L’athérosclérose est une maladie inflammatoire chronique de la paroi vasculaire à évolution lente et silencieuse dont les principaux facteurs de risque sont les dyslipidémies, l’obésité, le diabète et le tabagisme. Les macrophages jouent un rôle crucial dans le développement et la progression de cette maladie. Ils sont issus de la différentiation des monocytes et ils ne constituent pas une population homogène. On peut reconnaître au moins deux sous-populations: les macrophages pro-inflammatoire M1 et les macrophages alternatifs ou M2 qui montrent des propriétés anti-inflammatoires. Les fonctions des macrophages sont régulées par des facteurs de transcription. Mon laboratoire d’accueil a réalisé une analyse transcriptomique sur les facteurs de transcription régulés dans les macrophages alternatifs et parmi les plus induits dans les M2 il y a NOR1 (Neuron-derived Orphan Receptor 1) et TLE1 (Transducin Like Enhancer of Split 1). Pour cette raison nous les avons choisis pour en étudier le rôle dans les macrophages alternatifs humains. Etude de l’expression et rôle de NOR1 dans les macrophages alternatifsNOR1 fait partie de la famille NR4A3 ensemble à deux autres membres, Nurr1 et Nur77 : les trois sont exprimés dans les macrophages au sein de la lésion d’athérosclérose humaine. Cependant l’expression et le rôle de NOR1 dans les macrophages alternatifs n’a pas encore été étudié. En utilisant le model en vitro des macrophages primaires alternatifs humains polarisée en présence de l’IL-4, nous avons démontré que l’expression de NOR1 est induite dans les macrophages M2 chez l’homme, tandis que cette régulation n’est pas vérifiée chez la souris. D’ailleurs l’expression de NOR1 est plus importante dans les zones de la lésion atherosclerotique humaine enrichies par les macrophages CD68+MR+ . En utilisant l’approche de diminution de l’expression de NOR1 par un siRNA spécifique, nous démontrons que l’expression de certaines marqueurs de la polarisation alternative tels que Mannose Receptor (MR), Interleukin-1 receptor antagonist (IL1Ra), CD200 receptor (CD200R), coagulation factor XIII A1 polypeptide (F13A1), interleukin 10 (IL10) and the Peroxisome Proliferator-Activated Receptor (PPARg) sont diminués. De plus, l’expression et l’activité de la matrix metallopeptidase 9 (MMP9) sont induites suite au silencing de NOR1, cette régulation est confirmé par l’approche de surexpression de NOR1 par infection adenovirale. Ces données identifient NOR1 parmi les facteurs de transcription induits dans les macrophages alternatifs humains et permettent de mettre en évidence comme NOR1 soit capable de modifier le phénotype alternatif des macrophages.Etude de l’expression et fonctions potentielles de TLE1 dans les macrophages alternatifsTLE1, appartenant à la grande famille appelée chez la Drosophile avec le nome de Groucho, est connu pour être un répresseur incapable de se fixer directement à l’ADN et que par conséquence agit par interaction avec des autres facteurs de transcription. Aucune donnée n’est disponible quant à l’expression ou aux fonctions de TLE1 dans les macrophages. Nos résultats montrent que TLE1 est parmi les facteurs de transcription les plus exprimés dans les macrophages alternatifs humains. Cette régulation est aussi observée dans les macrophages de souris. Nous avons aussi montré que TLE1 est fortement exprimé dans les zones enrichies en macrophages M2 au sein de la plaque athérosclérotique humaine ainsi que dans les macrophages à phénotype mixte qui infiltrent le tissu adipeux (ATM). Nous avons caractérisé l’expression génique de TLE1 dans les patients obèses avec ou sans diabète et nous montrons que l’expression