Grâce aux nombreuses études sur le sujet, nous savons qu’une stimulation inflammatoire vasculaire excessive entraîne un débalancement des fonctions homéostatiques de l’endothélium. Ce débalancement est à l’origine d’une dysfonction endothéliale définie comme étant l’étape clé contribuant au développement de l’athérosclérose. Le Toll-like receptor-2 (TLR2) est impliqué dans l’activation cellulaire via la transcription des gènes liés à l’inflammation. Il reconnaît des molécules microbiennes mais également des facteurs endogènes non-infectieux tels que sécrétés par les tissus endommagés provenant de la dysfonction endothéliale. Ainsi, l’activation et la signalisation du TLR2 sont en étroite relation avec le développement de l’athérosclérose. Les études épidémiologiques ont confirmé le rôle athéroprotecteur de l’œstrogène via de nombreux mécanismes d’action. Ainsi, nous avons cherché à identifier de nouvelles cibles moléculaires permettant de mieux interpréter les bénéfices potentiels de l’œstrogène sur le système cardiaque. Pour la première fois chez les cellules endothéliales (CE) vasculaires de souris, nos travaux ont confirmé l’effet anti-inflammatoire de l’œstrogène via la diminution de l’expression et de l’activité du TLR2. Nous avons également déterminé l’influence de l’œstrogène sur le profil de la réponse inflammatoire de ce récepteur en mesurant les potentiels endothéliaux de migration et d’adhésion. De plus, nous avons caractérisé les voies de signalisation impliquées en démontrant l’influence négative de l’œstrogène sur la phosphorylation des kinases activées par le TLR2; illustrant l’interaction entre l’œstrogène et la signalisation de ce récepteur. Nos travaux amènent ainsi de nouvelles connaissances sur la régulation endothéliale du TLR2 et mettent en lumière les effets anti-inflammatoires et vasculaires rapides de l’œstrogène. / Evidence supports the contribution of immune responses in atherosclerosis development in part by alterations in the endothelium activation status and by the recruitment of inflammatory cells triggered by cardiovascular risk factors. These alterations are the principal cause of endothelial dysfunction defined as the key step contributing to the development of atherosclerosis. Via the transcription of genes related to inflammation, the Toll-like receptor-2 (TLR2) is involved in endothelial cell activation. It generally recognizes microbial molecules but also non-infectious endogenous factors such as those secreted by damaged tissues from the endothelial dysfunction. Thus, activation and signalization of the TLR2 are closely linked with the development of atherosclerosis. Epidemiological studies have confirmed the atheroprotective role of estrogen through multiple mechanisms of action. Thus, to better interpret the potential benefits of estrogen on the cardiovascular system, we sought to identify new molecular targets such as TLR2 regulation. For the first time in mouse vascular endothelial cells (EC), our results have confirmed the anti-inflammatory effect of estrogen via the decreased expression and activity of TLR2. We also determined the influence of estrogen on the profile of the inflammatory response triggered through this receptor by measuring endothelial migration and adhesion potentials. Furthermore, we demonstrated the interaction between estrogen and TLR2 signalling pathways with a negative influence of estrogen on the phosphorylation level of kinases activated by this receptor. Thus, our study brings new insights into the endothelial regulation of TLR2 and highlights rapid anti-inflammatory and cardioprotective effects from estrogen.

