Academic literature on the topic 'Organotypic cerebellar cultures'

ABSTRACT Borna disease virus (BDV) induces a nonpurulent CD4- and CD8-T-cell-dependent meningoencephalitis in susceptible animals. Upon intracerebral infection, BDV replicates in the mouse central nervous system (CNS), but only a few mouse strains develop neurological disorder. The antiviral T cells appear to suppress BDV replication by a noncytolytic mechanism. Since BDV does not replicate in standard mouse cell cultures, the putative role of gamma interferon (IFN-γ) in virus control could not be tested experimentally. Here, we report that mouse organotypic slice cultures can be used to elucidate the complex interactions of BDV, the CNS, and the immune system. We show that BDV replicated in various cell types of mouse cerebellar slice cultures in vitro. In infected slice cultures, a moderate upregulation of the chemokine genes CCL5 and CXCL10 was observed, while expression of various neural genes as well as other chemokine and cytokine genes was not altered. IFN-γ inhibited the multiplication of BDV in cerebellar and hippocampal slice cultures in a dose-dependent manner. However, while complete suppression of BDV was observed in cerebellar slice cultures, inhibition was incomplete in hippocampal slice cultures. Kinetic studies indicated that IFN-γ protects noninfected cells from infection rather than clearing the virus from infected cells. These results demonstrate that BDV can replicate in cultured neural cells of the mouse if organ integrity is well preserved. They further show that IFN-γ is a powerful inhibitor of BDV in the absence of blood-borne leukocytes in mouse cerebellar slice cultures.

Ex vivo models for the noninvasive study of myelin-related diseases represent an essential tool to understand the mechanisms of diseases and develop therapies against them. Herein, we assessed the potential of multimodal imaging traceable myelin-targeting liposomes to quantify myelin in organotypic cultures. Methods: MRI testing was used to image mouse cerebellar tissue sections and organotypic cultures. Demyelination was induced by lysolecithin treatment. Myelin-targeting liposomes were synthetized and characterized, and their capacity to quantify myelin was tested by fluorescence imaging. Results: Imaging of freshly excised tissue sections ranging from 300 µm to 1 mm in thickness was achieved with good contrast between white (WM) and gray matter (GM) using T2w MRI. The typical loss of stiffness, WM structures, and thickness of organotypic cultures required the use of diffusion-weighted methods. Designed myelin-targeting liposomes allowed for semiquantitative detection by fluorescence, but the specificity for myelin was not consistent between assays due to the unspecific binding of liposomes. Conclusions: With respect to the sensitivity, imaging of brain tissue sections and organotypic cultures by MRI is feasible, and myelin-targeting nanosystems are a promising solution to quantify myelin ex vivo. With respect to specificity, fine tuning of the probe is required. Lipid-based systems may not be suitable for this goal, due to unspecific binding to tissues.

Background: Microglia are the resident macrophages of the central nervous system (CNS). In multiple sclerosis (MS) and related experimental models, microglia have either a pro-inflammatory or a pro-regenerative/pro-remyelinating function. Inhibition of Bruton’s tyrosine kinase (BTK), a member of the Tec family of kinases, has been shown to block differentiation of pro-inflammatory macrophages in response to granulocyte–macrophage colony-stimulating factor in vitro. However, the role of BTK in the CNS is unknown. Methods: Our aim was to investigate the effect of BTK inhibition on myelin repair in ex vivo and in vivo experimental models of demyelination and remyelination. The remyelination effect of a BTK inhibitor (BTKi; BTKi-1) was then investigated in LPC-induced demyelinated cerebellar organotypic slice cultures and metronidazole-induced demyelinated Xenopus MBP-GFP-NTR transgenic tadpoles. Results: Cellular detection of BTK and its activated form BTK-phospho-Y223 (p-BTK) was determined by immunohistochemistry in organotypic cerebellar slice cultures, before and after lysophosphatidylcholine (LPC)-induced demyelination. A low BTK signal detected by immunolabeling under normal conditions in cerebellar slices was in sharp contrast to an 8.5-fold increase in the number of BTK-positive cells observed in LPC-demyelinated slice cultures. Under both conditions, approximately 75% of cells expressing BTK and p-BTK were microglia and 25% were astrocytes. Compared with spontaneous recovery, treatment of demyelinated slice cultures and MTZ-demyelinated transgenic tadpoles with BTKi resulted in at least a 1.7-fold improvement of remyelination. Conclusion: Our data demonstrate that BTK inhibition is a promising therapeutic strategy for myelin repair.

