No description available.

No description available.

The retinal pigment epithelium (RPE) is a monolayer of cells located directly behind the photoreceptor cells in the retina. These cells are involved in a variety of functions that support the visual process in the eye, namely 1) they form a blood-retina barrier which separates the neural retina from the choroid's blood supply, 2) the apical processes of RPE cells diurnally phagocytose the outer segments of photoreceptor cells, and 3) they participate in the renewal of the photopigment 11-cis retinal. Age-related macular degneration (AMD) is the leading cause of blindness in people over the age of 50 years in North America and other developed countries. AMD involves the death of retinal pigment epithelial (RPE) cells in the macula early in the progress of the disease. Like some other postmitotic cells, the RPE accumulates autofluorescent lysosomal storage bodies (lipofuscin) during senescence. Lipofuscin is reported to begin accumulating in the human RPE around age 20 and continues to accumulate throughout an individual's life. This progressive accumulation of lipofuscin can eventually occupy a substantial fraction of the RPE cytoplasmic volume and may lead to impairment of normal RPE functions, resulting in retinal degeneration and loss of visual function as in AMD. Another autofluorescent granule that accumulates in RPE cells and may contribute to the etiology of AMD is a complex granule exhibiting properties of both melanosomes and lipofuscin granules called melanolipofuscin (MLF). In contrast with the accumulation of LF in the RPE, MLF accumulation has been reported by Feeney-Burns to more closely reflect the onset of AMD. Although there have been significant advances in our understanding of AMD, knowledge of the mechanisms responsible for its progression remain unclear. This dissertation details experiments that were designed to better understand the factors that may play a causal role in AMD as well as the development of methods to assist in AMD research. Specifically, the protein composition of retinal LF was assessed to elucidate its origin. These findings are reported in chapter 2. The accumulation, composition and phototoxicity of MLF were analyzed to assess MLF's origin and possible contribution to AMD. These results are reported in chapter 3. Because protein oxidation is possibly a common posttranslational modification to proteins which accumulate in lipofuscin and melanolipofuscin granules, a method for the detection and analysis of oxidized proteins was developed and is reported in chapter 4. Chapter 5 details the proteomic differences between ARPE-19 cells - the only human RPE cell line available for research - in their differentiated and undifferentiated states and compares these to the proteome of human RPE cells. These results are also compared to the phenotypic difference of these cells as observed by transmission electron microscopy.

Age-related macular degeneration (AMD) is the leading cause of blindness in the United States of America. The pyridinium bis-retinoid A2-ethanolamine (A2E) has been implicated to play a role in AMD. We have observed novel pyridinium bis-retinoids through melanolipofuscin and human RPE extractions that may also play a role in the pathology of AMD. We have begun the construction of an amino-retinoid library in order to identify these ocular compounds. The compounds from the amino-retinoid library are also used in a targeted and triggered drug delivery system for treating cancer. Folic acid is coupled with the amino-retinoids to specifically target cancer cells. The first two amino-retinoids to be synthesized and characterized were A2-dopamine (A2D) and A2-cadaverine (A2C). Both pyridinium bis-retinoids were shown to generate cytotoxic oxidation products similar to A2E. Successful coupling of folic acid to A2C was achieved to form the folic acid-A2-cadaverine (FA-A2C) product. Preliminary irradiation results suggest that the FA-A2C product may be more photoreactive than initially anticipated. This could mean less drug and light exposure required to induce apoptosis and could eventually lead to a less invasive and toxic cancer treatment.

No description available.

No description available.

