Sex differences in cognitive impairment after focal ischemia in middle-aged rats and the effect of iv miR-20a-3p treatment.

Stroke is a major cause of death and disability worldwide and is also a leading cause of vascular dementia and Alzheimer's disease, with older women experiencing accelerated decline. Our previous studies show that intravenous (iv) injections of miR-20a-3p, a small noncoding RNA (miRNA) delivered after stroke improves acute stroke outcomes in middle-aged male and female rats. The present study tested whether mir-20a-3p treatment would also ameliorate stroke-induced cognitive decline in the chronic phase. Acyclic middle-aged females and age-matched male Sprague Dawley rats were subjected to middle cerebral artery occlusion using endothelin-1 or sham surgery, and treated iv with miR-20a-3p mimics or scrambled oligos at 4 hours, 24 hours, and 70 days post-stroke. Stroke resulted in a significant sensory motor deficit, while miR-20a-3p treatment reduced these deficits in both sexes. Cognitive impairment was assessed periodically for 3 months after stroke using contextual fear conditioning and the novel object recognition task. Overall, the tests of associative and episodic memory were affected by focal ischemia only in female rats, and miR-20a-3p ameliorated the rate of decline.

Short-term exposure to an obesogenic diet during adolescence elicits anxiety-related behavior and neuroinflammation: modulatory effects of exogenous neuregulin-1.

Childhood obesity leads to hippocampal atrophy and altered cognition. However, the molecular mechanisms underlying these impairments are poorly understood. The neurotrophic factor neuregulin-1 (NRG1) and its cognate ErbB4 receptor play critical roles in hippocampal maturation and function. This study aimed to determine whether exogenous NRG1 administration reduces hippocampal abnormalities and neuroinflammation in rats exposed to an obesogenic Western-like diet (WD). Lewis rats were randomly divided into four groups (12 rats/group): (1) control diet+vehicle (CDV); (2) CD + NRG1 (CDN) (daily intraperitoneal injections: 5 µg/kg/day; between postnatal day, PND 21-PND 41); (3) WD + VEH (WDV); (4) WD + NRG1 (WDN). Neurobehavioral assessments were performed at PND 43-49. Brains were harvested for MRI and molecular analyses at PND 49. We found that NRG1 administration reduced hippocampal volume (7%) and attenuated hippocampal-dependent cued fear conditioning in CD rats (56%). NRG1 administration reduced PSD-95 protein expression (30%) and selectively reduced hippocampal cytokine levels (IL-33, GM-CSF, CCL-2, IFN-γ) while significantly impacting microglia morphology (increased span ratio and reduced circularity). WD rats exhibited reduced right hippocampal volume (7%), altered microglia morphology (reduced density and increased lacunarity), and increased levels of cytokines implicated in neuroinflammation (IL-1α, TNF-α, IL-6). Notably, NRG1 synergized with the WD to increase hippocampal ErbB4 phosphorylation and the tumor necrosis alpha converting enzyme (TACE/ADAM17) protein levels. Although the results did not provide sufficient evidence to conclude that exogenous NRG1 administration is beneficial to alleviate obesity-related outcomes in adolescent rats, we identified a potential novel interaction between obesogenic diet exposure and TACE/ADAM17-NRG1-ErbB4 signaling during hippocampal maturation. Our results indicate that supraoptimal ErbB4 activities may contribute to the abnormal hippocampal structure and cognitive vulnerabilities observed in obese individuals.

Combined Therapy With Avastin, a PAF Receptor Antagonist and a Lipid Mediator Inhibited Glioblastoma Tumor Growth.

