Le développement de traitements thérapeutiques du cancer du sein reste limité par le niveau de connaissance des mécanismes moléculaires et cellulaires impliqués lors du développement normal et tumoral de la glande mammaire. L’épithélium mammaire est entouré d’une matrice extracellulaire (MEC) organisée, la membrane basale, dont le constituant principal est la laminine. Des études ont montré que les interactions entre les cellules mammaires et la MEC, dépendantes des intégrines, jouent un rôle majeur dans le développement et la tumorigenèse mammaires. Ces études n’ont cependant pas permis de déterminer les hétérodimères d’intégrine spécifiquement impliqués. Dans ce contexte, mon projet de thèse a visé à définir le rôle joué par les intégrines liant la laminine (dimères contenant les sous-unités 3 et/ou 6) dans le développement mammaire, dans le maintien de cellules souches mammaires fonctionnelles dans la glande adulte et dans le développement tumoral. Les résultats de mon travail suggèrent que :(i) l’intégrine 31 présente une fonction unique au cours de la lactation. Les mécanismes moléculaires impliqués en aval de 31 font intervenir la voie FAK/Rac1/PAK1 menant à l’inhibition de la MLCK, nécessaire à la relaxation des cellules myoépithéliales mammaires et permettant de nouveaux cycles de contraction. (ii) les interactions régulées par les intégrines entre les cellules basales mammaires et la laminine sont essentielles pour régénérer l’épithélium mammaire. Cependant, les intégrines 3 et 6 présentent des fonctions redondantes dans les cellules souches mammaires. (iii) l’intégrine 31 joue un rôle clef dans le développement tumoral mammaire. L’intégrine 31 active des voies de signalisation intracellulaires FAK/Rac1/PAK1, MAPK et JNK qui favorisent la survie et la prolifération des cellules tumorales. Ensembles, ces données permettent une meilleure compréhension des mécanismes moléculaires impliqués dans le développement mammaire, la fonction de la glande adulte et la tumorigenèse. / The improvement of breast cancer therapy requires thorough analysis of the pathways leading to tumorigenesis and clear understanding of the molecular and cellular mechanisms involved in normal mammary gland development. Mammary epithelium is surrounded by a specifically organized extracellular matrix (ECM), basement membrane, and secreted glycoproteins, laminins, are among its major constituents. Integrin-mediated interactions between mammary epithelial cells and ECM have been shown to play an essential role in the control of mammary development and tumorigenesis. However, specific roles played by distinct integrin heterodimers are yet poorly understood. My thesis project aimed to define the functions of laminin-binding integrins, i.e., heterodimers, containing 3 or 6 subunits, in normal mammary gland development, in control of mammary stem and progenitor cell functions in adult gland, and in mammary tumorigenesis. The results of my work suggest that: (i31 integrin has a unique function in the control of the myoepithelial cell contractile activity during lactation; it contributes to the activation of the FAK/Rac1/PAK1 pathway leading to MLCK inhibition required for myoepithelial cell relaxation, thereby, permitting further contractile cycles. (ii) integrin-mediated interactions of mammary basal cells with laminins are essential for the regeneration of the mammary epithelium. However, 31 and 6-contaning integrins have redundant functions in mammary stem cells.(iii) 31 integrin plays a major role in mammary tumorigenesis, it promotes survival and proliferation of tumor cells activating intracellular signaling pathways involving FAK/Rac1/PAK1, MAPK and JNK pathways. Altogether, these data provide new insights into the molecular mechanisms of mammary development, adult gland function and tumorigenesis.

