Cardiac function in a large animal model of myocardial infarction at 7 T: deep learning based automatic segmentation increases reproducibility.

Cardiac magnetic resonance (CMR) imaging allows precise non-invasive quantification of cardiac function. It requires reliable image segmentation for myocardial tissue. Clinically used software usually offers automatic approaches for this step. These are, however, designed for segmentation of human images obtained at clinical field strengths. They reach their limits when applied to preclinical data and ultrahigh field strength (such as CMR of pigs at 7 T). In our study, eleven animals (seven with myocardial infarction) underwent four CMR scans each. Short-axis cine stacks were acquired and used for functional cardiac analysis. End-systolic and end-diastolic images were labelled manually by two observers and inter- and intra-observer variability were assessed. Aiming to make the functional analysis faster and more reproducible, an established deep learning (DL) model for myocardial segmentation in humans was re-trained using our preclinical 7 T data (n = 772 images and labels). We then tested the model on n = 288 images. Excellent agreement in parameters of cardiac function was found between manual and DL segmentation: For ejection fraction (EF) we achieved a Pearson's r of 0.95, an Intraclass correlation coefficient (ICC) of 0.97, and a Coefficient of variability (CoV) of 6.6%. Dice scores were 0.88 for the left ventricle and 0.84 for the myocardium.

[Treatment of Acute Coronary Syndromes]. / Therapie des akuten Koronarsyndroms.

Despite significant advances in the detection and rapid management of acute coronary syndromes (ACS), it continues to lead the cause of death statistics and they continuously represent the leading cause of death and living with disabilities, globally. Since ACS combine a spectrum of different diagnoses, a high degree of variability in possible clinical presentation and relevant gender differences, Individualised treatment is not always easy and is constantly changing due to novel evidence from research studies. Therefore, the aim of this article is therefore to explain relevant treatment options and to present the current state of science in the context of clinical patient treatment.

Characterizing the immune response to myocardial infarction in pigs.

Though myocardial infarction (MI) in pigs is a well-established translational large animal model, it has not yet been widely used for immunotherapy studies, and a comprehensive description of the immune response to MI in this species is lacking. We induced MI in Landrace pigs by balloon occlusion of the left anterior descending artery over 90 min. Within 14 days, the necrotic myocardium was progressively replaced by scar tissue with involvement of myofibroblasts. We characterized the immune response in the heart ex vivo by (immuno)histology, flow cytometry, and RNA sequencing of myocardial tissue on days 3, 7, and 14 after MI. Besides a clear predominance of myeloid cells among heart-infiltrating leukocytes, we detected activated T cells and an increasing proportion of CD4+ Foxp3+ regulatory T cells (Treg), especially in the infarct core-findings that closely mirror what has been observed in mice and humans after MI. Transcriptome data indicated inflammatory activity that was persistent but markedly changing in character over time and linked to extracellular matrix biology. Analysis of lymphocytes in heart-draining lymph nodes revealed significantly higher proliferation rates of T helper cell subsets, including Treg on day 7 after MI, compared to sham controls. Elevated frequencies of myeloid progenitors in the spleen suggest that it might be a site of emergency myelopoiesis after MI in pigs, as previously shown in mice. We thus provide a first description of the immune response to MI in pigs, and our results can aid future research using the species for preclinical immunotherapy studies.

Role of CD4+ T-cells for regulating splenic myelopoiesis and monocyte differentiation after experimental myocardial infarction.

Myocardial infarction (MI) induces the generation of proinflammatory Ly6Chigh monocytes in the spleen and the recruitment of these cells to the myocardium. CD4+ Foxp3+ CD25+ T-cells (Tregs) promote the healing process after myocardial infarction by engendering a pro-healing differentiation state in myocardial monocyte-derived macrophages. We aimed to study the effects of CD4+ T-cells on splenic myelopoiesis and monocyte differentiation. We instigated MI in mice and found that MI-induced splenic myelopoiesis is abrogated in CD4+ T-cell deficient animals. Conventional CD4+ T-cells promoted myelopoiesis in vitro by cell-cell-contact and paracrine mechanisms, including interferon-gamma (IFN-γ) signalling. Depletion of regulatory T-cells enhanced myelopoiesis in vivo, as evidenced by increases in progenitor cell numbers and proliferative activity in the spleen 5 days after MI. The frequency of CD4+ T-cells-producing factors that promote myelopoiesis increased within the spleen of Treg-depleted mice. Moreover, depletion of Tregs caused a proinflammatory bias in splenic Ly6Chigh monocytes, which showed predominantly upregulated expression of IFN-γ responsive genes after MI. Our results indicate that conventional CD4+ T-cells promote and Tregs attenuate splenic myelopoiesis and proinflammatory differentiation of monocytes.

