Heart failure is a major health care problem with high mortality. Although advances have been made in treatment of patients suffering from heart failure with reduced ejection fraction, this is not... Show moreHeart failure is a major health care problem with high mortality. Although advances have been made in treatment of patients suffering from heart failure with reduced ejection fraction, this is not true for patients suffering from heart failure with preserved ejection fraction. The mechanism underlying heart failure with preserved ejection fraction is still unclear. Recent evidence suggests that factors circulating in blood might have an effect on the microvessels, including those in the heart. To diagnose and treat microvascular diseases, we aim to explore the association of circulating plasma factors with microvascular integrity. As current human 2D models with cultured endothelial cells lack sufficient complexity to assess the function of microvascular endothelial-pericyte interactions, research on microvascular loss largely depends on animal models. To mimic the microarchitecture and functions of the human blood vessel in a more efficient way for drug discovery, we developed the microvessel-on-a-chip. This system allowed us to screen microvascular destabilization factors in blood and study the efficacy of potential drugs for microvascular diseases. In conclusion, our platform may serve as a unique tool for microvascular destabilization studies as well as for the development of novel therapeutic strategies to combat microvascular complications. Show less
Abnormal vascular physiology and precipitating inflammatory pathways underlie many different diseases, including hemorrhage, stroke, vascular dementia and even cancer. Pluripotent stem cells (PSCs)... Show moreAbnormal vascular physiology and precipitating inflammatory pathways underlie many different diseases, including hemorrhage, stroke, vascular dementia and even cancer. Pluripotent stem cells (PSCs) can now be derived by reprogramming from any individual so that it is possible in principle to derive all somatic cells of the human body that would normally be difficult to access. In this thesis, I studied the derivation of myeloid cells from human induced pluripotent stem cells (hiPSCs) to model the inflammatory component of vascular disease and characterized the development path of hiPSC-derived endothelial cells (hiPSC-ECs) which form the vascular walls. Functional defects in either of these cell types can cause or exacerbate vascular disease. I then used these cell types to gain insight into the mechanisms underlying two genetic diseases: Hereditary Hemorrhagic Telangiectasia (HHT) which is caused by mutations in a gene called Endoglin expressed on cells of the vascular wall and inflammatory macrophages, and a vascular tumor called Pseudomyogenic hemangioendothelioma (PHE) in which endothelial cells are thought to be the tumor cell of origin. I developed new differentiation protocols to generate inflammatory cells from hiPSC, characterized these cells functionally and used Next-Generation Sequencing and bioinformatic analysis to gain insight into the molecular pathways controlling development of one particular type of endothelial cells from hiPSC and the underlying tumorigenic mechanisms of PHE. Show less
Von Willebrand disease (VWD) is the most common inherited bleeding disorder. Patients mainly develop mucocutaneous bleeding, like bruises, epistaxis and menorrhagia. The more severely affected... Show moreVon Willebrand disease (VWD) is the most common inherited bleeding disorder. Patients mainly develop mucocutaneous bleeding, like bruises, epistaxis and menorrhagia. The more severely affected patients may also develop joint bleeding, or bleeding from the gastrointestinal tract. Also, trauma, surgery or dental procedures may lead to critical bleeding events. VWD-related bleeding are caused by defects in von Willebrand factor (VWF), a large multimeric protein that is produced by endothelial cells and megakaryocytes. Most VWD patients develop the disease because of dominant-negative mutations in VWF. In this thesis we investigated whether inhibition of production of mutant VWF with limited inhibition of wildtype VWF positively affects the function of VWF and improves VWD phenotypes. We used small interfering RNAs (siRNAs) to selectively inhibit production of mutant VWF. These siRNAs were tested in several models for VWD. We indeed prove that siRNAs can distinguish a mutant and wildtype VWF allele in vitro in heterologous cell systems, ex vivo in patient-derived endothelial cells, and in vivo in a VWD mouse model. We also show in these disease models that we can improve several VWD phenotypes. These results are promising for further development of allele-specific siRNAs as a new treatment strategy for VWD. Show less