Purkinje cells are the principal neurons of the cerebellar cortex and have an extensive and elaborate dendritic tree. Chronic activation of type I metabotropic glutamate receptors inhibits Purkinje cell dendritic growth in organotypic cerebellar slice cultures. This effect is mediated by calcium influx through P/Q-type and T-type Ca2+channels. We have now studied the role of the plasma membrane Ca2+-ATPase2 (PMCA2), a major calcium extrusion pump, for Purkinje cell dendritic development. We found that PMCA2 is strongly expressed in the plasma membrane and dendritic spines of Purkinje cells in organotypic slice cultures compatible with a role for controlling the local dendritic calcium equilibrium. Inhibition of PMCA2 activity by carboxyeosin resulted in a moderate reduction of Purkinje cell dendritic tree size indicating that the extrusion of calcium by PMCA2 is important for maintaining the dendritic calcium concentration and controlling dendritic growth. When inhibition of PMCA2 was combined with stimulation of type I metabotropic glutamate receptors, it partially rescued dendritic morphology. This protection can be explained by a compensatory inactivation of voltage-gated calcium channels in Purkinje cells after PMCA2 inhibition. Our results demonstrate that PMCA2 activity is an important regulator of the dendritic calcium equilibrium controlling Purkinje cell dendritic growth.

Endogenous γ-aminobutyric acid (GABA)-dependent activity induces death of developing Purkinje neurons in mouse organotypic cerebellar cultures and the synthetic steroid mifepristone blocks this effect. Here, using brain-derived neurotrophic factor (BDNF) heterozygous mice, we show that BDNF plays no role in immature Purkinje cell death. However, interestingly, BDNF haploinsufficiency impairs neuronal survival induced by mifepristone and GABAA-receptors antagonist (bicuculline) treatments, indicating that the underlying neuroprotective mechanism requires the neurotrophin full expression.

Dans le système nerveux central (SNC), les oligodendrocytes (OL) enveloppent les axones de leurs prolongements membranaires formant ainsi les gaines de myéline. La mort des OL et la perte de myéline (démyélinisation) surviennent dans les maladies démyélinisantes telles que la sclérose en plaques, pour lesquelles il n'existe pas de traitement efficace. Notre objectif est de stimuler des processus de réparation endogène via la voie ADAM10/sAPPa. Le fragment soluble sAPPa est un peptide neuroprotecteur issu du clivage de la protéine précurseur de l'amyloïde (APP) par les a-secrétases de la famille ADAM (A Desintegrin And Metalloprotease). Nous étudions plus particulièrement ADAM10 car il s'agit de l'a-sécrétase principale dans le SNC. Nos résultats antérieurs montrent que l'activation pharmacologique des a-sécrétases stimule la différenciation des OL in vitro, la protection de la myéline contre la démyélinisation et la remyélinisation ex vivo et in vivo et améliore la fonction locomotrice. L'objectif de ma thèse était donc d'approfondir le rôle d'ADAM10 dans les OL, dans la formation et la maintenance de la myéline. Trois objectifs ont été menés. Le premier objectif était d'étudier l'expression régionale et cellulaire d'ADAM10 dans le SNC par immunomarquage de la protéine dans le SNC de souris adultes et dans des cultures neuronales et gliales primaires. Nous avons observé une large expression de l'enzyme dans le cerveau, le cervelet et la moelle épinière, plus forte dans l'hippocampe et le cortex piriforme. Bien que l'expression d'ADAM10 soit majoritairement neuronale dans les tissus, nous avons pu détecter ADAM10 in vitro dans les OL, les astrocytes et la microglie. Le second objectif était d'étudier le rôle de l'ADAM10 oligodendrocytaire dans la myélinisation. Nous avons donc généré une nouvelle lignée de souris (KOOLA10) permettant la délétion d'ADAM10 dans les OL à des moments spécifiques du développement des OL et de la myéline. Dans cette lignée, l'exon 3 du gène Adam10 flanqué de deux séquences loxP est excisé lors de l'induction par le tamoxifène de la recombinase Cre, exprimée sous le contrôle du promoteur PLP (Proteolipid Protein). Lorsque la déficience est induite à la naissance pendant l'oligodendrogenèse, des défauts d'exploration sont observés à P21, compensés par la suite. Lorsque la déficience est induite à l'âge adulte lors de la maintenance de la myéline, ces défauts s'aggravent avec le temps. Des analyses supplémentaires sont nécessaires pour expliquer ces déficits comportementaux. De manière inattendue, les niveaux de protéine MBP (Myelin Basic Protein) ne montrent pas de changement apparent chez les KO. Le troisième objectif était d'étudier le rôle d'ADAM10 dans le développement et la fonctionnalité des