Glioblastoma multiforme (GBM) is an aggressive, highly proliferative, invasive brain tumor with a poor prognosis and low survival rate. The current standard of care for GBM is chemotherapy combined with radiation following surgical intervention, altogether with limited efficacy, since survival averages 18 months. Improvement in treatment outcomes for patients with GBM requires a multifaceted approach due to the dysregulation of numerous signaling pathways. Recently emerging therapies to precisely modulate tumor angiogenesis, inflammation, and oxidative stress are gaining attention as potential options to combat GBM. Using a mouse model of GBM, this study aims to investigate Avastin (suppressor of vascular endothelial growth factor and anti-angiogenetic treatment), LAU-0901 (a platelet-activating factor receptor antagonist that blocks pro-inflammatory signaling), Elovanoid; ELV, a novel pro-homeostatic lipid mediator that protects neural cell integrity and their combination as an alternative treatment for GBM. Female athymic nude mice were anesthetized with ketamine/xylazine, and luciferase-modified U87MG tumor cells were stereotactically injected into the right striatum. On post-implantation day 13, mice received one of the following: LAU-0901, ELV, Avastin, and all three compounds in combination. Bioluminescent imaging (BLI) was performed on days 13, 20, and 30 post-implantation. Mice were perfused for ex vivo MRI on day 30. Bioluminescent intracranial tumor growth percentage was reduced by treatments with LAU-0901 (43%), Avastin (77%), or ELV (86%), individually, by day 30 compared to saline treatment. In combination, LAU-0901/Avastin, ELV/LAU-0901, or ELV/Avastin had a synergistic effect in decreasing tumor growth by 72, 92, and 96%, respectively. Additionally, tumor reduction was confirmed by MRI on day 30, which shows a decrease in tumor volume by treatments with LAU-0901 (37%), Avastin (67%), or ELV (81.5%), individually, by day 30 compared to saline treatment. In combination, LAU-0901/Avastin, ELV/LAU-0901, or ELV/Avastin had a synergistic effect in decreasing tumor growth by 69, 78.7, and 88.6%, respectively. We concluded that LAU-0901 and ELV combined with Avastin exert a better inhibitive effect in GBM progression than monotherapy. To our knowledge, this is the first study that demonstrates the efficacy of these novel therapeutic regimens in a model of GBM and may provide the basis for future therapeutics in GBM patients.

SPARC coordinates extracellular matrix remodeling and efficient recruitment to and migration of antigen-specific T cells in the brain following infection.

Central nervous system (CNS) injury and infection can result in profound tissue remodeling in the brain, the mechanism and purpose of which is poorly understood. Infection with the protozoan parasite Toxoplasma gondii causes chronic infection and inflammation in the brain parenchyma. Control of parasite replication requires the continuous presence of IFNγ-producing T cells to keep T. gondii in its slowly replicating cyst form. During infection, a network of extracellular matrix fibers, revealed using multiphoton microscopy, forms in the brain. The origin and composition of these structures are unknown but the fibers have been observed to act as a substrate for migrating T cells. In this study, we show a critical regulator of extracellular matrix (ECM) remodeling, Secreted Protein, Acidic, Rich in Cysteine (SPARC), is upregulated in the brain during the early phases of infection in the frontal cortex. In the absence of SPARC, a reduced and disordered fibrous network, increased parasite burden, and reduced antigen-specific T cell entry into the brain points to a role for SPARC in T cell recruitment to and migration within the brain. We also report SPARC can directly bind to CCR7 ligands CCL19 and CCL21 but not CXCL10, and enhance migration toward a chemokine gradient. Measurement of T cell behavior points to tissue remodeling being important for access of immune cells to the brain and facilitating cellular locomotion. Together, these data identify SPARC as an important regulatory component of immune cell trafficking and access to the inflamed CNS.

Multiple sensory illusions are evoked during the course of proton therapy.

Visual illusions from astronauts in space have been reported to be associated with the passage of high energy charged particles through visual structures (retina, optic nerve, brain). Similar effects have also been reported by patients under proton and heavy ion therapies. This prompted us to investigate whether protons at the Loma Linda University Proton Therapy and Research Center (PTRC) may also affect other sensory systems beside evoking similar perceptions on the visual system. A retrospective review of proton radiotherapy patient records at PTRC identified 29 sensory reports from 19 patients who spontaneously reported visual, olfactory, auditory and gustatory illusions during treatment. Our results suggest that protons can evoke neuronal responses sufficient to elicit conscious sensory illusion experiences, in four senses (auditory, taste, smell, and visual) analogous to those from normal sensory inputs. The regions of the brain receiving the highest doses corresponded with the anatomical structures associated with each type of illusion. Our findings suggest that more detailed queries about sensory illusions during proton therapy are warranted, possibly integrated with quantitative effect descriptions (such as electroencephalography) and can provide additional physiological basis for understanding the effects of protons on central nervous system tissues, needed for radiation risk assessment in advance of deep space human exploration.

