Rozprawy doktorskie na temat „Coronary vasculature”

Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Physiology, 1997?
"Running title: Perhexiline: effects on vasculature, contractility and the role of endothelium." Includes bibliographical references.

While previous research into the pathogenesis of ischaemic and reperfusion injuries has focussed on the cardiac myocyte, there is increasing evidence for a crucial role for coronary vascular injury in the genesis of the post-ischaemic phenotype [1-3]. Post-ischaemic vascular injury may be manifest as a transient or sustained loss of competent vessels, impairment of vascular regulatory mechanisms, and ultimately as the 'no-reflow' phenomenon (inability to sufficiently reperfuse previously ischaemic tissue despite the removal of the initial obstruction or occlusion). It is now appreciated that the earliest distinguishing feature of various forms of vascular injury (including atherosclerosis and infarction) is 'endothelial dysfunction', which is the marked reduction in endothelial-dependent relaxation due to reduced release or action of endothelial nitric oxide (NO). Importantly, vascular injury may worsen myocardial damage in vivo [4,5], significantly limiting tissue salvage and recovery. The pathogenesis of post-ischaemic vascular injury and endothelial dysfunction is incompletely understood, but has generally been considered to reflect a cardiovascular inflammatory response, neutrophils playing a key role. However, while blood-borne cells and inflammatory elements are undoubtedly involved in the 'progression' of vascular injury [6,7], accumulating evidence indicates that they are not the primary 'instigators' [8]. It should be noted that a wealth of controversial findings exists in the vascular injury literature and mechanisms involved remain unclear. Indeed, multiple mechanisms are likely to contribute to post-ischaemic vascular injury. Adenosine receptors are unique in playing a role in physical regulation of coronary function, and also in attenuating injury during and following ischaemia. While the adenosine receptor system has been extensively investigated in terms of effects on myocardial injury [9,10], little is known regarding potential effects of this receptor system on post-ischaemic coronary vascular injury. This thesis initially attempts to further our understanding of the role of adenosine in normal coronary vascular function, subsequent chapters assess the effect of ischaemia-reperfusion on vascular function, and adenosine receptor modification of vascular dysfunction in the isolated asanguinous mouse heart. Specifically, in Chapter 3 the receptor subtype and mechanisms involved in adenosine-receptor mediated coronary vasodilation were assessed in Langendorff perfused mouse and rat hearts. The study revealed that A2A adenosine receptors (A2AARs) mediate coronary dilation in the mouse vs. A2B adenosine receptors (A2BARs) in rat. Furthermore, responses in mouse involve a sensitive endothelial-dependent (NO-dependent) response and NO-independent (KATP-mediated) dilation. Interestingly, the ATP-sensitive potassium channel component predominates over NO-dependent dilation at moderate to high agonist levels. However, the high-sensitivity NO-dependent response may play an important role under physiological conditions when adenosine concentrations and the level of A2AAR activation are low. In Chapter 4 the mechanisms regulating coronary tone under basal conditions and during reactive hyperaemic responses were assessed in Langendorff perfused mouse hearts. The data support a primary role for KATP channels and NO in mediating sustained elevations in flow, irrespective of occlusion duration (5-40 s). However, KATP channels are of primary importance in mediating initial flow adjustments after brief (5-10 s) occlusions, while KATP (and NO) independent processes are increasingly important with longer (20-40 s) occlusion. Evidence is also presented for compensatory changes in KATP and/or NO mediated dilation when one pathway is blocked, and for a modest role for A2AARs in reactive hyperaemia. In Chapter 5 the impact of ischaemia-reperfusion on coronary function was examined, and the role of A1 adenosine receptor (A1AR) activation by endogenous adenosine in modifying post-ischaemic vascular function was assessed in isolated buffer perfused mouse hearts. The results demonstrate that ischaemia does modify vascular control and signficantly impairs coronary endothelial dilation in a model devoid of blood cells. Additionally, the data indicate that post-ischaemic reflow is significantly determined by A2AAR activation by endogenous adenosine, and that A1AR activation by endogenous adenosine protects against this model of vascular injury. Following from Chapter 5, the potential of A1, A2A and A3AR activation by exogenous and endogenous agonists to modulate post-ischaemic vascular dysfunction was examined in Chapter 6. Furthermore, potential mechanisms involved injury and protection were assessed by comparing effects of adenosine receptors to other 'vasoprotective' interventions, including anti-oxidant treatment, Na+/H+ exchange (NHE) inhibition, endothelin (ET) antagonism, and 2,3-butanedione monoxime (BDM). The data acquired confirm that post-ischaemic endothelial dysfunction is reduced by intrinsic A1AR activation, and also that exogenous A3AR activation potently reduces vascular injury. Protection appears unrelated to inhibition of ET or oxidant stress. However, preliminary data suggest A3AR vasoprotection may share signalling with NHE inhibition. Finally, the data reveal that coronary reflow in isolated buffer perfused hearts is not a critical determinant of cardiac injury, suggesting independent injury processes in post-ischaemic myocardium vs. vasculature. Collectively, these studies show that adenosine has a significant role in regulating coronary vascular tone and reactive hyperaemic responses via NO and KATP dependent mechanisms. Ischaemia-reperfusion modifies vascular control and induces significant endothelial dysfunction in the absence of blood, implicating neutrophil independent injury processes. Endogenous adenosine affords intrinsic vasoprotection via A1AR activation, while adenosinergic therapy via exogenous A3AR activation represents a new strategy for directly protecting against post-ischaemic vascular injury.

