Schizophrenia is a debilitating neuropsychiatric disorder that affects approximately one percent of the global population. Aberrant N-methyl-D-aspartate receptors and endoplasmic reticulum stress have been implicated in the pathogenesis of schizophrenia. Despite a century of extensive research, outcomes from best-practice treatments remain dismal. Lurasidone hydrochloride is a novel atypical antipsychotic drug with a unique receptor binding profile that can potentially treat the heterogeneous symptomology of schizophrenia. However, discrepancies in experimental design (i.e. animal models used, symptoms assessed etc.) have yielded conflicting results surrounding the procognitive and antidepressant properties of lurasidone. Furthermore, the limited aqueous solubility of lurasidone poses a considerable challenge for improving antipsychotic drug delivery to the brain and limiting the prevalence of adverse side effects. These obstacles coupled with the elusive pathophysiology of schizophrenia and its incurable nature, highlight the importance of investigating novel therapeutic targets and their underlying mechanisms to improve treatment and enhance the quality of life of patients with schizophrenia. This thesis sought to accomplish three primary objectives: (1) validate the behavioural efficacy of lurasidone hydrochloride; (2) investigate the role of mesencephalic astrocyte-derived neurotrophic factor as a potential therapeutic target of lurasidone; and (3) evaluate the therapeutic potential of intranasal lurasidone administration as a novel method for antipsychotic drug delivery. The data presented within this thesis suggest that repeated lurasidone treatment may be effective at treating the positive, negative, and cognitive symptoms of schizophrenia, but not sensorimotor gating deficits. Furthermore, sub-chronic lurasidone treatment in rats significantly increased the relative expression of mesencephalic astrocyte-derived neurotrophic factor in the rat prefrontal cortex, a primary site of impairment observed in schizophrenia. Lastly, we conclude that lurasidone administered via the nasal route using a novel poly(oligo ethylene glycol methacrylate)-based nanogel formulation required four times less drug to achieve a therapeutic response comparable to traditional intraperitoneal routes. The findings presented within this thesis suggest that lurasidone might be a favourable atypical antipsychotic drug that exerts its therapeutic effects through the modulation of neurotrophic factor expression in the brain regions affected by schizophrenia. This thesis offers new insight that can help guide future studies toward improving the prognosis of patients suffering from schizophrenia. / Thesis / Master of Science (MSc)

Fragile X Syndrome (FXS) is caused by the instability of a CGG-repeated tract at the 5’ end of the Fmr1 transcript. This instability causes silencing of the gene coding for FMRP. Higher levels of reactive oxygen species, lipid peroxidation, and protein oxidation within brain tissue have been found to be associated with the disease. These imbalances, along with altered levels of components of the glutathione system, provide evidence for increased oxidative stress. Astrocytes, glial cells within the brain, have many functions within neurodevelopment. Specifically, they regulate growth and synaptic contacts of neurons, regulate the level of excitability of synapses, and protect neurons at high levels of activity. To protect neurons from oxidative stress, astrocytes maintain oxidative homeostasis through their mitochondrial electron transport and antioxidant systems. This study examines the relationship between oxidative stress and FXS by assessing mitochondrial function and the antioxidant system of astrocytes. Using the Fmr1 knockout (KO) mouse model, mitochondrial respiration, and reactive oxygen species (ROS) production was analyzed in cultured cortical astrocytes. Astrocytes collected from male and female mice were analyzed under both normoxic and hypoxic conditions. In addition, western blots were conducted on both cortical tissue and cultured cortical astrocytes to determine potential differences in enzyme expression. Results indicate elevations of leak state respiration and ROS production in Fmr1 KO cultured cortical astrocytes alongside alterations in antioxidant and NADPH-oxidase expression. Characterization of mitochondrial function and the antioxidant system of astrocytes will be highly valuable to the understanding of glial roles during brain development and could provide future insight to direct clinically relevant studies of FXS and other neurodevelopment disorders. / Thesis / Master of Science (MSc) / Fragile X Syndrome (FXS) is the most common genetic cause of intellectual disability. It is characterized by the loss of FMRP, an important protein in brain development. Within the FXS brain there is evidence of oxidative stress. The cells that maintain oxidative homeostasis in the brain are astrocytes. Astrocytes are glial cells important for brain development. This thesis evaluated astrocytes' ability to maintain oxidative homeostasis in the FXS cortex. The findings of this thesis provide important insights into our understanding of FXS pathology and will help direct clinically relevant studies of FXS and other neurodevelopmental disorders.