de TLE1 varie selon le statut métabolique du donneur. / Atherosclerosis is an inflammatory disease in which macrophages play a crucial role. Macrophages are derived from the differentiation of circulating monocytes and they are not an homogenous population. We can distinguish at least two types of macrophages: The pro-inflammatory M1 macrophages and the alternative anti-inflammatory macrophages M2. Functions of macrophages are controlled by transcriptional factors. My laboratory has realised a transcriptomic analysis of transcriptional factors differently regulated among RM and M2 macrophages. Among the most regulated transcriptional factors there is NOR1 (Neuron-derived Orphan Receptor 1) and TLE1 (Transducin Like Enhancer of Split 1). According to these data, we have chose these two transcriptional factors in order to determine their role in human alternative macrophages. The neuron-derived orphan receptor 1 (NOR1) is induced upon human alternative macrophage polarization and stimulates the expression of markers of the M2 phenotypeThe neuron-derived orphan receptor 1 (NOR1), together with Nur77 and Nurr1, is a member of the NR4A orphan nuclear receptor family expressed in human atherosclerotic lesion macrophages. However, the expression and the functions of NOR1 in human alternative macrophages have not been studied yet. Using an in vitro model of IL-4 polarized primary human alternative macrophages we demonstrate that NOR1 expression increased in alternative M2 macrophages in humans but not in mice. Moreover NOR1 expression is also most abundant in CD68+MR+ alternative macrophage-enriched areas of human atherosclerotic plaques in vivo. Silencing NOR1 expression in human alternative macrophages decreases the expression of a panel of M2 markers such as the Mannose Receptor (MR), Interleukin-1 receptor antagonist (IL1Ra), CD200 receptor (CD200R), coagulation factor XIII A1 polypeptide (F13A1), interleukin 10 (IL10) and the Peroxisome Proliferator-Activated Receptor (PPARg). Moreover, expression and enzymatic activity of MMP9 are induced by NOR1 silencing in M2 macrophages, a regulation confirmed in NOR1 gain of function experiments. These data identify NOR1 among the transcription factors induced during alternative differentiation of human macrophages and demonstrate that NOR1 modifies the alternative macrophage phenotype. Study of TLE1 expression and potential functions in human alternative macrophagesTLE1 is a member of the Groucho family and it is mainly described as a transciptional co-repressor. Although lacking in DNA binding activity of their own, this protein is recruited to gene promoters through interaction with other factors. No data are available regarding the expression or role of TLE1 in macrophages. Our results show that TLE1 is among the highest expressed transcriptional factors in human alternative macrophages. This regulation is verified also in murine macrophages. Histological analysis showed that TLE1 expression in human carotid atherosclerotic lesions in vivo co-localizes with the macrophage marker CD68 and the alternative maker MR. Q-PCR analysis of macrophage-enriched areas isolated by LCM showed that the mRNA levels of TLE1 are higher in zones of alternative CD68+MR+ macrophages compared to zones enriched in CD68+MR- macrophages. Moreover we have shown that TLE1 expression is higher in adipose tissue macrophages (ATM) compared to resting macrophages isolated from blood of the same patients. Finally we have characterised the mRNA expression of TLE1 in obese patients affected or not by diabetes and we have shown that TLE1 expression is influenced by the metabolic state of the patients.

