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Hossein Nejadnik, Tobias D Henning,
Rosalinda T Castaneda,
Sophie Boddington,
Stefan Taubert,
Priyanka Jha,
Sidhartha Tavri,
Daniel Golovko,
Larry Ackerman,
Reinhard Meier,
Heike E Daldrup-Link
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ABSTRACT: Magnetic resonance (MR) imaging of superparamagnetic iron oxide (SPIO)-labeled stem cells offers a non-invasive evaluation of stem cell engraftment in host organs. Excessive cellular iron load from SPIO labeling, however, impairs stem cell differentiation. The purpose of this study was to magnetically label human embryonic stem cells (hESCs) via a reduced exposure protocol that maintains a significant MR signal and no significant impairment to cellular pluripotency or differentiation potential. hESCs were labeled by simple incubation with FDA-approved ferumoxides using concentrations of 50-200 μg Fe/ml and incubation times of 3-24 hours. The most reduced exposure labeling protocol that still provided a significant MR signal comparable to accepted labeling protocols was selected for subsequent studies. Labeled hESCs were compared to unlabeled controls for differences in: pluripotency as studied by fluorescence staining for SSEA-1, SSEA-4, TRA-60 and TRA-81 and differentiation capacity as studied by qPCR for hOCT4, hACTC1, hSOX1 and hAFP after differentiation into embryoid bodies. Subsequent MR and microscopy imaging were performed to evaluate for cellular iron distribution and long-term persistence of the label. An incubation concentration of 50μg Fe/ml and incubation time of 3 hours demonstrated a significantly reduced exposure protocol that yielded an intracellular iron uptake of 4.50 ± 0.27 pg Fe, an iron content comparable to currently accepted SPIO labeling protocols. Labeled and unlabeled hESCs showed no difference in pluripotency or differentiation capacity. Ferumoxide-labeled hESCs demonstrated persistent MR contrast effects as embryoid bodies for 21 days. Electron microscopy confirmed persistent lysosomal storage of iron oxideparticles in EBs up to 9 days while additional microscopy visualization confirmed the iron distribution within single and multiple EBs. Labeling hESCs with ferumoxides by this tailored protocol reduces exposure of cells to the labeling agent while allowing for long-term visualization with MR imaging and the retention of cellular pluripotency and differentiation potential.
Cell Transplantation 08/2012; · 5.13 Impact Factor
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Tobias D Henning,
Rakhee Gawande,
Aman Khurana,
Sidhartha Tavri,
Lydia Mandrussow,
Daniel Golovko,
Andrew Horvai,
Barbara Sennino,
Donald McDonald,
Reinhard Meier,
Michael Wendland,
Nikita Derugin,
Thomas M Link,
Heike E Daldrup-Link
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ABSTRACT: 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 06/2012; 11(3):197-209. · 3.18 Impact Factor
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Hossein Nejadnik, Tobias D Henning,
Thuy Do,
Elizabeth J Sutton,
Frederick Baehner,
Andrew Horvai,
Barbara Sennino,
Donald McDonald,
Reinhard Meier,
Bernd Misselwitz,
Thomas M Link,
Heike E Daldrup-Link
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ABSTRACT: The purpose of our study was to assess the chondrogenic potential and the MR signal effects of GadofluorineM-Cy labeled matrix associated stem cell implants (MASI) in pig knee specimen.
Human mesenchymal stem cells (hMSCs) were labeled with the micelle-based contrast agent GadofluorineM-Cy. Ferucarbotran-labeled hMSCs, non-labeled hMSCs and scaffold only served as controls. Chondrogenic differentiation was induced and gene expression and histologic evaluation were performed. The proportions of spindle-shaped vs. round cells of chondrogenic pellets were compared between experimental groups using the Fisher's exact test. Labeled and unlabeled hMSCs and chondrocytes in scaffolds were implanted into cartilage defects of porcine femoral condyles and underwent MR imaging with T1- and T2-weighted SE and GE sequences. Contrast-to-noise ratios (CNR) between implants and adjacent cartilage were determined and analyzed for significant differences between different experimental groups using the Kruskal-Wallis test. Significance was assigned for p<0.017, considering a Bonferroni correction for multiple comparisons.
