bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Targeted Enhanced Ultrasound Imaging of Flk1 Reveals Diagnosis and Prognosis Potential in a Genetically Engineered Mouse Prostate Cancer Model
Authors: Xuan Jim W. , Bygrave Michael , Valiyeva Fatma , Moussa Madeleine , Izawa Jonathan I. , Bauman Glenn S. , Klibanov Alexander , Wang Fen , Greenberg Norman M. , Fenster Aaron
Published: March 2018

Molecular imaging techniques used to detect the initiation of disease have the potential to provide the best opportunity for early treatment and cure. This report aimed at testing the possibility that Flk1+ (vascular endothelial growth factor receptor 2), a crucial angiogenesis factor of most tumor cells, could be a molecular targeted imaging marker for the diagnosis and prognosis of cancer. We performed Flk1-targeted microbubble-enhanced ultrasound (US) imaging of prostate cancer in a genetically engineered mouse model with normal-appearing intact US (negative) prostates and with three different tumor sizes (small, medium, and large). Higher levels of Flk1+ molecular signals were identified in the intact US (negative) prostate group by US-targeted imaging and immunohistochemical analysis. The increase in Flk1+ expression occurred prior to the angiogenesis switch-on phase and vascularity peak. After this peak accumulation stage of Flk1+ molecules, lower and stabilized levels of Flk1+ signals were maintained together with tumor growth from small, to medium, to large size. In a longitudinal observation in a subset ( n = 5) of mice with established tumors, elevated Flk1+ signals were observed in tissues surrounding the prostate cancer, for example, the ipsilateral boundary zones between two developing tumor lobes, new tumor blood vessel recruits, the urethra border, and the pelvic node basin. The potential of Flk1-targeted US imaging as a predictive imaging tool was confirmed by correlation studies of three-dimensional US B-mode imaging, gross pathology, and histology analyses. The results of the application in a genetically engineered mouse model with prostate cancer of molecular Flk1-targeted US imaging support the contention that Flk1 can be used as a molecular imaging marker for small tumors undetectable by microimaging and as a molecular diagnostic and prognosis marker for tumor metastasis and progression.
Positron Emission Tomography for Serial Imaging of the Contused Adult Rat Spinal Cord
Authors: Tewarie Rishi D.S. Nandoe , Yu Jianhua , Seidel Jurgen , Rahiem Sahar T. , Hurtado Andres , Tsui Benjamin M.W. , Grotenhuis J. Andre , Pomper Martin G. , Oudega Martin
Published: March 2018

We investigated whether small-animal positron emission tomography (PET) could be used in combination with computed tomography (CT) imaging techniques for longitudinal monitoring of the injured spinal cord. In adult female Sprague-Dawley rats ( n = 6), the ninth thoracic (T9) spinal cord segment was exposed by laminectomy and subsequently contused using the Infinite Horizon impactor (Precision System and Instrumentation, Lexington, KY) at 225 kDyn. In control rats ( n = 4), the T9 spinal cord was exposed by laminectomy but not contused. At 0.5 hours and 3, 7, and 21 days postinjury, 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) was given intravenously followed 1 hour later by sequential PET and CT. Regions of interest (ROIs) at T9 (contused) and T6 (uninjured) spinal cord segments were manually defined on CT images and aided by fiduciary markers superimposed onto the coregistered PET images. Monte Carlo simulation revealed that about 33% of the activity in the ROIs was due to spillover from adjacent hot areas. A simulation-based partial-volume compensation (PVC) method was developed and used to correct for this spillover effect. With PET-CT, combined with PVC, we were able to serially measure standardized uptake values of the T9 and T6 spinal cord segments and reveal small, but significant, differences. This approach may become a tool to assess the efficacy of spinal cord repair strategies.
Shifted Helical Computed Tomography to Optimize Cardiac Positron Emission Tomography–Computed Tomography Coregistration: Quantitative Improvement and Limitations
Authors: Johnson Nils P. , Pan Tinsu , Gould K. Lance
Published: March 2018

Positron emission tomography–computed tomography (PET-CT) uses CT attenuation correction but suffers from misregistration artifacts. However, the quantitative accuracy of helical versus cine CT in the same patient after optimized coregistration by shifting both CT data as needed for each patient is unknown. We studied 293 patients undergoing cardiac perfusion PET-CT using helical CT attenuation correction for comparison to cine CT. Objective, quantitative criteria identified perfusion abnormalities that were associated visually with PET-CT misregistration. Custom software shifted CT data to optimize coregistration with quantitative artifact improvement. The majority (58.1%) of cases with both helical and shifted helical CT data ( n = 93) had artifacts that improved or resolved by software shifting helical CT data. Translation of shifted helical CT was greatest in the x-direction (8.8 ± 3.3 mm) and less in the y- and z-directions (approximately 3.5 mm). The magnitude of differences in quantitative end points was greatest for helical ( p = .0001, n = 177 studies), less for shifted helical but significant ( p = .0001, n = 93 studies), and least for cine (not significant, n = 161 studies) CT compared to optimal attenuation correction for each patient. Frequent artifacts owing to attenuation-emission misregistration are substantially corrected by software shifting helical CT scans to achieve proper coregistration that, however, remains on average significantly inferior to cine CT attenuation quantitatively.
In Vivo Magnetic Resonance Imaging and Optical Imaging Comparison of Viable and Nonviable Mesenchymal Stem Cells with a Bifunctional Label
Authors: Sutton Elizabeth Jane , Henning Tobias D. , Boddington Sophie , Demos Stavros , Krug Christian , Meier Reinhardt , Kornak John , Zhao Shoujun , Baehner Rick , Sharifi Sheida , Daldrup-Link Heike
Published: March 2018

