Glutamine and GABA alterations in cingulate cortex may underlie alcohol drinking in a rat model of co-occurring alcohol use disorder and schizophrenia: an 1H-MRS study

Alcohol use disorder commonly occurs in patients with schizophrenia and significantly worsens the clinical course of the disorder. The neurobiological underpinnings of alcohol drinking are not well understood. Magnetic resonance spectroscopy (MRS) has been used to assess the neurochemical substrates that may be associated with alcohol drinking in patients; however, the causal impact of these findings remains elusive, highlighting the need for studies in animal models. This study performed MRS in the neonatal ventral hippocampal lesioned (NVHL) rat model, a model of co-occurring schizophrenia and substance use disorders. NVHL lesions (or sham surgeries) were performed on post-natal day 7 and animals were given brief exposure to alcohol during adolescence (10% v/v in a 2-bottle choice design). Animals were re-exposed to alcohol during adulthood (20% v/v) until a stable drinking baseline was established, and then forced into abstinence to control for the effects of differential alcohol drinking. Animals were scanned for MRS after one month of abstinence. NVHL rats consumed significantly more alcohol than sham rats and in the cingulate cortex showed significantly higher levels of GABA and glutamine. Significantly lower GABA levels were observed in the nucleus accumbens. No differences between the NVHL and sham animals were observed in the hippocampus. Correlation analysis revealed that GABA and glutamine concentrations in the cingulate cortex significantly correlated with the rats' alcohol drinking prior to 30 days of forced abstinence. These findings suggest that a potential dysfunction in the glutamate/GABA-glutamine cycle may contribute to alcohol drinking in a rat model of schizophrenia, and this dysfunction could be targeted in future treatment-focused studies.

Early postnatal exposure to intermittent hypoxia in rodents is proinflammatory, impairs white matter integrity, and alters brain metabolism

BackgroundPreterm infants are frequently exposed to intermittent hypoxia (IH) associated with apnea and periodic breathing that may result in inflammation and brain injury that later manifests as cognitive and executive function deficits. We used a rodent model to determine whether early postnatal exposure to IH would result in inflammation and brain injury.MethodsRat pups were exposed to IH from P2 to P12. Control animals were exposed to room air. Cytokines were analyzed in plasma and brain tissue at P13 and P18. At P20-P22, diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) were performed.ResultsPups exposed to IH had increased plasma Gro/CXCL1 and cerebellar IFN-γ and IL-1β at P13, and brainstem enolase at P18. DTI showed a decrease in FA and AD in the corpus callosum (CC) and cingulate gyrus, and an increase in RD in the CC. MRS revealed decreases in NAA/Cho, Cr, Tau/Cr, and Gly/Cr; increases in TCho and GPC in the brainstem; and decreases in NAA/Cho in the hippocampus.ConclusionsWe conclude that early postnatal exposure to IH, similar in magnitude to that experienced in human preterm infants, is associated with evidence for proinflammatory changes, decreases in white matter integrity, and metabolic changes consistent with hypoxia.

Obesity and fatty liver are prevented by inhibition of the aryl hydrocarbon receptor in both female and male mice

Inhibition of the aryl hydrocarbon receptor (AHR) prevents Western diet-induced obesity and fatty liver in C57Bl/6J (B6) male mice. The AHR is a ligand-activated nuclear receptor that regulates genes involved in xenobiotic metabolism and T-cell differentiation. Here, we tested the hypothesis that AHR antagonism would also prevent obesity and fatty liver in female mice and that B6 mice (higher-affinity AHR) and congenic B6.D2 mice (lower-affinity AHR) would differentially respond to AHR inhibition. Female and male adult B6 and B6.D2 mice were fed control and Western diets with and without α-naphthoflavone (NF), an AHR inhibitor. A nonlinear mixed-model analysis was developed to project asymptote body mass. We found that obesity, adiposity, and liver steatosis were reduced to near control levels in all female and male B6 and B6.D2 experimental groups fed Western diet with NF. However, differences were noted in that female B6.D2 vs B6 mice on Western diet became more obese; and in general, female mice compared with male mice had a greater fat mass to body mass ratio, were less responsive to NF, and had reduced liver steatosis and hepatomegaly. We report that male mice fed Western diet containing NF or CH-223191, another AHR inhibitor, caused reduced mRNA levels of several liver genes involved in metabolism, including Cyp1b1 and Scd1, offering evidence for a possible mechanism by which the AHR regulates obesity. In conclusion, although there are some sex- and Ahr allelic-dependent differences, AHR inhibition prevents obesity and liver steatosis in both males and females regardless of the ligand-binding capacity of the AHR. We also present evidence consistent with the notion that an AHR-CYP1B1-SCD1 axis is involved in obesity, providing potentially convenient and effective targets for treatment.

Cell Viability and Noninvasive In Vivo MRI Tracking of 3D Cell Encapsulating Self-Assembled Microcontainers

Several molecular therapies require the implantation of cells that secrete biotherapeutic molecules and imaging the location and microenvironment of the cellular implant to ascertain its function. We demonstrate noninvasive in vivo magnetic resonance imaging (MRI) of self-assembled microcontainers that are capable of cell encapsulation. Negative contrast was obtained to discern the microcontainer with MRI; positive contrast was obtained in the complete absence of background signal. MRI on a clinical scanner highlights the translational nature of this research. The microcontainers were loaded with cells that were dispersed in an extracellular matrix, and implanted both subcutaneously and in human tumor xenografts in SCID mice. MRI was performed on the implants, and microcontainers retrieved postimplantation showed cell viability both within and proximal to the implant. The microcontainers are characterized by their small size, three dimensionality, controlled porosity, ease of parallel fabrication, chemical and mechanical stability, and noninvasive traceability in vivo.

High-Resolution Diffusion Tensor Spinal Cord MRI Measures as Biomarkers of Disability Progression in a Rodent Model of Progressive Multiple Sclerosis

Disease in the spinal cord is a major component of disability in multiple sclerosis, yet current techniques of imaging spinal cord injury are insensitive and nonspecific. This study seeks to remove this major impediment to research in multiple sclerosis and other spinal cord diseases by identifying reliable biomarkers of disability progression using diffusion tensor imaging (DTI), a magnetic resonance imaging technique, to evaluate the spinal cord in a model of multiple sclerosis, i.e. the Theiler’s Murine Encephalitis Virus-Induced Demyelinating Disease (TMEV-IDD). Mice with TMEV-IDD with varying levels of clinical disease were imaged using a 9.4T small animal MRI scanner. Axial diffusivity, radial diffusivity, and fractional anisotropy were calculated. Disability was assessed periodically using Rotarod assay and data were expressed as a neurological function index. Correlation was performed between DTI measurements and disability scores. TMEV-IDD mice displayed significant increased neurological deficits over time when compared with controls (p<0.0001). Concurrently, the values of fractional anisotropy and axial diffusivity were both decreased compared to controls (both p<0.0001), while radial diffusivity was increased (p<0.0001). Overall, fractional anisotropy changes were larger in white matter than in grey matter and differences were more pronounced in the ventral region. Lower disability scores were associated with decreased fractional anisotropy values measured in the ventral (r = 0.68; p<0.0001) and ventral-lateral (r = 0.70; p<0.0001) regions of the white matter. These data demonstrate that DTI measures of the spinal cord contribute to strengthening the association between neuroradiological markers and clinical disability, and support the use of DTI measures in spinal cord imaging in MS patients.

