Andor Veltien

Sensitivity of magnetic resonance imaging of dendritic cells for in vivo tracking of cellular cancer vaccines

Success of immunotherapy with dendritic cells (DC) to treat cancer is highly dependent on their interaction with and activation of antigen specific T cells. To maximize DC–T cell contact accurate delivery of the therapeutic cells into the lymph node, or efficient trafficking of DC to the lymph nodes of the patient is essential. Since responses are seen in some patients but not in others, monitoring of the injected cells may be of major importance. Tracking of cells with magnetic resonance (MR) imaging is a non‐invasive method that provides detailed anatomical information and is therefore more informative for the evaluation of the localization of therapeutic cells after injection than e.g. scintigraphic imaging. To challenge the sensitivity of this novel technique, we investigated the minimum amount of label and the number of cells required for MR imaging and the effect of labeling on DC function. DC were labeled with different concentrations of a clinically approved MR contrast agent consisting of superparamagnetic iron oxide particles and were imaged at both 3 and 7 T. Our results demonstrate the following: (i) When loaded with 30 (±4) pg Fe/cell, cell numbers as low as 1,000 cells/mm3 at 3 T and 500 cells/mm3 at 7 T could be readily imaged; (ii) Labeling does not affect cell viability and function; (iii) Because of its high spatial resolution and sensitivity, MRI is ideally suited to track therapeutic cells in vivo.

Multinutrient diets improve cerebral perfusion and neuroprotection in a murine model of Alzheimer's disease.

Nutritional intervention may retard the development of Alzheimers disease (AD). In this study we tested the effects of 2 multi-nutrient diets in an AD mouse model (APPswe/PS1dE9). One diet contained membrane precursors such as omega-3 fatty acids and uridine monophosphate (DEU), whereas another diet contained cofactors for membrane synthesis as well (Fortasyn); the diets were developed to enhance synaptic membranes synthesis, and contain components that may improve vascular health. We measured cerebral blood flow (CBF) and water diffusivity with ultra-high-field magnetic resonance imaging, as alterations in these parameters correlate with clinical symptoms of the disease. APPswe/PS1dE9 mice on control diet showed decreased CBF and changes in brain water diffusion, in accordance with findings of hypoperfusion, axonal disconnection and neuronal loss in patients with AD. Both multinutrient diets were able to increase cortical CBF in APPswe/PS1dE9 mice and Fortasyn reduced water diffusivity, particularly in the dentate gyrus and in cortical regions. We suggest that a specific diet intervention has the potential to slow AD progression, by simultaneously improving cerebrovascular health and enhancing neuroprotective mechanisms.

Gray and white matter degeneration revealed by diffusion in an Alzheimer mouse model.

In patients with Alzheimers disease (AD) the severity of white matter degeneration correlates with the clinical symptoms of the disease. In this study, we performed diffusion-tensor magnetic resonance imaging at ultra-high field in a mouse model for AD (APP(swe)/PS1(dE9)) in combination with a voxel-based approach and tractography to detect changes in water diffusivity in white and gray matter, because these reflect structural alterations in neural tissue. We found substantial changes in water diffusion parallel and perpendicular to axonal tracts in several white matter regions like corpus callosum and fimbria of the hippocampus, that match with previous findings of axonal disconnection and myelin degradation in AD patients. Moreover, we found a significant increase in diffusivity in specific hippocampal subregions, which is supported by neuronal loss as visualized with Klüver-Barrera staining. This work demonstrates the potential of ultra-high field diffusion-tensor magnetic resonance imaging as a noninvasive modality to describe white and gray matter structural changes in mouse models for neurodegenerative disorders, and provides valuable knowledge to assess future AD prevention strategies in translational research.

Measurements of T1 and T2 relaxation times of colon cancer metastases in rat liver at 7 T

The purpose of this study was to investigate the magnetic resonance imaging (MRI) characteristics of colon cancer metastases in rat liver at 7 T. A dedicated RF microstrip coil of novel design was built in order to increase the signal-to-noise ratio and, in combination with respiratory triggering, to minimize motion artifacts. T1- and T2-weighted MR imaging was performed to follow tumor growth. T1-weighted images provided a good anatomical delineation of the liver structure, while the best contrast between metastases and normal liver tissue was achieved with T2-weighted images.Measurements of T1 and T2 relaxation times were performed with inversion recovery FLASH and Carr–Purcell–Meiboom–Gill and inversion recovery FLASH imaging sequences, respectively, for quantitative MR characterization of metastases. Both the T1 and T2 of the metastases were significantly higher than those of normal liver tissue. Further, an increase in the T1 relaxation time of the metastases was observed with tumor growth. These findings suggest that quantitative in vivo MR characterization provides information on tumor development and possibly response to therapy, though additional studies are needed to elucidate the correlation between the changes in relaxation times and tumor microenvironment.