Orientador: Carlos Alberto Vicentini / Banca: Classius de Oliveira / Banca: Sérgio Ricardo Batlouni / Resumo: O Cichla kelberi, espécie recentemente classificada e popularmente conhecida como tucunaré amarelo, é endêmico dos rios Araguaia e baixo Tocantins, sendo, entretanto, encontrado em muitas outras bacias, onde apresenta grande importância para a pesca profissional por seu alto valor econômico, devido a qualidade e sabor de sua carne, e pela pesca esportiva, como pode ser observado pelos campeonatos anuais de pesca ao tucunaré nos rios em que se encontra. Para entender esse rápido processo de ocupação e adaptação a novos ambientes, 78 exemplares de Cichla kelberi foram mensalmente coletados entre os meses de março de 2009 a fevereiro de 2010, com o auxílio de vara de pesca e anzol na Lagoa do Pernilongo (20º 29' 11,93"S, 51º 25' 33,27"O) e Ilha da Ferradura (20º 28' 27,11" S, 51º 25' 54,53"O), no Reservatório de Jupiá, rio Paraná, Ilha Solteira, São Paulo, Brasil, onde foi introduzido. Foram definidas quatro classes de maturação gonadal para o ciclo reprodutivo anual do tucunaré amarelo C. kelberi. A definição das classes de Maturação Inicial, Maturação Intermediária, Maturação Final e Regressão, tiveram como base as alterações do epitélio germinativo testicular associado aos estágios das células germinativas presentes. A Classe de Maturação Inicial é caracterizada pela presença de um epitélio germinativo totalmente contínuo, cistos com células germinativas em todos os estágios de desenvolvimento, intensa atividade espermatogênica por todo o testículo e raros "clusters" periféricos, formados por espermatogônias primárias. A Classe de Maturação Intermediária inicia com o surgimento de um epitélio germinativo descontínuo na região anastomosada, com diminuição da espermatogênese e estocagem de espermatozóides nesta região. Os agrupamentos periféricos de espermatogônias ou "clusters" estão ausentes... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Cichla kelberi, a recently classified specie and popularly known as yellow peacock bass, is endemic from the Araguaia an low Tocantins river, being, however, found in many other basins, where has great importance for the professional fishing for its high economic value due to the quality and flavor of their meat and fishing, as can be observed by annual championships of peacock in the rivers where it is. To understand this fast process of occupation and adaptation to new environments, 78 specimens of C. kelberi were caught monthly between the months of March 2009 to February 2010 with the aid of fishing pole and hook, from the Lagoa do Pernilongo (20º 29' 11,93"S, 51º 25' 33,27"O) and Ilha da Ferradura (20º 28' 27,11" S, 51º 25' 54,53"O), in the Jupiá Reservoir, Parana River, Ilha Solteira, São Paulo, Brazil, where it was introduced. It was defined four gonadal maturation class to the annual reproductive cycle of the yellow peacock bass C. kelberi. The definition of the Early Maturation, Mid Maturation, Final Maturation and Regression Classes, were based on the changes of the testicular germinal epithelium associated with the germ cell stages present. The Class of Early Maturation is characterized by the presence of a fully continuous germinal epithelium, cysts with germ cells at all stages of development, intense spermatogenic activity throughout the testis and rare "clusters" peripherals, consisting of primary spermatogonia. The Mid maturation Class starts with the appearance of a discontinuous germinal epithelium in the anastomosed region with spermatogenesis decrease and sperm storage in this region. The peripheral groups of spermatogonia or "clusters" are missing at the end of this class of maturation. In the Final Maturation Class the germinal epithelium discontinuity reaches the periphery of lobules... (Complete abstract click electronic access below) / Mestre

O objetivo do presente trabalho foi propiciar o acesso in vivo ao epitélio respiratório e estudar a frequência de batimento ciliar (FBC) e a diferença de potencial transepitelial (DP) em um modelo murino de doença alérgica das vias aéreas induzida por ovoalbumina. Camundongos Swiss foram sensibilizados com ovoalbumina (OVA) através de duas injeções intraperitoneais de alérgico com o adjuvante hidróxido de alumínio (dias 0 e 14) e quatro inalações de OA 1% (dias 22, 24, 26 e 28). O grupo controle (S) foi tratado com salina 0,9 % seguindo o mesmo protocolo. Após 48h da última inalação, os camundongos foram anestesiados, a traquéia foi exposta longitudinalmente (1x4 mm) e o epitélio pode ser visualizado. A FBC foi mensurada pela técnica estroboscópica antes (basal) e logo após a administração inalatória das drogas (salbutamol e brometo de ipratrópio). A DP foi mensurada nos grupos S e OVA. Foram avaliados o lavado broncoalveolar e o remodelamento do epitélio da cavidade nasal, traquéia e vias aéreas distais. Nenhuma diferença foi encontrada na FBC basal entre os grupos (OVA e S), no entanto o grupo OVA mostrou uma DP basal significativamente menor. A inalação de salbutamol (3.5.10-3M ou 3.5.10-4M) elevou a FBC nos grupos estudados (p<0,05). O brometo de ipratrópio (10- 4M e 6.10-4M) não influenciou a FBC basal. Nossos resultados mostraram que é possível avaliar a FBC e a DP in vivo em um modelo murino de doença pulmonar alérgica crônica, e indicam que o processo inflamatório não afeta a FBC, mas contribui para o aumento de muco nas vias aéreas com conseqüências deletérias ao transporte mucociliar facilitando a retenção / The aim of the present work was to propitiate the in vivo assessment of the respiratory epithelium. The effects of salbutamol and ipratropium bromide on ciliary beat frequency (CBF) in a murine model of allergic airway disease were addressed. Transepithelial electric potential difference (PD) was also measured in order to verify the integrity of the epithelial barrier. Mice were sensitized with ovalbumin (OVA) by two intraperitoneal injections of allergen (days 0 and 14) and four inhalations of OVA 1% (days 22, 24, 26 and 28). The control group was treated with saline following the same procedures. After 48 hs of the last inhalation, mice were