Functional L-lysine dendritic macromolecules as liver-imaging probes.

Macromol Biosci. 2009 Dec 8;9(12):1227-36

Authors: Luo K, Liu G, Zhang X, She W, He B, Nie Y, Li L, Wu Y, Zhang Z, Gong Q, Gao F, Song B, Ai H, Gu Z

Liver-imaging probes are prepared through the conjugation of Gd chelates and galactosyl moieties to peptide dendrimers. The dendritic probes possessing highly controlled structures and a single molecular weight have a two-fold increase in T(1) relaxivity to 9.1 x 10(3) (Gd M)(-1) s(-1) compared to Gd-DTPA. No obvious cytotoxicity of this multifunctional dendritic agent is discovered in vitro. The dendrimer bearing galactosyl moieties leads to a much-higher hepatocyte-cell uptake in vitro and provides good signal-intensity enhancement (35%) of mouse liver in vivo especially at 60 min after intravenous injection. In comparison, non-targeting Gd dendrimers provide only an 11% enhancement of imaging contrast at the same time point. Overall, the dendrimers bearing galactosyl moieties may be used as liver-imaging probes.

PMID: 19904726 [PubMed - indexed for MEDLINE]

Washout of small molecular contrast agent in carcinoma-derived experimental tumors.

Microvasc Res. 2009 Dec;78(3):370-8

Authors: Galiè M, Farace P, Merigo F, Fiorini S, Tambalo S, Nicolato E, Sbarbati A, Marzola P

The use of contrast-enhanced magnetic resonance imaging (MRI) for the assessment of breast carcinomas reveals satisfactory sensitivity, but due to low specificity, it does not obviate the need for subsequent tissue sampling. Its capability to differentiate benign from malignant lesion is under continuous investigation. Dynamic contrast-enhanced MRI (DCE-MRI) could improve specificity of MRI through the analysis of the kinetic of contrast enhancement. In particular, the study of the washout pattern is considered a promising tool to improve in vivo diagnosis and even to evaluate the response under chemotherapy. To provide a comprehensive characterization of this parameter in malignant tumor models, in vivo mapping of the washout of small molecular contrast agent (Gd-DTPA, molecular weight 0.57 kDa) was carried out in three transplanted/spontaneous mammary tumors, which differed in their histopathological and microvascular features. It resulted that in all models around 40% of tumor volume lacks efficient washout; washout areas are frequently, but not always, restricted to the tumor periphery and that non-washout areas are not restricted to necrotic regions. Difference in the distribution of lymphatic vessels characterized spontaneous vs. transplanted tumors but did not produce a corresponding different washout pattern, confirming that Gd-DTPA drainage does not mainly depend on lymphatic architecture. Finally, the efficiency of washout is correlated with parameters obtainable during the earlier phases of the enhancement curve and in malignant tumors it could be indirectly estimated from them.

PMID: 19804787 [PubMed - indexed for MEDLINE]

Tead-1 over-expression in the mouse heart promotes an age-dependent heart dysfunction.

J Biol Chem. 2010 Mar 1;

Authors: Tsika RW, Ma L, Kehat I, Schramm C, Simmer G, Morgan B, Fine DM, Hanft LM, McDonald KS, Molkentin JD, Krenz M, Yang S, Ji J

TEA-domain transcription factor-1 (TEAD-1) is essential for proper heart development, is implicated in cardiac-specific gene expression and the hypertrophic response of primary cardiomyocytes to hormonal and mechanical stimuli, and its activity increases in the pressure overloaded hypertrophied rat heart. To investigate whether TEAD-1 is an in vivo modulator of cardiac-specific gene expression and hypertrophy, we developed transgenic mice expressing HA-tagged TEAD-1 under the control of the muscle creatine kinase (MCK) promoter. We show that a sustained increase in TEAD-1 protein lead to an age-dependent dysfunction. Magnetic resonance imaging (MRI) revealed decreases in cardiac output, stroke volume, ejection fraction, and fractional shortening. Isolated TEAD-1 hearts revealed decreased left ventricular power output that correlated with increased betaMyHC protein. Histological analysis showed altered alignment of cardio-myocytes, septal wall thickening, and fibrosis while ECG displayed a left axis shift of mean electrical axis. Transcripts representing most members of the fetal heart gene program remained elevated from fetal- through adult-life. Western blot analyses revealed decreases in p-phospholamban, SERCA2a, p-CX43, p-GSK-3alpha/beta, nuclear beta-catenin, GATA4, NFATc3/c4, and increased NCX1, nuclear DYKR1A and Puralpha/beta protein. TEAD-1 mice did not display cardiac hypertrophy. TEAD-1 mice do not tolerate stress as they die 6-hours after surgical induction of pressure overload. These data provide the first in vivo evidence that increased TEAD-1 can induce characteristics of cardiac remodeling associated with cardiomyopathy and heart failure.

