Alterations in mGluR5 Expression and Signaling in Lewy Body Disease and in Transgenic Models of Alpha- Synucleinopathy – Implications for Excitotoxicity

Dementia with Lewy bodies (DLB) and Parkinson’s Disease (PD) are neurodegenerative disorders of the aging population characterized by the abnormal accumulation of alpha-synuclein (alpha-syn). Previous studies have suggested that excitotoxicity may contribute to neurodegeneration in these disorders, however the underlying mechanisms and their relationship to alpha-syn remain unclear. For this study we proposed that accumulation of alpha-syn might result in alterations in metabotropic glutamate receptors (mGluR), particularly mGluR5 which has been linked to deficits in murine models of PD. In this context, levels of mGluR5 were analyzed in the brains of PD and DLB human cases and alpha-syn transgenic (tg) mice and compared to age-matched, unimpaired controls, we report a 40% increase in the levels of mGluR5 and beta-arrestin immunoreactivity in the frontal cortex, hippocampus and putamen in DLB cases and in the putamen in PD cases. In the hippocampus, mGluR5 was more abundant in the CA3 region and co-localized with alpha-syn aggregates. Similarly, in the hippocampus and basal ganglia of alpha-syn tg mice, levels of mGluR5 were increased and mGluR5 and alpha-syn were co-localized and co-immunoprecipated, suggesting that alpha-syn interferes with mGluR5 trafficking. The increased levels of mGluR5 were accompanied by a concomitant increase in the activation of downstream signaling components including ERK, Elk-1 and CREB. Consistent with the increased accumulation of alpha-syn and alterations in mGluR5 in cognitive- and motor-associated brain regions, these mice displayed impaired performance in the water maze and pole test, these behavioral alterations were reversed with the mGluR5 antagonist, MPEP. Taken together the results from study suggest that mGluR5 may directly interact with alpha-syn resulting in its over activation and that this over activation may contribute to excitotoxic cell death in select neuronal regions. These results highlight the therapeutic importance of mGluR5 antagonists in alpha-synucleinopathies

Specific In Vivo Staining of Astrocytes in the Whole Brain after Intravenous Injection of Sulforhodamine Dyes

Fluorescent staining of astrocytes without damaging or interfering with normal brain functions is essential for intravital microscopy studies. Current methods involved either transgenic mice or local intracerebral injection of sulforhodamine 101. Transgenic rat models rarely exist, and in mice, a backcross with GFAP transgenic mice may be difficult. Local injections of fluorescent dyes are invasive. Here, we propose a non-invasive, specific and ubiquitous method to stain astrocytes in vivo. This method is based on iv injection of sulforhodamine dyes and is applicable on rats and mice from postnatal age to adulthood. The astrocytes staining obtained after iv injection was maintained for nearly half a day and showed no adverse reaction on astrocytic calcium signals or electroencephalographic recordings in vivo. The high contrast of the staining facilitates the image processing and allows to quantify 3D morphological parameters of the astrocytes and to characterize their network. Our method may become a reference for in vivo staining of the whole astrocytes population in animal models of neurological disorders

