Xin Yu - US grants

DESCRIPTION (provided by applicant): Elucidating the structure-function relationship in heart is key to the understanding of the underlying mechanisms of myocardial dysfunction. The pathologic progression of cardiac diseases is frequently associated with alterations/disruptions in myocardial fiber structure. Because the contractile property of the heart is prominently influenced by the unique organization of myocardial fibers, these structural changes frequently lead to abnormal ventricular function at both regional and global levels. However, characterization and identification of subtle changes in fiber architecture at sub-millimeter resolution have been challenging. The standard histological techniques are destructive and labor intensive. Therefore, they are not adequate for fast and 3D characterization of structural changes during ventricular contraction. As a result, the structure-function relationship in diseased hearts remains poorly defined. No direct association could be made between regional contractile abnormalities and alterations in myocardial fiber structure. The overall objective of the proposed study is to develop state-of-the-art MRI methods to explore the structural basis of myocardial function in both normal and diseased hearts. We have recently developed diffusion tensor magnetic resonance imaging (DTMRI) methods for 3D delineation of myocardial fiber and sheet architecture in perfused viable hearts. This technique was applied to elucidate the structural basis of myocardial wall thickening by directly assessing myocardial structural changes from diastole to systole. Further, we have also established in vivo MR tagging methods to assess regional myocardial wall motion in small animals such as rats and mice. In this project, we will further the application of DTMRI to delineate dynamic structural changes in perfused, contracting hearts. This technique will be used to characterize structural and functional changes in normal hearts by combining DTMRI studies with MR tagging characterization of regional myocardial function. Furthermore, the structure-function relationship will also be investigated in two disease models: 1) the hypertrophic hearts, induced by aortic banding, with global structural changes;and 2) the post-infarct hearts, created by LAD ligation, with focal infarct lesions.

DESCRIPTION (provided by applicant): Excitation-contraction (EC) coupling and calcium (Ca2+) cycling play an important role in regulating cardiac contractile force and in the development of cardiac diseases. Disturbance of Ca2+ handling occurs at multiple levels in heart failure and is closely related to pathological performance. However, there are limited means to evaluate alterations in EC coupling in vivo. Recent studies have indicated the role of neuronal NOS (nNOS) in regulating EC coupling, with several aspects of nNOS modulation of myocardial contractility and its role in cardiac diseases still poorly understood. In the heart, nNOS has been reported to be associated with the sarcolemma, sarcoplasmic reticulum (SR), and mitochondria. Co-localization of nNOS with its effector proteins has been suggested to be important mechanisms in myocardial control. However, studies that employ a global nNOS knockout model, the NOS1-/- mouse, cannot address the complexities of NO action through spatial confinement. Therefore, the objectives of the proposed research are 1) to develop manganese-enhanced magnetic resonance imaging (MEMRI) methods for in vivo characterization of Ca2+ uptake in myocardium, the first-step in Ca2+ cycling;2) to apply state-of-the-art MRI technology to the investigation of the differential roles of nNOS in the regulation of cardiac function and the development of cardiomyopathy. We will characterize two mouse models that differ in nNOS disruption, i.e., the global nNOS knockout mouse and the 1-dystrobrevin knockout mouse, which leads to the disruption of nNOS in cell membrane only. By combining in vivo MRI characterization of cardiac phenotypes such as function and Ca2+ uptake with in vitro molecular/cellular analysis of myocyte contractility and Ca2+ cycling in a systematic comparative study of novel mouse models with distinctive modes of nNOS disruption, this approach offers unique opportunity for dissecting the roles of nNOS in regulating cardiac function in distinct subcellular compartments. The mechanistic elucidation of the effects of nNOS on myocardial contraction and disease progression will allow nNOS to be a therapeutic target in cardiovascular diseases. PUBLIC HEALTH RELEVANCE: Excitation-contraction (EC) coupling and calcium cycling play an important role in regulating cardiac contractile force and in the development of cardiac diseases. Neuronal nitric oxide synthase (nNOS) regulates several key processes in EC coupling and is abnormal in heart failure. Pharmacological intervention that targets nNOS may be effective treatment for heart failure. The goal of the proposed research is to develop in vivo imaging method that is sensitive to altered calcium cycling, and to apply this method to elucidate the role of nNOS in EC coupling and cardiac function in mouse models of nNOS disruption.