anesthetized, trachea was opened longitudinally (1 x 4 mm) and the ciliated epithelium could be visualized. CBF was measured by a modification on the videoscopic technique. We measured the CBF before and just after the administration of aerosolized substances. The PD was also measured on groups OVA and S. Additionally, the eosinophil cell count was measured on broncoalveolar lavage (BAL) in order to access the magnitude of airway inflammation. No difference on baseline CBF was noticed between groups (OVA and S), however the OVA group had a significantly lower PD. The administration of aerosolized capsaicin (3.10-9M) and salbutamol (3.5.10-3M or 3.5.10-4M) increased CBF in all groups studied. Ipratropium bromide (10-4M and 6.10- 4M) did not influence the CBF. The eosinophil cell count in broncoalveolar lavage was higher in OVA group compared to S group. CBF and PD results indicate that the inflammatory process does not affect the ciliary beat frequency but augments the amount of mucus in the airway, with deleterious consequences to the mucociliary transport facilitating mucus retention. Our results demonstrated for the first time the possibiliy of studying airway epithelium in an in vivo murine model of allergic airway disease

Antimicrobial peptides (AMPs) are small proteins produced by epithelial surfaces, which have broad-spectrum antimicrobial and immunomodulatory activities. In the lung, skin and alimentary tract AMPs are known to be important in infectious and inflammatory conditions. Far less is known regarding the role of AMPs within the female reproductive tract, but as infection and inflammation are causes of preterm labour, AMPs may have a key function in maintain and protecting pregnancy. The major groups of human AMPs include the human beta defensins (HBDs), two antileukoproteinases (secretory leukocyte protease inhibitor (SLPI) and Trappin-2/Elafin), and the human cathelicidin hCAP18/LL-37, with several studies identifying their presence at sites throughout the reproductive tract. The cervix in pregnancy is positioned between the upper genital tract containing the developing fetus and the lower tract where infections usually arise. I hypothesise that AMPs are fundamental to mucosal immune defence of the cervix in pregnancy, preventing ascending infection and excessive inflammation that can cause preterm labour. This thesis focused on the human cathelicidin hCAP18/LL-37 and its role within the cervix and vagina. The aims of this thesis were to; investigate the inflammatory effects of LL-37 from cervical and vaginal derived epithelial cells and determine the pathways and receptors in which LL-37 may elicit its effects and how production may be regulated; investigate the role of CRAMP in a mouse model of preterm birth; and determine the production of AMPs by the pregnant cervix whilst investigating the relationship between AMP concentrations in cervicovaginal secretions and preterm labour. The inflammatory effect of LL-37 was investigated using cell lines derived from endocervical, ectocervical and vaginal epithelium. The study of these cell lines suggests divergent responses of cervical and vaginal epithelial cells. LL-37 mediated induction of IL-8 and IL-6 production from endocervical epithelial cells was observed in a dose-dependent and time-dependent manner, whilst ectocervical and vaginal cells also respond to treatment with LL-37 through IL-8 and IL-6 production. To determine a possible mechanism of action of LL-37 on IL-8 and IL-6 in the three cell lines, inhibitors against MAPK cascades, ERK, p38 MAPK and JNK, and known LL-37 receptors were investigated. In endocervical cells LL-37 mediated IL-8 occurs via activation of unidentified GPCRs, whilst in ectocervical cells this effect on IL‐8 and IL-6 is via the activation of ERK and p38 MAPK cascades. The mechanism by which LL-37 induces IL-8 secretion in vaginal epithelial cells remains unknown. Expression of LL-37 was shown to be mediated by vitamin D3 in vitro in cervical and vaginal epithelial cells. However when this relationship was investigated in vivo, using matched serum and cervicovaginal secretions from woman at early pregnancy, no correlation was observed between circulating vitamin D and cervicovaginal or circulating hCAP18/LL-37. However, the majority of women in this study reported with insufficient levels of vitamin D, which may effect the relationship observed with hCAP18/LL-37. Using a mouse model of LPS-induced preterm labour, to mimic the presence of intrauterine infection bacterial infection, I aimed to characterise the role of CRAMP, the mouse orthologue of hCAP18/LL-37, in the lower inflammatory and immune response that results in preterm labour. Wild type C57Bl/6J mice receiving an intrauterine injection of LPS deliver prematurely, within 24 hours of injection. However mice deficient in CRAMP (Camp -/-) receiving an intrauterine injection of LPS deliver significantly later and have a non-significant increase in pup survival compared to wild type C57Bl/6J mice. Cervical tissue collected post partum showed no difference in inflammatory markers between wild type C57Bl/6J and Camp -/- mice, however there was increased expression of the neutrophil chemoattractant marker, Cxcl5, and the neutrophil marker, Ngp in Camp -/- mice. In the lower genital tract, levels of antimicrobial peptides were determined in samples of cervicovaginal secretions collected from pregnant women. AMPs, hCAP18/LL-37, HBD-2 and SLPI were found in cervicovaginal secretions, and levels of hCAP18/LL-37 were increased in women with the common vaginal infection bacterial vaginosis. However no relationship was identified between the concentration of AMPs and preterm birth in this study. This work has shown that the lower genital tract, where infections that are associated with preterm labour originate, expresses the human cathelicidin hCAP18/LL-37. It may play an important role in modulating the immune response to invading infection associated with preterm labour. Further investigation of these responses may increase understanding of the physiology and pathophysiology of labour, and lead to strategies for the prevention of premature delivery.

