Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid-β peptide (Aβ) in the brain and intraneuronal hyperphosphorylated tau. Microglia in the brain adopt M1 (pro-inflammatory) or M2 (anti-inflammatory) phenotypes similar to peripheral monocytes. M1 microglia negatively affect neurogenesis and have reduced phagocytic capabilities whereas M2 microglia can enhance neurogenesis and support phagocytosis. Cluster of Differentiation-200 (CD200) is an anti-inflammatory glycoprotein physiologically expressed on neurons and lymphocytes, and its receptors (CD200R1 and CD200R3) are expressed on glia. Both AD patients and mouse models of AD show an age-related or Aβ-induced reduction in neural CD200 that may contribute to M1-skewing of microglia in AD. We hypothesize that CD200 skews microglia to an M2 phenotype, and that genetic over-expression of CD200 in transgenic mice expressing the Swedish familial AD mutation of human β-amyloid precursor protein (APP mice) can restore neurogenesis and enhance Aβ clearance in the hippocampus. In this study, we constructed a tetracycline-controlled transactivator-inducible adeno-associated virus serotype 2/1 expressing full-length CD200 (AAV2/1-CD200) or green fluorescent protein (AAV2/1- GFP). These were bilaterally injected into the hippocampi at 6 months of age, and mice were sacrificed at 12 months of age. AAV2/1-GFP-injected APP mice showed a reduction in number of proliferating neural stem cells (NSCs) by 65.0% and differentiating NSCs by 70.5% in the dentate gyrus compared to wild-type controls. AAV2/1-CD200 restored these neurogenic deficits to those of wild-type mouse levels. AAV2/1-CD200 reduced diffuse Aβ plaques in the hippocampal region by 65.5% compared to AAV2/1-GFP-injected APP mice, but did not alter thioflavin-S-positive compact plaques as measured by protein and immunohistochemical assays. In vitro studies demonstrated that CD200-stimulated microglia co-cultured in transwells increased differentiation and complexity of neural stem cells. CD200 also directly enhanced Aβ phagocytosis by microglia. CD200 enhanced expression of the adaptor protein TYRO protein tyrosine kinase binding protein (TYROBP), suggesting this may be the mechanism by which CD200 enhances phagocytosis of Aβ. Overall, the data presented here indicate that CD200 is a plausible therapeutic agent in patients with AD to enhance neural differentiation and microglial-mediated clearance of Aβ.

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京都大学 / 新制・課程博士 / 博士(医学) / 甲第24086号 / 医博第4862号 / 新制||医||1059(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 井上 治久, 教授 渡邉 大, 教授 高橋 淳 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

La tolérance immunitaire dépend de la distinction entre le soi et le non soi par le système immunitaire. Un bris dans la tolérance immunitaire mène à l'auto-immunité, qui peut provoquer la destruction des organes, des glandes, des articulations ou du système nerveux central. Le diabète auto-immun, également connu sous le nom diabète juvénile et diabète de type 1, résulte d'une attaque auto-immune sur les cellules β pancréatiques sécrétrices d’insuline, localisées au niveau des îlots de Langerhans du pancréas. Bien que le diabète auto-immun soit traitable par une combinaison d’injections quotidiennes d’insuline d’origine exogène, de régime et d'exercices, beaucoup de complications chroniques peuvent se manifester chez les patients, y compris, mais non limitées à, la cécité, les maladies cardiovasculaires, l’insuffisance rénale et l'amputation. En raison des nombreuses complications liées au diabète auto-immun à long terme, la recherche continue afin de mieux comprendre tous les facteurs impliqués dans la progression de la maladie dans le but de développer de nouvelles thérapies qui empêcheront, renverseront et/ou traiteront cette maladie. Un rôle primordial dans la génération et l'entretien de la tolérance immunitaire a été attribué au nombre et à la fonction des sous-populations de cellules régulatrices. Une de ces populations est constituée de cellules T CD4-CD8- (double négatives, DN), qui ont été étudiées chez la souris et l'humain pour leur contribution à la tolérance périphérique, à la prévention des maladies et pour leur potentiel associé à la thérapie cellulaire. En effet, les cellules de T DN sont d'intérêt thérapeutique parce qu'elles montrent un potentiel immunorégulateur antigène-spécifique dans divers cadres expérimentaux, y compris la prévention du diabète auto-immun. D’ailleurs, en utilisant un système transgénique, nous avons démontré que les souris prédisposées au diabète auto-immun présentent peu de cellules T DN, et que ce phénotype contribue à la susceptibilité au diabète auto-immun. En outre, un transfert des cellules T DN est suffisant pour empêcher la progression vers le diabète chez les souris prédisposées au diabète auto-immun. Ces résultats suggèrent que les cellules T DN puissent présenter un intérêt thérapeutique pour les patients diabétiques. Cependant, nous devons d'abord valider ces résultats en utilisant un modèle non-transgénique, qui est plus physiologiquement comparable à l'humain. L'objectif principal de cette thèse est de définir la fonction immunorégulatrice des cellules T DN, ainsi que le potentiel thérapeutique de celles-ci dans la prévention du diabète auto-immun chez un modèle non-transgénique. Dans cette thèse, on démontre que les souris résistantes au diabète auto-immun présentent une proportion et nombre absolu plus élevés de