VISUALIZING THE DYNAMICS OF IMMUNE SURVEILLANCE IN BRAIN TUMORS BY INTRAVITAL MULTIPHOTON MICROSCOPY

Visualizing the dynamics of immune surveillance in brain tumors by intravital multiphoton microscopy By Felix I. Nwajei, MD Supervisory Professor: Tomasz Zal, Ph.D. Brain tumors (BTs) generally have a bad prognosis despite conventional treatment strategies. Immunotherapy is a relatively novel treatment approach that has shown benefit for durable treatment of melanoma, and is a promising candidate for different tumor types including BTs. Immunotherapeutic strategies work by exploiting and/or enhancing natural anti-tumor immune response, a process that is critically dependent on adaptive immunity, T cell infiltration and surveillance of tumor. However, little is known about the dynamics and regulation of T cell surveillance in BTs. Resident immune cells of the myeloid lineage known as microglia are ubiquitous in the brain parenchyma while tissue-resident myeloid dendritic cells (DCs) known to activate T cells are relatively rare in the brain compared to DCs in other organs. Accumulating evidence indicates that myeloid cells infiltrate and create an immune suppressive microenvironment in BTs, but the identity of these myeloid cells and their role in the adaptive immune surveillance of BTs by T cells is unclear. Based on the predominance of microglia in the brain tissue, studies focused on understanding how BT immune surveillance is regulated, have been skewed toward microglia. Many conclusions regarding microglia function have been deduced from in vitro experiments. Nonetheless, in vivo studies in parallel models such as EAE indicate that DCs are superior to microglia in antigen presentation to T cells in the brain and to date, there is no direct in vivo evidence to suggest otherwise. In addition, DCs are well-established cellular regulators of T cell surveillance in extracranial tumors. Therefore, I hypothesized that DCs, rather than microglia, play a major role in regulating T cell surveillance in BTs. To address this hypothesis, I have developed experimental imaging systems for longitudinal intravital multiphoton microscopy of immune cell dynamics in BTs in living mice and used this approach to interrogate T cell behavior in orthotopic glioma and in experimental intracranial metastases in vivo. I found that the myeloid infiltration of BTs was dominated by CD11c+ DC cells rather than microglia. Quantitative in situ tissue cell image cytometry further revealed that myeloid-derived CCR2+ monocytes accumulated in the BT core, CD11c+ DCs at the tumor margin, and CX3CR1+ microglia outside the tumor. T cells formed clusters around CD11c+ DCs, but not the microglia. Within these clusters, T cells vigorously interacted directly with CD11c+ DCs. CD11c+ DCs retained T cells and controlled their motility patterns, indicating that CD11c+ DCs play a major role in regulating T cell retention and motility in BT. Corresponding to the preferential distribution of CD11c+ DCs at BT margins was expression of the neuronal chemokine Fractalkine (CX3CL1). Deficiency of the Fractalkine receptor CX3CR1 resulted in decreased CD11c+ DC recruitment. In addition, decreased CD11c+ DC recruitment was accompanied by decreased T cell recruitment, an increase in the spatial diffusion of the few BT-infiltrating T cells, and subsequent outgrowth of a fibrosarcoma BT, which spontaneously regresses in the brain of control wild type mice in a CD8 T cell dependent manner. In summary, by using novel intravital imaging systems for longitudinal visualization of BT immune surveillance across several types of cancer, I showed that the recruitment, migration and retention of tumor infiltrating T cells in the brain is mediated by incoming CD11c+ DCs rather than by the brain-resident CX3CR1 microglia, and identified the neuronal chemokine Fractalkine as a key molecule that promotes T cell surveillance in BTs by recruiting CD11c+ DCs. These findings suggest that the non-microglial tumor-associating CD11c+ myeloid cells and the fractalkine/CX3CR1 chemokine pathway control T cell surveillance in BT and represent attractive immunotherapeutic targets that could be modulated for guiding endogenous or adoptive transfer of T cells to BT sites and for therapeutic modulation to enhance immunity against BTs

Dynamics of myeloid cell infiltration and blood-spinal cord barrier disruption in a murine model of multiple sclerosis

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2013-2014.La rupture de la barrière hémoencéphalique (BHE) ainsi que l’infiltration cellulaire sont des évènements pathophysiologiques caractéristiques de la sclérose en plaques et de son modèle animal, l’encéphalomyélite autoimmune expérimentale (EAE). Cependant, leur relation avec l’évolution de l’EAE est obscure, notamment car les préparations histologiques standards recquièrent le sacrifice des animaux et nous privent d’informations cruciales quant à l’initiation, au développement et à la progression de la maladie. Nous utilisons le modèle EAE chez la lignée de souris lys-GFP ki, chez laquelle les cellules myéloïdes (i.e. neutrophiles et monocytes) expriment eGFP. De l’imagerie intravitale est effectuée à des moments précis, ce qui permet l’étude de l’infiltration cellulaire en plus de l’évaluation de l’intégrité de la barrière hémo-encéphalique (BHE) au cours de la pathologie. Les séances d’imagerie non-terminales offrent un contexte temporel considérable, puisqu’il est possible de suivre le développement de la maladie chez un animal qui a été précédemment imagé. La première étape a donc consisté à établir que la chirurgie et la séance d’imagerie n’avaient aucune influence sur le développement de l’EAE chez les animaux expérimentaux. Les résultats obtenus à l’aide d’imagerie intravitale tendent à démontrer qu’un affaiblissement de la BHE envers les molécules de petite taille (760 Da) est corrélé à l’infiltration de cellules GFP-positive dans la moelle épinière. Il est d’autant plus intéressant de constater que cette invasion cellulaire arrive en même temps que l’apparition des symptômes cliniques chez les animaux atteints d’EAE. Nous avançons l’hypothèse que les neutrophiles sont les cellules myéloïdes responsables de brèches initiales dans la BHE, qui influençent son intégrité aux stades précoces de la maladie. Des expériences de déplétion envers les neutrophiles ont donc été effectuées chez des animaux EAE afin de confirmer notre hypothèse. Les résultats suggèrent que les neutrophiles influencent l’initiation de la maladie et sa sévérité totale, en plus d’être intimement liés à l’état de la BHE tôt dans la pathologie.Blood-spinal cord barrier (BSCB) disruption and immune cell infiltration are early pathophysiological hallmarks of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Their relationship with the course of EAE remains unclear, however, notably because histological tissue preparations involve sacrifice and inherently result in the loss of crucial information regarding the initiation or development and progression of the disease. We use the EAE model in the lys-GFP ki mouse strain, in which blood-borne myeloid cells (i.e. neutrophils and monocytes) express eGFP. Intravital two-photon microscopy is performed at selected time points, enabling the investigation of cellular infiltration together with the assessment of the blood- barrier (BBB) integrity over the course of the pathology. Non-terminal imaging sessions offer extensive temporal context as it is possible to follow the development of the disease in an animal which has been previously imaged. One can appreciate the advantage of such a method as it is possible to relate, in the same animal, previous observations with clinical outcome. The first step thus consisted in establishing that the surgery and imaging session did not affect the development of EAE in experimental animals. Results obtained demonstrate that the permeability of the BBB to small molecular tracers (760 Da) correlates with the infiltration of GFP-positive myeloid cells into the spinal cord parenchyma. Interestingly, this cellular invasion is reminiscent of the appearance of clinical symptoms displayed by EAE animals. We put forward the hypothesis that neutrophils are the myeloid cells responsible for initial breaches in the BBB, influencing the latter’s integrity at early stages of the disease. Neutrophil depletion experiments have thus been performed in EAE mice in order to confirm this hypothesis. Results suggest that neutrophils influence the initiation and total severity of the disease, as well as being intimately linked to the status of the BBB early in the pathology

