L'insuffisance rénale chronique (IRC) demeure un problème de santé publique du fait de l'augmentation de sa prévalence. Malgré l'amélioration de la prise en charge, le taux de mortalité reste plus élevé comparé à la population générale. Parmi les causes de décès, les maladies cardiovasculaires, d'origine multifactorielle (élargissement et hypertrophie des artères, athérosclérose, calcifications vasculaires et valvulaires) sont au premier plan. A côté des facteurs de risque classiques, des facteurs non traditionnels, liés aux perturbations métaboliques de l'IRC, ont été mis en évidence, comme l'inflammation, la malnutrition, le stress oxydant, les anomalies du métabolisme minéralo-osseux. La meilleure connaissance de la physiopathologie de la vasculopathie de l'IRC permet d'émerger de nouveaux biomarqueurs pour stratifier le risque cardiovasculaire chez l'IRC.OBJECTIFS-METHODOLOGIE GENERALE : Nous avons réalisé une approche biochimique pour explorer trois composantes du risque cardiovasculaire chez l'IRC : stress oxydant, perturbations qualitatives des HDL (high-density lipoprotein) et métabolisme minéralo-osseux.RESULTATS : Dans une première publication la production d'anion superoxyde a été évaluée, via une méthode de chemoluminescence, en fonction du stade de l'IRC. Alors que la surproduction de formes réactives de l'oxygène est bien connue au stade 5d et peut être liée à la procédure dialytique, il existe peu de données aux stades précoces. Notre étude a porté sur 136 patients IRC non dialysés des stades 1à 5. Les résultats montrent que la production de FRO est assurée aux stades 4 et 5. Un bas débit de filtration glomérulaire (MDRD<30ml/min/1.73m2), l'inflammation (fibrinogène >3.7g/l) et des taux anormaux d' HDL (<1.42mM et >1.75mM) apparaissent comme les principaux déterminants du stress oxydant chez l'IRC non dialysé.Alors que dans la population générale, un taux bas de HDL est reconnu comme un facteur de risque important, nous avons montré (publication 1) que des taux anormaux de HDL, bas comme hauts, étaient indépendamment associés au stress oxydant chez les sujets IRC. Dans une deuxième publication, nous avons précisé la composition des HDL en se basant sur d'éventuelles modifications qualitatives des protéines associées à la structure des lipoprotéines. Une étude protéomique a été réalisée chez 7 patients hémodialysés versus 7 sujets sains. Nous avons retrouvé 40 protéines exprimées différemment sur les 122 identifiées, dont l'apoCII, l'apoCIII qui sont significativement augmentées et la transferrine abaissée. Ces protéines interviennent dans de nombreuses fonctions comme la réponse inflammatoire, l'activation du complément, la régulation de l'oxydation des lipoprotéines, l'homéostasie des cations.Dans une troisième publication, l'épuration du FGF23, phosphatonine impliquée dans les anomalies du métabolisme minéralo-osseux, été étudiée chez l'hémodialysé chronique en fonction de la techniques de dialyse (hémodialyse (HD) high flux versus hémodiafiltration on line (OL-HDF)). Notre étude a porté sur 53 patients dans le groupe HD et 32 patients dans le groupe OL-HDF. Dans les deux groupes le taux de FGF23 en post-dialyse est significativement plus bas qu'en pré-dialyse. Cependant, le taux de réduction, la clairance et le KT/V du FGF23 sont significativement plus bas dans le groupe OL-HDF.CONCLUSION-PERSPECTIVES : Chez l'IRC, avec l'appariation de facteurs de risque non traditionnels, de nouveaux biomarqueurs ont émergés dans la stratification du risque cardio-vasculaire. Ces biomarqueurs peuvent devenir des bioacteurs et représenter de nouvelles cibles d'action et de prévention de l'atteinte cardio-vasculaire chez l'IRC. La complexité des mécanismes physiopathologiques impliqués, nous incite à proposer des approches multimarqueurs. Actuellement des études biocliniques se poursuivent en mettant en place des cohortes régionales de patients aux stades 1 à 5 et de patients incidents en dialyse. / BACKGROUND: Chronic kidney disease (CKD) is a public health problem because of its increasing prevalence. Despite care improvements, the mortality rate remains higher compared to general population. Among causes of death, cardiovascular diseases with multifactorial origins (enlargement and hypertrophy of arteries, atherosclerosis, vascular and valvular calcifications) are in the foreground. Besides the traditional risk factors, non-traditional factors associated with metabolic disorders in CKD were bring out, such as inflammation, malnutrition, oxidative stress, mineral and bone disorder. A better knowledge of vasculopathy physiopathology in CKD allows the emergence of new biomarkers to stratify cardiovascular risk in CKD.AIMS-METHODOLOGY: We performed a biochemical approach to explore three components of cardiovascular risk in CKD: oxidative stress, qualitative alterations of HDL (high-density lipoprotein) and mineral and bone disorder.RESULTS: In a first publication, the superoxide anion production, according to the stage of CKD, was assessed using a chemiluminescence method. While the overproduction of reactive oxygen species is well known at the 5d stage of CKD and may be related to the dialysis procedure, there are few data in the early stages. Our study included 136 non-dialysis patients at stages 1 to 5 of CKD. Results showed an enhanced superoxide production at the pre-dialysis phase, stages 4 and 5 of CKD. Reduced glomerular filtration rate (MDRD <30 ml / min / 1.73m2), inflammation (fibrinogène≥3.7g / l) and abnormal levels of HDL (<1.42mM and ≥1.75mM) appears as main determinants