Introduction: Failure of coronary blood vessels to adequately supply cardiac myocytes with oxygen underlies ischaemic heart disease and ultimately myocardial infarction. Therefore, it is important to determine the factors that regulate coronary blood flow. Activation of Ca2+-activated chloride channels depolarises vascular smooth muscle cells sufficiently to cause Ca2+ influx through voltage-dependent channels and contraction of the cell. TMEM16A is the main molecular candidate for these channels. Hypothesis: TMEM16A is expressed in rat coronary arteries where it regulates vascular smooth muscle contraction. In coronary arteries from hypertensive rats the level of expression, and function of TMEM16A is altered. Methods: Quantitative polymerase chain reaction and immunodetection techniques assessed TMEM16A expression. Whole-cell patch clamp techniques were used to measure currents from freshly isolated rat coronary artery vascular smooth muscle cells (VSMCs). Wire myography and Langendorff perfused heart setup assessed coronary artery contractility and coronary blood flow respectively. Microelectrode impalement of rat coronary artery segments were combined with wire myography for membrane potential measurements. Results: TMEM16A was identified at mRNA and protein levels in rat coronary artery smooth muscle and TMEM16A-specific blockers attenuated the vasoconstricting effects of U46619 and 5-HT. These pharmacological agents also reduced the membrane depolarising effects of U46619 in sharp microelectrode studies and enhanced coronary flow in Langendorff set-ups. TMEM16A transcript was increased in coronary arteries from spontaneously hypertensive rats while the sensitivity to U46619 and 5HT was also increased in these vessels. This increased sensitivity was diminished in the presence of a novel TMEM16A inhibitor. Conclusion: TMEM16A is expressed in rat coronary arteries, where chloride is essential for optimal contraction and novel inhibitors of TMEM16A drastically effect vascular function. The expression of TMEM16A, contractility, and sensitivity to novel inhibitors of TMEM16A are all altered in coronary arteries from hypertensive rats.

While previous research into the pathogenesis of ischaemic and reperfusion injuries has focussed on the cardiac myocyte, there is increasing evidence for a crucial role for coronary vascular injury in the genesis of the post-ischaemic phenotype [1-3]. Post-ischaemic vascular injury may be manifest as a transient or sustained loss of competent vessels, impairment of vascular regulatory mechanisms, and ultimately as the 'no-reflow' phenomenon (inability to sufficiently reperfuse previously ischaemic tissue despite the removal of the initial obstruction or occlusion). It is now appreciated that the earliest distinguishing feature of various forms of vascular injury (including atherosclerosis and infarction) is 'endothelial dysfunction', which is the marked reduction in endothelial-dependent relaxation due to reduced release or action of endothelial nitric oxide (NO). Importantly, vascular injury may worsen myocardial damage in vivo [4,5], significantly limiting tissue salvage and recovery. The pathogenesis of post-ischaemic vascular injury and endothelial dysfunction is incompletely understood, but has generally been considered to reflect a cardiovascular inflammatory response, neutrophils playing a key role. However, while blood-borne cells and inflammatory elements are undoubtedly involved in the 'progression' of vascular injury [6,7], accumulating evidence indicates that they are not the primary 'instigators' [8]. It should be noted that a wealth of controversial findings exists in the vascular injury literature and mechanisms involved remain unclear. Indeed, multiple mechanisms are likely to contribute to post-ischaemic vascular injury. Adenosine receptors are unique in playing a role in physical regulation of coronary function, and also in attenuating injury during and following ischaemia. While the adenosine receptor system has been extensively investigated in terms of effects on myocardial injury [9,10], little is known regarding potential effects of this receptor system on post-ischaemic coronary vascular injury. This thesis initially attempts to further our understanding of the role of adenosine in normal coronary vascular function, subsequent chapters assess the effect of ischaemia-reperfusion on vascular function, and adenosine receptor modification of vascular dysfunction in the isolated asanguinous mouse heart. Specifically, in Chapter 3 the receptor subtype and mechanisms involved in adenosine-receptor mediated coronary vasodilation were assessed in Langendorff perfused mouse and rat hearts. The study revealed that A2A adenosine receptors (A2AARs) mediate coronary dilation in the mouse vs. A2B adenosine receptors (A2BARs) in rat. Furthermore, responses in mouse involve a sensitive endothelial-dependent (NO-dependent) response and NO-independent (KATP-mediated) dilation. Interestingly, the ATP-sensitive potassium channel component predominates over NO-dependent dilation at moderate to high agonist levels. However, the high-sensitivity NO-dependent response may play an important role under physiological conditions when adenosine