Haemorrhage within the germinal matrix with extension into the ventricle is commonly seen in very low birth weight babies. Outcome following severe haemorrhage, in particular when associated with post haemorrhagic hydrocephalus and congestive venous infarction is poor, whilst outcome following moderate degrees of haemorrhage remains variable. The Neural Stem Progenitor Cells (NSPC) within the GM have been shown to be exquisitely sensitive to micro-environmental cues, as such, haemorrhage within the GM is postulated to impact on neurological outcome through aberration of normal NSPC behaviour. Here we have developed a stereotactic model of autologous blood injection which recapitulates key features of Papile grade II/III Germinal Matrix Haemorrhage / Intraventricular Haemorrhage (GMH/IVH). This model demonstrates that GMH/IVH causes an activation of the NSPC within the wall of the lateral ventricle and increases the number of transient amplifying cells within the transcallosal pathway. Further to this RNA extraction from the NSPC (selected using a CD133 MACS protocol) revealed that GMH/IVH causes a significant down regulation of the transmembrane receptor Notch, a finding that was validated using Hes5 in situ hybridisation (ISH). Using a battery of behavioural tests including assessment of developmental landmarks, neuromotor and reflex development we found that GMH/IVH causes subtle but significant impacts on early neonatal development. GMH/IVH in transgenic mice overexpressing the polycomb group gene Bmi1 in NSC (Nestin+ve) revealed increased self-renewal and resistance to oxidative stress (properties of Bmi1 overexpression) reduced the impact of GMH on the oligodendrocyte population, it also revealed a unique behavioural phenotype. We propose that GMH/IVH down regulates Notch in the NSPC causing a burst of precocious proliferation and depleting the NSPC pool, which impacts on neurological outcome due to altered cortical architecture. Further we suggest that modulation of NSPC properties may play role in determining outcome and should be further explored for its therapeutic potential.

<p> Cell therapy for Parkinson's disease will greatly benefit from progress in methods aimed at visualizing the dopamine system and cell replacement techniques. Currently, cell therapy has been met with varied success, in part due to differences in cell sources, transplantation procedures, and our lack of understanding of cell fate post-transplantation. The standardization of transplantation procedures will enhance our ability to draw comparisons between studies and improve cell therapy outcomes. We developed a method to label neural stem/progenitor cells (NSPCs) with technetium-99m and then visualize the cells with single photon emission computed tomography (SPECT) subsequent to grafting in the brain. This labeling method permitted a high uptake of the tracer into the cells without causing damage to the DNA or altering cell viability. The labeling caused a significant decrease (75%) in the proliferative capacity of the SPCs and caused a trend towards an increase in neuronal differentiation. Using this technique paves the way to standardize the location of the transplant and quantify the number transplanted cells while increasing the production of neurons.</p> <p> Experiments were performed to visualize the dopamine system with [(123)I]altropane at pre-and post-transplant time points in the 6-0HDA rat model of Parkinson's disease. [(123)I]altropane binding correlated with the content of dopamine in the stria tum. However, [(123)I]altropane binding was not correlated with dopamine content in the substantia nigra and did not show a correlation with the amphetamine rotations. However, there was a significant correlation with the cylinder test and the postural instability test. When the data was assessed using linear regression, the r^2 value of the linear relationship was low indicating that [(123)I]altropane SPECT is not a good predictor of behavioural outcome due to a weak linear relationship. Our data indicates that [(123)I]altropane predicts the integrity of the striatal dopamine nerve terminals, but does not predict the integrity of the nigrostriatal system. The results are discussed in relation to the use of [(123)I]altropane in comparison to other dopamine SPECT and PET agents. </p> / Thesis / Doctor of Philosophy (PhD)