OL. Les résultats de l'invalidation d'ADAM10 à l'aide de siRNA dans la lignée d'OL 158N montrent une diminution de l'expression des gènes de la myéline sans différences dans la morphologie, la prolifération ou la migration des OL. Pour valider ces résultats, nous avons mis en place un protocole d'isolement et de culture primaires d'OL. Les données préliminaires indiquent une diminution de l'expression des gènes de la myéline dans les OL issus de souris KO. Enfin, des cultures organotypiques de cervelet de souris KO montrent une diminution significative du nombre d'axones myélinisés après une démyélinisation induite par lysolécithine, suggérant un effet protecteur d'OL ADAM10 dans la protection ou la réparation de la myéline. En conclusion, j'ai établi la cartographie d'ADAM10 dans le SNC, j'ai généré la lignée de souris KOOLA10 et mis en place différents outils permettant d'étudier le rôle de l'ADAM10 oligodendrocytaire dans la myélinisation. Mes données indiquent un rôle important de l'ADAM10 dans les OL, révélant même des conséquences comportementales. Des études complémentaires sont nécessaires pour mieux comprendre le rôle de cette enzyme dans la maintenance de la myéline et la re/myélinisation du SNC
In the central nervous system (CNS), oligodendrocytes (OL) envelop the axons with their membrane extensions, forming the myelin sheath. The OL death and the loss of myelin (demyelination) occur in demyelinating diseases such as multiple sclerosis, for which there is no specific cure nowadays. Our goal is to enhance an endogenous repair process via the ADAM10/sAPPa pathway. The Amyloid Precursor Protein (APP) can be cleaved by a-secretases, members of the ADAM (A Desintegrin And Metalloprotease) family such as ADAM10, the main a-secretase in the CNS. The enzymatic cleavage of APP generates a neuroprotective soluble peptide called sAPPa. Our previous results showed that the pharmacological activation of a-secretases was able to enhance OL differentiation in vitro, to promote myelin protection from demyelination, to enhance remyelination ex vivo and in vivo and to improve the locomotor function. The aim of my thesis was, thus, to further investigate the role of oligodendroglial ADAM10 in myelin formation and maintenance. Three lines of investigation have been pursued. The first aim was to investigate the regional and cellular expression of ADAM10 in the CNS by immunolabeling of ADAM10 protein in adult mice and in primary neuronal and glial cultures. ADAM10 was widely expressed in brain, cerebellum and spinal cord with high expression in the hippocampus and piriform cortex. Neurons expressed much more ADAM10 than glial cells in CNS tissues and in vitro we were able to detect ADAM10 in neurons, OL, astrocytes and microglia. The second aim was to investigate the role of oligodendroglial ADAM10 in myelination. Therefore, we have created a novel mouse strain (KOOLA10) that allows the deletion of OL ADAM10 at specific time points related to the process of oligodendrogenesis and myelination. In this mouse strain, the deficiency is induced by the excision of the exon 3 of Adam10 gene flanked by 2 loxP sequences by the Cre recombinase, which is under the control of the PLP (Proteolipid Protein) promoter. When ADAM10 deficiency was induced at birth during oligodendrogenesis, an impairment in exploratory activity was observed at P21 but it was compensated later on. When ADAM10 deficiency was induced during myelin maintenance in adult mice, the aforementioned behavior worsened over time. Further analysis is still required to explain the behavioral changes observed in KO mice. Surprisingly, the level of MBP (Myelin Basic Protein), assessed by western blot and immunohistological studies, did not show an apparent change in KO mice. The third aim was to investigate the role of ADAM10 in OL development and functionality. The ADAM10 knock-down using siRNA in the 158N OL cell line did not modify cell morphology, proliferation or migration but it induced a decrease in myelin gene expression. To validate these results, we set up a new OL primary cell isolation and culture protocol. Preliminary results also pointed to a reduction of myelin genes expression in ADAM10-deficient OL. Finally, we used organotypic culture of cerebellum, highly rich in myelin, to address the effect of ADAM10 deficiency. We set up a transfection protocol to knock down ADAM10 in cerebellar slices and further focused on the study of myelination in KOOLA10. A significant decrease in the number of myelinated axons was observed in cerebellar slices from KO mice after demyelination, suggesting a beneficial effect of OL ADAM10 in myelin protection or repair. In conclusion, I have shown the distribution of ADAM10 in the CNS, generated the KOOLA10 mouse strain and set up different protocols and tools that allow the investigation of the role of oligodendroglial ADAM10 in myelination. I have obtained evidence suggesting that OL ADAM10 affects exploratory behavior and myelin and is necessary for myelin protection and/or repair. Further investigation is required to better decipher the role of OL ADAM10 in myelin maintenance, and CNS re/myelination