concentrations and the level of A2AAR activation are low. In Chapter 4 the mechanisms regulating coronary tone under basal conditions and during reactive hyperaemic responses were assessed in Langendorff perfused mouse hearts. The data support a primary role for KATP channels and NO in mediating sustained elevations in flow, irrespective of occlusion duration (5-40 s). However, KATP channels are of primary importance in mediating initial flow adjustments after brief (5-10 s) occlusions, while KATP (and NO) independent processes are increasingly important with longer (20-40 s) occlusion. Evidence is also presented for compensatory changes in KATP and/or NO mediated dilation when one pathway is blocked, and for a modest role for A2AARs in reactive hyperaemia. In Chapter 5 the impact of ischaemia-reperfusion on coronary function was examined, and the role of A1 adenosine receptor (A1AR) activation by endogenous adenosine in modifying post-ischaemic vascular function was assessed in isolated buffer perfused mouse hearts. The results demonstrate that ischaemia does modify vascular control and signficantly impairs coronary endothelial dilation in a model devoid of blood cells. Additionally, the data indicate that post-ischaemic reflow is significantly determined by A2AAR activation by endogenous adenosine, and that A1AR activation by endogenous adenosine protects against this model of vascular injury. Following from Chapter 5, the potential of A1, A2A and A3AR activation by exogenous and endogenous agonists to modulate post-ischaemic vascular dysfunction was examined in Chapter 6. Furthermore, potential mechanisms involved injury and protection were assessed by comparing effects of adenosine receptors to other 'vasoprotective' interventions, including anti-oxidant treatment, Na+/H+ exchange (NHE) inhibition, endothelin (ET) antagonism, and 2,3-butanedione monoxime (BDM). The data acquired confirm that post-ischaemic endothelial dysfunction is reduced by intrinsic A1AR activation, and also that exogenous A3AR activation potently reduces vascular injury. Protection appears unrelated to inhibition of ET or oxidant stress. However, preliminary data suggest A3AR vasoprotection may share signalling with NHE inhibition. Finally, the data reveal that coronary reflow in isolated buffer perfused hearts is not a critical determinant of cardiac injury, suggesting independent injury processes in post-ischaemic myocardium vs. vasculature. Collectively, these studies show that adenosine has a significant role in regulating coronary vascular tone and reactive hyperaemic responses via NO and KATP dependent mechanisms. Ischaemia-reperfusion modifies vascular control and induces significant endothelial dysfunction in the absence of blood, implicating neutrophil independent injury processes. Endogenous adenosine affords intrinsic vasoprotection via A1AR activation, while adenosinergic therapy via exogenous A3AR activation represents a new strategy for directly protecting against post-ischaemic vascular injury.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Health Sciences
Full Text

Background: Research in heart disease can be aided by modelling myocardial hemodynamics with knowledge of coronary pressure and vascular resistance measured from the geometry and morphometry of coronary vasculature. This study presents methods to automatically reconstruct accurate detailed coronary vascular anatomical models from high-resolution three-dimensional optical fluorescence cryomicrotomography image volumes for simulating blood flow in coronary arterial trees. Methods: Images of fluorescent cast and bead particles perfused into the same heart comprise the vasculature and microsphere datasets, employed in a novel combined approach to measure vasculature and simulate a flow model on the extracted coronary vascular tree for estimating regional myocardial perfusion. The microspheres are used in two capacities - as fiducial biomarker point sources for measuring the image formation in order to accurately measure the vasculature dataset and as flowing particles for measuring regional myocardial perfusion through the reconstructed vasculature. A new model-based template-matching method of vascular radius estimation is proposed that incorporates a model of the optical fluorescent image formation measured from the microspheres and a template of the vessels’ tubular geometry. Results: The new method reduced the error in vessel radius estimation from 42.9% to 0.6% in a 170 micrometer vessel as compared to the Full-Width Half Maximum method. Whole-organ porcine coronary vascular trees, automatically reconstructed with the proposed method, contained on the order of 92,000+ vessel segments in the range 0.03 – 1.9 mm radius. Discrepancy between the microsphere perfusion measurements and regional flow estimated with a 1-D steady state linear static blood flow simulation on the reconstructed vasculature was modelled with daughter-to-parent area ratio and branching angle as the parameters. Correcting the flow simulation by incorporating this model of disproportionate distribution of microspheres reduced the error from 24% to 7.4% in the estimation of fractional microsphere distribution in oblique branches with angles of 100°-120°.

