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Over several months, representatives from the U.S. Department of Energy (DOE) Office of Science and National Institutes of Health (NIH) had a number of meetings that lead to the conclusion that innovations in the Nations health care could be realized by more directed interactions between NIH and DOE. It became clear that the expertise amassed and instrumentation advances developed at the DOE physical science laboratories to enable cutting-edge research in particle physics could also feed innovation in medical healthcare. To meet their scientific mission, the DOE laboratories created advances in such technologies as particle beam generation, radioisotope production, high-energy particle detection and imaging, superconducting particle accelerators, superconducting magnets, cryogenics, high-speed electronics, artificial intelligence, and big data. To move forward, NIH and DOE initiated the process of convening a joint workshop which occurred on July 12th and 13th, 2021. This Special Report presents a summary of the findings of the collaborative workshop and introduces the goals of the next one.

Chemokines and chemokine receptors play an important role in the initiation and progression of atherosclerosis by mediating the trafficking of inflammatory cells. Chemokine receptor 5 (CCR5) has major implications in promoting the development of plaques to advanced stage and related vulnerability. CCR5 antagonist has demonstrated the effective inhibition of atherosclerotic progression in mice, making it a potential biomarker for atherosclerosis management. To accurately determine CCR5 in vivo, we synthesized CCR5 targeted Comb nanoparticles through a modular design and construction strategy with control over the physiochemical properties and functionalization of CCR5 targeting peptide d-Ala-peptide T-amide (DAPTA-Comb). In vivo pharmacokinetic evaluation through 64Cu radiolabeling showed extended blood circulation of 64Cu-DAPTA-Combs conjugated with 10%, 25%, and 40% DAPTA. The different organ distribution profiles of the three nanoparticles demonstrated the effect of DAPTA on not only physicochemical properties but also targeting efficiency. In vivo positron emission tomography/computed tomography (PET/CT) imaging in an apolipoprotein E knockout mouse atherosclerosis model (ApoE-/-) showed that the three 64Cu-DAPTA-Combs could sensitively and specifically detect CCR5 along the progression of atherosclerotic lesions. In an ApoE-encoding adenoviral vector (AAV) induced plaque regression ApoE-/- mouse model, decreased monocyte recruitment, CD68+ macrophages, CCR5 expression, and plaque size were all associated with reduced PET signals, which not only further confirmed the targeting efficiency of 64Cu-DAPTA-Combs but also highlighted the potential of these targeted nanoparticles for atherosclerosis imaging. Moreover, the up-regulation of CCR5 and colocalization with CD68+ macrophages in the necrotic core of ex vivo human plaque specimens warrant further investigation for atherosclerosis prognosis.

Nanoparticles have been assessed in preclinical models of atherosclerosis for detection of plaque complexity and treatment. However, their successful clinical translation has been hampered by less than satisfactory plaque detection and lack of a general strategy for assessing the translational potential of nanoparticles. Herein, nanoparticles based on comb-co-polymer assemblies were synthesized through a modular construction approach with precise control over the conjugation of multiple functional building blocks for in vivo evaluation. This high level of design control also allows physicochemical properties to be varied in a controllable fashion. Through conjugation of c-atrial natriuretic factor (CANF) peptide and radiolabeling with 64Cu, the 64Cu-CANF-comb nanoparticle was assessed for plaque imaging by targeting natriuretic peptide clearance receptor (NPRC) in a double-injury atherosclerosis model in rabbits. The prolonged blood circulation and enhanced binding capacity of 64Cu-CANF-comb nanoparticles provided sensitive and specific imaging of NPRC overexpressed in atherosclerotic lesions by positron emission tomography at intervals during the progression of the disease. Ex vivo tissue validation using autoradiography and immunostaining on human carotid endarterectomy specimens demonstrated specific binding of 64Cu-CANF-comb to human NPRC receptors. Taken together, this study not only shows the potential of NPRC-targeted 64Cu-CANF-comb nanoparticles for increased sensitivity to an epitope that increases during atherosclerosis plaque development but also provides a useful strategy for the general design and assessment of the translational potential of nanoparticles in cardiovascular imaging.

