Lecture: Modelling liver disease using human pluripotent stem cells

Non-Alcoholic Fatty Liver Disease describes a broad spectrum of liver diseases ranging from simple fat accumulation in the liver (steatosis), inflammation and fibrosis (NASH or Non-Alcoholic Steatohepatitis) to advanced cirrhosis leading to hepatocellular carcinoma or end-stage liver disease. NAFLD incidence is increasing rapidly not only in developed countries where 20-40% of the population is suspected to be affected but also in developing countries due to a change in traditional diet. However, the variable severity of the illness and clinical evolution render effective prognostication difficult. Furthermore, liver transplantation is the only treatment available for end stage NASH. For all these reasons, the development of new therapies is urgently needed. However, the development of these new therapies is currently impaired by the absence of physiologically relevant models to study NAFLD/NASH in vitro and to identify potential drug targets. Indeed, current platforms rely on animal models which are not compatible with large scale screening and do not always reproduce the full human pathophysiology especially genetic aspects. Transformed cell lines such as HepG2 don’t have the key functional activity necessary to model NAFLD while primary hepatocytes are difficult to obtain in large quantity. Finally, several liver cells such as cholangiocytes, Kupffer cells and hepatic stellate cells are involved in the toxic lipid accumulation leading to NASH.

Here, we address these roadblocks by taking advantage of a system allowing 3D culture of hIPSCs derived hepatocytes, cholangiocytes, and macrophages to model NAFLD in vitro. This approach allows the creation of reproducible and tunable 96-well arrays of 3-D collagen matrices mimicking the architecture and cell-to-cell interactions found in the liver. Accordingly, we showed that hIPSCs derived hepatocytes organise with cholangiocytes in bile ducts tubes while other cell types appear to interact with Hepatocytes. Furthermore, hepatocytes grown in these culture conditions accumulate lipids and display apoptosis in the presence of fatty acids. These data suggest that our system can be used to model lipid accumulation/toxicity occurring in hepatocytes during NAFLD/NASH. We are now exploiting this in vitro model to validate the function genes recently identified by genetic studies on NASH patients and also to develop a drug screening platform for NAFLD/NASH.

Ludovic Vallier , Carola Morell, Samantha Tilson, Brandon Wesley and Rute Tomaz