Investigation of neuronal activity in a murine model of Alzheimer’s disease using in vivo two-photon calcium imaging

Alzheimer’s disease (AD) is one of the biggest challenges for biomedical research nowadays as with the growth of life span more and more people are affected by this disorder. Etiology of AD is unknown, yet growing evidence identifies alterations in neuronal activity as of the great importance for pathology. Although several significant studies of neuronal activity alteration in AD were done during the last decade, none of them addressed the question of the time course of these changes over the disease progression. Alzheimer’s disease (AD) is characterized by impairments of brain neurons that are responsible for the storage and processing of information. Studies have revealed decrease in the activity of neurons (Silverman et al., 2001; Prvulovic et al., 2005) and it was proposed that generalized hypoactivity and silencing of brain circuits takes place as formulated in the synaptic failure hypothesis (Selkoe, 2002). However, more recent studies also reported opposite effects – hyperexcitability and hyperactivity of neurons in the AD models (Busche et al., 2008; Sanchez et al., 2012; Liebscher et al., 2016). It still remains unclear if these are two sides of the same coin or if these are two stages, that follow each other. Moreover, it is not clear if observed neuronal activity alterations are caused by the dysfunction of individual neurons or if overall circuitry is disturbed because the crucial “activity controllers” (most probably - inhibitory neurons) alter their activity. This project aimed to examine spontaneous neuronal activity in the murine model of AD at the early stages of disease progression using chronic in vivo imaging to address the character and the stability of neuronal activity alterations as well relation of the activity alterations to amyloid plaque proximity. Compared to earlier studies the approach of in vivo awake calcium imaging used in the current study has many benefits for brain research. The main advantage is that brain activity can be measured without artifacts generated by anesthesia, which can exaggerate or mitigate experimental readouts. In this project, I used genetically encoded calcium indicator GCaMP6 that enables prolonged repetitive imaging of the same neurons in an intact environment. Recording of calcium transients in cell bodies of neurons was accompanied by in vivo imaging of Aβ plaques and followed by immunohistochemical staining of GCaMP6-expressing neurons to investigate how activity changes are correlated with proximity to the plaque. All the experiments were done in awake mice to ensure the absence of anesthesia-derived impact on spontaneous neuronal activity. My results support previously published reports of the increased proportion of hyperactive excitatory neurons in the AD mouse model. Importantly, my results also demonstrate that this increased activity is present in the awake state, is stable over a longer period of time (one month) and does not depend on the distance to the closest plaque. These findings support the hypothesis of permanent network alterations driving aberrant activity patterns that appear early in the disease progression, resulting in a chronic excitation/inhibition disbalance. Another important finding of my project is that individual neurons do not stay in the silent state and most of them remain functional demonstrating normal activity at the later time points. This finding requires further research as it has important implication for the development of the AD treatment, as in case many neurons remain functional and their normal neuronal activity can be recovered by addressing the cause of the circuit dysfunction with treatment. To summarize, the study presented in this PhD thesis is the first longitudinal study of neuronal activity changes in an AD mouse model, and while it provides important insight into pathology, it also emphasizes the importance of chronic in vivo studies to investigate neuronal activity and its role in the disease progression

