In 1868, the French experimental physiologist Goujon demonstrated the transplantability and osteogenic potential of bone marrow. More than a hundred years later, Friedenstein first isolated the cells responsible for this osteogenic capacity and demonstrated the existence of a non-hematopoietic stem cell within bone marrow. Since then, the field of mesenchymal stem cell (MSC) research has generated an incredible amount of data aimed at characterizing these cells and indentifying their true in vivo identity and localization, but also exploring their therapeutic potential in animal models. These studies served as a basis for more than 100 human clinical trials using MSCs in the last decade. However, many questions remain unanswered about MSCs. Current research thus aims at improving our understanding of these intriguing cells in order to better use them therapeutically. Four main themes can be identified in MSC research: 1) Characterization and identification of MSCs subsets, 2) Elucidation of the development origin and in vivo identity of MSCs, 3) Identification of the cellular and molecular mechanisms underlying the therapeutic effects of MSCs, and 4) pre-clinical (translational) and clinical use of MSCs. In the manuscript-based thesis presented here, I will present three original research articles covering all four of these themes. In chapter 2, I describe the use of novel cell surface markers to identify MSCs in vivo and in vitro. I initially show that FGF-receptors (FGFRs) are developmentally-regulated in both bone tissues and MSCs. Using these markers, I identified different MSCs subsets in bone tissues including perichondrium, periosteum and trabecular bone. Some of these cells appeared as pericytes in periosteum and trabecular marrow, supporting the model of a perichondrial MSC upstream of a pericytic osteo-stromal progenitor. Finally, I found that FGFRs activation leads to self-renewing proliferation of MSCs in vitro by reversibly inhibiting cellular senescence, providing a biological relevance for the expression of these markers. In chapter 3, I present the preliminary biochemical characterization of periostin, a poorly characterized matricellular protein abundantly expressed by MSCs in vitro and in vivo. I identify a post-translational modification in periostin that will undoubtedly help uncover its roles in MSCs (fate decision, proliferation, migration), in hematopoietic support, and in tissue repair. Finally, in chapter 4 I present our efforts to use MSCs in a cell-based gene therapy approach for hemophilia B. I show that the successful transplantation, engraftment, survival, differentiation, self-renewal and protein delivery by MSCs requires complex tissue engineering techniques and hierarchical scaffold design. More specifically, three-dimensional biomaterials scaffolds required optimization at the nano-, micro- and macroscale in order to sustain long term engraftment and protein delivery by MSCs in a murine model of hemophilia B. Taken together, the findings presented here provide significant advances in understanding MSCs, both in their fundamental biology and therapeutic potential. / En 1868, le physiologiste expérimental Goujon démontre que la moelle osseuse peut se transplanter et possède des propriétés ostéogéniques. Près de cent ans plus tard, Friedenstein réussi à isoler les cellules de la moelle responsables de ces propriétés et démontre ainsi l'existence d'une cellule souche non-hématopoïétique résidant dans la moelle osseuse. Depuis, la recherche sur les cellules souches mésenchymateuses (CSM) a généré un nombre considérable d'articles évaluant les caractéristiques in vitro de ces cellules, leur expression de marqueurs de surface, essayant de définir leur identité et leur localisation in vivo, mais aussi testant leurs propriétés thérapeutiques chez les animaux. Ces recherches servirent de base à plus de 100 études cliniques chez l'humain enregistrées jusqu'à maintenant, utilisant les CSM pour traiter diverses maladies. Cependant, plusieurs questions restent non résolues concernant ces intrigantes cellules souches. C'est pourquoi la recherche actuelle sur les CSM tente de répondre à ces questions fondamentales, de manière à pouvoir mieux comprendre les CSM et ainsi à mieux les utiliser thérapeutiquement. On note quatre thèmes majeurs dans la recherche sur les CSM actuelle : 1) la caractérisation in vitro des CSM et l'identification de nouveaux marqueurs de surface, 2) la recherche de