Les épithéliums jouent le rôle de barrière physique et chimique chez les Métazoires. Les épithéliums subissent des remodelages pendant l’embryogénèse. La morphogénèse des tissus est dirigée par des déformations cellulaires coordonnées fonctionnant grâce à des réseaux contractiles intracellulaires constitués d’actine et de myosine. Ce réseau d’actomyosine peut être soit pulsatile, soit stable. Un exemple est l’élongation de l’ectoderme ventro-latéral par intercalation cellulaire, le long de l’axe antéro-postérieur (AP) de l’embryon de la Drosophile. Les jonctions parallèles à l’axe dorso-ventral (DV) rétrécissent et forment de manière irréversible de nouvelles jonctions parallèles à l’axe AP. Des pulsations de myosine-II (Myo-II) médio-apicale se déplacent de manière anisotrope vers les jonctions parallèles à l’axe DV. Ceci provoque le rétrécissement graduel des jonctions, rétrécissement stabilisé par une population de Myo-II polarisée dans le plan du tissu et enrichie au niveau de ces jonctions. Les mécanismes cellulaires qui régulent la pulsatilité, la stabilité et la polarité de la Myo-II restent à élucider. Lors de ma thèse, j’ai identifié de nouveaux effecteurs régulant l’activation et la polarité planaire de la voie Rho1-Rok-Myo-II aux niveaux des jonctions. J'ai d'abord caractérisé le rôle de la kinase Misshapen dans l’activation polarisée de la voie Rho1 au niveau des jonctions. Misshapen agit en aval de la signalisation GPCR afin de favoriser l’activation de Rho1 et contrôle la polarisation de cette activation en transmettant l’information des récepteurs Toll. Puis j'ai identifié Pebble comme la RhoGEF régulant Rho1 et l'accumulation de Myo-II aux jonctions. / Epithelial build up strong mechanical and chemical barriers in Metazoans. Epithelia can be dramatically remodeled during embryogenesis. Tissue morphogenesis is driven by coordinated cellular deformations which are powered by intracellular contractile networks constituting actin and Myosin. Actomyosin networks can either be pulsatile or stable. One example is the elongation of the ventral-lateral ectoderm by cell intercalation, along antero-posterior (AP) axis of Drosophila embryo. Junctions parallel to the dorso-ventral (DV) axis shrink and form new junctions along AP axis. Medial apical Myosin-II (Myo-II) pulses flow anisotropically towards junctions aligned in DV axis, resulting in steps of junction shrinkage which are stabilized by a planar-polarized pool of Myo-II enriched at these junctions. Sequential deformation and stabilization drive irreversible tissue deformations akin to a ratchet. The cellular mechanisms that regulate Myo-II pulsatility, stability and polarity remained to be unfurled. During my PhD, I identified new regulators for Rho1-Rok-Myo-II pathway at junctions, and Myo-II planar polarity. On the one hand, I characterized the function of Misshapen kinase in polarized activation of Rho1 pathway at junctions. Misshapen acts downstream GPCR signaling to enhance Rho1 activation, and controls the polarization of this activation by transducing information from Toll receptors. Also, I identified Pebble as RhoGEF regulating Rho1 at junctions and Myo-II accumulation.