Magnetic resonance imaging studies on gadonanotube-reinforced biodegradable polymer nanocomposites

We report about the in vitro cytotoxicity and MRI studies of Gd(3+)ions-doped ultra-short single-walled carbon nanotube (gadonanotubes), gadonanotubes- reinforced poly(lactic-co-glycolic acid) (PLGA) polymer nanocomposites and in vivo small animal MRI studies using the gadonanotubes. These studies were performed to explore the suitability of gadonanotubes-reinforced PLGA polymer nanocomposite as a model scaffold for noninvasive magnetic resonance imaging (MRI) to evaluate nanotube release during the degradation process of the scaffold and their biodistribution upon release from the polymer matrix in vivo. The gadonanotubes at 1-100 ppm and the gadonanotubes/PLGA nanocomposites (2 wt % gadonanotubes) did not show any cytotoxicity in vitro as demonstrated using the LIVE/DEAD viability assay. For the first time, r(2) relaxivity measurements were obtained for the superparamagnetic gadonanotubes. In vitro 7T MRI of the superparamagnetic gadonanotubes ([Gd] = 0.15 mM) suspended in a biocompatible 1% Pluronic F127 solution, gave a r(2) value of 578 mM(-1) s(-1). Upon subcutaneous injection of the gadonanotubes suspension into the dorsal region of rats, the high r(2) value translated into excellent and prolonged negative contrast enhancement of in vivo T(2)weighted proton MRI images. The in vitro characterization of the nanocomposite discs and their degradation process by MRI, showed strong influence of the gadonanotube on water proton relaxations. These results indicate that the gadonanotubes/PLGA nanocomposites are suitable for further in vivo studies to track by MRI the biodegradation release and biodistribution of gadonanotubes.

Structural-functional connectivity deficits of neocortical circuits in the Fmr1−/y mouse model of autism

Structural and functional connectivity phenotype in the neocortex of Fmr1−/y mice supports a prominent hypothesis of autism. Fragile X syndrome (FXS), the most common inherited form of intellectual disability disorder and a frequent cause of autism spectrum disorder (ASD), is characterized by a high prevalence of sensory symptoms. Perturbations in the anatomical connectivity of neocortical circuits resulting in their functional defects have been hypothesized to contribute to the underlying etiology of these disorders. We tested this idea by probing alterations in the functional and structural connectivity of both local and long-ranging neocortical circuits in the Fmr1−/y mouse model of FXS. To achieve this, we combined in vivo ultrahigh-field diffusion tensor magnetic resonance imaging (MRI), functional MRI, and viral tracing approaches in adult mice. Our results show an anatomical hyperconnectivity phenotype for the primary visual cortex (V1), but a disproportional low connectivity of V1 with other neocortical regions. These structural data are supported by defects in the structural integrity of the subcortical white matter in the anterior and posterior forebrain. These anatomical alterations might contribute to the observed functional decoupling across neocortical regions. We therefore identify FXS as a “connectopathy,” providing a translational model for understanding sensory processing defects and functional decoupling of neocortical areas in FXS and ASD.

Dietary lipids do not contribute to the higher hepatic triglyceride levels of fructose- compared to glucose-fed mice

Fructose consumption has been associated with the surge in obesity and dyslipidemia. This may be mediated by the fructose effects on hepatic lipids and ATP levels. Fructose metabolism provides carbons for de novo lipogenesis (DNL) and stimulates enterocyte secretion of apoB48. Thus, fructose‐induced hepatic triglyceride (HTG) accumulation can be attributed to both DNL stimulation and dietary lipid absorption. The aim of this study was to assess the effects of fructose diet on HTG and ATP content and the contributions of dietary lipids and DNL to HTG. Measurements were performed in vivo in mice by magnetic resonance imaging (MRI) and novel magnetic resonance spectroscopy (MRS) approaches. Abdominal adipose tissue volume and intramyocellular lipid levels were comparable between 8‐wk fructose‐ and glucose‐fed mice. HTG levels were ~1.5‐fold higher in fructose‐fed than in glucose‐fed mice (P<0.05). Metabolic flux analysis by 13C and 2H MRS showed that this was not due to dietary lipid absorption, but due to DNL stimulation. The contribution of oral lipids to HTG was, after 5 h, 1.60 ± 0.23% for fructose and 2.16 ± 0.35% for glucose diets (P=0.26), whereas that of DNL was higher in fructose than in glucose diets (2.55±0.51 vs. 1.13±0.24%, P=0.01). Hepatic energy status, assessed by P MRS, was similar for fructose‐ and glucose‐fed mice. Fructose‐induced HTG accumulation is better explained by DNL and not by dietary lipid uptake, while not compromising ATP homeostasis.—Nunes, P. M., Wright, A. J., Veltien, A., van Asten, J. J. A., Tack, C. J., Jones, J. G., Heerschap, A. Dietary lipids do not contribute to the higher hepatic triglyceride levels of fructose‐ compared to glucose‐fed mice. FASEB J. 28, 1988–1997 (2014). www.fasebj.org