Integrable Magnetic Fluid Hyperthermia Systems for 3D Magnetic Particle Imaging.

Background: Combining magnetic particle imaging (MPI) and magnetic fluid hyperthermia (MFH) offers the ability to perform localized hyperthermia and magnetic particle imaging-assisted thermometry of hyperthermia treatment. This allows precise regional selective heating inside the body without invasive interventions. In current MPI-MFH platforms, separate systems are used, which require object transfer from one system to another. Here, we present the design, development and evaluation process for integrable MFH platforms, which extends a commercial MPI scanner with the functionality of MFH. Methods: The biggest issue of integrating magnetic fluid hyperthermia platforms into a magnetic particle imaging system is the magnetic coupling of the devices, which induces high voltage in the imaging system, and is harming its components. In this paper, we use a self-compensation approach derived from heuristic algorithms to protect the magnetic particle imaging scanner. The integrable platforms are evaluated regarding electrical and magnetic characteristics, cooling capability, field strength, the magnetic coupling to a replica of the magnetic particle imaging system's main solenoid and particle heating. Results: The MFH platforms generate suitable magnetic fields for the magnetic heating of particles and are compatible with a commercial magnetic particle imaging scanner. In combination with the imaging system, selective heating with a gradient field and steerable heating positioning using the MPI focus fields are possible. Conclusion: The proposed MFH platforms serve as a therapeutic tool to unlock the MFH functionality of a commercial magnetic particle imaging scanner, enabling its use in future preclinical trials of MPI-guided, spatially selective magnetic hyperthermia therapy.

In situ theranostic platform combining highly localized magnetic fluid hyperthermia, magnetic particle imaging, and thermometry in 3D.

Theranostic platforms, combining diagnostic and therapeutic approaches within one system, have garnered interest in augmenting invasive surgical, chemical, and ionizing interventions. Magnetic particle imaging (MPI) offers a quite recent alternative to established radiation-based diagnostic modalities with its versatile tracer material (superparamagnetic iron oxide nanoparticles, SPION). It also offers a bimodal theranostic framework that can combine tomographic imaging with therapeutic techniques using the very same SPION. Methods: We show the interleaved combination of MPI-based imaging, therapy (highly localized magnetic fluid hyperthermia (MFH)) and therapy safety control (MPI-based thermometry) within one theranostic platform in all three spatial dimensions using a commercial MPI system and a custom-made heating insert. The heating characteristics as well as theranostic applications of the platform were demonstrated by various phantom experiments using commercial SPION. Results: We have shown the feasibility of an MPI-MFH-based theranostic platform by demonstrating high spatial control of the therapeutic target, adequate MPI-based thermometry, and successful in situ interleaved MPI-MFH application. Conclusions: MPI-MFH-based theranostic platforms serve as valuable tools that enable the synergistic integration of diagnostic and therapeutic approaches. The transition into in vivo studies will be essential to further validate their potential, and it holds promising prospects for future advancements.

Prevalence of anti-beta-1 antibody 6 months after hospitalization for acute heart failure predicts adverse outcome.