Abstract 2052: Efficient thermoregulation of heat-induced enzyme-prodrug therapy using recombinant E. coli containing a modified λpR promoter

Introduction: The λpR-cI857 transcriptional promoter cassette drives heat-induced protein expression in recombinant E. coli by inhibiting transcription below 37 °C (1). We have earlier reported on the development of magnetic nanoparticle hyperthermia (MNP) induced enzyme-prodrug therapy based on recombinant E. coli cells. The E. coli are designed to express cytosine deaminase (CD) under the transcriptional control of the λpR-cI857 promoter (2). CD converts non-toxic 5-fluorocytosine (5-FC) to the toxic 5-fluorouracil (5-FU). E. coli cells were co-encapsulated with MNP in immunoisolative alginate microcapsules and heated to 43 °C using an external alternating magnetic field (AMF). Using in vitro MTT assays, we demonstrated that the cytotoxicity of the heat activated E. coli in the presence of 5-FC, against 9L, MCF-7 and PC-3 tumor cells, was comparable to direct 5-FU treatment (2). However, we observed significant cytotoxicity at 37 °C resulting from basal CD expression. We now report on an improved strain of E. coli cells using a modified λpR promoter to minimize CD expression at 37 °C.

Methods: A single base mutation was introduced in the λpR promoter during PCR amplification (1) from the pLDR20 vector. The modified promoter was ligated to the linearized pNEB206A vector and transformed into NEB-α cells using the USER™ cloning protocol (www.neb.com). NM522 cells containing the modified λpR-cI857 cassette and the CD gene were constructed and characterized following procedures established in our laboratory (2). The E. coli were then encapsulated in alginate microcapsules and heated at 43 °C to trigger CD expression. Cytotoxicity against CT26 colon cancer cells was evaluated using a MTT assay following the incubation of the cancer cells with the heated microcapsules and 5-FC (0.1 mM, 72 h, 37 °C).

Results summary: We observed thermoselective CD expression and catalytic activity in E. coli heated at 43 °C. MTT cell viability assay shows that the cytotoxicity of the encapsulated, heat-activated E. coli cells against CT26 colon cancer cells was comparable to direct treatment with 5-FU. Importantly, the basal cytotoxicity at 37 °C was significantly lower than the E. coli cells activated at 43 ºC. We are extending our work to express CD periplasmically in endotoxin free hosts for improved catalytic efficiency and to eliminate cytotoxicity arising from bacterial lipopolysaccharides. We expect that the improved E. coli cells should facilitate de novo synthesis of 5-FU, on-demand and locally in the tumor, thereby reducing systemic toxicity and increasing therapeutic gain.

Acknowledgement: This work is supported by a pilot grant from the Hitchcock Foundation.

References:

(1) Jechlinger et al, FEMS Microbiol Lett. 1999;173(2):347-52

(2) Nemani et al, J Biotechnol. 2015, 203:32-40.

Citation Format: Venkata K. Nemani, Barjor Gimi. Efficient thermoregulation of heat-induced enzyme-prodrug therapy using recombinant E. coli containing a modified λpR promoter. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2052.

Multi-site study of diffusion metric variability: effects of site, vendor, field strength, and echo time on regions-of-interest and histogram-bin analyses

It is now common for magnetic-resonance-imaging (MRI) based multi-site trials to include diffusion-weighted imaging (DWI) as part of the protocol. It is also common for these sites to possess MR scanners of different manufacturers, different software and hardware, and different software licenses. These differences mean that scanners may not be able to acquire data with the same number of gradient amplitude values and number of available gradient directions. Variability can also occur in achievable b-values and minimum echo times. The challenge of a multi-site study then, is to create a common protocol by understanding and then minimizing the effects of scanner variability and identifying reliable and accurate diffusion metrics. This study describes the effect of site, scanner vendor, field strength, and TE on two diffusion metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA) using two common analyses (region-of-interest and mean-bin value of whole brain histograms). The goal of the study was to identify sources of variability in diffusion-sensitized imaging and their influence on commonly reported metrics. The results demonstrate that the site, vendor, field strength, and echo time all contribute to variability in FA and MD, though to different extent. We conclude that characterization of the variability of DTI metrics due to site, vendor, field strength, and echo time is a worthwhile step in the construction of multi-center trials.

Multi-site Study of Diffusion Metric Variability: Characterizing the Effects of Site, Vendor, Field Strength, and Echo Time using the Histogram Distance

MRI-based multi-site trials now routinely include some form of diffusion-weighted imaging (DWI) in their protocol. These studies can include data originating from scanners built by different vendors, each with their own set of unique protocol restrictions, including restrictions on the number of available gradient directions, whether an externally-generated list of gradient directions can be used, and restrictions on the echo time (TE). One challenge of multi-site studies is to create a common imaging protocol that will result in a reliable and accurate set of diffusion metrics. The present study describes the effect of site, scanner vendor, field strength, and TE on two common metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA). We have shown in earlier work that ROI metrics and the mean of MD and FA histograms are not sufficiently sensitive for use in site characterization. Here we use the distance between whole brain histograms of FA and MD to investigate within- and between-site effects. We concluded that the variability of DTI metrics due to site, vendor, field strength, and echo time could influence the results in multi-center trials and that histogram distance is sensitive metrics for each of these variables.

Magnetic nanoparticle hyperthermia induced cytosine deaminase expression in microencapsulated E. coli for enzyme-prodrug therapy

Engineered bacterial cells that are designed to express therapeutic enzymes under the transcriptional control of remotely inducible promoters can mediate the de novo conversion of non-toxic prodrugs to their cytotoxic forms. In situ cellular expression of enzymes provides increased stability and control of enzyme activity as compared to isolated enzymes. We have engineered Escherichia coli (E. coli), designed to express cytosine deaminase at elevated temperatures, under the transcriptional control of thermo-regulatory λpL-cI857 promoter cassette which provides a thermal switch to trigger enzyme synthesis. Enhanced cytosine deaminase expression was observed in cultures incubated at 42°C as compared to 30°C, and enzyme expression was further substantiated by spectrophotometric assays indicating enhanced conversion of 5-fluorocytosine to 5-fluorouracil. The engineered cells were subsequently co-encapsulated with magnetic iron oxide nanoparticles in immunoprotective alginate microcapsules, and cytosine deaminase expression was triggered remotely by alternating magnetic field-induced hyperthermia. The combination of 5-fluorocytosine with AMF-activated microcapsules demonstrated tumor cell cytotoxicity comparable to direct treatment with 5-fluorouracil chemotherapy. Such enzyme-prodrug therapy, based on engineered and immunoisolated E. coli, may ultimately yield an improved therapeutic index relative to monotherapy, as AMF mediated hyperthermia might be expected to pre-sensitize tumors to chemotherapy under appropriate conditions.

Imaging tooth enamel using zero echo time (ZTE) magnetic resonance imaging

In an event where many thousands of people may have been exposed to levels of radiation that are sufficient to cause the acute radiation syndrome, we need technology that can estimate the absorbed dose on an individual basis for triage and meaningful medical decision making. Such dose estimates may be achieved using in vivo electron paramagnetic resonance (EPR) tooth biodosimetry, which measures the number of persistent free radicals that are generated in tooth enamel following irradiation. However, the accuracy of dose estimates may be impacted by individual variations in teeth, especially the amount and distribution of enamel in the inhomogeneous sensitive volume of the resonator used to detect the radicals. In order to study the relationship between interpersonal variations in enamel and EPR-based dose estimates, it is desirable to estimate these parameters nondestructively and without adding radiation to the teeth. Magnetic Resonance Imaging (MRI) is capable of acquiring structural and biochemical information without imparting additional radiation, which may be beneficial for many EPR dosimetry studies. However, the extremely short T2 relaxation time in tooth structures precludes tooth imaging using conventional MRI methods. Therefore, we used zero echo time (ZTE) MRI to image teeth ex vivo to assess enamel volumes and spatial distributions. Using these data in combination with the data on the distribution of the transverse radio frequency magnetic field from electromagnetic simulations, we then can identify possible sources of variations in radiation-induced signals detectable by EPR. Unlike conventional MRI, ZTE applies spatial encoding gradients during the RF excitation pulse, thereby facilitating signal acquisition almost immediately after excitation, minimizing signal loss from short T2 relaxation times. ZTE successfully provided volumetric measures of tooth enamel that may be related to variations that impact EPR dosimetry and facilitate the development of analytical procedures for individual dose estimates.

