Felix Vogt

Coronary artery stents in multislice computed tomography: in vitro artifact evaluation.

Rationale and ObjectiveThe aim of this study was to systematically compare the ability to assess the coronary artery lumen in the presence of coronary artery stents in multislice spiral CT (MSCT). MethodsTen different coronary artery stents were examined with 4- and 16-detector row MSCT scanners. For image reconstruction, a standard and a dedicated convolution kernel for coronary artery stent visualization were used. Images were analyzed regarding lumen visibility, intraluminal attenuation, and artifacts outside the stent lumen. Results were compared using repeated-measure analysis of variance. ResultsDepending on stent type, scanner hardware, and convolution kernel, artificial lumen narrowing ranged from 20% to 100%. The convolution kernel had the most significant influence on the visibility of the stent lumen. Artificial lumen narrowing and intraluminal attenuation changes decreased significantly using the dedicated convolution kernel. In general, most severe artifacts were caused by gold or gold-coated stents. ConclusionsIndependent of the scanner hardware or dedicated convolution kernels, routine evaluation of most coronary artery stents is not yet feasible using MSCT.

Characterization of Differential Gene Expression in Quiescent and Invasive Human Arterial Smooth Muscle Cells

Proliferation, migration and invasion of smooth muscle cells (SMCs) are essential pathogenic processes in the development of a broad spectrum of cardiovascular disorders, like arteriosclerosis, restenosis after percutaneous transluminal angioplasty and stent implantation as well as transplant vessel disease. As an in vitro model mimicking these processes, the Boyden chamber was employed to characterize the diverging migratory and invasive potentials of proliferating and nonproliferating human arterial SMCs (haSMCs). Using this model, differential gene expression of both phenotypes was analyzed by a cDNA array system (Clontech human cardiovascular array). With these arrays, 558 cardiovascular-associated genes could be compared. Further, gene expression was exactly quantified by real-time RT-PCR. Protein expression was analyzed by ELISA and Western blotting. In total, 47 genes were differentially expressed more than 1.5 times. Most of the differentially regulated genes in this study were associated with the extracellular matrix (ECM) and cell motility. In detail, the respective groups were matrix-organizing proteins, ECM proteins, cell adhesion proteins, extracellular communication and cytoskeleton motility proteins. Genes known to be differentially regulated during haSMC migration and invasion, like TIMP 2, TIMP 3, and MMP 3, were confirmed by the array data. Reduced expression of several cytoskeletal proteins, like vimentin, fibronectin, cytokeratins and β1 integrin, was shown in the invasive phenotype. Further, angio-associated protein, alpha E-catenin and atrial brain natriuretic peptide receptor were downregulated whereas TFPI 2 was strongly upregulated in invasive haSMCs. In conclusion, several relevant potential candidate genes for the quiescent and the invasive SMC phenotype were identified and genes already known to be differentially regulated by previous analysis were confirmed.

Development and characterization of a coronary polylactic acid stent prototype generated by selective laser melting

In-stent restenosis is still an important issue and stent thrombosis is an unresolved risk after coronary intervention. Biodegradable stents would provide initial scaffolding of the stenosed segment and disappear subsequently. The additive manufacturing technology Selective Laser Melting (SLM) enables rapid, parallel, and raw material saving generation of complex 3- dimensional structures with extensive geometric freedom and is currently in use in orthopedic or dental applications. Here, SLM process parameters were adapted for poly-l-lactid acid (PLLA) and PLLA-co-poly-ε-caprolactone (PCL) powders to generate degradable coronary stent prototypes. Biocompatibility of both polymers was evidenced by assessment of cell morphology and of metabolic and adhesive activity at direct and indirect contact with human coronary artery smooth muscle cells, umbilical vein endothelial cells, and endothelial progenitor cells. γ-sterilization was demonstrated to guarantee safety of SLM-processed parts. From PLLA and PCL, stent prototypes were successfully generated and post-processing by spray- and dip-coating proved to thoroughly smoothen stent surfaces. In conclusion, for the first time, biodegradable polymers and the SLM technique were combined for the manufacturing of customized biodegradable coronary artery stent prototypes. SLM is advocated for the development of biodegradable coronary PLLA and PCL stents, potentially optimized for future bifurcation applications.