L'athérosclérose est une maladie cardio-vasculaire immuno-inflammatoire se développant sur un terrain de dyslipidémie. De nombreuses composantes de la réponse immunitaire sont capables de moduler le développement des plaques d'athérome. Notamment, les lymphocytes T (LTs) CD4+ dont le rôle dans le processus athérogène dépend de la voie de polarisation. Le mécanisme de polarisation des LTs CD4+ est sous le contrôle des cellules dendritiques conventionnelles (cDCs) CD11b+. Ainsi, moduler ces cDCs et orienter la réponse adaptative vers une polarisation anti-athérogène pourraient représenter une potentielle cible thérapeutique dans la pathologie. Dans cette perspective, nous avons évalué le rôle des cDCs CD11b+ dans le développement de l'athérosclérose qui à ce jour reste totalement inexploré. Nous avons montré que la baisse du nombre des cDCs CD11b+ n'a pas d'impact sur le développement des lésions d'athérome. Cependant, nous montrons que l'absence du facteur de transcription IRF4 nécessaire au développement des cDCs CD11b+ altère le rôle anti-athérogène reconnu de l'adjuvant vaccinal à base d'aluminium (Alum). Nos données suggèrent que les cDCs CD11b+ n'ont pas d'impact direct sur le développement de l'athérosclérose, cependant, elles contrôlent l'effet athéroprotecteur de l'Alum. / Atherosclerosis is a disease characterized by arterial blood vessel thickening due to the accumulation of inflammatory cells in the arterial intima in response to cholesterol deposition. Several components of the immune response are able to modulate the development of atheromatous plaques. In particular, the role of conventional of CD4+ lymphocytes in the atherogenic process depends on their polarization pathway. The polarization mechanism of CD4+ T cells is under the control of conventional CD11b+ dendritic cells (cDCs). Thus, modulating these cDCs and orienting the adaptive response towards anti-atherogenic polarization could represent a potential therapeutic target in pathology. In this context, we evaluated the role of CD11b+ cDCs in the development of atherosclerosis which still remains totally unexplored. We have demonstrated that the decrease of the number of CD11b+ cDCs has no impact on the development of atheroma lesions. However, we show that the deletion of IRF4, the transcription factor necessary for the development of CD11b+ cDCs alters the recognized anti-atherogenic role of the aluminum-based vaccine adjuvant (Alum). However our data suggest that CD11b+ cDCs have no direct impact on the development of atherosclerosis but can control the atheroprotective effect of Alum adjuvant.

Atherosclerosis is the underlying cause for many serious cardiovascular diseases which causes over 50 % of all deaths in Sweden. Atherosclerotic plaque builds up in the vessel walls over decades that will eventually lead to a complete block of an artery or cause thrombosis when the plaque ruptures, this leads to myocardial infarction and stroke. A major contributing factor to the buildup of plaque is cholesterol, especially low density lipoprotein, LDL. LDL can oxidize and start an inflammation process and together with cells from the immune system form the basis for a plaque. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein which main function is to regulate the amount of LDL-receptors available by promoting their degradation. PCSK9 causes degradation of the receptors with the effect that more LDL is left in the blood stream. Evolocumab is a monoclonal antibody with PCSK9 as the target, with PCSK9 neutralised less LDL will be left in the blood stream which will help prevent atherosclerosis. This is a complex and expensive way of treating atherosclerosis, the primary treatment is statins and secondarily cholesterol absorbtion inhibitors, bile acid sequestrants and fibrates. The purpose of this study was to examine evolocumabs effect on cardiovascular events in high risk patients and for which patient groups it is cost-efficient. The method used was searching the medical database PubMed with the keywords “evolocumab” and “evolocumab cost-effectiveness”. 