cellules T DN non-transgéniques, lorsque comparées aux souris susceptibles. Cela confirme une association entre le faible nombre de cellules T DN et la susceptibilité à la maladie. On observe que les cellules T DN éliminent les cellules B activées in vitro par une voie dépendante de la voie perforine et granzyme, où la fonction des cellules T DN est équivalente entre les souris résistantes et prédisposées au diabète auto-immun. Ces résultats confirment que l'association au diabète auto-immun est due à une insuffisance en terme du nombre de cellules T DN, plutôt qu’à une déficience fonctionnelle. On démontre que les cellules T DN non-transgéniques éliminent des cellules B chargées avec des antigènes d'îlots, mais pas des cellules B chargées avec un antigène non reconnu, in vitro. Par ailleurs, on établit que le transfert des cellules T DN activées peut empêcher le développement du diabète auto-immun dans un modèle de souris non-transgénique. De plus, nous observons que les cellules T DN migrent aux îlots pancréatiques, et subissent une activation et une prolifération préférentielles au niveau des ganglions pancréatiques. D'ailleurs, le transfert des cellules T DN entraîne une diminution d'auto-anticorps spécifiques de l'insuline et de cellules B de centres germinatifs directement dans les îlots, ce qui corrèle avec les résultats décrits ci-dessus. Les résultats présentés dans cette thèse permettent de démontrer la fonction des cellules T DN in vitro et in vivo, ainsi que leur potentiel lié à la thérapie cellulaire pour le diabète auto-immun. / Immune tolerance is dependent on the immune system discriminating between self and non-self. A break in immune tolerance results in autoimmunity, which can lead to the destruction of healthy organs, glands, joints or the central nervous system. Any disease that results from such an aberrant immune response is termed an autoimmune disease. Autoimmune diabetes, which is also referred to as juvenile diabetes and type 1 diabetes, results from an autoimmune attack on the insulin-producing β cells located within the islets of Langerhans of the pancreas. Although autoimmune diabetes is treatable through a combination of insulin therapy, diet and exercise, many chronic complications may arise in patients, including, but not limited to, blindness, cardiovascular disease, kidney failure and amputation. Due to the many complications associated with long-term autoimmune diabetes, research continues to better understand all the factors implicated in disease progression in order to develop new therapies that will prevent, reverse and/or cure this disease. A prominent role in the generation and maintenance of immune tolerance has been attributed to the number and function of regulatory cell subsets. One of these regulatory cell populations, namely CD4-CD8- (double negative, DN) T cells, have been studied in both mice and humans for their contribution to peripheral tolerance, disease prevention and their potential for use in cellular therapy. DN T cells are of particular therapeutic interest because they exhibit an antigen-specific immunoregulatory potential in various experimental settings, including the prevention of autoimmune diabetes. Indeed, using a transgenic system, we have shown that autoimmune diabetes-prone mice carry fewer DN T cells and that this phenotype contributes to autoimmune diabetes susceptibility, where a single transfer of DN T cells is sufficient to prevent diabetes progression in otherwise autoimmune diabetes-prone mice. These results suggest that DN T cells may be of therapeutic interest for diabetic patients. However, we must first validate these results using a non-transgenic setting, which is more physiologically relevant to humans. The main objective of this thesis is to determine the immunoregulatory function of the DN T cells as well as the therapeutic potential of these cells in the prevention of autoimmune diabetes in the non-transgenic setting. Here, we show that diabetes-resistant mice present with a higher proportion and cell number of DN T cells than diabetes-susceptible mice in the non-transgenic setting, which associates a deficiency in DN T cell number with disease susceptibility. We determine that DN T cells eliminate activated B cells in vitro via a perforin/granzyme-dependent pathway, where the function of DN T cells is equal between the diabetes-resistant and -susceptible mice, demonstrating that the association to autoimmune diabetes is due to a deficiency in DN T cell number rather than function. Interestingly, we show that non-transgenic DN T cells eliminate B cells loaded with islet antigen, but not B cells loaded with an irrelevant antigen, in vitro. Importantly, we establish that the transfer of activated DN T cells could prevent autoimmune diabetes development in the non-transgenic setting. Interestingly, we reveal that DN T cells migrate to the pancreatic islets and undergo preferential activation and proliferation within the pancreatic lymph nodes. Moreover, the transfer of DN T cells results in a decrease in both germinal center B cells directly within the pancreatic islets as well serum insulin autoantibody levels, which correlates with the aforementioned findings. Altogether, the results presented in this thesis have allowed us to enhance our understanding of the function of DN T cells both in vitro and in vivo as well as demonstrate the therapeutic potential for DN T cells as a novel cellular therapeutic for autoimmune diabetes.