Toward Localized In Vivo Biomarker Concentration Measurements

We know a great deal about the biochemistry of cells because they can be isolated and studied. The biochemistry of the much more complex in vivo environment is more difficult to study because the only ways to quantitate concentrations is to sacrifice the animal or biopsy the tissue. Either method disrupts the environment profoundly and neither method allows longitudinal studies on the same individual. Methods of measuring chemical concentrations in vivo are very valuable alternatives to sacrificing groups of animals. We are developing microscopic magnetic nanoparticle (mNP) probes to measure the concentration of a selected molecule in vivo. The mNPs are targeted to bind the selected molecule and the resulting reduction in rotational freedom can be quantified remotely using magnetic spectroscopy. The mNPs must be contained in micrometer sized porous shells to keep them from migrating and to protect them from clearance by the immune system. There are two key issues in the development of the probes. First, we demonstrate the ability to measure concentrations in the porous walled alginate probes both in phosphate buffered saline and in blood, which is an excellent surrogate for the complex and challenging in vivo environment. Second, sensitivity is critical because it allows microscopic probes to measure very small concentrations very far away. We report sensitivity measurements on recently introduced technology that has allowed us to improve the sensitivity by two orders of magnitude, a factor of 200 so far.

Toward Localized In Vivo Biomarker Concentration Measurements

We know a great deal about the biochemistry of cells because they can be isolated and studied. The biochemistry of the much more complex in vivo environment is more difficult to study because the only ways to quantitate concentrations is to sacrifice the animal or biopsy the tissue. Either method disrupts the environment profoundly and neither method allows longitudinal studies on the same individual. Methods of measuring chemical concentrations in vivo are very valuable alternatives to sacrificing groups of animals. We are developing microscopic magnetic nanoparticle (mNP) probes to measure the concentration of a selected molecule in vivo. The mNPs are targeted to bind the selected molecule and the resulting reduction in rotational freedom can be quantified remotely using magnetic spectroscopy. The mNPs must be contained in micrometer sized porous shells to keep them from migrating and to protect them from clearance by the immune system. There are two key issues in the development of the probes. First, we demonstrate the ability to measure concentrations in the porous walled alginate probes both in phosphate buffered saline and in blood, which is an excellent surrogate for the complex and challenging in vivo environment. Second, sensitivity is critical because it allows microscopic probes to measure very small concentrations very far away. We report sensitivity measurements on recently introduced technology that has allowed us to improve the sensitivity by two orders of magnitude, a factor of 200 so far.

Diffusion-weighted and macromolecular contrast enhanced MRI of tumor response to antivascular therapy with ZD6126

The effects of the anti-vascular agent ZD6126 were studied in volume matched subcutaneous DU-145 human prostate cancer xenografts in SCID mice using two different MRI techniques, diffusion and vascular imaging. Diffusion weighted MRI was performed before and at 24 h, 48 h and 72 h following a single dose of 200 mg/kg. Tumor vascular volume and permeability surface area product (PSP) were determined 24 h post antivascular therapy following an identical dose using dynamic contrast enhanced MRI of the macromolecular contrast agent albumin-gadolinium diethylenetriaminepentaacetate (albumin-GdDTPA). Consistent with the mechanism of action of ZD6126, significantly lower vascular volume was detected at 24 h whereas diffusion changes were evident at 48 h. Diffusion MRI findings correlated well with histological determination of the necrotic fraction in the tumors by 48 h. Both diffusion and vascular imaging are useful noninvasive techniques to detect response of tumors to antivascular therapy with ZD6126 in the DU-145 human prostate cancer xenograft model.

Dynamic bioluminescence and fluorescence imaging of the effects of the antivascular agent Combretastatin-A4P (CA4P) on brain tumor xenografts

Combretastatin A-4 (CA4) is a natural product isolated from Combretum caffrum that inhibits tubulin polymerization by binding to the colchicine-binding site. A corresponding water soluble pro-drug (referred to as CA4P), has undergone extensive clinical trials and has been evaluated in pre-clinical studies using multiple modalities. We previously reported a novel assay based on dynamic bioluminescent imaging to assess tumor vascular disruption and now present its application to assessing multiple tumors simultaneously. The current study evaluated the vascular-disrupting activity of CA4P on subcutaneous 9L rat brain tumor xenografts in mice using dynamic bioluminescence imaging. A single dose of CA4P (120 mg/kg, intraperitoneally) induced rapid, temporary tumor vascular shutdown revealed by a rapid and reproducible decrease of light emission from luciferase-expressing 9L tumors following administration of luciferin as a substrate. A time-dependent reduction of tumor perfusion after CA4P treatment was confirmed by immunohistological assessment of the perfusion marker Hoechst 33342 and the tumor vasculature marker CD31. The vasculature showed distinct recovery within 24 h post therapy. Multiple tumors behaved similarly, although a size dependent vascular inhibition was observed. In conclusion, CA4P caused rapid, temporary tumor vascular shutdown and led to reduction of tumor perfusion in rat brain tumor xenografts and the multiple tumor approach should lead to more efficient studies requiring fewer animals and greater consistency.

Monitoring oxygen levels in orthotopic human glioma xenograft following carbogen inhalation and chemotherapy by implantable resonator-based oximetry

Hypoxia is a critical hallmark of glioma, and significantly compromises treatment efficacy. Unfortunately, techniques for monitoring glioma pO2 to facilitate translational research are lacking. Furthermore, poor prognosis of patients with malignant glioma, in particular glioblastoma multiforme, warrant effective strategies that can inhibit hypoxia and improve treatment outcome. EPR oximetry using implantable resonators was implemented for monitoring pO2 in normal cerebral tissue and U251 glioma in mice. Breathing carbogen (95% O2 + 5% CO2 ) was tested for hyperoxia in the normal brain and glioma xenografts. A new strategy to inhibit glioma growth by rationally combining gemcitabine and MK-8776, a cell cycle checkpoint inhibitor, was also investigated. The mean pO2 of left and right hemisphere were ∼56-69 mmHg in the normal cerebral tissue of mice. The mean baseline pO2 of U251 glioma on the first and fifth day of measurement was 21.9 ± 3.7 and 14.1 ± 2.4 mmHg, respectively. The mean brain pO2 including glioma increased by at least 100% on carbogen inhalation, although the response varied between the animals over days. Treatment with gemcitabine + MK-8776 significantly increased pO2 and inhibited glioma growth assessed by MRI. In conclusion, EPR oximetry with implantable resonators can be used to monitor the efficacy of carbogen inhalation and chemotherapy on orthotopic glioma in mice. The increase in glioma pO2 of mice breathing carbogen can be used to improve treatment outcome. The treatment with gemcitabine + MK-8776 is a promising strategy that warrants further investigation.