Les anévrysmes de l'aorte abdominale (AAAs) sont des dilatations artérielles qui exposent le patient au décès par rupture. Ils sont caractérisés notamment par la perte de la monocouche de cellules endothéliales et son remplacement par un épais thrombus mural. Cependant, le lienentre l'accroissement du diamètre anévrysmal, la présence d'un thrombus et la perte en cellules endothéliales reste inexploré. Notre hypothèse est que la perte de l'endothélium contribue au développement des AAAs et que sa restauration par thérapie cellulaire permettrait de stabiliser les AAAs. In vivo, la réparation endothéliale implique le recrutement des cellules endothéliales adjacentes mais également des cellules progénitrices endothéliales (EPCs). Chez l'homme, le nombre et l’activité fonctionnelle des EPCs sont inversement corrélés aux facteurs de risque cardiovasculaire, et très peu de données sont disponibles sur l’activité fonctionnelle des EPCs issues de patients porteurs d'AAA. La présence du thrombus pourrait ainsi diminuer le nombre et les propriétés cicatricielles des EPCs issues de patients porteurs d'AAA. / Summary not transmitted

INTRODUÇÃO: O impacto do aumento de expressão do fator de crescimento endotelial no curso da Leucemia Mielóide Crônica (LMC) ainda é desconhecido, porém há relatos de que estes pacientes apresentam maior densidade vascular em medula óssea do que em indivíduos saudáveis, principalmente em crise blástica. Outro fator recentemente associado ao aumento da angiogênese é a expressão anormal da proteína hsecurina, que, por sua vez, inibi uma protease denominada separase, responsável pela separação das cromátides irmãs durante a anáfase da mitose. Por esses motivos, quantificamos células endoteliais circulantes e VEGF em portadores de LMC como marcador de angiogênese e expressão do gene hsecurina. MÉTODOS: Realizamos análise prospectiva e consecutiva de uma coorte de 31 pacientes com LMC em fase crônica ao diagnóstico, 23 em crise blástica, 30 em fase acelerada, atendidos no ambulatório de Hematologia da FMUSP e 50 indivíduos saudáveis, doadores de plaquetas por aférese, para quantificação da porcentagem de células endoteliais circulantes e subtipos pelo método de citometria de fluxo no laboratório de Imunopatologia HC/FMUSP. Desta coorte 25 pacientes em fase crônica, 14 em crise blástica, 26 em fase acelerada e 32 indivíduos saudáveis foram analisados para os genes hsecurina e VEGF por PCR quantitativo em tempo real. RESULTADOS: A mediana da porcentagem das células endoteliais circulantes foi de 0, 0146% em LMC em crise blástica e 0,0059% no grupo controle, p < 0,01 às custas das células endoteliais maduras (p < 0,01). A mediana de células endoteliais circulantes em crise blástica foi de 0, 0146%, superior à da fase acelerada (0,0059%), p < 0,01 com predomínio de células endoteliais maduras (p < 0,01). Em relação à expressão do gene VEGF observamos aumento estatisticamente significativo nas fases crônica (p < 0,01), acelerada (p < 0,01) e crise blástica (p = 0,04). Encontramos aumento significativo da expressão do gene hsecurina na crise blástica da doença, com mediana de 0,390 em relação aos grupos controle com mediana de 0,125 (p < 0,01) e fase acelerada, com mediana de 0,230 (p = 0,04). Os pacientes na fase crônica da doença apresentaram mediana de 0,260 e p = 0,03 quando comparados com o grupo controle. CONCLUSÃO: Observamos neste estudo que a quantificação de CEC é uma ferramenta útil para predizer e identificar precocemente a progressão da LMC para fase blástica, diferentemente da variável VEGF que foi elevado em todas as fases da doença. A expressão do gene hSecurina na fase crônica da doença foi significantemente alta, demonstrando provável relação com a elevação da taxa de proliferação celular. Entretanto, estudos complementares do gene hSecurina deverão ser realizados na crise blástica da LMC, para entendermos com precisão o real significado nesta fase da doença. / INTRODUCTION: The impact of the increased expression of vascular endothelial growth factor in the course of chronic myeloid leukemia (CML) is still unknown, but there are reports that those patients have higher vascular density in bone marrow than healthy