AIMS: Agonistic antibodies against neurohumoral receptors can induce cardio-noxious effects by altering the baseline receptor activity. To estimate the prevalence of autoantibodies directed against the beta-1 receptor (b1-AAB) in patients admitted to the hospital for acute heart failure (HF) at (i) baseline and (ii) after 6 months of follow-up (F6) and (iii) after another 12 months of follow-up (i.e. 18 months after index hospitalization), to estimate their prognostic impact on clinical outcome (death or first hospitalization for HF). METHODS AND RESULTS: In 47 patients, b1-AAB were serially determined in serum samples collected at index hospitalization and at 6 months of follow-up (F6) with a flow cytometry-based assay: median age 71 years (quartiles 60, 80), 23 (49%) women, 24 (51%) HF with preserved ejection fraction. Beta1-AAB were detected in three subjects at index hospitalization (6%), and in eight subjects at F6 (17%). There were no differences apparent between patients with and without b1-AAB at F6 with regard to age, sex, type, duration, or main cause of HF. During the 12 month period following F6 (i.e. up to month 18), eight events occurred. Event-free survival was associated with prevalence of b1-AAB at F6. Compared with patients without b1-AAB at F6, age-adjusted Cox regression indicated a higher event risk in patients harbouring b1-AAB, with a hazard ratio of 8.96 (95% confidence interval 1.81-44.50, P = 0.007). CONCLUSIONS: Our results suggest a possible adverse prognostic relevance of b1-AAB in patients with acute HF, but this observation needs to be confirmed in larger patient collectives.

Advanced electrochemical potential monitoring for improved understanding of electrical neurostimulation protocols.

Objective.Current-controlled neurostimulation is increasingly used in the clinical treatment of neurological disorders and widely applied in neural prostheses such as cochlear implants. Despite its importance, time-dependent potential traces of electrodes during microsecond-scale current pulses, especially with respect to a reference electrode (RE), are not precisely understood. However, this knowledge is critical to predict contributions of chemical reactions at the electrodes, and ultimately electrode stability, biocompatibility, and stimulation safety and efficacy.Approach.We assessed the electrochemistry of neurostimulation protocolsin vitrowith Pt microelectrodes from millisecond (classical electroanalysis) to microsecond (neurostimulation) timescales. We developed a dual-channel instrumentation amplifier to include a RE in neurostimulation setups. Uniquely, we combined potential measurements with potentiostatic prepolarization to control and investigate the surface status, which is not possible in typical stimulation setups.Main results.We thoroughly validated the instrumentation and highlighted the importance of monitoring individual electrochemical electrode potentials in different configurations of neurostimulation. We investigated electrode processes such as oxide formation and oxygen reduction by chronopotentiometry, bridging the gap between milli- and microsecond timescales. Our results demonstrate how much impact on potential traces the electrode's initial surface state and electrochemical surface processes have, even on a microsecond scale.Significance.Our unique use of preconditioning in combination with stimulation reveals that interpreting potential traces with respect to electrode processes is misleading without rigorous control of the electrode's surface state. Especiallyin vivo, where the microenvironment is unknown, simply measuring the voltage between two electrodes cannot accurately reflect the electrode's state and processes. Potential boundaries determine charge transfer, corrosion, and alterations of the electrode/tissue interface such as pH and oxygenation, particularly in long-termin vivouse. Our findings are relevant for all use-cases of constant-current stimulation, strongly advocating for electrochemicalin situinvestigations in many applications like the development of new electrode materials and stimulation methods.

A case for hybrid BCIs: combining optical and electrical modalities improves accuracy.

Near-infrared spectroscopy (NIRS) is a promising research tool that found its way into the field of brain-computer interfacing (BCI). BCI is crucially dependent on maximized usability thus demanding lightweight, compact, and low-cost hardware. We designed, built, and validated a hybrid BCI system incorporating one optical and two electrical modalities ameliorating usability issues. The novel hardware consisted of a NIRS device integrated with an electroencephalography (EEG) system that used two different types of electrodes: Regular gelled gold disk electrodes and tri-polar concentric ring electrodes (TCRE). BCI experiments with 16 volunteers implemented a two-dimensional motor imagery paradigm in off- and online sessions. Various non-canonical signal processing methods were used to extract and classify useful features from EEG, tEEG (EEG through TCRE electrodes), and NIRS. Our analysis demonstrated evidence of improvement in classification accuracy when using the TCRE electrodes compared to disk electrodes and the NIRS system. Based on our synchronous hybrid recording system, we could show that the combination of NIRS-EEG-tEEG performed significantly better than either single modality only.

Ultra-high field cardiac MRI in large animals and humans for translational cardiovascular research.

