Sickle cell disease is a genetic disorder that affects 100,000 Americans and millions more worldwide. Although the sickle mutation affects one protein, which is only expressed in a single cell type, it has profound detrimental effects on nearly every organ system in the body. Young children with sickle cell disease have an 11\% chance of suffering a major stroke event by the age of 16, and a 35\% chance of developing ÒsilentÓ strokes that often result in significant learning and mental disabilities. Clinical investigations suggest that stroke development in people with sickle cell disease results from luminal narrowing of the carotid and cerebral arteries due to excess matrix deposition and fragmentation of the elastic lamina; however, the underlying cellular mechanisms that initiate arterial remodeling in sickle cell disease remain relatively unknown. Cathepsins K and V are members of the cysteine family of proteases and represent two of the most potent elastases yet identified in humans. Furthermore, the role of Cathepsins has been well established in other cardiovascular remodeling diseases, such as atherosclerosis. Due to the compelling histological similarities between vasculopathy in sickle cell disease and atherosclerosis, we tested the hypothesis that the unique inflammatory milieu, in conjunction with the biomechanical vascular environment of sickle cell disease upregulates cathepsin K and V activity in large artery endothelial cells, ultimately leading to arterial remodeling and stroke. Currently, there are few therapeutic options for the prevention of stroke in sickle cell disease; those that do exist carry significant health risks and side effects. Together, this body of work has generated a more mechanistic understanding of how the sickle milieu stimulates the endothelium to initiate arterial remodeling, which has enabled us to identify important pathways (JNK, NF$\kappa$B) downstream of inflammatory and biomechanical stimuli and validate new therapeutic targets within the JNK pathway to establish preclinical proof of efficacy for the prevention of arterial remodeling in sickle cell disease.

Cerebral vasospasm following subarachnoid hemorrhage has high morbidity and mortality. Mathematical modeling of the progression of the condition provides insight to improve clinical treatment of patients post subarachnoid hemorrhage. An existing model of the clotting cascade is expanded to include the theoretical conditions of cerebral vasospasm. We consider clotting factor XIIIa, which has been implicated as a primary cause of the entrenchment of the smaller diameter. Solutions for clotting are used as boundary conditions to solve the concentration of diffusible clotting factors in the vessel wall and cerebrospinal fluid (CSF). Each domain (clot, vessel wall, CSF) is described by a separate initial-boundary value problem, requiring unique conditions, reaction-diffusion equations, and diffusion coefficients. Additionally, the results from the first domain (the clot) provide a subset of the boundary conditions for the second and third domains (arterial wall and CSF, respectively). Although this approach captures many detailed components of the clotting process, a simpler method for investigating the formation and dissolution of a clot post subarachnoid hemorrhage is to neglect the bulk of the clot cascade to focus on the most salient features, namely, the formation of cross-linked fibrin and the degradation of fibrin by plasmin. By assuming first order kinetics in the initial hours following hemorrhage, we find a simplified expression with kinetic rates that may be adjusted depending on experimental conditions.

Major advances in highly active antiretroviral therapies (ARVs) have extended the lives of people living with HIV, but there still remains an increased risk of death by cardiovascular diseases (CVD). HIV proteins and ARVs have been shown to contribute to cardiovascular dysfunction with effects on the different cell types that comprise the arterial wall. In particular, HIV-1 transactivating factor, Tat, is a cationic polypeptide that binds to endothelial cells, inducing a range of responses that have been shown to contribute to vascular dysfunction. It is well established that hemodynamics also play an important role in endothelial cell mediated atherosclerotic development where upon exposure to low or oscillatory shear stress, such as that found at branches and bifurcations, endothelial cells contribute to proteolytic vascular remodeling, by upregulating cathepsins, potent elastases and collagenases. The results of this work demonstrate that upregulation of cathepsins in vivo and in vitro is caused by a synergism between pro-atherogenic shear stress and HIV-1 proteins, elucidates pathways that are activated by HIV-1 Tat and pro-atherogenic shear stress - leading to cathepsin-mediated ECM degradation, and identifies cathepsins as novel biomarkers to monitor the adherence of patients on efavirenz- and tenofovir-containing antiretroviral regimens.

