The Pursuit of Hepatic Resemblance

The liver is one of the most important organs in the human body. It carries out many vital functions, such as removing toxic substances and maintaining nutritional balance. Most of these functions are performed by specialized cells called hepatocytes. Because hepatocytes play diverse roles, they are also involved in many liver diseases. To study theses disease and develop cures, researchers need hepatocytes that can be grown in the laboratory. However, growing functional hepatocytes outside the human body is challenging. In contrast, another liver cell type, cholangiocytes, can be expanded much more easily in the lab. Although cholangiocytes have distinct functions from hepatocytes, they can be transformed to acquire hepatocyte-like characteristics. Unfortunately, the degree to which these transformed cholangiocytes truly resemble hepatocytes has not been well characterized. This characterization is essential to determine whether such cells can serve as a reliable substitute for hepatocytes in research. In this thesis, we thoroughly characterized cholangiocytes grown as 3D structures called organoids. We compared these cholangiocyte organoids to various hepatocyte models. Our analyses showed that cholangiocyte organoids only minimally resembled hepatocytes and instead displayed greater similarity to bile duct and intestinal cells. Hence, we developed a new cholangiocyte-derived organoid model named HeLLO, which more closely mimics the hepatocytes. We demonstrated that HeLLOs perform various key hepatocyte functions and can accurately predict drug-induced liver injury.