A key step in translational cardiovascular research is the use of large animal models to better understand normal and abnormal physiology, to test drugs or interventions, or to perform studies which would be considered unethical in human subjects. Ultrahigh field magnetic resonance imaging (UHF-MRI) at 7 T field strength is becoming increasingly available for imaging of the heart and, when compared to clinically established field strengths, promises better image quality and image information content, more precise functional analysis, potentially new image contrasts, and as all in-vivo imaging techniques, a reduction of the number of animals per study because of the possibility to scan every animal repeatedly. We present here a solution to the dual use problem of whole-body UHF-MRI systems, which are typically installed in clinical environments, to both UHF-MRI in large animals and humans. Moreover, we provide evidence that in such a research infrastructure UHF-MRI, and ideally combined with a standard small-bore UHF-MRI system, can contribute to a variety of spatial scales in translational cardiovascular research: from cardiac organoids, Zebra fish and rodent hearts to large animal models such as pigs and humans. We present pilot data from serial CINE, late gadolinium enhancement, and susceptibility weighted UHF-MRI in a myocardial infarction model over eight weeks. In 14 pigs which were delivered from a breeding facility in a national SARS-CoV-2 hotspot, we found no infection in the incoming pigs. Human scanning using CINE and phase contrast flow measurements provided good image quality of the left and right ventricle. Agreement of functional analysis between CINE and phase contrast MRI was excellent. MRI in arrested hearts or excised vascular tissue for MRI-based histologic imaging, structural imaging of myofiber and vascular smooth muscle cell architecture using high-resolution diffusion tensor imaging, and UHF-MRI for monitoring free radicals as a surrogate for MRI of reactive oxygen species in studies of oxidative stress are demonstrated. We conclude that UHF-MRI has the potential to become an important precision imaging modality in translational cardiovascular research.

An interferon gamma response signature links myocardial aging and immunosenescence.

AIMS: Aging entails profound immunological transformations that can impact myocardial homeostasis and predispose to heart failure. However, preclinical research in the immune-cardiology field is mostly conducted in young healthy animals, which potentially weakens its translational relevance. Herein, we sought to investigate how the aging T-cell compartment associates with changes in myocardial cell biology in aged mice. METHODS AND RESULTS: We phenotyped the antigen-experienced effector/memory T cells purified from heart-draining lymph nodes of 2-, 6-, 12-, and 18-month-old C57BL/6J mice using single-cell RNA/T cell receptor sequencing. Simultaneously, we profiled all non-cardiomyocyte cell subsets purified from 2- to 18-month-old hearts and integrated our data with publicly available cardiomyocyte single-cell sequencing datasets. Some of these findings were confirmed at the protein level by flow cytometry. With aging, the heart-draining lymph node and myocardial T cells underwent clonal expansion and exhibited an up-regulated pro-inflammatory transcription signature, marked by an increased interferon-γ (IFN-γ) production. In parallel, all major myocardial cell populations showed increased IFN-γ responsive signature with aging. In the aged cardiomyocytes, a stronger IFN-γ response signature was paralleled by the dampening of expression levels of transcripts related to most metabolic pathways, especially oxidative phosphorylation. Likewise, induced pluripotent stem cells-derived cardiomyocytes exposed to chronic, low grade IFN-γ treatment showed a similar inhibition of metabolic activity. CONCLUSIONS: By investigating the paired age-related alterations in the T cells found in the heart and its draining lymph nodes, we provide evidence for increased myocardial IFN-γ signaling with age, which is associated with inflammatory and metabolic shifts typically seen in heart failure.

High-resolution imaging of the excised porcine heart at a whole-body 7 T MRI system using an 8Tx/16Rx pTx coil.

INTRODUCTION: MRI of excised hearts at ultra-high field strengths ([Formula: see text]≥7 T) can provide high-resolution, high-fidelity ground truth data for biomedical studies, imaging science, and artificial intelligence. In this study, we demonstrate the capabilities of a custom-built, multiple-element transceiver array customized for high-resolution imaging of excised hearts. METHOD: A dedicated 16-element transceiver loop array was implemented for operation in parallel transmit (pTx) mode (8Tx/16Rx) of a clinical whole-body 7 T MRI system. The initial adjustment of the array was performed using full-wave 3D-electromagnetic simulation with subsequent final fine-tuning on the bench. RESULTS: We report the results of testing the implemented array in tissue-mimicking liquid phantoms and excised porcine hearts. The array demonstrated high efficiency of parallel transmits characteristics enabling efficient pTX-based B1+-shimming. CONCLUSION: The receive sensitivity and parallel imaging capability of the dedicated coil were superior to that of a commercial 1Tx/32Rx head coil in both SNR and T2*-mapping. The array was successfully tested to acquire ultra-high-resolution (0.1 × 0.1 × 0.8 mm voxel) images of post-infarction scar tissue. High-resolution (isotropic 1.6 mm3 voxel) diffusion tensor imaging-based tractography provided high-resolution information about normal myocardial fiber orientation.