Cardiovascular disease (CVD) is the leading cause of death for people of most ethnicities on a global scale, and countless research efforts on the pathology of CVD has been well-characterized over the years. However, advancement in modern technologies, such as nanotechnology, has generated environmental and occupational health concerns within the scientific community. Current investigation of nanotoxicity calls into question the negative effects nanomaterials may invoke from their environmental, commercial, and therapeutic usage. As a result, further research is needed to investigate and characterize the toxicological implications associated with nanomaterial-exposure and CVD. We investigated the toxicity of multi-walled carbon nanotubes (MWCNT) and titanium dioxide (TiO2), which are two prominently used nanomaterials that have been previously linked to upregulation of inflammatory and atherogenic factors. However, the mechanistic pathways involved in these nanomaterials mediating detrimental effects on the heart and/or coronary vasculature have not yet been fully determined. Thus, we utilized two different routes of exposure in rodent models to assess alterations in proinflammatory and proatherogenic signaling pathways, which are represented in contrast throughout the dissertation. In our MWCNT study, we used C57Bl/6 mice exposed to MWCNTs (1 mg/m3) or filtered air (FA-Controls), via inhalation, for 6 hr/d for 14d. Conversely, intravenous TiO2 was administered to F344 male fisher rats, following 24h and 28d post-exposure to a single injection of TiO2-NPs (1 mg/kg), compared to control animals. MWCNT-exposed endpoints investigated the alterations in cholesterol transport, such as lectin-like oxidized low-density lipoprotein receptor (LOX)-1 and ATP-binding cassette transporter (ABCA)-1, inflammatory markers [tumor necrosis factor (TNF)-α], interleukin (IL)-1β/IL-6, nuclear-factor kappa-light-chain-enhancer of activated B cells (NF-κB) and signaling factors involved in activation of the pathway, as well as intracellular/vascular adhesion molecule(s) (VCAM-1, ICAM-1), and miRNAs (miR-221/-21/-1), associated with CVD, were analyzed in cardiac tissue and coronary vasculature. Cardiac fibrotic deposition, matrix-metalloproteinases (MMP)-2/9, and reactive oxygen species (ROS) were also assessed. TiO2-exposure endpoints also involved alterations on cholesterol transport proteins via LOX-1 and ABCA-1, factors of inflammation, namely intracellular macrophages and interleukin (IL)-1β, MMP-2/9 activity and protein expression, fibrotic deposition, and ROS generation were analyzed via quantitative detection or histologically in both cardiac tissue and coronary vasculature. Results from both studies found alterations in fibrotic deposition, upregulation in LOX-1 expression and MMP-2/9 activity, and ROS generation; with a concurrent decrease in ABCA-1 expression in cardiac tissue and coronary vasculature. Individually, MWCNT-exposed endpoints had shown induction of cardiac TNF-α, MMP-9, IκB Kinase (IKK)-α/β, and miR-221 mRNAs; as well as increased coronary expression of TNF-α and VCAM-1. TiO2 studies found increases in IL-1β and MMP-9 protein expression, as well as intracellular macrophage induction. Both studies also found, through pre-treatment of NADPH oxidase inhibitor, apocynin, resulted in attenuation of nanomaterial-exposure mediated ROS production; with nitric oxide synthase inhibitor, L-NNA, also showing attenuation, but only in our MWCNT-exposed inhalation study. The results from both studies have demonstrated, through different routes of administration, exposures, and rodent models; that exposure to nanomaterials can mediate signaling pathways involved in initiation and/or progression of CVD.

Statins induce beneficial vascular effects. How statins induce beneficial vascular effects is yet to be determined. Here we examine Simvastatin and vascular endothelial growth factor (VEGF) acting through the phosphoinositide 3-kinase (PI3K) pathway in human coronary artery endothelial cells (HCAEC). While Simvastatin and VEGF both activated mediators in the PI3K pathway, the proteins and the rates of activation were not always consistent. This suggests that although Simvastatin and VEGF share a common PI3K pathway in HCAEC and similar vascular effects, the agonists diverge in the induction of cellular signaling cascades. Simvastatin also was shown to induce phosphoinositide 3, 4, 5-triphosphate (PIPS) organization and PI3K p110 gamma (y) perinuclear localization. Beneficial, non-lipid lowering effects of statins may occur through the PI3K pathway through activation of distinct mediators from those of VEGF. Better understanding of the pathways associated with statins is necessary for the discovery of better treatments for cardiovascular disease (CVD).