Made available in DSpace on 2017-07-10T14:17:08Z (GMT). No. of bitstreams: 1 Patricia Mata.pdf: 1374526 bytes, checksum: 67db6228e85d4c5c26a146b237710efc (MD5) Previous issue date: 2014-02-16 / The increase of fat tissue, in obesity, can be associated to physiological alterations, including important modifications in the concentration of circulating hormones, including the sexual steroid hormones. The epididymis, organ of the male genital system, is androgynous-dependent, therefore, susceptible to resulting modifications of sexual steroids hormones concentrations, which can compromise its main functions: transport, maturation, maintenance, protection and storage of the spermatozoids. The water transporting, in the epididymis, is essential to form the adequate luminal environment so the epididymal and spermatozoid related functions can happen; thus, alterations in aquaporins (AQPs), may intervene in the homeostasis of the duct and, consequently, negatively affect fertility. The accumulation of fat may increase the local temperature and alter the epididymal functions and, even, influence in the synthesis and secretion of cytokines such as the interleukin-6 (IL6), due to the chronicle inflammatory estate of low intensity as a consequence of obesity. The objective of this study was to evaluate the influence of the cafeteria diet over the morphology of the coating epithelium of the epididymal duct of rats and about the expression of IL6 and AQPs 1 and 9 in the mentioned epithelium. The analysis were made using tissue samples of the epididymis of Wistar rats of the groups control (CON, animals fed with the pattern diet) and cafeteria (CAF, animals fed with a cafeteria diet) treated throughout the experimental period of 24 weeks. The samples were submitted to a histological routine and immunohistochemical reactions for morphological, morphometric and the expression of IL6 and AQPs 1 and 9 analysis. The analysis evidenced a modification in the relative cellular distribution, with decrease of basal cells in the region of the epididymal body, and a significant increase of halo cells in the epididymal segments initial, head and tail of the CAF animals. The luminal diameter and the epithelial height didn t show significant differences between the animals. The intense expression of IL6 in the initial segment of the CAF animals was the outstanding result for this interleukin. The expression of AQP1 was altered in the CAF group animals, in general, with bigger expression in the vascular channels, mainly, the initial segment and the head; besides the bigger expression in the peritubular cells in the initial segment. The expression of AQP9 was altered only in the initial segment of the CAF group, which reactivity was average, while the reactivity was intense in this segment in the animals of the CON group. The results obtained indicate that the cafeteria diet promoted segment-specific alterations in the distribution of basal cell and halo and expression of IL6 and AQPs 1 and 9. These results allow us to deduce that the increase of body mass, induced by a cafeteria diet may promote alterations in the epididymal luminal environment with possible damage in the transport, maturation, maintenance, protection and storage of the spermatozoids. In order to enlighten the extension of the damage caused by the alterations resulting from the cafeteria diet, new studies such as epididymal biochemical alterations, ultrastructural analysis of the epididymal cell types and morphology and motility of the spermatozoids are necessary / O aumento de tecido adiposo, na obesidade, pode ser associado a alterações fisiológicas, incluindo modificações importantes nas concentrações circulantes de hormônios, inclusive dos hormônios esteroides sexuais. O epidídimo, órgão do sistema genital masculino, é andrógeno-dependente, portanto, susceptível a modificações resultantes das alterações nas concentrações de hormônios esteroides sexuais, as quais podem comprometer suas principais funções: transporte, maturação, manutenção, proteção e armazenamento dos espermatozoides. O transporte de água, no epidídimo, é essencial para formar o ambiente luminal adequado para que as funções epididimárias e relativas aos espermatozoides sejam realizadas; assim, alterações das, aquaporinas (AQPs), podem intervir na homeostase do ducto e, consequentemente, afetar negativamente a fertilidade. O acúmulo de gorduras pode aumentar a temperatura local e alterar as funções epididimárias e, ainda, influenciar na síntese e secreção de citocinas como a interleucina-6 (IL6), em razão do estado inflamatório crônico de baixa intensidade em consequência da obesidade. O objetivo este estudo foi avaliar a influência da dieta de cafeteria sobre a morfologia do epitélio de revestimento do ducto epididimário de ratos e sobre a expressão de IL6 e de AQPs 1 e 9 no referido epitélio. As análises foram realizadas utilizando amostras teciduais do epidídimo de ratos Wistar dos grupos controle (CON, animais alimentados com dieta padrão) e cafeteria (CAF, animais alimentados com dieta de cafeteria), tratados pelo período experimental de 24 semanas. As amostras foram submetidas à rotina histológica e reações imunohistoquímicas para análises morfológica, morfométrica e da expressão de IL6 e AQPs 1 e 9. As análises evidenciaram uma modificação na distribuição celular relativa, com diminuição de células basais na região de corpo epididimário, e aumento significativo de células halo no segmento inicial, cabeça e cauda epididimária dos animais CAF. O diâmetro luminal e altura epitelial