Spinal cord injury is a serious trauma and despite intensive research there is still no effective treatment for patients. The aim of this thesis is to study new possibilities of spinal cord injury therapy in animal models. We have focused on the use of natural materials, stem cells, gene therapy and the possibility of combining these approaches. The effect of extracellular matrix (ECM) based materials prepared by decellularization of porcine spinal cord and porcine urinary bladder on tissue regeneration after acute hemisection of the spinal cord was investigated. Another tested material was a hydrogel based on hyaluronic acid modified with RGD adhesion peptide, which was applied acutely and subacutely into the hemisection lesion. We have shown that both types of biomaterials have positive effect on regeneration of the spinal cord tissue by bridging the lesion and promotion of axonal ingrowth. In addition, ECM hydrogels promote the growth of blood vessels into the lesion site. The combination of hydrogels with mesenchymal stem cells derived from human umbilical cord (hWJ-MSCs) had synergistic effect, but since only a limited number of cells could be incorporated into hydrogels, this effect was not associated with improvement in motor skills. The limitation of ECM hydrogels is their rapid...

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No description available.

Articular cartilage is an avascular and flexible connective tissue found in joints. It produces a cushioning effect at the joints and provides low friction to protect the ends of the bones from wear and tear/damage. It has poor repair capacity and any injury can result pain and loss of mobility. One of the common forms of articular cartilage disease which has a huge impact on patient's life is arthritis. Research on cartilage cell/tissue engineering will help patients to improve their physical activity by replacing or treating the diseased/damaged cartilage tissue. Cartilage cell, called chondrocyte is embedded in the matrix (Lacunae) and has round shape in vivo. The in vitro monolayer culture of primary chondrocyte causes morphological change characterized as dedifferentiation. Transforming growth factor-beta (TGF-β), a cytokine superfamily, regulates cell function, including differentiation and proliferation. The effect of TGF-β1, 2, 3, and their manipulated forms in biological regulation of primary chondrocyte was investigated in this work. A novel method was developed to isolate and purify the primary chondrocytes from knee joint of neonate Sprague-Dawley rat, and the effect of some supplementations such as hyaluronic acid and antibiotics were also investigated to provide the most appropriate condition for in vitro culture of chondrocyte cells. Addition of 0.1mg/ml hyaluronic acid in chondrocyte culture media resulted an increase in primary chondrocyte proliferation and helped the cells to maintain chondrocytic morphology. TGF-β1, 2 and 3 caused chondrocytes to obtain fibroblastic phenotype, alongside an increase in apoptosis. The healing process of the wound closure assay of chondrocyte monolayers were slowed down by all three isoforms of TGF-β. All three types of TGF-β negatively affected the strength of chondrocyte adhesion. TGF-β1, 2 and 3 up regulated the expression of collagen type-II, but decreased synthesis of collagen type-I, Chondroitin sulfate glycoprotein, and laminin. They did not show any significant change in production of S-100 protein and fibronectin. TGF-β2, and 3 did not change expression of integrin-β1 (CD29), but TGF-β1 decreased the secretion of this adhesion protein. Manipulated TGF-β showed huge impact on formation of fibroblast like morphology of chondrocytes with chondrocytic phenotype. These isoforms also decreased the expression of laminin, chondroitin sulfate glycoprotein, and collagen type-I, but they increased production of collagen type-II and did not induce synthesis of fibronectin and S-100 protein. In addition, the strength of cell adhesion on solid surface was reduced by manipulated TGF-β. Only manipulated form of TGF-β1 and 2 could increase the proliferation rate. Manipulation of TGF-β did not up regulate the expression of integrin-β1 in planar culture system. The implications of this R&D work are that the manipulation of TGF-β by combination of TGF-β1, 2, and 3 can be utilized in production of superficial zone of cartilage and perichondrium. The collagen, fibronectin and hyaluronic acid could be recruited for the fabrication of a biodegradable scaffold that promotes chondrocyte growth for autologous chondrocyte implantation or for formation of cartilage.