of oxidative stress in non-dialysis CKD patients.While in general population, a low HDL rate is recognized as an important risk factor, we showed (publication 1) that abnormal levels of HDL, low as high, were independently associated with oxidative stress in CKD subjects. In a second publication, we have defined the HDL composition based on qualitative changes in the structure of proteins associated with lipoproteins. A proteomic study was performed in 7 patients on hemodialysis versus 7 healthy subjects. We found 40 proteins differently expressed on the 122 identified, including apoCII, apoCIII which are significantly increased and transferrin lowered. These proteins are involved in many functions such as inflammatory response, complement activation, regulation of lipoprotein oxidation and homeostasis cations. In a third publication, the removal of FGF23, phosphatonin involved in mineral and bone metabolism, was studied in chronic hemodialysis according to the dialysis techniques (high flux hemodialysis (HD) versus on line hemodiafiltration (OL- HDF)). Our study included 53 patients in the HD group and 32 patients in the OL-HDF group. In both groups the rate of FGF23 in post-dialysis was significantly lower than in pre-dialysis. However, rate of reduction, clearance and KT / V of FGF23 were significantly lower in the OL-HDF group.CONCLUSION-PROSPECTS: In the IRC, with the appearance of non traditional risk-factors, new biomarkers have emerged in the stratification of cardiovascular risk. These biomarkers can become bioactors and represent novel targets of action and prevention in the cardiovascular disease in CKD. The complexity of the involved physiopatholological mechanisms, leads us to propose multimarkers approaches. Currently bioclinical studies continue with the constitution of regional cohorts of patients at stages 1 to 5 of CKD and incident dialysis.

<p>Formation of blood vessels occurs through two processes: vasculogenesis and angiogenesis, which are regulated by various growth factors such as vascular endothelial growth factor, fibroblast growth factor and platelet-derived growth factor. The present study was carried out in order to investigate the roles of the Shb and Cbl proteins in growth factor-mediated signal transduction and blood vessel formation. Shb was found to be involved in NGF-stimulated Rap1 signaling in PC12 cells by forming a complex with CrkII and a 130-135 kDa protein. The Rap1 signaling pathway contributed to NGF-dependent neurite outgrowth. In immortomouse brain endothelial (IBE) cells, Shb increased cell spreading, migration and cytoskeletal rearrangements. Such effects may partly be due to altered Rap1 activation in Shb overexpressing IBE cells. Shb was required for tubular morphogenesis in collagen gels in the presence of FGF-2. In embryoid bodies (EBs) derived from murine embryonic stem cells, Shb up-regulated both VEGFR2 and Tal1 expression at early stages of EB development and thus promoted blood vessel formation both in the absence and in the presence of growth factors. In IBE cells, Cbl positively regulated FGF-2 signaling and increased cell proliferation. Mutation of RING finger alone did not affect blood vessel formation in EBs. However, EBs overexpressing the oncogenic form Cbl 70Z, which had a deletion of the linker region and the first cysteine of the RING finger, exhibited intense CD31 positive sheet-like staining and blood vessel. The results suggested that Cbl had dual roles in endothelial cells: it promoted FGF-2-induced proliferation whereas down-regulated proliferation of endothelial progenitor cells.</p><p>The present work suggests that Shb and Cbl play a crucial role in cell differentiation and blood vessel formation.</p>

Formation of blood vessels occurs through two processes: vasculogenesis and angiogenesis, which are regulated by various growth factors such as vascular endothelial growth factor, fibroblast growth factor and platelet-derived growth factor. The present study was carried out in order to investigate the roles of the Shb and Cbl proteins in growth factor-mediated signal transduction and blood vessel formation. Shb was found to be involved in NGF-stimulated Rap1 signaling in PC12 cells by forming a complex with CrkII and a 130-135 kDa protein. The Rap1 signaling pathway contributed to NGF-dependent neurite outgrowth. In immortomouse brain endothelial (IBE) cells, Shb increased cell spreading, migration and cytoskeletal rearrangements. Such effects may partly be due to altered Rap1 activation in Shb overexpressing IBE cells. Shb was required for tubular morphogenesis in collagen gels in the presence of FGF-2. In embryoid bodies (EBs) derived from murine embryonic stem cells, Shb up-regulated both VEGFR2 and Tal1 expression at early stages of EB development and thus promoted blood vessel formation both in the absence and in the presence of growth factors. In IBE cells, Cbl positively regulated FGF-2 signaling and increased cell proliferation. Mutation of RING finger alone did not affect blood vessel formation in EBs. However, EBs overexpressing the oncogenic form Cbl 70Z, which had a deletion of the linker region and the first cysteine of the RING finger, exhibited intense CD31 positive sheet-like staining and blood vessel. The results suggested that Cbl had dual roles in endothelial cells: it promoted FGF-2-induced proliferation whereas down-regulated proliferation of endothelial progenitor cells. The present work suggests that Shb and Cbl play a crucial role in cell differentiation and blood vessel formation.