A Biomarker for Predicting Responsiveness to Stem Cell Therapy Based on Mechanism-of-Action: Evidence from Cerebral Injury.

To date, no stem cell therapy has been directed to specific recipients-and, conversely, withheld from others-based on a clinical or molecular profile congruent with that cell's therapeutic mechanism-of-action (MOA) for that condition. We address this challenge preclinically with a prototypical scenario: human neural stem cells (hNSCs) against perinatal/neonatal cerebral hypoxic-ischemic injury (HII). We demonstrate that a clinically translatable magnetic resonance imaging (MRI) algorithm, hierarchical region splitting, provides a rigorous, expeditious, prospective, noninvasive "biomarker" for identifying subjects with lesions bearing a molecular profile indicative of responsiveness to hNSCs' neuroprotective MOA. Implanted hNSCs improve lesional, motor, and/or cognitive outcomes only when there is an MRI-measurable penumbra that can be forestalled from evolving into necrotic core; the core never improves. Unlike the core, a penumbra is characterized by a molecular profile associated with salvageability. Hence, only lesions characterized by penumbral > core volumes should be treated with cells, making such measurements arguably a regenerative medicine selection biomarker.

Diffusion tensor imaging identifies aspects of therapeutic estrogen receptor ß ligand-induced remyelination in a mouse model of multiple sclerosis.

Diffusion tensor imaging (DTI) has been shown to detect white matter degeneration in multiple sclerosis (MS), a neurodegenerative autoimmune disease that presents with diffuse demyelination of the central nervous system. However, the utility of DTI in evaluating therapeutic remyelination has not yet been well-established. Here, we assessed the ability of DTI to distinguish between remyelination and neuroprotection following estrogen receptor ß ligand (Indazole chloride, IndCl) treatment, which has been previously shown to stimulate functional remyelination, in the cuprizone (CPZ) diet mouse model of MS. Adult C57BL/6 J male and female mice received a normal diet (control), demyelination-inducing CPZ diet (9wkDM), or CPZ diet followed by two weeks of a normal diet (i.e., remyelination period) with either IndCl (RM + IndCl) or vehicle (RM + Veh) injections. We evaluated tissue microstructure of the corpus callosum utilizing in vivo and ex vivo DTI and immunohistochemistry (IHC) for validation. Compared to control mice, the 9wkDM group showed decreased fractional anisotropy (FA), increased radial diffusivity (RD), and no changes in axial diffusivity (AD) both in vivo and ex vivo. Meanwhile, RM + IndCl groups showed increased FA and decreased RD ex vivo compared to the RM + Veh group, in accordance with the evidence of remyelination by IHC. In conclusion, the DTI technology used in the present study can identify some changes in myelination and is a valuable translational tool for evaluating MS pathophysiology and therapeutic efficacy.

Up-regulation of Wnt/ß-catenin expression is accompanied with vascular repair after traumatic brain injury.

Recent data suggest that repairing the cerebral vasculature after traumatic brain injury (TBI) may help to improve functional recovery. The Wnt/ß-catenin signaling pathway promotes blood vessel formation during vascular development, but its role in vascular repair after TBI remains elusive. In this study, we examined how the cerebral vasculature responds to TBI and the role of Wnt/ß-catenin signaling in vascular repair. We induced a moderate controlled cortical impact in adult mice and performed vessel painting to visualize the vascular alterations in the brain. Brain tissue around the injury site was assessed for ß-catenin and vascular markers. A Wnt transgenic mouse line was utilized to evaluate Wnt gene expression. We report that TBI results in vascular loss followed by increases in vascular structure at seven days post injury (dpi). Immature, non-perfusing vessels were evident in the tissue around the injury site. ß-catenin protein expression was significantly reduced in the injury site at 7 dpi. However, there was an increase in ß-catenin expression in perilesional vessels at 1 and 7 dpi. Similarly, we found increased number of Wnt-GFP-positive vessels after TBI. Our findings suggest that Wnt/ß-catenin expression contributes to the vascular repair process after TBI.