Molecular sensing with magnetic nanoparticles using magnetic spectroscopy of nanoparticle Brownian motion

Functionalized magnetic nanoparticles (mNPs) have shown promise in biosensing and other biomedical applications. Here we use functionalized mNPs to develop a highly sensitive, versatile sensing strategy required in practical biological assays and potentially in vivo analysis. We demonstrate a new sensing scheme based on magnetic spectroscopy of nanoparticle Brownian motion (MSB) to quantitatively detect molecular targets. MSB uses the harmonics of oscillating mNPs as a metric for the freedom of rotational motion, thus reflecting the bound state of the mNP. The harmonics can be detected in vivo from nanogram quantities of iron within 5s. Using a streptavidin-biotin binding system, we show that the detection limit of the current MSB technique is lower than 150 pM (0.075 pmole), which is much more sensitive than previously reported techniques based on mNP detection. Using mNPs conjugated with two anti-thrombin DNA aptamers, we show that thrombin can be detected with high sensitivity (4 nM or 2 pmole). A DNA-DNA interaction was also investigated. The results demonstrated that sequence selective DNA detection can be achieved with 100 pM (0.05 pmole) sensitivity. The results of using MSB to sense these interactions, show that the MSB based sensing technique can achieve rapid measurement (within 10s), and is suitable for detecting and quantifying a wide range of biomarkers or analytes. It has the potential to be applied in variety of biomedical applications or diagnostic analyses.

In vitro and in vivo evaluation of SU-8 biocompatibility

SU-8 negative photoresist is a high tensile strength polymer that has been used for a number of biomedical applications that include cell encapsulation and neuronal probes. Chemically, SU-8 comprises, among other components, an epoxy based monomer and antimony salts, the latter being a potential source of cytotoxicity. We report on the in vitro and in vivo evaluation of SU-8 biocompatibility based on leachates from various solvents, at varying temperatures and pH, and upon subcutaneous implantation of SU-8 substrates in mice. MTT cell viability assay did not exhibit any cytotoxic effects from the leachates. The hemolytic activity of SU-8 is comparable to that of FDA approved implant materials such as silicone elastomer, Buna-S and medical steel. In vivo histocompatibility study in mice indicates a muted immune response to subcutaneous SU-8 implants.

Applications of Semiconductor Fabrication Methods to Nanomedicine: A Review of Recent Inventions and Techniques

We live in a world of convergence where scientific techniques from a variety of seemingly disparate fields are being applied cohesively to the study and solution of biomedical problems. For instance, the semiconductor processing field has been primarily developed to cater to the needs of the ever decreasing transistor size and cost while increasing functionality of electronic circuits. In recent years, pioneers in this field have equipped themselves with a powerful understanding of how the same techniques can be applied in the biomedical field to develop new and efficient systems for the diagnosis, analysis and treatment of various conditions in the human body. In this paper, we review the major inventions and experimental methods which have been developed for nano/micro fluidic channels, nanoparticles fabricated by top-down methods, and in-vivo nanoporous microcages for effective drug delivery. This paper focuses on the information contained in patents as well as the corresponding technical publications. The goal of the paper is to help emerging scientists understand and improvise over these inventions.

Abstract 3300: Heat-induced expression of cytosine deaminase for enzyme-prodrug therapy

Introduction: Bacterial cytosine deaminase (CD) mediates the de novo conversion of the non-toxic prodrug, 5-fluorocytosine (5-FC) to its cytotoxic form, 5-fluorouracil (5-FU). Enzyme localization at the tumor site reduces systemic toxicity while increasing local drug availability. The in situ cellular expression of enzymes provides greater stability and control of enzyme activity as compared to isolated enzymes, and their on-demand expression can be achieved through transcriptional factors activated by stimuli such as heat. Bacterial λ PR promoter in conjunction with the cI857 repressor gene imparts thermoselectivity to enzyme expression - cloned vectors containing CD gene under the transcriptional control of this expression system preferentially produce CD at elevated temperatures, providing a thermal switch to trigger enzyme synthesis. Such enzyme-prodrug therapy, when timed to perform as an adjuvant to other treatment modalities such as magnetic nanoparticle hyperthermia, has the potential to enhance therapeutic index as a combination therapy.

Methods: CD gene was PCR amplified from pbCD540FT vector and cloned into pLDR20 vector. The CD gene was placed under the transcriptional control of λ PR promoter and cI857 thermosensitive repressor cassette. The cloned vector was transformed into NM522 competent cells. Positive colonies selected from LB-Agar-Ampicillin plates were cultured in LB-Ampicillin medium. CD gene was characterized by PCR amplification and cycle sequencing of the isolated plasmid DNA. Protein expression in cells grown at 30 °C and 42 °C was analyzed by SDS-PAGE followed by Coomassie blue staining. Enzyme activity in cells grown at 30 °C and 42 °C was compared by incubating engineered cells with 5-FC and spectrophotometrically measuring its conversion to 5-FU.

Results summary: The presence of CD gene in competent cells was verified by PCR amplification and cycle sequencing. We observed an enhanced expression of CD gene in the transformed cells at 42 °C as compared to 30 °C, from SDS-PAGE. Spectrophotometric analysis of enzyme activity showed an enhancement in cells grown at 42 °C. We are extending our work to combine enzyme-prodrug therapy with magnetic nanoparticle hyperthermia. We will coencapsulate our engineered cells with magnetic iron oxide nanoparticles (IONP) in immunoisolative sodium alginate microspheres. Localized heating during IONP hyperthermia can be a source of thermal stress for triggering enzyme expression resulting in the in situ synthesis of 5-FU. This combined therapy should enhance therapeutic index as compared to each of the therapies alone.

Acknowledgement: pbCD540FT was a kind gift from Prof. J. M. Brown, Stanford University School of Medicine. This work is supported by the Dartmouth Center of Cancer Nanotechnology Excellence pilot project grant, NIH U54 CA151662 (BG, NVK).

Citation Format: Venkata K. Nemani, Riley E. Ennis, Karl E. Griswold, Barjor Gimi. Heat-induced expression of cytosine deaminase for enzyme-prodrug therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3300. doi:10.1158/1538-7445.AM2013-3300

Common pediatric cerebellar tumors: correlation between cell densities and apparent diffusion coefficient metrics

PURPOSE

To test whether there is correlation between cell densities and apparent diffusion coefficient (ADC) metrics of common pediatric cerebellar tumors.

MATERIALS AND METHODS

This study was reviewed for issues of patient safety and confidentiality and was approved by the Institutional Review Board of the University of Texas Southwestern Medical Center and was compliant with HIPAA. The need for informed consent was waived. Ninety-five patients who had preoperative magnetic resonance imaging and surgical pathologic findings available between January 2003 and June 2011 were included. There were 37 pilocytic astrocytomas, 34 medulloblastomas (23 classic, eight desmoplastic-nodular, two large cell, one anaplastic), 17 ependymomas (13 World Health Organization [WHO] grade II, four WHO grade III), and seven atypical teratoid rhabdoid tumors. ADCs of solid tumor components and normal cerebellum were measured. Tumor-to-normal brain ADC ratios (hereafter, ADC ratio) were calculated. The medulloblastomas and ependymomas were subcategorized according to the latest WHO classification, and tumor cellularity was calculated. Correlation was sought between cell densities and mean tumor ADCs, minimum tumor ADCs, and ADC ratio.

RESULTS

When all tumors were considered together, negative correlation was found between cellularity and mean tumor ADCs (ρ = -0.737, P < .05) and minimum tumor ADCs (ρ = -0.736, P < .05) of common pediatric cerebellar tumors. There was no correlation between cellularity and ADC ratio. Negative correlation was found between cellularity and minimum tumor ADC in atypical teratoid rhabdoid tumors (ρ = -0.786, P < .05). In atypical teratoid rhabdoid tumors, no correlation was found between cellularity and mean tumor ADC and ADC ratio. There was no correlation between the ADC metrics and cellularity of the pilocytic astrocytomas, medulloblastomas, and ependymomas.

