David Santer

Evaluation of the downstream aorta after frozen elephant trunk repair for aortic dissections in terms of diameter and false lumen status.

OBJECTIVES To analyse the clinical outcomes of surgical repair of DeBakey type I and III aortic dissection (AD) by using the frozen elephant trunk (FET) technique, and to evaluate the postoperative behaviour of the residual aorta. METHODS In total, 27 consecutive patients underwent treatment of the thoracic aorta for AD with the FET technique in a tertiary-care hospital in Vienna/Austria between 2005 and 2012, and were enrolled in this case series study. All operations were performed under circulatory arrest and bilateral antegrade cerebral perfusion. During the follow-up, a clinical examination was performed as well as aortic diameters and false lumen (FL) patency evaluated by computed tomography (CT) imaging at following levels: pulmonary bifurcation, diaphragm and coeliac trunk. RESULTS The mean age of the patient cohort was 56 ± 12 years; 21 patients were male. Twenty-two (82%) and 5 (18%) patients presented with DeBakey type I and type III AD, respectively. The hospital mortality rate was 7% (2/28); 2 patients died due to non-aortic-related reasons during a follow-up period of 48 ± 26 months. Three (11%) patients had a stroke, and 2 (7%) a spinal cord injury. The follow-up CT scans revealed FL thrombosis in 96% of the patients at the level of the pulmonary bifurcation (P < 0.001). Distal to the stent graft, at the level of the diaphragm and coeliac trunk, FL patency was observed in 52% (P = 0.1) and 78% (P = 0.6) of the patients, respectively. The true lumen of all analysed aortic segments increased significantly while the mean aortic diameter remained stable. CONCLUSIONS Compared with conventional surgery for extensive ADs, the FET technique provides a high rate of FL thrombosis of the thoracic aorta.

Myofilament protein carbonylation contributes to the contractile dysfunction in the infarcted LV region of mouse hearts

AIMS The region-specific mechanical function of left ventricular (LV) murine cardiomyocytes and the role of phosphorylation and oxidative modifications of myofilament proteins were investigated in the process of post-myocardial infarction (MI) remodelling 10 weeks after ligation of the left anterior descending (LAD) coronary artery. METHODS AND RESULTS Permeabilized murine cardiomyocytes from the remaining anterior and a remote non-infarcted inferior LV area were compared with those of non-infarcted age-matched controls. Myofilament phosphorylation, sulfhydryl (SH) oxidation, and carbonylation were also assayed. Ca(2+) sensitivity of force production was significantly lower in the anterior wall (pCa50: 5.81 ± 0.03, means ± SEM, at 2.3 µm sarcomere length) than that in the controls (pCa50: 5.91 ± 0.02) or in the MI inferior area (pCa50: 5.88 ± 0.02). The level of troponin I phosphorylation was lower and that of myofilament protein SH oxidation was higher in the anterior location relative to controls, but these changes did not explain the differences in Ca(2+) sensitivities. On the other hand, significantly higher carbonylation levels, [e.g. in myosin heavy chain (MHC) and actin] were observed in the MI anterior wall [carbonylation index (CI), CIMHC: 2.06 ± 0.46, CIactin: 1.46 ± 0.18] than in the controls (CI: 1). In vitro Fenton-based myofilament carbonylation in the control cardiomyocytes also decreased the Ca(2+) sensitivity of force production irrespective of the phosphorylation status of the myofilaments. Furthermore, the Ca(2+) sensitivity correlated strongly with myofilament carbonylation levels in all investigated samples. CONCLUSION Post-MI myocardial remodelling involves increased myofibrillar protein carbonylation and decreased Ca(2+) sensitivity of force production, leading potentially to contractile dysfunction in the remaining cardiomyocytes of the infarcted area.

Introducing a mouse model of brain death

Experimental animal models of brain death increasing intracranial pressure (ICP) by inflating an intracranial placed balloon-catheter are well established and used in transplant-associated studies. Our aim was to develop an experimental mouse model of brain death (BD) and to compare explosive and gradual brain death induction under ICP monitoring. We therefore induced BD in female OF-1 mice by injecting 40 microl saline every 5 min into an intracranial placed balloon increasing ICP rapidly [BD ex, n=7], or gradually [BD grad, n=7] with 20 microl volume every 5 min under electroencephalogram (EEG) and ICP monitoring until BD occurred. The major criterion for BD was a flat-line-EEG, confirmed by cessation of spontaneous respiration and maximally dilated and fixed pupils. ICP, central activity and heart rate were continuously monitored during the entire 6h follow-up. In sham-operated controls [control, n=7] a burr hole was drilled but no balloon inserted. The BD groups showed equal ICP levels at the time of BD. Both groups had increased heart rates (HR) 15 min after BD, HR decreased to 402+/-29.39 bpm (beats per minute) [BD ex] and 409.33+/-26.46 bpm [BD grad] (n.s. vs. control) by 30 min after the inflation of the balloon, but only BD ex showed a significant decrease in HR compared to control, progressively decreasing thereafter. On the basis of these results, we conclude that the mouse model of brain death can be performed in a standardized, reproducible and successful way.

