatment with TachoSil® or standard surgical treatment (resuturing, stapling or no further treatment at the surgeons discretion). Randomisation was performed during surgery using a centralised interactive voice response system. Duration of postoperative air leakage (primary end point), reduction of intra-operative air leakage intensity (secondary end point) and adverse events (AEs), including postoperative complications, were assessed.nnnRESULTSnA total of 486 patients were screened and 299 received trial treatment (intent-to-treat (ITT) population: TachoSil®, n=148; standard treatment, n=151). TachoSil® resulted in a reduction in the duration of postoperative air leakage (p=0.030). Patients in the TachoSil® group also experienced a greater reduction in intra-operative air leakage intensity (p=0.042). Median time until chest drain removal was 4 days with TachoSil® and 5 days in the standard group (p=0.054). There was no difference between groups in hospital length of stay. AEs were generally similar in both groups, including postoperative complications.nnnCONCLUSIONSnTachoSil® was superior to standard surgical treatment in reducing both postoperative air leakage duration and intra-operative air leakage intensity in patients undergoing elective pulmonary lobectomy.

Treprostinil inhibits the recruitment of bone marrow-derived circulating fibrocytes in chronic hypoxic pulmonary hypertension.

A unique subpopulation of peripheral blood mononuclear cells that exhibit a parallel expression of haematopoietic and mesenchymal markers has been described as “circulating fibrocytes”. These cells were demonstrated to obtain a fibroblastic phenotype in tissues or cell culture and contribute to pulmonary fibrotic disorders and tissue remodelling processes. The aim of our study was to characterise the recruitment of circulating fibrocytes in vivo in the model of chronic hypoxic pulmonary hypertension in mice and to analyse the therapeutic effect of the stable prostacyclin analogue trepostinil with respect to this cell population. To track circulating fibrocytes in vivo, we transplanted wild-type mice with bone marrow from ubiquitously eGFP expressing mice and subjected them to chronic hypoxia. We observed significantly increased recruitment of circulating fibrocytes to the remodelled pulmonary resistance arteries in response to hypoxia. Treatment with treprostinil significantly reduced the recruitment of these cells compared to normoxic mice. Treprostinil also reduced right ventricular systolic pressure and slightly reduced the vascular remodelling but failed to reverse the right ventricular hypertrophy. In summary, we show that circulating fibrocytes contribute to hypoxic pulmonary vascular remodelling and may be specifically targeted by a prostacyclin analogue. Further investigations of cellular and paracrine mechanisms are warranted to decipher their role in pulmonary hypertension.

Endothelin-1 is a useful biomarker for early detection of bronchiolitis obliterans in lung transplant recipients

OBJECTIVESnBronchiolitis obliterans (BO) is a severe complication limiting long-term survival after lung transplantation. To date, no cure exists for BO, and the mechanisms leading to BO are not well understood. Endothelin-1 (ET-1) is a potent mitogenic and profibrotic peptide produced by pulmonary vascular endothelial cells that play a role in the pathophysiology of lung allograft dysfunction. Whether ET-1 could predict BO syndrome (BOS) development is unknown.nnnMETHODSnTransbronchial biopsy specimens and serum and bronchoalveolar lavage were obtained from 30 lung transplantation patients with and 30 without BOS at 3 points. The serum and bronchoalveolar lavage ET-1 concentrations were measured by enzyme-linked immunosorbent assay, and the ET-1 mRNA expression in the transbronchial biopsy specimens was examined using real-time polymerase chain reaction.nnnRESULTSnThe pretransplant ET-1 serum concentrations were greater in the patients with BOS (P = .02); and ET-1 mRNA was significantly upregulated in the lung grafts of those with versus those without BOS at 3 and 12 months after transplant (P = .01). At 3 and 12 months after transplantation, the ET-1 concentrations were significantly elevated in the serum (P < .01 and P < .0001, respectively) and bronchoalveolar lavage (P < .01 and P = .02, respectively) of patients with compared with those without BOS. On logistic regression analysis, the pretransplant and 3-month post-transplant serum ET-1 level predicted for BOS (odds ratio, 1.01; 95% confidence interval, 1.004-1.025; P < .007; odds ratio, 2.9; 95% confidence interval, 1.01-8.52; P < .001). The serum ET-1 level at 12 months was diagnostic for BOS (odds ratio, 3.9; 95% confidence interval, 1.42-10.80; P = .008).nnnCONCLUSIONSnElevated serum ET-1 concentrations were predictive of BOS, and the assessment of circulating ET-1 might be beneficial in diagnosing and monitoring BO.

Extending Surgery for Pulmonary Metastasectomy: What Are the Limits?