l'identité in vivo des CSM et de leur niche ou localisation, 3) l'élucidation des mécanismes cellulaires et moléculaires impliqués dans leurs propriétés thérapeutiques, et 4) la recherche préclinique et clinique utilisant les CSM pour traiter des maladies. Dans la thèse par manuscrits présentée ici, je présente trois articles de recherche couvrant l'ensemble de ces quatre thèmes. Au chapitre 2, j'identifie une famille de récepteurs membranaires qui est régulée de façon développementale dans les tissus osseux et dans les CSM : les récepteurs FGF. Je démontre que ces récepteurs peuvent être utilisés pour identifier les CSM dans différents compartiments osseux tels que le perichondrium, le periosteum et l'os trabéculaire, de manière à suggérer l'existence de CSM primitives dans le perichondrium. Nous verrons également comment l'activation des récepteurs FGF sur les CSM permet leur prolifération tout en inhibant leur sénescence, leur permettant ainsi de s'auto-renouveller. Au chapitre 3, je présente la caractérisation biochimique préliminaire de periostin, une protéine matricellulaire peu connue et abondamment produite par les CSM. J'identifie une modification post-traductionnelle sur periostin qui permettra de mieux comprendre ses divers rôles dans la différentiation des CSM, leur capacité de supporter l'hématopoïèse et de participer à la réparation des tissus endommagés. Finalement, au chapitre 4 je présente une étude visant à utiliser les CSM pour la thérapie génique de l'hémophilie B. Je démontre que la survie, la différentiation, l'auto-renouvellement et la production de protéines thérapeutiques par les CSM après transplantation nécessitent l'utilisation de techniques d'ingénierie tissulaire complexes. Plus spécifiquement, j'ai dû optimiser des biomatériaux 3D à l'échelle nano-, micro- et macroscopique pour permettre la survie et la production de protéine à long-terme par les CSM dans des souris hémophiles. En conclusion, les résultats présentés ici représentent plusieurs avancées significatives dans notre compréhension de la biologie fondamentale des CSM mais également de leurs propriétés thérapeutiques.

The chemotherapeutic agents cisplatin and carboplatin are widely-used and highly-effective against a variety of malignancies. Unfortunately, these medications may sometimes cause ototoxicity. Cisplatin and carboplatin ototoxicity manifests as tinnitus and/or a permanent, bilateral and progressive hearing loss, leading to devastating consequences on the lives of cancer survivors. Earlier detection of ototoxicity during treatment allows clinicians to modify treatment plans, whenever possible, to prevent its progression. Audiological tests currently used for monitoring for platinum-induced ototoxicity are presented, as well as their advantages and disadvantages. A new paediatric evaluation method is also introduced, which uses patient-reported measures and could complement audiological testing in obtaining a more comprehensive assessment of ototoxicity.Different criteria are used in the literature in order to define ototoxicity, which makes comparison among studies difficult. A critical review was undertaken on commonly-used ototoxicity grading criteria. A retrospective chart review was also performed at the Montreal Children's Hospital, characterizing the incidence of long-term ototoxicity at our institution. Work done as part of this thesis led to the design of two novel studies: a prospective cohort study evaluating the pharmacogenomics of platinum-induced ototoxicity and a randomized controlled trial evaluating the efficacy of dexamethasone as a potential otoprotective agent. Comprehensive assessment of ototoxicity, including sensitive audiological tests, appropriate ototoxicity grading criteria, and self-reported outcomes, is urgently needed, in the clinic, in order to guide interventions, and in research, in order to gain greater understanding of the incidence and burden of platinum-induced ototoxicity. / Les anticancéreux cisplatine et carboplatine sont souvent utilisés et sont très efficaces contre une grande variété de cancers. Malheureusement, ces médicaments peuvent parfois causer l'ototoxicité. L'ototoxicité du cisplatine et du carboplatine consiste en acouphènes et/ou une perte auditive qui est souvent permanente, bilatérale et progressive, conduisant à des conséquences dévastatrices chez les survivants du cancer.Une détection plus précoce de l'ototoxicité permet aux cliniciens de modifier leurs plans de