L'objectif principal de ce travail était de comparer l'implication (i) de cellules vasculaires, cellules musculaires lisses vasculaires (CML) et cellules endothéliales (CE), ou des cellules circulantes, les plaquettes, et (ii) des microparticules (MP) issues de ces différentes cellules dans la génération de la thrombine mais également dans son inhibition par les systèmes anticoagulants de la protéine C activée (PCa) et de l'inhibiteur de la voie du facteur tissulaire (TFPI), et d'identifier les mécanismes et les déterminants responsables des différences observées entre ces supports cellulaires pour la coagulation. Nous avons démontré que l'intégrine [alpha]v[gamma]3 qui est le récepteur pour la prothrombine sur les surfaces vasculaires était impliquée dans la génération de thrombine à la surface des CML soumises ou non à des déformations mécaniques cycliques. A l'état de base, les CML et les CE ont un potentiel thrombinique similaire, mais moins important que celui des plaquettes. Nous avons montré un rôle synergique du TFPI avec la PCa dans l'inhibition de la génération de thrombine à la surface de ces cellules plus importante avec les CML qu'avec les CE. L'ensemble de nos résultats suggère que les CML pourraient exercer des effets procoagulants comparables aux CE mais avec des régulations différentes en réponse aux facteurs pro- et anticoagulants, et que les MP issues de cellules vasculaires ont un pouvoir thrombogène très supérieur à leurs cellules d'origine / The main objective of this study was to compare the implication (i) of vascular cells, smooth muscle cells (SMC) and endothelial cells (EC), or circulating cells, platelets, and (ii) microparticles (MP) derived from these different cells in the generation of thrombin but also in its inhibition by the activated protein C (APC) and the tissue factor pathway inhibitor (TFPI), and to identify the mechanisms and determinants responsibles for observed differences between these different cell supports for coagulation. We have demonstrated that [alpha]v[gamma]3 integrin, the prothrombin receptor on the vascular surfaces, was involved in the generation of thrombin on the surface of these cells subjected or not subjected to cyclic mechanical deformations. At baseline, SMC and EC, have equivalent thrombin generating capacities, but less than that of platelets. We have shown a synergistic role of TFPI with APC in the inhibition of thrombin generation at the surface of these cells, more important with SMC than with EC. Taken together, our results suggest that SMC may exert procoagulant effects comparable to EC but with different regulations in response to pro-and anticoagulant factors, and that MP derived from vascular cells have a very higher thrombogenic activity compared to their parent cells

A predisposição de recém-nascidos às doenças infecciosas é atribuída, em parte, a falta da memória imunológica pré-existente. Em recém-nascidos pré-termo, é presumido que o sistema imune seja menos desenvolvido ao nascimento, mas pouco se sabe sobre o tamanho e as características das subpopulações de linfócitos. Células T reguladoras (Treg) possuem papel crucial no controle do desenvolvimento de um sistema imune saudável incluindo a manutenção da autotolerância e, sua ausência, é responsável pela gama de manifestações inflamatórias e autoimunes observadas em pacientes com IPEX (Immunodeficiency, Poliendocrinopathy and Enteropathy X-linked Syndrome). Essas células são fenotipicamente caracterizadas pela presença do fator de transcrição Foxp3 (forkhead box P3) e pela alta expressão da cadeia ? do receptor de IL-2 (CD25), já que esta citocina é essencial para a geração, manutenção e funcionamento das células Treg. Pouco se sabe sobre a frequência destas células em recém-nascidos, particularmente em recém-nascidos muito prematuros ou moderados e recém-nascidos prematuros tardios, estudados como grupos separados. Resultados preliminares do nosso grupo revelaram uma maior capacidade dos recém-nascidos de produzir resposta pró-inflamatória em comparação aos adultos, a qual foi ainda mais acentuada pela diminuição da produção de IL-10, o que sugere uma função reguladora reduzida. Diante disso, o objetivo deste trabalho foi caracterizar fenotipicamente e quantificar a população de células Treg, por meio de citometria de fluxo, em sangue de cordão umbilical de 15 recém-nascidos pré-termo nascidos entre 30-336/7 semanas de gestação (Grupo 1), 19 recém-nascidos pré-termo nascidos entre 34-366/7 semanas de gestação (Grupo 2) e 20 recém-nascidos a termo nascidos entre 37-41 semanas de gestação (Grupo 3), todos clinicamente saudáveis e com peso adequado para a idade gestacional, em comparação com 26 adultos saudáveis. Os resultados demonstraram que