individuals, particularly in blast crisis. Another factor recently associated with increased angiogenesis is the abnormal expression of protein hSecurin, which, in turn, inhibits a protease called separase, responsible for the separation of sister chromatids during the anaphase of mitosis. For these reasons, we quantified circulating endothelial cells and VEGF in patients with CML as a marker of angiogenesis and hSecurin gene expression. METHODS: We performed a prospective analysis of consecutive cases in a cohort of 31 patients with CML in chronic phase at diagnosis, 23 in blast crisis, 30 in accelerated phase who attended the outpatient Hematology FMUSP ward, and 50 healthy subjects, platelet apheresis donors, for quantification of the percentage of circulating endothelial cells and subtypes through the flow cytometry method, at HC/FMUSP Immunopathology laboratory. In this cohort, 25 patients in chronic phase, 14 in blast crisis, 26 in accelerated phase, and 32 healthy subjects were tested for the genes VEGF and hSecurin by quantitative real-time PCR. RESULTS: The median percentage of circulating endothelial cells was 0.0146% in CML in blast crisis and 0.0059% in the control group, p <0.01 at the expense of mature endothelial cells (p <0.01). The median circulating endothelial cells in blast crisis was 0.0146% higher than in accelerated phase (0.0059%), p <0.01 with predominance of mature endothelial cells (p <0.01). Regarding the expression of the VEGF gene, a statistically significant increase was observed in chronic phase (p <0.01), accelerated (p <0.01) and blast crisis (p = 0.04). We found a significant increase in hSecurin gene expression in blast crisis disease, with a median of 0.390 compared to control groups, with a median of 0.125 (p <0.01) and accelerated phase, with a median of 0.230 (p = 0.04). Patients with chronic disease had a median of 0.260 and p = 0.03 compared with the control group. CONCLUSION: In this study, we observed that the quantification of CPB is a useful tool to predict and identify the early progression of CML to blast phase, unlike the VEGF variable, which was elevated in all stages of the disease. The expression of hSecurin gene in chronic phase was significantly higher, demonstrating a likely relationship with the increased cell proliferation rate. However, further studies of hSecurin gene should be made in the blastic crisis of CML to understand precisely the real meaning at this stage of the disease.

Apesar de sua importância clínica e epidemiológica, a fisiopatologia da préeclâmpsia ainda não foi completamente compreendida. Sabe-se que a doença constitui-se de uma fase pré-clínica e um estágio clínico. Durante a última década muito esforço tem se concentrado na identificação precoce da doença, ainda em sua fase pré-clínica. A literatura científica tem demonstrado claramente um desequilíbrio na regulação da angiogênese das gestantes com pré-eclâmpsia, marcado por níveis elevados do fator antiangiogênico soluble fms-like tyrosine kinase-1 (sFlt-1) e níveis diminuídos do fator pró-angiogênico placental growth fator (PlGF). Embora um número crescente de estudos em populações de alto risco tenha avaliado o papel desses biomarcadores no diagnóstico de pré-eclâmpsia, dados sobre sua utilização para a predição de pré-eclâmpsia superajuntada, cujo diagnóstico pode ser particularmente difícil, permanecem relativamente escassos e controversos. Com o presente estudo pretendemos avaliar o desempenho de medidas seriadas dos níveis maternos circulantes dos fatores sFlt-1 e PlGF, bem como da razão sFlt-1/PlGF, para predição de pré-eclâmpsia superajuntada e compará-lo ao seu desempenho na predição de pré-eclâmpsia em sua forma \"pura\", não superajuntada. Para este propósito, estudamos uma coorte prospectiva composta de dois braços, um de gestantes com hipertensão arterial crônica e outro de gestantes normotensas, e avaliamos os níveis séricos de sFlt-1 e de PlGF e a razão sFlt-1/PlGF nas idades gestacionais de 20, 26, 32 e 36 semanas, tendo como desfecho principal o diagnóstico de pré-eclâmpsia. Um total de 97 gestantes foram acompanhadas, 37 normotensas e 60 com hipertensão arterial crônica. Entre elas, 4 (10,8%) desenvolveram