A miniature human liver to transform toxicology testing of food contaminants

Assessing the toxicity of food contaminants—including carcinogenic potential—is a major challenge in evaluating the risks associated with exposure. In recent years, as part of efforts to reduce animal testing, two-dimensional (2D) analytical methods using human hepatic cell lines (which make up most of the liver) have advanced predictive toxicology for contaminants. However, these approaches have limitations, because they do not sufficiently capture the organ’s complexity. To improve toxicology studies of chemicals, the researchers developed a miniature, three-dimensional (3D) liver model that includes the different cell types that make up a human liver. 

A human-relevant mini-liver for toxicology studies

In laboratories, human cell lines are typically grown in two dimensions as a flat layer at the bottom of culture dishes. The team has developed a new three-dimensional, spherical cell culture model that enables several cell types to be grown together to mimic the structure of a human liver. This tiny 0.3-mm sphere contains around 2,000 cells and includes all four types of cells found in the human liver: hepatic cells (hepatocytes), cholangiocytes, stellate cells and immune cells^*. The mini liver demonstrates physiological and metabolic capabilities that mimic those of a human liver and are more representative than the models traditionally used (i.e. cell culture and animal models).

An innovative method for 3D toxicology analysis

Using this mini-liver, the research team developed an innovative confocal microscopy process that is high-throughput and high-resolution. For the first time, toxicology analyses can be conducted at single-cell scale within the mini-liver model. The method enables the detailed and simultaneous analysis of several contaminant-induced effects on cells, including DNA damage, the cell proliferation that is characteristic of cancer cells, inflammation, and the accumulation of fats often seen with liver disease or obesity. Scientists revealed certain effects not detected by conventional 2D cell-based analysis, such as the spatial distribution of effects and the types of cells affected. This method also makes it possible to test much lower doses—more representative of real-life exposure—than those typically used in 2D cell analysis. The process has been optimised to run as many as 72 toxicology tests simultaneously using multi-well cell culture plates.

“This mini-liver model mimics the human organ. Our approach maps the effects of contaminants and reveals certain impacts that conventional methods do not detect. In the medium term, using this type of human cell model should improve our ability to predict the toxicity of certain chemicals in humans and limit the need for animal testing.” Marc Audebert, INRAE Research Director

^* Hepatic cells account for 70% of liver cells and perform several metabolic functions, including storing and releasing glucose.  Cholangiocytes line the bile duct.  The main role of stellate cells is to store vitamin A, and immune cells neutralise and eliminate foreign substances.