La tolérance immunitaire dépend de la distinction entre le soi et le non soi par le système immunitaire. Un bris dans la tolérance immunitaire mène à l'auto-immunité, qui peut provoquer la destruction des organes, des glandes, des articulations ou du système nerveux central. Le diabète auto-immun, également connu sous le nom diabète juvénile et diabète de type 1, résulte d'une attaque auto-immune sur les cellules β pancréatiques sécrétrices d’insuline, localisées au niveau des îlots de Langerhans du pancréas. Bien que le diabète auto-immun soit traitable par une combinaison d’injections quotidiennes d’insuline d’origine exogène, de régime et d'exercices, beaucoup de complications chroniques peuvent se manifester chez les patients, y compris, mais non limitées à, la cécité, les maladies cardiovasculaires, l’insuffisance rénale et l'amputation. En raison des nombreuses complications liées au diabète auto-immun à long terme, la recherche continue afin de mieux comprendre tous les facteurs impliqués dans la progression de la maladie dans le but de développer de nouvelles thérapies qui empêcheront, renverseront et/ou traiteront cette maladie. Un rôle primordial dans la génération et l'entretien de la tolérance immunitaire a été attribué au nombre et à la fonction des sous-populations de cellules régulatrices. Une de ces populations est constituée de cellules T CD4-CD8- (double négatives, DN), qui ont été étudiées chez la souris et l'humain pour leur contribution à la tolérance périphérique, à la prévention des maladies et pour leur potentiel associé à la thérapie cellulaire. En effet, les cellules de T DN sont d'intérêt thérapeutique parce qu'elles montrent un potentiel immunorégulateur antigène-spécifique dans divers cadres expérimentaux, y compris la prévention du diabète auto-immun. D’ailleurs, en utilisant un système transgénique, nous avons démontré que les souris prédisposées au diabète auto-immun présentent peu de cellules T DN, et que ce phénotype contribue à la susceptibilité au diabète auto-immun. En outre, un transfert des cellules T DN est suffisant pour empêcher la progression vers le diabète chez les souris prédisposées au diabète auto-immun. Ces résultats suggèrent que les cellules T DN puissent présenter un intérêt thérapeutique pour les patients diabétiques. Cependant, nous devons d'abord valider ces résultats en utilisant un modèle non-transgénique, qui est plus physiologiquement comparable à l'humain. L'objectif principal de cette thèse est de définir la fonction immunorégulatrice des cellules T DN, ainsi que le potentiel thérapeutique de celles-ci dans la prévention du diabète auto-immun chez un modèle non-transgénique. Dans cette thèse, on démontre que les souris résistantes au diabète auto-immun présentent une proportion et nombre absolu plus élevés de cellules T DN non-transgéniques, lorsque comparées aux souris susceptibles. Cela confirme une association entre le faible nombre de cellules T DN et la susceptibilité à la maladie. On observe que les cellules T DN éliminent les cellules B activées in vitro par une voie dépendante de la voie perforine et granzyme, où la fonction des cellules T DN est équivalente entre les souris résistantes et prédisposées au diabète auto-immun. Ces résultats confirment que l'association au diabète auto-immun est due à une insuffisance en terme du nombre de cellules T DN, plutôt qu’à une déficience fonctionnelle. On démontre que les cellules T DN non-transgéniques éliminent des cellules B chargées avec des antigènes d'îlots, mais pas des cellules B chargées avec un antigène non reconnu, in vitro. Par ailleurs, on établit que le transfert des cellules T DN activées peut empêcher le développement du diabète auto-immun dans un modèle de souris non-transgénique. De plus, nous observons que les cellules T DN migrent aux îlots pancréatiques, et subissent une activation et une prolifération préférentielles au niveau des ganglions pancréatiques. D'ailleurs, le transfert des cellules T DN entraîne une diminution d'auto-anticorps spécifiques de l'insuline et de cellules B de centres germinatifs directement dans les îlots, ce qui corrèle avec les résultats décrits ci-dessus. Les résultats présentés dans cette thèse permettent de démontrer la fonction des cellules T DN in vitro et in vivo, ainsi que leur potentiel lié à la thérapie cellulaire pour le diabète auto-immun. / Immune tolerance is dependent on the immune system discriminating between self and non-self. A break in immune tolerance results in autoimmunity, which can lead to the destruction of healthy organs, glands, joints or the central nervous system. Any disease that results from such an aberrant immune response is termed an autoimmune disease. Autoimmune diabetes, which is also referred to as juvenile diabetes and type 1 diabetes, results from an autoimmune attack on the insulin-producing β cells located within the islets of Langerhans of the pancreas. Although autoimmune diabetes is treatable through a combination of insulin therapy, diet and exercise, many chronic complications may arise in patients, including, but not limited to, blindness, cardiovascular disease, kidney