Department of Biology

Le cil primaire est un organite présent à la surface de la plupart des cellules de Vertébrés. Il participe à l’organogénèse en régulant l’activité de voies de signalisation comme la voie Hedgehog. Une dysfonction du cil primaire mène à des maladies rares, sévères et pléiotropiques, les ciliopathies, qui peuvent inclure des défauts cardiaques. Cependant, le rôle que le cil primaire joue dans la morphogénèse cardiaque est encore mal compris. Le projet principal de la thèse porte sur l’étude du rôle du cil primaire des cellules cardiaques dans le développement du cœur. Dans ce but, nous avons utilisé un modèle murin de délétion conditionnelle de Ift20, un gène essentiel pour la ciliogénèse. La délétion est contrôlée par l’allèle Mesp1Cre exprimé dans la plupart des précurseurs précoces cardiaques. A la naissance, les mutants conditionnels présentent des défauts importants de septation des voies efférentes et des chambres cardiaques, les oreillettes et les ventricules. Ces défauts sont similaires à ceux caractérisés dans les mutants de la voie Hedgehog. Nous avons également identifié de nouveaux phénotypes associés à la suppression du cil. Les mutants présentent une augmentation significative de la taille du ventricule droit et des malformations du réseau de vascularisation coronaire. Pour mieux comprendre la cause des défauts de croissance observés à la naissance, nous avons analysé les comportements cellulaires sous-jacents. Aucune différence significative des taux de prolifération, de la taille et de la proportion des types cellulaires n’a été détectée au stade prénatal, suggérant que ces défauts ont une origine développementale plus précoce. Des expériences sont en cours pour déterminer les mécanismes moléculaires des défauts observés. Dans le cadre d’une collaboration avec le laboratoire de Julien Vermot, à Strasbourg, nous avons étudié le rôle du cil primaire dans le développement du proépicarde, un organe précurseur de l’épicarde du cœur mature. Nous avons montré que les embryons mutants Ift20 constitutifs présentent une augmentation significative du volume du proépicarde. Des analyses sont en cours pour identifier les voies de signalisation impliquées dans ce phénotype. Les travaux effectués durant ce projet de thèse ont permis de caractériser de nouveaux rôles du cil primaire dans le développement cardiaque. Nos résultats participent à une meilleure compréhension des ciliopathies et des défauts cardiaques qui leur sont associés
The primary cilium is an organelle present at the surface of most of Vertebrate cells. It is involved in organogenesis by regulating signalling pathways such as Hedgehog signalling. Primary cilium dysfunction leads to severe, rare and pleiotropic diseases, ciliopathies, which can include cardiac defects. Howevr, the role that the primary cilia plays in cardiac morphogenesis is still poorly understood. The main project of the PhD focuses on the study of the role of primary cilia in cardiac cells during heart development. We have used a mouse mode of conditional deletion of Ift20, a gene essential for ciliogenesis. The deletion is controlled by the Mesp1Cre allele, expressed in the majority of cardiac precursors. At birth, conditional mutants display severe defects in septation of the outflow tract, the atria and the ventricles. These defects are similar to the ones characterized in Hedgehog signalling mutants. We also have identified novel phenotypes linked to cilium suppression. The mutants display a significant increase in the size of the right ventricle and defective coronary vasculature development. To better understand the growh defects observed at birth, we analysed the underlying cell behaviour. No significant differences in the proliferation rates, nor in the size and proportions of different cell types were detected at prenatal stages, suggesting that these defects have an earlier developmental origin. Experiments are underway to determine the molecular mechanisms of the observed defects. In collaboration with the laboratory of Julien Vermot, in Strasbourg, we studied the role of the primary cilium in the development of the proepicardium, a precursor organ of the mature epicardium. We have shown that Ift20 constitutive mutants show a significant increase in proepicardial volume. Analyses are ongoing to identify the signalling pathways involved in this phenotype. The works performed during this PhD project allowed the characterization of new roles for the primary cilium in cardiac development. Our results participate in a better understanding of ciliopathies and their associated cardiac defects

Le cil primaire est un organite présent à la surface de la plupart des cellules de Vertébrés. Il participe à l’organogénèse en régulant l’activité de voies de signalisation comme la voie Hedgehog. Une dysfonction du cil primaire mène à des maladies rares, sévères et pléiotropiques, les ciliopathies, qui peuvent inclure des défauts cardiaques. Cependant, le rôle que le cil primaire joue dans la morphogénèse cardiaque est encore mal compris. Le projet principal de la thèse porte sur l’étude du rôle du cil primaire des cellules cardiaques dans le développement du cœur. Dans ce but, nous avons utilisé un modèle murin de délétion conditionnelle de Ift20, un gène essentiel pour la ciliogénèse. La délétion est contrôlée par l’allèle Mesp1Cre exprimé dans la plupart des précurseurs précoces cardiaques. A la naissance, les mutants conditionnels présentent des défauts importants de septation des voies efférentes et des chambres cardiaques, les oreillettes et les ventricules. Ces défauts sont similaires à ceux caractérisés dans les mutants de la voie Hedgehog. Nous avons également identifié de nouveaux phénotypes associés à la suppression du cil. Les mutants présentent une augmentation