não apresentaram diferenças significativas entre os grupos experimentais. Houve aumento na expressão de IL6 no segmento inicial do epidídimo dos animais CAF. A expressão de AQP1 foi alterada nos animais do grupo CAF, em geral, com maior expressão nos canais vasculares, principalmente, do segmento inicial e cabeça; além de maior expressão nas células peritubulares do segmento inicial. A expressão de AQP9 foi diminuída apenas no segmento inicial do grupo CAF, cuja reatividade foi média, enquanto a reatividade foi intensa neste segmento dos animais do grupo CON. Os resultados obtidos indicam que a dieta de cafeteria promoveu alterações segmento-específicas na distribuição de células basais e halo e na expressão de IL6 e de AQPs 1 e 9. Estes resultados permitem inferir que o aumento de massa corpórea, induzido por dieta de cafeteria, pode promover alterações no ambiente luminal epididimário com possível prejuízo das funções de transporte, maturação, manutenção, armazenamento e proteção dos espermatozoides. A fim de esclarecer a extensão do prejuízo causado pelas alterações resultantes da dieta de cafeteria, novos estudos tais como alterações bioquímicas epididimárias, análises ultraestruturais dos tipos celulares epididimários; capacidade reprodutiva e morfologia e motilidade dos espermatozoides são necessários

L'épithélium intestinal adulte des mammifères est un tissu hautement organisé entièrement renouvelé tous les 5 à 7 jours, grâce à la présence de cellules souches intestinales (CSI). Localisées à la base des cryptes, les CSI sont capables de s'auto-renouveler et de générer l'ensemble des types cellulaires de ce tissu. Afin de préserver l'équilibre entre leur auto-renouvellement et leur différenciation, véritable garant de l'homéostasie de l'épithélium intestinal, les CSI résident dans un microenvironnement finement régulé, « la niche », leur procurant l'ensemble des signaux nécessaires à leurs fonctions. La Nétrine-1, molécule sécrétée et apparentée à la famille des Laminines, est exprimée dans l'environnement des cryptes intestinales, mais également au cours du développement intestinal. Initialement découverte pour son rôle dans le guidage axonal, cette protéine est à ce jour considérée comme une molécule pléïotropique impliquée dans divers processus physiologiques tels que la morphogénèse, la migration, l'adhésion cellulaire, la prolifération mais également pathologiques comme la tumorigénèse. Considérant ces observations nous nous sommes donc intéressés au rôle potentiel de la Nétrine-1 dans la régulation du compartiment souche intestinal adulte, ainsi que lors de l'ontogénèse intestinale. Dans une première partie, nous montrons qu'ex vivo la Nétrine-1 promeut la croissance des entéroïdes et régule l'expression génique de certains marqueurs spécifiques des CSI. Dans une seconde partie, nous montrons, grâce à la génération et caractérisation de nouveaux modèles murins, que la Nétrine-1 est impliquée dans le développement de l'épithélium intestinal grêle et que sa délétion conduit à un retard d'émergence des villi / The adult intestinal epithelium is a highly organized tissue, which is completely self-renewed every 5 to 7 days, due to a pool of multipotent intestinal stem cells (ISC). Located at the base of intestinal crypts, ISC have the ability to self- renew and to give rise to all epithelial intestinal cell types. To preserve the balance between their self-renewal and their differentiation, and therefore to maintain the epithelial tissue homeostasis, ISC reside in a tightly regulated microenvironment - called “niche”- that provides them all factors required for their functions. Netrin-1, a laminin-related secreted protein, is expressed in the microenvironment of the crypt, and is also expressed during intestinal development. Initially described as an axonal guidance cue, Netrin-1 is now considered as a pleiotropic molecule involved in many different processes such as morphogenesis, cell migration, cell adhesion, proliferation and also tumorigenesis. Based on these observations, we hypothesized that Netrin-1 could play a role in the maintenance of the adult intestinal stem cell compartment, and also in the intestinal ontogenesis. In a first part, we showed that Netrin-1 promotes the growth of enteroids ex vivo while regulating gene expression of specific intestinal stem cell markers. In the second part, we demonstrated, by using two novel genetically engineered mouse models, that Netrin-1 is involved in the embryonic development of the intestinal epithelium and that its deletion leads to a delay in villi emergence

By performing microRNA microarrays to globally detect any novel miRNAs in the limbus, eleven microRNAs (hsa-miR-136, hsa-miR-373*, hsa-miR-150, hsa-miR-143, hsa-miR-455, hsa-miR-145, hsa-miR-381, hsa-miR-224, hsa-miR-338, hsa-miR-154, hsa-miR-377) were found to be upregulated while two microRNAs (hsa-miR-122a and hsa-miR-425-3p) were identified as downregulated by more than 2 folds. Among these, hsa-miR-143 and hsa-miR-145 were distingushed to be the most significantly up-regulated limbal miRNAs. Individual assessement of the microarray results of a recently reported stem cell specific microRNA, hsa-miR-21, were also upregulated by more than two thousand fold when comparing limbus and cornea. miR-21, miR-143 and miR-145 were therefore selected as the most likely microRNA candidates in the present study. The expression level of these miRNA candidates were validated and confirmed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). To localize these candidates, we performed in