Argon preconditioning enhances postischaemic cardiac functional recovery following cardioplegic arrest and global cold ischaemia

OBJECTIVES Previous studies demonstrated that preconditioning with argon gas provided a marked reduction in inflammation and apoptosis and increased myocardial contractility in the setting of acute myocardial ischaemia-reperfusion (IR). There is substantial evidence that myocardial IR injury following cardioplegic arrest is associated with the enhancement of apoptosis and inflammation, which is considered to play a role in cardiac functional impairment. Therefore, the present study was designed to clarify whether preconditioning with argon gas enhances recovery of cardiac function following cardioplegic arrest. METHODS Sprague-Dawley rats were anaesthetized and ventilated and allocated to (i) the control group (control IR, n = 10) and (ii) the in vivo group (argon IR), which received 3 cycles of argon (50% argon, 21% oxygen and 29% nitrogen, n = 10) administered for 5 min interspersed with 5 min of a gas mixture (79% nitrogen and 21% oxygen). The hearts were excised and then evaluated in an erythrocyte-perfused isolated working heart system. Cold ischaemia (4°C) for 60 min was induced by histidine-tryptophan-ketoglutarate cardioplegia, followed by 40 min of reperfusion. Cardiac functional parameters were assessed. In left ventricular tissue samples, the expressions of extracellular-regulated kinase (ERK1/2), AKT serine/threonine kinase (Akt), jun N-terminal kinase (JNK), endothelial nitric oxide synthase (eNOS) and HMGB1: high-mobility group box 1 (HMGB1) protein were assessed by western blot, and high-energy phosphates were evaluated by high-performance liquid chromatography. RESULTS At the end of reperfusion, the rats preconditioned with argon showed significantly enhanced recovery of cardiac output (101 ± 6% vs 87 ± 11%; P < 0.01), stroke volume (94 ± 4% vs 80 ± 11%; P = 0.001), external heart work (100 ± 6% vs 81 ± 13%; P < 0.001) and coronary flow (90 ± 13% vs 125 ± 21%; P < 0.01) compared with the control IR group. These results were accompanied by a significant increase in the levels of myocardial phosphocreatine (23.71 ± 2.07 µmol/g protein vs the control IR group, 13.50 ± 4.75; P = 0.001) and maintained adenosine triphosphate levels (13.62 ±1.89 µmol/g protein vs control IR group adenosine triphosphate: 10.08 ± 1.94 µmol/g; P = 0.017). Additionally, preconditioning with argon markedly reduced the activation of JNK (0.11 ± 0.01 vs 0.25 ± 0.03; P = 0.005) and the expression of HMGB1 protein (0.52 ± 0.04 vs 1.5 ± 0.10; P < 0.001) following reperfusion. CONCLUSIONS Preconditioning with argon enhanced cardiac functional recovery in rat hearts arrested with histidine-tryptophan-ketoglutarate cardioplegia, thereby representing a potential novel cardioprotective approach in cardiac surgery.

Differences in stem cell processing lead to distinct secretomes secretion — implications for differential results of previous clinical trials of stem cell therapy for myocardial infarction†

Stem cell therapy for acute myocardial infarction (AMI) seemed to be a promising therapy, however, large clinical trials brought differential outcome. It has been shown that paracrine effects of secretomes of stem cells rather than cell therapy might play a fundamental role. The present study seeks to compare cell processing protocols of clinical trials and investigate effects of differential cell culture conditions on chemokine secretion and functional effects. Different secretomes are compared regarding IL-8, VEGF, MCP-1, and TNF-alpha secretion. Secretome mediated effects are evaluated on endothelial cell (HUVEC) tube formation and migration. Cardioprotective signaling kinases in human cardiomyocytes are determined by Western immunoblotting. Cells processed according to the REPAIR-AMI protocol secrete significantly higher amounts of IL-8 (487.3 ± 1231.1 vs 9.1 ± 8.2 pg mL-1 ; p < 0.05). REAPIR-AMI supernatants lead to significantly pronounced tube formation and migration on HUVEC and enhance the phosphorylation of Akt, ERK, and CREB. Cell processing conditions have a major impact on the composition of the secretome. The REPAIR-AMI secretome significantly enhances proangiogenic chemokine secretion, angiogenesis, cell migration, and cardioprotective signaling pathways. These results might explain differential outcomes between clinical trials. Optimizing cell processing protocols with special regards to paracrine factors, might open a new therapeutic concept for improving patient outcome.

In vivo and ex vivo functional characterization of left ventricular remodelling after myocardial infarction in mice

The interest in cardiac remodelling (REM) has steadily increased during recent years. The aim of this study was to functionally characterize REM following myocardial infarction (MI) in mice using high‐end in vivo and ex vivo methods.

Formation of typical vascular lesions in a new experimental model of pulmonary arterial hypertension

Background: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by obstruction of small pulmonary arteries leading to increased pulmonary vascular resistance. The key pathologic finding is a negative vascular remodeling process with total vessel occlusion and a monoclonal expansion of endothelial cells. Vascular endothelial growth factor (VEGF) signaling plays a significant role in this process. Aim of our study was to investigate whether inhibition of VEGFR-2 (KDR) by gene manipulation may replicate classical pulmonary vasculopathy. Methods: We utilized mice with conditional KDR knock-out in endothelial cells (KDR-/-). KDRflox/flox/Tie-2Cre and KDRflox/flox/Tie-2 mice were injected intraperitoneally with tamoxifen for 3 weeks to induce knock-out. KDR-/- mice and wild type littermates were held in an environmental chamber with FiO2 of 0.1 or under normoxia for 2, 4, and 6 weeks. We investigated the effect of KDR deletion and chronic normobaric hypoxia on pulmonary hemodynamics and right ventricular hypertrophy. Results: KDR-/- mice showed significantly increased right ventricular pressures (RVSP’s) and Fulton indices after 2, 4, and 6 weeks under normoxic conditions, compared with wild type controls. Both KDR-/- and wild type mice showed increased RVSP’s under normobaric hypoxia. KDR-/- mice revealed significantly higher RVSP’s and Fulton indices than controls after 4 and 6 weeks. Lung histologies demonstrated neointimal thickening and vessel occlusions in lungs of KDR-/- mice resembling human pulmonary arteriopathy. Conclusion Classical pulmonary arterial hypertension was induced in C57/BL6J mice by direct ablative gene manipulation of KDR.