DESCRIPTION (provided by applicant): The heavy burden of cardiovascular disease as the world's number one killer is no longer a secret. Formerly regarded as mainly a problem of the richest nations in the world, low- and middle-income countries have surpassed the developed world and now have the lion's share of these chronic, disabling, and deadly diseases. Mental illness is slightly more under-appreciated, even though it is increasing as a major cause of DALYs worldwide and is expected to become number one by 2030. Combined, cardiovascular disease and mental illness form a cycle of ill health: having depression makes one more at risk for a cardiovascular event, and having a cardiovascular event makes one more likely to suffer from depression. Effective interventions for managing these illnesses independently exist, and there is already evidence in some countries such as the US that managing both conditions together can improve health outcomes. However, a model of healthcare service delivery for both mental illness and cardiovascular conditions like acute coronary syndromes (ACS) in China has not been developed. The overall goal of this study is to develop, pilot test, implement, and evaluate a nurse-coordinated depression care model integrated into ACS care, with rigorous assessment of effectiveness and cost-effectiveness through a large scale, randomized controlled trial involving a well-established research network of rural hospitals in 15 provinces across China. This study will train nurses in cardiology wards in low-resource hospitals in China to use validated mental health screening and treatment tools among patients with ACS. Specifically, the study will determine if the integrated model can: reduce symptoms and severity of depression following ACS, improve cardiovascular health by reducing the incidence of major cardiovascular events and re-hospitalization, improve patients' quality of life, and finally whethe the model can improve other issues related to their health such as increasing physical activity and better adherence to cardiovascular medications. The long-term object of the study is to find a way to provide mental health services for patients with any chronic illness - whether it be ACS, diabetes, stroke, or cancer - in a sustainable and cost-effective manner that can be implemented in low-resource hospitals lacking in mental health specialists. This study will fill ina knowledge gap in bridging two health fields in low-resource conditions and will pave the way for an integrated service model customized to low-resource settings that can be replicated or tested in other low-resource environments. This study represents a strong local and international collaboration of researchers and academics from around the world, including The George Institute for Global Health in China, Australia and India, Peking University Institute of Mental Health, the Chinese Ministry of Health, and Duke University.

DESCRIPTION (provided by applicant): Magnetic Resonance Spectroscopy (MRS) provides a powerful tool to interrogate various aspects to tissue metabolism. In particular, phosphorus-31 (31P) magnetization transfer spectroscopy (MT-MRS) has long been proposed as a means of measuring ATP synthesis rate in vivo. However, current 31P MT-MRS methods require prohibitively long data acquisition time to accurately quantify ATP synthesis rate. On the other hand, recent development of magnetic resonance fingerprinting (MRF) method provides a completely new framework of data acquisition that allows simultaneous measurement of several tissue properties, including relaxation times, at drastically reduced acquisition time. The measurement of chemical exchange rate in MT-MRS involves the measurement of the apparent relaxation time (T1app), i.e., the chemical exchange modified T1 relaxation, which is highly analogous to the measurement of T1 in proton imaging. Therefore, the overall objective of this proposal is to develop and validate novel 31P MT-MRF technique for fast and accurate quantification of ATP synthesis rate in hearts. This project has two specific aims. Aim 1 has three parts: 1) designing and evaluating 31P MT-MRF methods by computer simulation; 2) implementing and optimizing the 31P MT-MRF methods in phantom experiments, and 3) validating the 31P MT-MRF methods against established 31P MT-MRS methods in perfused hearts under varying workload. In Aim 2, the feasibility of performing spatially resolved measurement of chemical exchange rate by 31P MT-MRF will be investigated. A compressed sensing spiral 31P chemical shift imaging (CSI) sequence will be developed that will lead to 92-fold acceleration over the Cartesian CSI method. The 31P MT-MRF CSI method will be validated in rat model of ischemia/reperfusion injury in skeletal muscle. Methods developed in this pre-clinical project will lay the foundation for the development of clinical methods that can be applied to evaluating metabolic function in a variety of metabolic diseases such as diabetes and obesity.