situ hybridization on frozen corneal rim sections using locked nucleic acid (LNA)-modified oligonucleotide probes. Results showed that miR-2I, 143 and 145 were confined in the limbal region with gradation of expression level along the basal-suprabasal line. / Functional roles of these microRNAs were then deciphered by overexpressing human corneal epithelial cell line (HCE) with precursor microRNAs (pre-miRs) through lipophilic transfection. Results showed that high endogenous level of miR-145 could inhibit cell proliferation by 3.5 fold as shown from MTT proliferation assay at day 5, and could generate discrete spherical colonies that resembles the morphology of holoclones at day 8, but not the other two candidate miRNAs. / In conclusion, 1 have identified three novel microRNAs (hsa-miR-21, 143, 145) which were precisely upregulated in the limbus region, while miR-145 was being the most limbal specific. In addition, the functions of miR-145 were found to be inhibitory on cell proliferation, possibly through the indirect regulation of IFNB1. These unprecedented results may suggest a therapeutic potential of miR-145 on limbal stem cell deficiency and limbal tumors because miR-145 can affect cell survival and proliferation. / MicroRNAs is a family of small non-coding RNAs that, in human, binds imperfectly to the 3' untranslated region (UTR) of target mRNAs for translational repression or negative regulation. Recent studies have shown that such negative regulatory pathways may play pivotal roles in the maintenance of asymmetric cell division in embryonic and tissue specific stem cells. Human corneal epithelial progenitor cells (CEPC), a tissue specific stem cell lineage residing between cornea and conjunctiva in the Palisade of Vogt of the limbus region, is known to maintain corneal homeostasis throughout human life. They respond to injury and normal wearing by rapid proliferation and differentiation into transit amplifying cells (TACs) and eventually corneal epithelial cells, though the biological factors controlling this homeostatic switch are still largely unknown. Here I hypothesized that microRNAs can participate in CEPC regulation. Experiments elucidating the anatomical distribution and functional roles of microRNAs on the human cornea rims were performed to testify this proposition. / Protocols aim at enriching the CEPC population were then devised. For the first time a four parameter cell sorting system utilizing ABCG2, Connexin 43, Notch 1 and pyronin Y as markers was established for the prospective in vitro study. Nevertheless, manual microdissection isolating the limbus region and the cornea region was employed for the present study of microRNAs. / This study begins with the phenotypic validation of human cornea rims recruited from the Chinese Hong Kong population using immunohistochemistry. Conventional CEPC markers (p63, EGFR, cytochrome oxidase and cytokeratin 15), embryonic stem cell marker (stat1) and cancer stem cell markers (p73, MDM2 and pStat1) were expressed in the limbus region, suggesting that these specimens contained a source of CEPC for attesting our hypothesis. / To determine the mRNA targets of candidate microRNAs in HCE cells, Whole Human Genome Oligo Microarray Kits (Agilent Technologies) which contained 41K human genes and transcripts were employed. When compared to the scrambled control, HCE cells over-expressed with hsa-miR-21, 143 or 145 revealed differential expression of genes that participate in cell activation, motility and proliferation. Of note, interferon beta 1 fibroblast (IFNB1), a gene that is often deleted or rearranged in cancers, was significantly upregulated by a medium of 1093 fold in pre-miR-145 treated cells as confirmed by real time PCR assays. / Lee, Sharon Ka-wai. / "December 2009." / Advisers: Calvin Chi-Pui Pang; Gary Hin Fai Yam. / Source: Dissertation Abstracts International, Volume: 72-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 216-252). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Neuronal differentiation encompasses an elaborate developmental program which until recently was difficult to study in vitro. The advent of several cell lines able to differentiate in culture proved to be the turning point for gaining an understanding of molecular neuroscience. In particular the olfactory epithelium provides an attractive tool with which to investigate fundamental questions relating to neuronal differentiation, as it displays a unique capacity to regenerate and to retain a neurogenetic potential from its genesis and throughout adult life. The coordinated regulation of gene expression is fundamental to the control of neuronal differentiation. In order to reveal active processes at the molecular level and to dissect key components of molecular pathways, differential gene expression studies provide a foundation for the elucidation of dynamic molecular mechanisms. This thesis identified genes involved in neuronal differentiation by utilising a clonal olfactory receptor neuronal cell line (OLF442). Gene expression levels were identified using differential display and oligonucleotide array technology before and after serum deprivation. Differential display revealed two kinases whose expression levels were elevated during the differentiation of OLF442, identified as focal adhesion kinase (FAK) related non-kinase (FRNK) and mammalian ste20 like (MST)2 kinase. Furthermore, analysis of the oligonucleotide array data confirmed the expression of genes involved in altering presentation of extracellular matrix molecules, in mediating