Anhedonia Following Early-Life Adversity Involves Aberrant Interaction of Reward and Anxiety Circuits and Is Reversed by Partial Silencing of Amygdala Corticotropin-Releasing Hormone Gene.

BACKGROUND: Anhedonia, the diminished ability to experience pleasure, is an important dimensional entity linked to depression, schizophrenia, and other emotional disorders, but its origins and mechanisms are poorly understood. We have previously identified anhedonia, manifest as decreased sucrose preference and social play, in adolescent male rats that experienced chronic early-life adversity/stress (CES). Here we probed the molecular, cellular, and circuit processes underlying CES-induced anhedonia and tested them mechanistically. METHODS: We examined functional brain circuits and neuronal populations activated by social play in adolescent CES and control rats. Structural connectivity between stress- and reward-related networks was probed using high-resolution diffusion tensor imaging, and cellular/regional activation was probed using c-Fos. We employed viral-genetic approaches to reduce corticotropin-releasing hormone (Crh) expression in the central nucleus of the amygdala in anhedonic rats, and tested for anhedonia reversal in the same animals. RESULTS: Sucrose preference was reduced in adolescent CES rats. Social play, generally considered an independent measure of pleasure, activated brain regions involved in reward circuitry in both control and CES groups. In CES rats, social play activated Crh-expressing neurons in the central nucleus of the amygdala, typically involved in anxiety/fear, indicating aberrant functional connectivity of pleasure/reward and fear circuits. Diffusion tensor imaging tractography revealed increased structural connectivity of the amygdala to the medial prefrontal cortex in CES rats. Crh-short hairpin RNA, but not control short hairpin RNA, given into the central nucleus of the amygdala reversed CES-induced anhedonia without influencing other emotional measures. CONCLUSIONS: These findings robustly demonstrate aberrant interactions of stress and reward networks after early-life adversity and suggest mechanistic roles for Crh-expressing amygdala neurons in emotional deficits portending major neuropsychiatric disorders.

Response of the cerebral vasculature following traumatic brain injury.

The critical role of the vasculature and its repair in neurological disease states is beginning to emerge particularly for stroke, dementia, epilepsy, Parkinson's disease, tumors and others. However, little attention has been focused on how the cerebral vasculature responds following traumatic brain injury (TBI). TBI often results in significant injury to the vasculature in the brain with subsequent cerebral hypoperfusion, ischemia, hypoxia, hemorrhage, blood-brain barrier disruption and edema. The sequalae that follow TBI result in neurological dysfunction across a host of physiological and psychological domains. Given the importance of restoring vascular function after injury, emerging research has focused on understanding the vascular response after TBI and the key cellular and molecular components of vascular repair. A more complete understanding of vascular repair mechanisms are needed and could lead to development of new vasculogenic therapies, not only for TBI but potentially vascular-related brain injuries. In this review, we delineate the vascular effects of TBI, its temporal response to injury and putative biomarkers for arterial and venous repair in TBI. We highlight several molecular pathways that may play a significant role in vascular repair after brain injury.

Role of PDGF-D and PDGFR-ß in neuroinflammation in experimental ICH mice model.