pré-eclâmpsia e 14 (23,3%) desenvolveram pré-eclâmpsia superajuntada. Para predição de pré-eclâmpsia, a análise ROC (Receiver Operating Characteristics) apresentou área sob a curva (AUC - area under curve) de 0,83 (IC 95% = 0,68-0,99, P = 0,035) para dosagem de PlGF com 20 semanas e AUC = 0,92 (IC 95% = 0,81 - 1,00, P = 0,007) para a razão sFlt-1/PlGF com 26 semanas de gestação. A variação percentual dos níveis de PlGF entre 26 e 32 semanas de gestação apresentou AUC = 0,96 (IC de 95% = 0,89-1,00, P = 0,003). Para a predição de pré-eclâmpsia superajuntada, a razão sFlt-1/PIGF na idade gestacional de 32 semanas apresentou AUC = 0,69 (IC de 95% = 0,53-0,85, P = 0,039). Entre 20 e 26 semanas de gestação, a variação percentual do PIGF e da razão sFlt-1/PlGF apresentaram, respectivamente, AUC = 0,74 (IC de 95% = 0,58-0,90, P = 0,018) e AUC = 0,71 (IC 95% = 0,52-0,91, P = 0,034). Por nossos resultados podemos concluir que, embora os níveis de PlGF e a razão sFlt-1/ PlGF tenham apresentado bons desempenhos na predição de pré-eclâmpsia, é preciso ter cuidado ao usá-los para a predição de pré-eclâmpsia superajuntada. Nessas gestantes, a dosagem dos fatores angiogênicos apresenta capacidade de predição menor e mais tardia. Avaliações seriadas dos fatores podem melhorar o desempenho dos testes para predição de pré-eclâmpsia superajuntada em idades gestacionais mais precoces / Despite being a major public health problem, the pathophysiology of preeclampsia is incompletely understood. Preeclampsia progression comprises a pre-clinical stage and a clinical stage. During the last decade much work has focused on identifying the pre-clinical stage of preeclampsia. Many researchers have clearly demonstrated an anti-angiogenic imbalance that is marked by higher levels of soluble fms-like tyrosine kinase-1 (sFlt-1) and lower levels of placental growth factor (PlGF) in the subjects who develop preeclampsia compared with those who do not. Although a growing number of studies in the high-risk population have shown the role of these biomarkers in diagnosing preeclampsia, superimposed preeclampsia, which can be a challenging diagnosis, remains partially understudied and the literature regarding this subject continues to be relatively scarce as well as controversial. By this study, we aimed to evaluate the performance of serial measurements of maternal circulating sFlt-1 and PlGF levels for the prediction of superimposed preeclampsia in chronic hypertensive subjects and to compare it to the prediction of preeclampsia in normotensive control subjects. For this purpose, we evaluated a two-armed prospective cohort of women with normotensive and chronic hypertensive pregnancies and assessed the serum levels of sFlt-1 and PlGF and the sFlt-1/PlGF ratio at gestational ages of 20, 26, 32 and 36 weeks, having preeclampsia as the primary outcome to be predicted. A total of 97 women were followed-up, 37 in the normotensive group and 60 in the chronic hypertensive group. Among them, 4 (10.8%) women developed preeclampsia and 14 (23.3%) developed superimposed preeclampsia. For predicting preeclampsia, PlGF at 20 gestational weeks presented an AUC=0.83 (CI 95% = 0.68 - 0.99, P=0.035) and the sFlt-1/PlGF ratio at 26 gestational weeks presented an AUC=0.92 (CI95% = 0.81 - 1.00, P=0.007). The percent change of the PlGF levels between 26 and 32 gestational weeks presented an AUC=0.96 (CI 95% = 0.89 - 1.00, P=0.003). For predicting superimposed preeclampsia, the sFlt-1/PlGF ratio at 32 gestational weeks presented an AUC=0.69 (CI 95% = 0.53 - 0.85, P=0.039). Between 20 and 26 gestational weeks, the percent change of PlGF and the sFlt-1/PlGF ratio presented, respectively, an AUC=0.74 (CI 95% = 0.58 - 0.90, P=0.018) and an AUC=0.71 (CI 95% = 0.52 - 0.91, P=0.034). By our results, we concluded that, although the PlGF level and the sFlt-1/PlGF ratio present good performances in the prediction of preeclampsia, caution is required when using them for the prediction of superimposed preeclampsia. Sequential assessments slightly improve the test performances for predicting superimposed preeclampsia at earlier gestational ages

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2009. / Härtill 4 uppsatser.