5 articles was analysed and they showed that evolocumab lowered LDL-cholesterol with 55-60 % and significantly improved the lipid profile of patients. The hazard risk was lowered by 20-25 % for serious cardiovascular events and a 10 % lower rate of death was assessed after 5 years of treatment. Since no large studies have followed up on patients for over 5 years and measured cardiovascular events and deaths it is hard to know for sure how efficient evolocumab is at preventing death. The price of evolocumab is 50 000 SEK for one year of treatment and to assess which patients should be treated proved difficult due to the facts that the Swedish national regions have a side deal with the drug manufacturer Amgen in which they get compensation if evolocumab would prove to not be cost-efficient enough and there is no fixed acceptable price per quality adjusted life year (QALY) in Sweden. / Ateroskleros är grund till många allvarliga hjärt- och kärlsjukdomar och ligger bakom mer än hälften av alla dödsfall i Sverige. Sjukdomen innebär att plack byggs upp i kärlväggarna under flera decennier och till slut täpper igen ett kärl eller brister och en blodpropp bildas vilket leder till hjärtinfarkt och stroke. En bidragande faktor till bildningen av aterosklerotiska plack är kolesterol främst i form av lågdensitetlipoprotein (LDL), oxiderat LDL bidrar till att en inflammationsprocess startar i kärlet. Proprotein konvertas subtilisin/kexin typ 9 (PCSK9) är ett protein vars uppgift är att reglera antalet LDL-receptorer genom att binda in till receptorerna och ”märka” ut dem för nedbrytning. Evolokumab är en antikropp mot PCSK9 vars effekt ökar antalet LDL-receptorer vilket i sin tur minskar mängden LDL i blodet. Evolokumab är ett nytt och dyrt läkemedel, ateroskleros behandlas istället främst med statiner men också med kolesterolabsoptionshämmare, resiner och fibrater. Syftet med arbetet var att undersöka evolokumabs effekt att minska risk för hjärt- och kärlsjukdomar samt för vilka patientgrupper det är kostnadseffektivt. Metoden som användes var att söka artiklar på PubMed med sökorden ”Evolocumab” och ”Evolocumab cost effectiveness”. Fem artiklar undersöktes och de visade att evolokumab sänker LDL-kolesterolet i blodet med 55-60 % och även andra lipidvärden förbättras betydligt. Riskminskningen att drabbas av hjärt- och kärlsjukdomar bedömdes vara 20-25 % och riskminskningen att dö till följd av dessa sjukdomar uppskattades till 10 % efter 5 års behandling för patienter med hög risk att drabbas av dessa sjukdomar. Standardbehandling med evolokumab ger en kostnad på 50 000 kr per år för läkemedlet och angående vilka patienter som bör få Evolokumab är det svårt att göra en gränsdragning då det i Sverige finns en sidoöverenskommelse som innebär att tillverkaren kompenserar landstingen om behandlingen inte är kostnadseffektiv samt att i Sverige finns inget fast värde för ett kvalitetsjusterat levnadsår (QALY).

L'inflammation chronique en réponse à l'accumulation de lipoprotéines dans la paroi artérielle est centrale dans le développement de l'athérosclérose. L’immunité innée et adaptée sont impliquées dans ce processus. Les cellules Natural Killer (NK), un des éléments clés de l'immunité innée, ont été identifiées dans les lésions athérosclérotiques humaines et murines. Bien que plusieurs études aient cherché à évaluer le rôle des cellules NK dans des modèles animaux expérimentaux d'athérosclérose, les résultats restent contradictoires, certaines rapportant des effets pro-athérogéniques, d’autres anti-athérogéniques. L'une des principales limites de ces études est le manque de spécificité dans le ciblage de la perte ou du gain de fonction des cellules NK. Nous avons utilisé deux approches génétiques sélectives pour étudier le rôle des cellules NK dans l'athérosclérose: 1) des souris Ncr1iCre/+R26lslDTA/+ dans lesquelles les cellules NK ont été déplétées 2) des souris Noé, dont les cellules NK sont hyper-réactives. Les cellules de la moelle osseuse (BM) de ces souris ont été utilisées pour reconstituer le système hématopoïétique de souris Ldlr -/- irradiées. Après une période de récupération de 4 semaines, les souris ont été mises sous un régime riche en matières grasses (HFD) pendant 8 semaines. L'analyse morphométrique de la taille des lésions ‘athérosclérose dans le sinus aortique et l'aorte thoracique n'a montré aucune différence statistiquement significative entre les 3 groupes. De plus, aucune différence n'a été observée dans la composition de la plaque en termes de teneur en collagène, d'infiltration de macrophages ou de profil immunitaire dans le sang et la rate des souris Ncr1iCreR26lsl-DTA, Noé ou contrôles. Nous avons ensuite étudié la sélectivité de des anticorps anti-asialo-GM1 