Recent insights in the immunobiology of atherosclerosis show great potential for anti-inflammatory strategies to improve anti-atherosclerotic therapies. However, it is also clear that we will have to develop tailored therapies that spare important protective functions of the immune system. The hope is that nanotechnology will guide delivery to culprit cells and to plaque, for instance with specific engineering of drug delivery particle properties such as size, surface composition and affinity ligands. Preclinical studies investigating nanotherapeutic interventions in atherosclerosis are sparse. Our efforts are devoted towards designing and producing novel atherosclerotic-specific nanotherapeutics. We study their functionality and effects in preclinical studies using different animal models by combining traditional histological assessments of plaque phenotype, which are complemented with gene expression and immunological readouts. The imaging-based study of nanoparticle targeting in therosclerosis has been one of our key efforts the past years. The integration of noninvasive imaging readouts also allows longitudinal assessment of atherosclerotic plaque changes as function of nanotherapy treatment regimen. Nanotherapy trials in patients are very costly and difficult to execute, which restricts the number of patients that can be included. In atherosclerosis patients another major challenge includes the determination of primary endpoints, i.e. the direct effects the nanotherapy may exert on vessel wall inflammation. Therefore, the integration of clinically viable imaging endpoints is a prerequisite. In recently initiated human nanotherapy trials in human subjects we apply F-18-fluorodeoxyglucose positron emission tomography combined with CT (FDG-PET/CT) as well as dynamic contrast enhanced MRI (DCE-MRI) as inflammation/metabolic imaging biomarkers to determine atherosclerosis drug efficacy. The above-described integration of engineering, nanotechnology, immunology and cardiovascular may yield precision diagnostics and efficient therapeutics for atherosclerosis and its ischemic complications.

Cardiovascular disease is the leading cause of morbidity and mortality in the United States. Laboratory research aimed at understanding the cause and treatment of cardiovascular disorders holds the promise of bringing novel therapy for the future. Imaging modalities with application in small animal models that can precisely replicate clinical imaging techniques are necessary to carry out translational research in the laboratory setting. Several recent advances in imaging modalities have made this more feasible than ever in the past. The talk will address some of the more relevant cardiovascular imaging modalities currently used to evaluate both normal development and disease processes.

The aim of my presentation is twofold: Firstly, to explore the potential of simultaneously acquiring multimodal MR-PET-EEG data in a human 9.4T scanner to provide a platform for metabolic brain imaging; here, data from a 3T MR-PET as well as the 9.4T will be presented. Secondly, to demonstrate that the three modalities are complementary, with MRI having the potential to provide excellent structural and functional imaging, PET providing quantitative molecular imaging, and EEG providing superior temporal resolution.

A 9.4T MRI scanner equipped with a PET insert and a commercially available EEG device were used to acquire in vivo proton-based images, spectra, and sodium- and oxygen-based images with MRI; EEG signals from a human subject in a static 9.4T magnetic field; and demonstrate hybrid MR-PET capability in a rat model.

High-resolution images of the in vivo human brain with an isotropic resolution of 0.5mm and post mortem brain images of the cerebellum with an isotropic resolution of 320µm will be presented. A 1H spectrum was also acquired from 2x2x2mm voxel in the brain allowing 12 metabolites to be identified. Imaging based on sodium and oxygen will be demonstrated with isotropic resolutions of 2mm and 5mm, respectively. Preliminary data from auditory evoked potentials measured in a static field of 9.4T will also be shown. Finally, hybrid MR-PET capability at 9.4T in the human scanner will be demonstrated in a rat model. Initial progress on the road to 9.4 T multimodal MR-PET-EEG will be illustrated. Ultra-high resolution structural imaging, high-resolution images of the sodium distribution and proof-of-principle 17O data will be presented. Further, simultaneous MR-PET data without artefacts and EEG data acquired at 9.4 T will be shown.

The basic physics of image formation and interpretation in x-ray biomedical imaging, including x-ray computed tomography (CT), have remained essentially unchanged since Röntgen first discovered x-rays in 1895. As a result, the absorption effect remains the sole intrinsic contrast mechanism for x-ray biomedical imaging. This is unlike magnetic resonance imaging (MRI), where multiple contrast mechanisms are available for use in specific applications. In this seminar, advances in the exploration of the wave and particle nature of x-rays to generate multiple contrast mechanisms in x-ray imaging will be discussed. Unlike other multi-contrast imaging modalities, the multiple contrast mechanisms in x-ray imaging are generated from the same data acquisition. The potential applications of these contrast mechanisms in future medical diagnosis and industrial applications will be discussed.

Among acute coronary syndrome (ACS) cases, the presence of myocardial infarction (MI) can be diagnosed with a relatively high degree of confidence. However, the actual scope of myocardial injury can be variable and even extend substantially beyond the infarct zone. Such a parameter, which we call "global myocardial injury", will have important implications in the diagnosis, prognosis and management of ACS patients. In oncology, chemotherapeutic drugs are toxins for killing tumor cells, but their efficacy is often limited by the tolerance ceiling of normal tissues. We propose a whole-body imaging technique for characterizing the systemic tissue injury induced by anticancer drugs. A survey of systemic toxicity will provide information on a new drug candidate for pharmaceutical development, and on the therapeutic regimen for existing drug combinations for each patient. These goals can be accomplished using a new class of imaging agents with high target uptake and low systemic background. Data are presented for tracer development, with the introduction of new imaging concepts for assessing "global myocardial injury" in ACS and for detecting systemic tissue injury induced by anticancer drugs.