Endometriosis affects 5-10% of women and is characterized by the growth of endometrial tissue outside of the uterus. Treatment for endometriosis primarily focuses on symptom relief, is short term with severe side effects and often leads to recurrence of the condition. Establishing new blood supply is a fundamental requirement for endometriosis lesions growth. This has led to the idea that antiangiogenic therapy may be a successful approach for inhibiting endometriosis. Recent evidence indicates that endothelial progenitor cells (EPCs) contribute to neoangiogenesis of endometriotic lesions. These EPCs are recruited to the lesion site by stromal cell-derived factor-1 (SDF-1). We hypothesize that SDF-1 is central to the neoangiogenesis and survival of endometriotic lesions and that administration of SDF-1 blocking antibody will inhibit lesion growth by inhibiting angiogenesis in a murine model of endometriosis. Immunohistochemistry for SDF-1 and CD34 was performed on human endometriosis and normal endometrial samples. Quantification of SDF-1 and EPCs was performed in the blood of endometriosis patients and controls using ELISA and flow cytometry, respectively. A new mouse model of endometriosis was developed using BALB/c-Rag2-/-/IL2rg-/- mice to investigate role of SDF-1 in neoangiogenesis. Either SDF-1 blocking antibody or an isotype control was administered on a weekly basis for four weeks. Weekly samples of peripheral blood from mice were analyzed for SDF-1, other cytokines of interest and EPCs. Mice were euthanized at seven weeks to observe lesion growth and blood vessel development. Our results indicate overabundance of SDF-1 and CD34+ progenitor cells in human endometriotic lesions compared to eutopic endometrium. In the mouse model, SDF-1 and circulating EPC levels decreased from pre-treatment levels after one week, and remained constant over the course of the treatment in both SDF-1 blocking antibody and isotype control groups. In the SDF-1 blocking group, reduced vascularity of lesions, identified by immunofluorescence staining for CD31, was revealed compared to isotype controls. These findings suggest that SDF-1 may be responsible for CD34+ progenitor cell recruitment to the neoangiogenic sites in endometriosis. Blocking of SDF-1 reduces neovascularization of human endometriotic lesions in a mouse model. Further studies on blocking SDF-1 in combination with other antiangiogenic agents are needed. / Thesis (Master, Anatomy & Cell Biology) -- Queen's University, 2011-12-21 19:34:43.054

Grâce aux nombreuses études sur le sujet, nous savons qu’une stimulation inflammatoire vasculaire excessive entraîne un débalancement des fonctions homéostatiques de l’endothélium. Ce débalancement est à l’origine d’une dysfonction endothéliale définie comme étant l’étape clé contribuant au développement de l’athérosclérose. Le Toll-like receptor-2 (TLR2) est impliqué dans l’activation cellulaire via la transcription des gènes liés à l’inflammation. Il reconnaît des molécules microbiennes mais également des facteurs endogènes non-infectieux tels que sécrétés par les tissus endommagés provenant de la dysfonction endothéliale. Ainsi, l’activation et la signalisation du TLR2 sont en étroite relation avec le développement de l’athérosclérose. Les études épidémiologiques ont confirmé le rôle athéroprotecteur de l’œstrogène via de nombreux mécanismes d’action. Ainsi, nous avons cherché à identifier de nouvelles cibles moléculaires permettant de mieux interpréter les bénéfices potentiels de l’œstrogène sur le système cardiaque. Pour la première fois chez les cellules endothéliales (CE) vasculaires de souris, nos travaux ont confirmé l’effet anti-inflammatoire de l’œstrogène via la diminution de l’expression et de l’activité du TLR2. Nous