PMID: 20194497 [PubMed - as supplied by publisher]

Activatable magnetic resonance imaging agents for myeloperoxidase sensing: mechanism of activation, stability, and toxicity.

J Am Chem Soc. 2010 Jan 13;132(1):168-77

Authors: Rodríguez E, Nilges M, Weissleder R, Chen JW

Myeloperoxidase (MPO) is increasingly being recognized as an important factor in many inflammatory diseases, particularly cardiovascular and neurological diseases. MPO-specific imaging agents would thus be highly useful to diagnose early disease, monitor disease progression, and quantify treatment effects. This study reports in vitro and in vivo characterizations of the mechanism of interaction between MPO and paramagnetic enzyme substrates based on physical and biological measurements. We show that these agents are activated through a radical mechanism, which can combine to form oligomers and, in the presence of tyrosine-containing peptide, bind to proteins. We further identified two new imaging agents, which represent the near extremes in either oligomerization (mono-5HT-DTPA-Gd) or protein-binding in their activation mechanism (bis-o-dianisidine-DTPA-Gd). On the other hand, we found that the agent bis-5HT-DTPA-Gd utilizes both mechanisms when activated. These properties yield distinct in vivo pharmacokinetics profiles for each of these agents that may be exploited for different applications. Specificity studies show that only MPO, but not eosinophil peroxidase, can highly activate these agents, and that MPO activity as low as 0.005 U/mg of tissue can be detected. Gd kinetic lability and cytotoxicity studies further confirm stability of the Gd ion and low toxicity for the 5HT-based agents, suggesting that these agents are suitable for translational in vivo studies.

PMID: 19968300 [PubMed - indexed for MEDLINE]

Hyperpolarized [2-13C]-fructose: a hemiketal DNP substrate for in vivo metabolic imaging.

J Am Chem Soc. 2009 Dec 9;131(48):17591-6

Authors: Keshari KR, Wilson DM, Chen AP, Bok R, Larson PE, Hu S, Van Criekinge M, Macdonald JM, Vigneron DB, Kurhanewicz J

Hyperpolarized (13)C labeled molecular probes have been used to investigate metabolic pathways of interest as well as facilitate in vivo spectroscopic imaging by taking advantage of the dramatic signal enhancement provided by DNP. Due to the limited lifetime of the hyperpolarized nucleus, with signal decay dependent on T(1) relaxation, carboxylate carbons have been the primary targets for development of hyperpolarized metabolic probes. The use of these carbon nuclei makes it difficult to investigate upstream glycolytic processes, which have been related to both cancer metabolism as well as other metabolic abnormalities, such as fatty liver disease and diabetes. Glucose carbons have very short T(1)s (<1 s) and therefore cannot be used as an in vivo hyperpolarized metabolic probe of glycolysis. However, the pentose analogue fructose can also enter glycolysis through its phosphorylation by hexokinase and yield complementary information. The C(2) of fructose is a hemiketal that has a relatively longer relaxation time (approximately 16 s at 37 degrees C) and high solution state polarization (approximately 12%). Hyperpolarized [2-(13)C]-fructose was also injected into a transgenic model of prostate cancer (TRAMP) and demonstrated difference in uptake and metabolism in regions of tumor relative to surrounding tissue. Thus, this study demonstrates the first hyperpolarization of a carbohydrate carbon with a sufficient T(1) and solution state polarization for ex vivo spectroscopy and in vivo spectroscopic imaging studies.