Collagen type II gene expression levels were not significantly different between different groups (p>0.017). However, hMSC differentiation into chondrocytes was superior for unlabeled and GadofluorineM-Cy-labeled cells compared with Ferucarbotran-labeled cells, as evidenced by a significantly higher proportion of spindle cells in chondrogenic pellets (p<0.05). GadofluorineM-Cy-labeled hMSCs and chondrocytes showed a positive signal effect on T1-weighted images and a negative signal effect on T2-weighted images while Ferucarbotran-labeled cells provided a negative signal effect on all sequences. CNR data for both GadofluorineM-Cy-labeled and Ferucarbotran-labeled hMSCs were significantly different compared to unlabeled control cells on T1-weighted SE and T2*-weighted MR images (p<0.017).
hMSCs can be labeled by simple incubation with GadofluorineM-Cy. The labeled cells provide significant MR signal effects and less impaired chondrogenesis compared to Ferucarbotran-labeled hMSCs. Thus, GadoflurineM-Cy might represent an alternative MR cell marker to Ferucarbotran, which is not distributed any more in Europe or North America.
PLoS ONE 01/2012; 7(12):e49971. · 4.09 Impact Factor
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ABSTRACT: Human embryonic stem cells (hESC) can generate cardiomyocytes (CM), which offer promising treatments for cardiomyopathies in children. However, challenges for clinical translation result from loss of transplanted cell from target sites and high cell death. An imaging technique that noninvasively and repetitively monitors transplanted hESC-CM could guide improvements in transplantation techniques and advance therapies.
To develop a clinically applicable labeling technique for hESC-CM with FDA-approved superparamagnetic iron oxide nanoparticles (SPIO) by examining labeling before and after CM differentiation.
Triplicates of hESC were labeled by simple incubation with 50 μg/ml of ferumoxides before or after differentiation into CM, then imaged on a 7T MR scanner using a T2-weighted multi-echo spin-echo sequence. Viability, iron uptake and T2-relaxation times were compared between groups using t-tests.
hESC-CM labeled before differentiation demonstrated significant MR effects, iron uptake and preserved function. hESC-CM labeled after differentiation showed no significant iron uptake or change in MR signal (P < 0.05). Morphology, differentiation and viability were consistent between experimental groups.
hESC-CM should be labeled prior to CM differentiation to achieve a significant MR signal. This technique permits monitoring delivery and engraftment of hESC-CM for potential advancements of stem cell-based therapies in the reconstitution of damaged myocardium.
Pediatric Radiology 05/2011; 41(11):1384-92. · 1.67 Impact Factor
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ABSTRACT: Genetically modified natural killer (NK) cells that recognize tumor-associated surface antigens have recently shown promise as a novel approach for cancer immunotherapy. To determine NK cell therapy response early, a real-time, noninvasive method to quantify NK cell homing to the tumor is desirable. The purpose of this study was to evaluate if MR imaging could provide a noninvasive, in vivo diagnosis of NK cell accumulation in epithelial cell adhesion molecule (EpCAM)-positive prostate cancers in a rat xenograft model. Genetically engineered NK-92-scFv(MOC31)-ζ cells, which express a chimeric antigen receptor specific to the tumor-associated EpCAM antigen, and nontargeted NK-92 cells were labeled with superparamagnetic particles of iron-oxides (SPIO) ferumoxides. Twelve athymic rats with implanted EpCAM positive DU145 prostate cancers received intravenous injections of 1.5×10(7) SPIO labeled NK-92 and NK-92-scFv(MOC31)-ζ cells. EpCAM-positive prostate cancers demonstrated a progressive and a significant decline in contrast-to-noise-ratio data at 1 and 24 h after injection of SPIO-labeled NK-92-scFv(MOC31)-ζ cells. Conversely, tumor contrast-to-noise-ratio data did not change significantly after injection of SPIO-labeled parental NK-92 cells. Histopathology confirmed an accumulation of the genetically engineered NK-92-scFv(MOC31)-ζ cells in prostate cancers. Thus, the presence or absence of a tumor accumulation of therapeutic NK cells can be monitored with cellular MR imaging. EpCAM-directed, SPIO labeled NK-92-scFv(MOC31)-ζ cells accumulate in EpCAM-positive prostate cancers.
Magnetic Resonance in Medicine 10/2010; 65(3):756-63. · 2.96 Impact Factor
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Elizabeth Jane Sutton, Tobias D Henning,
Sophie Boddington,
Stavros Demos,
Christian Krug,
Reinhardt Meier,
John Kornak,
Shoujun Zhao,
Rick Baehner,
Sheida Sharifi,
Heike Daldrup-Link
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ABSTRACT: 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.