The telencephalon is the most highly evolved region of the vertebrate central nervous system (CNS). The major structures of the telencephalon - the cortex and basal ganglia – derive from the dorsally positioned pallium and the ventrally positioned subpallium, respectively. Differences in morphology, gene expression, and connectivity permit a subdivision of the developing telencephalon into domains that give rise to discrete regions of the adult brain. In mammals, the ventral region of the developing telencephalon can be subdivided into the medial (MGE) and lateral (LGE) ganglionic eminences. The dorsal midline cells give rise to the choroid plexus, and cells in the more lateral domain, the dorsal pallium, give rise to the cerebral cortex. Genetic studies have provided evidence that crossregulatory interactions between transcription factors contribute to the regionalization of the telencephalon. Less is known, however, about the secreted signals that induce the initial dorsoventral character of telencephalic cells. Sonic hedgehog (SHH) is required for the specification of ventral character along the entire anteroposterior (AP) extent of the developing CNS, including the telencephalon. We show that WNT activity imposes an early generic dorsal telencephalic character and that Fibroblast Growth Factor (FGF) act sequentially, and in concert with WNT, to specify cells of definitive dorsal telencephalic character. We also show that retinoic acid (RA)-mediated signaling induces intermediate character in telencephalic cells, and that FGFs maintain cells of ventral character by opposing RA activity. The following model emerges from these findings. At gastrula stages, most or all prospective telencephalic cells become specified as ventral cells in response to node-derived SHH signals. At neural fold- and early neural plate stages, cells in the prospective dorsal and intermediate regions of the telencephalon cells are exposed to WNT signaling that induce a generic dorsal character. The head ectoderm adjacent to the telencephalon then starts to express the retinoic acid producing enzyme, Raldh3, thus exposing telencephalic cells to RA signals. At the same time prospective dorsal cells start to express WNT signals. RA signaling appears to promote the generation of intermediate/prestriatal cells, whereas WNT signal suppress the actions of RA on dorsal cells, which therefore maintain their dorsal character. From the neural plate stage, prospective ventral 6 telencephalic cells are exposed to FGF8 derived from the anterior neural ridge, and FGF8 maintains ventral telencephalic character by opposing the influence of RA signals in ventral cells. At early neural tube stages, the domain of Fgf8 expression expands dorsally and FGF signals derived from the dorsal midline region induce definitive dorsal/precortical cells. In the intermediate region of the telencephalon cells evade high levels of WNT and FGF signals, resulting in an environment in which RA signaling is able to induce prestriatal character.

Genesis of life begins with the fusion of female and male haploid gametes through a process of fertilization leading to the formation of a diploid cell, the zygote. This undergoes successive cleavage divisions forming 2-, 4- and 8- cell embryos and their individual cells (blastomeres) are totipotent. As development proceeds, there is a gradual restriction in their totipotency, resulting in the generation of two distinct cell lineages i.e., the differentiated trophectoderm (TE) cells and the undifferentiated, inner cell mass (ICM) during blastocyst morphogenesis (Rossant and Tam 2009). During the course of development, the ICM cells can give rise to all cell types of an organism and can also provide embryonic stem (ES)-cells when cultured in vitro (Evan and Kaufman 1981). ES-cells are pluripotent cells, having the ability to self-renew indefinitely and differentiate into all the three primary germ layers (ectoderm, mesoderm and endoderm) derived-cell types. ES-cells are an excellent developmental model system to understand basic mechanisms of self-renewal, cell differentiation and function of various genes in vitro and in vivo (Capecchi 2001). Importantly, their cell derivatives could potentially be used for experimental cell-based therapy for a number of diseases. Although, human ES-cell lines have been successfully derived and differentiated to various cell types (Thomson et al., 1998; Odorico et al., 2001), their cell-therapeutic potential is far from being tested, in view of the lack of our understanding of lineage-specific differentiation, homing and structural-functional integration of differentiated cell types in the host environment. To understand these mechanisms, it is desirable to have fluorescently-marked ES-cells and their differentiated cell-types, which could facilitate experimental cell transplantation studies. In this regard, our laboratory has earlier generated enhanced green fluorescent protein (EGFP)-expressing FVB/N transgenic ‘green’ mouse, under the control of ubiquitous chicken -actin promoter (Devgan et al., 2003). This transgenic mouse has been an excellent source of intrinsically green fluorescent cell types. We have been attempting to derive ES-cell line from this transgenic mouse. Because the derivation of ES-cell line is genetic strain-dependent, with some strains being relatively permissible for ES-cell derivation while others are quite resistant (non permissive), it has been extremely difficult to derive ES-cell line from the FVB/N mouse strain. There is a need to evolve experimental strategies to derive ES-cell line from FVB/N mouse, a strain extensively used for transgenesis. Thus, the aims of the study described in the thesis are to: (1) develop an experimental system to derive EGFP-expressing fluorescently-marked ES-cell line from a non-permissive FVB/N mouse strain; (2) characterize the established ES-cell line; (3) achieve differentiation of various cell types from EGFP-expressing ES-cell line and (4) understand role of FGF signaling in cardiac differentiation from the established ES-cell line. In order to have an appropriate and relevant literature background, the 1st chapter in this thesis describes a comprehensive up-to-date review of literature, pertaining to the early mammalian development and differentiation