traitement, si possible, pour empêcher sa progression. Les examens audiologiques utilisés présentement pour la surveillance de l'ototoxicité induite par le platinum sont présentés, ainsi que leurs avantages et leurs inconvénients. Également, une nouvelle méthode d'évaluation pédiatrique est présentée. Celle-ci utilise des mesures auto déclarées, pouvant supplémenter les tests audiologiques pour obtenir une évaluation plus complète de l'ototoxicité. Différents critères sont utilisés pour définir l'ototoxicité, ce qui rend la comparaison entre études difficile. Une revue critique des critères les plus utilisés dans le classement de l'ototoxicité induite par le platinum a été menée. De plus, une étude rétrospective a été menée à l'Hôpital de Montréal pour Enfants pour caractériser l'incidence de l'ototoxicité au long-terme dans notre institution. Le travail effectué dans le cadre de cette thèse a conduit à la création de deux nouvelles études: une étude de cohorte prospective visant à évaluer la pharmacogénomique de l'ototoxicité induite par le platinum et un essai clinique évaluant l'efficacité de la dexamethasone tant qu'agent otoprotectif. Une évaluation globale de l'ototoxicité, incluant des tests audiologiques sensibles, des critères de classement appropriés, et des mesures auto déclarées, sont nécessaires, dans la clinique, afin de guider les interventions, et dans la recherche, afin d'acquérir une meilleure connaissance de l'incidence et les conséquences de l'ototoxicité induite par le platinum.

In the field of bioethics, the relatively recent phenomenon of cognitive enhancement—the idea that one might improve upon their typical, or "healthy," level of intellect through the use of pharmaceuticals developed to treat medical conditions—has garnered considerable interest from bioethicists and the popular media. The high level of coverage related to this phenomenon has prompted concern that a misrepresentation of the scientific facts related to the safety and efficacy of the drugs involved may encourage public interest, with potentially negative effects on social conformity and loss of diversity.One drug in particular, donepezil, has become known as a "cognitive enhancement agent" based mainly on the findings of one small-scale study. Its genesis from contested Alzheimer's drug to revolutionary "smart-pill" has provoked questions related to the level of evidence driving this reconceptualization. Recent reviews have determined that the findings of the primary study were limited, and additional analysis of a possible link between donepezil and a cognitive enhancement effect have also found the study to be lacking. This thesis characterizes how media and bioethics literature has shaped the discourse of donepezil as a cognitive enhancement agent in the absence of solid scientific evidence. A systematic content analysis was conducted to determine how media and bioethics articles portray donepezil and present the results of the landmark study. We found much hype of the possibility that donepezil could produce cognitive enhancement effects in typical individuals. Additionally, we identified a complex interaction between high expectations for a cognitive enhancement effect and ambiguous conclusions at the level of the primary paper. Together, these factors contribute to the portrayal of donepezil as a cognitive enhancement agent in secondary literature and point to important consequences for individual decision making, clinical care, and policy development. Further, hype of the phenomenon of cognitive enhancement implies that there is general interest in the goal of increasing intelligence and inspires interest in further examining why we are so involved in this end. Propagating the ideology driving those captivated by cognitive enhancement may negatively affect people with intellectual disabilities. To explore the connection between the desire to enhance cognition in typical individuals and a potential negative effect on people with intellectual disabilities, we introduce a distinct example of media hype related to drugs that target intelligence in this population. Failure to question the underlying assumptions that are driving the cognitive enhancement debate amongst individuals with typical intelligence risks further devaluing the lives of people with intellectual disability and subverting current social movements to empower these individuals and build a truly accepting and diverse society. / L'utilisation, par des