Modelling of human nonalcoholic fatty liver disease with hepatocyte like cells derived from pluripotent stem cells

• Published in: Zeitschrift für Gastroenterologie
• Main Authors: Graffmann, N, Kawala, MA, Ring, S, Wruck, W, Adjaye, J
• Format: Conference Proceeding
• Language: English
• Published: 14.12.2015
• ISSN: 0044-2771; 1439-7803
• DOI: 10.1055/s-0035-1568043

Nonalcoholic fatty liver disease (NAFLD) is an increasingly common diagnosis in the Western Hemisphere. It is defined by an accumulation of lipid droplets in more than 5% of hepatocytes. In the beginning the disease is rather benign, but later on patients develop steatohepatitis, cirrhosis and up to 27% of these patients end up with hepatocellular carcinoma. The molecular reasons of this disease are still questioned, but it is well-recognised that NAFLD is strongly associated with obesity and insulin resistance. In this metabolism-based field of research, results obtained from rodent model systems cannot be easily extended to humans as both organisms differ in their metabolisms. Unfortunately, liver cells from steatosis patients are very rarely available and not suitable for longer experiments as hepatocytes rapidly dedifferentiate in culture. Therefore, we have established a human model system for NAFLD based on hepatocyte like cells (HLCs) generated from pluripotent stem cells. We are able to induce the accumulation of lipid droplets (LDs) in these cells by adding oleic acid (OA) into the medium. LD formation has been documented by staining with Oil Red O or BODIPY. After fat induction with OA the expression of PLIN2, a protein covering LDs, was consistently up-regulated. As PLIN2 knockout mice are protected against the development of steatosis, we selected PLIN2 expression as a molecular marker for the successful induction of steatosis. We thoroughly investigated the consequences of LD accumulation on the level of gene expression. We found that many GO categories related to lipid, glucose and sterol metabolism were up-regulated in HLCs after OA induction. Interestingly, many members of the Peroxisome proliferator-activated receptor (PPAR) pathway, which is important for the regulation of lipid metabolism, were up-regulated after fat induction. Modelling PPARα in HLCs with small molecules resulted in profound gene expression changes. Inhibition of PPARα with GW6471 resulted in down-regulation of genes involved in lipid catabolism, while activation via Fenofibrate reduced expression of AGPAT2 and HMGCR, which are involved in biosynthesis of phospholipids and cholesterol, respectively. Also insulin signalling was affected by PPARα modulation. Although obesity and NAFLD are increasing health problems worldwide, there is no specific treatment for NAFLD at the moment. Our HLC-based NAFLD model can be used in the future to screen for drugs that might interfere with LD accumulation. Corresponding author: Adjaye, James E-Mail: James.Adjaye@med.uni-duesseldorf.de