avons également déterminé l’influence de l’œstrogène sur le profil de la réponse inflammatoire de ce récepteur en mesurant les potentiels endothéliaux de migration et d’adhésion. De plus, nous avons caractérisé les voies de signalisation impliquées en démontrant l’influence négative de l’œstrogène sur la phosphorylation des kinases activées par le TLR2; illustrant l’interaction entre l’œstrogène et la signalisation de ce récepteur. Nos travaux amènent ainsi de nouvelles connaissances sur la régulation endothéliale du TLR2 et mettent en lumière les effets anti-inflammatoires et vasculaires rapides de l’œstrogène. / Evidence supports the contribution of immune responses in atherosclerosis development in part by alterations in the endothelium activation status and by the recruitment of inflammatory cells triggered by cardiovascular risk factors. These alterations are the principal cause of endothelial dysfunction defined as the key step contributing to the development of atherosclerosis. Via the transcription of genes related to inflammation, the Toll-like receptor-2 (TLR2) is involved in endothelial cell activation. It generally recognizes microbial molecules but also non-infectious endogenous factors such as those secreted by damaged tissues from the endothelial dysfunction. Thus, activation and signalization of the TLR2 are closely linked with the development of atherosclerosis. Epidemiological studies have confirmed the atheroprotective role of estrogen through multiple mechanisms of action. Thus, to better interpret the potential benefits of estrogen on the cardiovascular system, we sought to identify new molecular targets such as TLR2 regulation. For the first time in mouse vascular endothelial cells (EC), our results have confirmed the anti-inflammatory effect of estrogen via the decreased expression and activity of TLR2. We also determined the influence of estrogen on the profile of the inflammatory response triggered through this receptor by measuring endothelial migration and adhesion potentials. Furthermore, we demonstrated the interaction between estrogen and TLR2 signalling pathways with a negative influence of estrogen on the phosphorylation level of kinases activated by this receptor. Thus, our study brings new insights into the endothelial regulation of TLR2 and highlights rapid anti-inflammatory and cardioprotective effects from estrogen.

Arteriosklerose führt zu schwerwiegenden klinischen Komplikationen bei Herz-Kreislauf-erkrankungen, welche die führenden Todesursachen in den westlichen Industrieländern sind. Die Arteriosklerose ist typischerweise eine Erkrankung arterieller Gefäße und betrifft nicht die venöse Gefäßwand. Bei der Entstehung von Arteriosklerose spielen die Endothelzellen als Barrierezellen und Regulatoren der Gefäßfunktion eine Schlüsselrolle. Ein wichtiger Schwerpunkt der Forschung ist die Differenzierung der Endothelzellen. Arterielle und venöse Endothelzellen weisen schon im frühen Embryonalstadium unterschiedliche Phänotypen auf. Ein besseres Verständnis der arterio-venösen Differenzierung wäre von großer Bedeutung für antiarteriosklerotische Therapien. Darüber hinaus könnte eine Reprogrammierung (z.B. von Vene in Arterie) entscheidend für neue Therapieansätze bei der Senkung der Restenoserate venöser Bypässe von Patienten mit koronarer Herzkrankheit und bei AV-Shunt-Operationen von dialysepflichtigen Patienten sein. In dieser Arbeit wurden differenzierte humane primäre arterielle und venöse Endothelzellen nach Genmodulation untersucht. Der Fokus der Genmodulation wurde auf das arterielle Markergen Hey2 und auf das venöse Markergen COUP-TFII gelegt. Das arterielle Markergen Hey2 ist ein Zielgen der Notch-Signalkaskade, während der molekulare Mechanismus der Rolle von COUP-TFII