of blastocyst, followed by origin and properties of ES-cells. Various ES-cell derivation strategies from genetically permissive and non-permissive mouse strains are described and also the ES-cell differentiation potential to various progenitors and differentiated cell types. Subsequently, details on molecular basis of cardiac differentiation and the therapeutic potential of ES-cell derived differentiated cell types to treat disease(s) are described. This chapter is followed by three data chapters (II-IV). Chapter-II describes the issues related to non-permissiveness of FVB/N strain for ES-cell derivation and strategies to overcome this hurdle. This is followed by detailed results pertaining to generation of homozygous EGFP-expressing transgenic mice and development of a two-pronged ES-cell derivation approach to successfully establish a permanent ES-cell line (named ‘GS-2’ ES-cell line) from the EGFP-transgenic ‘green’ mouse. This chapter also provides results pertaining to detailed characterization of the ‘GS-2’ ES-cell line which includes colony morphology, expansion efficiency, alkaline phosphatase staining, expression analysis of pluripotent markers by RT-PCR and immunostaining approaches and karyotyping. Following this, the outcome of results and significance in the context of reported information are discussed in detail. Having successfully derived the ‘GS-2’ ES-cell line, it is necessary to thoroughly assess the differentiation competence of the ‘GS-2’ ES-cell line. Therefore, the Chapter-III describes detailed assessment of the in vitro and in vivo differentiation potential of the ‘GS-2’ ES-cell line. For in vitro differentiation, results pertaining to ES-cell derived embryoid body (EB) formation and their differentiation to ectodermal, mesodermal and endodermal cell types, expressing nestin, BMP-4 and α-fetoprotein, respectively, are described. Besides, the robustness of adaptability of ‘GS-2’ ES-cells to various culture conditions for their maintenance and differentiation are described. Also shown in the chapter is the relatively greater propensity of this cell line to cardiac differentiation. For in vivo differentiation, the ‘GS-2’ ES-cell derived teratoma formation in nude mice and its detailed histological analysis showing three germ layer cell types and their derivatives are described. Last part of the data described in this chapter, pertains to generation of chimeric blastocysts by aggregation method. Because the ‘GS-2’ ES-cell line exhibited a robust differentiation potential, including an efficient cardiomyocyte differentiation, it is of interest to enhance the efficiency of cardiomyocyte differentiation by exogenous addition of one of the key growth factors i.e., FGF8b since this has been implicated to be critical for cardiogenesis in non-mammalian verterbrate species. Therefore, Chapter-IV is focused on assessing the ability of ‘GS-2’ ES-cell line for its cardiomyocyte differentiation property with particular emphasis on the FGF-induced cardiac differentiation. Results pertaining to the expressions of various FGF ligands and their receptors during differentiation of ES-cells are described. Besides, increases in the cardiac efficiency, following FGF8b treatment and the associated up-regulation of cardiac-specific markers such as GATA-4, ISL-1 and α-MHC are shown. At the end of data chapters, separate sections are devoted for ‘Summary and Conclusion’ and for ‘Bibliography’.

Ce travail a été mené afin d'étudier l'effet du FGF 2 et du TGF-β1 sur les étapes précoces de la régénération dentinaire en utilisant la micro-encapsulation de ces facteurs dans une matrice pour les protéger et contrôler leur libération et ensuite l'application des microparticules obtenues en coiffage pulpaire direct dans un modèle de culture de dents entières. Ce travail consiste d'abord à l'optimisation des moyens techniques mis en oeuvre pour réaliser l'encapsulation du TGFβ1, FGF-2 à l'aide de l'acide poly (lactique-glycolique) PLGA. Les études de la caractérisation colloïdal et physico chimique des microparticules montre que les microparticules gardent leurs caractéristiques physicochimiques après séchage et resuspension dans l'eau. La procèdes optimisé a été ensuite utilisé pour encapsuler les facteurs de croissance. L'encapsulation de FGF-2 et TGF-β1 a été obtenue avec une taille, une efficacité d'encapsulation et une profile de libération adaptés au type d'application choisi. Les études biologiques ne montrent aucun effet toxique des particules sur les fibroblastes pulpaires. Les facteurs de croissance ont gardé leur activité biologique spécifique. Un modèle de culture de dent entier humain a été utilisé pour réaliser l'application de nos microparticules comme un matériau de coiffage dentaire pour confirmer leurs activités biologiques ex-vivo. Ces microparticules peuvent être utiles dans les études des étapes précoces de la régénération dentinaire, l'activation et la migration des cellules progénitrices de la pulpe dentaire

Myofibroblast expansion is a critical event in the pathogenesis of liver fibrosis. The activation of hepatic stellate cells (HSC) to myofibroblast (MFB) results in the enhanced production of extracellular matrix (ECM). We have studied the effect of fibroblast growth factor 1 (FGF-1) on liver MFB. In the second part we investigated effect of transforming growth factor β1 (TGF-β1) and FGF-1 on cell line HSC-T6. Cells were cultured on plastic dishes and in 3D collagen gel mimicking fibrotic tissue. MFB were isolated by repeated passaging of nonparenchymal liver cell fraction. The transfer of MFB from plastic dishes to collagen gel resulted in the change in their shape and phenotype. The expression of cytokine TGF-β1 and of MFB markers, α-smooth muscle actin (α-SMA) and cellular fibronectin (EDA-FN) on protein level was significantly decreased in collagen gel. The experiments with SB 431542, the inhibitor of TGF-β receptor type I, showed that EDA-FN and α-SMA are differently regulated. EDA-FN expression is dependent on TGF-β1, while the expression of α-SMA is primarily determined by the environment and modified by TGF-β1. EDA-FN is more sensitive to the U0126, the inhibitor of protein kinases MEK 1 and 2. Collagen gel does not change the expression of metalloproteinase MMP-2 but activates the proenzyme....