霊長類脳における神経活動の操作やイメージングに適した新規モザイクアデノ随伴ウイルスベクターの開発

京都大学新制・課程博士博士(理学)甲第25150号理博第5057号京都大学大学院理学研究科生物科学専攻(主査)准教授 大石 高生, 教授 中村 克樹, 教授 明里 宏文学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

Investigation of neuronal activity in a murine model of Alzheimer’s disease using in vivo two-photon calcium imaging

Alzheimer’s disease (AD) is one of the biggest challenges for biomedical research nowadays as with the growth of life span more and more people are affected by this disorder. Etiology of AD is unknown, yet growing evidence identifies alterations in neuronal activity as of the great importance for pathology. Although several significant studies of neuronal activity alteration in AD were done during the last decade, none of them addressed the question of the time course of these changes over the disease progression. Alzheimer’s disease (AD) is characterized by impairments of brain neurons that are responsible for the storage and processing of information. Studies have revealed decrease in the activity of neurons (Silverman et al., 2001; Prvulovic et al., 2005) and it was proposed that generalized hypoactivity and silencing of brain circuits takes place as formulated in the synaptic failure hypothesis (Selkoe, 2002). However, more recent studies also reported opposite effects – hyperexcitability and hyperactivity of neurons in the AD models (Busche et al., 2008; Sanchez et al., 2012; Liebscher et al., 2016). It still remains unclear if these are two sides of the same coin or if these are two stages, that follow each other. Moreover, it is not clear if observed neuronal activity alterations are caused by the dysfunction of individual neurons or if overall circuitry is disturbed because the crucial “activity controllers” (most probably - inhibitory neurons) alter their activity. This project aimed to examine spontaneous neuronal activity in the murine model of AD at the early stages of disease progression using chronic in vivo imaging to address the character and the stability of neuronal activity alterations as well relation of the activity alterations to amyloid plaque proximity. Compared to earlier studies the approach of in vivo awake calcium imaging used in the current study has many benefits for brain research. The main advantage is that brain activity can be measured without artifacts generated by anesthesia, which can exaggerate or mitigate experimental readouts. In this project, I used genetically encoded calcium indicator GCaMP6 that enables prolonged repetitive imaging of the same neurons in an intact environment. Recording of calcium transients in cell bodies of neurons was accompanied by in vivo imaging of Aβ plaques and followed by immunohistochemical staining of GCaMP6-expressing neurons to investigate how activity changes are correlated with proximity to the plaque. All the experiments were done in awake mice to ensure the absence of anesthesia-derived impact on spontaneous neuronal activity. My results support previously published reports of the increased proportion of hyperactive excitatory neurons in the AD mouse model. Importantly, my results also demonstrate that this increased activity is present in the awake state, is stable over a longer period of time (one month) and does not depend on the distance to the closest plaque. These findings support the hypothesis of permanent network alterations driving aberrant activity patterns that appear early in the disease progression, resulting in a chronic excitation/inhibition disbalance. Another important finding of my project is that individual neurons do not stay in the silent state and most of them remain functional demonstrating normal activity at the later time points. This finding requires further research as it has important implication for the development of the AD treatment, as in case many neurons remain functional and their normal neuronal activity can be recovered by addressing the cause of the circuit dysfunction with treatment. To summarize, the study presented in this PhD thesis is the first longitudinal study of neuronal activity changes in an AD mouse model, and while it provides important insight into pathology, it also emphasizes the importance of chronic in vivo studies to investigate neuronal activity and its role in the disease progression

A review of intrinsic optical imaging serial blockface histology (ICI-SBH) for whole rodent brain imaging

In recent years, multiple serial histology techniques were developed to enable whole rodent brain imaging in 3-D. The main driving forces behind the emergence of these imaging techniques were the genome-wide atlas of gene expression in the mouse brain, the pursuit of the mouse brain connectome, and the BigBrain project. These projects rely on the use of optical imaging to target neuronal structures with histological stains or fluorescent dyes that are either expressed by transgenic mice or injected at specific locations in the brain. Efforts to adapt the serial histology acquisition scheme to use intrinsic contrast imaging (ICI) were also put forward, thus leveraging the natural contrast of neuronal tissue. This review focuses on these efforts. First, the origin of optical contrast in brain tissue is discussed with emphasis on the various imaging modalities exploiting these contrast mechanisms. Serial blockface histology (SBH) systems using ICI modalities are then reported, followed by a review of some of their applications. These include validation studies and the creation of multimodal brain atlases at a micrometer resolution. The paper concludes with a perspective of future developments, calling for a consolidation of the SBH research and development efforts around the world. The goal would be to offer the neuroscience community a single standardized open-source SBH solution, including optical design, acquisition automation, reconstruction algorithms, and analysis pipelines