Faculty Bibliography

Retinitis pigmentosa, caused predominantly by mutations in photoreceptor genes, currently lacks comprehensive treatment. We discover that retinal microglia contribute non-cell autonomously to rod photoreceptor degeneration by primary phagocytosis of living rods. Using rd10 mice, we found that the initiation of rod degeneration is accompanied by early infiltration of microglia, upregulation of phagocytic molecules in microglia, and presentation of "eat-me" signals on mutated rods. On live-cell imaging, infiltrating microglia interact dynamically with photoreceptors via motile processes and engage in rapid phagocytic engulfment of non-apoptotic rods. Microglial contribution to rod demise is evidenced by morphological and functional amelioration of photoreceptor degeneration following genetic ablation of retinal microglia. Molecular inhibition of microglial phagocytosis using the vitronectin receptor antagonist cRGD also improved morphological and functional parameters of degeneration. Our findings highlight primary microglial phagocytosis as a contributing mechanism underlying cell death in retinitis pigmentosa and implicate microglia as a potential cellular target for therapy.

Fetal alcohol spectrum disorders (FASD) are associated with cognitive and behavioral deficits, and decreased volume of the whole brain and cerebral cortex. Rodent models have shown that early postnatal treatments, which mimic ethanol toxicity in the third trimester of human pregnancy, acutely induce widespread apoptotic neuronal degeneration and permanent behavioral deficits. However, the lasting cellular and anatomical effects of early ethanol treatments are still incompletely understood. This study examined changes in neocortex volume, thickness, and cellular organization that persist in adult mice after postnatal day 7 (P7) ethanol treatment. Post mortem brain volumes, measured by both MRI within the skull and by fluid displacement of isolated brains, were reduced 10-13% by ethanol treatment. The cerebral cortex showed a similar reduction (12%) caused mainly by lower surface area (9%). In spite of these large changes, several features of cortical organization showed little evidence of change, including cortical thickness, overall neuron size, and laminar organization. Estimates of total neuron number showed a trend level reduction of about 8%, due mainly to reduced cortical volume but unchanged neuron density. However, counts of calretinin (CR) and parvalbumin (PV) subtypes of GABAergic neurons showed a striking >30% reduction of neuron number. Similar ethanol effects were found in male and female mice, and in C57BL/6By and BALB/cJ mouse strains. Our findings indicate that the cortex has substantial capacity to develop normal cytoarchitectonic organization after early postnatal ethanol toxicity, but there is a selective and persistent reduction of GABA cells that may contribute to the lasting cognitive and behavioral deficits in FASD.

Episodic memory decline, olfactory identification deficits and the ApoE-e4 allele constitute risk factors for incident Alzheimers' Disease (AD). However, the relationships among these three risk factors are poorly understood, in part due to the paucity of large longitudinal datasets that involve such assessments. The present study used data from the Betula study (n=1225), which involves memory testing every five years. Participants completed an odor identification test, were genotyped for the ApoE gene, and had completed episodic memory testing for a 10-year period (3 testing occasions) leading up to the olfactory assessment. The episodic memory measure was a composite of five tasks, and decline was defined as an estimated change >1SD below the age norm. Participants were thus classified as "decliners" (n=125) or "non-decliners" (n=1100). Results showed that decliners had a poorer olfactory identification than nondecliners. However, when ApoE-e4 was taken into consideration, the association between memory decline and odor identification deficit was only present in ApoE-e4 carriers, whereas odor identification in memory decliners without e4 reached the same level as that of non-decliners. Future research on the role of olfaction in age-related memory impairment and dementia should consider the mediating role played by the ApoE-e4

The present study aimed to investigate the antiatherosclerotic effect of rhizoma polygonati polysaccharide. Adult golden hamsters (Mesocricetus auratus) were fed an atherosclerotic diet containing 1.5 mL olive oil, 8 mg (320 000 IU) vitamin D2, and 40 mg cholesterol for 60 consecutive days to induce atherosclerosis. These hamsters then orally received either the reference drug simvastatin (5 mg/kg) or rhizoma polygonati polysaccharide (0.57 g/kg or 1.14 g/kg) once daily for 60 additional days before comparison to normal and atherosclerotic controls. Treatment with rhizoma polygonati polysaccharide resulted in significant improvement (p<0.01) in serum lipid profile, apolipoproteins, and endothelial dysfunction parameters. Histomorphological studies confirmed biochemical findings. The results showed that rhizoma polygonati polysaccharide has a protective effect against hyperlipidemia-induced atherosclerosis in hamsters.