OBJECTIVE: Inflammation plays a key role in the pathophysiological processes after intracerebral hemorrhage (ICH). Post-ICH macrophages infiltrate the brain and release pro-inflammatory factors (tumor necrosis factor-α), amplifying microglial activation and neutrophil infiltration. Platelet-derived growth factor receptor-ß (PDGFR-ß) is expressed on macrophages and it's activation induces the recruitment of macrophages. Platelet-derived growth factor-D (PDGF-D) is an agonist with a significantly higher affinity to the PDGFR-ß compared to another isoform of the receptor. In this study, we investigated the role of PDGF-D in the pro-inflammatory response after ICH in mice. METHODS: A blood injection model of ICH was used in eight-week old male CD1 mice (weight 30g). Some mice received an injection of plasmin or PDGF-D. Gleevec, a PDGFR inhibitor, was administered at 1, 3 or 6h post-ICH. Plasmin was administered with or without PDGF-D siRNAs mixture or scramble siRNA. A plasmin-antagonist, ε-Aminocaproic acid (EACA), was co-administrated with the blood. The effects of ICH and treatment on the brain injury and post-ICH inflammation were investigated. RESULTS: ICH resulted in the overexpression of PDGF-D, associated with the infiltration of macrophages. PDGFR-inhibition decreased ICH-induced brain injury, attenuating macrophage and neutrophil infiltration, reducing microglial activation and TNF-α production. Administration of recombinant PDGF-D induced TNF-α production, and PDGFR-inhibition attenuated it. A plasmin-antagonist suppressed PDGFR-ß activation and microglial activation. Plasmin increased PDGF-D expression, and PDGF-D inhibition reduced neutrophil infiltration. CONCLUSION: ICH-induced PDGF-D accumulation contributed to post-ICH inflammation via PDGFR activation and enhanced macrophage infiltration. The inhibition of PDGFR had an anti-inflammatory effect. Plasmin is a possible upstream effector of PDGF-D. The targeting of PDGF-D may provide a novel way to decrease brain injury after ICH.

Platelet-Derived Growth Factor Receptor-ß Regulates Vascular Smooth Muscle Cell Phenotypic Transformation and Neuroinflammation After Intracerebral Hemorrhage in Mice.

OBJECTIVE: Platelet-derived growth factor-BB activates platelet-derived growth factor receptor-ß and promotes vascular smooth muscle cell phenotypic transformation. Elevated levels of non-muscle myosin IIB (SMemb) are found in secretory smooth muscle cells along with inflammatory mediators, such as intercellular adhesion molecule-1, which can amplify neutrophil infiltration into the brain. In the present study, we investigated the role of platelet-derived growth factor-BB/platelet-derived growth factor receptor-ß following intracerebral hemorrhage-induced brain injury in mice, with emphasis on its ability to promote vascular smooth muscle cell phenotypic transformation followed by increased intercellular adhesion molecule-1 expression and elevated neutrophil infiltration in the vicinity of the hematoma. We also determined the extent to which plasmin from the hematoma influences the platelet-derived growth factor-BB/platelet-derived growth factor receptor-ß system subsequent to intracerebral hemorrhage. DESIGN: Controlled in vivo laboratory study. SETTING: Animal research laboratory. SUBJECTS: One hundred and fifty six eight-week-old male CD1 mice. INTERVENTIONS: Brain injury was induced by autologous arterial blood or plasmin injection into mouse brains. Small interfering RNA targeting platelet-derived growth factor receptor-ß was administered 24 hours before intracerebral hemorrhage. A platelet-derived growth factor receptor antagonist, Gleevec, was administered following intracerebral hemorrhage. A mitogen-activated protein kinase-activated protein kinase 2 inhibitor (KKKALNRQLGVAA) was delivered with platelet-derived growth factor-BB in naïve animals. Platelet-derived growth factor-BB was injected with a plasmin inhibitor (ε-aminocaproic acid) in intracerebral hemorrhage mice. Plasmin-injected mice were given platelet-derived growth factor receptor-ß small interfering RNA 24 hours before the operation. Neurological deficits, brain edema, western blots, and immunofluorescence were evaluated. MEASUREMENTS AND MAIN RESULTS: Platelet-derived growth factor receptor-ß small interfering RNA attenuated SMemb and intercellular adhesion molecule-1 expression and neutrophil infiltration at 24 hours post injury and reduced neurological deficits and brain edema at 24 and 72 hours following intracerebral hemorrhage. The platelet-derived growth factor receptor antagonist, Gleevec, reduced SMemb and intercellular adhesion molecule-1 expression. Platelet-derived growth factor receptor-ß activation led to increased expression of intercellular adhesion molecule-1 and was reversed by KKKALNRQLGVAA in naïve mice. Plasmin inhibition suppressed platelet-derived growth factor receptor-ß activation and neutrophil infiltration, whereas exogenous platelet-derived growth factor-BB increased platelet-derived growth factor receptor-ß activation, regardless of plasmin inhibition. Platelet-derived growth factor receptor-ß small interfering RNA decreased the expression of intercellular adhesion molecule-1 by plasmin injection. CONCLUSION: The platelet-derived growth factor-BB/platelet-derived growth factor receptor-ß system contributes to neuroinflammation through vascular smooth muscle cell phenotypic transformation near the hematoma via the p38 mitogen-activated protein kinase/mitogen-activated protein kinase-activated protein kinase 2 pathway following intracerebral hemorrhage. Plasmin is hypothesized to be upstream of the proposed neuroinflammatory system. The therapeutic intervention targeting the platelet-derived growth factor-BB/platelet-derived growth factor receptor-ß is a novel strategy to prevent plasmin-induced brain injury following intracerebral hemorrhage.