CONCLUSION

Negative correlation was found between cellularity and ADC metrics of common pediatric cerebellar tumors. Although ADC metrics are useful in the preoperative diagnosis of common pediatric cerebellar tumors and this utility is generally attributed to differences in cellularity of tumors, tumor cellularity may not be the sole determinant of the differences in diffusivity.

Imaging and modification of the tumor vascular barrier for improvement in magnetic nanoparticle uptake and hyperthermia treatment efficacy

The predicted success of nanoparticle based cancer therapy is due in part to the presence of the inherent leakiness of the tumor vascular barrier, the so called enhanced permeability and retention (EPR) effect. Although the EPR effect is present in varying degrees in many tumors, it has not resulted in the consistent level of nanoparticle-tumor uptake enhancement that was initially predicted. Magnetic/iron oxide nanoparticles (mNPs) have many positive qualities, including their inert/nontoxic nature, the ability to be produced in various sizes, the ability to be activated by a deeply penetrating and nontoxic magnetic field resulting in cell-specific cytotoxic heating, and the ability to be successfully coated with a wide variety of functional coatings. However, at this time, the delivery of adequate numbers of nanoparticles to the tumor site via systemic administration remains challenging. Ionizing radiation, cisplatinum chemotherapy, external static magnetic fields and vascular disrupting agents are being used to modify the tumor environment/vasculature barrier to improve mNP uptake in tumors and subsequently tumor treatment. Preliminary studies suggest use of these modalities, individually, can result in mNP uptake improvements in the 3-10 fold range. Ongoing studies show promise of even greater tumor uptake enhancement when these methods are combined. The level and location of mNP/Fe in blood and normal/tumor tissue is assessed via histopathological methods (confocal, light and electron microscopy, histochemical iron staining, fluorescent labeling, TEM) and ICP-MS. In order to accurately plan and assess mNP-based therapies in clinical patients, a noninvasive and quantitative imaging technique for the assessment of mNP uptake and biodistribution will be necessary. To address this issue, we examined the use of computed tomography (CT), magnetic resonance imaging (MRI), and Sweep Imaging With Fourier Transformation (SWIFT), an MRI technique which provides a positive iron contrast enhancement and a reduced signal to noise ratio, for effective observation and quantification of Fe/mNP concentrations in the clinical setting.

Advances in alginate gel microencapsulation of therapeutic cells

Rapid developments in the therapeutic applications of genetically engineered cells and stem cell research have increased the possibilities of addressing some pathologies by grafting therapeutic cells. Immunoprotective encapsulation of such therapeutic cells is often essential for their survival and function. Hydrogels provide a bioteolerable matrix for cellular encapsulation and support subsequent graft survival and function. The naturally occurring marine polysaccharide, alginate, is the hydrogel of choice for most applications. However, long-term graft survival is affected by the mechanical instability of alginate and adverse immune reaction to its grafting. So, a variety of modifications have been developed to enhance the physicochemical properties and biotolerance of alginate hydrogels. We highlight the developments in alginate hydrogel microencapsulation of therapeutic cells.

The diaphragms of fenestrated endothelia: gatekeepers of vascular permeability and blood composition

Fenestral and stomatal diaphragms are endothelial subcellular structures of unknown function that form on organelles implicated in vascular permeability: fenestrae, transendothelial channels, and caveolae. PV1 protein is required for diaphragm formation in vitro. Here, we report that deletion of the PV1-encoding Plvap gene in mice results in the absence of diaphragms and decreased survival. Loss of diaphragms did not affect the fenestrae and transendothelial channels formation but disrupted the barrier function of fenestrated capillaries, causing a major leak of plasma proteins. This disruption results in early death of animals due to severe noninflammatory protein-losing enteropathy. Deletion of PV1 in endothelium, but not in the hematopoietic compartment, recapitulates the phenotype of global PV1 deletion, whereas endothelial reconstitution of PV1 rescues the phenotype. Taken together, these data provide genetic evidence for the critical role of the diaphragms in fenestrated capillaries in the maintenance of blood composition.

Utility of apparent diffusion coefficient ratios in distinguishing common pediatric cerebellar tumors

RATIONALE AND OBJECTIVES

The aim of this study was to identify clinically useful tumor/normal brain apparent diffusion coefficient (ADC) ratios for distinguishing common pediatric cerebellar tumors.

MATERIALS AND METHODS

Review of medical records revealed 79 patients with cerebellar tumors who underwent preoperative magnetic resonance imaging, including diffusion-weighted imaging sequences, and surgery. There were 31 pilocytic astrocytomas, 27 medulloblastomas, 14 ependymomas, and seven atypical teratoid/rhabdoid tumors. ADC values were measured by placing regions of interest on the solid tumor and normal brain parenchyma by two reviewers. Tumor/normal brain ADC ratios were calculated.

RESULTS

Mean ADC values of the pilocytic astrocytomas were greater than those of ependymomas, whose mean ADC values were greater than those of medulloblastomas and atypical teratoid/rhabdoid tumors. Using a tumor/normal brain ADC ratio threshold of 1.70 to distinguish pilocytic astrocytomas from ependymomas, sensitivity of 92% and specificity of 79% were achieved. A tumor/normal brain ADC ratio threshold of 1.20 enabled the sorting of ependymomas from medulloblastomas with sensitivity of 93% and specificity of 88%.

CONCLUSIONS

Tumor/normal brain ADC ratios allow the distinguishing of common pediatric cerebellar tumors.

Abstract 5632: Immunoprotected, microencapsulated bacterial cytosine deaminase mediated conversion of 5-fluorocytosine to 5-fluorouracil

Introduction Enzymes of non-human origin possess tremendous potential as anticancer agents, especially in enzyme-prodrug therapy. Unfortunately, these enzymes are recognized as foreign agents by the human immune system and are targeted by an immune response. This immune reaction limits enzymes’ efficacy, particularly in treatments requiring repeated dosing. Current strategies for deimmunizing these therapeutic enzymes are labor/time intensive and yield limited success. Encapsulating enzymes in a hydrogel, such as sodium alginate, can confer immunoprotection and enhance in vivo stability. Alginate serves as a barrier between enzyme and host and its porosity can be controlled to prevent antibody infiltration while allowing the diffusion of the prodrug and the drug. The bacterial enzyme cytosine deaminase (bCD) mediates the conversion of 5-fluorocytosine (5-FC) to the anticancer drug 5-fluorouracil (5-FU). We encapsulated the bCD in sodium alginate microbeads and tested enzyme efficacy post encapsulation as determined by conversion of 5-FC to 5-FU, with concomitant cell kill assays. Methods bCD was encapsulated in sodium alginate microbeads, ∼200 microns, using a NISCO microencapsulation system (www.nisco.ch). The beads were incubated with 5-FC (25, 50, 100 and 200 microM), and conversion to 5-FU was monitored over time using spectrophotometry. Unencapsulated bCD was used as controls. Then, microbeads were incubated with 9L rat glioma cells in the presence of 5-FC. Cytotoxicity of the enzyme-prodrug system to 9L cells was evaluated using an MTT assay. 5-FC alone in the absence of bCD and 5-FU were used as controls. Experiments were repeated using beads stored for 72 h at 4°C and 37°C and temperature effects on the stability of encapsulated bCD were noted. Results summary We observed the complete conversion of 5-FC to 5-FU for all concentrations of encapsulated enzyme, albeit at a slower rate than unencapsulated controls. Cytotoxicity of the encapsulated enzyme-prodrug system toward 9L cells was similar to that of 5-FU alone, and of unencapsulated controls, indicating that encapsulation had no deleterious effect on enzyme efficacy. Though the enzyme kinetics were slower for the stored beads (at 4°C and 37°C), these beads resulted in similar cell kill. Our results suggest that sodium alginate microencapsulation of bCD maintained the enzyme's functionality and may therefore be a suitable platform for immunoisolative enzyme-prodrug therapy. We are extending our work to other cancer cell lines and to in vivo study of the anti-tumor effects of these encapsulated enzymes. This system has the advantage of localized 5-FC to 5-FU conversion, thereby potentially reducing systemic toxicity and increasing the locally available dose of the toxic drug. The strategy can be extended to the encapsulation of enzyme-producing cells that serve as de novo drug factories.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5632. doi:1538-7445.AM2012-5632