PurposeTo assess the physicochemical properties, pharmacokinetic profiles, and in vivo positron emission tomography (PET) imaging of natriuretic peptide clearance receptors (NPRC) expressed on atherosclerotic plaque of a series of targeted, polymeric nanoparticles.MethodsTo control their structure, non-targeted and targeted polymeric (comb) nanoparticles, conjugated with various amounts of c-atrial natriuretic peptide (CANF, 0, 5, 10 and 25%), were synthesized by controlled and modular chemistry. In vivo pharmacokinetic evaluation of these nanoparticles was performed in wildtype (WT) C57BL/6 mice after (64)Cu radiolabeling. PET imaging was performed on an apolipoprotein E-deficient (ApoE(-/-)) mouse atherosclerosis model to assess the NPRC targeting efficiency. For comparison, an in vivo blood metabolism study was carried out in WT mice.ResultsAll three (64)Cu-CANF-comb nanoparticles showed improved biodistribution profiles, including significantly reduced accumulation in both liver and spleen, compared to the non-targeted (64)Cu-comb. Of the three nanoparticles, the 25% (64)Cu-CANF-comb demonstrated the best NPRC targeting specificity and sensitivity in ApoE(-/-) mice. Metabolism studies showed that the radiolabeled CANF-comb was stable in blood up to 9 days. Histopathological analyses confirmed the up-regulation of NPRC along the progression of atherosclerosis.ConclusionThe 25% (64)Cu-CANF-comb demonstrated its potential as a PET imaging agent to detect atherosclerosis progression and status.

UnlabelledAtherosclerosis is inherently an inflammatory process that is strongly affected by the chemokine-chemokine receptor axes regulating the trafficking of inflammatory cells at all stages of the disease. Of the chemokine receptor family, some specifically upregulated on macrophages play a critical role in plaque development and may have the potential to track plaque progression. However, the diagnostic potential of these chemokine receptors has not been fully realized. On the basis of our previous work using a broad-spectrum peptide antagonist imaging 8 chemokine receptors together, the purpose of this study was to develop a targeted nanoparticle for sensitive and specific detection of these chemokine receptors in both a mouse vascular injury model and a spontaneously developed mouse atherosclerosis model.MethodsThe viral macrophage inflammatory protein-II (vMIP-II) was conjugated to a biocompatible poly(methyl methacrylate)-core/polyethylene glycol-shell amphiphilic comblike nanoparticle through controlled conjugation and polymerization before radiolabeling with (64)Cu for PET imaging in an apolipoprotein E-deficient (ApoE(-/-)) mouse vascular injury model and a spontaneous ApoE(-/-) mouse atherosclerosis model. Histology, immunohistochemistry, and real-time reverse transcription polymerase chain reaction were performed to assess the plaque progression and upregulation of chemokine receptors.ResultsThe chemokine receptor-targeted (64)Cu-vMIP-II-comb showed extended blood retention and improved biodistribution. PET imaging showed specific tracer accumulation at plaques in ApoE(-/-) mice, confirmed by competitive receptor blocking studies and assessment in wild-type mice. Histopathologic characterization showed the progression of plaque including size and macrophage population, corresponding to the elevated concentration of chemokine receptors and more importantly increased PET signals.ConclusionThis work provides a useful nanoplatform for sensitive and specific detection of chemokine receptors to assess plaque progression in mouse atherosclerosis models.

UnlabelledInflammation plays important roles at all stages of atherosclerosis. Chemokine systems have major effects on the initiation and progression of atherosclerosis by controlling the trafficking of inflammatory cells in vivo through interaction with their receptors. Chemokine receptor 5 (CCR5) has been reported to be an active participant in the late stage of atherosclerosis and has the potential as a prognostic biomarker for plaque stability. However, its diagnostic potential has not yet been explored. The purpose of this study was to develop a targeted nanoparticle for sensitive and specific PET/CT imaging of the CCR5 receptor in an apolipoprotein E knock-out (ApoE(-/-)) mouse vascular injury model.MethodsThe D-Ala1-peptide T-amide (DAPTA) peptide was selected as a targeting ligand for the CCR5 receptor. Through controlled conjugation and polymerization, a biocompatible poly(methyl methacrylate)-core/polyethylene glycol-shell amphiphilic comblike nanoparticle was prepared and labeled with (64)Cu for CCR5 imaging in the ApoE(-/-) wire-injury model. Immunohistochemistry, histology, and real-time reverse transcription polymerase chain reaction (RT-PCR) were performed to assess the disease progression and upregulation of CCR5 receptor.ResultsThe (64)Cu-DOTA-DAPTA tracer showed specific PET imaging of CCR5 in the ApoE(-/-) mice. The targeted (64)Cu-DOTA-DAPTA-comb nanoparticles showed extended blood signal and optimized biodistribution. The tracer uptake analysis showed significantly higher accumulations at the injury lesions than those acquired from the sham-operated sites. The competitive PET receptor blocking studies confirmed the CCR5 receptor-specific uptake. The assessment of (64)Cu-DOTA-DAPTA-comb in C57BL/6 mice and (64)Cu-DOTA-comb in ApoE(-/-) mice verified low nonspecific nanoparticle uptake. Histology, immunohistochemistry, and RT-PCR analyses verified the upregulation of CCR5 in the progressive atherosclerosis model.ConclusionThis work provides a nanoplatform for sensitive and specific detection of CCR5's physiologic functions in an animal atherosclerosis model.