dans la déplétion des cellules NK, qui avaient été utilisés précédemment pour démontrer le rôle pro-athérogène des cellules NK. Nous avons confirmé les effets non spécifiques de cet anticorps, qui déplète non seulement les cellules NK, mais aussi les lymphocytes NKT et CD8+. Enfin, pour déterminer si l'activation des cellules NK par un stimulus externe pouvait avoir des effets sur l’athérosclérose, nous avons traité les souris chimériques (souris Ldlr -/- irradiées reconstituées soit avec les cellules de moelle contrôle ou déficiente en cellules NK) avec du poly IC (un mimétique viral) pendant 8 semaines de HFD. Nous avons trouvé une réduction significative de la taille des lésions au niveau du sinus aortique et de l'aorte thoracique dans les souris déficientes en cellules NK. Nos résultats, à partir de modèles de souris spécifiques, contredisent les études antérieures et démontrent clairement que chez les souris hypercholestérolémiques, les cellules NK n'ont aucun effet direct sur l'athérosclérose, sauf si elles sont pré-stimulée, comme par exemple dans un contexte d’infection virale ou de présence de tumeurs. / Chronic inflammation is central in the development of atherosclerosis. Both innate and adaptive immunity are involved in this process. Although several studies have evaluated the functions of NK cells in experimental animal models of atherosclerosis, it is not yet clear whether NK cells behave as protective or pro-atherogenic effectors. One of the main caveats of previous studies was the lack of specificity in targeting loss- or gain-of-function of NK cells. Here, we used two selective genetic approaches to investigate the role of NK cells in atherosclerosis: 1) Ncr1iCre/+R26lslDTA/+ mice in which NK cells were depleted, 2) Noé mice in which NK cells are hyperresponsive. No difference in atherosclerotic lesion size was found in Ldlr-/- mice transplanted with bone marrow cells from Ncr1iCreR26Rlsl−DTA, Noé or WT mice. Also, no difference was observed in plaque composition in terms of collagen content, macrophage infiltration or the immune profile in blood and spleen, although Noé chimera had more IFN-y-producing NK cells in comparison with WT mice. Then, we investigated the NK cell selectivity of anti-asialo GM1 anti-serum, which was previously used to conclude to the pro-atherogenicity of NK cells. Anti-asialo GM1 treatment decreased atherosclerosis in both Ldlr-/- mice transplanted with Ncr1iCreR26Rlsl−DTA or WT BM, indicating that its anti-atherogenic effects are unrelated to NK cell depletion. Finally, to determine whether NK cells could contribute to the disease in conditions of pathological NK cell overactivation, we treated irradiated Ldlr-/- mice reconstituted with either WT or Ncr1iCreR26Rlsl−DTA BM with the viral mimic Poly(I:C) and found a significant reduction of plaque size in NK-cell deficient chimeric mice. Our findings, using state-of-the-art mouse models, clearly demonstrate that NK cells have no direct effect on the natural development of hypercholesterolemia-induced atherosclerosis, but may play a role when an additional systemic NK cell overactivation occurs.

Abstract not available

Atherosclerosis, the leading cause of mortality in Western societies, affects large elastic arteries, causing focal deposition of proliferative inflammatory and lipid-laden cells within the artery. Several risk factors have been causally implicated in the ???reaction to injury??? hypothesis first described by Ross in 1969. The ???injury??? sustained by endothelial cells may be either mechanical or chemical. Environmental factors have a role in the production of chemical agents that are injurious to the endothelium. Mechanical stresses such as wall tensile stress are proportional to systemic blood pressure and pulse pressure. Essentially, these systemic pressures are fairly evenly distributed throughout the circulation. However, atherosclerotic lesions characteristically occur at focal sites within the human vasculature; at or near bifurcations, within the ostia of branch arteries and at regions of marked or complex curvature, where local haemodynamic abnormalities occur. The most discussed haemodynamic factor seems to be low or highly oscillating wall shear stress which exists on the outer wall of bifurcations and on the inner aspect of curving vessels. The magnitude of these haemodynamic forces may not be great but the subtleties of their