Tobias Walker

Bioactive coronary stent coating based on layer-by-layer technology for siRNA release

One procedure to treat stenotic coronary arteries is the percutaneous transluminal coronary angioplasty (PTCA). In recent years, drug-eluting stents (DESs) have demonstrated elaborate ways to improve outcomes of intravascular interventions. To enhance DESs, the idea has evolved to design stents that elute specific small interfering RNA (siRNA) for better vascular wall regeneration. Layer-by-layer (LbL) technology offers the possibility of incorporating siRNA nanoplexes (NPs) to achieve bioactive medical implant coatings. The LbL technique was used to achieve hyaluronic acid/chitosan (HA/Chi) films with incorporated Chi-siRNA NPs. The multilayer growth was monitored by quartz crystal microbalance. The coating on the stents and its thickness were analyzed using fluorescence and scanning electron microscopy. All stents showed a homogeneous coating, and the polyelectrolyte multilayers (PEMs) were not disrupted after ethylene oxide sterilization or expansion. The in vitro uptake of fluorescent-labeled NPs from PEMs in primary human endothelial cells (ECs) was analyzed by flow cytometry for 2, 6 and 9 days. Furthermore, stents coated with HA/Chi and Chi-siRNA NPs were expanded into porcine arteries and showed ex vivo delivery of NPs. The films showed no critical results in terms of hemocompatibility. This study demonstrates that Chi-siRNA NPs can be incorporated into PEMs consisting of HA and Chi. We conclude that the NPs were delivered to ECs under in vitro conditions. Furthermore, under ex vivo conditions, NPs were transferred into porcine artery walls. Due to their good hemocompatibility, they might make an innovative tool for achieving bioactive coatings for coronary stents.

Inhibition of adhesion molecule expression on human venous endothelial cells by non-viral siRNA transfection.

Objective: Expression of adhesion molecule receptors on venous endothelial cells crucially influences the fate of venous grafts by mediating leukocyte‐endothelium interactions. These interactions include adhesion of leuko‐cytes to the endothelium, followed by transendothelial migration, leading to neointimal hyperplasia (NIH) and finally graft occlusion. Therefore, inhibition of adhesion molecule expression may be a promising strategy to improve the quality of venous grafts.We tested the efficiency of non‐viral transfection of human venous endothe‐lial cells (HVEC) with short interfering RNA (siRNA) to specifically down‐regulate adhesion molecule expression.

Trimodal Therapy for Histologically Proven N2/3 Non–Small Cell Lung Cancer: Mid-Term Results and Indicators for Survival

BACKGROUND Surgery alone for stage III non-small cell lung cancer provides a 5-year survival of 20% and competes with multimodal treatments. In 1999, a trimodal protocol was implemented at the Schillerhöhe Clinic. The aim of this study was to verify the feasibility and outcome of this trimodal protocol including survival, risk factors for survival, and comorbidity in a single institution. METHODS Included were all patients with potentially resectable, previously untreated stage III non-small cell lung cancer operated on between February 1999 and May 2006 in the General Thoracic Surgery Unit of the Schillerhöhe Clinic following the same neoadjuvant protocol. Treatment-related morbidity, recurrence, survival after R0 resection, and risk factors for survival (pN0 after trimodal therapy, downstaging of International Union Against Cancer stage, T downstaging, N downstaging, regression rate, and histologic type of tumor) were analyzed. RESULTS From 107 patients with stage III non-small cell lung cancer, 55 patients with mediastinoscopy-positive N2 or N3 were eligible for this study. Forty patients (72%) had the effect of International Union Against Cancer downstaging. Treatment-related comorbidity was 54% with hospital and 120-day mortality of 3.6% and 5.4%, respectively. Overall mean survival (Kaplan-Meier) was 43 months (95% confidence interval, 35 to 52) with an estimated 5-year survival rate of 49%. In multivariate testing, International Union Against Cancer downstaging after trimodal therapy achieved a level of significance (p = 0.031), and patients with UICC-downstaging after trimodal therapy had a mean survival of 53 months (95% confidence interval, 44 to 63) with an estimated 5-year survival rate of 60%. CONCLUSIONS Neoadjuvant trimodal treatment for histologically proven N2 or N3 stage III non-small cell lung cancer is promising and can, like no other approach at present time, considerably improve 5-year survival rates up to 63% in selected patients.

