Cardiac development in relation to clinical supraventricular arrhythmias : focus on structure-function relations

Supraventricular tachycardias (SVTs) are amongst the most commonly encountered cardiac arrhythmias in clinical practice in both children and adults. The causative mechanisms underlying the appearance of most of these SVTs have however still remained as intriguing as they are unexplained. In this thesis, cardiac development is analyzed in relation to the etiology of clinical supraventricular arrhythmias with a special focus on structure-function relations. Firstly, in PART I of this thesis, both the (patho) physiological development of the annulus fibrosus cordis and the etiological origin of clinical accessory AV pathway (AP) mediated AVRT in children and adults is analyzed in experimental animal models and human sections. Secondly, in PART II of this thesis a review of the different ontogenic theories on the embryonic development of the AV Node (AVN) in literature is followed by an experimental study postulating a new concept on the developmental origin of the AVN in relation to the etiology of AV Nodal Reentrant Tachycardia (AVNRT). As a general introduction to both these basic research (I & II) and the clinical (III) parts of this thesis, structural cardiac development in avians (with references to equivalent mouse and human developmental timelines) (Figure 1) will first be described since the development of the cardiac conduction system (CCS) and structural cardiogenesis are intimately related. Next, the developmental transitions in impulse propagation and the construction of the individual components of the specialized CCS and the AVN in particular will be shortly outlined. Following a description of the changes in electrocardiograms (ECGs) during cardiogenesis, current concepts on the transitions in ventricular activation sequences during embryogenesis will be discussed. Thereafter, contemporary knowledge on the development of the isolating annulus fibrosis, the key structure involved in AP persistence, in relation to general CCS development will be reviewed. Subsequently, relevant genera l characteristics of the different animal models and the immunohistochemical markers used in this thesis are briefly discussed. Following the description of the structural basics of cardiogenesis, attention will be focused on current knowledge of clinical SVTs in neonates and children and the treatment of these arrhythmias. These therapeutic clinical issues will be further outlined in PART III of this thesis.UBL - phd migration 201

Podoplanin and the posterior heart field : epicardial-myocardial interaction

This thesis introduces the posterior heart field contributing to the venous pole of the heart by epithelial-mesenchymal-transformation of the coelomic epithelium. Based on studying of podoplanin and Sp3 (novel genes in cardiogenesis) wildtype and knockout mouse embryos between stages 9.5-18.5, we postulate that the posterior heart field contributes through mesenchymal and myocardial cell populations. The mesenchymal population is involved in the formation of the proepicardial organ, epicardium and epicardium-derived cells. The hypoplastic proepicardial organ and impaired epicardial-myocardial interaction result from altered mesenchymal contribution of the posterior heart field by lack of podoplanin and SP3 leading to hypoplasia of the chamber myocardium and coronary arterial vascular wall as well as (atrioventricular) septal defects. Myocardial contribution concerns myocardium of the sinus venosus including the sinoatrial node, venous valves, primary atrial septum and the left atrial dorsal wall as well as the wall of the pulmonary and cardinal veins. Development of smooth-muscle-cells of the wall of the pulmonary vein is also related to the posterior heart field. Moreover, we have reported formation of a transient left-sided sinoatrial node which persists during development in 10% of the cases. Podoplanin mutants show cardiac malformations including a hypoplastic sinoatrial node. This thesis contributes to the understanding of the mechanism underlying the mentioned cardiac malformations and arrhythmias originating in the sinus venosus region.Nederlandse Hartstichting J.E. Jurriaanse Stichting Sanofi-aventis Netherlands B.V. Datascope Bristol-Myers SquibbUBL - phd migration 201

Cardiac development : the posterior heart field and atrioventricular reentry tachycardia

This thesis is separated in two parts (Part I and Part II) in which normal and abnormal heart development are studied and related to congenital heart disease, in particular to the etiology of supraventricular arrhythmias in fetuses and neonates. Part I describes the development of the posterior heart field derived venous pole of the heart specifically in correlation to the role of Shox2 and podoplanin in that particular area. Furthermore, the developmental processes in this region seem to have an important role in the anlage of the cardiac conduction system and epicardial lineage development of the heart. In the second part of this thesis (Part II) the aetiology of a specific subtype of supraventricular tachycardias i.e. atrioventricular reentry tachycardias (AVRTs) are related to normal heart development in human and mouse. AVRTs are one of the most common types of tachyarrhythmias at the perinatal period of development. We demonstrate that perinatal AVRTs might be related to incomplete formation of the isolating annulus fibrosus resulting in the temporary persistence of accessory myocardial connections between the atria and ventricles. We furthermore, demonstrate the late outcome of fetal brady- and tachyarrhythmia cases.UBL - phd migration 201