MRI is an excellent imaging modality for serially monitoring cellular events in vivo. Our laboratory is using magnetic biomaterials to label cells, and therefore allow their detection by MRI, in order to study a number of important biological phenomena ranging from stem cell transplantation, metastasis, immunotherapy and inflammation. This talk will describe the use of MRI cell tracking to study cancer cell metastasis and dormancy. Animal models of brain, breast and liver cancer will be highlighted. Advances in this field related to cell labeling, novel biomaterials, the MRI hardware and software for detection of cells and clinical implementation of our cellular MRI approaches will also be addressed.

Evidence Based Hypothesis: ALPHA (Acidic lactate sequentially induced lymphangiogenes, phlebogenesis, and arteriogenesis) Lactate triggered glycyolytic vasculogenesis which complements the traditional concept of hypoxia-based vasculogenesis

The importance of vasculogenesis for cancer has been clearly established. Vasculogenesis for aerobic cancers is well known, however vasculogenesis for glycolysis (ALPHA) has only recently been described. The major tenents of glycolytic vasculogenesis differ remarkably from aerobic metabolism, in that oxygen/arteries are not as important as waste products and drainage vessels. Glycolysis uses only glucose which diffuses well and is actively transported, but it also makes large amounts of lactate which must be cleared. Lymphatics and veins are needed to clear and reduce lactate to prevent excessive lactate levels. Moderate lactate level acts a powerful procancer modulator (source of building substrates, cellular motility, invasiveness, etc). However, high lactate levels causes end product inhibition or low pH which slows or inhibits glycolysis. When this occurs, ATP and essential building substrates from glycolytic side reactions are reduced preventing cell growth, division, and proliferation. To produce vasculogenesis, lactate independent of oxygenation levels (normoxia, hypoxia, or hyperoxia) induces Hypoxia Induction factor (HIF1a), vascular growth factors and attracts angioblastic stem cells. The ensuing vessel morphogenesis and development sequentially produces lymphatics first, then veins, and arteries. This sequence has been confirmed by numerous animal model studies (de novo cancer, transfected VEGF gene, corneal growth factor implants, tumor xenografts).

From an imaging perspective, the ALPHA vasculogenesis concept provides new insights into the biologic basis of imaging perfusion measurements using CT and MRI. Contrary to the traditional theory, increased arterialization alone has not been useful for characterizing cancer. The perfusion parameters which have proven most useful are blood volume, contrast washout, kinetic curve analysis and Ktrans/Kep permeability. These are mostly dependent upon veins rather than arteries. Kinetic curve analysis and contrast washout depend on venous outflow. Vessel permeability measured by Ktrans and Kep occurs in the veins. Veins are the major contributor to total blood volume.

With the recent advances in epigenetic research and improvement in our understanding of various epigenetic mechanisms, chromatin and DNA modifying enzymes, such as histone deacetylases (HDACs), histone methylases (HMs), and DNA methylating enzymes have emerged as important regulators of gene expression, development, physiology and life span. This presentation will cover a series of comprehensive imaging studies in rodents and non-human primates to assess the efficacy of novel radiolabeled agents non-invasive PET imaging of class-II and class-III histone deacetylase enzymes in the brain and other organs and tissues. The availability of novel HDAC class- and isoform-specific PET radiotracers will have a significant positive impact on the pace or research in the field of epigenetics.

Our group was first to develop a radiotracer for PET imaging of HDAC expression and activity, the 6-([¹⁸F]fluoroacetamido)-1-hexanoicanilide, termed ¹⁸F-FAHA [1]. We have demonstrated, that after i.v. injection ¹⁸F-FAHA rapidly accumulates in the brain in rats and in rhesus macaques, and that the rate of ¹⁸F-FAHA accumulation in the brain is inhibited in a dose-dependent manner by HDAC inhibitor SAHA (vorinostat) [2,3]. Using quantitative PET/CT/MRI imaging and pharmacokinetic modeling, a dose-dependent nature of SAHA-induced reduction in ¹⁸F-FAHA accumulation in the baboon brain was demonstrated. Based on these initial studies, we developed a novel HDAC class IIa specific radiotracer ¹⁸F-trifluoroacetamido-1hexanoicanilide, termed ¹⁸F-TFAHA, and performed initial using PET/CT evaluation of this novel radiotracer in vivo in non-human primates. Currently, we are developing ¹⁸F-labeled agents for PET imaging of expression-activity of HDAC class-III enzymes called sirtuins (SIRTs) that are involved in a variety of physiological and pathophysiological processes, including lifespan regulation, nitrogen metabolism, fatty acid oxidation, and mitigating reactive oxygen species damage, cardiomyopathy, and neurodegenerative disiases.

These PET imaging agents will enable non-invasive and repetitive in vivo imaging of expression and activity of HDACs in the brain and different organs and tissues (including cancer) and help to understand the mechanisms of HDACs involvement in normal physiology and in the mechanisms of different diseases. The utilization of invasive biopsies of normal tissues (i.e., brain, heart, etc.) is prohibitive in humans due to obvious reasons of traumatism and morbidity. Therefore, PET/CT(MR) imaging using HDACs-specific substrate-type radiotracers should enable non-invasive monitoring of pharmacodynamics and therapeutic efficacy of novel HDACs-specific inhibitors (or activators) in experimental animals and in humans, and facilitate their translation into clinic.

References:

• Mukhopadhyay U, Tet al. (2006) J Label Comp Radiopharm 49:997–1006.
• Yeh HH, et al. (2013) Neuroimage 64:630-9.
• Reid, A.E., et al. (2009) Nucl Med Biol 36:247-58.