Robust thrombus imaging is an unresolved clinical unmet need dating back to the mid 1970s. While early molecular imaging approaches began with nuclear SPECT imaging, contrast agents for virtually all biomedical imaging modalities have been demonstrated in vivo with unique strengths and common weaknesses. Two primary molecular imaging targets have been pursued for thrombus imaging: platelets and fibrin. Some common issues noted over 40 years ago persist today. Acute thrombus is readily imaged with all probes and modalities, but aged thrombus remains a challenge. Similarly, anti-coagulation continues to interfere with and often negate thrombus imaging efficacy, but heparin is clinically required in patients suspected of pulmonary embolism, deep venous thrombosis or coronary ruptured plaque prior to confirmatory diagnostic studies have been executed and interpreted. These fundamental issues can be overcome, but an innovative departure from the prior approaches will be needed.

Eighty percent of lung cancers originate as subtle premalignant changes in the airway mucosal epithelial layer of bronchi and alveoli, which evolve and penetrate deeper into the parenchyma. Liquid-ventilation, with perfluorocarbons (PFC) was first demonstrated in rodents in 1966 then subsequently applied as lipid-encapsulated PFC emulsions to improve pulmonary function in neonatal infants suffering with respiratory distress syndrome in 1996. Subsequently, PFC nanoparticles (NP) were extensively studied as intravenous (IV) vascular-constrained nanotechnologies for diagnostic imaging and targeted drug delivery applications. Methods: This proof-of-concept study compared intratumoral localization of fluorescent paramagnetic (M) PFC NP in the Vx2 rabbit model using proton (1H) and fluorine (19F) magnetic resonance (MR) imaging (3T) following intratracheal (IT) or IV administration. MRI results were corroborated by fluorescence microscopy. Results: Dynamic 1H-MR and 19F-MR images (3T) obtained over 72 h demonstrated marked and progressive accumulation of M-PFC NP within primary lung Vx2 tumors during the first 12 h post IT administration. Marked 1H and 19F MR signal persisted for over 72 h. In contradistinction, IV M-PFC NP produced a modest transient signal during the initial 2 h post-injection that was consistent circumferential blood pool tumor enhancement. Fluorescence microscopy of excised tumors corroborated the MR results and revealed enormous intratumor NP deposition on day 3 after IT but not IV treatment. Rhodamine-phospholipid incorporated into the PFC nanoparticle surfactant was distributed widely within the tumor on day 3, which is consistent with a hemifusion-based contact drug delivery mechanism previously reported. Fluorescence microscopy also revealed similar high concentrations of M-PFC NP given IT for metastatic Vx2 lung tumors. Biodistribution studies in mice revealed that M-PFC NP given IV distributed into the reticuloendothelial organs, whereas, the same dosage given IT was basically not detected beyond the lung itself. PFC NP given IT did not impact rabbit behavior or impair respiratory function. PFC NP effects on cells in culture were negligible and when given IV or IT no changes in rabbit hematology nor serum clinical chemistry parameters were measured. Conclusion: IT delivery of PFC NP offered unique opportunity to locally deliver PFC NP in high concentrations into lung cancers with minimal extratumor systemic exposure.

