Ventricular arrhythmia susceptibility in a new porcine model of heart failure (HF) with reduced ejection fraction

Introduction

Sudden death secondary to ventricular arrhythmias is common in HF patients, with no effective treatment available outside of implantable cardiac defibrillators. While animal models are essential for the discovery of anti-arrhythmic drugs, no reliable large animal HF models with associated ventricular arrhythmias have been described so far.

Objectives

We aimed at evaluating ventricular remodeling and arrhythmia susceptibility in an HF pig model with reduced ejection fraction (EF) following myocardial infarction (MI).

Methods

MI was induced in 53 male Göttingen minipigs (12–15 months, 20–25 kg) by coronary embolization in mid-left anterior descending and mid-left circumflex coronary arteries using endovascular coils. Seven other pigs underwent sham operation and were used as control. Two weeks after surgery, cardiac function was assessed by echocardiography, and animals were included based on EF<50% (n=15/53), assigned either to 12 weeks of vehicle (n=9) or perindopril (n=6, 1 mg/kg/d, per os) group. At the end of the study, their left ventricular (LV) electrical remodeling was studied by echocardiography/electrocardiography and a programmed-electrical stimulation protocol was performed to evaluate the susceptibility to develop ventricular arrhythmias.

Results

At the end of the study, animals in the vehicle group had a significant LV remodeling associated with a reduced EF (p<0.05 vs. sham, see table). This remodeling was associated with cardio-pulmonary congestion, significant increases in LV end-diastolic pressure, left atrial volume, and lung mass (all p<0.05 vs. sham, see table), fully prevented by perindopril treatment. They had also an electrical remodeling as evidenced by an increase in PR, QRS, and QTc intervals, as well as LV effective refractory period (+18%, 14%, 33%, and 13%, respectively, p<0.05, compared to sham animals). Electrical changes were mitigated by perindopril treatment (p=NS vs. sham). LV mechanical dispersion measured with speckle-tracking echocardiography was significantly increased in vehicle group (58±5 vs. 22±1 ms in sham group, respectively) as well as in perindopril group. Programmed-electrical stimulations induced in 6/8 vehicle animals either non-sustained (n=3) or sustained (n=2) ventricular tachycardia, or ventricular fibrillation (n=1). In sham group only 1/7 animal had a ventricular fibrillation. No inducible ventricular arrhythmia was observed in animals treated with Perindopril.

Conclusion

In this new pig model of congestive HF with reduced EF, LV remodeling was associated with electrical remodeling and susceptibility to develop arrhythmias. Chronic angiotensin-converting enzyme inhibitor treatment prevented congestion, mitigated electrical remodeling, and suppressed arrhythmia susceptibility.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Servier Research Institute - CardioVascular & Metabolic Diseases Center for Therapeutic Innovation Table 1

Rapid infrared mapping for highly accurate automated histology in Barrett's oesophagus

Barrett's oesophagus (BE) is a premalignant condition that can progress to oesophageal adenocarcinoma. Endoscopic surveillance aims to identify potential progression at an early, treatable stage, but generates large numbers of tissue biopsies. Fourier transform infrared (FTIR) mapping was used to develop an automated histology tool for detection of BE and Barrett's neoplasia in tissue biopsies. 22 oesophageal tissue samples were collected from 19 patients. Contiguous frozen tissue sections were taken for pathology review and FTIR imaging. 45 mid-IR images were measured on an Agilent 620 FTIR microscope with an Agilent 670 spectrometer. Each image covering a 140 μm × 140 μm region was measured in 5 minutes, using a 1.1 μm² pixel size and 64 scans per pixel. Principal component fed linear discriminant analysis was used to build classification models based on spectral differences, which were then tested using leave-one-sample-out cross validation. Key biochemical differences were identified by their spectral signatures: high glycogen content was seen in normal squamous (NSQ) tissue, high glycoprotein content was observed in glandular BE tissue, and high DNA content in dysplasia/adenocarcinoma samples. Classification of normal squamous samples versus 'abnormal' samples (any stage of Barrett's) was performed with 100% sensitivity and specificity. Neoplastic Barrett's (dysplasia or adenocarcinoma) was identified with 95.6% sensitivity and 86.4% specificity. Highly accurate pathology classification can be achieved with FTIR measurement of frozen tissue sections in a clinically applicable timeframe.