Susceptibility-Weighted Imaging Identifies Iron-Oxide-Labeled Human Neural Stem Cells: Automated Computational Detection.

Neonatal hypoxic-ischemic brain injury (HII) can lead to devastating neurological outcomes such as cerebral palsy, epilepsy, and mental retardation. Human neural stem cell (hNSC) therapy provides new hope for the treatment of neonatal HII. These multipotent cells can aid in HII recovery by activating multiple reparative mechanisms including secretion of neurotrophic factors that enhance brain repair and plasticity. For clinical use of implanted hNSCs, methods are required to identify, quantify, track, and visualize migration and replication in an automated and reproducible fashion. In the current study, we used a model of unilateral HII in 10-day-old rat pups that were implanted with 250,000 Feridex-labeled hNSCs into the contralateral ventricle 3 days after HII. In addition to standard noninvasively acquired serial magnetic resonance imaging (MRI) sequences (11.7 and 4.7 T) that included diffusion-weighted imaging and T2-weighted imaging, we also acquired susceptibility-weighted imaging (SWI) 1-90 days after hNSC implantation. SWI is an advanced MRI method that enhances the visualization of iron-oxide-labeled hNSCs within affected regions of the injured neonatal brain. hNSC contrast was further enhanced by creating minimal intensity projections from the raw SWI magnitude images combined with phase information. Automated computational analysis using hierarchical region splitting (HRS) was applied for semiautomatic detection of hNSCs from SWI images. We found hNSCs in the ipsilateral HII lesion within the striatum and cortex adjacent to the lesion that corresponded to histological staining for iron. Quantitative phase values (radians) obtained from SWI revealed temporally evolving increased phase which reflects a decreased iron oxide content that is possibly related to cell division and the replicative capacity of the implanted hNSCs. SWI images also revealed hNSC migration from the contralateral injection site towards the ipsilateral HII lesion. Our results demonstrate that MRI-based SWI can monitor iron-labeled hNSCs in a clinically relevant manner and that automated computational methods such as HRS can rapidly identify iron-oxide-labeled hNSCs.

Iron Accumulation Is Not Homogenous among Patients with Parkinson's Disease.

Background. Iron is considered to lead to neurodegeneration and has been hypothesized as a possible cause of Parkinson's disease (PD). Susceptibility-weighted imaging (SWI) is a powerful tool to measure phase related iron content of brain. Methods. Twelve de novo patients with PD were recruited from the Movement Disorders Clinic, Department of Neurology, Loma Linda University. Twelve age- and sex-matched non-PD subjects were recruited from neurology clinic as controls. Using SWI, the phase related iron content was estimated from different brain regions of interest (ROIs). Results. There was a trend between increasing age and iron accumulation in the globus pallidus and putamen in all subjects. Iron accumulation was not significant in different ROIs in PD patients compared to controls after adjustment for age. Our data revealed heterogeneity of phase values in different brain ROIs among all subjects with an exaggerated trend at SN in PD patients. Conclusions. Our data suggest a nonhomogeneous pattern of iron accumulation in different brain regions among PD patients. Further studies are needed to explore whether this may correlate to the progression of PD. To our knowledge, this is the first study demonstrating the heterogeneity of iron accumulation in the brain, among patients with PD.

Reparative effects of neural stem cells in neonatal rats with hypoxic-ischemic injury are not influenced by host sex.