Although angiogenesis is a hallmark feature of asthmatic inflammatory responses, therapeutic anti-angiogenesis interventions have received little attention. Objective: Assess the effectiveness of anti-angiogenic Sn2 lipase-labile prodrugs delivered via αvβ3-micellar nanotherapy to suppress microvascular expansion, bronchial remodeling, and airway hyper-responsiveness in Brown Norway rats exposed to serial house dust mite (HDM) inhalation challenges. Results: Anti-neovascular effectiveness of αvβ3-mixed micelles incorporating docetaxel-prodrug (Dxtl-PD) or fumagillin-prodrug (Fum-PD) were shown to robustly suppress neovascular expansion (p<0.01) in the upper airways/bronchi of HDM rats using simultaneous 19F/1H MR neovascular imaging, which was corroborated by adjunctive fluorescent microscopy. Micelles without a drug payload (αvβ3-No-Drug) served as a carrier-only control. Morphometric measurements of HDM rat airway size (perimeter) and vessel number at 21d revealed classic vascular expansion in control rats but less vascularity (p<0.001) after the anti-angiogenic nanotherapies. CD31 RNA expression independently corroborated the decrease in airway microvasculature. Methacholine (MCh) induced respiratory system resistance (Rrs) was high in the HDM rats receiving αvβ3-No-Drug micelles while αvβ3-Dxtl-PD or αvβ3-Fum-PD micelles markedly and equivalently attenuated airway hyper-responsiveness and improved airway compliance. Total inflammatory BAL cells among HDM challenged rats did not differ with treatment, but αvβ3+ macrophages/monocytes were significantly reduced by both nanotherapies (p<0.001), most notably by the αvβ3-Dxtl-PD micelles. Additionally, αvβ3-Dxtl-PD decreased BAL eosinophil and αvβ3+ CD45+ leukocytes relative to αvβ3-No-Drug micelles, whereas αvβ3-Fum-PD micelles did not. Conclusion: These results demonstrate the potential of targeted anti-angiogenesis nanotherapy to ameliorate the inflammatory hallmarks of asthma in a clinically relevant rodent model.

Fumagillin, an unstable anti-angiogenesis mycotoxin, was synthesized into a stable lipase-labile prodrug and incorporated into integrin-targeted lipid-encapsulated nanoparticles (αvβ3-Fum-PD NP). Dual anti-angiogenic therapy combining αvβ3-Fum-PD NP with zoledronic acid (ZA), a long-acting osteoclast inhibitor with proposed anti-angiogenic effects, was evaluated. In vitro, αvβ3-Fum-PD NP reduced (P<0.05) endothelial cell viability without impacting macrophage viability. ZA suppressed (P<0.05) macrophage viability at high dosages but not endothelial cell proliferation. 3D MR neovascular imaging of rabbit Vx2 tumors showed no effect with ZA, whereas αvβ3-Fum-PD NP alone and with ZA decreased angiogenesis (P<0.05). Immunohistochemistry revealed decreased (P<0.05) microvascularity with αvβ3-Fum-PD NP and ZA and further microvascular reduction (P<0.05) with dual-therapy. In vivo, ZA did not decrease tumor macrophage numbers nor cancer cell proliferation, whereas αvβ3-Fum-PD-NPs reduced both measures. Dual-therapy with ZA and αvβ3-Fum-PD-NP may provide enhanced neo-adjuvant utility if macrophage ZA uptake is increased. From the Clinical Editor: Although anti-angiogenesis is one of the treatment modalities in the fight against cancer, many cancers become resistant to VEGF pathway inhibitors. In this article, the authors investigated the use of dual therapy using fumagillin, integrin-targeted lipid-encapsulated nanoparticles (αvβ3- Fum-PD NP) and zoledronic acid (ZA), in both in-vitro and in-vivo experiments. This combination approach may provide an insight to the design of future drugs against cancers.