PMID: 19860409 [PubMed - indexed for MEDLINE]

Evidence for in vivo macrophage mediated tumor uptake of paramagnetic/fluorescent liposomes.

NMR Biomed. 2009 Dec;22(10):1084-92

Authors: Castelli DD, Terreno E, Cabella C, Chaabane L, Lanzardo S, Tei L, Visigalli M, Aime S

Dysprosium (Dy)-loaded liposomes act as excellent T(2)-susceptibility agents at high magnetic field strength. The R(2)-enhancement increases with the size of the liposomes and the concentration of entrapped paramagnetic metal complexes. Neuro-2a tumor cells are readily labeled when Dy-loaded liposomes, suitably functionalized with glutamine residues (Gln), are added to the culture medium as glutamine receptors are highly expressed in such proliferating tumor cells. By using fluorescent liposomes doped with fluorescent dyes (either incorporated in the membrane or included in the inner cavity), confocal microscopy experiments showed that targeted liposomes are taken up much more avidly than non-targeted vesicles. In vivo studies showed that glutamine-functionalized and non-functionalized liposomes accumulate in the tumor region to a similar extent. Confocal images of the excised tumor showed extensive co-localization of liposomes and macrophages in both cases. It is suggested that the loss of tumor specificity, shown by Gln-functionalized liposomes in vivo, has to be associated with the efficient removal of liposomes operated by the RES (reticulo endoplasmatic system) or tumor associated macrophages.

PMID: 19569084 [PubMed - indexed for MEDLINE]

Molecular neuroimaging in rodents: assessing receptor expression and function.

Eur J Neurosci. 2009 Nov;30(10):1860-9

Authors: Mueggler T, Baltes C, Rudin M

Multimodal non-invasive neuroimaging in rodents constitutes an attractive tool for studying neurobiological processes in vivo. At present, imaging studies of brain anatomy and function as well as the investigation of structure-function relationships belong to the standard repertoire of neuroscientists. Molecular imaging adds a new perspective. The mapping of the receptor distribution and receptor occupancy can nowadays be complemented by specific readouts of receptor function either by visualizing the activity of signaling pathways or mapping the physiological consequences of receptor stimulation. Molecular information is obtained through the use of imaging probes that combine a target-specific ligand with a reporter moiety that generates a signal that can be detected from outside the body. For imaging probes targeting the central nervous system, penetration of the intact blood-brain barrier constitutes a major hurdle. Molecular imaging generates specific information and therefore has a large potential for disease phenotyping (diagnostics), therapy development and monitoring of treatment response. Molecular imaging is still in its infancy and major developments in imaging technology, probe design and data analysis are required in order to make an impact. Rodent molecular neuroimaging will play an important role in the development of these tools.

PMID: 19912336 [PubMed - indexed for MEDLINE]

Prostate Cancer-Targeted Imaging Using Magnetofluorescent Polymeric Nanoparticles Functionalized with Bombesin.

Pharm Res. 2010 Feb 25;

Authors: Lee CM, Jeong HJ, Cheong SJ, Kim EM, Kim DW, Lim ST, Sohn MH

PURPOSE: In this work, the aim was to prepare and characterize a magnetofluorescent polymeric nanoparticle for prostate cancer imaging in vivo. METHODS: Glycol chitosan (GC) was chemically modified with N-acetyl histidine (NAHis) as a hydrophobic moiety, and bombesin (BBN) was conjugated to the hydrophobically modified GC for use in targeting gastric-releasing peptide receptors (GRPR) overexpressed in prostate cancer cells. NAHis-GC conjugates were labeled with the near-infrared (NIR) fluorophore Cy5.5 (C-NAHis-GC conjugate). RESULTS: BBN-conjugated C-NAHis-GC nanoparticles (BC-NAHis-GC nanoparticles) showed significantly higher binding to the PC3 cell surface than nanoparticles without BBN, and the cellular binding was clearly inhibited by BBN. The tumor-to-muscle ratios of C- and BC-NAHis-GC nanoparticles were 2.26 +/- 0.66 and 5.37 +/- 0.43, respectively. The tumor accumulation of BC-NAHis-GC nanoparticles was clearly reduced by co-injection of BBN. Further, iron oxide nanoparticles (IO) were loaded into BC-NAHis-GC nanoparticles to investigate the possibility of use as a probe for MRI. IO-BC-NAHis-GC nanoparticles were well observed in the PC3 cells, and the blocking with BBN significantly reduced the cellular binding of the nanoparticles. CONCLUSION: These results demonstrate that the BBN conjugation to NAHis-GC nanoparticles improves their tumor accumulation in PC3-bearing mice in comparison to nanoparticles without BBN, suggesting that BC-NAHis-GC nanoparticles may be useful for prostate cancer imaging.