Abstract The Interdisciplinary Biomedical Imaging Training Program will prepare predoctoral trainees to become leaders in organism-level, biomedical imaging technology and application research. Multi-disciplinary teams of engineers, physicists, biologists, and clinicians are required to advance biomedical imaging, especially with the advent of in vivo cellular and molecular imaging. We will create the next generation of interdisciplinary biomedical imaging scientists and engineers who will contribute to and lead such teams. Our training program will build upon continuing, significant institutional, state, federal, and commercial investment in faculty and imaging infrastructure. A training grant award will place students squarely in the center of on-going interdisciplinary/multidisciplinary research programs. Trainees will use imaging facilities in the Case Center for Imaging Research which includes state-of-the-art clinical and small animal imaging systems, along with labs of mentoring faculty. Predoctoral trainees will be from the highly-rated departments of Biomedical Engineering and Physics, both of which have a long history of training in biomedical imaging. Trainees will conduct research projects combining enabling technologies in imaging with biomedical research. Each trainee will have two or more mentors representing both imaging technology and biological/clinical applications of imaging. Our educational program includes a portfolio of imaging courses, including ones focusing on imaging physics, image analysis, and reconstruction, as well as nanomedicine. We will promote a culture of interdisciplinary research during a designated Imaging Hour. Our T32 has enabled us to increase recruitment of women and under- represented minorities. In general, it has helped make graduate students cost effective as compared to post docs and ensured training of domestic PhD's in this area of critical need. In less than nine years, our T32 program has already successfully trained several graduates, all with exemplary training records and with a trajectory towards success. Other trainees are moving through the program focusing on exciting interdisciplinary imaging research and with excellent research productivity.

Type 2 diabetes (T2D) is a prevalent disease affecting a large population worldwide. Emerging evidence suggests that impaired muscle metabolism plays a major role in the pathogenesis of T2D. Normalizing mitochondrial function has be proposed as an effective therapeutic target for T2D. Phophorus-31 (31P) magnetic resonance spectroscopy and imaging (MRS/I) methods provide a powerful tool to interrogate various aspects of tissue metabolism. Specifically, 31P MRS can directly monitor changes in phosphate metabolite concentrations during physiological and pathological processes such as exercise and ischemia/reperfusion. Furthermore, magnetization-transfer (MT) methods allows noninvasive quantification of metabolic activities that no other methods are capable of. These methods have the potential to be translated to clinical use that will permit noninvasive evaluation of tissue metabolism that is indicative of disease progression and therapeutic efficacy. However, because of the low concentrations of phosphate metabolites, current 31P MRS/I methods require prohibitively long acquisition time, which is not practical for routine clinical use. Consequently, most 31P MRS studies have employed either non-localized or single voxel techniques, rendering the assessment of metabolic heterogeneity impossible. Recent development in sparse sampling theory and subspace imaging have demonstrated potential by significantly reducing acquisition time for proton (1H) MRSI. Furthermore, the innovation brought forth by magnetic resonance fingerprinting (MRF) has been shown to drastically accelerate the mapping of 1H relaxation times in the brain. Based on these exciting progress, we propose to translate these 1H MRSI approaches to develop clinically feasible 31P MRS/I methods for in vivo assessment of mitochondrial function in diabetic muscle. The objectives of the proposed project are: 1) to develop 31P spatiospectral encoding method with sparse sampling of the (k, t)-space for highly accelerated metabolic mapping of phosphate metabolites; 2) to develop 31P spectroscopic MT-MRF methods for efficient quantification of ATP and PCr synthesis rates. These methods will be applied to delineate the alterations in metabolic fluxes and mitochondrial oxidative capacity in Zucker diabetic fatty rats, a rat model of obesity and insulin resistance. In addition, the effects of exercise training and metformin treatment, the commonly prescribed treatment for T2D, on muscle metabolism will also be evaluated. The successful completion of this project will pave the way for evaluating mitochondrial energetics in vivo. While the current project will employ a rodent model of T2D for the purpose of cost-saving, the proposed 31P MRSI and MRF methods are highly translatable to clinical scanners, which will lead to clinically feasible and relevant diagnostics, as well as novel strategies to assess the therapeutic efficacy for a spectrum of metabolic diseases.