individus sains, de médicaments pour améliorer leurs fonctions cognitives suscite l'attention autant des bioéthiciens que des médias. L'importante couverture médiatique de ce récent phénomène soulève la préoccupation qu'une fausse représentation des données scientifiques, relativement à la sécurité et à l'efficacité de ces médicaments, pourrait, par conséquent, éveiller l'intérêt du public. Potentiellement, cela pourrait causer des effets négatifs au plan social, par exemple, en encourageant la conformité et donc une perte de la diversité.Un médicament en particulier, le donépézil, s'est vu reconnu comme étant un « produit d'amélioration des fonctions cognitives ». Cette affirmation est basée essentiellement sur les résultats d'une seule étude, marquante dans le débat entourant le donépézil. L'évolution de ce médicament, passant d'un traitement contesté pour la maladie d'Alzheimer à une « pilule d'intelligence » (ou smart-pill), a soulevé des questions relativement aux données probantes justifiant ce nouvel étiquette de « produit d'amélioration des fonctions cognitives ». Par ailleurs, des articles de revue de littérature ont récemment conclu que les résultats de l'étude en question sont limités, et le lien entre le donépézil et l'amélioration des fonctions cognitives n'est pas clair.Le présent mémoire a pour objectif d'examiner comment la couverture médiatique et le débat bioéthique a influencé le discours sur le donépézil en tant que produit d'amélioration des performances cognitives, et cela, malgré l'absence de données probantes. Pour ce faire, nous avons procédé à une analyse systématique du contenu des médias et d'articles spécialisés en bioéthique afin d'examiner comment le donépézil et les résultats de l'étude y sont présentés. Nous avons identifié un enthousiasme débordant concernant la possibilité que le donépézil puisse améliorer les fonctions cognitives d'individus sains ainsi qu'une interaction complexe entre les attentes élevées et des conclusions ambigües au niveau de l'étude principale. Ensemble, ces facteurs ont contribué à la représentation du donépézil en tant qu'agent d'amélioration des fonctions cognitives dans la littérature et laissent supposer des conséquences importantes pour la prise de décision, les soins de santé et le développement de politiques.L'engouement entourant l'effet du donépézil au niveau de l'amélioration des performances cognitives démontre un intérêt général par rapport à la possibilité d'accroître l'intelligence et confirme ainsi la nécessité d'un examen plus approfondi à savoir pourquoi un tel but est recherché. L'augmentation, au sein de la population, du désir d'accroître l'intelligence pourrait avoir comme conséquence de nuire aux personnes atteintes d'une déficience intellectuelle. Afin d'établir le lien entre le phénomène de l'amélioration des fonctions cognitives d'individus sains et l'effet négatif potentiel sur les personnes atteintes d'une déficience intellectuelle, nous présentons dans ce mémoire un exemple d'engouement des médias autour de médicaments qui cible l'intelligence chez cette population. Ne pas s'interroger sur les présomptions sous-jacentes qui motivent le phénomène de l'amélioration des fonctions cognitives chez des individus sains risque de causer plus de tort dans le débat du « traitement » de la déficience intellectuelle et de rendre impuissants les mouvements sociaux qui visent à améliorer l'acceptabilité sociale et à promouvoir la diversité au sein de la société.

Dynamic cardiomyoplasty for hemodynamic support during acute pulmonary hypertension is studied. Five dogs underwent a right latissimus dorsi cardiomyoplasty. A graded acute pulmonary hypertension was later induced by infusion of glass microspheres into the pulmonary artery. A decrease in pulmonary artery flow, systemic pressure and systemic flow resulted. At an optimal level of hemodynamic impairment, the dynamic cardiomyoplasty was able to acutely improve pulmonary artery flow 26.4 $+/-$ 5.84% (SEM) (p $<$ 0.005), mean systemic arterial pressure 11.6 $+/-$ 3.7% (p $<$ 0.05), and the thoracic aorta flow 15.7 $+/-$ 6.3% (p $<$ 0.05). There was a significant beneficial hemodynamic effect demonstrated by dynamic cardiomyoplasty. The degree of improvement in hemodynamic variables could be correlated with the magnitude of hemodynamic impairment present. Dynamic cardiomyoplasty may be useful in patients with right heart failure associated with increased pulmonary vascular resistance.