Restoring an antithrombotic surface to suppress ongoing thrombosis is an appealing strategy for treatment of acute cardiovascular disorders such as erosion of atherosclerotic plaque. An antithrombotic surface would present an alternative to systemic anticoagulation with attendant risks of bleeding. We have designed thrombin-targeted nanoparticles (NPs) that bind to sites of active clotting to extinguish local thrombin activity and inhibit platelet deposition while exhibiting only transient systemic anticoagulant effects. Perfluorocarbon nanoparticles (PFC NP) were functionalized with thrombin inhibitors (either D-phenylalanyl-L-prolyl-L-arginyl-chloromethyl ketone or bivalirudin) by covalent attachment of more than 15 000 inhibitors to each PFC NP. Fibrinopeptide A (FPA) ELISA demonstrated that thrombin-inhibiting NPs prevented cleavage of fibrinogen by both free and clot-bound thrombin. Magnetic resonance imaging (MRI) confirmed that a layer of thrombin-inhibiting NPs prevented growth of clots in vitro. Thrombin-inhibiting NPs were administered in vivo to C57BL6 mice subjected to laser injury of the carotid artery. NPs significantly delayed thrombotic occlusion of the artery, whereas an equivalent bolus of free inhibitor was ineffective. For thrombin-inhibiting NPs, only a short-lived (∼10 min) systemic effect on bleeding time was observed, despite prolonged clot inhibition. Imaging and quantification of in vivo antithrombotic NP layers was demonstrated by MRI of the PFC NP. (19)F MRI confirmed colocalization of particles with arterial thrombi, and quantitative (19)F spectroscopy demonstrated specific binding and retention of thrombin-inhibiting NPs in injured arteries. The ability to rapidly form and image a new antithrombotic surface in acute vascular syndromes while minimizing risks of bleeding would permit a safer method of passivating active lesions than current systemic anticoagulant regimes.

Background Quantitative MR molecular imaging allows for the detection of targeted contrast agents to diagnose disease states and monitor response to therapy, such as anti-angiogenic therapy in atherosclerosis and cancer with aνb3-integrin targeted perfluorocarbon (PFC) nanoparticles. Recently, 19 FM R using a 19 F/ 1 H dual-tuned RF coil has been utilized to directly image and quantify the fluorinated core of these PFC nanoparticle (NP) emulsions. However, low concentrations of these fluorine agents in the body, in conjunction with varying RF coil sensitivity profiles (B1field inhomogeneities) raise obstacles to accurate quantification. This study presents a strategy to more accurately quantify the sparse 19 Fs ignal from PFC NP emulsions with a 1 H image-based Actual Flip-angle Imaging (AFI) B1-mapping correction to the 19 Fa nd 1 Hi mages.

Background CMR imaging has become a recognized gold-standard diagnostic technique for evaluating cardiovascular function, but has limited success in developing coronary imaging as a screening tool. With the faster image acquisition and reconstruction schemes, CMR can now be utilized as a non-invasive and robust screening modality of cardiovascular function and coronary disease in only 15 minutes of scanning. The 15 Minute Express Screening will enable further CMR imaging while maintaining a reasonable study length. To develop a high image-quality, repeatable, robust, and rapid clinical CMR diagnostic screening workflow, shorter than 15min, for cardiovascular function and coronary arteries.

PURPOSE To assess the dependence of neovascular molecular magnetic resonance (MR) imaging on relaxivity (r1) of αvβ3-targeted paramagnetic perfluorocarbon (PFC) nanoparticles and to delineate the temporal-spatial consistency of angiogenesis assessments for individual animals. MATERIALS AND METHODS Animal protocols were approved by the Washington University Animal Studies Committee. Proton longitudinal and transverse relaxation rates of αvβ3-targeted and nontargeted PFC nanoparticles incorporating gadolinium diethylenetrianime pentaacedic acid (Gd-DTPA) bisoleate (BOA) or gadolinium tetraazacyclododecane tetraacetic acid (Gd-DOTA) phosphatidylethanolamine (PE) into the surfactant were measured at 3.0 T. These paramagnetic nanoparticles were compared in 30 New Zealand White rabbits (four to six rabbits per group) 14 days after implantation of a Vx2 tumor. Subsequently, serial MR (3.0 T) neovascular maps were developed 8, 14, and 16 days after tumor implantation by using αvβ3-targeted Gd-DOTA-PE nanoparticles (n = 4) or nontargeted Gd-DOTA-PE nanoparticles (n = 4). Data were analyzed with analysis of variance and nonparametric statistics. RESULTS At 3.0 T, Gd-DTPA-BOA nanoparticles had an ionic r1 of 10.3 L · mmol(-1) · sec(-1) and a particulate r1 of 927000 L · mmol(-1) · sec(-1). Gd-DOTA-PE nanoparticles had an ionic r1 of 13.3 L · mmol(-1) · sec(-1) and a particulate r1 of 1 197000 L · mmol(-1) · sec(-1). Neovascular contrast enhancement in Vx2 tumors (at 14 days) was 5.4% ± 1.06 of the surface volume with αvβ3-targeted Gd-DOTA-PE nanoparticles and 3.0% ± 0.3 with αvβ3-targeted Gd-DTPA-BOA nanoparticles (P = .03). MR neovascular contrast maps of tumors 8, 14, and 16 days after implantation revealed temporally consistent and progressive surface enhancement (1.0% ± 0.3, 4.5% ± 0.9, and 9.3% ± 1.4, respectively; P = .0008), with similar time-dependent changes observed among individual animals. CONCLUSION Temporal-spatial patterns of angiogenesis for individual animals were followed to monitor longitudinal tumor progression. Neovasculature enhancement was dependent on the relaxivity of the targeted agent.