Molecular Imaging 10/2010; 9(5):278-90. · 3.18 Impact Factor
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ABSTRACT: To assess the capability of the folate receptor (FR)-targeted ultrasmall superparamagnetic iron oxide (USPIO) P1133 to provide FR-specific enhancement of breast cancers on magnetic resonance (MR) images.
This study was approved by the institutional Animal Care and Use Committee. The FR-targeted contrast agent P1133 was incubated with various FR-positive human breast cancer cell lines, with and without free folic acid (FFA) as a competitor. Labeling efficiencies were evaluated with MR imaging and inductively coupled plasma mass spectrometry. Subsequently, six athymic rats with implanted FR-positive MDA-MB-231 breast cancers underwent MR imaging at 3 T before and up to 1 hour and 24 hours after injection of P1133. Six athymic rats with implanted FR-positive MDA-MB-231 cancers injected with the non-FR-targeted USPIO P904 and nine athymic rats with implanted FR-negative A549 lung cancers injected with P1133 (n = 6) or P904 (n = 3) served as controls. Data of the in vitro studies were compared for significant differences with the Wilcoxon test for two independent samples. Tumor signal-to-noise-ratios (SNRs) were compared between different experimental groups by using the Kruskal-Wallis test and were correlated with histopathologic findings. Differences with P < .05 were considered significant.
FR-positive breast cancer cells showed a significant P1133 uptake which was inhibited by FFA. MDA-MB-231 cells showed the highest level of P1133 uptake and the strongest T2 effect on MR images. In vivo, all tumors showed an initial perfusion effect. At 24 hours after injection, only MDA-MB-231 tumors injected with P1133 showed significantly decreased SNR data compared with baseline data (P < .05). MR findings were confirmed by using histopathologic findings.
The FR-targeted USPIO P1133 demonstrates a specific retention in FR-positive breast cancers. Because FR expression correlates with tumor aggressiveness and prognosis, persistent P1133 tumor enhancement may be used as a noninvasive indicator for tumors with poor outcome.
Radiology 05/2010; 255(2):527-35. · 5.73 Impact Factor
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ABSTRACT: This study aims to determine the effect of human mesenchymal stem cell (hMSC) labeling with the fluorescent dye DiD and the iron oxide nanoparticle ferucarbotran on chondrogenesis.
hMSCs were labeled with DiD alone or with DiD and ferucarbotran (DiD/ferucarbotran). hMSCs underwent confocal microscopy, optical imaging (OI), and magnetic resonance (MR) imaging. Chondrogenesis was induced by transforming growth factor-b and confirmed by histopathology and glycosaminoglycan (GAG) production. Data of labeled and unlabeled hMSCs were compared with a t test.
Cellular uptake of DiD and ferucarbotran was confirmed with confocal microscopy. DiD labeling caused a significant fluorescence on OI, and ferucarbotran labeling caused a significant T2* effect on MR images. Compared to nonlabeled controls, progenies of labeled MSCs exhibited similar chondrocyte morphology after chondrogenic differentiation, but the labeled cells demonstrated significantly reduced GAG production (p < 0.05).
DiD and DiD/ferucarbotran labeling of hMSC does not interfere with cell viability or morphologic differentiation into chondrocytes, but labeled cells exhibit significantly less GAG production compared to unlabeled cells.