Small-Interfering RNA-Eluting Surfaces as a Novel Concept for Intravascular Local Gene Silencing

New drug-eluting stent (DES) methods have recently been demonstrated to improve outcomes of intravascular interventions. A novel technique is the design of gene-silencing stents that elute specific small-interfering RNAs (siRNAs) for better vascular wall regeneration. Although siRNAs used to alter gene expression have surpassed expectations in in vitro experiments, the functional and local delivery of siRNAs is still the major obstacle for the in vivo application of RNA interference. In this preliminary in vitro study we investigated a surface-immobilized siRNA delivery technique that would be readily adaptable for local intravascular applications in vivo. The transfection potency of gelatin coatings consisting of a specific siRNA complexed with polyethylenimine (PEI) was examined in primary human endothelial cells by flow cytometry and quantitative real-time polymerase chain reaction. Several media conditions, such as the presence or absence of serum during cultivation, were investigated. Furthermore, different siRNA and PEI amounts, as well as nitrogen/phosphate ratios, were tested for their transfection efficiency. Gelatin coatings consisting of PEI and siRNA against an exemplary endothelial adhesion molecule receptor achieved a significant knockdown of around 70%. The transfection efficiency of the coatings was not influenced by the presence of serum. The results of this preliminary study support the expectation that this novel coating may be favorable for local in vivo gene silencing (for example, when immobilized on stents or balloons for percutanous transluminal coronary angioplasty). However, further animal experiments are needed to confirm the translation into clinical practice. This intriguing technology leads the way to more sophisticated and individualized coatings for the post-DES era, toward silencing of genes involved in the pathway of intimal hyperplasia.

Impella 5.0 Support in INTERMACS II Cardiogenic Shock Patients Using Right and Left Axillary Artery Access

The catheter-based Impella 5.0 left ventricular assist device (LVAD) is a powerful and less invasive alternative for patients in cardiogenic shock. The use of this device as a primary mechanical circulatory support strategy in INTERMACS II patients should be evaluated. From April 2014 to August 2014, eight Impella 5.0 devices were implanted in seven patients via the axillary artery access (six right and two left). We analyzed the outcome of the four patients in whom the Impella 5.0 device was implanted for the purpose of primary stabilization of cardiogenic shock (INTERMACS II). The remaining three patients had a contraindication for a permanent LVAD and received the device for prolonged weaning from extracorporeal life support (ECLS) system. The implantation of the Impella 5.0 was technically successful in all patients and resulted in the stabilization of the clinical situation. All four patients could be bridged to a long-term device (n = 3) or to cardiac recovery (n = 1). In one patient, 2 days of ECLS support was necessary because of pump thrombosis after 31 days of Impella 5.0 support. One patient with bronchopneumonia had the Impella 5.0 exchanged from the right to the left axillary artery after 22 days of support because of the progressive loss of purge flow and the need for longer bridging to a permanent LVAD. The last patient was supported for giant-cell myocarditis for 22 days and bridged to cardiac recovery. All patients were transferred to the intensive care unit with the Impella device in place. In INTERMACS II situations, the implantation of the Impella 5.0 via the right or left axillary access allowed additional time for decision making. Early patient mobilization, including walking with the Impella device in place, optimized the conditions for either weaning or the implantation of a permanent LVAD. This novel technique of left axillary approach leads to more flexibility in the case of anatomical- or device-related contraindications to right-side access, or when the device needs to be exchanged while continuous support is necessary.