Le récepteur du glutamate de type N-méthyl-D-aspartate (NMDAR) est un transducteur clef dans la physiologie du système nerveux et dans nombre de ses pathologies, selon qu’il est localisé à la synapse ou en position extra-synaptique respectivement. Son activité est sous le contrôle étroit du ‘site-glycine’, dont l’activation est gouvernée par la disponibilité en coagoniste. Pourtant, on ignore encore largement les règles qui régissent cette étape limitante de l’activation des NMDARs in situ. Par ailleurs, l’ensemble des onnaissances actuelles suggère que les astrocytes pourraient contrôler les NMDARs dans le contexte des interactions entre cellules gliales et neurones, en particulier via la libération du gliotransmetteur D-sérine. Le principal objectif de ce travail de thèse a été de comprendre les modalités du contrôle endogène des NMDARs par leur site co-agoniste, dans la région CA1 de l’hippocampe. Nous avons porté notre attention, avant tout, sur les acteurs de ce contrôle : la glycine et la D-sérine, qui sont les ligands endogènes du site-co-agoniste. Nous nous sommes intéressés à leur contribution respective dans le contrôle des NMDARs, aux dynamiques de ce contrôle en fonction de l’activité neuronale, à ses variations en fonction de la localisation des NMDARs, ainsi qu’à ses modifications développementales. Nous montrons par des approches d’électrophysiologie que la D-sérine, et non la glycine, est le co-agoniste endogène des NMDARs à la synapse CA3-CA1 chez l’adulte. Elle est délivrée par les prolongements astrocytaires environnants, d’une manière qui est influencée par l’activité synaptique. Sa libération répond à un mécanisme vésiculaire et est dépendante de la signalisation calcique intra-astrocytaire. De cette manière, les astrocytes exercent un contrôle étroit et dynamique des NMDARs à l’état basal et au cours de phénomènes de plasticité synaptique. En contre partie, à l’inverse de leurs homologues localisés à la synapse, les NMDARs extrasynaptiques sont contrôlés par la glycine à l’âge adulte. Cette compartimentation spatiale est dictée par une disponibilité différentielle des deux co-agonistes aux différents sites. Elle est également favorisée par une composition en sous-unités des NMDARs synaptiques et extra-synaptiques différente qui leur confère une affinité distincte pour la glycine et la D-sérine. Enfin, le contrôle des NMDARs par la D-sérine astrocytaire observé à l’âge adulte n’est pas opérationnel à la naissance. En effet, il ne se met en place qu’au cours du premier mois post-natal, de façon concomitante au changement de composition en sous-unités des NMDARs. / N-methyl D-aspartate receptors (NMDARs) are central to many aspects of brain physiology and pathology, which they impact differently depending on their synaptic or extrasynaptic location, respectively. In addition to glutamate, they are gated by the necessary binding of a co-agonist on the so-called ‘glycine-binding site’. However, very little is known about the rules that govern the control of NMDARs through this site, in situ. Evidence now suggests that astrocytes could play a critical role in controlling NMDARs activity, in particular through the release of the gliotransmitter D-serine. In the present work, we aimed at understanding how NMDARs are endogenously controlled through their co-agonist binding site, in the CA1 region of rat hippocampus. We primarily focused on the role of two endogenous ligands of this site: glycine and D-serine. We investigated their relative contribution in the control of NMDARs at the different subcellular locations, the dynamics of such control according to synaptic activity, as well as possible changes during post-natal development. Using elecrophysiological approaches, we demonstrate that NMDARs are gated by Dserine, but not glycine, at CA3-CA1 synapses in adults. D-serine is supplied at least in part by surrounding astrocytes in an activity-dependant manner. Its release occurs in response to calcium signalling within the astrocyte and in a vesicular way. Correspondingly, we found astrocytic supply of D-serine to be essential for NMDARs-dependant functions such as synaptic plasticity. In contrast with their synaptic counterparts, extrasynaptic NMDARs are gated by endogenous glycine and not by D-serine. We provide evidence that this compartmentation relies on the differential availability of the two co-agonists at synaptic and extrasynaptic sites. Besides, due to differences in their subunit composition, synaptic and extrasynaptic NMDARs may have preferential affinity for D-serine and glycine respectively. Finally, we show that the control of the NMDAR co-agonist site is developmentally regulated. Early after birth, glycine is the endogenous co-agonist of synaptic NMDARs. The control exerted by D-serine only progressively appears during the first post-natal month, as the switch in NMDARs subunit composition occurs, suggesting a maturation of cellular interactions at the tripartite synapse.