In Vivo Imaging and Quantification of Iron Oxide Nanoparticle Uptake and Biodistribution

Recent advances in nanotechnology have allowed for the effective use of iron oxide nanoparticles (IONPs) for cancer imaging and therapy. When activated by an alternating magnetic field (AMF), intra-tumoral IONPs have been effective at controlling tumor growth in rodent models. To accurately plan and assess IONP-based therapies in clinical patients, noninvasive and quantitative imaging technique for the assessment of IONP uptake and biodistribution will be necessary. Proven techniques such as confocal, light and electron microscopy, histochemical iron staining, ICP-MS, fluorescent labeled mNPs and magnetic spectroscopy of Brownian motion (MSB), are being used to assess and quantify IONPs in vitro and in ex vivo tissues. However, a proven noninvasive in vivo IONP imaging technique has not yet been developed. In this study we have demonstrated the shortcomings of computed tomography (CT) and magnetic resonance imaging (MRI) for effectively observing and quantifying iron/IONP concentrations in the clinical setting. Despite the poor outcomes of CT and standard MR sequences in the therapeutic concentration range, ultra-short T2 MRI methods such as, Sweep Imaging With Fourier Transformation (SWIFT), provide a positive iron contrast enhancement and a reduced signal to noise ratio. Ongoing software development and phantom and in vivo studies, will further optimize this technique, providing accurate, clinically-relevant IONP biodistribution information.

Biofriendly bonding processes for nanoporous implantable SU-8 microcapsules for encapsulated cell therapy

Mechanically robust, cell encapsulating microdevices fabricated using photolithographic methods can lead to more efficient immunoisolation in comparison to cell encapsulating hydrogels. There is a need to develop adhesive bonding methods which can seal such microdevices under physiologically friendly conditions. We report the bonding of SU-8 based substrates through (i) magnetic self assembly, (ii) using medical grade photocured adhesive and (iii) moisture and photochemical cured polymerization. Magnetic self-assembly, carried out in biofriendly aqueous buffers, provides weak bonding not suitable for long term applications. Moisture cured bonding of covalently modified SU-8 substrates, based on silanol condensation, resulted in weak and inconsistent bonding. Photocured bonding using a medical grade adhesive and of acrylate modified substrates provided stable bonding. Of the methods evaluated, photocured adhesion provided the strongest and most stable adhesion.

Encapsulated cell grafts to treat cellular deficiencies and dysfunction

Cell transplantation provides a therapeutic alternative to whole organ transplantation in the management of diseases arising from the absence or failure of specialized cells. Though allogenic transplantation is favorable in terms of graft acceptance, xenotransplantation can provide a potentially unlimited source of cells and can overcome shortage of human donors. Effective immunoisolation of the xenografts is critical for their long term survival and function. Encapsulation of cells in polymeric matrices, organic or inorganic, provides a physical selectively permeable barrier between the host and the graft, thereby immunoisolating the graft. Microencapsulation of cells in alginate hydrogels has been pervasive, but this approach does not provide precise control over porosity, whereas micro- and nano-fabrication technologies can provide precise and reproducible control over porosity. We highlight both encapsulation approaches in this review, with their relative advantages and challenges. We also highlight the therapeutic potential of encapsulated cells for treating a variety of diseases, detailing the xenotransplantation of pancreatic islets in diabetes therapy as well as the grafting of engineered cells that facilitate localized enzyme-prodrug therapy of pancreatic cancer.

Making a case: nanofabrication techniques in encapsulated cell therapy for people with diabetes

A nanoporous immunoisolative case/capsule that encases/encapsulates insulin-secreting cells vastly expands the source of therapeutic cells available for grafting in people with diabetes, including cells from animal sources, stem cells, and genetically engineered cells. These encapsulated cellular grafts potentially provide an endogenous, renewable, and long-term source of insulin without the need for pharmacological immunosuppression. Micro- and nanofabrication techniques used principally in the semiconductor industry can play a positive role in encapsulated cell therapy. Many of these techniques do not have direct applicability in cell encapsulation, but can be leveraged to develop processes suitable for this application. This commentary highlights the salient features of an effective cell encapsulation system, enumerates limitations of existing encapsulation schemes, and touches upon progress in key areas of encapsulation technology; one example of how micro- and nanofabrication technology may be used to develop a more effective platform for cell encapsulation is presented. This commentary urges further exploration and expansion of techniques used traditionally in electronics and optics for cell-based therapy in people with diabetes.

Choline kinase overexpression increases invasiveness and drug resistance of human breast cancer cells

A direct correlation exists between increased choline kinase (Chk) expression, and the resulting increase of phosphocholine levels, and histological tumor grade. To better understand the function of Chk and choline phospholipid metabolism in breast cancer we have stably overexpressed one of the two isoforms of Chk-alpha known to be upregulated in malignant cells, in non-invasive MCF-7 human breast cancer cells. Dynamic tracking of cell invasion and cell metabolism were studied with a magnetic resonance (MR) compatible cell perfusion assay. The MR based invasion assay demonstrated that MCF-7 cells overexpressing Chk-alpha (MCF-7-Chk) exhibited an increase of invasion relative to control MCF-7 cells (0.84 vs 0.3). Proton MR spectroscopy studies showed significantly higher phosphocholine and elevated triglyceride signals in Chk overexpressing clones compared to control cells. A test of drug resistance in MCF-7-Chk cells revealed that these cells had an increased resistance to 5-fluorouracil and higher expression of thymidylate synthase compared to control MCF-7 cells. To further characterize increased drug resistance in these cells, we performed rhodamine-123 efflux studies to evaluate drug efflux pumps. MCF-7-Chk cells effluxed twice as much rhodamine-123 compared to MCF-7 cells. Chk-alpha overexpression resulted in MCF-7 human breast cancer cells acquiring an increasingly aggressive phenotype, supporting the role of Chk-alpha in mediating invasion and drug resistance, and the use of phosphocholine as a biomarker of aggressive breast cancers.

Abstract 5227: Dynamic bioluminescent imaging and fluorescent imaging evaluation of vascular targeting agents combretastatin-A4P on brain tumor xenografts

Bioluminescent imaging (BLI) is an inexpensive, high-throughput approach to assess tumor growth in small animals. Recent experiments show that vascular targeting agents, which disrupt the blood supply rapidly, cause reduction and delay in emitted light as assessed by the kinetics of BLI signal intensity in breast tumor.