Molecular imaging and biology: MIB: the official publication of the Academy of Molecular Imaging 04/2010; 13(1):3-9. · 2.47 Impact Factor
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Sophie E Boddington, Tobias D Henning,
Priyanka Jha,
Christopher R Schlieve,
Lydia Mandrussow,
David DeNardo,
Harold S Bernstein,
Carissa Ritner,
Daniel Golovko,
Ying Lu,
Shoujun Zhao,
Heike E Daldrup-Link
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ABSTRACT: Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) have demonstrated the ability to improve myocardial function following transplantation into an ischemic heart; however, the functional benefits are transient possibly due to poor cell retention. A diagnostic technique that could visualize transplanted hESC-CMs could help to optimize stem cell delivery techniques. Thus, the purpose of this study was to develop a labeling technique for hESCs and hESC-CMs with the FDA-approved contrast agent indocyanine green (ICG) for optical imaging (OI). hESCs were labeled with 0.5, 1.0, 2.0, and 2.5 mg/ml of ICG for 30, 45, and 60 min at 37 degrees C. Longitudinal OI studies were performed with both hESCs and hESC-CMs. The expression of surface proteins was assessed with immunofluorescent staining. hESCs labeled with 2 mg ICG/ml for 60 min achieved maximum fluorescence. Longitudinal studies revealed that the fluorescent signal was equivalent to controls at 120 h postlabeling. The fluorescence signal of hESCs and hESC-CMs at 1, 24, and 48 h was significantly higher compared to precontrast data (p < 0.05). Immunocytochemistry revealed retention of cell-specific surface and nuclear markers postlabeling. These data demonstrate that hESCs and hESC-CMs labeled with ICG show a significant fluorescence up to 48 h and can be visualized with OI. The labeling procedure does not impair the viability or functional integrity of the cells. The technique may be useful for assessing different delivery routes in order to improve the engraftment of transplanted hESC-CMs or other stem cell progenitors.
Cell Transplantation 01/2010; 19(1):55-65. · 5.13 Impact Factor
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ABSTRACT: The objective of this work is to establish an optical imaging technique that would enable monitoring of the integration of mesenchymal stem cells (MSC) in arthritic joints. Our approach is based on first developing a labeling technique of MSC with the fluorescent dye DiD followed by tracking the cell migration kinetics from the spatial distribution of the DiD fluorescence in optical images (OI). The experimental approach involves first the in vitro OI of MSC labeled with DiD accompanied by fluorescence microscopy measurements to establish localization of the signal within the cells. Thereafter, DiD-labeled MSC were injected into polyarthritic, athymic rats and the signal localization within the experimental animals was monitored over several days. The experimental results indicate that DiD integrated into the cell membrane. DiD-labeled MSC localization in the arthritic ankle joints was observed with OI indicating that this method can be applied to monitor MSC in arthritic joints.
Optics Express 12/2009; 17(26):24403-13. · 3.59 Impact Factor
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ABSTRACT: For in vivo applications of magnetically labeled stem cells, biological effects of the labeling procedure have to be precluded. This study evaluates the effect of different ferucarbotran cell labeling protocols on chondrogenic differentiation of human mesenchymal stem cells (hMSC) as well as their implications for MR imaging. hMSC were labeled with ferucarbotran using various protocols: cells were labeled with 100 microg Fe/ml for 4 and 18 h and additional samples were cultured for 6 or 12 days after the 18 h labeling. Supplementary samples were labeled by transfection with protamine sulfate. Iron uptake was quantified by ICP-spectrometry and labeled cells were investigated by transmission electron microscopy and by immunostaining for ferucarbotran. The differentiation potential of labeled cells was compared with unlabeled controls by staining with Alcian blue and Hematoxylin and Eosin, then quantified by measurements of glucosaminoglycans (GAG). Contrast agent effect at 3 T was investigated on days 1 and 14 of chondrogenic differentiation by measuring signal-to-noise ratios on T(2)-SE and T(2)*-GE sequences. Iron uptake was significant for all labeling protocols (p < 0.05). The uptake was highest after transfection with protamine sulfate (25.65 +/- 3.96 pg/cell) and lowest at an incubation time of 4 h without transfection (3.21 +/- 0.21 pg/cell). While chondrogenic differentiation was decreased using all labeling protocols, the decrease in GAG synthesis was not significant after labeling for 4 h without transfection. After labeling by simple incubation, chondrogenesis was found to be dose-dependent. MR imaging showed markedly lower SNR values of all labeled cells compared with the unlabeled controls. This contrast agent effect persisted for 14 days and the duration of differentiation. Magnetic labeling of hMSC with ferucarbotran inhibits chondrogenesis in a dose-dependent manner when using simple incubation techniques. When decreasing the incubation time to 4 h, inhibition of chondrogenesis was not significant.