Les grands prématurés sont particulièrement vulnérables aux lésions inflammatoires de la substance blanche (WMI) qui augmentent le risque de troubles cognitifs et neurodéveloppementaux à long terme dans cette population. L’utilisation de l’imagerie par résonance magnétique (IRM) dans cette population a permis une évaluation non invasive de la progression des WMI et une meilleure compréhension de la pathologie. Les WMI sont associées une activation de la microglie et des astrocytes et la production de facteurs pro-inflammatoires, dont l’interleukine 1 (IL-1). En utilisant un modèle de WMI induite par injection intracérébrale de lipopolysaccharides (LPS), nous avons évalué dans un premier temps les changements de méthylation de l’ADN durant la phase aigüe (24 h) et la phase chronique (21 jours) de l’inflammation. Par la suite, nous avons déterminé la capacité de l’IRM multimodale de détecter la lésion et la réponse thérapeutique à un antagoniste du récepteur de l’IL-1. Finalement, par le biais d’un antagoniste et d’un modulateur allostérique du récepteur à l’IL-1, nous avons évalué in vitro le rôle de la signalisation IL-1 durant la phase aigüe de la modulation de l’activation de la microglie et des astrocytes par le LPS. Nous avons démontré la présence d’une altération du méthylome cérébral dans divers mécanismes liés au neurodéveloppement et à la réponse immunitaire. De plus, l’application de l’IRM multimodale dans notre modèle a permis d’évaluer in vivo la lésion et le début de la réponse thérapeutique durant la phase aigüe (24 h) de l’inflammation. L’évaluation à l’IRM corrèle aux changements observés par immunomarquage post mortem. In vitro, le LPS induit une réponse mixte de la microglie et des astrocytes qui évoluent dans le temps vers une réponse pro-inflammatoire et neurotoxique. Bien que l’IL-1 est hautement exprimée par la microglie et les astrocytes, son inhibition a un effet limité sur la modulation de l’activation gliale dû à la multitude de voies activées par le LPS durant la phase aigüe de l’inflammation. / Very premature infants are particularly vulnerable to inflammatory white matter injury (WMI) which increases the risk of long-term cognitive and neurodevelopmental disorders in this population. The use of magnetic resonance imaging (MRI) in this population has allowed non-invasive assessment of the progression of WMI and a better understanding of the pathology. WMI is associated with activation of microglia and astrocytes and the production of pro-inflammatory mediators, including interleukin 1 (IL-1). Using a model of inflammatory WMI induced by intracerebral injection of lipopolysaccharides (LPS), we first evaluated the changes in DNA methylation during the acute phase (24 h) and the chronic phase (21 days) of inflammation. We then determined the ability of multimodal MRI to detect the lesion and the therapeutic response to an IL-1 receptor antagonist. Finally, using an antagonist and an allosteric modulator of the IL-1 receptor, we evaluated in vitro the contribution of IL-1 signaling during the acute phase of the modulation of microglia and astrocytes activation by LPS. We have shown the presence of persistent alteration DNA methylation profile in the brain that was associated with pathways involved in neurodevelopment and immune response. In addition, the application of multimodal MRI in our model made it possible to evaluate in vivo the lesion and the therapeutic response during the acute phase (24 h) of the inflammation. The changes at the MRI correlated to post-mortem evaluation by immunostaining. In vitro, LPS induce a mixed response of microglia and astrocytes which evolved over time toward a pro-inflammatory and neurotoxic phenotype. Although IL-1 is highly expressed by microglia and astrocytes, its inhibition has a limited effect on the modulation of glial activation due to the multitude of pathways activated by LPS during the acute phase of inflammation.

Hepatocellular carcinoma (HCC) is a devastating form of liver cancer that accounts for 80% of liver cancers. HCC has a poor prognosis with five-year survival of less than 12% in the United States. We in previous studies have identified Astrocyte Elevated Gene-1 (AEG-1) as an aberrantly overexpressed gene in many cancers including HCC, regulating tumor progression. Microarray studies identified the small transmembrane protein, tetraspanin8 (TSPAN8) as a downstream of AEG-1. TSPAN8 belongs to the family of TETRASPANINS with the characteristic of crossing the membrane four times, and regulating a wide range of cellular phenomena. TSPAN8 is implicated in metastasis and is classified as a metastasis promoting tetraspanin. To understand the role of TSPAN8 in the context of AEG-1 regulated tumor progression of HCC, we generated knockdown clones of TSPAN8 in AEG-1-8 cell lines (HepG3 cell lines with stable overexpression of AEG-1), and analyzed cellular events that mediate metastasis such as migration, invasion and in-vivo tumorogenesis. Our in-vitro studies show that knockdown of TSPAN8 in AEG-1 overexpressing cells significantly abrogated migration, matrigel invasion, proliferation and endothelial cell activation. Moreover, we show that knockdown of TSPAN8 significantly inhibited intrahepatic metastasis of orthotopic xenografts in the livers of athymic nude mice. TSPAN8 might be a useful diagnostic marker and potential therapeutic target for HCC. These findings indicate that upregulation of TSPAN8 might be an important event in mediating the oncogenic function of AEG-1.