PMID: 20182773 [PubMed - as supplied by publisher]

Noninvasively characterizing the different alphavbeta3 expression patterns in lung cancers with RGD-USPIO using a clinical 3.0T MR scanner.

Int J Nanomedicine. 2009;4:241-9

Authors: Jiang T, Zhang C, Zheng X, Xu X, Xie X, Liu H, Liu S

The adhesion molecule alphavbeta3 integrin plays an important role in tumor development and metastases. We demonstrated the specificity of the probe to alphavbeta3 integrin with transmission electron microcopy (TEM) and magnetic resonance imaging (MRI). The in vivo targeting behavior of the probe was examined in 2 tumor models with different alphavbeta3 expression patterns by a 3.0T MRI scanner. MR imaging showed that R2* pseudo-color pictures of A549 lung cancer tumor was different from that of 3LL lung cancer. For A549 tumor, an homogeneous decrease of signal intensity was observed throughout the tumor, which was more evident in the periphery or central areas. Histological studies revealed that alphavbeta3 integrin was expressed both on the tumor vessel and tumor cells for A549 tumor. Our findings indicated that it was possible to noninvasively characterize the different alphavbeta3 expression pattern in lung cancers with arginine-glycine-aspartic acid (RGD) peptide conjugated ultra-small superparamagnetic iron oxide nanoparticles (RGD-USPIO) using a clinical 3.0T MR scanner. Nevertheless, the way of imaging targeting presentation of the probe differed in tumors with different alphavbeta3 expression patterns.

PMID: 20011241 [PubMed - indexed for MEDLINE]

Detecting epidermal growth factor receptor tumor activity in vivo during cetuximab therapy of murine gliomas.

Acad Radiol. 2010 Jan;17(1):7-17

Authors: Gibbs-Strauss SL, Samkoe KS, O'Hara JA, Davis SC, Hoopes PJ, Hasan T, Pogue BW

RATIONALE AND OBJECTIVES: Noninvasive molecular imaging of glioma tumor receptor activity was assessed with diagnostic in vivo fluorescence monitoring during targeted therapy. The study goals were to assess the range of use for treatment monitoring and stratification of tumor types using epidermal growth factor (EGF) receptor (EGFR) status with administration of fluorescently labeled EGF and determine its utility for tumor detection compared to magnetic resonance imaging (MRI). MATERIALS AND METHODS: EGFR+ and EGFR- glioma tumor lines (human glioma [U251-GFP] and rat gliosarcoma [9L-GFP], respectively) were used to assess these goals, having a 20-fold difference between their EGF uptakes. RESULTS: Treatment with cetuximab in the EGFR+ tumor-bearing animals led to decreased EGF tumor uptake, whereas for the EGFR- tumors, no change in fluorescence signal followed treatment. This diagnostic difference in EGFR expression could be used to stratify the tumor-bearing animals into groups of potential responders and nonresponders, and receiver-operating characteristic curve analysis revealed an area under the curve (AUC) of 0.92 in separating these tumors. The nonlocalized growth pattern of U251-GFP tumors resulted in detection difficulty on standard MRI, but high EGFR expression made them detectable by fluorescence imaging (AUC = 1.0). The EGFR+ U251-GFP tumor-bearing animals could be noninvasively stratified into treated and untreated groups on the basis of fluorescence intensity difference (P = .035, AUC = 0.90). CONCLUSIONS: EGFR expression was tracked in vivo with fluorescence and determined to be of use for the stratification of EGFR+ and EGFR- tumors, the detection of EGFR+ tumors, and monitoring of molecular therapy.

PMID: 19796971 [PubMed - indexed for MEDLINE]

In vivo MR angiography and velocity measurement in mice coronary arteries at 9.4 T: assessment of coronary flow velocity reserve.