Contrairement à la vision fovéale qui assure une perception détaillée de notre environnement visuelle, la périphérie ne permet qu’une vision globale. C’est pourquoi, nous bougeons nos yeux en permanence afin que l’image visuelle soit localisée sur la fovéa, où la résolution spatiale est la meilleure. Cependant, certaines pathologies sont à l’origine d’une perte de la vision centrale et provoquent de nombreuses difficultés dans la vie quotidienne notamment pour lire, conduire, identifier un visage, un objet ou encore naviguer dans l’espace. Contrairement à la lecture, peu d’études ont été réalisées sur la perception des objets et de l’espace dans ces maculopathies où ne persiste que la vision périphérique. Nous nous sommes intéressés à l’étude des capacités de la vision périphérique dans la perception des scènes et des objets.Dans un premier temps, nous avons étudié les capacités de la vision périphérique chez le sujet sain. Nous avons montré qu’en dépit de sa faible résolution spatiale, il était possible de reconnaître des objets et des scènes même à grande excentricité.Dans un second temps, nous nous sommes focalisés sur les effets de la perte de la vision centrale sur la reconnaissance des objets et des scènes. Nous montrons que l’absence de vision centrale induit une plus faible stabilité de fixation associée à un déficit marqué sur l’identification des objets et des scènes, ainsi que sur la recherche visuelle, notamment en condition d’encombrement.Ces études contribuent à comprendre la contribution de la vision centrale et de la vision périphérique sur la reconnaissance des objets et des scènes mais aussi sur le rôle de l’information contextuelle et comment les patients ayant perdu la vision centrale perçoivent le monde réel. / Unlike foveal vision that allows a detailed perception of our visual environment, the periphery only allows a coarse vision. This is why we have to move our eyes all the time in order to localize the image on the fovea, where spatial resolution is better. However, some diseases induce a loss of central vision and cause many difficulties in everyday life especially in reading, driving, face recognition and spatial cognition in general. Unlike word and face perception scene and object perception have had litte investigations in maculopathies in which people have to rely on peripheral vision. This thesis is based on the study of the capabilities of peripheral vision in scenes and objects perception.In the first part we studied scne perception at very large eccentricities in normally sighted young people. We show that, in spite of its low resolution, peripheral vision is efficient to recognize objects and scenes even at very large eccentricities (above 50°).In the second part, we investigated on effects of central vision loss on object and scene perception in identification and visual search tasks on small or realistic panoramic displays. We report a series of experiments showing that central vision loss induced a lower fixation stability which had a strong impact on object and scene and on visual search, especially in crowded conditions.These studies contribute to the understanding of the contribution of central and peripheral vision on object and scene gist recognition but also on the role of contextual information and how patients with central vision loss perceive real-world scenes.

Première cause de baisse d'acuité visuelle dans les pays industrialisés, la dégénérescence maculaire liée l'âge (DMLA) est une pathologie de la rétine touchant principalement les personnes après 55 ans. Elle est caractérisée par une dégénérescence de la zone maculaire de la rétine et par la formation de drusens. Il existe deux formes de la maladie : la forme exsudative et la forme atrophique. Dans notre étude, nous nous sommes focalisés sur la DMLA atrophique, actuellement sans traitement curatif et qui correspond à environ 50% des cas cliniques en Europe. Malgré de nombreuses recherches, les causes de la DMLA restent encore mal comprises même si des facteurs environnementaux (sénescence, accumulation de lipofuscine, stress oxydatif) et génétiques sont probablement combinés. Selon l'hypothèse étiopathogénique, le dysfonctionnement des cellules de l'épithélium pigmenté de la rétine (EPR) est au centre des événements physiopathologiques de la DMLA. A partir de sujets sains et de patients atteints de la DMLA atrophique, nous avons obtenu des cellules de l'EPR dérivées de cellules souches pluripotentes induites et développé un modèle cellulaire humain utile pour la compréhension des mécanismes physiopathologiques de la DMLA. Ainsi, l'étude morphologique et fonctionnelle de ces deux populations de cellules a souligné un phénotype particulier des cellules de l'EPR provenant de patients atteints pas la DMLA en condition basale et en milieu pro-oxydant. Ce modèle cellulaire pourra nous permettre d'approfondir nos connaissances sur les mécanismes amenant au développement de la DMLA et pourra aussi être utilisé pour le screening des molécules au cours des étapes précliniques. / First cause of irreversible visual dysfunction in industrialized countries, age-related macular degeneration (AMD) is a retinal disease affecting people after 55 years old. AMD is characterized by the macular degeneration of retina and by formation of drusen. There exist two forms of the disease: the exudative and the atrophic forms. In our study, we focused only on the atrophic one, corresponding to approximately 50% of the clinical cases in Europe, that still today without curative therapy. Despite many researches, AMD's etiology remains unclear even if environmental and genetics factors would be involved. According to the etiopatogenic hypothesis, RPE cells dysfunction has a central role in the physiopathological events leading to AMD. From healthy subjects and patients affected by atrophic AMD, we obtained RPE cells derived from induced pluripotent stem cells and developed a useful human cellular model for the understanding of AMD mechanisms. Indeed, the morphological and functional study of the two types of cells populations underlined a particular phenotype for the RPE cells derived from AMD patients. This cellular model will allow us to have a better understanding of mechanisms leading to AMD and will also be used to screen therapeutic molecules before clinical studies.