significative de la taille du ventricule droit et des malformations du réseau de vascularisation coronaire. Pour mieux comprendre la cause des défauts de croissance observés à la naissance, nous avons analysé les comportements cellulaires sous-jacents. Aucune différence significative des taux de prolifération, de la taille et de la proportion des types cellulaires n’a été détectée au stade prénatal, suggérant que ces défauts ont une origine développementale plus précoce. Des expériences sont en cours pour déterminer les mécanismes moléculaires des défauts observés. Dans le cadre d’une collaboration avec le laboratoire de Julien Vermot, à Strasbourg, nous avons étudié le rôle du cil primaire dans le développement du proépicarde, un organe précurseur de l’épicarde du cœur mature. Nous avons montré que les embryons mutants Ift20 constitutifs présentent une augmentation significative du volume du proépicarde. Des analyses sont en cours pour identifier les voies de signalisation impliquées dans ce phénotype. Les travaux effectués durant ce projet de thèse ont permis de caractériser de nouveaux rôles du cil primaire dans le développement cardiaque. Nos résultats participent à une meilleure compréhension des ciliopathies et des défauts cardiaques qui leur sont associés
The primary cilium is an organelle present at the surface of most of Vertebrate cells. It is involved in organogenesis by regulating signalling pathways such as Hedgehog signalling. Primary cilium dysfunction leads to severe, rare and pleiotropic diseases, ciliopathies, which can include cardiac defects. Howevr, the role that the primary cilia plays in cardiac morphogenesis is still poorly understood. The main project of the PhD focuses on the study of the role of primary cilia in cardiac cells during heart development. We have used a mouse mode of conditional deletion of Ift20, a gene essential for ciliogenesis. The deletion is controlled by the Mesp1Cre allele, expressed in the majority of cardiac precursors. At birth, conditional mutants display severe defects in septation of the outflow tract, the atria and the ventricles. These defects are similar to the ones characterized in Hedgehog signalling mutants. We also have identified novel phenotypes linked to cilium suppression. The mutants display a significant increase in the size of the right ventricle and defective coronary vasculature development. To better understand the growh defects observed at birth, we analysed the underlying cell behaviour. No significant differences in the proliferation rates, nor in the size and proportions of different cell types were detected at prenatal stages, suggesting that these defects have an earlier developmental origin. Experiments are underway to determine the molecular mechanisms of the observed defects. In collaboration with the laboratory of Julien Vermot, in Strasbourg, we studied the role of the primary cilium in the development of the proepicardium, a precursor organ of the mature epicardium. We have shown that Ift20 constitutive mutants show a significant increase in proepicardial volume. Analyses are ongoing to identify the signalling pathways involved in this phenotype. The works performed during this PhD project allowed the characterization of new roles for the primary cilium in cardiac development. Our results participate in a better understanding of ciliopathies and their associated cardiac defects

Tese de Mestrado, Biologia Evolutiva e do Desenvolvimento, 2021, Universidade de Lisboa, Faculdade de Ciências
A vasculatura coronária é responsável por fornecer e remover o sangue do músculo cardíaco, sendo o seu correto desenvolvimento essencial para o funcionamento do coração em embriões e adultos. Os defeitos associados ao seu desenvolvimento constituem atualmente uma das principais causas de morte a nível mundial, conhecidos como doenças arteriais coronárias. O epicárdio, a camada epitelial externa que cobre todo o miocárdio, é um dos principais precursores da vasculatura coronária. Durante o seu desenvolvimento ocorre uma transição através da qual células com características epiteliais se transformam em células mesenquimais, denominadas células derivadas do epicárdio. Estas células derivadas do epicárdio migram para o interior do musculo, diferenciando-se e dando origem principalmente a células do músculo liso, pericitos e células endoteliais. Contribuindo assim para a formação morfológica do sistema vascular coronário. Estas células incorporam-se nas camadas íntima, media e adventícia dos vasos sanguíneos coronários em desenvolvimento. Eventualmente, os vasos de todas as origens diferentes acabam por se associar e formar a vasculatura coronária definitiva. O epicárdio não só coopera no desenvolvimento da vasculatura coronária por meio das células derivadas do epicárdio, mas também através de diferentes vias de sinalização celular. Ao mesmo tempo, o epicárdio desenvolve uma relação estreita com o miocárdio, através de uma comunicação retroativa entre o epicárdio e os cardiomiócitos do miocárdio. Tudo isso torna o epicárdio um elemento essencial para o desenvolvimento da vasculatura coronária, pelo que perceber o desenvolvimento do epicárdio e como este afeta a vasculatura coronária é essencial para o tratamento de doenças atuais associadas, abrindo igualmente caminhos para a criação de novas abordagens terapêuticas. Estudos recentes demonstraram que CCBE1, uma proteína conhecida pelo seu papel no desenvolvimento do sistema linfático, também é expressa no epicárdio, e que a perda de função da proteína causa defeitos na vasculatura coronária, nomeadamente um menor número de vasos coronários no miocárdio como um todo. CCBE1 também é conhecida pelo seu papel na maturação do VEGF-C, um conhecido regulador do desenvolvimento do sistema linfático, e também demonstrou