Effects of Mechanical Ventilation on Heart Geometry and Mitral Valve Leaflet Coaptation During Percutaneous Edge-to-Edge Mitral Valve Repair

OBJECTIVES This study sought to evaluate a ventilation maneuver to facilitate percutaneous edge-to-edge mitral valve repair (PMVR) and its effects on heart geometry. BACKGROUND In patients with challenging anatomy, the application of PMVR is limited, potentially resulting in insufficient reduction of mitral regurgitation (MR) or clip detachment. Under general anesthesia, however, ventilation maneuvers can be used to facilitate PMVR. METHODS A total of 50 consecutive patients undergoing PMVR were included. During mechanical ventilation, different levels of positive end-expiratory pressure (PEEP) were applied, and parameters of heart geometry were assessed using transesophageal echocardiography. RESULTS We found that increased PEEP results in elevated central venous pressure. Specifically, central venous pressure increased from 14.0 ± 6.5 mm Hg (PEEP 3 mm Hg) to 19.3 ± 5.9 mm Hg (PEEP 20 mm Hg; p < 0.001). As a consequence, the reduced pre-load resulted in reduction of the left ventricular end-systolic diameter from 43.8 ± 10.7 mm (PEEP 3 mm Hg) to 39.9 ± 11.0 mm (PEEP 20 mm Hg; p < 0.001), mitral valve annulus anterior-posterior diameter from 32.4 ± 4.3 mm (PEEP 3 mm Hg) to 30.5 ± 4.4 mm (PEEP 20 mm Hg; p < 0.001), and the medio-lateral diameter from 35.4 ± 4.2 mm to 34.1 ± 3.9 mm (p = 0.002). In parallel, we observed a significant increase in leaflet coaptation length from 3.0 ± 0.8 mm (PEEP 3 mm Hg) to 5.4 ± 1.1 mm (PEEP 20 mm Hg; p < 0.001). The increase in coaptation length was more pronounced in MR with functional or mixed genesis. Importantly, a coaptation length >4.9 mm at PEEP of 10 mm Hg resulted in a significant reduction of PMVR procedure time (152 ± 49 min to 116 ± 26 min; p = 0.05). CONCLUSIONS In this study, we describe a novel ventilation maneuver improving mitral valve coaptation length during the PMVR procedure, which facilitates clip positioning. Our observations could help to improve PMVR therapy and could make nonsurgical candidates accessible to PMVR therapy, particularly in challenging cases with functional MR.

Vascular Endostapling Systems for Vascular Endografts (T)EVAR—Systematic Review—Current State

Purpose: Recently, vascular endostapling systems were developed to achieve better sealing at the proximal neck of the aneurysm and to prevent endograft migration. The purpose of this study was to provide a systematic review about the current state and possible options of vascular endostapling systems. Results: No randomized controlled trials were published. The results showed that the use of an endostaple system considerably reduced the rates of endoleaks type 1a and endograft migration. Regarding the use of endostaples in different types of endografts, only a few results were available. Conclusion: The results are not conclusive. With endostaple systems, patients with difficult anatomic features and high risk can potentially be treated. These systems might reduce the high reintervention rates after endovascular aneurysm repair. Controlled randomized trials with larger number of patients are warranted with endostapling use in primary endograft implantation and for use in reintervention for late endoleaks or endograft migrations.

Impact of polyelectrolytes and their corresponding multilayers to human primary endothelial cells

The layer-by-layer technique, which allows simple preparation of polyelectrolyte multilayers, came into the focus of research for development of functionalized medical devices. Numerous literature exist that concentrate on the film build-up and the behaviour of cells on polyelectrolyte multilayers. However, in case of very soft polyelectrolyte multilayers, studies of the cell behaviour on these films are sometimes misleading with regard to clinical applications because cells do not die due to cytotoxicity but due to apoptosis by missing cell adhesion. It turns out that the adhesion in vitro, and thus, the viability of cells on polyelectrolyte multilayers is mostly influenced by their mechanical properties. In order to decide, which polyelectrolyte multilayers are suitable for implants, we take this problem into account by putting the substrates with soft films on top of pre-cultured human primary endothelial cells (‘reverse assay’). Hence, the present work aims giving a more complete and reliable study of typical polyelectrolyte multilayers with regard to clinical applications. In particular, coatings consisting of hyaluronic acid and chitosan as natural polymers and sulfonated polystyrene and polyallylamine hydrochlorite as synthetic polymers were studied. The adsorption of polyelectrolytes was characterized by physico-chemical methods which show regular buildup. Biological examination of the native or modified polyelectrolyte multilayers was based on their effect to cell adhesion and morphology of endothelial cells by viability assays, immunostaining and scanning electron microscopy. Using the standard method, which is typically applied in literature – seeding cells on top of films – shows that the best adhesion and thus, viability can be achieved using sulfonated polystyrene/polyallylamine hydrochlorite. However, putting the films on top of endothelial cells reveals that hyaluronic acid/chitosan may also be suitable for clinical applications: This result is especially remarkable, since hyaluronic acid and chitosan mediate per se no cytotoxic effects, whereas the individual polyelectrolytes, sulfonated polystyrene and polyallylamine hydrochlorite, and their complexes show slight cytotoxicity.

