Residing within the liver are specialized immune cells called Kupffer cells that protect the host by engulfing and destroying pathogens. Despite beneficial functions such as detoxifying chemicals and drugs, Kupffer cells can also cause liver inflammation in response to viruses, alcohol and drugs.
To accurately recapitulate these biological processes in liver toxicity bioassays, researchers need a renewable and sustainable source of mature human Kupffer cells. Capitalizing on the differentiation potential of induced pluripotent stem cells (iPSCs), scientists led by Hanry Yu at A*STAR’s Institute of Bioengineering and Nanotechnology (IBN) devised a method to generate mature human Kupffer cells from iPSCs, replacing the current reliance on primary Kupffer cells (pKCs) obtained from adult human livers.
“pKCs are expensive, exhibit donor variability, can have a low yield after tedious isolation procedures, and cannot be expanded in culture. They are also restricted by their availability, which depends on the amount of human tissue available,” said Farah Tasnim, Senior Research Scientist at IBN and first author of the study.
The researchers first generated immature immune cells known as macrophage precursors from iPSCs. They then differentiated these precursors into induced Kupffer cells (iKCs) using primary human hepatocyte conditioned media. The ability to mature iPSCs into Kupffer cells with an adult-like state in this study is an important breakthrough, since iPSC-derived cells typically retain an immature phenotype.
Using microarray analysis and immunostaining, Yu’s team observed that the expression of genes and proteins governing inflammatory and immune function in iKCs were comparable to that of pKCs. The iKCs also functioned similarly to pKCs—they were capable of engulfing fluorescent beads and could produce inflammatory mediators in response to lipopolysaccharide, a substance found on the surface of bacteria.
“Liver toxicity studies can now incorporate inflammation or immune-mediated aspects without being challenged by cell source issues. In addition, more physiologically relevant models for liver conditions such as fibrosis, viral hepatitis, cholestasis, steatohepatitis, alcoholic/non-alcoholic liver disease and drug-induced liver injury can be created,” Yu said.
Tasnim added that with their method, both iKCs and pKCs can be obtained from the same donor for use in liver toxicity bioassays, expanding the utility of such tests.
The team plans to use iKCs to create a disease model for non-alcoholic steatohepatitis (NASH), a major cause of liver disease globally.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Bioengineering and Nanotechnology (IBN).