existe uma correlação inversa entre a frequência de Treg e a idade gestacional, com frequências significativamente maiores de células Treg CD4+CD25hiCD127loFoxp3+ no Grupo 1 quando comparado aos Grupos 2 e 3 e no Grupo 2 comparado ao Grupo 3, assim como frequências e números de Treg mais elevados em todos os recém-nascidos comparados aos adultos. Todos os recém-nascidos exibiram maior frequência de células Treg com fenótipo naïve comparados aos adultos. A expressão de CTLA-4 nas células Treg naïve foi reduzida nos dois grupos de pré-termo comparados aos grupos de recém-nascidos a termo e adultos, assim como nas células Treg de memória do Grupo 1 comparado aos demais grupos. As frequências de Tregs alfa4beta7+ e alfa4beta1+ foram maiores em ambos os grupos de pré-termo, mas significativamente diferentes somente no Grupo 1, quando comparado aos recém-nascidos a termo e adultos. Em conclusão, foram observadas altas frequências de células Treg em recém-nascidos pré-termo e a termo, e essas frequências mostraram correlação inversa com a idade gestacional. Essas células exibiram um perfil naïve quando comparadas às dos adultos, com alta expressão de CD45RA e alfa4beta7+ e menor expressão de CTLA-4, sugerindo uma menor função, particularmente em recém-nascidos muito prematuros / The predisposition of newborn infants to infectious diseases is attributed, in part, to the lack of pre-existing immunological memory. In preterm newborns, it is assumed that the immune system is less developed at birth, but little is known about the size and characteristics of lymphocyte subpopulations. Regulatory T cells (Tregs) have a crucial role in controlling the development of a healthy immune system including the maintenance of self-tolerance and, their absence, is responsible for the range of inflammatory and autoimmune manifestations observed in patients with IPEX (Immunodysregulation Polyendocrinopathy Enteropathy X-linked Syndrome). These cells are phenotypically characterized by the presence of the transcription factor Foxp3 (forkhead box P3) and by the high expression of the ? chain of the IL-2 receptor (CD25), as this cytokine is essential for the generation, maintenance and function of Treg cells. Little is known about the frequency of these cells in neonates, particularly in very and moderate preterm newborns and late preterm newborns studied as separate groups. Preliminary results from our group revealed greater ability of newborns to produce proinflammatory response compared to adults, which was further accentuated by the decreased production of IL-10, which suggests a reduced regulatory function. Thus, the aim of this study was to phenotypically characterize and quantify the population of Treg cells, by flow cytometry, in the cord blood of 15 preterm newborns born at 30-336/7 gestation weeks (Group 1), 19 preterm newborns born at 34-366/7 gestation weeks (Group 2) and 20 term newborns born at 37-41 gestation weeks (Group 3), all clinically healthy and adequate-for-gestational-age, compared to 26 healthy adults. The results demonstrated that there is an inverse correlation of the Treg frequency and gestational age, with significantly higher frequencies of CD4+CD25hiCD127loFoxp3+ Treg cells in Group 1 compared to Groups 2 and 3 and in Group 2 compared to Group 3, as well as significantly higher Treg frequencies and numbers in all the neonates compared to the adults. All of the newborns exhibited increased Treg frequencies with a naive phenotype compared to the adults. CTLA-4 expression in the naive Tregs was decreased in both preterm groups compared with those from term newborns and adults, as well as in the memory Treg cells from Group 1 compared with the other groups. The frequencies of alfa4beta7+ and alfa4beta1+ Tregs were higher in both preterm groups, but significantly different only in Group 1, when compared with those from the term newborns and the adults. In conclusion, high frequencies of Tregs were observed in term and preterm newborns, and these frequencies showed an inverse correlation with gestational age. These cells exhibited a naive profile when compared with adults, with high expression of CD45RA and alfa4beta7+ and lower expression of CTLA-4, implying a decreased function, particularly in very preterm newborns