variable spatial distribution may help to explain the multifocal distribution of atherosclerotic plaques. With the altered haemodynamics there is endothelial injury and phenotypic changes in the endothelium result, which in turn lead to endothelial cell dysfunction. These haemodynamic variables are difficult to measure directly in vivo. In this work a novel model is developed utilising human autologous vein bypass grafts as a surrogate vessel for the observation of pathological structural changes in response to altered haemodynamics. The influence of haemodynamic factors (such as wall shear stress) in the remodeling of the vein graft wall and the pathogenesis of Myointimal Hyperplasia (MIH) and resultant wall thickening in femoral bypass grafts is analysed. The haemodynamic determinants of MIH (which have been established in many animal models) are similar to those implicated in atherosclerosis. The accelerated responses of the vein (Intimal hyperplasia develops much more rapidly than atherosclerotic lesions in native vessels) make it an ideal model to expediently examine the hypothesised relationships prospectively in an in vivo setting. Furthermore, the utilisation of in vivo data acquired from non-invasive diagnostic methods (such as Magnetic Resonance Angiography (MRA) and Duplex ultrasound) combined with the application of state-of-the-art Computational Fluid Dynamic (CFD) techniques makes the model essentially non-invasive. The following hypotheses are examined: 1) regions of Low shear and High tensile stress should develop disproportionately greater wall thickening, 2) regions of greater oscillatory blood flow should develop greater wall thickening, and 3) regions of lower wall shear should undergo inward (or negative) remodelling and result in a reduction in vessel calibre. The conclusions reached are that abnormal haemodynamic forces, namely low Time-averaged Wall Shear Stress, are associated with subsequent wall thickening. These positive findings have great relevance to the understanding of vein graft MIH and atherosclerosis. It was also evident that with non-invasive data and CFD techniques, some of the important haemodynamic factors are realistically quantifiable (albeit indirectly). The detection of parameters known to be causal in the development of graft intimal hyperplasia or other vascular pathology may improve ability to predict clinical problems. From a surgical perspective this might be employed to facilitate selection of at-risk grafts for more focused postoperative surveillance and reintervention. On a broader stage the utilisation of such analyses may be useful in predicting individuals at greater risk of developing atherosclerotic deposits, disease progression, and the likelihood of clinical events such as heart attack, stroke and threat of limb loss.

Today’s rapid development of powerful tools for geneexpression analysis provides unprecedented resources forelucidating complex molecular events. The objective of this workhas been to apply, combine andevaluate tools for analysis of differential gene expressionusing atherosclerosis as a model system. First, an optimisedsolid-phase protocol for representational difference analysis(RDA) was applied to twoin vitromodel systems. Initially, The RDA enrichmentprocedure was investigated by shotgun cloning and sequencing ofsuccessive difference products. In the subsequent steps,combinations of RDA and microarray analysis were used tocombine the selectivity and sensitivity of RDA with thehigh-throughput nature of microarrays. This was achieved byimmobilization of RDA clones onto microarrays dedicated forgene expression analysis in atherosclerosis as well ashybridisation of labelled RDA products onto global microarrayscontaining more than 32,000 human clones. Finally, RDA wasapplied for the investigation of the focal localisation ofatherosclerotic plaques in mice usingin vivotissue samples as starting material. A large number of differentially expressed clones wereisolated and confirmed by real time PCR. A very diverse rangeof gene fragments was identified in the RDA products especiallywhen they were screened with global microarrays. However, themicroarray data also seem to contain some noise which is ageneral problem using microarrays and should be compensated forby careful verification of the results. Quite a large number of candidate genes related to theatherosclerotic process were found