Endogenous bioelectric fields guide morphogenesis during embryonic development and regeneration by directly regulating the cellular functions responsible for these phenomena. Although this role has been extensively explored in many peripheral tissues, the ability of electric fields to regulate wound repair and stimulate regeneration in the mammalian central nervous system (CNS) has not been convincingly established. This dissertation explores the role of electric fields in regulating the injury response and controlling the regenerative potential of the mammalian CNS. We place particular emphasis on their influence on astrocytes, as specific differences in their injury-induced behaviors have been associated with differences in the regenerative potential demonstrated between mammalian and non-mammalian vertebrates. For example, astrocytes in both mammalian and non- mammalian vertebrates begin migrating towards the lesion within hours and begin to proliferate after an initial delay of two days; subsequently, astrocytes in non-mammalian vertebrates support neurogenesis and assume a bipolar radial glia-like morphology that guides regenerating axons, whereas astrocytes in mammals do not demonstrate robust neurogenesis and undergo a hypertrophic response that inhibits axon sprouting. To test whether injury-induced electric fields drive the astrocytic response to injury, we exposed separate populations of purified astrocytes from the rat cortex and cerebellum to electric field intensities associated with intact and injured mammalian tissues, as well as to those electric field intensities measured in regenerating non-mammalian vertebrate tissues. Upon exposure to electric field intensities associated with uninjured tissue, astrocytes showed little change in their cellular behavior. However, cortical astrocytes responded to electric field intensities associated with injured mammalian tissues by demonstrating dramatic increases in migration and proliferation, behaviors that are associated with their formation of a glial scar in vivo; in contrast, cerebellar astrocytes, which do not organize into a demarcated glial scar, did not respond to these electric fields. At electric field intensities associated with regenerating tissues, both cerebellar and cortical astrocytes demonstrated robust and sustained responses that included morphological changes consistent with a regenerative phenotype. These results support the hypothesis that physiologic electric fields drive the astrocytic response to injury, and that elevated electric fields may induce a more regenerative response among mammalian astrocytes.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

La sclérose en plaques (SEP) est une maladie neuro-inflammatoire chronique, première cause de handicap chez le jeune adulte. Actuellement, aucun traitement ne freine l'aggravation des symptômes liée aux formes progressives. Bien que connue, l'implication des macrophages et de la microglie dans la démyélinisation et l'atteinte axonale doit être plus finement caractérisée. Ce d'autant plus que la plasticité fonctionnelle de ces cellules suggère une réponse spécifique selon la pathologie, la localisation des lésions et le stade évolutif de la maladie. Ce travail de thèse a consisté en une caractérisation moléculaire des programmes d'activation macrophagique/ microgliale dans deux types d'altérations tissulaires du système nerveux central des patients SEP : les zones partiellement démyélinisées bordant les plaques de la moelle épinière et les lésions corticales. Cette étude a été réalisée sur des tissus post-mortem de patients atteints de formes progressives, formes dans lesquelles les lésions médullaires et corticales sont nombreuses et impliquées dans le handicap progressif et irréversible. Nous avons identifié des spécificités moléculaires caractérisant l'activation macrophagique/microgliale au cours de la SEP en comparant, par une approche in silico, les profils caractérisés à ceux observés dans des pathologies neuro-dégénératives à composantes inflammatoires, la maladie d'Alzheimer et de Parkinson notamment. Dans l'ensemble, ces résultats suggèrent que l'activation chronique des macrophages/cellules microgliales contribue à l'extension à bas bruit des lésions médullaires et corticales pendant la phase progressive de la SEP et proposent de nouvelles cibles thérapeutiques / Multiple sclerosis (MS) is a chronic neuro-inflammatory disease and the most common cause of chronic neurological disability in young adults. No treatment is currently available to prevent the aggravation of symptoms in the progressive forms of the disease. The involvement of macrophages and microglia in demyelination and axonal injury is well known but need to be further