Radiology. 2010 Feb;254(2):441-8

Authors: Cochet H, Montaudon M, Laurent F, Calmettes G, Franconi JM, Miraux S, Thiaudière E, Parzy E

PURPOSE: To demonstrate the feasibility of coronary magnetic resonance (MR) angiography in living mice and to evaluate a dynamic MR angiographic method for coronary flow measurement at 9.4-T field strength. MATERIALS AND METHODS: This study was conducted according to European law and was in full compliance with National Institutes of Health recommendations for animal care and a local institutional animal care committee. Mice were anesthetized by using isoflurane. First, time-of-flight MR angiography was performed in 10 mice to measure coronary diameters at 80-mum isotropic resolution. Second, left coronary artery (LCA) velocity measurements were performed at seven cardiac phases in nine other mice to assess the velocity curve profile. Third, coronary velocities were measured at the middiastolic phase in 13 mice at rest and during adenosine-induced hyperemia to calculate coronary flow velocity reserve (CFVR). The Pearson coefficient compared the correlation between isoflurane dose and CFVR. Paired t tests compared R-R intervals and respiratory rates between rest and hyperemia. RESULTS: Proximal diameters were, respectively, 404 mum +/- 34 [standard deviation] and 259 mum +/- 22 for the LCAs and the right coronary arteries, which were in accordance with reported values. The velocity curve profile throughout the cardiac cycle was similar to values from the literature. Baseline and hyperemic velocities were, respectively, 19.0 cm/sec +/- 4.4 and 33.7 cm/sec +/- 4.7 (P<.001), resulting in a CFVR of 1.77 +/- 0.19. CFVR did not correlate with isoflurane dose (r = 0.05, P = .88). R-R intervals shortened by 2.5% during hyperemia (P = .04). Respiratory rates showed no difference between rest and hyperemia (P = .39). CONCLUSION: High-spatial-resolution three-dimensional coronary MR angiography is feasible in living mice. Dynamic MR angiography depicts coronary velocity changes throughout the cardiac cycle and between rest and maximum hyperemia, providing a tool for CFVR assessment.

PMID: 20093516 [PubMed - indexed for MEDLINE]

In vivo bioluminescence tomography with a blocking-off finite-difference SP3 method and MRI/CT coregistration.

Med Phys. 2010 Jan;37(1):329-38

Authors: Klose AD, Beattie BJ, Dehghani H, Vider L, Le C, Ponomarev V, Blasberg R

PURPOSE: Bioluminescence imaging is a research tool for studying gene expression levels in small animal models of human disease. Bioluminescence light, however, is strongly scattered in biological tissue and no direct image of the light-emitting reporter probe's location can be obtained. Therefore, the authors have developed a linear image reconstruction method for bioluminescence tomography (BLT) that recovers the three-dimensional spatial bioluminescent source distribution in small animals. METHODS: The proposed reconstruction method uses third-order simplified spherical harmonics (SP3) solutions to the equation of radiative transfer for modeling the bioluminescence light propagation in optically nonuniform tissue. The SP3 equations and boundary conditions are solved with a finite-difference (FD) technique on a regular grid. The curved geometry of the animal surface was taken into account with a blocking-off region method for regular grids. Coregistered computed tomography (CT) and magnetic resonance (MR) images provide information regarding the geometry of the skin surface and internal organs. The inverse source problem is defined as an algebraic system of linear equations for the unknown source distribution and is iteratively solved given multiview and multispectral boundary measurements. The average tissue absorption parameters, which are used for the image reconstruction process, were calculated with an evolution strategy (ES) from in vivo measurements using an implanted pointlike source of known location and spectrum. Moreover, anatomical information regarding the location of the internal organs and other tissue structures within the animal's body are provided by coregistered MR images. RESULTS: First, the authors recovered the wavelength-dependent absorption coefficients (average error of 14%) with the ES under ideal conditions by using a numerical mouse model. Next, they reconstructed the average absorption coefficient of a small animal by using an artificial implanted light source and the validated ES. Last, they conducted two in vivo animal experiments and recovered the spatial location of the implanted light source and the spatial distribution of a bioluminescent reporter system located in the kidneys. The source reconstruction results were coregistered to CT and MR images. They further found that accurate bioluminescence image reconstructions could be obtained when segmenting a voidlike cyst with low-scattering and absorption parameters, whereas inaccurate image reconstructions were obtained when assuming a uniform optical parameter distribution instead. The image reconstructions were completed within 23 min on a 3 GHz Intel processor. CONCLUSIONS: The authors demonstrated on in vivo examples that the combination of anatomical coregistration, accurate optical tissue properties, multispectral acquisition, and a blocking-off FD-SP3 solution of the radiative transfer model significantly improves the accuracy of the BLT reconstructions.