Contrast Media & Molecular Imaging 09/2009; 4(4):165-73. · 3.33 Impact Factor
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ABSTRACT: Human mesenchymal stem cells (hMSCs) were labeled with Ferucarbotran by simple incubation and cultured for up to 14 d. Iron content was determined by spectrometry and the intracellular localization of the contrast agent uptake was studied by electron and confocal microscopy. At various time points after labeling, ranging from 1 to 14 d, samples with viable or lysed labeled hMSCs, as well as nonlabeled controls, underwent MRI. Spin-echo (SE) and gradient-echo (GE) sequences with multiple TRs and TEs were used at 1.5T and 3T on a clinical scanner. Spectrometry showed an initial iron oxide uptake of 7.08 pg per cell. Microscopy studies revealed lysosomal compartmentalization. Contrast agent effects of hMSCs were persistent for up to 14 d after labeling. A marked difference in the T(2) effect of compartmentalized iron oxides compared to free iron oxides was found on T(2)-weighted sequences, but not on T(2)*-weighted sequences. The observed differences may be explained by the loss of compartmentalization of iron oxide particles, the uniformity of distribution, and the subsequent increase in dephasing of protons on SE images. These results show that viable cells with compartmentalized iron oxides may-in principle-be distinguished from lysed cells or released iron oxides.
Magnetic Resonance in Medicine 05/2009; 62(2):325-32. · 2.96 Impact Factor
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ABSTRACT: Indocyanine green (ICG) is a contrast agent used for detecting angiogenesis with optical imaging (OI). The purpose of this study was to investigate whether cooling procedures increase the signal yield of ICG with OI. Test samples of 0.05 and 0.02 mM ICG in 40% DMSO and 60% DMEM underwent OI at four different temperatures (5, 37, 55 and 75 degrees C). In addition, six athymic rats with an antigen-induced arthritis of the knee and ankle joints underwent OI before and after injection of ICG (10 mg/ml, dose 15 mg/kg) on two separate days with and without cooling of the joints. The fluorescent signals of the test samples and arthritic joints were measured and evaluated for significant differences before and after cooling with a t-test. In vitro studies showed a strong negative correlation between ICG temperature and fluorescent signal. The mean fluorescent signal of arthritic joints (measured in efficiency) was 0.345 before ICG-injection, 4.55 after ICG-injection and before cooling and 9.71 after ICG-injection and after cooling. The fluorescent signal enhancement of arthritic joints with ICG-enhanced OI images increased significantly after cooling (p = 0.02). The signal yield of ICG can be significantly increased by cooling the target pathology. The primary underlying cause of the temperature dependence of ICG is enhanced collisional quenching with increasing temperature. This simple cooling method may be immediately helpful to increase the fluorescence signal yield in current ICG-enhanced OI-studies in patients.
Contrast Media & Molecular Imaging 10/2008; 3(5):191-7. · 3.33 Impact Factor
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ABSTRACT: To compare magnetic resonance imaging of the ankle joint at 1.5 Tesla (T) and 3.0 T in the assessment of cartilage and ligament pathology in fresh human cadaver specimens.
The study was performed in line with institutional and legislative requirements; all donors had dedicated their body for educational and research purposes before death. Thirteen fresh human cadaver ankle joints were imaged at 1.5 T and 3.0 T using an optimized clinical ankle protocol consisting of T1-weighted (T1-w), fat-saturated (fs) T2-w, and short tau inversion recovery fast spinecho (FSE) sequences. For dedicated cartilage imaging, fs-intermediate (IM)-w FSE, fs-spoiled gradient echo, and balanced free precession steady state sequences were acquired. Artificial cartilage and ligament lesions were created in 6 and 5 specimens, respectively. MR imaging was repeated in those ankles. Four radiologists independently assessed pathology in all image datasets. Macroscopic findings after dissection served as a reference standard.
Sensitivities and ROC-values were higher at 3.0 T for detecting cartilage pathology (sensitivity up to 0.71 at 3.0 T vs. 0.49 at 1.5 T; AZ up to 0.88 vs. 0.74; both differences P < 0.05) and highest for the fs-IM FSE sequence at 3.0 T. Average sensitivity for detecting ligament pathology was higher at 3.0 T (0.69 vs. 0.50; P < 0.05). Specificity was high among all protocols and both field strengths for assessing ligament and cartilage pathology (>0.95).
Compared with 1.5-T imaging, the 3.0-T imaging of the ankle joint at improved diagnostic performance in assessing cartilage significantly and there was a higher sensitivity for assessing ligamentous pathology.