bei der venösen Differenzierung noch nicht bekannt ist. Daher wurde der Einfluss des arteriellen Markergens Hey2 und des venösen Markergens COUP-TFII auf die Notch-Signalkaskade untersucht, um ein besseres Verständnis über die molekularen Mechanismen der arterio-venösen Differenzierung zu gewinnen. Da humane primäre Endothelzellen mit kommerziell verfügbaren Transfektionsmitteln schwer transfizierbar sind, wurde zunächst ein lentivirales Vektorsystem etabliert. Hiermit wurde eine erfolgreiche und stabile Genexpression bzw. Genrepression in arteriellen und venösen Endothelzellen ermöglicht. Die Genmodulationen in arteriellen Endothelzellen, die durch die Expression des venösen Markergen COUP-TFII bzw. durch die Repression des arterellen Markergen Hey2 verursacht wurden, führten zu der neuen Erkenntnis, dass das venöse Markergen COUP-TFII in arteriellen Endothelzellen als ein Repressor des arteriellen Markergens Hey2 fungiert. Diese Repression wird durch eine direkte Bindung von COUP-TFII an den Hey2-Promotor vermittelt. Die COUP-TFII Expression bewirkte keine Veränderung in der Expression von Notch4, Dll4 und Nrp1. Dies könnte bedeuten, dass (i) COUP-TFII in arteriellen Endothelzellen kein Regulator von diesen Genen ist, (ii) Kooperationspartner von COUP-TFII fehlen, die in arteriellen Endothelzellen nicht vorhanden sind, oder (iii) der molekulare Mechanismus dieser Gene aufgrund seiner wichtigen Rolle nicht durch die Modifikation eines einzigen Gens beeinflussbar ist, da die Gene der Notch-Signalkaskade redundant kontrolliert werden. In venösen Endothelzellen wurden Genmodulationen durch Expression des arteriellen Markergens Hey2 bzw. durch die Repression des venösen Markergens COUP-TFII durchgeführt. Eine Expression des arteriellen Markergens Hey2 in venösen Endothelzellen konnte nicht die Expression der Gene der Notch-Signalkaskade aktivieren. Dies bedeutet, dass die Regulation dieser Gene durch einen übergeordneten molekularen Mechanismus gesichert ist. Interessanterweise konnte die Expression von Hey2 eine Reduktion der Hey1 Expression bewirken. Dies ist ein alternativer Effekt von Hey2 im Vergleich zu arteriellen Endothelzellen. Eine Repression des venösen Markergens COUP-TFII konnte die Expression der Gene Dll4, EphrinB2 und EphB4 induzieren. Vermutlich ist die Induktion der EphB4 Expression ein Kompensationsmechanismus auf die reduzierte COUP-TFII Expression. COUP-TFII sichert den venösen Phänotyp wahrscheinlich durch die Repression von EphrinB2 und Dll4, wobei die Reduktion von Dll4 vermutlich eine größere Bedeutung hat. Da Dll4 ein Ligand und Aktivator der Notch-Signalkaskade ist, ist seine Repression entscheidend für venöse Endothelzellen. Das arterielle Markergen Hey2 ist für die normale Embryogenese von großer Bedeutung, jedoch ist Hey2 als eines der Zielgene der Notch-Signalkaskade wahrscheinlich nicht in der Lage, molekulare Mechanismen, die zu unterschiedlichen endothelialen Phänotypen führen, zu aktivieren. Um arterielle Endothelzellen zu einem Reprogramming zu bewegen, wären wahrscheinlich Genmodulationen der Mitglieder der Notch-Signalkaskade, die upstream von Hey2 liegen, nötig. Hingegen ist die Rolle des venösen Markergens COUP-TFII in der Regulation der arterio-venösen Differenzierung von entscheidender Bedeutung. COUP-TFII spielt eine direkte Rolle in der Aufrechterhaltung der venösen Identität. Die Repression von COUP-TFII in venösen Endothelzellen bewirkt, dass sich die Expression des Gens Dll4, das die Notch-Signalkaskade aktiviert, in Richtung des arteriellen Expressionsniveaus bewegt. Für eine Reprogrammierung der venösen Endothelzellen in einen arteriellen Phänotyp ist das venöse Markergen COUP-TFII eines der Zielgene.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 5 uppsatser.