by these studies. Inparticular several nuclear receptors with altered expression inresponse to oxidized LDL were identified and deserve furtherinvestigation. Extended functional annotation does not liewithin the scope of this thesis but raw data in the form ofnovel sequences and accession numbers of known sequences havebeen made publicly available in GenBank. Parts of the data arealso available for interactive exploration on-line through aninteractive software tool. The data generated thus constitute abase for new hypotheses to be tested in the field ofatherosclerosis. <b>Keywords:</b>representational difference analysis, geneexpression profiling, microarray analysis, atherosclerosis,foam cell formation

Background Anthropometric measurements are useful in clinical practice since they are non-invasive and cheap. Previous studies suggest that sagittal abdominal diameter (SAD) may be a better measure of visceral fat depots. The aim of this study was to prospectively explore and compare how laboratory and anthropometric risk markers predicted subclinical organ damage in 255 patients, with type 2 diabetes, after four years. Methods Baseline investigations were performed in 2006 and were repeated at follow-up in 2010. Carotid intima-media thickness (IMT) was evaluated by ultrasonography and aortic pulse wave velocity (PWV) was measured with applanation tonometry over the carotid and femoral arteries at baseline and at follow-up in a cohort of subjects with type 2 diabetes aged 55–65 years old. Results There were significant correlations between apolipoprotein B (apoB) (r = 0.144, p = 0.03), C - reactive protein (CRP) (r = 0.172, p = 0.009) at baseline and IMT measured at follow-up. After adjustment for sex, age, treatment with statins and Hba1c, the associations remained statistically significant. HbA1c, total cholesterol or LDL-cholesterol did not correlate to IMT at follow-up. Baseline body mass index (BMI) (r = 0.130, p = 0.049), waist circumference (WC) (r = 0.147, p = 0.027) and sagittal Abdominal Diameter (SAD) (r = 0.184, p = 0.007) correlated to PWV at follow-up. Challenged with sex, SBP and HbA1c, the association between SAD, not WC nor BMI, and PWV remained statistically significant (p = 0.036). In a stepwise linear regression, entering both SAD and WC, the association between SAD and PWV was stronger than the association between WC and PWV. Conclusions We conclude that apoB and CRP, but not LDL-cholesterol predicted subclinical atherosclerosis. Furthermore, SAD was more independent in predicting arterial stiffness over time, compared with WC, in middle-aged men and women with type 2 diabetes. / <p>Funding Agencies|Medical Research Council of Southeast Sweden||Center for Medical Image Science and Visualization (CMIV)||Linkoping University||Futurum||King Gustaf V and Queen Victoria Freemason Foundation||GE Healthcare||Swedish Heart-Lung Foundation||Swedish Research Council Grant|12661|</p>

Das humane CD90 (Thy-1), ein membrangebundenes Glykoprotein, wird auf der Oberfläche von aktivierten mikrovaskulären Endothelzellen (EC), Fibroblasten, Nervenzellen und einer Subpopulation von CD34+ hämatopoetischen Stammzellen exprimiert. CD90 fungiert als Adhäsionsmolekül auf aktivierten mikrovaskulären EC, indem es die Bindung von Leukozyten über die Interaktion mit dem Integrin alfambeta2 (Mac-1, CD11b/CD18) oder dem Adhäsions-GPCR CD97 an das Endothel vermittelt. Die Expression von CD90 auf mikrovaskulären EC wurde sowohl in-vitro als auch in-vivo nachgewiesen. Zur Expression von CD90 auf makrovaskulären EC gibt es nur wenige und sich zum Teil widersprechende in-vitro Daten. In-situ konnte die Expression von CD90 auf diesen Zellen bisher nicht gezeigt werden. Die Atherosklerose ist ein stufenweise verlaufendes chronisch-entzündliches Geschehen in den arteriellen Gefäßen. In der vorliegenden Arbeit wurde in atherosklerotisch-veränderten Gefäßen die Expression von CD90 auf humanen makrovaskulären EC in-situ demonstriert. Dabei wurden neben Operationspräparaten von Patienten mit einer Stenose der A. carotis interna, die entsprechend der American Heart Association Klassifikation die höchsten Atherosklerosestadien zeigen, auch Gefäßtransplantate von Organspendern, die meist nur eine geringe Ausprägung der Atherosklerose aufwiesen, untersucht. CD90 wurde in jedem Atherosklerosestadium auf EC nachgewiesen. Eine signifikante Zunahme der CD90 Expression in höheren