Investigative radiology 09/2008; 43(9):604-11. · 4.85 Impact Factor
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Reinhard Meier,
Morand Piert,
Guido Piontek,
Martina Rudelius,
Robert A Oostendorp,
Reingard Senekowitsch-Schmidtke, Tobias D Henning,
Winfried S Wels,
Christoph Uherek,
Ernst J Rummeny,
Heike E Daldrup-Link
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ABSTRACT: The objective of this study was to label the human natural killer (NK) cell line NK-92 with [(18)F]fluoro-deoxy-glucose (FDG) for subsequent in vivo tracking to HER2/neu-positive tumors.
NK-92 cells were genetically modified to NK-92-scFv(FRP5)-zeta cells, which express a chimeric antigen receptor that is specific to the tumor-associated ErbB2 (HER2/neu) antigen. NK-92 and NK-92-scFv(FRP5)-zeta cells were labeled with [(18)F]FDG by simple incubation at different settings. Labeling efficiency was evaluated by a gamma counter. Subsequently, [(18)F]FDG-labeled parental NK-92 or NK-92-scFv(FRP5)-zeta cells were intravenously injected into mice with implanted HER2/neu-positive NIH/3T3 tumors. Radioactivity in tumors was quantified by digital autoradiography and correlated with histopathology.
The NK-92 and NK-92-scFv(FRP5)-zeta cells could be efficiently labeled with [(18)F]FDG by simple incubation. Optimal labeling efficiencies (80%) were achieved using an incubation period of 60 min and additional insulin (10 IU/ml). After injection of 5x10(6) [(18)F]FDG-labeled NK-92-scFv(FRP5)-zeta cells into tumor-bearing mice, digital autoradiography showed an increased uptake of radioactivity in HER2/neu-positive tumors at 60 min postinjection. Conversely, injection of 5x10(6) NK-92 cells not directed against HER2/neu receptors did not result in increased uptake of radioactivity in the tumors. Histopathology confirmed an accumulation of the NK-92-scFv(FRP5)-zeta cells, but not the parental NK cells, in tumor tissues.
The human NK cell line NK-92 can be directed against HER2/neu antigens by genetic modification. The genetically modified NK cells can be efficiently labeled with [(18)F]FDG, and the accumulation of these labeled NK cells in HER2/neu-positive tumors can be monitored with autoradiography.
Nuclear Medicine and Biology 08/2008; 35(5):579-88. · 3.02 Impact Factor
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ABSTRACT: In recent years, stem cell research has led to a better understanding of developmental biology, various diseases and its potential impact on regenerative medicine. A non-invasive method to monitor the transplanted stem cells repeatedly in vivo would greatly enhance our ability to understand the mechanisms that control stem cell death and identify trophic factors and signaling pathways that improve stem cell engraftment. MR imaging has been proven to be an effective tool for the in vivo depiction of stem cells with near microscopic anatomical resolution. In order to detect stem cells with MR, the cells have to be labeled with cell specific MR contrast agents. For this purpose, iron oxide nanoparticles, such as superparamagnetic iron oxide particles (SPIO), are applied, because of their high sensitivity for cell detection and their excellent biocompatibility. SPIO particles are composed of an iron oxide core and a dextran, carboxydextran or starch coat, and function by creating local field inhomogeneities, that cause a decreased signal on T2-weighted MR images. This presentation will demonstrate techniques for labeling of stem cells with clinically applicable MR contrast agents for subsequent non-invasive in vivo tracking of the labeled cells with MR imaging.
Journal of Visualized Experiments 02/2008;
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ABSTRACT: Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo labeling of stem cells with a fluorescent dye, subsequent intravenous injection of the labeled cells and visualization of their accumulation in specific target organs or pathologies. The presented technique demonstrates how we label human mesenchymal stem cells (hMSC) by simple incubation with the lipophilic fluorescent dye DiD (C67H103CIN2O3S) and how we label human embryonic stem cells (hESC) with the FDA approved fluorescent dye Indocyanine Green (ICG). The uptake mechanism is via adherence and diffusion of the lypophilic dye across the phospholipid cell membrane bilayer. The labeling efficiency is usually improved if the cells are incubated with the dye in serum-free media as opposed to incubation in serum-containing media. Furthermore, the addition of the transfection agent Protamine Sulfate significantly improves contrast agent uptake.
Journal of Visualized Experiments 02/2008;
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ABSTRACT: The purpose of our study was to compare an autocalibrating parallel imaging technique at 3 T with standard acquisitions at 3 and 1.5 T for small-field-of-view imaging of the ankle.