The purpose of this study was to compare viable and nonviable bilabeled mesenchymal stem cells (MSCs) in arthritic joints with magnetic resonance imaging (MRI) and optical imaging (OI). MSCs were labeled with ferucarbotran and DiD. MRI and OI of bilabeled cells were compared with controls. Six rats with arthritis received intra-articular injections of bilabeled viable MSCs into the right knee and nonviable MSCs into the left knee. Animals underwent MRI and OI preinjection and at 4, 24, 48, and 72 hours postinjection. The results were analyzed with a mixed random effects model and Fisher probability. Bilabeled MSCs showed increased MRI and OI signals compared to unlabeled controls ( p < .0001). After intra-articular injection, bilabeled MSCs caused significant T2 and T2* effect on MRI and fluorescence on OI up to 72 hours postinjection ( p < .05). There was no significant difference between viable and nonviable MSC signal in the knee joints; however, some of the viable cells migrated to an adjacent inflamed ankle joint ( p < .05). Immunohistochemistry confirmed viable MSCs in right knee and ankle joints and nonviable MSCs in the left knee. Viable and nonviable cells could not be differentiated with MRI or OI signal intensity but were differentiated based on their ability to migrate in vivo.
Comparison of rNIS and hNIS as Reporter Genes for Noninvasive Imaging of Bone Mesenchymal Stem Cells Transplanted into Infarcted Rat Myocardium
Authors: Hu Shuo , Cao Wei , Lan Xiaoli , He Yong , Lang Juntao , Li Congjiao , Hu Jia , An Rei , Gao Zairong , Zhang Yongxue
Published: March 2018

The purpose of this study was to investigate and compare the feasibility of rat sodium iodide symporter ( rNIS) and human sodium iodide symporter ( hNIS) as reporter genes for noninvasive monitoring of rat bone marrow mesenchymal stem cells (rBMSCs) transplanted into infarcted rat myocardium. rBMSCs were isolated from rat bone marrow. Adenovirus (Ad) was reconstructed to contain rNIS-enhanced green fluorescent protein (eGFP) or hNIS-eGFP. The transfection efficiency of Ad/eGFP/rNIS and Ad/eGFP/hNIS to rBMSCs was measured by real-time polymerase chain reaction, flow cytometry, Western blot, and immunofluorescence staining. The transfected rBMSCs were transplanted into infarcted rat myocardium followed by a single-photon emission computed tomography (SPECT) study with 99mTc-pertechnetate as the radiotracer and by autoradiography. The isolated rBMSCs were CD29, CD44, and CD90 positive and CD34, CD45, and CD11b negative. The expression of rNIS and hNIS in the transfected rBMSCs at both gene and protein levels was obviously higher than that without transfection. The myocardium of rats transplanted with transfected rBMSCs could be visualized by SPECT owing to the accumulation of 99mTc-pertechnetate in rBMSCs mediated by exogenous NIS genes. The accumulation of 99mTc-pertechnetate in myocardium mediated by rNIS was higher than that by hNIS, which was also confirmed by autoradiography. Both rNIS and hNIS are useful reporter genes to monitor BMSCs transplanted into infarcted myocardium in vivo with rNIS being superior to hNIS as the reporter gene.
Increased Breast Density Correlates with the Proliferation-Seeking Radiotracer 99mTc(V)-DMSA Uptake in Florid Epithelial Hyperplasia and in Mixed Ductal Carcinoma in Situ with Invasive Ductal Carcinoma but Not in Pure Invasive Ductal Carcinoma or in Mild Epithelial Hyperplasia
Authors: Papantoniou Vassilios , Valsamaki Pipitsa , Sotiropoulou Evangelia , Tsaroucha Angeliki , Tsiouris Spyridon , Sotiropoulou Maria , Marinopoulos Spyridon , Kounadi Evangelia , Karianos Theodore , Fothiadaki Athina , Archontaki Aikaterini , Syrgiannis Konstantinos , Ptohis Nikolaos , Makris Nikolaos , Limouris Georgios , Antsaklis Aris
Published: March 2018

The purpose of this study was to assess the relationship of mammographic breast density (BD) and cell proliferation/focal adhesion kinase activation–seeking radiotracer technetium 99m pentavalent dimercaptosuccinic acid (99mTc(V)-DMSA) uptake in women with different breast histologies, that is, mild epithelial hyperplasia (MEH), florid epithelial hyperplasia (FEH), mixed ductal carcinoma in situ with invasive ductal carcinoma (DCIS + IDC), and pure IDC. Fifty-five women with histologically confirmed mammary pathologies were submitted preoperatively to mammography and 99mTc(V)-DMSA scintimammography. The percentage and intensity of 99mTc(V)-DMSA uptake and the percentage of BD were calculated by computer-assisted methods and compared ( t-test) between the breast pathologies. In breasts with increased BD, FEH and DCIS + IDC were found. On the contrary, pure IDC and MEH were identified in breasts with significantly lower BD values. In breasts with increased 99mTc(V)-DMSA area and intensity of uptake, FEH was the main lesion found compared to all other histologies. Linear regression analysis between BD and 99mTc(V)-DMSA uptake area and intensity revealed significant coefficients of correlation ( r = .689, p < .001 and r = .582, p < .001, respectively). Increased BD correlates with the presence of FEH and mixed DCIS + IDC but not with pure IDC or MEH. Its close relationship to 99mTc(V)-DMSA, which also showed an affinity to FEH, indicates that stromal microenvironment may constitute a specific substrate leading to progression to different subtypes of cancerous lesions originating from different pathways.
Gaussia Luciferase for Bioluminescence Tumor Monitoring in Comparison with Firefly Luciferase
Authors: Inoue Yusuke , Sheng Fugeng , Kiryu Shigeru , Watanabe Makoto , Ratanakanit Harnprasopwat , Izawa Kiyoko , Tojo Arinobu , Ohtomo Kuni
Published: March 2018