Arterial remodeling is a process by which arteries respond to sustained changes in their mechanical environment. This process occurs in a way such that an artery's local mechanical environment (circumferential, shear, and axial stress) is maintained at a homeostatic level. However, most studies utilize a methodology that controls the global parameters (pressure, flow rate, and axial stretch). This approach often confounds the results since the actual drivers of remodeling are not independently isolated. This research involved developing a methodology and system capable of independently controlling each of the local parameters and examining the effect of axial stress on remodeling. An organ culture system capable of monitoring and controlling the three global parameters and calculating the cross sectional geometry was developed. This combination of hardware was incorporated into LabVIEW which afforded the user the ability to define desired values for the local mechanical parameters. Porcine common carotid arteries were cultured for seven days in this system under physiologically normal circumferential and shear stresses and a constant axial stress of either 150 kPa or 300 kPa. Material response, general arterial morphology, tissue viability, and collagen synthesis were examined in order to gauge the effectiveness of the organ culture system and assess any arterial remodeling. The results of this study demonstrate the ability of the organ culture system in achieving and maintaining target values of stress throughout the culture period. Cell viability, general arterial morphology, and collagen synthesis rates were maintained for all arteries. The elevated axial stress appeared to cause a softening of the artery in both the axial and circumferential direction. It was hypothesized that this softening was the result of a changing collagen structure. Additional softening seen in arteries was attributed to the effects of the culture system.

Au cours de ma thèse, je me suis principalement intéressée aux interactions entre les systèmes angiotensine et gluco-minéralocorticoïde dans la paroi artérielle et particulièrement dans la physiopathologie du remodelage artériel. Pour cela, nous avons étudié les mécanismes moléculaires aboutissant au développement de l’athérome et qui impliqueraient ces deux systèmes. Notre hypothèse est qu’un excès local en gluco-et/ou minéralocorticoïdes dans la paroi favorise le développement de l’athérome en stimulant le système angiotensine. Nos résultats ont confirmé l’expression des éléments nécessaires à la synthèse et à l'action des gluco-minéralocorticoïdes dans la paroi carotidienne humaine et dans les CMLV, avec une prévalence de la voie des glucocorticoïdes. Cette prédominance se manifeste par l’effet stimulant du cortisol sur l’expression des marqueurs des processus fibrosants, lipogéniques et inflammatoire mis en jeu lors de la formation de l’athérome. La relation entre le taux d’expression pariétale de GRα et 11β-HSD1 d’une part et le collagène 1 d’autre part suggère une contribution majeure des glucocorticoïdes dans la rigidité artérielle. Il a également été observé que le cortisol a un effet stimulant sur l’expression du collagène dans les CMLV suggérant ainsi que le cortisol favoriserait la survenue des accidents cardiovasculaires. La relation inverse entre le taux d’expression pariétal de GRα et la mesure de la pression artérielle diastolique est en faveur de cette hypothèse. De même, l’augmentation du taux de l’ARNm de GRα chez les patients ayant fait un accident cardiovasculaire corrobore l’hypothèse d’un rôle délétère des glucocorticoïdes dans le remodelage athéromateux. Nos résultats montrent que le système glucocorticoïde est un puissant stimulateur du système angiotensine pariétal et suggère l’existence d’une régulation commune de la synthèse de l’angiotensine II, de l’aldostérone et du cortisol évoquant ainsi la possibilité d’interactions entre les systèmes angiotensine et gluco-minéralocorticoïde pariétaux. Par ailleurs, les concentrations basses du cortisol plasmatique chez les patients traités par des bloqueurs du système rénine angiotensine est en faveur de la théorie d’amplification mutuelle des systèmes angiotensine et glucocorticoïde. Notre étude souligne l’intérêt des bloqueurs du SRA comme approche thérapeutique préférentielle à utiliser afin d’atténuer les effets délétères du cortisol, améliorer le risque cardiovasculaire et le pronostic des patients / The involvement of the renin angiotensin system, cortisol and aldosterone in the increase of cardiovascular risk is well known as well as some of relationships between RAS and corticosteroids but their interactions within arterial wall and particularly during atheroma formation are not established. Considering all these data, we hypothesize that an increase in local gluco-and/or mineralocorticoid synthesis and activity within the arterial wall may favour atheroma development by stimulating tissue angiotensin system. Our results give argument in favour of an independence betweenthe parietal and endocrine corticosteroid systems. We have shown the prevailing involvement of the glucocorticoid pathway in the atherosclerotic remodelling both in terms of intra-parietal expression and regulation of fibrotic, inflammatory and lipogenic effects in VSMCs together with the further amplification of this involvement after adipocyte dedifferentiation of VSMCs. There is modulation of GR and MR effects with a change in the cell pathophysiological state. Interestingly, there is no “illicit” cortisol-dependent activation of MR-receptor. We conclude that cortisol involvement in atheroma formation could pass apart from its continuing stimulating effect on its own synthesis and action, through mutual stimulating effects of cortisol and angiotensin II on their reciprocal compounds. These processes could already take place at the initial stage of atheroma and might intensify as the atheroma development progresses. The up-regulation of parietal angiotensin system could be revealed by a low plasma renin. The lower plasma cortisol levels in patients on RAS blocker treatment corroborates the thesis of mutual amplification of effects between glucocorticoids and angiotensin system, and this treatment would be particularly beneficial in essential hypertensive patients with low plasma renin, to attenuate both angiotensin II and also cortisol up-regulation