characterized. Especially, the high level of functional plasticity harboured by macrophages/ microglia suggests that these cells engage specific activation programs depending on the disease, its evolution stage and the localization of lesions. In this context, this phD thesis was essentially aimed to characterize macrophage/microglia activation programs in two categories of tissue alterations observed in the post-mortem central nervous system from MS patients: 1) partially demyelinated areas at the border of spinal cord plaques and 2) cortical lesions. These two particular types of lesions are both highly frequent in progressive forms of MS and suspected to be involved in chronic and irreversible neurological disability. Using an in silico approach, the macrophage/microglia activation programs identified in MS were then compared to those observed in neurodegenerative and inflammatory disorders such as Alzheimer's disease and Parkinson's disease. Overall, our results suggest that the chronic activation of macrophages and microglia largely contributes to the slow and chronic expansion of MS lesions in progressive forms of the disease. Our work also proposes new therapeutic targets

O Acidente Vascular Encefálico (AVE) Hemorrágico representa mais de 10% de todos os casos de AVE e possui altas taxas de morbidade e de mortalidade. Os pacientes que sobrevivem a este evento permanecem com alguma disfunção motora, que algumas vezes é incapacitante. O extravasamento de sangue em um AVE hemorrágico ocorre, geralmente, em regiões onde há bifurcação de pequenas arteríolas penetrantes, como na região dos núcleos da base. O estriado, importante componente dessa região, está relacionado a funções motoras superiores, como o planejamento e a execução do movimento. Alguns estudos demonstram que o pré-condicionamento (PC) isquêmico pode gerar a tolerância a outros eventos que acometem o sistema nervoso. O PC é definido como fenômeno decorrente da exposição de um tecido ou órgão a um insulto sub-letal capaz de resultar em adaptações determinantes para a tolerância tecidual. Isso ocorre mesmo quando esses dois estímulos são de origens diferentes; neste caso diz-se que o PC desenvolveu tolerância cruzada. Desta forma, o presente estudo dedicou-se ao estudo de efeitos celulares e funcionais do pré-condicionamento isquêmico, por oclusão bilateral das artérias carótidas durante 10 minutos, sobre o modelo de hemorragia intracerebral (HIC), por administração intraestriatal de colagenase do tipo IV-S em ratos. A hipótese de trabalho era de que o PC causaria tolerância cruzada para a HIC, e consequente neuroproteção avaliada por testes motores, volume de lesão, com envolvimento de astrocitose e de micróglia reativa Foram usados 67 ratos machos Wistar adultos, divididos em 4 grupos: Sham (controle cirúrgico), PC, HIC, PC+HIC. Assim, os animais dos grupos PC e PC+HIC foram submetidos ao pré-condicionamento e 24 horas depois os animais HIC e PC+HIC receberam a injeção de colagenase, enquanto os animais Sham e PC receberam uma injeção de salina. A avaliação motora dos animais foi realizada a partir dos testes do cilindro e do Staircase. Trinta e quatro dias após a HIC os animais foram perfundidos e o estriado ipsilateral à injeção foi dissecada para obtenção de amostras teciduais necessárias à avaliação da perda tecidual e quantificação de intensidade de fluorescência de GFAP (proteína glial fibrilar ácida) e OX-42, importantes marcadores de astrócitos e microglia, respectivamente. Os resultados demonstram que: a) a HIC causa deficits motores em ambos os testes realizados, e que o PC reverte este efeito; b) a HIC causa lesão estriatal que não é revertido pelo pré-condicionamento; c) a HIC causa aumento da intensidade de fluorescência para GFAP e para OX-42, e o PC reverte apenas a reatividade da micróglia. Em conjunto, sugere-se que o pré-condicionamento isquêmico causa tolerância cruzada com a hemorragia intracerebral experimental, resultando em proteção funcional, mas não morfológica, possivelmente associada a uma diminuição da reatividade da microglia após o evento hemorrágico. / Hemorrhagic Vascular Stroke (EVA) represents more than 10% of all stroke cases with high rates of morbidity and mortality. Patients who survive this event, remain with some motor dysfunction, which is sometimes disabling. The extravasation of blood in a hemorrhagic stroke occurs, generally, in regions where there is bifurcation of small vessels, as in the region of striatum. The striatum is related to the higher motor functions, such as the planning and execution of the movement. Some studies have shown that preconditioning (PC) can generate a tolerance to other events that accompany the nervous system. The PC is presented as the