We transfected 9L rat glioma cells to express luciferin under the HRE promoter, and transduced these cells with a retrovirus to constitutively express GFP and mCherry. Different numbers of 9L-3HRE-luc/GFP/mCherry cells were implanted in the lower back regions of nude mice. When tumors reached about 3 to 7 mm diameter, they were imaged first with Fluorescence imaging (FLI) to detect GFP and mcherry signal. Then, 80 µl luciferin (40 mg/kg) was administered S.C and a BLI time course was acquired over 50 mins using a Caliper Xenogen Spectrum. Combretastatin-A4P (CA4P) was then administered IP (150 mg/kg in 100 μl saline) and FLI and BLI repeated following the administration of fresh luciferin 2 h and 4h later. The processes were repeated at the 24 h and 96 h time points.

We examined the effect of CA4P on 9L-3HRE-luc/GFP/mCherry that are implanted as S.C xenografts in nude mice, and found highly reproducible curves under control conditions. 2h following CA4P, the BLI signal was reduced by 90%, 4h later, some recovery was observed. After 24 h, the light emission continued to recover. After 96 h, signal was observed mainly from the periphery of larger tumors, probably owing to central necrosis. Notably, the GFP and mCherry fluorescent signals were slightly reduced after 2 h, further declined after 4 h, and GFP signal was completely eliminated after 24 h, attributable to the vascular hemorrhage absorbing GFP. Similarly, after 96 h, both GFP and mCherry signal could be detected in the periphery of larger tumors. Three tumors were developed under similar conditions and examined simultaneously, which provides a valid assessment of vascular shutdown. This technique can be utilized to optimize future therapeutic drug dosage and combinations.

Support: NIH R01 EB007456 and NCI SAIRP U24CA126608

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5227.

Cell encapsulation and oxygenation in nanoporous microcontainers

With strides in stem cell biology, cell engineering and molecular therapy, the transplantation of cells to produce therapeutic molecules endogenously is an attractive and achievable alternative to the use of exogenous drugs. The encapsulation of such cell transplants in semi-permeable, nanoporous constructs is often required to protect them from immune attack and to prevent their proliferation in the host. However, effective graft immunoisolation has been mostly elusive owing to the absence of a high-throughput method to create precisely controlled, high-aspect-ratio nanopores. To address the clinical need for effective cell encapsulation and immunoisolation, we devised a biocompatible cell-encapsulating microcontainer and a method to create highly anisotropic nanopores in the microcontainer's surface. To evaluate the efficacy of these nanopores in oxygenating the encapsulated cells, we engineered 9L rat glioma cells to bioluminesce under hypoxic conditions. The methods described above should aid in evaluating the long term survival and efficacy of cellular grafts.

Simple developmental dyslexia in children: alterations in diffusion-tensor metrics of white matter tracts at 3 T

PURPOSE

To determine whether there are detectable differences in tensor metrics between children who read normally and children with simple developmental dyslexia and/or differences between the right and left hemispheres in these groups by using 3.0-T diffusion-tensor (DT) magnetic resonance (MR) imaging focused on the superior longitudinal fasciculus (SLF), inferior fronto-occipital and inferior longitudinal fasciculi (IFO-ILF), and posterior limb of the internal capsule (PLIC).

MATERIALS AND METHODS

This was a prospective, HIPAA-compliant institutional review board-approved investigation with written informed parental consent. Nineteen English-speaking, right-handed children with a normal IQ and developmental dyslexia (16 male, three female; age range, 6-16 years; mean age, 9.9 years) and 18 normal-reading, age-matched pediatric control subjects (13 male, five female; age range, 6-15 years; mean age, 10.0 years) underwent DT imaging (30 directions, three signals acquired, voxel size of 2 mm). Regions of interest were placed on the SLF, IFO-ILF, and PLIC, and tensor metrics were calculated. Statistical analyses of differences in cognitive function between the dyslexic and control groups were performed by using the two-sample t test. Differences in tensor metrics were examined by using analysis of covariance models.

RESULTS

In the control subjects, the fractional anisotropy (FA) of all tracts studied increased with age. In the dyslexic subjects, the age-related increases in FA in the SLF were most similar to those in the control subjects (P = .504), while mean FA values for the IFO-ILF (P = .009) and PLIC (P < .0001) were higher than those in the control subjects up to around 11 years of age, after which they were lower. Apparent diffusion coefficients consistently decreased in both groups. There was a nonsignificant increase in mean axial diffusivity in the IFO-ILF in the control group but not in the dyslexia group. Increases in axial diffusivity seen in the PLIC in the control group were not seen in the dyslexia group. There were no marked differences in tensor metrics between the left and right hemispheres within or between the two groups.

CONCLUSION

Findings at 3.0-T DT imaging suggest that white matter differences in dyslexic children are not limited to the portion of the brain traditionally considered to be integral to word recognition and processing.

A nanoporous, transparent microcontainer for encapsulated islet therapy

Present-day islet encapsulation techniques such as polymer microcapsules and microelectromechanical system (MEMS)-based biocapsules have shown promise in insulin replacement therapy, but they each have limitations-the permeability characteristics of existing polymeric capsules cannot be strictly controlled because of tortuosity and the large size of present-day MEMS biocapsules leads to necrotic regions within the encapsulation volume. We report on a new microcontainer to encapsulate and immunoprotect islets/beta cells that may be used for allo- or xenotransplantation in cell-based therapy. The microcontainers have membranes containing nanoslots to permit the bidirectional transport of nutrients, secretagogues, and cellular products while immunoprotecting the encapsulated cells. The 300-microm microcontainers were fabricated from an epoxy-based polymer, SU-8, with 50-microm-thick walls. Arrays of 25-nm wide slots were created in the SU-8 microcontainer lid. Isolated mouse islets were encapsulated in the microcontainer, and their physiological response to glucose was studied with fluorescence and two-photon imaging over 48 hours. The physiological response of the encapsulated islets was indistinguishable from controls. An agarose-filled microcontainer was imaged with magnetic resonance imaging to demonstrate the feasibility of future noninvasive, in vivo imaging. The SU-8 microcontainers maintained mechanical integrity upon islet loading and mechanical manipulation. Islet encapsulation, as well as the ability to visualize islet function within these transparent microcontainers, was demonstrated.

An immunotolerant HER-2/neu transgenic mouse model of metastatic breast cancer

PURPOSE

Animal models of breast cancer metastases that recapitulate the pattern of metastatic progression seen in patients are lacking; metastatic breast cancer models do not currently exist for evaluation of immune-mediated therapies. We have developed and characterized a preclinical model for the evaluation of immune-mediated metastatic breast cancer therapies.

EXPERIMENTAL DESIGN

The NT2.5 mammary tumor cell line was injected into the left cardiac ventricle of immunotolerant transgenic neu-N mice and athymic nu/nu mice. Metastatic progression was monitored by bioluminescent, small-animal magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography/computed tomography imaging, and also by histopathology. Antigen expression in normal organs and tumor metastases was evaluated by Western blot analysis and flow cytometry.

RESULTS

Left cardiac ventricle injection of NT2.5 cells yielded widespread metastases in bones, liver, and spleen. Three to four weeks after injection, mice exhibited hind limb paralysis and occasional abdominal enlargement. Bioluminescence imaging of metastatic progression was successful in nude mice but the bioluminescent cells were rejected in immunocompetent mice. Other imaging modalities allowed successful imaging of nonbioluminescent cells. Small-animal positron emission tomography imaging allowed visualization of disease, in vivo, in the bones and liver. Magnetic resonance imaging revealed initial dissemination of the tumor cells to the bone marrow. Small-animal single-photon emission computed tomography/computed tomography imaging identified metastatic bone lesions targeted by a radiolabeled antibody.