Multi-centre Raman spectral mapping of oesophageal cancer tissues: a study to assess system transferability

The potential for Raman spectroscopy to provide early and improved diagnosis on a wide range of tissue and biopsy samples in situ is well documented. The standard histopathology diagnostic methods of reviewing H&E and/or immunohistochemical (IHC) stained tissue sections provides valuable clinical information, but requires both logistics (review, analysis and interpretation by an expert) and costly processing and reagents. Vibrational spectroscopy offers a complimentary diagnostic tool providing specific and multiplexed information relating to molecular structure and composition, but is not yet used to a significant extent in a clinical setting. One of the challenges for clinical implementation is that each Raman spectrometer system will have different characteristics and therefore spectra are not readily compatible between systems. This is essential for clinical implementation where classification models are used to compare measured biochemical or tissue spectra against a library training dataset. In this study, we demonstrate the development and validation of a classification model to discriminate between adenocarcinoma (AC) and non-cancerous intraepithelial metaplasia (IM) oesophageal tissue samples, measured on three different Raman instruments across three different locations. Spectra were corrected using system transfer spectral correction algorithms including wavenumber shift (offset) correction, instrument response correction and baseline removal. The results from this study indicate that the combined correction methods do minimize the instrument and sample quality variations within and between the instrument sites. However, more tissue samples of varying pathology states and greater tissue area coverage (per sample) are needed to properly assess the ability of Raman spectroscopy and system transferability algorithms over multiple instrument sites.

OECI TuBaFrost Tumor Biobanking

OECI TuBaFrost harbors a complete infrastructure for the exchange of frozen tumor samples between European countries. OECI TuBaFrost consists of: • A code of conduct on how to exchange human residual samples in Europe • A central database application accessible over the Internet ( www.tubafrost.org ) where data can be uploaded and searched from samples that can be selected and ordered • Access rules with incentives for collectors • Standardization needed to enable the analysis of high quality samples derived from different centers • Virtual Microscopy to support sample selection with difficult pathology

The entire infrastructure was, after completion, which was entirely financed by the European Commission, implemented in the OECI. But so far it has not been used to its capacity. A recent survey held amongst the OECI members shed light on the causes. The main conclusion is that all responders see OECI TuBaFrost as a good platform for exchange of samples, however, the biggest bottleneck found was that potential users are too unfamiliar with the communication between their own biobank tracking system and the TuBaFrost central database application. Therefore, new future plans are drawn. In addition, new infrastructure plans have been developed and the first preparatory steps have been set. For biobanks the BBMRI project has started aiming for Pan-European Biobanking and Biomolecular Resources Research Infrastructure.

Plasmonic labeling of subcellular compartments in cancer cells: multiplexing with fine-tuned gold and silver nanoshells

Fine-tuned gold and silver nanoshells were produced via an entirely reformulated synthesis. The new method yielded ultramonodisperse samples, with polydispersity indexes (PI) as low as 0.02 and narrow extinction bands suited for multiplex analysis. A library of nanoshell samples with localized surface plasmon resonances (LSPR) spanning across the visible range was synthesized. Hyperspectral analysis revealed that the average scattering spectrum of 100 nanoshells matched closely to the spectrum of a single nanoshell, indicating an unprecedented low level of nanoparticle-to-nanoparticle variation for this type of system. A cell labeling experiment, targeting different subcellular compartments in MCF-7 human breast cancer cells, demonstrated that these monodisperse nanoparticles can be used as a multiplex platform for single cell analysis at the intracellular and extracellular level. Antibody-coated gold nanoshells targeted the plasma membrane, while silver nanoshells coated with a nuclear localization signal (NLS) targeted the nuclear membrane. A fluorescence counterstaining experiment, as well as single cell hyperspectral microscopy showed the excellent selectivity and specificity of each type of nanoparticle for its designed subcellular compartment. A time-lapse photodegradation experiment confirmed the enhanced stability of the nanoshells over fluorescent labeling and their capabilities for long-term live cell imaging.

