Modeling Human Nonalcoholic Fatty Liver Disease (NAFLD) with an Organoids-on-a-Chip System

Nonalcoholic fatty liver disease (NAFLD) is a common metabolic and progressive disease, which has emerged as a major cause of chronic liver disease worldwide. It is characterized by the process ranging from simple steatosis to nonalcoholic steatohepatitis. However, a deep understanding of NAFLD progression remains challenging due to the lack of proper in vitro human disease models. In this work, we proposed a new strategy to establish a human NAFLD model based on a human-induced pluripotent stem cell (hiPSC)-derived liver organoids-on-a-chip system. This system allows us to characterize the pathological features of NAFLD in liver organoids by exposure to free fatty acids (FFAs) in perfused three-dimensional (3D) cultures during a prolonged period. Upon FFA induction, liver organoids exhibited lipid droplet formation and triglyceride accumulation. Moreover, they showed upregulated expressions of lipid metabolism-associated genes, indicating the abnormal lipid metabolic process in NAFLD. The FFA-exposed organoids also showed reactive oxygen species (ROS) production and elevated expression of various inflammatory cytokine genes and fibrogenic markers. These alterations represented the typical biochemical characteristics of NAFLD progression, which may provide insight into the potential mechanisms underlying steatosis. The proposed human NAFLD-on-a-chip model combines stem cell organoids with organs-on-chips, which may provide a promising platform for extending their applications for disease studies and effective therapies.