Gaussia luciferase (Gluc) is a secreted reporter, and its expression in living animals can be assessed by in vivo bioluminescence imaging (BLI) or blood assays. We characterized Gluc as an in vivo reporter in comparison with firefly luciferase (Fluc). Mice were inoculated subcutaneously with tumor cells expressing both Fluc and Gluc and underwent Flue BLI, Gluc BLI, blood assays of Glue activity, and caliper measurement. In Gluc BLI, the signal from the tumor peaked immediately and then decreased rapidly. In the longitudinal monitoring, all measures indicated an increase in tumor burden early after cell inoculation. However, the increase reached plateaus in Gluc BLI and Fluc BLI despite a continuous increase in the caliper measurement and Gluc blood assay. Significant correlations were found between the measures, and the correlation between the blood signal and caliper volume was especially high. Gluc allows tumor monitoring in mice and should be applicable to dual-reporter assessment in combination with Fluc. The Gluc blood assay appears to provide a reliable indicator of viable tumor burden, and the combination of a blood assay and in vivo BLI using Glue should be promising for quantifying and localizing the tumors.
In Vivo Imaging of Apoptosis in Oncology: An Update
Authors: Vangestel Christel , Peeters Marc , Mees Gilles , Oltenfreiter Ruth , Boersma Hendrikus H. , Elsinga Philip H. , Reutelingsperger Chris , Van Damme Nancy , De Spiegeleer Bart , Van de Wiele Christophe
Published: March 2018

In this review, data on noninvasive imaging of apoptosis in oncology are reviewed. Imaging data available are presented in order of occurrence in time of enzymatic and morphologic events occurring during apoptosis. Available studies suggest that various radiopharmaceutical probes bear great potential for apoptosis imaging by means of positron emission tomography and single-photon emission computed tomography (SPECT). However, for several of these probes, thorough toxicologic studies are required before they can be applied in clinical studies. Both preclinical and clinical studies support the notion that 99mTc-hydrazinonicoti-namide-annexin A5 and SPECT allow for noninvasive, repetitive, quantitative apoptosis imaging and for assessing tumor response as early as 24 hours following treatment instigation. Bioluminescence imaging and near-infrared fluorescence imaging have shown great potential in small-animal imaging, but their usefulness for in vivo imaging in humans is limited to structures superficially located in the human body. Although preclinical tumor-based data using high-frequency-ultrasonography (US) are promising, whether or not US will become a routinely clinically useful tool in the assessment of therapy response in oncology remains to be proven. The potential of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) for imaging late apoptotic processes is currently unclear. Neither 31 P MRS nor 1 H MRS signals seems to be a unique identifier for apoptosis. Although MRI-measured apparent diffusion coefficients are altered in response to therapies that induce apoptosis, they are also altered by nonapoptotic cell death, including necrosis and mitotic catastrophe. In the future, rapid progress in the field of apoptosis imaging in oncology is expected.
Controlled Modulation of Serum Protein Binding and Biodistribution of Asymmetric Cyanine Dyes by Variation of the Number of Sulfonate Groups
Authors: Hamann Franziska M. , Brehm Robert , Pauli Jutta , Grabolle Markus , Frank Wilhelm , Kaiser Werner A. , Fischer Dagmar , Resch-Genger Ute , Hilger Ingrid
Published: March 2018

To assess the suitability of asymmetric cyanine dyes for in vivo fluoro-optical molecular imaging, a comprehensive study on the influence of the number of negatively charged sulfonate groups governing the hydrophilicity of the DY-67x family of asymmetric cyanines was performed. Special attention was devoted to the plasma protein binding capacity and related pharmacokinetic properties. Four members of the DY-67x cyanine family composed of the same main chromophore, but substituted with a sequentially increasing number of sulfonate groups (n = 1−4; DY-675, DY-676, DY-677, DY-678, respectively), were incubated with plasma proteins dissolved in phosphate-buffered saline. Protein binding was assessed by absorption spectroscopy, gel electrophoresis, ultrafiltration, and dialysis. Distribution of dye in organs was studied by intraveneous injection of 62 nmol dye/kg body weight into mice (n = 12; up to 180 minutes postinjection) using whole-body near-infrared fluorescence imaging. Spectroscopic studies, gel electrophoresis, and dialysis demonstrated reduced protein binding with increasing number of sulfonate groups. The bovine serum albumin binding constant of the most hydrophobic dye, DY-675, is 18 times higher than that of the most hydrophilic fluorophore, DY-678. In vivo biodistribution analysis underlined a considerable influence of dye hydrophilicity on biodistribution and excretion pathways, with the more hydrophobic dyes, DY-675 and DY-676, accumulating in the liver, followed by strong fluorescence signals in bile and gut owing to accumulation in feces and comparatively hydrophilic DY-678-COOH accumulating in the bladder. Our results demonstrate the possibility of selectively controlling dye-protein interactions and, thus, biodistribution and excretion pathways via proper choice of the fluorophore's substitution pattern. This underlines the importance of structure-property relationships for fluorescent labels. Moreover, our data could provide the basis for the rationalization of future contrast agent developments.
Characterization and Evaluation of Two Novel Fluorescent Sigma-2 Receptor Ligands as Proliferation Probes
Authors: Zeng Chenbo , Vangveravong Suwanna , Jones Lynne A. , Hyrc Krzysztof , Chang Katherine C. , Xu Jinbin , Rothfuss Justin M. , Goldberg Mark P. , Hotchkiss Richard S. , Mach Robert H.
Published: March 2018