Pneumonectomy: calculable or non-tolerable risk factor in trimodal therapy for Stage III non-small-cell lung cancer?

OBJECTIVES Lung cancer is the leading cause of death in cancer statistics throughout developed countries. While single surgical approach provides best results in early stages, multimodality approaches have been employed in advanced disease and demonstrated superior results in selected patients. With either full-dose chemotherapy and/or radiotherapy, patients usually have a poor general condition when entering surgical therapy and therefore neoadjuvant therapy can lead to a higher morbidity and mortality. Especially in the case of pneumonectomy as the completing procedure, mortality rate can exceed over 40%. Therefore, chest physicians often shy away from recommending pneumonectomy as final step in trimodal protocols. We analysed our experience with pneumonectomy after neoadjuvant chemoradiotherapy in advanced non-small-cell lung cancer (NSCLC) with a focus on feasibility, outcome and survival. METHODS Retrospective, single-centre study of 146 patients with trimodal neoadjuvant therapy for NSCLC Stage III over 17 years time span. Follow-up was taken from our own outpatient files and with survival check of central registry office in Baden-Württemberg, Germany. RESULTS A total of 118 men and 28 women received 62 lobectomies, 6 bi-lobectomies and 78 pneumonectomies after two different neoadjuvant protocols for Stage III NSCLC. Overall morbidity rate was 53 and 56% after pneumonectomy. Overall hospital mortality rate was 4.8 and 6.4% after pneumonectomy. Overall median survival rate was 31 months with a 5-year survival rate of 38% (Kaplan-Meier). Pneumonectomy, right-sited pneumonectomy and initial T- and N-stages were no risk factors for survival (log-rank test). Significant factors for survival were ypT-stage, ypN-stage, yUICC-stage in univariate testing (log-rank test) and ypUICC-stage in multivariate testing (Coxs regression). CONCLUSIONS Pneumonectomy in neoadjuvant trimodal approach for Stage III NSCLC can be done safe with acceptable mortality rate. Patients should not withhold from operation because of necessitating pneumonectomy. Not the procedure but the selection, response rate and R0-resection are crucial for survival after trimodal therapy in experienced centres.

Hemocompatibility testing according to ISO 10993-4: discrimination between pyrogen- and device-induced hemostatic activation.

Next to good hemocompatibility performance of new medical devices, which has to be tested according to the ISO 10993-4, the detection of pyrogen-contaminated devices plays a pivotal role for safe device application. During blood contact with pyrogen-contaminated devices, intense inflammatory and hemostatic reactions are feared. The aim of our study was to investigate the influence of pyrogenic contaminations on stents according to the ISO 10993-4. The pyrogens of different origins like lipopolysaccharides (LPS), purified lipoteichoic acid (LTA) or zymosan were used. These pyrogens were dried on stents or dissolved and circulated in a Chandler-loop model for 90 min at 37°C with human blood. Before and after circulation, parameters of the hemostatic system including coagulation, platelets, complement and leukocyte activation were investigated. The complement system was activated by LPS isolated from Klebsiella pneumoniae and Pseudomonas aeruginosa and by LTA. Leukocyte activation was triggered by LPS isolated from K. pneumoniae, LTA and zymosan, whereas coagulation and platelet activation were only slightly influenced. Our data indicate that pyrogen-contaminated devices lead to an alteration in the hemostatic response when compared to depyrogenized devices. Therefore, pyrogenicity testing should be performed prior to hemocompatibility tests according to ISO 10993-4 in order to exclude hemostatic activation induced by pyrogen contaminations.