Staging Early Esophageal Cancer

Staging esophageal cancer provides a standardized measure of the extent of disease that can be used to inform decisions about therapy and guide prognosis. For esophageal cancer, the treatment pathways vary greatly depending on stage of disease, and accurate staging is therefore crucial in ensuring the optimal therapy for each patient. For early esophageal cancer (T1 lesions), endoscopic resection can be curative and simultaneously gives accurate staging of depth of invasion. For tumors invading the submucosa or more advanced disease, comprehensive investigation is required to accurately stage the tumor and assess suitability for curative resection. A combined imaging approach of computed tomography (CT), positron emission tomography (PET), and endoscopic ultrasound (EUS) offers complementary diagnostic information and gives the greatest chance of accurate staging. Staging laparoscopy can identify peritoneal disease and small superficial liver lesions that could be missed on CT or PET, and alters management in up to 20 % of patients. Optical diagnostic techniques offer the prospect of further extending the possibilities of endoscopic staging in real time. Optical coherence tomography can image superficial lesions and could provide information on depth of invasion for these lesions. Real-time lymph node analysis using optical diagnostics such as Raman spectroscopy could be used to support immediate endoscopic therapy without waiting for results of cytology or further investigations.

TuBaFrost: European virtual tumor tissue banking

TuBaFrost is a consortium responsible for the task to create a virtual European human frozen tumor tissue bank, composed of high quality frozen tumor tissue collections with corresponding accurate diagnosis stored in European cancer centers and universities, searchable on the Internet, providing rules for access and use and a code of conduct to comply with the various legal and ethical regulations in European countries. Such infrastructure would enlarge tissue availability and accessibility in large amounts of specified or even rare tumor samples. Design of an infrastructure for European residual tissue banking with the described characteristics, clear focus points emerge that can be broken down in dedicated subjects: (1) standardization and quality assurance (QA) to avoid inter-institute quality variation; (2) law and ethics enabling exchange of tissue samples possible between institutes in the different European countries, where law and ethics are characterized by a strong variability; (3) rules for access, with sufficient incentives for collectors; (4) central database application containing innovations on search and selection procedures; (5) support when needed with histology images; and (6) Internet access to search and upload, with in addition a solid website giving proper information on the procedures, intentions and activities not only to the scientific community, but also to the general public. One consortium decision, part of the incentives for collectors, had major impact on the infrastructure; custodianship over the tissues as well as the tissues stay with the collector institute. Resulting in specimens that are not given to an organization, taking decisions on participation of requests, but instead the local collected tissues stay very easy to access by the collector and allows autonomous negotiation between collector and requestor on cooperation, coauthorship in publication or compensation in costs. Thereby, improving availability of large amounts of high quality samples of a highly specified or rare tumor types and contact opportunities for cooperation with other institutes.

TuBaFrost 6: Virtual microscopy in virtual tumour banking

Many systems have already been designed and successfully used for sharing histology images over large distances, without transfer of the original glass slides. Rapid evolution was seen when digital images could be transferred over the Internet. Nowadays, sophisticated Virtual Microscope systems can be acquired, with the capability to quickly scan large batches of glass slides at high magnification and compress and store the large images on disc, which subsequently can be consulted through the Internet. The images are stored on an image server, which can give simple, easy to transfer pictures to the user specifying a certain magnification on any position in the scan. This offers new opportunities in histology review, overcoming the necessity of the dynamic telepathology systems to have compatible software systems and microscopes and in addition, an adequate connection of sufficient bandwidth. Consulting the images now only requires an Internet connection and a computer with a high quality monitor. A system of complete pathology review supporting bio-repositories is described, based on the implementation of this technique in the European Human Frozen Tumor Tissue Bank (TuBaFrost).

TuBaFrost 5: multifunctional central database application for a European tumor bank

Developing a tissue bank database has become more than just logically arranging data in tables combined with a search engine. Current demand for high quality samples and data, and the ever-changing legal and ethical regulations mean that the application must reflect TuBaFrost rules and protocols for the collection, exchange and use of tissue. To ensure continuation and extension of the TuBaFrost European tissue bank, the custodianship of the samples, and hence the decision over whether to issue samples to requestors, remains with the local collecting centre. The database application described in this article has been developed to facilitate this open structure virtual tissue bank model serving a large group. It encompasses many key tasks, without the requirement for personnel, hence minimising operational costs. The Internet-accessible database application enables search, selection and request submission for requestors, whereas collectors can upload and edit their collection. Communication between requestor and involved collectors is started with automatically generated e-mails.