We synthesized and characterized two novel fluorescent sigma-2 receptor selective ligands, SW120 and SW116, and evaluated these ligands as potential probes for imaging cell proliferation. Both ligands are highly selective for sigma-2 receptors versus sigma-1 receptors. SW120 and SW116 were internalized into MDA-MB-435 cells, and 50% of the maximum fluorescent intensity was reached in 11 and 24 minutes, respectively. In vitro studies showed that 50% of SW120 or SW116 washed out of cells in 1 hour. The internalization of SW120 was reduced ≈30% by phenylarsine oxide, an inhibitor of endocytosis, suggesting that sigma-2 ligands are internalized, in part, by an endocytotic pathway. Subcellular localization studies using confocal and two-photon microscopy showed that SW120 and SW116 partially colocalized with fluorescent markers of mitochondria, endoplasmic reticulum, lysosomes, and the plasma membrane, suggesting that sigma-2 receptors localized to the cytoplasmic organelles and plasma membrane. SW120 did not colocalize with the nuclear dye 4′,6-diamidino-2-phenylindole. In vivo studies showed that the uptake of SW120 in solid tumors and peripheral blood mononuclear cells of mice positively correlated with the expression level of the cell proliferation marker Ki-67, suggesting that sigma-2 fluorescent probes may be used to image cell proliferation in mice.
Imaging of Non— or Very Subtle Contrast-Enhancing Malignant Gliomas with [11C]-Methionine Positron Emission Tomography
Authors: Galldiks Norbert , Kracht Lutz W. , Dunkl Veronika , Ullrich Roland T. , Vollmar Stefan , Jacobs Andreas H. , Fink Gereon R. , Schroeter Michael
Published: March 2018

In patients with World Health Organization (WHO) grade III glioma with a lack of or minimal (< 1 cm3) magnetic resonance imaging (MRI) contrast enhancement, the volume of the metabolically active part of the tumor was assessed by [ 11 C]-methionine positron emission tomography (MET-PET). Eleven patients with WHO grade III gliomas underwent MET-PET and MRI (contrast-enhanced T1-and T2-weighted images). To calculate the volumes in cubic centimeters, threshold-based volume of interest analyses of the metabolically active tumor (MET uptake index ≥ 1.3), contrast enhancement, and the T2 lesion were performed after coregistration of all images. In all patients, the metabolically active tumor volume was larger than the volume of gadolinium–diethylenetriamine pentaacetic acid (Gd-DTPA) enhancement (20.8 ± 18.8 vs 0.29 ± 0.25 cm3; p < .001). With the exception of one patient, the volumes of contrast enhancement were located within the metabolically active tumor volume. In contrast, in the majority of patients, MET uptake overlapped with the T2 lesion and reached beyond it (in 10 of 12 MRIs/MET-PET scans). The present data suggest that in patients with WHO grade III glioma with minimal or a lack of contrast enhancement, MET-PET delineates metabolically active tumor tissue. These findings support the use of combined PET-MRI with radiolabeled amino acids (eg, MET) for the delineating of the true extent of active tumor in the diagnosis and treatment planning of patients with gliomas.
[18F]FDG Labeling of Neural Stem Cells for in Vivo Cell Tracking with Positron Emission Tomography: Inhibition of Tracer Release by Phloretin
Authors: Stojanov Katica , de Vries Erik F.J. , Hoekstra Dick , van Waarde Aren , Dierckx Rudi A.J.O. , Zuhorn Inge S.
Published: March 2018

The introduction of neural stem cells into the brain has promising therapeutic potential for the treatment of neurodegenerative diseases. To monitor the cellular replacement therapy, that is, to determine stem cell migration, survival, and differentiation, in vivo tracking methods are needed. Ideally, these tracking methods are noninvasive. Noninvasive tracking methods that have been successfully used for the visualization of blood-derived progenitor cells include magnetic resonance imaging and radionuclide imaging using single-photon emission computed tomography (SPECT) and positron emission tomography (PET). The SPECT tracer In-111-oxine is suitable for stem cell labeling, but for studies in small animals, the higher sensitivity and facile quantification that can be obtained with PET are preferred. Here the potential of 2′-[18F]fluoro-2′-deoxy-D-glucose ([18F]-FDG), a PET tracer, for tracking of neural stem cell (NSCs) trafficking toward an inflammation site was investigated. [18F]-FDG turns out to be a poor radiopharmaceutical to label NSCs owing to the low labeling efficiency and substantial release of radioactivity from these cells. Efflux of [18F]-FDG from NSCs can be effectively reduced by phloretin in vitro, but inhibition of tracer release is insufficient in vivo for accurate monitoring of stem cell trafficking.
Imaging in Vivo Extracellular pH with a Single Paramagnetic Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agent
Authors: Liu Guanshu , Li Yuguo , Sheth Vipul R. , Pagel Mark D.
Published: March 2018

The measurement of extracellular pH (pHe) has potential utility for cancer diagnoses and for assessing the therapeutic effects of pH-dependent therapies. A single magnetic resonance imaging (MRI) contrast agent that is detected through paramagnetic chemical exchange saturation transfer (PARACEST) was designed to measure tumor pHe throughout the range of physiologic pH and with magnetic resonance saturation powers that are not harmful to a mouse model of cancer. The chemical characterization and modeling of the contrast agent Yb3+-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, 10-o-aminoanilide (Yb-DO3A-oAA) suggested that the aryl amine of the agent forms an intramolecular hydrogen bond with a proximal carboxylate ligand, which was essential for generating a practical chemical exchange saturation transfer (CEST) effect from an amine. A ratio of CEST effects from the aryl amine and amide was linearly correlated with pH throughout the physiologic pH range. The pH calibration was used to produce a parametric pH map of a subcutaneous flank tumor on a mouse model of MCF-7 mammary carcinoma. Although refinements in the in vivo CEST MRI methodology may improve the accuracy of pHe measurements, this study demonstrated that the PARACEST contrast agent can be used to generate parametric pH maps of in vivo tumors with saturation power levels that are not harmful to a mouse model of cancer.
Endothelial Adhesion of Targeted Microbubbles in Both Small and Great Vessels Using Ultrasound Radiation Force
Authors: Liu Jia , Zhang Ping , Liu Ping , Zhao Yang , Gao Shunji , Tan Kaibin , Liu Zheng
Published: March 2018