PMID: 20175496 [PubMed - in process]

Gadolinium-based contrast agents and NSF: evidence from animal experience.

J Magn Reson Imaging. 2009 Dec;30(6):1268-76

Authors: Sieber MA, Steger-Hartmann T, Lengsfeld P, Pietsch H

Nephrogenic systemic fibrosis (NSF) is a potentially severe systemic disease typically characterized by fibrosis of the skin and connective tissues. The etiology of NSF is still unknown but is likely to be multifactorial. Specific triggers under scientific evaluation have included surgery and/or the occurrence of thrombosis or other vascular injury, proinflammatory state, the administration of high doses of erythropoietin, and more recently the use of gadolinium-based contrast agents (GBCAs). The aim of this review is to summarize knowledge regarding the pathogenesis of NSF and the potential role of GBCAs in its pathology, with a focus on animal experiments. The potential role of complex stability of GCBAs will be highlighted by results from several in vitro and in vivo experiments in rodent models of NSF. J. Magn. Reson. Imaging 2009;30:1268-1276. (c) 2009 Wiley-Liss, Inc.

PMID: 19938039 [PubMed - indexed for MEDLINE]

Primer on gadolinium chemistry.

J Magn Reson Imaging. 2009 Dec;30(6):1240-8

Authors: Sherry AD, Caravan P, Lenkinski RE

Gadolinium is widely known by all practitioners of magnetic resonance imaging (MRI) but few appreciate the basic solution chemistry of this trivalent lanthanide ion. Given the recent linkage between gadolinium contrast agents and nephrogenic systemic fibrosis, some basic chemistry of this ion must be more widely understood. This short primer on gadolinium chemistry is intended to provide the reader the background principles necessary to understand the basics of chelation chemistry, water hydration numbers, and the differences between thermodynamic stability and kinetic stability or inertness. We illustrate the fundamental importance of kinetic dissociation rates in determining gadolinium toxicity in vivo by presenting new data for a novel europium DOTA-tetraamide complex that is relatively unstable thermodynamically yet extraordinarily inert kinetically and also quite nontoxic. This, plus other literature evidence, forms the basis of the fundamental axiom that it is the kinetic stability of a gadolinium complex, not its thermodynamic stability, that determines its in vivo toxicity. J. Magn. Reson. Imaging 2009;30:1240-1248. (c) 2009 Wiley-Liss, Inc.

PMID: 19938036 [PubMed - indexed for MEDLINE]

High-resolution magnetic resonance angiography in the mouse using a nanoparticle blood-pool contrast agent.

Magn Reson Med. 2009 Dec;62(6):1447-56

Authors: Howles GP, Ghaghada KB, Qi Y, Mukundan S, Johnson GA

High-resolution magnetic resonance angiography is already a useful tool for studying mouse models of human disease. Magnetic resonance angiography in the mouse is typically performed using time-of-flight contrast. In this work, a new long-circulating blood-pool contrast agent-a liposomal nanoparticle with surface-conjugated gadolinium (SC-Gd liposomes)-was evaluated for use in mouse neurovascular magnetic resonance angiography. A total of 12 mice were imaged. Scan parameters were optimized for both time-of-flight and SC-Gd contrast. Compared to time-of-flight contrast, SC-Gd liposomes (0.08 mmol/kg) enabled improved small-vessel contrast-to-noise ratio, larger field of view, shorter scan time, and imaging of venous structures. For a limited field of view, time-of-flight and SC-Gd were not significantly different; however, SC-Gd provided better contrast-to-noise ratio when the field of view encompassed the whole brain (P < 0.001) or the whole neurovascular axis (P < 0.001). SC-Gd allowed acquisition of high-resolution magnetic resonance angiography (52 x 52 x 100 micrometer(3) or 0.27 nL), with 123% higher (P < 0.001) contrast-to-noise ratio in comparable scan time ( approximately 45 min). Alternatively, SC-Gd liposomes could be used to acquire high-resolution magnetic resonance angiography (0.27 nL) with 32% higher contrast-to-noise ratio (P < 0.001) in 75% shorter scan time (12 min).