CONCLUSION

The model closely recapitulates the pattern of metastatic spread in breast cancer. This immunotolerant metastatic model is a novel addition to existing breast cancer models and coupling the model with in vivo imaging greatly facilitates the evaluation of targeted immunotherapies of metastasis.

Optic nerve and chiasm enlargement in a case of infantile Krabbe disease: quantitative comparison with 26 age-matched controls

Hypertrophy of the optic nerves and optic chiasm is described in a 5-month-old boy with infantile Krabbe disease. Optic nerve and optic chiasm hypertrophy is a rarely described feature of Krabbe disease. The areas of the prechiasmatic optic nerves and optic chiasm were measured and compared with those of 26 age-matched controls. The areas of the prechiasmatic optic nerves and optic chiasm were 132% and 53% greater than normal, respectively.

MRI of regular-shaped cell-encapsulating polyhedral microcontainers

We devised cubic and pyramidal microcontainers for cell encapsulation. While the cube is easier to manipulate, the pyramid offers a higher surface area-to-volume ratio and may therefore provide the encapsulated cells with increased access to nutrients. To discern the microcontainers' implant location and environment, and to aid in image-guided therapy, we showed noninvasive detection of microcontainers using MRI. Diamagnetic microcontainers were imaged using the radio frequency (RF) shielding effect, with negative contrast localized to the interior of the microcontainers. For applications in which it is difficult to distinguish the microcontainers from other hypointensities, positive contrast can be used to discern them. We showed positive-contrast MRI of a diamagnetic microcontainer. To image microcontainers that are smaller than the spatial resolution of MRI, we performed in vivo negative-contrast MRI of a ferromagnetic microcontainer. As opposed to the diamagnetic microcontainer, the ferromagnetic microcontainer created a region of MRI contrast several times larger than the microcontainer's dimensions.

Subependymoma of the cerebellopontine angle and prepontine cistern in a 15-year-old adolescent boy

SUMMARY

A case of cerebellopontine angle and prepontine cistern subependymoma in a 15-year-old adolescent boy is presented with a review of the literature. Apparent diffusion coefficient values for subependymoma are reported. Differential considerations for the unusual location of this rare tumor are discussed.

Anti-inflammatory agent indomethacin reduces invasion and alters metabolism in a human breast cancer cell line

Hostile physiological environments such as hypoxia and acidic extracellular pH, which exist in solid tumors, may promote invasion and metastasis through inflammatory responses and formation of eicosanoids. Here, we have investigated the effects of the anti-inflammatory agent indomethacin on the invasion and metabolism of the human breast cancer cell line MDA-MB-435 in Dulbecco's Modified Eagles (DME)-based or Roswell Park Memorial Institute (RPMI)-based cell medium, using a magnetic resonance-compatible invasion assay. Indomethacin treatment significantly reduced the invasion of MDA-MB-435 cells independent of the culture and perfusion conditions examined. Significant changes were detected in levels of intracellular choline phospholipid metabolites and in triglyceride (TG) concentrations of these cells, depending on indomethacin treatment and basal cell medium used. Additionally, genetic profiling of breast cancer cells, grown and treated with low-dose indomethacin in cell culture using an RPMI-based medium, revealed the upregulation of several genes implicating cyclooxygenase-independent targets of indomethacin. These data confirm the ability of an anti-inflammatory agent to reduce breast cancer invasion and demonstrate, depending on cell culture and perfusion conditions, that the indomethacin-induced decrease in invasion is associated with changes in choline phospholipid metabolism, TG metabolism, and gene expression.

Noninvasive MRI of endothelial cell response to human breast cancer cells

We have developed a noninvasive magnetic resonance imaging (MRI) assay to characterize human umbilical vein endothelial cell (HUVEC) motility, invasion, and network formation in response to the presence of cancer cells. HUVECs were labeled with a superparamagnetic iron oxide T(2) contrast agent and cocultured with MDA-MB-231 breast cancer cells in the presence of an extracellular matrix (ECM) gel. Invasion into the ECM gel by HUVECs in response to paracrine factors secreted by MDA-MB-231 cancer cells, as well as network formation by HUVECs, was easily tracked with MRI. The invasive behavior of HUVECs was not observed in the absence of cancer cells. This noninvasive assay used to characterize the response of endothelial cells (ECs) can be used to understand the role of proangiogenic or antiangiogenic stimuli, and to study the interactions between ECs and other disease-specific cells in pathologies with aberrant angiogenesis, such as retinopathy and arthritis.

Functional MR microimaging of pancreatic beta-cell activation

The increasing incidence of diabetes and the need to further understand its cellular basis has resulted in the development of new diagnostic and therapeutic techniques. Nonetheless, the quest to noninvasively ascertain beta-cell mass and function has not been achieved. Manganese (Mn)-enhanced MRI is presented here as a tool to image beta-cell functionality in cell culture and isolated islets. Similar to calcium, extracellular Mn was taken up by glucose-activated beta-cells resulting in 200% increase in MRI contrast enhancement, versus nonactivated cells. Similarly, glucose-activated islets showed an increase in MRI contrast up to 45%. Although glucose-stimulated Ca influx was depressed in the presence of 100 microM Mn, no significant effect was seen at lower Mn concentrations. Moreover, islets exposed to Mn showed normal glucose sensitivity and insulin secretion. These results demonstrate a link between image contrast enhancement and beta-cell activation in vitro, and provide the basis for future noninvasive in vivo imaging of islet functionality and beta-cell mass.

Magnetic resonance microscopy: concepts, challenges, and state-of-the-art

Recent strides in targeted therapy and regenerative medicine have created a need to identify molecules and metabolic pathways implicated in a disease and its treatment. These molecules and pathways must be discerned at the cellular level to meaningfully reveal the biochemical underpinnings of the disease and to identify key molecular targets for therapy. Magnetic resonance (MR) techniques are well suited for molecular and functional imaging because of their noninvasive nature and their versatility in extracting physiological, biochemical, and functional information over time. However, MR is an insensitive technique; MR microscopy seeks to increase detection sensitivity, thereby localizing biochemical and functional information at the level of single cells or small cellular clusters. Here, we discuss some of the challenges facing MR microscopy and the technical and phenomenological strategies used to overcome these challenges. Some of the applications of MR microscopy are highlighted in this chapter.

Self-Assembled Three Dimensional Radio Frequency (RF) Shielded Containers for Cell Encapsulation

This paper describes the construction of three dimensional (3D) encapsulation devices in large numbers, using a novel self-assembling strategy characterized by high mechanical stability, controlled porosity, extreme miniaturization, high reproducibility and the possibility of integrating sensing and actuating electromechanical modules. We demonstrated encapsulation of microbeads and cells within the containers, thereby demonstrating one possible application in cell encapsulation therapy. Magnetic resonance (MR) images of the containers in fluidic media suggest radio frequency (RF) shielding and a susceptibility effect, providing characteristic hypointensity within the container, thereby allowing the containers to be easily detected. This demonstration is the first step toward the design of 3D, micropatterned, non-invasively trackable, encapsulation devices.

Molecular Imaging of Cancer: Applications of Magnetic Resonance Methods

Cancer is a complex disease exhibiting a host of phenotypic diversities. Noninvasive multinuclear magnetic resonance imaging (MRI) and spectroscopic imaging (MRSI) provide an array of capabilities to characterize and understand several of the vascular, metabolic, and physiological characteristics unique to cancer. The availability of targeted contrast agents has widened the scope of MR techniques to include the detection of receptor and gene expression. In this paper, we have highlighted the application of several MR techniques in imaging and understanding cancer.