BACKGROUND: Gender is increasingly recognized as an important influence on brain development, disease susceptibility, and response to pharmacologic/rehabilitative treatments. In regenerative medicine, it remains entirely unknown whether there is an interaction between transplanted stem cells and host gender that might bias efficacy and safety in some patients but not others. METHODS: We examined the role of recipient gender in a neonatal rat hypoxic-ischemic injury (HII) model, treated with female human neuronal stem cells (hNSCs), labeled with superparamagnetic iron oxide particles implanted into the contralateral cerebral ventricle. We monitored HII evolution (by magnetic resonance imaging, histopathology, behavioral testing) and hNSC fate (migration, replication, viability). RESULTS: Recipient gender after implantation did not influence the volume or location of ischemic injury (1, 30, or 90 d) or behavior (90 d). Superparamagnetic iron oxide labeling did not influence HII evolution. Implantation had its greatest benefit on mild/moderate injuries, which remained stable rather than increasing as in severe HII as is the natural history for such lesions. CONCLUSION: Our results suggest that hNSC treatment (including using hNSCs that are prelabeled with iron to allow tracking in real time by magnetic resonance imaging) would be equally safe and effective for male and female human newborns with mild-to-moderate HII.

Comparison of T2 and T2*-weighted MR molecular imaging of a mouse model of glioma.

BACKGROUND: Standard MRI has been used for high-grade gliomas detection, albeit with limited success as it does not provide sufficient specificity and sensitivity to detect complex tumor structure. Therefore targeted contrast agents based on iron oxide, that shorten mostly T2 relaxation time, have been recently applied. However pulse sequences for molecular imaging in animal models of gliomas have not been yet fully studied. The aim of this study was therefore to compare contrast-to-noise ratio (CNR) and explain its origin using spin-echo (SE), gradient echo (GE), GE with flow compensation (GEFC) as well as susceptibility weighted imaging (SWI) in T2 and T2* contrast-enhanced molecular MRI of glioma. METHODS: A mouse model was used. U87MGdEGFRvIII cells (U87MG), derived from a human tumor, were injected intracerebrally. A 9.4 T MRI system was used and MR imaging was performed on the 10 day after the inoculation of the tumor. The CNR was measured prior, 20 min, 2 hrs and 24 hrs post intravenous tail administration of glioma targeted paramagnetic nanoparticles (NPs) using SE, SWI, GE and GEFC pulse sequences. RESULTS: The results showed significant differences in CNR among all pulse sequences prior injection. GEFC provided higher CNR post contrast agent injection when compared to GE and SE. Post injection CNR was the highest with SWI and significantly different from any other pulse sequence. CONCLUSIONS: Molecular MR imaging using targeted contrast agents can enhance the detection of glioma cells at 9.4 T if the optimal pulse sequence is used. Hence, the use of flow compensated pulse sequences, beside SWI, should to be considered in the molecular imaging studies.

Susceptibility-weighted imaging in the experimental autoimmune encephalomyelitis model of multiple sclerosis indicates elevated deoxyhemoglobin, iron deposition and demyelination.

BACKGROUND: Susceptibility-weighted imaging (SWI) is an iron-sensitive magnetic resonance imaging (MRI) method that has shown iron-related lesions in multiple sclerosis (MS) patients. The contribution of deoxyhemoglobin to the signals seen in SWI has not been well characterized in MS. OBJECTIVES: To determine if SWI lesions (seen as focal hypointensities) exist in the experimental autoimmune encephalomyelitis (EAE) animal model of MS, and to determine whether the lesions relate to iron deposits, inflammation, demyelination, and/or deoxyhemoglobin in the vasculature. METHODS: We performed SWI on the lumbar spinal cord and cerebellum of EAE and control mice (both complete Freund's adjuvant/pertussis toxin (CFA/PTX)-immunized and naive). We also performed SWI on mice before and after perfusion (to remove blood from vessels). SWI lesions were counted and their locations were compared to histology for iron, myelin and inflammation. RESULTS: SWI lesions were found to exist in the EAE model. Many lesions seen by SWI were not present after perfusion, especially at the grey/white matter boundary of the lumbar spinal cord and in the cerebellum, indicating that these lesion signals were associated with deoxyhemoglobin present in the lumen of vessels. We also observed SWI lesions in the white matter of the lumbar spinal cord that corresponded to iron deposition, inflammation and demyelination. In the cerebellum, SWI lesions were present in white matter tracts, where we found histological evidence of inflammatory perivascular cuffs. CONCLUSIONS: SWI lesions exist in EAE mice. Many lesions seen in SWI were a result of deoxyhemoglobin in the blood, and so may indicate areas of hypoxia. A smaller number of SWI lesions coincided with parenchymal iron, demyelination, and/or inflammation.