Brain dynamic low-frequency (<1Hz) fluctuation (LFF) signal has been observed using different brain imaging modalities cross multiple scales. For example, the large-scale whole brain resting-state (rs) fMRI signal fluctua- tion (<0.1Hz) has been linked to specific brain states, e.g. sleep, arousal switches, and anesthetic states. Animal fMRI has played a critical role in mapping brain function with multi-modality techniques to link the LFF temporal features across different spatial scales. The LFF correlation feature has been reported with concurrent fMRI and electrophysiology or calcium recordings at the single cortical site or through wide-field optical imaging methods at the cortical surface. However, the large-scale functional connectivity has not been well interpreted at the cellular level with laminar specificity or through subcortical/cortico-cortical projections. This gap of knowledge is primarily due to the lack of technologies to detect the multi-site laminar-specific fMRI LFF with concurrent cell- specific neurovascular signaling events at different cortical layers in animals. The goal of this proposal is to build an advanced multi-modal fMRI platform to study the laminar-specific LFF in awake animal models. We will merge the advanced fMRI methods, e.g. the line-scanning fMRI, based on a novel design of Switchable, Wireless, Implantable RF coil Array (SWIRFA) with a photonic crystal fiber (PCF)-based multi-channel MR-compatible laminar-specific imaging device for intracellular calcium (Ca2+ sensor: GCaMP6f) and extracellular Glutamate (Glu sensor: GluSnRf) recordings in awake rodents. The SWIRFA will be mounted with the head-post above the skull to reduce the distance between the RF coil and the cortex so as to boost the SNR for the line-scanning based laminar rs-fMRI with a >10 Hz fast sampling rate. Using the PCF array with beveled tips, the layer-specific Ca2+/Glu signals of individual cells can be recorded from multi-channels by parallel beam projection to a fast Silicon Photomultiplier (SiPM) sensor array. Three aims will be addressed: 1). Develop the Multi-site line scan- ning fMRI: Implement the SWIRFA for multi-slice line-scanning fMRI. We will apply the Wireless Amplified Nu- clear MR Detector (WAND) scheme to build a coil-array for switchable and wireless parallel RF signal transmis- sion and develop the multi-site line scanning methods for laminar-specific rs-fMRI. 2) Establish the Laminar- specific Ca2+/Glu recording: Develop a PCF-based multi-channel single-cell recording device across different cortical layers with the ultrafast sampling rate. 3). Validate the Multi-modal fMRI platform in awake mice: Combine the SWIRFA-based line-scanning fMRI with PCF-based cellular recordings for laminar-specific multi- modal fMRI studies. Eventually, the integrated multi-modal fMRI approach provides key strategies to not only improve the mechanistic understanding of resting-state networks (RSNs) at the cellular and circuit levels in ani- mal models but also elucidate the LFF-specific neural correlates of fMRI in the human brain at varied states and validate the clinical indications of altered RSNs in the diseased brain.