Motor evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS) are used to asses corticospinal tract (CST) function in clinical practice. Advancements in technology have increased TMS precision yet clinical protocols do not reflect the gain in precision required for neuroscientific research. The aim of this study was to determine whether parameters extrapolated from MEP responses accurately reflect CST function. TMS was administered to healthy controls and acute subcortical stroke patients. A sigmoid-shaped dose-response curve was observed in control subjects and patients with lesions outside the CST. Relative amplitude of MEPs is the best descriptor of CST integrity. Absence of a sigmoid relationship indicates CST impairment. / Les potentiels évoqués moteurs (PEM) élicités par la stimulation magnétique trancrânienne (SMT) sont utilisés en clinique pour évaluer la fonction du faisceau corticospinal (FCS). Les avancements technologiques ont amélioré la précision de la SMT. Toutefois, les méthodologies cliniques ne reflète pas la précision requise pour la recherche neuroscientifique. Le but de cette étude était d'analyser les caractéristiques des courbes de doses-effets des PEM pour déterminer s'ils reflètent la fonction du FCS. La SMT a été appliquée chez des sujets sains ainsi que chez des patients ayant subi un accident vasculaire cérébral (AVC). Une relation sigmoïde est présente dans les courbes de doses-effets chez les sujets sains et chez les patients ne présentant pas de lésions directement sur le FCS. De plus, l'amplitude absolue n'est pas un bon descripteur de l'excitabilité cortical à cause de la grande variabilité interindividuelle. L'absence d'une relation sigmoïde indique une déficience grave de la FCS.

A radioimmunoassay was developed to determine the concentration of immunoreactive somatostatin (IRS) in crude and partially-purified extracts of various anatomical regions of the nervous system, including the retina. Affinity chromatography using somatostatin antiserum served to concentrate IRS from the retina and other brain regions. Retinal IRS from rats and humans inhibited the release of growth hormone in a bioassay in a similar manner as did synthetic somatostatin. Affinity chromatography-purified extracts of rat median eminence, anterior hypothalamic-preoptic area, amygdala and cerebral cortex, when subjected to gel filtration chromatography, eluted with similar profiles characterized by four IRS peaks of which the third to elute was largest and had a coincidental elution position with synthetic somatostatin. The IRS in each peak from all four brain regions was biologically active as assessed by its ability to inhibit growth hormone secretion.

Lipid peroxidation has been implicated in the development of atherosclerosis. It is responsible for modification of low density lipoprotein (LDL), injury to endothelial cells and has been reported to alter prostacyclin synthesis. We therefore investigated lipid peroxidation in human LDL and in LDL and aortae from rabbits fed cholesterol-supplemented diets. We also studied the correlation between lipid peroxidation and prostanoid production in vivo and in vitro. / Unsaturated fatty acids in human LDL are oxidized to their monohydroxy derivatives during the incubation with CuSO$ sb4$ and endothelial cells. Gas chromatographic-mass spectrometric analysis of monohydroxy fatty acids revealed a similar mechanism of peroxidation of LDL lipids by endothelial cells as that by CuSO$ sb4,$ i.e., autooxidation of LDL lipids. / Increased amounts of monohydroxy fatty acids in LDL and aorta were observed in rabbits fed cholesterol-supplemented diets. The increased amounts of monohydroxy derivatives of oleic and linoleic acids, but not those of arachidonic acid, were due to the increased amounts of their fatty acid precursors. The increased amounts of aortic monohydroxy derivatives of arachidonic acid, but not those of oleic and linoleic acids, were positively correlated with the severity of the atherosclerotic lesions. / Prostacyclin production by aortae was slightly increased after cholesterol-supplemental diets despite evidence for increased lipid peroxidation in this tissue. This may be because esterified hydroperoxy fatty acids in aorta are not very effective in inhibiting prostaglandin synthesis. In contrast to the moderate changes in aortic PGI$ sb2$ synthesis, there was a dramatic increase in the synthesis of thromboxane B$ sb2$ by aortae from hypercholesterolemic rabbits, suggesting a role for thromboxane A$ sb2$ in atherogenesis.