Les voies d’endocytose qui régissent l’internalisation d’éléments extracellulaires peuvent être classées selon que la protéine de manteau, la clathrine, est impliquée ou non dans le processus. Les voies indépendantes de la clathrine sont utilisées par de nombreuses toxines, des virus et des protéines endogènes. Les mécanismes permettant d’induire le recrutement des protéines cargoes et la déformation de la membrane plasmique dans le contexte de l'endocytose clathrine-indépendant restent encore mal compris. Cette étude montre que la galectine 3, une protéine humaine qui se lie aux glucides, induit la formation d’invaginations de la membrane plasmique de manière indépendante de la clathrine. Les glycosphingolipides (molécules jouant un rôle majeur dans la physiologie de la cellule) sont essentielles pour permettre à la galectine 3 d’induire ces invaginations et d’être internalisée dans la cellule. Les structures tubulaires induites par la galectine 3 présentent une morphologie étonnamment similaire à celle de compartiments intermédiaires de transport décrits dans la littérature pour l’endocytose indépendante de la clathrine. Des cargos utilisant la voie indépendante de la clathrine, tels que CD44 et les intégrines α5 et β1, sont retrouvés dans les tubules induits par la galectine 3. De plus, cette dernière est nécessaire à l’internalisation de CD44. Cela indique donc que la galectine 3 pourrait relier des protéines cargos glycosylés à des glycosphyngolipides de la membrane plasmique et ainsi induire une déformation de la membrane et leur internalisation dans les cellules. Ce mécanisme diffère de celui utilisé par la toxine pentamérique de Shiga et par la toxine cholérique, qui sont leur protéines cargos propores et interagissant directement avec le glycosphyngolipide leur servant de récepteur. Les tubules induits par la galectine 3 sont distincts de ceux induit par les autres lectines. Celles-ci présentent des spécificités différentes de liaison aux glucides, montrant ainsi la l'importance des interactions entre les lectines et les sucres dans ce processus. De plus, nous avons constaté que la galectine 3 module l’équilibre à l’état basal de l’intégrine β1 à la surface de la cellule. Cette protéine étant capitale pour les phénomènes d’adhésion et de migration cellulaires, nous avons donc exploré le rôle conjoint de la galectine 3 et des glycosphingolipides dans la migration cellulaire. La galectine 3 inhibe la migration des cellules humaines de carcinomes mammaires alors qu’elle stimule au contraire celle de cellules de tumeurs mammaires murines. Or, nous avons montré que la régulation par la galactine 3 de la migration de différentes lignées cellulaires est dépendante des glycosphingolipides. Il ressort donc de cette étude que la galectine 3 et les glycosphingolipides contribuent de manière synergique au processus d’induction de déformation de la membrane, à l’endocytose de protéines cargos et à la migration cellulaire. / Endocytic processes which govern the uptake of extracellular material into the cell can be classified based on their dependence on the coat protein, clathrin. Clathrin-independent mechanisms are used by many toxins, viruses and endogenous proteins. How cargo is recruited and membranes are bent is not well understood in these cases. Here, we discovered that galectin 3, a human carbohydrate binding protein induced the clathrin-independent formation of endocytic plasma membrane invaginations. Glycosphingolipids, which have established functions in key physiological processes, were found to be essential for the formation of galectin 3-induced invaginations and for the efficient uptake of the protein into the cell. Galectin 3-induced tubular structures were found to have a strikingly similar morphology to that of the clathrin-independent carriers described in literature. Clathrin-independent endocytic cargoes such as CD44, α5 and β1 integrin were present in galectin 3-induced tubules, and galectin activity and glycosphingolipids were required for the uptake of CD44. This indicated that galectin 3 could link glycosylated cargoes with glycosphingolipids for cargo recruitment and membrane bending. In contrast, the pentameric Shiga and cholera toxins are their own cargoes and drive membrane deformations by directly binding to their respective glycosphingolipid receptors. Galectin 3-induced tubules were distinct from those induced by lectins with different carbohydrate binding specificities, which revealed the importance of lectin-glycan interaction in this process. Further, we observed that galectin 3 modulated the steady state surface dynamics of β1 integrin, a protein which like CD44 is critical for cell adhesion and migration. Subsequently, we explored the interplay of galectins and glycosphingolipids in cell migration. Galectin 3 inhibited cell migration in human breast carcinoma cells, and stimulated migration in a mouse mammary tumor cell line. However, the regulation of migration by galectin 3 was in both cases found to be dependent on glycosphingolipids. In conclusion, galectin 3 and glycosphingolipids synergistically contribute to the clathrin-independent curvature generation process, cargo endocytosis and cell migration.