The effectiveness of microbubble-mediated ultrasound molecular imaging and drug delivery has been significantly affected by the axial laminar flow of vessels which prevents ultrasound contrast agents (UCAs) from targeting vascular endothelium. Studies show that acoustic manipulation could increase targeted UCA adhesion in microcirculation and some small vessels. In this study we demonstrate that ultrasound radiation force (USRF) can also significantly enhance the targeted adhesion of microbubbles in both small and great vessels. Our results indicate that the UCA adhesion targeted to ICAM-1 expressed on mouse cremaster microvascular endothelial cells increase about 9-fold when USRF is applied at 1 MHz and 73.9 kPa. The adhesion of anti-CD34 microbubbles to the endothelia of rat abdominal aorta was visually analyzed using scanning electron microscopy for the first time and thousands of microbubbles were found attached to the aortic endothelia after USRF application at the same acoustic parameters. Our data illustrate that targeted adhesion of anti-CD34 microbubbles is possible in normal abdominal aorta and we demonstrate the potential of using USRF in molecular imaging of a vascular target.
Magnetic Resonance Imaging of Ferumoxide-Labeled Mesenchymal Stem Cells in Cartilage Defects: In Vitro and in Vivo Investigations
Authors: Henning Tobias D. , Gawande Rakhee , Khurana Aman , Tavri Sidhartha , Mandrussow Lydia , Golovko Daniel , Horvai Andrew , Sennino Barbara , McDonald Donald , Meier Reinhard , Wendland Michael , Derugin Nikita , Link Thomas M. , Daldrup-Link Heike E.
Published: March 2018

The purpose of this study was to (1) compare three different techniques for ferumoxide labeling of mesenchymal stem cells (MSCs), (2) evaluate if ferumoxide labeling allows in vivo tracking of matrix-associated stem cell implants (MASIs) in an animal model, and (3) compare the magnetic resonance imaging (MRI) characteristics of ferumoxide-labeled viable and apoptotic MSCs. MSCs labeled with ferumoxide by simple incubation, protamine transfection, or Lipofectin transfection were evaluated with MRI and histopathology. Ferumoxide-labeled and unlabeled viable and apoptotic MSCs in osteochondral defects of rat knee joints were evaluated over 12 weeks with MRI. Signal to noise ratios (SNRs) of viable and apoptotic labeled MASIs were tested for significant differences using t-tests. A simple incubation labeling protocol demonstrated the best compromise between significant magnetic resonance signal effects and preserved cell viability and potential for immediate clinical translation. Labeled viable and apoptotic MASIs did not show significant differences in SNR. Labeled viable but not apoptotic MSCs demonstrated an increasing area of T2 signal loss over time, which correlated to stem cell proliferation at the transplantation site. Histopathology confirmed successful engraftment of viable MSCs. The engraftment of iron oxide–labeled MASIs by simple incubation can be monitored over several weeks with MRI. Viable and apoptotic MASIs can be distinguished via imaging signs of cell proliferation at the transplantation site.
Molecular Imaging of Autoimmune Diseases and Inflammation
Authors: Sargsyan S. Anna , Thurman Joshua M.
Published: March 2018

Molecular imaging methods allow the noninvasive detection and localization of specific molecules. Agents that report on molecular disease biomarkers can be used to diagnose and monitor disease. Many inflammatory diseases have molecular signatures within altered tissues. Although tissue biopsy is still the gold standard for detecting these signatures, several molecular imaging markers have been developed. Pharmacologic agents that block specific immune molecules have recently entered the clinic, and these drugs have already transformed the way we care for patients with immune-mediated diseases. The use of immunomodulatory drugs is usually guided by clinical assessment of the patient's response. Unfortunately, clinical assessment may miss the signs of inflammation, and many of the serologic markers of immune-mediated diseases correlate poorly with the underlying inflammatory activity within target tissues. Molecular imaging methods have the potential to improve our ability to detect and characterize tissue inflammation. We discuss some of the molecular signatures of immune activation and review molecular imaging methods that have been developed to detect active tissue inflammation.
Norepinephrine Transporter Imaging in the Brain of a Rat Model of Depression Using Radioiodinated (2S, αS)-2-(α-(2-iodophenoxy)benzyl)morpholine
Authors: Kanegawa Naoki , Kiyono Yasushi , Sugitaa Taku , Kuge Yuji , Fujibayasi Yasushisa , Saji Hideo
Published: March 2018

To visualize the norepinephrine transporters (NETs) in various brain diseases, we developed radioiodinated (2S,αS)-2-(α-(2-iodophenoxy)benzyl)morpholine ((S,S)-IPBM). This radioligand achieved the basic requirements for NET imaging. In this study, we assessed the potential of radioiodinated (S,S)-IPBM as an imaging biomarker of NET to obtain diagnostic information about depression in relation to NET expression in the brain using a rat depression model. The ex vivo autoradiographic experiments using the (S,S)-[125I]IPBM showed significantly lower accumulation of radioactivity in the locus coeruleus (LC) and the anteroventricular thalamic nucleus (AVTN) of the depression group than in those of the control group. Consequently, in vitro autoradiographic experiments showed that NET maximum binding (Bmax) values in the LC and AVTN, known as NET-rich regions, were significantly decreased in the rat model of depression when compared to those of the control rats. In addition, there was an extremely good correlation between NET Bmax and (S,S)-IPBM accumulation ( r = .98), an indication of radioiodinated IPBM as a quantitative NET imaging biomarker. The reduction in(S,S)-[125I]IPBM accumulation in the rat model of depression correlated with that of NET density. These results suggest that (S,S)-[123I]IPBM has potential as an imaging biomarker of NET to obtain diagnostic information about major depression.
Integrin αvβ3–Targeted Dynamic Contrast–Enhanced Magnetic Resonance Imaging Using a Gadolinium-Loaded Polyethylene Gycol–Dendrimer–Cyclic RGD Conjugate to Evaluate Tumor Angiogenesis and to Assess Early Antiangiogenic Treatment Response in a Mouse Xenograft Tumor Model
Authors: Chen Wei-Tsung , Shih Tiffany Ting Fang , Chen Ran-Chou , Tu Shin-Yang , Wen-Yuen Hsieh , Yang Pang-Chyr
Published: March 2018