ser essencial para a formação da vasculatura coronária subepicardial e do pedúnculo das artérias coronárias. Sabe-se que os mutantes de Ccbe1 apresentam um desenvolvimento incorreto da vasculatura coronária, mas a contribuição direta do epicárdio nestes mutantes ainda é desconhecida. Como tal, propomos estudar o impacto de CCBE1 na participação do epicárdio embrionário e dos seus derivados no desenvolvimento da vasculatura coronária. Para tentarmos desvendar a função de CCBE1 no desenvolvimento coronário, usámos duas linhas de ratinhos mutantes. Uma linha sistémica (Ccbe1tm1lex) onde Ccbe1 é deletado de todas as células do organismo, e outra linha mutante (Nkx2.5cre;Ccbe1fEl1/−), usando uma linha condicional recentemente criada no nosso laboratório, Ccbe1flE1, junto com o Nkx2.5Cre driver, que, após cruzamento, é feita a perda de função de CCBE1 em todos os tecidos Nkx2.5+ , desta forma teremos embriões sem CCBE1 no primeiro e segundo campo do coração e nos seus derivados. Nas experiências realizadas com o mutante sistémico focámos o nosso estudo no epicárdio. Primeiro, avaliámos o fenótipo das células epicardiais e a sua morfologia através de imunofluorescência. Usando Raldh2 um marcador das células epicardiais, observamos que in vivo e in vitro mantém a forma de paralelepípedo que as caracteriza. A seguir, para descrever o fenótipo in vitro usamos os marcadores ZO-1, um marcador de junções celulares nas células epiteliais, e N-caderina, um marcador de células mesenquimais. Observámos que as células dos corações controlos e mutantes tinham um fenótipo epitelial, mas nas células mutantes foi também detetada a expressão de N-caderina. O que nos leva a sugerir que a falta de CCBE1 nos ratinhos mutantes causou a sobrexpressão de N-caderina, tendo assim como resultado um fenótipo híbrido. As capacidades migratórias e proliferativas também foram analisadas, observámos que os mutantes têm um defeito em ambas já que apresentam menores proliferação celular e capacidade de invasão. Contudo, a expressão de N-caderina costuma ser um indicador do início da transição de células epiteliais para mesenquimais, o que deveria levar a um aumento da proliferação e migração das células que apresentam o sinal, o que não se verifica nos nossos mutantes. Por esse motivo, consideramos que o defeito na migração é causado pelo fenótipo híbrido, que faz com que as células migrem em subgrupos, retardando assim a migração. Ainda assim, a baixa taxa de proliferação nos mutantes continua a contrariar a expressão de N-caderina nos mutantes. Tendo em conta estes resultados, propusemos estudar a expressão relativa do RNA em genes envolvidos na transição epitelial-mesenquimal usando como amostra os ventrículos de corações em diferentes estadios de desenvolvimento da vasculatura coronária (E11.5, E12.5 e E14.5). Verificámos a expressão de 4 genes (Meox1, Tbx2, Has2 e BMPER) retirados de uma análise previa através de RNA-seq, onde foram encontrados estes genes diferencialmente subexpressos a E11.5. Comparando estes resultados com os nossos de RT-qPCR, conseguimos observar que embora o padrão de expressão seja semelhante entre analises nos tempos de desenvolvimento estudados, no RT-qPCR verificámos que os genes estão sobrexpressos nos corações mutantes em comparação com os controlos. O que vai ao encontro dos resultados da migração e proliferação, já que estes genes são conhecidos por aumentarem a capacidade proliferativa e migratória para estimular a transição. Contudo, pensamos que isto pode ser causado pelo tipo de amostra usado, pelo que de seguida testamos um novo protocolo para recolher amostras só de células epicardiais. Não obstante, os resultados não foram os esperados. Devido a grande variação observada e a uma reduzida quantidade de amostra genética, não conseguimos detetar nenhuma desregulação na expressão dos genes testados. No entanto, achamos que usando um conjunto de amostras com esta abordagem seria o mais adequado para o estudo da transição nas células epicardiais. Adicionalmente, no mutante condicional recentemente gerado foi realizada a caracterização do desenvolvimento da vasculatura coronária. Para isso, observámos o pedúnculo das artérias coronárias, que se forma através da ligação de uma rede de vasos sanguíneos com a aorta. O pedúnculo costuma estar completamente estabelecido a E13.5. Nos mutantes condicionais observámos que a perda de função de CCBE1 nestes tecidos causa uma perturbação na formação do pedúnculo, onde a E13.5 só um mutante condicional de 5 tinha a haste formada, no entanto, esta era mais baixa do normal. Estes resultados levam-nos acreditar que CCBE1 é necessário para a conexão entre a rede de vasos sanguíneos e a aorta. Finalmente, quisemos observar se o crescimento cardíaco estava a ser afetado pela perda de função de CCBE1 nos tecidos derivados de Nkx2.5. Para aferir se existe algum defeito, medimos o comprimento do miocárdio compacto e trabecular em alguns estádios de desenvolvimento (E12.5, E13.5, E14.5 e E16.5). Os resultados demonstraram que os mutantes condicionais apresentavam uma parede compacta mais delgada e a trabecular mais comprida, quando comparados com os controlos, o que nos leva acreditar que CCBE1 pode ser preciso para a correta compactação e/ou trabeculação do miocardio. Em conclusão, postulamos que CCBE1 contribui para as células do epicárdio através da regulação da proliferação e migração celular e que pode ser necessário para a subregulação de N-caderina, e assim manter o fenótipo epitelial das células. Nas nossas experiências o mutante condicional demonstrou que CCBE1 é critico para a correta compactação e trabeculação do miocárdio. De igual modo, com o novo mutante condicional conseguimos estudar estadios mais avançados de desenvolvimento, o que não nos era possível com o mutante sistémico.