Na busca por agonistas, antagonistas e inibidores de natureza peptídica do fator de crescimento de fibroblastos ácido humano (hFGF-1), iniciamos o presente trabalho fazendo uma análise conformacional teórica do peptídeo Ac- WFVGLKKNGSSKRGPRT-NH2 (107-123 [hFGF-1]). Em trabalho anterior, este composto havia se mostrado um agonista da atividade mitogênica da proteína capaz de inibir a ligação de 125I-hFGF-1 aos seus receptores celulares e de se ligar à resina heparina-Sepharose (Oyama et al. 1996). Os cálculos das propriedades dinâmicas deste peptídeo (I; Tabela 1) demonstraram que ele não adotava nenhuma conformação preferencial, o que poderia justificar a baixa atividade apresentada pelo mesmo (104 vêzes menor do que a da proteína nativa). Este peptídeo foi ressintetizado, purificado, caracterizado química e biologicamente, confirmando os resultados anteriores. Seu comportamento randômico foi comprovado experimentalmente através de uma análise estrutural parcial por 1H-RMN. O resultado desta análise demonstrou que este peptídeo exibe uma configuração random coil, em solução aquosa (Kiyota et al., 1996, 1999). Diante desta constatação e com base em dados descritos na literatura (Harper & Lobb 1988; Burgess et al., 1991; Pantoliano et al., 1994, Springer et al., 1994; Thompson et al., 1994; Imamura et al., 1995; Blaber et al., 1996; Ornitz et al., 1996; Zhu et al.,1991, 1995, 1997; Schwizer, 1995; Sieber & Moe, 1996; Rizo et al., 1996); desenhamos dezessete peptídeos relacionados ao Sítio 2 (97-132) do hFGF-1 mostrados na Tabela 1 (ver arquivo PDF). Todos os peptídeos foram sintetizados manualmente por síntese em fase sólida, sempre que possível purificados à homogeneidade por RP-HPLC e caracterizados quimicamente por RP-HPLC, análise de aminoácidos e espectrometria de massas. Os peptídeos cíclicos foram obtidos por: a) oxidação das sulfidrilas das cisteínas e formação de ponte dissulfeto intramolecular; b) reação entre os grupos amina e carboxila de cadeias laterais de dois diferentes resíduos de aminoácidos com formação de uma ligação lactama. Os testes de atividade mitogênica foram realizados sempre que os peptídeos eram obtidos com pureza &#8805;90% determinada por RP-HPLC analítica em dois sistemas diferentes de solventes. Os resultados obtidos em culturas de fibroblastos de camundongos Balb/c 3T3 mostraram que: 1) II, III, VI-IX e XIII eram inativos; 2) o cíclico IV era mitogênico (ED50 ~50 &#181;M) ao contrário do seu análogo linear correspondente (III); 3) V, um análogo de IV que apresenta deleção de um resíduo (Asn), exibia uma atividade mitogênica menor do que a de IV; 4) X exibia uma atividade mitogênica menor do que a do I; 5) os cíclicos XII e XV exibiam atividades comparáveis a do I, enquanto que os seus análogos lineares correspondentes (XI e XIV) eram inativos; 6) XVI e XVII exibiam atividades mitogênicas também comparáveis à de I. Paralelamente a estes estudos, foi desenvolvido um modelo teórico dos domínios extracelulares DII e DIII do FGFR-1&#946;. A partir do posicionamento gráfico das moléculas de hFGF-1 e de um hexassacarídeo de heparina junto a este modelo do receptor, foram desenhados os peptídeos Ac-170NTTDKENEVLH180-NH2 (XVIII) e Ac-194SLAGNSIGLSH204-NH2 (XIX) (Oyama et al., 1997). Estes dois peptídeos cujas seqüências primárias são, respectivamente, relacionadas àquelas dos loops DE e FG do domínio DIII, foram também sintetizados e testados neste trabalho como possíveis ligantes do sítio 2 do hFGF-1.Os testes biológicos demonstraram que o peptídeo XIX, na faixa de concentração testada, não exibia nenhuma atividade inibitória sobre as atividades mitogênicas dos FGFs -1 e -2. Por outro lado, notou-se um claro efeito inibitório de XVIII sobre a atividade mitogênica de ambas as proteínas, sendo este efeito mais significativo para o FGF-2 (Kiyota et al., 1998). Alguns dos peptídeos estudados foram submetidos a análises espectroscópicas com o objetivo de determinar suas conformações em solução. Este conhecimento forneceria subsídios para o desenho de novos peptídeos mitogênicos e, mais ainda, para determinação dos requisitos estruturais destes peptídeos e, como reflexo, do hFGF1 para expressão de suas atividades mitogênicas. Assim, foi feita uma análise parcial do peptídeo