A Degeneração da Mácula Relacionada a Idade (DMRI) acomete pessoas com mais de 50 anos, comprometendo gravemente a visão. Desde 2005, têm-se sugerido uma correlação entre DMRI e o polimorfismo Y402H do Fator H (FH). Os mecanismos pelos quais a proteína FH participa da etiopatogenia dessa doença têm sido alvo de muitos estudos, desde então. Neste trabalho, investigamos a correlação entre esse polimorfismo e a expressão de proteínas da via alternativa e parâmetros do perfil lipídico de pacientes com DMRI. As concentrações de FH, Fator B, C3 e Proteína C-reativa foram semelhantes entre os grupos controle e paciente. As concentrações de Fator D e os autoanticorpos encontravam-se reduzidos nos pacientes; enquanto Fator I e os demais parâmetros do perfil lipídico estavam aumentados nesses pacientes. A variante Y402 aparentemente aderiu melhor à superfície das leptospiras (superfície ativadora da via alternativa) em relação à variante H402, mas não houve diferença entre as variantes em relação à ligação a células endoteliais (superfície não ativadora). / Age-related Macular Degeneration (AMD) affects people over 50 years, and severely prejudice the vision. Since 2005, it has been suggested a correlation between AMD and the Y402H polymorphism of Factor H (FH). After this, the mechanisms by which FH protein participates in the pathogenesis of this disease have been extensively studied. In this study, we investigated the correlation between this polymorphism and expression of proteins of the alternative pathway and lipid profile of patients with AMD. The concentrations of FH, Factor B, C3 and C-reactive protein were similar between the control and patient groups.Factor D concentrations and autoantibodies levels were reduced in patients, while Factor I concentrations and the levels of the other parameters of lipid profile were increased in these patients.Apparently, Y402 variant displays better adhesion to the surface of Leptospira (alternative pathway activating surface) than the H402 variant, but no difference between the variants of the linkage to endothelial cells (non-alternative pathway activating surface).

La Dégénérescence Maculaire Liée à l’Age (DMLA) est la première cause de cécité légale dans les pays industrialisés chez les personnes âgées. L’atrophie géographique – l’une des formes tardives de la DMLA - est caractérisée par la perte de l’épithélium pigmentaire et la dégénérescence des photorécepteurs. Nous groupe a montré précédemment que dans l’atrophie géographique, les phagocytes mononucléés (PMs) s’accumulent dans l’espace sous-rétinien, et induisent la dégénérescence rétinienne via la production d’IL-1β. Dans un premier temps, nous montrons que la présence de PMs sous-rétiniens est associée à la perte des bâtonnets et la dégénérescence des segments de cônes dans la zone de transition de patients atrophiques. Nous montrons ensuite dans différents modèles in vivo et ex vivo que les macrophages récapitulent ces effets, et qu’IL-1β est nécessaire à la perte des segments externes des cônes induite par les PMs. Dans un deuxième temps, nos résultats montrent qu’IL-1β induit indirectement la mort des bâtonnets, en perturbant l’homéostasie rétinienne du glutamate. L’inhibition des récepteurs glutamatergiques pour prévenir l’excitotoxicité du glutamate, ou la supplémentation en cystine favorisant la restauration de la machinerie neuronale antioxydante, permettent de protéger les bâtonnets de la toxicité induite par IL-1β. L’ensemble de nos résultats démontre le rôle joué par IL-1β dans la dégénérescence des segments de cônes et la perte des bâtonnets dans l’inflammation sous-rétinienne. Cette étude permettra la mise au point de thérapies innovantes, afin de lutter contre la forme atrophique de la DMLA, pour laquelle il n’existe actuellement aucun traitement. / In geographic atrophy (GA), one of the late forms of Age-related Macular Degeneration (AMD), an extending atrophic zone forms, characterized by the loss of retinal pigment epithelium and photoreceptor degeneration. Subretinal mononuclear phagocytes (MPs) accumulate in GA, and are associated with IL-1β-dependent retinal degeneration. First, we confirmed that subretinal accumulation of MPs is associated with rod degeneration and cone segment loss in the transitional zone in GA human samples. Using ex vivo and in vivo models, we then demonstrated that MPs-derived IL-1β leads to severe cone segment degeneration. Therefore, inhibiting subretinal MP accumulation or IL-1β might protect the cone segment, and help preserve high acuity daytime vision in conditions characterized by subretinal inflammation. Second, we showed that IL-1β effect on rod degeneration is indirect, and mediated by glutamate. Our results indicate that IL-1β impairs Müller glial cells glutamate recycling, and subsequently leads to the extracellular increase in glutamate content. Inhibiting glutamate receptors to prevent excitotoxicity, or exogenous cystine supplementation to supply antioxidant metabolism, are sufficient to protect rods from IL-1β-induced neurotoxicity. Our results provide new perspectives to treat pathologies associated with subretinal inflammation such as late AMD. Our results collectively demonstrated that MP-derived IL-1β induces cone segment loss, and glutamate homeostasis disruption associated with rod degeneration. This study will help with the development of new therapeutic strategies in dealing with inflammatory retinal pathologies as geographic atrophy.