Coronary artery disease is one of the most common causes of death globally. Identifying coronary vascular progenitors and their developmental pathways could inspire novel regenerative treatments. Several studies have shown that the epicardium critically contributes to the proper formation of the primitive coronary endothelial plexus through the epicardial derived cells that migrate to the myocardium wall of the developing heart, where the coronary vessels will arise. Recently, Ccbe1 has been described as required for coronary vasculature development in the mouse heart, as the absence of CCBE1 leads to underdeveloped coronary vessels. Accordingly, Ccbe1 expression has been detected in the embryonic epicardium. However, whether the defect in coronary vasculature development of Ccbe1-/- mutant hearts is a consequence of the alteration of epicardial function, such as epicardial cell migration and proliferation due to the lack of CCBE1 remains unstudied. Here, we used two Ccbe1 mutant mouse lines, a systemic-KO (Ccbe1tm1lex) and a conditional-KO (Nkx2.5cre;Ccbe1flE1/−) line. In the conditional line, we used a Nkx2.5Cre driver, which is expressed in the first and second heart fields, to selectively have the loss of function of CCBE1. We show evidence that CCBE1 has an impact on the contribution of the epicardium to coronary development, specifically in the proliferation and migration during the epithelial to mesenchymal transition (EMT). Additionally, using the conditional-KO, we demonstrated that the trabeculation/compaction of the ventricles is impaired in later stages of development and that the lack of function of CCBE1 in the Nkx2.5-derived tissue is necessary for the formation of the coronary artery stem. Finally, the results suggest a disruption in the EMT program. Simultaneously, there is a disruption in the cell division and invasion rate of the epicardial cells in the mutant hearts that could be caused for the hybrid phenotype observed in the cells, resulting for the lack of CCBE1.

Coronary heart diseases (CHD) remain the most prevalent cause of premature death. Ischemic hearts often result from coronary vasculature occlusion. Significant efforts have been made for the treatment of CHD, including medications and surgical procedures. Currently there are still no effective drugs or therapeutics available for the treatment of the disease. Growing new coronary vessels to naturally bypass narrowed/occluded arteries or forming sufficient collaterals to the ischemic region would lead to substantially improved blood perfusion and correction of ischemia. However, this aim remains a theoretical ideal due to the negligible ability to grow new coronary vessels even with current advances in therapeutic angiogenesis. In the present study, we have isolated and identified an active fraction of Geum japonicum (AFGJ) showing significant activity in induction of efficient coronary angiogenesis and heart function improvement.
In addition, proteomics methods were applied to investigate the protein alterations in CHD ischemic hearts and HUVECs. Two dimensional polyacrylamide gel electrophoresis (2-D PAGE) of the heart tissues of CHD rats showed 16 differentially expressed spots compared with sham and vehicle hearts, of which 8 were identified. Furthermore, 11 identified proteins of HUVECs treated with AFGJ or Angio-G at different time points were also observed by 2-D PAGE. The majority of identified proteins was found to be involved in the process of energy metabolisms.
In conclusion, these results have demonstrated therapeutic properties of AFGJ to induce early reconstitution of damaged coronary vasculature through both angiogensis and vasculogenesis. AFGJ treatments may provide a novel therapeutic modality for effective treatment of ischemic heart diseases.
The therapeutic effect of AFGJ on CHD through reconstitution of partially occluded coronary vessels in CHD animal models was demonstrated with underlying signaling mechanisms identified. Briefly, AFGJ could promote the proliferation of human umbilical vein endothelial cells (HUVECs) in vitro and the growth of new blood vessels or coronary collaterals in CHD models after 2-week treatment. The number of newly formed coronary vessels in treated hearts was more than that of vehicle treated hearts, as indicated by both MicroCT and histology analysis. Echocardiography studies demonstrated significant improvement of heart functions 2 weeks after treatment with AFGJ. Furthermore, ECG measurements showed that the altered ST segment in AFGJ treated CHD models almost had full recovery to a normal level while rats in the vehicle group consistently suffered from heart ischemia. Moreover, the results of MicroCT reconstruction directly demonstrated the reconstitution of the damaged coronary vessels with newly formed functional coronary collaterals, as illustrated by more blood vessels density (AFGJ vs vehicle [%]: 4.5+/-0.5 vs 2+/-0.35) and more branching points (AFGJ vs vehicle: 0.94+/-0.07 vs 0.65+/-0.10). These data suggest that AFGJ treatment significantly corrects the ischemia of the affected regions of the heart.
We also explored possible mechanisms underlying the effect of AFGJ. Firstly, AFGJ could induce mesenchymal stem cell (MSC) differentiation into vascular endothelial cells and the differentiated MSCs were involved in the tube formation. Secondly, Angio-G, the component derived from AFGJ, was able to stimulate significant proliferation of HUVECs in a dose dependent manner. Thirdly, in our tube-like capillary formation test of HUVECs in vitro, the length of formed tubes was greatly amplified with increasing concentration of Angio-G. Furthermore, the total length of Angio-G induced tubes was significantly reduced with increasing concentrations of AG490, an inhibitor of JAK/STAT pathways indicating possible involvement of the JAK/STAT signaling pathway.
Chen, Hao.
"December 2009."
Source: Dissertation Abstracts International, Volume: 72-01, Section: B, page: .
Thesis (Ph.D.)--Chinese University of Hong Kong, 2010.
Includes bibliographical references (leaves 136-145).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

Thesis (M.S.)--State University of New York at Buffalo, 2005.
Title from PDF title page (viewed on Apr. 13, 2006) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Crassidis, John L. Includes bibliographical references.