Summary Mathematical modeling studies have suggested that nonspherical, disc-shaped nanoparticles may have optimal intravascular flow and homing characteristics. In this study, we report the development of a fibrin-specific high-relaxivity bialy-shaped polymeric nanoparticle using porphyrin-chelated manganese. We anticipate that this agent would be highly effective for molecular imaging of microthrombi in ruptured atherosclerotic plaques. Background Detection of microthrombi within fissures of vulnerable atherosclerotic plaques requires a sensitive molecular imaging contrast agent. Moreover, recent reports based on mathematical modeling suggest that nonspherical, disc-shaped nanoparticles could have improved intravascular flow characteristics, which may improve liganddirected targeting. In light of the concern surrounding the use of gadolinium in patients with severe renal disease, the goal of this research was to develop a nonspherical fibrin-targeted manganese-based molecular imaging agent.

Summary Perfluorocarbon nanoparticles functionalized for thombin inhibition with Bivalirudin or PPACK were tested as an inhibitor of thrombin in vitro and in acute thrombosis models. The particles significantly inhibited occlusive arterial thrombi. The particles also manifested binding providing magnetic resonance contrast highlighting thrombi.

This study describes a novel T1-weighted MR molecular imaging approach for sparse epitopes, such as the αvβ3integrin receptor in atherosclerotic angiogenesis, utilizing a soft Mn-based nanoparticle with high-relaxivity augmented by minute amounts of surface gadolinium.This new agent utilizes about 1/30th the amount of lanthanide used for PFC paramagnetic particles and reduces gadolinium exposure by 300-fold compared with clinical single dose Gd-DTPA.

We describe the design, synthesis, and biological characterization of manganese oxocluster-based "single molecule magnets (SMMs)". We demonstrate that polymeric micellar nanoparticles can serve as a carrier and help to stabilize delicate SMM molecules from breaking down easily and thus prevent their property loss. Concentrating thousands of Mn-clusters per micelle provided a high ionic and per-particle relaxivity allowing sensitive MR imaging in vivo. This reports one of the earliest examples of in vivo imaging of a rationally designed polymeric micelle that features SMM.

Herein, initial results are presented as obtained in a hypercholesterol rabbit model with the simultaneous 19F/1H balanced UTE-SSFP technique and using ανβ3-targeted PFOB nanoparticles to establish the feasibility of high sensitivity MR molecular imaging of Gd-free, fluorine-based, clinically-relevant contrast agents.