ABSTRACT The goal of this proposal is to purchase a Bruker AV-Neo console to replace the out-of-date Siemens console of the 14T horizontal MR scanner (13cm bore), which has been dedicated to supporting the high-resolution anatomical and functional dynamic brain mapping of animals and ex-vivo imaging. The Martinos Center at the Massachusetts General Hospital has been at the forefront of developing advanced functional mapping methods, e.g., functional MRI, and implementing the cutting-edge MRI methods to bridge the basic and translational studies. To pursue the next-generation cutting-edge imaging methodology and prepare for the higher field MRI translational studies, there is an urgent need to improve our 14T MRI preclinical platform for high-resolution animal and ex vivo imaging. In particular, the proposed 14T MR console upgrade will boost the translational potentials of the eight NIMH-funded projects with a synergistic goal to bridge cellular and microvascular anatomy and functional dynamics from animal to human brains. In addition, this proposal will support nine mental-health- related projects funded by other NIH Institutes, presenting critical translational efforts on the mechanistic studies of brain disorders including Alzheimer?s Diseases (AD), cerebrovascular dementia, migraine, brain tumor, traumatic brain injury, and cardiac arrest (AC)-induced coma. The highly synergistic and collaborative brain research projects outlined in our proposal can be summarized in three main themes related to mental health: 1) Neurovascular dynamic signaling, 2) Cutting-edge neuroimaging methodology, 3) Multimodal mechanistic signatures of brain disorders and injury models. We have established the 14T-based multi-modal neuroimaging platform to combine the high-resolution anatomical and functional MRI imaging with the emerging neuro- techniques, e.g. optogenetics, optical fiber-mediated biosensor recording of Calcium, Glutamate, etc, promoting novel mechanistic understanding of the complexity of brain function. The Bruker AV-Neo system will provide key technological innovations to improve the performance of the novel brain mapping methods, e.g. the single-vessel fMRI, line-scanning fMRI, RF slab-specific diffusion-weighted MRI, given the state-of-the-art electronics and software design. Therefore, the proposed instrument upgrade would not only accelerate the progress of the listed projects but also facilitate the translation of cutting-edge MR methodologies as a truly multidisciplinary, regional resource for PHS funded investigators.

Human brain activity is modified by a group of molecules called neuromodulators. However, little is known about how these molecules work and affect brain activity, due to inadequate tools. This project seeks to develop a state-of-the-art toolbox to study these important molecules. These new tools will enable scientists to track the movement of neuromodulators in the brain, determine their action on brain circuits, and reveal how they alter behavior. The interdisciplinary team takes a broad approach of combining bioengineering, cellular physiology, whole-brain imaging and behavior to develop and optimize these tools. Completion of this project will have several broad impacts. Scientifically, researchers will have access to a new set of tools for turning on or off the delivery of neuromodulators to specific regions of the brain in awake animals using light. The results will advance our understanding of how neuromodulators impact brain activity in localized brain regions and across the brain. The collaborative team will provide interdisciplinary training for graduate students and postdoctoral researchers with cutting-edge technologies in the fields of nanotechnology, engineering, chemistry, and neuroscience. This project will provide STEM education to K-12 students both in the lab and through community outreach programs. Finally, this project will also offer mentoring and research opportunities for women and underrepresented minorities.