TuBaFrost 1: Uniting local frozen tumour banks into a European network: an overview

TuBaFrost is the consortium responsible for the creation of a virtual European human frozen tumour tissue bank: a collection of high quality frozen residual, accurately classified tumour tissue samples, which are stored in European cancer centres and universities. This virtual tissue bank, searchable on the internet, has rules for access and use, and a code of conduct to comply with the various legal and ethical regulations in European countries. The easy accessibility and the European scale of the bank will result in the availability of a large number of samples even of rarer tumour types. Standardisation of collection, storage and quality control throughout the network is achieved minimising inter-institutional variability. A website providing access to upload, search and request samples is a key tool of the tissue bank. The search engine makes use of virtual microscopy. An overview of the development of the European virtual frozen tissue bank infrastructure is described in this paper. The various key aspects are described in more detail in a series of articles to appear in this Journal.

TuBaFrost 4: access rules and incentives for a European tumour bank

When designing infrastructure for a networked virtual tumour bank (samples remain at the collector institutes and sample data are collected in a searchable central database), it is apparent that this can only function properly after developing an adequate set of rules for use and access. These rules must include sufficient incentives for the tissue sample collectors to remain active within the network and maintain sufficient sample levels in the local bank. These requirements resulted in a key TuBaFrost rule, stating that the custodianship of the samples remains under the authority of the local collector. As a consequence, the samples and the decision to issue the samples to a requestor are not transferred to a large organisation but instead remain with the collector, thus allowing autonomous negotiation between collector and requestor, potential co-authorship in publications or compensation for collection and processing costs. Furthermore, it realises a streamlined cost effective network, ensuring tissue visibility and accessibility thereby improving the availability of large amounts of samples of highly specific or rare tumour types as well as providing contact opportunities for collaboration between scientists with cutting edge technology and tissue collectors. With this general purpose in mind, the rules and responsibilities for collectors, requestors and central office were generated.

TuBaFrost 2: Standardising tissue collection and quality control procedures for a European virtual frozen tissue bank network

Tumour Bank Networking presents a great challenge for oncological research as in order to carry out large-scale, multi-centre studies with minimal intrinsic bias, each tumour bank in the network must have some fundamental similarities and be using the same standardised and validated procedures. The European Human Frozen Tumour Tissue Bank (TuBaFrost) has responded to this need by the promotion of an integrated platform of tumour banks in Europe. The operational framework for TuBaFrost has drawn upon the best practice of standard workflows and operating procedures employed by members of the TuBaFrost project and key initiatives worldwide.

Virtual Microscopy in Virtual Tumor Banking

Many systems have already been designed and successfully used for sharing histology images over large distances, without transfer of the original glass slides. Rapid evolution was seen when digital images could be transferred over the Internet. Nowadays, sophisticated virtual microscope systems can be acquired, with the capability to quickly scan large batches of glass slides at high magnification and compress and store the large images on disc, which subsequently can be consulted through the Internet. The images are stored on an image server, which can give simple, easy to transfer pictures to the user specifying a certain magnification on any position in the scan. This offers new opportunities in histology review, overcoming the necessity of the dynamic telepathology systems to have compatible software systems and microscopes and in addition, an adequate connection of sufficient bandwidth. Consulting the images now only requires an Internet connection and a computer with a high quality monitor. A system of complete pathology review supporting biorepositories is described, based on the implementation of this technique in the European Human Frozen Tumor Tissue Bank (TuBaFrost).

Human tissue research

Improvement in cancer care is possible by applying new treatment modalities, which are emerging from knowledge and discoveries coming from laboratory research. This is possible through international collaboration and the collection of tumour tissues. Creation of a European Organisation for Research and Treatment of Cancer (EORTC) Tumor Bank is a natural step in this direction, by offering tumour sample collection from patients entered in EORTC trials. The aim of such a bank is not only to improve the diagnostic review process, but also to facilitate translational research by allowing clinicians and basic scientists to enter into close collaborations. The EORTC Tissue Research Policy is developed to assure, under the EORTC legal framework, an ethical and scientific review of research projects, guarantee adequate information is given to patients, establish procedures on the use of materials, including legal aspects, and publication policies. Being part of the EU TubaFrost project, the EORTC will provide a common international platform for the use of tissues for research purposes, finding a balance between different laws and assuring scientific progress.