Blockade of Angio-Associated Migratory Cell Protein Inhibits Smooth Muscle Cell Migration and Neointima Formation in Accelerated Atherosclerosis

OBJECTIVES The aim of this study was to elucidate the role of angio-associated migratory cell protein (AAMP) for the migration of vascular smooth muscle cells (SMCs) and for the development of neointimal hyperplasia after vascular injury. BACKGROUND Although AAMP has been shown to participate in angiogenesis and cancerogenesis and is predominantly expressed in cells with a migratory phenotype, involvement of AAMP during neointima (NI) formation after arterial injury has not been analyzed previously. METHODS The AAMP content in SMCs was examined using 2-photon laser-scanning microscopy and subcellular fractioning. Migratory potential of SMCs transiently transfected with AAMP expression vectors, transfected with small interfering ribonucleic acid (siRNA), or treated with antirecombinant angio-associated migratory cell protein-antibody (anti-rAAMP-ab) was examined using transwell migration chamber assays. Expression of AAMP was determined in the atherogenic apolipoprotein E knockout (apoE(-/-)) mouse model and in the porcine coronary restenosis model by immunohistochemistry and by Western blot. ApoE(-/-) mice were treated intraperitoneally with anti-rAAMP-ab, and wire-injured carotid arteries were examined. RESULTS Angio-associated migratory cell protein is localized in the membrane of SMCs, and its expression is enhanced in NI-derived SMCs. The AAMP overexpression increases, while both treatment with anti-rAAMP-ab and transfection with siRNA decreases SMC migration. Knockdown of AAMP decreases RhoA activity in the membrane fraction of SMCs. The AAMP expression by SMCs is enhanced in both animal models. Anti-rAAMP-ab reduces neointimal SMC density at 1 week and NI formation at 4 weeks in apoE(-/-) mice without affecting proliferation of SMCs. CONCLUSIONS These data reveal an important functional role of AAMP in the migration of SMCs, identifying AAMP as a potential target to limit lesion formation after injury.

Progress in interventional cardiology: challenges for the future

Cardiovascular disease is the leading cause of death in the western and developing countries. Percutaneous transluminal coronary interventions have become the most prevalent treatment option for coronary artery disease; however, due to serious complications, such as stent thrombosis and in-stent restenosis (ISR), the efficacy and safety of the procedure remain important issues to address. Strategies to overcome these aspects are under extensive investigation. In this review, we summarise relevant milestones during the time to overcome these limitations of coronary stents, such as the development of polymer-free drug-eluting stents (DES) to avoid pro-inflammatory response due to the polymer coating or the developement of stents with cell-directing drugs to, simultaneously, improve re-endothelialisation and inhibit ISR amongst other techniques most recently developed, which have not fully entered the clinical stage. Also the novel concept of fully biodegradable DES featured by the lack of a permanent foreign body promises to be a beneficial and applicable tool to restore a natural vessel with maintained vasomotion and to enable optional subsequent surgical revascularisation.

Bioengineered vascular constructs as living models for in vitro cardiovascular research.

Cardiovascular diseases represent the most common cause of morbidity and mortality worldwide. In this review, we explore the potential of bioengineered vascular constructs as living models for in vitro cardiovascular research to advance the current knowledge of pathophysiological processes and support the development of clinical therapies. Bioengineered vascular constructs capable of recapitulating the cellular and mechanical environment of native vessels represent a valuable platform to study cellular interactions and signaling cascades, test drugs and medical devices under (patho)physiological conditions, with the additional potential benefit of reducing the number of animals required for preclinical testing.

Follow-up results after interventional treatment of infarct-related saphenous vein graft occlusion.

BackgroundAcute occlusion of saphenous vein grafts resulting in acute coronary syndromes may be treated with interventional revascularization. Few data are available on intermediate and long-term results after revascularization of acute saphenous vein graft occlusion. MethodsFifty patients (67±10 years, 47 male) with troponin-positive acute coronary syndrome because of acute total or subtotal occlusion [thrombolysis in myocardial infarction (TIMI) flow 0=39, TIMI 1=8, TIMI 2=3] of one saphenous vein graft (12.0±5.3 years after surgery, 3.6±0.9 grafts) were treated with percutaneous coronary intervention (39 patients using bare-metal stents, 11 patients using drug-eluting stents). Clinical follow-up was obtained in all patients. Angiographic 6-month follow-up was performed in 35 patients (70%). ResultsAcute revascularization of the infarct-related saphenous vein graft (lesion length 17.6±10.3 mm, reference diameter 3.1±0.8 mm) was possible in 94% of patients. After a mean follow-up of 32.5±17.4 months, 13 patients (26%) died, 13 patients (26%) had recurrent myocardial infarction, and 20 patients (40%) had recurrent coronary revascularization (percutaneous coronary intervention or coronary artery bypass grafting). Angiographic follow-up showed reocclusion of the vein graft in three cases (9%). Twenty-one percent of lesions were found to be restenotic. ConclusionAcute revascularization of an infarct-related saphenous vein graft is possible in the majority of cases. Angiographic follow-up data show a high patency rate at 6-month follow-up. Still, the clinical prognosis of patients with revascularized infarct-related saphenous vein graft is quite poor.