Characterization of the effect of the GLUT-1 inhibitor BAY-876 on T cells and macrophages.

Increased aerobic glycolysis is a metabolic hallmark of proinflammatory leukocytes including macrophages and T cells. To take up glucose from the environment and fuel glycolysis, activated leukocytes upregulate the glucose transporter GLUT1. The orally bioavailable selective GLUT1 inhibitor BAY-876 was developed primarily as an anti-tumor drug. Our study assessed its activity on activated macrophages and CD4+ T cells. BAY-876 significantly attenuated glucose uptake by cultured CD4+ T cells and macrophages by 41% and 15%, respectively. Extracellular flux analysis of activated CD4+ T cells in vitro showed that BAY-876 significantly decreases glycolytic proton flux rate and lactate production, effects that are accompanied by an increased oxidative phosphorylation-mediated ATP production rate, leaving intracellular ATP levels per cell unchanged. However, GLUT1 inhibition reduced CD4+ T cell proliferation without compromising cell viability and reduced IFN-γ secretion by 20%. Moreover, TNF secretion from macrophages was reduced by 27%. We conclude that GLUT1-specific inhibitors, like BAY-876, deserve further in vivo testing in a broad range of (auto-) inflammatory disease models.

Myocardial Milieu Favors Local Differentiation of Regulatory T Cells.

BACKGROUND: In the past years, several studies investigated how distinct immune cell subsets affects post-myocardial infarction repair. However, whether and how the tissue environment controls these local immune responses has remained poorly understood. We sought to investigate how antigen-specific T-helper cells differentiate under myocardial milieu's influence. METHODS: We used a transgenic T cell receptor (TCR-M) model and major histocompatibility complex-II tetramers, both myosin-specific, combined with single-cell transcriptomics (single-cell RNA sequencing [scRNA-seq]) and functional phenotyping to elucidate how the antigen-specific CD4+ T cells differentiate in the murine infarcted myocardium and influence tissue repair. Additionally, we transferred proinflammatory versus regulatory predifferentiated TCR-M-cells to dissect how they specially contribute to post-myocardial infarction inflammation. RESULTS: Flow cytometry and scRNA-/TCR-seq analyses revealed that transferred TCR-M cells acquired an induced regulatory phenotype (induced regulatory T cell) in the infarcted myocardium and blunted local inflammation. Myocardial TCR-M cells differentiated into 2 main lineages enriched with either cell activation and profibrotic transcripts (eg, Tgfb1) or suppressor immune checkpoints (eg, Pdcd1), which we also found in human myocardial tissue. These cells produced high levels of LAP (latency-associated peptide) and inhibited IL-17 (interleukin-17) responses. Endogenous myosin-specific T-helper cells, identified using genetically barcoded tetramers, also accumulated in infarcted hearts and exhibited a regulatory phenotype. Notably, TCR-M cells that were predifferentiated toward a regulatory phenotype in vitro maintained stable in vivo FOXP3 (Forkhead box P3) expression and anti-inflammatory activity whereas TH17 partially converted toward a regulatory phenotype in the injured myocardium. Overall, the myosin-specific Tregs dampened post-myocardial infarction inflammation, suppressed neighboring T cells, and were associated with improved cardiac function. CONCLUSIONS: These findings provide novel evidence that the heart and its draining lymph nodes actively shape local immune responses by promoting the differentiation of antigen-specific Tregs poised with suppressive function.

Features of metabolic syndrome and inflammation independently affect left ventricular function early after first myocardial infarction.