The rodent piriform cortex (PCX) is a paleocortical structure known to support olfactory perception toward learned behavior. While the anterior PCX is used in associative odor object information decoding, the posterior PCX receives more descending input fibers from brain structures such as the amygdala that are thought to provide a qualitative relevance to raw odor percepts. Here we investigate the influence of top-down influence of specific brain regions on spontaneous and odor-induced activity in the posterior PCX at the single unit level. Using optogenetic techniques, we artificially stimulated descending fibers in the posterior PCX that were virally transduced from one of two interconnected brain regions. Specifically, the lateral and basolateral amygdala (LA/BLA) and the lateral entorhinal cortex (LEC) were independently targeted to express Channelrhodopsin in pyramidal neurons that also express CaMKII. Photostimulation at 473nm and 1mW near infected axon terminals in the posterior piriform was sufficient to drive temporally coincident responses of unit activity and local field potential, as recorded in anaesthetized animals injected at any one of the two target regions. Odorpaired photostimulation of descending fibers at the posterior PCX modulated local single unit response patterns compared to odor only. Photo-induced effects on unit odor responses ranged from suppressive to stimulatory, which often varied depending on the combinatorial timing of odor and light stimulation. These results demonstrate the importance of top-down inputs to piriform cortex in odor coding, and highlight that cortical odor processing takes place in a rich milieu of sensory, emotional and contextual information

Purpose: Oral squamous cell carcinoma (SCC) invasion and metastasis result in treatment failure and correlate with increased pain. We have previously shown that the "endothelin axis," consisting of endothelin A and B receptors (ETAR and ETBR), mediates oral SCC pain, and that inhibiting ETAR with macitentan alleviates pain. We now hypothesize that the endothelin axis also mediates oral SCC growth and metastasis. We explore the therapeutic effect of concurrent ETAR antagonism (with macitentan) and ETBR re-expression on oral SCC growth and invasion in vitro and in vivo. Methods: We quantified the effect of macitentan treatment and targeted ETBR re-expression on oral SCC cell invasion and proliferation, in vitro indices of metastasis and growth, using a Matrigel invasion chamber assay and the Real Time Cell Analyzer (RTCA). We then created an oral SCC mouse model to determine the effect of macitentan treatment on oral SCC growth. Results: Macitentan treatment or ETBR re-expression alone significantly inhibited oral SCC proliferation and invasion in a dose-dependent manner; macitentan combined with ETBR re-expression had the strongest inhibitory effect on cancer proliferation and invasion. In the oral SCC mouse model, macitentan treatment and ETBR re-expression had significant anti-proliferative and anti-metastatic effects compared to control treatment. Conclusion: Our strategy of targeting the endothelin axis inhibited cancer growth and invasion in vitro and in a preclinical model. These results establish the therapeutic potential of macitentan, an orally available ETAR antagonist, for oral SCC metastasis

The widespread use of the mouse as a model system to study brain development has created the need for noninvasive neuroimaging methods that can be applied to early postnatal mice. The goal of this study was to optimize in vivo three- (3D) and four-dimensional (4D) manganese (Mn)-enhanced MRI (MEMRI) approaches for acquiring and analyzing data from the developing mouse brain. The combination of custom, stage-dependent holders and self-gated (motion-correcting) 3D MRI sequences enabled the acquisition of high-resolution (100-mum isotropic), motion artifact-free brain images with a high level of contrast due to Mn-enhancement of numerous brain regions and nuclei. We acquired high-quality longitudinal brain images from two groups of FVB/N strain mice, six mice per group, each mouse imaged on alternate odd or even days (6 3D MEMRI images at each day) covering the developmental stages between postnatal days 1 to 11. The effects of Mn-exposure, anesthesia and MRI were assessed, showing small but significant transient effects on body weight and brain volume, which recovered with time and did not result in significant morphological differences when compared to controls. Metrics derived from deformation-based morphometry (DBM) were used for quantitative analysis of changes in volume, position and signal intensity of a number of brain regions. The cerebellum, a brain region undergoing significant changes in size and patterning at early postnatal stages, was analyzed in detail to demonstrate the spatiotemporal characterization made possible by this new atlas of mouse brain development. These results show that MEMRI is a powerful tool for quantitative analysis of mouse brain development, with great potential for in vivo phenotype analysis in mouse models of neurodevelopmental diseases.

While the dopamine hypothesis has dominated schizophrenia research for several decades, more recent studies have highlighted the role of fast synaptic transmitters and their receptors in schizophrenia etiology. Here we review evidence that schizophrenia is associated with a reduction in N-methyl-d-aspartate receptor (NMDAR) function. By highlighting postmortem, neuroimaging and electrophysiological studies, we provide evidence for preferential disruption of GABAergic circuits in the context of NMDAR hypo-activity states. The functional relationship between NMDARs and GABAergic neurons is realized at the molecular, cellular, microcircuit and systems levels. A synthesis of findings across these levels explains how NMDA-mediated inhibitory dysfunction may lead to aberrant interactions among brain regions, accounting for key clinical features of schizophrenia. This synthesis of schizophrenia unifies observations from diverse fields and may help chart pathways for developing novel diagnostics and therapeutics.

Structural brain connections develop atypically in very preterm children, and altered functional connectivity is also evident in fMRI studies. Such alterations in brain network connectivity are associated with cognitive difficulties in this population. Little is known, however, about electrophysiological interactions among specific brain networks in children born very preterm. In the present study, we recorded magnetoencephalography while very preterm children and full-term controls performed a visual short-term memory task. Regions expressing task-dependent activity changes were identified using beamformer analysis, and inter-regional phase synchrony was calculated. Very preterm children expressed altered regional recruitment in distributed networks of brain areas, across standard physiological frequency ranges including the theta, alpha, beta and gamma bands. Reduced oscillatory synchrony was observed among task-activated brain regions in very preterm children, particularly for connections involving areas critical for executive abilities, including middle frontal gyrus. These findings suggest that inability to recruit neurophysiological activity and interactions in distributed networks including frontal regions may contribute to difficulties in cognitive development in children born very preterm.