L’objectif ici était de développer une méthode de détection des tumeurs cérébrales via des agents de contraste pour l’IRM du 19F à 7 teslas. Nous évaluons en particulier le potentiel de cette méthode à mettre en évidence l’angiogenèse tumorale à l’aide d’agents de contraste fonctionnalisés avec le peptide RGD et ciblant l’intégrine ανβ3, biomarqueur surexprimé à la surface des néo-vaisseaux irriguant la tumeur. Du fait des basses concentrations locales en agent de contraste, les efforts portent dans un premier temps sur l’optimisation d’une séquence multi échos de spin dédiée à l’imagerie du PFOB (perfluorooctyl bromure), perfluorocarbure biocompatible choisi pour constituer la base de nos agents de contraste. Nous montrons qu’un paramétrage minutieux de cette séquence permet la suppression de la J-modulation et un rehaussement du T2, conduisant à une excellente sensibilité in vitro. La séquence est ensuite testée pour des mesures d’oxygénation dans le foie et la rate chez la souris, après injection d’une émulsion de PFOB. Les résultats indiquent une très bonne précision des mesures après injection d’une seule dose d’émulsion. Notre séquence est également utilisée pour réaliser une étude de biodistribution dynamique, permettant de suivre l’accumulation des nanoparticules d’émulsion dans le foie et la rate juste après injection. Nous montrons par ailleurs qu’il est possible d’évaluer la furtivité d’émulsions contenant différentes quantités de PEG (Poly Ethylène Glycol) en ajustant les données expérimentales sur un modèle pharmacocinétique empirique. La séquence est enfin utilisée pour détecter des nanoparticules d’émulsions fonctionnalisées pour cibler l’intégrine ανβ3 dans un modèle souris U87 de glioblastome. Nous comparons les concentrations en agent de contraste obtenues dans la tumeur avec une émulsion contenant le peptide RGD, et une émulsion contrôle. Les résultats indiquent des concentrations significativement plus élevées avec l’émulsion RGD qu’avec l’émulsion contrôle, supposant un ciblage spécifique d’ανβ3 par les nanoparticules fonctionnalisées. Un dernier chapitre est dédié à une nouvelle méthode de spectroscopie de diffusion en 19F, dont le but est d’éliminer le signal vasculaire provenant des nanoparticules de PFOB circulantes afin d’évaluer le signal ne provenant que des particules liées. / This study aimed at developing a method for detection of brain tumors at 7 teslas thanks to 19F MRI contrast agents. We particularly assessed the potential of this method to highlight tumor angiogenesis with RGD-functionalized contrast agents targeting ανβ3 integrin, a biomarker over-expressed at the surface of new capillary blood vessels. Owing to low local concentrations in contrast agent, the first step consisted in optimizing a multi spin echo sequence dedicated to a well-known biocompatible perfluorocarbon, perfluorooctylbromide (PFOB). We show that careful adjustment of sequence parameters allows cancellation of J-modulation and T2 enhancement, and yields an excellent sensitivity in vitro. Our sequence was then tested for oxygenation measurements in the mouse liver and spleen after injection of a PFOB emulsion. The results demonstrate very good accuracy of the measurements after one single infusion of emulsion. We also perform a dynamic biodistribution study in order to monitor emulsion nanoparticle uptake in the liver and spleen. Moreover, we show that stealth of emulsions grafted with different quantities of polyethylene glycol (PEG) can be assessed by fitting experimental data with a pharmacokinetic empirical model. Our sequence was finally used to visualize ανβ3-targeted nanoparticles in a U87 glioblastoma mouse model. Concentrations found in tumors after injection of an RGD-functionalized emulsion and a control emulsion are compared. Concentrations are found to be significantly higher with the RGD emulsion than with the control emulsion, suggesting specific binding of functionalized nanoparticles with ανβ3 integrin. The last part is dedicated to a new diffusion-weighted 19F NMR spectroscopy sequence. This method aims at suppressing vascular signal coming from circulating PFOB nanoparticles in order to evaluate signal coming from bound nanoparticles only.