failure and amputation. Due to the many complications associated with long-term autoimmune diabetes, research continues to better understand all the factors implicated in disease progression in order to develop new therapies that will prevent, reverse and/or cure this disease. A prominent role in the generation and maintenance of immune tolerance has been attributed to the number and function of regulatory cell subsets. One of these regulatory cell populations, namely CD4-CD8- (double negative, DN) T cells, have been studied in both mice and humans for their contribution to peripheral tolerance, disease prevention and their potential for use in cellular therapy. DN T cells are of particular therapeutic interest because they exhibit an antigen-specific immunoregulatory potential in various experimental settings, including the prevention of autoimmune diabetes. Indeed, using a transgenic system, we have shown that autoimmune diabetes-prone mice carry fewer DN T cells and that this phenotype contributes to autoimmune diabetes susceptibility, where a single transfer of DN T cells is sufficient to prevent diabetes progression in otherwise autoimmune diabetes-prone mice. These results suggest that DN T cells may be of therapeutic interest for diabetic patients. However, we must first validate these results using a non-transgenic setting, which is more physiologically relevant to humans. The main objective of this thesis is to determine the immunoregulatory function of the DN T cells as well as the therapeutic potential of these cells in the prevention of autoimmune diabetes in the non-transgenic setting. Here, we show that diabetes-resistant mice present with a higher proportion and cell number of DN T cells than diabetes-susceptible mice in the non-transgenic setting, which associates a deficiency in DN T cell number with disease susceptibility. We determine that DN T cells eliminate activated B cells in vitro via a perforin/granzyme-dependent pathway, where the function of DN T cells is equal between the diabetes-resistant and -susceptible mice, demonstrating that the association to autoimmune diabetes is due to a deficiency in DN T cell number rather than function. Interestingly, we show that non-transgenic DN T cells eliminate B cells loaded with islet antigen, but not B cells loaded with an irrelevant antigen, in vitro. Importantly, we establish that the transfer of activated DN T cells could prevent autoimmune diabetes development in the non-transgenic setting. Interestingly, we reveal that DN T cells migrate to the pancreatic islets and undergo preferential activation and proliferation within the pancreatic lymph nodes. Moreover, the transfer of DN T cells results in a decrease in both germinal center B cells directly within the pancreatic islets as well serum insulin autoantibody levels, which correlates with the aforementioned findings. Altogether, the results presented in this thesis have allowed us to enhance our understanding of the function of DN T cells both in vitro and in vivo as well as demonstrate the therapeutic potential for DN T cells as a novel cellular therapeutic for autoimmune diabetes.

Stem cells are endowed with unique qualities: they can both self-renew and give rise to new mature cell types. Central nervous system (CNS) stem cells can give rise to neurons and glia. What factors regulate stem cell fate decisions? Identifying signals that are involved in the regulation of CNS stem cell proliferation, survival, differentiation and migration is fundamental to the understanding of CNS development. In addition, this knowledge hopefully will contribute to more efficient therapies of CNS damages and diseases. The focus of this thesis was to investigate mechanisms of CNS stem cell proliferation and differentiation. We have studied the role for platelet-derived growth factor (PDGF) in these cellular events both in vitro and in vivo. Previous reports have shown that PDGF are implicated in brain tumorigenesis and also supports neuronal differentiation of CNS stem cells. We have found that PDGF promotes survival and proliferation of immature neurons, thereby supporting neuronal differentiation. The intracellular Ras/ERK signaling pathway probably mediates the mitogenic activity of PDGF. In contrast, neuronal differentiation is not dependent on the Ras/ERK pathway. A genetic expression profile of stem cells during their differentiation was obtained. This microarray analysis suggests that PDGF-treated stem cells are at an intermediate stage between proliferation and differentiation. Furthermore, we generated transgenic mice that overexpress Pdgf-b in neural stem cells. Preliminary data indicate no signs of enhanced proliferation of immature neurons. Instead, increased apoptosis was detected in the developing striatum. The results presented in this thesis show how CNS stem cells are regulated by PDGF. PDGFs are widely expressed in the developing CNS and also in some brain tumors, which are thought to arise from CNS stem cells. Thus, this knowledge may contribute to an increased understanding of brain tumorigenesis in addition to normal CNS development.