Influence of the epicardium on cardiac regeneration after cryoinjury during embryonic development - analysis of morphological and physiological changes

Millions of people die from myocardial infarction every year. In the heart, damaged cardiomyocytes do not regenerate and fibrotic scar forms. Surface layer of the heart - epicardium, improve heart regeneration processes by producing signalling factors. Epicardial cells undergo epithelial-mesenchymal transition and give rise to various cells involved in heart regeneration (coronary vessel formation and possibly new cardiomyocytes). To study the effect of epicardium on cardiac regeneration, I introduced a novel method of myocardial cryoinjury in avian embryos. In embryonic stages, where the heart is already covered by a layer of epicardium. Probe cooled in liquid nitrogen, injured the left ventricle of the heart and simulate myocardial infarction. Cryoinjury is an appropriate alternative to induce myocardial infarction as the coronary ligation is not feasible in early embryos. After cryoinjury, were observed changes in the epicardium. Epicardium is activated (expression of WT1) and detached from myocardium and form protrusions. In subepicardium we observed a large number of migrating cells. These cells undergo epithelial-mesenchymal transition were detected by cytokeratin and vimentin antibodies. We observed α-SMA positive cells and undifferentiated cardiomyocytes (N2.261 antibody) in the...Na infarkt myokardu ročně umírají miliony osob. V srdci následkem ischémie nedochází k dostatečnému nahrazení poškozených kardiomyocytů, vytváří se fibrotická jizva a srdce ztrácí schopnost pumpy. Vrstva buněk, která produkuje množství signalizačních faktorů a vzniká z ní řada buněk, které by mohli napomoci regeneraci po poškození, se nazývá epikard. Jedná se o zevní vrstvu srdeční stěny, jejíž buňky podstupují epiteliálně-mezenchymální tranzici za vzniku buněk účastnících se mimo jiné i formace koronárních cév a pravděpodobně i nových kardiomyocytů. Pro studium vlivu epikardu na regeneraci srdce jsem zavedla novou metodu myokardiálního cryoinjury na ptačích stádiích embryí, kdy je srdce již pokryto vrstvou epikardu a ovlivňuje tak samotnou regeneraci. Pomocí sondy zchlazené v tekutém dusíku bylo indukováno poškození levé komory srdeční, simulující infarkt myokardu. Jedná se o vhodnou alternativu například k podvazům koronárních cév, které u takto raných embryí nejsou proveditelné. Následkem cryoinjury byly pozorovány razantní změny na úrovni epikardu. V této vrstvě byla následkem cryoinjury aktivována exprese (WT1), což se projevovalo odchlípnutím epikardu, zvlněním a tvorbou neobvyklých výběžků. Tím se zvětšila i oblast subepikardu, ve které jsme zaznamenali velké množství migrujících buněk....Katedra fyziologieDepartment of PhysiologyFaculty of SciencePřírodovědecká fakult

Extracellular Matrix in Development and Disease

The extracellular matrix in development and disease deals with the molecular and cellular aspects of development and disease. Cells exist in three-dimensional scaffolding called the extracellular matrix. The matrix holds together the millions of cells that make up our blood vessels, organs, skin, and all tissues of the body. The matrix serves as a reservoir of signaling molecules as well. In bacterial cultures, biofilms form as an extracellular matrix and play essential roles in disease and drug resistance. Topics such as matrix structure and function, cell attachment and cell surface proteins mediating cell-matrix interactions, synthesis, regulation, composition, structure, assembly, remodeling, and function of the matrix are included. A common thread uniting the topics is the essential nature that the matrix plays in normal development and pathophysiology. Providing new knowledge will lead us to improved diagnostics, the preventions of disease progression, and therapeutic strategies for the repair and regeneration of tissues. Topics such as the extracellular matrix in hereditary diseases, reproduction, cancer, muscle, and tissue engineering applications, and diverse roles for integrins, are included in this collection