Introduction: The purpose of pulmonary metastasectomy is to remove all known remaining cancer with the purpose of cure or to lengthen survival. Little information is available on the extent of surgery that is justified and or on reasonable evidence based limits to the extent of surgery. Methods: A systematic review was designed to evaluate the role of extended surgery in the treatment of lung metastasis. For this analysis, the following three research questions were formulated.Q1) Is pneumonectomy indicated for pulmonary metastasectomy?Q2) What is the number of repeat operations justified and what might be the criteria?Q3) What number of individual metastases is it justified to remove in a single procedure? A MEDLINE search of English language articles was conducted using key words appropriate to the three questions posed. We excluded reports with little or no data, single cases, small series, and review articles without data. Results: Most information concerning extremes of surgery is in the form of case reports, small series, or sporadic cases within a retrospective report of a larger group of patients undergoing pulmonary metastasectomy. Meta-analysis was ruled out because of the insufficient quantity and quality of data in the available literature.Q1) extended resection for pulmonary metastasis is feasible and may be justified in individualized circumstances. We believe caution is warranted before performing pneumonectomy because it is debatable whether any possible benefit justifies the adverse consequences of this surgery and long-term survival is poor.Q2) multiple attempts to re-establish intrathoracic control of metastatic disease supported by some authors in carefully selected patients, but apparent benefit may be a result of survivor bias, and the ratio of harm to benefit is likely to increase with each subsequent attempt.Q3) if on accepted criteria specific to the primary cancer the patient is a candidate for pulmonary metastastasecomy, then the goal should be to resect all metastases that are there, irrespective of the number. However, with increasing pulmonary metastatic count, there is less good survival and greater loss of lung tissue. These issues should be fully considered at the planning stage. Conclusions: Evidence-based recommendations for extended treatment of lung metastasis are at best weak. We have summarized the available data to provide the most up to date information regarding extended surgery in an attempt to define limits in the treatment of lung metastasis.

Concomitant endothelin-1 overexpression in lung transplant donors and recipients predicts primary graft dysfunction.

Primary graft dysfunction (PGD) causes significant morbidity following lung transplantation (LTX). Mortality is high in PGD and therapeutic strategies are limited. To investigate whether endothelin‐1 (ET‐1) that mediates increased vascular permeability and edema formation in lung grafts can predict PGD, ET‐1 mRNA expression was examined in lung tissue biopsies of 105 donors and recipients obtained shortly before LTX. Serum ET‐1 concentration was assessed by ELISA. PGD grade was diagnosed and scored by oxygenation and radiological characteristics according to ISHLT guidelines. PGD grade 3 developed in 11% of patients. ET‐1 mRNA expression was significantly increased in both donor (p < 0.0001) and recipient (p = 0.01) developing PGD as compared to no PGD group. Pretransplant ET‐1 serum concentrations were elevated in recipients with PGD as compared to no PGD group (p < 0.0001), although serum ET‐1 was not different between donors whose grafts developed PGD grades 0–3. In regression analysis, concomitant elevated donor tissue ET‐1 and recipient serum ET‐1 predicted PGD grade 3. This study indicates that pretransplant ET‐1 mRNA overexpression in donors associated with elevated pretransplant serum ET‐1 in recipients contribute to PGD development and that their assessment might be beneficial to predict PGD and to identify recipients who could benefit from a targeted ET‐1 blockade.

Inhibition of c-Met with the Specific Small Molecule Tyrosine Kinase Inhibitor SU11274 Decreases Growth and Metastasis Formation of Experimental Human Melanoma

The hepatocyte growth factor/scatter factor (HGF/SF) tyrosine kinase (TK) receptor c-Met plays a crucial role in the development of the invasive phenotype of tumors and thus represents an attractive candidate for targeted therapies in a variety of malignancies, including human malignant melanoma (MM). In contrast to what has been shown previously, we were not able to detect any genetic alterations, either in the juxtamembrane- or in the TK-domain of c-Met, in the studied MM cell lines. Nevertheless, c-Met was constitutively active in these cell lines without exogenous HGF/SF stimulation. The active receptor was localized to the adhesion sites of the cells. Addition of the c-Met TK inhibitor SU11274 specifically decreased the phosphotyrosine signal at the focal adhesions sites, which was accompanied by a decrease in cell proliferation as well as an increase in apoptotic cells. In addition, non-apoptotic concentrations of SU11274 significantly reduced the in vitro migratory capacity of MM cells in the modified Boyden-chamber assay. Administration of SU11274 significantly decreased primary tumor growth as well as the capacity for liver colony formation of MM cells in SCID mice. Our study provides the first evidence for an in vivo antitumor activity of SU11274 in a human melanoma xenograft model, and suggests c-Met as a valid target for the therapy of MM. Consequently, SU11274 treatment might represent a useful strategy for controlling melanoma progression and metastasis in patients with MM.

Phosphodiesterase 6 subunits are expressed and altered in idiopathic pulmonary fibrosis.

BackgroundIdiopathic Pulmonary Fibrosis (IPF) is an unresolved clinical issue. Phosphodiesterases (PDEs) are known therapeutic targets for various proliferative lung diseases. Lung PDE6 expression and function has received little or no attention. The present study aimed to characterize (i) PDE6 subunits expression in human lung, (ii) PDE6 subunits expression and alteration in IPF and (iii) functionality of the specific PDE6D subunit in alveolar epithelial cells (AECs).Methodology/Principal FindingsPDE6 subunits expression in transplant donor (n = 6) and IPF (n = 6) lungs was demonstrated by real-time quantitative (q)RT-PCR and immunoblotting analysis. PDE6D mRNA and protein levels and PDE6G/H protein levels were significantly down-regulated in the IPF lungs. Immunohistochemical analysis showed alveolar epithelial localization of the PDE6 subunits. This was confirmed by qRT-PCR from human primary alveolar type (AT)II cells, demonstrating the down-regulation pattern of PDE6D in IPF-derived ATII cells. In vitro, PDE6D protein depletion was provoked by transforming growth factor (TGF)-β1 in A549 AECs. PDE6D siRNA-mediated knockdown and an ectopic expression of PDE6D modified the proliferation rate of A549 AECs. These effects were mediated by increased intracellular cGMP levels and decreased ERK phosphorylation.Conclusions/SignificanceCollectively, we report previously unrecognized PDE6 expression in human lungs, significant alterations of the PDE6D and PDE6G/H subunits in IPF lungs and characterize the functional role of PDE6D in AEC proliferation.