Neuropeptides are important neuromodulators in the brain and yet remarkably little is known about their spatiotemporal spread, action on neural circuits, and effect on behavior. This proposal focuses on developing new neurotechnologies to study neuropeptide diffusion upon spatiotemporally controlled release (thread 1), their actions on brain circuits and behavior (thread 2), and brain-wide and circuit-specific activation patterns (thread 3). Specifically, this work will develop and understand a new class of photoswitchable nanovesicles that can be activated with widely available diode lasers and light emitting diodes. We will integrate this with a neuropeptide sensor, namely the cell-based neurotransmitter fluorescent-engineered receptor (CNiFER), to study neuropeptide (somatostatin, oxytocin) diffusion in the cortex and striatum upon photorelease. We will then investigate the impact of photoreleased oxytocin on brain circuits and social behavior in freely-moving animals. These efforts are closely integrated with the development of a new fluorescence resonance energy transfer (FRET)-based miniscope to detect behaviorally released neurotransmitters. Through a multi-modal functional magnetic resonance imaging platform, this research will determine the brain-wide and circuit- specific activation patterns of photoreleased oxytocin, thus enabling for the first time the integration of determining local neuropeptide signaling with brain-wide effects. These newly developed techniques will advance our understanding of the role of neuromodulators in the brain and more broadly, promote new neuropharmacology research where targeted delivery and localized release of a compound are currently unavailable.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Among millions of comatose cases per year, brainstem injury-induced coma shows a high death rate and a high chance for patients remaining in a permanent vegetative state. For those who recovered consciousness, the longer patients remain in a coma the poorer outcomes of their recovery. How to promote acute coma recovery in a serious unmet need. Yet, although neuro-glio-vascular (NGV) restoration is crucial for acute coma recovery, detailed NGV signaling, e.g. astrocytic function, and circuit-based mechanisms underlying NGV restoration have not been thoroughly investigated in comatose patients due to inherent technical difficulties. We have recently developed a brainstem coma rat model, providing an unprecedented opportunity to enable mechanistic studies of coma recovery within an acute 12 hour time window, during which novel therapeutic interventions are of translational interest to patients with brainstem injuries. Our goal here is to elucidate the mechanistic regulation of NGV restoration underlying acute coma recovery. We will target the thalamocortical circuit with optogenetic tools to elucidate circuit-specific mechanisms underlying NGV restoration during acute coma recovery. To study NGV restoration, we will combine functional MRI with multi-channel fiber photometry-based Calcium (Ca2+) and glutamate (Glu) recordings. This multi-modal fMRI platform reveals that central thalamic activation is coupled with Intrinsic Astrocytic Ca2+ (IAC) transients during arousal fluctuation. This novel observation leads us to test a central hypothesis that the thalamic regulation of IAC-specific NGV restoration underlies the acute coma re- covery. Three specific aims will be assessed: 1). To test the hypothesis that arousal-related NGV signaling is associated with acute coma recovery. 2). To test the hypothesis that thalamic stimulation promotes acute coma recovery via IAC-specific NGV signaling. 3). To test the hypothesis that Glu-astrocyte signaling underlies the thalamic regulation of IAC-specific NGV restoration during acute coma recovery. We hope that the first glimpse of IAC-specific NGV restoration will help refine the therapeutic paradigm to target astrocyte function to promote acute coma recovery. Our proposal is a timely convergence of novel brainstem coma rat model, advanced multi- modal imaging technologies, and growing insights of NGV signaling, opening an unprecedented window into investigating circuit-based mechanisms that underlie NGV restoration in acute coma recovery.

ABSTRACT Micromagnetic stimulation (µMS) has several advantages over electrical stimulation. First, µMS does not require charge-balanced stimulation waveforms as in electrical stimulation. In µMS, neither sinks nor sources are present when the time-varying magnetic field induces a current. Thus µMS does not suffer from charge buildup as can occur with electrical stimulation. Second, magnetic stimulation via µMS is capable of activating neurons with specific axonal orientations. Third, it is contactless, so biocompatible materials such as parylene will allow implantation with minimal or no reaction. Moreover, as the probes can be insulated entirely from the brain tissue, we show to significantly reduce the problem of excessive power deposition into the tissue during magnetic resonance imaging (MRI). In this application, we propose to design, fabricate, and test microcoil structures for next-generation Nervous System Stimulation: the micro coils arrays will be designed for cortical stimulation like ECoGs and deep brain stimulation. The array will be novel in the sense that it will allocate optical fibers to perform onsite optogenetic calcium channels recording in awake and behaving animals, thus allowing for direct study of the underlying mechanisms of magnetic stimulation. All the micromagnetic stimulators will also be MRI compatible, allowing for large scale neural recordings with fMRI. This technology will serve Neuroscience research? investigating the function of neurons and neural networks in the peripheral and central nervous system (PNS and CNS)?enhancing or creating new applications for neuromodulation. All of these applications will allow us to employ neuromodulation and study how micromagnetic field pulses can be used for stimulating or blocking the flow of Action Potentials (APs) through the nervous system, as similarly transcranial magnetic stimulation (TMS) produces excitation and inhibition. The proposed µMS tools will also provide the community with a way to reach a more in-depth understanding of the mechanisms of actions of TMS.