A thrombin‐inhibiting perfluorocarbon nanoparticle (PFC NP), functionalized by PPACK (Phe(D)‐Pro‐Arg‐Chloromethylketone), was recently presented as a prototype for a novel class of targeted antithrombotic. Here, a NP functionalized with Bivalirudin (BVR), was compared to BVR and the PPACK NP. PPACK or BVR were covalently attached to PFC NPs. Optical assay verified that PPACK and BVR selectivity and activity against thrombin was not diminished on the NPs. In vivo activity was assessed for PPACK NPs, PPACK, BVR, BVR NPs, heparin, non‐functionalized NPs, or saline in C57BL6 mice subjected to laser injury of the carotid artery. Time to thrombotic occlusion of the injured artery was assessed via Doppler flow measurement. Selected arteries were excised to assess NP retention via 19 F magnetic resonance (MR). 3T MRI of thrombosis following administration of PPACK NPs was also demonstrated in cholesterol‐fed rabbits. Previously, PPACK NPs outperformed both heparin (p=.001) and PPACK (p=.0006) in delaying occlusion of the carotid artery. PPACK or non‐functionalized NPs failed to delay occlusion of the carotid artery. BVR NPs significantly delayed occlusion (p=.02) whereas an equivalent dose of free BVR (120 mg/kg) did not (figure 1a). 19 F MR captured thrombin‐specific PFC NP retention in occluded arteries of mice (figure 1b) and rabbits (figure 2).

Human prolyl‐4‐hydroxylase (P4H) catalyzes hydroxylation of peptidyl proline to 4‐hydroxyproline (4‐Hyp) in collagen, essential for extracellular matrix stabilization. P4H overexpression is associated with fibrosis and cancer. Little structural information is available for the α2 catalytic domain of human‐P4H. We are studying a putative P4H from Bacillus anthracis (anthrax‐P4H), α2 dimer, as a model for human‐P4H. Since there is no precedent for peptidyl 4‐Hyp in bacteria, we conducted amino acid analysis of total protein extracts from B. anthracis. Under nutrient‐rich conditions, B. anthracis forms vegetative cells and, upon starvation, forms spores. We detected peptidyl 4‐Hyp in exosporium (outermost spore layer) and vegetative cells of B. anthracis by multiple reaction monitoring triple quadruple mass spectrometry. This is the first example of peptidyl 4‐Hyp in bacteria and anthrax‐P4H is most likely responsible for the post‐translational modification. Using immunostaining, we detected the most anthrax‐P4H in vegetative cells without endospores, less after forming endospores, a small amount in nude spores, and no anthrax‐P4H in the exosporium. Our results suggest that the native substrate for anthrax‐P4H (precursor peptidyl‐proline) exists in vegetative cells and the product (peptidyl 4‐Hyp) is secreted into the exosporium after post‐translational modifications.