cytoskeletal rearrangements, and in ceasing the cell cycle, supporting the use of OLF442 as a model for studying differentiation. The differentiation of OLF442 results from the synchronisation of multiple transduction cascades and cellular responses as evidenced by the microarray data. A protein that can synchronise such signalling is the non-receptor protein tyrosine kinase, FAK. Thus the finding of the endogenous FAK inhibitor FRNK by differential display was intriguing as there was no difference in the expression level of FAK induced by differentiation, contrasting that of FRNK. This induced FRNK expression was derived autonomously as it was not responsive to the caspase-3 inhibitor, DEVD-CHO. This is particularly pertinent since the primary role of FRNK is to act as an inhibitor of FAK by competing with its substrates and reducing the phosphorylation of both FAK and its associated proteins. Differential display also revealed the upregulation of another kinase, which had 90% homology with rat MST2 kinase within the 3' UTR. Both mouse MST2 kinase (sequence submitted to GenBank, accession number AY058922) and the closely related family member MST1 kinase were sequenced and cloned. Moreover, evidence to support an autonomously expressed carboxyl-terminal domain of MST2 kinase is presented in Chapter 3 and provides a unique way in which MST2 may regulate its own activity. To further understand the role of MST in neuronal differentiation, a series of stable OLF442 transfections (with mutant and wild-type MST constructs) were carried out. MST was localised with cytoplasmic structures that may represent actin stress fibres, indicating a potential cytoskeletal role during neuronal differentiation. This indicated that MST1 may play a role in the morphological processes involved in neuronal differentiation. The identification of two kinases by differential display provided the motivation to understand the cellular context of OLF442 and to determine the phosphorylation status of the mitogen-activated protein kinase (MAPK) signalling cascades. Differentiation of OLF442 induced high-level phosphorylation of a putative B-Raf isoform, MEK2 and ERK1/2. Interestingly, there was a switch between preferential phosphorylation of MEK1 in undifferentiated OLF442 to preferential phosphorylation of MEK2 following differentiation. SAPK/JNK was also phosphorylated, as was the transcription factor c-Jun, which is a common substrate of both the ERK and SAPK/JNK signalling modules. The mapping of the cellular context of differentiating OLF442 has identified a promising model of a novel MAPK module. This consists of FAK signalling through Rap1 to ERK providing sustained activation, which is buffered or terminated by the expression of the endogenous FAK inhibitor FRNK. Furthermore, MST kinase could potentially play a role in regulating the cytoskeletal re-arrangements that are necessary for neuronal differentiation. MST kinase may signal transiently via the SAPK pathway to provide concomitant activation of c-Jun that is required for neuronal differentiation. An understanding of the gene expression pattern of the normal neuronal differentiation program allows a greater understanding of potential developmental aberrations. This could provide an opportunity for therapies to be conceived, while understanding the complexity of neuronal determination could also provide opportunities for stem cell transplantation.

<p>S-nitrosogluthatione is an endogenous substance, present at decreased levels in the lungs of CF patients and was recently found to induce mature CFTR in airway epithelial CF cell lines. We show that S-nitrosoglutathione in physiological concentrations increases the presence of ΔF508 CFTR in the cell membrane and induces cAMP dependent chloride transport in cystic fibrosis airway epithelial cells. The properties of S-nitrosoglutathione include other potential benefits for the CF patient and make this agent an interesting candidate for pharmacological treatment of CF that needs to be further evaluated.</p><p>Genistein was found to increase the chloride efflux in both normal and ΔF508 cells without stimulation of cAMP elevating agents and without prior treatment with phenylbutyrate. Genistein, in concentrations close to those that can be detected in plasma after a high soy diet, could induce chloride efflux in cells with the ΔF508 CFTR mutation and its possible use in the treatment of CF should therefore be further investigated.</p><p>Studies on nasal epithelial cells from CF patients showed cAMP dependent chloride efflux in some of the patients with severe genotypes. This may complicate <i>in vitro</i> evaluation of clinical treatment of these patients. The presence of cAMP dependent chloride transport did not necessarily lead to a milder phenotype. Other factors than CFTR may influence the clinical development of the disease.</p><p>Cystic fibrosis (CF) is the most common monogenetic disease among Caucasians. A defective cAMP regulated chloride channel (cystic fibrosis transmembrane conductance regulator, CFTR) in epithelial cells leads to viscous mucus, bacterial infections, inflammation and tissue damage in the lungs that cause death in 95% of the cystic fibrosis patients. There is no cure for the disease although existing treatment has dramatically prolonged the life expectancy. The aim of this thesis was to study pharmacological agents for their ability to restore the cellular deficiency in CF airway epithelial cells. X-ray microanalysis, MQAE fluorescence and immunocytochemistry were used to evaluate the effects.</p>