Organoid modelling of NAFLD

A novel method to co-differentiate parenchymal and nonparenchymal liver cells from pluripotent stem cells (PSCs) can generate multicellular human liver organoids (HLOs) to model NAFLD, reports a new study.

Despite huge interest from industry in developing therapies for NAFLD, efforts to translate promising agents from animal and cell models have failed to yield any regulatory approvals. One contributing factor might be a lack of human modelling systems suitable for high-throughput compound screening. Cell-based culture systems have increased in sophistication over the past few years, yet often fail to model the complex multicellular environment in NAFLD. Prior co-culture approaches with PSCs used a parallel differentiation approach, whereby individual hepatic cell types are derived independently and then combined in culture. However, this method only models inflammation and fibrosis, limiting its use in NAFLD research.

Image courtesy of T. Takebe, Cincinnati Children’s Hospital Medical Center, USA.

To create an improved in vitro model of NAFLD, Takanori Takebe and colleagues generated an organoid model by co-differentiating human PSCs into epithelial and stromal lineages to form multicellular HLOs. Using an established approach, they first differentiated PSCs into foregut spheroids. These spheroids were then embedded in Matrigel and cultured with retinoic acid, before hepatocyte differentiation was induced using hepatocyte maturation media.

Single-cell RNA sequencing of the resulting HLOs revealed five distinct cell clusters, comprising cells expressing markers of hepatocytes, stellate cells, cholangiocytes, biliary stem cells and Kupffer cells. Functional characterization of hepatocyte-like, stellate-like and Kupffer-like cells supported the presence of distinct hepatic cell types similar to those seen in human liver. When HLOs were exposed to fatty acids (FAs), hepatocyte-like cells developed steatosis and ballooning, and Kupffer-like cells released pro-inflammatory cytokines. Stellate-like cells displayed markers of activation, and levels of collagen were markedly increased in FA-treated HLOs.

“efforts to translate promising agents from animal and cell models have failed to yield any regulatory approvals”

The authors hope that further refinement of their model will enable the investigation of human genetic factors influencing NAFLD development. “As a next step, coupled with our unique organoid steatohepatitis model, we plan to investigate genetic variations for studying personalized NAFLD mechanisms that reflect clinical variations found in vivo,” says Takebe.