PMID: 19902507 [PubMed - indexed for MEDLINE]

A histology-based atlas of the C57BL/6J mouse brain deformably registered to in vivo MRI for localized radiation and surgical targeting.

Phys Med Biol. 2009 Dec 21;54(24):7315-27

Authors: Purger D, McNutt T, Achanta P, Quiñones-Hinojosa A, Wong J, Ford E

The C57BL/6J laboratory mouse is commonly used in neurobiological research. Digital atlases of the C57BL/6J brain have been used for visualization, genetic phenotyping and morphometry, but currently lack the ability to accurately calculate deviations between individual mice. We developed a fully three-dimensional digital atlas of the C57BL/6J brain based on the histology atlas of Paxinos and Franklin (2001 The Mouse Brain in Stereotaxic Coordinates 2nd edn (San Diego, CA: Academic)). The atlas uses triangular meshes to represent the various structures. The atlas structures can be overlaid and deformed to individual mouse MR images. For this study, we selected 18 structures from the histological atlas. Average atlases can be created for any group of mice of interest by calculating the mean three-dimensional positions of corresponding individual mesh vertices. As a validation of the atlas' accuracy, we performed deformable registration of the lateral ventricles to 13 MR brain scans of mice in three age groups: 5, 8 and 9 weeks old. Lateral ventricle structures from individual mice were compared to the corresponding average structures and the original histology structures. We found that the average structures created using our method more accurately represent individual anatomy than histology-based atlases alone, with mean vertex deviations of 0.044 mm versus 0.082 mm for the left lateral ventricle and 0.045 mm versus 0.068 mm for the right lateral ventricle. Our atlas representation gives direct spatial deviations for structures of interest. Our results indicate that MR-deformable histology-based atlases represent an accurate method to obtain accurate morphometric measurements of a population of mice, and that this method may be applied to phenotyping experiments in the future as well as precision targeting of surgical procedures or radiation treatment.

PMID: 19926915 [PubMed - indexed for MEDLINE]

PEI-PEG-Chitosan Copolymer Coated Iron Oxide Nanoparticles for Safe Gene Delivery: synthesis, complexation, and transfection.

Adv Funct Mater. 2009 Jul 24;19(14):2244-2251

Authors: Kievit FM, Veiseh O, Bhattarai N, Fang C, Gunn JW, Lee D, Ellenbogen RG, Olson JM, Zhang M

Gene therapy offers the potential of mediating disease through modification of specific cellular functions of target cells. However, effective transport of nucleic acids to target cells with minimal side effects remains a challenge despite the use of unique viral and non-viral delivery approaches. Here we present a non-viral nanoparticle gene carrier that demonstrates effective gene delivery and transfection both in vitro and in vivo. The nanoparticle system (NP-CP-PEI) is made of a superparamagnetic iron oxide nanoparticle (NP), which enables magnetic resonance imaging, coated with a novel copolymer (CP-PEI) comprised of short chain polyethylenimine (PEI) and poly(ethylene glycol) (PEG) grafted to the natural polysaccharide, chitosan (CP), which allows efficient loading and protection of the nucleic acids. The function of each component material in this nanoparticle system is illustrated by comparative studies of three nanoparticle systems of different surface chemistries, through material property characterization, DNA loading and transfection analyses, and toxicity assessment. Significantly, NP-CP-PEI demonstrates an innocuous toxic profile and a high level of expression of the delivered plasmid DNA in a C6 xenograft mouse model, making it a potential candidate for safe in vivo delivery of DNA for gene therapy.

PMID: 20160995 [PubMed - as supplied by publisher]

MRI-coupled Fluorescence Tomography Quantifies EGFR Activity in Brain Tumors.