The purpose of this study was to validate an integrin αvβ3–targeted magnetic resonance contrast agent, PEG-G3-(Gd-DTPA)6-(cRGD-DTPA)2, for its ability to detect tumor angiogenesis and assess early response to antiangiogenic therapy using dynamic contrast–enhanced (DCE) magnetic resonance imaging (MRI). Integrin αvβ3–positive U87 cells and control groups were incubated with fluorescein-labeled cRGD-conjugated dendrimer, and the cellular attachment of the dendrimer was observed. DCE MRI was performed on mice bearing KB xenograft tumors using either PEG-G3-(Gd-DTPA)6-(cRGD-DTPA)2 or PEG-G3-(Gd-DTPA)6-(cRAD-DTPA)2. DCE MRI was also performed 2 hours after anti–integrin αvβ3 monoclonal antibody treatment and after bevacizumab treatment on days 3 and 6t. Using DCE MRI, the 30-minute contrast washout percentage was significantly lower in the cRGD-conjugate injection groups. The enhancement patterns were different between the two contrast injection groups. In the antiangiogenic therapy groups, a rapid increase in 30-minute contrast washout percentage was observed in both the LM609 and bevacizumab treatment groups, and this occurred before there was an observable decrease in tumor size. The integrin αvβ3 targeting ability of PEG-G3-(Gd-DTPA)6-(cRGD-DTPA)2 in vitro and in vivo was demonstrated. The 30-minute contrast washout percentage is a useful parameter for examining tumor angiogenesis and for the early assessment of antiangiogenic treatment response.
A Novel Paramagnetic Substrate for Detecting Myeloperoxidase Activity in Vivo
Authors: Shazeeb Mohammed S. , Xie Yang , Gupta Suresh , Bogdanov Alexei A.
Published: March 2018

Bis-phenylamides and bis-hydroxyindolamides of diethylenetriaminepentaacetic acid-gadolinium (DTPA(Gd)) are paramagnetic reducing substrates of peroxidases that enable molecular imaging of peroxidase activity in vivo. Specifically, gadolinium chelates of bis-5-hydroxytryptamide-DTPA (bis-5HT-DTPA(Gd)) have been used to image localized inflammation in animal models by detecting neutrophil-derived myeloperoxidase (MPO) activity at the inflammation site. However, in other preclinical disease models, bis-5HT-DTPA(Gd) presents technical challenges due to its limited solubility in vivo. Here we report a novel MPO-sensing probe obtained by replacing the reducing substrate serotonin (5-HT) with 5-hydroxytryptophan (HTrp). Characterization of the resulting probe (bis-HTrp-DTPA(Gd)) in vitro using nuclear magnetic resonance spectroscopy and enzyme kinetic analysis showed that bis-HTrp-DTPA(Gd) (1) improves solubility in water; (2) acts as a substrate for both horseradish peroxidase and MPO enzymes; (3) induces cross-linking of proteins in the presence of MPO; (4) produces oxidation products, which bind to plasma proteins; and (5) unlike bis-5HT-DTPA(Gd), does not follow first-order reaction kinetics. In vivo magnetic resonance imaging (MR!) in mice demonstrated that bis-HTrp-DTPA(Gd) was retained for up to 5 days in MPO-containing sites and cleared faster than bis-5HT-DTPA(Gd) from MPO-negative sites. Bis-HTrp-DTPA(Gd) should offer improvements for MR! of MPO-mediated inflammation in vivo, especially in high-field MR!, which requires a higher dose of contrast agent.
Cellular Immunogenicity of Novel Gene Immunogens in Mice Monitored by in Vivo Imaging
Authors: Starodubova Elizaveta , Krotova Olga , Hallengärd David , Kuzmenko Yulia , Engström Gunnel , Legzdina Diana , Latyshev Oleg , Eliseeva Olesja , Maltais Anna Karin , Tunitskaya Vera , Karpov Vadim , Bråve Andreas , Isaguliants Maria
Published: March 2018

The efficient cell-mediated immune response clears cells expressing deoxyribonucleic acid (DNA) immunogens, but there are no methods to monitor this in vivo. We hypothesized that immune-mediated clearance can be monitored in vivo if DNA immunogens are coexpressed with reporter(s). To test this, we designed genes encoding human immunodeficiency virus 1 (HIV-1) reverse transcriptase (RT) fused via its N- or C-terminus to 30–amino acid-long Gly-Ala-repeat of Epstein-Barr virus nuclear antigen 1 or via the N-terminus to the transport signal of invariant chain/Ii or inserted between the cytoplasmic and luminal domains of lysosome-associated membrane protein I (LAMP). DNA immunogens mixed with luciferase gene were injected into BALB/c mice with subsequent electroporation. Reporter expression seen as luminescence was monitored by in vivo imaging. When luminescence faded, mice were sacrificed, and their splenocytes were stimulated with RT-derived antigens. Fading of luminescence correlated with the RT-specific secretion of interferon-γ and interleukin-2. Both immune and in vivo imaging techniques concordantly demonstrated an enhanced immunogenicity of RT-LAMP and of the N-terminal Gly-Ala-RT fusion genes. In vivo imaging performed as an animal-sparing method to estimate the overall performance of DNA immunogens, predicting it early in the experiment. So far, in vivo imaging cannot be a substitute for conventional immune assays, but it is supplementary to them. Further experiments are needed to identify which arms of cellular immune response in vivo imaging monitors best.
Efficient 18F Labeling of Cysteine-Containing Peptides and Proteins Using Tetrazine–Trans-Cyclooctene Ligation
Authors: Liu Shuanglong , Hassink Matthew , Selvaraj Ramajeyam , Yap Li-Peng , Park Ryan , Wang Hui , Chen Xiaoyuan , Fox Joseph M. , Li Zibo , Conti Peter S.
Published: March 2018

