Epilepsy affects about 500.000 people in Germany and represents a major challenge for health care and neuromedical research striving to understand the underlying mechanisms. This will facilitate the development of novel therapeutic strategies. Despite enormous efforts by numerous groups worldwide, the mechanisms of how aberrant neural circuit activity is exactly generated remain elusive. Control of epileptic seizures has previously been achieved by targeting nodes of epileptic networks. However recently, epileptic choke points, located in remote brain regions, have been recognized as possible alternative targets. In general, the identification of nodes and choke points requires brain mapping methods, each of which is inherently limited by the sensitivity and specificity of the detection technique. We propose to use our unique setup, integrating optical recordings, novel MRI methods and optogenetics to provide seizure maps and to directly interfere at to date undetected nodes or choke points. MRI has the particular advantage of providing quantitative and reproducible data of the entire brain at high spatial resolution, which is difficult to obtain with any other method. We hypothesize that by using an integrated opto-fMRI approach, more sensitive seizure maps can be created than currently available. Combining spatial and temporal information on seizure dynamics obtained from these maps with brain slice electrophysiology will provide us with the ability to select the most efficient optogenetic tools for seizure control before we perform in vivo experiments. This will enable novel manipulation approaches, which can be efficiently performed with optogenetics and monitored by opto-fMRI.
The overall goal of this project is to identify brain regions that serve as seizure hubs in the GAERS model and to optogenetically interfere with seizure onset and duration, in order to finally control epileptic seizures. The specific aims are:
Generate a seizure-hub map of GAERS, using the combination of Ca2+ recordings and BOLD fMRI and, alternatively MEMRI, to reveal nodes and choke points of epileptic networks in unprecedented detail and sensitivity. (ii) Characterize and optimize the impact of optogenetic interference at seizure hubs in brain slices. (iii) Establish optogenetic control of seizure onset and duration in the GAERS model in vivo, targeting novel choke points of the epileptic network.
Funding Period: 10.2016 – 04.2021

Chemical exchange saturation transfer (CEST) and chemical exchange spin-lock (CESL) MRI are powerful tools for metabolic imaging. Detection of specific neurometabolites can be performed using CEST/CESL MRI with enhanced sensitivity, and temporal and spatial resolution compared to NMR Spectroscopy (MRS), by imaging the reduction in bulk water signal after application of dedicated presaturation or spin-locking modules. CEST protocols for imaging a large number of different metabolites have been developed, and promising applications in different disciplines have been demonstrated. Recently, our French partners employed CEST MRI to image glucose (glucoCEST) changes induced by sensory stimulation, and have shown that CEST functional MRI (CEST-fMRI) is a promising surrogate for detecting increased glycolytic activity during neural activation11. One general limitation for CEST-fMRI is that signal changes cannot be unambiguously assigned to exclusively one metabolite. This is of particular concern for neuroimaging since multiple transient changes in energy metabolites and neurotransmitter levels are involved.
In this project, we aim to elucidate the contributions of three major neurometabolites, glucose, lactate and glutamate, to the contrast detected during functional CEST/CESL experiments. We will then develop and optimize these new CEST/CESL-fMRI techniques to study the coupling between energy metabolism and neurotransmission during neural activation. Our CEST/CESL-fMRI protocols will be implemented conjointly at high magnetic field strength on two small animal scanners, in France and Germany, and used to map concentration changes of these metabolites in the rat brain. To verify the specificity of CEST/CESL-fMRI and to separate the contributions of individual metabolites, localized 1H and indirect 1H-{13C} MRS techniques will be employed by the French partners. To further assess cell-type-specific contributions to the CEST/CESL signal, optogenetic methods will be used simultaneously with MRI in Münster. Viral transduction will be used to express both opsins and fluorescence reporter proteins for calcium, lactate12, or glutamate13 in defined cell types (neurons, astrocytes). Cell-type-specific read-out of fluorescence signals upon sensory or cell type-specific (optogenetic) stimulation will enable us to identify individual contributions to the observed functional CEST/CESL signal.

The outcome of this work will consist of robust and validated acquisition protocols with a strong potential for use in other organs. Application in humans may be facilitated by upcoming high magnetic field clinical systems. At a more fundamental level, the use of CEST/CESL-fMRI methods could help to explore the metabolic coupling within the glial-neuronal-vascular functional unit during specifically designed activation paradigms in normal and pathological conditions, or following pharmacological challenges
Funding Period: 02.2019 – 01.2022

Pluripotent c-kit+ cells have shown promising therapeutic effects in experimental models of myocardial infarction. On the other side, several negative reports from clinical pilot studies applying pluripotent bone-marrow-derived stem cells have led to disappointment. Potential causes for failure in translating stem cell therapy to patients are being discussed controversially. To determine the pathophysiological reasons for failure or success of such novel therapy approaches, dedicated diagnostic tools are required, which track c-kit dependent specific aspects of myocardial injury and healing, at best non-invasively and quantitatively.
In the previous funding period, it was shown that specific c-kit dependent aspects of myocardial injury and healing can be assessed by specific non-invasive imaging approaches. The current project further explores and develops these approaches and establishes quantitative imaging biomarkers for c-kit dependent mechanisms of myocardial injury and healing. First, imaging by semi-quantitative MR mapping techniques of several molecular contrast agents will be established. Second, imaging approaches will be used to assess c-kit effects on key mechanisms of myocardial injury and healing, such as oedema and permeability, extracellular matrix formation and synthesis of elastic fibres in c-kit deficient mice. Third, in vivo imaging results will be further explored by novel mass spectrometry imaging (MSI) technologies and MSI will be applied to quantify the presence of gadolinium-based molecular contrast agents in tissue, which can then be correlated to in vivo imaging results. And fourth, we will apply the combined MRI-MSI approach to provide quantitative assessments of therapy response to novel therapies of ischemic myocardial injury. This approach has the potential to render quantitative imaging biomarkers for myocardial healing and remodelling.
Funding Period: 02.2020 – 01.2023