Introduction: Asthma is a chronic inflammatory lung disease that affects an estimated 25 million Americans (7 million children). The symptoms of asthma cause significant economic burden on the healthcare systems ($18B in 2008) as well as dramatic impact on the quality of patients' lives. Recently, the long recognized increase in airway wall microvessel density and expanded blood volume associated with asthma have been suggested to contribute significantly to airway obstruction and decreased lung function [1]. We have previously shown MR imaging of angiogenesis in several animal models by targeting the neovascular biomarker αvβ3-integrin, which is upregulated on proliferating versus quiescent endothelial cells [2-4]. We hypothesized that αvβ3-integrin targeted perfluorocarbon nanoparticles may be used for high resolution, dual H/F 3D MR molecular imaging at 3T for noninvasive characterization of bronchial angiogenesis. Methods: Perfluorocarbon (PFC) nanoparticles (NPs) were prepared as previously described [5]: 20% (v/v) perfluorooctylbromide (PFOB, Exfluor Inc., Round Rock, TX), 2.0% (w/v) of a surfactant comixture, and 1.7% (w/v) glycerin in pH 6.5 carbonate buffer. The surfactant co-mixture of the NPs consisted of ~ 98 mole% lecithin, 1.7 mole% phosphatidylethanolamine (PE), 0.2 mole% AlexaFluor488 (Invitrogen) coupled to PE, and 0.1 mole % of a peptidomimetic αvβ3-integrin antagonist[6]. The surfactant components were combined with the PFOB, buffer, and glycerin with pH adjusted to 6.5, and the mixtures were emulsified. Nominal particle sizes measured by dynamic light scattering was ~200 nm with a polydispersity of ~0.2 (Brookhaven Instrument Corp.) A left pulmonary artery ligation (LPAL) model of inflammation-induced angiogenesis was used to study the bronchial artery proliferation in rats by MR. The response to pulmonary ischemia in the rat most closely resembles bronchial neovascularization in human subjects after pulmonary artery obstruction [7]. Briefly, in anesthetized, ventilated rats, a left thoracotomy was performed through the 3rd intercostal space and ribs separated for exposure. Under microscopic visualization, the LPA was dissected from the airway, ligated, the ribs and skin were opposed, and the wound sutured. Three days following LPAL, rats (n=5) were administered αvβ3-targeted PFOB NPs (1.0 ml i.v./kg). After allowing the NPs to circulate for 2 hours, rats were sacrificed and imaged with high-resolution H/F MRI to characterize the spatial distribution of bronchial angiogenesis. Images were acquired at 3T (Philips Achieva) using an in-house, custom dual-tuned open birdcage transmit-receive coil. Simultaneous 3D H/F imaging was used employing a novel steady state (aka, 'balanced') ultrashort echo time (UTE) technique (TE/TR=0.1ms/1.96ms) with the frequencies set to the resonance of H and the CF2 groups of the PFOB spectrum (representing 12 of 17 total F nuclei)[8]. Using a highly oversampled 3D radial readout scheme, the reconstructed image datasets have a nominal resolution of 1.25x1.25x1.25 mm, but can be reconstructed, post facto, at lower resolutions if required to optimize the signal-to-noise ratio (SNR). Typical total scan time was 28min. Results: Fluorine images were reconstructed offline at a range of resolutions to maximize SNR. Fluorine signal located in the left lung was obvious for all animals and was minimal in the uninjured right lung.. A representative image is shown in Fig. 1. The fluorine signal on the MR images revealed the marked expansion of angiogenesis at the left thoracotomy wound site and the left mediastinal lung where the LPA was occluded. Other prominent sites of signal were appreciated in the spleen, liver and intestine, associated with reticuloendothelial clearance and biliary excretion. As shown in panels A-D, angiogenesis targeting in the lung was corroborated histopathologically using fluorescent-labeled αvβ3-targeted PFC NPs. Fig 1. A. αvβ3-targeted PFC NP with AF488 (green) targeted near airway (B, H&E) associated with neovessel proliferation (C, CD31) and increased inflammatory macrophages (D, CD68). E. H/F 3T MR coronal slice showing angiogenesis expressed in the thoracotomy wound (W) and bronchial angiogenesis (BA). Negligible signal was seen in the right, uninjured lung. NP clearance was appreciated in the liver (L), spleen (S), and small intestine (SI). Conclusion: In this study, we have used a novel application of dual H/F MR molecular imaging with a clinical 3T scanner to noninvasively image bronchial angiogenesis. The unique k-space data acquisition techniques employed supported multi-resolution, multi-sensitivity retrospective reconstruction of the simultaneously acquired H/F data. This molecular imaging approach to asthma employs quantitative image stratification to assess the temporal-spatial changes in airway vascularity, and has the potential to deliver acute antiangiogenic nanotherapy in conjunction with current standard of care drugs to offer a clinically translatable approach to ameliorate the progression of moderate to severe asthma ultimately to reduce hospitalizations and home health-care costs. 1. Voelkel, N.F. et al., Immunol Cell Biol, 2009 2. Winter, P.M., et al., Cancer Res, 2003. 3. Schmieder, A.H., et al., Magn Reson Med, 2005. 4. Winter, P.M., et al., Circulation, 2003. 5. Flacke, S., et al., Circulation, 2001. 6. Meoli, D.F., et al., J Clin Invest, 2004. 7. Endrys, J., et al., Heart, 1997. 8. Keupp J., et al., Proc. Intl. Soc. Magn. Reson. Med., 2011(#2828).