18F positron emission tomography (PET) has a number of attributes that make it clinically attractive, including nearly 100% positron efficiency, very high specific radioactivity, and a short half-life of ≈ 110 minutes. However, the short half-life of 18F and the poor nucleophilicity of fluoride introduce challenges for the incorporation of 18F into complex molecules. Recently, the tetrazine- trans-cyclooctene ligation was introduced as a novel 18F labeling method that proceeds with fast reaction rates without catalysis. Herein we report an efficient method for 18F labeling of free cysteines of peptides and proteins based on sequential ligation with a bifunctional tetrazinyl-maleimide and an 18F-labeled trans-cyclooctene. The newly developed method was tested for site-specific labeling of both c(RGDyC) peptide and vascular endothelial growth factor (VEGF)-SH protein. Starting with 4 mCi of 18F- trans-cyclooctene and only 10 μg of tetrazine-RGD (80–100 μM) or 15 μg of tetrazine-VEGF (6.0 μM), 18F-labeled RGD peptide and VEGF protein could be obtained within 5 minutes in 95% yield and 75% yield, respectively. The obtained tracers were then evaluated in mice. In conclusion, a highly efficient method has been developed for site-specific 18F labeling of cysteine-containing peptides and proteins. The special characteristics of the tetrazine– trans-cyclooctene ligation provide unprecedented opportunities to synthesize 18F-labeled probes with high specific activity for PET applications.
Positron Emission Tomographic Imaging of Iodine 124 Anti–Prostate Stem Cell Antigen–Engineered Antibody Fragments in LAPC-9 Tumor–Bearing Severe Combined Immunodeficiency Mice
Authors: Leyton Jeffrey V. , Olafsen Tove , Lepin Eric J.M. , Hahm Scott , Fonge Humphrey , Reiter Robert E. , Wu Anna M.
Published: March 2018

The humanized antibody (hu1G8) has been shown to localize to prostate stem cell antigen (PSCA) and image PSCA-positive xenografts. We previously constructed hu1G8 anti-PSCA antibody fragments and tested them for tumor targeting and the ability to image prostate cancer at early and late time points postinjection by positron emission tomography (PET). We now then compare the PET imaging and the radioactivity accumulation properties in prostate cancer tumors and nontarget tissues to determine the superior 124I-labeled hu1G8 antibody format. 124I-labeled diabody, minibody, scFv-Fc, scFv-Fc double mutant (DM), and parental IgG were administered into severe combined immunodeficiency (SCID) mice bearing LAPC-9 xenografts and followed by whole-body PET imaging of mice at preselected time points. Regions of interest were manually drawn around tumor and nontarget tissues and evaluated for radioactivity accumulation. The 124I-hu1G8 IgG has its best time point for tumor high-contrast imaging at 168 hours postinjection. The 124I-hu1G8 minibody at 44 hours postinjection results in superior tumor high-contrast imaging compared to the other antibody formats. The 124I-hu1G8 minibody at 44 hours postinjection also has comparable percent tumor radioactivity compared to 124I-hu1G8 IgG at 168 hours postinjection. The 124I-hu1G8 minibody is the best engineered hu1G8 antibody format for imaging prostate cancer.
Synthesis and Characterization of Theranostic Poly(HPMA)-c(RGDyK)-DOTA-64Cu Copolymer Targeting Tumor Angiogenesis: Tumor Localization Visualized by Positron Emission Tomography
Authors: Yuan Jianchao , Zhang Haiyuan , Kaur Harpreet , Oupicky David , Peng Fangyu
Published: March 2018

Poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers were synthesized and characterized for tumor localization in vivo as a theranostic scaffold for cancer imaging and anticancer drug delivery targeting tumor angiogenesis. Tumor localization of the poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers was visualized in mice bearing human prostate cancer xenografts by positron emission tomography (PET) using a microPET scanner. PET quantitative analysis demonstrated that tumor 64Cu radioactivity (2.75 ± 0.34 %ID/g) in tumor-bearing mice 3 hours following intravenous injection of the poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers was significantly higher than the tumor 64Cu radioactivity (1.29 ± 0.26 %ID/g) in tumor-bearing mice injected with the nontargeted poly(HPMA)-DOTA-64Cu copolymers ( p = .004). The poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers hold potential as a theranostic scaffold for cancer imaging and radiochemotherapy of prostate cancer targeting tumor angiogenesis by noninvasive tracking with PET.
Measuring Response to Therapy by Near-Infrared Imaging of Tumors Using a Phosphatidylserine-Targeting Antibody Fragment
Authors: Gong Jian , Archer Richard , Brown Michael , Fisher Seth , Chang Connie , Peacock Matthew , Hughes Christopher , Freimark Bruce
Published: March 2018