mitogênico IV e de seu análogo linear III inativo em solução aquosa empregando fluorescência e 1HRMN ( (Kiyota et al., 1998). Estes peptídeos foram analisados também por técnicas de CD e 1H-NMR (Kiyota et al., 1999). Os resultados obtidos mostraram que III e IV parece se organizarem de forma semelhante em suas porções N-terminais, em estruturas correspondentes a &#946;-turns. Por outro lado, as conformações das porções C-terminais destes peptídeos diferiram; somente em IV, observouse a presença de uma família de confôrmeros com estruturas helicoidais nessa porção do esqueleto e que eram superponíveis. O mesmo não foi observado na porção C-terminal de III. A análise conformacional do peptídeo XVIII em solução foi também realizada empregando-se CD e 1H-RMN. Os resultados obtidos indicaram que este peptídeo tem forte tendência em assumir uma estrutura helicoidal em solução aquosa contendo 50% CD3OH. O conjunto dos resultados obtidos neste trabalho nos permitem concluir que: 1) a presença de W107 e F108 é, de fato, essencial para a expressão da atividade mitogênica de peptídeos derivados do sítio 2 do hFGF-1; 2) a presença de N106 adjacente ao core hidrofóbico constituído pelos resíduos W107F108 é importante; 3) a ciclização do peptídeo IV foi decisiva para a expressão de sua atividade, indicando que, não apenas a presença, mas o posicionamento adequado das cadeias laterais de N106, W107 e F108 são determinantes; 4) apenas uma das lisinas (K112 ou K113) é essencial para a atividade mitogênica (X, XVI e XVII); 5) o importante parece ser a manutenção do posicionamento das cadeias laterais em relação aos dos outros resíduos contidos na seqüência, uma vez que, a substituição do segmento 112KKNGS116 por uma prolina e/ou deleção de 120GPRT123 (XI e XIV) abolem a atividade mitogênica do peptídeo; 6) a ciclização que mantem a distância e as orientações relativas entre WF e KR (considerados essenciais para a atividade) em seqüência (XII e XV), leva à recuperação da atividade; 7) a atividade inibitória específica para o FGF-2 exibida pelo peptídeo XVIII parece ser um indicativo de que a alça DE do domínio DIII do receptor pode estar envolvido na ligação a esta proteína. Estas conclusões são relevantes e essenciais para: 1) o entendimento dos requisitos estruturais para a atividade mitogênica dos peptídeos estudados e, como reflexo, do hFGF-1, 2) o desenho de novos agonistas, antagonistas ou inibidores do sistema FGF. / In our search for small potent agonists or inhibitors related to hFGF-1(97-132), we first investigated the preferred conformation in solution of Ac -WFVGLKKNGSSKRGPRT-NH2 (I), by 1H-NMR. This compound has been described as a weak agonist of the mitogenic activity of this growth factor able to inhibit the binding of 125I-hFGF-1 to their cellular receptors, and to heparin-Sepharose columns (Oyama et al., 1996). We found that this peptide is in a random coil configuration, which could explain its low activity (104 times less potent than the native protein). On the basis on these results and on several data available in the literature (Harper & Lobb 1988; Burgess et al., 1991; Pantoliano et al., 1994, Springer et al., 1994; Thompson et al., 1994; Imamura et al., 1995; Ornitz et al., 1996; Blaber et al., 1996; Zhu et al., 1991, 1995; 1997; Schwizer, 1995; Sieber & Moe, 1996; Rizo et al., 1996), we designed seventeen peptides related to the Site 2 (97-132)[hFGF-1] listed on the Table 1: some were linear and some were cyclic. They were synthesized manually using the solid phase method, purified by RP-HPLC, and chemically characterized by RP-HPLC, amino acid analysis and mass spectrometry. Conformational constraints of certain peptides were achieved by cyclization. Intramolecular dissulfide bonds were formed by the oxidation of the thiol groups of two cysteins residues with air oxigen and/or K2Fe(CN)6. Lactama bonds were formed between the functional side chain group of acidic and basic residue. The synthetic peptides were tested in of their ability to inducing mitogenic response on Balb/c 3T3, A-31 clone fibroblasts cultures. The results obtained were the following: 1) peptides II, III, VI-IX were essentially inactive on Balb/c 3T3 fibroblasts in the range of concentrations used (up to 200 &#181;M), 