Background Ischemia of the bile duct is a common feature in liver disease and transplantation, which represents a major cause of morbidity and mortality, especially after liver transplantation.... Show moreBackground Ischemia of the bile duct is a common feature in liver disease and transplantation, which represents a major cause of morbidity and mortality, especially after liver transplantation. Detailed knowledge of its pathogenesis remains incomplete due to the lack of appropriate in vitro models.Methods To recapitulate biliary damage induced by ischemia and reperfusion in vitro, human intrahepatic cholangiocyte organoids (ICOs) were grown at low oxygen levels of 1% up to 72 h, followed by re-oxygenation at normal levels.Findings ICOs stressed by ischemia and subsequent re-oxygenation represented the dynamic change in biliary cell proliferation, upregulation of epithelial-mesenchymal transition (EMT)-associated markers, and the evocation of phase-dependent cell death programs similar to what is described in patients. Clinical-grade alpha-1 antitrypsin was identified as a potent inhibitor of both ischemia-induced apoptosis and necroptosis.Interpretation These findings demonstrate that ICOs recapitulate ischemic cholangiopathy in vitro and enable drug assessment studies for the discovery of new therapeutics for ischemic cholangiopathies. 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