A predisposição de recém-nascidos às doenças infecciosas é atribuída, em parte, a falta da memória imunológica pré-existente. Em recém-nascidos pré-termo, é presumido que o sistema imune seja menos desenvolvido ao nascimento, mas pouco se sabe sobre o tamanho e as características das subpopulações de linfócitos. Células T reguladoras (Treg) possuem papel crucial no controle do desenvolvimento de um sistema imune saudável incluindo a manutenção da autotolerância e, sua ausência, é responsável pela gama de manifestações inflamatórias e autoimunes observadas em pacientes com IPEX (Immunodeficiency, Poliendocrinopathy and Enteropathy X-linked Syndrome). Essas células são fenotipicamente caracterizadas pela presença do fator de transcrição Foxp3 (forkhead box P3) e pela alta expressão da cadeia ? do receptor de IL-2 (CD25), já que esta citocina é essencial para a geração, manutenção e funcionamento das células Treg. Pouco se sabe sobre a frequência destas células em recém-nascidos, particularmente em recém-nascidos muito prematuros ou moderados e recém-nascidos prematuros tardios, estudados como grupos separados. Resultados preliminares do nosso grupo revelaram uma maior capacidade dos recém-nascidos de produzir resposta pró-inflamatória em comparação aos adultos, a qual foi ainda mais acentuada pela diminuição da produção de IL-10, o que sugere uma função reguladora reduzida. Diante disso, o objetivo deste trabalho foi caracterizar fenotipicamente e quantificar a população de células Treg, por meio de citometria de fluxo, em sangue de cordão umbilical de 15 recém-nascidos pré-termo nascidos entre 30-336/7 semanas de gestação (Grupo 1), 19 recém-nascidos pré-termo nascidos entre 34-366/7 semanas de gestação (Grupo 2) e 20 recém-nascidos a termo nascidos entre 37-41 semanas de gestação (Grupo 3), todos clinicamente saudáveis e com peso adequado para a idade gestacional, em comparação com 26 adultos saudáveis. Os resultados demonstraram que existe uma correlação inversa entre a frequência de Treg e a idade gestacional, com frequências significativamente maiores de células Treg CD4+CD25hiCD127loFoxp3+ no Grupo 1 quando comparado aos Grupos 2 e 3 e no Grupo 2 comparado ao Grupo 3, assim como frequências e números de Treg mais elevados em todos os recém-nascidos comparados aos adultos. Todos os recém-nascidos exibiram maior frequência de células Treg com fenótipo naïve comparados aos adultos. A expressão de CTLA-4 nas células Treg naïve foi reduzida nos dois grupos de pré-termo comparados aos grupos de recém-nascidos a termo e adultos, assim como nas células Treg de memória do Grupo 1 comparado aos demais grupos. As frequências de Tregs alfa4beta7+ e alfa4beta1+ foram maiores em ambos os grupos de pré-termo, mas significativamente diferentes somente no Grupo 1, quando comparado aos recém-nascidos a termo e adultos. Em conclusão, foram observadas altas frequências de células Treg em recém-nascidos pré-termo e a termo, e essas frequências mostraram correlação inversa com a idade gestacional. Essas células exibiram um perfil naïve quando comparadas às dos adultos, com alta expressão de CD45RA e alfa4beta7+ e menor expressão de CTLA-4, sugerindo uma menor função, particularmente em recém-nascidos muito prematuros / The predisposition of newborn infants to infectious diseases is attributed, in part, to the lack of pre-existing immunological memory. In preterm newborns, it is assumed that the immune system is less developed at birth, but little is known about the size and characteristics of lymphocyte subpopulations. Regulatory T cells (Tregs) have a crucial role in controlling the development of a healthy immune system including the maintenance of self-tolerance and, their absence, is responsible for the range of inflammatory and autoimmune manifestations observed in patients with IPEX (Immunodysregulation Polyendocrinopathy Enteropathy X-linked Syndrome). These cells are phenotypically characterized by the presence of the transcription factor Foxp3 (forkhead box P3) and by the high expression of the ? chain of the IL-2 receptor (CD25), as this cytokine is essential for the generation, maintenance and