MRI of the ankle was performed in three fresh human cadaver specimens and three healthy volunteers. Axial and sagittal T1-weighted, axial fat-saturated T2-weighted, and coronal intermediate-weighted fast spin-echo sequences, as well as a fat-saturated spoiled gradient-echo sequence, were acquired at 1.5 and 3 T. At 3 T, reduced data sets were reconstructed using a generalized autocalibrating partially parallel acquisition (GRAPPA) technique, with a scan time reduction of approximately 44%. All images were assessed by two radiologists independently concerning image quality. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in every data set. In the cadaver specimens, macroscopic findings after dissection served as a reference for the pathologic evaluation.
SNR and CNR in the GRAPPA images were comparable to the standard acquisition at 3 T. The image quality was rated significantly higher at 3 T with both normal and parallel acquisition compared with 1.5 T. There was no significant difference in ligament and cartilage visualization or in image quality between standard and GRAPPA reconstruction at 3 T. Ankle abnormalities were better seen at 3 T than at 1.5 T for both normal and parallel acquisitions.
Using higher field strength combined with parallel technique, MR images of the ankle were obtained with excellent diagnostic quality and a scan time reduction of about 44%. In addition, parallel imaging can provide more flexibility in protocol design.
American Journal of Roentgenology 08/2007; 189(1):240-5. · 2.78 Impact Factor
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ABSTRACT: We investigated the influence of soft tissue (ST) on image quality by high-resolution multidetector computed tomography (MDCT) scans and assessed the effect of surrounding ST on the quantification of trabecular bone structure. Eight bone cores obtained from human proximal femoral heads discarded during hip replacement surgery were scanned with micro-computed tomography (microCT) as well as with MDCT both without (w/o) and with (w) simulated surrounding ST, where a phantom imitated a human torso. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in all scans. Apparent trabecular bone structure parameters were calculated and compared to similar parameters obtained in coregistered sections of the microCT scans. Residual errors were calculated as root-mean-square (RMS) errors relative to the microCT measurements. Compared to microCT results, trabecular structure parameters were overestimated by MDCT both w and w/o ST. SNR and CNR were significantly higher in the scans w/o ST. Significant correlations between microCT and MDCT results were found for bone fraction (r = 0.90 w/o ST, r = 0.84 w ST), trabecular number, and separation. RMS ranged from 10% to 15% for MDCT w/o ST and from 10% to 17% for MDCT w ST. Only bone fraction showed significantly different RMS and correlations for scans w/o vs. w ST (P < 0.05). This study showed that MDCT is able to visualize trabecular bone structure in an in vivo-like setting at skeletal sites within the torso such as the proximal femur. Even though ST scatter compromises image quality substantially, the major characteristics of the trabecular network can still be appreciated and quantified.
Calcified Tissue International 07/2007; 80(6):366-73. · 2.38 Impact Factor
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ABSTRACT: The objective of this study was to optimize ankle joint MR imaging in volunteers at 1.5 Tesla (T) and 3.0 T, and to compare these optimized sequences concerning image quality and performance in assessing cartilage, ligament and tendon pathology in fresh human cadaver specimens. Initially our clinical ankle protocol consisting of T1-weighted (-w), fat-saturated (fs) T2-w, and short tau inversion-recovery fast spinecho (FSE) sequences was optimized at 1.5 T and 3.0 T by two radiologists. For dedicated cartilage imaging, fs-intermediate (IM)-w FSE, fs spoiled gradient echo, and balanced free-precession steady-state sequences were optimized. Using the optimized sequences, thirteen cadaver ankle joints were imaged. Four radiologists independently assessed these images concerning image quality and pathology. All radiologists consistently rated image quality higher at 3.0 T (all sequences p<0.05). For detecting cartilage pathology, diagnostic performance was significantly higher at 3.0 T (ROC-values up to 0.93 vs. 0.77; p<0.05); the fs-IM FSE sequence showed highest values among the different sequences. Average sensitivity for detecting tendon pathology was 63% at 3.0 T vs. 41% at 1.5 T and was significantly higher at 3.0 T for 2 out of 4 radiologists (p<0.05). Compared to 1.5 T, imaging of the ankle joint at 3.0 T significantly improved image quality and diagnostic performance in assessing cartilage pathology.
European Radiology 06/2007; 17(6):1518-28. · 3.22 Impact Factor