2) in the same range of concentration, peptide IV showed an ED50 60&#181;M (similar to that found for peptide I) while its correspondent linear analog (III) was inactive; 3) V, analog of IV, that has Asn deleted, exibihited mitogenic activity lower than IV; 4) X showed a mitogenic activity on Balb/c fibroblasts lower than I, 5) cyclic peptides XII and XV showed mitogenic activities similar to that of I, while their correspondent linear (XI and XIV) and cyclic (XIII) analogs were inactive; 6) XVI and XVII showed mitogenic activities similar to that found for I. In parallel, two peptides [Ac-170NTTDKENEVLH180-NH2 (XVIII) and Ac-194SLAGNSIGLSH204-NH2 (XIX)], derived from DIII FGFR-1&#946; and designed as putative ligands of Site2 hFGF-1, were synthesized and tested. In the range of concentration used (up to 200 &#181;M), XIX was inactive and exhibited no inhibitory effect on FGF-1 and FGF-2 mitogenic activities. Nevertheless, XVIII inhibited the mitogenic activity of both proteins, being this effect clearly more significant for the FGF-2 (Kiyota et al., 1998). Some of synthetic peptides have been spectroscopically analyzed in order to disclose the structural features that characterize the active (Kiyota et al., 1999). A detailed analysis was undertaken with peptides III and IV using circular dichroism (CD) and 1H-NMR. Although the similarities in their primary sequences, III has shown inactive when tested on Balb/c 3T3 fibroblasts culture while IV was mitogenic with ED50 values around 50 &#181;M. I was also not capable of inhibiting the binding of hFGF-1 to its cellular receptors, I was inactive while II inhibits it with ID50 values of about 30 &#181;M. Circular dichroism study showed that while at increasing SDS concentrations the spectra of III suggested the presence of an equilibrium among partially structured states, those of IV indicated that this peptide exists in unordered extended conformation, folds into a &#946;-conformation and, finally, assumes a helix rich structure. 1H-NMR analysis revealed the existence of a well defined &#947;-turn encompassing residues 4-6 that nicely fits with that present in the same portion of the crystallized hFGF-1. Superposition of the final structures of III and IV over the entire sequence revealed that only the C-terminal portion of III has the tendency to fold into a regular structure. Together these data indicate that the turn existence in IV allowed it to acquire the structural determinants for the expression of mitogenicity probably through a more appropriate arrangement of residues 8-10. More importantly, they demonstrate that we have found a short agonist of hFGF-1 able to structurally mimic its corresponding stretch. Conformational analysis of XVIII in solution was undertaken also by using CD e 1HRMN. The results obtained indicated that it has a strong tendency to assume helicoidal configuration in aqueous solution containing 50% CD3OH. Altogether these data led us to conclude that: 1) the presence of Asn106 adjacent to hydrophobic core constituted by W107F108 is essential for the mitogenic activity of IV; 2) conformation constraint by cyclization was efficient for the correct N106, W107 and F108 side chains orientation in peptide IV for an effective cellular receptors binding; 3) peptides related to hFGF-1 (114-123) seem to be promising mitogenic agonists; 4) the only one lysine between L126 and N129 is enough for the mitogenic activity expression (X, XVI and XVII); 5) deletions of residues, replacement of deleted fragment by Pro followed by restriction of peptide conformation might keep the frame of the residues considered essential for the mitogenic activity along the peptides backbones; 6)The inhibitory effect on the FGF-2 mitogenic activity observed in peptide XVIII was indicative that the loop DE of DIII FGFRs seems to be involved in the binding of this protein.These conclusions are very relevant in terms of the knowledge of the structural requirements for the mitogenic activity of studied peptides and, as a reflex, of the hFGF-1. Furthermore, they constitute additional guidelines for designing new constrained peptides derived from this segment of FGF-1, which may result in more potent agonists, antagonists or inhibitors of such important target.