Introduction The standard of care and outcomes for anti-angiogenic therapy could be profoundly changed by patient stratification based on MR Molecular Imaging of angiogenesis in diagnosis, treatment, and response monitoring [1]. Previously, ανβ3-integrin targeted nanoparticle (NP) emulsions [2] have been shown to detect and quantify angiogenesis for multiple tumor models in small animals. NP were visualized in preand post-injection H-MRI via a Gadolinium-chelate (Gd) label [3, 4] or directly quantified using the F-MR signal from the perfluoro-carbon core [5]. Early in vivo successes exploited the single resonance peak of perfluoro-crown-ether NP (PFCE; C10F20O5) [5]. However, perfluoro-octyl-bromide (PFOB; CF3-(CF2)6-CF2Br) is a more clinically-relevant NP with a better-understood human safety profile, but it has a much more complex spectrum (i.e., 7 F resonance peaks and multiple relaxation conditions). Furthermore, although Gd has been shown to enhance the F signal through T1 shortening, the absence of Gd is more attractive from a translational point of view. A new technique—dual-frequency balanced ultra-short echo time (UTE-SSFP) sequence with 3D radial readout—offers high sensitivity imaging of PFOB without the need for Gd. The current objective is to image angiogenesis in a rabbit adenocarcinoma model with the simultaneous F/H UTE-SFFP technique using ανβ3-targeted PFOB nanoparticles with and without Gd to establish the feasibility of high sensitivity MR molecular imaging of Gd-free, fluorine-based, clinically-relevant contrast agents.

OBJECTIVES The objectives of this study were to use magnetic resonance (MR) molecular imaging to 1) characterize the aortic neovascular development in a rat model of atherosclerosis and 2) monitor the effects of an appetite suppressant on vascular angiogenesis progression.BACKGROUND The James C. Russell: LA corpulent rat strain (JCR:LA-cp) is a model of metabolic syndrome characterized by obesity, insulin resistance, hyperlipidemia, and vasculopathy, although plaque neovascularity has not been reported in this strain. MR molecular imaging with alpha(v)beta(3)-targeted nanoparticles can serially map angiogenesis in the aortic wall and monitor the progression of atherosclerosis.METHODS Six-week old JCR:LA-cp (+/?; lean, n = 5) and JCR:LA-cp (cp/cp; obese, n = 5) rats received standard chow, and 6 obese rats were fed the appetite suppressant benfluorex over 16 weeks. Body weight and food consumption were recorded at baseline and weeks 4, 8, 12, and 16. MR molecular imaging with alpha(nu)beta(3)-targeted paramagnetic nanoparticles was performed at weeks 0, 8, and 16. Fasted plasma triglyceride, cholesterol, and glucose were measured immediately before MR scans. Plasma insulin and leptin levels were assayed at weeks 8 and 16.RESULTS Benfluorex reduced food consumption (p < 0.05) to the same rate as lean animals, but had no effect on serum cholesterol or triglyceride levels. MR (3-T) aortic signal enhancement with alpha(nu)beta(3)-targeted nanoparticles was initially equivalent between groups, but increased (p < 0.05) in the untreated obese animals over 16 weeks. No signal change (p > 0.05) was observed in the benfluorextreated or lean rat groups. MR differences paralleled adventitial microvessel counts, which increased (p < 0.05) among the obese rats and were equivalently low in the lean and benfluorex-treated animals (p > 0.05). Body weight, insulin, and leptin were decreased (p < 0.05) from the untreated obese animals by benfluorex, but not to the lean control levels (p < 0.05).CONCLUSIONS Neovascular expansion is a prominent feature of the JCR: LA-cp model. MR imaging with alpha(nu)beta(3)-targeted nanoparticles provided a noninvasive assessment of angiogenesis in untreated obese rats, which was suppressed by benfluorex. (J Am Coll Cardiol Img 2010; 3:824-32) (C) 2010 by the American College of Cardiology Foundation