BACKGROUND: A high body mass index (BMI) is often associated with metabolic syndrome, which is accompanied by systemic low-grade chronic inflammation. Here, we analyzed whether BMI, other components of metabolic syndrome, and/or inflammatory markers correlate with left ventricular geometry, function, and infarct size as assessed by serial cardiac magnetic resonance imaging (MRI) after a first (clinically evident) ST-elevation MI (STEMI). METHODS: Within the Etiology, Titre-Course, and effect on Survival (ETiCS) study, cardiac MRI conducted 7-9 days and 12 months after MI enabled longitudinal characterization of patients with a first STEMI along with serial routine blood counts and multiplex cytokine measurements. RESULTS: Of 91 locally included STEMI patients, 47% were overweight (25 kg/m2 < BMI < 30 kg/m2) and 24% were obese (BMI ≥ 30 kg/m2). No patient died during 12 months of follow-up. Left ventricular ejection fraction (LVEF), measured 7-9 days after STEMI, was significantly lower in overweight (49.5 ± 7.1%) and obese (45.8 ± 12.0%) patients than in the normal weight group (56.2 ± 7.7%). Along with BMI (T = -3.8; p < 0.001), hemoglobin A1c (HbA1c; T = -3.1; p = 0.004) and peak C-reactive protein (T = -2.6; p = 0.013) emerged as independent predictors of worse LVEF 7-9 days post MI (R2 = 0.45). Only peak C-reactive protein (T = -4.4; p < 0.001), but not parameters of the metabolic syndrome, predicted worse LVEF 12 months after STEMI (R2 = 0.20). CONCLUSION: Both BMI and HbA1c correlated negatively with LVEF only early, but not late after STEMI. Peak CRP evolved as strongest predictor of cardiac function at all time points independent of the metabolic syndrome.

Adaptive Micro-liter Fiducials for Pre-clinical MPI and MRI Imaging.

Magnetic Particle imaging (MPI) allows to measure and quantify background-free tracer distribution with a high temporal resolution. Anatomical structures are not displayed in MPI, rendering orientation within a sample error-prone and necessitating co-registration with other imaging modalities such as MRI. To support this challenge, defined external landmarks (fiducials) made from materials visible in each of the imaging modalities respectively were used in this work. Resulting signals can be aligned with the merged image containing both anatomical data and information about the tracer distribution. Defining the optimal fiducial placement is demanding and can drastically impact the 3D MPI-MRI image presentation. Here we present an adaptable 3D-printed fiducial system for preclinical co-registration of MRI and MPI data designed for easy visualisation. Clinical relevance- MPI is a promising imaging modality with many conceivable clinical applications. Simple and reliable co-registration with other imaging modalities will be crucial for a seamless transition into the clinic.

Machine Learning Approaches to Classify Anatomical Regions in Rodent Brain from High Density Recordings.

Identifying different functional regions during a brain surgery is a challenging task usually performed by highly specialized neurophysiologists. Progress in this field may be used to improve in situ brain navigation and will serve as an important building block to minimize the number of animals in preclinical brain research required by properly positioning implants intraoperatively. The study at hand aims to correlate recorded extracellular signals with the volume of origin by deep learning methods. Our work establishes connections between the position in the brain and recorded high-density neural signals. This was achieved by evaluating the performance of BLSTM, BGRU, QRNN and CNN neural network architectures on multisite electrophysiological data sets. All networks were able to successfully distinguish cortical and thalamic brain regions according to their respective neural signals. The BGRU provides the best results with an accuracy of 88.6 % and demonstrates that this classification task might be solved in higher detail while minimizing complex preprocessing steps.

Identification of a novel cardiac epitope triggering T-cell responses in patients with myocardial infarction.

T-cells contribute to pathophysiological processes in myocardial diseases, including myocardial infarction (MI) and heart failure (HF). Antigen-specificity is a hallmark of T-cell responses but the cardiac antigens that trigger heart-directed T-cell responses in patients have not yet been uncovered, thus posing a roadblock to translation. In the present exploratory study, we identified a peptide fragment of the beta-1 adrenergic receptor (ADRB1) that elicits CD4+ T-cell responses after myocardial infarction in patients with a defined HLA haplotype. Our observations may advance the development of tools to monitor other antigen-specific immune responses in patients.