Atherosklerosestadien konnte gezeigt werden. Die histologischen Merkmale der Plaque, wie Verkalkung, Blutung, Plaqueruptur oder Thrombusformation korrelieren nicht mit der CD90 Expression. Ein statistisch signifikanter Zusammenhang zwischen symptomatischer und asymptomatischer A.carotis interna-Stenose konnte bezüglich der CD90 Expression auf makrovaskulären EC ebenfalls nicht nachgewiesen werden. Weiterhin sollte mittels Stimulationsversuchen in-vitro geklärt werden, wie die CD90 Expression auf makrovaskulären EC im Rahmen der Atherosklerose auf den makrovaskulären EC reguliert wird. Denkbar ist, dass Zytokine, die eine Rolle im atherosklerotischen Prozess spielen, einen Einfluss auf die CD90 Expression ausüben. Deshalb wurde die Expression von CD90 auf makrovaskulären EC nach Stimulation mit proinflammatorischen Zytokinen untersucht. Die Expression von CD90 konnte in-vitro durch pro-inflammatorische Zytokine tendenziell erhöht werden. Die Stimulation mit CXCL12, einem bedeutsamen Trigger der Mobilisation der endothelialen Vorläuferzellen, der in atherosklerotischen, aber nicht in gesunden Gefäßen nachweisbar ist, bewirkte einen signifikanten Anstieg der CD90 Expression. Durch die Stimulation mit den lipid-beladenen Schaumzellen, die zahlreich in atherosklerotischen Läsionen vorhanden sind, konnte die CD90 Expression eher reduziert werden. Da Diabetes mellitus mit einem früheren Auftreten einer Atherosklerose assoziiert ist, wurden die makrovaskulären EC auch mit D-Glukose inkubiert. Dies führte ebenfalls zur tendenziellen Reduktion der CD90 Expression. Zusammenfassend konnte in der vorliegenden Arbeit die CD90-Expression auf den makrovaskulären EC in-situ eindeutig demonstriert werden. Im Rahmen der Atherosklerose nimmt CD90-Expression auf den makrovaskulären EC in den höheren Atherosklerosestadien zu. Eine tendenzielle Zunahme der CD90 Expression nach Stimulation mit proinflammatorischen Zytokinen, die an der Atheroskleroseentwicklung beteiligt sind, sowie eine signifikante Hochregulation der CD90 Expression nach Stimulation mit einem Trigger der EPC-Migration, dem CXCL12, konnte in dieser Arbeit gezeigt werden. Die Ergebnisse deuten auf eine wichtige Rolle des CD90 auf makrovaskulären EC in dem atherosklerotischen Prozess hin. Die publizierten Daten zeigen, dass CD90 in die Leukozytenmigration durch das aktivierte mikrovaskuläre Endothel involviert ist. In der vorliegenden Arbeit konnte jedoch nicht eindeutig nachgewiesen werden, welche Funktion das CD90 auf makrovaskulären EC besitzt. Hierbei ergaben sich zusammenfassend zwei an sich unterschiedliche Hypothesen. Zum einen zeigt die tendenzielle Zunahme der CD90-Expression nach Stimulation mit proinflammatorischen Zytokinen, dass CD90 an der Migration der neutrophilen Granulozyten und somit z.B. durch die Freisetzung von MMP-9 an der Destruktion der Plaque beteiligt sein kann. Zum anderen könnte man behaupten, dass die signifikante Hochregulation der CD90-Expression nach Stimulation mit dem CXCL12 auf die Beteiligung des CD90 an der EPC-Migration hindeutet. Somit könnte CD90 durch die EPC-Migration sowie z.B. zusätzlich durch die eingewanderten neutrophilen Granulozyten, welche den Zelldebris phagozytieren, in die Neointimaformation involviert sein. Um eine sichere Aussage diesbezüglich treffen zu können sind weitere Untersuchungen notwendig.

The O’Brien lab has demonstrated that Heat shock protein 27 (HSP27)shows attenuated expression in human coronary arteries as the degree of atherosclerosis progresses. Moreover, over-expression of HSP27 reduces atherogenesis in mice. The precise mechanism(s) for HSP27-mediated "atheroprotection" are incompletely understood. Nuclear Factor-kappaB (NF-κB) is a key signaling modulator in atherogenesis. Hence, this project sought to determine if recombinant HSP27 (rHSP27) alters NF-κB signaling to affect atheroprotection. Treatment of THP1 macrophages with rHSP27 resulted in degradation of IκBα, coincided with nuclear translocation of the p65 subunit and produced transcriptional evidence of activation of NF-κB signaling. When the transcriptional profile of THP1 macrophages treated with rHSP27 was analyzed using NF-κB-pathway-specific qRT-PCR arrays, among the regulated genes, IL-10 and GM-CSF mRNA levels were markedly increased, as were parallel translational effects observed. These data provide new mechanistic insights into the atheroprotective effects of HSP27.