function of Treg cells. Little is known about the frequency of these cells in neonates, particularly in very and moderate preterm newborns and late preterm newborns studied as separate groups. Preliminary results from our group revealed greater ability of newborns to produce proinflammatory response compared to adults, which was further accentuated by the decreased production of IL-10, which suggests a reduced regulatory function. Thus, the aim of this study was to phenotypically characterize and quantify the population of Treg cells, by flow cytometry, in the cord blood of 15 preterm newborns born at 30-336/7 gestation weeks (Group 1), 19 preterm newborns born at 34-366/7 gestation weeks (Group 2) and 20 term newborns born at 37-41 gestation weeks (Group 3), all clinically healthy and adequate-for-gestational-age, compared to 26 healthy adults. The results demonstrated that there is an inverse correlation of the Treg frequency and gestational age, with significantly higher frequencies of CD4+CD25hiCD127loFoxp3+ Treg cells in Group 1 compared to Groups 2 and 3 and in Group 2 compared to Group 3, as well as significantly higher Treg frequencies and numbers in all the neonates compared to the adults. All of the newborns exhibited increased Treg frequencies with a naive phenotype compared to the adults. CTLA-4 expression in the naive Tregs was decreased in both preterm groups compared with those from term newborns and adults, as well as in the memory Treg cells from Group 1 compared with the other groups. The frequencies of alfa4beta7+ and alfa4beta1+ Tregs were higher in both preterm groups, but significantly different only in Group 1, when compared with those from the term newborns and the adults. In conclusion, high frequencies of Tregs were observed in term and preterm newborns, and these frequencies showed an inverse correlation with gestational age. These cells exhibited a naive profile when compared with adults, with high expression of CD45RA and alfa4beta7+ and lower expression of CTLA-4, implying a decreased function, particularly in very preterm newborns

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood, with two predominant histologic subtypes: embryonal and alveolar. These histologies display distinct clinical courses, and despite refinements in dose and duration of multimodality therapy, the 5-year overall survival of patients diagnosed with metastatic RMS remains <30%. Thus, there is an urgent need to define novel targets for therapeutic intervention. Interrogation of cancer cell signal transduction pathways that regulate the pathogenic behaviours of tumor cells has been successful in defining targets in numerous tumor types. These have ultimately yielded clinically-relevant drugs that have improved the disease-free and overall survival of patients diagnosed with cancer. Work contained in this thesis describes the interrogation of several potential targets for inhibition in RMS. Interruption of RMS cell proliferation, survival and apoptosis is examined through disruption of the protein kinase integrin-linked kinase (ILK) and the nuclear receptor estrogen-receptor β. ILK, in particular, is demonstrated to have dual competing functions through the regulation of c-jun amino-terminal kinase (JNK) signaling: an oncogene in alveolar, and a tumor suppressor in embryonal RMS. These findings are recapitulated in other tumor cell lines, indicating that expression levels of JNK1 correlate with ILK function in a broad spectrum of tumor types. Furthermore, interruption of rhabdomyosarcoma cell migration as a surrogate marker of metastasis is examined through disruption of the stromal-cell derived factor 1α/chemokine (CXC)receptor 4 signaling network, as well as through cooperative interactions between ILK and the mammalian target of rapamycin. Finally, we demonstrate that the insulin-like growth factor pathway is a potential target for therapeutic inhibition, which also distinguishes tumors of embryonal and alveolar histology. These studies provide a rationale for the development of novel agents, as well as the use of established drugs targeting these pathways in rhabdomyosarcoma.