The bicuspid aortic valve (BAV) is a congenital heart defect which is characterized by the formation of two aortic leaflets instead of the normal three leaflets within the tricuspid aortic valve ... Show moreThe bicuspid aortic valve (BAV) is a congenital heart defect which is characterized by the formation of two aortic leaflets instead of the normal three leaflets within the tricuspid aortic valve (TAV). Whilst all BAV patients have a bicuspid valve, extended patient monitoring has revealed a large variation of disease progression trajectories during a patient’s lifetime. This large variation troubles clinical decision making due to the uncertain proliferation of BAV disease. More knowledge of the biological mechanisms underlying BAV could address that uncertainty and thus help stratify patient risk with more accuracy. Therefore this thesis aims to advance our current understanding regarding the biological impact and developmental mechanisms underlying congenital BAV and BAV related aortopathy. Show less
Whilst knowledge regarding the pathophysiology of congenital heart disease (CHDs) has advanced greatly in recent years, the underlying developmental processes affecting the cardiac outflow tract ... Show moreWhilst knowledge regarding the pathophysiology of congenital heart disease (CHDs) has advanced greatly in recent years, the underlying developmental processes affecting the cardiac outflow tract (OFT) such as bicuspid aortic valve, tetralogy of Fallot and transposition of the great arteries remain poorly understood. Common among CHDs affecting the OFT, is a large variation in disease phenotypes. Even though the different cell lineages contributing to OFT development have been studied for many decades, it remains challenging to relate cell lineage dynamics to the morphologic variation observed in OFT pathologies. We postulate that the variation observed in cellular contribution in these congenital heart diseases might be related to underlying cell lineage dynamics of which little is known. We believe this gap in knowledge is mainly the result of technical limitations in experimental methods used for cell lineage analysis. The aim of this review is to provide an overview of historical fate mapping and cell tracing techniques used to study OFT development and introduce emerging technologies which provide new opportunities that will aid our understanding of the cellular dynamics underlying OFT pathology. Show less
Patients with a congenital bicuspid aortic valve (BAV), a valve with two instead of three aortic leaflets, have an increased risk of developing thoracic aneurysms and aortic dissection. The... Show morePatients with a congenital bicuspid aortic valve (BAV), a valve with two instead of three aortic leaflets, have an increased risk of developing thoracic aneurysms and aortic dissection. The mechanisms underlying BAV-associated aortopathy are poorly understood. This study examined BAV-associated aortopathy in Nos3(-/-) mice, a model with congenital BAV formation. A combination of histological examination and in vivo ultrasound imaging was used to investigate aortic dilation and dissections in Nos3(-/-) mice. Moreover, cell lineage analysis and single-cell RNA sequencing were used to observe the molecular anomalies within vascular smooth muscle cells (VSMCs) of Nos3(-/-) mice. Spontaneous aortic dissections were found in ascending aortas located at the sinotubular junction in similar to 13% of Nos3(-/-) mice. Moreover, Nos3(-/-) mice were prone to developing aortic dilations in the proximal and distal ascending aorta during early adulthood. Lower volumes of elastic fibres were found within vessel walls of the ascending aortas of Nos3(-/-) mice, as well as incomplete coverage of the aortic inner media by neural crest cell (NCC)-derived VSMCs. VSMCs of Nos3(-/-) mice showed downregulation of 15 genes, of which seven were associated with aortic aneurysms and dissections in the human population. Elastin mRNA was most markedly downregulated, followed by fibulin-5 expression, both primary components of elastic fibres. This study demonstrates that, in addition to congenital BAV formation, disrupted endothelial-mediated nitric oxide (NO) signalling in Nos3(-/-) mice also causes aortic dilation and dissection, as a consequence of inhibited elastic fibre formation in VSMCs within the ascending aorta. Show less
ObjectivesIn congenital heart malformations with pulmonary stenosis to atresia an abnormal lateral ductus arteriosus to left pulmonary artery connection can lead to a localised narrowing (pulmonary... Show moreObjectivesIn congenital heart malformations with pulmonary stenosis to atresia an abnormal lateral ductus arteriosus to left pulmonary artery connection can lead to a localised narrowing (pulmonary ductal coarctation) or even interruption We investigated embryonic remodelling and pathogenesis of this area.Material and methodsNormal development was studied in WntCre reporter mice (E10.0-12.5) for neural crest cells and Nkx2.5 immunostaining for second heart field cells. Data were compared to stage matched human embryos and a VEGF120/120 mutant mouse strain developing pulmonary atresia.ResultsNormal mouse and human embryos showed that the mid-pharyngeal endothelial plexus, connected side-ways to the 6th pharyngeal arch artery. The ventral segment formed the proximal pulmonary artery. The dorsal segment (future DA) was solely surrounded by neural crest cells. The ventral segment had a dual outer lining with neural crest and second heart field cells, while the distal pulmonary artery was covered by none of these cells. The asymmetric contribution of second heart field to the future pulmonary trunk on the left side of the aortic sac (so-called pulmonary push) was evident. The ventral segment became incorporated into the pulmonary trunk leading to a separate connection of the left and right pulmonary arteries. The VEGF120/120 embryos showed a stunted pulmonary push and a variety of vascular anomalies.SummarySide-way connection of the DA to the left pulmonary artery is a congenital anomaly. The primary problem is a stunted development of the pulmonary push leading to pulmonary stenosis/atresia and a subsequent lack of proper incorporation of the ventral segment into the aortic sac. Clinically, the aberrant smooth muscle tissue of the ductus arteriosus should be addressed to prohibit development of severe pulmonary ductal coarctation or even interruption of the left pulmonary artery. Show less
A common requirement, in field of life sciences, is the quantification of specific cells in a given fluorescent microscopy image. ImageJ is a popular tool for researchers to develop custom scripts... Show moreA common requirement, in field of life sciences, is the quantification of specific cells in a given fluorescent microscopy image. ImageJ is a popular tool for researchers to develop custom scripts for automated cell quantification. Validating the quality of cell quantification measurements is a common challenge for such researchers. The Fluorescent Nuclei Measurements Macro (FNMM) was developed to assist researchers performing cell quantification by presenting the results in an intuitive manner whilst simultaneously facilitating processed data collection and measurement assurance. Show less