These studies were aimed at investigating the potential application of nanoparticles engineered from oil-in-water microemulsion precursors for enhancing immune responses to HIV-1 Tat and Gag p24 proteins. Both of the HIV-1 proteins have been reported to be critical in the virus life cycle and are being evaluated in clinical trials as vaccine candidates. Anionic nanoparticles were prepared using emulsifying wax as the oil phase and Brij 78 and sodium dodecyl sulfate as the surfactants. The resulting nanoparticles were coated with Tat and were demonstrated to produce superior immune responses after administration to BALB/c mice compared to Tat adjuvanted with Alum. Similarly, cationic nanoparticles were prepared using emulsifying wax and Brij 78 and cetyl trimethyl ammonium bromide as the surfactants. The cationic nanoparticles were investigated for delivery of immunostimulatory adjuvants, namely three Toll-like receptor ligands, for obtaining synergistic enhancements in immune responses to a model antigen, Ovalbumin (OVA). In vitro and in vivo studies were carried out to elucidate possible mechanisms by which nanoparticles may result in enhancements in immune responses. In vitro studies were carried out to evaluate the uptake of nanoparticles into dendritic cells and to assess the release of pro-inflammatory cytokines from dendritic cells in the presence of nanoparicles. In vivo studies were carried out using a MHC class I restricted transgenic mouse model to investigate the potential for nanoparticles coated with OVA to enhance presentation of the protein to CD8+ T cells compared to OVA alone. Finally, the preparation of nanoparticles with a low amount of surface chelated nickel for high affinity binding to histidine-tagged (his-tag) proteins was investigated. It was hypothesized that this strengthened interaction of his-tag protein to the nickel chelated nanoparticles (Ni-NPs) would result in a greater uptake of antigen in vivo; therefore, enhanced immune responses compared to protein bound to anionic nanoparticles. In vivo evaluation of his-tag HIV-1 Gag p24 bound to Ni-NPs resulted in enhanced immune responses compared to protein either adjuvanted with Alum or coated on the surface of nanoparticles.

Synucleins are highly conserved presynaptic proteins with unknown function. α-synuclein plays a key role regulating dopamine homeostasis and is intimately involved in Parkinson’s disease (PD) pathogenesis. However, the normal/pathological role of α-synuclein remains unidentified. Studies exploring its function are limited as current transgenic mouse models do not fully recapitulate PD pathology. This thesis reports the functional characterisation of two novel synuclein-based mouse models. I report the molecular and functional characterisation of transgenic mouse lines with wild-type or A30P-mutant human α-synuclein genomic locus carried within a bacterial artificial chromosome. SNCA-A30P^+Snca-/- mice exhibited a highly physiologically relevant expression pattern of the transgene, including expression in the substantia nigra pars compacta (SNpc) and a specific, age-related loss of TH^+ cells in the SNpc, the key region of preferential cell loss in PD, compared with non-transgenic Snca -/- littermate controls. Analysis of dopamine signalling using fast-scan cyclic voltammetry (FCV) showed young adult SNCA-A30P^+Snca-/- mice had an approximately 20% lower evoked extracellular dopamine concentration ([DA]o) compared with non-transgenic Snca -/- littermate controls, a decrease specific to the dorsal striatum. This difference diminished with age and could not be attributed to changes in dopamine reuptake/content. I detail the behavioural and neurochemical phenotype in mice lacking all three synucleins (α/β/γ). Functional compensation between synucleins emphasises the importance of studying their effects by removing all three proteins simultaneously. Triple-null mice exhibited hyperactivity in a novel environment reminiscent of a hyperdopaminergic-like phenotype, but showed no phenotype in anxiety or motor related tests. FCV revealed synuclein triple-null mice had a two-fold increase in [DA]o, specific to the dorsal striatum and not attributable to changes in dopamine reuptake/content, changes in striatal nicotinic receptor activity nor calcium-dependent changes in dopamine exocytosis. Together, the analysis from these two novel mouse models reveal synucleins play an important role in altering synaptic function in the dorsal striatum (the region selectively affected in PD) and contributes to growing evidence suggesting synucleins are negative regulators of synaptic dopamine release.