La démyélinisation et la mort oligodendrocytaire sont bien connues dans la sclérose en plaques (SEP). Au cours de ces dernières années, plusieurs études ont également décrit ce type de lésion après un traumatisme crânien (TC), participant à l’aggravation des lésions de la substance blanche, responsables des dysfonctionnements cognitifs et moteurs. Malgré de nombreux efforts, aucune thérapie efficace n’est disponible à ce jour pour traiter les lésions de la substance blanche. Dans ce contexte, une stratégie thérapeutique prometteuse serait de freiner la neuro-inflammation et la démyélinisation, en plus de promouvoir la maturation des oligodendrocytes afin de favoriser la remyélinisation des axones et de limiter ainsi leur dégénérescence. Notre choix de stratégie porte sur la stimulation des processus de réparation endogène via la protéine neuroprotectrice et neurotrophique sAPPα, forme soluble de la protéine βAPP libérée par l’action des α-sécrétases (ADAM10). Dans ce contexte, l’objectif de mes travaux de thèse était d’étudier l’intérêt thérapeutique de l’étazolate, un activateur desα-sécrétases, sur les conséquences biochimiques, histologiques et fonctionnelles, dans différents modèles de TC et de SEP in vivo chez la souris, et ex vivo sur des tranches organotypiques de cervelet. Les résultats obtenus sur le modèle de TC par percussion mécanique chez la souris ont montré pour la première fois le potentiel anti-inflammatoire de l’étazolate, associé à la restauration du taux de la sAPPα. De plus, l’étazolate s’est également opposé aux troubles fonctionnels post-TC tels que l’hyperactivité locomotrice et le déficit cognitif à court et à long terme. Par la suite, j’ai développé un nouveau modèle ex vivo de TC par percussion mécanique sur des tranches organotypiques de cervelet. Nous avons montré pour la première fois que l’étazolate était neuroprotecteur dans le tissu cérébelleux, et qu’il s’opposait à la démyélinisation post-traumatique. Par ailleurs, les effets bénéfiques de l’étazolate sur les gaines de myéline ont été reproduits dans un modèle ex vivo de démyélinisation induite par la lysolécithine, modèle ex vivo de SEP. De façon intéressante nous avons montré que l’étazolate exerçait un effet remyélinisant en stimulant la différenciation des oligodendrocytes. Cet effet a été reproduit in vitro dans des cultures primaires mixtes de cellules gliales issues de souris PLP-eGFP, où la maturation morphologique des oligodendrocytes a été favorisée en présence d’étazolate. L’ensemble des effets bénéfiques exercés par l’étazolate a été inhibé en présence d’un inhibiteur pharmacologique spécifique d’ADAM10, le GI254023X, suggérant que l’effet remyélinisant de l’étazolate dépend, au moins en partie, d’ADAM10. Par la suite, l’effet remyélinisant de l’étazolate a été étudié dans un modèle in vivo de démyélinisation chronique induite par la cuprizone. Dans ce modèle, l’étazolate a été capable de promouvoir la remyélinisation en stimulant la différenciation des oligodendrocytes, confirmant nos résultats in vitro et ex vivo. L’ensemble de mon travail permet de considérer le potentiel thérapeutique de l’étazolate, en visant l’ADAM10 comme nouvelle cible thérapeutique neuroprotectrice et remyélinisante. Cela aura pour intérêt de limiter la neuro-inflammation, la démyélinisation, ainsi que de promouvoir la différenciation des oligodendrocytes et la remyélinisation, afin de favoriser la récupération fonctionnelle suite aux lésions de la substance blanche survenant après un TC ou la SEP chez l’homme
Demyelination and oligodendrocyte cell death are well established in multiple sclerosis (MS) and are increasingly described after traumatic brain injury (TBI), participating in the aggravation of white matter injury responsible of motor and cognitive deficits. Despite many efforts in clinical research, no efficient therapy against white matter injury progression is available nowadays. Thus, promoting remyelination and counteracting neuroinflammation and demyelination are major therapeutic strategies in order to restore white matter integrity. Here, we studied the stimulation of endogenous repair mechanisms through the neuroprotective and neurotrophic protein sAPPα, the soluble form of βAPP protein released by the α-secretases (ADAM10). In this context, the aim of this work was to evaluate the therapeutic