Decrease of vascular smooth muscle cell locomotion by abciximab, but not tirofiban: a possible role of different affinity to alpha v beta 3 integrins

AimThe EPISTENT and EPIC studies demonstrated a reduction of clinically driven re-interventions after percutaneous transluminal coronary angioplasty (PTCA) and stent implantation in patients treated with abciximab, while for tirofiban no similar effects could be demonstrated. This may be explained by the different effects on the migratory and invasive potential of vascular smooth muscle cells (VSMCs) by integrin alpha v beta 3 blockade. Therefore, the objective of this study was to compare the effectiveness of abciximab and tirofiban to affect VSMC migration and invasion. MethodsVascular smooth muscle cells were treated with abciximab (0.1–1 μg/ml), tirofiban (0.1–1 μg/ml), and the alpha v beta 3 specific antibody LM609 (1–5 μg/ml), that was used as a positive control during the assay (treatment) over 24 h before the assay (pre-treatment), or before and during the assay (combined treatment). Sodium 3′-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis (4-methoxyy-6-nitro) benzene sulfonic acid (XTT)-assay and cell counting measured the influence of the substances on VSMC proliferation. Using a Boyden Chamber model, the capability of VSMCs for migration and invasion was tested with different chemo-attractants and barriers. ResultsAny influence of the platelet glycoprotein (GP) IIb/IIIa receptor (integrin alpha IIb beta 3) antagonists on VSMC proliferation could be excluded. After combined treatment, abciximab demonstrated a dose-dependent inhibition of migration (IC50 = 33 μg/ml) and invasion (IC50 = 0.5 μg/ml) of VSMCs. Administration during the assay without pre-treatment inhibited migration similarly (IC50 = 32 μg/ml) but invasion to a significant lower extent (IC50 = 44 μg/ml). Administration of tirofiban during the assay with or without pre-treatment had no inhibitory effect on VSMC migration and invasion. Pre-treatment alone with one of the substances also did not alter VSMC migration or invasion. ConclusionAbciximab administration in physiological concentrations was capable of significantly inhibiting the migratory and invasive potential of VSMCs, while for tirofiban no similar effect could be demonstrated.

Microgel-functionalised fibres with pH-optimised degradation behaviour – a promising approach for short-term medical applications

Abstract Resorbable polymers have been established for several decades in biomedical applications. The most frequently used resorbable polymers are still the aliphatic polyesters polylactides (PLA), polyglycolid (PGA) and polycaprolactone (PCL) homo- and copolymers. However, inherent pH dropping during degradation of some biomaterials may provoke inflammation and, thus, hamper the healing process. In this study we investigate the manufacturing method of microgel functionalised PLA Fibres in a dry-spinning process and the buffering effect of the poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate) vinylimidazole (VCL/AAEM/Vlm) microgels during the degradation of the fibres. Furthermore we examine the biocompatibility of the produced fibres and established a mathematical model to describe and analyse the pH level in the vicinity of the PLA fibre.

In vivo Molecular Imaging of Glutamate Carboxypeptidase II Expression in Re-endothelialisation after Percutaneous Balloon Denudation in a Rat Model

The short- and long-term success of intravascular stents depends on a proper re-endothelialisation after the intervention-induced endothelial denudation. The aim of this study was to evaluate the potential of in vivo molecular imaging of glutamate carboxypeptidase II (GCPII; identical with prostate-specific membrane antigen PSMA) expression as a marker of re-endothelialisation. Fifteen Sprague Dawley rats underwent unilateral balloon angioplasty of the common carotid artery (CCA). Positron emission tomography (PET) using the GCPII-targeting tracer [18F]DCFPyL was performed after 5–21 days (scan 60–120 min post injection). In two animals, the GCPII inhibitor PMPA (23 mg/kg BW) was added to the tracer solution. After PET, both CCAs were removed, dissected, and immunostained with the GCPII specific antibody YPSMA-1. Difference of GCPII expression between both CCAs was established by PCR analysis. [18F]DCFPyL uptake was significantly higher in the ipsilateral compared to the contralateral CCA with an ipsi-/contralateral ratio of 1.67 ± 0.39. PMPA blocked tracer binding. The selective expression of GCPII in endothelial cells of the treated CCA was confirmed by immunohistological staining. PCR analysis verified the site-specific GCPII expression. By using a molecular imaging marker of GCPII expression, we provide the first non-invasive in vivo delineation of re-endothelialisation after angioplasty.