The objective of the present study was to determine the relationship between dietary intake and the formation of idiopathic upper urinary tract stones. More specifically, the aim of this study was to test the relationship between the formation of idiopathic upper urinary tract stones and diet in new cases and demonstrate how the inclusion of recurrent cases in a study could affect the relationship mentioned above. / A case-control approach was used. A total of 61 new cases was compared to 58 controls. A parallel analysis was made for 62 recurrent cases and 59 controls in order to demonstrate the possible effect of dietary advice received in the past in relation to previous episodes of kidney stones. All controls were selected from patients who had an intravenous pyelogram for a reason other than one related to the formation of a kidney stone and were matched to cases for age and sex. The dietary history of patients was established and constituted the main part of a home interview. Logistic regression was used and potential confounding factors were adjusted for, including family history of stones, ethnic group, and source of the patients. / Some differences in nutrient intake were observed between new cases and their controls. Differences involved oxalates, vitamin D and the combination of proteins, purines and magnesium. As the direction of the observed differences did not fit the research hypotheses and likely explanations were found, it was concluded that there was no relationship between diet and kidney stone formation. / The analysis involving recurrent cases and their controls revealed that there was effectively a dietary bias which affected the estimated intake of calcium, water, magnesium, purines, and possibly proteins and vitamin C as well. It is concluded that any case-control study on kidney stone formation should be done separately for new and recurrent cases.

The mechanisms implicated in voiding and continence are far from being settled in the normal as well as in neurogenic bladder dysfunction. Understanding these mechanisms is an essential step in the management of the bladder dysfunction secondary to neurological lesions. In the course of our studies, we demonstrated the existence of a fine coordination "synergism" between the several components of the lower urinary tract i.e., detrusor, proximal urethral muscle and periurethral striated muscles. This synergism is found to be responsible for adequate bladder emptying during voiding in the animal model with intact neural axis. The synergism between the bladder and its outlet is under the control of a higher centre in the brain stem and mediated through the spinal cord and peripheral nerves. The cause of failure of bladder emptying following a spinal lesion was shown to be a lack of synergism between the bladder and its outlet. An animal model for chronic multiple sclerosis-like disease was developed and proved to show a good urodynamic and neurological correlation with that found in the human afflicted with multiple sclerosis. / The pharmacological investigation on the bladder and urethra shows that there is selective distribution of cholinergic, adrenergic and purinergic receptors along the individual layers of the smooth muscles of the urethra. On the other hand, the importance of the Calcium ions in the contractility of the detrusor muscle was also studied. The effect of some Calcium ions antagonists on the detrusor contractility was evaluated. They show selective inhibition on the detrusor contraction both in vivo and in vitro. The calcium antagonists may present a new treatment modality for controlling bladder instability.

The hypothalamic supraoptic nucleus (SON) in the rat contains neurons that synthesize either vasopressin (VP) or oxytocin and that receive prominent afferent connections of cardiovascular origin. In vivo electrophysiological studies were undertaken to characterise the selective depression of VP-secreting cell activity consequent to activation of peripheral baroreceptors. Electrical stimulation of the diagonal band of Broca evoked a similar selective inhibition of supraoptic VP neurons. Extracellular recordings in the diagonal band confirmed the involvement of this site in the baro-reflex input to the SON. Local application of bicuculline, a GABA antagonist, abolished both the diagonal band-evoked and the baroreceptor-induced inhibition of VP-secreting neurons. Anatomical observations at the ultrastructural level indicated that the diagonal band projection to the SON is indirect and involves an GABAergic interneuron located in the perinuclear zone adjacent to the SON. / Another input to the SON that was studied arises in the subfornical organ, a circumventricular structure known to contain angiotensin II immunoreactive neurons. Electrical stimulation of the subfornical organ evoked an excitatory response in SON neurons that could be selectively attenuated by locally applied saralasin, an angiotensin II antagonist. This finding suggests a role for the peptide angiotensin II as a neurotransmitter in this projection. / The collective results are discussed in the context of the three major neurocardiovascular pathways that influence vasopressin secretion from the neurohypophysis.