Nuclear magnetic resonance in laboratory animals.

Publisher Summary This chapter elaborates the use of nuclear magnetic resonance (NMR) in the study of laboratory animals. NMR has been applied to a wide range of animals, including pinnipeds, birds, sheep, and monkeys, among others and by far the majority of animals undergoing NMR examinations are rats and mice as these serve as the main model systems in biomedical research, mostly for practical reasons. An endogenous contrast agent is provided by deoxyhemoglobin, which affects the intensity of the water signal, using particular MR image recordings. The water signal may be affected by magnetic active compounds, of which the clinically used lanthanide-based NMR contrast agent Gd-DTPA is best known. It is found that when this compound is administered intravenously to the animal it only has an effect on the water signal at locations where it passes by, and thus acts as a contrast agent. By using the strong signal of water protons from the tissue itself, the local homogeneity of the magnetic field can be optimized and NMR images can be made as guides for localization. The anesthesia and physiological monitoring of animals in NMR experiments is also elaborated in this chapter.

Localized sensitivity enhanced in vivo 13C MRS to detect glucose metabolism in the mouse brain

The application of in vivo 13C MR spectroscopy to mouse brain models is potentially valuable for improving the understanding of cerebral carbohydrate metabolism and glutamatergic neurotransmission in various neuropathologies. However, the low sensitivity of 13C nuclei and contaminating signals of lipids in the relatively small mouse brain make this application rather challenging. To meet these technical challenges, localized semi‐adiabatic distortionless enhanced polarization transfer (DEPT) MR spectroscopy in combination with a continuous intravenous [1,6‐13C2] glucose infusion was implemented to detect glucose metabolism in isoflurane‐anesthetized mice at 7T. The signal enhancement and high spectral resolution obtained in these experiments enabled the separate determination of 13C label incorporation into as much as 13 metabolites from a 175 μL volume. Signal increases of glucose (C6), glutamine (C3, C4), and glutamate (C3, C4) were determined with a time resolution of 8.6 min. This study demonstrates an optimized MR method for the application of in vivo 13C MRS in mouse brain. Magn Reson Med, 2008.

A longitudinal study of cognition, proton MR spectroscopy and synaptic and neuronal pathology in aging wild-type and AβPPswe-PS1dE9 mice.

Proton magnetic resonance spectroscopy (1H MRS) is a valuable tool in Alzheimer’s disease research, investigating the functional integrity of the brain. The present longitudinal study set out to characterize the neurochemical profile of the hippocampus, measured by single voxel 1H MRS at 7 Tesla, in the brains of AβPPSswe-PS1dE9 and wild-type mice at 8 and 12 months of age. Furthermore, we wanted to determine whether alterations in hippocampal metabolite levels coincided with behavioral changes, cognitive decline and neuropathological features, to gain a better understanding of the underlying neurodegenerative processes. Moreover, correlation analyses were performed in the 12-month-old AβPP-PS1 animals with the hippocampal amyloid-β deposition, TBS-T soluble Aβ levels and high-molecular weight Aβ aggregate levels to gain a better understanding of the possible involvement of Aβ in neurochemical and behavioral changes, cognitive decline and neuropathological features in AβPP-PS1 transgenic mice. Our results show that at 8 months of age AβPPswe-PS1dE9 mice display behavioral and cognitive changes compared to age-matched wild-type mice, as determined in the open field and the (reverse) Morris water maze. However, there were no variations in hippocampal metabolite levels at this age. AβPP-PS1 mice at 12 months of age display more severe behavioral and cognitive impairment, which coincided with alterations in hippocampal metabolite levels that suggest reduced neuronal integrity. Furthermore, correlation analyses suggest a possible role of Aβ in inflammatory processes, synaptic dysfunction and impaired neurogenesis.