Imaging tumors and their response to treatment could be a valuable biomarker toward early assessment of therapy in patients with cancer. Phosphatidylserine (PS) is confined to the inner leaflet of the plasma membrane in normal cells but is externalized on tumor vascular endothelial cells (ECs) and tumor cells, and PS exposure is further enhanced in response to radiation and chemotherapy. In the present study, we evaluated the potential of a PS-targeting human F(ab')2 antibody fragment, PGN650, to detect exposure of PS in tumor-bearing mice. Tumor uptake of PGN650 was measured by near-infrared optical imaging in human tumor xenografts in immunodeficient mice. PGN650 specifically targeted tumors and was shown to target CD31-positive ECs and tumor cells. Tumor uptake of PGN650 was significantly higher in animals pretreated with docetaxel. The peak tumor to normal tissue (T/N) ratio of probe was observed at 24 hours postinjection of probe, and tumor binding was detected for at least 120 hours. In repeat dose studies, PGN650 uptake in tumors was significantly higher following pretreatment with docetaxel compared to baseline uptake prior to treatment. PGN650 may be a useful probe to detect PS exposed in tumors and to monitor enhanced PS exposure to optimize therapeutic agents to treat tumors.
Improvement of in Vivo Quantification of [123I]-Iodobenzovesamicol in Single-Photon Emission Computed Tomography/Computed Tomography Using Anatomic Image to Brain Atlas Nonrigid Registration
Authors: Lamare Frederic , Mazere Joachim , Attila Mathieu , Mayo Willy , Clermont-Gallerande Henri De , Meissner Wassilios , Fernandez Philippe , Allard Michele
Published: March 2018

Brain anatomy variability is a major problem in quantifying functional images in nuclear medicine, in particular relative to aging and neurodegenerative diseases. The aim of this study was to compare affine and elastic model–based methods for magnetic resonance imaging (MRI) to brain atlas registration and to assess their impact on the quantification of cholinergic neurotransmission. Patients with multiple system atrophy (MSA) and age-matched healthy subjects underwent an MRI and a single-photon emission computed tomographic (SPECT) examination using [123I]-iodobenzovesamicol (IBVM). Both affine and elastic methods were compared to register the subjects' MRI with the Montreal Neurological Institute brain atlas. Performance of the registration accuracy was quantitatively assessed and the impact on the IBVM quantification was studied. For both subject groups, elastic registration achieved better quantitative performance compared to the affine model. For patients suffering from neurogenerative disease, this study demonstrates the importance and relevance of MRI to atlas registration in quantification of neuronal integrity. In this context, in comparison with rigid registrations, an elastic model–based registration provides the best relocation of the brain structures to the atlas for accurately quantifying cholinergic neurotransmission.
Attenuation of Apoptosis by Telmisartan in Atherosclerotic Plaques of Apolipoprotein E−/− Mice: Evaluation Using Technetium 99m–Annexin A5
Authors: Zhao Yan , Zhao Songji , Kuge Yuji , Strauss H. William , Blankenberg Francis G. , Tamaki Nagara
Published: March 2018

Technetium 99m (99mTc)–annexin A5, a marker of ongoing apoptosis, is supposed to be useful in the detection of metabolically active atheroma. The aim of this study was to determine the potential of 99mTc–annexin A5 for evaluating the therapeutic effects of an angiotensin II receptor type 1 blocker (ARB) (telmisartan) on atherosclerosis. Male apolipoprotein E−/− mice were divided into telmisartan-treated (3 mg/kg/d, n = 10) and control ( n = 10) groups. After 16 to 21 weeks of treatment, 99mTc–annexin A5 was injected and cryostat sections of aortic tissues ( n = 10–12/aorta) were prepared. The 99mTc–annexin A5 accumulation level in the plaques was evaluated by autoradiography. Serial sections of the plaques were histologically examined to identify the lesion phenotypes (normal vessels, early lesions, atheromatous lesions, and fibrotic lesions), plaque size, macrophage infiltration levels, and lipid deposition levels. Telmisartan treatment significantly decreased the plaque size (0.05 ± 0.05 vs 0.11 ± 0.08, mm2), macrophage infiltration level (0.02 ± 0.02 vs 0.03 ± 0.02, mm2), lipid deposition level (0.01 ± 0.01 vs 0.02 ± 0.02, mm2), and 99mTc–annexin A5 accumulation level (1.30 ± 1.09 vs 2.15 ± 1.91, × 10−6/g). 99mTc–annexin A5 accumulation levels in the plaques positively correlated with macrophage infiltration ( r = .69, p < .05) and lipid deposition ( r = .66, p < .05) levels. Apoptosis imaging with 99mTc–annexin A5 may be useful for evaluating the therapeutic effects of ARBs on atherosclerosis.
In Vivo Monitoring of Survival and Proliferation of Hair Stem Cells in a Hair Follicle Generation Animal Model
Authors: Kim Jung Eun , Ahn Byeong-Cheol , Lee Ho Won , Hwang Mi-Hye , Shin Seung Hyun , Lee Sang Woo , Sung Young Kwan , Lee Jaetae
Published: March 2018

The purpose of this study was to investigate in vivo monitoring of hair follicle stem cells (newborn mouse fibroblasts [NFs]) expressing enhanced firefly luciferase (effluc) (NF-effluc) using noninvasive bioluminescence imaging (BLI). Effluc gene transduction into NFs was performed by retroviral vector, and effluc messenger ribonucleic acid expression and function were evaluated by reverse transcription–polymerase chain reaction and luciferase assay. After in vivo transplantation of NF-effluc cells to generate hair follicles, BLI was performed on days 1, 3, 7, 14, and 21 after transplantation. Additionally, hair follicle generation by the implanted stem cells was investigated using microscopy. The luciferase activity of NF-effluc was 41,175-fold higher compared to that of untransfected NFs. Bioluminescence signals from the transplantation site decreased gradually over 2 weeks; then the signal plateaued. Hair follicles were confirmed at the NF-effluc cell implantation site on day 14 after transplantation. We successfully monitored hair generation by hair stem cell implantation noninvasively with optical molecular strategy in an in vivo model.