HARP (Heparin Affin regulatory peptide) est un facteur de croissance qui constitue avec la midkine une sous-famille des Heparin Binding Growth Factors (HBGFs). HARP est impliqué dans de nombreux processus physiologiques comme la neurogenèse et la vasculogenèse mais aussi dans des processus physiopathologiques comme l’angiogenèse et la progression tumorale. HARP interagit avec différents récepteurs (N-syndécan, RPTPβ/ζ, et ALK). Plus récemment, il a été montré au laboratoire que la nucléoline, protéine navette entre le noyau, le cytoplasme, et la surface cellulaire est un nouveau récepteur à HARP. Malgré les avancées dans ce domaine, l’interaction de HARP avec ses récepteurs n’est pas totalement élucidée. L'objectif de ce projet de thèse était la recherche de nouveaux partenaires moléculaires qui interagissent avec HARP, de comprendre le mécanisme de leurs interaction et d’analyser les effets biologiques. A ce titre, j’ai participé à l’étude de l’interaction de HARP avec le facteur de croissance des fibroblastes, le FGF-2. Ce facteur liant l’héparine est également mitogène et angiogène. En utilisant des techniques de biocapteurs optiques et d’interaction protéine-protéine, nous avons montré une interaction directe entre HARP et le FGF-2 et qui implique les domaines C-TSR-I et C-terminale de HARP. De plus, cette interaction inhibe la migration et la prolifération des cellules endothéliales, induites par le FGF-2 ou par HARP seuls. En parallèle, j’ai mis en évidence l’interaction entre HARP et la NRP-1. NRP-1 est une protéine transmembranaire, ayant comme ligands principaux, les sémaphorines de classe 3 (SEMA 3A), le facteur de croissance endothélial vasculaire (VEGF) et le FGF-2. En plus de son rôle crucial dans le développement des systèmes nerveux et cardiovasculaires, la NRP-1 est impliquée dans les processus physiopathologiques tels que l’angiogenèse et l’invasion tumorale. Ainsi, la NRP-1 présente un profil biologique similaire à HARP. En utilisant des tests d’ELISA, d’immunoprécipitation et de « pull-down », nous avons montré que HARP interagit avec la NRP-1. Cette interaction semble être directe et s’effectue via les domaines de liaison à l’héparine TSR-I. HARP induit l’internalisation de la NRP-1 au bout de 15 minutes et son recyclage partiel à la surface cellulaire au bout d’une heure. L’internalisation de la NRP-1 s’accompagne par la phosphorylation des voies MAPK (ERK1/2), Akt et FAK. L’interaction HARP/NRP-1 est cruciale pour la migration des cellules endothéliales et l’invasion des cellules tumorales. En conclusion, ces résultats apportent de nouvelles avancées concernant les partenaires moléculaires de HARP en particulier et montrent également la complexité des interactions des facteurs de croissance entre eux et avec leurs récepteurs. Plus généralement, cette étude permet d'envisager des stratégies thérapeutiques ciblant l’interaction de la NRP-1 avec HARP et aussi les autres facteurs de croissance. / HARP (Heparin Affin regulatory peptide) is a growth factor that constitutes with midkine a subfamily of Heparin Binding Growth Factors (HBGFs). HARP is involved in many physiological processes such as neurogenesis and vasculogenesis but also in pathophysiological processes such as angiogenesis and tumor progression. HARP interacts with different receptors (N-syndecan, RPTPβ / ζ and ALK). More recently, it has been shown in the laboratory that nucleolin, a protein shuttle between the nucleus, cytoplasm, and cell surface, is a new HARP receptor. Despite the advances in this field, the interaction of HARP with its receptors is not fully understood. The aim of this thesis was the search for new molecular partners that interact with HARP, to understand the mechanism of their interaction and analyze the biological effects. My work was firstly to participate to the study of the interaction of HARP with the fibroblast growth factor-2, FGF-2. This factor is also an heparin-binding factor, with mitogenic and angiogenic activities. Using techniques of optical biosensors and protein-protein interaction, we have shown a direct interaction between HARP and FGF-2 that involves C-TSR-I and C-terminus domains of HARP. In addition, HARP inhibits the migration and proliferation of endothelial cells induced by FGF-2. In parallel, I highlighted the interaction between HARP and NRP-1. NRP-1 is a transmembrane protein having as main ligands, semaphorins class 3 (SEMA 3A), the vascular endothelial growth factor (VEGF) and FGF-2. In addition to its crucial role in the development of the nervous and cardiovascular systems, the NRP-1 is involved in physiopathological processes such as angiogenesis and tumor invasion. Thus, NRP-1 has a biological profile similar to HARP. Using ELISA, immunoprecipitation and "pull-down" tests, we have shown that HARP interacts with NRP-1. This interaction appears to be direct and occurs via heparin binding domains of HARP: TSR-I. HARP induces internalization of NRP-1 after 15 minutes and partial recycling to the cell surface after one hour. The internalization of the NRP-1 is accompanied by the phosphorylation of MAPK pathways (ERK1 / 2), Akt and FAK. HARP/NRP-1 interaction is crucial for endothelial cell migration and invasion of tumor cells. In conclusion, these results provide new advances on molecular partners of HARP in particular and also show the complexity of the interactions between these growth factors and their receptors. More generally, this study allows considering therapeutic strategies targeting the interaction of NRP-1 with HARP as well as other growth factors.

Fibroblast growth factor (Fgf) signaling plays multiple inductive roles during development of vertebrates (Itoh 2007). Some Fgfs, such as Fgf8, are locally secreted and signal over a long range to provide positional information in the target tissue (Scholpp and Brand 2004). Fgf ligands signal in a receptor-dependent manner via tyrosine kinase receptors, four of which have been so far identified. Fgf8 signaling was shown to depend both on receptor activation as well as endocytosis. The specificity of Fgf ligands and receptors as well as the function of receptors in the control of the Fgf signaling range have been, however, largely unclear. In this study, we show that the putative Fgf8 receptor Fgfr1 is duplicated in zebrafish and that it acts redundantly in the formation of the posterior mesoderm. Also, in overexpression studies we confirm the notion that receptor endocytosis influences Fgf8 signaling range. Through TILLING mutant recovery and morpholino knockdown studies we also show that Fgfr2 is required for growth and skeletal development in zebrafish, whereas Fgfr4 is required for pectoral fin specification and growth.