In vivo iron quantification in collagenase-induced microbleeds in rat brain.

Brain microbleeds (BMB) are associated with chronic and acute cerebrovascular disease. Because BMB present in the brain is a source of potentially cytotoxic iron proportional to the volume of extravasated blood, BMB iron content is a potentially valuable biomarker both to assess tissue risk and small cerebral vessel health. We recently reported methods to quantify focal iron sources using phase images that were tested in phantoms and BMB in postmortem tissue. In this study, we applied our methods to small hemorrhagic lesions induced in the in vivo rat brain using bacterial collagenase. As expected by theory, measurements of geometric features in phase images correlated with lesion iron content measured by graphite furnace atomic absorption spectrometry. Iron content estimation following BMB in an in vivo rodent model could shed light on the role and temporal evolution of iron-mediated tissue damage and efficacy of potential treatments in cerebrovascular diseases associated with BMB.

Iron quantification of microbleeds in postmortem brain.

Brain microbleeds (BMB) are associated with chronic and acute cerebrovascular disease and present a source of pathologic iron to the brain proportional to extravasated blood. Therefore, BMB iron content is potentially a valuable biomarker. We tested noninvasive phase image methods to quantify iron content and estimate true source diameter (i.e., unobscured by the blooming effect) of BMB in postmortem human tissue. Tissue slices containing BMB were imaged using a susceptibility weighted imaging protocol at 11.7T. BMB lesions were assayed for iron content using atomic absorption spectrometry. Measurements of geometric features in phase images were related to lesion iron content and source diameter using a mathematical model. BMB diameter was estimated by image feature geometry alone without explicit relation to the magnetic susceptibility. A strong linear relationship (R(2) = 0.984, P < 0.001) predicted by theory was observed in the experimental data, presenting a tentative standardization curve where BMB iron content in similar tissues could be calculated. In addition, we report BMB iron mass measurements, as well as upper bound diameter and lower bound iron concentration estimates. Our methods potentially allows the calculation of brain iron load indices based on BMB iron content and classification of BMB by size unobscured by the blooming effect.

Brain irradiation improves focal cerebral ischemia recovery in aged rats.

BACKGROUND: Studies have shown that aging is a significant factor in worsening stroke outcomes. While many mechanisms may aggravate brain injury in the elderly, one such potential system may involve increased glial proliferation in the aged stroke patient that could result in increased scar formation. We hypothesized that in aged rats a single brain-only exposure to a low radiation dose prior to focal brain ischemia would reduce glial proliferation and confer a long-term neuroprotective effect. METHODS: Brain-only proton irradiation (8 Gy) was performed ten days prior to middle cerebral artery occlusion (MCAO) in aged male rats. Magnetic resonance imaging (MRI) was undertaken in naive, radiation-only (Rad), MCAO, and MCAO+Rad groups at 2, 14 and 28 days post-stroke followed by immunohistochemistry (day 28). RESULTS: Ischemic lesion volume in MCAO+Rad group was decreased by 50.7% with an accelerated temporal reduction in peri-lesional brain edema and increased water mobility within the ischemic core (39.8%) compared to MCAO-only rats. In the peri-lesional brain region of MCAO+Rad rats there was a decreased scar formation (49%, glial fibrillary acidic protein), brain tissue sclerosis (30%, aquaporin-4) and necrosis/apoptosis (58%, TUNEL positive cells) compared to those in MCAO animals. CONCLUSION: In aged animals a single exposure to brain-only radiation prior to focal cerebral ischemia is neuroprotective as it prevents glial hyperproliferation, progressive brain tissue sclerosis and reduces the apoptosis/necrosis in the peri-lesional region. Decreased lesion volume is in agreement with accelerated reduction of brain edema in these animals.