La documentation scientifique fait état de la présence, chez l’adulte, de cellules souches et progénitrices neurales (CSPN) endogènes dans les zones sous-ventriculaire et sous-granulaire du cerveau ainsi que dans le gyrus denté de l’hippocampe. De plus, un postulat selon lequel il serait également possible de retrouver ce type de cellules dans la moelle épinière et le néocortex des mammifères adultes a été énoncé. L’encéphalopathie de Wernicke, un trouble neurologique grave toutefois réversible qui entraîne un dysfonctionnement, voire une défaillance du cerveau, est causée principalement par une carence importante en thiamine (CT). Des observations récentes laissent envisager que les facteurs en cause dans la prolifération et la différenciation des CSPN pourraient également jouer un rôle important lors d’un épisode de CT. L’hypothèse, selon laquelle l’identification de nouveaux métabolites entrant dans le mécanisme ou la séquence de réactions se soldant en une CT pourraient en faciliter la compréhension, a été émise au moyen d'une démarche en cours permettant d’établir le profil des modifications métaboliques qui surviennent en de telles situations. Cette approche a été utilisée pour constater les changements métaboliques survenus au niveau du foyer cérébral dans un modèle de rats déficients en thiamine (rats DT), particulièrement au niveau du thalamus et du colliculus inférieur (CI). La greffe de CSPN a quant à elle été envisagée afin d’apporter de nouvelles informations sur la participation des CSPN lors d’un épisode de CT et de déterminer les bénéfices thérapeutiques potentiels offerts par cette intervention. Les sujets de l’étude étaient répartis en quatre groupes expérimentaux : un premier groupe constitué de rats dont la CT était induite par la pyrithiamine (rats DTiP), un deuxième groupe constitué de rats-contrôles nourris ensemble (« pair-fed control rats » ou rats PFC) ainsi que deux groupes de rats ayant subi une greffe de CSPN, soit un groupe de rats DTiP greffés et un dernier groupe constitué de rats-contrôles (rats PFC) greffés. Les échantillons de foyers cérébraux (thalamus et CI) des quatre groupes de rats ont été prélevés et soumis à des analyses métabolomiques non ciblées ainsi qu’à une analyse visuelle par microscopie à balayage électronique (SEM). Une variété de métabolites-clés a été observée chez les groupes de rats déficients en thiamine (rats DTiP) en plus de plusieurs métabolites dont la documentation ne faisait pas mention. On a notamment constaté la présence d’acides biliaires, d’acide cynurénique et d’acide 1,9— diméthylurique dans le thalamus, alors que la présence de taurine et de carnosine a été observée dans le colliculus inférieur. L’étude a de plus démontré une possible implication des CSPN endogènes dans les foyers cérébraux du thalamus et du colliculus inférieur en identifiant les métabolites-clés ciblant les CSPN. Enfin, les analyses par SEM ont montré une amélioration notable des tissus à la suite de la greffe de CSPN. Ces constatations suggèrent que l’utilisation de CSPN pourrait s’avérer une avenue thérapeutique intéressante pour soulager la dégénérescence symptomatique liée à une grave carence en thiamine chez l’humain. / Endogenous neural-stem progenitor cells (NSPC) have been documented to be found in the subventricular and subgranular zones, the dentate gyrus, and suggestions of the possibility of these cells being found in the spinal cord and neocortex in adult mammalian brain have been postulated. Thiamine deficiency (TD) is the major cause of Wernicke's Encephalopathy, a reversible neurological disorder that results in cerebral dysfunction and impairment. Recent evidence suggests factors involved in neural NSPC proliferation and differentiation are involved during TD. By means of a current approach for profiling metabolic changes occurring in focal areas of the TD rat brain, specifically the thalamus and the inferior colliculus (IC), it was hypothesized that new metabolites that might offer a better understanding into the sequel and/or mechanism of TD could be identified. It was also considered that the use of NSPC transplantation could offer new information into the involvement of NSPC and potential therapeutic benefit in TD. Non-targeted metabolomics analysis, fluorescences microscopy, and scanning election microscopy (SEM) analysis visualization was performed on samples of the focal areas (thalamus and IC) of pyrithiamine induced TD rats (PTD), pair-fed controls (PFC) rats, and NSPC transplanted TD and PFC rats. Various key metabolites were identified in rats with TD, including previous undocumented metabolites such as bile acids, kynurenic acid, and 1,9-dimethyluric acid in the thalamus and taurine and carnosine in the IC. The study also demonstrated a possible involvement of endogenous NSPC in focal areas of the thalamus and IC identifying key metabolites targeting NSPC and showed tissue amelioration (observed through SEM) following NSPC transplantation. The findings suggested that NSPC could offer a therapeutic alternative to alleviate some of symptomatic degeneration of TD.