potential of etazolate, an α-secretase activator on short- and long-term biochemical, histological and functional outcome in different mouse models of TBI and MS in vivo, and ex vivo on organotypic cerebellar slices. The results obtained from the TBI mouse model by mechanical percussion showed for the first time the anti-inflammatory effect of etazolate associated to a restoration of sAPPα levels. The same treatment was able to attenuate functional deficits (hyperactivity, cognitive deficit). We also developed a new ex vivo model of TBI by mechanical percussion on organotypic cerebellar slices. We confirmed the neuroprotective effect of etazolate on cerebellar tissue reducing the lesion size. Interestingly, etazolate treatment attenuated post-traumatic ex vivo demyelination. Moreover, the beneficial effect of etazolate on myelin sheaths have been well reproduced after lysolecithin-induced demyelination, an ex vivo model of MS. Interestingly, etazolate was able to enhance remyelination promoting oligodendrocyte differentiation. This effect has been reproduced in the primary mixed glial culture from PLP-eGFP mice, enhancing oligodendrocyte morphological maturation. However, etazolate failed to promote its beneficial effects in the presence of GI254023X, a specific ADAM10 (α-secretase) inhibitor, suggesting that the mechanism of action of etazolate is partly through the activation of ADAM10. Furthermore, etazolate reproduced in vivo the oligodendrocyte differentiation, accompanied by an increase of the myelinated axons, observed by electron microscopy in a mouse model of cuprizone-induced chronic demyelination. Taken together, the findings of this work provide a first evidence for the therapeutic potential of etazolate, with ADAM10 as new therapeutic target in white matter repair. The interest of this approach is to attenuate neuroinflammation and demyelination and to enhance oligodendrocyte differentiation and thus remyelination, in order to promote functional recovery following white matter lesions arising after TBI or MS

碩士
國立臺灣師範大學
生命科學研究所
101
Spinocerebellar ataxia (SCA) is an autosomal dominant and progressive neurodegenerative disease chartered by ataxia, parkinsonism, dementia and seizures. Although there remains lots unclarified mechanism in SCA17, it is believed that the mutation on the TATA box binding protein (TBP) is responsible for the disease. The CAG repeat expansion of TBP gene leads to the reduced solubility of polyglutamine (polyQ) TBP and induces aggregate formation. For TBP plays an important role in transcription initiation, the abnormal aggregate is believed to cause neuron degeneration especially in the cerebellar Purkinje cells. Cerebellar organotypic culture is a system which could provide research evidence on tissue level. In addition, the cerebellar organotypic culture could provide the normal interaction between Purkinje cells and the other cells in vitro. We have established this system to study and monitor the cerebellar cell development, neuron survival, Purkinje cell aggregate forming and death and for a drug screening platform. Trehalose is reported to prevent protein degradation and aggregate formation in several disease models, including Huntington’s diseases, Alzheimer's disease, SCA14 and some other neurodegenerative diseases caused by polyQ expansion. In this study, we evaluated the therapeutic effect of trehalose using SCA17 cerebellar organotypic culture system. Our results showed that TBP aggregation formed in the Purkinje cells at in vitro day 3 (DIV3) and became more obvious at DIV7 in the SCA17 cerebellar slice culture. Furthermore, we found that the TBP aggregation significant decreased in our slice culture at DIV7 after treatment with trehalose. To identify the effect of trehalose in vivo, trehalose supplied in the drinking water of SCA17 transgenic mice was conducted. In the behavior test, we found that mice drinking trehalose ameliorated their hyperactivity and improved their coordination in rotarod test. Furthermore, we confirmed that the calbindin expression level was upregulated in the trehalose treatment mouse cerebellum. In addition, the cerebellum size in trehalose treatment mouse is bigger than that of vehicle treatment mouse. In our 4% trehalose treatment study, we found the gait behavior and motor coordination of SCA17 mice were rescued in the footprint and rotarod task, respectively. We also could observe the astrocyte gliosis performance was downregulated after trehalose treatment. However, the microglia cell was activated especially in transgenic trehalose treatment group. Furthermore, the MnSOD was also upregulated after trehalose treatment. These data suggest that trehalose could be a potential non-toxic treatment for SCA17.