Acad Radiol. 2010 Mar;17(3):271-276

Authors: Davis SC, Samkoe KS, O'Hara JA, Gibbs-Strauss SL, Payne HL, Hoopes PJ, Paulsen KD, Pogue BW

RATIONALE AND OBJECTIVES: This report demonstrates the diagnostic potential of magnetic resonance imaging (MRI)-coupled fluorescence molecular tomography (FMT) to determine epidermal growth factor receptor (EGFR) status in brain cancer. MATERIALS AND METHODS: Two orthotopic glioma xenograft models were used in this study: one represented high EGFR expression and the other low expression. Nude mice were inoculated with cells from either one of the tumor lines or were used in a sham surgery control group. Animals were imaged using a unique MRI-FMT scanner 48 hours after intravenous injection of a near-infrared fluorophore bound to epidermal growth factor (EGF) ligand. Coronal images of fluorescence activity of the injected dye in the mouse brain were recovered using the MRI images as anatomical templates. RESULTS: In vivo images of fluorescence activity showed significant differences between animal populations, an observation confirmed by receiver operating characteristic analysis that revealed 100% sensitivity and specificity between animal groups implanted with EGFR((+)) and EGFR((-)) tumor lines. Similar performance was observed between EGFR((+)) and sham surgery control animals. CONCLUSIONS: This preclinical study suggests that MRI-FMT with fluorescent EGF provides excellent discrimination between tumors based on EGFR status. Reliable quantification of receptor status using minimally invasive techniques would be an important innovation for investigating new and existing cancer treatments that target these cellular mechanisms in research animals, and may be applied to identify receptor amplification in human brain cancer patients. This study represents the first systematic multianimal validation of receptor-specific imaging using MRI-guided fluorescence tomography.

PMID: 20152724 [PubMed - as supplied by publisher]

Myelin mapping in the living mouse brain using manganese-enhanced magnetization transfer MRI.

Neuroimage. 2010 Jan 15;49(2):1200-4

Authors: Watanabe T, Frahm J, Michaelis T

This work demonstrates manganese-enhanced magnetization transfer (MT) MRI to improve the contrast of myelinated structures in mouse brain in vivo. Systemic administration of manganese chloride led to a reduction of the MT ratio by 23% in white matter and 35% in gray matter. The effect increased their contrast-to-noise ratio by 48% and facilitated a mapping of myelin-rich white matter tissues. Relaxation time measurements revealed the manganese-induced shortening of T1 to be smaller in the corpus callosum (-42%) than in the cortex (-52%) or hippocampus (-60%). These findings are in line with the assumption that a high myelin and correspondingly low water content hinder the free diffusion and uptake of manganese ions. The resulting preferential accumulation of manganese in gray matter structures causes a stronger reduction of the MT saturation in gray matter than in white matter. Extending MRI assessments with conventional MT contrast, manganese-enhanced MT MRI at 76 x 80 x 160 microm(3) resolution and 2.35 T field strength allowed for a delineation of small myelinated structures such as the fornix, mammillothalamic tract, and fasciculus retroflexus in the living mouse brain.

PMID: 19796698 [PubMed - indexed for MEDLINE]

Molecular MRI for sensitive and specific detection of lung metastases.

Proc Natl Acad Sci U S A. 2010 Feb 8;

Authors: Branca RT, Cleveland ZI, Fubara B, Kumar CS, Maronpot RR, Leuschner C, Warren WS, Driehuys B

Early and specific detection of metastatic cancer cells in the lung (the most common organ targeted by metastases) could significantly improve cancer treatment outcomes. However, the most widespread lung imaging methods use ionizing radiation and have low sensitivity and/or low specificity for cancer cells. Here we address this problem with an imaging method to detect submillimeter-sized metastases with molecular specificity. Cancer cells are targeted by iron oxide nanoparticles functionalized with cancer-binding ligands, then imaged by high-resolution hyperpolarized (3)He MRI. We demonstrate in vivo detection of pulmonary micrometastates in mice injected with breast adenocarcinoma cells. The method not only holds promise for cancer imaging but more generally suggests a fundamentally unique approach to molecular imaging in the lungs.

PMID: 20142483 [PubMed - as supplied by publisher]