source of the exposure of a sub-lethal, resulting in an adaptation of determinants to a tissue tolerance. Thus, the present study aimed shows the ischemic preconditioning effects, by bilateral occlusion of the carotid arteries for 10 minutes, on the intracerebral hemorrhage (ICH) model, by intra- striatum administration of type IV S collagenase in rats. The working hypothesis was tolerance to HIC, and consequent neuroprotection by motor function, lesion volume, astrocytosis and reactive microglia. A total of 84 male Wistar adult rats were divided into 4 groups: Sham (surgical control), PC, HIC, PC + HIC Thus, the animals of the PC and PC + HIC groups were introduced to the preconditioning and 24 hours later, the HIC and PC + HIC animals received a collagenase injection, while the Sham and PC animals received a saline injection. The evaluation of the animal function was performed from cylinder and Staircase tests. Thirty-four days after the surgery, the striatum was dissected and prepared to lesion volume analysis and fluorescence intensity of GFAP quantification (acid glial fibrillary protein) and OX-42, important astrocyte and microglia markers respectively. The results demonstrate that: a) an HIC causes motor deficits in both tests performed, and that the PC reverses this effect; b) an ICH causes a striatal lesion that is not reversed by preconditioning; c) an HIC promoted high fluorescence intensity for GFAP and OX-42, and PC reverses the microglia reactivity. Taken together, we suggest that ischemic preconditioning combined with experimental intracerebral hemorrhage, promotes functional but not morphological protection, being associated with the microglial reactivity decrease after the hemorrhagic event.

Les astrocytes sont des cellules gliales jouant un rôle primordial dans le fonctionnement cérébral. Ils remplissent de nombreuses fonctions allant de la régulation de l'homéostasie ionique, à la modulation de la transmission synaptique en passant par la régulation du métabolisme énergétique. Les transporteurs astrocytaires au glutamate GLAST et GLT-1 tiennent un rôle particulièrement important dans ces fonctions astrocytaires. La recapture du glutamate libéré dans la synapse module la neurotransmission et évite la stimulation excessive des récepteurs glutamatergiques qui peut induire des phénomènes d'excitotoxicité provoquant la mort des neurones. Le couplage neurométabolique entre astrocytes et neurones repose également sur l'activité de ces transporteurs. De nombreuses données indiquent que des déficits des transporteurs au glutamate sont impliqués dans la plupart des maladies neurodégénératives. Les astrocytes et les transporteurs au glutamate représentent ainsi de potentielles cibles thérapeutiques dans le cadre des maladies neurodégénératives. L'étude de ces interactions neurones-astrocytes, en particulier sur des modèles in vivo, nécessite des outils particuliers permettant de disséquer le rôle de chaque type cellulaire. Cependant, il existe peu d'outils spécifiques et efficaces pour cibler les astrocytes in vivo. Notre objectif a été de développer un nouveau vecteur viral permettant une transduction spécifique des astrocytes in vivo, avec une efficacité importante et pouvant être utilisé dans l'ensemble du cerveau avec de nombreux transgènes. Au cours de ce travail nous avons développé trois voies de recherche. Ainsi, nous avons modifié l'enveloppe du vecteur et tester trois glycoprotéines d'enveloppe, VSV, Mokola et Rabies. Nous avons également utilisé trois promoteurs différents, PGK, CMV et EAAT1 afin de moduler l'expression du transgène dans les astrocytes. Et enfin, nous avons développé une nouvelle méthode de régulation post-transcriptionnelle utilisant les microARN. Nos résultats permettent de conclure qu'un vecteur lentiviral avec l'enveloppe Mokola, contenant le promoteur PGK et des cibles de microARN spécifiques des neurones est un outil efficace pour cibler les astrocytes in vivo. Nous avons utilisé ce nouvel outil pour surexprimer les transporteurs astrocytaires au glutamate (GLAST et GLT-1) et pour inhiber leur expression grâce aux techniques de « RNA silencing ». La surexpression du transporteur GLAST permet une neuroprotection significative en condition excitotoxique tandis que l'inhibition de GLT-1 induit une diminution du métabolisme cérébral. Ces résultats préliminaires apportent la preuve de principe de l'efficacité de notre outil in vivo et confirment le rôle central des transporteurs astrocytaires. Il est ainsi possible d'anticiper que ce nouvel outil permettra à la fois une meilleure compréhension du fonctionnement des astrocytes in vivo et qu'il peut représenter un vecteur de choix dans la perspective d'une thérapie génique ciblant ces cellules.